CN118841621A - Lithium ion battery and electricity utilization device comprising same - Google Patents

Abstract

The application relates to a lithium ion battery, which comprises a positive electrode plate and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode film layer with a lithium-containing multi-cation positive electrode active material, and the lithium-containing multi-cation positive electrode active material comprises other cations with larger radius than lithium ions; the negative electrode sheet comprises a negative electrode film layer with an alkali metal salt, wherein the alkali metal salt comprises at least one of sulfate, nitrate, carbonate or halide of alkali metal; the obtained lithium ion battery not only has equivalent battery energy density under the condition of adopting a thinner shell large surface and a higher shell group entering margin, but also has obviously improved battery volume expansion rate and cycle performance. The application also relates to an electric device comprising the lithium ion battery.

Description

Lithium ion battery and electricity utilization device comprising same

Technical Field

The application relates to the technical field of lithium batteries, in particular to a lithium ion battery. In addition, the application also relates to an electric device comprising the lithium ion battery.

Background

In recent years, along with the wider application range of lithium ion batteries, the lithium ion batteries are widely applied to energy storage power supply systems such as hydraulic power, firepower, wind power, solar power stations and the like, and a plurality of fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, aerospace and the like.

With the expansion of application fields of lithium ion batteries, demands for lithium ion batteries are increasing, so that higher demands are placed on energy density, electrochemical performance and portability of the batteries. However, since the electrodes (positive electrode and negative electrode) of the lithium ion battery undergo volume expansion during the deintercalation of lithium, resulting in a decrease in energy density and electrochemical performance of the battery, and in order to reduce the volume expansion rate of the battery, a case having a thick case wall and a large cavity is generally used, resulting in a heavy and bulky battery, which is not easy to carry.

Therefore, there is a need to develop a lithium ion battery that has a low battery expansion rate and good cycle performance at a comparable energy density using a battery with a thinner housing face and a higher housing group margin.

Disclosure of Invention

The present application has been made in view of the above-described problems, and an object of the present application is to provide a lithium ion battery having a low battery expansion rate and good cycle performance while having a battery energy density equivalent to that of a battery using a thinner large-surface battery and a high battery pack margin; and provides an electric device comprising the lithium ion battery.

In order to achieve the above object, a first aspect of the present application provides a lithium ion battery, which includes a positive electrode tab and a negative electrode tab; the positive electrode plate comprises a positive electrode film layer with a lithium-containing multi-cation positive electrode active material, wherein the lithium-containing multi-cation positive electrode active material comprises other cations with a radius larger than that of lithium ions; the negative electrode sheet comprises a negative electrode film layer with an alkali metal salt, wherein the alkali metal salt comprises at least one of sulfate, nitrate, carbonate or halide of alkali metal;

Alternatively, the lithium-containing multi-cation positive electrode active material includes a positive electrode active material of the general formula (I): li _aL_(1-a)Ni_gCo_hMn_iM_(1-g-h-i)O_eN_f is a metal oxide,

Wherein the L ion is a cation having an ionic radius greater than that of the Li ion, N includes at least one of F, S, P, M includes at least one of Mg, zr, al, B, ta, mo, W, nb, sb, la, 0.2.ltoreq.a <1,0< (1-a) <0.8, 0.ltoreq.g <1, 0.ltoreq.h <1, 0.ltoreq.i <1, 0.ltoreq.1-g-h-i) <1, 0.ltoreq.e.ltoreq.2, 0.ltoreq.f < 2, e+f=2;

still alternatively, the element of the L ion includes at least one of an alkali metal element, an alkaline earth metal element, a transition metal element, and other metal elements of the main group other than the lithium element; the alkali metal element includes at least one of Na, K, rb, cs; the alkaline earth metal element comprises at least one of Mg, ca and Sr; the transition metal element includes yttrium Y; other metallic elements of the main group include Bi.

According to the application, part of lithium of the positive electrode active material is replaced by cations with larger ionic radius in the lithium ion battery, so that the function of supporting a layered structure is realized, the volume expansion of the electrode is reduced, and a compact solid electrolyte interface film (SEI film) is formed on the surface of the electrode, so that the energy density of the lithium ion battery is equivalent under the conditions of a thinner shell large surface and a higher shell group entering margin, and the expansion rate and the cycle performance of the battery are obviously improved.

In some embodiments, in the lithium ion battery of the present application, the positive electrode material includes a lithium-containing multi-cation positive electrode active material of general formula (I), the element of the L ion includes an alkali metal element other than the lithium element, and the alkali metal element includes at least one of Na, K, rb, cs; e=2, f=0; further alternatively, the positive electrode material includes a lithium-containing multi-cation positive electrode active material including positive electrode active materials of the following general formulae (II) to (IV), and mixtures thereof:

Li _aNa_bK_cRb_dCs_eNi_yCo_zMn_1-y-zO₂, (II)、Li_aNa_bK_cRb_dCs_eNi_yCo_zAl_1-y-zO₂, (III)、JLi₂MnO₃·(1-J)Li_aNa_bK_cRb_dCs_eNi_yCo_zMn_1-y-zO₂, formula (IV);

Wherein 0< J < 1,0< y < 1,0< z < 1, and a, b, c, d, e satisfies 0.2.ltoreq.a < 1,0< b <0.8, 0.ltoreq.c < 1, 0.ltoreq.d < 1, 0.ltoreq.e < 1, a+b+c+d+e=1, 0< (b+c+d+e) <0.8. By replacing part of lithium of the positive electrode active material with alkali metal cations with larger ionic radius, the battery expansion rate of the lithium ion battery is further reduced, and the cycle life of the battery is prolonged.

In some embodiments, in formulas (II) to (IV) of the lithium-containing multi-cation positive electrode active material of the present application, b satisfies 0 < b < 1, optionally 0.001.ltoreq.b.ltoreq.0.05, and further optionally 0.005.ltoreq.b.ltoreq.0.04. Thereby, at least alkali metal element sodium is doped in the lithium-containing multi-cation positive electrode active material.

In some embodiments, the lithium ion battery of the present application comprises a positive electrode sheet comprising a lithium-containing multi-cation positive electrode active material of formula (II) Li _aNa_bK_cRb_dCs_eNi_yCo_zMn_1-y-zO₂. Thereby, the volume expansion of the positive electrode is further reduced.

In some embodiments, in the lithium ion battery of the application, the alkali metal salt in the negative electrode film layer includes at least one of alkali metal carbonates; optionally, at least one of Na ₂CO₃、K₂CO₃、Rb₂CO₃、Cs₂CO₃; and further alternatively Na ₂CO₃. Therefore, the volume expansion of the negative electrode is further reduced, a compact solid electrolyte interface film is formed on the surface of the negative electrode, and the structure of the negative electrode is further stabilized.

In some embodiments, in the lithium ion battery of the present application, the sum of the mole fractions of the alkali metal elements Na, K, rb, cs in the lithium-containing polycation positive electrode active material is X _{Positive direction} = (1-a) ×100% or X _{Positive direction} ＝(b+c+d+e)×100％,X _{Positive direction} is 0.05% to 5%, alternatively 0.5% to 4%; the mass content of the alkali metal salt relative to the total mass of the negative electrode film layer is X _{Negative pole} ,X _{Negative pole} from 0.5% to 5%, optionally from 1% to 4%; thereby improving the volume expansion rate and cycle life of the battery while maintaining the battery energy density.

In some embodiments, the lithium ion battery of the present application, the X _{Positive direction} and X _{Negative pole} satisfy the following relationship: less than or equal to 0.01/(X _{Positive direction} +5X _{Negative pole} ) less than or equal to 0.5; alternatively, 0.03.ltoreq.1/(X _{Positive direction} +5X _{Negative pole} ). Ltoreq.0.2. Therefore, the volume expansion rate and the cycle life of the battery are further improved by limiting the proportion of alkali metal elements in the positive electrode material and the negative electrode material, and the energy density of the battery is not damaged.

In some embodiments, the lithium ion battery of the present application further comprises a housing, wherein the positive electrode tab and the negative electrode tab are accommodated in a cavity of the housing, and the thickness of the wall of the large face of the housing is t, wherein t is 0.4mm to 1mm, optionally 0.5mm to 0.7mm.

In some embodiments, in the lithium ion battery of the present application, the shell wall thickness t (mm) of the large face of the shell, the sum of mole fractions X _{Positive direction} of the alkali metal element Na, K, rb, cs in the lithium-containing polycationic positive electrode active material, the mass content X _{Negative pole} of the alkali metal salt relative to the total mass of the negative electrode film layer, the t, X _{Positive direction} , and X _{Negative pole} satisfy the following relation: 0< (0.6-t)/(X _{Positive direction} +5X _{Negative pole} ) <1. By further defining the above-described relationship between the shell wall thickness of the large face of the shell and the doping amount of the alkali metal in the positive and negative electrode materials, the lithium ion battery thus obtained can have an improved volume expansion ratio and cycle life without impairing the volume energy density.

In some embodiments, the lithium ion battery of the present application has a group-in-shell margin m of 0.86 to 0.96, alternatively 0.88 to 0.94, further alternatively 0.90 to 0.92.

In some embodiments, the lithium ion battery of the present application has a shell group entering margin of m, a sum of mole fractions of alkali metal elements Na, K, rb, cs in the lithium-containing polycation positive electrode active material, X _{Positive direction} , and a mass content of alkali metal salt X _{Negative pole} relative to the total mass of the negative electrode film layer satisfy the following relationship, wherein the m, X _{Positive direction} , and X _{Negative pole} satisfy the following relationship: 0< (m-0.91)/(X _{Positive direction} +5X _{Negative pole} ) <0.2, alternatively 0.025< (m-0.91)/(X _{Positive direction} +5X _{Negative pole} ) <0.18. Thus, by further defining the battery shell group entering margin and the doping amount of alkali metal in the positive electrode and negative electrode materials to satisfy the above relation, the lithium ion battery thus obtained can have improved volume expansion rate and cycle life without impairing the volume energy density.

A second aspect of the application provides an electrical device comprising a lithium ion battery according to the first aspect of the application.

Drawings

Fig. 1 is a schematic view of a lithium ion battery according to an embodiment of the present application.

Fig. 2 is an exploded view of the lithium ion battery of the embodiment of the present application shown in fig. 1.

Fig. 3 is a cross-sectional view of a single electrode assembly in the lithium ion battery of an embodiment of the application shown in fig. 2, which illustrates a winding manner of the electrode assembly in a top view.

Fig. 4 is a schematic view of a battery module according to an embodiment of the present application.

Fig. 5 is a schematic view of a battery pack according to an embodiment of the present application.

Fig. 6 is an exploded view of the battery pack of the embodiment of the present application shown in fig. 7.

Fig. 7 is a schematic view of an electrical device for use in a lithium ion battery according to an embodiment of the present application.

Reference numerals illustrate:

1, a battery pack; 2, upper box body; 3, lower box body; 4, a battery module; a5 lithium ion battery; 51 a housing; 52 electrode assembly; 53 top cap assembly.

Detailed Description

Hereinafter, embodiments of the lithium ion battery and the electrical device of the present application are specifically disclosed with reference to the accompanying drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.

The "range" disclosed herein is defined in terms of lower and upper limits, with the given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-6. In the present application, unless otherwise indicated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed throughout, and "0-5" is simply a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2,3,4,5, 6, 7, 8, 9, 10, 11, 12 or the like.

All embodiments of the application and alternative embodiments may be combined with each other to form new solutions, unless otherwise specified.

All technical features and optional technical features of the application may be combined with each other to form new technical solutions, unless specified otherwise.

All the steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise specified. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, or may comprise steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), may include steps (c), (a) and (b), and the like.

The terms "comprising" and "including" as used herein mean open ended or closed ended, unless otherwise noted. For example, the terms "comprising" and "comprises" may mean that other components not listed may be included or included, or that only listed components may be included or included.

The term "or" is inclusive in this application, unless otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or absent); a is false (or absent) and B is true (or present); or both A and B are true (or present).

With the expansion of application fields of lithium ion batteries, demands for lithium ion batteries are increasing, so that higher demands are placed on energy density, electrochemical performance and portability of the batteries. However, in the process of removing lithium from the electrode of the lithium ion battery, the active material layer of the electrode expands in volume, so that the active material layer is separated from the current collector, and the battery has the problems of large volume expansion, low cycle performance, short service life and the like. Meanwhile, in order to reduce the influence of battery deformation caused by volume expansion, the large-surface shell wall of the currently commonly adopted shell is thicker, and the shell group entering margin of the battery is smaller, so that the battery is thicker and has lower energy density.

The inventor has found that by using positive and negative electrode materials doped with alkali metal elements in a lithium ion battery, the supporting effect of the alkali metal elements in the electrode materials can be fully exerted, which is beneficial to reducing the volume expansion rate of the electrode, thereby allowing a shell with thinner wall thickness to be used and allowing the battery to have higher shell group entering margin; in addition, the alkali metal element is also favorable for forming a compact solid electrolyte interface film (SEI film) on the surface of the electrode, thereby stabilizing the structure of the electrode and improving the cycle performance of the battery. Therefore, the lithium ion battery obtained by the application has equivalent energy density, lower volume expansion rate and good cycle performance under the condition of adopting a thinner shell large surface and a higher shell group entering margin.

The first aspect of the application provides a lithium ion battery, which comprises a positive electrode plate and a negative electrode plate; the positive electrode plate comprises a positive electrode film layer with a lithium-containing multi-cation positive electrode active material, wherein the lithium-containing multi-cation positive electrode active material comprises other cations with a radius larger than that of lithium ions; the negative electrode sheet comprises a negative electrode film layer with an alkali metal salt, wherein the alkali metal salt comprises at least one of sulfate, nitrate, carbonate or halide of alkali metal;

Alternatively, the lithium-containing multi-cation positive electrode active material includes a positive electrode active material of the general formula (I): li _aL_(1-a)Ni_gCo_hMn_iM_(1-g-h-i)O_eN_f is a metal oxide,

Wherein the L ion is a cation having an ionic radius greater than that of the Li ion, N includes at least one of F, S, P, M includes at least one of Mg, zr, al, B, ta, mo, W, nb, sb, la, 0.2.ltoreq.a <1,0< (1-a) <0.8, 0.ltoreq.g <1, 0.ltoreq.h <1, 0.ltoreq.i <1, 0.ltoreq.1-g-h-i) <1, 0.ltoreq.e.ltoreq.2, 0.ltoreq.f < 2, e+f=2;

still alternatively, the element of the L ion includes at least one of an alkali metal element, an alkaline earth metal element, a transition metal element, and other metal elements of the main group other than the lithium element; the alkali metal element includes at least one of Na, K, rb, cs; the alkaline earth metal element comprises at least one of Mg, ca and Sr; the transition metal element includes yttrium Y; other metallic elements of the main group include Bi.

According to the application, part of lithium of the positive electrode active material is replaced by cations with larger ionic radius in the lithium ion battery, and sulfate, nitrate, carbonate or halide containing alkali metal is doped in the negative electrode film layer, so that the effect of supporting a layered structure is achieved, the volume expansion of the electrode in the lithium intercalation process is reduced, and the formation of a compact solid electrolyte interface film (SEI film) on the surface of the electrode is facilitated; therefore, when the lithium ion battery adopts a thinner shell large surface and a higher shell entering group margin, the lithium ion battery not only has lower volume expansion rate and good cycle performance, but also has no damage to the energy density of the battery, namely, the battery keeps a comparable level.

In some embodiments, in the lithium ion battery of the present application, the positive electrode material includes a lithium-containing multi-cation positive electrode active material of general formula (I), the element of the L ion includes an alkali metal element other than the lithium element, and the alkali metal element includes at least one of Na, K, rb, cs; e=2, f=0.

In an alternative embodiment, the positive electrode material comprises a lithium-containing multi-cation positive electrode active material comprising positive electrode active materials of the following general formulas (II) to (IV), and mixtures thereof:

Li _aNa_bK_cRb_dCs_eNi_yCo_zMn_1-y-zO₂, (II)、Li_aNa_bK_cRb_dCs_eNi_yCo_zAl_1-y-zO₂, (III)、JLi₂MnO₃·(1-J)Li_aNa_bK_cRb_dCs_eNi_yCo_zMn_1-y-zO₂, formula (IV);

Wherein J is more than 0 and less than 1, y is more than 0 and less than 1, z is more than 0 and less than 1, a, b, c, d, e satisfies a is more than or equal to 0.2 and less than 1, b is more than or equal to 0 and less than 0.8, c is more than or equal to 0 and less than or equal to 1, d is more than or equal to 0 and less than or equal to e is less than 1, a+b+c+d+e=1, and 0< (b+c+d+e) <0.8; the alkali metal salt in the negative electrode film layer comprises one or more compounds NaCl、NaNO₃、Na₂SO₄、Na₂CO₃、KCl、KNO₃、K₂SO₄、K₂CO₃、RbCl、RbNO₃、Rb₂SO₄、Rb₂CO₃、CsCl、CsNO₃、Cs₂SO₄、Cs₂CO₃.

In the present application, the positive electrode active materials of the general formulae (II) to (IV) contain alkali metal cations having larger ionic radii than lithium ions.

The inventor finds that partial lithium in the positive electrode active material is replaced by alkali metal cations with larger ionic radius, which not only plays a supporting role for the layered positive electrode active material, can effectively reduce electrochemical expansion caused by lithium intercalation, but also can reduce lithium nickel rearrangement in the positive electrode active material, can effectively reduce volume change caused by lattice degradation, and thus achieves the aim of reducing the volume expansion of the positive electrode; meanwhile, the alkali metal salt is doped in the negative electrode film layer, so that the supporting effect of alkali metal elements can be exerted, and the formation of a compact solid electrolyte interface film on the surface of the negative electrode can be promoted, thereby achieving the purposes of reducing the volume expansion of the negative electrode and improving the structural stability of the electrode. Therefore, under the combined action of the anode material and the cathode material doped with alkali metal elements, the volume energy density of the lithium ion battery is not damaged when the lithium ion battery adopts a thinner large shell surface and a higher shell group entering margin, and the lithium ion battery has improved volume expansion rate and cycle life.

In some embodiments, in formulas (II) to (IV) of the lithium-containing multi-cation positive electrode active material of the present application, b satisfies 0< b < 1, optionally 0.001.ltoreq.b.ltoreq.0.05, and further optionally 0.005.ltoreq.b.ltoreq.0.04.

In some embodiments, in formulas (II) to (IV) of the lithium-containing multi-cation positive electrode material, b is not 0, at least one of c, d, and e is 0, at least two are 0, or both are 0. This indicates that Na must be present in the lithium-containing polycation cathode material, while K, rb, cs may or may not be present. b. c, d and e may be the same or different. b. The values of c, d and e can be achieved by adjusting the types and doping amounts of the respective elements, for example, by selecting specific doping elements and the relative molar amounts of the respective doping elements added in the process of preparing the positive electrode material. The specific composition of the final positive electrode material may be determined by means of inductively coupled plasma emission chromatography (ICP) or the like.

In some embodiments, the lithium ion battery of the present application comprises a positive electrode sheet comprising a lithium-containing multi-cation positive electrode active material of formula (II) Li _aNa_bK_cRb_dCs_eNi_yCo_zMn_1-y-zO₂. Thereby, the volume expansion of the positive electrode is further reduced.

In some embodiments, in the lithium ion battery of the application, the alkali metal salt in the negative electrode film layer includes at least one of alkali metal carbonates; optionally, at least one of Na ₂CO₃、K₂CO₃、Rb₂CO₃、Cs₂CO₃; and further alternatively Na ₂CO₃. Therefore, the volume expansion of the negative electrode is further reduced, a compact solid electrolyte interface film is formed on the surface of the negative electrode, and the structure of the negative electrode is further stabilized.

In some embodiments, in the lithium ion battery of the present application, the sum of the mole fractions of the alkali metal elements Na, K, rb, cs in the lithium-containing polycation positive electrode active material is X _{Positive direction} = (1-a) ×100% or X _{Positive direction} ＝(b+c+d+e)×100％,X _{Positive direction} is 0.05% to 5%, alternatively 0.5% to 4%; the mass content of the alkali metal salt relative to the total mass of the negative electrode film layer is X _{Negative pole} ,X _{Negative pole} from 0.5% to 5%, optionally from 1% to 4%; thereby improving the volume expansion rate and the cycle life of the battery while maintaining the energy density of the battery.

In alternative embodiments, X _{Positive direction} is 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 3.7%, 3.8%, 4%, 4.2%, or 4.5%.

In alternative embodiments, X _{Negative pole} is 0.6%, 0.8%, 1%, 1.2%, 1.5%, 2%, 2.5%, 3%, 3.5%, 3.7%, 3.8%, 4%, 4.2% or 4.5%.

In some embodiments, the ratio of X _{Positive direction} to X _{Negative pole} in the lithium ion battery of the present application is 0.08 to 6, alternatively 0.1 to 4.5.

In some embodiments, in the lithium ion battery of the present application, X _{Positive direction} and X _{Negative pole} satisfy the following relationship: less than or equal to 0.01/(X _{Positive direction} +5X _{Negative pole} ) less than or equal to 0.5; alternatively, 0.03.ltoreq.1/(X _{Positive direction} +5X _{Negative pole} ). Ltoreq.0.2, further alternatively, 0.04.ltoreq.1/(X _{Positive direction} +5X _{Negative pole} ). Ltoreq.0.15. Therefore, the volume expansion rate and the cycle life of the battery are further improved by limiting the proportion of alkali metal elements in the positive electrode material and the negative electrode material, and the energy density of the battery is not damaged.

In alternative embodiments, 1/(X _{Positive direction} +5X _{Negative pole} ) is 0.03、0.04、0.045、0.05、0.055、0.60、0.70、0.80、0.90、0.95、0.10、0.105、0.110、0.115、0.12、0.13、0.14、0.15、0.16、0.17、0.175、0.18、0.185、0.19、0.195 or 0.20.

In some embodiments, the lithium ion battery of the present application, the lithium-containing multi-cation positive electrode active material comprises at least one ：Li_0.995Na_0.005Ni_0.8Co_0.1Mn_0.1O₂、Li_0.96Na_0.04Ni_0.8Co_0.1Mn_0.1O₂. of the following materials, the mass fraction of the lithium-containing multi-cation positive electrode active material being 70% to 99% based on the mass of the positive electrode film layer.

The lithium-containing multi-cation positive electrode active material can be prepared by the following method: firstly, preparing a conventional precursor by mixing cobalt, nickel, manganese or aluminum and other compounds, then mixing the precursor, lithium salt and an alkali metal element Na, K, rb, cs compound to be doped, grinding and calcining, and cooling to obtain the doped lithium-containing multi-cation positive electrode active material. The compound may be a salt of an alkali metal element Na, K, rb, cs, such as a carbonate salt. The dosing of the compound containing the alkali metal element may be determined according to the desired final composition of the lithium-containing polycationic positive electrode active material, for example by the molar ratio of the respective alkali metal element in the final composition. The lithium salt is typically lithium carbonate, added in excess to compensate for losses during calcination.

In some embodiments the lithium ion battery of the application further comprises a housing, wherein the positive electrode pole piece and the negative electrode pole piece are accommodated in a cavity of the housing, the thickness of a wall of a large surface of the housing is t, and t is 0.4mm to 1mm, optionally 0.5mm to 0.7mm; for example t is 0.53, 0.54, 0.55, 0.56, 0.57, 0.58mm.

In the present application, the large face of the battery case is opposite to the large face of the bare cell accommodated in the battery case. The large surface of a bare cell is typically the surface of the bare cell with the largest area.

In one embodiment, as shown in fig. 2, the length, width, and thickness of the battery case correspond to the illustrated y-axis, x-axis, and z-axis directions, respectively, with length > width > thickness. The large surface of the battery shell is the surface with the largest area of the battery shell and is positioned at two sides of the thickness z direction, namely, the large surface consists of the length y and the width x of the battery shell; which is opposite the large face of the bare cell. The width W, the length L and the thickness T of the bare cell are respectively parallel to the y-axis, the x-axis and the z-axis directions shown in fig. 2, and the width W is greater than the length L and the thickness T, so that the large surface of the bare cell is a surface formed by the width W and the length L.

In the application, the preparation method of the bare cell is a method known in the art, and the specific process is as follows: and sequentially stacking the positive pole piece, the isolating film and the negative pole piece, enabling the isolating film to be positioned between the positive pole piece and the negative pole piece to play a role in isolation, and then winding to form the bare cell with a flat structure. In the fabricated bare cell, a surface formed by winding (referred to as a winding surface) is opposed to the bottom surface of the battery case (composed of the length y and the thickness z) as shown in fig. 3. Specifically, the width of the winding surface is the width W of the bare cell and is parallel to the y direction of the battery shell; the length of the winding surface is the thickness T of the bare cell and is parallel to the z direction of the battery shell; wherein the width W of the bare cell is greater than the thickness T.

In one embodiment, the bare cell is enclosed in the battery case as follows: as shown in fig. 2 and 3, the bare cell is mounted along the opening of the width x direction of the battery case shown in fig. 2, with the large face of the bare cell facing the side surface of the battery case made up of x and y; as shown in fig. 3, the winding face of the bare cell faces the bottom surface of the battery case, which is composed of y and z. In the application, a bare cell is accommodated in a battery shell, wherein the thickness T of the bare cell is 10-15mm, the width W is 130-150mm and the length L is 70-90mm; the bare cell is of a flat structure, and the large surface of the bare cell is the surface with the largest area of the bare cell. The width x of the battery case is 90-110mm, the length y is 140-160mm, and the thickness z is 25-35mm, wherein the length > width > thickness.

In one embodiment, the battery housing may house one or several bare cells. When the battery is in a working state, the positive electrode and the negative electrode generate stress on the large surface of the bare cell due to the volume expansion of the positive electrode and the negative electrode in the lithium removal process, the large surface of the bare cell is deformed and protrudes outwards, and accordingly the stress on the large surface of the shell is also protruding outwards. When the battery case is an aluminum case, the thickness of the large face of the case is usually not less than 0.6mm. In the present application, the large-surface case wall thickness of the battery case can be made thinner, and even at a thickness of 0.56mm, the battery has a small EOL (end of life) expansion ratio and cycle life, while the battery energy density is comparable.

In some embodiments, in the lithium ion battery of the present application, the shell wall thickness t (mm) of the large face of the shell, the sum of mole fractions X _{Positive direction} of the alkali metal element Na, K, rb, cs in the lithium-containing polycationic positive electrode active material, the mass content X _{Negative pole} of the alkali metal salt relative to the total mass of the negative electrode film layer, the t, X _{Positive direction} , and X _{Negative pole} satisfy the following relation: 0< (0.6-t)/(X _{Positive direction} +5X _{Negative pole} ) <1, alternatively 0.03.ltoreq.1/(X _{Positive direction} +5X _{Negative pole} ). Ltoreq.0.2; still alternatively, 0.08< (0.6-t)/(X _{Positive direction} +5X _{Negative pole} ) <0.8. The wall thickness of the large surface of the housing is thus defined in relation to the doping levels of alkali metals in the positive and negative electrode materials, so that the lithium ion battery has a comparable battery volume energy density with a thinner large surface of the housing, as well as a significantly improved volume expansion rate and cycle life.

In some embodiments, the lithium ion battery of the present application has a group-in margin m of 0.86 to 0.96, optionally 0.88 to 0.94, further optionally 0.90 to 0.92; for example, m is 0.913, 0.916, 0.917, 0.918, 0.919, or 0.92.

In some embodiments, the lithium ion battery of the present application has a shell group entering margin of m, a sum of mole fractions of alkali metal elements Na, K, rb, cs in the lithium-containing polycation positive electrode active material, X _{Positive direction} , and a mass content of alkali metal salt X _{Negative pole} relative to the total mass of the negative electrode film layer satisfy the following relationship, wherein the m, X _{Positive direction} , and X _{Negative pole} satisfy the following relationship: 0< (m-0.91)/(X _{Positive direction} +5X _{Negative pole} ) <0.2, alternatively 0.025< (m-0.91)/(X _{Positive direction} +5X _{Negative pole} ) <0.18, and yet alternatively 0.029< (m-0.91)/(X _{Positive direction} +5X _{Negative pole} ) <0.11. Therefore, the shell group entering margin of the battery and the doping amount of alkali metal in the anode and cathode materials are limited to meet the above relation, so that the lithium ion battery has equivalent battery energy density under the condition of adopting higher shell group entering margin, and simultaneously has improved EOL expansion rate and cycle life.

A second aspect of the application provides an electrical device comprising a lithium ion battery according to the first aspect of the application.

The composition and structure of the lithium ion battery will be described in detail.

[ Positive electrode sheet ]

In the lithium ion battery, the positive electrode plate comprises a current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the lithium-containing multi-cation positive electrode active material in the lithium ion battery according to the first aspect of the application.

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the positive electrode film layer comprises a lithium-containing multi-cation positive electrode active material in a lithium ion battery according to the first aspect of the application, and optionally a positive electrode active material for a battery as known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (e.g., liCoO ₂), lithium nickel oxide (e.g., liNiO ₂), lithium manganese oxide (e.g., liMnO ₂、LiMn₂O₄), lithium nickel cobalt oxide, Lithium manganese cobalt oxide, lithium nickel manganese oxide, Lithium nickel cobalt manganese oxide (such as LiNi _1/3Co_1/3Mn_1/3O₂ (which may also be abbreviated as NCM ₃₃₃)、LiNi_0.5Co_0.2Mn_0.3O₂ (which may also be abbreviated as NCM ₅₂₃)、LiNi_0.5Co_0.25Mn_0.25O₂ (which may also be abbreviated as NCM ₂₁₁)、LiNi_0.6Co_0.2Mn_0.2O₂ (which may also be abbreviated as NCM ₆₂₂)、LiNi_0.8Co_0.1Mn_0.1O₂ (which may also be abbreviated as NCM ₈₁₁)), a metal oxide, at least one of lithium nickel cobalt aluminum oxide (such as LiNi _0.85Co_0.15Al_0.05O₂) and modified compounds thereof, and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO ₄ (which may also be referred to simply as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄), a composite of lithium manganese phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon. The mass fraction of the conductive agent is 0% to 3% based on the mass of the positive electrode film layer.

In some embodiments, the positive electrode film layer optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The mass fraction of the conductive agent is 0% to 8% based on the mass of the positive electrode film layer.

In the present application, the positive electrode film layer optionally contains a binder, which may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin, as examples. The mass fraction of the binder is 0% to 8% based on the mass of the positive electrode film layer. The single-side coating unit surface density of the positive electrode plate is 15-25 mg/cm ² (dry weight), and the compacted density is 3.1-3.8 g/cm ³.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the lithium-containing multi-cation positive electrode active material, the conductive agent, the binder and any other components of the present application, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like. The single-side coating unit surface density of the positive electrode plate is 15-25 mg/cm ² (dry weight), and the compacted density is 2.5-3.5 g/cm ³.

[ Negative electrode plate ]

The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer with alkali metal salt in the lithium ion battery according to the first aspect of the application, wherein the negative electrode film layer is arranged on at least one surface of the negative electrode current collector.

As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode film layer is provided on either one or both of the two surfaces opposing the anode current collector.

In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the negative electrode film layer with alkali metal salt in the lithium ion battery of the application further comprises a negative electrode active material. The negative electrode active material may be a negative electrode active material for a battery, which is known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more. The mass fraction of the anode active material in the anode film layer is 70-100% based on the mass of the anode film layer.

In some embodiments, the negative electrode film layer with alkali metal salt in the lithium ion battery of the application may further optionally include a binder. The binder may be at least one selected from Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The mass fraction of the binder in the negative electrode film layer is 0-30% based on the mass of the negative electrode film layer.

In some embodiments, the negative electrode film layer with alkali metal salt in the lithium ion battery of the application may further optionally include a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers. The mass fraction of the conductive agent in the negative electrode film layer is 0-20% based on the mass of the negative electrode film layer.

In some embodiments, the negative electrode film layer with alkali metal salt in the lithium ion battery of the application may optionally further include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like. The mass fraction of other auxiliary agents in the negative electrode film layer is 0-15%, based on the mass of the negative electrode film layer.

In some embodiments, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as alkali metal salt, negative electrode active material, conductive agent, binder and any other components described in the lithium ion battery of the present application, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like. The single-side coating unit surface density of the negative pole piece is 9-14mg/cm ² (dry weight), and the compaction density is 1.5-2.0g/cm ³.

[ Electrolyte ]

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The application is not particularly limited in the kind of electrolyte, and may be selected according to the need. For example, the electrolyte may be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolytic solution).

In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF ₆), lithium tetrafluoroborate (LiBF ₄), lithium perchlorate (LiClO ₄), lithium hexafluoroarsenate (LiAsF ₆), lithium bis-fluorosulfonimide (LiFSI), lithium bis-trifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (lipfob), lithium dioxaato borate (LiBOB), lithium difluorophosphate (LiPO ₂F₂), lithium difluorodioxaato phosphate (LiDFOP), and lithium tetrafluorooxalato phosphate (LiTFOP). The concentration of the electrolyte salt is usually 0.5 to 5mol/L.

In some embodiments, the solvent may be selected from one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene Carbonate (BC), fluoroethylene carbonate (FEC), methyl Formate (MF), methyl Acetate (MA), ethyl Acetate (EA), propyl Acetate (PA), methyl Propionate (MP), ethyl Propionate (EP), propyl Propionate (PP), methyl Butyrate (MB), ethyl Butyrate (EB), 1, 4-butyrolactone (GBL), sulfolane (SF), dimethylsulfone (MSM), methylsulfone (EMS), and diethylsulfone (ESE). The solvent is present in an amount of 70 to 98 wt% based on the weight of the electrolyte.

In some embodiments, additives are optionally also included in the electrolyte. For example, the additives may include negative electrode film-forming additives, or may include positive electrode film-forming additives, or may include additives that improve certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high temperature performance of the battery, additives that improve the low temperature performance of the battery, and the like.

[ Isolation Membrane ]

In some embodiments, the lithium ion battery of the present application further comprises a separator. The isolating film is arranged between the positive pole piece and the negative pole piece to play a role in isolation. The type of the separator is not particularly limited, and any known porous separator having good chemical stability and mechanical stability can be used.

In some embodiments, the thickness of the separator is 6-40 μm, optionally 10-20 μm.

In some embodiments, the material of the isolating film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

[ External packing ]

In some embodiments, the outer package of the lithium ion battery is a housing in the lithium ion battery according to the first aspect of the application for encapsulating the positive electrode tab, the negative electrode tab and the electrolyte. As one example, the positive pole piece, the negative pole piece and the isolation film may be laminated or wound to form a laminated cell or a wound bare cell, which is encapsulated in the housing; the electrolyte can be electrolyte, and the electrolyte wets the bare cell. The number of bare cells in the lithium ion battery can be one or more, and can be adjusted according to requirements.

In one embodiment, the present application provides an electrode assembly. In some embodiments, the positive electrode tab, the negative electrode tab, and the separator are manufactured into an electrode assembly through a winding process. The overwrap may be used to encapsulate the electrode assembly and electrolyte described above.

In some embodiments, the lithium ion battery outer package may be a hard plastic shell, an aluminum shell, a steel shell, or the like. The shape of the case is not particularly limited, and may be selected as required.

Alternatively, the housing is an aluminum square housing, as shown in fig. 2, having a length direction y, a width direction x, and a thickness direction z.

Preparation method of lithium ion battery

In one embodiment, the present application provides a method for preparing a lithium ion battery according to the first aspect of the present application.

In some embodiments, the positive electrode plate, the isolating film and the negative electrode plate can be sequentially stacked, so that the isolating film is positioned between the positive electrode plate and the negative electrode plate to play a role of isolation, and then the battery cell is obtained through a winding process. And placing the battery core in the aluminum square shell, injecting electrolyte and sealing to obtain the lithium ion battery.

The shape of the lithium ion battery is not particularly limited, and may be cylindrical, square, or any other shape. Fig. 1 is a lithium ion battery 5 of a square structure as an example.

In some embodiments, referring to fig. 2, the overpack may include a housing 51 and a cap assembly 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate enclose a receiving chamber. The housing 51 has an opening communicating with the accommodating chamber, and the top cover assembly 53 can be provided to cover the opening to close the accommodating chamber. The positive electrode tab, the negative electrode tab, and the separator may be wound to form an electrode assembly 52 (also referred to as a bare cell). The electrode assembly 52 is enclosed in the accommodating chamber. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 included in the lithium-ion battery 5 may be one or more, and those skilled in the art may choose according to specific practical requirements.

Power utilization device

The application provides an electric device, wherein the electric device comprises the lithium ion battery or the lithium ion battery prepared by the method.

The lithium ion battery comprises a battery cell form, a battery module form and a battery pack form. In some embodiments, the battery cells may be assembled into a battery module, and the number of battery cells included in the battery module may be one or more, and the specific number may be selected by one skilled in the art according to the application and capacity of the battery module.

Fig. 4 is a battery module 4 as an example. Referring to fig. 4, in the battery module 4, a plurality of battery cells 5 may be sequentially arranged in the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of battery cells 5 may be further fixed by fasteners.

Alternatively, the battery module 4 may further include a housing having an accommodating space in which the plurality of battery cells 5 are accommodated.

In some embodiments, the above-described battery cells may be assembled into a battery pack. In some embodiments, the above battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and a specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

Fig. 5 and 6 are battery packs 1 as an example. Referring to fig. 5 and 6, a battery case and a plurality of battery modules 4 disposed in the battery case may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

In addition, the application also provides an electric device, which comprises the lithium ion battery provided by the application. The lithium ion battery can be used as a power source of the power utilization device and also can be used as an energy storage unit of the power utilization device. The power utilization device may include mobile devices (e.g., cell phones, notebook computers, etc.), electric vehicles (e.g., electric-only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

As the electricity utilization device, a lithium ion battery may be selected according to the use requirement thereof.

Fig. 7 is an electrical device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. To meet the high power and high energy density requirements of the power device for lithium ion batteries, a battery pack or battery module may be employed.

As another example, the device may be a cell phone, tablet computer, notebook computer, or the like. The device is generally required to be light and thin, and a lithium ion battery can be used as a power supply.

Examples

Hereinafter, embodiments of the present application are described. The following examples are illustrative only and are not to be construed as limiting the application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention. Unless otherwise indicated, all experimental steps were carried out at normal pressure.

Example 1

Preparation of sodium-doped high-nickel cathode material Li _0.995Na_0.005Ni_0.8Co_0.1Mn_0.1O₂

Firstly, nickel acetate, cobalt acetate and manganese acetate are added into deionized water according to stoichiometric ratio, and are stirred uniformly. The sodium carbonate solution is rapidly poured into the transition metal salt solution, the reaction is continued for 9 hours, and then the mixture is kept stand and aged for 4 hours, so as to enable primary particles to grow. Washing with deionized water for 3 times, drying in a blast drier, vacuum drying at 100deg.C for 12 hr, and collecting dried solid as precursor with molecular formula of Ni _0.8Co_0.1Mn_0.1CO₃.

The precursor, lithium carbonate and sodium carbonate are uniformly mixed according to the mol ratio of 1:1.05:0.005, and then ground. The excess lithium carbonate is to compensate for the loss of lithium during high temperature calcination. And transferring the fully ground solid powder to a crucible, and placing the crucible in a muffle furnace with programmed temperature for calcination. The calcination procedure is as follows: precalcination is carried out for 5 hours from room temperature to 500 ℃, and the temperature rising rate is 3 ℃ min ^-1; then the mixture is heated to the high temperature of 800 ℃ for calcination for 12 hours, and the heating rate is 3 ℃ for min ^-1. After cooling to room temperature, the sodium-doped high-nickel cathode material described in this example was obtained.

[ Preparation of Positive electrode sheet ]

The positive electrode material (Li _0.995Na_0.005Ni_0.8Co_0.1Mn_0.1O₂) prepared in the above way is mixed with the binder polyvinylidene fluoride (PVDF) and the conductive agent (carbon black Super-P) according to the mass ratio of 90:5:5, and N methyl-pyrrolidone (NMP) is used as a solvent, and the addition amount of the solvent is regulated, so that the slurry viscosity is controlled at 100-20000 Pa.s. The slurry was coated on the surface of an aluminum foil using a coater, and then transferred to a vacuum drying oven to be completely dried. And (3) drying at 85 ℃, cold pressing, trimming, cutting pieces, splitting, drying at 85 ℃ under vacuum for 4 hours, and welding the tab to prepare the positive electrode plate. The single-sided coating unit surface density of the positive electrode plate is 20mg/cm ² (dry weight), and the compacted density is 3g/cm ³.

[ Preparation of negative electrode sheet ]

Adding sodium carbonate, active substance graphite, conductive agent Super-P, thickener CMC and binder SBR into solvent deionized water according to the mass ratio of 1:95.5:1:1:1.5, and uniformly mixing to prepare negative electrode slurry; and (3) coating the negative electrode slurry on a current collector copper foil, drying at 85 ℃, trimming, cutting pieces, splitting, drying at 110 ℃ under vacuum for 4 hours, and welding the tab to prepare the negative electrode plate. The single-sided coating unit surface density of the negative electrode plate is 10mg/cm ² (dry weight), and the compacted density is 1.6g/cm ³.

[ Preparation of electrolyte ]

The electrolyte containing LiPF ₆ with a molar concentration of 1M is prepared by taking a mixture of Ethylene Carbonate (EC), propylene Carbonate (PC) and diethyl carbonate (DEC) as a nonaqueous organic solvent, wherein the mass ratio of the components is EC to PC to DEC=30 to 30 to 40, and lithium hexafluorophosphate (LiPF ₆) as a lithium salt.

[ Isolation Membrane ]

A12 μm polypropylene film was used as a separator.

[ Preparation of lithium ion Battery ]

The positive pole piece, the isolating film and the negative pole piece are sequentially stacked, so that the isolating film is positioned between the positive pole piece and the negative pole piece to play a role of isolation, and then the bare cell with the thickness T of 12mm, the width W of 140mm and the length L of 80mm is wound, and the bare cell is parallel to the z direction, the y direction and the x direction of the battery shell shown in figure 2. Specifically, the opening (shown in fig. 2) of one bare cell along the width x direction of the battery case prepared as described above is filled into an aluminum square case, and the width W of the bare cell is parallel to the length y direction of the battery case, and the length L of the bare cell is parallel to the width x direction of the battery case; i.e., the large surface of the bare cell consisting of length L and width W, is opposite to the side surface consisting of x and y shown in fig. 2, which is the large surface of the battery case described herein. Wherein the thickness of the shell wall of the large surface of the shell is 0.58mm, the thickness of the shell wall of the side surface (the side surface formed by x and z) perpendicular to the large surface of the shell is 0.8mm, the thickness of the bottom surface of the shell is 1.2mm, and the thickness of the top cover (the top cover component 53 in figure 2) is 2mm; the length y, width x and thickness z of the case were 150mm, 100mm and 30mm, respectively, and the group-in-case margin of the battery was 91.6%. Then, baking for 10 hours at 75 ℃ under vacuum, injecting 150g of electrolyte, vacuum packaging, standing for 24 hours, charging to 4.25V by constant current of 0.1C, charging to 0.05C by constant voltage of 4.25V, discharging to 2.8V by constant current of 0.1C, repeating the charging and discharging for 2 times, and finally charging to 3.8V by constant current of 0.1C, thereby completing the preparation of the lithium ion battery, and obtaining the lithium ion battery of the embodiment.

Example 2

The procedure for the preparation of a lithium ion battery is generally described with reference to example 1, except that the molar ratio of sodium carbonate addition is varied during the preparation of the sodium-doped high nickel cathode material.

Example 3

The preparation process of the lithium ion battery was generally referred to example 1, except that the mass ratio of sodium carbonate added was changed during the preparation of the negative electrode tab as shown in table 1.

Example 4

The manufacturing process of the lithium ion battery was generally referred to example 1, except that the wall thickness of the large surface of the case was changed during the manufacturing process of the lithium ion battery as shown in table 1.

Example 5

The manufacturing process of the lithium ion battery was generally referred to example 1, except that the in-shell group margin of the battery was changed during the manufacturing process of the lithium ion battery as shown in table 1.

Comparative example 1

Preparation of sodium-free cathode material LiNi _0.8Co_0.1Mn_0.1O₂

Firstly, nickel acetate, cobalt acetate and manganese acetate are added into deionized water according to stoichiometric ratio, and are stirred uniformly. The sodium carbonate solution is rapidly poured into the transition metal salt solution, the reaction is continued for 9 hours, and then the mixture is kept stand and aged for 4 hours, so as to enable primary particles to grow. Washing with deionized water for 3 times, drying by a blast drier, vacuum drying at 100 ℃ for 12 hours, and collecting dried solid to obtain a precursor.

The precursor and lithium carbonate are uniformly mixed according to the mol ratio of 1:1.07, and then ground. The excess lithium carbonate is to compensate for the loss of lithium during high temperature calcination. And transferring the fully ground solid powder to a crucible, and placing the crucible in a muffle furnace with programmed temperature for calcination. The calcination procedure is as follows: pre-calcining for 5h from room temperature to 500 ℃, and calcining for 12h at 800 ℃ with the temperature rising rate of 3 ℃ min < -1 >. The resulting material was collected after subsequent cooling to room temperature.

The procedure for preparing the lithium ion battery of comparative example 1 was generally referred to in example 1, except that the high nickel positive electrode material, which was not doped with sodium as described above, was used in the preparation of the positive electrode sheet, and sodium carbonate was not added in the preparation of the negative electrode sheet, in which graphite: conductive agent: the mass ratio of CMC to SBR is 96.5:1:1:1.5.

Comparative example 2

The procedure for preparing a lithium ion battery was generally described with reference to example 1, except that the sodium-undoped high-nickel positive electrode material prepared in comparative example 1 was used in the preparation of the positive electrode sheet.

Comparative example 3

The preparation process of the lithium ion battery is generally referred to in example 1, except that sodium carbonate is not added in the preparation process of the negative electrode tab, wherein graphite: conductive agent: CMC: SBR mass ratio = 96.5:1:1:1.5.

[ Battery Performance test ]

Determination of eol expansion Rate

Caliper (model 530-123, sanfeng, japan) measures the thickness of the large face of the battery case, and the specific operation is as follows:

The distance in the thickness direction of the cell at the beginning is measured by using a caliper and is recorded as t ₀; the thickness of the material is t _EOL when the cycle is finished; expansion ratio= (t _EOL-t₀)/t₀ ×100%.

In the present application, the distance t ₀ in the thickness direction of the battery cell at the beginning is the thickness of the battery case measured in the z direction using a caliper for the lithium ion batteries prepared in examples 1 to 5 and comparative examples 1 to 3; the distance t _EOL in the thickness direction at the end of the cycle means that the battery is subjected to the following cycle: the lithium ion battery was subjected to a 1C/1C cycle test at 25 ℃, the charge-discharge voltage range was 4.25V, and when the capacity decayed to 80% of the first discharge specific capacity, the cycle was ended, and the thickness of the battery case in the z direction at this time was measured.

2. Energy density measurement of battery

Electrochemical workstation (model Zahner XC, manufacturer germany, zhana) 1/3C was charged to 4.25V, constant voltage to 0.05C, battery 1/3C rate was discharged to 2.8V, and the energy E of the discharge was measured divided by the cell volume V, ρ=e/V.

In the present application, the cell volume refers to the volume of the battery cases used in examples 1 to 5 and comparative examples 1 to 3, i.e., 150×100×30=4.5×10 ⁵mm³.

3. Measurement of cycle performance of battery

The cycle number test conditions were: at 25 ℃, the lithium ion battery is subjected to 1C/1C cycle test, the charging and discharging voltage range is 4.25V, and the test is stopped when the capacity is attenuated to 80% of the first discharging specific capacity.

Examples and comparative examples were tested according to the procedure described above, respectively, with specific values in table 1.

As can be seen from the results of table 1, by using both positive and negative electrode materials having alkali metals, which have a larger ionic radius than lithium ions, in a lithium ion battery, the volume expansion rate of the battery and the cycle life of the battery can be significantly improved with a thinner battery case large surface and a higher in-case group margin (the thickness of the case large surface case wall is 0.56 to 0.58mm, and the in-case group margin is 0.916 to 0.919%), while the energy density of the battery is comparable.

In contrast, in comparative examples 1 to 3, when a large-surface battery case corresponding to the thickness shown in the examples of the present invention and a group-in margin (the thickness of the large-surface case wall is 0.53 to 0.58mm, the group-in margin is 0.916 to 0.94%) were employed, if neither the positive electrode material nor the negative electrode material of the battery was doped with an alkali metal having a radius larger than that of Li ions, or such an alkali metal was present only in the positive electrode or the negative electrode material, the EOL expansion ratio, the cycle life, and the volumetric energy density of the battery were not effectively improved.

As can be seen from examples 1 to 3, under the condition that the large-surface shell thickness and the shell group entering margin of the battery are the same, the doping amounts of the alkali metal ions in the positive electrode and the negative electrode are controlled within a certain range, when 1/(X _{Positive direction} +5X _{Negative pole} ) is within a range of 0.049 to 0.182, the EOL expansion rate of the battery is not more than 1%, and the cycle life is not less than 4010 turns; further, when 1/(X _{Positive direction} +5X _{Negative pole} ) is in the range of 0.049 to 0.111, the EOL expansion rate and cycle life of the battery are further improved.

The present application is not limited to the above embodiment. The above embodiments are merely examples, and embodiments having substantially the same configuration and the same effects as those of the technical idea within the scope of the present application are included in the technical scope of the present application. Further, various modifications that can be made to the embodiments and other modes of combining some of the constituent elements in the embodiments, which are conceivable to those skilled in the art, are also included in the scope of the present application within the scope not departing from the gist of the present application.

Claims (12)

1. A lithium ion battery comprising a positive electrode plate and a negative electrode plate, wherein the positive electrode plate comprises a positive electrode film layer with a lithium-containing multi-cation positive electrode active material, and the lithium-containing multi-cation positive electrode active material comprises other cations with a radius larger than that of lithium ions;

The negative electrode sheet comprises a negative electrode film layer with an alkali metal salt, wherein the alkali metal salt comprises at least one of sulfate, nitrate, carbonate or halide of alkali metal;

Alternatively, the lithium-containing multi-cation positive electrode active material includes a positive electrode active material of the general formula (I): li _aL_(1-a)Ni_gCo_hMn_iM_(1-g-h-i)O_eN_f is represented by the general formula (I),

Wherein the L ion is a cation having an ionic radius greater than that of the Li ion, N includes at least one of F, S, P, M includes at least one of Mg, zr, al, B, ta, mo, W, nb, sb, la, 0.2.ltoreq.a <1,0< (1-a) <0.8, 0.ltoreq.g <1, 0.ltoreq.h <1, 0.ltoreq.i <1, 0.ltoreq.1-g-h-i) <1, 0.ltoreq.e.ltoreq.2, 0.ltoreq.f < 2, e+f=2;

Still alternatively, the element of the L ion includes at least one of an alkali metal element, an alkaline earth metal element, a transition metal element, and other metal elements of the main group other than the lithium element;

The alkali metal element comprises at least one of Na, K, rb, cs;

The alkaline earth metal element comprises at least one of Mg, ca and Sr;

the transition metal element includes Y;

the main group other metal elements include Bi.

2. The lithium ion battery according to claim 1, wherein in the general formula (I), the element of the L ion includes an alkali metal element other than a lithium element, the alkali metal element including at least one of Na, K, rb, cs; e=2, f=0;

Further alternatively, the lithium-containing multi-cation positive electrode active material includes positive electrode active materials of the following general formulas (II) to (IV), and mixtures thereof:

Li _aNa_bK_cRb_dCs_eNi_yCo_zMn_1-y-zO₂ of the formula (II),

Li _aNa_bK_cRb_dCs_eNi_yCo_zAl_1-y-zO₂ formula (III)、JLi₂MnO₃·(1-J)Li_aNa_bK_cRb_dCs_eNi_yCo_zMn_1-y-zO₂ formula (IV);

wherein 0< J < 1,0< y < 1,0< z < 1, and a, b, c, d, e satisfies 0.2.ltoreq.a < 1,0< b <0.8, 0.ltoreq.c < 1, 0.ltoreq.d < 1, 0.ltoreq.e < 1, a+b+c+d+e=1, 0< (b+c+d+e) <0.8.

3. The lithium ion battery according to claim 2, wherein in the general formulae (II) to (IV) of the lithium-containing polycation positive electrode active material, b satisfies 0.001.ltoreq.b.ltoreq.0.05, further optionally 0.005.ltoreq.b.ltoreq.0.04.

4. A lithium ion battery according to claim 2 or 3, wherein the positive electrode sheet comprises a lithium-containing multi-cation positive electrode active material of formula (II) Li _aNa_bK_cRb_dCs_eNi_yCo_zMn_1-y-zO₂.

5. The lithium ion battery of any of claims 1 to 4, wherein the alkali metal salt in the negative electrode tab comprises at least one of an alkali metal carbonate; optionally, at least one of Na ₂CO₃、K₂CO₃、Rb₂CO₃、Cs₂CO₃; and further alternatively Na ₂CO₃.

6. The lithium ion battery according to any one of claims 1 to 5, wherein the sum of the mole fractions of alkali metal elements Na, K, rb, cs in the lithium-containing polycation positive electrode active material is X _{Positive direction} = (1-a) X100% or X _{Positive direction} = (b+c+d+e) X100%, the X _{Positive direction} being 0.05% to 5%, optionally 0.5% to 4%; the mass content of the alkali metal salt relative to the total mass of the anode film layer is X _{Negative pole} , and the X _{Negative pole} is 0.5% to 5%, alternatively 1% to 4%.

7. The lithium ion battery of claim 6, wherein X _{Positive direction} and X _{Negative pole} satisfy the following relationship: less than or equal to 0.01/(X _{Positive direction} +5X _{Negative pole} ) less than or equal to 0.5; alternatively, 0.03.ltoreq.1/(X _{Positive direction} +5X _{Negative pole} ). Ltoreq.0.2.

8. The lithium ion battery of any of claims 1 to 7, further comprising a housing having the positive electrode tab and the negative electrode tab received in a cavity of the housing, wherein the large face of the housing has a wall thickness t of 0.4mm to 1mm, optionally 0.5mm to 0.7mm.

9. The lithium ion battery of claim 8, wherein t, X _{Positive direction} , and X _{Negative pole} satisfy the following relationship: 0< (0.6-t)/(X _{Positive direction} +5X _{Negative pole} ) <1, alternatively 0.08< (0.6-t)/(X _{Positive direction} +5X _{Negative pole} ) <0.8.

10. The lithium ion battery of any of claims 1 to 9, wherein the lithium ion battery has a population-in margin of m, the m being 0.86 to 0.96, optionally 0.88 to 0.94, and optionally 0.90 to 0.92.

11. The lithium ion battery of claim 10, wherein m, X _{Positive direction} , and X _{Negative pole} satisfy the following relationship: 0< (m-0.91)/(X _{Positive direction} +5X _{Negative pole} ) <0.2, alternatively 0.025< (m-0.91)/(X _{Positive direction} +5X _{Negative pole} ) <0.18.

12. An electrical device comprising the lithium ion battery of any one of claims 1 to 11.