WO2024149318A1

WO2024149318A1 - Lithium-supplementing material and preparation method therefor, and positive electrode sheet and battery

Info

Publication number: WO2024149318A1
Application number: PCT/CN2024/071745
Authority: WO
Inventors: 张磊; 陈瑶
Original assignee: 珠海冠宇动力电池有限公司
Priority date: 2023-01-12
Filing date: 2024-01-11
Publication date: 2024-07-18
Also published as: CN116598608A

Abstract

The present application relates to the field of batteries, and in particular relates to a lithium-supplementing material and a preparation method therefor, a positive electrode sheet comprising the lithium-supplementing material, and a battery comprising the lithium-supplementing material. The lithium-supplementing material has a core-shell structure, wherein a core of the core-shell structure is a lithium-rich metal oxide, and a shell of the core-shell structure is lithium aluminum silicate. The lithium-supplementing material of the present application has a stable surface structure, and can prevent a high residual alkali content on the surface of the lithium-supplementing material caused by a reaction with water vapor in air, such that the safety performance of the battery is improved; and an irreversible loss on active lithium when an SEI film is formed can be supplemented during the first charge-discharge cycle of a lithium-ion battery, thereby greatly improving the energy density of the battery.

Description

Lithium supplement material and preparation method thereof, positive electrode sheet and battery

This application claims the priority of the Chinese patent application filed with the China Patent Office on January 12, 2023, with application number 202310039442.6 and application name “Lithium Supplement Materials and Preparation Methods, Positive Electrode Sheets and Batteries”, the entire contents of which are incorporated by reference in this application.

Technical Field

The present application belongs to the field of batteries, and specifically relates to a lithium supplement material and a preparation method thereof, a positive electrode sheet containing the lithium supplement material, and a battery containing the lithium supplement material.

Background technique

At present, during the first charge and discharge process of commercial lithium-ion batteries, a portion of the active lithium will form a SEI film on the surface of the negative electrode, which will cause some of the active lithium in the positive electrode material to be consumed, resulting in irreversible losses and reducing the battery's initial coulombic efficiency.

In order to solve this problem, lithium replenishment technology has received more and more attention. That is, during the first charging process of the battery, the consumption of active lithium in the positive electrode material is offset by replenishing the lithium ions consumed by the formation of the SEI film, thereby improving the battery's first coulombic efficiency and energy density. The existing lithium replenishment methods mainly include positive electrode lithium replenishment, negative electrode lithium replenishment, diaphragm lithium replenishment and electrolyte lithium replenishment. Among them, negative electrode lithium replenishment, diaphragm lithium replenishment and electrolyte lithium replenishment are less used due to strict environmental requirements, high requirements for preparation level and narrow coverage. Positive electrode lithium replenishment is easy to process and has safety and stability, making it have the prospect of large-scale commercial application.

Currently, the most commonly used positive electrode lithium supplement additive Li ₂ MO ₂ (where M is Ni, Fe, Cu, Ti or Mn) is a layered lithium-rich metal oxide with a high theoretical capacity, which can greatly improve the energy density of lithium-ion batteries. However, its surface structure stability is poor, it easily absorbs water in the air environment, and its residual alkalinity value is high. After being made into a battery, it is easy to cause flatulence, posing a serious safety hazard.

Therefore, it is necessary to find ways to improve the surface structure stability of the positive electrode _lithium supplement additive _Li2MO2 .

Summary of the invention

The purpose of the present application is to overcome the problem of unstable surface structure of positive electrode lithium supplement agent in the prior art, to provide a lithium supplement material and a preparation method thereof, a positive electrode sheet containing the lithium supplement material and a positive electrode sheet containing the lithium supplement material The lithium supplement material of the present application has a stable surface structure, which can prevent the high residual alkali on the surface of the lithium supplement material caused by reaction with water vapor in the air, improve the safety performance of the battery, and can effectively supplement the irreversible loss of active lithium caused by the formation of SEI film during the first charge and discharge cycle of the lithium-ion battery, greatly improving the energy density of the battery.

In a first aspect, the present application provides a lithium supplement material, wherein the lithium supplement material has a core-shell structure, wherein the core of the core-shell structure is a lithium-rich metal oxide, and the shell of the core-shell structure is lithium aluminum silicate.

The lithium-supplementing material as described above, wherein the lithium-rich metal oxide is represented by the following chemical formula (I):
Li ₂ M ¹ _x M ² _1-x O ₂ (I),

Wherein, ^M1 is selected from at least one of Ni, Fe, Cu, Co, Ti and Mn, ^M2 is selected from at least one of W, Zr, Nb, Nd, Mo, Al, Ta, Ru, Sr and Y, and 0.01≤x≤1.

The lithium supplement material as described above, wherein 0.5≤x＜1.

The lithium supplement material as described above, wherein the ratio of the mass of silicon element in the lithium aluminum silicate to the mass of the lithium-rich metal oxide is (0.02-0.3):100.

The lithium supplement material as described above, wherein the particle size D50 of the lithium supplement material is 3 μm-10 μm, preferably 4 μm-6 μm.

The lithium supplement material as described above, wherein the thickness of the shell is 100nm-600nm, preferably 300nm-500nm.

The second aspect of the present application provides a method for preparing the lithium-supplementing material described in the first aspect of the present application, comprising the following steps: mixing a mixture of an aluminum source, a silicon source and an alcohol solvent with a core material in a lithium hydroxide solution, and performing a first roasting on the obtained solid material; the core material is a lithium-rich metal oxide.

The third aspect of the present application provides a positive electrode sheet, which includes a positive electrode collector and a positive electrode active material layer coated on one side or both sides of the positive electrode collector, and the positive electrode active material layer includes the lithium supplement material described in the first aspect of the present application and/or the lithium supplement material prepared by the method described in the second aspect of the present application.

The positive electrode sheet as described above, wherein the positive electrode active material layer further comprises a positive electrode active material, a binder and a conductive agent, and/or, based on 100 parts by weight of the positive electrode active material, the content of the lithium supplement material is 0.4-12 parts by weight, preferably 0.5-10 parts by weight, more preferably 1-7 parts by weight, and/or, the positive electrode active material is selected from at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese iron phosphate and lithium iron phosphate.

The positive electrode sheet as described above, wherein the content of the binder is 0.55-5.5 parts by weight based on 100 parts by weight of the positive electrode active material; and/or, the content of the conductive agent is 0.55-5.5 parts by weight based on 100 parts by weight of the positive electrode active material.

The fourth aspect of the present application provides a battery, which includes at least one of the lithium-supplementing material described in the first aspect of the present application, the lithium-supplementing material prepared by the method described in the second aspect of the present application, and the positive electrode sheet described in the third aspect of the present application.

Through the above technical solution, the present application has at least the following advantages compared with the prior art:

(1) The lithium supplement material of the present application has a more stable surface structure, which can prevent the high residual alkali on the surface caused by reaction with water vapor in the air, alleviate the generation of gel in the slurry preparation process, and further improve the safety performance of the battery;

(2) The lithium supplement material of the present application can effectively supplement the irreversible loss of active lithium caused by the formation of the SEI film during the first charge and discharge cycle of the lithium-ion battery, thereby significantly improving the energy density of the battery.

The endpoints and any values of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a graph showing the thickness change rate of batteries of Example II1, Example II7 and Comparative Example DD1 as a function of high temperature storage time;

FIG2 is a SEM image of the lithium supplement material prepared in step (2) of Example I1.

Detailed ways

The specific implementation of the present application is described in detail below. It should be understood that the specific implementation described here is only used to illustrate and explain the present application, and is not used to limit the present application.

Lithium aluminum silicate, with the chemical formula LiAlSi ₂ O ₆ , has fast ion conductor characteristics and stable chemical properties. The inventors of the present application have found that coating the lithium aluminum silicate as a shell on the outer surface of the lithium-rich metal oxide can effectively isolate the lithium-rich metal oxide from the external environment and prevent The lithium-rich metal oxide reacts with water vapor in the air, thereby causing a relatively high residual alkali on the surface of the lithium-supplementing material, and enabling the lithium-supplementing material to have good lithium ion conductivity and electronic conductivity.

In the present application, the term "lithium-rich metal oxide" has the conventional meaning in the art. It is generally believed that the term "lithium-rich metal oxide" refers to a compound in which the ratio of the molar mass of lithium ions to the molar mass of metal ions is greater than 1, that is, n(Li ⁺ ):n(metal ions)>1.

The lithium-rich metal oxide can be represented by the following chemical formula (I):
Li ₂ M ¹ _x M ² _1-x O ₂ (I)

Wherein, ^M1 can be selected from at least one of Ni, Fe, Cu, Co, Ti and Mn, ^M2 can be selected from at least one of W, Zr, Nb, Nd, Mo, Al, Ta, Ru, Sr and Y, 0.01≤x≤1, for example, x is equal to 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.

In the present application, x may be less than 1 or equal to 1.

In one example, x is less than 1.

When x is equal to 1, the lithium-rich metal oxide is a conventional lithium supplement, namely Li ₂ M ¹ O ₂ , wherein M ¹ is selected from at least one of Ni, Fe, Cu, Co, Ti and Mn. The above lithium supplement has the problem of poor bulk structural stability. Taking _Li2NiO2 as an example, it is a layered lithium-rich metal oxide with a theoretical capacity of 486mAh/g, which can effectively improve the energy density of lithium-ion batteries. However, due to the close ionic radius of _Li ⁺ and Ni2 ⁺ , lithium-nickel mixing is very likely to occur during the high-temperature preparation process and the charge and discharge test process. That is, Ni2 ⁺ occupies the lithium site to form an inactive site. Lithium ions need to bypass Ni2 ⁺ when diffusing, which causes the diffusion path of lithium ions to become relatively longer, directly leading to a slower diffusion rate of lithium ions, increasing the lithium ion deintercalation impedance, and thus affecting the battery's first discharge efficiency and increasing the irreversible capacity; and Ni2 ⁺ occupying the lithium site will reduce the thickness of the intergranular layer. During the charging process, Ni2 ⁺ is oxidized to Ni3 ⁺ or Ni4 ⁺ , and the ionic radius is reduced, further causing local collapse of the intergranular layer space, hindering the normal migration of lithium ions during the charge and discharge process, increasing the impedance, and causing the battery's cycle stability to deteriorate.

The inventors of the present application have discovered that by doping the above-mentioned lithium-rich metal oxide (Li ₂ M ¹ O ₂ , wherein M ¹ is selected from at least one of Ni, Fe, Cu, Co, Ti and Mn) with metal cations, the purpose of stabilizing its bulk structure can be achieved. The reason may be that: doping with metal cations can stabilize the metal layer structure, and after doping, the crystal particle size is reduced, the contact area with the carbonate organic electrolyte is larger, the electrical conductivity of the material is improved, the charge impedance is reduced, and the surface layer and the internal structure of the bulk phase are more uniform, thereby improving the stability of the bulk structure.

In one example, 0.5≤x＜1. By doping with this specific content of metal oxide, the core active material of the positive electrode lithium supplement material maintains a higher activity while having a stable structure, so that the lithium supplement material can achieve an ideal lithium supplement effect. Specifically, doping within this range can effectively widen the lithium layer spacing, promote the transmission of lithium ions, reduce the migration energy barrier of heterogeneous atoms, increase the diffusion rate and doping efficiency of heterogeneous atoms, and reduce surface defects of the doped modified material; effectively adjust the valence distribution of transition metals, reduce lithium-nickel mixing, and maintain the integrity of the layered structure. At the same time, heterogeneous atoms can play a supporting role, which is beneficial to the transmission of lithium ions.

The ratio of the mass of silicon element in the lithium aluminum silicate to the mass of the lithium-rich metal oxide can be (0.02-0.3):100, for example, 0.02:100, 0.03:100, 0.04:100, 0.05:100, 0.06:100, 0.07:100, 0.08:100, 0.09:100, 0.1:100, 0.15:100, 0.2:100, 0.25:100 or 0.3:100.

In one example, the ratio of the mass of silicon element in the lithium aluminum silicate to the mass of the lithium-rich metal oxide is (0.05-0.15):100.

When the mass ratio is within this range, a good coating effect can be formed to ensure the electrochemical performance and structural stability of the lithium-supplementing material. If the mass ratio is higher than this range, it will cause excessive coating, and the ionic conductivity and electronic conductivity of the lithium-supplementing material will be greatly affected; if the mass ratio is lower than this range, it will cause insufficient coating, making it impossible to form an effective coating layer on the surface of the lithium-rich metal oxide, and the effect of stabilizing the structure cannot be achieved; therefore, this mass ratio range is crucial to optimizing the electrochemical performance and structural stability of the material.

The inventors of the present application have discovered that the particle size D50 of the lithium supplement material has a specific range, within which the risk of battery internal resistance increase due to the longer lithium ion migration path, which in turn causes battery bloating and increases in battery thickness, can be effectively avoided.

The particle size D50 of the lithium supplement material may be 3 μm-10 μm, for example, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm.

In one example, the particle size D50 of the lithium supplementing material is 4 μm-6 μm.

In the present application, the particle size D50 can be measured using a Malvern laser particle size analyzer.

It should be noted that when the particle size of the lithium supplement material is tested, since the particles of the lithium supplement material may be agglomerated, the "particle size D50 of the lithium supplement material" includes the D50 of primary particles and the D50 of agglomerated particles.

The shell may have a thickness of 100 nm to 600 nm, for example 100 nm, 200 nm, 300 nm, 400 nm, 500 nm or 600 nm.

The lithium-supplementing material of the present application uses the lithium aluminum silicate to coat the lithium-rich metal oxide, so that the surface structure of the lithium-supplementing material is more stable, and the high surface residual alkali caused by the reaction of the lithium-rich metal oxide with water vapor in the air and the occurrence of flatulence after the battery manufacturing process are prevented. At the same time, the gel phenomenon in the slurry preparation process during the battery preparation process is also alleviated, and the processing performance in the process of preparing the positive electrode sheet is improved; the conventional lithium-supplementing agent is doped and modified with metal cations, which can stabilize the bulk structure stability of the lithium-supplementing material, while improving the ionic conductivity of lithium ions, and effectively improving the electrochemical properties of the lithium-supplementing material.

The specific selection of materials and their dosage used in the method of the second aspect of the present application are the same as those described in the first aspect of the present application and will not be repeated here.

The lithium-rich metal oxide can be purchased commercially or prepared.

In one example, the lithium-rich metal oxide is commercially available.

In one example, the lithium-rich metal oxide is prepared.

The method for preparing the lithium-rich metal oxide includes, for example, performing a second calcination on a mixture of a lithium source, an ^M1 source, and optionally an ^M2 source in an inert atmosphere.

The term "optionally" means that it may or may not be present, that is, the mixed material may include a lithium source and an ^M1 source, or may include a lithium source, an ^M1 source and an ^M2 source.

The lithium source may be selected from at least one of LiOH, Li ₂ CO ₃ and Li ₂ O.

The ^M1 source is at least one selected from the group consisting of metal ^M1 oxides, metal ^M1 hydroxides, metal ^M1 carbonates, metal ^M1 phosphates and hydrates thereof, and metal ^M1 nitrates and hydrates thereof.

The ^M2 source is selected from at least one of a carbonate of metal ^M2 , a phosphate of metal ^M2 , a nitrate of metal ^M2 and an oxide of metal ^M2 .

The inventors of the present application have found that an excess amount of lithium source can prevent the crystallinity of the lithium-supplementing material from being deteriorated due to lithium volatilization during the sintering process.

The molar ratio of the lithium element in the lithium source, the ^M1 element in the ^M1 source and the ^M2 element in the ^M2 source can be (2-2.06):x:(1-x), for example, 2:x:(1-x), 2.01:x:(1-x), 2.02:x:(1-x), 2.03:x:(1-x), 2.04:x:(1-x), 2.05:x: (1-x) or 2.06:x:(1-x), where 0.01≤x≤1.

The inventors of the present application have discovered that calcining in an inert atmosphere can prevent the metal ions of ^M1 and ^M2 from undergoing oxidation reactions to generate unstable corresponding high-valent metal ions, thereby contributing more capacity under low test voltage, and calcining in an inert atmosphere can effectively decompose _Li2CO3 and metal _salts and allow them to participate in the reaction to synthesize a material with good crystalline order, and at the same time can better reduce the residual alkali value on the surface of the lithium-supplementing material.

The inert atmosphere may include a mixed atmosphere of Ar and _H2 .

In one example, the volume fraction of H ₂ may be 10%-25% (eg, 10%, 15%, 20% or 25%), and the volume fraction of Ar may be 75%-90% (eg, 90%, 85%, 80% or 75%).

The second calcination may be performed in a muffle furnace.

Preferably, the second calcination includes a first stage and a second stage.

The first stage may include calcining at 400° C.-1000° C. for 4 h-30 h, and the second stage may include calcining at 850° C.-950° C. for 4 h-30 h.

In one example, the first stage is calcined at 500° C. for 5 h, and the second stage is calcined at 900° C. for 10 h.

The inventors of the present application have discovered that the preparation method of the present application can make the lithium aluminum silicate uniformly formed on the surface of the lithium-rich metal oxide, so that the lithium-supplementing material has good structural stability and good lithium ion and electron conductivity properties, and the preparation method of the present application has simple steps and can be applied on a large scale.

The silicon source may be at least one of silicon dioxide and tetraethyl orthosilicate.

The inventors of the present application have discovered that the silicon source may be silicon dioxide, which has low cost, wide sources, is environmentally friendly, and has good application prospects.

In one example, the silicon source is silicon dioxide.

The aluminum source may be at least one of aluminum oxide and aluminum hydroxide.

The alcohol solvent may include alcohol solvents commonly used in the art.

In one example, the alcohol solvent includes ethanol.

The mixing conditions may include: stirring for 1 hour to 5 hours and then separating and drying.

The first calcination conditions may include: calcination at 400° C.-950° C. for 2 h-20 h in air or oxygen atmosphere.

It is understood that the mixture of the aluminum source, silicon source and alcohol solvent refers to the silicon The material is obtained by mixing the silicon source, the aluminum source and the alcohol solvent, wherein the feeding order of the silicon source, the aluminum source and the alcohol solvent is not particularly limited; for example, the aluminum source, the silicon source and the alcohol solvent are added and mixed at the same time; for another example, the aluminum source and a part of the alcohol solvent are mixed first, and then the silicon source and the remaining part of the alcohol solvent are added; the feeding methods listed above can all achieve good technical effects.

The mass ratio of the silicon source to the alcohol solvent may be 1:(30-100), for example 1:30, 1:35, 1:40, 1:45, 1:50, 1:55, 1:60, 1:65, 1:70, 1:75, 1:80, 1:85, 1:90, 1:95 or 1:100.

The mass ratio of the aluminum source to the silicon source may be 1:(2-3), for example 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9 or 1:3.

The concentration of the lithium hydroxide solution may be 2 wt% to 12 wt%, for example 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 wt%.

In one example, the concentration of the lithium hydroxide solution is 3 wt%-10 wt%.

It should be noted that the numerical expressions such as "first" and "second" in this application are only used to distinguish different usages and do not represent the difference in order.

The positive electrode active material layer may further include a positive electrode active material, a binder and a conductive agent.

The inventors of the present application have discovered that in the positive electrode active material layer, the positive electrode active material and the lithium replenishing material exist in a specific ratio, so that the electrode of the present application has a good lithium replenishing effect, thereby greatly improving the energy density of the battery.

Based on 100 parts by weight of the positive electrode active material, the content of the lithium supplement material can be 0.1-15 parts by weight, for example 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 parts by weight.

In one example, based on 100 parts by weight of the positive electrode active material, the content of the lithium supplement material is 0.5-10 parts by weight.

In one example, based on 100 parts by weight of the positive electrode active material, the content of the lithium supplement material is 1-7 parts by weight.

Based on 100 parts by weight of the positive electrode active material, the content of the binder can be 0.55-5.5 parts by weight, the content of the conductive agent can be 0.55-5.5 parts by weight.

The positive electrode active material may be selected from at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese iron phosphate and lithium iron phosphate.

In one embodiment, the positive electrode active material is lithium nickel cobalt manganese oxide.

The binder and the conductive agent may be selected from binders and conductive agents commonly used in the art.

For example, the binder is selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyacrylic acid and carboxymethyl cellulose.

For another example, the conductive agent is selected from at least one of conductive carbon black, acetylene black, conductive graphite, carbon nanotubes and carbon fibers.

The components of the battery other than the positive electrode sheet (such as the negative electrode sheet, the separator and the electrolyte, etc.) can all be conventionally selected in the art.

The battery can be assembled in a conventional manner in the art.

The present application will be described in detail below through embodiments. The embodiments described in this application are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

In the following examples, unless otherwise specified, all materials used were commercially available analytical grade.

The following group I of embodiments is used to illustrate the positive electrode sheet of the present application. In the lithium supplement materials prepared in the following embodiments, the thickness of the lithium aluminum silicate is in the range of 100nm-600nm.

Example I1

Prepare the positive electrode sheet as follows:

(1) Preparation of lithium-rich metal oxide Li ₂ Ni _0.7 Zr _0.3 O ₂ : Li ₂ CO ₃ , NiCO ₃ and ZrO ₂ were weighed according to n(Li):n(Ni):n(Zr)=2.01:0.7:0.3, mixed at high speed, and calcined in a muffle furnace, wherein the calcination atmosphere was H ₂ /Ar (the volume ratio of H ₂ to Ar was 1:5). The calcination process was divided into two stages, the first stage was calcined at 650° C. for 5 h, and the second stage was calcined at 900° C. for 12 h. After the calcination was completed, the muffle furnace was cooled to room temperature, and the mixture was taken out and sieved through a 300-mesh sieve;

(2) preparing a lithium supplement material: mixing aluminum oxide, silicon dioxide and ethanol in a mass ratio of 1:2.5:150, adding 6wt% lithium hydroxide solution and the material obtained in step (1), stirring for 2h, separating and drying, and calcining the obtained solid material at 750°C for 10h in an oxygen atmosphere. After the calcination is completed, the solid material is cooled to room temperature and passed through a 300-mesh sieve to obtain a lithium supplement material, wherein the mass ratio of _silicon in lithium _aluminum _{silicate to Li2Ni0.7Zr0.3O2} _is 0.1:100, the particle size D50 of the lithium supplement material is 5μm, and the shell thickness of the lithium supplement material is 350nm;

(3) Preparation of positive electrode sheet: Lithium nickel cobalt manganese oxide (NCM613), the lithium supplement material prepared in step (2), conductive carbon black and polyvinylidene fluoride are added into a homogenizing tank in a mass ratio of 92.5:3.7:2.3:1.5, and then N-methylpyrrolidone is added to prepare a slurry with a solid content of 55% and a viscosity of 4500 mPa·s, which is then coated and rolled to form a positive electrode sheet.

Example 12

Prepare the positive electrode sheet as follows:

(1) Preparation of lithium-rich metal oxide Li ₂ Ni _0.5 W _0.5 O ₂ : Li ₂ CO ₃ , NiCO ₃ and WO ₃ were weighed according to n(Li):n(Ni):n(W)=2.01:0.5:0.5, mixed at high speed, and calcined in a muffle furnace, wherein the calcination atmosphere was H ₂ /Ar (the volume ratio of H2 to Ar was 1:5). The calcination process was divided into two stages, the first stage was calcined at 800° C. for 4 h, and the second stage was calcined at 950° C. for 10 h. After the calcination was completed, the muffle furnace was cooled to room temperature, and the calcined metal was taken out and sieved through a 300-mesh sieve;

(2) preparing a lithium supplement material: mixing aluminum oxide, silicon dioxide and ethanol in a mass ratio of 1:2:60, adding 3 wt % lithium hydroxide solution and the material obtained in step (1), stirring for 2 h, separating and drying, and calcining the obtained solid material at 750° C. for 10 h in an oxygen atmosphere. After the calcination is completed, the solid material is cooled to room temperature, taken out and sieved through a 300 mesh sieve to obtain a lithium supplement material, wherein the mass ratio of silicon in lithium aluminum silicate to Li ₂ Ni _0.5 W _0.5 O ₂ is 0.05:100, the particle size D50 of the lithium supplement material is 4 μm, and the shell thickness of the lithium supplement material is 320 nm;

(3) Preparation of positive electrode sheet: Lithium nickel cobalt manganese oxide (NCM613), the lithium supplement material prepared in step (2), conductive carbon black and polyvinylidene fluoride were added to a homogenization tank at a mass ratio of 92.5:0.93:5:1.57, and then N-methylpyrrolidone was added to prepare a slurry with a solid content of 52% and a viscosity of 3000 mPa·s, which was then coated and rolled to form a positive electrode sheet.

Example 13

Prepare the positive electrode sheet as follows:

(1) Preparation of lithium-rich metal oxide Li ₂ Ni _0.9 Ti _0.1 O ₂ : Li ₂ CO ₃ , NiCO ₃ and TiO ₂ were weighed according to n(Li):n(Ni):n(W)=2.01:0.9:0.1, mixed at high speed, and calcined in a muffle furnace, wherein the calcination atmosphere was H ₂ /Ar (the volume ratio of H ₂ to Ar was 1:5). The calcination process was divided into two stages, the first stage was calcined at 500° C. for 5 h, and the second stage was calcined at 850° C. for 20 h. After the calcination was completed, the muffle furnace was cooled to room temperature, and the calcined metal was taken out and sieved through a 300-mesh sieve;

(2) preparing a lithium supplement material: mixing aluminum oxide, silicon dioxide and ethanol in a mass ratio of 1:3:300, adding 10 wt% lithium hydroxide solution and the material obtained in step (1), stirring for 2 h, separating and drying, and calcining the obtained solid material at 750° C. for 10 h in an oxygen atmosphere. After the calcination is completed, the solid material is cooled to room temperature, taken out and sieved through a 300-mesh sieve to obtain a lithium supplement material, wherein the mass ratio of silicon in lithium aluminum silicate to Li ₂ Ni _0.9 Ti _0.1 O ₂ is 0.15:100, the particle size D50 of the lithium supplement material is 6 μm, and the shell thickness of the lithium supplement material is 330 nm;

(3) Preparation of positive electrode sheet: Lithium nickel cobalt manganese oxide (NCM613), the lithium supplement material prepared in step (2), conductive carbon black and polyvinylidene fluoride are added into a homogenizing tank at a mass ratio of 92.5:6.5:0.5:0.5, and then N-methylpyrrolidone is added to prepare a slurry with a solid content of 60% and a viscosity of 6000 mPa·s, which is then coated and rolled to form a positive electrode sheet.

Example 14

This group of embodiments is used to illustrate the effect of changing the ratio of the mass of silicon in the lithium aluminum silicate to the mass of the lithium-rich metal oxide.

This group of examples is carried out with reference to Example I1, except that the mass ratio of the lithium aluminum silicate to Li ₂ Ni _0.7 Zr _0.3 O ₂ is changed, specifically:

Example I4a: The mass ratio of silicon in lithium aluminum silicate to Li ₂ Ni _0.7 Zr _0.3 O ₂ is 0.02:100, and the shell thickness of the lithium supplement material is 300 nm;

Example I4b: The mass ratio of silicon in lithium aluminum silicate to Li ₂ Ni _0.7 Zr _0.3 O ₂ is 0.3:100, and the shell thickness of the lithium supplement material is 400 nm.

Example 15

This group of embodiments is used to illustrate the influence of the change in the mass ratio of the positive electrode active material and the lithium supplement material in the positive electrode active material layer.

This group of examples is carried out with reference to Example I1, except that the mass ratio of the positive electrode active material to the lithium supplement material is changed, specifically:

Example I5a: Lithium nickel cobalt manganese oxide (NCM613), the lithium supplement material prepared in step (2), conductive carbon black and polyvinylidene fluoride in a mass ratio of 92.5:0.46:5:2.04;

Example I5b: Lithium nickel cobalt manganese oxide (NCM613), the lithium supplement material prepared in step (2), conductive carbon black and polyvinylidene fluoride in a mass ratio of 90:9:0.5:0.5;

Example I5c: Lithium nickel cobalt manganese oxide (NCM613), the lithium supplement material prepared in step (2), conductive carbon black and polyvinylidene fluoride in a mass ratio of 85:11.05:2:1.95.

Example 16

This embodiment is carried out with reference to the embodiment I1, except that the lithium-rich metal oxide is changed, specifically:

(1) Preparation of lithium-rich metal oxide Li ₂ Ni _0.2 Zr _0.8 O ₂ : Li ₂ CO ₃ , NiCO ₃ and ZrO ₂ were weighed according to n(Li):n(Ni):n(Zr)=2.01:0.2:0.8, mixed at high speed, and calcined in a muffle furnace, wherein the calcination atmosphere was H ₂ /Ar (the volume ratio of H ₂ to Ar was 1:5). The calcination process was divided into two stages, the first stage was calcined at 650° C. for 5 h, and the second stage was calcined at 900° C. for 12 h. After the calcination was completed, the muffle furnace was cooled to room temperature, and the mixture was taken out and sieved through a 300-mesh sieve;

(2) Preparation of lithium supplement material: Alumina, silicon dioxide and ethanol were mixed uniformly in a mass ratio of 1:2.5:150, 6 wt% lithium hydroxide solution and the material obtained in step (1) were added, stirred for 2 h, separated and dried, and the obtained solid material was calcined at 750°C for 10 h in an oxygen atmosphere. After the calcination was completed, the solid material was cooled to room temperature and passed through a 300-mesh sieve to obtain a lithium supplement material _, wherein the mass ratio of silicon in lithium aluminum _silicate to _{Li2Ni0.2Zr0.8O2} was 0.1: ₁₀₀ , the particle size D50 of the lithium supplement material was 5 μm, and the shell thickness of the lithium supplement material was 310 nm.

Example 17

This example is carried out with reference to Example I1, except that the temperature of the second stage of sintering for preparing the lithium-rich metal oxide Li ₂ Ni _0.7 Zr _0.3 O ₂ is changed, thereby changing the particle size D50 of the lithium supplementing material. Specifically:

The second stage in step (1) is calcination at 950° C. for 12 h;

The particle size D50 of the lithium supplement material in step (2) is 9 μm.

Example 18

This embodiment is carried out with reference to the embodiment I1, except that the lithium supplement material is changed to Li ₂ Ni _0.7 Zr _0.3 O ₂ is replaced by Li ₂ NiO ₂ , specifically:

(1) Preparation of lithium-rich metal oxide Li ₂ NiO ₂ : Li ₂ CO ₃ and NiCO ₃ were weighed according to n(Li):n(Ni)=2.01:1, mixed at high speed, and calcined in a muffle furnace, wherein the calcination atmosphere was H ₂ /Ar (the volume ratio of H ₂ to Ar was 1:5). The calcination process was divided into two stages, the first stage was calcined at 650°C for 5 h, and the second stage was calcined at 900°C for 12 h. After the calcination was completed, the muffle furnace was cooled to room temperature, and the product was taken out and sieved through a 300-mesh sieve;

(2) Preparation of lithium supplement material: Alumina, silicon dioxide and ethanol were mixed in a mass ratio of 1:2.5:150, 6wt% lithium hydroxide solution and the material obtained in step (1) were added, stirred for 2h, separated and dried, and the obtained solid material was calcined at 750°C for 10h in an oxygen atmosphere. After the calcination was completed, the solid material was cooled to room temperature and passed through a 300-mesh sieve to obtain a lithium supplement material, wherein the mass ratio of silicon in lithium _aluminum silicate to _Li2NiO2 was 0.1:100, the particle size D50 of the lithium supplement material was 5μm, and the shell thickness of the lithium supplement material was 305nm.

Example 19

This example is carried out with reference to Example I1, except that the mass ratio of silicon element in lithium aluminum silicate to lithium-rich metal oxide is changed, specifically:

In step (2), the mass ratio of silicon in lithium aluminum silicate to Li ₂ Ni _0.7 Zr _0.3 O ₂ is 0.01:100, and the shell thickness of the lithium supplement material is 280 nm.

Embodiment I10

The second stage in step (1) is calcination at 800°C for 12h;

The particle size D50 of the lithium supplement material in step (2) is 2.8 μm.

Comparative Example D1

Refer to Example I1, except that the lithium-rich metal oxide Li ₂ Ni _0.7 Zr _0.3 O ₂ prepared in step (1) is used as the lithium supplement material.

Comparative Example D2

Referring to Example I1, the difference is that the outer shell of the lithium supplementing material is changed, specifically:

In step 2), the aluminum oxide and the material obtained in step (1) are mixed and stirred for 2 hours, sintered at 600° C. in an oxygen atmosphere for 10 hours, and then sieved to obtain a lithium supplement material.

Comparative Example D3

In step 2), the boric acid and the material obtained in step (1) are mixed and stirred for 2 hours, placed in an oxygen atmosphere and sintered at 290° C. for 10 hours, and then sieved to obtain a lithium supplement material.

Test Case I

Surface residual alkali test

The lithium supplement materials prepared in the examples and comparative examples of group I were tested for residual alkali on the surface. The residual lithium on the surface was measured by potentiometric titration. Specifically, hydrochloric acid reacted with the acid and alkali to indicate the end point with a pH electrode, and the residual alkali value was calculated based on the volume of the consumed hydrochloric acid standard solution. The residual alkali value was expressed as Li ₂ CO ₃ (wt%). The results are recorded in Table 1. Since the lithium supplement materials used in the examples of group I5 were the same as those in example I1, the residual alkali results of examples I5a-I5c were not shown.

Table 1

It can be seen from Table 1 that the residual alkali value of the lithium supplement material prepared in the embodiment of the present application is significantly reduced compared with that prepared in the comparative example.

Example II

This group II of embodiments is used to illustrate the battery of the present application.

Batteries were prepared using the electrodes obtained from group I of examples and comparative examples. Specifically, the positive electrode obtained above was die-cut, stacked with a diaphragm and a negative electrode, injected with electrolyte and packaged to obtain a battery (the battery design capacity is 2.4Ah).

Test Case II

(1) Performance at 60°C for 30 days

Specific test method: after the battery is charged and discharged once at 25°C, the discharge capacity is recorded; when charged at 1C to reach 100% SOC, it is placed in an open circuit state for 10 minutes. During the storage process, voltage, internal resistance and thickness tests are performed according to the corresponding frequency requirements. After the test, the battery is taken out to record the remaining capacity and the corresponding voltage, internal resistance and thickness at room temperature; then the battery is charged and discharged once at 1C, and the recovery capacity is recorded. The test results show that the thickness expansion change rate of the battery prepared in Group I of Examples is small after high-temperature storage, and is controlled within 5%, while the thickness expansion change rate of the battery prepared in the comparative example is greater than 7% after high-temperature storage. The test results of Example II1, Example II7 and Comparative Example DD1 are now recorded in Figure 1.

(2) Comparison of first cycle charge and discharge capacity

Specific test method: The battery is tested on a cabinet at 25°C, the test voltage range is set to 3.0-4.2V, the test current is 0.2C for charging and discharging, and the test results are recorded in Table 2.

Table 2

As can be seen from Figure 1, compared with the battery prepared in comparative example DD1, the thickness change rate of the batteries prepared in Examples II1 and II7 of the present application is significantly reduced after being stored at a high temperature of 60°C for 30 days, which significantly improves the stability of the battery.

FIG. 2 is a SEM image of the lithium supplement material prepared in step (2) of Example I1 of the present application. It can be seen from the image that the coating layer is evenly distributed on the surface of the particles.

It can be seen from Table 2 that compared with the batteries prepared in the comparative examples, the first cycle charge and discharge capacity of the batteries prepared in the embodiments of the present application is significantly improved, and the capacity and first discharge efficiency of the batteries are significantly improved.

The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, the technical solution of the present application can be subjected to a variety of simple modifications, including combining various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed in the present application and belong to the protection scope of the present application.

Claims

A lithium supplement material, wherein the lithium supplement material has a core-shell structure, the core of the core-shell structure is a lithium-rich metal oxide, and the shell of the core-shell structure is lithium aluminum silicate.
The lithium-supplementing material according to claim 1, wherein the lithium-rich metal oxide is represented by the following chemical formula (I):
Li 2 M 1 x M 2 1-x O 2 (I),

Wherein, M1 is selected from at least one of Ni, Fe, Cu, Co, Ti and Mn, M2 is selected from at least one of W, Zr, Nb, Nd, Mo, Al, Ta, Ru, Sr and Y, and 0.01≤x≤1.
The lithium supplement material according to claim 2, wherein 0.5≤x＜1.
The lithium supplement material according to claim 1, wherein the ratio of the mass of silicon element in the lithium aluminum silicate to the mass of the lithium-rich metal oxide is (0.02-0.3):100.
The lithium supplement material according to claim 1, wherein the particle size D50 of the lithium supplement material is 3 μm-10 μm; preferably 4 μm-6 μm.
The lithium supplement material according to claim 1, wherein the thickness of the shell is 100nm-600nm; preferably 300nm-500nm.
A method for preparing the lithium supplement material according to any one of claims 1 to 6, comprising the following steps: mixing a mixture of an aluminum source, a silicon source and an alcohol solvent with a core material in a lithium hydroxide solution, and subjecting the obtained solid material to a first roasting; the core material is a lithium-rich metal oxide.
A positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on one side or both sides of the positive electrode current collector, and the positive electrode active material layer comprises the lithium supplement material according to any one of claims 1 to 6 and/or the lithium supplement material prepared by the method according to claim 7.
The positive electrode sheet according to claim 8, wherein the positive electrode active material layer further comprises a positive electrode active material, a binder and a conductive agent; and/or, based on 100 parts by weight of the positive electrode active material, the content of the lithium supplement material is 0.4-12 parts by weight, preferably 0.5-10 parts by weight, and more preferably 1-7 parts by weight; and/or, the positive electrode active material is selected from at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese iron phosphate and lithium iron phosphate.
The positive electrode sheet according to claim 8 or 9, wherein, based on 100 parts by weight of the positive electrode active material, the content of the binder is 0.55-5.5 parts by weight; and/or, based on 100 parts by weight of the positive electrode active material, the content of the conductive agent is 0.55-5.5 parts by weight.
A battery, wherein the battery comprises at least one of the lithium supplement material described in any one of claims 1 to 6, the lithium supplement material prepared by the method described in claim 7, and the positive electrode sheet described in any one of claims 8 to 10.