WO2024183705A1 - Composite lithium replenishment material, preparation method therefor, and use thereof - Google Patents

Abstract

A composite lithium replenishment material, a preparation method therefor, and a use thereof. The composite lithium replenishment material comprises a lithium-rich core and an amino acid substance; the lithium-rich core comprises a lithium-containing compound; and the amino acid substance is bonded to the outer surface layer or/and the interior of the lithium-rich core. According to the composite lithium replenishment material, by bonding an amino acid substance to a lithium-rich core, the amino acid substance can react with oxygen species generated by the lithium-rich core and residual alkali, so as to inhibit the reaction between the oxygen species and an electrolyte to achieve the effect of inhibiting gas production, thereby achieving the purpose of improving the electrochemical performance and safety performance of the material.

Description

A composite lithium supplement material and its preparation method and application

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on the Chinese patent application with application number 202310275890.6 and application date March 9, 2023, and claims the priority of the Chinese patent application. The entire content of the Chinese patent application is hereby introduced into this application as a reference.

Technical Field

The present disclosure relates to the technical field of lithium-ion batteries, and in particular to a composite lithium supplement material and a preparation method and application thereof.

Background Art

During the first charge and discharge process of a lithium-ion battery, a large amount of solid electrolyte interface film will be produced on the surface of the negative electrode of the battery, which consumes the limited lithium ions and electrolyte in the battery, causing irreversible capacity loss, reducing the energy density of the lithium-ion secondary battery and reducing the charge and discharge efficiency of the electrode material, limiting the application of lithium-ion batteries. In the prior art, the first irreversible capacity loss of a lithium battery can be effectively compensated by adding lithium-supplementing materials to the positive electrode material. However, the existing lithium-supplementing materials still have the problem of negative electrode transition metal ion deposition, and are prone to produce gas during the first charging process. The residual alkali substances on the surface may react with the electrolyte at high temperatures to generate gas substances such as carbon dioxide, resulting in increased battery gas production or increased battery impedance, and ultimately causing a decrease in battery performance.

Therefore, it is very necessary to develop a lithium-supplementing material that can prevent the deposition of transition metal ions at the negative electrode of the battery and improve the problems of gas production and high residual alkalinity on the surface interface of the lithium-supplementing material.

Summary of the invention

In view of this, one purpose of the present disclosure is to provide a composite lithium supplement material, in which amino acid substances are combined with a lithium-rich core. The amino acid substances can not only act as chelating agents to coordinate with transition metal ions dissolved in positive electrode materials and lithium supplement materials to prevent them from depositing on the negative electrode, but also react with oxygen species to inhibit the side reaction of oxygen species with electrolyte to produce gas, thereby achieving the purpose of improving the electrochemical performance of the composite lithium supplement material.

Another object of the present disclosure is to provide a method for preparing a composite lithium supplement material.

Yet another object of the present disclosure is to provide a positive electrode.

Yet another object of the present disclosure is to provide a secondary battery.

To achieve the above-mentioned purpose, the first embodiment of the present disclosure provides a composite lithium supplement material, comprising:

a lithium-rich core, including a lithium-containing compound;

Amino acid substances are combined with the outer layer and/or the interior of the lithium-rich core.

In some embodiments of the present disclosure, the amino acid substance includes one or more of reducing amino acids and polymers of reducing amino acids.

In some embodiments of the present disclosure, the reducing amino acids and polymers thereof include one or more of arginine, threonine, proline, serine, cysteine and polymers thereof.

In some embodiments of the present disclosure, the mass ratio of the lithium-rich core to the amino acid substance is 100: (0.2- 15).

In some embodiments of the present disclosure, the amino acid substance is coated on the outer surface of the lithium-rich core to form a coating layer.

In some embodiments of the present disclosure, the thickness of the coating layer formed by the amino acid substance is 2-200 nm.

In some embodiments of the present disclosure, the composite lithium-supplementing material further includes a first coating material, and the first coating material is coated on the outer surface layer of the lithium-rich core.

In some embodiments of the present disclosure, the first coating material is continuously coated on the outer surface of the lithium-rich core, and at least a portion of the amino acid substance is coated on the outer surface of the first coating material as the second coating material.

In some embodiments of the present disclosure, the first coating material is discontinuously coated on the outer surface of the lithium-rich core, part of the amino acid substance is coated on the outer surface of the first coating material as the second coating material, and part of the amino acid substance is doped in the lithium-rich core.

In some embodiments of the present disclosure, the first coating material includes at least one of a carbon material, a conductive polymer, or a conductive oxide.

In some embodiments of the present disclosure, the first coating material is a carbon material, and the mass ratio of the lithium-containing compound, the first coating material, and all amino acid substances is 100:0.1-5:0.1-10.

In some embodiments of the present disclosure, the thickness of the first coating layer formed by the first coating material and the second coating layer formed by the amino acid substance are both 1-100 nm.

In some embodiments of the present disclosure, the lithium-containing compound includes a material with a general structural formula of Li _1+x A _y O _z or/and a material with a general structural formula of Li _w O _r ; wherein 0.3﹤x﹤10, 0﹤y﹤6, 0﹤z﹤13, and A is selected from at least one of Fe, Ni, Mn, Co, Cu, Zn, Si, Sn, Al, Zr, and Ge, and 1≤w≤2, 1≤r≤2.

In some embodiments of the present disclosure, the median particle size of the lithium-rich core is 0.5-20 μm.

In some embodiments of the present disclosure, the median particle size of the amino acid substance is 0.05-10 μm.

In some embodiments of the present disclosure, the median particle size of the composite lithium supplementing material is 1-45 μm.

In some embodiments of the present disclosure, the BET specific surface area of the lithium-rich core is 0.5-50 m ² /g.

In some embodiments of the present disclosure, the residual basicity of the composite lithium supplementing material is less than 5 wt %.

To achieve the above-mentioned purpose, a second embodiment of the present disclosure provides a method for preparing a composite lithium supplement material, comprising:

After the lithium-rich core and the amino acid substance are mixed, a first sintering is performed at 100-300° C. in a first inert atmosphere to obtain the composite lithium supplement material.

In some embodiments of the present disclosure, the method for preparing the lithium-rich core is: after uniformly mixing the A source and the lithium source in a molar ratio, sintering at 650-900°C in an inert atmosphere for 4-10 hours to prepare a lithium-containing compound with a general structural formula of Li1 _{+xAyOz ,} wherein the A source includes but is not limited to at least one of the sulfate, carbonate, acetate, oxide, and hydroxide of element A, _and the lithium source includes but is not limited to one or more of lithium oxide, lithium hydroxide, lithium oxalate, lithium sulfate, and lithium carbonate.

In some embodiments of the present disclosure, the preparation method of the composite lithium supplement material further includes: before mixing the lithium-rich core with the amino acid substance, first mixing the lithium-rich core with the source material of the first coating material, performing a second sintering in a second inert atmosphere to obtain the lithium-rich core coated with the first coating material, and the temperature of the first sintering is is lower than the temperature of the second sintering.

To achieve the above objectives, a third aspect of the present disclosure provides a positive electrode, including the composite lithium-replenishing material of the embodiment of the present disclosure or a composite lithium-replenishing material prepared by the preparation method of the composite lithium-replenishing material of the embodiment of the present disclosure.

To achieve the above objectives, a fourth aspect of the present disclosure provides a secondary battery, comprising a positive electrode, a negative electrode and a separator, wherein the positive electrode is the positive electrode of the embodiment of the present disclosure.

In the present disclosure, amino acid substances are combined with the lithium-rich core. The amino acid substances can act as chelating agents to coordinate with transition metal ions dissolved in the positive electrode material and the lithium-supplementing material to prevent them from depositing on the negative electrode, thereby achieving the purpose of improving the electrochemical performance of the composite lithium-supplementing material.

The amino acid substances select reducing amino acids and their polymers, which can react with the lithium-rich core and the oxygen species produced by the residual alkali, thereby inhibiting the reaction of the oxygen species with the electrolyte, achieving the effect of inhibiting gas production, thereby achieving the purpose of further improving the electrochemical properties and safety performance of the material.

The first coating material and the amino acid substance are sequentially arranged outside the lithium-rich core to form a double-layer coating structure, which has the following functions:

(1) It can reduce the residual alkali value on the surface of the material;

(2) Inhibiting the gelation phenomenon during the preparation of slurry of composite lithium supplement materials;

(3) It can isolate the water in the air from corroding the lithium-rich core material, improve the stability of the composite lithium-supplementing material in the air, make it not require a harsh operating environment, and facilitate large-scale production.

The first coating material can improve the conductivity of the composite lithium supplement material.

Additional aspects and advantages of the present disclosure will be given in part in the following description and in part will be obvious from the following description or learned through practice of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or additional aspects and advantages of the present disclosure will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a simple structure of a composite lithium supplement material according to an embodiment of the present disclosure.

FIG. 2 is a schematic diagram of a simple structure of a composite lithium supplement material according to another embodiment of the present disclosure.

FIG3 is a schematic diagram of a simple structure of a composite lithium supplement material according to another embodiment of the present disclosure.

FIG. 4 is a schematic diagram of a simple structure of a composite lithium supplement material according to another embodiment of the present disclosure.

FIG5 is a schematic diagram of a simple structure of a composite lithium supplement material according to another embodiment of the present disclosure.

Reference numerals:
1-lithium-rich core; 2-amino acid substance; 3-first coating material.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present disclosure, but should not be understood as limiting the present disclosure.

In the application, the disclosure of numerical ranges includes all values within the entire range and the disclosure of further subdivided ranges, including Endpoints and subranges are given for these ranges.

In the application, the raw materials, equipment, etc. involved, unless otherwise specified, are all raw materials and equipment that can be made through commercial channels or known methods; the methods involved, unless otherwise specified, are all conventional methods.

A composite lithium supplement material according to an embodiment of the present disclosure is described below with reference to the accompanying drawings.

The composite lithium supplement material of the embodiment of the present disclosure includes a lithium-rich core 1 and an amino acid substance 2. The lithium-rich core 1 includes a lithium-containing compound; the amino acid substance 2 can be completely combined with the outer layer of the lithium-rich core 1 (as shown in FIG. 1), can be completely combined with the inside of the lithium-rich core 1 (as shown in FIG. 2), or can be partially combined with the outer layer of the lithium-rich core 1 and partially combined with the inside of the lithium-rich core 1 (as shown in FIG. 3).

It can be understood that the "combination" in the present disclosure can be coating, blending, etc., depending on the relative position of the amino acid substance and the lithium-rich core. For example, when the amino acid substance is completely combined with the outer layer of the lithium-rich core 1, the "combination" here can be coating, and specifically, the amino acid substance can be discontinuously or continuously coated on the outer surface of the lithium-rich core; when the amino acid substance is completely combined with the inside of the lithium-rich core, or partially combined with the outer layer of the lithium-rich core and partially combined with the inside of the lithium-rich core, the "combination" can be blending, and the specific blending method can be uniform blending or non-uniform blending.

The composite lithium-supplementing material of the disclosed embodiment combines amino acid substances with a lithium-rich core. The amino acid substances can act as chelating agents to coordinate with transition metal ions dissolved in the positive electrode material and the lithium-supplementing material to prevent them from depositing on the negative electrode, thereby achieving the purpose of improving the electrochemical performance of the composite lithium-supplementing material.

It should be noted that in the present disclosure, the reaction of oxygen species with electrolyte does not necessarily produce only oxygen, but more likely other gases, such as methane, ethane, ethylene, CO, _CO2 , etc. Most of the oxygen should be produced by the decomposition of lithium-rich core materials.

In addition, it should be noted that in the present disclosure, when the amino acid substance is partially bound to the outer surface of the lithium-rich core and partially bound to the interior of the lithium-rich core 1, the mass ratio of the amino acid substance bound to the interior of the lithium-rich core to the amino acid substance bound to the outer surface of the lithium-rich core is not limited and can be any ratio.

In some embodiments of the present disclosure, amino acid substances include, but are not limited to, one or more of reducing amino acids and polymers of reducing amino acids. Among them: reducing amino acids and their polymers include, but are not limited to, one or more of arginine, threonine, proline, serine, cysteine and their polymers. Amino acid substances are selected from reducing amino acids and their polymers, which can not only coordinate with transition metal ions dissolved in positive electrode materials and lithium supplement materials to prevent their deposition on the negative electrode, but also react with oxygen species produced by lithium-rich cores and residual alkali, thereby inhibiting the reaction of oxygen species with electrolytes, thereby achieving the effect of inhibiting gas production in lithium-ion batteries.

In some embodiments of the present disclosure, the median particle size (D50) of the amino acid substance is 0.05-10 μm, including but not limited to 0.05 μm, 0.1 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, etc. The median particle size of the amino acid substance within the above range can better combine with the lithium-rich core; if it is less than 0.05 μm, the dispersibility is poor and it is easy to agglomerate; if it is greater than 10 μm, the contact area with the lithium-rich core is reduced, which is not conducive to inhibiting the oxygen species generated by the lithium-rich core.

In some embodiments of the present disclosure, when the composite lithium supplement material contains only a lithium-rich core and amino acid substances, the mass ratio of the lithium-rich core to the amino acid substances is 100: (0.2-15), including but not limited to 100: 0.2, 100: 1, 100: 2, 100: 3, 100: 4, 100: 5, 100: 6, 100: 7, 100: 8, 100: 9, 100: 10, 100: 11, 100: 12, 100: 13, 100: 14 or 100: 15. When the composite lithium supplement material contains only a lithium-rich core and amino acid substances, the mass ratio of the lithium-rich core to the amino acid substances is 100: (0.2-15), including but not limited to 100: 0.2, 100: 1, 100: 2, 100: 3, 100: 4, 100: 5, 100: 6, 100: 7, 100: 8, 100: 9, 100: 10, 100: 11, 100: 12, 100: 13, 100: 14 or 100: 15. When the mass ratio of the core and the amino acid substance is within the above range, it can ensure the lithium replenishment of the lithium-rich core while playing a role in inhibiting oxygen species; if the mass ratio is too small, the effect of inhibiting oxygen species cannot be achieved; if the mass ratio is too large, the lithium replenishment of the lithium-rich core will be reduced.

In some embodiments of the present disclosure, when the composite lithium-supplementing material contains only a lithium-rich core and amino acid substances, and the amino acid substances are all bound to the surface of the lithium-rich core in the form of coating, the thickness of the amino acid substances as a coating layer is 2-200nm, including but not limited to 2nm, 50nm, 100nm, 150nm or 200nm, etc. When the composite lithium-supplementing material contains only a lithium-rich core and amino acid substances, and the amino acid substances are all bound to the surface of the lithium-rich core in the form of coating, the thickness of the amino acid substances as a coating layer is within the above range, the coating layer has good stability, and can ensure the timely release of active lithium; if it is less than 2nm, the coating layer has weak stability; if it is greater than 200nm, it affects the timely release of active lithium and increases battery impedance.

In the present disclosure, the lithium-containing compound is a material that easily generates gas during the initial charging process and the residual alkali substances present on the surface may react with the electrolyte at high temperature to generate gas substances such as carbon dioxide.

In some embodiments of the present disclosure, the lithium-containing compound includes a material with a general structural formula of Li _1+x A _y O _z , wherein 0.3﹤x﹤10, 0﹤y﹤6, 0﹤z﹤13, and A is selected from at least one of Fe, Ni, Mn, Co, Cu, Zn, Si, Sn, Al, Zr, and Ge. As a non-limiting example, the value of x includes, but is not limited to, 0.4, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 9.9, the value of y includes, but is not limited to, 0.1, 1, 2, 3, 4, 5, or 5.9, and the value of z includes, but is not limited to, 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 12.9. The values of x, y, and z are respectively within the above ranges, and the lithium-replenishing performance of the lithium-containing compound can be fully exerted; if they exceed the above ranges, the lithium-replenishing effect of the lithium-containing compound is weak and the impedance is large. As a possible example, when the lithium-rich core is a lithium _- containing compound with _a general structural formula of Li1 _{+xAyOz ,} the lithium-containing compound is selected from one or more of _{Li5FeO4 , Li6CoO4 , Li6MnO4} , _{Li8ZrO6 , Li2CoO2 , Li2MnO2 , and Li2NiO2} .

In other embodiments of the present disclosure, the lithium-containing compound includes a material with the general structural formula Li _w O _r , wherein 1≤w≤2, 1≤r≤2. As a non-limiting example, the value of w includes but is not limited to 1, 1.2, 1.5, 1.8 or 2, and the value of r includes but is not limited to 1, 1.2, 1.5, 1.8 or 2, etc. When the values of w and r are within the above ranges, the lithium-replenishing performance of the lithium-containing compound can be fully exerted; if the values exceed the above ranges, the lithium-replenishing effect of the lithium-containing compound is weak and the impedance is large. As a possible example, the material with the general structural formula Li _w O _r is selected from one or more of Li ₂ O, Li ₂ O ₂ , etc.

In some further embodiments of the present disclosure, the lithium-rich core is a mixture of the lithium-containing compound having the general structural formula Li _1+x A _y O _z and a material having the general structural formula Li _w O _r .

In some embodiments of the present disclosure, the median particle size (D50) of the lithium-rich core is 0.5-20 μm, including but not limited to 0.5 μm, 1 μm, 5 μm, 10 μm, 15 μm or 20 μm, etc. When the median particle size of the lithium-rich core is within the above range, it has good dispersibility in the slurry, does not affect the electronic conduction and ion conduction of the pole piece, and can ensure the electrical performance of the lithium-ion secondary battery; when it is less than 0.5 μm, it is not conducive to its dispersion in the slurry; when it is greater than 20 μm, it will affect the electronic conduction and ion conduction of the pole piece, thereby affecting the electrical performance of the lithium-ion secondary battery.

In some embodiments of the present disclosure, the BET specific surface area of the lithium-rich core is 0.5-50 ^m2 /g, including but not limited to 0.5 ^m2 /g, ¹ m2/g, ¹⁰ m2/g, ²⁰ m2/g, ²⁵ m2/g, ³⁰ m2/g, ⁴⁰ m2/g or 50 ^m2 /g.

In some embodiments of the present disclosure, as shown in FIG4 and FIG5, the composite lithium supplement material further includes a first coating material 3, and the first coating material 3 is coated on the outer surface of the lithium-rich core 1. The first coating material can improve the conductivity of the composite lithium supplement material. electrical properties, which is beneficial to reduce the impedance inside the electrode; at the same time, during and after the release of the lithium-rich core as a "sacrificial victim", the first coating material can also be reused to play an auxiliary role as a conductive agent inside the positive electrode. As a non-limiting example, the first coating material in the present disclosure includes at least one of a carbon material, a conductive polymer, or a conductive oxide. Among them, the carbon material may include but is not limited to one or more of amorphous carbon, carbon nanotubes, graphite, carbon black, graphene _, etc. The conductive oxide may include but is not limited to one or more of _In2O3 , ZnO, _SnO2 . By adjusting the material of the electronic conductor encapsulation layer, its electronic conductivity can be further improved. The conductive polymer may include, but is not limited to, one or more of an organic polymer with a [C ₆ H ₇ O ₆ Na] _n structure, an organic polymer with a [C ₆ H ₇ O ₂ (OH) ₂ OCH ₂ COONa] _n structure, an organic polymer with a [C ₃ H ₄ O ₂ ] _n structure, an organic polymer with a [C ₃ H ₃ O _{2 Ma} ] _n structure, an organic polymer with a [C ₃ H ₃ N] _n structure, an organic polymer containing a -[CH ₂ -CF ₂ ] _n - structure, an organic polymer containing a -[NHCO]- structure, an organic polymer containing an imide ring -[CO-N-CO]- structure on the main chain, and polyvinylpyrrolidone, wherein Ma _is an alkali metal element. In some embodiments, the polymer includes one or more of polyvinylidene fluoride, sodium alginate, sodium carboxymethyl cellulose, polyacrylic acid, polyacrylic acid salt, polyacrylonitrile, polyamide, polyimide, polyvinyl pyrrolidone, polyethylene oxide (PEO), polypyrrole (PPy), polytetrafluoroethylene (PTFE), and polyurethane (PU). In other embodiments, the polymer includes one or more of sodium carboxymethyl cellulose and polyacrylic acid. Sodium carboxymethyl cellulose and polyacrylic acid are two-dimensional surface polymers with good bonding effects, which can effectively coat the core of the manganese-based lithium supplement material, thereby avoiding contact between the core of the composite lithium supplement material and the air and improving the stability of the composite lithium supplement material. In the disclosed embodiment, the molecular weight of the polymer is greater than or equal to 100,000. The molecular weight of the polymer can be specifically but not limited to 100,000, 150,000, 200,000, 300,000, 500,000 or 1 million. The larger the molecular weight of the polymer, the higher the density and structural strength of the polymer layer, and the more conducive to the protection of the core 10.

In some embodiments of the present disclosure, the first coating material 3 is continuously coated on the outer surface of the lithium-rich core 1, and at least part of the amino acid substance 2 is coated on the outer surface of the first coating material 3 as the second coating material. It should be noted that in this case of the present disclosure, the amino acid substance 2 as the second coating material can be continuously coated on the outer surface of the first coating material, or can be non-continuously coated on the outer surface of the first coating material 3. As a possible example, as shown in Figure 4, the first coating material 3 is continuously coated on the outer surface of the lithium-rich core 1, and all the amino acid substances 2 are continuously coated on the outer surface of the first coating material 3 as the second coating material. In this way, the first coating material and the amino acid substance together constitute a double-layer coating structure of the lithium-rich core, which can isolate the erosion of the lithium-rich core material by water in the air, improve the stability of the composite lithium supplement material in the air, and make it not require a harsh operating environment, which is conducive to large-scale production. It is particularly important to note that at this time, when the first coating material is continuously coated on the core material, and all the amino acid substances 2 are also continuously coated on the first coating layer as the second coating material, the density of the first coating material can also alleviate the impact of a large number of oxygen species on the second coating material, thereby inhibiting gas production. As another possible example, the first coating material 3 is continuously coated on the outer surface of the lithium-rich core 1, and part of the amino acid substances 2 are continuously or discontinuously coated on the outer surface of the first coating material 3 as the second coating material, and another part of the amino acid substances 2 can be doped into the lithium-rich core 1. It should be noted that at this time, the mass ratio of the amino acid substances mixed in the lithium-rich core and the amino acid substances as the second coating material is (0.1-5): (90-99.1), including but not limited to 0.1:90, 0.1:99.1, 5:90, 5:99.1 or 2.5:94.5, etc. When appropriate amino acids are doped in the lithium-rich core, these amino acids can absorb the oxygen species produced by the lithium-rich core material, preventing the lithium-rich core material from releasing too many oxygen species, so that the amino acids in the coating layer cannot suppress the generation of oxygen species. It can inhibit a large amount of oxygen from impacting the coating layer; if there are too many amino acids in the lithium-rich core, the unit cell volume of the lithium-rich core will increase, affecting the stability of the lithium-rich core material structure.

In other embodiments of the present disclosure, as shown in FIG5 , the first coating material 3 is non-continuously coated on the outer surface of the lithium-rich core 1, part of the amino acid substance 2 is coated on the outer surface of the first coating material 3 as the second coating material, and part of the amino acid substance is doped in the lithium-rich core 1. It should be noted that the mass ratio of the amino acid substance mixed in the lithium-rich core and the amino acid substance as the second coating material is (0.1-5): (90-99.1), including but not limited to 0.1:90, 0.1:99.1, 5:90, 5:99.1 or 2.5:94.5, etc. When appropriate amino acid substances are doped in the lithium-rich core, these amino acid substances can absorb oxygen species generated by the lithium-rich core material to prevent the amino acid substances in the coating layer from being unable to suppress the generation of oxygen species when the lithium-rich core material releases too many oxygen species. If the amino acid substance in the lithium-rich core is too low, it will not play the role of inhibiting a large amount of oxygen from impacting the coating layer; if the amino acid substance in the lithium-rich core is too much, the volume of the lithium-rich core unit cell will increase, affecting the stability of the lithium-rich core material structure. It should also be noted that this situation disclosed in the present invention has a better technical effect than the aforementioned situation of "the first coating material 3 is continuously coated on the outer surface of the lithium-rich core 1, and at least part of the amino acid substance 2 is coated on the outer surface of the first coating material 3 as the second coating material", because the amino acid substance in the outer layer enters the lithium-rich core material through the action of heat treatment, so the amino acid substance can be distributed not only in the inner core and the outer layer, but also continuously distributed in the middle area. This gradient distribution structure is more conducive to inhibiting the generation of gas.

In some embodiments of the present disclosure, when the first coating material is a carbon material, the mass ratio of the lithium-containing compound, the first coating material, and all amino acid substances is 100:0.1-5:0.1-10, including but not limited to 100:0.1:0.1, 100:0.1:10, 100:5:0.1, 100:5:10, 100:1:0.1, 100:2.5:0.1, 100:2.5:5 or 100:2.5:10, etc. When the first coating material is a carbon material, the mass ratio of the lithium-containing compound, the first coating material, and all amino acid substances is within the above range, and the lithium-containing compound, the first coating material, and all amino acid substances can fully exert their respective effects; if the first coating material and the amino acid substance are used in excessive amounts, the coating layer on the surface of the material will be too thick or even the coating will agglomerate, which will affect the reaction process kinetics of the composite lithium supplement material, thereby affecting the performance of the composite lithium supplement material; if the first coating material and the amino acid substance are used in excessive amounts, it will be difficult to achieve the coating effect.

In some embodiments of the present disclosure, the thickness of the first coating layer formed by the first coating material and the second coating layer formed by the amino acid substance are both 1-100nm, including but not limited to 1nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm, etc. When the thickness of the first coating layer and the second coating layer is within the above range, the lithium-containing compound, the first coating layer, and the second coating layer can give full play to their respective effects; if the thickness of the first coating layer and the second coating layer is too large, the coating layer on the surface of the material will be too thick or even the coating will agglomerate, which will affect the reaction process kinetics of the composite lithium supplement material, thereby affecting the performance of the composite lithium supplement material; if the thickness of the first coating layer and the second coating layer is too small, it is difficult to achieve the coating effect.

It should be noted that in the present disclosure, the thickness of the first coating layer formed by the first coating material and the second coating layer formed by the amino acid substance may be the same or different.

In some embodiments of the present disclosure, the median particle size of the composite lithium supplement material is 1-45 μm, including but not limited to 1 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm or 45 μm, etc. The median particle size of the composite lithium supplement material is within the above range; if it is less than 1 μm, it is not conducive to dispersion in the positive electrode slurry; if it is greater than 45 μm, it will affect the electronic conduction and ion conduction of the positive electrode sheet, thereby affecting the electrical performance of the lithium ion secondary battery.

In some embodiments of the present disclosure, the residual alkalinity of the composite lithium supplement material is less than 5wt%, including but not limited to 0.01wt%, 0.1wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt% or 4.5wt%, etc. The lower the residual alkalinity of the composite lithium supplement material, the better, which can improve the surface stability and structural stability of the composite lithium supplement material; if the residual alkalinity of the composite lithium supplement material is too large, it will have the opposite effect, and at the same time, it will cause a gelation reaction when the slurry is prepared, reducing the number of lithium ions released by the composite lithium supplement material.

The preparation method of the composite lithium-supplementing material of the embodiment of the present disclosure includes: mixing the lithium-rich core with the amino acid substance, and then performing a first sintering at 100-300° C. in a first inert atmosphere to obtain the composite lithium-supplementing material.

In some embodiments of the present disclosure, the temperature of the first sintering includes but is not limited to 100° C., 150° C., 200° C., 250° C. or 300° C., etc. The temperature of the first sintering is within the above range, which can ensure that the amino acid substance has a good binding force with the lithium-rich core and the effect of inhibiting gas production; if it is lower than 100° C., the binding force between the amino acid substance and the lithium-rich core is weak; if it is higher than 300° C., the amino acid substance is carbonized and the effect of inhibiting gas production cannot be achieved.

In some embodiments of the present disclosure, the first sintering time is 1-6 hours, including but not limited to 1 hour, 2 hours, 3 hours, 4 hours, 5 hours or 6 hours, etc. The first sintering time is within the above range; if it is less than 1 hour, if the amino acid substance is combined with the outer surface of the lithium-rich core in the form of a coating, the coating will be uneven; if it is higher than 6 hours, unnecessary side reactions will occur.

In some embodiments of the present disclosure, the first inert atmosphere includes, but is not limited to, one or more of argon, nitrogen, helium, and neon.

In the present disclosure, the lithium-rich core is a lithium-containing compound, which can be obtained through commercial channels or made by yourself. In some embodiments of the present disclosure, the lithium-containing compound includes a material with a general structural formula of Li _1+x A _y O _z , wherein 0.3﹤x﹤10, 0﹤y﹤6, 0﹤z﹤13, and A is selected from at least one of Fe, Ni, Mn, Co, Cu, Zn, Si, Sn, Al, Zr, and Ge elements. The preparation method of the lithium-rich core is: after the A source and the lithium source are uniformly mixed in a molar ratio, sintered at 650-900°C in an inert atmosphere for 4-10h, a lithium-containing compound with a general structural formula of Li _1+x A _y O _z is prepared. Among them, the A source includes but is not limited to at least one of the sulfate, carbonate, acetate, oxide, hydroxide, etc. of element A, and the lithium source includes but is not limited to one or more of lithium oxide, lithium hydroxide, lithium oxalate, lithium sulfate, lithium carbonate, etc. In the preparation process of the lithium-containing compound with the general structural formula Li _1+x A _y O _z , the sintering temperature includes but is not limited to 650° C., 700° C., 750° C., 800° C., 850° C. or 900° C., and the sintering time includes but is not limited to 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h, etc. In the preparation process of the lithium-containing compound with the general structural formula Li _1+x A _y O _z , the sintering temperature and sintering time are within the above ranges, and a lithium-containing compound core material with the general structural formula Li _1+x A _y O _z with higher purity can be synthesized.

In some embodiments of the present disclosure, during the preparation of the lithium _- containing compound with the general structural formula Li1 _{+ xAyOz} , the mixing method of the A source and the lithium source includes but is not limited to mixing using one or both of a ball mill, a fusion machine or a dual-motion mixer.

In other embodiments of the present disclosure, when the composite lithium-supplementing material further contains a first coating material, the preparation method of the composite lithium-supplementing material includes: before mixing the lithium-rich core with the amino acid substance, first mixing the lithium-rich core with the source material of the first coating material, and performing a second sintering in a second inert atmosphere to obtain the lithium-rich core coated with the first coating material. After that, the lithium-rich core coated with the first coating material is mixed with the amino acid substance, and the aforementioned first sintering is performed in the first inert atmosphere to obtain the composite lithium-supplementing material.

In some embodiments of the present disclosure, when the first coating material is a carbon material, the source material of the first coating material includes but Not limited to one or more of glucose, asphalt, sucrose, fructose, polyvinylpyrrolidone (PVP) and the like.

In some embodiments of the present disclosure, the second sintering temperature is higher than the first sintering temperature. As a non-limiting example, the temperature of the second sintering is 500-800°C, including but not limited to 500°C, 550°C, 600°C, 650°C, 700°C, 750°C or 800°C, etc. When the temperature of the second sintering is within the above range, a carbon material with higher purity can be obtained with moderate energy consumption; if it is lower than 500°C, a carbon material with higher purity cannot be sintered, and the interaction with the lithium-rich core is weak; if it is higher than 800°C, energy consumption is increased.

In some embodiments of the present disclosure, the second sintering time is 2-6 hours, including but not limited to 2 hours, 3 hours, 4 hours, 5 hours or 6 hours, etc. The second sintering time is within the above range; if it is less than 2 hours, if the electronic conductor encapsulation layer is combined with the outer surface of the lithium-rich core in the form of a coating, the coating will be uneven; if it is higher than 6 hours, unnecessary side reactions will occur.

In some embodiments of the present disclosure, the second inert atmosphere includes, but is not limited to, one or more of argon, nitrogen, helium, and neon.

In some embodiments of the present disclosure, sintering, the first sintering and the second sintering in the preparation process of the lithium-containing _compound with the general structural formula Li1 _{+xAyOz can} be carried out in any one of a rotary furnace, a rotary furnace, a box furnace, a tubular furnace, a roller kiln, a push plate kiln or a fluidized bed.

The preparation method of the composite lithium supplement material of the embodiment of the present disclosure, when the composite lithium supplement material also contains the first coating material, adopts the dry mixing technology, successively adds a certain amount of the source material of the first coating material and the amino acid substance into the lithium-rich core material, mixes evenly, and then respectively performs high and low temperature sintering to obtain the composite lithium supplement material with a double coating layer structure. The method is simple in process and easy to operate.

The positive electrode of the embodiment of the present disclosure includes the composite lithium-replenishing material of the embodiment of the present disclosure or the composite lithium-replenishing material prepared by the preparation method of the composite lithium-replenishing material of the embodiment of the present disclosure.

In some embodiments of the present disclosure, the content of the composite lithium supplement material accounts for 0.5-15wt% of the entire positive electrode. As a non-limiting example, the content of the composite lithium supplement material accounts for 3wt%, 6wt%, 9wt%, 12wt% or 15wt% of the entire positive electrode. When the content of the composite lithium supplement material accounts for the mass percentage of the entire positive electrode within the above range, the amount of lithium supplement is moderate, which can improve the energy density of the lithium-ion battery; if it is lower than 0.5wt%, the amount of lithium supplement is low, and the effect of improving the energy density of the lithium-ion battery cannot be achieved; if it is higher than 15wt%, the proportion of the positive electrode material in the lithium-ion battery is affected, and the effect of improving the energy density of the lithium-ion battery cannot be achieved.

In some embodiments of the present disclosure, in addition to the composite lithium supplement material, the positive electrode may also include a positive electrode active material, and at least one of a positive electrode conductor and a positive electrode binder. The positive electrode active material includes, but is not limited to, one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium fluorinated vanadium phosphate, lithium titanate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminum oxide. The positive electrode active material is capable of lithium insertion and extraction, alloying and dealloying, or plating and stripping. The positive electrode conductor includes, but is not limited to, one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotubes. Adding a positive electrode conductor to the positive electrode material can enhance the conductivity of the electrode material layer, improve the conductivity of the lithium supplement material, and facilitate the transmission of electrons and ions. The positive electrode binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), sodium alginate, sodium carboxymethyl cellulose, and polyacrylic acid.

In some embodiments of the present disclosure, the positive electrode further comprises a current collector, which may be selected to comprise aluminum or any other suitable conductive metal foil (such as solid or mesh or covered foil) known to those skilled in the art, a metal grid or screen, or Porous Metal. In certain variations, the surface of the current collector may comprise a metal foil that has been surface treated (eg, carbon coated and/or etched).

The secondary battery of the embodiment of the present disclosure comprises a positive electrode, a negative electrode and a separator, wherein the positive electrode is the positive electrode of the embodiment of the present disclosure.

In some embodiments of the present disclosure, the positive electrode sheet, the separator and the negative electrode sheet can be processed by a lamination process or a winding process to form a secondary battery. It should be noted that the secondary battery of the embodiments of the present disclosure includes but is not limited to a lithium-ion battery.

The secondary battery of the embodiment of the present disclosure can be widely used in the fields of new energy vehicles, aerospace, electronic products, etc.

Certain features of the present technology are further illustrated in the following non-limiting examples.

1. Examples and Comparative Examples

Example 1

As shown in FIG3 , the composite lithium supplement material of this embodiment includes a lithium-rich core 1, an amino acid substance 2 and a first coating material 3. The first coating material 3 is continuously coated on the outer surface of the lithium-rich core 1, and the amino acid substance 2 is continuously coated on the outer surface of the first coating material 3. The first coating material 3 and the amino acid substance 2 constitute a double-layer coating structure of the lithium-rich core 1. The mass percentage ratio of the lithium-rich core 1, the first coating material 3 and the amino acid substance is 100:0.1:0.1. The lithium-rich core 1 is a lithium-containing compound Li ₅ FeO ₄ , with a median particle size (D50) of 2.16 μm and a BET specific surface area of 4.32 m ² /g; the first coating material 3 is made of hard carbon, and the thickness of the first coating layer formed by it is 5 nm; the amino acid substance 2 is arginine, with a median particle size (D50) of 0.5 μm, and the thickness of the second coating layer formed by the amino acid substance 2 is 4 nm. The composite lithium supplement material of this embodiment has a median particle size of 3.45 μm and a residual alkalinity of 1.02 wt %.

The method for preparing the composite lithium supplement material of the embodiment of the present disclosure comprises the following steps:

S1. Preparation of lithium-rich core: Iron oxide and lithium hydroxide were uniformly mixed in a ball mill at a molar ratio of 0.5:5 (ball milling rate was 1000 r/min, ball milling time was 6 h), and then sintered at 850° C. for 10 h in a nitrogen atmosphere to obtain Li ₅ FeO ₄ lithium-containing metal compound.

S2. Prepare a lithium-rich core coated with a first coating material: mix the Li ₅ FeO ₄ lithium-containing compound and glucose in a mass ratio of 5:0.005 in a ball mill (ball milling rate of 700 r/min, ball milling time of 1 h), and then sinter at 600° C. for 2 h in a nitrogen atmosphere to obtain a lithium-rich core coated with the first coating material.

S3. Preparation of composite lithium supplement material: Take 3 g of the lithium-rich core coated with the first coating material prepared in step S2, add 0.003 g of arginine, mix evenly in a ball mill (ball milling rate of 350 r/min, ball milling time of 2 h), and then sinter at 150° C. for 1 h in a nitrogen atmosphere to obtain a composite lithium supplement material.

The positive electrode of this embodiment includes a positive electrode current collector and a positive electrode material coated on the surface of the positive electrode current collector, wherein the positive electrode current collector is aluminum foil, and the positive electrode material includes the following components in parts by weight: 93 parts of lithium iron phosphate, a positive electrode active material, 2 parts of a composite lithium supplement material of this embodiment, 2 parts of a positive electrode conductive agent Super P, and 3 parts of a positive electrode binder polyvinylidene fluoride.

The secondary battery of this embodiment includes a positive electrode, a negative electrode, a separator stacked between the positive electrode and the negative electrode, and an electrolyte, wherein: the positive electrode is the positive electrode of this embodiment; the negative electrode includes a negative electrode current collector and a negative electrode material coated on the surface of the negative electrode current collector, the negative electrode current collector is a copper foil, and the negative electrode material includes the following components in parts by weight: 95 parts of graphite as a negative electrode active material, 2 parts of Super P as a negative electrode conductive agent, 0.5 parts of carboxymethyl cellulose (CMC) as a thickener, and 2.5 parts of styrene-butadiene rubber (SBR) as a negative electrode binder; the separator adopts a polyethylene (PE) microporous separator; the electrolyte includes ethylene carbonate (EC), ethyl methyl carbonate (DEC) and _LiPF6 , wherein the volume ratio of ethylene carbonate (EC) to ethyl methyl carbonate (DEC) is 3:7, and the concentration of _LiPF6 is 1 mol/L.

The method for preparing the secondary battery of this embodiment comprises the following steps:

1) Preparation of positive electrode: N-methylpyrrolidone, lithium iron phosphate, composite lithium supplement material, conductive agent Super P and polyvinylidene fluoride were mixed in a mass ratio of 100:93:2:2:3, and the positive electrode slurry was obtained by ball milling. The ball milling time was 60 min and the rotation speed was 30 Hz. The positive electrode slurry was coated on the surface of aluminum foil, rolled, and vacuum dried at 100°C overnight to obtain a positive electrode sheet.

2) Preparation of negative electrode: The negative electrode active material (graphite), conductive agent (conductive carbon black, Super P), thickener (carboxymethyl cellulose, CMC), and binder (styrene-butadiene rubber, SBR) are placed in deionized water at a mass ratio of 95:2:0.5:2.5 and mixed evenly to form a negative electrode slurry. The negative electrode slurry is coated on the surface of the current collector copper foil. After drying-rolling-secondary drying steps, a negative electrode sheet is obtained.

3) Preparation of electrolyte: Ethylene carbonate (EC) and ethyl methyl carbonate (DEC) were mixed in a volume ratio of 3:7, and LiPF ₆ was added to form an electrolyte, wherein the concentration of LiPF ₆ was 1 mol/L.

4) Secondary battery (lithium-ion battery) assembly: A lithium-ion battery is assembled in an argon inert atmosphere glove box in the order of negative electrode-diaphragm-electrolyte-positive electrode.

Example 2

This embodiment is basically the same as Embodiment 1, except that:

In the composite lithium supplement material, the first coating material 3 and the amino acid substance 2 constitute a double-layer coating structure of the lithium-rich core 1, and the mass percentage ratio of the lithium-rich core 1, the first coating material 3 and the amino acid substance 2 is 100:2:5. The thickness of the first coating layer formed by the first coating material 3 is 10nm; the amino acid substance 2 is threonine, and the thickness of the second coating layer formed by it is 6nm. The median particle size (D50) of the composite lithium supplement material of this embodiment is 4.15μm, and the residual alkalinity is 0.02wt%.

In the preparation method of amino acid composite lithium supplement material, in step S2, the lithium-containing compound Li ₅ FeO ₄ and glucose are in a mass ratio of 5:0.01; in step S3, 3g of the lithium-rich core coated with the first coating material prepared in step S2 is taken and 0.15g of threonine is added.

Example 3

This embodiment is basically the same as Embodiment 1, except that:

In the composite lithium supplement material, the first coating material 3 and the amino acid substance 2 constitute a double-layer coating structure of the lithium-rich core 1, and the mass percentage ratio of the lithium-rich core 1, the first coating material 3 and the amino acid substance 2 is 100:5:10. The thickness of the first coating layer formed by the first coating material 3 is 15nm; the amino acid substance 2 is threonine, and the thickness of the second coating layer formed by it is 10nm. The median particle size (D50) of the composite lithium supplement material of this embodiment is 5.20μm, and the residual alkalinity is 0.01wt%.

In the preparation method of the composite lithium supplement material, in step S2, the lithium-containing compound Li ₅ FeO ₄ and glucose are in a mass ratio of 5:0.25; in step S3, 3g of the lithium-rich core coated with the first coating material prepared in step S2 is taken and 0.3g of threonine is added.

Example 4

This embodiment is basically the same as Embodiment 1, except that:

As shown in Figure 5, in the composite lithium-supplementing material, the first coating material 3 is completely discontinuously coated on the surface of the lithium-rich core 1, 98wt% of the amino acid substance 2 is coated on the outer surface of the first coating material 3 as the second coating material, and 2wt% of the amino acid substance 2 is doped into the lithium-rich core 1.

The thickness of the first coating layer formed by the first coating material 3 is 4.3 nm; the amino acid substance 2 is arginine, wherein The median particle size (D50) is 0.5 μm, and the thickness of the second coating layer formed by the amino acid substance as the second coating material is 3.5 nm. The median particle size of the composite lithium supplement material of this embodiment is 4.18 μm, and the residual alkalinity is 2.15 wt%.

In the preparation method of the composite lithium supplement material: the sintering temperature of step S2 is 500°C.

Example 5

This embodiment is basically the same as Embodiment 1, except that:

In the composite lithium supplement material, as shown in FIG1 , there is no first coating material, and the amino acid substance 2 is directly and continuously coated on the outer surface of the lithium-rich core 1, and the thickness of the coating layer formed by the amino acid substance 2 is 5.2 nm. The median particle size (D50) of the composite lithium supplement material of this embodiment is 1.05 μm, and the residual alkalinity is 3.01 wt%.

The preparation method of the composite lithium supplementing material does not include step S2. In step S3, the lithium-rich core prepared in step S1 is directly sintered together with arginine.

Example 6

This embodiment is basically the same as Embodiment 1, except that:

In the composite lithium supplement material, the amino acid substance 2 is a mixture of proline and serine in a mass ratio of 1:1, and the coating thickness of the second coating layer formed by the amino acid substance 2 is 5.25nm. The median particle size (D50) of the composite lithium supplement material of this embodiment is 1.26μm, and the residual alkalinity is 3.35wt%.

In the preparation method of the composite lithium supplement material, in step S3, the amino acid substance components are proline and serine.

Example 7

This embodiment is basically the same as Embodiment 1, except that:

The composite lithium-supplementing material, as shown in FIG2 , has no first coating material, and all the amino acid substances are mixed in the lithium-rich core. The median particle size (D50) of the composite lithium-supplementing material of this embodiment is 3.92 μm, and the residual alkalinity is 4.91 wt %.

The preparation method of the composite lithium supplement material does not include step S2. In step S3, the lithium-rich core prepared in step S1 is directly sintered with arginine, and the sintering temperature is 300° C. and the sintering time is 1 hour.

Comparative Example 1

This comparative example is basically the same as Example 1, except that:

The lithium supplement material does not contain a first coating material and amino acid substances.

Comparative Example 2

This comparative example is basically the same as Example 1, except that:

In the preparation method of the composite lithium supplement material, the "sintering at 150° C. for 1 h in a nitrogen atmosphere" in step S3 is replaced by "carbonization treatment at 700° C. for 1 h in a nitrogen atmosphere".

Comparative Example 3

This comparative example is basically the same as Example 1, except that:

In the preparation method of the composite lithium supplement material, the sintering temperature in step S3 is set to 95°C.

2. Performance Test

1. Test methods

(1) Residual alkali value

The test method for residual alkali is:

Weigh 5g of the composite lithium supplement material of Examples 1-7 and Comparative Examples 1-3 respectively, add 50mL of ultrapure water decarbonated with carbon dioxide to dissolve in a beaker, and ultrasonically oscillate the sample for 5min at an ultrasonic frequency of 5KHz and a power of 50w, and stir once every 1min during the ultrasonic oscillation; then, filter the mixed solution obtained by ultrasonic oscillation into a 100ml volumetric flask with quantitative filter paper, fix the volume, and record the volume of the filtrate. Finally, take the above sample solution, titrate it with a standard hydrochloric acid solution, and record the volume _V1 and _V2 of the consumed standard hydrochloric acid solution, where _V1 is the volume of the standard hydrochloric acid solution consumed by titration to the first jump point; _V2 is the volume of the standard hydrochloric acid solution consumed by titration from the first jump point to the second jump point. Calculate the ^OH- and _CO32- ^residual base values according to formula (1) and formula (2):

In formula (1) and/or formula (2):

m——actual mass of the sample, g;

c——Concentration of hydrochloric acid standard solution, 12 mol/L;

V ₁ ——The volume of hydrochloric acid standard solution consumed in titration to the first sudden jump point, mL;

V ₂ ——The volume of hydrochloric acid standard solution consumed in titration from the first jump point to the second jump point, mL;

V ₃ ——filtrate volume, mL;

V ₄ ——volume of filtrate after constant volume, 100ml;

w(OH ^- )——OH ^- residual alkali value, wt%;

w(CO ₃ ^2- )——CO ₃ ^2- residual alkali value, wt%.

(2) Stability

The method for judging stability is: when preparing slurry examples 1-7 and comparative examples 1-3, observe whether a jelly-like state appears; if so, it is judged that a gel phenomenon occurs and the slurry stability is poor; if not, it indicates that the gel phenomenon is suppressed and the slurry stability is good.

(3) Electrochemical performance

The lithium ion batteries of the embodiment and the comparative example were placed at room temperature (25° C.) for 6 hours and then subjected to charge and discharge tests. The charge and discharge voltage was 2.0-4.3V. The initial gas production and initial charging capacity were tested at 0.2C and 1C, respectively.

2. Test results

The residual alkali value and stability test results of the embodiments and comparative examples are shown in Table 1.

Table 1 Residual alkali value and stability test results of the embodiments and comparative examples

It can be seen from Table 1 that the composite lithium-replenishing material of the embodiment of the present disclosure has a lower residual alkali value on the surface. Therefore, when preparing the slurry, it is found that there is no jelly state in the slurry containing the composite lithium-replenishing material of the embodiment of the present disclosure, while the comparative example is the opposite.

The electrochemical performance test results of the lithium ion batteries of the embodiments and comparative examples are shown in Table 2.

Table 2 Electrochemical performance test results of lithium ion batteries of embodiments and comparative examples

It can be seen from Table 2 that the initial gas production of the lithium-ion battery prepared by using the composite lithium-supplementing material of the embodiment of the present disclosure is much lower than the initial gas production of the lithium-ion battery prepared by using the composite lithium-supplementing material of the comparative example, and from the data in the embodiment, it can be found that when the gas production in the lithium-ion battery is low, its initial charging capacity will be improved; when the rate is increased, the gas production of the lithium-ion battery prepared by using the composite lithium-supplementing material of the embodiment of the present disclosure increases less, while the gas production of the lithium-ion battery in the comparative example increases more, indicating that the use of amino acids can significantly inhibit the gas production phenomenon of the composite lithium-supplementing material. Specifically, we can observe from Examples 1-3 that the content of the first coating material and the amino acid substance in the composite lithium supplement material disclosed in the present invention is not the more the better, but the appropriate amount can effectively exert the effect of the composite lithium supplement material; in Examples 1 and 4, because the second coating material, i.e., the amino acid substance, is combined with the inner core in different ways, the electrochemical properties of the lithium ion battery prepared by using these two materials will also change, but both can improve the performance of the lithium ion battery; in Examples 5 and 7, because the first coating material is not contained, the first charge specific capacity will be low, but its capacity is higher than the capacity in the comparative example. In the comparative example, because the comparative example 1 does not contain the first coating material and the amino acid substance, the first charge capacity is lower than the first charge capacity in other comparative examples, and the gas production is higher than the gas production in other comparative examples.

In summary, the composite lithium-supplementing material containing the first coating material and amino acid substances can improve the conductivity of the material, reduce the residual alkali value on the surface of the material, inhibit the gelation phenomenon in the process of preparing the slurry of the composite lithium-supplementing material, and inhibit the generation of gas, thereby improving the electrochemical properties and safety performance of lithium-ion batteries.

In the present disclosure, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that a specific feature, structure, material or characteristic described in conjunction with the embodiment or example is included in at least one embodiment of the present disclosure. In the present specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

Although the embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are illustrative and are not to be construed as limitations of the present disclosure. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present disclosure.

Claims (17)

1. A composite lithium supplement material, comprising:

   a lithium-rich core, including a lithium-containing compound;

   Amino acid substances are combined with the outer layer and/or the interior of the lithium-rich core.
2. The composite lithium supplement material according to claim 1, wherein the amino acid substance includes one or more of reducing amino acids and polymers of reducing amino acids.
3. The composite lithium supplement material according to claim 2, wherein the reducing amino acids and polymers thereof include one or more of arginine, threonine, proline, serine, cysteine and polymers thereof.
4. The composite lithium-supplementing material according to claim 1, wherein the mass ratio of the lithium-rich core to the amino acid substance is 100:(0.2-15).
5. The composite lithium-supplementing material according to claim 1, wherein the amino acid substance is coated on the outer surface of the lithium-rich core to form a coating layer.
6. The composite lithium supplement material according to claim 5, wherein the thickness of the coating layer formed by the amino acid substance is 2-200 nm.
7. The composite lithium-supplementing material according to claim 1, wherein the composite lithium-supplementing material further comprises a first coating material, and the first coating material is coated on the outer layer of the lithium-rich core.
8. The composite lithium supplement material according to claim 7, wherein:

   The first coating material is continuously coated on the outer surface of the lithium-rich core, and at least part of the amino acid substance is coated on the outer surface of the first coating material as the second coating material; or,

   The first coating material is discontinuously coated on the outer surface of the lithium-rich core, part of the amino acid substance is coated on the outer surface of the first coating material as the second coating material, and part of the amino acid substance is doped in the lithium-rich core.
9. The composite lithium supplement material according to claim 8, wherein the first coating material comprises at least one of a carbon material, a conductive polymer or a conductive oxide.
10. The composite lithium supplement material according to claim 8, wherein the first coating material is a carbon material, and the mass ratio of the lithium-containing compound, the first coating material, and all amino acid substances is 100:0.1-5:0.1-10;

    And/or, the thickness of the first coating layer formed by the first coating material and the second coating layer formed by the amino acid substance are both 1-100 nm.
11. The composite lithium supplement material according to any one of claims 1 to 10, wherein the lithium-containing compound comprises a material having a general structural formula of Li _1+x A _y O _z or/and a material having a general structural formula of Li _w O _r ;

    Among them, 0.3﹤x﹤10, 0﹤y﹤6, 0﹤z﹤13, and A is selected from at least one of Fe, Ni, Mn, Co, Cu, Zn, Si, Sn, Al, Zr, and Ge elements, 1≤w≤2, and 1≤r≤2.
12. The composite lithium supplement material according to any one of claims 1 to 10, wherein the median particle size of the lithium-rich core is 0.5-20 μm;

    And/or, the median particle size of the amino acid substance is 0.05-10 μm;

    And/or, the median particle size of the composite lithium supplement material is 1-45 μm;

    and/or, the BET specific surface area of the lithium-rich core is 0.5-50 m ² /g;

    And/or, the residual alkalinity of the composite lithium supplementing material is lower than 5wt%.
13. A method for preparing the composite lithium supplement material according to any one of claims 1 to 12, comprising:

    After the lithium-rich core and the amino acid substance are mixed, a first sintering is performed at 100-300° C. in a first inert atmosphere to obtain the composite lithium supplement material.
14. The method for preparing a composite lithium-supplementing material according to claim 13, wherein the method for preparing the lithium-rich core is: after the A source and the lithium source are uniformly mixed in a molar ratio, sintering at 650-900° C. in an inert atmosphere for 4-10 hours to prepare a lithium-containing compound with a general structural formula of Li _1+x A _y O _z , wherein the A source includes but is not limited to at least one of the sulfate, carbonate, acetate, oxide, and hydroxide of element A, and the lithium source includes but is not limited to one or more of lithium oxide, lithium hydroxide, lithium oxalate, lithium sulfate, and lithium carbonate.
15. The method for preparing a composite lithium supplement material according to claim 13, further comprising:

    Before mixing the lithium-rich core with the amino acid substance, the lithium-rich core is first mixed with the source material of the first coating material, and a second sintering is performed in a second inert atmosphere to obtain the lithium-rich core coated with the first coating material, and the temperature of the first sintering is lower than the temperature of the second sintering.
16. A positive electrode, comprising the composite lithium-supplementing material according to any one of claims 1 to 12 or the composite lithium-supplementing material prepared by the preparation method according to any one of claims 13 to 15.
17. A secondary battery comprises a positive electrode, a negative electrode and a separator, wherein the positive electrode is the positive electrode as claimed in claim 16.