Preparation method and application of a cathode lithium supplement additive

Abstract

The present invention relates to a cathode lithium supplement additive, which is a lithium-containing compound with the chemical formula Li x M y O z coated with carbon, and the morphology is nanoparticles. Among them, M is one or more combinations of silicon (Si), germanium (Ge), and tin (Sn), 2 ≤ x ≤ 8, 1 ≤ y ≤ 3, and 3 ≤ z ≤ 6. Compared with the same type of cathode lithium supplement additive, the cathode lithium supplement additive of the present invention provides a better lithium supplement effect and higher capacity, further improving the energy density of the battery. The novel cathode lithium supplement additive prepared by the present invention has been modified by carbon coating and ion doping, and its electronic conductivity and ionic conductivity have been improved. The small particle size makes it easy for lithium ions to diffuse in the material and easier to escape from the material, constructing an ion-electron double conduction network inside the material and improving the lithium supplement effect. The synthesis steps implemented in the present invention are simple and easy to operate, safe, pollution-free, with low costs for equipment and post-treatment, and are suitable for large-scale amplification.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion batteries, and relates to a preparation method and application of a lithium supplement additive for the positive electrode of a lithium battery. Background Art

[0002] The current information age in which humanity lives is driven by secondary lithium-ion batteries. The lithium-ion batteries commonly used in current electronic products mainly consist of a lithium cobalt oxide (LiCoO2) positive electrode, a graphite negative electrode, a polyolefin separator, and a carbonate electrolyte containing a lithium salt and various additives. The lithium cobalt oxide-graphite lithium-ion battery has advantages such as an energy density exceeding 265 Wh / kg, a working voltage as high as about 3.8 V, no need for maintenance, a long shelf life, a wide application temperature range, a high Coulombic efficiency, and no memory effect. However, with the increasing improvement of people's quality of life, the energy density of this system can no longer meet the needs of people's production and life, and the commercialization of a lithium-ion battery system with a higher energy density is imperative, such as a battery system using a silicon negative electrode or a silicon monoxide (SiOx) negative electrode. However, the commercialization of high-energy negative electrodes faces many obstacles. In addition to the volume change during the reaction process, it also includes the irreversible loss of active lithium caused by the formation of SEI in the initial cycle, resulting in a relatively low Initial Coulombic Efficiency (ICE).

[0003] The irreversible loss of active lithium in the first cycle mainly comes from the irreversible formation of SEI on the negative electrode side during the first charge and discharge. The lithium ions consumed in this process will not return to the positive electrode to participate in subsequent cycles, resulting in a decrease in the battery energy density. The ICE of a graphite negative electrode can reach more than 90%, while the ICE of a high-energy density silicon negative electrode can only reach 55% - 85%. To improve the ICE, the solution strategy provided by researchers is the battery prelithiation technology. The prelithiation technology includes three directions: positive electrode lithium supplementation, negative electrode lithium supplementation, and separator lithium supplementation. Negative electrode lithium supplementation has certain safety hazards because it requires the use of highly active lithium foil, lithium powder, or organolithium reagents, and is not compatible with today's negative electrode production process; in the positive electrode lithium supplementation direction, there are three methods: lithiated positive electrode materials, using an excessive amount of positive electrode materials, and adding a positive electrode lithium supplement additive. Among them, the positive electrode lithium supplement additive lithium supplementation is a safer and more efficient lithium supplementation method; separator lithium supplementation is developed based on positive and negative electrode lithium supplementation, and its advantage lies in adapting to the existing battery process. Therefore, it is very valuable to synthesize a new type of positive electrode lithium supplement additive with high capacity, low cost, safety, and environmental protection.

[0004] Existing cathode lithium supplement additives all have various defects. For example, CN113178568A discloses a preparation method of a double-layer coated cathode lithium supplement additive Li2NiO2. Li2NiO2 has high reactivity and is very sensitive to air. Therefore, it needs to be double-layer coated with ZrO2 and B2O3 before it can be used. This manufacturing process is not only costly and troublesome, but also further reduces the first-cycle charging capacity of the lithium supplement additive.

[0005] CN111370657A discloses the preparation methods and applications of surface-passivated cathode lithium supplement additives LiN3, Li2O2, and LiC2. First, LiN3, Li2O2, LiC2, etc. are dispersed in an organic solvent, and then a gas is introduced to passivate the surface layer. This invention uses costly and extremely unstable lithium-containing compounds LiN3, Li2O2, and LiC2, which have high safety hazards during the production and manufacturing process; and a large amount of gas is generated after de-lithiation, causing cracks inside the battery, and the gas may also react with the battery materials.

[0006] CN11439056A discloses a cathode lithium supplement additive with the chemical formula Li6MnO4. CN112490518A and CN110294494A disclose lithium supplement additives containing vanadium, and the chemical formulas are Li 4+x V2O5, and Li3VO4, Li4V3O8. However, the main problem with these lithium supplement additives is that their first-cycle charging irreversible capacity is relatively low. For example, the first-cycle irreversible charging capacity of Li6MnO4 is less than 250 mAh / g, and a relatively large amount needs to be added to achieve the lithium supplement effect, reducing the amount of cathode active material and lowering the cathode energy density. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to prepare a new type of cathode lithium supplement additive for lithium batteries, which can not only achieve a good lithium supplement effect to overcome the first-cycle capacity loss of lithium batteries, but also be directly applicable to the current slurry coating process.

[0008] The present invention provides a cathode lithium supplement additive, which is a lithium-containing compound with the chemical formula Li x M y O z after carbon coating, with a morphology of nanoparticles. Among them, M is one or a combination of silicon (Si), germanium (Ge), and tin (Sn), 2 ≤ x ≤ 8, 1 ≤ y ≤ 3, 3 ≤ z ≤ 6. The values of x, y, and z satisfy the valence conservation.

[0009] Furthermore, the thickness of the carbon coating layer is 1 - 50 nm, preferably 2 - 10 nm, and more preferably 3 - 6 nm.

[0010] Further, the particle size of the nanoparticles is 100 nm to 3000 nm, preferably 200 - 500 nm.

[0011] Further, when M is silicon (Si), Li x Si y O z The lithium-containing compounds include one or a combination of more of Li2Si3O7, Li2Si2O5, Li2SiO3, Li6Si2O7, Li8SiO6, etc.; when M is germanium (Ge), Li x Ge y O z The lithium-containing compounds include one or a combination of more of Li4Ge5O 12 、Li2GeO3, Li4GeO4, etc.; when M is tin (Sn), Li x Sn y O z The lithium-containing compounds include one or a combination of more of Li2SnO3, Li8SnO6, etc.

[0012] Further, the positive electrode lithium supplement additive of the present invention can also be element-doped, that is, the following lithium-containing compounds obtained after doping Li x M y O z : Li x-2a L a M y-b N b O z-0.5c F c , where L, N, and F are doping elements at the Li, M, and O positions. Among them, L is one or a combination of more of calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni); N is one or a combination of more of phosphorus (P), vanadium (V), titanium (Ti), aluminum (Al), etc.; F is fluorine (F). If L, N, and F exist, the ratio of a / x is between 0.0025 and 0.25, preferably 0.005 - 0.1; the ratio of b / y is between 0.005 and 0.5, preferably 0.01 - 0.3; the ratio of c / z is between 0.01 and 0.5, preferably 0.02 - 0.2; L, N, and F may also not exist, that is, a, b, and c can be 0, but not all 0.

[0013] The present invention also provides a preparation method for the above positive electrode lithium supplement additive, including the following steps:

[0014] (S1) Weigh a certain amount of lithium source compound, M source compound (including but not limited to one or a combination of more of silicon source, germanium source, tin source) and complexing agent, and uniformly disperse them in a solvent to obtain a sol;

[0015] (S2) Heat the sol in (S1) to dry the solvent, and then dry it to obtain a xerogel.

[0016] (S3) Grind the xerogel obtained in (S2) into powder, and calcine the powder in a protective gas atmosphere; then take out the product, crush it and set it aside for use.

[0017] Furthermore, in step (S1), the M-source compound is one or more combinations of a silicon source, a germanium source, and a tin source. Specifically, the silicon source compound includes one or more combinations of gaseous SiO2, nano-SiO2, gaseous SiO2, silicic acid (H2SiO3), tetraethyl orthosilicate (C8H 20 O4Si, TEOS), tetrabutyl orthosilicate (C 16 H 36 O4Si), diatomite, vermiculite, zeolite, SBA-15, waste silicon, biomass ash, fly ash, halloysite, etc.; the germanium source compound includes one or more combinations of germanium dioxide (GeO2), germanium hydroxide (Ge(OH)4), etc.; the tin source compound includes one or more combinations of tin dioxide (SnO2), nano-SnO2, tin tetrachloride pentahydrate (SnCl4·5H2O), dimethyltin oxide (C2H6OSn), etc.

[0018] Furthermore, in step (S1), the lithium source compound is a lithium-containing solid compound, including but not limited to one or more combinations of lithium carbonate (Li2CO3), lithium hydroxide monohydrate (LiOH·H2O), lithium nitrate (LiNO3), lithium acetate (CH3COOLi), lithium oxide (Li2O), etc.

[0019] Furthermore, in step (S1), the complexing agent package is a carbon-containing polydentate ligand, including one or more combinations of small molecule polydentate ligands such as citric acid (C6H8O7), ethylene glycol ((CH2OH)2), and polymer polydentate ligands such as polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), etc.

[0020] Preferably, an auxiliary complexing agent cyclic polyamine polycarboxylic acid compound is also added; more preferably, the cyclic polyamine polycarboxylic acid compound includes at least one of 1,4,7,10-tetraazacyclododecane-N-tetraacetic acid, 1,5,8,11-tetraazacyclotridecane-N-tetraacetic acid, 1,5,8,12-tetraazacyclotetradecane-N-tetraacetic acid, 1,4,7,10,13,16-hexaazacyclooctadecane-N-hexaacetic acid; even more preferably, the addition amount of the cyclic polyamine polycarboxylic acid compound is 8-15 wt% of the complexing agent.

[0021] The complexing agent plays two roles: First, as a carbon source, it becomes a carbon coating layer under subsequent calcination conditions; Li x My O z (where M is one or more combinations of silicon (Si), germanium (Ge), and tin (Sn)) The electronic conductivity of the material itself is relatively low. Affected by this, if the material without carbon coating is directly added to the positive electrode, the capacity advantage cannot be exerted; while the electronic conductivity of the material is improved after carbon coating, and an ion-electron double-conducting network can be constructed, greatly reducing the polarization of the material during charging and enabling the capacity of the material to be more fully exerted. Further, after adding an auxiliary complexing agent, the complexing agent sintering can obtain nitrogen-doped coated conductive carbon, and its conductivity is better than that of the coated carbon obtained by sintering with a general complexing agent without nitrogen element. Secondly, the complexing agent plays a role in regulating the particle size during the preparation process of the sol-gel method. During the formation of the gel precursor, the complexing agent can provide steric hindrance to form a nanostructure, and form nanoparticles after sintering. By selecting complexing agents with different structures and adding auxiliary complexing agents, nanoparticles with stable size, controllable particle size and uniform particle size dispersion can be obtained; compared with the materials obtained by calcination using other methods (such as the solid-phase method), the path for Li + to escape from the particles is shorter, so it is easier to escape, reducing the polarization caused by diffusion in the solid phase and enabling the capacity of the material to be more fully exerted; and the smaller the particle size of the nanoparticles, the better the effect of reducing polarization and the higher the material capacity. Compared with the sol-gel method that only adds a single complexing agent, in the present invention, a cyclic polyamino polycarboxylic acid compound is added as an auxiliary complexing agent, which has a large steric hindrance, can further reduce the particle size of the product, and can also make the particle size distribution of the final product more uniform.

[0022] Based on the conventional complexing agent, the inventor adds a certain amount of cyclic polyamino polycarboxylic acid compound as an auxiliary complexing agent, which can further reduce the size of the nanoparticles, improve the morphology of the nanoparticles, make the size dispersion better, and then further improve the performance of the lithium supplement additive, realize the lithium supplement function, and extend the cycle life of the lithium battery.

[0023] The dosages of the lithium source compound and the M source compound satisfy Li x M y O z, that is, the number of lithium atoms in the lithium source compound and the number of M atoms in the M source compound satisfy x:y. For example, for Li8SiO6, the usage ratio of the lithium source compound and the silicon source compound satisfies that the number of lithium atoms and the number of silicon atoms is 8:1; for another example, for Li4GeO4, the usage ratio of the lithium source compound and the germanium source compound satisfies that the number of lithium atoms and the number of germanium atoms is 4:1; for another example, for Li8SnO6, the usage ratio of the lithium source compound and the tin source compound satisfies that the number of lithium atoms and the number of tin atoms is 8:1. Those skilled in the art can understand that the number of lithium atoms in the lithium source compound and the number of M atoms in the M source compound satisfy x:y, but it is not necessary to strictly feed the lithium source compound and the M source compound according to the equivalent ratio of x:y. For any one of the materials, it can be slightly excessive, and the excess does not exceed 10 mol%, preferably not more than 5 mol%. Considering that lithium may volatilize to a certain extent in the preparation process, generally, the lithium source is selected to be 1-10% excessive, preferably 2-5%.

[0024] The dosage of the complexing agent is 2-4 times, preferably 2.5-3.5 times, the number of M atoms in the M source compound.

[0025] Further, in step (S1), the solvent is not particularly limited as long as it can fully dissolve the lithium source compound and the M source compound. For example, one or a combination of deionized water, ethanol, acetone, etc. The dosage of the solvent is not particularly limited as long as a uniformly dispersed sol can be obtained. In an embodiment of the present invention, the dosage of the solvent is such that the concentration of lithium ions in the solution system is in the range of 0.1-1 mol / L after the lithium source compound is dissolved.

[0026] Further, in step (S2), the temperature for heating and drying the solvent is 60-80 °C, and the heating time is not particularly limited as long as the solvent is dried to obtain a dry gel, which depends on the amount of the solvent, such as 2-10 h; the drying temperature is 60-200 °C, preferably 100-180 °C, and the drying time is not particularly limited as long as it is fully dried, such as 10-48 h.

[0027] Further, in step (S3), in the calcination process, the calcination temperature is preferably 650-1000 °C, the heating rate is preferably 2-10 °C / min, and the calcination time is preferably 2-10 h; the protective gas includes but is not limited to one or a combination of argon, nitrogen, helium, etc.; the pulverization means high-energy ball milling at 300-600 rpm and a ball-to-material ratio of 5-80:1 for 5-40 h.

[0028] Further, in order to prepare an element-doped cathode lithium supplement additive, a doping source compound is further added in step (S1). The doping source compound is a solid compound containing a doping element and can be dissolved in the solvent in step (S1), including but not limited to one or more combinations of its oxides, hydroxides, and various salts, such as oxalates, acetates, carbonates, etc.

[0029] For the doping source, for example, the phosphorus source for phosphorus doping includes but not limited to ammonium phosphate ((NH4)3PO4), ammonium hydrogen phosphate ((NH4)2HPO4), phosphorus pentoxide (P2O5), phosphates containing another doping atom, such as iron phosphate octahydrate (Fe3(PO4)2·8H2O), cobalt phosphate octahydrate (Co3(PO4)2·8H2O), manganese phosphate (Mn3(PO4)2), nickel phosphate octahydrate (Ni3(PO4)2·8H2O), and corresponding hydrogen phosphates, etc., one or more combinations thereof;

[0030] The vanadium source for vanadium doping includes but not limited to vanadium pentoxide (V2O5);

[0031] The germanium source for germanium doping includes but not limited to one or more combinations of germanium dioxide (GeO2), germanium hydroxide (Ge(OH)4), etc.;

[0032] The silicon source for silicon doping includes but not limited to one or more combinations of gaseous SiO2, nano-SiO2, gaseous SiO2, silicic acid (H2SiO3), tetraethyl orthosilicate (C8H 20 O4Si, TEOS), etc.

[0033] The iron source for iron doping refers to ferrous oxide and various ferrous salts, including but not limited to one or more combinations of ferrous oxalate (FeC2O4), ferrous acetate (Fe(C2H3O2)2), ferrous oxide (FeO), ferrous carbonate (FeCO3), ferrous hydroxide (Fe(OH)2), etc.;

[0034] The manganese source for manganese doping refers to manganese oxide and various manganese salts, including but not limited to one or more combinations of manganese oxalate (MnC2O4), manganese acetate (Mn(C2H3O2)2), manganese oxide (MnO), manganese carbonate (MnCO3), manganese hydroxide (Mn(OH)2), etc.;

[0035] The nickel source for nickel doping refers to nickel oxide and various nickel salts, including but not limited to one or more combinations of nickel oxalate (NiC2O4), nickel acetate (Ni(C2H3O2)2), nickel oxide (NiO), nickel carbonate (NiCO3), nickel hydroxide (Ni(OH)2), etc.;

[0036] The cobalt source for cobalt doping refers to cobalt oxide and various cobalt salts, including but not limited to one or more combinations of cobalt oxalate (CoC2O4), cobalt acetate (Co(C2H3O2)2), cobalt oxide (CoO), cobalt carbonate (CoCO3), cobalt hydroxide (Co(OH)2), etc.;

[0037] The titanium source for titanium doping refers to titanium oxide and various titanium-containing compounds, including but not limited to one or more combinations of titanium oxalate (Ti(C2O4)2), titanium oxide (TiO2), titanium hydroxide (Ti(OH)4), etc.;

[0038] The magnesium source for magnesium doping refers to magnesium oxide and various magnesium salts, including but not limited to one or more combinations of magnesium oxalate (MgC2O4), magnesium acetate (Mg(C2H3O2)2), magnesium oxide (MgO), magnesium carbonate (MgCO3), magnesium hydroxide (Mg(OH)2), etc.;

[0039] The aluminum source for aluminum doping refers to aluminum oxide and various aluminum salts, including but not limited to one or more combinations of aluminum oxalate (Al2(C2O4)3), aluminum acetate (Al(C2H3O2)3), basic aluminum acetate (Al(C2H3O2)2OH), aluminum oxide (Al2O3), aluminum carbonate (Al2(CO3)3), aluminum hydroxide (Al(OH)3), etc.;

[0040] The calcium source for calcium doping refers to calcium oxide and various calcium salts, including but not limited to one or more combinations of calcium oxalate (CaC2O4), calcium acetate (Ca(C2H3O2)2), calcium oxide (CaO), calcium carbonate (CaCO3), calcium hydroxide (Ca(OH)2), etc.;

[0041] The fluorine source for fluorine doping includes but not limited to one or more combinations of lithium fluoride (LiF), ammonium fluoride (NH4F), solid fluorides containing another doping atom, such as iron fluoride (FeF2), cobalt fluoride (CoF2), manganese fluoride (MnF2), etc.

[0042] The dosage of the doping source satisfies the chemical formula of the element-doped cathode lithium supplement additive Li x-2a L a M y-b N b O z-0.5c F c That's all.

[0043] The present invention also provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte; the cathode lithium supplement additive is included in the lithium-ion battery in at least one of the following ways:

[0044] (a) The cathode lithium supplement additive is coated on the positive electrode side of the separator;

[0045] (b) the positive electrode lithium supplement additive and the active positive electrode material are mixed into a slurry and coated on a current collector;

[0046] (c) The positive electrode lithium supplement additive is slurried and coated on the positive electrode plate.

[0047] Furthermore, the positive electrode lithium supplement additive provided by the present invention can be used in a variety of lithium battery systems, and there is no particular limitation on the positive electrode material and the negative electrode material. The positive electrode material can be a layered positive electrode material, a spinel positive electrode material, an olivine positive electrode material, and a corresponding doped and modified positive electrode material, specifically including but not limited to LiCoO2, LiFePO4, LiMn2O4, LiNi x Co y Mn z O2(x+y+z=1), LiNi x Co y Al z O2(x+y+z=1), LiNiO2, LiVO2, LiCrO2, LiCoMnO4, Li2NiMn3O8, LiNi 0.5 Mn 1.5 O4, etc.; the negative electrode materials in the lithium battery system include but are not limited to lithium metal negative electrode, carbon-based active substances, silicon-based active substances, wherein the carbon active substances include but are not limited to natural graphite, artificial graphite, soft carbon, hard carbon, one or more of mesophase carbon microspheres, and the silicon-based active substances include but are not limited to one or more of silicon element, silicon alloy, and silicon oxide.

[0048] Furthermore, the diaphragm is a polyolefin porous diaphragm, including but not limited to polypropylene (PP), polyethylene (PE) and other single or multiple material combination diaphragms, with a thickness controlled at 9-50 μm, preferably 9-20 μm.

[0049] Furthermore, method (a) comprises the following steps: dispersing the positive electrode lithium supplement additive and the binder in an organic solvent to prepare a slurry, coating the slurry on the positive electrode side of the separator, and drying the organic solvent to obtain a coating layer with a thickness in the range of 0.5-10 μm.

[0050] Furthermore, method (b) comprises the following steps: mixing raw materials including the positive electrode lithium supplement additive, active positive electrode material, conductive additive, and adhesive to prepare a slurry, and coating the slurry on a current collector to obtain a working electrode. The active positive electrode material includes layered positive electrode materials, spinel positive electrode materials, olivine positive electrode materials, and corresponding doped and modified positive electrode materials, specifically including but not limited to LiCoO2, LiFePO4, LiMn2O4, LiNi x Co y Mn zO2 (x + y + z = 1), LiNi x Co y Al z O2 (x + y + z = 1), LiNiO2, LiVO2, LiCrO2, LiCoMnO4, Li2NiMn3O8, LiNi 0.5 Mn 1.5 One or more combinations of O4, etc.

[0051] Further, method (c) includes the following steps: Making a slurry by dispersing the positive electrode lithium supplement additive and the binder in an organic solvent, coating it on the positive electrode plate, drying the solvent, and controlling the coating thickness within the range of 0.5 - 10 μm. The lithium supplement additive accounts for 1 - 20 wt% of the active positive electrode material, preferably 1 - 5 wt%.

[0052] In the above method, the types and dosages of the binder, conductive additive, and organic solvent are well-known in the art. For example, the binder includes, but is not limited to, one or more combinations of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyethylene glycol (PEG), etc., preferably polyvinylidene fluoride (PVDF); the conductive additive includes, but is not limited to, one or more combinations of SuperP, Ketjen black, carbon nanotubes, graphene, etc.; the organic solvent includes, but is not limited to, one or more combinations of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), etc., preferably N-methylpyrrolidone (NMP).

[0053] In one embodiment of the present invention, if slurry making is required, the mass ratio of the positive electrode lithium supplement additive to the binder is 80 - 95:5 - 20. The dosage of the solvent is such that the solid content of the slurry obtained from slurry making is 0.1 - 1 mg / μL.

[0054] Compared with the existing invention, the advantages of the present invention are:

[0055] First, among the novel positive electrode lithium supplement additives prepared by the present invention, there is a relatively high theoretical capacity. For example, the theoretical capacity of Li8SiO6 is 1191 mAh / g, the theoretical capacity of Li4GeO4 is 652 mAh / g, and the theoretical capacity of Li8SnO6 is 575 mAh / g. Compared with the positive electrode lithium supplement additives in the same type of invention, a higher capacity can provide a better lithium supplement effect and further improve the energy density of the battery.

[0056] II. The novel cathode lithium supplement additive prepared by the present invention has been modified by carbon coating and ion doping, resulting in improved electronic and ionic conductivities. Its particle size is between 200 and 500 nm, with a uniform particle size distribution. The small particle size enables easy diffusion of lithium ions in the material and easier extraction from the material, constructing an ion-electron double conduction network within the material and enhancing the lithium supplement effect.

[0057] III. By adding specific complexing agents, controlling the ratio of the complexing agents, and adding auxiliary complexing agents, the present invention can control the particle size and distribution of the lithium supplement additive during the preparation process, control the carbon content of the finally sintered product, and the design of sintering the complexing agent into carbon-coated enables the present invention to obtain carbon-coated nanoparticles through one-step sintering, which is simpler than other carbon coating methods.

[0058] IV. The cost of the novel cathode lithium supplement additive prepared by the present invention is lower than that of other similar inventions. In particular, the novel cathode lithium supplement additive mainly composed of Li8SiO6 has an extremely low cost. The abundance of Si element in the earth's crust reaches 25.7%, second only to oxygen, and the silicon source used can adopt very cheap materials, reducing costs during large-scale production.

[0059] V. The synthesis steps implemented by the present invention are simple and easy to perform, not only safe, pollution-free, with low costs for equipment and post-treatment, but also suitable for large-scale amplification. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 is a schematic flow diagram of the present invention;

[0061] Figure 2 is the scanning electron microscope (SEM) image ([ Figure 2 a) and high-resolution transmission electron microscope (HR-TEM) image ([ Figure 2 b) of carbon-coated nano-Li8SiO6 in Example 1;

[0062] Figure 3 is the first-cycle charge-discharge curve of the half-cell assembled with the separator coated with the lithium supplement additive Li8SiO6 and the LiNi 0.8 Co 0.1 Mn 0.1 O2 cathode electrode sheet (the side of the separator coated with the lithium supplement additive is in contact with the cathode electrode sheet);

[0063] Figure 4 is the scanning electron microscope (SEM) image of carbon-coated nano-Li8SiO6 in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0064] The present invention will be further described below in conjunction with specific embodiments, but is not limited to the specific embodiments.

[0065] In the following examples, the experimental methods are conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial sources unless otherwise specified.

[0066] Example 1

[0067] (1) Synthesis of carbon-coated nano-Li8SiO6: Weigh 17.623 g (420 mmol) of LiOH·H2O powder and 25.618 g (133.3 mmol) of citric acid powder, and dissolve them in 600 mL of deionized water; then weigh 3.005 g (50 mmol) of fumed SiO2 and add it to the solution. Use stirring and ultrasound to disperse it evenly to form a sol; then, heat the sol in a water bath at 80 °C to evaporate the deionized water to form a gel. Then, heat and dry the gel at 150 °C for 24 h to obtain a dry gel, scrape it off and grind it into powder; calcine the dry gel powder in an Ar atmosphere at 700 °C for 8 h with a heating rate of 5 °C / min; finally, ball-mill the calcined product for 10 h under the conditions of 500 rpm and a ball-to-material ratio of 10:1. The obtained powder is used as a cathode lithium supplement additive. Its scanning electron microscope (SEM) photo and high-resolution transmission electron microscope (HR-TEM) image are respectively as Figure 2 a and Figure 2 b. It can be seen that the particle size of the obtained cathode lithium supplement additive is 200 - 500 nm, and the particle size is evenly dispersed. The nano-particles of the cathode lithium supplement additive have a carbon coating layer with a thickness of about 3 - 6 nm. The spacing of the lattice fringes in the transmission electron microscope image is d = 0.241 nm, which is the (112) crystal plane of the Li8SiO6 crystal, proving that the obtained cathode lithium supplement additive is Li8SiO6.

[0068] (2) Preparation of the cathode lithium supplement separator: Take 270 mg of the cathode lithium supplement additive obtained in (1), add 30 mg of PVDF, and then add 800 μL of NMP, and mix them evenly into a slurry. Coat the slurry evenly on a Celgard polypropylene separator and dry it at 60 °C for 3 h, and then place it in a vacuum oven at 60 °C overnight to obtain the cathode lithium supplement separator. Among them, the thickness of the lithium supplement coating on the separator is about 3 μm.

[0069] (3) Cut the lithium supplement separator prepared in (2) into circular pieces with Φ = 16 mm. The active cathode material LiNi 0.8 Co 0.1 Mn 0.1O2, Super P, and polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 80:10:10 to form a slurry, which was uniformly coated onto an aluminum foil current collector. After drying, the thickness of the positive electrode coating was approximately 50 μm to obtain a positive electrode sheet. Subsequently, the electrode sheet was cut and punched into circular wafers with Φ = 10 mm to obtain working electrodes; the negative electrode material graphite, Super P, and polyacrylate binder were mixed in a mass ratio of 80:10:10 to form a slurry, which was uniformly coated onto a copper foil current collector and cut and punched into circular wafers with Φ = 10 mm to obtain counter electrodes; 1 mol / L ternary electrolyte (1 M LiPF6 EC / DEC / DMC (volume ratio 1:1:1)) was used as the electrolyte, and the prepared lithium - supplementing separator circular wafer was used as the separator to assemble a 2032 - type coin cell in a glove box. The assembled coin cell was subjected to charge - discharge tests on a LAND charge - discharge tester. During the test, the ambient temperature was maintained at 25 °C, and the charge - discharge range was 2.8 - 4.3 V (Vs. Li / Li + ), and the charge - discharge rate was 0.1C. Figure 3 was the first - cycle charge - discharge curve.

[0070] Example 2

[0071] (1) The same as step (1) in Example 1, carbon - coated nano - Li8SiO6 particles were synthesized.

[0072] (2) Preparation of the lithium - supplementing positive electrode sheet: The active positive electrode material LiNi 0.8 Co 0.1 Mn 0.1 O2, the lithium - supplementing additive for the positive electrode, carbon - coated Li8SiO6 particles, Super P, and polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 72:8:10:10 to form a slurry, which was uniformly coated onto an aluminum foil current collector to obtain a lithium - supplementing positive electrode sheet. The sheet was cut and punched into circular wafers with Φ = 10 mm as the working electrode;

[0073] (3) Together with the lithium - supplementing positive electrode sheet prepared in (2), the negative electrode material graphite, Super P, and polyacrylate binder were mixed in a mass ratio of 80:10:10 to form a slurry, which was uniformly coated onto a copper foil current collector and cut and punched into circular wafers with Φ = 10 mm to obtain counter electrodes; 1 mol / L ternary electrolyte (1 M LiPF6 EC / DEC / DMC (volume ratio 1:1:1)) was used as the electrolyte, and a polypropylene circular wafer with Φ = 16 mm (purchased from Celgard, USA) was used as the separator. A 2032 - type coin cell was assembled in a glove box, and the assembled cell was subjected to charge - discharge tests on a LAND charge - discharge tester under the same test conditions as in Example 1.

[0074] Example 3

[0075] (1) The same as step (1) in Example 1, carbon-coated nano-Li8SiO6 particles were synthesized.

[0076] (2) Preparation of the positive electrode sheet: The active positive electrode material LiNi 0.8 Co 0.1 Mn 0.1 O2, Super P, and polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 80:10:10 to form a slurry, which was uniformly coated on an aluminum foil current collector. After drying, the thickness of the positive electrode coating was about 50 μm to obtain the positive electrode sheet;

[0077] (3) Pulping of the positive electrode lithium supplement additive for secondary coating: Take 270 mg of the positive electrode lithium supplement additive obtained in (1), add 30 mg of PVDF, and then add 800 μL of NMP, and mix uniformly to form a slurry. Coat it on the positive electrode sheet prepared in (2) with a thickness of 3 μm, and cut and punch it into a circular sheet with Φ = 10 mm as the working electrode; The negative electrode material graphite, Super P, and polyacrylate binder were mixed in a mass ratio of 80:10:10 to form a slurry, which was uniformly coated on a copper foil current collector and cut and punched into a circular sheet with Φ = 10 mm to obtain the counter electrode; 1 mol / L ternary electrolyte (1 M LiPF6 EC / DEC / DMC (volume ratio 1:1:1)) was used as the electrolyte, and polypropylene (purchased from Celgard, USA) cut and punched into a circular sheet with Φ = 16 mm was used as the separator. A 2032-type coin cell was assembled in a glove box, and the assembled battery was subjected to charge and discharge tests on a LAND charge and discharge tester, and the test conditions were the same as those in Example 1.

[0078] Example 4

[0079] The rest is the same as in Example 1, except that in step (1), 2.5 g of 1,5,8,11-tetraazatridecane-N-tetraacetic acid was further added as an auxiliary complexing agent.

[0080] Example 5

[0081] The rest is the same as in Example 1, except that in step (1), 4.5 g of 1,4,7,10-tetraazadodecane-N-tetraacetic acid was further added as an auxiliary complexing agent. Figure 4 It is the scanning electron microscope (SEM) image of the carbon-coated nano-Li8SiO6 in Example 5. By Figure 2 , Figure 4 comparison, it can be seen that by adding a small amount of cyclic polyamine polycarboxylic acid compound as an auxiliary complexing agent, its steric hindrance is large, which can further reduce the particle size of the product, make the particle size distribution of the final product more uniform, and further facilitate the exertion of the electrochemical performance of the positive electrode lithium supplement agent.

[0082] Example 6

[0083] (1) Synthesis of carbon-coated nano-Li4GeO4: Weigh 8.812 g (210 mmol) of LiOH·H2O powder, 12.809 g (66.7 mmol) of citric acid powder, and 5.232 g (50 mmol) of GeO2 powder, dissolve them in 300 mL of deionized water to form a sol; then, heat the sol in a water bath at 80 °C to evaporate the deionized water to form a gel, and then heat and dry the gel at 150 °C for 24 h to obtain a dry gel, scrape it off and grind it into powder; calcine the dry gel powder in an Ar atmosphere at 800 °C for 10 h with a heating rate of 5 °C / min; finally, ball-mill the calcined product for 10 h under the conditions of 500 rpm and a ball-to-material ratio of 10:1, and the obtained powder is used as a cathode lithium supplement additive.

[0084] (2) Preparation of the cathode lithium supplement separator: Take 270 mg of the cathode lithium supplement additive obtained in (1), add 30 mg of PVDF, and then add 800 μL of NMP, mix them evenly to form a slurry, coat it on a Celgard polypropylene separator with a thickness of 3 μm, dry it at 60 °C for 3 h, and then place it in a vacuum oven at 60 °C overnight to obtain the cathode lithium supplement separator.

[0085] (3) Cut the lithium supplement separator prepared in (2) into circular pieces with Φ = 16 mm. Mix the active cathode material LiNi 0.8 Co 0.1 Mn 0.1 O2, Super P, and polyvinylidene fluoride (PVDF) binder in a mass ratio of 80:10:10 to form a slurry, evenly coat it on an aluminum foil current collector, and cut it into circular pieces with Φ = 10 mm to obtain a working electrode; mix the anode material graphite, Super P, and polyacrylate binder in a mass ratio of 80:10:10 to form a slurry, evenly coat it on a copper foil current collector, and cut it into circular pieces with Φ = 10 mm to obtain a counter electrode; use 1 mol / L ternary electrolyte (1 M LiPF6 EC / DEC / DMC (volume ratio 1:1:1)) as the electrolyte, and use the prepared lithium supplement separator circular piece as the separator to assemble a 2032-type button cell in a glove box, and the assembled battery is subjected to charge and discharge tests on a LAND charge and discharge tester, and the test conditions are the same as those in Example 1.

[0086] Example 7

[0087] (1) Synthesis of carbon-coated nano-Li8SnO6: Weigh 17.623 g (420 mmol) of LiOH·H2O powder, 25.618 g (133.3 mmol) of citric acid powder, and 17.530 g (50 mmol) of SnCl4·5H2O powder, and dissolve them in 600 mL of deionized water to form a sol. Then, heat the sol in a water bath at 80 °C to evaporate the deionized water and form a gel. Next, dry the gel by heating at 150 °C for 24 h to obtain a dry gel, scrape it off and grind it into powder. Calcinate the dry gel powder in an Ar atmosphere at 700 °C for 20 h with a heating rate of 5 °C / min. Finally, ball-mill the calcined product for 10 h under the conditions of 500 rpm and a ball-to-material ratio of 10:1. The obtained powder is used as a cathode lithium supplement additive.

[0088] (2) Preparation of the cathode lithium supplement separator: Take 270 mg of the cathode lithium supplement additive obtained in (1), add 30 mg of PVDF, and then add 800 μL of NMP, mix them evenly to form a slurry, coat it on a Celgard polypropylene separator with a thickness of 3 μm, dry it at 60 °C for 3 h, and then place it in a vacuum oven at 60 °C overnight to obtain the cathode lithium supplement separator.

[0089] (3) Cut the lithium supplement separator prepared in (2) into circular pieces with Φ = 16 mm. Mix the active cathode material LiNi 0.8 Co 0.1 Mn 0.1 O2, Super P, and polyvinylidene fluoride (PVDF) binder in a mass ratio of 80:10:10 to form a slurry, and evenly coat it on an aluminum foil current collector, then cut it into circular pieces with Φ = 10 mm to obtain a working electrode; Mix the anode material graphite, Super P, and polyacrylate binder in a mass ratio of 80:10:10 to form a slurry, and evenly coat it on a copper foil current collector, then cut it into circular pieces with Φ = 10 mm to obtain a counter electrode; Use 1 mol / L ternary electrolyte (1 M LiPF6 EC / DEC / DMC (volume ratio 1:1:1)) as the electrolyte, and use the obtained lithium supplement separator circular piece as the separator to assemble a 2032-type button cell in a glove box. The assembled battery is subjected to charge and discharge tests on a LAND charge and discharge tester, and the test conditions are the same as those in Example 1.

[0090] Example 8

[0091] The rest is the same as in Example 1, except that in step (1), the original materials are changed to: Weigh 2.705 g (45 mmol) of gaseous SiO2, 17.623 g (420 mmol) of LiOH·H2O powder, 25.618 g (133.3 mmol) of citric acid powder, and 0.660 g (5 mmol) of (NH4)2HPO4 powder, and synthesize carbon-coated nano-Li8Si 0.9 P0.1 The O6 powder is used as a cathode lithium supplement additive.

[0092] Example 9

[0093] The rest is the same as in Example 1, except that in step (1), the raw materials become: weigh 3.005 g (50 mmol) of fumed SiO2, 17.623 g (420 mmol) of LiOH·H2O powder, 25.618 g (133.3 mmol) of citric acid powder, and 1.85 g (50 mmol) of NH4F powder, and synthesize carbon-coated nano Li8SiO 5.5 The F powder is used as a cathode lithium supplement additive.

[0094] Example 10

[0095] The rest is the same as in Example 1, except that in step (1), the raw materials become: weigh 3.005 g (50 mmol) of fumed SiO2, 17.183 g (410 mmol) of LiOH·H2O powder, 25.618 g (133.3 mmol) of citric acid powder, and 0.865 g (5 mmol) of Mn(CH3COO)2 powder, and synthesize carbon-coated nano Li 7.8 Mn 0.1 The MnSiO6 powder is used as a cathode lithium supplement additive.

[0096] Example 11

[0097] The rest is the same as in Example 6, except that in step (1), the raw materials become: weigh 5.232 g (50 mmol) of GeO2 powder, 8.371 g (199 mmol) of LiOH·H2O powder, 12.809 g (66.7 mmol) of citric acid powder, and 0.865 g (5 mmol) of Mn(CH3COO)2 powder, and synthesize carbon-coated nano Li 3.8 Mn 0.1 The MnGeO4 powder is used as a cathode lithium supplement additive.

[0098] Example 12

[0099] The rest is the same as in Example 7, except that in step (1), the raw materials become: weigh 17.530 g (50 mmol) of SnCl4·5H2O powder, 17.183 g (410 mmol) of LiOH·H2O powder, 25.618 g (133.3 mmol) of citric acid powder, and 0.865 g (5 mmol) of Mn(CH3COO)2 powder, and synthesize carbon-coated nano Li 7.8 Mn 0.1 The MnSnO6 powder is used as a cathode lithium supplement additive.

[0100] Example 13

[0101] The rest is the same as in Example 1, except that in step (1), 2.5 g of 1,5,8,11-tetraazatridecane-N-tetraacetic acid is further added as an auxiliary complexing agent, and at the same time the raw materials become: weigh 3.005 g (50 mmol) of fumed SiO₂, 17.183 g (410 mmol) of LiOH·H₂O powder, 25.618 g (133.3 mmol) of citric acid powder, 0.865 g (5 mmol) of Mn(CH₃COO)₂ powder, and synthesize carbon-coated nano-Li 7.8 Mn 0.1 SiO₆ powder as a cathode lithium supplement additive.

[0102] Comparative Example 1

[0103] Mix the active cathode material LiNi 0.8 Co 0.1 Mn 0.1 O₂, Super P and polyvinylidene fluoride (PVDF) binder in a mass ratio of 80:10:10 to form a slurry, uniformly coat it on an aluminum foil current collector, cut and punch it into a Φ = 10 mm round piece to obtain a working electrode; mix the anode material graphite, Super P and polyacrylate binder in a mass ratio of 80:10:10 to form a slurry, uniformly coat it on a copper foil current collector, cut and punch it into a Φ = 10 mm round piece to obtain a counter electrode; 1 mol / L ternary electrolyte (1 M LiPF₆ EC / DEC / DMC (volume ratio 1:1:1)) is used as the electrolyte, and polypropylene (purchased from Celgard, USA) cut and punched into a Φ = 16 mm round piece is used as the separator, and a 2032-type button cell is assembled in a glove box, and the assembled battery is subjected to charge and discharge tests on a LAND charge and discharge tester.

[0104] Comparative Example 2

[0105] Others are the same as in Example 1, except that the complexing agent citric acid is not added in step (1).

[0106] In the examples and comparative examples included in the present invention, the electrochemical properties of the assembled batteries for the positive electrode in different examples and comparative examples are shown in Table 1.

[0107] Table 1 Comparison table of the electrochemical properties of full batteries in different examples

[0108]

[0109]

[0110] As can be seen from the above embodiments, different novel lithium battery cathode lithium supplement additives all have good lithium supplement effects. The carbon-coated nano-Li8SiO6 has a more significant effect, better lithium supplement effect on the battery, and the initial charge specific capacity after lithium supplement increases by 74.9 mAh / g. In addition, in Examples 4 and 5, an auxiliary complexing agent cyclic polyamino polycarboxylic acid was introduced. On the one hand, it can further help the dispersion of each material in the obtained sol. During the subsequent calcination process, the presence of nitrogen elements in the cyclic polyamino polycarboxylic acid is equivalent to nitrogen-doped carbon coating, which is more conducive to the performance of the lithium supplement additive. In Examples 8-10, different doping elements were introduced respectively, which also had a certain improvement effect on the performance of the cathode lithium supplement agent. Experiments found that when Mn was used as the doping element, the performance improvement was the most obvious.

[0111] The lithium supplement method in the present invention can be extended to other various lithium battery systems, including but not limited to lithium iron phosphate-graphite batteries, lithium cobalt oxide-graphite batteries, lithium nickel cobalt manganese oxide-graphite batteries, and lithium nickel cobalt aluminum oxide-graphite batteries, as well as the corresponding battery systems with the anode replaced by silicon-based materials (such as silicon monoxide anode).

[0112] In summary, the novel lithium battery cathode lithium supplement additive of the present invention has a simple preparation method, low cost, realizes efficient lithium supplement on the cathode side, improves the initial cycle efficiency, and is safe, pollution-free, and has high application prospects.

Claims

1. A preparation method of a cathode lithium supplement additive, characterized in that It includes the following steps: (S1) Weigh a certain amount of lithium source compound, M source compound and complexing agent, and uniformly disperse them in a solvent to obtain a sol; the M source compound is selected from one or more combinations of silicon source, germanium source, and tin source; the complexing agent is a carbon-containing polydentate ligand, including one or more combinations of citric acid, ethylene glycol, polyvinylpyrrolidone, and polyacrylic acid; the dosage of the complexing agent is 2-4 times the number of M atoms in the M source compound; In step (S1), an auxiliary complexing agent cyclic polyamine polycarboxylic acid compound is also added; the cyclic polyamine polycarboxylic acid compound includes at least one of 1,4,7,10-tetraazacyclododecane-N-tetraacetic acid, 1,5,8,11-tetraazacyclotridecane-N-tetraacetic acid, 1,5,8,12-tetraazacyclotetradecane-N-tetraacetic acid, and 1,4,7,10,13,16-hexaazacyclooctadecane-N-hexaacetic acid; the addition amount of the cyclic polyamine polycarboxylic acid compound is 8-15 wt% of the complexing agent; (S2) Heat and dry the solvent of the sol in (S1), and then dry to obtain a xerogel; (S3) Grind the xerogel obtained in (S2) into powder, and calcine the powder in a protective gas atmosphere; then take out the product, crush it, and set it aside; The positive electrode lithium supplement additive is a lithium-containing compound with the chemical formula Li x M y O z that is coated with carbon. The morphology is nanoparticles with a particle size of 200 - 500 nm. Among them, M is one or a combination of silicon, germanium, and tin, 2 ≤ x ≤ 8, 1 ≤ y ≤ 3, 3 ≤ z ≤ 6; the thickness of the carbon coating layer is 2 - 10 nm.

2. The preparation method according to claim 1, wherein The thickness of the carbon coating layer is 3-6 nm.

3. The preparation method according to claim 1, characterized in that, When M is silicon, Li x Si y O z The lithium-containing compounds include one or more combinations of Li2Si3O7, Li2Si2O5, Li2SiO3, Li6Si2O7, and Li8SiO6; when M is germanium, Li x Ge y O z The lithium-containing compounds include one or more combinations of Li4Ge5O 12 , Li2GeO3, and Li4GeO4; when M is tin, Li x Sn y O z The lithium-containing compounds include one or more combinations of Li2SnO3 and Li8SnO6.

4. The preparation method according to claim 1, wherein The positive electrode lithium supplement additive is subjected to element doping, that is, doping of Li x M y O z to obtain the following lithium-containing compound: Li x-2a L a M y-b N b O z-0.5c F c , where L, N, and F are doping elements at the Li, M, and O positions. Among them, L is one or a combination of calcium, magnesium, iron, manganese, cobalt, and nickel; N is one or a combination of phosphorus, vanadium, titanium, and aluminum; F is fluorine. If L, N, and F exist, the ratio of a / x ranges from 0.0025 to 0.25; the ratio of b / y ranges from 0.005 to 0.5; the ratio of c / z ranges from 0.01 to 0.

5.

5. The preparation method according to claim 4, characterized in that, The ratio of a / x ranges from 0.005 to 0.1, the ratio of b / y ranges from 0.01 to 0.3, and the ratio of c / z ranges from 0.02 to 0.

2.

6. The preparation method according to claim 1, wherein In step (S1), the silicon source compound includes one or more combinations of gaseous SiO2, nano-SiO2, silicic acid, tetraethyl orthosilicate, tetrabutyl orthosilicate, and diatomite; the germanium source compound includes one or more combinations of germanium dioxide and germanium hydroxide; the tin source compound includes one or more combinations of tin dioxide, stannic chloride pentahydrate, and dimethyltin oxide; and / or The lithium source compound is a lithium-containing solid compound, including one or more combinations of lithium carbonate, lithium hydroxide monohydrate, lithium nitrate, lithium acetate, and lithium oxide.

7. The preparation method according to claim 1, wherein In step (S1), the dosage of the complexing agent is 2.5-3.5 times the number of M atoms in the M source compound.

8. The preparation method according to claim 4, wherein The phosphorus source for phosphorus doping includes one or more combinations of ammonium phosphate, ammonium hydrogen phosphate, phosphorus pentoxide, iron phosphate octahydrate, cobalt phosphate octahydrate, manganese phosphate, and nickel phosphate octahydrate; The vanadium source for vanadium doping includes vanadium pentoxide; The germanium source for germanium doping includes one or more combinations of germanium dioxide and germanium hydroxide; The silicon source for silicon doping includes one or more combinations of gaseous SiO2, nano-SiO2, silicic acid, and tetraethyl orthosilicate; The iron source for iron doping includes one or more combinations of ferrous oxalate, ferrous acetate, ferrous oxide, ferrous carbonate, and ferrous hydroxide; The manganese source for manganese doping includes one or more combinations of manganese oxalate, manganese acetate, manganese oxide, manganese carbonate, and manganese hydroxide; The nickel source for nickel doping includes one or more combinations of nickel oxalate, nickel acetate, nickel oxide, nickel carbonate, and nickel hydroxide; The cobalt source for cobalt doping includes one or more combinations of cobalt oxalate, cobalt acetate, cobalt oxide, cobalt carbonate, and cobalt hydroxide; The titanium source for titanium doping includes one or more combinations of titanium oxide and titanium hydroxide; The magnesium source for magnesium doping includes one or more combinations of magnesium oxalate, magnesium acetate, magnesium oxide, magnesium carbonate, and magnesium hydroxide; The aluminum source for aluminum doping includes one or more combinations of aluminum oxalate, aluminum acetate, basic aluminum acetate, aluminum oxide, aluminum carbonate, and aluminum hydroxide; The calcium source for calcium doping includes one or more combinations of calcium oxalate, calcium acetate, calcium oxide, calcium carbonate, and calcium hydroxide; The fluorine source for fluorine doping includes one or more combinations of lithium fluoride, ammonium fluoride, ferrous fluoride, cobalt fluoride, and manganese fluoride.

9. A lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, an electrolyte, and a positive electrode lithium supplement additive prepared by the preparation method according to any one of claims 1-8; the positive electrode lithium supplement additive is included in the lithium-ion battery in at least one of the following manners: (a) The positive electrode lithium supplement additive is coated on the positive electrode side of the separator; (b) The positive electrode lithium supplement additive and the active positive electrode material are mixed to make a slurry and coated on the current collector; (c) The positive electrode lithium supplement additive is made into a slurry and coated on the positive electrode plate.

10. The lithium-ion battery according to claim 9, characterized in that, Manner (a) includes the following steps: dispersing the positive electrode lithium supplement additive and the binder in an organic solvent to make a slurry, coating it on the positive electrode side of the separator, and drying the organic solvent so that the thickness of the coating layer is in the range of 0.5-10 μm; or Manner (b) includes the following steps: mixing raw materials including the positive electrode lithium supplement additive, the active positive electrode material, the conductive additive, and the binder to make a slurry, and coating it on the current collector to obtain a working electrode; wherein the active positive electrode material includes a layered positive electrode material, a spinel-type positive electrode material, an olivine-type positive electrode material, and the corresponding doped and modified positive electrode materials; or Manner (c) includes the following steps: dispersing the positive electrode lithium supplement additive and the binder in an organic solvent to make a slurry, coating it on the positive electrode plate, drying the solvent, and controlling the coating thickness within the range of 0.5-10 μm; the lithium supplement additive accounts for 1-20 wt% of the active positive electrode material.

11. The lithium ion battery according to claim 10, wherein, In method (b), the active cathode material includes LiCoO2, LiFePO4, LiMn2O4, LiNi x Co y Mn z O2, where x + y + z = 1, LiNi x Co y Al z O2, where x + y + z = 1, LiNiO2, LiVO2, LiCrO2, LiCoMnO4, Li2NiMn3O8, LiNi 0 .5 Mn 1 .5 O4, or a combination of one or more thereof.

12. The lithium ion battery according to claim 10, wherein, In manner (c), the lithium supplement additive accounts for 1-5 wt% of the active positive electrode material.

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