Positive electrode self-replenishing lithium agent, preparation method and application thereof

Abstract

The present invention provides a cathode self-complementary lithium agent, a preparation method thereof and an application. The preparation method includes: mixing a cobalt salt, a first ligand and a second ligand and reacting to obtain a cobalt-containing complex, performing pre-sintering to obtain CoO nanoparticles, mixing with a lithium source, performing first sintering to obtain a first sintered material, performing intermediate crushing, and then performing second sintering to obtain the cathode self-complementary lithium agent, and the cathode self-complementary lithium agent contains Li6CoO4; the first ligand is PVA and / or PAM, and the second ligand is aminobenzoic acid and / or aminobenzenesulfonic acid. By optimizing the synthesis process of CoO and the sintering process of the cathode self-complementary lithium agent, the present invention improves the reaction efficiency of preparing Li6CoO4, further reduces the residual alkali content, the prepared cathode self-complementary lithium agent has lower environmental requirements, excellent electrical properties, and lower raw material costs, and can well balance low cost and high performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a positive electrode self-replenishing lithium agent, a preparation method and application thereof. Background Art

[0002] Nowadays, lithium-ion batteries have been widely used in various fields, especially in 3C, electric vehicle power batteries, and energy storage. People have higher and higher requirements for battery life, and they are also increasingly demanding high-capacity batteries in the field of energy storage. When lithium-ion batteries are formed and charged for the first time, a SEI film will form at the interface between the negative electrode and the electrolyte. The formation of the SEI film will consume the Li in the positive electrode. + , which leads to a decrease in the lithium content in the positive electrode, and then destroys the lattice structure of the positive electrode material, affecting the overall capacity and cycle performance of the battery. By adding a positive electrode self-replenishing agent to the positive electrode material, an additional lithium source can be provided for the SEI film, thereby avoiding the consumption of Li in the positive electrode material. + .

[0003] Li6CoO4 has the characteristics of high specific capacity, low first charge efficiency, and high irreversible capacity. Its theoretical specific capacity can reach more than 985mAh / g, making it an ideal positive electrode self-replenishing lithium agent. The existing technology CN107658138A actually uses submicron-grade 100-300nm CoO raw materials, which are still relatively large in size, affecting the combination efficiency of CoO and lithium source, thereby affecting the electrochemical performance of Li6CoO4. In addition, its lithium source is directly selected from Li2O, and the raw material cost is relatively high. Summary of the invention

[0004] The main purpose of the present invention is to provide a positive electrode self-replenishing lithium agent, a preparation method and application thereof, so as to solve the problem that the positive electrode self-replenishing lithium agent of lithium ion batteries in the prior art cannot achieve both low cost and high performance.

[0005] In order to achieve the above-mentioned object, according to one aspect of the present invention, there is provided a method for preparing a positive electrode self-lithium replenishing agent, comprising the following steps: step S1, mixing and reacting a cobalt salt, a first ligand and a second ligand to obtain a cobalt-containing complex; step S2, pre-sintering the cobalt-containing complex to obtain CoO nanoparticles; step S3, mixing the CoO nanoparticles with a lithium source, performing a first sintering, and obtaining a first sintered material; step S4, intermediately crushing the first sintered material, and then performing a second sintering to obtain a positive electrode self-lithium replenishing agent, wherein the positive electrode self-lithium replenishing agent contains Li6CoO4; wherein the first ligand is PVA and / or PAM, and the second ligand is aminobenzoic acid and / or aminobenzenesulfonic acid.

[0006] Further, in step S1, the cobalt salt is one or more of cobalt chloride or its hydrate, cobalt sulfate or its hydrate, cobalt nitrate or its hydrate, cobalt acetate or its hydrate and cobalt oxalate or its hydrate; preferably, the cobalt salt is added in the form of a cobalt salt aqueous solution, preferably, the mass concentration of cobalt ions in the cobalt salt aqueous solution is 35-55 g / L; and / or the first ligand is one or more of PVA-105, PVA-124, PVA-350, PVA-1788, PVA-1797 and PVA-1799; preferably, the first ligand is added in the form of a first ligand aqueous solution, preferably, the mass concentration of the first ligand aqueous solution is 25-55 g / L; and / or the second ligand is one or more of p-aminobenzoic acid, o-aminobenzoic acid, p-aminobenzenesulfonic acid and o-aminobenzenesulfonic acid; preferably, the second ligand is added in the form of a second ligand alcohol solution, preferably, the mass concentration of the second ligand alcohol solution is 110-150 g / L, and preferably the second ligand alcohol solution is an ethanol solution.

[0007] Furthermore, in step S1, the mass ratio of Co atoms, the first ligand and the second ligand in the cobalt salt is 1:(0.6-1.3):(2.2-3.3); preferably, the cobalt salt, the first ligand and the second ligand are mixed and heated to react, and the heating temperature is preferably 80-95°C.

[0008] Furthermore, in step S2, the sintering temperature of the pre-sintering is 500-600°C, the sintering time is 2-5h, the heating rate is 1-4°C / min, and the sintering atmosphere is an inert atmosphere, preferably a nitrogen atmosphere and / or an argon atmosphere; preferably, the particle size of the CoO nanoparticles is 50-100nm.

[0009] Furthermore, in step S3, the lithium source is one or more of lithium hydroxide or its hydrate, lithium acetate or its hydrate, lithium oxalate or its hydrate, lithium sulfate or its hydrate, lithium nitrate or its hydrate, lithium carbonate and lithium oxide; preferably, the molar ratio of Co atoms in the CoO nanoparticles to Li atoms in the lithium source is 1:(4.8-6.4); more preferably 1:(5.4-6.4).

[0010] Furthermore, the sintering temperature of the first sintering is 600-900°C, the sintering time is 10-14h, the heating rate is 1-4°C / min, the sintering atmosphere is a nitrogen atmosphere and / or an argon atmosphere, and the oxygen content in the sintering atmosphere is 10-20ppm; preferably, the first sintering is cooled to obtain the first sintered material; and / or the sintering temperature of the second sintering is 600-900°C, the sintering time is 10-14h, the heating rate is 1-4°C / min, the sintering atmosphere is a nitrogen atmosphere and / or an argon atmosphere, and the oxygen content in the sintering atmosphere is 10-20ppm; preferably, the second sintering is cooled to obtain a positive electrode self-lithium supplement; preferably, the ratio of oxygen content in the sintering atmosphere of the first sintering and the second sintering is (0.8-1.2):1.

[0011] Furthermore, in the positive electrode self-replenishing lithium agent, the mass percentage of Li6CoO4 is ≥96%, and the mass percentage of residual alkali is ≤2.5%; preferably, the particle size of the positive electrode self-replenishing lithium agent is 3 to 10 μm.

[0012] According to another aspect of the present invention, a positive electrode self-lithium replenishing agent is provided, which is obtained by the above-mentioned preparation method of the present invention.

[0013] According to another aspect of the present invention, a positive electrode plate is provided, comprising a positive electrode material and a positive electrode self-lithium replenishing agent, wherein the positive electrode self-lithium replenishing agent is the positive electrode self-lithium replenishing agent described above in the present invention.

[0014] According to another aspect of the present invention, a lithium-ion battery is provided, comprising a positive electrode plate, wherein the positive electrode plate is the positive electrode plate described above in the present invention.

[0015] By applying the technical solution of the present invention, by optimizing the synthesis process of CoO and the sintering process of the positive electrode self-replenishing lithium agent, a coordination wet method is adopted to prepare smaller and more suitable CoO nanoparticles, so that when the CoO nanoparticles are mixed with the lithium source, the contact with the lithium source is more complete, the reaction interface is increased during sintering to prepare Li6CoO4, the reaction efficiency is improved, and the residual alkali content in Li6CoO4 is further reduced. The Li6CoO4 positive electrode self-replenishing lithium agent prepared using the nano-scale CoO synthesized by the present invention has low environmental requirements, excellent electrical properties, simple preparation, and lower raw material costs, that is, the preparation method of the present invention can well balance low cost and high performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0017] Figure 1 shows a SEM image of CoO nanoparticles in Example 1 of the present invention; and

[0018] Figure 2 The XRD spectrum of the Li6CoO4 positive electrode self-lithium supplement agent in Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0019] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0020] As described in the background of the present invention, there is a problem in the prior art that the positive electrode self-replenishing agent for lithium-ion batteries cannot take into account both low cost and high performance. In order to solve the above problem, in a typical embodiment of the present invention, a preparation method of a positive electrode self-replenishing agent is provided, comprising the following steps: step S1, mixing and reacting a cobalt salt, a first ligand and a second ligand to obtain a cobalt-containing complex; step S2, pre-sintering the cobalt-containing complex to obtain CoO nanoparticles; step S3, mixing the CoO nanoparticles with a lithium source, performing a first sintering, and obtaining a first sintered material; step S3, intermediately crushing the first sintered material, and then performing a second sintering to obtain a positive electrode self-replenishing agent, and the positive electrode self-replenishing agent contains Li6CoO4; wherein the first ligand is PVA (polyvinyl alcohol) and / or PAM (polyacrylamide), and the second ligand is aminobenzoic acid and / or aminobenzenesulfonic acid.

[0021] The present invention firstly mixes cobalt salt, a first ligand and a second ligand and then reacts them, wherein the first ligand is PVA and the second ligand is aminobenzoic acid and / or aminobenzenesulfonic acid. During this process, the hydroxyl group in PVA and / or the amide group in PAM, the amino group in aminobenzoic acid and / or aminobenzenesulfonic acid will react with the Co ions in the cobalt salt to form a cobalt-containing complex. The cobalt-containing complex is then pre-sintered, during which the ligand is detached and volatilized by heat to obtain pure CoO nanoparticles; then the CoO nanoparticles are mixed with a lithium source and subjected to a first sintering, during which the lithium source is heated and melted, and Li + Embedded in the CoO unit cell, reorganized and crystallized to obtain the first sintered material. At this time, since the high-temperature material will crystallize into blocks, part of the lithium source and CoO will not react fully, so that the residual alkali on the surface of the positive electrode self-replenishing lithium agent increases and affects the performance. Therefore, the present invention finally performs intermediate crushing on the first sintered material, and then re-sintering for the second time. In this process, the lithium source that has not reacted fully continues to react with CoO, thereby improving the purity of the material, reducing the residual alkali and improving the performance, and obtaining the positive electrode self-replenishing lithium agent. The positive electrode self-replenishing lithium agent mainly contains Li6CoO4, and a small amount of residual alkali and other impurities.

[0022] The present invention optimizes the synthesis process of CoO and the sintering process of the positive electrode self-replenishing lithium agent, and adopts a coordination wet method to prepare smaller and more suitable CoO nanoparticles, so that when the CoO nanoparticles are mixed with the lithium source, the contact with the lithium source is more complete, the reaction interface is increased during sintering to prepare Li6CoO4, the reaction efficiency is improved, and the residual alkali content in Li6CoO4 is further reduced. The Li6CoO4 positive electrode self-replenishing lithium agent prepared using the nano-scale CoO synthesized by the present invention has low environmental requirements, excellent electrical properties, simple preparation, and lower raw material costs, that is, the preparation method of the present invention can well balance low cost and high performance.

[0023] In a preferred embodiment, in step S1, the cobalt salt is one or more of cobalt chloride or its hydrate, cobalt sulfate or its hydrate, cobalt nitrate or its hydrate, cobalt acetate or its hydrate and cobalt oxalate or its hydrate, and the above cobalt salts are easily soluble in water and can better accept ligands; preferably, the cobalt salt is added in the form of a cobalt salt aqueous solution, and preferably, the mass concentration of cobalt ions in the cobalt salt aqueous solution is 35-55 g / L, so that the cobalt salt can be fully and quickly dissolved.

[0024] And / or the first ligand is one or more of PVA-105, PVA-124, PVA-350, PVA-1788, PVA-1797 and PVA-1799. The above-mentioned first ligands have good water solubility, are relatively cheap, have good coordination effect, are non-toxic, biodegradable and environmentally friendly. Preferably, the first ligand is added in the form of an aqueous solution of the first ligand, and the mass concentration of the aqueous solution of the first ligand is preferably 25 to 55 g / L, so that the first ligand can be fully and quickly dissolved.

[0025] And / or the second ligand is one or more of p-aminobenzoic acid, o-aminobenzoic acid, p-aminobenzenesulfonic acid and o-aminobenzenesulfonic acid. The above second ligands have low cost and are more fully coordinated with cobalt ions. Preferably, the second ligand is added in the form of a second ligand alcohol solution, and the mass concentration of the second ligand alcohol solution is preferably 110-150g / L. The second ligand alcohol solution is preferably an ethanol solution, so that the second ligand can be fully and quickly dissolved.

[0026] In order to make the coordination and complex reaction of the cobalt salt, the first ligand and the second ligand proceed more fully and completely, while further reducing the amount of raw materials used, thereby further reducing costs, in a preferred embodiment, in step S1, the mass ratio of the Co atom in the cobalt salt, the first ligand and the second ligand is 1:(0.6~1.3):(2.2~3.3); preferably, the cobalt salt, the first ligand and the second ligand are mixed and heated to react, and the preferred heating temperature is 80~95°C.

[0027] In a preferred embodiment, in step S2, the sintering temperature of the pre-sintering is 500-600°C, the sintering time is 2-5h, the heating rate is 1-4°C / min, and the sintering atmosphere is an inert atmosphere, preferably a nitrogen atmosphere and / or an argon atmosphere. Under the above conditions, Co 2+ Preferably, the particle size of the CoO nanoparticles is 50 to 100 nm. It can be seen that the CoO nanoparticles obtained by the preparation method of the present invention are relatively small, and can be more fully contacted with the lithium source in the subsequent preparation of Li6CoO4, which can further improve the reaction efficiency and reduce the residual alkali in Li6CoO4.

[0028] Since the preparation method of the present invention improves the preparation process of CoO nanoparticles and Li6CoO4, the lithium source used may not be limited to expensive LiO. In a preferred embodiment, in step S3, the lithium source is one or more of lithium hydroxide or its hydrate, lithium acetate or its hydrate, lithium oxalate or its hydrate, lithium sulfate or its hydrate, lithium nitrate or its hydrate, lithium carbonate and lithium oxide, preferably one or more of anhydrous LiOH, LiOH·H2O, CHCOOLi·H2O, LiNO3·H2O. The above lithium sources are lower in price, which is conducive to further reducing the preparation cost of the positive electrode self-replenishing lithium agent; preferably, the molar ratio of Co atoms in the CoO nanoparticles to Li atoms in the lithium source is 1:(4.8-6.4); more preferably 1:(5.4-6.4). Under the above ratio, CoO can fully react with the lithium source, and reduce the residual alkali while ensuring the electrical performance, thereby reducing the difficulty of using the finished product of the positive electrode self-replenishing lithium agent.

[0029] In order to simplify the process flow as much as possible and remove the process adjustment link, in a preferred embodiment, in step S3, the sintering temperature of the first sintering is 600-900°C, the sintering time is 10-14h, the heating rate is 1-4°C / min, the sintering atmosphere is a nitrogen atmosphere and / or an argon atmosphere, and the oxygen content in the sintering atmosphere is 10-20ppm; preferably, cooling is performed after the first sintering to obtain the first sintered material; under the above conditions, the Co 2+ While not being oxidized, CoO and the lithium source are allowed to react as fully as possible; and / or the sintering temperature of the second sintering is 600-900°C, the sintering time is 10-14h, the heating rate is 1-4°C / min, the sintering atmosphere is a nitrogen atmosphere and / or an argon atmosphere, and the oxygen content in the sintering atmosphere is 10-20ppm; preferably, cooling is performed after the second sintering to obtain a positive electrode self-replenishing lithium agent; under the above conditions, Co 2+ It will not be oxidized, and the residual alkali will further react; preferably, the ratio of oxygen content in the sintering atmosphere of the first sintering and the second sintering is (0.8-1.2):1. Under the above conditions, Co 2+Will not be oxidized.

[0030] As described above, the present invention adopts the coordination wet method to prepare CoO nanoparticles with smaller and more suitable size, so that when the CoO nanoparticles are mixed with the lithium source, the contact with the lithium source is more sufficient, the reaction interface is increased when sintering to prepare Li6CoO4, the reaction efficiency is improved, and the residual alkali content in Li6CoO4 can be further reduced. The residual amount of inactive substances is small, and the weight of the positive electrode will not be increased to affect the specific energy density of the battery, which can further improve the comprehensive performance of the battery. In a preferred embodiment, in the positive electrode self-replenishing lithium agent, the mass percentage of Li6CoO4 is ≥96%, and the mass percentage of residual alkali is ≤2.5%; preferably, the particle size of the positive electrode self-replenishing lithium agent is 3 to 10 μm, which has a small and suitable particle size, a large specific surface area, and better electrical properties of the material.

[0031] In another typical embodiment of the present invention, a positive electrode self-replenishing lithium agent is also provided, which is obtained by the preparation method of the present invention. The Li6CoO4 positive electrode self-replenishing lithium agent prepared using the nano-scale CoO synthesized by the present invention has low environmental requirements, excellent electrical properties, simple preparation, and lower raw material costs.

[0032] Correspondingly, in another typical embodiment of the present invention, a positive electrode plate is provided, comprising a positive electrode material and a positive electrode self-lithium replenishing agent, wherein the positive electrode self-lithium replenishing agent is the positive electrode self-lithium replenishing agent mentioned above in the present invention.

[0033] In another typical embodiment of the present invention, a lithium-ion battery is provided, including a positive electrode sheet, wherein the positive electrode sheet is the positive electrode sheet of the present invention. The positive electrode self-replenishing agent of the present invention can provide an additional lithium source for the SEI film, thereby avoiding the consumption of Li in the positive electrode material. + , which makes the lithium-ion battery using it have higher first charge capacity and first coulombic efficiency.

[0034] Typically but not limiting, in step S1, the mass concentration of cobalt ions in the cobalt salt aqueous solution is 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L or a range consisting of any two of them; the mass concentration of the first ligand aqueous solution is 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L or a range consisting of any two of them; the mass concentration of the second ligand alcohol solution is 110 g / L, 115 g / L, 120 g / L, 125 g / L, 130 g / L, 135 g / L, 140 g / L, 145 g / L, 150 g / L or a range consisting of any two of them.

[0035] Typically but not limiting, in step S1, when the atomic mass of Co in the cobalt salt is 1, the first ligand is 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3 or a range consisting of any two of them, and the second ligand is 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3 or a range consisting of any two of them.

[0036] Typically but not limiting, in step S2, the sintering temperature of the pre-sintering is 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C or a range consisting of any two of them; the sintering time is 2h, 3h, 4h, 5h or a range consisting of any two of them; the heating rate is 1°C / min, 2°C / min, 3°C / min, 4°C / min or a range consisting of any two of them; the particle size of the CoO nanoparticles is 50nm, 54nm, 55nm, 60nm, 62nm, 65nm, 70nm, 75nm, 80nm, 83nm, 85nm, 90nm, 92nm, 95nm, 100nm or a range consisting of any two of them.

[0037] Typically but not limiting, in step S3, the molar ratio of Co atoms in the CoO nanoparticles to Li atoms in the lithium source is 1:4.8, 1:4.9, 1:5.0, 1:5.1, 1:5.2, 1:5.3, 1:5.4, 1:5.5, 1:5.6, 1:5.7, 1:5.8, 1:5.9, 1:6.0, 1:6.1, 1:6.2, 1:6.3, 1:6.4 or a range consisting of any two of them; the sintering temperature of the first sintering is 600°C, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃ or a range consisting of any two of them; the sintering time is 10h, 11h, 12h, 13h, 14h or a range consisting of any two of them; the heating rate is 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min or a range consisting of any two of them; the oxygen content in the sintering atmosphere is 10ppm, 12ppm, 14ppm, 16ppm, 18ppm, 20ppm.

[0038] Typically but not limiting, in step S4, the sintering temperature of the second sintering is 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C or a range consisting of any two of them; the sintering time is 10h, 11h, 12h, 13h, 14h or a range consisting of any two of them; the heating rate is 1°C / min, 2°C / min, 3°C / min, 4°C / min or a range consisting of any two of them; the oxygen content in the sintering atmosphere is 10ppm, 12ppm, 14ppm, 16ppm, 18ppm, 20ppm or a range consisting of any two of them.

[0039] Typically but not limiting, the ratio of oxygen content in the sintering atmospheres of the first sintering and the second sintering is 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1 or a range consisting of any two of these ratios.

[0040] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0041] Example 1

[0042] (1) CoO nanoparticles were prepared by the coordination wet method: PVA-1788 was prepared into a 40 g / L aqueous solution, CoCl2·6H2O was dissolved into a 45 g / L aqueous solution of cobalt ions, and p-aminobenzoic acid was prepared into a 125 g / L ethanol solution. The above three solutions were mixed and heated to reflux at 90°C. After cooling, washing, filtering and drying, they were pre-sintered at a sintering temperature of 550°C, a heating rate of 2°C / min, a sintering time of 3h, and a nitrogen atmosphere. After cooling, CoO nanoparticles were obtained. The particle size of the nanoparticles was 54 nm. The SEM image of the CoO nanoparticles in Example 1 is shown in Figure 1 ;

[0043] (2) CoO nanoparticles and anhydrous LiOH were mixed at a molar ratio of Co atoms to Li atoms of 1:5.4, and then a first sintering was performed under argon protection at a sintering temperature of 900°C, a heating rate of 2°C / min, an oxygen content of 12 ppm, and a sintering time of 12 h. After cooling, the mixture was crushed and sieved to obtain a first sintered material;

[0044] (3) The first sintered material was placed under argon protection and sintered again, with a sintering temperature of 900°C, a heating rate of 2°C / min, an oxygen content of 14ppm, and a sintering time of 12h. After cooling, the material was crushed and sieved to obtain a positive electrode self-replenishing lithium agent. The XRD spectrum of the positive electrode self-replenishing lithium agent Li6CoO4 obtained in Example 1 is shown in Figure 2 .

[0045] Example 2

[0046] (1) CoO nanoparticles were prepared by the coordination wet method: PVA-350 was prepared into a 35 g / L aqueous solution, CoSO4·7H2O was dissolved into a 55 g / L aqueous solution of cobalt ions, and anthranilic acid was prepared into a 120 g / L ethanol solution. The above three solutions were mixed and heated to reflux at 90°C, cooled, washed, filtered, and dried, and then pre-sintered at a sintering temperature of 500°C, a heating rate of 1°C / min, a sintering time of 3h, and a nitrogen atmosphere. After cooling, CoO nanoparticles were obtained, and the particle size of the nanoparticles was 92nm;

[0047] (2) CoO nanoparticles and LiNO3·H2O were mixed at a molar ratio of Co atoms to Li atoms of 1:6, and then a first sintering was performed under nitrogen protection at a sintering temperature of 600°C, a heating rate of 1°C / min, an oxygen content of 15 ppm, and a sintering time of 10 h. After cooling, the mixture was crushed and sieved to obtain a first sintered material;

[0048] (3) The first sintered material was placed under nitrogen protection and sintered again at a sintering temperature of 600° C., a heating rate of 1° C. / min, an oxygen content of 13 ppm, and a sintering time of 10 h. After cooling, the material was crushed and sieved to obtain a positive electrode self-replenishing lithium agent.

[0049] Example 3

[0050] (1) CoO nanoparticles were prepared by the coordination wet method: PVA-1797 was prepared into a 45 g / L aqueous solution, Co(NO3)2·6H2O was dissolved into a 35 g / L aqueous solution of cobalt ions, and p-aminobenzoic acid was prepared into a 115 g / L ethanol solution. The above three solutions were mixed and heated to reflux at 90°C, cooled, washed, filtered, and dried, and then pre-sintered at a sintering temperature of 600°C, a heating rate of 4°C / min, a sintering time of 5h, and an argon atmosphere. After cooling, CoO nanoparticles were obtained, and the particle size of the nanoparticles was 62nm;

[0051] (2) CoO nanoparticles were mixed with a LiOH·H2O / Li2O mixture (mixing molar ratio of 4:6) at a molar ratio of Co atoms to Li atoms of 1:5.6, and then a first sintering was performed under nitrogen protection at a sintering temperature of 850°C, a heating rate of 4°C / min, an oxygen content of 19 ppm, and a sintering time of 14 h. After cooling, the mixture was crushed and sieved to obtain a first sintered material;

[0052] (3) The first sintered material was placed under nitrogen protection and sintered again at a sintering temperature of 850°C, a heating rate of 4°C / min, an oxygen content of 17 ppm, and a sintering time of 14 h. After cooling, the material was crushed and sieved to obtain a positive electrode self-replenishing lithium agent.

[0053] Example 4

[0054] (1) CoO nanoparticles were prepared by the coordination wet method: PVA-1799 was prepared into a 55 g / L aqueous solution, Co(CH3COO)2·4H2O was dissolved into a 50 g / L aqueous solution of cobalt ions, and o-aminobenzenesulfonic acid was prepared into a 110 g / L ethanol solution. The above three solutions were mixed and heated to reflux at 85°C, cooled, washed, filtered, and dried, and then pre-sintered at a sintering temperature of 500°C, a heating rate of 2°C / min, a sintering time of 2.5 h, and an argon atmosphere. After cooling, CoO nanoparticles were obtained, and the particle size of the nanoparticles was 70 nm.

[0055] (2) CoO nanoparticles and CHCOOLi·H2O were mixed at a molar ratio of Co atoms to Li atoms of 1:6.4, and then the mixture was first sintered under nitrogen protection at a sintering temperature of 700°C, a heating rate of 3°C / min, an oxygen content of 13 ppm, and a sintering time of 11 h. After cooling, the mixture was crushed and sieved to obtain a first sintered material;

[0056] (3) The first sintered material was placed under argon protection and sintered again at a sintering temperature of 700°C, a heating rate of 3°C / min, an oxygen content of 15 ppm, and a sintering time of 11 h. After cooling, the material was crushed and sieved to obtain a positive electrode self-replenishing lithium agent.

[0057] Example 5

[0058] (1) CoO nanoparticles were prepared by the coordination wet method: PVA-105 was prepared into a 25 g / L aqueous solution, CoC2O4·2H2O was dissolved into a 40 g / L aqueous solution of cobalt ions, and p-aminobenzenesulfonic acid was prepared into a 130 g / L ethanol solution. The above three solutions were mixed and heated to reflux at 95°C, cooled, washed, filtered, and dried, and then pre-sintered at a sintering temperature of 550°C, a heating rate of 3°C / min, a sintering time of 4h, and a nitrogen atmosphere. After cooling, CoO nanoparticles were obtained, and the particle size of the nanoparticles was 83nm;

[0059] (2) CoO nanoparticles and LiOH·H2O were mixed at a molar ratio of Co atoms to Li atoms of 1:4.8, and then the first sintering was performed under nitrogen protection at a sintering temperature of 750°C, a heating rate of 2°C / min, an oxygen content of 16 ppm, and a sintering time of 13 h. After cooling, the first sintered material was crushed and sieved;

[0060] (3) The first sintered material was placed under argon protection and sintered again at a sintering temperature of 750°C, a heating rate of 2°C / min, an oxygen content of 20 ppm, and a sintering time of 13 h. After cooling, the material was crushed and sieved to obtain a positive electrode self-replenishing lithium agent.

[0061] Comparative Example 1

[0062] (1) Preparation of CoO by solution heat method: Anhydrous CoCl2 was prepared into a 30 g / L anhydrous ethanol solution, and then stearic acid was added, with the volume ratio of anhydrous ethanol to stearic acid being 15:1. After stirring evenly, the mixture was reacted at 190°C for 8 h. After natural cooling, the mixture was washed with anhydrous ethanol, filtered, and dried to obtain CoO with a particle size of 253 nm.

[0063] (2) The obtained CoO and Li2O were mixed at a molar ratio of Co atoms to Li atoms of 6:1, and then sintered for the first time under nitrogen protection at a sintering temperature of 900°C, a heating rate of 2°C / min, an oxygen content of 11 ppm, and a sintering time of 12 h. After cooling, the mixture was crushed and sieved to obtain a sintered material;

[0064] (3) The sintered material was placed under nitrogen protection and sintered again at a sintering temperature of 900°C, a heating rate of 2°C / min, an oxygen content of 13 ppm, and a sintering time of 12 h. After cooling, the sintered material was crushed and sieved to obtain a positive electrode self-replenishing lithium agent.

[0065] Comparative Example 2

[0066] (1) Preparation of CoO by solution heat method: Anhydrous CoCl2 was prepared into a 30 g / L anhydrous ethanol solution, and then stearic acid was added, with the volume ratio of anhydrous ethanol to stearic acid being 15:1. After stirring evenly, the mixture was reacted at 190°C for 8 h. After natural cooling, the mixture was washed with anhydrous ethanol, filtered, and dried to obtain CoO with a particle size of 253 nm.

[0067] (2) The CoO obtained in step 1 was mixed with anhydrous LiOH at a molar ratio of Co atoms to Li atoms of 5.4:1, and then sintered for the first time under nitrogen protection at a sintering temperature of 700° C., a heating rate of 2° C. / min, an oxygen content of 15 ppm, and a sintering time of 14 h. After cooling, the mixture was crushed and sieved to obtain a sintered material;

[0068] (3) The sintered material was placed under nitrogen protection and sintered again at a sintering temperature of 700°C, a heating rate of 2°C / min, an oxygen content of 12ppm, and a sintering time of 14h. After cooling, the sintered material was crushed and sieved to obtain a positive electrode self-replenishing lithium agent.

[0069] The positive electrode self-lithium supplement agent prepared in the above-mentioned embodiment and comparative example was used to prepare a positive electrode sheet and a half-cell, and the electrochemical performance was tested.

[0070] Preparation of positive electrode sheet: The positive electrode self-replenishing agent (40wt%), Super P (50wt%) and PVDF (10wt%) are mixed evenly, and then slurry mixing, coating, drying and rolling are carried out in sequence to obtain the positive electrode sheet.

[0071] Preparation of half-cell: Assemble the above-mentioned positive electrode plate, separator, and negative electrode plate (lithium metal) into a button cell and let it stand for about 4 hours to prepare a positive electrode self-replenishing lithium agent half-cell.

[0072] Test method:

[0073] Mass percentage of Li6CoO4 in positive electrode self-replenishing lithium agent: XRD internal standard method.

[0074] Mass percentage of residual alkali in positive electrode self-replenishing lithium agent: alcohol titration method.

[0075] Particle size: GB / T 19077-2016 particle size tester, SEM image particle size measurement.

[0076] Electrical performance test: Blue Battery Performance Tester 0.2C / 4.35V.

[0077] The particle size of the CoO particles prepared in the above embodiments and comparative examples, the mass percentage of Li6CoO4 and residual alkali in the positive electrode self-replenishing lithium agent, the particle size, and the half-cell electrical performance are shown in Table 1.

[0078] Table 1

[0079]

[0080] It can be seen from the above that, compared with the comparative example, the embodiments of the present invention optimize the synthesis process of CoO and the sintering process of the positive electrode self-replenishing lithium agent, and adopt a coordination wet method to prepare smaller and more suitable CoO nanoparticles, so that when the CoO nanoparticles are mixed with the lithium source, the contact with the lithium source is more sufficient, the reaction interface is increased during sintering to prepare Li6CoO4, the reaction efficiency is improved, and the residual alkali content in Li6CoO4 is further reduced. The prepared positive electrode self-replenishing lithium agent has low environmental requirements, excellent electrical properties, and lower raw material costs, which can well balance low cost and high performance.

[0081] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a positive electrode self-lithium supplement agent, characterized in that: The following steps are involved: Step S1, mixing and reacting a cobalt salt, a first ligand and a second ligand to obtain a cobalt-containing complex; Step S2, pre-sintering the cobalt-containing complex to obtain CoO nanoparticles; Step S3, mixing the CoO nanoparticles with a lithium source, and performing a first sintering to obtain a first sintered material; Step S4, performing intermediate crushing on the first sintered material, and then performing a second sintering to obtain the positive electrode self-lithium supplement agent, wherein the positive electrode self-lithium supplement agent contains Li6CoO4; Wherein, the first ligand is PVA and / or PAM, and the second ligand is aminobenzoic acid and / or aminobenzenesulfonic acid.

2. The preparation method according to claim 1, characterized in that: In the step S1, The cobalt salt is one or more of cobalt chloride or its hydrate, cobalt sulfate or its hydrate, cobalt nitrate or its hydrate, cobalt acetate or its hydrate and cobalt oxalate or its hydrate, and the cobalt salt is added in the form of a cobalt salt aqueous solution, wherein the mass concentration of cobalt ions in the cobalt salt aqueous solution is 35 to 55 g / L; and / or The first ligand is one or more of PVA-105, PVA-124, PVA-350, PVA-1788, PVA-1797 and PVA-1799, the first ligand is added in the form of a first ligand aqueous solution, and the mass concentration of the first ligand aqueous solution is 25-55 g / L; and / or The second ligand is one or more of p-aminobenzoic acid, o-aminobenzoic acid, p-aminobenzenesulfonic acid and o-aminobenzenesulfonic acid. The second ligand is added in the form of a second ligand alcohol solution. The mass concentration of the second ligand alcohol solution is 110-150g / L. The second ligand alcohol solution is an ethanol solution.

3. The preparation method according to claim 1 or 2, characterized in that: In the step S1, the mass ratio of the Co atoms in the cobalt salt, the first ligand and the second ligand is 1:(0.6-1.3):(2.2-3.3).

4. The preparation method according to claim 3, characterized in that: In the step S1, the cobalt salt, the first ligand and the second ligand are mixed and heated to carry out the reaction, and the heating temperature is 80-95°C.

5. The preparation method according to claim 1 or 2, characterized in that: In the step S2, the sintering temperature of the pre-sintering is 500-600°C, the sintering time is 2-5h, the heating rate is 1-4°C / min, and the sintering atmosphere is nitrogen atmosphere and / or argon atmosphere.

6. The preparation method according to claim 5, characterized in that: In the step S2, the particle size of the CoO nanoparticles is 50-100 nm.

7. The preparation method according to claim 1 or 2, characterized in that: In step S3, the lithium source is one or more of lithium hydroxide or its hydrate, lithium acetate or its hydrate, lithium oxalate or its hydrate, lithium sulfate or its hydrate, lithium nitrate or its hydrate, lithium carbonate and lithium oxide.

8. The preparation method according to claim 7, characterized in that: In the step S3, the molar ratio of Co atoms in the CoO nanoparticles to Li atoms in the lithium source is 1:(4.8-6.4).

9. The preparation method according to claim 8, characterized in that: In the step S3, the molar ratio of Co atoms in the CoO nanoparticles to Li atoms in the lithium source is 1:(5.4-6.4).

10. The preparation method according to claim 1 or 2, characterized in that: The sintering temperature of the first sintering is 600-900°C, the sintering time is 10-14h, the heating rate is 1-4°C / min, the sintering atmosphere is a nitrogen atmosphere and / or an argon atmosphere, and the oxygen content in the sintering atmosphere is 10-20ppm; the first sintering is followed by cooling to obtain the first sintered material; and / or The sintering temperature of the second sintering is 600-900° C., the sintering time is 10-14 hours, the heating rate is 1-4° C. / min, the sintering atmosphere is a nitrogen atmosphere and / or an argon atmosphere, and the oxygen content in the sintering atmosphere is 10-20 ppm; the second sintering is followed by cooling to obtain the positive electrode self-lithium supplementing agent; In the sintering atmospheres of the first sintering and the second sintering, the ratio of the oxygen content is (0.8-1.2):

1.

11. The preparation method according to claim 1, characterized in that: In the positive electrode self-replenishing lithium agent, the mass percentage of Li6CoO4 is ≥96%, and the mass percentage of residual alkali is ≤2.5%.

12. The preparation method according to claim 1, characterized in that: The particle size of the positive electrode self-replenishing lithium agent is 3 to 10 μm.

13. A positive electrode self-replenishing lithium agent, characterized in that: Obtained by the preparation method according to any one of claims 1 to 12.

14. A positive electrode sheet, comprising a positive electrode material and a positive electrode self-replenishing lithium agent, characterized in that: The positive electrode self-lithium replenishing agent is the positive electrode self-lithium replenishing agent according to claim 13.

15. A lithium ion battery, comprising a positive electrode plate, characterized in that: The positive electrode sheet is the positive electrode sheet according to claim 14.

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