Lithium-supplementing positive electrode material, and preparation method therefor and use thereof

Abstract

The present application provides a lithium-supplementing positive electrode material, and a preparation method therefor and a use thereof. The lithium-supplementing positive electrode material comprises an active material core and a coating layer coating the surface of the active material core. The coating layer comprises lithium-supplementing particles and carbon; the active material core includes one or more of LixFeyPO4 and LiFezMn1-zPO4, wherein 0.9≤x≤1.1, 0.9≤y≤1.1, and 0<z<1; and the lithium-supplementing particles include LiaMbOc, wherein M is selected from one or more of Fe, Mn, Ni, Zr, Co, Cr, and Cu, 0<a≤6, 0<b≤3, and 0<c≤5.

Description

A lithium supplement positive electrode material, a preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202411337178.5, filed on September 24, 2024, and entitled "A lithium supplement positive electrode material, a preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] Embodiments of the present application relate to the technical field of lithium ion batteries, in particular to a lithium supplement positive electrode material, a preparation method and application thereof. BACKGROUND

[0003] Lithium supplement technology is an effective means to improve the energy density of lithium ion batteries while improving the cycle life and energy storage performance of the battery. The existing commonly used lithium supplement technologies include negative electrode lithium supplement, positive electrode lithium supplement, electrolyte lithium supplement, separator lithium supplement, current collector lithium supplement and electrochemical lithium supplement. Among them, positive electrode lithium supplement is one of the most commonly used methods. Currently, the method for positive electrode lithium supplement is usually to add a lithium supplement agent directly into the positive electrode slurry during the homogenizing process, which will result in poor contact between the lithium supplement agent and the positive electrode active material particles, leading to a high decomposition voltage, and thus causing problems such as gas production after the battery is supplemented with lithium. In addition, the residual lithium supplement agent residues in the positive electrode sheet in a high oxidation state will increase the risk of side reactions when in contact with the electrolyte, thereby increasing the risk of gas production during the use of the battery, especially in high temperature environments. SUMMARY

[0004] In view of this, the present application provides a lithium supplement positive electrode material, a preparation method and application thereof. The lithium supplement positive electrode material is prepared by in-situ compounding lithium supplement particles in the core of the positive electrode active material, so that the size of the lithium supplement particles in the lithium supplement positive electrode material is much smaller than that of the lithium supplement agent commonly added in the positive electrode active slurry, thereby effectively reducing the risk of gelation of the positive electrode active slurry caused by residual alkali on the surface of the lithium supplement agent, and effectively improving the electronic and ionic conduction capabilities of the lithium supplement positive electrode material. In addition, the carbon-containing coating layer can effectively slow down the rate of water absorption failure of the lithium supplement particles. Furthermore, the structure of the lithium supplement positive electrode material can also effectively reduce the decomposition voltage, thereby solving the problem of gas production during the later use of the battery, and thus improving the rate performance and cycle performance of the battery.

[0005] The first aspect of the present application provides a lithium supplement positive electrode material, which comprises an active material core and a coating layer coated on the surface of the active material core, the coating layer comprising lithium supplement particles and carbon; the active material core comprises Li x Fe y PO4 and LiFe z Mn 1-zone or more of PO4, wherein 0.9≤x≤1.1, 0.9≤y≤1.1, 0<z<1; the lithium supplementing particles comprise Li a M b O c , wherein M is selected from one or more of Fe, Mn, Ni, Zr, Co, Cr and Cu, 0

[0006] In the embodiments of the present application, the carbon is coated on the surface of the active material core and / or the surface of the lithium supplementing particles.

[0007] In the embodiments of the present application, at least part of the lithium supplementing particles are grown in situ on the surface of the active material core.

[0008] In the embodiments of the present application, the mass ratio of the lithium supplementing particles to the active material core is (0.1-10):100.

[0009] In the embodiments of the present application, the mass percentage of the carbon in the lithium supplementing positive electrode material is 0.1%-5%.

[0010] In the embodiments of the present application, the particle size of the active material core is 0.1 μm-15 μm; and the particle size of the lithium supplementing particles is 0.1 μm-12 μm.

[0011] In the embodiments of the present application, the specific surface area of the lithium supplementing positive electrode material is 3 m 2 / g-20 m 2 / g.

[0012] The second aspect of the present application provides a preparation method of the lithium supplementing positive electrode material provided in the first aspect, comprising:

[0013] mixing a lithium source, a phosphorus source, an iron source, a carbon source and an M metal source to obtain a lithium supplementing positive electrode material precursor; or mixing a lithium source, a phosphorus source, an iron source, a carbon source, a manganese source and an M metal source to obtain a lithium supplementing positive electrode material precursor;

[0014] sintering the lithium supplementing positive electrode material precursor in sections to obtain a lithium supplementing positive electrode material.

[0015] In the embodiments of the present application, the sintering in sections comprises first sintering treatment and second sintering treatment performed in sequence; the sintering temperature of the first sintering treatment is 450-750 ℃, and the sintering time is 3-18 h; the sintering temperature of the second sintering treatment is 750-1000 ℃, and the sintering time is 4-36 h; the temperature of the second sintering treatment is higher than that of the first sintering treatment.

[0016] In the embodiments of the present application, the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium nitrate, lithium oxide, lithium peroxide and lithium acetate.

[0017] In the embodiments of the present application, the phosphorus source includes one or more of lithium dihydrogen phosphate, ferric phosphate, ammonium phosphate, sodium dihydrogen phosphate, lithium monohydrogen phosphate, lithium phytate and sodium tripolyphosphate.

[0018] In the embodiments of the present application, the iron source includes one or more of ferrous oxide, diiron trioxide, ferric nitrate, ferric phosphate, ferrous oxalate and ferrous sulfate.

[0019] The carbon source includes one or more of sugar, high-molecular organic matter and conductive carbon, and specifically includes one or more of glucose, sucrose, fructose, chitosan, lignin, carboxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, phenol formaldehyde resin, needle coke, petroleum coke, pitch coke, pitch, polystyrene, polyphenylacetylene, carbon black, acetylene black, super-P, carbon nanotube, graphene, ketjen black and vapor grown carbon fiber.

[0020] The manganese source includes one or more of trimanganese tetraoxide, manganese sulfate, manganese oxalate, manganese carbonate, manganese dioxide and manganese acetate.

[0021] The third aspect of the present application further provides a positive electrode sheet, which includes a current collector and a positive electrode active layer loaded on the current collector, and the positive electrode active layer includes the lithium supplementing positive electrode material provided in the first aspect or the lithium supplementing positive electrode material prepared by the preparation method provided in the second aspect.

[0022] The fourth aspect of the present application provides a lithium ion battery, which includes the positive electrode sheet provided in the third aspect of the present application.

[0023] The fifth aspect of the present application provides an electric device, which includes the lithium ion battery provided in the fourth aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0024] FIG. 1 is a schematic diagram of the cross-sectional structure of the lithium supplementing positive electrode material provided in an embodiment of the present application;

[0025] FIG. 2 is a schematic diagram of the cross-sectional structure of the lithium supplementing positive electrode material provided in another embodiment of the present application.

[0026] REFERENCE NUMERALS 100 - lithium supplementing positive electrode material; 101 - active material core; 102 - lithium supplementing particle; 103 - carbon. DETAILED DESCRIPTION

[0027] The present application will be further described in detail below in combination with preferred embodiments, but the scope of protection of the present application is not limited to the following specific embodiments.

[0028] In the present application, all the professional terms have the same meaning as generally understood by those skilled in the art, and the professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present application.

[0029] Lithium supplement technology is an effective means to improve the energy density of lithium ion batteries while improving the cycle life and energy storage performance of the batteries. The commonly used lithium supplement technologies include negative electrode lithium supplement, positive electrode lithium supplement, electrolyte lithium supplement, separator lithium supplement, current collector lithium supplement, and electrochemical lithium supplement. Among them, positive electrode lithium supplement is one of the most commonly used means. Currently, the method for positive electrode lithium supplement is usually to directly add a lithium supplement agent into the positive electrode slurry during the homogenizing process, which will result in poor contact between the lithium supplement agent and the positive electrode active material particles, leading to a high decomposition voltage, and thus causing problems such as gas production after lithium supplement of the battery. In addition, the residual lithium supplement agent residues in a high oxidation state remaining in the positive electrode sheet will increase the risk of side reactions when in contact with the electrolyte, thereby increasing the risk of gas production during the use of the battery, especially in a high temperature environment.

[0030] To solve the above problems, the present application provides a lithium supplement positive electrode material, a preparation method and application thereof. The lithium supplement positive electrode material is prepared by in-situ compounding lithium supplement particles in the core of the positive electrode active material, which can effectively reduce the risk of gelation of the positive electrode active slurry caused by residual alkali on the surface of the lithium supplement agent, and can effectively improve the electronic and ionic conductivity of the lithium supplement positive electrode material. In addition, the structure of the lithium supplement positive electrode material can effectively solve the problem of gas production during the later use of the battery, thereby improving the rate performance and cycle performance of the battery.

[0031] Referring to FIG. 1, the present application provides a lithium supplement positive electrode material 100, which includes an active material core 101 and a coating layer covering the surface of the active material core 101, wherein the coating layer includes lithium supplement particles 102 and carbon 103. In the embodiments of the present application, the active material core 101 includes Li x Fe y PO4and LiFe z Mn 1-z PO4, wherein 0.9≤x≤1.1, 0.9≤y≤1.1, and 0<z<1. In some specific embodiments, x may, for example, be 0.9, 0.95, 1, 1.05, or 1.1; y may, for example, be 0.9, 0.95, 1, 1.05, or 1.1; and z may, for example, be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9. In the embodiments of the present application, the lithium supplement particles 102 include Li a M b O cwherein M is selected from one or more of Fe, Mn, Ni, Zr, Co, Cr, and Cu, 0 < a < 6, 0 < b < 3, 0 < c < 5. In some embodiments, a can be, for example, 1, 2, 3, 4, 5, 6; b can be, for example, 0, 1, 2, 3; c can be, for example, 1, 2, 3, 4. The lithium supplementing cathode material of the present application provides the function of supplementing lithium by in-situ compounding lithium supplementing particles in the core of the cathode active material, without affecting the energy density of the active material core 101. Compared with the common method of supplementing lithium by directly adding a lithium supplementing agent to the active slurry, the lithium supplementing particles 102 are compounded with the active material core 101 in an in-situ growth manner, which can effectively improve the contact between the lithium supplementing particles 102 and the active material core 101, on the one hand, can effectively reduce the decomposition voltage required for decomposition polarization, effectively avoid the gas production problem of the battery during the cyclic use process, and also reduce the risk of molten iron residue of the lithium supplementing particles after decomposition, thereby improving the service life and safety performance of the battery, on the other hand, can effectively shorten the electron transport path and lithium ion transport path, and improve the electronic conductivity and ionic conductivity of the lithium supplementing cathode material 100. Moreover, the lithium supplementing particles of the present application adopt lithium-rich metal oxides, which can release part of oxygen or oxygen radicals during the decomposition of lithium supplementing process, which can improve the low temperature performance of the battery to a certain extent and reduce its impedance. In addition, the coating layer containing carbon 103 at least partially wraps the lithium supplementing particles 102, which can to a certain extent play a role in isolating the lithium supplementing particles 102 from the external environment, thereby effectively reducing the risk of gel phenomenon of the positive active slurry caused by residual alkali on the surface of the lithium supplementing particles, and also can shield the moisture in the environment from attacking the lithium supplementing particles, effectively slowing down the rate of water absorption failure of the lithium supplementing particles 102, thereby widening the application scenarios of the lithium supplementing cathode material and reducing the production cost.

[0032] In the embodiments of the present application, at least part of the lithium supplementing particles 102 are in-situ grown on the surface of the active material core 101. In the present application, in-situ growth refers to that, under the condition of one-time sintering, the lithium supplementing particles 102 are distributed around the active material core 101 and are in close physical proximity to the active material core 101, and the lithium supplementing particles 102 and the active material core 101 form the form of secondary particles.

[0033] In some embodiments of the present application, the structure of the lithium supplementing cathode material 100 is shown in FIG. 1, which includes an active material core 101, lithium supplementing particles 102 combined on the surface of the active material core 101, and a carbon 103 coating layer coated on the surface of the active material core 101 and / or the surface of the lithium supplementing particles 102, wherein the lithium supplementing particles 102 are in-situ grown on the surface of the active material core 101. In some embodiments of the present application, the lithium supplementing particles 102 are in direct contact with the surface of the active material core 101. The lithium supplementing particles in the lithium supplementing cathode material of this structure are larger in size, which further makes the specific surface area of the lithium supplementing cathode material smaller, and the stability of the lithium supplementing cathode material better.

[0034] In some other embodiments of the present application, the structure of the lithium supplementing cathode material 100 is shown in FIG. 2, which includes an active material core 101, and a coating layer coated on the surface of the active material core 101, wherein the coating layer includes lithium supplementing particles 102 and carbon 103, and the lithium supplementing particles 102 are distributed inside the coating layer formed by the carbon 103. In some embodiments of the present application, the lithium supplementing particles 102 are not in direct contact with the surface of the active material core 101, but are connected to the surface of the active material core 101 through the carbon 103.

[0035] In some embodiments of the present application, the carbon 103 is coated on the surface of the active material core 101 and / or the lithium supplementing particles 102. In some embodiments of the present application, the coating of the carbon 103 on the active material core 101 and the lithium supplementing particles 102 can be complete coating or incomplete coating. Through the coating of the carbon 103, the lithium supplementing cathode material 100 of the present application effectively reduces the contact area of the lithium supplementing particles 102 with air, which further reduces the rate of water absorption failure of the lithium supplementing particles 102 and effectively avoids the agglomeration, gelation and other phenomena caused by the mixing of residual alkali on the surface of the lithium supplementing particles with the positive active paste, thereby improving the utilization rate and service life of the lithium supplementing particles and reducing the cost of preparation, and further improving the electrochemical performance of the battery product. The coating of the carbon 103 can also optimize the conductive network structure of the lithium supplementing cathode material, ensure the electron path of the lithium supplementing particles 102 and the active material core 101, improve the lithium supplementing efficiency of the lithium supplementing particles 102, ensure the conductivity of the lithium supplementing cathode material 100, and further improve the lithium ion deintercalation path of the lithium supplementing particles 102 and the active material core 101, improve the ionic conductivity of the lithium supplementing cathode material 100, and further improve the comprehensive electrochemical performance of the battery. Moreover, through the coating of the carbon 103, the active material core 101 and the lithium supplementing particles 102 are more closely combined, the electrochemical environment around the residues after the decomposition of the lithium supplementing particles during charging is more stable, which is conducive to inhibiting the molten iron phenomenon, and further improving the safety of the lithium supplementing cathode material.

[0036] In the embodiments of the present application, the mass ratio of the lithium supplement particles 102 and the active material core 101 is (0.1-10):100. In some specific embodiments, the mass ratio of the lithium supplement particles 102 and the active material core 101 may, for example, be 0.1:100, 0.2:100, 0.3:100, 0.5:100, 0.8:100, 1:100, 2:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, 9:100, or 10:100. By controlling the mass ratio of the lithium supplement particles and the active material core within a suitable range, the present application can enable the lithium supplement positive electrode material to have a higher specific capacity while improving the utilization rate of the lithium supplement particles, effectively avoiding the waste of lithium supplement particles and the side reactions caused by excessive lithium supplement particles, so that the lithium supplement positive electrode material has better comprehensive performance and meets the application requirements of different scenarios.

[0037] In the embodiments of the present application, the mass percentage of carbon 103 in the lithium supplement positive electrode material 100 is 0.1%-5%. In some specific embodiments, the mass percentage of carbon 103 in the lithium supplement positive electrode material 100 may, for example, be 0.1%, 0.2%, 0.3%, 0.5%, 0.6%, 0.8%, 1%, 2%, 3%, 4%, or 5%. By reasonably controlling the carbon content in the lithium supplement positive electrode material, the present application can further control the thickness of the coating layer and comprehensively adjust the coating mode and degree of carbon 103 on the active material core 101 and the lithium supplement particles 102, thereby regulating the power performance, cycle performance, and storage performance of the battery and meeting different requirements of the battery.

[0038] In the embodiments of the present application, the particle size of the active material core 101 is 0.1-15 μm. In some specific embodiments, the particle size of the active material core 101 may, for example, be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, or 15 μm. In some embodiments of the present application, the particle size of the active material core 101 is 0.1-10 μm. In some embodiments, the particle size of the active material core 101 is 0.2-5 μm. In the embodiments of the present application, the particle size of the active material core 101 may be the particle size of primary particles or the particle size of secondary particles formed by agglomeration of primary particles. In the present application, the particle size specifically refers to the median particle size D50, i.e., DV50, which refers to the particle size corresponding to the cumulative particle size distribution percentage of 50% of the measured sample, and the physical meaning is that the particles with a particle size greater than it account for 50%, and the particles with a particle size less than it also account for 50%.

[0039] In some embodiments of the present application, the particle size of the lithium supplementing particles 102 is 0.1 μm-12 μm. In some specific embodiments, the particle size of the lithium supplementing particles 102 can be, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 8 μm, 10 μm, or 12 μm. In some embodiments of the present application, the particle size of the lithium supplementing particles 102 is 0.1 μm-10 μm. In some embodiments, the particle size of the lithium supplementing particles 102 is 0.2 μm-5 μm. In some embodiments of the present application, the particle size of the lithium supplementing particles 102 can be the particle size of primary particles or the particle size of secondary particles formed by agglomeration of primary particles. Currently commonly used lithium supplementing agents usually have a particle size that is one order of magnitude larger than that of the positive electrode active material, which causes the lithium supplementing agent to shrink after decomposition, resulting in the formation of a collapse cavity around the lithium supplementing agent particles, and further causing the deterioration of the electrical contact between the positive electrode active materials in the positive electrode sheet. The lithium supplementing particles 102 of the present application have a particle size that is about one order of magnitude smaller than that of the conventional lithium supplementing agent particles directly added to the positive electrode active slurry, which effectively shortens the migration path of lithium ions and enhances the ion transport capacity of the lithium supplementing positive electrode material; and effectively increases the interface area of the lithium supplementing particles and reduces the upper limit voltage of the lithium supplementing particles during the first charge decomposition process. In addition, since the decomposition polarization of the lithium supplementing particles during the first charge is effectively alleviated, the current density during the decomposition process is improved, thereby effectively shortening the decomposition time of the lithium supplementing particles, and further reducing the side reactions caused by high voltage environment and improving the production efficiency of the battery.

[0040] In some embodiments of the present application, the particle size of the active material core 101 and the lithium supplementing particles 102 can be the same or different; the particle size of the active material core 101 can be larger or smaller than that of the lithium supplementing particles 102. By controlling the particle size of the active material core and the lithium supplementing particles within a suitable range, the processing of the lithium supplementing positive electrode material particles is facilitated, the processing stability of the slurry during the preparation of the slurry is improved, and the specific capacity and rate performance of the lithium supplementing positive electrode material are further improved and the decomposition voltage is further reduced.

[0041] In some embodiments of the present application, the specific surface area of the lithium supplementing positive electrode material 100 is 3 m 2 / g-20 m 2 / g. In some specific embodiments, the specific surface area of the lithium supplementing positive electrode material 100 can be, for example, 3 m 2 / g, 5 m 2 / g, 6 m 2 / g, 8 m 2 / g, 10 m 2 / g, 12 m 2 / g, 14 m 2 / g, 15m 2 / g, 16m 2 / g, 18m 2 / g, 20m 2 / g. In some embodiments, the specific surface area of the lithium supplementing cathode material 100 can be 5m 2 / g-18m 2 / g. By controlling the particle size of the active material inner core and the lithium supplementing particles within a suitable range, and further controlling the specific surface area of the lithium supplementing cathode material within a suitable range, the stability of the lithium supplementing cathode material can be further improved, and the cycle performance and service life of the battery can be improved.

[0042] The lithium supplementing cathode material provided in the present application can effectively avoid the gelation of the cathode active slurry, and improve the electronic conductivity and ionic conductivity of the lithium supplementing cathode material, by special design of the structure of the lithium supplementing cathode material, in-situ compounding of the lithium supplementing particles and the active material inner core, and coating with carbon. In addition, the structure of the lithium supplementing cathode material can effectively reduce the decomposition voltage, thereby solving the gas production problem of the battery in the later use process, and further improving the cycle performance, service life and safety performance of the battery.

[0043] The present application also provides a preparation method of the lithium supplementing cathode material provided in the foregoing.

[0044] S101, mixing a lithium source, a phosphorus source, an iron source, a carbon source and an M metal source to obtain a lithium supplementing cathode material precursor; or, mixing a lithium source, a phosphorus source, an iron source, a carbon source, a manganese source and an M metal source to obtain a lithium supplementing cathode material precursor;

[0045] S102, segmentally sintering the lithium supplementing cathode material precursor to obtain a lithium supplementing cathode material.

[0046] In step S101, the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium nitrate, lithium oxide, lithium peroxide and lithium acetate; the phosphorus source includes one or more of lithium dihydrogen phosphate, iron phosphate, ammonium phosphate, sodium dihydrogen phosphate, lithium monohydrogen phosphate, lithium phytate and sodium tripolyphosphate; the iron source includes one or more of ferrous oxide, diiron trioxide, iron nitrate, iron phosphate, ferrous oxalate and ferrous sulfate; the carbon source includes one or more of sugar, high molecular organic matter and conductive carbon, and specifically includes one or more of glucose, sucrose, fructose, chitosan, lignin, carboxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, phenol formaldehyde resin, needle coke, petroleum coke, pitch coke, pitch, polystyrene, polyphenylacetylene, carbon black, acetylene black, super-P, carbon nanotube, graphene, ketjen black and vapor grown carbon fiber; and the manganese source includes one or more of trimanganese tetraoxide, manganese sulfate, manganese oxalate, manganese carbonate, manganese dioxide and manganese acetate.

[0047] In some embodiments of the present application, the preparation raw materials of the lithium supplementing cathode material precursor include a lithium source, a phosphorus source, an iron source, a carbon source, and an M metal source. The active material core of the prepared lithium supplementing cathode material is Li x Fe y PO4, 0.9≤x≤1.1, 0.9≤y≤1.1. In embodiments of the present application, the feeding ratio of the lithium source, the phosphorus source, the iron source, the carbon source, and the M metal source is (1-1.2):(0.9-1.1):(0.9-1.1):(0.05-0.1):(0.01-0.05).

[0048] In some other embodiments of the present application, the preparation raw materials of the lithium supplementing cathode material precursor include a lithium source, a phosphorus source, an iron source, a carbon source, a manganese source, and an M metal source. The active material core of the prepared lithium supplementing cathode material is Li z Mn 1-z PO4, 0<z<1. In embodiments of the present application, the feeding ratio of the lithium source, the phosphorus source, the iron source, the carbon source, the manganese source, and the M metal source is (1-1.2):(0.9-1.1):(0.4-0.6):(0.05-0.1):(0.4-0.6):(0.01-0.05).

[0049] In embodiments of the present application, the M metal source is selected from one or more of an iron source, a manganese source, a nickel source, a zirconium source, a cobalt source, and a copper source. In embodiments of the present application, the M metal source includes but is not limited to one or more of an oxide, a hydroxide, a sulfate, an acetate of M.

[0050] In embodiments of the present application, the mixing method includes but is not limited to ball milling.

[0051] In step S102, the sequentially performed segmental sintering includes a first sintering treatment and a second sintering treatment. In embodiments of the present application, the sintering temperature of the first sintering treatment is 450-750°C, and the sintering time is 3-18h. In some specific embodiments, the sintering temperature of the first sintering treatment can be, for example, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C; and the sintering time can be, for example, 3h, 5h, 6h, 9h, 10h, 12h, 15h, 18h. By controlling the temperature and time of the first sintering treatment within a suitable range, the present application can make the active material core particles from the lithium source, the phosphorus source, and the iron source. In embodiments of the present application, the first sintering treatment is performed in a protective atmosphere, which includes but is not limited to a nitrogen atmosphere or an argon atmosphere. The oxygen source of the active material core particles and the lithium supplementing particles in the present application comes from at least one of the lithium source, the phosphorus source, the iron source, the carbon source, and the M metal source.

[0052] In the embodiments of the present application, the sintering temperature of the second sintering treatment is 750-1000°C, and the sintering time is 4-36 h. In some specific embodiments, the sintering temperature of the second sintering treatment can be, for example, 750°C, 800°C, 850°C, 900°C, 950°C, or 1000°C; and the sintering time can be, for example, 4 h, 5 h, 8 h, 10 h, 12 h, 15 h, 16 h, 20 h, 24 h, 28 h, 30 h, 32 h, or 36 h. By controlling the temperature and time of the second sintering treatment within a suitable range, the present application can in-situ composite the lithium supplement particles with the active material core particles prepared, and at this temperature, the carbon source can play a reducing role on one hand, and can also obtain a carbon coating layer on the surface of the lithium supplement positive electrode material on the other hand. In some embodiments, the phosphorus source used to prepare the active material core can be doped into the lithium supplement particles to obtain phosphorus-doped lithium supplement particles, which further reduces the polarization effect in the decomposition process of the lithium supplement particles, and further improves the conductivity and stability of the lithium supplement particles. In the embodiments of the present application, the second sintering treatment is carried out in a protective atmosphere, which includes but is not limited to a nitrogen atmosphere or an argon atmosphere.

[0053] In the embodiments of the present application, the temperature of the second sintering treatment is higher than the temperature of the first sintering treatment. By using two-stage sintering, the present application can obtain the lithium supplement positive electrode material in which the lithium supplement particles coated with carbon are in-situ combined with the active material core in the same sintering equipment, without using two sets of sintering equipment, thereby reducing the cost of synthesizing the lithium supplement particles. In the present application, the active material core can be first formed at the first sintering temperature, and then the temperature is continuously increased to the second sintering temperature, so that the lithium supplement particles and the carbon coating layer can be in-situ combined on the basis of the active material core.

[0054] In the embodiments of the present application, the lithium supplement positive electrode material prepared in step S102 can include one or more of the lithium supplement positive electrode material 100 shown in FIG. 1 and the lithium supplement positive electrode material shown in FIG. 2. In some specific embodiments, the lithium supplement positive electrode material prepared in step S102 can include both the lithium supplement positive electrode material 100 shown in FIG. 1 and the lithium supplement positive electrode material shown in FIG. 2.

[0055] The method for preparing the lithium supplement positive electrode material provided by the present application can in-situ combine the lithium supplement particles with the active material core and coat the lithium supplement particles with carbon by controlling the feeding ratio of each raw material within a suitable range and through two-stage sintering treatment. The size of the lithium supplement particles of the lithium supplement positive electrode material is much smaller than that of the conventional lithium supplement agent, the lithium supplement positive electrode material prepared has lower requirements for the feeding and coating process of the positive electrode preparation and is less likely to cause gelation in the preparation of the slurry, thereby shortening the preparation process, reducing the production cost, and improving the yield of the finished product.

[0056] The application also provides a positive electrode sheet, which comprises a current collector and a positive electrode active layer loaded on the current collector, wherein the positive electrode active layer comprises the lithium supplementing positive electrode material provided in the foregoing or is prepared by the preparation method provided in the foregoing. In the embodiments of the application, the positive electrode active layer further comprises a binder and a conductive agent. In the embodiments of the application, the conductive agent can be any conductive agent known in the art, including but not limited to one or more of super P-Li, super P, acetylene black, graphene and carbon nanotube. In the embodiments of the application, the binder can be any binder known in the art, including but not limited to polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene oxide (PEO) and polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and the like.

[0057] The application also provides a lithium ion battery, which comprises a positive electrode sheet, a negative electrode sheet, and a separator and an electrolyte between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet comprises the positive electrode sheet provided in the foregoing. In the embodiments of the application, the separator comprises but is not limited to a high molecular polymer film. In the embodiments of the application, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active layer arranged on the negative electrode current collector, and the negative electrode active material in the negative electrode material layer can be any negative electrode active material for a lithium ion battery known in the art. In the embodiments of the application, the negative electrode active material in the negative electrode material layer can be any negative electrode active material for a lithium ion battery known in the art. Exemplarily, the negative electrode active material can be selected from one or more of a carbon-based negative electrode active material, a silicon-based negative electrode active material, a tin-based negative electrode active material and a lithium metal negative electrode active material. Among them, the carbon-based negative electrode includes but is not limited to natural graphite, artificial graphite, hard carbon, soft carbon, graphene; the silicon-based negative electrode includes but is not limited to silicon, silicon-carbon, silicon-oxygen and the like; the tin-based negative electrode includes but is not limited to tin, tin-carbon, tin-oxygen, tin metal compounds.

[0058] The application also provides an electric device comprising the lithium ion battery described in the foregoing. The electric device can be, for example, an electric vehicle, a mobile phone, a tablet computer, a notebook computer, a wearable device (watch, bracelet), a digital camera and the like.

[0059] The application is further described in the following embodiments:

[0060] Embodiment 1

[0061] Lithium carbonate, iron phosphate, diiron trioxide and glucose with a molar ratio of 1.1:2:0.02:0.05 were weighed and mixed to obtain a lithium supplementing positive electrode material precursor;

[0062] The obtained lithium supplementing positive electrode material precursor is subjected to segmented sintering, first a first sintering treatment at 650 ℃ for 12 h, and then a second sintering treatment at 850 ℃ for 8 h, to obtain a lithium supplementing positive electrode material, the active material core of the lithium supplementing positive electrode material being LiFePO4, and the lithium supplementing particle being Li5FeO4.

[0063] The prepared lithium supplementing positive electrode material is dissolved in an N-methyl pyrrolidone solvent to prepare a positive electrode slurry, the obtained positive electrode slurry is uniformly coated on an aluminum foil and vacuum dried to obtain a lithium supplementing positive electrode sheet.

[0064] Example 2

[0065] The difference from Example 1 is that the raw materials of the lithium supplementing positive electrode material precursor are lithium carbonate, iron phosphate, cobalt oxide and glucose in a molar ratio of 1.12:2:0.02:0.05, the active material core of the lithium supplementing positive electrode material is LiFePO4, and the lithium supplementing particle is Li6CoO4.

[0066] Example 3

[0067] The difference from Example 1 is that the raw materials of the lithium supplementing positive electrode material precursor are lithium carbonate, iron phosphate, copper oxide and glucose in a molar ratio of 1.05:2:0.05:0.05, the active material core of the lithium supplementing positive electrode material is LiFePO4, and the lithium supplementing particle is Li2CuO2.

[0068] Example 4

[0069] The difference from Example 1 is that the raw materials of the lithium supplementing positive electrode material precursor are lithium carbonate, iron phosphate, manganese phosphate, diiron trioxide and glucose in a molar ratio of 1.1:0.8:1.2:0.02:0.08, the active material core of the lithium supplementing positive electrode material is LiFePO4, and the lithium supplementing particle is Li5FeO4. 0.4 Mn 0.6 PO4.

[0070] Example 5

[0071] The difference from Example 1 is that the molar ratio of lithium carbonate, iron phosphate, diiron trioxide and glucose is 1.2:2:0.04:0.05, the active material core of the lithium supplementing positive electrode material is LiFePO4, and the lithium supplementing particle is Li5FeO4.

[0072] Example 6

[0073] The difference from Example 1 is that the molar ratio of lithium carbonate, iron phosphate, diiron trioxide and glucose is 1.05:2:0.01:0.05, the active material core of the lithium supplementing positive electrode material is LiFePO4, and the lithium supplementing particle is Li5FeO4.

[0074] Example 7

[0075] The difference from Example 1 is that the temperature of the first sintering treatment is 600℃, and the time is 8h; the temperature of the second sintering treatment is 900℃, and the time is 4h; the active material core of the lithium supplementing positive electrode material is LiFePO4, and the lithium supplementing particle is Li5FeO4.

[0076] Comparative Example 1

[0077] 100 parts by weight of the lithium iron phosphate slurry prepared by dissolving the active material lithium iron phosphate in N-methyl pyrrolidone solvent was weighed, and 2 parts by weight of the lithium supplementing agent Li5FeO4 was added to the lithium iron phosphate slurry, and stirred uniformly to obtain a positive electrode slurry. The obtained positive electrode slurry was uniformly coated on an aluminum foil and vacuum dried to obtain a lithium supplementing positive electrode sheet.

[0078] Performance detection

[0079] Specific surface area: the lithium supplementing positive electrode materials of Examples 1-7 were tested according to the national standard “Gas adsorption BET method for determining the specific surface area of solid substances” (GB / T 19587-2017), and the specific surface area was measured. The results are shown in Table 1.

[0080] Particle size Dv50: the particle size of the active material core and the lithium supplementing particle of Examples 1-7 and the active material of Comparative Example 1 was tested by using a laser particle size distribution instrument. The measured particle size Dv50 is shown in Table 1.

[0081] The lithium supplementing positive electrode sheets prepared in Examples 1-7 and Comparative Example 1 were combined with a negative electrode, a separator, and an electrolyte to form a soft package battery.

[0082] Gas production performance: the soft package batteries prepared in Examples 1-7 and Comparative Example 1 were adjusted to 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, and 0% SOC, respectively. After 28 days of storage at 60℃, the battery weight was tested by the drainage method. The gas production performance of the battery was calculated and counted by the weight difference. The results are shown in Table 1.

[0083] Cycle performance: the soft package batteries prepared in Examples 1-7 and Comparative Example 1 were cycled at 45℃, 0.5C CC-CV to 3.7V cutoff current of 0.05C charging condition, and 0.5C discharging to 2.3V. After 1000 cycles, the battery capacity retention rate relative to the battery capacity before cycling was observed. The results are shown in Table 1.

[0084] Rate performance: the soft package batteries prepared from Example 1-Example 7 and Comparative Example 1 were tested at 25℃, 0.5C CC-CV to 3.7V cutoff current was 0.05C charging condition, 0.1C discharge to 2.3V, the capacity was recorded as C1; at 25℃, 0.5C CC-CV to 3.7V cutoff current was 0.05C charging condition, 2C discharge to 2.3V, the capacity was recorded as C2; the calculation formula of 2C / 0.1C capacity retention rate was: C2 / C1*100%, the results are shown in Table 1.

[0085] Table 1

[0086] As can be seen from Table 1, compared with Comparative Example 1 which directly adds lithium supplement particles in the active slurry, the lithium supplement particles in the lithium supplement positive electrode material of the present application are coated by carbon material, and the lithium supplement particles are in-situ compounded in the core of the positive electrode active material, so that the particle size of the lithium supplement particles is significantly reduced, the risk of gelation of the positive electrode active slurry caused by residual alkali on the surface of the lithium supplement particles is effectively reduced, the electronic conductivity and ionic conductivity of the lithium supplement positive electrode material are improved, the decomposition voltage of the lithium supplement positive electrode material is reduced, the gas production of the battery is reduced, and the cycle performance and rate performance of the battery are improved.

[0087] Example 1-Example 7 by in-situ compounding lithium supplement particles in the core of the positive electrode active material and coating with carbon material, significantly reduces the particle size of the lithium supplement particles, effectively reduces the risk of gelation of the positive electrode active slurry caused by residual alkali on the surface of the lithium supplement particles, and can improve the electronic conductivity and ionic conductivity of the lithium supplement positive electrode material, also reduces the decomposition voltage, reduces the gas production of the battery, and further improves the cycle performance and rate performance of the battery.

[0088] The preferred embodiments are described in detail above, but the present application is not limited to the above specific embodiments, and those skilled in the art can make various specific modifications under the inspiration of the present application without departing from the scope of the present application, which are all within the scope of protection of the present application.

Claims

1. A lithium supplemented cathode material, wherein, The lithium supplementing cathode material comprises an active material inner core and a coating layer coated on the surface of the active material inner core, the coating layer comprises lithium supplementing particles and carbon; the active material inner core comprises Li x Fe y PO4and LiFe z Mn 1-z PO4, wherein 0.9≤x≤1.1, 0.9≤y≤1.1, 0<z<1; the lithium supplementing particles comprise Li a M b O c , wherein M is selected from one or more of Fe, Mn, Ni, Zr, Co, Cr and Cu, 0 2. The lithium supplemented cathode material of claim 1, wherein, The carbon is coated on the surface of the active material inner core and / or the surface of the lithium supplementing particles.

3. The lithium supplementing cathode material of claim 1 or 2, wherein, At least part of the lithium supplementing particles are grown in-situ on the surface of the active material inner core.

4. The lithium supplementing cathode material of any one of claims 1-3, wherein, The mass ratio of the lithium supplementing particles to the active material inner core is (0.1-10):

100.

5. The lithium supplementing cathode material of any one of claims 1-4, wherein, The mass percentage of the carbon in the lithium supplementing positive electrode material is 0.1%-5%.

6. The lithium supplementing cathode material of any one of claims 1-5, wherein, The particle size of the active material inner core is 0.1-15 μm; and the particle size of the lithium supplementing particles is 0.1-12 μm.

7. The lithium supplementing cathode material of any one of claims 1-6, wherein, The specific surface area of the lithium supplementing positive electrode material is 3m 2 / g-20m 2 / g.

8. A method of preparing a lithium supplemented cathode material as claimed in any one of claims 1 to 7, wherein, Comprising: Mixing a lithium source, a phosphorus source, an iron source, a carbon source and an M metal source to obtain a lithium supplementing positive electrode material precursor; Or, mixing a lithium source, a phosphorus source, an iron source, a carbon source, a manganese source and an M metal source to obtain a lithium supplementing positive electrode material precursor; Segmented sintering the lithium supplementing positive electrode material precursor to obtain a lithium supplementing positive electrode material.

9. The method of preparing a lithium supplemented cathode material of claim 8, wherein, The segmented sintering comprises sequentially performed first sintering treatment and second sintering treatment; the sintering temperature of the first sintering treatment is 450-750 ℃, and the sintering time is 3-18 h; the sintering temperature of the second sintering treatment is 750-1000 ℃, and the sintering time is 4-36 h; the temperature of the second sintering treatment is higher than that of the first sintering treatment.

10. The method of producing a lithium supplementing cathode material according to claim 8 or 9, wherein, The lithium source comprises one or more of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium nitrate, lithium oxide, lithium peroxide and lithium acetate; The phosphorus source comprises one or more of lithium dihydrogen phosphate, iron phosphate, ammonium phosphate, sodium dihydrogen phosphate, lithium monohydrogen phosphate, lithium phytate and sodium tripolyphosphate; The iron source comprises one or more of ferrous oxide, diiron trioxide, iron nitrate, iron phosphate, ferrous oxalate and ferrous sulfate; The carbon source comprises one or several of sugar, high molecular organic matter and conductive carbon, and specifically comprises one or more of glucose, sucrose, fructose, chitosan, lignin, carboxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, phenol formaldehyde resin, needle coke, petroleum coke, pitch coke, pitch, polystyrene, polyphenylacetylene, carbon black, acetylene black, super-P, carbon nanotube, graphene, ketjen black and vapor grown carbon fiber; The manganese source comprises one or more of trimanganese tetraoxide, manganese sulfate, manganese oxalate, manganese carbonate, manganese dioxide and manganese acetate.

11. A positive electrode sheet, wherein The positive electrode sheet comprises a current collector and a positive electrode active layer loaded on the current collector, and the positive electrode active layer comprises the lithium supplementing positive electrode material according to any one of claims 1-7 or the lithium supplementing positive electrode material prepared by the preparation method according to any one of claims 8-10.

12. A lithium-ion battery, wherein, The lithium ion battery comprises the positive electrode sheet according to claim 11.

13. An electrical device, comprising: The electric device comprises the lithium ion battery according to claim 12.

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