Lithium-containing phosphate material, lithium-ion battery positive electrode, preparation method and use

Abstract

A lithium-containing phosphate material, a lithium-ion battery positive electrode, and a preparation method and use. The lithium-containing phosphate material comprises lithium-containing phosphate micron-sized particles having pore channels on the surface thereof, wherein lithium-containing phosphate nano-sized particles are embedded in the pore channels of the lithium-containing phosphate micron-sized particles.

Description

Lithium-containing phosphate material, lithium ion battery positive electrode and preparation method and application

[0001] Cross-reference to related applications

[0002] The present disclosure claims priority to the Chinese patent application No. 202410793743.2, filed on June 19, 2024, entitled "Lithium-containing phosphate material, lithium ion battery positive electrode and preparation method and application", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of lithium ion batteries, in particular, to a lithium-containing phosphate material, a lithium ion battery positive electrode and a preparation method and application. BACKGROUND

[0004] Lithium iron phosphate (LiFePO4) as a positive electrode material for lithium batteries has the advantages of good structural stability, high safety, good cycle performance, etc., and has been widely used in lithium ion batteries of power devices of new energy vehicles. Lithium manganese iron phosphate positive electrode material (LiMn x Fe 1-x PO4, 0 < x < 1) is a new material formed by using manganese to partially replace iron in LiFePO4 positive electrode material. Such doping improves the voltage platform of LiFePO4 and further improves its energy density, thus attracting much attention.

[0005] The lithium manganese iron phosphate material has the problem of slow electron / ion conduction rate. Nanocrystallization modification is an important technology to improve the electron / ion conduction rate of the lithium manganese iron phosphate material. The use of nanocrystallized lithium manganese iron phosphate particles can increase the specific surface area of the positive electrode material, allowing the electrolyte and the positive electrode material to fully contact, increasing the active sites, greatly shortening the transmission distance of Li + , and improving the reversible capacity and rate performance of the battery. However, the nanocrystallized lithium manganese iron phosphate particles have high surface energy and are prone to agglomeration, which makes it difficult to disperse uniformly in the slurry during the preparation of the positive electrode. In addition, the increase in the specific surface area of the nanocrystallized positive electrode material makes the positive electrode material easily absorb water. After the water contacts with the surface hydrophilic Li in the positive electrode material, a lithiation reaction occurs, which affects the storage capacity retention rate of the battery. Moreover, the alkaline substances generated by the lithiation reaction will eliminate the reaction with the binder polyvinylidene fluoride, and the double bonds generated will cause crosslinking reactions between the molecular chains of the binder polyvinylidene fluoride, forming a gel, which results in poor coating of the positive electrode material on the aluminum foil or the formation of gel spots, hindering the migration of lithium ions, causing uneven current distribution, lithium precipitation and other risks. In short, the existing LiMn x Fe 1-xPO4 materials are difficult to achieve a balance in the number of active sites, material water absorption and ion conduction rate, thereby affecting the further improvement of the reversible capacity and rate performance of the battery. SUMMARY

[0006] The purpose of the present disclosure is to provide a lithium-containing phosphate material, a lithium ion battery positive electrode and a preparation method and application, which can provide more reaction active sites, and the specific surface area and water absorption of the material are appropriate, and when used in a lithium ion battery, it can provide sufficient lithium ion transmission channels, and improve the reversible capacity and rate performance of the battery under the premise of reducing the risk of gel.

[0007] To achieve the above purpose, the first aspect of the present disclosure provides a lithium-containing phosphate material, which comprises lithium-containing phosphate micro-particles with pores on the surface, and the pores of the lithium-containing phosphate micro-particles are embedded with lithium-containing phosphate nano-particles.

[0008] Optionally, the D 50 particle size of the lithium-containing phosphate micro-particles is 5-10 times the D 50 particle size of the lithium-containing phosphate nano-particles.

[0009] Optionally, the D 50 pore size of the pores of the lithium-containing phosphate micro-particles is 0.8-1 times the D 50 particle size of the lithium-containing phosphate nano-particles.

[0010] Optionally, the D 50 particle size of the lithium-containing phosphate nano-particles is 0.5-0.9 μm.

[0011] Optionally, the D 50 particle size of the lithium-containing phosphate micro-particles is 2.5-10 μm, and the D 50 pore size of the pores is 0.4-0.9 μm.

[0012] Optionally, the porosity of the lithium-containing phosphate material is 10-15%.

[0013] Optionally, the lithium-containing phosphate micro-particles have a chemical formula LiA x B 1-x PO4, wherein A is one or more of Ti, V, Mn, Fe, Co and Ni, B is one or more of Ti, V, Mn, Fe, Co and Ni, and x is any number between 0 and 1.

[0014] The lithium-containing phosphate nano-particles have a chemical formula LiA′ y B′ 1-yA'4PO4yB' represents a composition, wherein A' is one or more of Ti, V, Mn, Fe, Co and Ni, B' is one or more of Ti, V, Mn, Fe, Co and Ni, and y is any number between 0 and 1.

[0015] The second aspect of the present disclosure provides a preparation method of a lithium-containing phosphate material, comprising the following steps:

[0016] (1) mixing a first lithium source, a first metal source and a first phosphorus source, pre-sintering the mixture to obtain a first pre-sintered product; secondarily sintering the first pre-sintered product, a first carbon source and a pore-forming agent, and performing a first crushing treatment or a first granulation treatment on the secondarily sintered product to obtain lithium-containing phosphate micrometer-sized particles;

[0017] mixing a second lithium source, a second metal source and a second phosphorus source, pre-sintering the mixture to obtain a second pre-sintered product; secondarily sintering the second pre-sintered product and a second carbon source, and performing a second crushing treatment or a second granulation treatment on the secondarily sintered product to obtain lithium-containing phosphate nanometer-sized particles;

[0018] (2) mixing the lithium-containing phosphate nanometer-sized particles and the lithium-containing phosphate micrometer-sized particles.

[0019] Optionally, the first metal source and the second metal source are each independently a compound containing one or more elements of Ti, V, Mn, Fe, Co and Ni; and the first carbon source and the second carbon source are each independently selected from one or more of sucrose, glucose, citric acid, phenolic resin, starch and carbon black.

[0020] Optionally, in step (1), the mass of the pore-forming agent accounts for 1-5% of the total mass of the first pre-sintered product and the pore-forming agent; and the pore-forming agent is selected from one or more of ethanol, oxalic acid, ammonium bicarbonate, ammonium carbonate, urea and ammonium chloride.

[0021] Optionally, in step (1), the pre-sintering conditions include: pre-sintering under a protective gas, a pre-sintering temperature of 500-650°C, and a pre-sintering time of 2-6h.

[0022] The secondarily sintering conditions include: sintering under a protective gas, a sintering temperature of 710-900°C, and a sintering time of 6-12h.

[0023] The first crushing treatment conditions include: crushing the secondarily sintered product using a ball mill, a ball mill rotation speed of 400-500r / min, and a ball milling time of 8-10h.

[0024] The first granulation treatment condition includes: the feeding gas pressure is 0.8-1.2 MPa, the inert protective gas flow is 30-50 L / min, the gas preheating temperature is 100-150℃, and the feeding solid content is 45-55%.

[0025] Optionally, in step (1), the second pre-sintering condition includes: being carried out under a protective gas, the pre-sintering temperature is 500-650℃, and the pre-sintering time is 2-6 h.

[0026] The second two-time sintering condition includes: being carried out under a protective gas, the sintering temperature is 600-700℃, and the sintering time is 4-8 h.

[0027] The second two-time sintering condition includes: being carried out under a protective gas, the sintering temperature is 600-700℃, and the sintering time is 4-8 h.

[0028] The second granulation treatment condition includes: the feeding gas pressure is 1-1.5 MPa, the inert protective gas flow is 40-60 L / min, the gas preheating temperature is 100-150℃, and the feeding solid content is 45-55%.

[0029] Optionally, in step (2), the mixing is solid-phase mixing, and is carried out under stirring, the stirring rate is 500-1200 rpm, the mixing temperature is 25-35℃, and the mixing time is 30-60 min.

[0030] Optionally, in step (2), the D 50 of the lithium-containing phosphate nanoscale particles is 0.5-0.9 μm; the D 50 of the lithium-containing phosphate microscale particles is 2.5-10 μm; the D 50 of the lithium-containing phosphate microscale particles is 2.5-10 μm; the D 50 of the lithium-containing phosphate microscale particles is 2.5-10 μm; the D

[0031] The third aspect of the present disclosure provides a lithium-containing phosphate material prepared by the preparation method of the second aspect of the present disclosure.

[0032] The fourth aspect of the present disclosure provides a method for preparing a lithium ion battery positive electrode, which includes: mixing a lithium-containing phosphate material, a conductive agent, a binder, and a solvent to form a positive electrode slurry; forming a positive electrode slurry layer on a positive electrode current collector from the positive electrode slurry, removing the solvent in the positive electrode slurry layer, and forming a positive electrode sheet containing a positive electrode material layer.

[0033] The lithium-containing phosphate material is the lithium-containing phosphate material of the first aspect of the present disclosure and / or the third aspect of the present disclosure.

[0034] Optionally, the method further comprises: before forming the positive electrode slurry layer, subjecting the positive electrode slurry to a shearing treatment, the shearing treatment being performed at a shearing rate of 4000-8000 rpm and a temperature of 20-35℃.

[0035] Optionally, the mass ratio of the lithium-containing phosphate micrometer-sized particles to the lithium-containing phosphate nanometer-sized particles is 1:(50-200).

[0036] The fifth aspect of the present disclosure provides a lithium ion battery positive electrode prepared by the method of the fourth aspect of the present disclosure.

[0037] The sixth aspect of the present disclosure provides a lithium ion battery positive electrode, which comprises a current collector and a positive electrode material layer arranged on at least one side of the positive electrode current collector; the positive electrode material layer contains a lithium-containing phosphate material; wherein the lithium-containing phosphate material is the lithium-containing phosphate material of the first aspect of the present disclosure and / or the third aspect of the present disclosure.

[0038] Optionally, the porosity of the positive electrode material layer is 15-25%.

[0039] Optionally, the positive electrode material layer further contains positive electrode material nanometer-sized particles.

[0040] The positive electrode material nanometer-sized particles have a chemical formula of LiA" z B" 1-z PO4, wherein A" is one or more of Ti, V, Mn, Fe, Co and Ni, B" is one or more of Ti, V, Mn, Fe, Co and Ni, and z is an arbitrary number between 0 and 1.

[0041] The mass ratio of the positive electrode material nanometer-sized particles to the lithium-containing phosphate material is (50-200):1.

[0042] The seventh aspect of the present disclosure provides a lithium ion battery comprising the lithium ion battery positive electrode of the sixth aspect of the present disclosure.

[0043] The eighth aspect of the present disclosure provides an electric device comprising the lithium ion battery of the seventh aspect of the present disclosure.

[0044] By the technical solution, the lithium-containing phosphate material includes lithium-containing phosphate nanoscale particles and lithium-containing phosphate microscale particles with pores on the surface, the nanoscale particles are embedded in the surface pores of the microscale particles to form embedded lithium-containing phosphate material; the lithium-containing phosphate material has pores on the surface, which improves the porosity of the material, forms more reactive sites, and can provide more lithium ion transmission channels. Compared with the positive electrode material using nanoscale particles, the pores of the microscale particles of the lithium-containing phosphate material of the present disclosure are embedded with nanoscale particles, so that the water absorption and surface energy of the lithium-containing phosphate material are lower, which can avoid particle agglomeration in the preparation of the positive electrode slurry, avoid the phenomenon of lithiation reaction with water, and facilitate the dispersion of the binder and the conductive agent, which can inhibit the crosslinking and gelation in the slurry preparation process, and improve the uniformity of the distribution of each component in the positive electrode material layer.

[0045] The lithium ion battery positive electrode of the present disclosure contains the lithium-containing phosphate material described above, which has a balanced number of active sites, specific surface area and water absorption, and the pores of the microscale particles can improve the porosity of the positive electrode material, provide lithium ion transmission channels for the electrolyte, improve the rate performance of the lithium ion battery without gelation, and the mutual grading of the microscale particles and the nanoscale particles can improve the compaction density of the positive electrode material layer, thereby improving the reversible capacity of the lithium ion battery.

[0046] Other features and advantages of the present disclosure will be described in detail in the following specific embodiments. DETAILED DESCRIPTION

[0047] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0048] The first aspect of the present disclosure provides a lithium-containing phosphate material, which includes lithium-containing phosphate microscale particles with pores on the surface, and the pores of the lithium-containing phosphate microscale particles are embedded with lithium-containing phosphate nanoscale particles.

[0049] The lithium-containing phosphate material of the present disclosure comprises lithium-containing phosphate nanoscale particles and lithium-containing phosphate microscale particles with pores on the surface, the nanoscale particles are embedded in the pores of the microscale particles with porous surface to form embedded lithium-containing phosphate material. The lithium-containing phosphate material has pores on the surface, which increases the porosity of the material, forms more active sites and provides more lithium ion transmission channels. Compared with the positive electrode material using nanoscale particles, the microscale particles of the lithium-containing phosphate material of the present disclosure have nanoscale particles embedded in the pores, which has lower water absorption and surface energy, can avoid particle agglomeration in the preparation of positive electrode slurry and avoid the phenomenon of lithiation reaction with water, and is beneficial to the dispersion of the binder, can inhibit the crosslinking and gelation in the slurry preparation process, and improve the uniformity of the components in the positive electrode material layer.

[0050] According to an embodiment of the present disclosure, the D 50 The particle size is 0.5-0.9 μm, preferably 0.6-0.8 μm. The above embodiment is beneficial for the grading of the two kinds of particles and provides more active sites for the positive electrode material.

[0051] According to an embodiment of the present disclosure, the D 50 The particle size is 2.5-10 μm, preferably 4-8 μm; the D 50 The pore size is 0.4-0.9 μm, preferably 0.6-0.8 μm. The surface of the lithium-containing phosphate microscale particles comprises one or more pores, preferably a porous structure. In the present disclosure, the D 50 The pore size refers to the D 50 The diameter of the surface opening. The above embodiment is beneficial for providing lithium ion transmission channels for the electrolyte, increasing the porosity of the lithium-containing phosphate material and improving the rate performance of the battery.

[0052] According to an embodiment of the present disclosure, the D 50 The particle size of the lithium-containing phosphate microscale particles is 5-10 times the D 50 The particle size of the lithium-containing phosphate nanoscale particles. The above embodiment is beneficial for the reasonable packing of the microscale particles and the nanoscale particles, the grading of the two kinds of particles, the balance of the pressure compaction and wettability of the pole piece, and can meet the requirements of reversible capacity and rate performance of the battery when used in the battery.

[0053] According to an embodiment of the present disclosure, the D 50 The pore size of the lithium-containing phosphate microscale particles is 5-10 times the D 50The ratio of the particle sizes is 0.8-1. The above embodiment is advantageous to improve the porosity of the lithium-containing phosphate material and the positive electrode sheet, to provide a lithium ion transmission channel for the electrolyte, and to further improve the reversible capacity and rate performance of the battery.

[0054] According to the present disclosure, the proportion of the lithium-containing phosphate nanoscale particles embedded in the pores of the lithium-containing phosphate microscale particles in the lithium-containing phosphate material is not particularly limited.

[0055] According to an embodiment of the present disclosure, the porosity of the lithium-containing phosphate material is 10-15%, preferably 12-14%. The above embodiment is advantageous to improve the porosity of the positive electrode sheet, to provide a lithium ion transmission channel for the electrolyte, and to further improve the reversible capacity and rate performance of the battery. In the present disclosure, the porosity of the lithium-containing phosphate material refers to the porosity of a single lithium-containing phosphate material particle. In actual applications, the porosity of the lithium-containing phosphate material can have certain errors. For example, in a specific embodiment, the mass proportion of the single lithium-containing phosphate particle with a porosity of 10-15% can be 95% or more, based on the total weight of the lithium-containing phosphate material; in a further embodiment, the mass proportion can be 96% or more, 97% or more, or 98% or more.

[0056] Further, in the lithium-containing phosphate material provided by the present disclosure, the mass ratio of the lithium-containing phosphate microscale particles to the lithium-containing phosphate nanoscale particles can vary in a large range, and the present disclosure does not particularly limit the mass ratio of the two. For example, the mass ratio of the lithium-containing phosphate microscale particles to the lithium-containing phosphate nanoscale particles can be 1:(50-200), preferably 1:(50-150). The specific surface area of the lithium-containing phosphate material is 14-20 m 2 / g, preferably 14-16 m 2 / g. The above embodiment is advantageous to obtain a lithium-containing phosphate material with a small specific surface area, so as to reduce the water absorption degree of the positive electrode raw material; in the mixing and slurry preparation process, since most of the nanoscale particles are embedded in the pores of the microscale particles and do not directly exist in the slurry, the probability of particle agglomeration can be reduced, the dispersion of the binder and the conductive agent is uniform, the components are uniformly distributed, and the crosslinking of the components to cause gelation is inhibited. The above embodiment provides more reactive sites and improves the compaction density and porosity of the positive electrode material layer, so as to have a high reversible capacity of the lithium ion battery and a better rate performance of the battery.

[0057] According to an embodiment of the present disclosure, the lithium-containing phosphate microscale particles have a chemical formula LiA x B 1-xA represents one or more of Ti, V, Mn, Fe, Co and Ni, B represents one or more of Ti, V, Mn, Fe, Co and Ni, and x is an arbitrary value between 0 and 1; the lithium-containing phosphate microparticles have a chemical formula of LiA'PO4, wherein A' represents one or more of Ti, V, Mn, Fe, Co and Ni, and B' represents one or more of Ti, V, Mn, Fe, Co and Ni, and y is an arbitrary value between 0 and 1. y B' 1-y A represents one or more of Ti, V, Mn, Fe, Co and Ni, B represents one or more of Ti, V, Mn, Fe, Co and Ni, and x is an arbitrary value between 0 and 1; the lithium-containing phosphate microparticles have a chemical formula of LiA'PO4, wherein A' represents one or more of Ti, V, Mn, Fe, Co and Ni, and B' represents one or more of Ti, V, Mn, Fe, Co and Ni, and y is an arbitrary value between 0 and 1. x Fe 1-x A' represents Mn and B' represents Fe; the lithium-containing phosphate microparticles have a chemical formula of LiMnPO4. y Fe 1-y A' represents Mn and B' represents Fe; the lithium-containing phosphate microparticles have a chemical formula of LiMnPO4. The above embodiments are advantageous in improving the rate capability of the battery.

[0058] The second aspect of the present disclosure provides a preparation method of a lithium-containing phosphate material, which comprises the following steps:

[0059] (1) mixing a first lithium source, a first metal source and a first phosphorus source, and performing first pre-sintering on the obtained mixture to obtain a first pre-sintering product; performing first secondary sintering on the first pre-sintering product, a first carbon source and a pore-forming agent, and performing first crushing treatment or first granulation treatment on the first secondary sintering product to obtain lithium-containing phosphate microparticles;

[0060] mixing a second lithium source, a second metal source and a second phosphorus source, and performing second pre-sintering on the obtained mixture to obtain a second pre-sintering product; performing second secondary sintering on the second pre-sintering product and a second carbon source, and performing second crushing treatment or second granulation treatment on the second secondary sintering product to obtain lithium-containing phosphate microparticles;

[0061] (2) mixing the lithium-containing phosphate microparticles and the lithium-containing phosphate microparticles.

[0062] The preparation method of the present disclosure can provide more reactive sites, improve the porosity of the positive electrode material, provide a transmission channel for lithium ions of the electrolyte, and improve the reversible capacity of the lithium ion battery and the rate capability of the battery by improving the compaction density of the positive electrode material layer through the appropriate grading of the microparticles and the nanoparticles.

[0063] According to the present disclosure, the composition of the lithium-containing phosphate micrometer-sized particles and the lithium-containing phosphate nanometer-sized particles can be the same or different. Those skilled in the art can understand that in the embodiment where the composition of the nanometer-sized particles and the micrometer-sized particles is the same, the steps of preparing the first pre-sintered product and preparing the second pre-sintered product can also be combined, for example, a part of the obtained first pre-sintered product is used for the first secondary sintering to prepare micrometer-sized particles, and another part of the first pre-sintered product is used for the second secondary sintering to prepare nanometer-sized particles.

[0064] According to the present disclosure, the first lithium source and the second lithium source are each independently a lithium-containing elemental compound, and in an embodiment of the present disclosure, the lithium-containing elemental compound can be selected from one or more of lithium carbonate, lithium bicarbonate, lithium dihydrogen phosphate, lithium hydroxide, and lithium oxalate.

[0065] According to an embodiment of the present disclosure, the first metal source and the second metal source are each independently a compound containing one or more elements of Ti, V, Mn, Fe, Co, and Ni; the Ti-containing compound can be selected from one or more of titanium dioxide, titanium tetrachloride, titanium nitrate, titanium tetraalkoxide, and acyl titanium; the V-containing compound can be selected from one or more of vanadium pentoxide, ammonium metavanadate, and vanadyl oxalate; the Mn-containing compound can be selected from one or more of manganese carbonate, manganous sulfate, manganese phosphate, manganese nitrate, and manganese oxide; the Fe-containing compound can be selected from one or more of ferrous oxide, iron oxide, iron oxalate, and ferrous acetate; the Co-containing compound can be selected from one or more of cobalt oxide, cobalt carbonate, cobalt chloride, and cobalt acetate; and the Ni-containing compound can be selected from one or more of nickel oxide, nickel carbonate, nickel chloride, and nickel acetate.

[0066] According to an embodiment of the present disclosure, the first phosphorus source and the second phosphorus source can each independently be selected from one or more of phosphoric acid, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, and lithium dihydrogen phosphate.

[0067] According to an embodiment of the present disclosure, the first carbon source and the second carbon source can each independently be selected from an organic carbon source and / or an inorganic carbon source, and further can be selected from one or more of sucrose, glucose, citric acid, phenolic resin, starch, and carbon black.

[0068] According to an embodiment of the present disclosure, the pore-forming agent is a substance that can be easily decomposed into a gas, and can generate a pore structure in the material. The pore-forming agent can be selected from one or more of ethanol, oxalic acid, ammonium bicarbonate, ammonium carbonate, urea, and ammonium chloride. In the above embodiment, the micrometer-sized particles have a pore structure, which provides a channel for lithium ion transmission, and thus the lithium ion battery has a high reversible capacity and better rate performance.

[0069] In a further embodiment, in step (1), the mass of the pore-forming agent is 1-5%, preferably 3-5%, of the total mass of the first pre-sintered product and the pore-forming agent. The above embodiment is advantageous for forming lithium phosphate microparticles with more appropriate size and number of pores, providing lithium ion transport channels for electrolyte, making the lithium ion battery have high reversible capacity and better rate performance; on the other hand, it is beneficial for the embedding of nanoscale particles, reducing the specific surface area of the material, and further reducing the water absorption of the raw material, which can reduce the agglomeration of nanoscale particles during the mixing and slurry preparation process, and is beneficial for the uniform distribution of the binder and the conductive agent, and inhibits the crosslinking of the binder and the conductive agent to form a gel.

[0070] In the present disclosure, the amounts of the first / second lithium source, the first / second metal source and the first / second phosphorus source are not particularly limited, and those skilled in the art can determine the amounts according to the stoichiometric ratio of each element in the chemical formula of the lithium phosphate material to be prepared. The present disclosure does not particularly limit the order of preparing the lithium phosphate microparticles and the lithium phosphate nanoscale particles in step (1), for example, those skilled in the art can first prepare the lithium phosphate microparticles, or first prepare the lithium phosphate nanoscale particles.

[0071] According to an embodiment of the present disclosure, in step (1), the first pre-sintering conditions include: being carried out under a protective gas, the protective gas including one or more of nitrogen, argon, helium and hydrogen; the pre-sintering temperature is 500-650°C, preferably 550-600°C, and the pre-sintering time is 2-6h, preferably 2-4h. The above embodiment is advantageous for forming microparticles with appropriate size and appropriate pores, providing lithium ion transport channels, and further improving the rate performance of the battery.

[0072] According to an embodiment of the present disclosure, in step (1), the first pre-sintering conditions include: being carried out under a protective gas, the protective gas including one or more of nitrogen, argon, helium and hydrogen; the pre-sintering temperature is 500-650°C, preferably 550-600°C, and the pre-sintering time is 2-6h, preferably 2-4h. The above embodiment is advantageous for forming microparticles with appropriate size and appropriate pores, providing lithium ion transport channels, and further improving the rate performance of the battery.

[0073] According to one embodiment of the present disclosure, the first secondary sintered product is formed into micron-sized particles of lithium-containing phosphate by a first crushing process, and the conditions of the first crushing process can be conventional conditions in the art that can form the sintered product into micron-sized particles. In a further embodiment, the conditions of the first crushing process include crushing the first secondary sintered product using a ball mill at a rotation speed of 400-500 r / min, preferably 420-480 r / min, for 8-10 h, preferably 8.5-9.5 h. The above embodiment is advantageous for forming micron-sized particles of suitable size and suitable pores, providing lithium ion transport channels, and further improving the rate performance of the battery.

[0074] According to another embodiment of the present disclosure, the first secondary sintered product is formed into micron-sized particles by a first granulation process, and the conditions of the first granulation process can be conventional conditions in the art that can form the sintered product into micron-sized particles. In a further embodiment, the conditions of the first granulation process include a feed gas pressure of 0.8-1.2 MPa, preferably 0.9-1.1 MPa, an inert protective gas flow rate of 30-50 L / min, preferably 40-45 L / min, a gas preheating temperature of 100-150 °C, preferably 120-140 °C, and a feed solid content of 45-55%, preferably 48-52%. In a further embodiment, the first granulation process includes mixing the first secondary sintered product with a solvent to obtain a slurry with a solid content of 45-55%, and subjecting the slurry to the first granulation process. The solvent used can be water or anhydrous ethanol. The above embodiment is advantageous for forming micron-sized particles of suitable size and suitable pores, providing lithium ion transport channels, and further improving the rate performance of the battery.

[0075] According to one embodiment of the present disclosure, in step (1), the conditions of the second pre-sintering include being performed under a protective gas, the protective gas including one or more of nitrogen, argon, helium, and hydrogen; a pre-sintering temperature of 500-650 °C, preferably 550-600 °C; and a pre-sintering time of 2-6 h, preferably 2-4 h. The above embodiment is advantageous for forming lithium-containing phosphate nanoscale particles of suitable size, providing reactive sites, and further improving the rate performance of the battery.

[0076] According to one embodiment of the present disclosure, in step (1), the conditions of the second pre-sintering include being performed under a protective gas, the protective gas including one or more of nitrogen, argon, helium, and hydrogen; a pre-sintering temperature of 500-650 °C, preferably 550-600 °C; and a pre-sintering time of 2-6 h, preferably 2-4 h. The above embodiment is advantageous for forming lithium-containing phosphate nanoscale particles of suitable size, providing reactive sites, and further improving the rate performance of the battery.

[0077] According to one embodiment of the present disclosure, in step (1), the second secondary sintered product is formed into lithium-containing phosphate nanoscale particles by a second crushing treatment, and the conditions of the first crushing treatment can be conventional conditions in the art that can form the sintered product into nanoscale particles. In a further embodiment, the conditions of the second crushing treatment include crushing the second secondary sintered product using a ball mill at a speed of 450-600 r / min for 10-15 h. The above embodiment is advantageous for forming lithium-containing phosphate nanoscale particles of suitable size, providing reactive sites, and further improving the rate performance of the battery.

[0078] According to another embodiment of the present disclosure, the second secondary sintered product is formed into nanoscale particles by a second granulation treatment, and the conditions of the second granulation treatment can be conventional conditions in the art that can form the sintered product into nanoscale particles. In a further embodiment, the conditions of the second granulation treatment include a feed gas pressure of 1-1.5 MPa, preferably 1.2-1.4 MPa, an inert protective gas flow rate of 40-60 L / min, preferably 45-55 L / min, a gas preheating temperature of 100-150°C, preferably 120-140°C, and a feed solid content of 45-55%, preferably 48-52%. In a further embodiment, the second granulation treatment includes mixing the second secondary sintered product with a solvent to obtain a slurry with a solid content of 45-55%, and then subjecting the slurry to the second granulation treatment. The solvent used can be water or anhydrous ethanol. The above embodiment is advantageous for forming lithium-containing phosphate nanoscale particles of suitable size, providing reactive sites, and further improving the rate performance of the battery.

[0079] According to one embodiment of the present disclosure, in step (2), the mixing is solid-phase mixing and is carried out under stirring at a rate of 500-1200 rpm, a temperature of 25-35°C, and for a time of 30-60 min. The present disclosure does not specifically limit the equipment for mixing, which can be a conventional commercially available product. The above embodiment is advantageous for improving the compaction density of the positive electrode material layer while providing a larger number of reactive sites, and for providing a suitable number of pores to provide a transmission channel for lithium ions, further improving the rate performance of the battery.

[0080] According to one embodiment of the present disclosure, in step (2), the lithium-containing phosphate nanoscale particles have a D 50 of 0.5-0.9 μm, preferably 0.6-0.8 μm; the lithium-containing phosphate microscale particles have a D 50 of 2.5-10 μm, preferably 4-8 μm; and the lithium-containing phosphate microscale particles have a D 50 of 0.5-0.9 μm, preferably 0.6-0.8 μm.50 The particle size is preferably 5-10 times, more preferably 6-8 times the size of the micropores. The above embodiment is advantageous in providing more reactive sites, and at the same time providing a suitable amount of micropores to provide a transport path for lithium ions, thereby further improving the rate capability of the battery.

[0081] The third aspect of the present disclosure provides a lithium-containing phosphate material prepared by the method of the second aspect of the present disclosure.

[0082] The fourth aspect of the present disclosure provides a method for preparing a positive electrode of a lithium ion battery, the method comprising: mixing a lithium-containing phosphate material, a conductive agent, a binder and a solvent to form a positive electrode slurry; forming a positive electrode slurry layer on a positive electrode current collector from the positive electrode slurry, and removing the solvent in the positive electrode slurry layer to form a positive electrode tab comprising a positive electrode material layer; wherein the lithium-containing phosphate material is the lithium-containing phosphate material of the first aspect of the present disclosure and / or the third aspect of the present disclosure.

[0083] The present disclosure uses a lithium-containing phosphate material to prepare a positive electrode, wherein the nanoscale particles and the microscale particles can provide more reactive sites, and the microscale particles have micropores to improve the porosity of the positive electrode material and provide a transport path for lithium ions for the electrolyte, and a suitable grading of the two can improve the compaction density of the positive electrode material layer, thereby improving the reversible capacity of the lithium ion battery and the rate capability of the battery.

[0084] According to the present disclosure, the mass ratio of the lithium-containing phosphate material, the conductive agent, the binder, the dispersant and the solvent can be varied within a wide range. According to one embodiment of the present disclosure, the mass ratio of the lithium-containing phosphate material, the conductive agent, the binder, the dispersant and the solvent can be 1:(0.02-0.05):(0.03-0.06):(0.6-0.8), preferably 1:(0.02-0.03):(0.04-0.05):(0.65-0.75). The conductive agent, the binder and the solvent are well known to those skilled in the art, for example, the conductive agent can be one or more of carbon black, carbon nanotubes, acetylene black and graphene; the binder can be one or more of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA) and polytetrafluoroethylene (PTFE); and the solvent can be one or more of N-methylpyrrolidone, N-methylformamide, ethanol and acetone.

[0085] According to an embodiment of the present disclosure, the positive electrode slurry further comprises a dispersant, which can be one or more of polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), polyethyleneimine (PEI), and acrylic acid-maleic acid copolymer (PAMA); the mass ratio of the lithium-containing phosphate material to the dispersant can vary in a large range, for example, can be 1:(0.01-0.03), preferably 1:(0.015-0.025).

[0086] According to an embodiment of the present disclosure, the method further comprises: before forming the positive electrode slurry layer, performing shear treatment on the positive electrode slurry, the shear treatment being performed under conditions comprising: a shear rate of 4000-8000 rpm, preferably 5000-7000 rpm; the solid content of the positive electrode slurry can be 45-60 wt%, preferably 50-55 wt%; in an optional embodiment, the shear treatment is performed at a temperature of 20-35°C, preferably 25-30°C. The shear rate in the present disclosure is 1.2-2 times the conventional shear rate. The above-mentioned embodiment is advantageous in that the weak parts of the lithium-containing phosphate material particles, i.e., the intercalation boundaries, are broken under stress, the positive electrode material wrapped with the auxiliary material is further divided into nano-sized particles and micro-sized particles, the stable dispersion of the slurry is ensured, more reactive sites in the positive electrode sheet are provided, the nano-sized particles are combined with the porous micro-sized large particles to improve the compaction density of the positive electrode sheet, the pore structure is exposed to provide lithium ion transmission channels for the electrolyte, and the reversible capacity and the rate performance of the battery are further improved.

[0087] According to an embodiment of the present disclosure, the mass ratio of the lithium-containing phosphate micro-sized particles to the lithium-containing phosphate nano-sized particles can vary in a large range, for example, can be 1:(50-200), preferably 1:(100-150). The above-mentioned embodiment is advantageous in that a properly graded positive electrode material layer is obtained, lithium ion transmission channels are provided while more reactive sites are provided, the porosity of the positive electrode material is improved, the compaction density of the positive electrode material layer is improved, and the reversible capacity and the rate performance of the battery are further improved.

[0088] According to an embodiment of the present disclosure, the positive electrode slurry further comprises positive electrode material nano-sized particles, and further, the mass ratio of the positive electrode material nano-sized particles to the lithium-containing phosphate material is (50-200):1, preferably (100-150):1. The above-mentioned embodiment is advantageous in that a properly graded positive electrode material layer is obtained, lithium ion transmission channels are provided while more reactive sites are provided, the porosity of the positive electrode material is improved, the compaction density of the positive electrode material layer is improved, and the reversible capacity and the rate performance of the battery are further improved.

[0089] In a further embodiment, the positive electrode material nanoparticles can be added in the step of preparing the slurry.

[0090] In another further embodiment, the positive electrode material nanoparticles can be added in the preparation of the lithium-containing phosphate material, for example, in the step of mixing the nanoscale particles and the microscale particles. In the embodiment where the positive electrode material nanoparticles have the same composition as the nanoscale particles, the nanoscale particles and the microscale particles can be prepared directly according to the mass ratio of the positive electrode material nanoparticles to the lithium-containing phosphate material of (50-200): 1. In the above embodiment, the probability of agglomeration of the nanoparticles during the mixing process is reduced, the binder and the conductive agent are uniformly dispersed, the components are uniformly distributed, and the cross-linking of the components to form gel is inhibited. The positive electrode material nanoparticles and the lithium-containing phosphate material are properly graded, the number of active sites is increased, the compaction density of the positive electrode material layer is increased, and the reversible capacity and the rate capability of the battery are further improved.

[0091] In a fifth aspect, the present disclosure provides a lithium ion battery positive electrode prepared by the method of the fourth aspect of the present disclosure.

[0092] In a sixth aspect, the present disclosure provides a lithium ion battery positive electrode, which comprises a positive electrode current collector and a positive electrode material layer arranged on at least one side of the positive electrode current collector, and the positive electrode material layer contains a lithium-containing phosphate material. The lithium-containing phosphate material is the lithium-containing phosphate material of the first aspect and / or the third aspect of the present disclosure. In the positive electrode material layer of the positive electrode of the present disclosure, the microscale particles and the nanoscale particles with porous surfaces are distributed, which ensures a large number of active sites, and the compaction density and the porosity of the positive electrode sheet are increased by matching the nanoscale particles with the porous microscale particles, and the reversible capacity of the battery and the rate capability of the battery are further improved.

[0093] In an embodiment, the positive electrode comprises a positive electrode current collector and positive electrode material layers arranged on both sides of the positive electrode current collector.

[0094] According to an embodiment of the present disclosure, the positive electrode material layer further contains positive electrode material nanoparticles. The mass ratio of the positive electrode material nanoparticles to the lithium-containing phosphate material can be in a large range, for example, can be (50-200): 1, and preferably (100-150): 1. In this embodiment, the composition of the positive electrode material nanoparticles can be the same as or different from that of the nanoscale particles of the lithium-containing phosphate material. Further, the positive electrode material nanoparticles have the chemical formula LiA" z B" 1-zPO4represents a composition, wherein A" is one or more of Ti, V, Mn, Fe, Co and Ni, B" is one or more of Ti, V, Mn, Fe, Co and Ni, and z is an arbitrary number between 0 and 1. The above embodiment is advantageous for the suitable grading of the positive electrode material nanoparticles and the lithium-containing phosphate material, which provides more reactive sites and improves the compaction density of the positive electrode material layer, further improving the reversible capacity and rate performance of the battery.

[0095] In a further embodiment, the porosity of the positive electrode material layer is 15-25%, preferably 17-20%. The above embodiment is advantageous for improving the porosity of the positive electrode material layer, providing lithium ion transport channels for the electrolyte and improving the rate performance of the lithium ion battery.

[0096] The seventh aspect of the present disclosure provides a lithium ion battery comprising the lithium ion battery positive electrode of the fifth aspect of the present disclosure and / or the sixth aspect of the present disclosure.

[0097] The eighth aspect of the present disclosure provides an electric device comprising the lithium ion battery of the seventh aspect of the present disclosure. The electric device can include, but is not limited to, mobile communication devices, automobiles, electrical appliances, etc.

[0098] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited in any way by the following examples.

[0099] The following examples and comparative examples are used to prepare lithium manganese iron phosphate lithium-containing phosphate material as an example, wherein LiMn x Fe 1-x x = 0.8 in LiFePO4. The raw materials and reagents used in the examples and comparative examples are battery grade; if not otherwise specified, the chemical reagents used in the following examples and comparative examples are commercially available products.

[0100] In the present disclosure, the specific surface area of the composite particles is tested by BET method on a gas adsorption instrument of model TriStar II 3020; the porosity of the composite particles, the porosity of the lithium-containing phosphate material, the porosity of the positive electrode material layer and the D 50 The pore size is tested on a focused ion beam scanning electron microscope of model ZEISS Crossbeam 550; the D 50 The particle size of the micron-sized particles and the D 50 The particle size is tested on a laser particle size analyzer of model PSA200702. The viscosity of the positive electrode slurry is tested by a rotational rheometer of model ViscoQC 300(L).

[0101] Example 1

[0102] (1) According to the stoichiometric ratio, lithium carbonate, iron oxide, manganese carbonate and ammonium dihydrogen phosphate with a molar ratio of 0.5:0.8:0.1:1 are ball-milled and stirred until they are evenly mixed. The above-mixed raw materials are added to a high-temperature sintering furnace, argon gas is introduced, the pre-sintering temperature is maintained at 600℃, and sintering is continued for 2 hours to obtain the first pre-sintered product.

[0103] The first pre-sintered product, after being allowed to cool, was poured into a ball mill, and glucose was added for ball milling until the particles were evenly dispersed. Then, 3% by weight of ammonium bicarbonate (based on the total weight of the first pre-sintered product) was added and mixed. The powder containing the pore-forming agent was then placed back into a sintering furnace for first and second sintering at 750℃ for 8 hours. The products from the first and second sintering were then mixed with anhydrous ethanol to obtain a slurry with a solid content of 50%. The slurry was then subjected to spray granulation treatment with a feed pressure of 1MPa, an argon flow rate of 40L / min, and an argon preheating temperature of 120℃ to obtain porous micron-sized LMFP particles. 50 Particle size is 4μm, D 50 The pore size is 0.6 μm;

[0104] Lithium carbonate, iron oxide, manganese carbonate, and ammonium dihydrogen phosphate in a stoichiometric ratio of 0.5:0.8:0.1:1 were ball-milled until homogeneous. The mixture was then added to a high-temperature sintering furnace, purged with argon gas, and sintered at 600°C for 2 hours to obtain a second pre-sintered product. This second pre-sintered product, after cooling, was fed into a ball mill, and glucose was added and ball-milled until uniformly dispersed. The glucose-mixed powder was then placed back into the sintering furnace for a second sintering at 650°C for 6 hours. The resulting product was then mixed with anhydrous ethanol to obtain a slurry with a solid content of 50%. The slurry was then spray-granulated at a feed pressure of 1.2 MPa and an argon flow rate of 50 L / min to obtain nano-sized LMFP particles. The argon preheating temperature was 120°C. The Di of the nano-sized LMFP particles was determined. 50 The particle size is 0.65 μm;

[0105] (2) The porous micron-sized particles and nano-sized particles obtained above are stirred and mixed at a mass ratio of 1:100. Through mixing, most of the nano-sized particles enter the pores of the micron-sized particles to form composite particles. The mixing temperature is 25℃, the mixing time is 40min, and the stirring speed is 800rpm.

[0106] (3) The above composite particles are mixed with the conductive agent CNT, the binder PVDF, the dispersant PVP and the solvent NMP in a mass ratio of 1:0.02:0.04:0.02:0.7 to form a positive electrode slurry, and the solid content of the positive electrode slurry is 50% by weight; then the positive electrode slurry is sheared at a shearing rate of 6000 rpm at 25°C, and after stirring for 20 minutes, the sheared slurry is coated on the current collector, and the slurry forms a positive electrode slurry layer on the current collector. During shearing, part of the nano-sized particles are separated from the micrometer-sized particles, and the sheared positive electrode slurry contains lithium-containing phosphate materials with embedded structures and dispersed positive electrode material nano-particles; the solvent in the positive electrode slurry layer is removed to form a positive electrode sheet containing a positive electrode material layer, and the full battery is assembled with a separator, a graphite negative electrode, etc. for testing.

[0107] Example 2

[0108] The same as Example 1, except that the mass ratio of the pore-forming agent ammonium bicarbonate in step (1) is 1%.

[0109] Example 3

[0110] The same as Example 1, except that the conditions for preparing the porous micrometer-sized particles in step (1) are different, as follows:

[0111] The first pre-sintered product after standing and cooling is poured into a ball mill, and glucose is added for ball milling until it is evenly dispersed, and then 3% by weight of ammonium bicarbonate based on the total weight of the first pre-sintered product and ammonium bicarbonate is added for mixing. The powder of the mixed pore-forming agent is again placed in a sintering furnace for the first and second sintering, at a temperature of 850°C for 6 hours. The product after the first and second sintering is mixed with anhydrous ethanol to obtain a slurry with a solid content of 50%. The slurry is subjected to spray granulation treatment, with a feed gas pressure of 1 MPa, an argon gas flow rate of 40 L / min, and an argon gas preheating temperature of 120°C. Porous micrometer-sized LMFP particles are obtained, with a micrometer-sized particle size of 4 μm, a D 50 particle size of 4 μm, a D 50 pore size of 0.5 μm.

[0112] Example 4

[0113] The same as Example 1, except that the conditions for preparing the porous micrometer-sized particles in step (1) are different, as follows:

[0114] The first pre-sintering product after standing cooling was poured into a ball mill, and glucose was added for ball milling until uniformly dispersed, then 3% by weight of ammonium bicarbonate based on the total weight of the first pre-sintering product and ammonium bicarbonate was added for mixing, and the mixed pore-forming agent powder was again placed into a sintering furnace for the first secondary sintering at a temperature of 750°C for 8 hours, then the product after the first secondary sintering was mixed with anhydrous ethanol to obtain a slurry with a solid content of 50%, and the slurry was subjected to spray granulation treatment, with an inlet gas pressure of 1.3 MPa, an argon gas flow rate of 52 L / min, and an argon gas preheating temperature of 120°C, to obtain porous micron-sized LMFP particles, with a D 50 a particle size of 3 μm, and a D 50 a pore size of 0.6 μm.

[0115] Example 5

[0116] The same as Example 1, except that in step (2), the mass ratio of the mixed porous micron-sized particles and nano-sized particles was 1:50.

[0117] Example 6

[0118] The same as Example 1, except that in step (3), the shearing rate was 4800 rpm.

[0119] Example 7

[0120] The same as Example 1, except that in step (1), when preparing the nano-sized particles, the inlet gas pressure was 1 MPa, the argon gas flow rate was 40 L / min, and the argon gas preheating temperature was 120°C, and the D 50 the particle size was 0.9 μm.

[0121] Example 8

[0122] The same as Example 1, except that in step (1), when preparing the micron-sized particles, the first secondary sintering temperature was 900°C for 12 hours, the inlet gas pressure was 0.8 MPa, the argon gas flow rate was 30 L / min, and the argon gas preheating temperature was 120°C, and the D 50 the particle size was 10 μm, and the D 50 the pore size was 0.6 μm.

[0123] Example 9

[0124] The same as Example 1, except that in step (1), when preparing the nano-sized particles, the second secondary sintering temperature was 600°C for 4 hours, the inlet gas pressure was 1.5 MPa, the argon gas flow rate was 60 L / min, and the argon gas preheating temperature was 120°C, and the D 50 the particle size was 0.5 μm.

[0125] Comparative Example 1

[0126] The lithium carbonate, iron oxide, manganese carbonate, and ammonium dihydrogen phosphate were ball-milled and stirred in a stoichiometric ratio of 0.5:0.8:0.1:1 until uniformly mixed. The mixed raw materials were then added to a high-temperature sintering furnace, argon was introduced, the pre-sintering temperature was maintained at 600°C, and sintering was continued for 2 hours to obtain a pre-sintered product. The pre-sintered product was poured into a ball mill, and glucose was added and ball-milled until uniformly dispersed. The powder was then placed into a sintering furnace for secondary sintering at a temperature of 650°C for 6 hours. The secondary sintered product was then mixed with anhydrous ethanol to obtain a slurry with a solid content of 50%. The slurry was subjected to spray granulation treatment, the feed gas pressure was 1.2 MPa, the argon flow rate was 50 L / min, and the argon preheating temperature was 120°C to obtain nanoscale LMFP particles with a D 50 The particle size was 0.65 μm. The nanoscale LMFP particles were mixed with a conductive agent CNT, a binder PVDF, a dispersant PVP, and a solvent NMP in a mass ratio of 1:0.02:0.04:0.02:0.7 to prepare a slurry, which was coated on a current collector and assembled with a separator, a graphite negative electrode, and the like to form a full cell for testing.

[0127] Comparative Example 2

[0128] The method of the present comparative example was the same as that of Example 1, except that no pore-forming agent ammonium bicarbonate was added in step (1), and the details were as follows:

[0129] (1) The lithium carbonate, iron oxide, manganese carbonate, and ammonium dihydrogen phosphate were ball-milled and stirred in a stoichiometric ratio of 0.5:0.8:0.1:1 until uniformly mixed. The mixed raw materials were then added to a high-temperature sintering furnace, argon was introduced, the pre-sintering temperature was maintained at 600°C, and sintering was continued for 2 hours to obtain a first pre-sintered product. The first pre-sintered product was poured into a ball mill, and glucose was added and ball-milled until uniformly dispersed. The powder was then placed into a sintering furnace for secondary sintering at a temperature of 750°C for 8 hours. The secondary sintered product was then mixed with anhydrous ethanol to obtain a slurry with a solid content of 50%. The slurry was subjected to spray granulation treatment, the feed gas pressure was 1 MPa, the argon flow rate was 40 L / min, and the argon preheating temperature was 120°C to obtain micrometer-scale LMFP particles without pores, with a D 50 The particle size was 4 μm.

[0130] The lithium carbonate, iron oxide, manganese carbonate, and ammonium dihydrogen phosphate in a molar ratio of 0.5:0.8:0.1:1 were ball-milled and stirred until uniformly mixed, and the mixed raw materials were added to a high-temperature sintering furnace, argon was introduced, the pre-sintering temperature was maintained at 600°C, and sintering was continued for 2 hours to obtain a second pre-sintered product. The second pre-sintered product after standing and cooling was poured into a ball mill, and glucose was added for ball milling until uniformly dispersed. The powder mixed with glucose was again placed in a sintering furnace for secondary sintering at a temperature of 650°C for 6 hours. Then, the secondary sintered product was mixed with anhydrous ethanol to obtain a slurry with a solid content of 50%. The slurry was subjected to spray granulation treatment, and the conditions were as follows: feed gas pressure, 1.2 MPa; argon flow rate, 50 L / min; and argon preheating temperature, 120°C. Nanoscale LMFP particles were obtained, and the D 50 particle size of the nanoscale LMFP particles was 0.65 μm.

[0131] (2) The non-porous micrometer-scale particles and the nanoscale particles obtained above were mixed by stirring at a mass ratio of 1:100 to obtain mixed particles containing the non-porous micrometer-scale particles and the nanoscale particles, and the mixing temperature was 25°C and the stirring rate was 800 rpm.

[0132] (3) The composite particles were mixed with a conductive agent CNT, a binder PVDF, a dispersant PVP, and a solvent NMP at a mass ratio of 1:0.02:0.04:0.02:0.7 to form a positive electrode slurry. The positive electrode slurry was then sheared at a shearing rate of 6000 rpm, and the solid content of the positive electrode slurry was 50% by weight. The sheared slurry was coated on a current collector after stirring at 25°C for 20 minutes, and a positive electrode slurry layer was formed on the current collector. The solvent in the positive electrode slurry layer was removed to form a positive electrode tab containing a positive electrode material layer, and a full cell was assembled with a separator, a graphite negative electrode, and the like for testing.

[0133] Test Example 1

[0134] The D 50 particle size of the micrometer-scale particles obtained in Examples 1 to 9 and Comparative Examples 1 and 2 was tested. 50 The D 50 particle size of the nanoscale particles, the specific surface area and porosity of the composite particles, the specific surface area of the lithium-containing phosphate material, and the porosity of the positive electrode material layer were tested, and the test results are shown in Table 1.

[0135] In the present disclosure, the characterization of the lithium-containing phosphate material is a test performed on particles after filtration, drying, and sieving of the sheared slurry.

[0136] The specific surface area of the composite particles of Examples 1 to 9 in Table 1 refers to the specific surface area of the composite particles obtained by mixing in step (2).

[0137] The porosity of the composite particles in the present disclosure refers to the percentage of the volume of the internal pores of a single composite particle to the total volume. The porosity of the composite particles of Examples 1-9 in Table 1 is tested for the composite particles obtained by mixing in step (2).

[0138] The porosity of the lithium-containing phosphate material refers to the percentage of the volume of the internal pores of a single particle to the total volume.

[0139] The porosity of the positive electrode material layer refers to the percentage of the volume of the pores in a unit block-shaped positive electrode material layer to the total volume of the positive electrode material in a natural state.

[0140] Table 1

[0141] The specific surface area of the mixed particles containing the non-porous micron-sized particles and the nano-sized particles obtained in Comparative Example 2 through step (2) is 18.6 m 2 / g. According to the data in Table 1, the specific surface area of the composite particles obtained by mixing in Example 1 through step (2) is smaller than that of Comparative Example 2, indicating that the nano-sized particles are embedded into the pores of the micron-sized particles during the mixing process. According to the comparison of the porosity of the composite particles and the porosity of the lithium-containing phosphate material in Example 1, the porosity of the lithium-containing phosphate material after the shearing treatment through step (3) is higher than that of the composite particles, indicating that part of the nano-sized particles are detached from the pores of the micron-sized particles by shearing.

[0142] Test Example 2

[0143] The state of the positive electrode slurry after shearing of Examples 1-9 and Comparative Examples 1-2 is observed, and the viscosity of the slurry is tested at 0 h, 2 h, 8 h and 12 h after discharging. If the viscosity of the slurry exceeds 3500 mPa·s, it is defined that the slurry forms a gel. If the viscosity does not exceed 3500 mPa·s within 12 h, it is determined that the state of the slurry is good. The results are shown in Table 2.

[0144] Table 2

[0145] Test Example 3

[0146] The rate performance of the full cells assembled from Examples 1-9 and Comparative Examples 1-2 is tested. The test method is 1 / 3C constant current and constant voltage charge / discharge at room temperature, and the test results are shown in Table 3.

[0147] Table 3

[0148] The specific surface area of the nano-sized particles in Comparative Example 1 is 21 m 2According to the data in Tables 1, 2 and 3, compared with Comparative Example 1, the specific surface area of the lithium-containing phosphate material prepared by the method of the present disclosure is small, and when used for preparing a positive electrode sheet of a lithium ion battery, the water absorption degree of the positive electrode raw material can be reduced; in the mixing and slurry preparation process, the probability of particle agglomeration can be reduced, which is conducive to the uniform dispersion of the binder and the conductive agent and inhibits the crosslinking of the binder and the conductive agent to cause gelation, thereby ensuring the stable dispersion of the slurry and improving the reversible capacity of the battery and the rate performance of the battery by using the nano-sized particles in combination with the porous micrometer-sized large particles to increase the compaction density of the positive electrode material and expose the pore structure of the micrometer-sized particles to provide a lithium ion transmission channel for the electrolyte.

[0149] As can be seen from Examples 1 to 7 and Comparative Example 1, the positive electrode slurry prepared by the method of the present disclosure has less particle agglomeration, and the positive electrode slurry does not form gel within 4 hours; Comparative Example 1 forms serious gel within 1 hour and continuous particle agglomeration, which significantly affects the ion transmission rate of the battery.

[0150] As can be seen from Example 2 and Example 1, the content of the pore-forming agent in Example 1 is within the preferred range of the present disclosure, which enables the micrometer-sized particles to better form a porous structure and more favorably embed the nano-sized particles, thereby reducing the water absorption probability and avoiding gelation of the slurry. Similarly, as can be seen from Example 3 and Example 1, the ratio of the D 50 pore diameter of the micrometer-sized particles to the D 50 particle diameter of the nano-sized particles in Example 1 is within the preferred range of the present disclosure, which more favorably enables the nano-sized particles to embed the micrometer-sized particles and improves the rate performance of the battery. As can be seen from Example 4 and Example 1, the ratio of the D 50 particle diameter of the micrometer-sized particles to the D 50 particle diameter of the nano-sized particles in Example 1 is within the preferred range of the present disclosure, which avoids gelation of the slurry within 4 hours and more favorably improves the rate performance of the battery. As can be seen from Example 5 and Example 1, the gradation of the porous micrometer-sized particles and the nano-sized particles in Example 1 is better than that in Example 5, which more favorably improves the active sites and further improves the rate performance of the battery. As can be seen from Example 6 and Example 1, the shear rate in Example 1 is within the preferred range of the present disclosure, which more favorably separates the nano-sized particles from the micrometer-sized particles and improves the rate performance of the battery. As can be seen from Example 7 and Example 1, the ratio of the D 50 particle diameter of the micrometer-sized particles to the D 50 particle diameter of the nano-sized particles, the D 50 pore diameter of the micrometer-sized particles and the D 50The particle size ratio within the preferred range of this disclosure is more conducive to the embedding of nano-sized particles into the pores of micron-sized particles, avoiding agglomeration and improving the rate performance of the battery. Compared to Example 1, Example 8 shows that the D of the micron-sized particles in Example 1... 50 Particle size and D of nanoscale particles 50 The particle size ratio is within the preferred range of this disclosure, which is beneficial for increasing the porosity of the cathode material layer, facilitating lithium-ion transport, and resulting in better rate performance of the battery. Compared to Example 1, Example 9 shows that the micron-sized particles in Example 1 have a higher D... 50 Pore ​​size and D of nanoscale particles 50 The particle size ratio is within the preferred range of this disclosure, which avoids agglomeration and prevents the slurry from gelling within 4 hours, thus improving the rate performance of the battery.

[0151] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0152] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

Claims

1. A lithium phosphate-containing material, characterized in that, The lithium phosphate material includes lithium phosphate micron-sized particles with pores on their surface, and lithium phosphate nanon-sized particles are embedded in the pores of the lithium phosphate micron-sized particles.

2. The lithium phosphate material according to claim 1, wherein, The ratio of the D50 particle size of the lithium phosphate micron-sized particles to the D50 particle size of the lithium phosphate nano-sized particles is 5 to 10.

3. The lithium phosphate material according to claim 1 or 2, wherein, The ratio of the D50 pore size of the lithium phosphate micron-sized particles to the D50 particle size of the lithium phosphate nano-sized particles is 0.8 to 1.

4. The lithium-containing phosphate material according to any one of claims 1 to 3, wherein, The D50 particle size of the lithium phosphate nanoparticles is 0.5–0.9 μm.

5. The lithium phosphate material according to any one of claims 1 to 4, wherein, The D50 particle size of the lithium phosphate micron-sized particles is 2.5–10 μm, and the D50 pore size of the channels is 0.4–0.9 μm.

6. The lithium phosphate material according to any one of claims 1 to 5, wherein, The porosity of the lithium phosphate-containing material is 10-15%.

7. The lithium phosphate material according to any one of claims 1 to 6, wherein, The lithium phosphate micron-sized particles have the chemical formula LiA x B 1-x PO4 represents the composition, where A is one or more of Ti, V, Mn, Fe, Co and Ni, B is one or more of Ti, V, Mn, Fe, Co and Ni, and x is any value between 0 and 1; The lithium phosphate nanoparticles have the chemical formula LiA′ y B′ 1-y PO4 represents the composition, where A′ is one or more of Ti, V, Mn, Fe, Co and Ni, B′ is one or more of Ti, V, Mn, Fe, Co and Ni, and y is any value between 0 and 1.

8. A method for preparing a lithium phosphate material, characterized in that, The preparation method includes the following steps: (1) Mix the first lithium source, the first metal source and the first phosphorus source, and perform a first pre-sintering on the resulting mixture to obtain a first pre-sintered product; perform a first and second sintering on the first pre-sintered product, the first carbon source and the pore-forming agent, and perform a first crushing treatment or a first granulation treatment on the first and second sintered product to obtain lithium phosphate micron-sized particles. The second lithium source, the second metal source, and the second phosphorus source are mixed, and the resulting mixture is subjected to a second pre-sintering to obtain a second pre-sintered product. The second pre-sintered product and the second carbon source are subjected to a second sintering process, and the second sintered product is subjected to a second crushing process or a second granulation process to obtain lithium phosphate nanoparticles. (2) Mix the lithium phosphate nanoparticles and the lithium phosphate microparticles.

9. The preparation method according to claim 8, wherein, The first metal source and the second metal source are each independently a compound containing one or more elements selected from Ti, V, Mn, Fe, Co and Ni; the first carbon source and the second carbon source are each independently selected from one or more of sucrose, glucose, citric acid, phenolic resin, starch and carbon black.

10. The preparation method according to claim 8 or 9, wherein, In step (1), the mass of the pore-forming agent accounts for 1 to 5% of the total mass of the first pre-sintered product and the pore-forming agent; the pore-forming agent is selected from one or more of ethanol, oxalic acid, ammonium bicarbonate, ammonium carbonate, urea and ammonium chloride.

11. The preparation method according to any one of claims 8-10, wherein, In step (1), the conditions for the first pre-sintering include: being carried out under a protective gas, a pre-sintering temperature of 500-650°C, and a pre-sintering time of 2-6 hours; The conditions for the first and second sintering include: being carried out under a protective gas, a sintering temperature of 710–900°C, and a sintering time of 6–12 hours; The conditions for the first crushing process include: crushing the first secondary sintering product using a ball mill, with a ball mill speed of 400-500 r / min and a ball milling time of 8-10 h; The conditions for the first granulation process include: feed gas pressure of 0.8–1.2 MPa, inert protective gas flow rate of 30–50 L / min, gas preheating temperature of 100–150 °C, and feed solid content of 45–55%.

12. The preparation method according to any one of claims 8-11, wherein, In step (1), the conditions for the second pre-sintering include: being carried out under a protective gas, a pre-sintering temperature of 500-650°C, and a pre-sintering time of 2-6 hours; The conditions for the second and third sintering include: being carried out under a protective gas, a sintering temperature of 600-700℃, and a sintering time of 4-8 hours; The conditions for the second crushing process include: crushing the second secondary sintering product using a ball mill, with a ball mill speed of 450-600 r / min and a ball milling time of 10-15 h; The conditions for the second granulation process include: feed gas pressure of 1-1.5 MPa, inert protective gas flow rate of 40-60 L / min, gas preheating temperature of 100-150 °C, and feed solid content of 45-55%.

13. The preparation method according to any one of claims 8-12, wherein, In step (2), the mixing is a solid-phase mixing and is carried out under stirring conditions. The stirring rate is 500-1200 rpm, the mixing temperature is 25-35℃, and the mixing time is 30-60 min.

14. The preparation method according to any one of claims 8-13, wherein, In step (2), the D50 particle size of the lithium phosphate nanoparticles is 0.5–0.9 μm; The D50 particle size of the lithium phosphate micron-sized particles is 2.5 to 10 μm; the D50 particle size of the lithium phosphate micron-sized particles is 5 to 10 times that of the lithium phosphate nanoparticles.

15. A lithium phosphate material prepared by the preparation method according to any one of claims 8 to 14.

16. A method for preparing a lithium-ion battery cathode, characterized in that, The method includes: mixing a lithium phosphate material, a conductive agent, a binder, and a solvent to form a positive electrode slurry; forming a positive electrode slurry layer on a positive electrode current collector; removing the solvent from the positive electrode slurry layer; and forming a positive electrode sheet containing a positive electrode material layer. The lithium-containing phosphate material is any one of the lithium-containing phosphate materials described in claims 1 to 7 and claim 15.

17. The method according to claim 16, wherein, The method further includes: before forming the positive electrode slurry layer, shearing the positive electrode slurry, wherein the shearing conditions include: a shearing rate of 4000 to 8000 rpm and a shearing temperature of 20 to 35°C.

18. The method according to claim 16 or 17, wherein, The mass ratio of lithium phosphate micron-sized particles to lithium phosphate nano-sized particles is 1:(50-200).

19. A lithium-ion battery cathode prepared by the preparation method according to any one of claims 16 to 18.

20. A lithium-ion battery positive electrode, characterized in that, It includes a positive electrode current collector and a positive electrode material layer disposed on at least one side of the positive electrode current collector; the positive electrode material layer contains a lithium phosphate material; The lithium-containing phosphate material is any one of the lithium-containing phosphate materials described in claims 1 to 7 and claim 15.

21. The lithium-ion battery cathode according to claim 20, wherein, The porosity of the positive electrode material layer is 15-25%.

22. The lithium-ion battery cathode according to claim 20 or 21, wherein, The cathode material layer also contains cathode material nanoparticles; The cathode material nanoparticles have the chemical formula LiA″. z B″ 1-z PO4 represents the composition, where A″ is one or more of Ti, V, Mn, Fe, Co and Ni, B″ is one or more of Ti, V, Mn, Fe, Co and Ni, and z is any value between 0 and 1; The mass ratio of the cathode material nanoparticles to the lithium phosphate-containing material is (50-200):

1.

23. A lithium-ion battery, characterized in that, The lithium-ion battery cathode includes any one of claims 19 to 22.

24. An electrical appliance, characterized in that, Including the lithium-ion battery as described in claim 23.

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