A positive electrode material precursor and its preparation method and application

Abstract

The present invention relates to the field of lithium batteries and discloses a positive electrode material precursor, its preparation method, and its application. The positive electrode material precursor is a secondary microsphere formed by the accumulation of primary particles. It comprises a three-layer structure from the inside out: an inner core layer, an intermediate layer, and an outermost layer. The intermediate layer has a higher packing density than the inner core layer and the outermost layer, and the inner core layer has a higher packing density than the outermost layer. The positive electrode material prepared using the positive electrode material precursor of the present invention has improved discharge capacity and cycle stability and can be used in high-performance lithium batteries.

Description

Technical Field

[0001] The present invention relates to the field of lithium batteries, and in particular to a positive electrode material precursor and a preparation method and application thereof. Background Art

[0002] With the increasing popularity of electric vehicles and mobile devices, lithium-ion battery shipments are growing. Lithium-ion batteries are primarily composed of key materials such as the positive electrode, negative electrode, separator, and electrolyte. The positive electrode material determines key lithium-ion battery performance indicators such as energy density, cycle life, safety, and cost, and is therefore a key research focus.

[0003] Currently, commercial cathode materials mainly include olivine-structured LiFePO4, spinel-structured LiMn2O4, layered LiCoO2, and layered ternary cathode materials. Among them, ternary cathode materials have comprehensive advantages such as high charge and discharge capacity and low cost, and have huge market demand and potential. The main disadvantage of ternary cathode materials is that they have the problem of rapid capacity decay during battery cycling. Improving and improving the cycle stability of ternary cathode materials is of great significance for the commercial promotion of the material. At present, the performance of the material is mainly improved through modification processes such as ion doping and surface coating. There are relatively few studies on improving the cycle stability of materials from the perspective of ternary material structure.

[0004] The synthesis methods of ternary positive electrode materials include high-temperature solid-phase method, co-precipitation method, sol-gel method, spray drying method, combustion method, etc. Among them, the mainstream method for producing ternary positive electrode materials is to prepare the precursor material by co-precipitation process and then react it with lithium salt by high-temperature solid-phase reaction. In the above process, the precursor material prepared by the co-precipitation process determines the electrical properties of the positive electrode material, including charge and discharge capacity, charge and discharge efficiency, cycle stability, etc., and is the key to the production process of ternary positive electrode materials. CN107915263A discloses a method for preparing a ternary positive electrode material precursor by co-precipitation process, using a metal mixed solution of nickel, cobalt and manganese as raw material, and adding the metal salt solution, complexing agent ammonia water and precipitant sodium hydroxide into the reactor in a stoichiometric ratio. The temperature is controlled at 20-60 ° C, the pH value is controlled at 11-12, the rotation speed is 200-500r / min, and the entire reaction is carried out under N2 protection to obtain a precursor material with a size of 3.5-4.0μm.

[0005] The co-precipitation method can produce secondary microspheres formed by the agglomeration of primary particles by controlling process parameters. However, controlling the morphology and stacking of the primary particles to improve material performance has always been a difficult problem and challenge. Summary of the Invention

[0006] The present invention provides a cathode material precursor, a preparation method thereof, and an application thereof. The cathode material precursor has a novel morphology and can well control its stacking form. The cathode material prepared therefrom has good electrochemical performance, and its discharge capacity and cycle stability are improved.

[0007] A first aspect of the present invention provides a positive electrode material precursor, which is a secondary microsphere formed by the accumulation of primary particles, wherein the positive electrode material precursor is composed of a three-layer structure from the inside to the outside, namely, an inner core layer, an intermediate layer and an outermost layer; wherein the stacking density of the intermediate layer is higher than the stacking density of the inner core layer and the outermost layer, and the stacking density of the inner core layer is higher than the stacking density of the outermost layer.

[0008] In the above technical solution, the chemical composition of the positive electrode material precursor is Ni x Co y M z T p (OH) 2-q , wherein M is selected from at least one of Fe, Cr, Cu, Ti, Mg, W, Mo, Nb, Ca, Zn, Sn, Zr, Ga, Mn and Al, and T is selected from at least one of F, P and B; wherein 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤p≤0.5, wherein at least one of the values ​​of x, y and z is not 0; and the value range of q is determined according to the principle of electrical neutrality.

[0009] In the above technical solution, the positive electrode material precursor, with the total thickness of the three-layer structure as 100%, the thickness of the inner core layer accounts for 0.1%-50%, the thickness of the middle layer accounts for 40%-95%, and the thickness of the outermost layer accounts for 0.1%-20%.

[0010] In the above technical solution, in the positive electrode material precursor, the primary particles are in the form of flakes, and the thickness of the flakes is 1-200 nm.

[0011] In the above technical solution, the particle size of the positive electrode material precursor is 1-30 μm.

[0012] A second aspect of the present invention provides a method for preparing a cathode material precursor, comprising the steps of mixing and reacting a metal salt solution, a precipitant solution, and a complexing agent solution;

[0013] The time for the reaction system to reach a stable concentration of not less than 80% of the complexing agent from the time the complexing agent is added is controlled to be no more than 12 hours, and before the concentration of the complexing agent reaches the stable concentration, the concentration of the complexing agent in the reaction system is controlled to gradually increase, and the concentration change rate of the complexing agent is below 1 mol / L·h, preferably 0.001-1 mol / L·h.

[0014] In the above technical solution, preferably, before the concentration of the complexing agent reaches a stable concentration, the concentration change rate of the complexing agent in the reaction system is controlled to be 0.001-0.50 mol / L·h, more preferably 0.005-0.20 mol / L·h.

[0015] In the above technical solution, in the reaction system, the stable concentration of the complexing agent is 0.05-2.0 mol / L, preferably 0.05-1.2 mol / L.

[0016] In the above technical solution, a base liquid is selectively added to the reactor before the metal salt solution, precipitant solution, and complexing agent solution are added to the reactor. The base liquid is an aqueous solution containing a complexing agent. The volume of the base liquid is 0-100% of the reactor volume, preferably 0-80%, and more preferably 10%-60%. The concentration of the complexing agent in the base liquid is 0-1.8 mol / L, preferably 0.05-1.5 mol / L, and more preferably 0.1-1.0 mol / L.

[0017] In the above technical solution, the concentration of the complexing agent in the base solution is at least 0.05 mol / L lower than the stable concentration of the complexing agent, and preferably at least 0.1 mol / L lower.

[0018] In the above technical solution, preferably, before the complexing agent reaches a stable concentration in the reaction system, the solid content in the reaction system is not higher than 40 wt%, preferably not higher than 20 wt%, and more preferably not higher than 10 wt%.

[0019] In the above technical solution, the metal salt solution, the precipitant solution and the complexing agent solution are added dropwise to the reactor, and the reaction process controlled includes the pH value of the reaction system, the dropping speed, the reaction temperature, the reaction time, the stirring speed, the reaction atmosphere, etc.

[0020] In the above technical solution, the metal salt is selected from at least one of metal sulfate, metal nitrate, metal acetate and metal oxalate.

[0021] In the above technical solution, the precipitant is selected from at least one of hydroxides, carbonates and bicarbonates of Na, K and Li.

[0022] In the above technical solution, the complexing agent is selected from at least one of ammonium ion donors, alcoholamine complexing agents, aminocarboxylic acid complexing agents, hydroxyaminocarboxylic acids, carboxylic acid salts, and thiocyanate complexing agents.

[0023] In the above technical solution, the process conditions of the reaction include: temperature of 20-70°C, preferably 45-60°C; pH value of 8-14, preferably 10-12; the reaction is carried out under stirring conditions, preferably, the stirring speed is 50-1200r / min.

[0024] In the above technical solution, the reaction product can be subjected to conventional post-processing (such as solid-liquid separation and drying steps) to obtain a positive electrode material precursor.

[0025] In the above technical solution, preferably, before the concentration of the complexing agent reaches a stable concentration, the concentration change rate of the complexing agent in the reaction system is controlled to gradually decrease.

[0026] The third aspect of the present invention provides a cathode material precursor prepared by the preparation method described above.

[0027] A fourth aspect of the present invention provides a positive electrode material, which comprises the positive electrode material precursor as described above and lithium element.

[0028] A fifth aspect of the present invention provides the use of the positive electrode material precursor or the positive electrode material as described above in a lithium battery.

[0029] The positive electrode material precursor provided by the present invention is different from the precursor prepared by the prior art in that it is a secondary microsphere formed by the aggregation and accumulation of primary flakes, and the secondary microsphere includes a three-layer structure from the inside to the outside, namely an inner core layer, an intermediate layer and an outermost layer. Among them, the primary flakes in the inner core layer are relatively loosely stacked, the intermediate layer outside the inner core layer is very densely stacked, and the primary flakes in the outermost layer are even looser. The loose structure of the internal stacking is conducive to releasing the stress accumulated inside the material during the solid phase reaction and preventing the secondary particles from breaking. The dense stacking structure of the intermediate layer outside the inner core layer is conducive to improving the tap density of the precursor material. The looser stacking form of the outermost layer is conducive to the diffusion reaction of lithium ions to the interior of the precursor during the solid phase reaction. The above structural characteristics can give the positive electrode material precursor a higher volume energy density and better electrochemical performance. This is what the inventors discovered after a lot of research.

[0030] The positive electrode material and lithium battery positive electrode prepared using this positive electrode material precursor exhibit excellent cycling stability. At a 1C rate, the lithium battery can achieve a capacity retention rate of 99.9% after 100 charge and discharge cycles. At a 0.1C rate, the initial discharge capacity can reach 215.3 mAh / g, demonstrating high discharge capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is one of the SEM images of the cathode material precursor prepared in Example 1 of the present invention;

[0032] Figure 2 This is the second SEM image of the cathode material precursor prepared in Example 1 of the present invention;

[0033] Figure 3 This is a SEM image of the positive electrode material precursor prepared in Comparative Example 1 of the present invention;

[0034] Figure 4 This is the cycling result of a lithium battery assembled with the positive electrode material prepared in Example 1 of the present invention;

[0035] Figure 5 is a graph showing the concentration of the complexing agent in the reaction system of Example 1 of the present invention as a function of reaction time;

[0036] Figure 6 is a graph showing the concentration of the complexing agent in the reaction system of Example 9 of the present invention as a function of reaction time;

[0037] Figure 7 is a graph showing the concentration of the complexing agent in the reaction system of Example 10 of the present invention as a function of reaction time;

[0038] Figure 8 Cycling results of a lithium battery assembled with the positive electrode material prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is described in detail below.

[0040] The first aspect of the present invention provides a cathode material precursor, wherein the cathode material precursor is a secondary microsphere formed by the accumulation of primary particles, and the secondary microsphere comprises a three-layer structure from the inside to the outside, namely, an inner core layer, an intermediate layer, and an outermost layer;

[0041] The packing density of the inner core layer and the packing density of the outermost layer are both smaller than the packing density of the middle layer, and the packing density of the inner core layer is higher than the packing density of the outermost layer.

[0042] In one embodiment of the present invention, the precursor, based on the total thickness of the three-layer structure as 100%, the inner core layer thickness accounts for 0.1%-50%, the middle layer thickness accounts for 40%-95%, and the outermost layer thickness accounts for 0.1%-20%.

[0043] In one embodiment of the present invention, in the precursor, the primary particles are in the form of flakes, and the thickness of the flakes is 1-200 nm.

[0044] In one embodiment of the present invention, the precursor particle size is 1-30 μm.

[0045] In one embodiment of the present invention, the positive electrode material precursor has a chemical composition of Ni x Co y M z T p (OH) 2-q, wherein Co, M or T may or may not be contained, M is selected from at least one of Fe, Cr, Cu, Ti, Mg, W, Mo, Nb, Ca, Zn, Sn, Zr, Ga, Mn and Al, and T is selected from at least one of F, P, and B; wherein 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤p≤0.5, wherein at least one of the values ​​of x, y, and z is not 0, and the value of q is determined according to the principle of electrical neutrality.

[0046] In one embodiment of the present invention, preferably, M is selected from Mn and / or Al. That is, preferably, the chemical formula of the positive electrode material precursor is Ni x Co y Mn z (OH)2 or Ni x Co y Al z (OH)2.

[0047] It should be understood that the values ​​of x, y, and z satisfy the principle of electrical neutrality.

[0048] In a preferred embodiment of the present invention, the SEM image of the cathode material precursor is as follows: Figure 1 and Figure 2 As shown. Figure 1 It can be seen that the cathode material precursor of the present invention is a spherical particle, which is formed by the accumulation of primary flakes. Figure 2 It can be seen that the cathode material precursor of the present invention has a three-layer structure from the inside out: an inner core layer, an intermediate layer, and an outermost layer. The inner core layer is formed by a primary lamellar stacking, which is relatively loose and has a thickness of approximately 1.5 μm. The outermost layer is also formed by a lamellar stacking, which is even looser than the inner core layer and has a thickness of approximately 0.14 μm. The intermediate layer between the inner core layer and the outermost layer is very densely stacked and has a thickness of approximately 8.56 μm.

[0049] In the present invention, the scanning electron microscope (SEM) images were obtained using a ZEISS Merlin scanning electron microscope manufactured by ZEISS, Germany.

[0050] In the present invention, the medium particle size of the positive electrode material precursor is determined by dynamic light scattering technology using a Mastersizer 3000 laser particle size analyzer from Malvern Panalytical, UK.

[0051] The inventors of the present invention, through in-depth research on the co-precipitation process, creatively controlled the concentration variation range of the complexing agent and the relationship between the stable concentration of the complexing agent and time in the process of preparing the positive electrode material precursor, thereby obtaining secondary microsphere precursor particles formed by the accumulation of primary flakes. In addition, the accumulation form of the primary flakes can be controlled so that the inner core layer is relatively loosely accumulated, the middle layer is very densely accumulated, and the outermost layer is relatively loosely accumulated. The precursor material with such characteristics has good cycle stability and can be used in high-energy-density lithium batteries.

[0052] A second aspect of the present invention provides a method for preparing a positive electrode material precursor, comprising:

[0053] (1) selectively adding a bottom liquid into the reactor;

[0054] (2) adding a metal salt solution, a precipitant solution, and a complexing agent solution into a reactor, mixing, and reacting; wherein the time from the addition of the complexing agent in step (2) to the time when the concentration of the complexing agent in the reaction system reaches not less than 80% of the stable concentration of the complexing agent is controlled to be no more than 12 hours, and before the concentration of the complexing agent reaches the stable concentration, the concentration of the complexing agent in the reaction system is controlled to be gradually increased, and the concentration change rate of the complexing agent is less than 1 mol / L·h, preferably 0.001-1 mol / L·h, more preferably 0.001-0.50 mol / L·h, and even more preferably 0.005-0.20 mol / L·h;

[0055] (3) The product obtained in step (2) is subjected to solid-liquid separation and drying treatment to obtain the positive electrode material precursor.

[0056] The positive electrode material precursor has a chemical composition of Ni x Co y M z T p (OH) 2-q , wherein M is selected from at least one of Fe, Cr, Cu, Ti, Mg, W, Mo, Nb, Ca, Zn, Sn, Zr, Ga, Mn and Al, and T is selected from at least one of F, P and B;

[0057] Among them, the molar usage ratio of Ni element, Co element, M element and T element is (0-1): (0-1): (0-1): (0-0.5), among which, the usage of at least one of Ni element, Co element and M element is not 0, and the value range of q is determined by the value range of the above elements according to the principle of electrical neutrality.

[0058] In one embodiment of the present invention, the M is selected from at least one of Fe, Cr, Cu, Ti, Mg, W, Mo, Nb, Ca, Zn, Sn, Zr, Ga, Mn and Al; the metal salt solution optionally contains the element T, and T is selected from at least one of F, P and B.

[0059] In one embodiment of the present invention, the type of metal salt contained in the metal salt solution is not particularly limited. Preferably, the metal salt contained in the metal salt solution is selected from at least one of metal sulfates, metal nitrates, metal acetates, and metal oxalates. For example, the nickel salt may be at least one of nickel sulfate, nickel nitrate, nickel acetate, nickel oxalate, and nickel chloride; the cobalt salt may be at least one of cobalt nitrate, cobalt chloride, cobalt acetate, and cobalt sulfate; the manganese salt may be at least one of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride; and the aluminum salt may be at least one of aluminum nitrate, aluminum chloride, aluminum acetate, and aluminum sulfate.

[0060] In one embodiment of the present invention, preferably, the molar concentration of the metal salt solution is 0.01-5.0 mol / L, calculated as the metal element, for example, 0.01 mol / L, 0.1 mol / L, 0.5 mol / L, 1.0 mol / L, 2.0 mol / L, 3.0 mol / L, 4.0 mol / L, 5.0 mol / L and any range between any two values, more preferably 0.01-3.0 mol / L, further preferably 0.01-2.0 mol / L.

[0061] In one embodiment of the present invention, the type of the precipitant is not particularly limited. Preferably, the precipitant is selected from at least one of hydroxides, carbonates, and bicarbonates of Na, K, and Li.

[0062] In one embodiment of the present invention, the concentration of the precipitant solution may not be particularly limited. Preferably, the concentration of the precipitant solution is 0.01-16.0 mol / L, such as 0.01 mol / L, 0.02 mol / L, 0.1 mol / L, 0.5 mol / L, 1.0 mol / L, 2.0 mol / L, 3.0 mol / L, 4.0 mol / L, 5.0 mol / L, 6.0 mol / L, 7.0 mol / L, 8.0 mol / L, 9.0 mol / L, 10.0 mol / L, 11.0 mol / L, 12.0 mol / L, 13.0 mol / L, 14.0 mol / L, 15.0 mol / L, 16.0 mol / L and any range between any two values, preferably 0.02-10.0 mol / L.

[0063] In one embodiment of the present invention, the type of the complexing agent is not particularly limited and is a compound that can form a complex with Ni, Co and M in aqueous solution; preferably, the complexing agent is selected from at least one of ammonium ion donors, alcoholamine complexing agents, aminocarboxylic acid complexing agents, hydroxyaminocarboxylic acid complexing agents, carboxylic acid salt complexing agents and thiocyanate complexing agents.

[0064] In one embodiment of the present invention, the ammonium ion donor is preferably selected from at least one of aqueous ammonia, ammonium oxalate, ammonium carbonate and ammonium hydroxide.

[0065] In one embodiment of the present invention, the alcoholamine complexing agent is preferably selected from at least one of ethanolamine, diethanolamine, 2-dibutylaminoethanol, 2-diethylaminoethanol and N,N-diethylethanolamine.

[0066] In one embodiment of the present invention, the aminocarboxylic acid complexing agent is preferably selected from at least one of sodium nitrilotriacetate (NTA), potassium nitrilotriacetate, ethylenediaminetetraacetic acid and its salts (EDTA) and diethylenetriaminepentaacetic acid (DTPA).

[0067] In one embodiment of the present invention, the hydroxyaminocarboxylic acid complexing agent is preferably selected from at least one of hydroxyethylenediaminetetraacetic acid (HEDTA) and its salts, ethylene glycol bis(β-diaminoethyl)ethyl ether-N,N,N'N'-tetraacetic acid (EGTA) and its salts, and dihydroxyglycine and its salts.

[0068] In one embodiment of the present invention, the carboxylic acid salt complexing agent is preferably selected from at least one of oxalic acid and its salts, tartaric acid and its salts, citric acid and its salts, gluconic acid and its salts, carboxymethyl hydroxymalonic acid (CMOM) and its salts, carboxymethyl hydroxysuccinic acid (CMOS) and its salts, and hydroxyethylaminoacetic acid (DHEG) and its salts.

[0069] In one embodiment of the present invention, the thiocyanate complexing agent is preferably selected from at least one of sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate, calcium thiocyanide, and zinc thiocyanide.

[0070] In one embodiment of the present invention, the concentration of the complexing agent solution may not be particularly limited. Preferably, the concentration of the complexing agent solution is 0.01-16.0 mol / L, such as 0.01 mol / L, 0.1 mol / L, 0.5 mol / L, 1.0 mol / L, 2.0 mol / L, 3.0 mol / L, 4.0 mol / L, 5.0 mol / L, 6.0 mol / L, 7.0 mol / L, 8.0 mol / L, 9.0 mol / L, 10.0 mol / L, 11.0 mol / L, 12.0 mol / L, 13.0 mol / L, 14.0 mol / L, 15.0 mol / L, 16.0 mol / L and any range between any two values, more preferably 2.0-15.0 mol / L.

[0071] In one embodiment of the present invention, the stable concentration of the complexing agent in the reaction system is 0.05-2.0 mol / L, preferably 0.05-1.2 mol / L.

[0072] In one embodiment of the present invention, in order to regulate the morphology and exposed crystal planes of the primary particles in the precursor, the time for the reaction system to reach a stable concentration of not less than 80% of the complexing agent from the time the complexing agent is added in step (2) does not exceed 12 hours, and, preferably, before the complexing agent reaches a stable concentration in the reaction system, the solid content in the reaction system is not higher than 40 wt%, preferably not higher than 20 wt%, and further preferably not higher than 10 wt%.

[0073] In one embodiment of the present invention, in step (1), a base liquid is selectively added to the reactor. The base liquid is an aqueous solution containing a complexing agent. The volume of the base liquid is 0-100% of the volume of the reactor, preferably 0-80%, and more preferably 10%-60%. The concentration of the complexing agent in the base liquid is 0-1.8 mol / L, preferably 0.05-1.5 mol / L, and more preferably 0.1-1.0 mol / L.

[0074] In one embodiment of the present invention, the concentration of the complexing agent in the base solution is at least 0.05 mol / L lower than the stable concentration of the complexing agent, preferably at least 0.1 mol / L lower.

[0075] In one embodiment of the present invention, in step (2), before the concentration of the complexing agent in the reaction system reaches a stable concentration, the concentration change rate of the complexing agent in the reaction system is controlled to gradually decrease.

[0076] In the present invention, the "rate of change of the concentration of the complexing agent in the reaction system" refers to the difference between the final concentration and the initial concentration of the complexing agent in the reaction system within any time period, which is measured per hour in the present invention. The "rate of change of the concentration of the complexing agent in the reaction system gradually decreases" means that during the entire time period from the moment the complexing agent is added to the reaction system to the time when the stable concentration of the complexing agent is reached, the rate of change of the concentration of the complexing agent in the reaction system (on the whole) shows a trend of gradually decreasing, but one or more local intervals are allowed; within the local intervals, the concentration change of the complexing agent in the reaction system shows different trends (such as maintaining a constant and / or gradually increasing and / or disordered state). The premise is that the existence of such local intervals is inevitable for the level of technological development in this field, and the existence of these local intervals does not affect the technical personnel in this field from still determining that the rate of change of the concentration of the complexing agent in the reaction system within the entire time period is "(on the whole) showing a trend of gradually decreasing". In addition, the existence of such local intervals does not affect the realization of the intended purpose of the present invention, is acceptable, and is also included in the scope of protection of the present invention.

[0077] In one embodiment of the present invention, preferably, in step (2), the reaction process further includes pH of the reaction system, dropwise addition rate, reaction temperature, reaction time, stirring speed, etc.

[0078] In one embodiment of the present invention, in step (2), the pH of the reaction system is 8-14. As a preferred technical solution, the pH of the reaction system is 10-12. It should be understood that the control of pH can be to control a constant pH within the reaction time, or the pH of the reaction process can be changed according to the product target, but the pH variation range should be within the above-mentioned reaction system range. In a further preferred embodiment, the pH of the reaction system remains constant within the above-mentioned range. According to the present invention, the metal salt solution, complexing agent and precipitant, the drop rate of each material is selected in a wide range, and only needs to meet the stable concentration of the complexing agent in the reaction system, the concentration change rate of the complexing agent and the time to reach a stable concentration, as well as the above-mentioned pH range and solid content. Those skilled in the art can control the drop rate of each material as required.

[0079] In one embodiment of the present invention, in step (2), the reaction conditions preferably include: a temperature of 20-70°C, preferably 45-60°C; and a total reaction time of not less than 10 h, preferably 12-96 h.

[0080] In one embodiment of the present invention, the mixing is carried out under stirring conditions. More preferably, the stirring speed is 50-1200r / min, such as 50r / min, 80r / min, 100r / min, 200r / min, 300r / min, 400r / min, 500r / min, 600r / min, 700r / min, 800r / min, 900r / min, 1000r / min, 1200r / min, more preferably 600-1200r / min, and any value in the range formed by any two of these values.

[0081] In the present invention, there is no particular limitation on the solid-liquid separation in step (3), as long as the obtained precursor is separated, for example, by filtration or centrifugation.

[0082] In the present invention, preferably, the product obtained by solid-liquid separation is subjected to a washing treatment, and the washing solvent is preferably water, and more preferably the washing solvent is hot water at a temperature of 30-90°C.

[0083] In the present invention, the drying method may be any conventional method in the art, such as vacuum drying, freeze drying, air drying, or oven drying. Preferably, vacuum heating drying is used. There are no particular requirements for the drying temperature and time, as long as the precursor can be dried. For example, the vacuum heating drying temperature may be 50-150° C. and the drying time may be 4-24 hours.

[0084] The third aspect of the present invention provides a cathode material precursor prepared by the preparation method described above.

[0085] The properties of the positive electrode material precursor have been described in detail in the first aspect and will not be repeated here.

[0086] A fourth aspect of the present invention provides a positive electrode material, which comprises the positive electrode material precursor as described above and lithium element.

[0087] Preferably, the molar ratio of lithium element to battery positive electrode material precursor is 0.9-1.3:1, calculated as metal element, for example, 0.9, 0.95, 1.00, 1.05, 1.10, 1.15, 1.20, 1.30, and any value in the range formed by any two of these values.

[0088] The lithium element of the present invention may be present in the form of a lithium salt, and the lithium salt is preferably selected from at least one of lithium nitrate, lithium chloride, lithium carbonate, lithium hydroxide and lithium acetate.

[0089] The method of preparing positive electrode materials using positive electrode material precursors is well known in the art and will not be described here.

[0090] A fifth aspect of the present invention provides the use of the positive electrode material precursor or the positive electrode material as described above in a lithium battery.

[0091] The application provided by the present invention specifically includes mixing, coating, and slicing the above-mentioned battery positive electrode material with a conductive agent and a binder for use as a battery positive electrode. The conductive agent and binder can be various conductive agents and binders conventionally used in the art. For example, the conductive agent can be selected from at least one of acetylene black, Ketjen black, graphite, carbon tubes, and graphene. The binder can be selected from at least one of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC). The amount of the conductive agent and binder can also be the amount conventionally used in the art. For example, based on the total amount of the positive electrode, the mass content of the positive electrode material can be 50%-98%, the mass content of the conductive agent can be 1%-25%, and the mass content of the binder can be 1%-25%.

[0092] The lithium-ion battery includes a positive electrode, a negative electrode, a separator and an electrolyte. There are no particular restrictions on the negative electrode, separator and electrolyte, and those skilled in the art can reasonably select them without having to make creative efforts. For comparison, in the embodiment of the present invention, metallic lithium is used for the negative electrode, the separator is a US Celllgard 2400 polypropylene separator, the electrolyte is a 1 mol / L LiPF6 solution, and the solvent is a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1:1.

[0093] The batteries were assembled in an inert atmosphere glove box, where moisture and oxygen levels were kept below 0.1 ppm. While the battery model is not particularly limited, 2032 button cells are commonly used in the present invention. Electrochemical performance was tested on a Sunway BTS4000 system.

[0094] The electrochemical test conditions were as follows: temperature was 25°C; voltage range was 2.5-4.3V.

[0095] The method of preparing a lithium battery using a positive electrode material precursor or a positive electrode material is well known in the art and will not be described here.

[0096] The present invention will be described in detail below through examples.

[0097] In the following examples and comparative examples, the metal salt solution is a sulfate solution of Ni, Mn and Co elements or Al element.

[0098] Example 1

[0099] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0100] (1) Preparation of cathode material precursor

[0101] Prepare a metal salt solution with a metal ion concentration of 2 mol / L (wherein the molar ratio of nickel, cobalt and manganese elements is 8:1:1); prepare a NaOH solution with a concentration of 4 mol / L; prepare a complexing agent solution with an ammonia concentration of 6 mol / L.

[0102] The prepared metal salt solution, NaOH solution and complexing agent solution are added dropwise to the reactor simultaneously under stirring to cause precipitation reaction. Ammonia solution accounting for 30% of the reactor volume is added in advance to the reactor, and the ammonia concentration is 0.5 mol / L. The flow rates of the metal salt solution, NaOH solution and complexing agent solution are controlled, wherein the ratio of the initial volume flow rate of the metal salt solution to the complexing agent solution is 5. Then, the dropwise addition rate of the metal salt solution is kept constant, the concentration of the complexing agent in the system is gradually increased, and the rate of increase of the complexing agent concentration is gradually reduced until the concentration of the complexing agent reaches a stable concentration. The concentration of the complexing agent in the system changes with time. Figure 5 . The stable concentration of ammonia water in the reaction system is about 0.8 mol / L, and the pH value of the reaction system is controlled to be 11. The time for the reaction system to reach a stable concentration of not less than 80% of ammonia water from the time of adding ammonia water is about 10 hours, and the solid content in the reaction system is not higher than 10wt%. During the reaction, the stirring speed is controlled to be 800 rpm, the reaction temperature is 55°C, the total reaction time is 48 hours, and the solid content in the system is about 9wt% after the reaction. The precipitation reaction is terminated after natural cooling, and the above slurry is vacuum filtered, washed with deionized water 3 times, and then dried and dehydrated in a vacuum drying oven at 120°C for 12 hours to obtain a positive electrode material precursor.

[0103] (2) Evaluation of cathode material precursors

[0104] The SEM image of the ternary cathode material precursor is as follows: Figure 1 As shown, from Figure 1 As can be seen from the figure, the preparation method provided by the present invention can produce a ternary cathode material precursor with good sphericity. The precursor is a secondary microsphere formed by the accumulation of primary flakes. The median particle size D50 of the precursor is 10.2 μm, and the average thickness of the primary flakes is 11.2 nm.

[0105] In order to further analyze the stacking form of the primary flakes, the cathode material precursor was subjected to ion beam cutting and then characterized by scanning electron microscopy. The SEM image of the cross section of the cathode material precursor is shown in FIG. Figure 2 As shown, from Figure 2As can be seen, the precursor obtained by the preparation method provided by the present invention has a three-layer structure from the inside out: an inner core layer, an intermediate layer, and an outermost layer. The inner core layer is formed by a single lamellar stacking process, which is relatively loose and has a thickness of approximately 1.5 μm. The outermost layer is also formed by a lamellar stacking process, which is even looser than the inner core layer and has a thickness of approximately 0.14 μm. The intermediate layer between the inner core layer and the outermost layer is very densely stacked and has a thickness of approximately 8.56 μm.

[0106] (3) Preparation and evaluation of positive electrode materials

[0107] The cathode material precursor obtained in step (1) was fully mixed with the lithium source LiOH·H2O by ball milling for 30 min, and the molar ratio of Li:(Ni+Co+Mn) was controlled to be 1.05:1. The cathode material was pre-calcined at 500°C for 4 h in an oxygen atmosphere, and then calcined at 900°C for 12 h to perform a solid phase reaction to obtain the cathode material.

[0108] Take 10 g of the above-mentioned positive electrode material, add 1.25 g of acetylene black and 12.5 g of 10% polyvinylidene fluoride solution, mix well, coat, slice, and assemble into a lithium battery in a glove box.

[0109] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The material had a capacity retention rate of 99.9% after 100 cycles. Figure 4 The first discharge capacity at a rate of 0.1C is 215.3mAh / g, which is relatively high and can be used in high-performance lithium batteries.

[0110] Example 2

[0111] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0112] (1) Preparation of cathode material precursor

[0113] Prepare a metal salt solution with a metal ion concentration of 2 mol / L (wherein the molar ratio of nickel, cobalt, and aluminum elements is 8:1.5:0.5); prepare a NaOH solution with a concentration of 4 mol / L; prepare a complexing agent solution with an ammonia concentration of 6 mol / L.

[0114] The prepared metal salt solution, NaOH solution and complexing agent solution are added dropwise to the reactor simultaneously under stirring to cause precipitation reaction. An ammonia solution accounting for 30% of the reactor volume is added in advance in the reactor, and the ammonia concentration is 0.5mol / L. The flow velocity of the metal salt solution, NaOH solution and complexing agent solution is controlled, wherein the ratio of the initial volume flow rate of the metal salt solution to the complexing agent solution is 5, and then the dropwise addition rate of the metal salt solution is kept constant, the concentration of the complexing agent in the system gradually increases, and the rate of increase of the complexing agent concentration gradually decreases until the concentration of the complexing agent reaches a stable concentration, and the concentration of the complexing agent in the system changes with time as in Example 1. The stable concentration of ammonia in the reaction system is about 0.8mol / L, and the pH value of the reaction system is controlled to 11. The time from the dripping of ammonia in the reaction system to reaching a stable concentration of not less than 80% of ammonia is about 10h, and the solid content in the reaction system is not higher than 10wt%. During the reaction, the stirring speed was controlled at 800 rpm, the reaction temperature was 55°C, and the reaction time was 48 hours. After the reaction, the solid content of the system was approximately 9 wt%. The precipitation reaction was terminated after natural cooling. The slurry was vacuum filtered, washed three times with deionized water, and then dried in a vacuum drying oven at 120°C for 12 hours to obtain a positive electrode material precursor.

[0115] (2) Evaluation of cathode material precursors

[0116] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 10.9 μm and an average thickness of 15.9 nm.

[0117] (3) Preparation and evaluation of positive electrode materials

[0118] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0119] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 99.3%.

[0120] Example 3

[0121] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0122] (1) Preparation of cathode material precursor

[0123] Prepare a metal salt solution with a metal ion concentration of 2 mol / L (wherein the molar ratio of nickel, cobalt and manganese elements is 9:0.5:0.5); prepare a NaOH solution with a concentration of 4 mol / L; prepare a complexing agent solution with an ammonia concentration of 6 mol / L.

[0124] The prepared metal salt solution, NaOH solution and complexing agent solution are added dropwise to the reactor simultaneously under stirring to cause precipitation reaction. An ammonia solution accounting for 30% of the reactor volume is added in advance in the reactor, and the ammonia concentration is 0.5mol / L. The flow velocity of the metal salt solution, NaOH solution and complexing agent solution is controlled, wherein the ratio of the initial volume flow rate of the metal salt solution to the complexing agent solution is 5, and then the dropwise addition rate of the metal salt solution is kept constant, the concentration of the complexing agent in the system gradually increases, and the rate of increase of the complexing agent concentration gradually decreases until the concentration of the complexing agent reaches a stable concentration, and the concentration of the complexing agent in the system changes with time as in Example 1. The stable concentration of ammonia in the reaction system is 0.8mol / L, and the pH value of the reaction system is controlled to 11. The time from the dripping of ammonia in the reaction system to reaching a stable concentration of not less than 80% of ammonia is about 10h, and the solid content in the reaction system is not higher than 10wt%. During the reaction, the stirring speed was controlled at 800 rpm, the reaction temperature was 55°C, and the reaction time was 48 hours. After the reaction, the solid content of the system was approximately 9 wt%. The precipitation reaction was terminated after natural cooling. The slurry was vacuum filtered, washed three times with deionized water, and then dried in a vacuum drying oven at 120°C for 12 hours to obtain a positive electrode material precursor.

[0125] (2) Evaluation of cathode material precursors

[0126] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 10.7 μm and an average thickness of 12.4 nm.

[0127] (3) Preparation and evaluation of positive electrode materials

[0128] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0129] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 96.7%.

[0130] Example 4

[0131] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0132] (1) Preparation of cathode material precursor

[0133] Prepare a metal salt solution with a metal ion concentration of 2 mol / L (wherein the molar ratio of nickel, cobalt and manganese elements is 6:2:2); prepare a NaOH solution with a concentration of 4 mol / L; prepare a complexing agent solution with an ammonia concentration of 6 mol / L.

[0134] The prepared metal salt solution, NaOH solution and complexing agent solution are added dropwise to the reactor simultaneously under stirring to cause precipitation reaction. An ammonia solution accounting for 30% of the reactor volume is added in advance in the reactor, and the ammonia concentration is 0.5mol / L. The flow velocity of the metal salt solution, NaOH solution and complexing agent solution is controlled, wherein the ratio of the initial volume flow rate of the metal salt solution to the complexing agent solution is 5, and then the dropwise addition rate of the metal salt solution is kept constant, the concentration of the complexing agent in the system gradually increases, and the rate of increase of the complexing agent concentration gradually decreases until the concentration of the complexing agent reaches a stable concentration, and the concentration of the complexing agent in the system changes with time as in Example 1. The stable concentration of ammonia in the reaction system is 0.8mol / L, and the pH value of the reaction system is controlled to 11. The time from the dripping of ammonia in the reaction system to reaching a stable concentration of not less than 80% of ammonia is about 10h, and the solid content in the reaction system is not higher than 10wt%. During the reaction, the stirring speed was controlled at 800 rpm, the reaction temperature was 55°C, and the reaction time was 48 hours. After the reaction, the solid content of the system was approximately 9 wt%. The precipitation reaction was terminated after natural cooling. The slurry was vacuum filtered, washed three times with deionized water, and then dried in a vacuum drying oven at 120°C for 12 hours to obtain a positive electrode material precursor.

[0135] (2) Evaluation of cathode material precursors

[0136] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 10.5 μm and an average thickness of 19.7 nm.

[0137] (3) Preparation and evaluation of positive electrode materials

[0138] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0139] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 99.8%.

[0140] Example 5

[0141] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0142] (1) Preparation of cathode material precursor

[0143] Prepare a cobalt sulfate solution with a concentration of 2 mol / L; prepare a NaOH solution with a concentration of 4 mol / L; prepare a complexing agent solution, wherein the ammonia concentration is 6 mol / L.

[0144] The prepared metal salt solution, NaOH solution and complexing agent solution are added dropwise to the reactor simultaneously under stirring to cause precipitation reaction. An ammonia solution accounting for 30% of the reactor volume is added in advance in the reactor, and the ammonia concentration is 0.5mol / L. The flow velocity of the metal salt solution, NaOH solution and complexing agent solution is controlled, wherein the ratio of the initial volume flow rate of the metal salt solution to the complexing agent solution is 5, and then the dropwise addition rate of the metal salt solution is kept constant, the concentration of the complexing agent in the system gradually increases, and the rate of increase of the complexing agent concentration gradually decreases until the concentration of the complexing agent reaches a stable concentration, and the concentration of the complexing agent in the system changes with time as in Example 1. The stable concentration of ammonia in the reaction system is 0.8mol / L, and the pH value of the reaction system is controlled to 11. The time from the dripping of ammonia in the reaction system to reaching a stable concentration of not less than 80% of ammonia is about 10h, and the solid content in the reaction system is not higher than 10wt%. During the reaction, the stirring speed was controlled at 800 rpm, the reaction temperature was 55°C, and the reaction time was 48 hours. After the reaction, the solid content of the system was approximately 9 wt%. The precipitation reaction was terminated after natural cooling. The slurry was vacuum filtered, washed three times with deionized water, and then dried in a vacuum drying oven at 120°C for 12 hours to obtain a positive electrode material precursor.

[0145] (2) Evaluation of cathode material precursors

[0146] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 10.4 μm and an average thickness of primary flakes of 15.4 nm.

[0147] (3) Preparation and evaluation of positive electrode materials

[0148] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0149] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 99.8%.

[0150] Example 6

[0151] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0152] (1) Preparation of cathode material precursor

[0153] Prepare a manganese sulfate solution with a concentration of 2 mol / L; prepare a NaOH solution with a concentration of 4 mol / L; prepare a complexing agent solution, wherein the ammonia concentration is 6 mol / L.

[0154] The prepared metal salt solution, NaOH solution and complexing agent solution are added dropwise to the reactor simultaneously under stirring to cause precipitation reaction. An ammonia solution accounting for 30% of the reactor volume is added in advance in the reactor, and the ammonia concentration is 0.5mol / L. The flow velocity of the metal salt solution, NaOH solution and complexing agent solution is controlled, wherein the ratio of the initial volume flow rate of the metal salt solution to the complexing agent solution is 5, and then the dropwise addition rate of the metal salt solution is kept constant, the concentration of the complexing agent in the system gradually increases, and the rate of increase of the complexing agent concentration gradually decreases until the concentration of the complexing agent reaches a stable concentration, and the concentration of the complexing agent in the system changes with time as in Example 1. The stable concentration of ammonia in the reaction system is 0.8mol / L, and the pH value of the reaction system is controlled to 11. The time from the dripping of ammonia in the reaction system to reaching a stable concentration of not less than 80% of ammonia is about 10h, and the solid content in the reaction system is not higher than 10wt%. During the reaction, the stirring speed was controlled at 800 rpm, the reaction temperature was 55°C, and the reaction time was 48 hours. After the reaction, the solid content of the system was approximately 9 wt%. The precipitation reaction was terminated after natural cooling. The slurry was vacuum filtered, washed three times with deionized water, and then dried in a vacuum drying oven at 120°C for 12 hours to obtain a positive electrode material precursor.

[0155] (2) Evaluation of cathode material precursors

[0156] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 10.5 μm and an average thickness of primary flakes of 16.8 nm.

[0157] (3) Preparation and evaluation of positive electrode materials

[0158] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0159] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 99.7%.

[0160] Example 7

[0161] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0162] (1) Preparation of cathode material precursor

[0163] Prepare a metal salt solution with a metal ion concentration of 5 mol / L (wherein the molar ratio of nickel, cobalt and manganese elements is 8:1:1); prepare a NaOH solution with a concentration of 10 mol / L; prepare a complexing agent solution with an ammonia concentration of 15 mol / L.

[0164] The prepared metal salt solution, NaOH solution and complexing agent solution are added dropwise to the reactor simultaneously under stirring to cause precipitation reaction. An ammonia solution accounting for 30% of the reactor volume is added in advance in the reactor, and the ammonia concentration is 0.5mol / L. The flow velocity of the metal salt solution, NaOH solution and complexing agent solution is controlled, wherein the ratio of the initial volume flow rate of the metal salt solution to the complexing agent solution is 5, and then the dropwise addition rate of the metal salt solution is kept constant, the concentration of the complexing agent in the system gradually increases, and the rate of increase of the complexing agent concentration gradually decreases until the concentration of the complexing agent reaches a stable concentration, and the concentration of the complexing agent in the system changes with time as in Example 1. The stable concentration of ammonia in the reaction system is 0.8mol / L, and the pH value of the reaction system is controlled to 11. The time from the dripping of ammonia in the reaction system to reaching a stable concentration of not less than 80% of ammonia is about 10h, and the solid content in the reaction system is not higher than 10wt%. During the reaction, the stirring speed was controlled at 800 rpm, the reaction temperature was 55°C, and the reaction time was 48 hours. After the reaction, the solid content of the system was approximately 12 wt %. The precipitation reaction was terminated after natural cooling. The slurry was vacuum filtered, washed three times with deionized water, and then dried in a vacuum drying oven at 120°C for 12 hours to obtain a positive electrode material precursor.

[0165] (2) Evaluation of cathode material precursors

[0166] The SEM image of the cathode material precursor shows that it is a spherical particle formed by the accumulation of primary flakes. It has a three-layer structure from the inside out: an inner core layer, an intermediate layer, and an outermost layer. The inner core layer is formed by the accumulation of primary flakes, which is relatively loose. The outermost layer is also formed by the accumulation of flakes, which is even looser than the inner core layer. The intermediate layer between the inner core layer and the outermost layer is very dense. A representative cathode material precursor has an inner core layer thickness of approximately 0.78μm, an intermediate layer thickness of approximately 10.46μm, and an outermost layer thickness of approximately 0.16μm. The product has a median particle size (D50) of 11.3μm, and an average thickness of the primary flakes of 16.8nm.

[0167] (3) Preparation and evaluation of positive electrode materials

[0168] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0169] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 99.4%.

[0170] Example 8

[0171] This example is used to illustrate the preparation and evaluation methods of the positive electrode material precursor and positive electrode material of the present invention.

[0172] (1) Preparation of cathode material precursor

[0173] Prepare a metal salt solution with a metal ion concentration of 0.01 mol / L (wherein the molar ratio of nickel, cobalt and manganese elements is 8:1:1); prepare a NaOH solution with a concentration of 0.01 mol / L; prepare a complexing agent solution with an ammonia concentration of 0.01 mol / L.

[0174] According to the method described in Example 1, a positive electrode material precursor was obtained.

[0175] (2) Evaluation of cathode material precursors

[0176] The SEM image of the cathode material precursor shows that it is a spherical particle formed by the accumulation of primary flakes. It has a three-layer structure from the inside out: an inner core layer, an intermediate layer, and an outermost layer. The inner core layer is formed by the accumulation of primary flakes, which is relatively loose. The outermost layer is also formed by the accumulation of flakes, which is even looser than the inner core layer. The intermediate layer between the inner core layer and the outermost layer is very dense. For a representative cathode material precursor, the inner core layer is approximately 4.7μm thick, the intermediate layer is approximately 6.2μm thick, and the outermost layer is approximately 1.2μm thick. The product has a median particle size D50 of 12.5μm, and the average thickness of the primary flakes is 43.5nm.

[0177] (3) Preparation and evaluation of positive electrode materials

[0178] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0179] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 98.4%.

[0180] Example 9

[0181] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0182] (1) Preparation of cathode material precursor

[0183] Prepare a metal salt solution with a metal ion concentration of 2 mol / L (wherein the molar ratio of nickel, cobalt and manganese elements is 8:1:1); prepare a NaOH solution with a concentration of 4 mol / L; prepare a complexing agent solution with an ammonia concentration of 6 mol / L.

[0184] The prepared metal salt solution, NaOH solution and complexing agent solution are added dropwise to the reactor under stirring to cause precipitation reaction. Water accounting for 30% of the reactor volume is added to the reactor in advance. The flow rates of the metal salt solution, NaOH solution and complexing agent solution are controlled, wherein the ratio of the initial volume flow rate of the metal salt solution to the complexing agent solution is 5. Then, the dropwise addition rate of the metal salt solution is kept constant, and the concentration of the complexing agent in the system is gradually increased, and the rate of increase of the complexing agent concentration is gradually reduced until the concentration of the complexing agent reaches a stable concentration. The concentration of the complexing agent in the system changes with time. Figure 6 . The stable concentration of ammonia water in the reaction system is about 1.0 mol / L, and the pH value of the reaction system is controlled to be 11. The time for the reaction system to reach a stable concentration of not less than 80% of ammonia water from the time of adding ammonia water is about 8 hours, and the solid content in the reaction system is not higher than 10wt%. During the reaction, the stirring speed is controlled to be 800 rpm, the reaction temperature is 55°C, the reaction time is 48 hours, and the solid content in the system is about 9wt% after the reaction. The precipitation reaction is terminated after natural cooling, and the slurry is vacuum filtered, washed with deionized water 3 times, and then dried and dehydrated in a vacuum drying oven at 120°C for 12 hours to obtain a positive electrode material precursor.

[0185] (2) Evaluation of cathode material precursors

[0186] The SEM image of the cathode material precursor shows that it is a spherical particle formed by the accumulation of primary flakes. It has a three-layer structure from the inside out: an inner core layer, an intermediate layer, and an outermost layer. The inner core layer is formed by the primary flakes, which are relatively loose. The outermost layer is also formed by the flakes, which are even looser than the inner core layer. The intermediate layer between the inner core and the outermost layer is very dense. For a representative cathode material precursor, the inner core layer is approximately 3.9μm thick, the intermediate layer is approximately 5.5μm thick, and the outermost layer is approximately 1.3μm thick. The product has a median particle size (D50) of 10.8μm, and the average thickness of the primary flakes is 64.4nm.

[0187] (3) Preparation and evaluation of positive electrode materials

[0188] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0189] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 98.2%.

[0190] Example 10

[0191] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0192] (1) Preparation of cathode material precursor

[0193] Prepare a metal salt solution with a metal ion concentration of 2 mol / L (wherein the molar ratio of nickel, cobalt and manganese elements is 8:1:1); prepare a NaOH solution with a concentration of 4 mol / L; prepare a complexing agent solution with an ammonia concentration of 6 mol / L.

[0194] The prepared metal salt solution, NaOH solution and complexing agent solution are added dropwise to the reactor simultaneously under stirring to cause precipitation reaction. Ammonia solution accounting for 30% of the reactor volume is added in advance to the reactor, and the ammonia concentration is 0.5 mol / L. The flow rates of the metal salt solution, NaOH solution and complexing agent solution are controlled, wherein the ratio of the initial volume flow rate of the metal salt solution to the complexing agent solution is 5. Then, the dropwise addition rate of the metal salt solution is kept constant, the concentration of the complexing agent in the system is gradually increased, and the rate of increase of the complexing agent concentration is gradually reduced until the concentration of the complexing agent reaches a stable concentration. The concentration of the complexing agent in the system changes with time. Figure 7 . The stable concentration of ammonia water in the reaction system is 0.8 mol / L, and the pH value of the reaction system is controlled at 11. The time for the reaction system to reach a stable concentration of not less than 80% of ammonia water from the time of adding ammonia water is about 2 hours, and the solid content in the reaction system is not higher than 10wt%. During the reaction, the stirring speed is controlled to 800 rpm, the reaction temperature is 55°C, the reaction time is 48 hours, and the solid content in the system is about 9wt% after the reaction. The precipitation reaction is terminated after natural cooling, and the slurry is vacuum filtered, washed with deionized water 3 times, and then dried and dehydrated in a vacuum drying oven at 120°C for 12 hours to obtain a positive electrode material precursor.

[0195] (2) Evaluation of cathode material precursors

[0196] The SEM image of the cathode material precursor shows that it is a spherical particle formed by a primary flaky accumulation. It has a three-layer structure from the inside out: an inner core layer, an intermediate layer, and an outermost layer. The inner core layer is formed by a primary flaky accumulation, which is relatively loose. The outermost layer is also formed by a flaky accumulation, which is even looser than the inner core layer. The intermediate layer between the inner core layer and the outermost layer is very dense. A representative cathode material precursor has an inner core layer thickness of approximately 2.1μm, an intermediate layer thickness of approximately 7.57μm, and an outermost layer thickness of approximately 0.83μm. The product has a median particle size (D50) of 10.3μm, and an average thickness of 11.9nm for the primary flaky particles.

[0197] (3) Preparation and evaluation of positive electrode materials

[0198] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0199] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 99.1%.

[0200] Example 11

[0201] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0202] (1) Preparation of cathode material precursor

[0203] The method described in Example 1 was followed, except that the pH value of the system was controlled to be 14 by adjusting the dropping rate of the NaOH solution during the dropping process, thereby obtaining a cathode material precursor.

[0204] (2) Evaluation of cathode material precursors

[0205] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 10.9 μm and an average thickness of 73.5 nm for the primary flakes.

[0206] (3) Preparation and evaluation of positive electrode materials

[0207] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0208] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 92.5%.

[0209] Example 12

[0210] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0211] (1) Preparation of cathode material precursor

[0212] The method described in Example 1 was followed, except that the pH value of the system was controlled to be 8 by adjusting the dropping rate of the NaOH solution during the dropping process, thereby obtaining a cathode material precursor.

[0213] (2) Evaluation of cathode material precursors

[0214] SEM images of cathode material precursor and Figure 1 and Figure 2The product has a median particle size D50 of 15.9 μm and an average thickness of primary flakes of 112.4 nm.

[0215] (3) Preparation and evaluation of positive electrode materials

[0216] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0217] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 91.6%.

[0218] Example 13

[0219] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0220] (1) Preparation of cathode material precursor

[0221] The method described in Example 1 was followed, except that the reaction temperature was controlled at 70° C. during the dropwise addition process to obtain a positive electrode material precursor.

[0222] (2) Evaluation of cathode material precursors

[0223] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 9.5 μm and an average thickness of 20.3 nm for the primary flakes.

[0224] (3) Preparation and evaluation of positive electrode materials

[0225] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0226] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 97.7%.

[0227] Example 14

[0228] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0229] (1) Preparation of cathode material precursor

[0230] The method described in Example 1 was followed, except that the reaction temperature was controlled at 20° C. during the dropwise addition process to obtain a positive electrode material precursor.

[0231] (2) Evaluation of cathode material precursors

[0232] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 10.8 μm and an average thickness of primary flakes of 22.6 nm.

[0233] (3) Preparation and evaluation of positive electrode materials

[0234] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0235] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 97.4%.

[0236] Example 15

[0237] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0238] (1) Preparation of cathode material precursor

[0239] The operation was carried out in accordance with the method described in Example 1, except that the reaction time was 12 h, to obtain a positive electrode material precursor.

[0240] (2) Evaluation of cathode material precursors

[0241] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 6.4 μm and an average thickness of primary flakes of 11.5 nm.

[0242] (3) Preparation and evaluation of positive electrode materials

[0243] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0244] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 99.5%.

[0245] Example 16

[0246] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0247] (1) Preparation of cathode material precursor

[0248] The method described in Example 1 was followed, except that the stirring speed was 50 r / min, to obtain a positive electrode material precursor.

[0249] (2) Evaluation of cathode material precursors

[0250] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 13.7 μm and an average thickness of primary flakes of 24.5 nm.

[0251] (3) Preparation and evaluation of positive electrode materials

[0252] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0253] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 97.4%.

[0254] Example 17

[0255] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0256] (1) Preparation of cathode material precursor

[0257] The method described in Example 1 was followed, except that the stirring speed was 1200 r / min, to obtain a positive electrode material precursor.

[0258] (2) Evaluation of cathode material precursors

[0259] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 10.3 μm and an average thickness of primary flakes of 12.4 nm.

[0260] (3) Preparation and evaluation of positive electrode materials

[0261] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0262] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 99.5%.

[0263] Example 18

[0264] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0265] (1) Preparation of cathode material precursor

[0266] The method described in Example 1 was followed, except that TiSO 4 was added to the metal salt solution, wherein Ti / (Ni+Co+Mn)=1% mol, to obtain a positive electrode material precursor.

[0267] (2) Evaluation of cathode material precursors

[0268] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 10.2 μm and an average thickness of 1 primary platelets of 11.7 nm.

[0269] (3) Preparation and evaluation of positive electrode materials

[0270] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0271] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 99.6%.

[0272] Example 19

[0273] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0274] (1) Preparation of cathode material precursor

[0275] The method described in Example 1 was followed, except that MgSO 4 ·7H 2 O was added to the metal salt solution, wherein Mg / (Ni+Co+Mn)=1% mol, to obtain a positive electrode material precursor.

[0276] (2) Evaluation of cathode material precursors

[0277] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 10.1 μm and an average thickness of primary flakes of 11.9 nm.

[0278] (3) Preparation and evaluation of positive electrode materials

[0279] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0280] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 99.7%.

[0281] Example 20

[0282] This example is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material of the present invention.

[0283] (1) Preparation of cathode material precursor

[0284] The method described in Example 1 was followed, except that B2O3 was added to the metal salt solution, wherein B / (Ni+Co+Mn)=1% mol, to obtain a cathode material precursor.

[0285] (2) Evaluation of cathode material precursors

[0286] SEM images of cathode material precursor and Figure 1 and Figure 2 The product has a median particle size D50 of 10.5 μm and an average thickness of 1 primary platelets of 11.8 nm.

[0287] (3) Preparation and evaluation of positive electrode materials

[0288] The positive electrode material and lithium battery were prepared according to the method described in Example 1.

[0289] The electrochemical performance of the material was measured at a 1C rate, with a charge and discharge voltage range of 2.5-4.3V and an ambient temperature of 25°C. The capacity retention rate of the material after 100 cycles was 99.6%.

[0290] The above results demonstrate that the method described in this invention produces a novel cathode material precursor. Unlike conventional precursors, this precursor comprises secondary microspheres formed by the accumulation of primary flakes. These microspheres comprise a three-layer structure: an inner core, an intermediate layer, and an outermost layer. This unique structure imparts improved electrochemical properties, such as higher discharge capacity and improved cycling stability, enabling its use in high-performance lithium batteries.

[0291] Comparative Example 1

[0292] According to the method described in Example 1, a metal salt solution with a metal ion concentration of 2 mol / L (wherein the molar ratio of nickel, cobalt and manganese elements is 8:1:1) was prepared; a NaOH solution with a concentration of 4 mol / L was prepared; and a complexing agent solution with an ammonia concentration of 6 mol / L was prepared.

[0293] The prepared metal salt solution and NaOH solution were simultaneously added dropwise to a reactor under stirring to cause a precipitation reaction. Ammonia solution, accounting for 30% of the reactor volume and having an ammonia concentration of 0.5 mol / L, was pre-added to the reactor. The metal salt solution was added at the same rate as in Example 1, and the NaOH solution was added at a rate such that the pH of the reaction system was 11. The total amount of ammonia solution (the same as in Example 1) was added to the reaction system in three equal portions, one hour, 10 hours, and 30 hours after the start of the reaction. During the reaction, the stirring speed was controlled at 800 rpm, the reaction temperature was maintained at 55°C, and the total reaction time was 48 hours. After cooling naturally, the precipitation reaction terminated. The slurry was vacuum filtered, washed three times with deionized water, and then dried in a 120°C vacuum drying oven for 12 hours to obtain a positive electrode material precursor.

[0294] The SEM image of the prepared cathode material precursor is as follows: Figure 3 As shown, the precursor is an irregular agglomerate formed by loose stacking of nanoparticles, and the sphericity of the particles is very poor. Precursors of this morphology cannot meet the demand for precursor materials in the battery field.

[0295] The cathode material precursor prepared in Comparative Example 1 was used to prepare cathode material according to the method of Example 1 and assembled into a lithium battery. The electrochemical performance of the material at 1C rate was measured. The cycling results are shown in Figure 8 As can be seen from the figure, the capacity retention rate of the material after 100 cycles is only 35.9%, which is far lower than the effect of the embodiment of the present invention.

[0296] The above describes in detail the specific embodiments of the present invention, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as the contents disclosed by the present invention and fall within the scope of protection of the present invention.

Claims

1. A cathode material precursor, wherein the cathode material precursor is a secondary microsphere formed by accumulation of primary particles, characterized in that: The positive electrode material precursor is composed of a three-layer structure from the inside to the outside, namely, an inner core layer, an intermediate layer, and an outermost layer; wherein the packing density of the intermediate layer is higher than the packing density of the inner core layer and the outermost layer, and the packing density of the inner core layer is higher than the packing density of the outermost layer; The chemical composition of the positive electrode material precursor is Ni x Co y M z T p (OH) 2-q , wherein M is selected from at least one of Fe, Cr, Cu, Ti, Mg, W, Mo, Nb, Ca, Zn, Sn, Zr, Ga, Mn and Al, and T is selected from at least one of F, P and B; wherein 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤p≤0.5, wherein at least one of the values ​​of x, y and z is not 0; and the value range of q is determined according to the principle of electrical neutrality.

2. The cathode material precursor according to claim 1, characterized in that: The positive electrode material precursor has a total thickness of 100% of the three-layer structure, the thickness of the inner core layer accounts for 0.1%-50%, the thickness of the middle layer accounts for 40%-95%, and the thickness of the outermost layer accounts for 0.1%-20%.

3. The cathode material precursor according to claim 1, characterized in that: In the positive electrode material precursor, the primary particles are in the form of flakes, and the thickness of the flakes is 1-200 nm.

4. The cathode material precursor according to claim 1, characterized in that: The particle size of the positive electrode material precursor is 1-30 μm.

5. The method for preparing the cathode material precursor according to any one of claims 1 to 4, comprising: a step of mixing and reacting a metal salt solution, a precipitant solution and a complexing agent solution; The time from the addition of the complexing agent to the reaching of no less than 80% of the stable concentration of the complexing agent in the reaction system is controlled to be no more than 12 hours, and before the concentration of the complexing agent reaches the stable concentration, the concentration of the complexing agent in the reaction system is controlled to gradually increase, and the concentration change rate of the complexing agent is less than 1 mol / L·h.

6. The method according to claim 5, characterized in that The concentration change rate of the complexing agent is 0.001-1 mol / L·h.

7. The preparation method according to claim 5, characterized in that: Before the concentration of the complexing agent reaches a stable concentration, the concentration change rate of the complexing agent in the reaction system is controlled to be 0.001-0.50 mol / L·h; And / or, the stable concentration of the complexing agent is 0.05-2.0 mol / L.

8. The preparation method according to claim 5, characterized in that: Before the concentration of the complexing agent reaches a stable concentration, the concentration change rate of the complexing agent in the reaction system is controlled to be 0.005-0.20 mol / L·h; And / or, the stable concentration of the complexing agent is 0.05-1.2 mol / L.

9. The preparation method according to claim 5, characterized in that: Before adding the metal salt solution, precipitant solution and complexing agent solution into the reactor, adding the bottom liquid into the reactor; The base liquid is an aqueous solution containing a complexing agent; the concentration of the complexing agent in the base liquid is 0-1.8 mol / L; And / or, the concentration of the complexing agent in the base solution is at least 0.05 mol / L lower than the stable concentration of the complexing agent.

10. The preparation method according to claim 9, characterized in that: In the base solution, the concentration of the complexing agent is 0.05-1.5 mol / L; and / or, the volume of the bottom liquid is 10-80% of the volume of the reactor; And / or, the concentration of the complexing agent in the base solution is at least 0.1 mol / L lower than the stable concentration of the complexing agent.

11. The preparation method according to claim 10, characterized in that: In the base solution, the concentration of the complexing agent is 0.1-1.0 mol / L; And / or, the volume of the bottom liquid is 10%-60% of the volume of the reactor.

12. The preparation method according to claim 5, characterized in that: Before the complexing agent reaches a stable concentration in the reaction system, the solid content in the reaction system is not higher than 40 wt %.

13. The preparation method according to claim 12, characterized in that: Before the complexing agent reaches a stable concentration in the reaction system, the solid content in the reaction system is not higher than 20 wt %.

14. The preparation method according to claim 13, characterized in that: Before the complexing agent reaches a stable concentration in the reaction system, the solid content in the reaction system is not higher than 10 wt %.

15. The preparation method according to claim 5, characterized in that: The metal salt is selected from at least one of metal sulfate, metal nitrate, metal acetate and metal oxalate; and / or, the precipitant is selected from at least one of hydroxides, carbonates, and bicarbonates of Na, K, and Li; and / or, the complexing agent is selected from at least one of ammonium ion donors, alcoholamine complexing agents, aminocarboxylic acid complexing agents, hydroxyaminocarboxylic acids, carboxylic acid salts, and thiocyanate complexing agents; And / or, the process conditions of the reaction include: temperature of 20-70° C.; pH value of 8-14; and the reaction is carried out under stirring conditions.

16. The preparation method according to claim 15, characterized in that: The process conditions of the reaction include: temperature of 45-60° C.; pH value of 10-12; and stirring speed of 50-1200 r / min.

17. The preparation method according to any one of claims 5 to 16, characterized in that: Before the concentration of the complexing agent reaches a stable concentration, the concentration change rate of the complexing agent in the reaction system is controlled to gradually decrease.

18. A positive electrode material, characterized in that The positive electrode material comprises lithium and the positive electrode material precursor according to any one of claims 1 to 4.

19. Use of the cathode material precursor according to any one of claims 1 to 4 or the cathode material according to claim 18 in a lithium-ion battery.

Images