A high-stability positive electrode material precursor, a preparation method and application thereof

Abstract

This invention relates to the field of lithium-ion batteries, and discloses a highly stable cathode material precursor, its preparation method, and its application. The cathode material precursor is a secondary microsphere formed by the agglomeration of primary particles. The secondary microsphere includes a core layer, an intermediate layer, and an outermost layer. In the X-ray diffraction pattern of the outermost layer, the intensity ratio of the (110) and (102) crystal plane diffraction peaks is 0.1-1.5, and the diameter spacing of the secondary microsphere is 0.1-1. The preparation method of the cathode material precursor includes: subjecting a metal source solution, a precipitant solution, and a complexing agent solution to a precipitation reaction to obtain a reaction product; subjecting the reaction product to solid-liquid separation and drying; wherein the total reaction time is denoted as R hours, and the solid content of the reaction system varies within the range of less than 3 wt% from 1 / 12R hours before the end of the reaction to the end of the reaction. When the cathode material prepared by this cathode material precursor is applied to a lithium-ion battery, its cycle stability is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, specifically to a cathode material precursor and its preparation method, a cathode material, and a lithium-ion battery. Background Technology

[0002] Layered ternary cathode materials offer the advantage of high energy density, meeting the application requirements of electric vehicles, laptops, and other terminals. However, as energy density increases, the cycle stability of layered ternary cathode materials decreases, a problem that urgently needs to be addressed.

[0003] Currently, the main approach to improving the cycle stability of ternary cathode materials is through modification. For example, patent application CN109742347A discloses a coated high-nickel cathode material and its preparation method. This method improves cycle stability by using a solvent and a phosphate coating precursor soluble in that solvent to form a phosphate coating layer on the surface of the high-nickel cathode material. Patent application CN102210045A discloses doping modification using components such as Mg, Ti, Zr, Al, and Fe to improve the cycle stability of Ni, Co, and Mn-based cathode active materials under high voltage conditions. While these modification processes improve the cycle stability of ternary cathode materials, they also suffer from problems such as complex operation, high cost, poor controllability, and poor consistency.

[0004] Ternary cathode materials are generally produced by preparing precursor materials through a co-precipitation process, followed by a high-temperature solid-state reaction with lithium salts. The properties of the precursor have a significant impact on the properties of the final cathode material. Improving the cycle stability and other properties of ternary cathode materials through the structural design of the precursor material is a novel approach. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of poor cycle stability of ternary cathode materials in the battery cycle process in the prior art, and to provide a cathode material precursor and its preparation method, cathode material and lithium-ion battery. The cathode material provided by this invention has good electrochemical performance and significantly improved cycle stability.

[0006] To achieve the above objectives, the first aspect of the present invention provides a cathode material precursor, wherein the cathode material precursor is a secondary microsphere formed by the agglomeration of primary particles; wherein the secondary microsphere comprises a core layer, an intermediate layer and an outermost layer from the inside out, wherein in the X-ray diffraction pattern of the outermost layer, the intensity ratio of the diffraction peaks of the (110) and (102) crystal planes is 0.1-1.5, preferably 0.5-1.5; and the radial distance of the secondary microsphere is 0.1-1.

[0007] A second aspect of the present invention provides a method for preparing a cathode material precursor, the method comprising the following steps:

[0008] (1) The metal source solution, precipitant solution and complexing agent solution are subjected to a precipitation reaction to obtain the reaction product;

[0009] (2) The reaction product is subjected to solid-liquid separation and drying to obtain the cathode material precursor;

[0010] The total reaction time is denoted as R hours. From 1 / 12R hours before the end of the reaction to the end of the reaction, the solid content of the precipitation reaction system varies within the range of less than 3 wt%.

[0011] Preferably, in the last 1 / 12R hour before the end of the reaction, the solid content of the precipitation reaction system is not less than 9 wt%.

[0012] Preferably, the concentration of the complexing agent in the precipitation reaction system gradually increases, and the rate of change of the concentration of the complexing agent gradually decreases.

[0013] Preferably, the concentration change rate of the complexing agent is below 1 mol / L·h, more preferably 0.001-1 mol / L·h, and even more preferably 0.001-0.5 mol / L·h.

[0014] Preferably, from 1 / 12R hour before the end of the reaction to the end of the reaction, the rate of change of the complexing agent concentration is less than 0.005 mol / L·h.

[0015] A third aspect of the present invention provides a cathode material precursor prepared by the method described in the second aspect above.

[0016] A fourth aspect of the present invention provides a cathode material, the cathode material comprising a lithium source and a cathode material precursor as described in the first or third aspect above.

[0017] The fifth aspect of the present invention provides a lithium-ion battery, the lithium-ion battery comprising the positive electrode material described in the fourth aspect above.

[0018] Through the above technical solution, the present invention can achieve the following beneficial effects:

[0019] The cathode material precursor provided by this invention differs from precursors prepared by existing technologies in that it is a secondary microsphere formed by the aggregation of primary particles. The secondary microsphere comprises a three-layer structure from the inside out: a core layer, an intermediate layer, and an outermost layer. The outermost layer has a specific diffraction peak structure, with the intensity ratio of the (110) and (102) crystal plane diffraction peaks being 0.1-1.5, preferably 0.5-1.5, and the radial distance of the secondary microsphere is 0.1-1.

[0020] In this invention, by controlling the solid content of the precipitation reaction system to vary within the range of less than 3 wt% from 1 / 12R hour before the reaction ends to the end of the reaction, the outermost layer of the obtained cathode material precursor has a specific diffraction peak structure. At the same time, the secondary microspheres have a relatively narrow diameter, which improves the side reactions between the material interface and the electrolyte, improves the consistency of the charge state of different particles during the charging and discharging process, and enhances the cycle stability of the material.

[0021] When the cathode material prepared using this cathode material precursor is applied to lithium-ion batteries, the cycle stability of the lithium-ion batteries is improved. As can be seen from the examples, at 1C rate, the lithium-ion battery can output an energy density of 674.2 Wh / kg based on the mass of the cathode material in the first cycle, and after 200 charge-discharge cycles, the capacity retention rate can reach 101% of the initial capacity at 1C. The cathode material precursor provided by this invention can be used in high-energy-density and high-stability lithium-ion batteries. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the cathode material precursor provided by the present invention;

[0023] Figure 2 This is a graph showing the change in the concentration of the complexing agent in the reaction system of Example 1 of the present invention over reaction time;

[0024] Figure 3 This is a SEM image of the cathode material precursor obtained in Example 1 of this invention;

[0025] Figure 4 This is a SEM image of a cross-section of the cathode material precursor obtained in Example 1 of this invention;

[0026] Figure 5 This is the XRD pattern of the outermost layer of the cathode material precursor obtained in Example 1 of this invention;

[0027] Figure 6 This is a diagram showing the cycling results of a lithium-ion battery assembled from the cathode material obtained in Example 1 of this invention.

[0028] Figure 7 This is a graph showing the cycling results of a lithium-ion battery assembled from the cathode material prepared in Comparative Example 1 of this invention. Detailed Implementation

[0029] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0030] The first aspect of this invention provides a cathode material precursor, wherein the cathode material precursor is a secondary microsphere formed by the agglomeration of primary particles; wherein the secondary microsphere comprises a core layer, an intermediate layer, and an outermost layer from the inside out, and in the X-ray diffraction pattern of the outermost layer, the intensity ratio of the diffraction peaks of the (110) and (102) crystal planes is 0.1-1.5, preferably 0.5-1.5, more preferably 0.8-1.3, for example, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, and any value within the range formed by any two of these values. The radial distance of the secondary microsphere is 0.1-1, preferably 0.3-1, for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, and any value within the range formed by any two of these values.

[0031] In this invention, the outermost X-ray diffraction pattern (XRD) was obtained using a Bruker D8 AdvanceSS X-ray diffractometer. In the outermost XRD pattern, the diffraction peaks at 2θ positions of 56°-61° and 48°-54° correspond to the (110) and (102) crystal planes, respectively. The intensity ratio of the (110) and (102) crystal plane diffraction peaks refers to the ratio of the peak height of the (110) crystal plane diffraction peak to the peak height of the (102) crystal plane diffraction peak.

[0032] In this invention, the diameter of the secondary microspheres is measured using a Mastersizer 3000 laser particle size analyzer from Malvern Panalytical, UK. The diameter of the secondary microspheres is obtained using the formula (D90-D10) / D50, where D10 refers to the particle size corresponding to a particle size distribution of 10%, D50 refers to the particle size corresponding to a particle size distribution of 50%, and D90 refers to the particle size corresponding to a particle size distribution of 90%.

[0033] The inventors of this invention discovered in their research that the outermost layer of the cathode material precursor has the aforementioned specific diffraction peak structure. This diffraction peak structure has low activity, which is beneficial for stabilizing the material interface. At the same time, the particle size distribution of the secondary microspheres is relatively narrow, and the charge state of different particles is consistent during the charge and discharge process, thereby improving the cycle stability of the material.

[0034] In this invention, the core layer refers to the first region extending from the center of the secondary microsphere outwards; the intermediate layer refers to the second region enclosing the core layer and extending from the outer surface of the core layer outwards to the outer surface of the secondary microsphere; and the outermost layer refers to the third region enclosing the intermediate layer and extending from the outer surface of the intermediate layer outwards to the outer surface of the secondary microsphere. A detailed structural diagram is shown below. Figure 1 As shown.

[0035] In a preferred embodiment of the present invention, the density of the kernel layer, the intermediate layer and the outermost layer is in the following order: intermediate layer > kernel layer > outermost layer.

[0036] In a preferred embodiment of the present invention, with the radius of the secondary microspheres as 100%, the thickness of the core layer accounts for 0.1-50%, the thickness of the intermediate layer accounts for 40-95%, and the thickness of the outermost layer accounts for 0.1-20%.

[0037] In a preferred embodiment of the present invention, the shape of the primary particles is selected from at least one of flake-shaped, slat-shaped, needle-shaped, and spindle-shaped.

[0038] In this invention, the morphology of the cathode material precursor is characterized by scanning electron microscopy (SEM), using a ZEISS Merlin microscope (ZEISS GmbH, Germany). The SEM images of the cathode material precursor (e.g.) are shown below. Figure 3 , Figure 4 It can be observed that the cathode material precursor provided by the present invention is a spherical particle, which is formed by the aggregation of a primary plate-like body and includes a three-layer structure from the inside out, namely the core layer, the middle layer and the outermost layer.

[0039] Furthermore, through SEM images of the cathode material precursor (such as...) Figure 3 , Figure 4 Furthermore, the density of the agglomeration of the core layer, intermediate layer, and outermost layer can be observed, and the thickness of the core layer, intermediate layer, and outermost layer can be measured. Specifically, from the SEM image of the cathode material precursor (e.g., Figure 3 , Figure 4 It can be observed that the core layer is formed by a primary sheet-like aggregation, which is relatively loose, with a thickness of about 1.1 μm. The outermost layer is also formed by a primary sheet-like aggregation, which is even looser than the core layer, with a thickness of about 0.22 μm. The intermediate layer between the core layer and the outermost layer is very dense, with a thickness of about 3.8 μm.

[0040] The inventors of this invention discovered that the core layer has a low density, which can further reduce the resistance to lithium ion insertion and extraction within the core layer. Simultaneously, it can effectively buffer the volume changes of the active material during charging and discharging, effectively suppressing cracking and breakage caused by volume expansion and contraction during charging and discharging, thus improving the cycle stability of the material. The intermediate layer has the highest density, which can effectively increase the volumetric energy density of the active material. The outermost layer has the lowest density, allowing for rapid insertion of external lithium ions into the bulk phase of the material, effectively reducing the interfacial resistance and significantly improving the cycle stability of the active material.

[0041] In a preferred embodiment of the present invention, the particle size of the secondary microspheres is 1-30 μm, preferably 1-20 μm, and more preferably 1-15 μm.

[0042] In this invention, the particle size of the secondary microspheres refers to the medium particle size D50 of the secondary microspheres, which is measured by dynamic light scattering technology, specifically by a Mastersizer 3000 laser particle size analyzer from Malvern Panalytical, UK.

[0043] In a preferred embodiment of the present invention, the general chemical formula of the cathode material precursor is Ni. x Co y M z T p (OH) 2-q Wherein, M is selected from at least one of Cu, Ge, Mg, W, Mo, Zn, Sn, Ce, Mn and Al, preferably at least one of Mn, Al, Zn, Ge and Ce; T is selected from at least one of N, P and S; 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤p≤0.5, preferably 0.5≤x≤0.95, 0≤y≤0.5, 0≤z≤0.5, 0≤p≤0.3, wherein at least one of x, y and z is not 0, and the range of q is determined according to the principle of electroneutrality.

[0044] A second aspect of the present invention provides a method for preparing a cathode material precursor, the method comprising the following steps:

[0045] (1) The metal source solution, precipitant solution and complexing agent solution are subjected to a precipitation reaction to obtain the reaction product;

[0046] (2) The reaction product is subjected to solid-liquid separation and drying to obtain the cathode material precursor;

[0047] The total reaction time is denoted as R hours. From 1 / 12R hours before the end of the reaction to the end of the reaction, the solid content of the precipitation reaction system varies within a range of less than 3 wt%, for example, 0 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, and any value within any two of these values.

[0048] Through in-depth research on the precipitation reaction process, the inventors of this invention discovered that by controlling the solid content of the precipitation reaction system within the range of 1 / 12R hour before the end of the reaction and until the end of the reaction, they creatively obtained secondary microsphere precursor particles formed by primary particle aggregation. Furthermore, they were able to control the aggregation form of the primary particles, resulting in a relatively loose aggregation of the core layer, a very dense aggregation of the middle layer, and a relatively loose aggregation of the outermost layer. They were also able to control the outermost layer to exhibit a specific diffraction peak structure and a relatively narrow secondary microsphere size distribution. The cathode material precursor material with these characteristics has better cycle stability and can be used in high-performance lithium-ion batteries.

[0049] In a preferred embodiment of the present invention, the precipitation reaction includes: simultaneously adding a metal source solution, a precipitant solution, and a complexing agent solution into a reaction vessel under stirring to carry out the reaction.

[0050] In a preferred embodiment of the present invention, the metal source is selected from at least one of nickel source, cobalt source and M source, and M is selected from at least one of Cu, Ge, Mg, W, Mo, Zn, Sn, Ce, Mn and Al, preferably at least one of Ge, Ce, Zn, Mn and Al.

[0051] In this invention, there is no particular limitation on the type of nickel source. Preferably, the nickel source is selected from at least one of nickel sulfate, nitrate, acetate, oxalate and hydrochloride. More preferably, the nickel source is selected from at least one of nickel sulfate, nickel nitrate, nickel acetate, nickel oxalate and nickel chloride.

[0052] In this invention, there is no particular limitation on the type of cobalt source. Preferably, the cobalt source is selected from at least one of cobalt sulfate, nitrate, acetate, oxalate and hydrochloride. More preferably, the cobalt source is selected from at least one of cobalt sulfate, cobalt nitrate, cobalt acetate and cobalt chloride.

[0053] In this invention, there is no particular limitation on the type of M source. Preferably, the M source is selected from at least one of the sulfate, nitrate, acetate, oxalate and hydrochloride of M, and more preferably from at least one of manganese sulfate, manganese nitrate, manganese acetate, manganese chloride, aluminum nitrate, aluminum chloride, aluminum acetate, aluminum sulfate, zinc sulfate, magnesium sulfate and titanium sulfate.

[0054] In a preferred embodiment of the present invention, the molar concentration of the metal source solution, calculated by metal element, is 0.01-5 mol / L, preferably 0.01-4 mol / L, and more preferably 0.5-4 mol / L.

[0055] In a preferred embodiment of the present invention, the precipitation reaction further includes adding a T source to the metal source solution, wherein T is selected from at least one of N, P, and S.

[0056] In a preferred embodiment of the present invention, the molar ratio of nickel source, cobalt source, M source and T source in the metal source solution, calculated as metal elements, is (0-1):(0-1):(0-1):(0-0.5), preferably (0.5-0.95):(0-0.5):(0-0.5):(0-0.3), wherein at least one of the nickel source, cobalt source and M source is not 0.

[0057] In this invention, there are no particular limitations on the type of precipitant, as long as it can satisfy the precipitation reaction of the metal source. Preferably, the precipitant is selected from at least one of alkali metal hydroxides, carbonates, and bicarbonates, and the alkali metal is preferably selected from at least one of Na, K, and Li. More preferably, the precipitant is selected from at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, lithium hydroxide, lithium carbonate, and lithium bicarbonate. Sodium hydroxide is used as an example in this embodiment, but the invention is not limited thereto.

[0058] In this invention, there is no particular limitation on the concentration of the precipitant solution. Preferably, the concentration of the precipitant solution is 0.01-16 mol / L, and more preferably 2-12 mol / L.

[0059] In this invention, there is no particular limitation on the type of complexing agent, as long as it 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, alkanolamine complexing agents, aminocarboxylic acid complexing agents, hydroxyaminocarboxylic acid complexing agents, carboxylate complexing agents and thiocyanate complexing agents.

[0060] In a preferred embodiment of the present invention, the ammonium ion donor is selected from at least one of ammonia, ammonium oxalate, ammonium carbonate, and ammonium hydroxide. Ammonia is used as an example in this embodiment, but the invention is not limited thereto.

[0061] In a preferred embodiment of the present invention, the alkanolamine complexing agent is selected from at least one of ethanolamine, diethanolamine, 2-dibutylaminoethanol, 2-diethylaminoethanol and N,N-diethylethanolamine.

[0062] In a preferred embodiment of the present invention, the aminocarboxylic acid complexing agent is selected from at least one of sodium nitrilotriacetate (NTA), potassium nitrilotriacetate, ethylenediaminetetraacetic acid and its salts (EDTA), and diethylenetriaminepentaacetic acid (DTPA).

[0063] In a preferred embodiment of the present invention, the hydroxyaminocarboxylic acid complexing agent is selected from at least one of ethylenediaminetetraacetic 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.

[0064] In a preferred embodiment of the present invention, the carboxylate complexing agent is 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 hydroxyethyl aminoacetic acid (DHEG) and its salts.

[0065] In a preferred embodiment of the present invention, the thiocyanate complexing agent is selected from at least one of sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate, calcium thiocyanate, and zinc thiocyanate.

[0066] In this invention, there is no particular limitation on the concentration of the complexing agent solution. Preferably, the concentration of the complexing agent solution is 0.01-16 mol / L, and more preferably 2-15 mol / L.

[0067] In a preferred embodiment of the present invention, a base liquid is added to the reactor before the metal source solution, precipitant solution and complexing agent solution are added to the reactor.

[0068] In a preferred embodiment of the present invention, 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 reaction vessel, 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.

[0069] In a preferred 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 concentration of the complexing agent at the end of the reaction, preferably at least 0.1 mol / L lower.

[0070] In a preferred embodiment of the present invention, the concentration of the complexing agent in the precipitation reaction system gradually increases, and the rate of change of the concentration of the complexing agent gradually decreases; the rate of change of the concentration of the complexing agent is below 1 mol / L·h, preferably 0.001-1 mol / L·h, and more preferably 0.001-0.5 mol / L·h.

[0071] In a preferred embodiment of the present invention, the total reaction time is denoted as R hours. From 1 / 12R hours before the end of the reaction until the end of the reaction, the rate of change of the complexing agent concentration is less than 0.005 mol / L·h, preferably 0.001-0.005 mol / L·h, for example, 0.001 mol / L·h, 0.0015 mol / L·h, 0.002 mol / L·h, 0.0025 mol / L·h, 0.003 mol / L·h, 0.0035 mol / L·h, 0.004 mol / L·h, 0.0045 mol / L·h, 0.005 mol / L·h, and any value within any two of these ranges. Using this preferred embodiment, the cycle stability of the prepared cathode material precursor can be significantly improved.

[0072] In this invention, the "concentration change rate of the complexing agent" refers to the difference between the final concentration and the initial concentration of the complexing agent in the reaction system within any given time period, measured in hourly increments. The "gradually decreasing concentration change rate of the complexing agent in the precipitation reaction system" means that, from the moment the complexing agent is added to the end of the reaction, the concentration change rate of the complexing agent in the reaction system generally shows a gradually decreasing trend, but one or more local intervals are allowed; within these local intervals, the concentration change of the complexing agent in the reaction system exhibits different trends (e.g., remaining constant and / or gradually increasing and / or a disordered state). The premise is that the existence of such local intervals is unavoidable given the current level of technical development in this field, and the existence of these local intervals does not affect those skilled in the art from still determining that the concentration change rate of the complexing agent in the reaction system over the entire time period "(generally) shows a gradually decreasing trend." Furthermore, the existence of these local intervals does not affect the achievement of the intended purpose of this invention, is acceptable, and is also included within the scope of protection of this invention.

[0073] In a preferred embodiment of the present invention, the concentration of the complexing agent at the end of the reaction is 0.05-2 mol / L, preferably 0.05-1.2 mol / L.

[0074] In a preferred embodiment of the present invention, during the last 1 / 12R hour of the reaction, the solid content of the precipitation reaction system is not less than 9 wt%, preferably 9-40 wt%, more preferably 9-20 wt%, for example 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, and any value within any range of any two of these values. Using this preferred embodiment, an outermost layer with a specific structure can be obtained, further improving the cycle stability of the prepared cathode material precursor.

[0075] In this invention, to promote the full reaction of the metal source solution, precipitant solution, and complexing agent solution, the precipitation reaction conditions include: a temperature of 20-70℃, preferably 45-60℃; a pH value of 8-14, preferably 10-12; a reaction time of not less than 10h, preferably 12-96h, more preferably 12-48h; and the precipitation reaction is carried out under stirring conditions, with a stirring speed of 50-1200r / min, preferably 600-1200r / min.

[0076] It should be understood that pH control can be achieved by maintaining a constant pH during the reaction time, or by varying the pH of the reaction process according to product objectives. However, the pH variation range should be within the range of the above-mentioned reaction system. In a further preferred embodiment, the pH of the reaction system remains constant within the above-mentioned range.

[0077] In this invention, the solid content of the precipitation reaction system is related to the amount of metal source solution, complexing agent solution and precipitant solution added, and the amount added is related to the flow rate and concentration of each material. Therefore, those skilled in the art can control the solid content of the precipitation reaction system and its variation range by controlling the flow rate and concentration of the metal source solution, complexing agent solution and precipitant solution.

[0078] This invention offers a wide range of selectable flow rates and concentrations for the metal source solution, complexing agent solution, and precipitant solution, allowing those skilled in the art to control the flow rates and concentrations of each material as needed. In some preferred embodiments, given a fixed concentration of the metal source solution, complexing agent solution, and precipitant solution, the initial volumetric flow rate ratio of the metal source to the complexing agent is preferably set to 1-10, more preferably 2-5. Then, the flow rate of the metal source solution is kept constant. By controlling the flow rate of the complexing agent, the concentration and rate of change of the complexing agent in the precipitation reaction system are kept within the aforementioned range. By controlling the flow rate of the precipitant solution, the pH of the precipitation reaction system is kept within the aforementioned range, thus achieving the regulation of the solid content and its variation range in the precipitation reaction system. If the solid content does not meet the requirements using the above method, it can also be increased to the specified range using an online thickener.

[0079] In this invention, there are no particular limitations on the solid-liquid separation described in step (2), as long as the reaction product obtained after the precipitation reaction can be separated, for example, by filtration or centrifugation.

[0080] In this invention, preferably, the product obtained from solid-liquid separation is washed, and the washing solvent is preferably water, more preferably hot water, at a temperature of 30-90°C.

[0081] In this invention, the drying method can be a conventional method in the art, such as vacuum drying, freeze drying, air drying, or oven drying. Vacuum heating drying is preferred in this invention. There are no special requirements for the drying temperature and time, as long as the washed product can be dried. For example, the vacuum heating drying temperature is 50-150℃, and the time is 4-24 hours.

[0082] A third aspect of this invention provides a cathode material precursor prepared by the method described in the second aspect above. The properties of the cathode material precursor have been described in detail in the first aspect and will not be repeated here.

[0083] A fourth aspect of the present invention provides a cathode material, the cathode material comprising a lithium source and a cathode material precursor as described in the first or third aspect above.

[0084] In a preferred embodiment of the present invention, the cathode material is obtained by mixing a cathode material precursor and a lithium source and then sintering them.

[0085] In this invention, there are no particular limitations on the mixing method of the cathode material precursor and the lithium source, as long as uniform mixing is ensured. Preferably, the mixing can be achieved using a high-speed mixer, ball mill, or similar methods. The mixed material is then sintered in an atmosphere furnace, where the sintering atmosphere can be at least one of air, oxygen, or an inert atmosphere such as nitrogen.

[0086] In a preferred embodiment of the present invention, the molar ratio of the lithium source to the battery cathode material precursor, calculated by metal element, is 0.9-1.3:1, for example, 0.9, 0.95, 1.00, 1.05, 1.10, 1.15, 1.20, 1.30, and any value within the range formed by any two of these values.

[0087] In this invention, the lithium source may exist in the form of a lithium salt, which is preferably selected from at least one of lithium nitrate (LiNO3), lithium chloride (LiCl), lithium carbonate (Li2CO3), lithium hydroxide (LiOH), lithium oxide (Li2O), lithium phosphate (Li3PO4), lithium dihydrogen phosphate (LiH2PO4), and lithium acetate (CH3COOLi).

[0088] A fifth aspect of this invention provides a lithium-ion battery, the lithium-ion battery comprising the positive electrode material described in the fourth aspect above. The inventors of this invention have discovered in their research that using the positive electrode material provided by this invention in a lithium-ion battery can improve the cycle stability of the lithium-ion battery.

[0089] The structure of the lithium-ion battery provided by the present invention is known to those skilled in the art. Generally, the lithium-ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. The positive electrode and the negative electrode can be prepared by coating and drying a composite material containing a positive electrode material and a composite material containing a negative electrode material on their respective current collectors.

[0090] In this invention, the positive electrode composite can be prepared by using a positive electrode material, a conductive agent, a binder, and a solvent.

[0091] In this invention, there are no particular limitations on the conductive agent used in the positive electrode composite, as long as it is conductive and remains stable within the charge-discharge range. Preferably, the conductive agent is selected from at least one of acetylene black, Ketjen black, artificial graphite, natural graphite, carbon nanotubes, graphene, superconducting carbon, carbon nanofibers, carbon dots, aluminum powder, nickel powder, titanium dioxide, and conductive polymers.

[0092] In this invention, there are no particular limitations on the binder used in the positive electrode composite, as long as it can provide adhesion between the positive electrode material, the conductive agent, and the current collector. Preferably, the binder is selected from at least one of polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), waterborne acrylic resin, polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate (EVA), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoroethylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylic resin.

[0093] In this invention, there are no particular limitations on the positive current collector, as long as it has suitable conductivity. Preferably, the material of the positive current collector can be aluminum, nickel, copper, titanium, silver, stainless steel, or carbon material, and the positive current collector can be processed into various forms such as foil, sheet, film, mesh, perforation, or non-woven fabric.

[0094] In a preferred embodiment of the present invention, the solvent used in the positive electrode complex may be N-methylpyrrolidone.

[0095] In this invention, the negative electrode composite can be prepared by using a negative electrode material, a conductive agent, a binder, and a solvent.

[0096] In this invention, there are no particular limitations on the type of negative electrode material, and those skilled in the art can select it according to actual needs. Preferably, the negative electrode material is selected from at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesophase microspheres (MCMB), carbon fiber, lithium metal, silicon, silicon oxide, lithium metal alloy, and lithium titanate.

[0097] In this invention, there are no particular restrictions on the conductive agents and binders used in the negative electrode composite. Preferably, the conductive agents and binders used in the negative electrode composite can be of the same type and content as those used in the preparation of the positive electrode composite.

[0098] In a preferred embodiment of the present invention, the solvent used in the negative electrode composite may be water.

[0099] In this invention, there are no particular limitations on the negative electrode current collector, as long as it has suitable conductivity. Preferably, the negative electrode current collector can be made of aluminum, nickel, copper, titanium, silver, stainless steel, or carbon materials, and can be processed into various forms such as foil, sheet, film, mesh, perforation, or non-woven fabric.

[0100] In this invention, the electrolyte can be a solid electrolyte, such as a polymer electrolyte or an inorganic solid electrolyte; or it can be a liquid electrolyte containing lithium salt and solvent.

[0101] In a preferred embodiment of the present invention, the polymer electrolyte is selected from at least one of polyvinyl alcohol, phosphate polymer, polyvinylidene fluoride, polyethylene oxide derivative, polypropylene oxide derivative, polyethylene derivative, and polyester sulfide.

[0102] In a preferred embodiment of the present invention, the inorganic solid electrolyte is selected from at least one of Li2S, Li2S-P2S5, LiI, Li-La-Zr-O, Li-Ge-VO, Li3N, Li4SiO4, LiPON, LISION, Li-Al-Ti-P, Li3PO4-Li2S-SiS2, LiBH4, LiBH4-LiX (X = Cl, Br or I), LiBH4-LiNH2, LiNH2, Li3AlH6, Li2NH and Li2O-B2O3-P2O5.

[0103] In this invention, the liquid electrolyte is a solution of lithium salt in a solvent, and the solvent can be a non-aqueous solvent, preferably selected from at least one of ethylene carbonate (EC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), propylene carbonate (PC), ethyl propyl carbonate (EPC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), methyl formate (MF), ethyl formate (Eft), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), and propyl butyrate (BP).

[0104] In a preferred embodiment of the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate borate) borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate phosphate (LiDFOP), and lithium tetrafluorooxalate borate (LiTFOP).

[0105] In this invention, to improve the performance of lithium-ion batteries, additives may be selectively added to the electrolyte. The additives are preferably selected from at least one of the following: vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), tris(trimethylsilane) phosphate (TMSP), sulfonate cyclic quaternary ammonium salts, ethylene sulfite (DTO), dimethyl sulfite (DMS), 1-propylene-1,3-sulfonyl lactone (PST), 4-propyl ethylene sulfate (PEGLST), diethyl sulfite (DES), adiponitrile (ADN), succinate (SN), 1,3-propane sulfonyl lactone (1,3-PS), vinyl sulfate (DTD), and 4-methyl ethylene sulfate (PCS).

[0106] In this invention, the separator is disposed between the positive and negative electrodes, serving to isolate them. The separator can be any type of separator commonly used in the art; preferably, it can be a polyolefin, such as polyethylene, polypropylene, or a polyethylene-polypropylene composite, or it can be a sheet formed of glass fiber or a non-woven fabric. When a solid electrolyte is used, the solid electrolyte can also be used as the separator.

[0107] The present invention does not particularly limit the preparation method of the lithium-ion battery, and conventional methods in the art can be used for preparation. Preferably, the preparation method of the lithium-ion battery includes: uniformly mixing positive electrode material, conductive agent, binder and solvent, coating it on at least one surface of positive electrode current collector, drying, rolling and slicing it for use as a positive electrode; uniformly mixing negative electrode material, conductive agent, binder and solvent, coating it on at least one surface of negative electrode current collector, drying, rolling and slicing it for use as a negative electrode; assembling the positive electrode, separator and negative electrode into a stacked or wound cell, placing the cell in a shell, injecting electrolyte and encapsulating it to obtain a lithium-ion battery.

[0108] In this invention, the amount of the positive and negative electrode materials, conductive agent, and binder is not specifically limited. Preferably, based on the solid content of the positive or negative electrode composite, the mass content of the positive or negative electrode material is 50-99 wt%, the mass content of the conductive agent is 0.5-25 wt%, and the mass content of the binder is 0.5-25 wt%.

[0109] The present invention will be described in detail below through embodiments. In the following embodiments and comparative examples,

[0110] Scanning electron microscope (SEM) images were obtained using a ZEISS Merlin scanning electron microscope from ZEISS GmbH, Germany.

[0111] The X-ray diffraction pattern (XRD) was obtained using a Bruker D8 Advance SS X-ray diffractometer from Germany.

[0112] The diameter was obtained using a Mastersizer 3000 laser particle size analyzer from Malvern Panalytical, UK.

[0113] Unless otherwise stated, all raw materials used in the following examples and comparative examples are commercially available products.

[0114] Example 1

[0115] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0116] (1) Preparation of cathode material precursor

[0117] A metal source solution with a concentration of 2 mol / L was prepared, based on the metal element concentration, wherein the molar ratio of nickel, cobalt, and manganese in the metal source solution was 8:1:1, and nickel sulfate, cobalt sulfate, and manganese sulfate were used in the preparation process; a NaOH solution with a concentration of 10 mol / L was prepared; and an ammonia solution as a complexing agent with a concentration of 6 mol / L was prepared.

[0118] Ammonia solution (0.5 mol / L) accounting for 40% of the reactor volume was added to the reactor. An appropriate amount of NaOH was added to adjust the pH of the solution to 11.9. The bottom solution was heated to 50°C and maintained until the reaction was complete. The metal source solution, NaOH solution, and complexing agent solution were simultaneously added to the reactor while stirring at 900 rpm. The initial flow rate ratio of the metal source solution to the complexing agent solution was controlled at 4. Then, the flow rate of the metal source solution was kept constant, while the flow rate of the NaOH solution was controlled to maintain the pH of the reaction system at approximately 11.9. The flow rate of the ammonia complexing agent was controlled to gradually increase the concentration of the complexing agent in the system, with the rate of increase gradually decreasing, until the concentration of the complexing agent in the reaction system was approximately 0.8 mol / L at the end of the reaction. The change in the concentration of the complexing agent in the reaction system over time is shown in the figure. Figure 2 Eight hours before the end of the reaction, the solid content of the reaction system was increased to approximately 12 wt% using a concentrator. During the last 8 hours of the reaction, the variation range of the solid content in the reaction system was less than 1 wt%, and the variation range of the complexing agent concentration was less than 0.005 mol / L·h. Timing began from the simultaneous addition of the metal source solution, NaOH solution, and complexing agent solution. The reaction was stopped after 48 hours. The slurry was then vacuum filtered, washed three times with deionized water, and dried in a vacuum drying oven at 120℃ for 12 hours to obtain the cathode material precursor.

[0119] (2) Evaluation of cathode material precursors

[0120] The cathode material precursor prepared above was characterized by SEM, such as... Figure 3 As shown. From Figure 3 As can be seen from the above, the preparation method provided by the present invention can obtain a cathode material precursor with good sphericity. This cathode material precursor is a secondary microsphere formed by the aggregation of primary sheet-like bodies.

[0121] To further analyze the aggregation morphology of the primary sheet-like structures, the cathode material precursor was ion-beam cut and then characterized by SEM. The SEM image of the cross-section of the cathode material precursor is shown below. Figure 4 As shown, from Figure 4 As can be seen, the cathode material precursor obtained by the preparation method provided by this invention contains a three-layer structure from the inside out: a core layer, an intermediate layer, and an outermost layer. The core layer is formed by primary sheet-like aggregation, which is relatively loose, and the thickness of the core layer is about 1.1 μm. The outermost layer is also formed by sheet-like aggregation, which is even looser than the core layer, and the thickness of the outermost layer is about 0.22 μm. The intermediate layer, located between the core layer and the outermost layer, is very densely aggregated, and the thickness of the intermediate layer is about 3.8 μm.

[0122] The particle size of the cathode material precursor prepared in Example 1 was tested, and the results showed that the medium particle size D50 of the secondary microspheres of the cathode material precursor was 10.2 μm and the diameter spacing of the secondary microspheres was 0.46.

[0123] X-ray diffraction analysis was performed on the outermost layer of the cathode material precursor prepared in Example 1, and the results are as follows: Figure 5 As shown. From Figure 5 It can be seen that the diffraction peak intensity of the outermost (102) crystal plane is high, and the ratio of the diffraction peak intensity of (110) and (102) crystal plane is 0.86.

[0124] (3) Preparation and evaluation of cathode materials

[0125] The cathode material precursor prepared in Example 1 was ball-milled with lithium source LiOH·H2O for 30 min to fully mix. The molar ratio of Li:(Ni+Co+Mn) was controlled to be 1.05:1. The mixture was pre-calcined at 520°C for 4 h in an oxygen atmosphere, and then calcined at 800°C for 16 h to carry out a solid-state reaction to obtain the cathode material.

[0126] The prepared positive electrode material, conductive agent, and binder were mixed evenly at a mass ratio of 90:5:5 and coated onto aluminum foil. After drying the solvent and slicing, the mixture was used as the positive electrode. The conductive agent used was acetylene black, and the binder was a 10% (w / w) polyvinylidene fluoride solution. The negative electrode used lithium metal, the separator was a Celllgard 2400 polypropylene separator, and the electrolyte was a liquid electrolyte. The solvent was a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a 1:1 volume ratio, and the solute was lithium hexafluorophosphate (LiPF6) with a molar concentration of 1 mol / L. The mixture was assembled into a 2032 coin cell in an inert atmosphere glove box, where the moisture and oxygen content were below 0.1 ppm.

[0127] The electrochemical performance of the cathode material at a 1C rate was measured under charge / discharge voltage ranges of 2.5–4.3V and an ambient temperature of 25℃. The charge / discharge cycle results are as follows: Figure 6 As shown. From Figure 6 As can be seen, the electrochemical activity of the cathode material gradually increases during cycling. Based on the mass of the cathode material, the energy density of the first cycle at 1C rate is 674.2Wh / kg. After 200 cycles, the capacity exceeds the capacity of the first cycle at 1C rate, with a capacity retention rate of 101%. It exhibits excellent cycle stability and can be used in high-stability lithium-ion batteries.

[0128] Example 2

[0129] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0130] (1) Preparation of cathode material precursor

[0131] A metal source solution with a concentration of 4 mol / L was prepared, based on the metal element concentration. The molar ratio of nickel, cobalt, and aluminum in the metal source solution was 8:1.5:0.5. Nickel sulfate, cobalt sulfate, and aluminum sulfate were used in the preparation process. A NaOH solution with a concentration of 10 mol / L was also prepared. An ammonia solution as a complexing agent with a concentration of 6 mol / L was also prepared.

[0132] Ammonia solution (0.5 mol / L) accounting for 30% of the reactor volume was added to the reactor. An appropriate amount of NaOH was added to adjust the pH of the solution to 11.2. The bottom solution was heated to 60°C and maintained until the reaction was complete. The metal source solution, NaOH solution, and complexing agent solution were simultaneously added to the reactor while stirring at 900 rpm. The initial flow rate ratio of the metal source solution to the complexing agent solution was controlled at 4. Then, the flow rate of the metal source solution was kept constant, while the flow rate of the NaOH solution was controlled to maintain the pH of the reaction system at 11.2. The flow rate of the ammonia complexing agent was controlled to gradually increase the concentration of the complexing agent in the system, with the rate of increase gradually decreasing, until the concentration of the complexing agent in the reaction system was approximately 0.8 mol / L at the end of the reaction. The change in the concentration of the complexing agent in the reaction system over time is shown in the figure. Figure 2 Six hours before the end of the reaction, the solid content of the reaction system was controlled at approximately 17 wt% using a concentrator. During the last 6 hours, the variation range of the solid content in the reaction system was less than 2 wt%, and the variation range of the complexing agent concentration was less than 0.005 mol / L·h. Timing began from the simultaneous addition of the metal source solution, NaOH solution, and complexing agent solution. The reaction was stopped after 48 hours. The slurry was then vacuum filtered, washed three times with deionized water, and dried in a vacuum drying oven at 120℃ for 12 hours to obtain the cathode material precursor.

[0133] (2) Evaluation of cathode material precursors

[0134] The prepared cathode material precursor was subjected to SEM testing, and the SEM images were compared with... Figure 3 and Figure 4 resemblance.

[0135] The particle size of the cathode material precursor prepared in Example 2 was tested, and the results showed that the diameter of the secondary microspheres was 0.58.

[0136] XRD tests were performed on the outermost layer of the prepared cathode material precursor. The results showed that the ratio of the diffraction peak intensities of the (110) and (102) crystal planes in the XRD spectrum of the outermost layer was 0.94.

[0137] (3) Preparation and evaluation of cathode materials

[0138] The cathode material and lithium-ion battery were prepared according to the method described in Example 1.

[0139] Under the conditions of charge-discharge voltage range of 2.5-4.3V and ambient temperature of 25℃, the electrochemical performance of the cathode material at 1C rate was measured. The energy density of the first cycle at 1C rate was calculated to be 668.7Wh / kg based on the mass of the cathode material. The charge-discharge cycle results showed that the capacity retention rate was 100.2% after 200 cycles.

[0140] Example 3

[0141] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0142] (1) Preparation of cathode material precursor

[0143] A metal source solution with a concentration of 4 mol / L was prepared, based on the metal element concentration, wherein the molar ratio of nickel, cobalt, and manganese in the metal source solution was 8:1:1, and nickel sulfate, cobalt sulfate, and manganese sulfate were used in the preparation process; an 8 mol / L NaOH solution was prepared; and an ammonia solution as a complexing agent was prepared, wherein the ammonia concentration was 10 mol / L.

[0144] Ammonia solution (0.5 mol / L) was added to the reactor, comprising 60% of the reactor volume. An appropriate amount of NaOH was added to adjust the pH of the solution to 10.2. The bottom solution was heated to 60°C and maintained until the reaction was complete. The metal source solution, NaOH solution, and complexing agent solution were simultaneously added to the reactor while stirring at 700 rpm. The initial flow rate ratio of the metal source solution to the complexing agent solution was controlled at 5. Then, the flow rate of the metal source solution was kept constant, while the flow rate of the NaOH solution was controlled to maintain the pH of the reaction system at 10.2. The flow rate of the ammonia complexing agent was controlled to gradually increase the concentration of the complexing agent in the system, with the rate of increase gradually decreasing, until the concentration of the complexing agent in the reaction system was approximately 0.8 mol / L at the end of the reaction. The change in the concentration of the complexing agent in the reaction system over time is shown in the figure. Figure 2 Five hours before the end of the reaction, the solid content of the reaction system was increased to approximately 19 wt% using a concentrator. During the last five hours of the reaction, the solid content in the reaction system remained below 2.8 wt%, and the concentration of the complexing agent remained below 0.005 mol / L·h. Timing began when the metal source solution, NaOH solution, and complexing agent solution were simultaneously added. The reaction was stopped after 48 hours. The slurry was then vacuum filtered, washed three times with deionized water, and dried in a vacuum drying oven at 120°C for 12 hours to obtain the cathode material precursor.

[0145] (2) Evaluation of cathode material precursors

[0146] The prepared cathode material precursor was subjected to SEM testing, and the SEM images were compared with... Figure 3 and Figure 4 resemblance.

[0147] The particle size of the cathode material precursor prepared in Example 3 was tested, and the results showed that the diameter of the secondary microspheres was 0.95.

[0148] XRD tests were performed on the outermost layer of the prepared cathode material precursor. The results showed that the ratio of the diffraction peak intensities of the (110) and (102) crystal planes in the XRD spectrum of the outermost layer was 1.24.

[0149] (3) Preparation and evaluation of cathode materials

[0150] The cathode material and lithium-ion battery were prepared according to the method described in Example 1.

[0151] Under the conditions of charge-discharge voltage range of 2.5-4.3V and ambient temperature of 25℃, the electrochemical performance of the cathode material at 1C rate was measured. The energy density of the first cycle at 1C rate was calculated to be 656.5Wh / kg based on the mass of the cathode material. The charge-discharge cycle results showed that the capacity retention rate was 96.7% after 200 cycles.

[0152] Example 4

[0153] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0154] (1) Preparation of cathode material precursor

[0155] The procedure was carried out according to the method described in Example 1, except that ZnSO4 was added to the metal source solution, wherein Zn / (Ni+Co+Mn)=1%mol, to obtain the cathode material precursor.

[0156] (2) Evaluation of cathode material precursors

[0157] The prepared cathode material precursor was subjected to SEM testing, and the SEM images were compared with... Figure 3 and Figure 4 resemblance.

[0158] The particle size of the cathode material precursor prepared in Example 4 was tested, and the results showed that the diameter of the secondary microspheres was 0.71.

[0159] XRD tests were performed on the outermost layer of the prepared cathode material precursor. The results showed that the ratio of the diffraction peak intensities of the (110) and (102) crystal planes in the XRD spectrum of the outermost layer was 1.07.

[0160] (3) Preparation and evaluation of cathode materials

[0161] The cathode material and lithium-ion battery were prepared according to the method described in Example 1.

[0162] Under the conditions of charge-discharge voltage range of 2.5-4.3V and ambient temperature of 25℃, the electrochemical performance of the cathode material at 1C rate was measured. The energy density of the first cycle at 1C rate was calculated to be 664.6Wh / kg based on the mass of the cathode material. The charge-discharge cycle results showed that the capacity retention rate was 99.5% after 200 cycles.

[0163] Example 5

[0164] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0165] (1) Preparation of cathode material precursor

[0166] The procedure was carried out according to the method described in Example 1, except that Ce(NO3)3·6H2O was added to the metal source solution, wherein Ce / (Ni+Co+Mn)=1%mol, to obtain the cathode material precursor.

[0167] (2) Evaluation of cathode material precursors

[0168] The prepared cathode material precursor was subjected to SEM testing, and the SEM images were compared with... Figure 3 and Figure 4 resemblance.

[0169] The particle size of the cathode material precursor prepared in Example 5 was tested, and the results showed that the diameter of the secondary microspheres was 0.63.

[0170] XRD tests were performed on the outermost layer of the prepared cathode material precursor. The results showed that the ratio of the diffraction peak intensities of the (110) and (102) crystal planes in the XRD spectrum of the outermost layer was 0.96.

[0171] (3) Preparation and evaluation of cathode materials

[0172] The cathode material and lithium-ion battery were prepared according to the method described in Example 1.

[0173] Under the conditions of charge-discharge voltage range of 2.5-4.3V and ambient temperature of 25℃, the electrochemical performance of the cathode material at 1C rate was measured. The energy density of the first cycle at 1C rate was calculated to be 667.9Wh / kg based on the mass of the cathode material. The charge-discharge cycle results showed that the capacity retention rate was 99.9% after 200 cycles.

[0174] Example 6

[0175] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0176] (1) Preparation of cathode material precursor

[0177] The procedure was performed according to the method described in Example 1, except that H3PO4 was added to the metal source solution, where P / (Ni+Co+Mn)=1%mol, to obtain the cathode material precursor.

[0178] (2) Evaluation of cathode material precursors

[0179] The prepared cathode material precursor was subjected to SEM testing, and the SEM images were compared with... Figure 3 and Figure 4 resemblance.

[0180] The particle size of the cathode material precursor prepared in Example 6 was tested, and the results showed that the diameter of the secondary microspheres was 0.84.

[0181] XRD tests were performed on the outermost layer of the prepared cathode material precursor. The results showed that the ratio of the diffraction peak intensities of the (110) and (102) crystal planes in the XRD spectrum of the outermost layer was 1.08.

[0182] (3) Preparation and evaluation of cathode materials

[0183] The cathode material and lithium-ion battery were prepared according to the method described in Example 1.

[0184] Under the conditions of charge-discharge voltage range of 2.5-4.3V and ambient temperature of 25℃, the electrochemical performance of the cathode material at 1C rate was measured. The energy density of the first cycle at 1C rate was calculated to be 663.5Wh / kg based on the mass of the cathode material. The charge-discharge cycle results showed that the capacity retention rate was 99.1% after 200 cycles.

[0185] Example 7

[0186] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0187] (1) Preparation of cathode material precursor

[0188] A metal source solution with a concentration of 0.5 mol / L was prepared, based on the metal element concentration. The molar ratio of nickel, cobalt, and manganese in the metal source solution was 8:1:1. Nickel sulfate, cobalt sulfate, and manganese sulfate were used in the preparation process. A NaOH solution with a concentration of 10 mol / L was prepared. An ammonia solution as a complexing agent with a concentration of 2 mol / L was also prepared.

[0189] Ammonia solution (0.5 mol / L) accounting for 30% of the reactor volume was added to the reactor. An appropriate amount of NaOH was added to adjust the pH of the solution to 10.5. The bottom solution was heated to 55°C and maintained until the reaction was complete. The metal source solution, NaOH solution, and complexing agent solution were simultaneously added to the reactor while stirring at 1000 rpm. The initial flow rate ratio of the metal source solution to the complexing agent solution was controlled at 2. Then, the flow rate of the metal source solution was kept constant, while the flow rate of the NaOH solution was controlled to maintain the pH of the reaction system at 10.5. The flow rate of the ammonia complexing agent was controlled to gradually increase the concentration of the complexing agent in the system, with the rate of increase gradually decreasing, until the concentration of the complexing agent in the reaction system was approximately 0.8 mol / L at the end of the reaction. The change in the concentration of the complexing agent in the reaction system over time is shown in the figure. Figure 2 Six hours before the end of the reaction, the solid content of the reaction system was controlled to be approximately 15 wt% using a concentrator. During the last six hours, the solid content in the reaction system varied by less than 1.2 wt%, and the concentration of the complexing agent varied by less than 0.005 mol / L·h. Timing began when the metal source solution, NaOH solution, and complexing agent solution were added simultaneously. The reaction was stopped after 48 hours. The slurry was then vacuum filtered, washed three times with deionized water, and dried in a vacuum drying oven at 120℃ for 12 hours to obtain the cathode material precursor.

[0190] (2) Evaluation of cathode material precursors

[0191] The prepared cathode material precursor was subjected to SEM testing, and the SEM images were compared with... Figure 3 and Figure 4 resemblance.

[0192] The particle size of the cathode material precursor prepared in Example 7 was tested, and the results showed that the diameter of the secondary microspheres was 0.62.

[0193] XRD tests were performed on the outermost layer of the prepared cathode material precursor. The results showed that the ratio of the diffraction peak intensities of the (110) and (102) crystal planes in the XRD spectrum of the outermost layer was 0.97.

[0194] (3) Preparation and evaluation of cathode materials

[0195] The cathode material and lithium-ion battery were prepared according to the method described in Example 1.

[0196] Under the conditions of charge-discharge voltage range of 2.5-4.3V and ambient temperature of 25℃, the electrochemical performance of the cathode material at 1C rate was measured. The energy density of the first cycle at 1C rate was calculated to be 681.5Wh / kg based on the mass of the cathode material. The charge-discharge cycle results showed that the capacity retention rate was 99.7% after 200 cycles.

[0197] The results above demonstrate that the method described in this invention yields a novel cathode material precursor. This precursor differs from precursors prepared using existing technologies. It consists of secondary microspheres formed by the aggregation of primary particles. Each secondary microsphere comprises a three-layer structure from the inside out: a core layer, a middle layer, and an outermost layer. The outermost layer exhibits a specific diffraction peak structure, and the secondary microspheres have a relatively narrow diameter. This unique structure endows the precursor with better electrochemical performance, such as improved cycle stability, making it suitable for use in high-performance lithium-ion batteries.

[0198] Comparative Example 1

[0199] A metal source solution with a concentration of 2 mol / L was prepared, based on the metal element concentration, wherein the molar ratio of nickel, cobalt, and manganese in the metal source solution was 8:1:1, and nickel sulfate, cobalt sulfate, and manganese sulfate were used in the preparation process; a NaOH solution with a concentration of 10 mol / L was prepared; and an ammonia solution as a complexing agent with a concentration of 6 mol / L was prepared.

[0200] The prepared metal source solution and NaOH solution were simultaneously added to the reaction vessel under stirring to initiate a precipitation reaction. An ammonia solution (0.5 mol / L) accounting for 40% of the vessel volume was pre-added to the reaction vessel. The flow rate of the metal source solution was the same as in Example 1, and the flow rate of the NaOH solution was controlled to maintain the pH of the reaction system at approximately 11.9. The total amount of ammonia (the same as in Example 1) was added to the reaction system in three equal portions at 6h, 24h, and 45h after the start of the reaction. At 8h before the end of the reaction, the solid content of the reaction system was approximately 8.5 wt%, and the variation range of the solid content in the reaction system within the last 8h was higher than 3.2 wt%. During the reaction, the stirring speed was controlled at 900 rpm, the reaction temperature at 55℃, and the total reaction time was 48h. After natural cooling, the precipitation reaction was terminated. The slurry was vacuum filtered, washed three times with deionized water, and then dried in a vacuum drying oven at 120℃ for 12h to obtain the cathode material precursor.

[0201] The outermost layer of the prepared cathode material precursor was subjected to XRD test. In the XRD spectrum, the ratio of the diffraction peak intensities of (110) and (102) crystal planes was 1.98.

[0202] The particle size of the prepared cathode material precursor was tested, and the results showed that the diameter of the precursor was as high as 1.97.

[0203] The cathode material precursor obtained in Comparative Example 1 was used to prepare cathode materials according to the method in Example 1 and assembled into a lithium-ion battery.

[0204] The electrochemical performance of the cathode material at a 1C rate was measured under charge / discharge voltage ranges of 2.5–4.3V and an ambient temperature of 25℃. The charge / discharge cycle results are as follows: Figure 7 As shown, the energy density of the first cycle at 1C rate, calculated based on the mass of the cathode material, is 588.8 Wh / kg. The cathode material precursor prepared using the method in Comparative Example 1 has a capacity retention rate of only 31.0% after 200 cycles, which is far lower than the effect of the embodiment of this invention.

[0205] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A cathode material precursor, characterized in that, The cathode material precursor is a secondary microsphere formed by the agglomeration of primary particles; wherein the secondary microsphere comprises a core layer, an intermediate layer and an outermost layer from the inside out, and the ratio of the intensity of the (110) and (102) crystal plane diffraction peaks in the X-ray diffraction pattern of the outermost layer is 0.1-1.5; the radial distance of the secondary microsphere is 0.1-1. The general chemical formula of the cathode material precursor is Ni. x Co y M z T p (OH) 2-q Wherein, M is selected from at least one of Cu, Ge, Mg, W, Mo, Zn, Sn, Ce, Mn and Al; T is selected from at least one of N, P and S; 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤p≤0.5, wherein at least one of x, y and z is not 0, and the range of q is determined according to the principle of electroneutrality.

2. The cathode material precursor according to claim 1, wherein, The density relationship between the kernel layer, the intermediate layer, and the outermost layer is: intermediate layer > kernel layer > outermost layer.

3. The cathode material precursor according to claim 1, wherein, With the radius of the secondary microspheres as 100%, the thickness of the core layer accounts for 0.1-50%, the thickness of the intermediate layer accounts for 40-95%, and the thickness of the outermost layer accounts for 0.1-20%.

4. The cathode material precursor according to claim 1, wherein, The secondary microspheres have a particle size of 1-30 μm.

5. The cathode material precursor according to any one of claims 1-4, wherein, The shape of the primary particles is selected from at least one of the following: flake-shaped, lamellar-shaped, needle-shaped, and spindle-shaped.

6. The cathode material precursor according to claim 1, wherein, The intensity ratio of the diffraction peaks of the (110) and (102) crystal planes is 0.5-1.

5.

7. A method for preparing the cathode material precursor according to any one of claims 1-6, characterized in that, Includes the following steps: (1) The metal source solution, precipitant solution and complexing agent solution are subjected to a precipitation reaction to obtain the reaction product; (2) The reaction product is subjected to solid-liquid separation and drying to obtain the cathode material precursor; The total reaction time is denoted as R hours. From 1 / 12 of R hours before the end of the reaction to the end of the reaction, the solid content of the precipitation reaction system varies within the range of less than 3 wt%.

8. The method according to claim 7, wherein, As the concentration of the complexing agent in the precipitation reaction system gradually increases, the rate of change of the complexing agent concentration gradually decreases.

9. The method according to claim 8, wherein, The concentration change rate of the complexing agent is less than 1 mol / L·h.

10. The method according to claim 9, wherein, The concentration of the complexing agent changes at a rate of 0.001-1 mol / L·h.

11. The method according to claim 10, wherein, The concentration of the complexing agent changes at a rate of 0.001-0.5 mol / L·h.

12. The method according to any one of claims 7-11, wherein, From 1 / 12R hour before the end of the reaction to the end of the reaction, the rate of change of the complexing agent concentration was less than 0.005 mol / L·h.

13. The method according to any one of claims 7-11, wherein, At the end of the reaction, the concentration of the complexing agent is 0.05-2 mol / L.

14. The method according to claim 13, wherein, At the end of the reaction, the concentration of the complexing agent is 0.05-1.2 mol / L.

15. The method according to any one of claims 7-11, wherein, In the last 1 / 12R hour before the reaction ends, the solid content of the precipitation reaction system is not less than 9 wt%.

16. The method according to any one of claims 7-11, wherein, The conditions for the precipitation reaction include: a temperature of 20-70℃; a pH value of 8-14; a reaction time of not less than 10 hours; and a stirring speed of 50-1200 r / min.

17. The method according to claim 16, wherein, The conditions for the precipitation reaction include: a temperature of 45-60℃; a pH value of 10-12; a reaction time of 12-96h; and a stirring speed of 600-1200r / min.

18. The method according to any one of claims 7-11, wherein, The precipitation reaction includes simultaneously adding a metal source solution, a precipitant solution, and a complexing agent solution into a reaction vessel under stirring to carry out the reaction.

19. The method according to claim 18, wherein, Before adding the metal source solution, precipitant solution, and complexing agent solution to the reactor, add the bottom liquid to the reactor; The base solution is an aqueous solution containing a complexing agent; the concentration of the complexing agent in the base solution is 0-1.8 mol / L.

20. The method according to claim 19, wherein, The concentration of the complexing agent in the substrate is at least 0.05 mol / L lower than the concentration of the complexing agent at the end of the reaction.

21. The method according to claim 20, wherein, The concentration of the complexing agent in the substrate is at least 0.1 mol / L lower than the concentration of the complexing agent at the end of the reaction.

22. The method according to claim 19, wherein, The volume of the bottom liquid is 10-60% of the volume of the reactor.

23. The method according to any one of claims 7-11, wherein, The metal source is selected from at least one of nickel source, cobalt source and M source, where M is selected from at least one of Cu, Ge, Mg, W, Mo, Zn, Sn, Ce, Mn and Al.

24. The method according to any one of claims 7-11, wherein, The precipitant is selected from at least one of alkali metal hydroxides, carbonates, and bicarbonates.

25. The method according to claim 24, wherein, The alkali metal is selected from at least one of Na, K and Li.

26. The method according to any one of claims 7-11, wherein, The complexing agent is selected from at least one of ammonium ion donors, alkanolamine complexing agents, aminocarboxylic acid complexing agents, hydroxyaminocarboxylic acid complexing agents, carboxylate complexing agents, and thiocyanate complexing agents.

27. The method according to claim 23, wherein, The nickel source is selected from at least one of nickel sulfate, nickel nitrate, nickel acetate, nickel oxalate, and nickel chloride; And / or, the cobalt source is selected from at least one of cobalt nitrate, cobalt chloride, cobalt acetate, and cobalt sulfate; And / or, the M source is selected from at least one of the sulfate, nitrate, acetate and oxalate of M.

28. The method according to any one of claims 7-11, wherein, The concentration of the metal source solution, calculated by metal element, is 0.01-5 mol / L; And / or, the concentration of the precipitant solution is 0.01-16 mol / L; And / or, the concentration of the complexing agent solution is 0.01-16 mol / L.

29. The method according to any one of claims 7-11, wherein, The concentration of the metal source solution, calculated by metal element, is 0.01-4 mol / L; And / or, the concentration of the precipitant solution is 2-12 mol / L; And / or, the concentration of the complexing agent solution is 2-15 mol / L.

30. The method according to any one of claims 7-11, wherein, The precipitation reaction further includes adding a T source to the metal source solution, wherein T is selected from at least one of N, P, and S.

31. The method according to claim 30, wherein, The molar ratio of nickel source, cobalt source, M source and T source (calculated as metal element) is (0-1):(0-1):(0-1):(0-0.5), wherein at least one of the nickel source, cobalt source and M source is not 0.

32. The cathode material precursor prepared by the method according to any one of claims 7-31.

33. A positive electrode material, characterized in that, The cathode material includes a lithium source and a cathode material precursor as described in any one of claims 1-6 and 32.

34. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode material as described in claim 33.

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