Cathode material precursors and their preparation methods, cathode materials and lithium-ion batteries

Abstract

This invention relates to the field of lithium-ion batteries, and discloses a cathode material precursor and its preparation method, a cathode material, and a lithium-ion battery. 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 core layer, the intensity ratio of the (110) and (102) crystal plane diffraction peaks is 1-8, and the specific surface area of ​​the secondary microsphere is 0.5-15 m². 2 / g. 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 precipitation reaction system is not higher than 7 wt% in the first 1 / 8R hours of the reaction. When the cathode material prepared by this cathode material precursor is applied to a lithium-ion battery, its discharge specific capacity 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] The development of power tools and electronic devices requires cathode materials with high energy density and long cycle stability. Layered lithium nickel cobalt manganese or lithium nickel cobalt aluminum composite oxides are important cathode active materials for lithium secondary batteries.

[0003] In lithium nickel-cobalt-manganese or lithium nickel-cobalt-aluminum composite oxides, nickel, cobalt, manganese, and aluminum exhibit a synergistic effect. Increasing the nickel content in the cathode material can improve its discharge specific capacity, thereby increasing the energy density of the lithium battery. However, once the nickel content reaches a certain level, the improvement in discharge specific capacity becomes less significant, necessitating the development of new mechanisms to enhance it. Furthermore, as the discharge specific capacity of the cathode material increases, its electrochemical activity also increases, leading to deterioration in cycle stability. These issues require further solutions.

[0004] Lithium nickel cobalt manganese (LCM) or lithium nickel cobalt aluminum (LCA) composite oxides are typically prepared as precursor materials through a co-precipitation process, followed by high-temperature solid-state reaction with lithium salts to produce the final cathode material. The properties of the precursor determine the discharge specific capacity and cycle stability of the final cathode material. Designing and developing new precursor materials is expected to improve the energy density and cycle stability of LCM or LCA composite oxides. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of low discharge specific capacity of ternary cathode materials in the battery charging and discharging 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 precursor provided by this invention has good electrochemical performance and the discharge specific capacity at different rates is significantly improved.

[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 core layer, the intensity ratio of the (110) and (102) crystal plane diffraction peaks is 1-8, preferably 1.5-4; and the specific surface area of ​​the secondary microsphere is 0.5-15 m². 2 / g.

[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. In the first 1 / 8 of R hours after the start of the reaction, the solid content of the precipitation reaction system is not higher than 7 wt%, preferably not higher than 5 wt%.

[0011] 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.

[0012] 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.

[0013] Preferably, in the first 1 / 8R hour of the reaction, the concentration change rate of the complexing agent is not less than 0.021 mol / L·h, more preferably 0.021-1 mol / L·h, and even more preferably 0.021-0.5 mol / L·h.

[0014] Preferably, the time from the addition of the complexing agent to reaching a complexing agent concentration of not less than 80% at the end of the reaction in the precipitation reaction system does not exceed 1 / 4R hour.

[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 agglomeration 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 core layer has a specific diffraction peak structure, with the intensity ratio of the (110) and (102) crystal plane diffraction peaks being 1-8, preferably 1.5-4; the specific surface area of ​​the secondary microsphere is 0.5-15 m². 2 / g.

[0020] In this invention, by controlling the solid content of the precipitation reaction system to be no higher than 7 wt%, preferably no higher than 5 wt%, during the first 1 / 8R hour of the reaction, the core layer of the prepared cathode material precursor has a specific diffraction peak structure. Simultaneously, the cathode material precursor has a high specific surface area. This diffraction peak structure and high specific surface area facilitate the insertion and extraction of lithium ions, effectively solving the problem of difficult utilization of active materials, especially internal active materials, and improving the discharge specific capacity of the material at different rates, thereby enhancing the energy density and kinetic performance of lithium-ion batteries. When the cathode material prepared using this cathode material precursor is applied to lithium-ion batteries, the lithium-ion battery exhibits a high discharge specific capacity. As can be seen from the examples, the initial discharge specific capacity at 0.1C rate can reach 215.6 mAh / g, and the discharge specific capacity at 1C rate can reach 190.7 mAh / g, demonstrating high discharge specific capacity at different rates. The cathode material precursor provided by this invention can be used in high-energy-density lithium-ion batteries. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the cathode material precursor provided by the present invention;

[0022] 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;

[0023] Figure 3 This is a graph showing the change in the concentration of the complexing agent in the reaction system of Example 3 of the present invention over reaction time;

[0024] Figure 4 This is a SEM image of the cathode material precursor obtained in Example 1 of this invention;

[0025] Figure 5 This is a SEM image of a cross-section of the cathode material precursor obtained in Example 1 of this invention;

[0026] Figure 6 This is an XRD pattern of the core layer of the cathode material precursor obtained in Example 1 of the present invention;

[0027] Figure 7 The 0.1C charge-discharge curve is shown for a lithium-ion battery assembled from the cathode material prepared in Example 1 of this invention.

[0028] Figure 8 This is the 1C charge / discharge curve of a lithium-ion battery assembled from the cathode material prepared in 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 core layer, the intensity ratio of the (110) and (102) crystal plane diffraction peaks is 1-8, preferably 1.5-4, for example, 1.5, 2, 2.5, 3, 3.5, 4, and any value within the range formed by any two of these values, more preferably 1.5-3. The specific surface area of ​​the secondary microsphere is 0.5-15 m². 2 / g, preferably 1-14m 2 / g, for example, 1m 2 / g、2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g, 10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g and any value within the range formed by any two of these values.

[0031] In this invention, to test the X-ray diffraction (XRD) pattern of the core layer, the outermost and intermediate layers of the cathode material precursor must first be removed. This invention does not particularly limit the method for removing the outermost and intermediate layers; preferably, acid washing can be used. A specific acid washing method is provided here, but this invention is not limited thereto. The preferred acid washing method includes: adding 10g of the cathode material precursor to 400mL of a 0.4mol / L hydrochloric acid solution, stirring for 15min, filtering, washing three times with deionized water, and drying in a vacuum drying oven at 120℃ for 6h to obtain the core layer product.

[0032] In this invention, the XRD pattern of the core layer was measured using a Bruker D8 Advance SS X-ray diffractometer. In the XRD pattern of the core layer, 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 diffraction peaks of the (110) and (102) crystal planes 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.

[0033] In this invention, the specific surface area of ​​the precursor product was measured using a TriStar 3000 physical adsorption instrument from Micromeritics Instrument Corporation, USA, in a nitrogen atmosphere.

[0034] The inventors of this invention discovered in their research that the core layer of the cathode material precursor has the aforementioned specific diffraction peak structure and the cathode material precursor has the aforementioned specific surface area, which is beneficial for the insertion and extraction of lithium ions. This effectively solves the problem of the active material, especially the internal structure, being difficult to utilize, thereby improving the discharge specific capacity and rate performance of the material, and thus improving the energy density and kinetic performance of the lithium-ion battery.

[0035] 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.

[0036] 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.

[0037] 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%.

[0038] 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.

[0039] 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 4 , Figure 5It 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.

[0040] Furthermore, through SEM images of the cathode material precursor (such as...) Figure 4 , Figure 5 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 4 , Figure 5 It can be observed that the core layer is formed by a primary sheet-like aggregation, which is relatively loose and has a thickness of about 1.4 μm. The outermost layer is also formed by a primary sheet-like aggregation, which is even looser than the core layer and has a thickness of about 0.33 μm. The intermediate layer between the core layer and the outermost layer is very dense and has a thickness of about 4.6 μm.

[0041] 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, suppressing cracking and breakage caused by volume expansion and contraction during charging and discharging. The middle layer has the highest density, effectively encapsulating the highly active core layer structure, improving the material's cycle stability, and also effectively increasing 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 material's interfacial resistance and improving the rate performance of the active material.

[0042] 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.

[0043] 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.

[0044] 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-qWherein, M is selected from at least one of Cu, Nd, Mg, W, Mo, Zn, Sn, Sr, Mn and Al, preferably at least one of Mn, Al, Sr, Nd and Mg; 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.

[0045] A second aspect of the present invention provides a method for preparing a cathode material precursor, the method comprising the following steps:

[0046] (1) The metal source solution, precipitant solution and complexing agent solution are subjected to a precipitation reaction to obtain the reaction product;

[0047] (2) The reaction product is subjected to solid-liquid separation and drying to obtain the cathode material precursor;

[0048] The total reaction time is denoted as R hours. In the first 1 / 8 of R hours after the start of the reaction, the solid content of the precipitation reaction system is not higher than 7 wt%, preferably not higher than 5 wt%, for example, 0 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, and any value within the range formed by any two of these values.

[0049] 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 aforementioned range during the first 1 / 8R hour of the reaction, they creatively obtained secondary microsphere precursor particles formed by primary particle aggregation. The aggregation form of the primary particles exhibits a relatively loose core layer, a very dense middle layer, and a relatively loose outermost layer. Furthermore, the core layer can be controlled to exhibit a specific diffraction peak structure, and the secondary microspheres have a high specific surface area. The cathode material precursor material with these characteristics has a higher discharge specific capacity and can be used in high-energy-density lithium-ion batteries.

[0050] 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.

[0051] 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, Nd, Mg, W, Mo, Zn, Sn, Sr, Mn and Al, preferably at least one of Nd, Mg, Sr, Mn and Al.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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 of the invention, but the invention is not limited thereto.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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).

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] In a preferred embodiment of the present invention, the total reaction time is denoted as R hours. During the first 1 / 8 of R hours of the reaction, the concentration change rate of the complexing agent is not less than 0.021 mol / L·h, preferably 0.021-1 mol / L·h, more preferably 0.021-0.5 mol / L·h, for example, 0.021 mol / L·h, 0.026 mol / L·h, 0.031 mol / L·h, 0.036 mol / L·h, 0.041 mol / L·h, 0.046 mol / L·h, 0.5, and any value within the range formed by any two of these values. Using this preferred embodiment, the discharge capacity, rate performance, and cycle stability of the prepared cathode material precursor can be significantly improved.

[0073] 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.

[0074] In a preferred embodiment of the present invention, the time from the addition of the complexing agent to reaching a concentration of not less than 80% of the complexing agent concentration at the end of the reaction in the precipitation reaction system does not exceed 1 / 4R hour.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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 by controlling the flow rate and concentration of the metal source solution, complexing agent solution and precipitant solution.

[0079] This invention offers a wide range of options for the flow rates and concentrations of 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 2-6. 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 solids content of the precipitation reaction system.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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).

[0089] 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 discharge specific capacity of the lithium-ion battery.

[0090] 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.

[0091] In this invention, the positive electrode composite can be prepared by using a positive electrode material, a conductive agent, a binder, and a solvent.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] In a preferred embodiment of the present invention, the solvent used in the positive electrode complex may be N-methylpyrrolidone.

[0096] In this invention, the negative electrode composite can be prepared by using a negative electrode material, a conductive agent, a binder, and a solvent.

[0097] 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.

[0098] 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.

[0099] In a preferred embodiment of the present invention, the solvent used in the negative electrode composite may be water.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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).

[0105] 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).

[0106] 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).

[0107] 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, the separator can be a polyolefin, such as polyethylene, polypropylene, or a composite of polyethylene and polypropylene, 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.

[0108] 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.

[0109] 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%.

[0110] The present invention will be described in detail below through embodiments. In the following embodiments and comparative examples,

[0111] Scanning electron microscope (SEM) images were obtained using a ZEISS Merlin scanning electron microscope from ZEISS GmbH, Germany.

[0112] The X-ray diffraction pattern (XRD) was obtained using a Bruker D8 Advance SS X-ray diffractometer from Germany.

[0113] The specific surface area was measured using a TriStar3000 physical adsorption analyzer from Micromeritics Instrument Corporation, USA.

[0114] Medium particle size was obtained using a Mastersizer 3000 laser particle size analyzer from Malvern Panalytical, UK.

[0115] Unless otherwise stated, all raw materials used in the following examples and comparative examples are commercially available products.

[0116] Example 1

[0117] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0118] (1) Preparation of cathode material precursor

[0119] A metal source solution with a concentration of 3 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 5 mol / L was prepared; and an ammonia solution as a complexing agent with a concentration of 5 mol / L was prepared.

[0120] The prepared metal source solution, NaOH solution, and complexing agent solution were simultaneously added to the reaction vessel under stirring to induce a precipitation reaction. An ammonia solution (0.5 mol / L) was pre-added to the reaction vessel, comprising 30% of its volume. The initial volumetric flow rate ratio of the metal source solution to the complexing agent solution was controlled at 3. Then, while maintaining a constant flow rate of the metal source solution, the feed flow rate of the complexing agent was controlled, causing the concentration of the complexing agent in the system to gradually increase, with the rate of increase gradually decreasing. The change in the concentration of the complexing agent in the system over reaction time is shown in the figure. Figure 2 The flow rate of the NaOH solution was controlled to maintain the pH of the reaction system at around 11.6 throughout the reaction. The solid content of the reaction system was 4.5 wt% at 6 hours, and the concentration of ammonia in the system at the end of the reaction was approximately 1.13 mol / L. The stirring speed was 800 rpm, the reaction temperature was 55℃, and the total reaction time was 48 hours. After the precipitation reaction was terminated and the mixture was allowed to cool naturally, the slurry was vacuum filtered, washed three times with deionized water, and then dried in a vacuum drying oven at 120℃ for 12 hours to obtain the cathode material precursor.

[0121] (2) Evaluation of cathode material precursors

[0122] The cathode material precursor prepared above was characterized by SEM, such as... Figure 4 As shown. From Figure 4 As can be seen from the above, the preparation method provided by the present invention can obtain a cathode material precursor with good sphericity. The cathode material precursor is a secondary microsphere formed by the aggregation of primary sheet-like bodies.

[0123] 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 5 As shown, from Figure 5As 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 1.4 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 0.33 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 4.6 μm.

[0124] The medium 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 12.4 μm.

[0125] The specific surface area of ​​the cathode material precursor prepared in Example 1 was tested, showing that the specific surface area of ​​the secondary microspheres of the cathode material precursor was 8.53 m². 2 / g.

[0126] 10g of the cathode material precursor prepared above was added to 400mL of 0.4mol / L hydrochloric acid solution, stirred for 15min, filtered, washed three times with deionized water, and then dried in a vacuum drying oven at 120℃ for 6h to obtain the core layer product. The XRD pattern of the core layer was tested, and the results are as follows. Figure 6 As shown, from Figure 6 It can be seen that the ratio of the diffraction peak intensities of the (110) and (102) crystal planes in the XRD spectrum of the core layer is 2.93.

[0127] (3) Preparation and evaluation of cathode materials

[0128] The cathode material precursor prepared above 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 500℃ for 4 h in an oxygen atmosphere, and then calcined at 900℃ for 12 h to carry out a solid-state reaction to obtain the cathode material.

[0129] The prepared positive electrode material, conductive agent, and binder were mixed uniformly 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 2025 type coin cell in an inert atmosphere glove box, where the moisture and oxygen content were below 0.1 ppm.

[0130] The electrochemical performance of the cathode material was measured under charge / discharge voltage ranges of 2.5–4.3 V and an ambient temperature of 25 °C. The results showed an initial discharge specific capacity of 215.6 mAh / g at 0.1 C rate and a discharge specific capacity of 190.7 mAh / g at 1 C rate. Specific charge / discharge curves are shown below. Figure 7 and Figure 8 Different discharge rates result in higher specific capacity.

[0131] Example 2

[0132] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0133] (1) Preparation of cathode material precursor

[0134] A metal source solution with a concentration of 2 mol / L was prepared, based on the metal element, wherein the molar ratio of nickel, cobalt and aluminum elements in the metal source solution was 8:1.5:0.5, and nickel sulfate, cobalt sulfate and aluminum sulfate were used in the preparation process; a NaOH solution with a concentration of 5 mol / L was prepared; and an ammonia solution as a complexing agent with a concentration of 4 mol / L was prepared.

[0135] The prepared metal source solution, NaOH solution, and complexing agent solution were simultaneously added to the reaction vessel under stirring to induce a precipitation reaction. An ammonia solution (0.5 mol / L) was pre-added to the reaction vessel, comprising 30% of its volume. The initial flow rate ratio of the metal source solution to the complexing agent solution was controlled at 4. The flow rate of the metal source solution was then kept constant while the feed flow rate of the complexing agent was controlled, causing the concentration of the complexing agent in the system to gradually increase, with the rate of increase gradually decreasing. The change in the concentration of the complexing agent with reaction time was the same as in Example 1. The flow rate of the NaOH solution was controlled to maintain the pH of the reaction system at approximately 11.4 throughout the reaction. The solid content of the reaction system was 4.1 wt% at 6 hours, and the concentration of ammonia in the system at the end of the reaction was approximately 1.13 mol / L. The stirring speed was 1000 rpm, the reaction temperature was 50°C, and the total reaction time was 48 hours. After the precipitation reaction was terminated and the mixture was allowed to cool naturally, 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 the cathode material precursor.

[0136] (2) Evaluation of cathode material precursors

[0137] The prepared cathode material precursor was subjected to SEM testing, and the SEM images were compared with... Figure 4 and Figure 5 resemblance.

[0138] The specific surface area of ​​the prepared cathode material precursor was tested, and the specific surface area of ​​the secondary microspheres was 10.87 m². 2 / g.

[0139] The core layer of the prepared cathode material precursor was subjected to XRD test according to the method of Example 1. The results showed that the ratio of the diffraction peak intensities of (110) and (102) crystal planes in the XRD spectrum of the core layer was 2.79.

[0140] (3) Preparation and evaluation of cathode materials

[0141] The cathode material and lithium-ion battery were prepared according to the method described in Example 1.

[0142] The electrochemical performance of the cathode material was measured under the conditions of charge-discharge voltage range of 2.5-4.3V and ambient temperature of 25℃. The results showed that the initial discharge specific capacity at 0.1C rate was 215.1mAh / g and the discharge specific capacity at 1C rate was 190.2mAh / g.

[0143] Example 3

[0144] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0145] (1) Preparation of cathode material precursor

[0146] A metal source solution with a concentration of 3 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 solution concentration was 8 mol / L.

[0147] The prepared metal source solution, NaOH solution, and complexing agent solution were simultaneously added to the reaction vessel under stirring to induce a precipitation reaction. An ammonia solution (0.5 mol / L) was pre-added to the reaction vessel, comprising 30% of its volume. The initial volumetric flow rate ratio of the metal source solution to the complexing agent solution was controlled at 6. Then, while maintaining a constant flow rate of the metal source solution, the feed flow rate of the complexing agent was controlled, causing the concentration of the complexing agent in the system to gradually increase, with the rate of increase gradually decreasing. The change in the concentration of the complexing agent in the system over reaction time is shown in the figure. Figure 3The flow rate of the NaOH solution was controlled to maintain the pH of the reaction system around 11 throughout the reaction. The solid content of the reaction system was 6.9 wt% at 6 hours, and the ammonia concentration at the end of the reaction was approximately 1.06 mol / L. The stirring speed was 800 rpm, the reaction temperature was 55℃, and the total reaction time was 48 hours. After the precipitation reaction was terminated and the mixture was allowed to cool naturally, the slurry was vacuum filtered, washed three times with deionized water, and then dried in a vacuum drying oven at 120℃ for 12 hours to obtain the cathode material precursor.

[0148] (2) Evaluation of cathode material precursors

[0149] The prepared cathode material precursor was subjected to SEM testing, and the SEM images were compared with... Figure 4 and Figure 5 resemblance.

[0150] The specific surface area of ​​the prepared cathode material precursor was tested, and the specific surface area of ​​the secondary microspheres was 3.53 m². 2 / g.

[0151] The core layer of the prepared cathode material precursor was subjected to XRD test according to the method of Example 1. The results showed that the ratio of the diffraction peak intensities of (110) and (102) crystal planes in the XRD spectrum of the core layer was 1.87.

[0152] (3) Preparation and evaluation of cathode materials

[0153] The cathode material and lithium-ion battery were prepared according to the method described in Example 1.

[0154] The electrochemical performance of the cathode material was measured under the conditions of charge-discharge voltage range of 2.5-4.3V and ambient temperature of 25℃. The results showed that the specific capacity of the first discharge at 0.1C rate was 210.6mAh / g and the specific capacity of the discharge at 1C rate was 186.8mAh / g.

[0155] Example 4

[0156] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0157] (1) Preparation of cathode material precursor

[0158] The procedure was performed according to the method described in Example 1, except that neodymium nitrate was added to the metal source solution, wherein Nd / (Ni+Co+Mn) = 1%mol, to obtain the cathode material precursor.

[0159] (2) Evaluation of cathode material precursors

[0160] The prepared cathode material precursor was subjected to SEM testing, and the SEM images were compared with... Figure 4 and Figure 5 resemblance.

[0161] The specific surface area of ​​the prepared cathode material precursor was tested, and the specific surface area of ​​the secondary microspheres was 6.67 m². 2 / g.

[0162] The core layer of the prepared cathode material precursor was subjected to XRD test according to the method of Example 1. The results showed that the ratio of the diffraction peak intensities of (110) and (102) crystal planes in the XRD spectrum of the core layer was 2.64.

[0163] (3) Preparation and evaluation of cathode materials

[0164] The cathode material and lithium-ion battery were prepared according to the method described in Example 1.

[0165] The electrochemical performance of the cathode material was measured under the conditions of charge-discharge voltage range of 2.5-4.3V and ambient temperature of 25℃. The results showed that the specific capacity of the first discharge at 0.1C rate was 214.5mAh / g and the specific capacity of the discharge at 1C rate was 189.5mAh / g.

[0166] Example 5

[0167] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0168] (1) Preparation of cathode material precursor

[0169] The procedure was performed according to the method described in Example 1, except that MgSO4·7H2O was added to the metal source solution, wherein Mg / (Ni+Co+Mn)=1%mol, to obtain the cathode material precursor.

[0170] (2) Evaluation of cathode material precursors

[0171] The prepared cathode material precursor was subjected to SEM testing, and the SEM images were compared with... Figure 4 and Figure 5 resemblance.

[0172] The specific surface area of ​​the prepared cathode material precursor was tested, and the specific surface area of ​​the secondary microspheres was 5.19 m². 2 / g.

[0173] The core layer of the prepared cathode material precursor was subjected to XRD test according to the method of Example 1. The results showed that the ratio of the diffraction peak intensities of (110) and (102) crystal planes in the XRD spectrum of the core layer was 2.59.

[0174] (3) Preparation and evaluation of cathode materials

[0175] The cathode material and lithium-ion battery were prepared according to the method described in Example 1.

[0176] The electrochemical performance of the cathode material was measured under the conditions of charge-discharge voltage range of 2.5-4.3V and ambient temperature of 25℃. The results showed that the specific capacity of the first discharge at 0.1C rate was 214.2mAh / g and the specific capacity of the discharge at 1C rate was 188.9mAh / g.

[0177] Example 6

[0178] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0179] (1) Preparation of cathode material precursor

[0180] 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.

[0181] (2) Evaluation of cathode material precursors

[0182] The prepared cathode material precursor was subjected to SEM testing, and the SEM images were compared with... Figure 4 and Figure 5 resemblance.

[0183] The specific surface area of ​​the prepared cathode material precursor was tested, and the specific surface area of ​​the secondary microspheres was 1.37 m². 2 / g.

[0184] The core layer of the prepared cathode material precursor was subjected to XRD test according to the method of Example 1. The results showed that the ratio of the diffraction peak intensities of (110) and (102) crystal planes in the XRD spectrum of the core layer was 2.24.

[0185] (3) Preparation and evaluation of cathode materials

[0186] The cathode material and lithium-ion battery were prepared according to the method described in Example 1.

[0187] The electrochemical performance of the cathode material was measured under the conditions of charge-discharge voltage range of 2.5-4.3V and ambient temperature of 25℃. The results showed that the specific capacity of the first discharge at 0.1C rate was 209.7mAh / g and the specific capacity of the discharge at 1C rate was 185.4mAh / g.

[0188] Example 7

[0189] This embodiment is used to illustrate the preparation and evaluation methods of the cathode material precursor and cathode material described in this invention.

[0190] (1) Preparation of cathode material precursor

[0191] 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.

[0192] The prepared metal source solution, NaOH solution, and complexing agent solution were simultaneously added to the reaction vessel under stirring to induce a precipitation reaction. An ammonia solution (0.5 mol / L) was pre-added to the reaction vessel, accounting for 40% of its volume. The initial flow rate ratio of the metal source solution to the complexing agent solution was controlled at 5:1. The flow rate of the metal source solution was then kept constant while the feed flow rate of the complexing agent was controlled, causing the concentration of the complexing agent in the system to gradually increase, with the rate of increase gradually decreasing. The change in the concentration of the complexing agent with reaction time was the same as in Example 1. The flow rate of the NaOH solution was controlled to maintain the pH value of the reaction system around 10 throughout the reaction. The solid content of the reaction system was 3 wt% at 6 hours, and the concentration of ammonia in the system at the end of the reaction was approximately 1.13 mol / L. The stirring speed was 1000 rpm, the reaction temperature was 50°C, and the total reaction time was 48 hours. After the precipitation reaction was terminated and the mixture was allowed to cool naturally, 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 the cathode material precursor.

[0193] (2) Evaluation of cathode material precursors

[0194] The prepared cathode material precursor was subjected to SEM testing, and the SEM images were compared with... Figure 4 and Figure 5 resemblance.

[0195] The specific surface area of ​​the prepared cathode material precursor was tested, and the specific surface area of ​​the secondary microspheres was 13.85 m². 2 / g.

[0196] The core layer of the prepared cathode material precursor was subjected to XRD test according to the method of Example 1. The results showed that the ratio of the diffraction peak intensities of (110) and (102) crystal planes in the XRD spectrum of the core layer was 1.74.

[0197] (3) Preparation and evaluation of cathode materials

[0198] The cathode material and lithium-ion battery were prepared according to the method described in Example 1.

[0199] The electrochemical performance of the cathode material was measured under the conditions of charge-discharge voltage range of 2.5-4.3V and ambient temperature of 25℃. The results showed that the initial discharge specific capacity at 0.1C rate was 210.8mAh / g and the discharge specific capacity at 1C rate was 186.9mAh / g.

[0200] 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. Furthermore, the core layer exhibits a specific diffraction peak structure, and the secondary microspheres possess a high specific surface area. This unique structure endows the precursor with superior electrochemical performance, such as higher discharge specific capacity, making it suitable for use in high-performance lithium-ion batteries.

[0201] Comparative Example 1

[0202] A metal source solution with a concentration of 3 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 5 mol / L was prepared; and an ammonia solution as a complexing agent with a concentration of 5 mol / L was prepared.

[0203] The prepared metal source solution and NaOH solution were simultaneously added to the reaction vessel under stirring to induce a precipitation reaction. An ammonia solution (0.5 mol / L) accounting for 30% 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 11. The total amount of ammonia (the same as in Example 1) was added to the reaction system in three equal portions at 1h, 10h, and 30h after the start of the reaction. The solid content of the reaction system was 8.5 wt% at 6h. The stirring speed was 800 rpm, the reaction temperature was 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.

[0204] The prepared cathode material precursor was subjected to SEM testing. The cathode material precursor is an irregular aggregate formed by loose aggregation of nanoparticles. The sphericity of the particles is very poor. This type of precursor cannot meet the requirements of the battery field for precursor materials.

[0205] The core layer of the prepared cathode material precursor was subjected to XRD test according to the method of Example 1. The results showed that the ratio of the diffraction peak intensities of (110) and (102) crystal planes in the XRD spectrum of the core layer was 0.64.

[0206] The specific surface area of ​​the prepared cathode material precursor was tested, and the specific surface area of ​​the secondary microspheres was 0.48 m². 2 / g.

[0207] 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. The electrochemical performance of the cathode material was measured under charge / discharge voltage ranges of 2.5-4.3V and an ambient temperature of 25℃. The results showed that the initial discharge specific capacity at 0.1C rate was 170.2 mAh / g, and the discharge specific capacity at 1C rate was 158.6 mAh / g, which is far lower than the performance of the embodiments of the present invention.

[0208] In summary, the core layer of the cathode material precursor prepared by the method provided by this invention has a specific diffraction peak structure, and the cathode material precursor has a high specific surface area. When the cathode material prepared using this cathode material precursor is applied to lithium-ion batteries, the lithium-ion battery has a high discharge specific capacity.

[0209] 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 intensity ratio of the (110) and (102) crystal plane diffraction peaks in the X-ray diffraction pattern of the core layer is 1.5-8; the specific surface area of ​​the secondary microsphere is 0.5-15m². 2 / g.

2. The cathode material precursor according to claim 1, wherein, In the X-ray diffraction pattern of the core layer, the intensity ratio of the diffraction peaks of the (110) and (102) crystal planes is 1.5-4.

3. 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.

4. The cathode material precursor according to any one of claims 1-3, 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%.

5. The cathode material precursor according to any one of claims 1-3, wherein, The secondary microspheres have a particle size of 1-30 μm.

6. The cathode material precursor according to any one of claims 1-3, 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.

7. The cathode material precursor according to any one of claims 1-3, wherein, 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, Nd, Mg, W, Mo, Zn, Sn, Sr, 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.

8. A method for preparing a cathode material precursor, 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. During the first 1 / 8 of R hours of the reaction, the solid content of the precipitation reaction system is no higher than 7 wt%. 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 total reaction time is denoted as R hours. In the first 1 / 8 of R hours after the start of the reaction, the solid content of the precipitation reaction system is not higher than 5 wt%.

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

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

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

13. The method according to claim 8, wherein, Within the first 1 / 8R hour of the reaction, the concentration of the complexing agent changes at a rate not less than 0.021 mol / L·h.

14. The method according to claim 8, wherein, In the precipitation reaction system, the time from the addition of the complexing agent to reaching a concentration of no less than 80% of the complexing agent concentration at the end of the reaction shall not exceed 1 / 4R hour.

15. The method according to claim 14, wherein, At the end of the reaction, the concentration of the complexing agent is 0.05-2 mol / L.

16. The method according to claim 15, wherein, At the end of the reaction, the concentration of the complexing agent is 0.05-1.2 mol / L.

17. The method according to any one of claims 8-16, 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.

18. The method according to claim 17, 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.

19. The method according to any one of claims 8-16, 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.

20. The method according to any one of claims 8-16, wherein, Before adding the metal source solution, precipitant solution, and complexing agent solution to the reactor, a bottom liquid is added to the reactor.

21. The method according to claim 20, wherein, 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.

22. The method according to claim 21, wherein, The concentration of the complexing agent in the substrate is 0.05-1.5 mol / L.

23. The method according to claim 21, 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.

24. The method according to claim 23, 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.

25. The method according to claim 20, wherein, The volume of the bottom liquid is 0-100% of the volume of the reactor.

26. The method of claim 25, wherein, The volume of the bottom liquid is 0-80% of the volume of the reactor.

27. The method according to claim 26, wherein, The volume of the bottom liquid is 10-60% of the volume of the reactor.

28. The method according to any one of claims 8-16, 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, Nd, Mg, W, Mo, Zn, Sn, Sr, Mn and Al; And / or, the precipitant is selected from at least one of alkali metal hydroxides, carbonates and bicarbonates; And / or, the alkali metal is selected from at least one of Na, K and Li; And / or, 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.

29. The method according to claim 28, 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.

30. The method according to any one of claims 8-16, 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.

31. The method according to claim 30, 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.

32. The method according to any one of claims 8-16, 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.

33. The method according to claim 32, 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.

34. The cathode material precursor prepared by the method according to any one of claims 8-33.

35. 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 1-7 and 34.

36. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode material as described in claim 35.

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