Core-shell ternary precursor and preparation method therefor, and positive electrode material

Abstract

A core-shell ternary precursor and a preparation method therefor, and a positive electrode material. The core-shell ternary precursor comprises a core and a shell that coats the core. The core is expressed as NixCoyMnz(OH)2-a(WO4)a, wherein x is greater than 0, but less than 1; y is greater than 0, but less than 1; z is greater than 0, but less than 1; x+y+z=1; and the value range of a is 0.01-1. The shell contains aluminum. By means of a combination of tungsten doping and aluminum doping, the advantages of the both are incorporated, and a high-performance precursor is prepared. In addition, the core-shell precursor can effectively improve the surface structure of a precursor, suppress the propagation of cracks on the surface of a high-nickel large-particle precursor, and also effectively inhibit the corrosion of a positive electrode material by an electrolyte, thereby prolonging the battery life.

Description

Nucleus-shell type ternary precursor, preparation method thereof and positive electrode material TECHNICAL FIELD

[0001] The present application relates to the technical field of ternary precursors, in particular to a nucleus-shell type ternary precursor, a preparation method thereof and a positive electrode material. BACKGROUND

[0002] Lithium ion batteries are environmentally friendly new energy sources, and are widely used due to their high energy density, cycle performance and stability. Among them, the battery positive electrode material is the key breakthrough of the development of lithium ion battery technology. The early LiCoO2 positive electrode material has high cost and high toxicity, and is no longer suitable for use. The ternary positive electrode material with other elements (Ni, Mn) replacing part of Co has high specific capacity, low cost, large reversible capacity and cycle stability, and has become a research hotspot.

[0003] The 5 series and 6 series ternary precursors on the market have high cobalt content and low energy density. In order to improve the energy density, 8 series and 9 series ternary precursors are prepared, which have high nickel content and high energy density but poor stability, and the precursors are prone to cracks during preparation.

[0004] In order to improve the defects existing in the above-mentioned materials, doping elements in the bulk phase and surface coating are simple and feasible improvement strategies. The doping elements can enhance the structural stability of the material to a certain extent, and the surface coating can inhibit crack propagation, prevent the collapse of the battery structure during charging and discharging, and also effectively prevent the corrosion of the electrolyte to the positive electrode material. However, in the specific preparation process, there are problems such as uneven element doping and coating, complex process, and low content of doping elements.

[0005] Doping Al elements in the ternary precursor can improve the stability of the material, improve the cation mixing phenomenon of high-nickel materials, thereby weakening the lattice distortion phenomenon, inhibiting the precipitation of nickel ions and manganese ions from the material interior, and thus playing a role in improving the cycle performance of the material. Doping W can improve the working voltage and energy density of lithium ion batteries, increase the spacing of the layered structure, improve the rate capability, and also stabilize the structure of the precursor and strengthen the thermal stability of the positive electrode material.

[0006] CN117430173A prepared a ternary precursor with an Al concentration gradient by mixing and calcining an Al source and a Li source, and prepared a positive electrode material. This method first uniformly coats the aluminum source on the surface of the nickel-cobalt-manganese precursor, and then mixes it with the lithium source, thereby avoiding the technical difficulty that part of the aluminum cannot be doped into the crystal lattice of the positive electrode material during high-temperature solid-phase reaction. However, after the precursor is mixed with the Al source by ball milling, the coating degree of Al on the surface of the precursor is not high, and the coating effect of Al is not effectively exerted.

[0007] CN104916837A prepares an aluminum-doped ternary positive electrode material precursor by using a coprecipitation method, then calcines the precursor after mixing with a lithium source and a boron source to obtain a positive electrode material, which improves the cycle performance of the material, but B 3+ and Ni 2+ have a large difference in ionic radius, and are prone to delamination at the coating interface.

[0008] CN109904432A dopes tungsten in the ternary precursor by mixing the ternary precursor with a tungsten source and a lithium source and calcining, which has poor uniformity of the grinding mixture, affecting the uniformity of tungsten doping, and in addition, the common sintering with the lithium source will exist competitive occupation, thereby affecting the sintering effect of the positive electrode material.

[0009] In summary, the doping element cannot be effectively coated on the surface of the precursor, the coating layer and the precursor appear delamination, the doping and coating are carried out twice, and the process is complex, the equipment requirement is high, which is a problem to be solved at present.

[0010] SUMMARY

[0011] The following is a summary of the subject matter detailed in the detailed description. This summary is not intended to limit the scope of the claims.

[0012] The present application provides a core-shell type ternary precursor, a preparation method thereof and a positive electrode material. The ternary precursor is prepared by a one-step co-precipitation method, which is simple, fast, high in production efficiency, and adaptable to various different metal liquids. The positive electrode material prepared by doping modification of the precursor often has high stability, high battery operating voltage and energy density, and high rate capability.

[0013] In a first aspect, the present application provides a core-shell type ternary precursor, which comprises a core and a shell coated outside the core; the core has a formula of Ni x Co y Mn z (OH) 2-a (WO4) a , wherein 0

[0014] The core-shell ternary precursor core doped with tungsten can enhance the structural stability of the positive electrode material, thereby reducing the collapse and degradation of the structure during charging and discharging, prolonging the service life of the battery. Moreover, the doping of tungsten can help reduce the phase transition of the positive electrode material at high voltage, thereby reducing the capacity decay and improving the cycle stability of the battery. Furthermore, the high melting point property of tungsten can help improve the thermal stability of the battery and reduce the risk of thermal runaway. Due to the conductivity of tungsten, the doped material can perform better during high-current charging and discharging, i.e., the rate performance is improved. Moreover, the shell contains aluminum, and the aluminum coating can help reduce the cation mixing phenomenon in the core-shell ternary precursor, maintain the order of the crystal structure, and at the same time, synergize with the tungsten doping in the core to improve the application prospect of the core-shell ternary precursor.

[0015] wherein 0 < x < 1, for example, can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc., but is not limited to the listed values, and other values not listed in this range are also applicable; 0 < y < 1, for example, can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc., but is not limited to the listed values, and other values not listed in this range are also applicable; 0 < z < 1, for example, can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc., but is not limited to the listed values, and other values not listed in this range are also applicable. The value of a is in the range of 0.01-1, for example, can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, etc., but is not limited to the listed values, and other values not listed in this range are also applicable.

[0016] In one embodiment, the expression of the shell is Ni b Co c Mn d Al e (OH)2(b+c+d)+3e, wherein 0 < b < 1, 0 < c < 1, 0 < d < 1, and 0 < e < 1.

[0017] Specifically, 0 < b < 1, for example, can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc., but not limited to the listed values, other values not listed in the range are also applicable; 0 < c < 1, for example, can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc., but not limited to the listed values, other values not listed in the range are also applicable; 0 < d < 1, for example, can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc., but not limited to the listed values, other values not listed in the range are also applicable; 0 < e < 1, for example, can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0018] In one embodiment, the content of aluminum in the shell is 0.01-2wt%, for example, can be 0.01wt%, 0.1wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, or 12wt%, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0019] In one embodiment, the size of the core is 3-14μm, for example, can be 3μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, or 14μm, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0020] In one embodiment, the shell layer thickness of the shell is 0.1-4μm, for example, can be 0.1μm, 0.2μm, 0.3μm, 0.5μm, 0.8μm, 1μm, 1.2μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, or 4μm, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0021] In one embodiment, the particle size of the core-shell type ternary precursor is in the range of 3.1-18μm, for example, can be 3.1μm, 3.2μm, 3.5μm, 4μm, 5μm, 6μm, 8μm, 10μm, 12μm, 14μm, 15μm, or 18μm, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0022] The core-shell ternary precursor has the advantages of high controllability of particle size, and can control the particle size in the above range, thereby having better electrochemical performance.

[0023] In a second aspect, the application provides a preparation method of the core-shell ternary precursor of the first aspect, and the preparation method comprises the following steps:

[0024] In a reaction atmosphere, an ammonia-containing bottom solution is configured, and then a ternary salt solution, a tungstate solution, a precipitating agent and a complexing agent are introduced into the bottom solution to perform a first reaction to form a core.

[0025] The introduction of the ternary salt solution is stopped, and a mixed salt solution containing an aluminum salt is introduced at the same time to perform a second reaction to form a shell wrapped outside the core.

[0026] The core-shell ternary precursor of the first aspect of the application can be prepared by the preparation method of the second aspect, and the core-shell ternary precursor is formed by co-precipitation to ensure one-time growth of the precursor in the kettle. The preparation method is simple, has high controllability of particle size, has a wide application prospect, and is not prone to separation of the aluminum coating layer from the core.

[0027] It should be noted that in the present application, the ternary salt solution is introduced first, and then the mixed salt solution containing the aluminum salt is introduced, so that the core is formed first, and then the shell is wrapped outside the core. This can ensure that the particle size of the finally prepared core-shell ternary precursor is within the ideal range. The core-shell precursor prepared by this method can effectively improve the surface structure of the precursor, inhibit the expansion of surface cracks of high-nickel large-particle precursors, and effectively inhibit the corrosion of the electrolyte on the positive electrode material, thereby improving the battery life.

[0028] In an embodiment, the reaction atmosphere comprises nitrogen and / or air.

[0029] In an embodiment, the precipitating agent comprises an alkali solution, and the precipitating agent can be a sodium hydroxide solution.

[0030] In an embodiment, the concentration of the alkali solution is 20-40 wt%, for example, it can be 20 wt%, 23 wt%, 25 wt%, 27 wt%, 29 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt% or 40 wt%, etc., but is not limited to the listed values, and other values not listed in this range are also applicable.

[0031] In an embodiment, the complexing agent comprises ammonia water and / or an ammonium salt solution.

[0032] In one embodiment, the concentration of the ammonia water and / or ammonium salt solution is 10-20 wt%, for example, it can be 10 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, or 20 wt%, etc., but is not limited to the listed values, and other values not listed in this range are also applicable.

[0033] In one embodiment, the ammonia concentration of the base solution is 6-10 g / L, for example, it can be 6 g / L, 6.5 g / L, 7 g / L, 7.5 g / L, 8 g / L, 9 g / L, 9.5 g / L, or 10 g / L, etc., but is not limited to the listed values, and other values not listed in this range are also applicable.

[0034] In one embodiment, the pH of the base solution is 9-12, for example, it can be 9, 9.5, 10, 10.3, 10.5, 10.7, 10.9, 11.2, 11.4, 11.6, 11.8, or 12, etc., but is not limited to the listed values, and other values not listed in this range are also applicable.

[0035] In one embodiment, the ternary salt solution comprises a nickel salt, a cobalt salt, and a manganese salt.

[0036] In one embodiment, the nickel salt comprises nickel nitrate and / or nickel sulfate.

[0037] In one embodiment, the cobalt salt comprises cobalt nitrate and / or cobalt sulfate.

[0038] In one embodiment, the manganese salt comprises manganese nitrate and / or manganese sulfate.

[0039] In one embodiment, the molar ratio of Ni:Co:Mn in the ternary salt solution is x:y:z, wherein 0

[0040] In one embodiment, the temperature of the first reaction is 50-60°C, for example, it can be 50°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, or 60°C, etc., but is not limited to the listed values, and other values not listed in this range are also applicable.

[0041] In one embodiment, the flow rate of the ternary salt solution is 1-10 L / h, for example, it can be 1 L / h, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 6 L / h, 7 L / h, 8 L / h, 9 L / h, or 10 L / h, etc., but is not limited to the listed values, and other values not listed in this range are also applicable.

[0042] The feeding speed of the ternary salt solution in the present application can be optionally controlled in the above range, which can better ensure that the precipitation reaction is completely carried out, and can further control the growth particle size of the core-shell precursor in a reasonable range.

[0043] In one embodiment, the tungstate solution has a tungsten concentration of 100-5000 mg / L, for example, 100 mg / L, 200 mg / L, 500 mg / L, 700 mg / L, 800 mg / L, 1000 mg / L, 1200 mg / L, 2000 mg / L, 3000 mg / L, 4000 mg / L or 5000 mg / L, etc., but not limited to the listed values, and other values not listed in the range are also applicable.

[0044] In one embodiment, the feeding speed of the tungstate solution is 0.1-5 L / h, for example, 0.1 L / h, 0.2 L / h, 0.3 L / h, 0.4 L / h, 0.5 L / h, 0.6 L / h, 0.7 L / h, 0.8 L / h, 0.9 L / h, 1 L / h, 1.2 L / h, 2 L / h, 3 L / h, 4 L / h, 4.5 L / h or 5 L / h, etc., but not limited to the listed values, and other values not listed in the range are also applicable.

[0045] The feeding speed of the tungstate solution in the present application can be optionally controlled in the above range, which can further avoid the problem that the tungsten doping amount is small and the electrical performance is not obviously improved due to the small feeding speed, and can ensure the particle size of the ternary precursor particles, effectively reduce the preparation difficulty, and reduce the waste of raw materials.

[0046] In one embodiment, the tungstate solution includes ammonium tungstate.

[0047] In one embodiment, the feeding speed of the precipitant is 0.1-10 L / h, for example, 0.1 L / h, 0.2 L / h, 0.3 L / h, 0.4 L / h, 0.5 L / h, 0.6 L / h, 0.7 L / h, 0.8 L / h, 0.9 L / h, 1 L / h, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 8 L / h, 9 L / h or 10 L / h, etc., but not limited to the listed values, and other values not listed in the range are also applicable.

[0048] In one embodiment, the complexing agent is introduced at a rate of 0.1-10 L / h, for example, 0.1 L / h, 0.2 L / h, 0.3 L / h, 0.4 L / h, 0.5 L / h, 0.6 L / h, 0.7 L / h, 0.8 L / h, 0.9 L / h, 1 L / h, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 8 L / h, 9 L / h, or 10 L / h, etc., but not limited to the listed values, and other values not listed within the range are also applicable.

[0049] In one embodiment, the rate of introduction of the precipitant is adjusted to control the pH to be 9-12, for example, 9, 9.4, 9.7, 10, 10.4, 10.7, 11, 11.4, 11.7, or 12, etc., but not limited to the listed values, and other values not listed within the range are also applicable.

[0050] The application can optionally control the pH during the precipitation process to be within the above range, which is more conducive to forming a core-shell precursor of the target particle size.

[0051] In one embodiment, the rate of introduction of the complexing agent is adjusted to control the ammonia concentration to be 4-10 g / L, for example, 4 g / L, 5 g / L, 5.6 g / L, 6.2 g / L, 6.7 g / L, 7.3 g / L, 7.8 g / L, 8.4 g / L, 8.9 g / L, 9.5 g / L, or 10 g / L, etc., but not limited to the listed values, and other values not listed within the range are also applicable.

[0052] The application can optionally control the ammonia concentration to be within the above range, which is more conducive to obtaining a core-shell precursor with moderate density, thereby avoiding the problem of lithium ions being difficult to diffuse during the sintering process, ultimately leading to a decline in the charge-discharge performance of the positive electrode material; and it is also possible to obtain larger primary crystalline grains, further improving the stability of the positive electrode material.

[0053] In one embodiment, the particle size of the core is 5-14 μm, for example, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 8 μm, 9 μm, 9.5 μm, 10 μm, 11 μm, 12 μm, 13 μm, or 14 μm, etc., but not limited to the listed values, and other values not listed within the range are also applicable.

[0054] In one embodiment, the mixed salt solution containing aluminum salt includes a ternary salt solution and an aluminum salt.

[0055] In one embodiment, the aluminum salt includes aluminum sulfate and / or aluminum nitrate.

[0056] In one embodiment, the concentration of aluminum in the mixed salt solution containing aluminum salt is 100-5000 mg / L, for example, it can be 100 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, 500 mg / L, 600 mg / L, 1000 mg / L, 1200 mg / L, 1500 mg / L, 2000 mg / L, 3000 mg / L, 4000 mg / L or 5000 mg / L, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0057] In one embodiment, the feeding rate of the mixed salt solution containing aluminum salt is 1-10 L / h, for example, it can be 1 L / h, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 6 L / h, 7 L / h, 8 L / h, 9 L / h or 10 L / h, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0058] The application must first control the mixed salt solution containing aluminum salt to be added after the formation of the core, and the aluminum-doped shell is in the growth end stage when growing, the particle size is large, and it is not suitable for separate feeding during the reaction, so the Al is doped in the ternary salt solution for common feeding, which is more conducive to the combination between the aluminum shell and the core, and avoids the peeling phenomenon of the aluminum shell.

[0059] Moreover, the application further optionally controls the feeding rate of the mixed salt solution containing aluminum salt to be 1-10 L / h, so as to ensure that the particle size is uniform and large during the growth process, and small particle products are not easy to appear.

[0060] In one embodiment, the temperature of the second reaction is 50-60°C, for example, it can be 50°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0061] In one embodiment, the preparation method further comprises: sequentially performing solid-liquid separation, washing the solid phase and drying on the reaction material after the shell is formed, to obtain the core-shell ternary precursor.

[0062] The application has no special limitation on the solid-liquid separation in the above process, any device and method for solid-liquid separation known to those skilled in the art can be used, and adjustment can also be made according to the actual process, for example, it can be filtration, centrifugation or sedimentation separation, etc., or a combination of different ways.

[0063] The drying in the above process is not particularly limited in the present application, and any device and mode known to those skilled in the art that can be used for drying can be used, and the actual process can be adjusted, for example, air drying, vacuum drying, drying or freeze drying, or a combination of different modes.

[0064] As an optional technical solution of the present application, the preparation method comprises the following steps:

[0065] Under a protective atmosphere, a bottom solution with a pH of 9-12 and an ammonia concentration of 6-10 g / L is configured, then a ternary salt solution is introduced into the bottom solution at a flow rate of 1-10 L / h, a tungstate solution with a tungsten concentration of 100-5000 mg / L is introduced at a flow rate of 0.1-5 L / h, a precipitant is introduced at a flow rate of 0.1-10 L / h, and a complexing agent is introduced at a flow rate of 0.1-10 L / h, the flow rate of the precipitant is adjusted to control the pH to be 9-12, the flow rate of the complexing agent is adjusted to control the ammonia concentration to be 5-10 g / L, and a first reaction is carried out at 50-60℃ to form a core;

[0066] The introduction of the ternary salt solution is stopped, and a mixed salt solution containing an aluminum salt with an aluminum concentration of 100-5000 mg / L is introduced at a flow rate of 1-10 L / h at the same time, and a second reaction is carried out at 50-60℃ to form an outer shell wrapped outside the core;

[0067] The reaction material after the formation of the outer shell is sequentially subjected to solid-liquid separation, washing of the solid phase, and drying to obtain the core-shell type ternary precursor.

[0068] In a third aspect, the present application provides a positive electrode material, wherein the positive electrode material comprises a positive electrode active material prepared from the core-shell type ternary precursor of the first aspect.

[0069] The positive electrode material prepared in the third aspect of the present application has excellent electrochemical performance, which can improve the battery life.

[0070] The present application does not limit the structure of the positive electrode material and other materials, and any structure and other materials known to those skilled in the art that can be used for the positive electrode material can be used.

[0071] Compared with the related art, the present application has at least the following beneficial effects:

[0072] (1) The core-shell ternary precursor provided in the application is internally doped with tungsten and externally doped with aluminum, and has the advantages of both, and the core and the shell are mutually synergistic, which can effectively improve the surface structure of the precursor, inhibit the expansion of surface cracks of high-nickel large-particle precursors, and effectively inhibit the corrosion of the electrolyte on the positive electrode material, thereby improving the battery life. Under the preferred conditions, the rate performance of the positive electrode material prepared therefrom and assembled into a battery is 91.59% or more, the 0.1C charge-discharge efficiency is 88.26% or more, and the discharge capacity retention rate after 100 cycles is 93.25% or more;

[0073] (2) The preparation method of the core-shell ternary precursor provided in the application is prepared by using the co-precipitation method, which is simple and easy to operate, low in cost, and can strictly control the particle size of the core-shell ternary precursor by controlling the preparation of the core first and then the shell, thereby improving the electrochemical performance;

[0074] (3) The positive electrode material provided in the application has excellent performance, can better inhibit the corrosion of the electrolyte on the positive electrode material when applied in a battery, and has a wide application prospect.

[0075] Other aspects can be appreciated upon reading and understanding the drawings and detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0076] The accompanying drawings are included to provide a further understanding of the technical solutions of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0077] FIG. 1 is an electron probe X-ray microanalysis diagram of the core-shell ternary precursor provided in the embodiment 1 of the present application. DETAILED DESCRIPTION

[0078] In order to facilitate the understanding of the present application, the present application is listed as follows. It should be understood by those skilled in the art that the embodiments are only used to help understand the present application, and should not be regarded as a specific limitation on the present application.

[0079] It should be understood that, in the description of the present application, the terms "first", "second", etc. are only used for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second", etc. can explicitly or implicitly include one or more features. In the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0080] Embodiment 1

[0081] The present embodiment provides a core-shell ternary precursor, which comprises a core and a shell covering the outside of the core; the expression of the core is Ni xCo y Mn z (OH) 2-a (WO4) a wherein x is 0.9, y is 0.06, z is 0.04, and a is 0.1; the shell contains aluminum. The shell is expressed as Ni b Co c Mn d Al e (OH)(2(b+c+d)+3e), wherein b is 0.9, c is 0.06, d is 0.04, and e is 0.017. The shell contains 0.5wt% of aluminum. The core has a size of 7μm. The shell has a shell thickness of 1μm. The core-shell ternary precursor D50 is 8.0μm.

[0082] The present embodiment also provides a preparation method of the above core-shell ternary precursor, which comprises the following steps:

[0083] The ternary salt solution is prepared by dissolving nickel sulfate, cobalt sulfate and manganese sulfate in water, wherein the concentration of the solute is 100g / L.

[0084] The mixed salt solution containing aluminum is prepared by mixing aluminum sulfate with the ternary salt solution.

[0085] The precipitant is 31wt% sodium hydroxide solution; and the complexing agent is 15wt% ammonia water.

[0086] Under a nitrogen atmosphere, a bottom solution is prepared with 100L of initial pH of 11.4 and ammonia concentration of 8g / L (prepared by using sodium hydroxide and ammonia water), then the ternary salt solution (Ni:Co:Mn molar ratio of 90:6:4, nitrate, solute concentration of 2500mg / L) is introduced into the bottom solution at a rate of 8L / h, the tungsten acid ammonia solution with tungsten concentration of 200mg / L is introduced at a rate of 6L / h, the precipitant is introduced at a rate of 2.4L / h, and the complexing agent is introduced at a rate of 1L / h, the introduction rate of the precipitant is adjusted to control the pH between 11 and 11.2, the introduction rate of the complexing agent is adjusted to control the ammonia concentration between 7 and 8g / L, and the first reaction is carried out at 58°C for 82h to form a core with an average particle size of 7μm.

[0087] The introduction of the ternary salt solution is stopped, and the mixed salt solution containing aluminum (aluminum nitrate, nickel nitrate, manganese nitrate and manganese nitrate, Ni:Co:Mn molar ratio of 90:6:4) with aluminum concentration of 450mg / L is introduced at a rate of 8L / h, and the second reaction is continued at 58°C until the particle size reaches 8μm to form a shell covering the outside of the core with a shell thickness of 1μm.

[0088] The reaction post-matter after forming the shell is sequentially filtered, the solid phase is washed and dried to obtain the core-shell ternary precursor.

[0089] Test method: The particle size of the core-shell ternary precursor is tested by Malvern 3000, and the aluminum content of the shell of the core-shell ternary precursor is tested by ICP.

[0090] The electron probe X-ray microanalysis diagram of the core-shell ternary precursor prepared in Example 1 is shown in Figure 1. As can be seen from Figure 1, the core-shell ternary precursor has uniform particle size distribution, large particle size, and obvious core and coating shell structure.

[0091] Example 2

[0092] The present embodiment provides a core-shell ternary precursor, which comprises a core and a shell coated outside the core; the expression of the core is Ni x Co y Mn z (OH) 2-a (WO4) a , wherein x is 0.8, y is 0.1, z is 0.1, and the value of a is 0.5; the shell contains aluminum. The expression of the shell is Ni b Co c Mn d Al e (OH)(2(b+c+d)+3e), wherein b is 0.8, c is 0.1, d is 0.1, and e is 0.034. The content of aluminum in the shell is 1wt%. The size of the core is 5.5μm. The shell layer thickness of the shell is 1.5μm. The D50 of the core-shell ternary precursor is 8.0μm.

[0093] The present embodiment also provides a preparation method of the above-mentioned core-shell ternary precursor, which comprises the following steps:

[0094] Ternary salt solution: dissolve nickel nitrate, cobalt nitrate and manganese nitrate in water to obtain, wherein the concentration of the solute is 100g / L.

[0095] Mixed salt solution containing aluminum salt: mix aluminum nitrate with the ternary salt solution to obtain.

[0096] Precipitating agent: 32wt% sodium hydroxide solution; complexing agent: 10wt% ammonia water.

[0097] Under nitrogen atmosphere, a 120L initial solution with pH of 11.5 and ammonia concentration of 9g / L is prepared (using sodium hydroxide and ammonia water), then a ternary salt solution (Ni:Co:Mn molar ratio of 80:10:10, nitrate, solute concentration of 3500mg / L) is introduced into the solution at a rate of 6L / h, a tungsten acid ammonia solution with tungsten concentration of 250mg / L is introduced at a rate of 8L / h, a precipitant is introduced at a rate of 2L / h and a complexing agent is introduced at a rate of 0.8L / h, the rate of the precipitant is adjusted to control the pH between 11.5 and 12, the rate of the complexing agent is adjusted to control the ammonia concentration between 8 and 9g / L, and the first reaction is carried out at 60℃ for 63h to form a core with an average particle size of 5.5μm.

[0098] The introduction of the ternary salt solution is stopped, and a mixed salt solution containing aluminum salt (aluminum nitrate, nickel nitrate, manganese nitrate and manganese nitrate, Ni:Co:Mn molar ratio of 80:10:10) with aluminum concentration of 300mg / L is introduced at a rate of 4L / h, and the second reaction is continued at 60℃ until the particle size reaches 7μm to form a shell covering the outside of the core, and the shell thickness is 1.5μm.

[0099] The reaction material after forming the shell is sequentially filtered, the solid phase is washed and dried to obtain the core-shell ternary precursor.

[0100] Example 3

[0101] The present embodiment provides a core-shell ternary precursor, which comprises a core and a shell covering the outside of the core; the core has the expression of Ni x Co y Mn z (OH) 2-a (WO4) a , wherein x is 0.6, y is 0.1, z is 0.3, and the value of a is 1; the shell contains aluminum. The shell has the expression of Ni b Co c Mn d Al e (OH)(2(b+c+d)+3e), wherein b is 0.6, c is 0.1, d is 0.3 and e is 0.07. The content of aluminum in the shell is 2wt%. The size of the core is 6.0μm. The shell thickness of the shell is 2.0μm. The particle size range of the core-shell ternary precursor is 8.0μm.

[0102] The present embodiment also provides a preparation method of the above-mentioned core-shell ternary precursor, which comprises the following steps:

[0103] Ternary salt solution: nickel sulfate, cobalt sulfate and manganese sulfate are dissolved in water to obtain a solution, wherein the concentration of solute is 100 g / L.

[0104] Mixed salt solution containing aluminum salt: aluminum sulfate is mixed with the ternary salt solution to obtain.

[0105] Precipitating agent: 25 wt% sodium hydroxide solution; complexing agent: 12 wt% ammonia water.

[0106] Under a nitrogen atmosphere, a 90 L bottom solution (prepared by using sodium hydroxide and ammonia water) with an initial pH of 10.0 and an ammonia concentration of 7 g / L is prepared, and then the ternary salt solution (molar ratio of Ni:Co:Mn is 60:10:30, sulfate, solute concentration is 3800 mg / L) is introduced into the bottom solution at a rate of 10 L / h, the tungsten acid ammonia solution with a tungsten concentration of 250 mg / L is introduced at a rate of 2 L / h, the precipitating agent is introduced at a rate of 3 L / h, and the complexing agent is introduced at a rate of 1.2 L / h, the introduction rate of the precipitating agent is adjusted to control the pH to be between 9 and 10; the introduction rate of the complexing agent is adjusted to control the ammonia concentration to be between 5 and 7 g / L, and the first reaction is carried out at 50°C for 72 h to form a core with an average particle size of 6.0 μm.

[0107] The introduction of the ternary salt solution is stopped, and at the same time, the mixed salt solution containing aluminum salt (aluminum sulfate, nickel sulfate, manganese sulfate and manganese sulfate, molar ratio of Ni:Co:Mn is 90:6:4) with an aluminum concentration of 280 mg / L is introduced at a rate of 10 L / h, and the second reaction is continued at 50°C until the D50 reaches 8 μm to form a shell coated outside the core, and the shell thickness is 2 μm.

[0108] The reaction material after forming the shell is sequentially filtered, the solid phase is washed and dried to obtain the core-shell ternary precursor.

[0109] Example 4

[0110] The core-shell ternary precursor provided in the embodiment is the same as that in Example 1 except that the ternary salt solution is introduced at a rate of 12 L / h in the preparation method, which is not described herein again.

[0111] Example 5

[0112] The core-shell ternary precursor provided in the embodiment is the same as that in Example 1 except that the ternary salt solution is introduced at a rate of 4 L / h in the preparation method, which is not described herein again.

[0113] Example 6

[0114] The present example provides a core-shell ternary precursor, which is the same as that of Example 1 except that in the preparation method, 12 L / h of tungsten is introduced into a tungstate solution of 200 mg / L.

[0115] Example 7

[0116] The present example provides a core-shell ternary precursor, which is the same as that of Example 1 except that in the preparation method, 1 L / h of tungsten is introduced into a tungstate solution of 200 mg / L.

[0117] Example 8

[0118] The present example provides a core-shell ternary precursor, which is the same as that of Example 1 except that in the preparation method, 12 L / h of aluminum is introduced into a mixed salt solution containing aluminum salt with an aluminum concentration of 450 mg / L.

[0119] Example 9

[0120] The present example provides a core-shell ternary precursor, which is the same as that of Example 1 except that in the preparation method, 1 L / h of aluminum is introduced into a mixed salt solution containing aluminum salt with an aluminum concentration of 450 mg / L.

[0121] Example 10

[0122] The present example provides a core-shell ternary precursor, which is the same as that of Example 1 except that in the preparation method, the introduction rate of the complexing agent is adjusted to control the ammonia concentration to be between 11-12 g / L.

[0123] Example 11

[0124] The present example provides a core-shell ternary precursor, which is the same as that of Example 1 except that in the preparation method, the introduction rate of the complexing agent is adjusted to control the ammonia concentration to be between 3-4 g / L.

[0125] Example 12

[0126] The present example provides a core-shell ternary precursor, which is the same as that of Example 1 except that in the preparation method, the introduction rate of the precipitant is adjusted to control the pH to be between 13-14.

[0127] Comparative Example 1

[0128] The comparative example 1 provides a core-shell ternary precursor, which is the same as that of Example 1 except that the ammonium tungstate is replaced by ammonium molybdate in the preparation method, and details are not repeated here.

[0129] Comparative Example 2

[0130] The comparative example 1 provides a core-shell ternary precursor, which is the same as that of Example 1 except that the ammonium tungstate is replaced by ammonium molybdate in the preparation method, and details are not repeated here.

[0131] Comparative Example 3

[0132] The comparative example 1 provides a core-shell ternary precursor, which is the same as that of Example 1 except that the ammonium tungstate is replaced by ammonium molybdate in the preparation method, and details are not repeated here.

[0133] The core-shell ternary precursors of the above examples and comparative examples are mixed with lithium and calcined, the negative electrode is graphite, an organic solution containing lithium salt is used as electrolyte, and a battery is assembled. The charge-discharge efficiency of the battery at 0.1C is tested, and the 100-week cycle retention rate of the battery is tested. The rate performance of the battery is also tested.

[0134] The test results of the above examples and comparative examples are shown in Table 1.

[0135] Table 1

[0136] From Table 1, the following points can be seen:

[0137] (1) From Examples 1-3, it can be seen that the core-shell ternary precursor provided by the present application has excellent rate performance, and the rate performance of the positive electrode material prepared therefrom and assembled into a battery is above 91.59%, the 0.1C charge-discharge efficiency is above 88.26%, and the discharge capacity retention rate after 100-week cycles is above 93.25%, and the cycle stability is high;

[0138] (2) From Examples 1 and 4-5, it can be seen that in Example 1, the ternary salt solution is introduced at a speed of 8L / h, compared with Examples 4-5, which are introduced at speeds of 12L / h and 4L / h respectively, the rate performance of Example 1 is 92.96%, the 0.1C charge-discharge efficiency is 90.12%, and the discharge capacity retention rate after 100-week cycles is 93.25%, while the rate performance of Examples 4-5 is only 90.89% and 89.25% respectively, and the discharge capacity retention rate after 100-week cycles is only 91.63% and 90.32% respectively, which shows that by introducing the ternary salt solution at an appropriate speed, the growth of the precursor can be better realized, the particle size is moderate, and the rate performance and cycle stability of the battery can be further improved;

[0139] (3) From the combination of Example 1 and Examples 6-7, it can be seen that in Example 1, the rate capability is 92.96%, the 0.1C charge-discharge efficiency is 90.12%, and the discharge capacity retention rate after 100 cycles is 93.25% when the ammonium tungstate solution is introduced at a rate of 6L / h, compared with Examples 6-7 in which the ammonium tungstate solution is introduced at a rate of 12L / h and 1L / h, respectively. In Example 6, the tungsten element is not completely precipitated, and small particles are grown by re-nucleation, resulting in an increase in process difficulty. In Example 7, the electrical performance of the positive electrode material is less improved. Specifically, the rate capability in Examples 6-7 is only 90.16% and 91.69%, respectively, and the discharge capacity retention rate after 100 cycles is only 90.32% and 91.22%, respectively. Thus, it is shown that by introducing the tungstate solution at an appropriate rate, the growth of the precursor can be better achieved, the particle size is moderate, and the rate capability and cycle stability of the battery can be further improved. From the combination of Example 1 and Examples 8-9, it can also be seen that by controlling the introduction rate of the mixed salt solution containing aluminum salt within a specific range, the performance of the precursor can be better improved.

[0140] (4) From the combination of Example 1 and Examples 10-12, it can be seen that by controlling the ammonia concentration and pH within a reasonable range during the precipitation process, the growth of the precursor can be better achieved, and the particle size of the final product is more moderate, further improving the rate capability, cycle stability, and charge-discharge efficiency of the battery.

[0141] (5) From the combination of Example 1 and Comparative Examples 1-3, it can be seen that in Comparative Example 1, ammonium molybdate is used, which has a lower effect on improving the electrical performance of the positive electrode material than ammonium tungstate used in Example 1. In Comparative Example 2, iron salt is used for precipitation, but iron is easily oxidized, making it difficult to prepare a viable core-shell ternary precursor. In Comparative Example 3, tungsten is doped in the outer layer and aluminum is doped in the inner layer, and the rate capability, cycle stability, and charge-discharge efficiency of the final battery are all lower than those of Example 1. Thus, it is shown that by combining the inner layer doping of tungsten with the outer layer doping of aluminum, the advantages of both are taken into account, and the performance of the precursor is significantly improved, which has a wide application prospect.

[0142] The above examples are used to illustrate the detailed features of the present application, but the present application is not limited to the above detailed features, i.e., it does not mean that the present application must rely on the above detailed features to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of the technical features selected by the present application, addition of auxiliary technical features, selection of specific modes, etc., all fall within the protection scope and disclosure scope of the present application.

Claims

1. A core-shell ternary precursor, comprising a core and a shell covering the core; The expression of the core is Ni x Co y Mn z (OH) 2-a (WO4) a Wherein 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1, and a is in the range of 0.01 to 1. the shell contains aluminum.

2. The core-shell ternary precursor according to claim 1, wherein, a is in the range of 0.1 to 1.

3. The core-shell ternary precursor according to claim 1 or 2, wherein The expression of the shell is Ni b Co c Mn d Al e (OH)(2(b+c+d)+3e), where 0 4. The core-shell ternary precursor according to any one of claims 1 to 3, wherein, the content of aluminum in the shell is in the range of 0.01 to 2 wt%.

5. The core-shell ternary precursor according to any one of claims 1 to 4, wherein, the size of the core is in the range of 3 to 14 μm; optionally, the shell thickness of the shell is in the range of 0.1 to 4 μm; optionally, the particle size of the core-shell ternary precursor is in the range of 3.1 to 18 μm. 6.A method for preparing the core-shell ternary precursor according to any one of claims 1 to 5, comprising the following steps: under a reaction atmosphere, a bottom solution containing ammonia is configured, then a ternary salt solution, a tungstate solution, a precipitant and a complexing agent are introduced into the bottom solution to perform a first reaction to form a core; the introduction of the ternary salt solution is stopped, and a mixed salt solution containing aluminum salt is introduced at the same time to perform a second reaction to form a shell covering the core.

7. The production method according to claim 6, wherein the reaction atmosphere comprises nitrogen and / or air.

8. The production method according to claim 6 or 7, wherein the precipitant comprises an alkali solution, and the alkali solution is optionally a sodium hydroxide solution; optionally, the concentration of the alkali solution is in the range of 20 to 40 wt%.

9. The process according to any one of claims 6 to 8, wherein, the complexing agent comprises ammonia and / or an ammonium salt solution; optionally, the concentration of the ammonia and / or the ammonium salt solution is in the range of 10 to 20 wt%.

10. The process according to any one of claims 6 to 9, wherein, the ammonia concentration of the bottom solution is in the range of 6 to 10 g / L; optionally, the pH of the bottom solution is in the range of 9 to 12.

11. The process according to any one of claims 6 to 10, wherein, the ternary salt solution comprises nickel salt, cobalt salt and manganese salt; optionally, the nickel salt comprises nickel nitrate and / or nickel sulfate; optionally, the cobalt salt comprises cobalt nitrate and / or cobalt sulfate; optionally, the manganese salt comprises manganese nitrate and / or manganese sulfate; optionally, the molar ratio of Ni:Co:Mn in the ternary salt solution is x:y:z, wherein 0 12. The process of any one of claims 6 to 11, wherein, the temperature of the first reaction is in the range of 50 to 60℃; optionally, the introduction speed of the ternary salt solution is in the range of 1 to 10 L / h.

13. The process of any one of claims 6 to 12, wherein, the tungsten concentration of the tungstate solution is in the range of 100 to 5000 mg / L; optionally, the introduction speed of the tungstate solution is in the range of 0.1 to 5 L / h; optionally, the introduction speed of the precipitant is in the range of 0.1 to 10 L / h; optionally, the introduction speed of the complexing agent is in the range of 0.1 to 10 L / h; optionally, the introduction speed of the precipitant is adjusted to control the pH in the range of 9 to 12; optionally, the introduction speed of the complexing agent is adjusted to control the ammonia concentration in the range of 4 to 10 g / L; optionally, the particle size of the core is in the range of 5 μm to 14 μm.

14. The process of any one of claims 6 to 13, wherein, the mixed salt solution containing aluminum salt comprises a ternary salt solution and an aluminum salt; optionally, the aluminum salt comprises aluminum sulfate and / or aluminum nitrate; optionally, the aluminum concentration of the mixed salt solution containing aluminum salt is in the range of 100 to 5000 mg / L; optionally, the introduction speed of the mixed salt solution containing aluminum salt is in the range of 1 to 10 L / h; optionally, the temperature of the second reaction is in the range of 50 to 60℃; optionally, the method further comprises: sequentially performing solid-liquid separation, washing the solid phase and drying on the reaction material after the shell is formed to obtain the core-shell ternary precursor.

15. A positive electrode material, wherein, The positive electrode material comprises a positive electrode active material prepared from the core-shell type ternary precursor according to any one of claims 1 to 5. The positive electrode material comprises a positive electrode active material prepared from the core-shell type ternary precursor according to any one of claims 1 to 5.

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