Coated and doped dual-modified positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a coated and doped dual-modified positive electrode material as well as a preparation method and application thereof. The coated and doped dual-modified positive electrode material comprises a positive electrode core and a coating layer coated on the surface of the core, phosphate radicals are doped in the core, the coating layer comprises conductive ceramic, and the conductive ceramic is a composite oxide comprising at least two metal elements. The positive electrode material is doped with phosphate anions, the intrinsic property of the positive electrode material can be regulated and controlled, coating of multi-metal conductive ceramic is matched, the electron and ion transmission property of the positive electrode material can be effectively improved through the synergistic effect of the two, and the electrochemical performance of the material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and relates to a cathode material modified by double coating and doping, a preparation method thereof, and an application thereof. Background Art

[0002] With the wide application of lithium-ion batteries, people have put forward higher requirements for the performance of lithium-ion batteries. High-nickel ternary materials (such as Ni content > 80%) have the advantage of high energy density, but face the problems of poor stability and poor conductivity.

[0003] CN113571692A discloses a high-safety conductive material modified high-nickel cathode material and a preparation method thereof. The preparation method includes the following steps: an organosilicon monomer and a phosphorus-containing compound are subjected to a dehydration condensation reaction to prepare a modified polysiloxane; the modified polysiloxane, a polyol, a diisocyanate, and a chain extender are reacted to obtain a flame-retardant polymer; the flame-retardant polymer is compounded with a conductive material and then coated on the surface of the high-nickel cathode material to obtain the high-safety conductive material modified high-nickel cathode material. Through the synergistic effect of the flame-retardant polymer and the aniline-p-phenylenediamine copolymer, the conductivity of the high-nickel cathode material is increased, the interfacial electrochemical reaction environment is effectively optimized, and the electrochemical performance of the material is improved.

[0004] CN118738357A discloses a high-nickel ternary cathode material with low residual alkali, high specific capacity, and high cycle stability and a preparation method thereof. The preparation method includes the preparation of a primary coating agent dispersion liquid, the mixing of the high-nickel ternary cathode material and the primary coating agent dispersion liquid, the vacuum drying of the primary mixed material, the solid-phase sintering of the high-nickel ternary cathode material coated for the first time, the preparation of a secondary coating agent dispersion liquid, the mixing of the high-nickel ternary cathode material matrix coated for the first time and the secondary coating agent dispersion liquid, and the vacuum drying of the secondary mixed material; the obtained high-nickel ternary cathode material includes an active substance with the molecular formula LiNi x Co y Mn z O 2 (0.8 ≤ x < 1, 0 < y < 0.2, 0 < z < 0.2, and x + y + z = 1), and a coating layer formed by the primary co-coating of aluminum phosphate and lithium phosphate and the secondary coating of a composite coating agent of graphene, carbon nanotubes, and conductive carbon black, which can effectively reduce the residual alkali content in the high-nickel ternary cathode material and improve the conductivity of the high-nickel ternary cathode material at the same time, thereby significantly improving its specific capacity and cycle stability.

[0005] CN118367145A discloses a multidimensional carbon network / polymer double-coated high nickel ternary positive electrode material and its preparation method and application, the preparation method comprises: graphene, carbon nanotubes, polymer A are uniformly dispersed in an organic solvent in sequence to obtain a carbon coating liquid of a multidimensional carbon network; a high nickel ternary material is added to the carbon coating liquid, and after uniform dispersion, a mixed slurry is obtained; the mixed slurry is heated to evaporate the solvent, sealed and allowed to stand, dried, ground, and sintered to obtain a high nickel ternary material coated with a multidimensional carbon network; the high nickel ternary material coated with the multidimensional carbon network is added to a modified solution of an electron-conducting / lithium-conducting polymer B, uniformly dispersed, and heated to evaporate the solvent to obtain a high nickel ternary positive electrode material with a multidimensional carbon network / polymer double coating. The high nickel ternary positive electrode material prepared by the method has a two-layer coating structure, which improves the structural stability and electrochemical performance of the high nickel ternary material during the charge and discharge process.

[0006] The above method can improve the conductivity and stability of high-nickel ternary materials by coating, which can improve the electrochemical properties of the materials to a certain extent. However, on the one hand, the preparation of conductive materials such as graphene is complex and expensive, which increases the preparation cost; on the other hand, the method of coating the ternary positive electrode material with conductive substances cannot regulate the intrinsic properties of the ternary positive electrode material, and the effect of improving the electrochemical performance is limited.

[0007] Therefore, providing an improvement strategy for high-nickel ternary materials to effectively improve their electrochemical performance and reduce preparation costs is a technical problem that needs to be solved urgently. Summary of the invention

[0008] To achieve the above-mentioned object, the purpose of the present invention is to provide a coated doped dual-modified positive electrode material and a preparation method and application thereof.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a coated doped dual-modified positive electrode material, wherein the coated doped dual-modified positive electrode material comprises a positive electrode core and a coating layer coated on the surface of the core, wherein the core is doped with phosphate, and the coating layer comprises a conductive ceramic, which is a composite oxide comprising at least two metal elements.

[0011] The present invention can regulate the intrinsic properties of the positive electrode material by doping the positive electrode material with phosphate anions, and cooperate with the coating of multi-metal conductive ceramics, the two can synergistically improve the electron and ion transport properties of the positive electrode material and enhance the electrochemical performance of the material

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0013] Preferably, the particle size of the inner core is 10 μm to 15 μm, for example, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm or 15 μm.

[0014] Preferably, the core is a ternary positive electrode material doped with phosphate, and the molar content of nickel in the core is ≥80%.

[0015] Preferably, based on the total mass of the coated doped dual-modified positive electrode material as 100%, the doping amount of the phosphate is 0.2wt% to 2wt%, for example, it can be 0.2wt%, 0.4wt%, 0.5wt%, 0.8wt%, 1wt%, 1.2wt%, 1.5wt%, 1.6wt%, 1.8wt% or 2wt%, etc.

[0016] Preferably, the conductive ceramic is CaO·ZrO 2 .

[0017] Preferably, based on the total mass of the coated doped dual-modified positive electrode material as 100%, the coating amount of the conductive ceramic is 0.1wt% to 0.8wt%, for example, it can be 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt% or 0.8wt%, etc.

[0018] In one embodiment, the chemical formula of the coated doped dual-modified positive electrode material is Li[Ni x Co y Mn z ]O 2 A@B, x+y+z=1, 0.8≤x, 0<y, 0<z; A is a lithium salt doped with anions (phosphate); B is a conductive ceramic coating layer.

[0019] In a second aspect, the present invention provides a method for preparing the coated doped dual-modified positive electrode material as described in the first aspect, the preparation method comprising the following steps:

[0020] (1) preparing a first metal salt solution, an ammonium phosphate solution, and a second metal salt solution respectively, wherein the first metal salt solution is used to form a core, and the second metal salt solution is used to form a conductive ceramic;

[0021] (2) under the protection of protective gas, adding the first metal salt solution, ammonium phosphate solution, complexing agent solution and precipitant solution into the base liquid for reaction;

[0022] (3) When the reaction reaches a preset particle size of the inner core, the first metal salt solution and the ammonium phosphate solution are stopped and replaced with the second metal salt solution to react and obtain a precursor;

[0023] (4) Mixing the precursor with lithium salt and calcining to obtain the coated, doped and double-modified positive electrode material.

[0024] The method of the present invention uses ammonium phosphate as the raw material of anionic phosphate in the precursor preparation stage, reacts, reacts to a preset particle size of the inner core, and then coats the conductive ceramic precursor to obtain a precursor. After the precursor is sintered with lithium, a phosphate-doped and conductive ceramic-coated positive electrode material can be obtained. Compared with directly using ternary positive electrode materials for doping and coating, the method of the present invention can improve the effect of doping and coating, and is more conducive to improving the electrochemical properties of the material. As a preferred technical solution of the method of the present invention, the first metal salt solution in step (1) is a nickel-cobalt-manganese ternary salt solution.

[0025] Preferably, the concentration of the first metal salt solution is 1 mol / L to 3 mol / L, for example, it can be 1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.7 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.4 mol / L, 2.7 mol / L or 3 mol / L, etc.

[0026] Preferably, the concentration of the ammonium phosphate solution is 0.01 mol / L to 0.1 mol / L, for example, it can be 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L or 0.1 mol / L, etc.

[0027] Preferably, the second metal salt solution is a calcium zirconium metal salt solution.

[0028] Preferably, in the calcium zirconium metal salt solution, the molar ratio of calcium to zirconium is (1-2):(1-2), wherein the selection range of calcium is "1-2", for example, it can be 1, 1.2, 1.5, 1.6, 1.8 or 2, etc.; the selection range of zirconium is "1-2", for example, it can be 1, 1.2, 1.5, 1.6, 1.8 or 2, etc.

[0029] Preferably, the concentration of the second metal salt solution is 0.01 mol / L to 0.1 mol / L, for example, it can be 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L or 0.1 mol / L, etc.

[0030] As a preferred technical solution of the method of the present invention, the pH of the base solution in step (2) is 10-12, for example, it can be 10, 10.2, 10.5, 10.7, 11, 11.3, 11.5, 11.6, 11.8 or 12; the ammonia concentration of the base solution is 0.5 mol / L-2 mol / L, for example, it can be 0.5 mol / L, 1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.7 mol / L, 1.8 mol / L or 2 mol / L.

[0031] Preferably, in step (2), the flow rate of the first metal salt solution is 2 L / h to 5 L / h, for example, it can be 2 L / h, 2.2 L / h, 2.4 L / h, 2.5 L / h, 2.7 L / h, 3 L / h, 3.3 L / h, 3.6 L / h, 3.8 L / h, 4 L / h, 4.2 L / h, 4.4 L / h, 4.6 L / h, 4.8 L / h or 5 L / h, etc.

[0032] Preferably, in step (2), the flow rate of the ammonium phosphate is 0.3 L / h to 1 L / h, for example, it can be 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 or 1 L / h, etc.

[0033] Preferably, the concentration of the complexing agent solution in step (2) is 5 mol / L to 10 mol / L, for example, it can be 5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, 8 mol / L, 8.5 mol / L, 9 mol / L, 9.5 mol / L or 10 mol / L, etc.

[0034] Preferably, in step (2), the flow rate of the complexing agent solution is 0.2 to 0.5 L / h, for example, 0.2 L / h, 0.25 L / h, 0.3 L / h, 0.35 L / h, 0.4 L / h, 0.45 L / h or 0.5 L / h.

[0035] Preferably, the concentration of the precipitant solution in step (2) is 3 mol / L to 6 mol / L, for example, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, 5.5 mol / L or 6 mol / L.

[0036] Preferably, in step (2), the flow rate of the precipitant solution is 2 L / h to 5 L / h, for example, it can be 2 L / h, 2.5 L / h, 3 L / h, 3.5 L / h, 4 L / h, 4.5 L / h or 5 L / h.

[0037] As a preferred technical solution of the method of the present invention, in step (3), the concentration of the second metal salt solution is 7 L / h to 13 L / h, for example, it can be 7 L / h, 7.5 L / h, 8 L / h, 8.5 L / h, 9 L / h, 9.5 L / h, 10 L / h, 10.5 L / h, 11 L / h, 11.5 L / h, 12 L / h, 12.5 L / h or 13 L / h, etc.

[0038] Preferably, in step (3), the flow rate of the complexing agent solution is 0.002 L / h to 0.005 L / h, for example, 0.002 L / h, 0.003 L / h, 0.004 L / h or 0.005 L / h.

[0039] Preferably, in step (3), the flow rate of the precipitant solution is 0.1 L / h to 0.5 L / h, for example, it can be 0.1 L / h, 0.2 L / h, 0.25 L / h, 0.3 L / h, 0.35 L / h, 0.4 L / h, 0.45 L / h or 0.5 L / h, etc.

[0040] Preferably, the reaction time of step (3) is 5 h to 15 h, for example, it can be 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, 10 h, 10.5 h, 11 h, 11.5 h, 12 h, 12.5 h, 13 h, 13.5 h, 14 h or 15 h.

[0041] As a preferred technical solution of the method of the present invention, the calcination in step (4) is a step-by-step calcination, which includes a one-step calcination, a two-step calcination and a three-step calcination. The two-step calcination is followed by cooling, crushing, washing and drying, and the three-step calcination is followed by drying; wherein the temperature of the two-step calcination is greater than the temperature of the one-step calcination, and the temperature of the two-step calcination is greater than the temperature of the three-step calcination.

[0042] By calcining using the above method, the residual alkali on the surface of the positive electrode material is effectively removed, reducing the side reaction between the material surface and the electrolyte. At the same time, the composite oxide coating on the surface further inhibits the corrosion of HF on the positive electrode material and stabilizes the structure of the material, thereby exhibiting good comprehensive electrochemical performance.

[0043] Preferably, the temperature of the one-step calcination is 500°C to 700°C, for example, it may be 500°C, 525°C, 550°C, 570°C, 600°C, 620°C, 640°C, 660°C, 680°C or 700°C.

[0044] Preferably, the one-step calcination time is 3 h to 6 h, for example, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h or 6 h.

[0045] Preferably, the temperature of the second-step calcination is 750°C to 950°C, for example, it can be 750°C, 770°C, 800°C, 825°C, 850°C, 860°C, 880°C, 900°C, 925°C or 950°C.

[0046] Preferably, the time of the two-step calcination is 10 h to 18 h, for example, it can be 10 h, 10.5 h, 11 h, 11.5 h, 12 h, 12.5 h, 13 h, 13.5 h, 14 h, 14.5 h, 15 h, 15.5 h, 16 h, 17 h or 18 h.

[0047] Preferably, the temperature of the three-step calcination is 650°C to 750°C, for example, it can be 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 715°C, 730°C, 740°C or 750°C.

[0048] Preferably, the three-step calcination time is 0.5 h to 3 h, for example, it can be 0.5 h, 0.7 h, 0.8 h, 1 h, 1.2 h, 1.3 h, 1.5 h, 1.7 h, 2 h, 2.3 h, 2.6 h, 2.8 h or 3 h.

[0049] In a third aspect, the present invention provides a positive electrode, comprising the coated, doped and double-modified positive electrode material described in the first aspect.

[0050] In a fourth aspect, the present invention provides a battery, comprising the positive electrode described in the third aspect.

[0051] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] (1) The present invention can regulate the intrinsic properties of the positive electrode material by doping the positive electrode material with phosphate anions, and the synergistic effect of the two, combined with the coating of multi-metal conductive ceramics, can effectively improve the electron and ion transport properties of the positive electrode material and enhance the electrochemical performance of the material.

[0054] (2) The method of the present invention uses ammonium phosphate as the raw material of anionic phosphate in the precursor preparation stage, reacts to a preset particle size of the inner core, and then coats the conductive ceramic precursor to obtain a precursor. After the precursor is lithium-coated and sintered, a phosphate-doped and conductive ceramic-coated positive electrode material can be obtained. Compared with directly using ternary positive electrode materials for doping and coating, the method of the present invention can improve the effect of doping and coating, and is more conducive to improving the electrochemical performance of the material. DETAILED DESCRIPTION

[0055] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0056] Example 1

[0057] This embodiment provides a coated doped dual-modified positive electrode material, the coated doped dual-modified positive electrode material comprises a positive electrode core and a coating layer coated on the surface of the core, the core is doped with phosphate, the coating layer comprises a conductive ceramic, and the conductive ceramic is CaO·ZrO 2 ;

[0058] The particle size of the core is 12 μm; based on the total mass of the coated doped dual-modified positive electrode material being 100%, the doping amount of the phosphate radical is 1wt%, and the coating amount of the conductive ceramic is 0.5wt%.

[0059] This embodiment also provides a method for preparing the above-mentioned coated doped dual-modified positive electrode material, comprising the following steps:

[0060] (1) dissolving nickel chloride, cobalt chloride and manganese chloride in water to obtain a first solution, wherein the metal molar ratio is Ni:Co:Mn=90:5:5, and the total metal ion concentration is 2 mol / L;

[0061] Dissolve ammonium phosphate in water to obtain a second solution with a concentration of 0.02 mol / L;

[0062] Dissolving zirconium chloride and calcium chloride in water to obtain a third solution, wherein the metal molar ratio is Zr:Ca=1:1 and the metal ion concentration is 0.01 mol / L;

[0063] Liquid alkali is used as the precipitant, with a concentration of 4 mol / L;

[0064] Ammonia water is used as the complexing agent with a concentration of 8 mol / L;

[0065] (2) Under the protection of inert gas, add 40L of water, liquid alkali and ammonia water to the reactor to prepare a bottom solution with a pH of 11.2 and an ammonia concentration of 0.6mol / L. Control the reaction temperature to 65°C and the stirring speed to 220rpm. Feed the reactor with a metering pump. The flow rate of the first solution is 2L / h, the flow rate of the second solution is 0.5L / h, the flow rate of the liquid alkali is 1L / h, and the flow rate of the ammonia water is 0.35L / h. When the particle size of the material in the reactor grows to 10μm, change to the third solution, liquid alkali, and ammonia water feed. The flow rate of the third solution is 10L / h, the flow rate of the liquid alkali is 0.1L / h, and the flow rate of the ammonia water is 0.003L / h. Stop the reaction after 10h, wash the material in the reactor with liquid alkali and water, respectively, and dry to obtain the first product;

[0066] (5) The first product was mixed with lithium hydroxide at a ratio of 1:1.05, placed in a crucible and calcined at 550°C for 5 hours, then calcined at 900°C for 15 hours, then cooled to room temperature, crushed, washed with water, dried and calcined at 700°C for 1 hour. After cooling, the second product was screened and iron removed to obtain the second product, the chemical formula of which is Li[Ni 0.9 Co 0.05 Mn 0.05 ]O 2 ·Li 3 PO 4 @CaO·ZrO 2 .

[0067] Example 2

[0068] This embodiment provides a coated doped dual-modified positive electrode material, the coated doped dual-modified positive electrode material comprises a positive electrode core and a coating layer coated on the surface of the core, the core is doped with phosphate, the coating layer comprises a conductive ceramic, and the conductive ceramic is CaO·ZrO 2 ;

[0069] The particle size of the core is 10 μm; based on the total mass of the coated doped dual-modified positive electrode material as 100%, the doping amount of the phosphate radical is 1.5 wt%, and the coating amount of the conductive ceramic is 0.3 wt%.

[0070] This embodiment also provides a method for preparing the above-mentioned coated doped dual-modified positive electrode material, comprising the following steps:

[0071] (1) dissolving nickel chloride, cobalt chloride and manganese chloride in water to obtain a first solution, wherein the metal molar ratio is Ni:Co:Mn=88:6:6, and the total metal ion concentration is 1.5 mol / L;

[0072] Dissolve ammonium phosphate in water to obtain a second solution with a concentration of 0.05 mol / L;

[0073] Dissolving zirconium chloride and calcium chloride in water to obtain a third solution, wherein the metal molar ratio is Zr:Ca=2:1 and the metal ion concentration is 0.03 mol / L;

[0074] Liquid alkali is used as the precipitant, with a concentration of 5 mol / L;

[0075] Ammonia water is used as the complexing agent with a concentration of 10 mol / L;

[0076] (2) Under the protection of inert gas, add 40L of water, liquid alkali and ammonia water to the reactor to prepare a bottom solution with a pH of 11.5 and an ammonia concentration of 1 mol / L. Control the reaction temperature to 60°C and the stirring speed to 300rpm. Feed the reactor with a metering pump. The flow rate of the first solution is 4L / h, the flow rate of the second solution is 0.8L / h, the flow rate of the liquid alkali is 1.3L / h, and the flow rate of the ammonia water is 0.2L / h. When the particle size of the material in the reactor grows to 13μm, change to the third solution, liquid alkali, and ammonia water feed. The flow rate of the third solution is 8L / h, the flow rate of the liquid alkali is 0.2L / h, and the flow rate of the ammonia water is 0.005L / h. Stop the reaction after 8h, wash the material in the reactor with liquid alkali and water, respectively, and dry to obtain the first product;

[0077] (5) The first product was mixed with lithium hydroxide at a ratio of 1:1.05, calcined at 600°C for 5 h, then calcined at 850°C for 15 h, then cooled to room temperature, crushed, washed with water, dried, and then calcined at 750°C for 1 h. After cooling, the second product was screened and iron removed to obtain the second product, the chemical formula of which is Li[Ni 0.88 Co 0.06 Mn 0.06 ]O 2 ·Li 3 PO 4 @CaO·ZrO 2 .

[0078] Example 3

[0079] This embodiment provides a coated doped dual-modified positive electrode material, the coated doped dual-modified positive electrode material comprises a positive electrode core and a coating layer coated on the surface of the core, the core is doped with phosphate, the coating layer comprises a conductive ceramic, and the conductive ceramic is CaO·ZrO 2 ;

[0080] The particle size of the core is 15 μm; based on the total mass of the coated doped dual-modified positive electrode material as 100%, the doping amount of the phosphate radical is 0.5wt%, and the coating amount of the conductive ceramic is 0.8wt%.

[0081] This embodiment also provides a method for preparing the above-mentioned coated doped dual-modified positive electrode material, comprising the following steps:

[0082] (1) dissolving nickel chloride, cobalt chloride and manganese chloride in water to obtain a first solution, wherein the metal molar ratio is Ni:Co:Mn=90:6:4 and the total metal ion concentration is 3 mol / L;

[0083] Dissolving ammonium phosphate in water to obtain a second solution having a concentration of 0.1 mol / L;

[0084] Dissolving zirconium chloride and calcium chloride in water to obtain a third solution, wherein the metal molar ratio is Zr:Ca=1:2 and the metal ion concentration is 0.05 mol / L;

[0085] Liquid alkali is used as the precipitant, with a concentration of 6 mol / L;

[0086] Ammonia water is used as the complexing agent with a concentration of 5 mol / L;

[0087] (2) Under the protection of inert gas, add 40L of water, liquid alkali and ammonia water to the reactor to prepare a bottom solution with a pH of 11.8 and an ammonia concentration of 1.5mol / L. Control the reaction temperature to 68°C and the stirring speed to 275rpm. Feed the reactor with a metering pump. The flow rate of the first solution is 5L / h, the flow rate of the second solution is 0.3L / h, the flow rate of the liquid alkali is 4.5L / h, and the flow rate of the ammonia water is 0.45L / h. When the particle size of the material in the reactor grows to 6μm, change to the third solution, liquid alkali, and ammonia water feed. The flow rate of the third solution is 12L / h, the flow rate of the liquid alkali is 0.5L / h, and the flow rate of the ammonia water is 0.004L / h. Stop the reaction after 15h, wash the material in the reactor with liquid alkali and water, respectively, and dry to obtain the first product;

[0088] (5) The first product was mixed with lithium hydroxide in a ratio of 1:1.05, placed in a crucible and calcined at 500°C for 5 hours, then calcined at 800°C for 12 hours, then cooled to room temperature, crushed, washed with water, dried and calcined at 650°C for 3 hours. After cooling, the second product was screened and iron removed to obtain the second product, the chemical formula of which is Li[Ni 0.9 Co 0.06 Mn 0.04 ]O 2 ·Li 3 PO 4 @CaO·ZrO 2 .

[0089] Example 4

[0090] This embodiment provides a coated doped dual-modified positive electrode material, which is different from Embodiment 1 in that, based on the total mass of the coated doped dual-modified positive electrode material being 100%, the doping amount of the phosphate radical is 0.1 wt%.

[0091] Example 5

[0092] This embodiment provides a coated doped dual-modified positive electrode material, which is different from Embodiment 1 in that, based on the total mass of the coated doped dual-modified positive electrode material being 100%, the doping amount of the phosphate radical is 2.5 wt%.

[0093] Example 6

[0094] This embodiment provides a coated doped dual-modified positive electrode material, which is different from Embodiment 1 in that, based on the total mass of the coated doped dual-modified positive electrode material being 100%, the coating amount of the conductive ceramic is 0.05wt%.

[0095] Example 7

[0096] This embodiment provides a coated doped dual-modified positive electrode material, which is different from Embodiment 1 in that, based on the total mass of the coated doped dual-modified positive electrode material being 100%, the coating amount of the conductive ceramic is 1.2 wt%.

[0097] Comparative Example 1

[0098] A positive electrode material is provided, which differs from Example 1 in that phosphate doping is not performed.

[0099] Comparative Example 2

[0100] A positive electrode material is provided, which differs from Example 1 in that it is not coated with a conductive ceramic.

[0101] The positive electrode materials of Examples 1-7 and Comparative Examples 1-2 are used to prepare positive electrodes and assemble batteries, comprising the following steps:

[0102] 80wt% of positive electrode material, 10wt% of Super P and 10wt% of polyvinylidene fluoride (PVDF) are dispersed in N-methylpyrrolidone (NMP) solution to prepare positive electrode slurry, which is coated on aluminum foil and dried to obtain a positive electrode;

[0103] The lithium sheet is the negative electrode;

[0104] The separator is a PP microporous membrane (Celgard2500);

[0105] The composition of the electrolyte is: 1M LiPF 6(The solvent is a mixed solvent of EC, DMC and EMC, wherein the volume ratio of EC:DMC:EMC=1:1:1).

[0106] The positive electrode, separator, negative electrode and electrolyte are assembled to obtain a button battery.

[0107] Performance test: Cycle 200 times at room temperature, 2.7~4.3V voltage range, 1C rate, and record the first discharge capacity and the capacity retention rate after 1000 cycles.

[0108] Table 1

[0109]

[0110]

[0111] It can be seen from Table 1 that the present invention can effectively improve the conductivity and stability of the positive electrode material by doping with anionic phosphate and coating with conductive ceramic, and the initial discharge capacity and cycle performance are improved.

[0112] At the same time, by comparing Example 1 with Examples 4-5 and Comparative Example 1, it can be seen that too little phosphate doping has a poor effect and fails to significantly improve the conductivity of the material, while too much phosphate doping reduces the conductivity of the material, and at the same time, the first discharge capacity and cycle performance are also reduced.

[0113] By comparing Example 1 with Examples 6-7 and Comparative Example 2, it can be seen that coating the high-nickel positive electrode material with calcium-zirconium composite oxide ceramic can improve the cycle stability of the material. If the coating amount is too little, although the cycle performance can be improved, the first discharge capacity will also be reduced; too much coating greatly reduces the capacity of the material itself, and the improvement in the cycle performance will also be reduced.

[0114] The applicant declares that the present invention illustrates the detailed method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed method, that is, it does not mean that the present invention must rely on the above-mentioned detailed method to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A coated doped double-modified positive electrode material, characterized in that: The coated doped dual-modified positive electrode material comprises a positive electrode core and a coating layer coated on the surface of the core, the core is doped with phosphate, the coating layer comprises conductive ceramics, and the conductive ceramics are composite oxides comprising at least two metal elements.

2. The coated doped double-modified positive electrode material according to claim 1, characterized in that: The particle size of the core is 10 μm to 15 μm; Preferably, the core is a ternary positive electrode material doped with phosphate, and the molar content of nickel in the core is ≥80%; Preferably, based on the total mass of the coated doped dual-modified positive electrode material being 100wt%, the doping amount of the phosphate radical is 0.2wt% to 2wt%.

3. The coated doped double-modified positive electrode material according to claim 1 or 2, characterized in that: The conductive ceramic is CaO·ZrO2; Preferably, based on the total mass of the coated doped dual-modified positive electrode material being 100wt%, the coating amount of the conductive ceramic is 0.1wt% to 0.8wt%.

4. A method for preparing a coated, doped and double-modified positive electrode material as claimed in any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: (1) preparing a first metal salt solution, an ammonium phosphate solution, and a second metal salt solution respectively, wherein the first metal salt solution is used to form a core, and the second metal salt solution is used to form a conductive ceramic; (2) under the protection of protective gas, adding the first metal salt solution, ammonium phosphate solution, complexing agent solution and precipitant solution into the base liquid for reaction; (3) When the reaction reaches a preset particle size of the inner core, the first metal salt solution and the ammonium phosphate solution are stopped and replaced with the second metal salt solution to react and obtain a precursor; (4) Mixing the precursor with lithium salt and calcining to obtain the coated, doped and double-modified positive electrode material.

5. The preparation method according to claim 4, characterized in that: Step (1) The first metal salt solution is a nickel-cobalt-manganese ternary salt solution; Preferably, the concentration of the first metal salt solution is 1 mol / L to 3 mol / L; Preferably, the concentration of the ammonium phosphate solution is 0.01 mol / L to 0.1 mol / L; Preferably, the second metal salt solution is a calcium zirconium metal salt solution; Preferably, in the calcium zirconium metal salt solution, the molar ratio of calcium to zirconium is (1-2):(1-2); Preferably, the concentration of the second metal salt solution is 0.01 mol / L to 0.1 mol / L.

6. The preparation method according to claim 4 or 5, characterized in that: The pH of the base solution in step (2) is 10 to 12, and the ammonia concentration of the base solution is 0.5 mol / L to 2 mol / L; Preferably, in step (2), the flow rate of the first metal salt solution is 2 L / h to 5 L / h; Preferably, in step (2), the flow rate of the ammonium phosphate is 0.3 L / h to 1 L / h; Preferably, the concentration of the complexing agent solution in step (2) is 5 mol / L to 10 mol / L; Preferably, in step (2), the flow rate of the complexing agent solution is 0.2 to 0.5 L / h; Preferably, the concentration of the precipitant solution in step (2) is 3 mol / L to 6 mol / L; Preferably, in step (2), the flow rate of the precipitant solution is 1 L / h to 5 L / h.

7. The preparation method according to any one of claims 4 to 6, characterized in that: In step (3), the concentration of the second metal salt solution is 7 L / h to 13 L / h; Preferably, in step (3), the flow rate of the complexing agent solution is 0.002L / h to 0.005L / h; Preferably, in step (3), the flow rate of the precipitant solution is 0.1 L / h to 0.5 L / h; Preferably, the reaction time in step (3) is 5 h to 15 h.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The calcination in step (4) is performed in stages, and the staged calcination includes one-step calcination, two-step calcination and three-step calcination. The two-step calcination is followed by cooling, crushing, water washing and drying, and the three-step calcination is performed after the drying. The temperature of the two-step calcination is higher than the temperature of the one-step calcination, and the temperature of the two-step calcination is higher than the temperature of the three-step calcination. Preferably, the temperature of the one-step calcination is 500°C to 700°C; Preferably, the one-step calcination time is 3h to 6h; Preferably, the temperature of the second-step calcination is 750°C to 950°C; Preferably, the two-step calcination time is 10h to 18h; Preferably, the temperature of the three-step calcination is 650°C to 700°C; Preferably, the three-step calcination takes 0.5 h to 3 h.

9. A positive electrode, characterized in that The positive electrode comprises the coated, doped and double-modified positive electrode material according to any one of claims 1 to 3.

10. A battery, characterized in that: The battery comprises the positive electrode according to claim 9.

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