Surface coated and doped lithium-rich manganese-based positive electrode material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of new materials, and provides a surface-coated and doped lithium-rich manganese-based positive electrode material as well as a preparation method and application of the surface-coated and doped lithium-rich manganese-based positive electrode material. The doping layer is positioned on the surface of the internal layered structure; the chemical formula of the doping layer is Li Ni Co < c > Mn < d > Ti < e > M < f > G O < 2 >; the coating layer is positioned on the surface of the doping layer; the chemical formula of the coating layer is LigRhTiiVjOk; wherein M is selected from one or a combination of more than two of Al, Mg, Ti and La, and f is more than or equal to 0 and less than or equal to 0.05; g is selected from one or two of S and P, and p is more than 0 and less than or equal to 0.05; r is selected from one or a combination of more than two of Al, Mg, Ti and La, and h is more than or equal to 0 and less than or equal to 3; v is selected from one or two of S and P, and j is greater than or equal to 1 and less than or equal to 4. The stability of the obtained lithium-rich manganese-based positive electrode material can be remarkably improved, and the high-temperature cycling stability of the lithium ion battery is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and relates to a lithium-rich manganese-based cathode material, a preparation method and an application thereof, and particularly relates to a surface-coated and doped lithium-rich manganese-based cathode material, a preparation method and an application thereof. Background Art

[0002] Ion batteries are widely used in fields such as electric vehicles, smart grids, and electronic products. High energy density and safety are prerequisites for their large-scale applications. The cathode material plays a key role in the energy density and thermal stability of the battery. Lithium-rich manganese-based materials are considered to be one of the most promising cathode materials for power lithium batteries due to their high specific capacity (>250 mAh / g), and they have attracted more attention due to their good thermal stability and low cost. However, poor conductivity, low lithium-ion diffusion coefficient, and poor structural stability resulting in poor rate performance and high-temperature stability have also become the main obstacles and research difficulties for their commercialization.

[0003] The structural decline of the cathode material has the characteristic of "occurring from the surface and diffusing into the bulk phase". High-temperature conditions will accelerate the erosion of the material surface by the electrolyte. Therefore, isolating the contact between the surface active substances of the material and the electrolyte and inhibiting the phase transition of the near-surface layered structure are the keys to improving the high-temperature cycle stability. Currently, common cathode material modification methods include: coating electrochemically inert substances, active substances, conductive polymers, solid lithium-ion conductors, etc. on the material surface; doping of anions and cations; constructing composite phase structures, etc. to improve the cycle stability, discharge specific capacity, and rate performance of the material. However, the above modification methods still do not achieve ideal effects on the improvement of high-temperature cycle stability. In view of this, the present invention is proposed. Summary of the Invention

[0004] The present invention provides a surface-coated and doped lithium-rich manganese-based cathode material, a preparation method and an application thereof, to solve the defect that it is difficult to improve the high-temperature cycle stability of lithium-ion batteries in the prior art.

[0005] In a first aspect, the present invention provides a lithium-rich manganese-based cathode material, comprising: an internal layered structure; the chemical formula of the main component of the internal layered structure is Li a Ni b Co c Mn d O2; And a doping layer located on the surface of the internal layered structure; the chemical formula of the main component of the doping layer is Li a Ni b Co c Mn d Ti e M f G p O2; and a coating layer located on the surface of the doped layer; the chemical formula of the main component of the coating layer is Li g R h Ti i V j O k ; wherein, M is selected from one or more combinations of Al, Mg, Ti, and La, and 0 ≤ f ≤ 0.05; G is selected from one or two of S and P, and 0 < p ≤ 0.05; R is selected from one or more combinations of Al, Mg, Ti, and La, and 0 ≤ h ≤ 3; V is selected from one or two of S and P, and 1 ≤ j ≤ 4; 0 < a ≤ 1.2; 0 < b < 1; 0 < c < 1; 0 < d < 1; 0 ≤ e ≤ 0.05; 0 ≤ g ≤ 3; 0 ≤ i ≤ 2; 0 < k ≤ 16.

[0006] By constructing the lithium-rich manganese-based cathode material with the above specific structure, the doped layer and the coating layer contained therein can act synergistically to improve the stability of the lithium-rich manganese-based cathode material, thereby effectively improving the high-temperature cycle performance of the lithium-ion battery.

[0007] According to the lithium-rich manganese-based cathode material provided by the present invention, the doping elements in the doped layer include Ti and one or more of the M and the G; Preferably, the doping elements diffuse from the surface layer of the internal layered structure to the bulk phase to form a gradient doping to obtain the doped layer.

[0008] According to the lithium-rich manganese-based cathode material provided by the present invention, when the chemical formula of the main component of the doped layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 P p O2, the chemical formula of the main component of the coating layer is Li3PO4; When the chemical formula of the main component of the doped layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 S p O2, the chemical formula of the main component of the coating layer is Li2SO4; When the chemical formula of the main component of the doped layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Al f P p O2, the chemical formula of the main component of the coating layer is AlPO4; When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Mg f P p O2, the chemical formula of the main component of the coating layer is Mg3(PO4)2; When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Ti f P p O2, the chemical formula of the main component of the coating layer is Ti3(PO4)4; When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 La f S p O2, the chemical formula of the main component of the coating layer is La2(SO4)3; When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Al e Ti f P p O2, the chemical formula of the main component of the coating layer is Li 1.3 Al 0.3 Ti 1.7 (PO4)3; When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Mg f P p O2, the chemical formula of the main component of the coating layer is LiMgPO4.

[0009] It is found in the present invention that the lithium-rich manganese-based cathode material containing the above structure is more conducive to improving the comprehensive performance of the lithium-ion battery.

[0010] According to the lithium-rich manganese-based cathode material provided by the present invention, the thickness of the coating layer is 1 to 20 nm.

[0011] The structural schematic diagram of the lithium-rich manganese-based cathode material in the present invention is as Figure 1As shown, it includes a layered structure 3 formed by an internal layered structure, a doping layer 1 and a cladding layer 2.

[0012] According to the lithium-rich manganese-based positive electrode material provided by the present invention, the mass proportion of the doping layer in the lithium-rich manganese-based positive electrode material is 0.1% to 3%; The coating layer accounts for 0.1% to 3% by mass in the lithium-rich manganese-based positive electrode material.

[0013] The study found that the structure of the internal layered structure, the surface doping layer and the coating layer have an impact on the performance of lithium-rich manganese-based positive electrode materials. The coating layer and the doping layer are interrelated. Effective control of the two can be used to regulate the comprehensive performance of lithium-rich manganese-based positive electrode materials.

[0014] The present invention provides a method for preparing the lithium-rich manganese-based positive electrode material as described above, comprising: With a layered structure and a chemical formula of Li a Ni b Co c Mn d O2 material is used as raw material, and a solution containing additives is pumped into the fluidized raw material by spray coating to form a doping layer and a coating layer on its surface; The additive includes at least anions; the anions include SO4 2- 、HPO4 2- 、H2PO4 - and PO4 3- One or a combination of two or more.

[0015] The present invention is prepared by a fluidized bed dissolution spray drying method, specifically: the raw materials are added into the cavity of the fluidized bed, and the solid particles are suspended by the fluidizing gas, so that they continue to roll and disperse evenly in the fluidizing gas, ensuring that the spray liquid is in full contact with the surface of the material. For the target coating layer, a soluble salt is selected as an additive, the additive is dissolved in a dispersant to form a coating solution, the positive electrode material is spray-coated and dried, and the coating layer is formed in situ during the subsequent heat treatment process. At the same time, the anions in the additive are diffused to a certain depth to obtain a surface-coated, locally gradient-doped lithium-rich manganese-based positive electrode material, and the modified material has excellent electrochemical properties.

[0016] At the same time, the fluidized bed dissolution spray coating method of the present invention can also achieve precise control of the composition and thickness of the coating layer and the doping layer, and has good application prospects.

[0017] According to the method for preparing the lithium-rich manganese-based positive electrode material provided by the present invention, the additive further includes a cation; The additives providing the cations include AlCl3, Al2(SO4)3, Al(NO3)3, C9H21 AlO3, Ac2Mg, MgSO4, MgCO3, LaCl3 and C 16 H 36 one or a combination of two or more of O4Ti; The additives providing the anions include one or a combination of two or more of (NH4)2SO4, (NH4)2HPO4, NH4H2PO4 and (NH4)3PO4; According to the preparation method of the lithium-rich manganese-based cathode material provided by the present invention, the raw materials are added into the cavity of a fluidized bed for fluidization; The solution containing the cation and the solution containing the anion are independently atomized through a nozzle, disposed on the surface of the raw materials, and dried to obtain the coated raw materials; preferably, the solution containing the cation is first mixed with the raw materials to obtain a first product, and then the solution containing the anion is mixed with the first product and dried to obtain the coated raw materials; further preferably, the drying temperature is 50~300 °C; The coated raw materials are sintered to obtain the lithium-rich manganese-based cathode material; preferably, the sintering temperature is 100~800 °C and the sintering time is 1~10 h.

[0018] The method of spray coating includes: adding raw materials into the cavity of a fluidized bed for fluidization. During fluidization, the matrix material realizes uniform and disordered fluidization under the action of the circulating air flow of the blowers at the upper and lower ends. For the target coating layer, a suitable soluble salt is reasonably selected as an additive. The additive is added to the dispersant respectively, stirred and ultrasonicated until it is in a clarified state to make the additive salt solution uniformly dispersed. Then it is pumped into the nozzle through a peristaltic pump, atomized through the nozzle, and sprayed on the surface of the cathode material once or multiple times. Preferably, the solution containing the cation is first uniformly coated on the surface of the material, and then the solution containing the anion is spray-coated to obtain a lithium-rich manganese-based cathode material with surface coating and subsurface gradient doping, which is rapidly dried, controlling the short-time contact between the solvent and the matrix material, and constructing one or more coating layers with uniform thickness on the surface of the lithium-rich material. The internal heating temperature of the device is 50~300 °C for fluidizing and drying the particles.

[0019] The present invention effectively realizes the control of the coating amount, doping amount and coating layer thickness by flexibly configuring the concentration of the coating solution; by reducing the usage amount of the dispersant, the coating cost is reduced.

[0020] Preferably, a heating plate is disposed at the bottom of the fluidized bed. By adjusting the heating temperature and time, it is rapidly dried after solid-liquid coating, effectively reducing the damage to the material surface caused by the long-time contact between the dispersant solution and the matrix material, and at the same time reducing the mutual adhesion and agglomeration phenomena between the wet particles.

[0021] Furthermore, the spray-coated material is sintered to achieve bulk-phase gradient doping, and the high-temperature cycling performance of the material is improved through the synergistic effect of coating and doping, thereby effectively improving the high-temperature cycling performance of the lithium-ion battery.

[0022] According to the preparation method of the lithium-rich manganese-based cathode material provided by the present invention, the solvent used for the solution containing the cation is selected from one or a combination of two or more of water, ethanol, ether, acetone, isopropanol, n-butanol, isobutanol, and cyclohexanol; and / or, the solvent used for the solution containing the anion is selected from one or a combination of two or more of water, ethanol, ether, acetone, isopropanol, n-butanol, isobutanol, and cyclohexanol.

[0023] The present invention provides a lithium-ion battery, including the lithium-rich manganese-based cathode material as described above or the lithium-rich manganese-based cathode material prepared according to the preparation method as described above.

[0024] Preferably, the lithium-ion battery includes a positive electrode sheet; the positive electrode sheet includes the lithium-rich manganese-based cathode material, acetylene black, and polyvinylidene fluoride as described above.

[0025] For the surface-coated and doped lithium-rich manganese-based cathode material, its preparation method and application provided by the present invention, by setting a specific doping layer and coating layer on the surface of the internal layered structure, the stability of the obtained lithium-rich manganese-based cathode material can be significantly improved. Further, the fluidized bed dissolution spray coating technology adopted by the present invention can effectively improve the stability of the surface and bulk-phase structure of the lithium-rich manganese-based cathode material, thereby effectively isolating the erosion of the electrolyte during the charge and discharge process. The doping layer can inhibit the dissolution of transition metals in the internal layered structure, reduce the release of lattice oxygen, and effectively improve the high-temperature cycling stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 It is a schematic structural diagram of the preparation method of the lithium-rich manganese-based cathode material provided by the present invention.

[0028] Figure 2 It is an HR-TEM image of the lithium-rich manganese-based cathode material of Example 1A provided by the present invention.

[0029] Figure 3 It is an SEM image of the lithium-rich manganese-based cathode material of Example 1A provided by the present invention.

[0030] Figure 4 It is the XRD image of the lithium-rich manganese-based cathode material of Example 1A provided by the present invention.

[0031] Figure 5 It is the HR-TEM image of the lithium-rich manganese-based cathode material of Comparative Example 1 provided by the present invention.

[0032] Figure 6 It is the SEM image of the lithium-rich manganese-based cathode material of Comparative Example 1 provided by the present invention.

[0033] Figure 7 It is the XRD image of the lithium-rich manganese-based cathode material of Comparative Example 1 provided by the present invention.

[0034] Figure 8 It is the comparison chart of the XRD images of the lithium-rich manganese-based cathode materials of Comparative Example 1 and Example 1A provided by the present invention.

[0035] Reference numerals: 1: Doping layer; 2: Coating layer; 3: Layered structure. Detailed implementation manners

[0036] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] The following combines Figures 1 - 8 to describe the surface-coated and doped lithium-rich manganese-based cathode material of the present invention, its preparation method and application.

[0038] For those not specifying specific techniques or conditions in the embodiments, they shall be carried out according to the techniques or conditions described in the literature in the field or according to the product specifications. For reagents or instruments not indicating the manufacturer, they are all conventional products that can be obtained through regular channels.

[0039] Example 1A A preparation method of a lithium-rich manganese-based cathode material, the steps are as follows: (1) Dissolve aluminum sulfate in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear aluminum sulfate solution.

[0040] Dissolve diammonium hydrogen phosphate in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear diammonium hydrogen phosphate solution.

[0041] (2) Add 1 kg of the positive electrode material (its chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2) into the fluidized bed cavity through the feed inlet, and turn on the upper and lower blowers for disordered fluidization. Pump the aluminum sulfate solution obtained in step (1) into the pipeline through a peristaltic pump, and determine the dosage of the aluminum sulfate solution according to 1.5 wt% of the total mass of the positive electrode material, and atomize and spray. Subsequently, pump the diammonium hydrogen phosphate solution obtained in step (1) into the pipeline through a peristaltic pump, and determine the dosage of the diammonium hydrogen phosphate solution according to 1.5 wt% of the total mass of the positive electrode material, and atomize and spray. After the spraying is completed, set the temperature of the heating plate to 200 °C, heat for 10 min to dry the material, and discharge it through the discharge outlet.

[0042] (3) Directly perform secondary calcination on the coated positive electrode material, calcine at 500 °C for 3 h under air conditions, and screen the sintered material through a 300-mesh sieve to obtain a lithium-rich manganese-based positive electrode material with a surface AlPO4 coating and Al and P gradient doping. Among them, the chemical formula of the main component of the doping layer formed by Al and P gradient doping is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Al 0.05 P 0.05 O2.

[0043] Example 2A A preparation method of a lithium-rich manganese-based positive electrode material, the steps are as follows: (1) Dissolve diammonium hydrogen phosphate in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear diammonium hydrogen phosphate solution.

[0044] (2) Add 1 kg of the positive electrode material (its chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2) into the fluidized bed cavity through the feed inlet, and turn on the upper and lower blowers for disordered fluidization. Pump the diammonium hydrogen phosphate solution obtained in step (1) into the pipeline through a peristaltic pump, and determine the dosage of the diammonium hydrogen phosphate solution according to 1.5 wt% of the total mass of the positive electrode material, and atomize and spray. After the spraying is completed, set the temperature of the heating plate to 200 °C, heat for 10 min to dry the material, and discharge it through the discharge outlet.

[0045] (3) Directly perform secondary calcination on the coated positive electrode material, calcine at 500 °C for 3 h under air conditions, and screen the sintered material through a 300-mesh sieve to obtain a lithium-rich manganese-based positive electrode material with a surface Li3PO4 coating and P gradient doping. Among them, the chemical formula of the main component of the doping layer formed by P gradient doping is Li1.2 Mn 0.54 Ni 0.13 Co 0.13 P 0.05 O2。

[0046] Example 3A A preparation method of a lithium-rich manganese-based cathode material, the steps of which are as follows: (1) Dissolve ammonium sulfate in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear ammonium sulfate solution.

[0047] (2) Add 1 kg of the cathode material (its chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2) into the fluidized bed cavity through the feed port, and turn on the upper and lower blowers for disordered fluidization. Pump the ammonium sulfate solution obtained in step (1) into the pipeline through a peristaltic pump, and determine the dosage of the ammonium sulfate solution according to 1.5 wt% of the total mass of the cathode material, and atomize and spray. After the spraying is completed, set the temperature of the heating plate to 200 °C, heat for 10 min to dry the material, and discharge it through the discharge port.

[0048] (3) Directly perform secondary calcination on the coated cathode material, calcine at 500 °C for 3 h under air conditions, and screen the sintered material through a 300-mesh sieve to obtain a lithium-rich manganese-based cathode material with a surface coated with Li2SO4 and S gradient doping, wherein the main component of the doping layer formed by S gradient doping has the chemical formula Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 S 0.05 O2。

[0049] Example 4A A preparation method of a lithium-rich manganese-based cathode material, the steps of which are as follows: (1) Dissolve magnesium acetate in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear magnesium acetate solution.

[0050] Dissolve diammonium hydrogen phosphate in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear diammonium hydrogen phosphate solution (2) Add 1 kg of the cathode material (its chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13O2) is added into the fluidized bed cavity through the feed inlet, and the upper and lower blowers are turned on for disordered fluidization. The magnesium acetate solution obtained in step (1) is pumped into the pipeline by a peristaltic pump, and the dosage of the magnesium acetate solution is determined according to 1.5 wt% of the total mass of the cathode material, and atomized spraying is carried out. Subsequently, the diammonium hydrogen phosphate solution obtained in step (1) is pumped into the pipeline by a peristaltic pump, and the dosage of the diammonium hydrogen phosphate solution is determined according to 1.5 wt% of the total mass of the cathode material, and atomized spraying is carried out. After the spraying is completed, the temperature of the heating plate is set to 200 °C, and the material is dried by heating for 10 min and discharged through the discharge outlet.

[0051] (3) The coated cathode material is directly subjected to secondary calcination, calcined at 500 °C for 3 h under air conditions, and the sintered material is sieved through a 300-mesh sieve to obtain a lithium-rich manganese-based cathode material coated with Mg3(PO4)2 on the surface and doped with Mg and P gradients. Among them, the chemical formula of the main component of the doped layer formed by the Mg and P gradient doping is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Mg 0.05 P 0.05 O2.

[0052] Example 5A A preparation method of a lithium-rich manganese-based cathode material, the steps are as follows: (1) Dissolve lanthanum chloride in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear lanthanum chloride solution.

[0053] Dissolve ammonium sulfate in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear ammonium sulfate solution.

[0054] (2) Add 1 kg of cathode material (its chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2) is added into the fluidized bed cavity through the feed inlet, and the upper and lower blowers are turned on for disordered fluidization. The lanthanum chloride solution obtained in step (1) is pumped into the pipeline by a peristaltic pump, and the dosage of the lanthanum chloride solution is determined according to 1.5 wt% of the total mass of the cathode material, and atomized spraying is carried out. Subsequently, the ammonium sulfate solution obtained in step (1) is pumped into the pipeline by a peristaltic pump, and the dosage of the ammonium sulfate solution is determined according to 1.5 wt% of the total mass of the cathode material, and atomized spraying is carried out. After the spraying is completed, the temperature of the heating plate is set to 200 °C, and the material is dried by heating for 10 min and discharged through the discharge outlet.

[0055] (3) The coated positive electrode material is directly subjected to secondary calcination at 500°C for 3 h under air conditions, and the sintered material is sieved with 300 mesh to obtain a lithium-rich manganese-based positive electrode material with La2(SO4)3 coating on the surface and La and S gradient doping, wherein the main component of the doping layer formed by La and S gradient doping is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 La 0.05 S 0.05 O2.

[0056] Example 6A A method for preparing a lithium-rich manganese-based positive electrode material, the steps of which are as follows: (1) C 16 H 36 O4Ti was dissolved in ethanol to prepare a 20% mass concentration solution and stirred for 10 min to obtain a clear C 16 H 36 O4Ti solution.

[0057] Dissolve diammonium hydrogen phosphate in deionized water to prepare a solution with a mass concentration of 20%, and stir for 10 minutes to obtain a clear diammonium hydrogen phosphate solution.

[0058] (2) 1 kg of positive electrode material (whose chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2) is added into the fluidized bed chamber through the feed port, and the upper and lower blowers are turned on for disordered fluidization. 16 H 36 O4Ti solution is pumped into the pipeline by a peristaltic pump. 16 H 36 O4Ti accounts for 1.5wt% of the total mass of the positive electrode material to determine C 16 H 36 The amount of O4Ti solution is atomized and sprayed. Then, the diammonium hydrogen phosphate solution obtained in step (1) is pumped into the pipeline through a peristaltic pump, and the amount of diammonium hydrogen phosphate solution is determined according to the diammonium hydrogen phosphate accounting for 1.5wt% of the total mass of the positive electrode material, and atomized and sprayed. After the spraying is completed, the temperature of the heating plate is set to 200°C, and the material is dried by heating for 10 minutes and discharged through the discharge port.

[0059] (3) The coated positive electrode material is directly subjected to secondary calcination at 600°C for 3 h under air conditions, and the sintered material is sieved with 300 mesh to obtain a lithium-rich manganese-based positive electrode material coated with Ti3(PO4)4 and gradient-doped with Ti and P, wherein the chemical formula of the main component of the doping layer formed by the gradient doping of Ti and P is Li 1.2 Mn0.54 Ni 0.13 Co 0.13 Ti 0.05 P 0.05 O2。

[0060] Example 1B A lithium-ion battery, and its preparation method is as follows: The lithium-rich manganese-based cathode material, acetylene black, and polyvinylidene fluoride N-methylpyrrolidone obtained in Example 1A are mixed with a solvent (N-methylpyrrolidone) in a mass ratio of 1:1:1 to form a slurry, which is uniformly coated on the surface of an aluminum foil sheet to obtain a positive electrode sheet. A lithium sheet is used as the negative electrode sheet, and a 1 mol / L solution of lithium hexafluorophosphate in ethylene carbonate (EC) and dimethyl carbonate (DMC) (the volume ratio of EC to DMC is 1:1) is used as the electrolyte, and it is assembled in a glove box to obtain a button cell.

[0061] Example 2B A lithium-ion battery, and its preparation method is basically the same as that of Example 1B, except that: the lithium-rich manganese-based cathode material obtained in Example 1A is replaced with the lithium-rich manganese-based cathode material obtained in Example 2A.

[0062] Example 3B A lithium-ion battery, and its preparation method is basically the same as that of Example 1B, except that: the lithium-rich manganese-based cathode material obtained in Example 1A is replaced with the lithium-rich manganese-based cathode material obtained in Example 3A.

[0063] Example 4B A lithium-ion battery, and its preparation method is basically the same as that of Example 1B, except that: the lithium-rich manganese-based cathode material obtained in Example 1A is replaced with the lithium-rich manganese-based cathode material obtained in Example 4A.

[0064] Example 5B A lithium-ion battery, and its preparation method is basically the same as that of Example 1B, except that: the lithium-rich manganese-based cathode material obtained in Example 1A is replaced with the lithium-rich manganese-based cathode material obtained in Example 5A.

[0065] Example 6B A lithium-ion battery, and its preparation method is basically the same as that of Example 1B, except that: the lithium-rich manganese-based cathode material obtained in Example 1A is replaced with the lithium-rich manganese-based cathode material obtained in Example 6A.

[0066] Comparative Example 1 A lithium-ion battery, and its preparation method is basically the same as that of Example 1B, except that: the lithium-rich manganese-based cathode material obtained in Example 1A is replaced with a cathode material (its chemical formula is Li 1.2 Mn 0.54 Ni0.13 Co 0.13 O2).

[0067] Comparative Example 2 A lithium-ion battery, the preparation method of which is basically the same as that of Example 1B, the difference is only that: the lithium-rich manganese-based cathode material prepared in Example 1A is replaced with a cathode material prepared by the following method: (1) Dissolve aluminum sulfate in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear aluminum sulfate solution.

[0068] Dissolve ammonium dihydrogen phosphate in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear ammonium dihydrogen phosphate solution.

[0069] (2) Disperse 1 kg of cathode material (its chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2) in deionized water, and pump the aluminum sulfate solution and ammonium dihydrogen phosphate solution obtained in step (1) into the lithium-rich mixed solution through a peristaltic pump at a flow rate of 3 mL / min respectively, stir for 3 h, filter, wash, and dry at 100 °C for 10 h to obtain a cathode material with a liquid-phase coated AlPO4.

[0070] (3) Directly perform secondary calcination on the coated cathode material, calcine at 500 °C for 3 h under air conditions, and screen the sintered material through a 300-mesh sieve to obtain a cathode material coated with AlPO4, and its chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2@AlPO4.

[0071] Comparative Example 3 A lithium-ion battery, the preparation method of which is basically the same as that of Example 1B, the difference is only that: the lithium-rich manganese-based cathode material prepared in Example 1A is replaced with a cathode material prepared by the following method: (1) Place 1 kg of cathode material (its chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2) and AlPO4 in a high-speed mixer, AlPO4 accounts for 1.5 wt% of the total mass of the cathode material, premix at a speed of 800 rpm, and then mix evenly at a speed of 1500 rpm to obtain a cathode material with a solid-phase coated AlPO4.

[0072] (2) Directly perform secondary calcination on the coated cathode material, calcine it at 500 °C for 3 h under air conditions, and screen the sintered material through a 300-mesh sieve to obtain the AlPO4-coated cathode material, whose chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2@AlPO4.

[0073] Comparative Example 4 A lithium-ion battery, whose preparation method is basically the same as that of Example 1B, except that: replace the lithium-rich manganese-based cathode material obtained in Example 1A with the cathode material prepared by the following method: (1) Dissolve zirconium acetate in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear zirconium acetate solution.

[0074] Dissolve diammonium hydrogen phosphate in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear diammonium hydrogen phosphate solution.

[0075] (2) Add 1 kg of cathode material (whose chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2) into the fluidized bed cavity through the feed port, and turn on the upper and lower blowers for disordered fluidization. Pump the zirconium acetate solution obtained in step (1) into the pipeline through a peristaltic pump, and determine the dosage of the zirconium acetate solution according to 1.5 wt% of the total mass of the cathode material, and atomize and spray. Subsequently, pump the diammonium hydrogen phosphate solution obtained in step (1) into the pipeline through a peristaltic pump, and determine the dosage of the diammonium hydrogen phosphate solution according to 1.5 wt% of the total mass of the cathode material, and atomize and spray. After the spraying is completed, set the temperature of the heating plate to 200 °C, heat for 10 min to dry the material, and discharge it through the discharge port.

[0076] (3) Directly perform secondary calcination on the coated cathode material, calcine it at 500 °C for 3 h under air conditions, and screen the sintered material through a 300-mesh sieve.

[0077] Comparative Example 5 A lithium-ion battery, whose preparation method is basically the same as that of Example 1B, except that: replace the lithium-rich manganese-based cathode material obtained in Example 1A with the cathode material prepared by the following method: (1) Dissolve aluminum sulfate in deionized water to prepare a solution with a mass concentration of 10%, and stir for 10 min to obtain a clear aluminum sulfate solution.

[0078] (2) Add 1 kg of cathode material (whose chemical formula is Li 1.2 Mn 0.54 Ni0.13 Co 0.13 CoO₂) is added into the fluidized bed cavity through the feed inlet, and the upper and lower blowers are turned on for disordered fluidization. The aluminum sulfate solution obtained in step (1) is pumped into the pipeline by a peristaltic pump, and the dosage of the aluminum sulfate solution is determined according to 1.5 wt% of the total mass of the cathode material. Then it is atomized and sprayed. After the spraying is completed, the temperature of the heating plate is set to 200 °C, and the material is dried for 10 min and discharged through the discharge outlet.

[0079] (3) The coated cathode material is directly subjected to secondary calcination, calcined at 500 °C for 3 h under air conditions, and the sintered material is sieved through a 300-mesh sieve.

[0080] Test Example (1) Use a high-resolution transmission electron microscope to test the microstructure of the lithium-rich manganese-based cathode material obtained in Example 1A and the cathode material in Comparative Example 1 (its chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O₂). As shown in Figure 2 and Figure 5 , it can be seen from the HR-TEM photos in Figure 2 that the lithium-rich manganese-based cathode material obtained in Example 1A has a uniform coating layer with a thickness of 12 - 13 nm. It can be seen from the HR-TEM photos in Figure 5 that the cathode material of Comparative Example 1 has a layered structure and no obvious coating layer.

[0081] (2) Use a scanning electron microscope to test the microtopography of the lithium-rich manganese-based cathode material obtained in Example 1A and the cathode material in Comparative Example 1 (its chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O₂). As shown in Figure 3 and Figure 6 , it can be seen from the scanning electron microscope photos in Figure 3 that there are obvious coatings attached to the surface of the lithium-rich manganese-based cathode material obtained in Example 1A. It can be seen from Figure 3 that there are obvious coatings attached to the surface of the lithium-rich manganese-based cathode material obtained in Example 1A.

[0082] (3) The lithium-rich manganese-based cathode material obtained in Example 1A and the cathode material in Comparative Example 1 (its chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O₂) are tested for X-ray diffraction patterns. The results are as shown in Figure 4 . As can be seen from Figure 4 , this material has obvious characteristic peaks of lithium-rich materials. As can be seen fromFigure 7 It can be seen that, except for the obvious characteristic peaks of the lithium-rich material, there are no impurity peaks in this material.

[0083] The XRD of the lithium-rich manganese-based cathode material obtained in Example 1A and the cathode material in Comparative Example 1 (whose chemical formula is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2) was compared. The comparison images are as Figure 8 shown. It can be seen that the diffraction peaks of the modified sample shift to the left, confirming the existence of gradient doping.

[0084] Furthermore, through testing, for the lithium-rich manganese-based cathode material prepared in the examples of the present invention, the thickness of the coating layer is 1 - 20 nm. The mass ratio of the doping layer in the lithium-rich manganese-based cathode material is 0.1% - 3%; the mass ratio of the coating layer in the lithium-rich manganese-based cathode material is 0.1% - 3%.

[0085] (4) The coin cells obtained in the examples and comparative examples were tested for their electrochemical performance at a test temperature of 25°C / 45°C. At a current density of 0.1C (1C = 200 mA / g), the charging voltage range was 2 - 4.8V, and the first charge-discharge and cycle performance of the test cells were tested. The detailed results are shown in Table 1.

[0086] Table 1

[0087] The lithium-ion batteries obtained in Examples 1B - 6B all showed relatively excellent first discharge specific capacity and high-temperature cycle capacity retention rate. The performance improvement of the lithium-rich manganese-based cathode material is the key to enhancing the overall performance of lithium-ion batteries. It can be seen from Comparative Examples 1 - 5 that the selection of the specific components in the lithium-rich manganese-based cathode material proposed in the present invention, as well as the preparation method of the lithium-rich manganese-based cathode material, both play a key role in the performance improvement of the lithium-rich manganese-based cathode material.

[0088] The fluidized bed dissolution spray coating method, with its advantages of simple operation, uniform coating layer, and short time consumption, provides an innovative solution to solve the deficiencies of traditional coating technologies. In the future, with the further improvement and popularization of this technology, it will play an important role in the lithium-ion battery industry and provide strong support for the research and development of high-energy density batteries.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A lithium-rich manganese-based cathode material, characterized in that, Comprising: Internal layered structure; the chemical formula of the main component of the internal layered structure is Li a Ni b Co c Mn d O2; and a doping layer located on the surface of the inner layered structure; the chemical formula of the main component of the doping layer is Li a Ni b Co c Mn d Ti e M f G p O2; and a coating layer located on the surface of the doped layer; the chemical formula of the main component of the coating layer is Li g R h Ti i V j O k ; Wherein, M is selected from one or more combinations of Al, Mg, Ti, and La, and 0 ≤ f ≤ 0.05; G is selected from one or both of S and P, and 0 < p ≤ 0.05; R is selected from one or more combinations of Al, Mg, Ti, and La, and 0 ≤ h ≤ 3; V is selected from one or both of S and P, and 1 ≤ j ≤ 4; 0 < a ≤ 1.2; 0 < b < 1; 0 < c < 1; 0 < d < 1; 0 ≤ e ≤ 0.05; 0 ≤ g ≤ 3; 0 ≤ i ≤ 2; 0 < k ≤ 16.

2. The lithium-rich manganese-based cathode material according to claim 1, wherein The doping elements in the doping layer include Ti and more than one of the M and the G; Preferably, the doping elements diffuse from the surface layer of the inner layered structure to the bulk phase to form gradient doping to obtain the doping layer.

3. The lithium-rich manganese-based cathode material according to claim 1 or 2, characterized in that, When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 P p O2, the chemical formula of the main component of the coating layer is Li3PO4; When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 S p O2, the chemical formula of the main component of the coating layer is Li2SO4; When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Al f P p O2, the chemical formula of the main component of the coating layer is AlPO4; When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Mg f P p O2, the chemical formula of the main component of the coating layer is Mg3(PO4)2; When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Ti f P p O2, the chemical formula of the main component of the coating layer is Ti3(PO4)4; When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 La f S p O2, the chemical formula of the main component of the coating layer is La2(SO4)3; When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Al e Ti f P p O2, the chemical formula of the main component of the coating layer is Li 1.3 Al 0.3 Ti 1.7 (PO4)3; When the chemical formula of the main component of the doping layer is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Mg f P p O2, the chemical formula of the main component of the coating layer is LiMgPO4.

4. The lithium-rich manganese-based cathode material according to any one of claims 1 to 3, characterized in that, The thickness of the coating layer is 1 to 20 nm.

5. The lithium-rich manganese-based cathode material according to any one of claims 1 to 4, characterized in that, The mass ratio of the doping layer in the lithium-rich manganese-based cathode material is 0.1% to 3%; The mass ratio of the coating layer in the lithium-rich manganese-based cathode material is 0.1% to 3%.

6. The preparation method of the lithium-rich manganese-based cathode material according to any one of claims 1 to 5, characterized in that, Comprising: Using a material with a layered structure and a chemical formula of Li a Ni b Co c Mn d O2 as the raw material, a solution containing an additive is pumped into the fluidized raw material by means of spray coating to form a doped layer and a coating layer on the surface of the active material; The additive includes at least an anion; the anion includes SO4 2- , HPO4 2- , H2PO4 - and PO4 3- or a combination of two or more thereof.

7. The preparation method of the lithium-rich manganese-based cathode material according to claim 6, characterized in that, The additive further includes a cation; Additives providing the cations include one or more combinations of AlCl3, Al2(SO4)3, Al(NO3)3, C9H 21 AlO3, Ac2Mg, MgSO4, MgCO3, LaCl3, and C 16 H 36 O4Ti; Preferably, the additive providing the anion includes one or more combinations of (NH4)2SO4, (NH4)2HPO4, NH4H2PO4, and (NH4)3PO4.

8. The preparation method of the lithium-rich manganese-based cathode material according to claim 7, wherein, Adding the raw materials into the cavity of the fluidized bed for fluidization; Atomizing the solution containing the cation and the solution containing the anion independently through nozzles, disposing them on the surface of the raw materials, and drying to obtain the coated raw materials; preferably, the solution containing the cation is first mixed with the raw materials to obtain a first product, and then the solution containing the anion is mixed with the first product and dried to obtain the coated raw materials; further preferably, the drying temperature is 50 to 300 °C; Sintering the coated raw materials to obtain the lithium-rich manganese-based cathode material; preferably, the sintering temperature is 100 to 800 °C, and the sintering time is 1 to 10 h.

9. The preparation method of the lithium-rich manganese-based cathode material according to claim 7 or 8, characterized in that, The solvent used in the solution containing the cation is selected from one or more combinations of water, ethanol, ether, acetone, isopropanol, n-butanol, isobutanol, and cyclohexanol; And / or, the solvent used in the solution containing the anion is selected from one or more combinations of water, ethanol, ether, acetone, isopropanol, n-butanol, isobutanol, and cyclohexanol.

10. A lithium-ion battery, characterized in that, Including the lithium-rich manganese-based cathode material according to any one of claims 1 to 5 or the lithium-rich manganese-based cathode material prepared by the preparation method according to any one of claims 6 to 9.

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