Positive electrode material and preparation method thereof, positive electrode sheet, battery and electrical device

Abstract

The present application relates to the field of lithium battery technology, and in particular to a positive electrode material and its preparation method, a positive electrode sheet, a battery and an electrical device. The positive electrode material includes a positive electrode material and a coating layer coated on the surface of the positive electrode material. The material forming the coating layer includes a solid electrolyte and a sintering aid. The molecular formula of the solid electrolyte is Li 1+x Al x Ti 2‑x (PO4)3, 0.1≤x≤1.5. In the above-mentioned positive electrode material, LATP can uniformly and densely coat the positive electrode material, and the electrochemical performance of the positive electrode material is significantly improved.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a positive electrode material and a preparation method thereof, a positive electrode sheet, a battery, and an electrical device. Background Art

[0002] The long driving range and fast charging of electric vehicles currently require high-performance lithium-ion batteries, of which cathode materials are one of the most critical components. However, cathode materials are prone to cracking during long cycles and persistent side reactions with the electrolyte, seriously compromising the battery's cycle life and storage performance. Surface coating of cathode materials can reduce stress, increase liquid electrolyte wettability, lower interfacial charge transfer resistance, and mitigate side reactions, effectively optimizing cathode materials.

[0003] NASICON type lithium ion conductor Li 1+x Al x Ti 2-x (PO4)3 (LATP) is one of the electrolytes with the highest room-temperature conductivity among the oxide lithium-ion conductors discovered to date. It has attracted a lot of attention from researchers and has been widely used in surface coating and modification of positive electrode materials. However, the methods currently used to coat LATP are mostly solid-phase sintering or wet coating. However, the sintering temperature required for solid-phase sintering is relatively high, and LATP needs to be ground into fine particles before coating, which involves many steps and high costs. Wet coating requires many parameters to be controlled during the precipitation process, and a large amount of industrial wastewater will be generated, which will cause environmental pollution and increase costs. Moreover, the electrochemical performance of positive electrode materials obtained by either solid-phase sintering or wet coating is still not ideal. Summary of the Invention

[0004] Based on this, it is necessary to provide a positive electrode material and its preparation method, a positive electrode sheet, a battery and an electrical device that can improve the coating effect of LATP and the electrochemical performance of the positive electrode material.

[0005] On the one hand, the present application provides a positive electrode material, which includes a positive electrode material matrix and a coating layer coated on the surface of the positive electrode material matrix, wherein the material forming the coating layer includes a solid electrolyte and a sintering aid; wherein the molecular formula of the solid electrolyte is Li 1+x Al x Ti 2-x (PO4)3, 0.1≤x≤1.5.

[0006] In one embodiment, the sintering aid includes one or more of lithium metaborate, lithium tetraborate, lithium borate, lithium bis(oxalatoborate), boric acid, and boron oxide.

[0007] Optionally, the specific surface area of ​​the sintering aid is 50 to 500 m 2 / g.

[0008] In one embodiment, the mass ratio of the solid electrolyte to the positive electrode material matrix is ​​(0.01-10):100.

[0009] In one embodiment, the mass ratio of the solid electrolyte to the sintering aid is 100:(0.1-50).

[0010] In one aspect, the present application further provides a method for preparing the positive electrode material as described above, which comprises the following steps:

[0011] The positive electrode material matrix, the solid electrolyte and the sintering aid are mixed and sintered; wherein the molecular formula of the solid electrolyte is Li 1+x Al x Ti 2-x (PO4)3, 0.1≤x≤1.5.

[0012] In one embodiment, the sintering process conditions include:

[0013] In an oxygen-containing atmosphere with a pressure of 0 to 30 Pa, the temperature is increased to 200 to 600° C. at a heating rate of 2 to 5° C. / min and kept at this temperature for 2 to 10 hours.

[0014] In one embodiment, the solid electrolyte is prepared by a preparation method comprising the following steps:

[0015] A lithium source, an aluminum source, a titanium source and a phosphorus source in a preset mass ratio are mixed and sintered.

[0016] In one embodiment, the solid electrolyte and the sintering aid are in-situ coated on the surface of the positive electrode material substrate, and the specific steps of the in-situ coating include:

[0017] The positive electrode material matrix, the sintering aid, the lithium source, the aluminum source, the titanium source and the phosphorus source are mixed and sintered.

[0018] In one embodiment, the method for preparing the solid electrolyte has at least one of the following characteristics:

[0019] 1) The lithium source includes one or more of Li2CO3, LiOH, CH3COOLi and LiNO3;

[0020] 2) The aluminum source includes Al2O3, Al(OH)3, C9H 21 One or more of AlO3, γ-AlOOH and Al(NO3)3·9H2O;

[0021] 3) The titanium source includes TiO2 and / or Ti(OH)4;

[0022] 4) The phosphorus source includes NH4H2PO4 and / or (NH4)2HPO4.

[0023] On the other hand, the present application further provides a positive electrode sheet, which includes a positive electrode current collector and a positive electrode active material layer formed on the surface of the positive electrode current collector, and the positive electrode active material in the positive electrode active material layer includes the positive electrode material described above.

[0024] In another aspect of the present application, a battery is provided, which includes the positive electrode sheet described above.

[0025] In another aspect of the present application, an electrical device is provided, which includes the battery described above.

[0026] The positive electrode material provided above makes the solid electrolyte Li 1+x Al x Ti 2-x (PO4)3(LATP) uniformly crystallizes and grows on the surface of the cathode material matrix to form a coating layer, which enhances the bonding between LATP and the cathode material matrix, increases the structural stability and particle strength of the cathode material matrix, effectively inhibits the dissolution of metal ions in the cathode material matrix, and can significantly reduce the initial DC resistance (DCR) and cyclic DCR growth rate of the cathode material, significantly improving the structural stability of the cathode material at high temperatures. It is particularly suitable for coating single-crystal or polycrystalline cathode materials. The solid electrolyte used in the coating layer is a solid substance. Therefore, the resulting cathode material has good application prospects in solid-state batteries.

[0027] In addition, the addition of sintering aids can not only promote the uniform crystallization and growth of LATP, but also reduce the sintering temperature and process costs. The preparation process is simple, does not produce waste gas or waste water, is environmentally friendly, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 The single crystal positive electrode material LiNi in Example 1 0.65 Co 0.15 Mn 0.20Scanning electron microscope image of O2;

[0030] Figure 2 The Li-coated 1.3 Al 0.3 Ti 1.7 Scanning electron microscope image of the positive electrode material of (PO4)3;

[0031] Figure 3 Single crystal LiNi without LATP coating 0.65 Co 0.15 Mn 0.20 O2, the first charge and discharge curves of the CR2032 button batteries assembled in Example 1 and Comparative Example 1;

[0032] Figure 4 Single crystal LiNi without LATP coating 0.65 Co 0.15 Mn 0.20 Cycling performance curves of CR2032 button batteries assembled in O2, Example 1 and Comparative Example 1;

[0033] Figure 5 Single crystal LiNi without LATP coating 0.65 Co 0.15 Mn 0.20 Cyclic DCR growth rate curves of CR2032 button batteries assembled in O2, Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0034] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the accompanying drawings. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] When LATP is conventionally coated, the coating layer usually contains only LATP, and it is difficult for LATP to uniformly coat the cathode material matrix. To this end, in the first aspect of the present application, a cathode material is provided, which includes a cathode material matrix and a coating layer coated on the surface of the cathode material matrix, wherein the materials forming the coating layer include a solid electrolyte and a sintering aid; wherein the molecular formula of the solid electrolyte is Li1+x Al x Ti 2-x (PO4)3, 0.1≤x≤1.5, wherein x can be any value between 0.1 and 1.5, for example, 0.1, 0.3, 0.5, 0.7, 0.9, 1.1, 1.3, or 1.5.

[0037] By adding a sintering aid to the coating layer, the solid electrolyte (LATP) can be uniformly crystallized and grown on the surface of the cathode material matrix, forming a uniform coating layer. This improves the bonding force between the LATP and the cathode material matrix, increases the structural stability and particle strength of the cathode material matrix, effectively inhibits the dissolution of metal ions in the cathode material matrix, and can significantly reduce the initial DC resistance (DCR) and cycle DCR growth rate of the cathode material, significantly improving the structural stability of the cathode material at high temperatures. It is particularly suitable for coating single crystal or polycrystalline cathode materials. Moreover, the solid electrolyte used in the coating layer is a solid substance. Therefore, the resulting cathode material has good application prospects in solid-state batteries.

[0038] In some embodiments, the cathode material matrix may be a single crystal cathode material or a polycrystalline cathode material, wherein the chemical formula of the cathode material matrix may be Li 1+α Ni x Co y Mn z O2, 0≤α≤0.2, 0≤x<1.0, 0≤y≤1.0, 0≤z<1.0, α+x+y+z=1.0.

[0039] In some embodiments, the sintering aid may be any sintering aid commonly used in the art. As an example, the sintering aid may be a boride. For example, the sintering aid may specifically include one or more of lithium metaborate (LiBO2), lithium tetraborate (Li2B4O7), lithium borate (Li3BO3), lithium bis(oxalatoborate) (C4BLiO8), boric acid (H3BO3) and boron oxide (B2O3).

[0040] In some embodiments, the specific surface area of ​​the sintering aid may be 50 to 500 m 2 By adjusting the specific surface area of ​​the sintering aid, it is possible to further ensure that the coating layer uniformly and stably coats the positive electrode material matrix. For example, the specific surface area of ​​the sintering aid can also be 100m 2 / g, 150m 2 / g, 200m 2 / g, 250m 2 / g、300m 2 / g、350m 2 / g, 400m 2 / g, 450m 2 / g.

[0041] In some embodiments, the average particle size of the sintering aid is nanometer-scale, specifically any value between 10 and 100 nm.

[0042] In some embodiments, the mass ratio of the solid electrolyte to the positive electrode material matrix can be any value between (0.01 and 10):100, for example, it can also be 0.05:100, 0.1:100, 0.5:100, 1:100, 1.5:100, 2:100, 2.5:100, 3:100, 4:100, 5:100, 6:100, 7:100, 8:100, or 9:100.

[0043] In some embodiments, the mass ratio of the solid electrolyte to the sintering aid can be any value between 100:(0.1~50), for example, it can also be 100:0.5, 100:1, 100:5, 100:10, 100:15, 100:20, 100:30, 100:40.

[0044] When using traditional solid-phase coating methods or wet coating methods, there are problems such as poor LATP coating effect, multiple steps, high cost, and environmental friendliness. To this end, the second aspect of the present application also provides a method for preparing the positive electrode material as described above, which includes the following steps S100, S200, and S300:

[0045] Step S100: Mix the cathode material matrix, solid electrolyte and sintering aid to prepare mixed powder; wherein the molecular formula of the solid electrolyte is Li 1+x Al x Ti 2-x (PO4)3, 0.1≤x≤1.5.

[0046] The addition of sintering aids can not only promote the uniform crystallization and growth of LATP, but also reduce the sintering temperature and process costs. The preparation process is simple, does not produce waste gas or waste water, is environmentally friendly, and is suitable for industrial production.

[0047] In some embodiments, the mixing method is not limited and any mixing method known in the art can be selected, as long as the positive electrode material matrix, solid electrolyte and sintering aid can be mixed uniformly. As an example, the mixing method may specifically include the following steps:

[0048] The positive electrode material matrix, the solid electrolyte and the sintering aid are mixed at a rotation speed of 100 to 300 rpm for 1 to 10 minutes; and then mixed at a rotation speed of 500 to 1000 rpm for 10 to 30 minutes.

[0049] In some embodiments, the preparation method may further include the step of preparing a solid electrolyte, wherein the preparation method of the solid electrolyte may include the following steps:

[0050] The lithium source, aluminum source, titanium source and phosphorus source of the preset mass ratio are mixed and sintered. The preset mass ratio specifically refers to the molecular formula of the solid electrolyte Li 1+x Al x Ti 2-x (PO4)3, 0.1≤x≤1.5 calculated.

[0051] In some embodiments, the solid electrolyte and the sintering aid are in-situ coated on the surface of the positive electrode material matrix, and the specific steps of in-situ coating include:

[0052] The positive electrode material matrix, the sintering aid, the lithium source, the aluminum source, the titanium source and the phosphorus source are mixed and sintered.

[0053] Usually, when LATP is directly used to coat the positive electrode material matrix, the increase in LATP content (for example, exceeding 8:100) will lead to a decrease in battery capacity. However, when LATP is in situ formed on the surface of the positive electrode material matrix through the reaction of the positive electrode material matrix with the lithium source, aluminum source, titanium source and phosphorus source, the battery capacity can still be improved when the content increases.

[0054] In some embodiments, the lithium source, aluminum source, titanium source and phosphorus source can be selected from lithium-containing compounds, aluminum-containing compounds, titanium-containing compounds and phosphorus-containing compounds commonly used in the art. For example, the lithium source includes but is not limited to one or more of lithium carbonate (Li2CO3), lithium hydroxide (LiOH), lithium acetate (CH3COOLi) and lithium nitrate (LiNO3); the aluminum source includes but is not limited to Al2O3, Al(OH)3, C9H 21 One or more of AlO3, boehmite (diaspore, γ-AlOOH) and Al(NO3)3·9H2O; titanium sources include but are not limited to TiO2 and / or Ti(OH)4; phosphorus sources include but are not limited to NH4H2PO4 and / or (NH4)2HPO4.

[0055] In some embodiments, the specific surface areas of the aluminum source, titanium source, and phosphorus source can be independently selected from 50 to 500 m 2 / g, for example, the specific surface areas of the aluminum source, titanium source and phosphorus source can also be independently selected from 100m 2 / g, 150m 2 / g, 200m 2 / g, 250m 2 / g、300m 2 / g、350m 2 / g, 400m 2 / g, 450m 2 The activity of LATP can be regulated by adjusting the specific surface areas of the aluminum source, titanium source, and phosphorus source, thereby ensuring that the capacity of the cathode material matrix will not decrease when a large amount of LATP is used to coat the cathode material matrix.

[0056] In some embodiments, the preparation method of the positive electrode material can be specifically as follows:

[0057] The positive electrode material matrix, lithium source, aluminum source, titanium source, phosphorus source and sintering aid are mixed and sintered.

[0058] Step S200: sintering the mixed powder prepared in step S100.

[0059] In some embodiments, the sintering process conditions may include:

[0060] In an oxygen-containing atmosphere at a pressure of 0-30 Pa, the temperature is raised to 200-600°C at a rate of 2-5°C / min and maintained at this temperature for 2-10 hours. The sintering temperature can be lowered by adding a sintering aid. The oxygen-containing atmosphere can specifically be an oxygen atmosphere and / or an air atmosphere. It will be appreciated that sintering can be carried out in an apparatus commonly used in the art, such as a roasting furnace.

[0061] Step S300: Screening the material sintered in step S200. It is understood that in some embodiments, step S300 may be omitted.

[0062] On the other hand, the present application further provides a positive electrode sheet, which includes a positive electrode current collector and a positive electrode active material layer formed on the surface of the positive electrode current collector, and the positive electrode active material in the positive electrode active material layer includes the positive electrode material described above.

[0063] In another aspect of the present application, a battery is provided, which includes the positive electrode sheet described above.

[0064] In some embodiments, the battery may be a lithium secondary battery.

[0065] It should be noted that the lithium secondary battery further includes a negative electrode and a separator. In some embodiments, the lithium secondary battery may further include an electrolyte.

[0066] Among them, the specific material and type of the negative electrode are not limited. As an exemplary illustration, the negative electrode can be only a carbon-based negative electrode material or composed of a carbon-based negative electrode material and a negative electrode current collector. The carbon-based negative electrode material includes one or more of artificial graphite, natural graphite, graphitized carbon fiber, graphitized medium carbon microbeads, fullerene and amorphous carbon; the negative electrode current collector can be an aluminum current collector.

[0067] The main function of the separator is to prevent short circuits between the positive and negative electrodes and provide a path for lithium ions. Separators that meet the requirements may include known separators, which may be selected from polyolefin-based polymer films, wherein the polyolefin-based polymer may include polypropylene or polyethylene. It is understood that the polyolefin-based polymer film may specifically be a multilayer film, a microporous film, a woven fabric, or a non-woven fabric.

[0068] The electrolyte can be a solid electrolyte or an electrolyte, specifically an electrolyte formed by a lithium salt and an organic solvent. The lithium salt can be one or more of LiPF6, LiBF4, LiSbF6 and LiAsF6, and the organic solvent is mainly selected from carbonate solvents, such as ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC).

[0069] In another aspect of the present application, an electrical device is provided, which includes the battery described above.

[0070] In some embodiments, the power-consuming device can specifically be a device that uses a lithium secondary battery as a power supply device. As an example, the power-consuming device can be a small electronic device (mobile phone, PDA, laptop computer, camera, portable game console, etc.), or a large transportation device such as a vehicle (hybrid vehicle, electric vehicle, etc.), or an electric tool, such as an electric drill, electric hammer, electric saw, cutting machine, etc.

[0071] The present application is further described in detail below with reference to specific embodiments.

[0072] Example 1

[0073] 1) Lithium carbonate, Al(OH)3, TiO2 and (NH4)2HPO4 are mixed according to the chemical formula Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is calculated and weighed with LiBO2 and single crystal positive electrode material LiNi 0.65 Co 0.15 Mn 0.20 O2 was mixed at a low speed of 200 rpm for 3 min and then at a high speed of 800 rpm for 20 min to prepare a mixed material; wherein, the specific surface areas of Al(OH)3, TiO2, (NH4)2HPO4 and LiBO2 were 400 m 2 / g、100m 2 / g, 200m 2 / g and 300m 2 / g,Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and LiNi 0.65 Co 0.15 Mn0.20 The mass ratio of O2 is 1:100, LiBO2 and Li 1.3 Al 0.3 Ti 1.7 The mass ratio of (PO4)3 is 2:100.

[0074] 2) The mixture obtained in step 1) is directly placed in a sagger, heat-treated in a roasting furnace under air atmosphere, and sieved to obtain a mixture coated with Li 1.3 Al 0.3 Ti 1.7 The positive electrode material of (PO4)3 is denoted as S1. The specific process parameters of the heat treatment are heating to 500°C at a heating rate of 3°C / min, keeping the temperature for 5 hours, and controlling the furnace pressure of the roasting furnace at 0-5Pa.

[0075] Single crystal cathode material LiNi 0.65 Co 0.15 Mn 0.20 The scanning electron microscope image of O2 is as follows Figure 1 As shown. Coated with Li 1.3 Al 0.3 Ti 1.7 The scanning electron microscope image of the positive electrode material (S1) of (PO4)3 is as follows Figure 2 shown.

[0076] Example 2

[0077] 1) Lithium acetate, Al2O3, TiO2 and (NH4)2HPO4 are mixed according to the chemical formula Li 1.5 Al 0.5 Ti 1.5 (PO4)3 is calculated and weighed with Li3BO3 and polycrystalline positive electrode material LiNi 0.8 Co 0.1 Mn 0.1 O2 was mixed at a low speed of 150 rpm for 4 min and then at a high speed of 700 rpm for 25 min to prepare a mixed material; wherein the specific surface areas of Al2O3, TiO2, (NH4)2HPO4 and Li3BO3 were 150 m 2 / g, 200m 2 / g, 200m 2 / g and 100m 2 / g,Li 1.5 Al 0.5 Ti 1.5 (PO4)3 and LiNi 0.8 Co 0.1 Mn 0.1 The mass ratio of O2 is 0.5:100, Li3BO3 and Li 1.5 Al 0.5 Ti1.5 The mass ratio of (PO4)3 is 4:100.

[0078] 2) The mixture obtained in step 1) is directly placed in a sagger, heat-treated in a roasting furnace under an oxygen atmosphere, and then sieved to obtain a Li-coated 1.5 Al 0.5 Ti 1.5 The specific process parameters of the heat treatment are heating to 350°C at a heating rate of 2°C / min, holding for 6 hours, and controlling the furnace pressure of the calcination furnace at 20Pa to 25Pa.

[0079] Example 3

[0080] 1) Lithium hydroxide, Al(NO3)3·9H2O, Ti(OH)4 and (NH4)2HPO4 are mixed according to the chemical formula Li 1.7 Al 0.7 Ti 1.3 (PO4)3 is calculated and weighed with H3BO3 and polycrystalline positive electrode material Li 1.2 Ni 0.2 Mn 0.6 O2 was mixed at a low speed of 300 rpm for 2 min and then at a high speed of 900 rpm for 20 min to prepare a mixed material; wherein, the specific surface areas of Al(NO3)3·9H2O, Ti(OH)4, (NH4)2HPO4 and H3BO3 were 80 m 2 / g, 250m 2 / g、100m 2 / g and 200m 2 / g,Li 1.7 Al 0.7 Ti 1.3 (PO4)3 and Li 1.2 Ni 0.2 Mn 0.6 The mass ratio of O2 is 1.5:100, H3BO3 and Li 1.7 Al 0.7 Ti 1.3 The mass ratio of (PO4)3 is 5:100.

[0081] 2) The mixture obtained in step 1) is directly placed in a sagger, heat-treated in a roasting furnace under an oxygen atmosphere, and then sieved to obtain a mixture coated with Li 1.7 Al 0.7 Ti 1.3 (PO4)3 cathode material. Specific process parameters for heat treatment are heating to 300°C at a heating rate of 4°C / min, holding for 8 hours, and controlling the furnace pressure of the calcination furnace at 15Pa to 20Pa.

[0082] Example 4

[0083] 1) Lithium nitrate, C9H 21 AlO3, Ti(OH)4 and (NH4)2HPO4 according to the chemical formula Li 2.3 Al 1.3 Ti 0.7 (PO4)3 was weighed and mixed with C4BLiO8 and single crystal positive electrode material LiCoO2 at a low speed of 200 rpm for 3 minutes, and then at a high speed of 750 rpm for 30 minutes to prepare a mixed material; wherein, C9H 21 The specific surface areas of AlO3, Ti(OH)4, (NH4)2HPO4 and C4BLiO8 are 200m 2 / g, 150m 2 / g、100m 2 / g and 400m 2 / g,Li 2.3 Al 1.3 Ti 0.7 The mass ratio of (PO4)3 to LiCoO2 is 2:100, and the mass ratio of C4BLiO8 to Li 1.3 Al 0.3 Ti 1.7 The mass ratio of (PO4)3 is 3.5:100.

[0084] 2) The mixture obtained in step 1) is directly placed in a sagger, heat-treated in a roasting furnace under air atmosphere, and sieved to obtain a mixture coated with Li 2.3 Al 1.3 Ti 0.7 The specific process parameters of the heat treatment are heating to 400°C at a heating rate of 3°C / min, holding for 6 hours, and controlling the furnace pressure of the calcination furnace at 10Pa to 15Pa.

[0085] Example 5

[0086] The preparation method of this embodiment is basically the same as that of embodiment 1, except that: Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and LiNi 0.65 Co 0.15 Mn 0.20 The mass ratio of O2 is 8:100. The specific steps are as follows:

[0087] 1) Lithium carbonate, Al(OH)3, TiO2 and (NH4)2HPO4 are mixed according to the chemical formula Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is calculated and weighed with LiBO2 and single crystal positive electrode material LiNi0.65 Co 0.15 Mn 0.20 O2 was mixed at a low speed of 200 rpm for 3 min and then at a high speed of 800 rpm for 20 min to prepare a mixed material; wherein, the specific surface areas of Al(OH)3, TiO2, (NH4)2HPO4 and LiBO2 were 400 m 2 / g、100m 2 / g, 200m 2 / g and 300m 2 / g,Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and LiNi 0.65 Co 0.15 Mn 0.20 The mass ratio of O2 is 8:100, LiBO2 and Li 1.3 Al 0.3 Ti 1.7 The mass ratio of (PO4)3 is 2:100.

[0088] 2) The mixture obtained in step 1) is directly placed in a sagger, heat-treated in a roasting furnace under air atmosphere, and sieved to obtain a mixture coated with Li 1.3 Al 0.3 Ti 1.7 The specific process parameters of the heat treatment are heating to 500°C at a heating rate of 3°C / min, holding the temperature for 5 hours, and controlling the furnace pressure of the calcination furnace at 0-5 Pa.

[0089] Example 6

[0090] The preparation method of this embodiment is basically the same as that of embodiment 5, except that the conventional commercial Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is coated. The specific steps are as follows:

[0091] 1) Commercializing traditional 1.3 Al 0.3 Ti 1.7 (PO4)3, LiBO2 and single crystal cathode material LiNi 0.65 Co 0.15 Mn 0.20 O2 was mixed at a low speed of 200 rpm for 3 min and then at a high speed of 800 rpm for 20 min to prepare a mixed material; Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and LiNi 0.65 Co 0.15 Mn0.20 The mass ratio of O2 is 8:100, LiBO2 and Li 1.3 Al 0.3 Ti 1.7 The mass ratio of (PO4)3 is 2:100.

[0092] 2) The mixture obtained in step 1) is directly placed in a sagger, heat-treated in a roasting furnace under air atmosphere, and sieved to obtain a mixture coated with Li 1.3 Al 0.3 Ti 1.7 The specific process parameters of the heat treatment are heating to 500°C at a heating rate of 3°C / min, holding the temperature for 5 hours, and controlling the furnace pressure of the calcination furnace at 0-5 Pa.

[0093] Example 7

[0094] The preparation method of this embodiment is basically the same as that of embodiment 1, except that: LiBO2 and Li 1.3 Al 0.3 Ti 1.7 The mass ratio of (PO4)3 is 10:100. The specific steps are as follows:

[0095] 1) Lithium carbonate, Al(OH)3, TiO2 and (NH4)2HPO4 are mixed according to the chemical formula Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is calculated and weighed with LiBO2 and single crystal positive electrode material LiNi 0.65 Co 0.15 Mn 0.20 O2 was mixed at a low speed of 200 rpm for 3 min and then at a high speed of 800 rpm for 20 min to prepare a mixed material; wherein, the specific surface areas of Al(OH)3, TiO2, (NH4)2HPO4 and LiBO2 were 400 m 2 / g、100m 2 / g, 200m 2 / g and 300m 2 / g,Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and LiNi 0.65 Co 0.15 Mn 0.20 The mass ratio of O2 is 1:100, LiBO2 and Li 1.3 Al 0.3 Ti 1.7 The mass ratio of (PO4)3 is 10:100.

[0096] 2) The mixture obtained in step 1) is directly placed in a sagger, heat-treated in a roasting furnace under air atmosphere, and sieved to obtain a mixture coated with Li 1.3 Al 0.3 Ti 1.7 The specific process parameters of the heat treatment are heating to 500°C at a heating rate of 3°C / min, holding the temperature for 5 hours, and controlling the furnace pressure of the calcination furnace at 0-5 Pa.

[0097] Example 8

[0098] The preparation method of this embodiment is basically the same as that of embodiment 1, except that: LiBO2 and Li 1.3 Al 0.3 Ti 1.7 The mass ratio of (PO4)3 is 40:100. The specific steps are as follows:

[0099] 1) Lithium carbonate, Al(OH)3, TiO2 and (NH4)2HPO4 are mixed according to the chemical formula Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is calculated and weighed with LiBO2 and single crystal positive electrode material LiNi 0.65 Co 0.15 Mn 0.20 O2 was mixed at a low speed of 200 rpm for 3 min and then at a high speed of 800 rpm for 20 min to prepare a mixed material; wherein, the specific surface areas of Al(OH)3, TiO2, (NH4)2HPO4 and LiBO2 were 400 m 2 / g、100m 2 / g, 200m 2 / g and 300m 2 / g,Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and LiNi 0.65 Co 0.15 Mn 0.20 The mass ratio of O2 is 1:100, LiBO2 and Li 1.3 Al 0.3 Ti 1.7 The mass ratio of (PO4)3 is 40:100.

[0100] 2) The mixture obtained in step 1) is directly placed in a sagger, heat-treated in a roasting furnace under air atmosphere, and sieved to obtain a mixture coated with Li 1.3 Al 0.3 Ti 1.7The specific process parameters of the heat treatment are heating to 500°C at a heating rate of 3°C / min, holding the temperature for 5 hours, and controlling the furnace pressure of the calcination furnace at 0-5 Pa.

[0101] Comparative Example 1

[0102] The preparation method of this comparative example is basically the same as that of Example 1, except that LiBO2 is not added. The specific steps are as follows:

[0103] 1) Lithium carbonate, Al(OH)3, TiO2 and (NH4)2HPO4 are mixed according to the chemical formula Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is calculated and weighed with the single crystal positive electrode material LiNi 0.65 Co 0.15 Mn 0.20 O2 was mixed at a low speed of 200 rpm for 3 min and then at a high speed of 800 rpm for 20 min to prepare a mixed material; wherein, the specific surface areas of Al(OH)3, TiO2 and (NH4)2HPO4 were 400 m 2 / g、100m 2 / g and 200m 2 / g,Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and LiNi 0.65 Co 0.15 Mn 0.20 The mass ratio of O2 is 1:100.

[0104] 2) The mixture obtained in step 1) is directly placed in a sagger, heat-treated in a roasting furnace under air atmosphere, and sieved to obtain a mixture coated with Li 1.3 Al 0.3 Ti 1.7 The positive electrode material of (PO4)3 is denoted as S2. The specific process parameters of the heat treatment are heating to 500°C at a heating rate of 3°C / min, keeping the temperature for 5 hours, and controlling the furnace pressure of the calcination furnace at 0-5Pa.

[0105] Comparative Example 2

[0106] The preparation method of this comparative example is basically the same as that of Example 1, except that the specific surface area of ​​LiBO2 is 30m 2 / g.

[0107] Comparative Example 3

[0108] The preparation method of this comparative example is basically the same as that of Example 1, except that: Li 2.8 Al 1.8Ti 0.2 (PO4)3 replaces Li 1.3 Al 0.3 Ti 1.7 (PO4)3 is coated. The specific steps are as follows:

[0109] 1) Lithium carbonate, Al(OH)3, TiO2 and (NH4)2HPO4 are mixed according to the chemical formula Li 2.8 Al 1.8 Ti 0.2 (PO4)3 is calculated and weighed with LiBO2 and single crystal positive electrode material LiNi 0.65 Co 0.15 Mn 0.20 O2 was mixed at a low speed of 200 rpm for 3 min and then at a high speed of 800 rpm for 20 min to prepare a mixed material; wherein, the specific surface areas of Al(OH)3, TiO2, (NH4)2HPO4 and LiBO2 were 400 m 2 / g、100m 2 / g, 200m 2 / g and 300m 2 / g,Li 2.8 Al 1.8 Ti 0.2 (PO4)3 and LiNi 0.65 Co 0.15 Mn 0.20 The mass ratio of O2 is 1:100, LiBO2 and Li 2.8 Al 1.8 Ti 0.2 The mass ratio of (PO4)3 is 2:100.

[0110] 2) The mixture obtained in step 1) is directly placed in a sagger, heat-treated in a roasting furnace under air atmosphere, and sieved to obtain a mixture coated with Li 2.8 Al 1.8 Ti 0.2 The specific process parameters of the heat treatment are heating to 500°C at a heating rate of 3°C / min, holding the temperature for 5 hours, and controlling the furnace pressure of the calcination furnace at 0-5 Pa.

[0111] The preparation process parameters of Examples 1 to 8 and Comparative Examples 1 to 3 are shown in Table 1 below:

[0112] Table 1

[0113]

[0114] The positive electrode materials prepared in Example 1, Examples 5 and 6 and Comparative Examples 1 to 3 were subjected to electrochemical performance tests. The test steps are as follows:

[0115] 1) Single crystal LiNi without LATP coating 0.65 Co 0.15 Mn 0.20 O2, the positive electrode materials prepared in Examples 1, 5 and 6 and Comparative Examples 1 to 3 were assembled to form CR2032 button batteries. The first capacity and efficiency test conditions were 25°C, 3.0-4.4V, and charge and discharge at 0.1C / 0.1C. 0.65 Co 0.15 Mn 0.20 The first charge and discharge curves of the CR2032 button batteries assembled in Example 1 and Comparative Example 1 are as follows: Figure 3 As shown in the figure; the cycle test conditions are 45 ° C, 3.0 ~ 4.5 V, according to 0.5C / 1.0C charge and discharge, a total of 50 cycles, the single crystal LiNi without LATP coating 0.65 Co 0.15 Mn 0.20 The cycle performance curves of the CR2032 button batteries assembled in Example 1 and Comparative Example 1 are as follows: Figure 4 As shown in the figure, DC resistance (DCR) = (terminal voltage V1 after 1 minute of discharge - voltage V2 before discharge) / discharge current I. 0.65 Co 0.15 Mn 0.20 The cycle DCR growth rate curves of the CR2032 button batteries assembled in Example 1 and Comparative Example 1 are as follows: Figure 5 The test results are shown in Table 2 below.

[0116] 2) A fully charged CR2032 button cell (4.4V, 0.1C) was disassembled, and the positive electrode was removed and placed in an electrolyte. After storage at 80°C for 30 days, the amount of Ni, Co, and Mn metal dissolution in the electrolyte was measured using ICP. The test results are shown in Table 3.

[0117] Table 2

[0118]

[0119] Table 3

[0120]

[0121]

[0122] Depend on Figure 1 and Figure 2 It can be clearly seen that there is a layer of coating material on the surface of the positive electrode material prepared in Example 1, and the coating material is LATP fast lithium ion conductor. Figure 3 The test results show that compared to the uncoated LATP-coated cathode material and the cathode material prepared in Comparative Example 1, the cathode material coated with the sintering aid and LATP (Example 1) significantly improved the battery's discharge specific capacity and initial efficiency, and significantly reduced the initial DCR. The amounts of Ni, Co, and Mn metal ion dissolution from the cathode materials prepared in Examples 1 and 5 shown in Table 3 were significantly lower than those from the cathode materials in Comparative Examples 1-3 and the uncoated cathode material. Figure 4 and Figure 5 The results show that the cycle retention rate and DCR growth rate of the cathode material prepared in Example 1 both show a good trend. These results indicate that LATP has high electronic conductivity, which can reduce the internal resistance of the cathode material and facilitate the lithium ion insertion and extraction process. In addition, LATP has high strength, which can improve the stability of the interface coating layer, effectively blocking the interface contact between the cathode material and the electrolyte, and reducing the interfacial side reactions between the two.

[0123] Compared to Example 1, the amount of Ni, Co, and Mn metal dissolution in the positive electrode material prepared in Example 5 was reduced, the discharge specific capacity was increased, the efficiency was slightly reduced, and the improvement in the initial DCR was less obvious, but the performance improvement was still significantly better than that of Comparative Example 1. The positive electrode material prepared in Comparative Example 1 showed a certain degree of improvement in performance compared to the positive electrode material not coated with LATP, but the degree of crystallization and structural stability of the coating layer material were still defective, resulting in overall performance worse than that of Example 1. This shows that the introduction of the sintering aid not only reduces the heat treatment temperature, but also increases the crystallization and structural stability of LATP, further improving the performance of LATP, thereby improving the electrochemical performance of the positive electrode material.

[0124] In Example 6, a high content of traditional commercial LATP is directly coated on the surface of the positive electrode material substrate. The discharge specific capacity of the obtained positive electrode material shows a downward trend, and its performance is significantly lower than that of Example 5. This shows that the use of aluminum source, titanium source and phosphorus source to crystallize and grow on the surface of the positive electrode material substrate to form a coating layer, and regulating the specific surface area of ​​the aluminum source, titanium source, phosphorus source and sintering aid can achieve a high content of LATP coating on the positive electrode material substrate without adversely affecting the electrochemical properties of the positive electrode material.

[0125] The metal dissolution amounts of Ni, Co, and Mn in the positive electrode materials obtained in Comparative Examples 2 to 3 are improved compared to those without coating, and are all reduced to a certain extent. Moreover, after reducing the specific surface area of ​​the sintering aid (Comparative Example 2), the electrochemical performance and metal dissolution of the positive electrode material are better than those of the positive electrode material without sintering aid (Comparative Example 1), but are relatively weaker than those of Example 1, and it is difficult to significantly improve the electrochemical performance and metal dissolution of the positive electrode material such as capacity and efficiency. The discharge specific capacity of Comparative Example 3 is close to that of the positive electrode material without LATP coating, indicating that the effect of using LATP, whose x is not within the scope of this application, as a coating material is not good.

[0126] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0127] The above-described embodiments merely represent several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art may make a number of variations and improvements without departing from the spirit of the present invention, and these variations and improvements fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be based on the appended claims, and the description and drawings shall be used to interpret the scope of the claims.

Claims

1. A positive electrode material, characterized in that The invention comprises a positive electrode material matrix and a coating layer coated on the surface of the positive electrode material matrix, wherein the material forming the coating layer comprises a solid electrolyte and a sintering aid, wherein the sintering aid comprises one or more of lithium metaborate, lithium tetraborate, lithium borate, lithium bis(oxalatoborate), boric acid and boron oxide, and the specific surface area of ​​the sintering aid is 50 to 500 m 2 / g; Wherein, the molecular formula of the solid electrolyte is Li 1+x Al x Ti 2-x (PO4)3, 0.1≤x≤1.5; the solid electrolyte and the sintering aid are in-situ coated on the surface of the positive electrode material matrix, and the specific steps of the in-situ coating include: The positive electrode material matrix, the sintering aid, a lithium source, an aluminum source, a titanium source and a phosphorus source are mixed and sintered.

2. The positive electrode material according to claim 1, wherein The mass ratio of the solid electrolyte to the positive electrode material matrix is ​​(0.01-10):

100.

3. The positive electrode material according to claim 1 or 2, characterized in that The mass ratio of the solid electrolyte to the sintering aid is 100:(0.1~50).

4. A method for preparing the positive electrode material according to any one of claims 1 to 3, characterized in that: The following steps are involved: The positive electrode material matrix, the solid electrolyte and the sintering aid are mixed and sintered; wherein the molecular formula of the solid electrolyte is Li 1+x Al x Ti 2-x (PO4)3, 0.1≤x≤1.

5.

5. The method for preparing the positive electrode material according to claim 4, wherein: The sintering process conditions include: In an oxygen-containing atmosphere with a pressure of 0~30Pa, the temperature is increased to 200℃~600℃ at a heating rate of 2~5℃ / min and kept at this temperature for 2~10h.

6. The method for preparing the positive electrode material according to claim 4, wherein: The solid electrolyte is prepared by a preparation method comprising the following steps: A lithium source, an aluminum source, a titanium source and a phosphorus source in a preset mass ratio are mixed and sintered.

7. The method for preparing the positive electrode material according to claim 4 or 5, wherein: The preparation method has at least one of the following characteristics: 1) The lithium source includes one or more of Li2CO3, LiOH, CH3COOLi and LiNO3; 2) The aluminum source includes Al2O3, Al(OH)3, C9H 21 One or more of AlO3, γ-AlOOH and Al(NO3)3∙9H2O; 3) The titanium source includes TiO2 and / or Ti(OH)4; 4) The phosphorus source includes NH4H2PO4 and / or (NH4)2HPO4.

8. A positive electrode sheet, characterized in that: The invention comprises a positive electrode current collector and a positive electrode active material layer formed on the surface of the positive electrode current collector, wherein the positive electrode active material in the positive electrode active material layer comprises the positive electrode material according to any one of claims 1 to 3.

9. A battery, characterized in that: Including the positive electrode sheet according to claim 8.

10. An electrical device, characterized in that: A battery comprising the battery of claim 9.

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