A non-stoichiometric lithium niobate combination-coated positive electrode material and a preparation method thereof

Abstract

The application belongs to the field of batteries, and discloses a positive electrode material coated with a non-stoichiometric lithium niobate combination and a preparation method thereof. 1.05 The non-stoichiometric lithium niobate combination includes at least two of LiNbO3, LiNbO3 and LiNbO3. 0.9 The application effectively improves the capacity and cycle performance of the positive electrode material through the non-stoichiometric lithium niobate combination.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more particularly to a cathode material coated with non-stoichiometric lithium niobate and its preparation method. Background Technology

[0002] Sodium-ion and lithium-ion batteries, as important components of modern technology, are widely used in the power systems of digital products, electric vehicles, and even spacecraft. One of the key factors affecting battery performance is the choice of cathode material, which is a critical factor limiting the energy density, charge / discharge rate, and safety of lithium batteries. Currently, conventional cathode materials are widely used globally, each with its own advantages and disadvantages. Therefore, many existing technological research directions focus on improving the performance of conventional cathode materials by doping or coating them with other materials.

[0003] For example, in prior art 1, Chinese patent application 202211554637.6 discloses a method for preparing high-energy-density lithium iron phosphate material, which uses niobium pentoxide as a dopant compound to dope the lithium iron phosphate material. The main function of niobium doping is to improve the stability of the crystal structure and suppress oxygen evolution, but it does not significantly improve the conductivity of the cathode material.

[0004] Therefore, prior art 2 uses niobium coating technology to improve the conductivity of the cathode material. Prior art 2: Chinese patent application 201711448285.5 discloses a method for preparing a nanofiber-like niobium pentoxide-coated sulfur-lithium-sulfur battery cathode material. It uses niobium pentoxide to coat the cathode material to improve the conductivity of the cathode material. However, as a coating layer, Nb is difficult to react and enter the crystal lattice, which does not help the stability of the material structure.

[0005] Therefore, it is necessary to find a technical solution that can improve both the structural stability and conductivity of the cathode material. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a cathode material coated with a non-stoichiometric lithium niobate combination. By using a non-stoichiometric lithium niobate combination, the cathode material can not only be coated to improve its conductivity, but also partially doped to enhance its structural stability, thereby effectively improving the overall performance of the cathode material.

[0007] Another objective of this invention is to provide a method for preparing a cathode material with non-stoichiometric lithium niobate combined coating, which achieves both doping and coating effects through a single sintering process.

[0008] To achieve the above objectives, this application discloses a non-stoichiometric lithium niobate composite coated cathode material, comprising a lithium or sodium-containing core layer material and a non-stoichiometric lithium niobate composite coated on the core layer material, wherein the non-stoichiometric lithium niobate composite comprises Li 1.05 NbO3, LiNbO3 and Li 0.9 At least two of NbO3.

[0009] Li 1.05 NbO3 can compensate for lithium volatilization during high-temperature sintering, maintain the integrity of the crystal structure, and prevent the collapse of the spinel phase due to lithium deficiency.

[0010] Li 0.9 The lithium-deficient environment provided by NbO3 introduces oxygen vacancies, enhances surface active sites, promotes electrolyte interface reaction kinetics, and inhibits manganese dissolution.

[0011] The normal stoichiometry in LiNbO3 provides a stable lattice framework, balancing volume changes during electrochemical processes.

[0012] The technical solution of the present invention has the following characteristics:

[0013] (1) Through Li 1.05 NbO3 and Li 0.9 The NbO3 combination effectively improves the stability of the crystal structure while inhibiting the dissolution of manganese, and effectively improves the cycle stability while ensuring the material capacity.

[0014] (2) via Li 1.05 The combination of NbO3 and LiNbO3 synergistically strengthens the stability of the structure, and the excess lithium prevents the decrease in conductivity of the cathode material.

[0015] (3) Through Li 0.9 The combination of NbO3 and LiNbO3 can stabilize the crystal framework while promoting the reaction kinetics at the electrolyte interface.

[0016] Furthermore, this application also experimentally discovered that when Li is used... 1.05 NbO3, LiNbO3 and Li 0.9 When NbO3, the three components are combined in a specific ratio, they can synergistically enhance electrical performance, further improving the electrical properties of the cathode material. The optimal non-stoichiometric lithium niobate combination obtained through experiments includes Li... 1.05 NbO3, LiNbO3 and Li 0.9 NbO3, L i1.05 NbO3, LiNbO3 and Li 0.9 The mass ratio of NbO3 is 0.35-1:0.45-1:0.25-1.

[0017] In theory, the key to the technical solution of this application lies in using a non-stoichiometric lithium niobate combination to coat the cathode material, thereby further improving the performance of the cathode material. Therefore, the core material itself is not very limited.

[0018] Preferably, the lithium or sodium-containing core material includes one of lithium cobalt oxide, lithium nickel oxide, lithium multi-element oxide, lithium manganese oxide, lithium iron phosphate, sodium nickel oxide, sodium manganese oxide, and sodium iron oxide.

[0019] This invention also discloses a method for preparing a cathode material with non-stoichiometric lithium niobate composite coating, comprising the following steps:

[0020] Step 1: Preparation of non-stoichiometric lithium niobate combination;

[0021] Step 2: Prepare the raw materials for the core layer material;

[0022] Step 3: Mix the non-stoichiometric lithium niobate combination with the raw materials, and then calcine them.

[0023] Furthermore, the specific operation of step 1 is as follows:

[0024] Step 11: Prepare lithium carbonate and niobium pentoxide;

[0025] Step 12: After mixing lithium carbonate and niobium pentoxide, the mixture is ball-milled, calcined, and cooled to obtain non-stoichiometric lithium niobate;

[0026] Among them, Li preparation 1.05 The molar ratio of lithium to niobium in lithium carbonate and niobium pentoxide of NbO3 is 1.05:1;

[0027] In the preparation of LiNbO3, the molar ratio of lithium to niobium in lithium carbonate and niobium pentoxide is 1:1.

[0028] Preparation of Li 0.9 The lithium to niobium molar ratio in lithium carbonate and niobium pentoxide of NbO3 is 0.9:1.

[0029] It should be noted that the non-stoichiometric lithium niobate combination of this application can be prepared using other lithium and niobium sources, not just lithium carbonate and niobium pentoxide. Those skilled in the art can refer to existing technologies to select appropriate lithium and niobium sources and preparation methods to prepare the corresponding non-stoichiometric lithium niobate combination.

[0030] Furthermore, the specific operation of calcination in step 12 is as follows: under an air atmosphere, the temperature is raised to 800-1000℃ and calcined for 1-2 hours, and then the temperature is raised to 1200-1300℃ and calcined for 6-12 hours; the heating rate is 10-50℃ / h.

[0031] The specific operation of ball milling in step 12 is as follows: using zirconium beads with a diameter of 1 to 5 mm to ball mill the mixed lithium carbonate and niobium pentoxide, the ball milling speed is 100 to 300 r / min, and the ball milling time is 5 to 12 h.

[0032] The specific cooling operation in step 12 is as follows: the molten material after calcination is quickly poured out and immersed in the cooling liquid, and cooled to room temperature within 1-5 minutes; the cooling liquid can be at least one of deionized water, ethanol, and ethylene glycol.

[0033] Furthermore, the raw materials for preparing the core layer material in step 2 are lithium compounds and manganese compounds;

[0034] The specific operation of step 3 is as follows:

[0035] Step 31: Mix the lithium compound, manganese compound and non-stoichiometric lithium niobate together to obtain a mixture;

[0036] Step 32: Calcine the mixture in air at 800-900℃ for 12-14 hours.

[0037] The lithium manganese oxide cathode material currently has the following problems: (1) lattice distortion caused by the Ginger-Taylor effect; (2) electrolyte decomposition caused by the high oxidizing power of manganese; (3) destruction of the spinel structure of lithium manganese oxide caused by the dissolution of manganese. Therefore, the advantage of the technical solution of this application is that the lithium manganese oxide cathode material can give full play to the role of the stoichiometric lithium niobate combination as the core layer material.

[0038] Preferably, the molar ratio of lithium to manganese in the lithium compound and manganese compound is 1.02 to 1.05:2; preferably, the manganese compound is at least one of manganese tetroxide and electrolytic manganese dioxide; and the lithium compound is at least one of lithium oxide, lithium hydroxide, and lithium carbonate.

[0039] More preferably, in the preparation method of this application, the weight of niobium in the non-stoichiometric lithium niobate combination is 0.1 to 0.5 wt% of the theoretical weight of lithium manganese oxide.

[0040] In the preferred embodiment of this application, the lithium compound is lithium carbonate and the manganese compound is manganese tetroxide; the theoretical weight of lithium manganese oxide is (weight of manganese tetroxide + weight of lithium carbonate) × 0.945, and this formula for calculating the theoretical weight of lithium manganese oxide is a formula obtained through multiple experiments.

[0041] In the technical solution of this application, niobium is doped with lithium and manganese sources. During the high-temperature calcination process, lithium manganese oxide is synthesized first at a low temperature (approximately 500°C), and niobium is initially adsorbed onto the surface of the formed lithium manganese oxide to form a coating layer. Subsequently, as the temperature increases, and due to the presence of niobium... 5+ radius and Mn 3+ Similarly, some Nb diffuses into the lithium manganese oxide lattice, which can suppress Jahn-Teller distortion and improve the cycle performance of the cathode material.

[0042] Preferably, the non-stoichiometric lithium niobate combined coated cathode material obtained in step 32 of this application is a block material, and a non-stoichiometric lithium niobate combined coated cathode material with a certain median particle size can be obtained by means of crushing, grading and other methods; more preferably, the particle size D50 of the non-stoichiometric lithium niobate combined coated cathode material is 8~12um.

[0043] The beneficial effects of this invention are:

[0044] This application effectively improves the capacity and cycle performance of cathode materials by combining non-stoichiometric lithium niobate. Detailed Implementation

[0045] In the description of this invention, it should be noted that unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0046] Product Information:

[0047] Manganese tetroxide: Purchased from Sinosteel Tianyuan Co., Ltd.;

[0048] Lithium carbonate: purchased from Hunan Jinkai Recycling Technology Co., Ltd.;

[0049] Niobium pentoxide: Purchased from CITIC Metals Co., Ltd.

[0050] In the following examples and comparative examples, the theoretical weight of lithium manganese oxide is calculated as (weight of manganese tetroxide + weight of lithium carbonate) × 0.945. This formula for calculating the theoretical weight of lithium manganese oxide is derived from numerous experiments.

[0051] Li in non-stoichiometric lithium niobate combinations 1.05 NbO3, LiNbO3 and Li 0.9 NbO3 was prepared using the following steps:

[0052] Niobium pentoxide and lithium carbonate were mixed at a molar ratio of Li / Nb of 1.05:1 (Li 1.05 NbO3), 50:50(LiNbO3) or 0.9:1(Li0.9 The mixture was prepared by mixing NbO3 in a specific molar ratio, and then ball-milled at 200 rpm for 9 h using 3 mm diameter zirconium beads. The mixture was then calcined at 900 °C for 1.5 h at a heating rate of 30 °C / h, followed by calcination at 1250 °C for 10 h at a heating rate of 30 °C / h. The molten material was then rapidly poured out and immersed in deionized water, cooled to room temperature within 3 min, calcined again, and then rapidly cooled and crushed to obtain Li particles with a particle size D50 = 6 μm. 0.9 NbO3, LiNbO3, Li 1.05 NbO3.

[0053] Example 1

[0054] A non-stoichiometric lithium niobate composite-coated cathode material is prepared by the following method:

[0055] 8.5 kg of manganese tetroxide, 2.11 kg of lithium carbonate, and 31.89 g of non-stoichiometric lithium niobate were mixed evenly in a small high-speed mixer to obtain a mixture. The mixture was then calcined at 800°C for 14 h in an air atmosphere roller furnace. After calcination, it was naturally cooled to room temperature, pulverized, and sieved to obtain a cathode material coated with non-stoichiometric lithium niobate.

[0056] The non-stoichiometric lithium niobate combination is Li 1.05 NbO3 and Li 0.9 The composition of NbO3, and Li 1.05 NbO3 and Li 0.9 The mass ratio of NbO3 is 0.75:0.60;

[0057] In the non-stoichiometric lithium niobate combination, the weight of niobium is 0.2 wt% of the theoretical weight of lithium manganese oxide.

[0058] Example 2

[0059] A non-stoichiometric lithium niobate composite-coated cathode material is prepared by the following method:

[0060] 8.5 kg of manganese tetroxide, 2.11 kg of lithium carbonate, and 31.95 g of non-stoichiometric lithium niobate were mixed evenly in a small high-speed mixer to obtain a mixture. The mixture was then calcined at 800°C for 14 h in an air atmosphere roller furnace. After calcination, it was naturally cooled to room temperature, pulverized, and sieved to obtain a cathode material coated with non-stoichiometric lithium niobate.

[0061] The non-stoichiometric lithium niobate combination is Li 1.05 A composition of NbO3 and LiNbO3, and Li 1.05The mass ratio of NbO3 to LiNbO3 is 0.75:0.88;

[0062] In the non-stoichiometric lithium niobate combination, the weight of niobium is 0.2 wt% of the theoretical weight of lithium manganese oxide.

[0063] Example 3

[0064] 8.5 kg of manganese tetroxide, 2.11 kg of lithium carbonate, and 31.85 g of non-stoichiometric lithium niobate were mixed evenly in a small high-speed mixer to obtain a mixture. The mixture was then calcined at 800°C for 14 h in an air atmosphere roller furnace. After calcination, it was naturally cooled to room temperature, pulverized, and sieved to obtain a cathode material coated with non-stoichiometric lithium niobate.

[0065] The non-stoichiometric lithium niobate combination is LiNbO3 and Li 0.9 A composition of NbO3, and LiNbO3 and Li 0.9 The mass ratio of NbO3 is 0.88:0.60;

[0066] In the non-stoichiometric lithium niobate combination, the weight of niobium is 0.2 wt% of the theoretical weight of lithium manganese oxide.

[0067] Example 4

[0068] A non-stoichiometric lithium niobate composite-coated cathode material is prepared by the following method:

[0069] 8.5 kg of manganese tetroxide, 2.11 kg of lithium carbonate, and 31.90 g of non-stoichiometric lithium niobate were mixed evenly in a small high-speed mixer to obtain a mixture. The mixture was then calcined at 800°C for 14 h in an air-atmosphere roller furnace. After calcination, it was naturally cooled to room temperature, pulverized, and sieved to obtain a cathode material coated with non-stoichiometric lithium niobate.

[0070] The non-stoichiometric lithium niobate combination is Li 1.05 NbO3, LiNbO3 and Li 0.9 The composition of NbO3, and Li 1.05 NbO3, LiNbO3 and Li 0.9 The mass ratio of NbO3 is 0.75:0.88:0.60;

[0071] In the non-stoichiometric lithium niobate combination, the weight of niobium is 0.2 wt% of the theoretical weight of lithium manganese oxide.

[0072] Example 5

[0073] A non-stoichiometric lithium niobate composite-coated cathode material is prepared by the following method:

[0074] 8.5 kg of manganese tetroxide, 2.087 g of lithium carbonate, and 15.91 g of non-stoichiometric lithium niobate were mixed evenly in a small high-speed mixer to obtain a mixture. The mixture was then calcined at 900 °C for 12 h in an air atmosphere roller furnace. After calcination, it was naturally cooled to room temperature, pulverized, and sieved to obtain a cathode material coated with non-stoichiometric lithium niobate.

[0075] The non-stoichiometric lithium niobate combination is Li 1.05 NbO3, LiNbO3 and Li 0.9 The composition of NbO3, and Li 1.05 NbO3, LiNbO3 and Li 0.9 The mass ratio of NbO3 is 0.75:0.88:0.60;

[0076] In the non-stoichiometric lithium niobate combination, the weight of niobium is 0.1 wt% of the theoretical weight of lithium manganese oxide.

[0077] Example 6

[0078] A non-stoichiometric lithium niobate composite-coated cathode material is prepared by the following method:

[0079] 8.5 kg of manganese tetroxide, 2.15 kg of lithium carbonate, and 80.04 g of non-stoichiometric lithium niobate were mixed evenly in a small high-speed mixer to obtain a mixture. The mixture was then calcined at 8500 °C for 13 h in an air atmosphere roller furnace. After calcination, it was naturally cooled to room temperature, pulverized, and sieved to obtain a cathode material coated with non-stoichiometric lithium niobate.

[0080] The non-stoichiometric lithium niobate combination is Li 1.05 NbO3, LiNbO3 and Li 0.9 The composition of NbO3, and Li 1.05 NbO3, LiNbO3 and Li 0.9 The mass ratio of NbO3 is 0.75:0.88:0.60;

[0081] In the non-stoichiometric lithium niobate combination, the weight of niobium is 0.5 wt% of the theoretical weight of lithium manganese oxide.

[0082] Example 7

[0083] The method is basically the same as in Example 4, except that the amount of the non-stoichiometric lithium niobate combination is 31.90 g; and the amount of Li in the non-stoichiometric lithium niobate combination is... 1.05 NbO3, LiNbO3 and Li 0.9 The mass ratio of NbO3 is 0.35:1:0.25.

[0084] Example 8

[0085] The method is basically the same as in Example 4, except that the amount of the non-stoichiometric lithium niobate combination is 31.88 g; and the amount of Li in the non-stoichiometric lithium niobate combination is... 1.05 NbO3, LiNbO3 and Li 0.9 The mass ratio of NbO3 is 1:0.45:1.

[0086] Example 9

[0087] The method is basically the same as in Example 4, except that the amount of the non-stoichiometric lithium niobate combination is 3.19 g; and the weight of niobium in the non-stoichiometric lithium niobate combination is 0.02 wt% of the theoretical weight of lithium manganese oxide.

[0088] Example 10

[0089] The method is basically the same as in Example 4, except that the amount of the non-stoichiometric lithium niobate combination is 95.69 g; and the weight of niobium in the non-stoichiometric lithium niobate combination is 0.6 wt% of the theoretical weight of lithium manganese oxide.

[0090] Comparative Example 1

[0091] 8.5 kg of manganese tetroxide and 2.11 kg of lithium carbonate were mixed evenly in a small high-speed mixer to obtain a mixture. The mixture was then calcined at 800°C for 14 hours in an air atmosphere roller furnace. After calcination, the mixture was naturally cooled to room temperature, crushed, graded, and sieved to obtain lithium manganese oxide material.

[0092] Comparative Example 2

[0093] This is essentially the same as Example 4, except that the non-stoichiometric lithium niobate combination is Li 1.05 The amount of NbO3 and non-stoichiometric lithium niobate combination used was 31.99 g.

[0094] Comparative Example 3

[0095] This is essentially the same as Example 4, except that the non-stoichiometric lithium niobate combination is Li 0.9 The amount of NbO3 and non-stoichiometric lithium niobate combination used was 31.76 g.

[0096] Comparative Example 4

[0097] It is basically the same as implementation 4, except that the non-stoichiometric lithium niobate combination is replaced with LiNbO3; the amount of LiNbO3 is 31.91g.

[0098] All-electric performance test

[0099] The obtained non-stoichiometric lithium niobate composite-coated cathode material was uniformly mixed with 97 wt% non-stoichiometric lithium niobate composite-coated cathode material, 1.5 wt% PVDF, and 1.5 wt% carbon nanotubes to prepare a coating slurry. The steps are as follows:

[0100] 1. Dissolve PVDF in NMP to prepare a slurry with a solid content of 8%, then add carbon nanotube slurry and mix and disperse at high speed for 1.5 h. Then add this product and knead and stir for 6 h. Add an appropriate amount of NMP to adjust the slurry viscosity to 4500-7500 mPa.s; obtain a positive electrode slurry for lithium batteries, and coat the positive electrode slurry onto aluminum foil.

[0101] 2. Graphite material, carboxymethyl cellulose and styrene-butadiene rubber are dissolved in deionized water at a mass ratio of 96.5:1.5:1, and the solid content is controlled at 50%. The mixture is then coated onto a copper foil current collector and vacuum dried to obtain the negative electrode sheet.

[0102] 3. After drying, rolling, powdering, welding of tabs, winding, electrolyte injection, and sealing, soft-pack batteries were prepared. Battery capacity, cycle life, and short-circuit tests were conducted. The test results are shown in Table 1.

[0103] Table 1. Results of All-Electrical Performance Tests

[0104]

[0105]

[0106] Results analysis:

[0107] As can be seen from the data in Table 1, the cathode materials prepared in Examples 1-10 of this case exhibit excellent performance in various electrical properties.

[0108] A comparison of data from Example 4 and Examples 1-3 reveals that this application... 1.05 NbO3, LiNbO3 and Li 0.9 When NbO3 is combined with other materials, even if the amount of niobium used for coating and doping is the same, the improvement in electrical performance in Example 4 is significantly stronger than that in Examples 1-3. This is likely because:

[0109] Li 0.9 NbO3 (lithium acceptor) and Li 1.05 NbO3 (lithium donor) constructs a core-shell-bridge structure through the ion conduction pathway of the stoichiometric phase LiNbO3 to promote contact and transport; during charge and discharge, it dynamically adjusts the local lithium concentration to suppress lithium dendrite formation and concentration polarization. The three factors work synergistically to improve the high-rate electrochemical performance of the lithium manganese oxide cathode.

[0110] Meanwhile, based on the data comparison of Examples 4-6, 9, and 10, it can be seen that when the same non-stoichiometric lithium niobate combination is used as the coating layer, the coating amount has a significant impact on the electrical performance of the cathode material. It is speculated that the performance first increases and then decreases. Therefore, it can be concluded that when the non-stoichiometric lithium niobate combination is used as the coating layer in this application, the weight of niobium element is most suitable at 0.2-0.5 wt%.

[0111] Based on the data comparison between Examples 4, 7, and 8, it can be seen that Li 1.05 NbO3, LiNbO3 and Li 0.9 When NbO3 is combined with other materials, the ratio of the three components also has a certain impact on the overall electrical performance of the cathode material.

[0112] A comparison of the data from Examples 1-3 and Comparative Examples 1-4 shows that the non-stoichiometric lithium niobate combination of this application can synergistically improve the electrical performance of the cathode material; however, different non-stoichiometric lithium niobate combinations have different focuses in improving the performance. A comparison of the data from Comparative Example 1 and Comparative Examples 2-3 shows that using Li alone... 1.05 NbO3, LiNbO3 or Li 0.9 When lithium manganese oxide is coated with NbO3, its electrical performance is improved in different directions, but the improvement is worse than that in Examples 1-3. This indicates that the combination of non-stoichiometric lithium niobate has a certain synergistic effect on improving the electrical performance of the cathode material.

[0113] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A non-stoichiometric lithium niobate combination-coated positive electrode material, characterized by, This includes a lithium or sodium-containing core layer material and a non-stoichiometric lithium niobate assembly coated on the core layer material, wherein the non-stoichiometric lithium niobate assembly includes Li 1.05 NbO3, LiNbO3 and Li 0.9 At least two of the NbO3; the weight of niobium in the non-stoichiometric lithium niobate combination is 0.2-0.5 wt% of the theoretical weight of lithium manganese oxide.

2. The non-stoichiometric lithium niobate composite-coated cathode material of claim 1, wherein, The lithium or sodium-containing core material includes one of lithium cobalt oxide, lithium nickel oxide, lithium multi-element oxide, lithium manganese oxide, lithium iron phosphate, sodium nickel oxide, sodium manganese oxide, and sodium iron oxide.

3. The non-stoichiometric lithium niobate composite-coated cathode material of claim 1 or 2, wherein, The non-stoichiometric lithium niobate combination includes Li 1.05 NbO3, LiNbO3 and Li 0.9 NbO3, L i1.05 NbO3, LiNbO3 and Li 0.9 The mass ratio of NbO3 is 0.35-1:0.45-1:0.25-1.

4. A method of producing a non-stoichiometric lithium niobate composite-coated positive electrode material according to any one of claims 1 to 3, characterized by, Includes the following steps: Step 1: Preparation of non-stoichiometric lithium niobate combination; Step 2: Prepare the raw materials for the core layer material; Step 3: Mix the non-stoichiometric lithium niobate combination with the raw materials, and then calcine them.

5. The method for preparing the cathode material with non-stoichiometric lithium niobate composite coating according to claim 4, characterized in that, The specific operation of step 1 is as follows: Step 11: Prepare lithium carbonate and niobium pentoxide; Step 12: After mixing lithium carbonate and niobium pentoxide, the mixture is ball-milled, calcined, and cooled to obtain non-stoichiometric lithium niobate; wherein the Li 1.05 The lithium to niobium molar ratio in the lithium carbonate and the niobium pentoxide used to prepare LiNbO3 is 1.05:

1. In the preparation of LiNbO3, the molar ratio of lithium to niobium in lithium carbonate and niobium pentoxide is 1:

1. Li 0.9 The lithium to niobium molar ratio in the lithium carbonate and the niobium pentoxide used to prepare LiNbO3 was 0.9:

1.

6. The method for preparing the cathode material with non-stoichiometric lithium niobate composite coating according to claim 5, characterized in that, The specific operation of calcination in step 12 is as follows: heat to 800-1000℃ and calcine for 1-2 hours, then heat to 1200-1300℃ and calcine for 6-12 hours; the heating rate is 10-50℃ / h.

7. The method for preparing the non-stoichiometric lithium niobate combined-coated cathode material according to any one of claims 4-6, characterized in that, The raw materials for preparing the core layer material in step 2 are lithium compounds and manganese compounds; The specific operation of step 3 is as follows: Step 31: Mix the lithium compound, manganese compound and non-stoichiometric lithium niobate together to obtain a mixture; Step 32: Calcine the mixture in air at 800-900℃ for 12-14 hours.

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