A NC@Li5FeO 4-X N y Lithium supplement and its preparation and application

Abstract

The present invention belongs to the technical field of lithium-ion batteries, and specifically relates to N‑C@Li5FeO 4‑X Ny lithium supplement, has a core-shell structure, in which the core is N-hybridized Li5FeO4, and the chemical formula is Li5FeO 4‑X Ny, 3y=2x, the shell is N-doped amorphous carbon; the y is 0.1-0.4. The present invention also provides a preparation method of the material and its application in lithium-ion batteries. Studies have found that the material of the present invention, thanks to the N co-hybridization of the core-shell, can effectively improve the stability of the structure and air resistance, and improve its lithium supplementation effect. For example, it can participate in the construction of the negative electrode SEI in priority to the positive electrode active material, improve the initial efficiency of the battery, and improve the electrochemical performance.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage devices, and in particular relates to a lithium supplement and a preparation method of a lithium ion battery and a lithium ion battery. Background Art

[0002] Lithium ion battery (LIB) is currently the most promising and fastest-growing high-efficiency secondary battery, with many advantages such as high specific energy, low self-discharge, good cycle performance, and no memory effect.

[0003] Lithium in lithium-ion batteries + All of them come from the positive electrode material, and the negative electrode generally uses graphite material. When the battery is charged for the first time, the negative electrode surface of the lithium-ion battery consumes Li + The formation of a layer of SEI film causes the initial charge and discharge capacity loss problem (Initial Capacity Loss, ICL). The ICL of lithium-ion batteries with graphite negative electrodes is about 7% to 10%. High-capacity silicon negative electrode materials are gradually being used in lithium-ion batteries, but the ICL of silicon negative electrodes is as high as 50% to 70%. Therefore, it is extremely important to develop a simple and efficient lithium replenishment technology.

[0004] The current lithium replenishment scheme is mainly negative electrode lithium replenishment, which can be subdivided into primary battery lithium replenishment technology and auxiliary anode lithium replenishment technology. However, research results show that the existing lithium replenishment technology has the following problems: the lithium insertion current of the primary battery lithium replenishment is uncontrollable, the production process is extremely demanding and there are safety hazards; the auxiliary anode lithium replenishment is difficult to produce continuously and is prone to safety hazards. In recent years, domestic and foreign researchers have gradually turned their attention to positive electrode lithium replenishment. Positive electrode lithium replenishment is to select a positive electrode material with a high lithium content in addition to the traditional positive electrode material, mix it with the traditional positive electrode material in a certain proportion and use it as a new positive electrode material for battery assembly. During the first charge and discharge process, the excess Li released by the high-lithium-containing positive electrode material as an additive + It will fill the irreversible Li + loss, thereby reducing the ICL of the entire battery. Compared with negative electrode lithium replenishment technology, positive electrode lithium replenishment is safer and easier to industrialize. It does not require changes to the existing equipment and processes of the factory, and is a very promising lithium replenishment technology. However, the high-lithium positive electrode material required for positive electrode lithium replenishment still needs further research. In other words, the core of positive electrode lithium replenishment technology lies in finding a positive electrode material with high lithium content, which can release lithium to the maximum extent under the charge and discharge conditions of existing batteries, and is low-cost and easy to prepare.

[0005] Li5FeO4 is a lithium-rich transition metal oxide with an inverse fluorite structure. It has a very high specific capacity of up to 867mAh / g. Its initial charge and discharge efficiency is very low. It can remove lithium to the maximum extent and replenish the ICL on the negative electrode. Therefore, Li5FeO4 has great application potential in solving the ICL problem of lithium-ion batteries. However, the sintering process conditions for the preparation of traditional Li5FeO4 reported so far are harsh, the air stability is extremely poor, the synthesized Li5FeO4 has a large particle size, and the electronic conductivity is low, which affects the electrochemical performance and application of Li5FeO4. Summary of the invention

[0006] In order to solve the shortcomings and defects of the prior art, the first object of the present invention is to provide a NC@Li5FeO 4-X Ny lithium supplement is designed to improve its structure and air stability and improve the lithium supplement effect.

[0007] The second object of the present invention is to provide a NC@Li5FeO 4-X The preparation method of the Ny lithium supplement agent aims to obtain a material with uniform and dense carbon coating, good structure and air resistance stability, and excellent lithium supplement performance.

[0008] The third object of the present invention is to provide the use of the lithium supplement additive in lithium ion batteries and the obtained positive electrode and battery.

[0009] A NC@Li5FeO 4-X Ny lithium supplement, has a core-shell structure, in which the core is N-hybridized Li5FeO4, and the chemical formula is Li5FeO 4-X Ny, 3y=2x, y is 0.1-0.4 (preferably 0.1-0.3); the shell is N-doped amorphous carbon;.

[0010] The present invention provides a new material having a core-shell structure, wherein the core is N-lattice hybridized Li5FeO4 (Li5FeO 4-X Ny), wherein the shell is amorphous carbon doped with N. Studies have found that, thanks to the N co-hybridization of the core-shell, the stability and air resistance of the structure can be effectively improved, and its lithium replenishment effect can be improved. For example, it can participate in the construction of the negative electrode SEI in priority to the positive electrode active material, improve the first efficiency of the battery, and improve the electrochemical performance.

[0011] The present invention discovers for the first time that N-to-lattice oxygen hybridization in Li5FeO4 and N-to-coated carbon doping can synergistically improve the structural stability and air stability of the material and significantly improve the lithium replenishment performance.

[0012] Preferably, in the material, the carbon content is 2-15 atm%; the nitrogen content is 0.1-2 atm%.

[0013] As a preferred option, NC@Li5FeO 4-X The particle size of Ny lithium supplement is less than or equal to 5μm; the specific surface area is 200~800m 2 ·g -1 .

[0014] The present invention also provides the NC@Li5FeO 4-X The preparation method of Ny lithium supplement comprises the following steps:

[0015] Step (1):

[0016] The mixed solution of carbon source, lithium source, iron source and surfactant is ball-milled and activated to obtain slurry; the weight ratio of carbon source to iron source is 0.05-0.8:1; the element molar ratio of Li:Fe in lithium source and iron source is 4.5-9.5:1; the addition amount of surfactant is 2-10wt% of iron source;

[0017] Step (2):

[0018] The slurry is sprayed to obtain a precursor; the spraying temperature is 160-200°C;

[0019] Step (3):

[0020] The precursor is subjected to ammoniation sintering in an ammonia atmosphere at a temperature of 600-900°C to obtain the NC@Li5FeO 4-X Ny lithium supplement.

[0021] The present invention innovatively obtains the carbon-coated precursor by spraying, and further cooperates with ammoniation roasting and coordinated control of various conditions, so that the grain and crystal phase structure can be controlled, and a new core-shell co-N hybrid material can be obtained. Studies have found that the obtained material has a uniform and dense coating layer, excellent structural stability and air resistance stability, and also has good ion-electron conductivity. Using this material as a lithium supplement additive can effectively improve the initial efficiency and improve the performance of the battery.

[0022] In the present invention, the synergy of the raw material ball milling activation-spraying-ammoniation roasting process and the combined control of process conditions (such as material ratio, temperature and other conditions) is the key to improving the unit cell and crystal phase structure, realizing core-shell co-doping with N, improving coating uniformity and density, and improving lithium replenishment performance.

[0023] In the present invention, the carbon source is a carbon-containing organic matter, preferably at least one of citric acid, glucose, sucrose, acetic acid, and p123;

[0024] Preferably, the lithium source is at least one of Li2O, Li2CO3, LiF, Li3PO4, and Li2C2O4; more preferably, it is at least one of Li2CO3, LiF, and Li2C2O4.

[0025] Preferably, the Fe source is at least one of Fe2O3, Fe3O4, iron powder, and FeC2O4; more preferably, it is at least one of Fe2O3 and Fe3O4.

[0026] Preferably, the surfactant is at least one of dodecyltrimethylammonium bromide, stearic acid, sodium dodecylbenzenesulfonate and polyvinylpyrrolidone;

[0027] Preferably, the weight ratio of the carbon source to the iron source is 0.1 to 0.3:1; more preferably 0.1 to 0.2:1;

[0028] Preferably, the element molar ratio of Li:Fe in the lithium source and the iron source is 5 to 6:1;

[0029] Preferably, the added amount of the surfactant is 2-4 wt % of the iron source.

[0030] The solvent in the ball milling activation process is at least one of water and alcohol;

[0031] Preferably, the alcohol is a C1-C4 monoalcohol or a polyol, preferably ethanol.

[0032] In the present invention, the raw materials are activated by ball milling with the assistance of a surfactant, which helps to further activate the materials and improve the performance of the prepared materials.

[0033] Preferably, the rotation speed of the ball mill is 200 to 400 r / min;

[0034] Preferably, the ball milling time is 1 to 15 h; more preferably 2 to 12 h; and even more preferably 2 to 4 h.

[0035] In the present invention, under the above-mentioned synergistically innovative raw materials and ball milling activation, spraying, ammoniating roasting and synergistic conditions are further coordinated to help further improve structural stability, air resistance stability and lithium supplementation performance.

[0036] Preferably, the temperature of the spray treatment is 160-180°C;

[0037] Preferably, the feed rate during the spray treatment process is 10 to 30 ml / min.

[0038] In the present invention, under the ball milling-spraying process of the material, an innovative ammoniacal roasting process is further carried out, which can realize the internal-external co-doping of N in situ, which is beneficial to significantly improve the stability of the material and improve the lithium supplementation performance.

[0039] Preferably, the ammonia-containing atmosphere is a pure ammonia atmosphere, or a mixture of ammonia and a protective atmosphere.

[0040] The ammonia atmosphere can be provided by introduced ammonia or by materials that can be converted into ammonia at the required calcination temperature.

[0041] Preferably, in the ammonia-containing atmosphere, the volume content of ammonia is greater than or equal to 20%, for example, 50 to 100%.

[0042] Preferably, the calcination temperature is 600-750° C., and more preferably 700-750° C. At this preferred sintering temperature, the electrochemical properties of the obtained material can be further improved.

[0043] Preferably, the calcination time is 20 to 48 hours; more preferably, it is 20 to 30 hours.

[0044] The present invention also includes NC@Li5FeO prepared by the preparation method 4-X Ny. The material has the physical and chemical properties imparted by the preparation method, has better structural stability and air resistance stability, and has better lithium supplementation performance.

[0045] In the present invention, the NC@Li5FeO 4-X The initial charge capacity of Ny is 450-750 mAh g -1 The initial charge and discharge efficiency is 1-10%, the particle size is less than 5 μm, and the specific surface area is 200-800 m 2 ·g -1 .

[0046] The present invention also provides the NC@Li5FeO 4-X Application of Ny composite lithium supplement additive as an additive for preparing lithium ion batteries;

[0047] Preferably, it is used to prepare the positive electrode of a lithium ion battery;

[0048] Preferably, it is used to prepare positive electrode materials for lithium-ion batteries.

[0049] In the present invention, the NC@Li5FeO 4-X Lithium-ion batteries and their associated components and materials are prepared using Ny composite lithium supplement additives.

[0050] The present invention also provides a lithium-ion battery lithium supplement positive electrode material, comprising a positive electrode active material and the NC@Li5FeO 4-X Ny composite lithium supplement additive.

[0051] The positive electrode active material may be an existing conventional positive electrode active material.

[0052] Preferably, the positive electrode active material is at least one of LiCoO2, LiFePO4, and NCM ternary materials;

[0053] Preferably, the NC@Li5FeO 4-X The weight percentage of Ny composite lithium supplement additive is 2-15%; more preferably 3-8%; more preferably 3-5%; the study found that NC@Li5FeO 4-X When the Ny lithium supplement material is controlled within the above range, the performance of the additive can be further exerted, the electrical performance can be further improved, and the initial charge and discharge coulomb efficiency can be improved.

[0054] In the present invention, the lithium-supplementing positive electrode material, in addition to the lithium-supplementing additive and the positive electrode active material, also contains other components allowed to be added to the positive electrode material, such as a conductive agent, a binder, etc.

[0055] The conductive agent can be a material with conductive properties that can be used for the positive electrode and is known in the industry; for example, at least one of acetylene black and Ketjen black. The weight percentage of the conductive agent is 1 to 15%, preferably 5 to 10%.

[0056] The binder can be a material known in the industry that can be used to bond the positive electrode components to each other; for example, it can be at least one of PVDF and PTFE. The weight percentage of the binder is 1 to 15%, preferably 5 to 10%.

[0057] In the present invention, the balance is the positive electrode active material.

[0058] In the present invention, the preparation method of the lithium-supplementing positive electrode material comprises slurrying the lithium-supplementing additive, positive electrode active material, conductive agent, binder and solvent to obtain positive electrode slurry, coating the positive electrode slurry on the surface of the positive electrode collector, curing, and compounding on the surface of the positive electrode collector to obtain the lithium-supplementing positive electrode material.

[0059] The present invention also provides a lithium-ion battery, which includes the NC@Li5FeO4-XNy composite lithium-replenishing additive; preferably, includes the lithium-replenishing positive electrode material.

[0060] In the present invention, the lithium-ion battery, except for the positive electrode containing the NC@Li5FeO4-XNy composite lithium supplement additive of the present invention, other components and materials can be known. For example, the negative electrode active material is one or more of graphite, hard carbon, and silicon-carbon materials.

[0061] The lithium-replenishing positive electrode material is used to replenish lithium in the assembled lithium-ion battery. Preferably, the lithium-replenishing treatment is a charge-discharge cycle. The first charge is charged with a constant current or constant voltage of 0.02-0.1C, and the cut-off voltage is 4.0-4.5V. The first discharge is discharged with a constant current of 0.02-0.1C, and the cut-off voltage is 1.5-2.0V. A small current is used during charging to completely remove the lithium in the material, and a large current is used during discharge to destroy the material structure and prevent the lithium from returning.

[0062] As a general technical concept, the present invention also provides a lithium-ion battery assembled from the lithium-supplementing positive electrode material. The initial charge and discharge coulomb efficiency of the lithium-ion battery is 90-99%.

[0063] Compared with the prior art, the advantages of the present invention are:

[0064] 1. The present invention provides a new material, which significantly improves the structural stability and air stability, and significantly improves the lithium replenishment performance based on the synergy of N to lattice oxygen hybridization in Li5FeO4 and N to carbon doping; research has found that it can effectively reduce the capacity loss problem of the battery during the first charge and discharge process, and improve the energy density and cycle performance of the entire battery.

[0065] 2. In view of the problems such as the harsh conditions of the existing Li5FeO4 preparation process, large grains of the obtained materials, low crystal phase purity, uneven coating, unsatisfactory air stability and electrochemical performance, the present invention is innovatively based on the coordination of the raw material ball milling activation-spraying-ammoniation roasting process, which can realize the lattice oxygen N hybridization of the core and simultaneously realize the N doping of the coated carbon, so that the size of the crystal nucleus and the crystal structure can be effectively improved, the collapse of the crystal nucleus structure can be avoided, and the stability of the structure can be improved. In addition, a uniform and dense coating layer can be formed to improve air stability and lithium supplementation performance. The material obtained by the synthesis method of the present invention has a smaller particle size and a high specific surface area. The high specific surface area can provide more active sites for the action of active ions. In addition, the method of the present invention has loose environmental requirements, can be co-coated with existing positive electrode materials, has a simple process, is easy to control and is low in cost.

[0066] 3. In the present invention, C-coated and N-substituted Li5FeO 4-X Ny has a synergistic effect on the air stability of Li5FeO4 and can effectively improve the stability of the material in air. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 NC@Li5FeO 4-X Ny's graph;

[0068] Figure 2 This is the cycle diagram of the material prepared in Example 1 at 0.1C. DETAILED DESCRIPTION

[0069] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully in combination with preferred embodiments below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0070] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0071] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0072] Embodiment 1:

[0073] 1. Preparation of lithium supplement materials

[0074] A method using NC@Li5FeO 3.7 N 0.2 A method for preparing a lithium-ion battery containing a lithium supplement comprises the following steps:

[0075] (1) Li2O, Fe2O3, glucose, and dodecyltrimethylammonium bromide were ball-milled in anhydrous ethanol for 2 h at a ball-milling speed of 200 r / min;

[0076] The molar ratio of Li / Fe in Li2O and Fe2O3 is 5.5:1;

[0077] The mass ratio of Fe2O3 to glucose is 1:0.2;

[0078] Dodecyltrimethylammonium bromide is 2% of the mass of Fe2O3;

[0079] (2) spraying the slurry obtained in step (1) at 160° C. to obtain a uniformly mixed precursor at a feed rate of 30 ml / min;

[0080] (3) The precursor obtained in step (2) was placed in an ammonia atmosphere and sintered at 700°C for 24 hours. After cooling, a uniform NC@Li5FeO 3.7 N 0.2Among them, the C content is 10atm%; the N content is 1%; the particle size is 1μm; the specific surface area is 400m 2 ·g -1 .

[0081] 2. Preparation of positive electrode

[0082] NCM811 (75wt%), NC@Li5FeO 3.7 N 0.2 After uniformly mixing PVDF (5wt%), SuperP (10wt%) and PVDF (10wt%), the positive electrode sheet is obtained by slurry preparation, coating, drying and rolling.

[0083] 3. Negative electrode preparation

[0084] After graphite (90wt%), SuperP (5wt%) and PVDF (5wt%) are uniformly mixed, the negative electrode sheet is obtained by slurry preparation, coating, drying and rolling.

[0085] 4. After assembling the positive and negative electrode sheets, a lithium-ion battery is obtained, and lithium replenishment of the negative electrode material is achieved in the first charge and discharge cycle.

[0086] Example 2

[0087] Compared with Example 1, the only difference is that the iron source is Fe3O4, the Li / Fe stoichiometric ratio is 6:1, and the other conditions are the same as Example 1.

[0088] Example 3

[0089] Compared with Example 1, the only difference is that the iron source is FeC2O4, the Li / Fe stoichiometric ratio is 5:1, and the other conditions are the same as Example 1.

[0090] Example 4

[0091] Compared with Example 1, the only difference is that the mass ratio of glucose to Fe2O3 is 0.1; other conditions are the same as Example 1.

[0092] Example 5

[0093] Compared with Example 1, the only difference is that citric acid is used as the carbon source, and the mass ratio of citric acid to Fe2O3 is 0.3; the surfactant is sodium dodecylbenzene sulfonate, and the mass ratio of citric acid to Fe2O3 is 0.1. Other conditions are the same as in Example 1.

[0094] Example 6

[0095] Compared with Example 1, the only difference is that the ball milling time in step (2) is 12 hours; the temperature of the spray treatment is 200° C., and the other conditions are the same as in Example 1.

[0096] Example 7

[0097] Compared with Example 1, the only difference is that the temperature of the ammoniation roasting process is 900° C. and the time is 20 hours. Other conditions are the same as Example 1.

[0098] Example 8

[0099] Compared with Example 1, the only difference is that the temperature of the ammoniation calcination process is 850°C, and the other conditions are the same as Example 1. 3.775 N 0.15 .

[0100] Example 9

[0101] Compared with Example 1, the only difference is that the temperature of the ammoniation calcination process is 600°C and the time is 30 hours. Other conditions are the same as Example 1. 3.55 N 0.3 .

[0102] Example 10

[0103] Compared with Example 1, the only difference is that in the positive electrode material, NC@Li5FeO 3.7 N 0.2 The content is 3wt%; SuperP (10wt%) and PVDF (10wt%), NCM811 (77wt%).

[0104] Embodiment 11

[0105] Compared with Example 1, the only difference is that in the positive electrode material, NC@Li5FeO 3.7 N 0.2 The content is 8wt%; SuperP (10wt%) and PVDF (10wt%), NCM811 (72wt%).

[0106] Example 12

[0107] Compared with Example 1, the only difference is that in the positive electrode material, the positive electrode active material is LiFePO4, and the other conditions are the same as Example 1.

[0108] Comparative Example 1

[0109] Compared with Example 1, the only difference is that sintering is carried out under argon atmosphere in step (3), and other conditions are the same as Example 1.

[0110] Comparative Example 2

[0111] Compared with Example 1, the only difference is that the Li2O source and the Fe2O3 source are first sintered under ammonia conditions (the calcination temperature is 800°C and the time is 24h), and then they are coated with glucose, and then carbonized under argon atmosphere (the carbonization temperature is 800°C and the time is 2h). The other conditions are the same as Example 1; the N-doped core @C coated material is obtained.

[0112] Comparative Example 3

[0113] Compared with Example 1, the only difference is that the temperature of the ammoniation sintering is 500°C.

[0114] Comparative Example 4

[0115] Compared with Example 1, the only difference is that the temperature of the ammoniation sintering is 1000°C.

[0116] Comparative Example 5

[0117] Compared with Example 1, the only difference is that the mass ratio of Fe2O3 source to glucose is 1:1.5.

[0118] Comparative Example 6

[0119] Compared with Example 1, the only difference is that in step (1), a magnetic stirring step is used to replace ball milling.

[0120] Comparative Example 7

[0121] Compared with Example 1, the only difference is that no spray treatment is performed, but the slurry is placed in an oven (temperature is 160° C.) for treatment for 12 hours.

[0122] Comparative Example 8

[0123] Compared with Example 1, the only difference is that the outlet temperature of the spray treatment in step (1) is 110°C.

[0124] Performance data:

[0125] 1. Air stability test

[0126] The cyclic stability data of the lithium supplement additives prepared in each case after being stored in an air atmosphere at a temperature of 30°C and a humidity of 30% for different periods of time are shown in Table 1:

[0127] Table 1

[0128]

[0129]

[0130] Note: The 0h mentioned above refers to materials not exposed to air, for example, stored under Ar atmosphere.

[0131] 2. Full battery cycle data:

[0132] The test results are shown in Table 2:

[0133] Table 2

[0134]

[0135]

[0136] It can be seen from the embodiments and comparative examples that the technical solution of the present invention can effectively improve stability and improve its cyclic stability under air resistance.

Claims

1. NC@Li5FeO 4-X Ny lithium supplement, characterized in that It has a core-shell structure, in which the core is N-hybridized Li5FeO4, and the chemical formula is Li5FeO 4-X Ny, 3y=2x, y is 0.1~0.4, and the shell is N-doped amorphous carbon.

2. NC@Li5FeO as claimed in claim 1 4-X Ny lithium supplement, characterized in that The NC@Li5FeO 4-X In the Ny lithium supplement, the carbon content is 2~15atm; the N content is 0.1~2atm; NC@Li5FeO 4-X The particle size of Ny lithium supplement is less than or equal to 5μm; the specific surface area is 200~800m 2 ·g -1 .

3. NC@Li5FeO according to claim 1 or 2 4-X The preparation method of Ny lithium supplement is characterized in that: The following steps are involved: Step (1): The mixed solution of carbon source, lithium source, iron source and surfactant is ball-milled and activated to obtain slurry; the weight ratio of carbon source to iron source is 0.05-0.8:1; the molar ratio of Li:Fe in lithium source and iron source is 4.5-9.5:1; The amount of surfactant added is 2~10wt% of the iron source; Step (2): The slurry is sprayed to obtain a precursor; the spraying temperature is 160-200°C; Step (3): The precursor is subjected to ammoniation sintering in an ammonia atmosphere at a temperature of 600-900°C to obtain the NC@Li5FeO 4-X Ny lithium supplement.

4. NC@Li5FeO as claimed in claim 3 4-X The preparation method of Ny lithium supplement is characterized in that: The carbon source is carbon-containing organic matter.

5. NC@Li5FeO as claimed in claim 4 4-X The preparation method of Ny lithium supplement is characterized in that: The carbon source is at least one of citric acid, glucose, sucrose, acetic acid and p123.

6. NC@Li5FeO as claimed in claim 3 4-X The preparation method of Ny lithium supplement is characterized in that: The lithium source is at least one of Li2O, Li2CO3, LiF, Li3PO4, and Li2C2O4.

7. NC@Li5FeO as claimed in claim 3 4-X The preparation method of Ny lithium supplement is characterized in that: The Fe source is at least one of Fe2O3, Fe3O4, iron powder and FeC2O4.

8. NC@Li5FeO as claimed in claim 3 4-X The preparation method of Ny lithium supplement is characterized in that: The surfactant is at least one of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, stearic acid, sodium dodecylbenzenesulfonate and polyvinylpyrrolidone.

9. NC@Li5FeO as claimed in claim 3 4-X The preparation method of Ny lithium supplement is characterized in that: The ball mill speed is 200~400r / min.

10. NC@Li5FeO as claimed in claim 9 4-X The preparation method of Ny lithium supplement is characterized in that: The ball milling time is 1~15h.

11. NC@Li5FeO as claimed in claim 3 4-X The preparation method of Ny lithium supplement is characterized in that: The temperature of the spray treatment is 160~180℃.

12. NC@Li5FeO as claimed in claim 3 4-X The preparation method of Ny lithium supplement is characterized in that: The feed rate during the spray treatment process is 10~30ml / min.

13. NC@Li5FeO as claimed in claim 3 4-X The preparation method of Ny lithium supplement is characterized in that: In the ammonia-containing atmosphere, the volume content of ammonia is greater than or equal to 20%.

14. NC@Li5FeO as claimed in claim 3 4-X The preparation method of Ny lithium supplement is characterized in that: The calcination time is 20 to 48 hours.

15. NC@Li5FeO according to any one of claims 1 to 2 4-X Ny lithium supplement or NC@Li5FeO prepared by any one of the preparation methods of claims 3 to 14 4-X The application of Ny lithium supplement is characterized in that: It is used to prepare lithium-ion batteries.

16. The use according to claim 15, characterized in that It is used to prepare the positive electrode of lithium-ion batteries.

17. The use according to claim 16, characterized in that It is used to prepare positive electrode materials for lithium-ion batteries.

18. A lithium-ion battery lithium-supplementing positive electrode material, characterized in that: Comprising a positive electrode active material and NC@Li5FeO as claimed in any one of claims 1 to 2 4-X Ny lithium supplement or NC@Li5FeO prepared by any one of the preparation methods of claims 3 to 14 4- X Ny lithium supplement.

19. The lithium-ion battery lithium-supplementing positive electrode material according to claim 18, characterized in that: The positive electrode active material is at least one of LiCoO2, LiFePO4 and NCM ternary materials.

20. The lithium-ion battery lithium-supplementing positive electrode material according to claim 18, characterized in that: Also includes a conductive agent and a binder; Among them, the NC@Li5FeO 4-X The weight percentage of Ny lithium supplement is 2~15%; The weight percentage of the conductive agent is 1-15%; The weight percentage of the binder is 1-15%; The balance is positive electrode active material.

21. A lithium ion battery, characterized in that: The NC@Li5FeO comprising any one of claims 1 to 2 4-X Ny lithium supplement or NC@Li5FeO prepared by any one of the preparation methods of claims 3 to 14 4-X Ny lithium supplement.

22. The lithium ion battery according to claim 21, characterized in that Contains the lithium-supplementing positive electrode material according to any one of claims 18 to 20.

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