Preparation method of composite lithium-rich lithium supplementing additive

Abstract

The application discloses a preparation method of a composite lithium-rich lithium supplement additive, and lithium ferrite is taken as a core, NiO@ lithium salt is prepared by adopting an ALD atomic deposition method, and the composite lithium-rich lithium supplement additive is prepared by fully mixing and uniformly sintering the carbon-coated lithium ferrite and the NiO@ lithium salt. The application fully gives play to the advantages of high lithium supplement capacity of lithium ferrite, low gas production of lithium nickelate and good environmental adaptability, and obtains a lithium supplement agent with high capacity and good stability; the contact of nano-nickel protoxide and the lithium salt coating layer prepared by the ALD method is sufficient, which is beneficial to subsequent sintering, can be prepared at a lower temperature, is beneficial to cost reduction, and the residual lithium on the surface of the core lithium ferrite can be obtained through the solid solution reaction of the nickel protoxide and the peripheral lithium salt coating layer, and the 'double-channel lithium acquisition mode' can reduce the overall residual alkali amount of the material, which is beneficial to improving the subsequent battery slurry processing performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and particularly relates to a method for preparing a composite lithium-rich lithium-replenishing additive. Background Technology

[0002] During the initial charge and discharge cycle of a lithium-ion battery, a solid electrolyte interphase (SEI) film forms on the surface of the negative electrode. This process consumes the active lithium in the positive electrode, resulting in the initial capacity loss of the lithium-ion battery. Currently, the irreversible capacity loss of graphite negative electrodes widely used in mass production lines can reach 10%, while for silicon-based and tin-based negative electrodes with high specific capacities, the irreversible capacity loss can exceed 30%, significantly reducing the energy density of lithium-ion batteries. Therefore, lithium replenishment is typically used to compensate for the irreversible capacity loss of lithium-ion batteries, restore the capacity of the positive electrode, and improve the energy density of the lithium-ion battery.

[0003] Currently, common lithium replenishment methods include positive electrode lithium replenishment, negative electrode lithium replenishment, and electrochemical lithium replenishment. Negative electrode lithium replenishment often uses lithium powder and lithium foil, but because metallic lithium reacts violently with water, it has very high environmental requirements, necessitating significant investment in production line modifications and equipment procurement. However, positive electrode lithium replenishment, due to its higher safety and ease of operation, has become the most promising method for industrial production. Commonly used positive electrode lithium replenishment additives include Li5FeO4, Li2NiO2, Li6CoO4, Li6MnO4, and Li5ReO6, among others. Li5FeO4, theoretically, can release five Li ions. + With a theoretical specific capacity exceeding 850 mAh / g, Li₅FeO₄ is considered an ideal lithium-ion additive for cathode materials. Adding a certain amount of Li₅FeO₄ to traditional cathode materials can significantly improve the initial efficiency and energy density of lithium-ion batteries. However, pure Li₅FeO₄ has poor conductivity, making it difficult to guarantee the electrical performance of lithium-ion batteries.

[0004] To improve the lithium replenishment effect and conductivity of lithium replenishing agents, researchers have developed various lithium replenishing materials. The mainstream lithium replenishing materials involve preparing various coating layers on the surface of commonly used lithium replenishing agents. Patent CN112490415 A discloses a lithium replenishing additive for lithium-ion cathode materials. By sequentially coating a carbon layer and a transition metal oxide layer on the surface of a Li5FeO4 substrate, it significantly improves the electronic and ionic conductivity of Li5FeO4, enhancing the material's lithium replenishment performance and electrochemical performance, and extending the lifespan of lithium-ion batteries. However, batteries assembled using lithium replenishing agents prepared by this method have low specific capacity and poor charging efficiency. Patent CN 114497514 B discloses a cathode lithium replenishing agent that effectively improves the battery's energy density and stability by coating Li5FeO4 with Li2NiO2, and improves the lithium replenishment effect and conductivity of the lithium replenishing agent. However, the process of combining Li2NiO2 and Li5FeO4 is difficult, and the stability of the lithium replenishing agent still needs improvement.

[0005] Therefore, it is particularly important to prepare a conductive lithium-replenishing additive that combines excellent lithium replenishment performance, conductivity, and stability. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a method for preparing a composite lithium-rich lithium-replenishing additive. This method involves mixing and sintering a carbon-coated lithium-rich compound, Li5FeO4, with NiO@lithium salt prepared using ALD technology to produce a lithium nickelate-coated lithium ferrite composite lithium-replenishing additive with a carbon coating. The proposed composite lithium-rich lithium-replenishing additive, Li5FeO4@C@Li2NiO2, fully leverages the advantages of both lithium nickelate and lithium ferrite. Furthermore, the environmentally adaptable lithium nickelate acts as a shell, providing a degree of protection for the lithium ferrite. Additionally, the lithium-rich lithium-replenishing additive of this invention reduces the overall residual alkali content of the material, improving the subsequent battery slurry processing performance.

[0007] To achieve the above objectives, the present invention first provides a method for preparing a composite lithium-rich lithium-supplementing additive, comprising the following steps:

[0008] (1) Mix iron oxide powder and lithium source powder evenly to obtain a blended powder;

[0009] (2) The blended powder obtained in step (1) is sintered in an inert gas atmosphere, cooled, crushed and sieved to obtain lithium supplementary additive base material A, chemical formula Li5FeO4.

[0010] (3) The substrate A obtained in step (2) is placed in the CVD equipment and a carbon source and protective gas are introduced. After the reaction, carbon-coated lithium ferrite Li5FeO4@C is obtained.

[0011] (4) The nano-nickel oxide was modified by atomic layer deposition (ALD) and a lithium salt was coated on the surface of the nano-nickel oxide to obtain the shell material precursor NiO@lithium salt.

[0012] (5) After thoroughly mixing Li5FeO4@C and NiO@lithium salt, high-temperature sintering is carried out under nitrogen protection to obtain composite lithium-rich lithium supplement Li5FeO4@C@Li2NiO2.

[0013] In one embodiment of the present invention, the particle size range of the iron oxide powder in step (1) is 50 nm to 20 μm.

[0014] In one embodiment of the present invention, the lithium source powder mentioned in step (1) is at least one of Li2O, LiOH, LiOH·H2O, and Li2CO3.

[0015] In one embodiment of the present invention, in step (1), the molar ratio of Fe element in the iron oxide powder to Li element in the lithium source powder is 1:(5-5.5).

[0016] In one embodiment of the present invention, in step (2), the inert gas includes nitrogen and / or argon.

[0017] In one embodiment of the present invention, in step (2), the sintering refers to pre-sintering at 500-600℃ for 5-15h, followed by high-temperature sintering at 700-1000℃ for 10-24h, with a heating rate of 2-5℃ / min, and cooling down at room temperature after sintering.

[0018] In one embodiment of the present invention, in step (2), the sieving is performed through a 300-mesh screen.

[0019] In one embodiment of the present invention, in step (3), the carbon source includes at least one of acetylene, carbon monoxide, ethylene, and propylene, and the protective gas is nitrogen and / or argon.

[0020] In one embodiment of the present invention, in step (3), the flow rate of the carbon source is 200-300 mL / min, and the flow rate of the protective gas is 200-1000 mL / min.

[0021] In one embodiment of the present invention, in step (3), the reaction temperature is 600-650°C, the reaction time is 2-3 hours, and the heating rate is 6°C / min.

[0022] In one embodiment of the present invention, in step (3), the carbon coating amount is 0.5-5%.

[0023] In one embodiment of the present invention, step (4) of the preparation method of NiO@lithium salt includes the following steps: placing the nano-nickel oxide matrix material into the reaction chamber of the ALD device, first introducing a mixed gas of lithium source precursor and carrier gas, and under the action of lithium source pulse, the lithium source is adsorbed on the matrix material, then purging with carrier gas for 10s, then introducing a mixed gas of oxygen source precursor and carrier gas, and under the action of oxygen source pulse, the oxygen source reacts with the lithium source precursor, then purging with carrier gas for 10s, then sequentially introducing a mixed gas of lithium source precursor and carrier gas, purging with carrier gas for 10s, then introducing a mixed gas of oxygen source precursor and carrier gas, purging with carrier gas for 10s, repeating 3-5 times to prepare NiO@lithium salt composite coating material.

[0024] In one embodiment of the present invention, in step (4), the coating thickness of the lithium layer is 20-50 nm, and the molar ratio of Li / Ni is 2.0 ± 0.05.

[0025] In one embodiment of the present invention, in step (4), the lithium source precursor is lithium tert-butoxide (C4H9LiO), the oxygen source precursor is ozone (O3), and the carrier is nitrogen or argon.

[0026] In one embodiment of the present invention, in step (4), the volume ratio of the lithium source precursor to the carrier gas in the mixed gas is 1:1 to 1:5, and the flow rate of the mixed gas is 200-400 mL / min.

[0027] In one embodiment of the present invention, in step (4), the temperature of the lithium source during pulse is 100-150°C and the pulse duration is 1.6-2.5s.

[0028] In one embodiment of the present invention, in step (4), the volume ratio of the oxygen-lithium source precursor to the carrier gas in the mixed gas of the oxygen source precursor and the carrier gas is 1:1 to 1:5, and the flow rate of the mixed gas of the oxygen source precursor and the carrier gas is 200-400 mL / min.

[0029] In one embodiment of the present invention, in step (4), the temperature of the oxygen source during pulse is 100-150°C and the pulse duration is 4-5 seconds.

[0030] In one embodiment of the present invention, in step (4), the flow rate of the carrier gas during purging is 100-250 cm³. 3 / min.

[0031] In one embodiment of the present invention, in step (5), the molar ratio of Li5FeO4@C and NiO@lithium salt is (99-98):(1-2).

[0032] In one embodiment of the present invention, the sintering temperature in step (5) is 500-700℃, preferably 550-650℃, and the holding time is 5-20h.

[0033] The present invention also discloses a composite lithium-rich lithium supplement additive prepared by the above method.

[0034] This invention also discloses the application of the above-mentioned composite lithium-rich additive in the field of lithium-ion batteries.

[0035] In one embodiment of the present invention, the application includes adding a lithium supplement to a lithium battery positive electrode material to prepare a positive electrode sheet by homogenization, and forming a lithium battery by positive electrode sheet, negative electrode sheet, separator, electrolyte, positive and negative current collectors and casing, or forming a button battery by positive electrode sheet, negative electrode sheet, separator, electrolyte and positive / negative electrode casing.

[0036] Beneficial effects:

[0037] (1) Lithium ferrite lithium supplement has the advantage of high lithium supplement capacity, generally up to 800 mAh / g. However, due to its high intrinsic lithium content, it has disadvantages such as high residual alkali content, high requirements for the use environment, and large gas production during the lithium supplementation process. Although lithium nickelate lithium supplement is better than lithium ferrite in terms of processability and gas production, its own lithium supplement capacity is low, less than 300 mAh / g. The composite lithium-rich lithium supplement Li5FeO4@C@Li2NiO2 prepared in this invention fully utilizes the advantages of both materials, and uses lithium nickelate with good environmental adaptability as the shell, which to a certain extent serves as a protective layer for lithium ferrite.

[0038] (2) The contact between nano-nickel oxide and the lithium salt coating layer prepared by the ALD method is sufficient to facilitate subsequent sintering. It can be prepared at a lower temperature, which is beneficial to the reduction of cost. At the same time, in addition to the solid solution reaction between nickel oxide and the outer lithium salt coating layer, residual lithium on the surface of the core lithium ferrite can also be obtained. Its "dual-channel lithium acquisition mode" can reduce the overall residual alkali content of the material, which is beneficial to improving the subsequent battery slurry processing performance.

[0039] (3) The button battery prepared by using Li5FeO4@C@Li2NiO2 prepared by the method of the present invention as a lithium replenishing agent has a high charging specific capacity and the stability of the lithium replenishing agent is also very good. After being placed for two days, the charging specific capacity retention rate of the prepared battery can be as high as 75.96%. Attached Figure Description

[0040] Figure 1 The diagram shows the structure of the composite lithium-rich lithium supplementation additive prepared according to an embodiment of the present invention, with the right figure being a partially enlarged view.

[0041] Figure 2 The charge-discharge curves for Example 3 at a rate of 0.1C are shown. Detailed Implementation

[0042] The present invention will be further described and illustrated below through specific embodiments, comparative examples, and accompanying drawings.

[0043] The argon gas used in this invention is high-purity argon gas with a purity of 99.999%.

[0044] Methods for testing charging specific capacity:

[0045] Composite lithium-rich additive material, conductive carbon black and polyvinylidene fluoride were mixed in a mass ratio of 92:4:4, and N-methylpyrrolidone was added to prepare an electrode sheet. A CR2032 button battery was formed with a lithium sheet as the counter electrode and a charge-discharge test was conducted at a rate of 0.1C.

[0046] Example 1

[0047] A method for preparing a composite lithium-rich lithium supplement additive includes the following steps:

[0048] (1) Mix 20g of iron oxide powder with 55.03g of lithium source powder (LiOH·H2O) evenly to obtain a blended powder;

[0049] (2) The blended powder obtained in step (1) was pre-sintered at 580°C for 12 hours in a nitrogen atmosphere, and then sintered at 850°C for 20 hours with a heating rate of 3°C / min. It was then naturally cooled to room temperature, pulverized, and sieved through a 300-mesh sieve to obtain lithium supplementary additive substrate A, with the chemical formula Li5FeO4.

[0050] (3) The prepared substrate A was placed in a CVD device, acetylene was used as the carbon source, nitrogen was used as the protective gas, the acetylene flow rate was 200 mL / min, the nitrogen flow rate was 800 mL / min, the heating rate was 6℃ / min, the temperature was raised to 650℃, held for 2 h, and then cooled to room temperature in a natural environment to obtain Li5FeO4@C with a carbon coating of 1.5%.

[0051] (4) The nano-nickel oxide matrix material was placed in the reaction chamber of the ALD equipment. First, a mixed gas of lithium tert-butoxide and argon (1:4, 250 mL / min) was introduced. Under the action of lithium source pulse (2s) at 135℃, the lithium source was adsorbed on the matrix material. Then, argon was purged for 10s. Then, a mixed gas of O3 and argon (1:4, 250 mL / min) was introduced. Under the action of oxygen source pulse (4.6s), O3 reacted with lithium tert-butoxide. Then, argon was purged for 10s. Then, a mixed gas of lithium tert-butoxide and argon was introduced in sequence, argon was purged for 10s, and a mixed gas of O3 and argon was introduced, argon was purged for 10s. This process was repeated 5 times to prepare NiO@lithium salt composite coating material. During the whole process, the flow rate of argon purging was 200 mL / min. The final prepared NiO@lithium salt had a Li / Ni ratio of 2.04 and a lithium coating thickness of 36 nm.

[0052] (5) After thoroughly mixing 80gLi5FeO4@C and 20gNiO@lithium salt, sinter at 650℃ for 15h with nitrogen as the protective gas and a heating rate of 2℃ / min, and then naturally cooling to room temperature, the composite lithium-rich lithium supplement Li5FeO4@C@Li2NiO2 is obtained.

[0053] Example 2

[0054] The difference between Example 2 and Example 1 is that the carbon coating amount in step (3) is changed by 2.0%.

[0055] In step (3), the flow rate of acetylene was changed to 250 mL / min, the flow rate of nitrogen was changed to 800 mL / min, the heating rate was 6℃ / min, the temperature was raised to 650℃, held for 2 hours, and then cooled to room temperature in a natural environment to obtain Li5FeO4@C.

[0056] Example 3

[0057] The difference between Example 3 and Example 1 is that the carbon coating amount in step (3) is changed by 2.5%.

[0058] Step (3) is changed to CVD carbon coating of the prepared substrate A, using acetylene as the carbon source and nitrogen as the protective gas. The acetylene flow rate is 300 mL / min, the nitrogen flow rate is 800 mL / min, the heating rate is 6℃ / min, the temperature is raised to 650℃, held for 2 hours, and then cooled to room temperature in a natural environment to obtain Li5FeO4@C.

[0059] Example 4

[0060] The difference between Example 4 and Example 3 is that the carbon source in step (3) is changed.

[0061] The carbon source in step (3) was changed to propylene, nitrogen was used as the protective gas, the propylene flow rate was 300 mL / min, the nitrogen flow rate was 800 mL / min, the heating rate was 6℃ / min, the temperature was raised to 700℃, the temperature was held for 2 hours, and the temperature was cooled to room temperature in a natural environment to obtain Li5FeO4@C.

[0062] Example 5

[0063] The difference between Example 5 and Example 1 is that the ratio of Li5FeO4@C to NiO@lithium salt in step (5) is changed.

[0064] The mass of Li5FeO4@C in step (5) was changed to 70g, and after being thoroughly mixed with 30g of NiO@lithium salt, it was sintered to obtain the composite lithium-rich lithium supplement agent Li5FeO4@C@Li2NiO2.

[0065] Example 6

[0066] The difference between Example 6 and Example 1 is that the ratio of Li5FeO4@C to NiO@lithium salt in step (5) is changed.

[0067] The mass of Li5FeO4@C in step (5) was changed to 90g, and after being thoroughly mixed with 10g of NiO@lithium salt, it was sintered to obtain the composite lithium-rich lithium supplement Li5FeO4@C@Li2NiO2.

[0068] Comparative Example 1

[0069] The difference between Comparative Example 1 and Example 1 is that the carbon coating step is omitted in Example 1, and the Li5FeO4 prepared in step (2) is directly mixed and sintered with the NiO@lithium salt prepared in step (4).

[0070] Comparative Example 2

[0071] The difference between Comparative Example 2 and Example 1 is that the amount of carbon coating in step (3) is changed to exceed 5%.

[0072] Step (3) is changed to CVD carbon coating of the prepared substrate A, using acetylene as the carbon source and nitrogen as the protective gas. The acetylene flow rate is 400 mL / min (carbon coating amount 5.5%), the nitrogen flow rate is 800 mL / min, the heating rate is 6℃ / min, the temperature is raised to 650℃, held for 3h, and then cooled to room temperature in a natural environment to obtain Li5FeO4@C.

[0073] Comparative Example 3

[0074] The difference between Comparative Example 3 and Example 1 is that purchased Li2NiO2 was used to co-sinter with Li5FeO4@C obtained in step (3).

[0075] Comparative Example 4

[0076] A method for preparing lithium supplement Li5FeO4@C:

[0077] (1) Mix 20g of iron oxide powder with 55.03g of lithium source powder (LiOH·H2O) evenly to obtain a blended powder;

[0078] (2) The blended powder obtained in step (1) was pre-sintered at 580°C for 12 hours in a nitrogen atmosphere, and then sintered at 850°C for 20 hours with a heating rate of 3°C / min. It was then naturally cooled to room temperature, pulverized, and sieved through a 300-mesh sieve to obtain lithium supplementary additive substrate A, with the chemical formula Li5FeO4.

[0079] (3) Place the substrate A prepared in step (2) in a CVD device, use acetylene as the carbon source and nitrogen as the protective gas, acetylene flow rate 200 mL / min, nitrogen flow rate 800 mL / min, heating rate 6℃ / min, heat to 650℃, keep warm for 3h, and cool to room temperature in a natural environment to obtain Li5FeO4@C.

[0080] Comparative Example 5

[0081] A method for preparing lithium supplement Li2NiO2:

[0082] (1) The nano-nickel oxide matrix material was placed in the reaction chamber of the ALD equipment. First, a mixed gas of lithium tert-butoxide and argon (1:4, 250 mL / min) was introduced. Under the action of lithium source pulse (2s) at 135℃, the lithium source was adsorbed onto the matrix material. Then, it was purged with argon for 10s. Next, a mixed gas of O3 and argon (1:4, 250 mL / min) was introduced. Under the action of oxygen source pulse (4.6s), O3 reacted with lithium tert-butoxide. Then, it was purged with argon for 10s. Then, a mixed gas of lithium tert-butoxide and argon was introduced in sequence, purged with argon for 10s, and a mixed gas of O3 and argon was introduced, purged with argon for 10s. This process was repeated 5 times to prepare NiO@lithium salt composite coating material. The flow rate of argon during the entire process was 130 cm. 3 / min, the final prepared NiO@lithium salt has a Li / Ni molar ratio of 2.04 and a lithium coating thickness of 36nm;

[0083] (2) The NiO@lithium salt obtained in step (1) was sintered at 650℃ for 15h with nitrogen as the protective gas, the heating rate was 2℃ / min, and the temperature was naturally cooled to room temperature to obtain Li2NiO2.

[0084] The lithium replenishing agents from Examples 1-6 and Comparative Examples 1-5 were assembled into button batteries with lithium replenishing agents stored for different numbers of days, and their charge specific capacity at a 0.1C rate was tested. The results are shown in Table 1. As can be seen from the data in Table 1, the battery using Li5FeO4@C as the lithium replenishing agent has a high charge specific capacity, reaching 806 mAh / g, but the lithium replenishing agent has poor stability; after only one day of storage, the charge specific capacity of the prepared battery decreased by approximately 74%. While the lithium replenishing agent Li2NiO2 has good stability, its charge specific capacity is very low, only 404 mAh / g, far from meeting the requirements of lithium-ion batteries. This invention combines the above two lithium replenishing agents to prepare a lithium replenishing agent with high charge specific capacity and good stability. Furthermore, preparing NiO@lithium salt using ALD deposition and then mixing and sintering the NiO@lithium salt with Li5FeO4@C can further improve the charge specific capacity and stability.

[0085] Table 1. Charge specific capacity and stability data of the lithium replenishing agents prepared in Examples 1-6 and Comparative Examples 1-5.

[0086]

[0087] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing a composite lithium-rich lithium-supplementing additive, characterized in that, Includes the following steps: (1) Mix iron oxide powder and lithium source powder evenly to obtain a blended powder; (2) The blended powder obtained in step (1) is sintered in an inert gas atmosphere, cooled, crushed and sieved to obtain lithium supplementary additive base material A, chemical formula Li5FeO4. (3) The substrate A obtained in step (2) is placed in the CVD equipment and a carbon source and protective gas are introduced. After the reaction, carbon-coated lithium ferrite Li5FeO4@C is obtained. (4) Place the nano-nickel oxide matrix material into the reaction chamber of the ALD equipment. First, introduce a mixture of lithium source precursor and carrier gas. Under the action of lithium source pulse, the lithium source is adsorbed on the matrix material. Then, purge with carrier gas for 10s. Next, introduce a mixture of oxygen source precursor and carrier gas. Under the action of oxygen source pulse, the oxygen source reacts with the lithium source precursor. Then, purge with carrier gas for 10s. Then, introduce a mixture of lithium source precursor and carrier gas in sequence, purge with carrier gas for 10s, introduce a mixture of oxygen source precursor and carrier gas, purge with carrier gas for 10s, repeat 3-5 times to obtain the shell material precursor NiO@lithium salt. (5) After thoroughly mixing the Li5FeO4@C obtained in step (3) and the NiO@lithium salt obtained in step (4), the mixture is sintered at high temperature under nitrogen protection to obtain the composite lithium-rich lithium supplement Li5FeO4@C@Li2NiO2.

2. The preparation method according to claim 1, characterized in that, The particle size range of the iron oxide powder in step (1) is 50 nm to 20 μm, the lithium source powder is at least one of Li2O, LiOH, LiOH·H2O, and Li2CO3, and the molar ratio of Fe element in the iron oxide powder to Li element in the lithium source powder is 1:(5 to 5.5).

3. The preparation method according to claim 1, characterized in that, In step (2), the inert gas includes nitrogen and / or argon. The sintering refers to pre-sintering at 500-600℃ for 5-15 hours, followed by high-temperature sintering at 700-1000℃ for 10-24 hours with a heating rate of 2-5℃ / min. After sintering, the temperature is lowered to room temperature. The sieving is passing through a 300-mesh sieve.

4. The preparation method according to claim 1, characterized in that, In step (3), the carbon source includes at least one of acetylene, carbon monoxide, ethylene, and propylene, the protective gas is nitrogen and / or argon, the flow rate of the carbon source is 200-300 mL / min, the flow rate of the protective gas is 200-1000 mL / min, the reaction temperature is 600-650℃, the reaction time is 2-3 h, and the heating rate is 6℃ / min.

5. The preparation method according to claim 1, characterized in that, In step (4), the lithium source precursor is lithium tert-butoxide, the oxygen source precursor is ozone, and the carrier gas is nitrogen or argon.

6. The preparation method according to claim 1, characterized in that, In step (4), the volume ratio of the lithium source precursor to the carrier gas in the mixed gas is 1:1 to 1:5, the flow rate of the mixed gas is 200-400 mL / min, the temperature of the lithium source during pulse is 100-150℃, and the pulse time is 1.6-2.5 s.

7. The preparation method according to claim 1, characterized in that, In step (4), the volume ratio of the oxygen-lithium source precursor to the carrier gas in the mixed gas of the oxygen source precursor and the carrier gas is 1:1 to 1:5, the flow rate of the mixed gas of the oxygen source precursor and the carrier gas is 200-400 mL / min, the temperature of the oxygen source during pulse is 100-150℃, the pulse time is 4-5 s, and the flow rate of the carrier gas during purging is 100-250 cm³. 3 / min.

8. The preparation method according to claim 1, characterized in that, In step (5), the molar ratio of Li5FeO4@C and NiO@lithium salt is (99-98):(1-2), the sintering temperature is 500-700℃, and the holding time is 5-20h.

9. The composite lithium-rich lithium supplementation additive prepared according to any one of claims 1 to 8.

10. The application of the composite lithium-rich lithium-replenishing additive as described in claim 9 in the field of lithium-ion batteries.

Images