Lithium-rich lithium supplement agent with high air stability and preparation method thereof

Abstract

The invention provides a lithium-rich lithium supplement agent with high air stability and a preparation method thereof, and relates to the field of lithium ion battery lithium supplement agents. The preparation method of the lithium-rich lithium supplement agent with high air stability comprises the following steps: low-temperature carbonization coating and polymerization coating. According to the lithium-rich lithium supplement agent with high air stability and the preparation method, the air stability, the isolation performance and the water absorption of the lithium-rich lithium supplement agent are improved, the dynamic performance of the lithium-rich lithium supplement agent is improved, and the matching performance of the lithium-rich lithium supplement agent and a positive electrode material is improved; and the electrical performance is further improved.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion battery lithium supplement agents, and particularly to a lithium-rich lithium supplement agent with high air stability and a preparation method thereof. Background Art

[0002] During the first charge-discharge cycle of a lithium-ion battery, a solid electrolyte interface film (SEI) is formed on the surface of the negative electrode through the side reaction of the electrolyte with lithium ions. This process will permanently consume the active lithium reserve in the system, directly leading to a decrease in the energy density of the battery (the theoretical capacity loss is about 5-20%) and the deterioration of cycle stability. This problem is particularly significant in battery systems adopting high-energy density design strategies such as high nickel / high silicon.

[0003] In view of this defect, the lithium supplement technology has become the key solution to improve battery performance. According to the difference in the object of action, the lithium supplement process can be divided into two major paths: negative electrode prelithiation and positive electrode lithium supplementation. The negative electrode lithium supplement technology has problems such as complex process and poor safety, while the positive electrode lithium supplement technology has become the research focus in this field at present due to its strong process compatibility and inherent safety advantages. The implementation mechanism of positive electrode lithium supplementation is to mix a lithium-containing compound with a high irreversible lithium capacity (such as Li2S, Li2O2, Li2C2O4, Li3N, Li2NiO2 or Li5FeO4, etc.) in the positive electrode active material slurry, and then decompose and release active lithium during the formation process to compensate for the irreversible loss of active lithium.

[0004] However, most lithium-rich lithium supplement agents have poor air stability. Their surfaces are alkaline, have strong water absorption, and are prone to react with moisture in the air, etc., which will lead to defects such as material deterioration and increased internal resistance, affecting the lithium supplement effect. This problem greatly limits the practical application of lithium-rich lithium supplement agent materials in high-energy density batteries and batteries with ultra-long cycle life, and directly increases the stringent requirements for gas protection and the corresponding production costs in the processes of material preparation, storage, transportation, battery assembly, etc. In addition, most lithium-rich lithium supplement agent materials have poor kinetic performance and high decomposition voltage, which puts forward higher requirements for the electrochemical stability of the matched positive electrode materials, electrolytes, etc., and cannot be effectively adapted.

[0005] Currently, the prior art mostly suppresses its contact with air through forms such as carbon coating, oxide coating, fluoride coating, etc.; however, for the existing composite coating processes for lithium-rich lithium supplement agents, uniform and complete coating cannot be achieved, and the isolation effect is not good; and the improvement effects on the air stability, kinetic performance and electrical performance of lithium-rich lithium supplement agents need to be further improved.

[0006] Therefore, there is an urgent need to provide a lithium-rich lithium supplementing agent with high air stability and a preparation method thereof, which can improve the air stability of the lithium-rich lithium supplementing agent, enhance the isolation performance, reduce its water absorption, while improving its kinetic performance, enhancing its compatibility with the cathode material; and further improving its electrical performance. Summary of the Invention

[0007] To solve the technical problems existing in the prior art, the present invention provides a lithium-rich lithium supplementing agent with high air stability and a preparation method thereof, which can improve the air stability of the lithium-rich lithium supplementing agent, enhance the isolation performance, reduce its water absorption, while improving its kinetic performance, enhancing its compatibility with the cathode material; and further improving its electrical performance.

[0008] To solve the above technical problems, the technical solutions adopted by the present invention are as follows: A preparation method of a lithium-rich lithium supplementing agent with high air stability, comprising the following steps: low-temperature carbonization coating, polymerization coating; The method of the low-temperature carbonization coating is to put the high-lithium compound / composite powder into a fluidized bed reactor, continuously introduce an inert gas into the fluidized bed reactor, and keep the material in the fluidized bed reactor in a fluidized state; heat up to 300-400 °C, keep the temperature and introduce acetylene; after the introduction of acetylene is completed, continue to heat up to 400-500 °C, keep the temperature and react, and then complete the low-temperature carbonization coating; The method of the polymerization coating is that after the low-temperature carbonization coating is completed, under the condition of keeping the material in the fluidized bed reactor in a fluidized state, when the temperature of the fluidized bed reactor drops to 100-120 °C, keep the temperature, spray the coating raw material liquid into the fluidized bed reactor, and continue to keep the material in a fluidized state; then spray ammonia water into the fluidized bed reactor, and continue to keep the material in a fluidized state to complete the polymerization coating, and obtain a lithium-rich lithium supplementing agent with high air stability; The coating raw material liquid is a mixture of alkoxysilane, tetraethyl orthosilicate, and ethanol solution.

[0009] Preferably, the high-lithium compound / composite is at least one of the following: Li2O, Li2O2, Li3N, Li2S, Li x Si, Li2CuO 2、 Li2NiO2, Li5FeO4, Li6CoO4, Li2CO3, Li2C2O4, Li2C4O4, Li2S / M, LiF / M, Li2O / M, Li x Si / M; where M is one of the following: Fe, Ni, Co, Mn, Zn, Cu; X takes a value of 2-3.

[0010] Preferably, in the low-temperature carbonization coating, the time for keeping the temperature at 300-400 °C and introducing acetylene is 1-4 h; The holding reaction time at 400 - 500 °C is 1 - 2 h.

[0011] Preferably, in the low-temperature carbonization coating, the mass ratio of the high lithium-containing compound / compound powder to acetylene is 5 - 6:1.

[0012] Preferably, in the polymerization coating, the time for maintaining the fluidization of the material after the spraying of the coating raw material liquid is 20 - 60 min; The time for maintaining the fluidization of the material after the spraying of ammonia water is 5 - 30 min.

[0013] Preferably, in the polymerization coating, the mass ratio of alkoxysilane, tetraethyl orthosilicate, and ethanol solution in the coating raw material liquid is 1 - 2:1.5 - 3:4 - 8; The volume ratio of ethanol to deionized water in the ethanol solution is 30 - 70:30 - 70.

[0014] Preferably, in the polymerization coating, the alkoxysilane is at least one of the following: perfluorodecyltriethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, octyltriethoxysilane, phenyltriethoxysilane, p-tolyltriethoxysilane, trifluoromethyltriethoxysilane, perfluoroethyltriethoxysilane, γ-glycidyltriethoxysilane, aminotriethoxysilane, mercaptotriethoxysilane.

[0015] Preferably, in the polymerization coating, the mass ratio of tetraethyl orthosilicate in the coating raw material liquid to the high lithium-containing compound / compound powder used in the low-temperature carbonization coating is 1:40 - 200.

[0016] Preferably, in the polymerization coating, the mass concentration of ammonia water is 5.5 - 6.5 wt%; The mass ratio of ammonia water to the ethanol solution in the coating raw material liquid is 1:4.5 - 5.5.

[0017] A highly air-stable lithium-rich lithium supplement agent prepared by the foregoing method, the lithium-rich lithium supplement agent from the inside to the outside is in turn: a high lithium-containing compound / compound, a carbon coating layer, a polymer coating layer; the particle size of the lithium-rich lithium supplement agent is 1 - 15 μm, the thickness of the carbon coating layer is 5 - 20 nm; the thickness of the polymer coating layer is 20 - 200 nm Compared with the prior art, the beneficial effects of the present invention are: The preparation method of the lithium-rich lithium supplement with high air stability of the present invention involves contacting acetylene with a fluidized high-lithium compound / composite powder, followed by low-temperature carbonization coating to form a carbon coating layer (i.e., the inner coating layer) on the outer surface of the high-lithium compound / composite powder. Then, under fluidized conditions, a coating raw material solution containing an alkoxysilane material and tetraethyl orthosilicate is pre-distributed on the outer surface of the above carbon coating layer, and then ammonia water is introduced to catalyze the formation of a polysiloxane coating layer (i.e., the outer coating layer), forming a double isolation protection. Moreover, the carbon coating layer can also improve the electronic conductivity of the lithium-rich lithium supplement material, enhance the reaction kinetics, and contribute to the capacity performance.

[0018] Furthermore, the preparation method of the lithium-rich lithium supplement with high air stability of the present invention, in combination with the efficient heat transfer, mass transfer, and uniform dispersion characteristics of the fluidized bed fluidization technology, shortens the processing time of low-temperature carbonization coating and polymerization coating under industrial-scale production conditions, ensuring the uniformity and integrity of the polymer coating layer and the carbon coating layer. Through the synergistic cooperation of the aforementioned technical means, while improving the air stability of the lithium-rich lithium supplement, enhancing the isolation performance, and reducing its water absorption, the kinetic performance is improved, the matching with the cathode material is enhanced; and the electrical performance is further improved. Brief Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the preparation method of the lithium-rich lithium supplement with high air stability according to the embodiment of the present invention. Detailed Embodiments

[0020] In order to have a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention are now described. It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0021] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, "first", "second", etc. are used to distinguish similar objects and are not used to describe a specific order or sequence. In addition, it should also be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or their combinations.

[0022] As Figure 1 shown, the embodiment of the present invention provides a preparation method of a lithium-rich lithium supplement with high air stability, including the following steps: low-temperature carbonization coating and polymerization coating.

[0023] The method of low-temperature carbonization coating is as follows: Put the high-lithium compound / compound powder into the reaction chamber of a fluidized bed reactor. Under the protection of an inert gas (nitrogen / argon) atmosphere, start stirring and purge with a carrier gas (nitrogen / argon). Under the action of stirring / carrier gas, keep the high-lithium compound / compound powder in the reaction chamber of the fluidized bed reactor continuously fluidized. Control the temperature in the reaction chamber of the fluidized bed reactor to rise to 300 - 400 °C, keep warm and continuously introduce acetylene, and control the introduction time of acetylene to be 1 - 4 h. After the introduction of acetylene is completed, close the acetylene gas source and keep stirring and carrier gas purging (i.e., keep the material fluidized). Control the temperature in the reaction chamber of the fluidized bed reactor to continue to rise to 400 - 500 °C, keep warm and react for 1 - 2 h to complete the low-temperature carbonization coating treatment, and form a carbon coating layer (i.e., the inner coating layer) on the outer surface of the high-lithium compound / compound powder.

[0024] In the low-temperature carbonization coating, the mass ratio of the high-lithium compound / compound powder to acetylene is 5 - 6:1.

[0025] The high-lithium compound / compound is at least one of the following: Li2O, Li2O2, Li3N, Li2S, Li x Si, Li2CuO 2、 Li2NiO2, Li5FeO4, Li6CoO4, Li2CO3, Li2C2O4, Li2C4O4, Li2S / M, LiF / M, Li2O / M, Li x Si / M; where M is one or more of Fe, Ni, Co, Mn, Zn, Cu; X takes a value of 2 - 3.

[0026] The method of polymerization coating is as follows: After the low-temperature carbonization coating treatment is completed, cool down under the conditions of stirring and purge with a carrier gas (nitrogen / argon) (i.e., keep the material fluidized and cool down). When the temperature drops to 100 - 120 °C, keep warm. Use a mixture of alkoxysilane, tetraethyl orthosilicate, and ethanol solution as the coating raw material liquid. Spray the coating raw material liquid into the reaction chamber of the fluidized bed reactor through a spraying device. After spraying is completed, continue to keep stirring and carrier gas purging (i.e., keep the material fluidized) for 20 - 60 min, and then spray ammonia water into the reaction chamber of the fluidized bed reactor through the spraying device. After spraying is completed, continue to keep stirring and carrier gas purging (i.e., keep the material fluidized) for 5 - 30 min to complete the polymerization coating, and form a polymer coating layer (i.e., the outer coating layer) on the outer surface of the carbon coating inner layer. Cool down to room temperature to obtain a high-air-stability lithium-rich lithium supplement agent.

[0027] In the polymerization coating, the mass ratio of alkoxysilane, tetraethyl orthosilicate, and ethanol solution is 1 - 2:1.5 - 3:4 - 8; the volume ratio of ethanol to deionized water in the ethanol solution is 30 - 70:30 - 70; The alkoxysilane is at least one of the following: perfluorodecyltriethoxysilane (PFDTES), methyltriethoxysilane (MTES), ethyltriethoxysilane (ETES), octyltriethoxysilane (OTES), phenyltriethoxysilane (PTES), p-tolyltriethoxysilane (p-TES), trifluoromethyltriethoxysilane (TFMES), perfluoroethyltriethoxysilane (PFEES), γ-glycidyltriethoxysilane (γ-GTES), aminotriethoxysilane (ATES), and mercaptotriethoxysilane (MTES).

[0028] In the polymer coating, the mass ratio of tetraethyl orthosilicate to the high lithium-containing compound / composite powder used in the low-temperature carbonization coating in the coating raw material liquid is 1:40 - 200; The mass concentration of ammonia water is 5.5 - 6.5 wt%, and the mass ratio of ammonia water to the ethanol solution in the coating raw material liquid is 1:4.5 - 5.5.

[0029] The embodiment of the present invention also provides a high lithium-rich lithium supplementing agent with high air stability prepared by the aforementioned method, which successively comprises a high lithium-containing compound / composite, a carbon coating layer, and a polymer coating layer from the inside to the outside.

[0030] The particle size of the lithium-rich lithium supplementing agent is 1 - 15 μm; the thickness of the carbon coating layer is 5 - 20 nm; the polymer coating layer is composed of one or more polysiloxane materials, and the thickness of the polymer coating layer is 20 - 200 nm.

[0031] The high lithium-containing compound / composite is at least one of the following: Li2O, Li2O2, Li3N, Li2S, Li x Si, Li2CuO 2、 Li2NiO2, Li5FeO4, Li6CoO4, Li2CO3, Li2C2O4, Li2C4O4, Li2S / M, LiF / M, Li2O / M, Li x Si / M; wherein, M is one or more of Fe, Ni, Co, Mn, Zn, and Cu; X takes a value of 2 - 3.

[0032] The following combines some specific embodiments to further illustrate the present invention.

[0033] Example 1 This example provides a preparation method of a high lithium-rich lithium supplementing agent with high air stability, which processes a ternary lithium-rich lithium supplementing agent (Li5FeO4), and the specific steps are as follows: 1. Low-temperature carbonization coating Put the Li5FeO4 powder (D 50Li5FeO4 powder (with a particle size of 7 μm) was put into the reaction chamber of a fluidized bed reactor. Under the protection of an inert gas (nitrogen) atmosphere, stirring and carrier gas (nitrogen) purging were started. Under the action of stirring / carrier gas, the Li5FeO4 powder in the reaction chamber of the fluidized bed reactor was continuously fluidized. The temperature in the reaction chamber of the fluidized bed reactor was controlled to rise to 400 °C, kept warm, and acetylene was continuously introduced. The introduction time of acetylene was controlled to be 2 h. After the introduction of acetylene was completed, the acetylene gas source was closed, and stirring and carrier gas purging were maintained (i.e., the material fluidization was maintained). The temperature in the reaction chamber of the fluidized bed reactor was controlled to continue to rise to 500 °C, and the reaction was kept warm for 1 h to complete the low-temperature carbonization coating treatment, and a carbon coating layer (inner layer) was formed on the outer surface of the Li5FeO4 powder.

[0034] Among them, the mass ratio of Li5FeO4 powder to acetylene is 6:1.

[0035] 2. Polymer coating After the low-temperature carbonization coating treatment was completed, the temperature was lowered under the conditions of stirring and carrier gas (nitrogen) purging (i.e., the material fluidization was maintained and the temperature was lowered). When the temperature was lowered to 100 °C, it was kept warm. A mixture of perfluorodecyltriethoxysilane PFDTES, tetraethyl orthosilicate, and ethanol solution was used as the coating raw material liquid. The coating raw material liquid was sprayed into the reaction chamber of the fluidized bed reactor through a spraying device. After the spraying was completed, stirring and carrier gas purging were continued (i.e., the material fluidization was maintained) for 20 min. Then, ammonia water with a concentration of 6 wt% was sprayed into the reaction chamber of the fluidized bed reactor through the spraying device. After the spraying was completed, stirring and carrier gas purging were continued (i.e., the material fluidization was maintained) for 5 min to complete the polymer coating, and a polymer coating layer (outer layer) was formed on the outer surface of the carbon coating inner layer. The temperature was lowered to room temperature to obtain a lithium-rich lithium supplement agent with high air stability.

[0036] Among them, the mass ratio of perfluorodecyltriethoxysilane PFDTES, tetraethyl orthosilicate, and ethanol solution is 1:1.5:8; the volume ratio of ethanol to deionized water in the ethanol solution is 50:50.

[0037] The mass ratio of tetraethyl orthosilicate in the coating raw material liquid to the Li5FeO4 powder used in the low-temperature carbonization coating is 1:200.

[0038] The mass ratio of ammonia water to the ethanol solution in the coating raw material liquid is 1:5.

[0039] This example also provides a lithium-rich lithium supplement agent with high air stability prepared by the aforementioned method, which consists of a high lithium-containing compound, a carbon coating layer, and a polymer coating layer from the inside to the outside; the particle size of the lithium-rich lithium supplement agent is 7.1 μm, the high lithium-containing compound is Li5FeO4, the thickness of the carbon coating layer is 15 nm, and the thickness of the polymer coating layer is 30 nm.

[0040] Example 2 This embodiment provides a preparation method of a lithium-rich lithium supplement with high air stability, which is used to treat the ternary lithium-rich lithium supplement (Li6CoO4). The specific steps are as follows: 1. Low-temperature carbonization coating Put the Li6CoO4 powder (D 50 is 3μm) into the reaction chamber of the fluidized bed reactor. Under the protection of an inert gas (nitrogen) atmosphere, start stirring and purging with the carrier gas (nitrogen). Under the action of stirring / carrier gas, keep the Li6CoO4 powder in the reaction chamber of the fluidized bed reactor in a continuous fluidized state; control the temperature in the reaction chamber of the fluidized bed reactor to rise to 350°C, keep the temperature constant and continuously introduce acetylene, and control the introduction time of acetylene to be 1h; after the introduction of acetylene is completed, close the acetylene gas source and keep stirring and purging with the carrier (i.e., keep the material in a fluidized state), and control the temperature in the reaction chamber of the fluidized bed reactor to continue to rise to 450°C, keep the temperature constant and react for 1h to complete the low-temperature carbonization coating treatment, and form a carbon coating layer (inner layer) on the outer surface of the Li6CoO4 powder.

[0041] Among them, the mass ratio of Li6CoO4 powder to acetylene is 18:1.

[0042] 2. Polymer coating After the low-temperature carbonization coating treatment is completed, cool down under the conditions of stirring and purging with the carrier gas (nitrogen / argon) (i.e., keep the material in a fluidized state and cool down). When the temperature drops to 110°C, keep the temperature constant. Use a mixture of trifluoromethyltriethoxysilane TFMES, tetraethyl orthosilicate, and ethanol solution as the coating raw material liquid. Spray the coating raw material liquid into the reaction chamber of the fluidized bed reactor through a spraying device. After the spraying is completed, continue to keep stirring and purging with the carrier (i.e., keep the material in a fluidized state) for 60min, and then spray ammonia water with a concentration of 6wt% into the reaction chamber of the fluidized bed reactor through the spraying device. After the spraying is completed, continue to keep stirring and purging with the carrier (i.e., keep the material in a fluidized state) for 25min to complete the polymer coating, and form a polymer coating layer (outer layer) on the outer surface of the carbon coating inner layer. Cool down to room temperature to obtain a lithium-rich lithium supplement with high air stability.

[0043] Among them, the mass ratio of trifluoromethyltriethoxysilane TFMES, tetraethyl orthosilicate, and ethanol solution is 1:1.5:4; the volume ratio of ethanol to deionized water in the ethanol solution is 50:50.

[0044] The mass ratio of tetraethyl orthosilicate in the coating raw material liquid to the Li6CoO4 powder used in the low-temperature carbonization coating is 1:40.

[0045] The mass ratio of ammonia water to the ethanol solution in the coating raw material liquid is 1:5.

[0046] This embodiment also provides a lithium-rich lithium supplement agent with high air stability prepared by the aforementioned method, which consists of a high-lithium compound, a carbon coating layer, and a polymer coating layer from the inside to the outside; the particle size of the lithium-rich lithium supplement agent is 3.2 μm, the high-lithium compound is Li6CoO4, the thickness of the carbon coating layer is 6 nm, and the thickness of the polymer coating layer is 160 nm.

[0047] Example 3 This embodiment provides a preparation method of a lithium-rich lithium supplement agent with high air stability, which treats a binary lithium-rich lithium supplement agent (Li3N), and the specific steps are as follows: 1. Low-temperature carbonization coating Put Li3N powder (particle size D 50 is 10 μm) into the reaction chamber of a fluidized bed reactor. Under the protection of an inert gas (argon) atmosphere, start stirring and carrier gas (argon) purging, and keep the Li3N powder in the reaction chamber of the fluidized bed reactor in a continuous fluidized state under the action of stirring / carrier gas; control the temperature in the reaction chamber of the fluidized bed reactor to rise to 400 °C, keep warm and continuously introduce acetylene, and control the introduction time of acetylene to be 4 h; after the acetylene introduction is completed, close the acetylene gas source and keep stirring and carrier gas purging (i.e., keep the material in a fluidized state), and control the temperature in the reaction chamber of the fluidized bed reactor to continue to rise to 450 °C, and keep the reaction at this temperature for 1 h to complete the low-temperature carbonization coating treatment, and form a carbon coating layer (inner layer) on the outer surface of the Li3N powder.

[0048] Among them, the mass ratio of Li3N powder to acetylene is 10:1.

[0049] 2. Polymer coating After the low-temperature carbonization coating treatment is completed, cool down under the conditions of stirring and carrier gas (argon) purging (i.e., keep the material in a fluidized state and cool down). When the temperature drops to 120 °C, keep it warm. Use a mixture of phenyltriethoxysilane PTES, tetraethyl orthosilicate, and ethanol solution as the coating raw material liquid, spray the coating raw material liquid into the reaction chamber of the fluidized bed reactor through a spraying device. After the spraying is completed, continue to keep stirring and carrier gas purging (i.e., keep the material in a fluidized state) for 30 min, and then spray 6 wt% ammonia water into the reaction chamber of the fluidized bed reactor through the spraying device. After the spraying is completed, continue to keep stirring and carrier gas purging (i.e., keep the material in a fluidized state) for 15 min to complete the polymer coating, and form a polymer coating layer (outer layer) on the outer surface of the carbon coating inner layer. Cool down to room temperature to obtain a lithium-rich lithium supplement agent with high air stability.

[0050] Among them, the mass ratio of phenyltriethoxysilane PTES, tetraethyl orthosilicate, and ethanol solution is 2:1.5:8; the volume ratio of ethanol to deionized water in the ethanol solution is 50:50.

[0051] The mass ratio of tetraethyl orthosilicate in the coating raw material liquid to the Li3N powder used in the low-temperature carbonization coating is 1:80.

[0052] The mass ratio of ammonia water to the ethanol solution in the coating raw material liquid is 1:5.

[0053] This example also provides a lithium-rich lithium supplementing agent with high air stability prepared by the aforementioned method, which consists of a high lithium-containing compound, a carbon coating layer, and a polymer coating layer from the inside to the outside; the particle size of the lithium-rich lithium supplementing agent is 10.1 μm, the high lithium-containing compound is Li3N, the thickness of the carbon coating layer is 10 nm, and the thickness of the polymer coating layer is 90 nm.

[0054] Example 4 This example provides a preparation method of a lithium-rich lithium supplementing agent with high air stability, which is used to treat the alloy lithium-rich lithium supplementing agent (Li2O / Ni). The specific steps are as follows: 1. Low-temperature carbonization coating Put the Li2O / Ni powder (particle size D 50 is 3 μm) into the reaction chamber of the fluidized bed reactor. Under the protection of an inert gas (nitrogen) atmosphere, start stirring and carrier gas (nitrogen) purging. Keep the Li2O / Ni powder in the reaction chamber of the fluidized bed reactor continuously fluidized under the action of stirring / carrier gas; control the temperature in the reaction chamber of the fluidized bed reactor to rise to 300 °C, keep the temperature and continuously introduce acetylene, and control the introduction time of acetylene to be 1 h; after the introduction of acetylene is completed, close the acetylene gas source and keep stirring and carrier gas purging (i.e., keep the material fluidized), and control the temperature in the reaction chamber of the fluidized bed reactor to continue to rise to 400 °C, keep the temperature for reaction for 2 h, complete the low-temperature carbonization coating treatment, and form a carbon coating layer (inner layer) on the outer surface of the Li2O / Ni powder.

[0055] Among them, the mass ratio of Li2O / Ni powder to acetylene is 8:1.

[0056] 2. Polymer coating After the low-temperature carbonization coating treatment is completed, cool down under the conditions of stirring and carrier gas (nitrogen / argon) purging (i.e., keep the material fluidized and cool down). When the temperature drops to 110 °C, keep the temperature. Use a mixture of perfluorodecyltriethoxysilane PFDTES, tetraethyl orthosilicate, and ethanol solution as the coating raw material liquid. Spray the coating raw material liquid into the reaction chamber of the fluidized bed reactor through a spraying device. After spraying is completed, continue to keep stirring and carrier gas purging (i.e., keep the material fluidized) for 40 min, and then spray ammonia water with a concentration of 6 wt% into the reaction chamber of the fluidized bed reactor through the spraying device. After spraying is completed, continue to keep stirring and carrier gas purging (i.e., keep the material fluidized) for 20 min to complete the polymer coating, and form a polymer coating layer (outer layer) on the outer surface of the carbon coating inner layer. Cool down to room temperature to obtain a lithium-rich lithium supplementing agent with high air stability.

[0057] Among them, the mass ratio of perfluorodecyltriethoxysilane PFDTES, tetraethyl orthosilicate, and ethanol solution is 1:1.5:6; the volume ratio of ethanol to deionized water in the ethanol solution is 50:50.

[0058] The mass ratio of tetraethyl orthosilicate in the coating raw material liquid to the Li2O / Ni powder used in the low-temperature carbonization coating is 1:60.

[0059] The mass ratio of ammonia water to the ethanol solution in the coating raw material liquid is 1:5.

[0060] This embodiment also provides a lithium-rich lithium supplementing agent with high air stability prepared by the aforementioned method, which successively includes a high lithium-containing compound, a carbon coating layer, and a polymer coating layer from the inside to the outside; the particle size of the lithium-rich lithium supplementing agent is 3.2 μm, the high lithium-containing compound is Li2O / Ni, the thickness of the carbon coating layer is 8 nm, and the thickness of the polymer coating layer is 120 nm.

[0061] The electrochemical performances of the lithium-rich lithium supplementing agents of Examples 1-4 were respectively detected, as well as the electrochemical performances after storage in a humid environment with a relative humidity of 70%. Among them, for the detection of the electrochemical performances of the lithium-rich lithium supplementing agents, each of the lithium-rich lithium supplementing agents was assembled into a half-cell to detect the first charge capacity and the first discharge capacity. The specific steps are as follows: ① According to a weight ratio of 8:1:1, the lithium-rich lithium supplementing agent, super conductive carbon black SP, and polyvinylidene fluoride PVDF were put into the solvent N-methylpyrrolidone, and the total mass of the lithium-rich lithium supplementing agent, super conductive carbon black SP, and polyvinylidene fluoride PVDF was controlled to be 7% of the mass of N-methylpyrrolidone, and they were mixed evenly to obtain a stable slurry.

[0062] ② The slurry was coated on an aluminum foil current collector by a small coating machine, and after drying and rolling, it was cut into small round pieces for standby.

[0063] ③ The small round pieces prepared in step ② were used as the positive electrode, and a metallic lithium foil was used as the negative electrode, and the electrolyte was dropped to assemble a half-cell; after standing for 12 h, the first charge capacity and the first discharge capacity were detected and recorded on a charge-discharge tester.

[0064] The electrochemical performances of the lithium-rich lithium supplementing agent after storage in a humid environment with a relative humidity of 70% were respectively that the lithium-rich lithium supplementing agents prepared in Examples 1-4 were placed in a humid environment with a relative humidity of 70% and left to stand for storage for 2 h, and then after being made into a half-cell by the aforementioned method, the first charge capacity and the first discharge capacity were detected.

[0065] The specific results are shown in the following table:

[0066] Comparative Example 1 Comparative Example 1 adopted the technical solution of Example 1, and the difference was that: in the low-temperature carbonization coating step, after the acetylene was introduced, the temperature was not raised to 500 °C, and the low-temperature carbonization coating treatment was directly completed. The carbon coating layer in the lithium-rich lithium supplement agent prepared in Comparative Example 1 was amorphous carbon, which had poor conductivity and there were various functional groups on the surface, significantly affecting the stability of the lithium-rich lithium supplement agent in the battery.

[0067] Comparative Example 2 Comparative Example 2 adopted the technical solution of Example 2, and the difference was that: in the low-temperature carbonization coating step, the temperature during the acetylene introduction was controlled at 500 °C. During the preparation process of Comparative Example 2, the metal elements in the lithium-rich lithium supplement agent would be reduced, resulting in a significant deterioration of its electrochemical performance.

[0068] Comparative Example 3 Comparative Example 3 adopted the technical solution of Example 1, and the difference was that: for the polymerization coating, a fluidized bed reactor was not used. After the coating raw material liquid was introduced into a conventional reactor, under stirring conditions, the low-temperature carbonization coating product was put into the reactor and stirred and dispersed, and then ammonia water was added for catalysis; under the stirring action, a polymer coating layer was formed on the outer surface of the inner carbon coating layer.

[0069] During the preparation process of Comparative Example 3, forming the polymer coating layer not only required cumbersome post-treatment processes such as centrifugation, washing, filtration, and drying, but also the recycling of production waste liquid was difficult; at the same time, the particles were prone to self-aggregation during the polymerization coating process, affecting the coating effect.

[0070] Comparative Example 4 Comparative Example 4 adopted the technical solution of Example 1, and the difference was that: the polymerization coating step was omitted.

[0071] For the lithium-rich lithium supplement agent with a carbon coating layer prepared in Comparative Example 4, after being stored statically in a humid environment with a relative humidity of 70% for 2 h, a large amount of lithium hydroxide and lithium carbonate products would be generated on the surface. In the electrochemical performance test of making a half-cell, the initial charge capacity was only 210 mAh / g, far lower than that of Example 1.

[0072] Unless otherwise specified, the percentages used in the present invention are all mass percentages.

[0073] Finally, it should be noted that: the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a lithium-rich lithium supplement agent with high air stability, characterized in that: The following steps are involved: Low temperature carbonization coating, polymerization coating; The low-temperature carbonization coating method comprises the following steps: putting a high-lithium compound / composite powder into a fluidized bed reactor, continuously introducing an inert gas into the fluidized bed reactor to keep the material in the fluidized bed reactor fluidized; heating the reactor to 300-400° C., introducing acetylene while maintaining the temperature; after the introduction of acetylene is completed, heating the reactor to 400-500° C., maintaining the temperature for reaction, and then completing the low-temperature carbonization coating; The polymerization coating method comprises the following steps: after the low-temperature carbonization coating is completed, while maintaining the fluidization of the material in the fluidized bed reactor, the fluidized bed reactor is kept warm when the temperature drops to 100-120° C., and the coating raw material liquid is sprayed into the fluidized bed reactor, and the material is kept fluidized; then, ammonia water is sprayed into the fluidized bed reactor, and the material is kept fluidized to complete the polymerization coating, so as to obtain a lithium-rich lithium supplement agent with high air stability; The coating raw material liquid is a mixture of alkoxysilane, tetraethyl orthosilicate and ethanol solution.

2. The method for preparing the lithium-rich lithium supplementing agent with high air stability according to claim 1, characterized in that: The high lithium-containing compound / composite powder is at least one of the following: Li2O, Li2O2, Li3N, Li2S, Li x Si、Li2CuO 2、 Li2NiO2, Li5FeO4, Li6CoO4, Li2CO3, Li2C2O4, Li2C4O4, Li2S / M, LiF / M, Li2O / M, Li x Si / M; Wherein, M is one of the following: Fe, Ni, Co, Mn, Zn, Cu; The value of X is 2-3.

3. The method for preparing the lithium-rich lithium supplementing agent with high air stability according to claim 1, characterized in that: In the low-temperature carbonization coating, the acetylene is introduced at 300-400°C for 1-4 hours; The reaction time at 400-500℃ is 1-2h.

4. The method for preparing the lithium-rich lithium supplementing agent with high air stability according to claim 1, characterized in that: In the low-temperature carbonization coating, the mass ratio of the high-lithium-containing compound / composite powder to acetylene is 5-6:

1.

5. The method for preparing the lithium-rich lithium supplement agent with high air stability according to claim 1, characterized in that: In the polymerization coating, the material fluidization time is maintained for 20-60 minutes after the coating raw material liquid is sprayed; After the ammonia spraying is completed, the material fluidization time is maintained for 5-30 minutes.

6. The method for preparing the lithium-rich lithium supplement agent with high air stability according to claim 1, characterized in that: In the polymerization coating, the mass ratio of alkoxysilane, tetraethyl orthosilicate and ethanol solution in the coating raw material liquid is 1-2:1.5-3:4-8; The volume ratio of ethanol to deionized water in the ethanol solution is 30-70:30-70.

7. The method for preparing the lithium-rich lithium supplementing agent with high air stability according to claim 1, characterized in that: In the polymer coating, the alkoxysilane is at least one of the following: perfluorodecyltriethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, octyltriethoxysilane, phenyltriethoxysilane, p-tolyltriethoxysilane, trifluoromethyltriethoxysilane, perfluoroethyltriethoxysilane, γ-glycidyltriethoxysilane, aminotriethoxysilane, and mercaptotriethoxysilane.

8. The method for preparing the lithium-rich lithium supplementing agent with high air stability according to claim 1, characterized in that: In the polymerization coating, the mass ratio of tetraethyl orthosilicate in the coating raw material liquid to the high lithium-containing compound / composite powder used in the low-temperature carbonization coating is 1:40-200.

9. The method for preparing the lithium-rich lithium supplementing agent with high air stability according to claim 1, characterized in that: In the polymer coating, the mass concentration of ammonia water is 5.5-6.5wt%; The mass ratio of ammonia water to ethanol solution in the coating raw material solution is 1:4.5-5.

5.

10. A lithium-rich lithium supplement with high air stability prepared by the method of any one of claims 1 to 9, characterized in that: The lithium-rich lithium supplement agent comprises, from the inside to the outside, a high-lithium-containing compound / composite, a carbon coating layer, and a polymer coating layer; The particle size of the lithium-rich lithium supplement agent is 1-15 μm, the thickness of the carbon coating layer is 5-20 nm, and the thickness of the polymer coating layer is 20-200 nm.

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