A fast ion conductor composite material, a preparation method thereof, a secondary battery, and an electrical device

Abstract

The present application discloses a fast ion conductor composite material, a preparation method thereof, a secondary battery and an electrical device, relating to the field of batteries. The fast ion conductor composite material includes a core, the material of the core includes graphite, and a coating composite layer, the coating composite layer at least partially coats the core, and the coating composite layer includes a first functional layer and a second functional layer extending sequentially outward from the surface of the core. Among them, the material of the first functional layer includes a mixture of a porous oxide, a MOF material and a lithium salt, the material of the second functional layer includes amorphous carbon, the lithium salt mixture includes at least two lithium salts, the lithium salt mixture includes lithium aluminum oxide and lithium cobalt oxide, and the molar ratio of the lithium aluminum oxide to the lithium cobalt oxide is (1-5):1, which improves the energy density, high temperature performance and first efficiency, thereby improving the charge and discharge rate performance of the battery and enhancing its power output ability, having good flame retardancy, and also taking into account the safety performance of the battery.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a fast ion conductor composite material and a preparation method thereof, a secondary battery and an electrical device. Background Art

[0002] At present, the fast-charging negative electrode materials used in the market are mainly artificial graphite, which mainly improves the fast-charging performance of negative electrode materials by selecting negative electrodes with good isotropy, reducing particle size, secondary granulation and increasing carbon coating. For example, increasing the carbon coating amount will improve the fast-charging performance, but at the same time, the energy density of the material will decrease, the high-temperature performance will decrease, and the first efficiency will decrease. This will cause the fast-charging performance of the negative electrode material to be unable to take into account the energy density, first efficiency, and high-temperature performance at the same time. Alternatively, some fast ion conductor materials can be added to improve the fast-charging performance of the negative electrode material, but the improvement is limited, and there is a problem that the first efficiency and high-temperature performance of the material have not been improved. Summary of the invention

[0003] The main purpose of this application is to propose a fast ion conductor composite material and its preparation method, a secondary battery and an electrical device, aiming to improve the battery's charge and discharge rate performance and power output capacity by improving energy density, high temperature performance and initial efficiency, having good flame retardancy while also taking into account the battery's safety performance.

[0004] To achieve the above object, the present invention provides a fast ion conductor composite material, comprising:

[0005] a core, the material of the core comprising graphite; and,

[0006] A coating composite layer at least partially coats the inner core, the coating composite layer comprising a first functional layer and a second functional layer extending outward from the inner core surface in sequence, wherein the material of the first functional layer comprises a porous oxide, an MOF material and a lithium salt mixture, the material of the second functional layer comprises amorphous carbon, the lithium salt mixture comprises at least two lithium salts, the at least two lithium salts comprise lithium aluminum oxide and lithium cobalt oxide, and the molar ratio of the lithium aluminum oxide to the lithium cobalt oxide is (1-5):1.

[0007] In one embodiment, the porous oxide comprises porous alumina; and / or,

[0008] The porous oxide comprises porous alumina: the specific surface area of ​​the porous alumina is 10-100 m 2 / g, and / or, the porosity of the porous alumina is 50-80%; and / or,

[0009] The lithium salt mixture comprises lithium aluminum oxide and lithium cobalt oxide; and / or,

[0010] The MOF material includes at least one of ZnO@Mg-MOF, Zn-MOF808, MOF-74(Zn), MOF-818, and ZIF-8.

[0011] In one embodiment, in the fast ion conductor composite material, the mass ratio of the graphite, the porous oxide, and the lithium salt mixture is 100:(1 - 10):(1 - 10).

[0012] In one embodiment, the thickness of the first functional layer is 10 nm to 500 nm; and / or,

[0013] the thickness of the second functional layer is 100 nm to 500 nm.

[0014] The present invention also provides a method for preparing the fast ion conductor composite material as described above, including the following steps:

[0015] S10. Mix a metal chloride, a first dispersant, an alkali solution, a MOF material, and graphite to obtain a mixed liquid, and perform a first heat treatment on the mixed liquid and then dry it to obtain a precursor material;

[0016] S20. Mix the precursor material obtained in step S10 with a solvent, a lithium supplement agent, a second dispersant, and an initiator, and perform a second heat treatment and then carbonize it to obtain an ion conductor composite material.

[0017] In one embodiment, in step S10:

[0018] The mass ratio of the metal chloride, the first dispersant, the alkali solution, the MOF material, and the graphite is (10 - 100):(1 - 10):(500 - 1000):(5 - 15):1000; and / or,

[0019] The metal chloride includes aluminum chloride; and / or, the mass concentration of the alkali solution in the mixture is 1 - 2 wt%; and / or,

[0020] The first dispersant includes at least one of glycerol, polyvinylpyrrolidone, and polyethylene glycol; and / or,

[0021] The alkali solution includes at least one of ammonia water, sodium hydroxide, potassium hydroxide, and calcium hydroxide; and / or,

[0022] The steps of the first heat treatment include: heating and reacting at 50 - 100 °C for 1 - 3 h.

[0023] In one embodiment, in step S20:

[0024] The solvent is ethylene glycol, and the mass ratio of the precursor material, the ethylene glycol, the lithium supplement agent, the second dispersant, and the initiator is 100:(10 - 30):(5 - 10):(1 - 3):(1 - 5); and / or,

[0025] The lithium supplement agent includes at least one of 5 Li 4 FeO 6 Li 4 CoO 2 Li 2 NiO; and / or,

[0026] The second dispersant includes at least one of polyoxyethylene alkylphenol ether, stearyl trimethyl ammonium chloride, triethylhexyl phosphate, and methyl pentanol; and / or,

[0027] The initiator includes at least one of diacyl peroxides, peresters, dicarbonates, ketone peroxides, and monoperoxydicarbonates; and / or,

[0028] The steps of the second heat treatment include heating and reacting at 50 - 100°C for 1 - 3 h; and / or,

[0029] The carbonization step includes sintering at 800 - 1200°C for 1 - 6 h.

[0030] The present invention also provides a battery, including the fast ion conductor composite material described in any one of the above.

[0031] The present invention also provides an electrical device, including the battery described above.

[0032] The present invention provides a fast ion conductor composite material, which includes a core and a coating composite layer. The coating composite layer at least partially coats the core. Among them, the material of the core includes graphite, which has high conductivity and provides an electron conduction path as the core. The coating composite layer can avoid the contact between graphite and the electrolyte and reduce side reactions. The porous oxide and MOF material in the first functional layer have a high specific surface area and a high porosity, providing more active sites for the migration and storage of lithium ions. The lithium salt mixture contains at least two lithium salts, which can provide a fast ion transport path, embed into the pores of the porous oxide and MOF material, and can improve the electrochemical performance of the graphite anode, improve its charge and discharge efficiency, reduce irreversible capacity loss. At the same time, it can also serve as a lithium ion transport channel to promote the rapid and uniform insertion / extraction of lithium ions into / from the graphite interlayer, ensuring good electron conduction ability. The second functional layer includes amorphous carbon, which coats the first functional layer to form a conductive network, further improving the electrochemical performance of the fast ion conductor composite material. The fast ion conductor composite material of the present invention improves the energy density, high temperature performance and first efficiency, thereby improving the charge and discharge rate performance of the battery, enhancing its power output ability, having good flame retardancy, and also taking into account the safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0034] Figure 1 It is a scanning electron microscope image (SEM) of the fast ion conductor composite material in Embodiment 4 provided by the present invention.

[0035] The realization of the purpose, functional characteristics and advantages of the present invention will be further described in conjunction with the embodiments and with reference to the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase. In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement it. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0037] Currently, the fast-charging anode materials used in the market are mainly artificial graphite. Its fast-charging performance is mainly improved by selecting an anode with good isotropy, reducing the particle size, secondary granulation, and increasing the carbon coating amount. For example, when increasing the carbon coating amount, while the fast-charging performance is improved, there are defects such as a decrease in the energy density of the material, a decline in the high-temperature performance, and a reduction in the first efficiency, resulting in problems such as the inability to simultaneously consider the fast-charging performance, energy density, first efficiency, and high-temperature performance of the anode material. Or adding some fast ion conductor materials to improve the fast-charging performance of the material, but the improvement amplitude is limited, and there are problems that the first efficiency and high-temperature performance of the material have not been improved.

[0038] In view of this, to achieve the above objectives, the present invention proposes a fast ion conductor composite material, including a core and a coating composite layer. The core material includes graphite; and the coating composite layer includes a first functional layer and a second functional layer extending outward in sequence from the surface of the core. Among them, the material of the first functional layer includes a porous oxide, a MOF material, and a lithium salt mixture, the material of the second functional layer includes amorphous carbon, the lithium salt mixture includes at least two lithium salts, the at least two lithium salts include lithium aluminum oxide and lithium cobalt oxide, the molar ratio of the lithium aluminum oxide to the lithium cobalt oxide is (1-5):1, the lithium salt mixture includes lithium aluminum oxide and lithium cobalt oxide, and the molar ratio of the lithium aluminum oxide to the lithium cobalt oxide is (1-5):1.

[0039] The present invention provides a fast ion conductor composite material, which includes a core and a coating composite layer that at least partially coats the core. Among them, graphite has high conductivity and provides an electron conduction path as the core. The coating composite layer can avoid the contact between graphite and the electrolyte to reduce side reactions. The porous oxide and MOF material in the first functional layer have a relatively high specific surface area and a relatively high porosity, providing more active sites for the migration and storage of lithium ions. The lithium salt mixture contains at least two lithium salts, which can provide a fast ion transport path, embed into the pores of the porous oxide and MOF material, and can improve the electrochemical performance of the graphite anode, increase its charge-discharge efficiency, reduce irreversible capacity loss. At the same time, it can also serve as a lithium ion transport channel to promote the rapid and uniform embedding / delithiation of lithium ions into / from the graphite interlayer, ensuring good electron conduction ability. The second functional layer includes amorphous carbon, which coats the first functional layer to form a conductive network, further improving the electrochemical performance of the fast ion conductor composite material. The fast ion conductor composite material of the present invention improves the energy density, high-temperature performance and first efficiency, thereby improving the charge-discharge rate performance of the battery, enhancing its power output ability, having good flame retardancy, and also taking into account the safety performance of the battery. Within this molar ratio range, the two can interact with each other, improving the rate performance of the material while also enhancing the structural stability and safety performance of the material. Further, the lithium salt mixture includes lithium aluminate and lithium cobalt oxide, and the molar ratio of the lithium aluminate to the lithium cobalt oxide is (1-5):1. If the content of lithium cobalt oxide is too low, then as the main source of lithium ions, the reduction in the amount of lithium cobalt oxide means a decrease in the number of lithium ions, which will lead to a reduction in battery capacity. At the same time, it will also lead to the construction of diffusion channels for lithium ions in the material, reducing the rate performance of the battery.

[0040] In some embodiments of the present invention, the porous oxide includes porous alumina. The porous alumina has a specific surface area of 10-100 m 2 / g and a porosity of 50-80%. The porous alumina has a relatively large specific surface area and a relatively high porosity, which can provide more active sites and electrolyte penetration channels, thereby improving the ionic conductivity and still having good discharge capacity and capacitance retention rate under high-speed current.

[0041] In some embodiments of the present invention, the lithium salt mixture includes lithium aluminate and lithium cobalt oxide. Selecting the above lithium salt mixture can improve the first efficiency of the material and the transport rate of lithium ions during charge and discharge.

[0042] In some embodiments of the present invention, the MOF material includes at least one of ZnO@Mg-MOF, Zn-MOF808, MOF-74(Zn), MOF-818 and ZIF-8.

[0043] It is understandable that the MOF material is a metal-organic framework, which is a porous crystal material formed by the self-assembly of metal ions or clusters and organic ligands, and can improve the liquid absorption capacity of the material, reduce swelling, and improve the cycling performance.

[0044] In some embodiments of the present invention, the MOF material includes at least one of ZnO@Mg-MOF, Zn-MOF808, MOF-74(Zn), MOF-818, and ZIF-8. That is, the MOF material can be any one of ZnO@Mg-MOF, Zn-MOF808, MOF-74(Zn), MOF-818, and ZIF-8, or can simultaneously contain two or more of ZnO@Mg-MOF, Zn-MOF808, MOF-74(Zn), MOF-818, and ZIF-8, all of which fall within the protection scope of the present invention. By selecting the above MOF materials, a framework support and a porous structure can be provided to provide more attachment points, reduce swelling and improve cycling performance.

[0045] In some embodiments of the present invention, in the fast ion conductor composite material, the mass ratio of the graphite, the porous oxide, and the lithium salt mixture is 100:(1 - 10):(1 - 10). Within the above range, the electrochemical performance of the battery can be optimized.

[0046] In some embodiments of the present invention, the thickness of the first functional layer is 100 nm to 500 nm. A suitable thickness can improve the mechanical strength of the electrode and also improve the interfacial stability of the electrode.

[0047] In some embodiments of the present invention, the thickness of the second functional layer is 100 nm to 500 nm. It mainly acts as a separator, can play a role in protecting the active material, and at the same time, prevent side reactions of the active material during cycling, thereby improving the cycling stability of the battery.

[0048] The present invention also provides a preparation method of the fast ion conductor composite material as described above, which is characterized by including the following steps:

[0049] S10. Mix metal chloride, a first dispersant, an alkali solution, a MOF material, and graphite to obtain a mixed liquid, and perform a first heat treatment on the mixed liquid and then dry it to obtain a precursor material;

[0050] S20. Mix the precursor material obtained in step S10 with a solvent, a lithium supplement agent, a second dispersant, and an initiator, and perform a second heat treatment and carbonization to obtain an ion conductor composite material.

[0051] In the technical solution of the present invention, in step S10: First, graphite has a high specific surface area and good electrical conductivity, while the MOF material has a porous structure and an ordered framework, providing a high-speed channel for ion transport. Mix metal chloride, the first dispersant, alkali solution, MOF material and graphite. The dispersant will evenly disperse the metal chloride and alkali solution on the surfaces of graphite and MOF material. The excessive metal chloride reacts with the alkali solution to form metal hydroxide or metal oxide, and through the first heat treatment, part of the metal hydroxide will further dehydrate to form porous metal oxide. Specifically, it can be porous alumina, so that the metal oxide generated by the reaction coats the surfaces of graphite and MOF material to form a first functional layer to improve safety performance. The first functional layer improves the ionic conductivity and mobility of the fast ion conductor composite material, and at the same time inhibits the growth of dendrites. Therefore, after further using the above fast ion conductor composite material to prepare a battery, the safety and cycle life of the battery can be improved.

[0052] In step S20: The solvent is ethylene glycol. This solvent can participate in the reaction as a reducing agent and reaction medium under heat treatment conditions, and can also generate intermediate products such as ethylene glycol ether and release gas, further improving the pore structure of the material. Under the second heat treatment conditions, part of the lithium supplement agent will undergo thermal decomposition to generate a second lithium salt mixture and release lithium ions, so that the remaining metal chloride reacts with part of the lithium ions under alkaline conditions to obtain a lithium salt mixture, improving the first efficiency of the material. Among them, the two obtained lithium salt mixtures adhere to the surface of the first functional layer, and the released lithium ions increase the number of lithium ions during the charge and discharge process, improving the rate performance. Another part of the lithium supplement agent, under the action of the initiator, the lithium supplement agent reacts with the hydroxyl groups (-OH) or other active sites on the surface of ethylene glycol to form covalent bonds or other types of strong interactions to form a lithium-containing polymer. This helps to firmly attach the newly generated polymer to the first functional layer to form a coating layer with high ionic conductivity and stable structure. At the same time, the cross-linking between polymer chains will also increase the mechanical strength and stability of the whole system, making the coating layer not easy to fall off. After subsequent carbonization, amorphous carbon is formed, that is, a second functional layer is formed to coat the first functional layer to form a conductive network, further improving the electrochemical performance of the fast ion conductor composite material.

[0053] In some embodiments of the present invention, in step S10, the mass ratio of the metal chloride, the first dispersant, the alkali solution, the MOF material and the graphite is (10~100):(1~10):(500~1000):(5~15):1000. In the above range, the excessive metal chloride participates in the reaction. Part of it reacts to form metal oxide to coat the surfaces of graphite and MOF material, improving the electrical conductivity. Another part of the metal chloride participates in the next round of reaction to generate a lithium salt mixture.

[0054] In some embodiments of the present invention, the metal chloride includes aluminum chloride. The metal chloride of the present invention is preferably aluminum chloride. The mass concentration of the alkali solution in the mixture is 1-2 wt%, preferably 1 wt%, which helps to ensure that all substances participating in the reaction can be uniformly dispersed in the solution, thereby ensuring that the subsequently formed MOF material or other compounds have good crystallinity and repeatability.

[0055] In some embodiments of the present invention, the first dispersant includes at least one of glycerol, polyvinylpyrrolidone, and polyethylene glycol. That is, the first dispersant can be any one of glycerol, polyvinylpyrrolidone, and polyethylene glycol, or two or three of glycerol, polyvinylpyrrolidone, and polyethylene glycol, all of which are within the scope of protection. Using the above first dispersant can be used to disperse the mixed solution, so that the metal oxide is uniformly dispersed on the surfaces of graphite and MOF materials.

[0056] In some embodiments of the present invention, the alkali solution includes at least one of ammonia water, sodium hydroxide, potassium hydroxide, and calcium hydroxide. Using the above alkali solution is mainly to provide hydroxide ions to generate metal oxides, thereby improving the conductivity of the battery.

[0057] In some embodiments of the present invention, the steps of the first heat treatment include: heating and reacting at 50-100 °C for 1-3 h. In the above heat treatment range, residual solvents and moisture can be removed, and the structure of the precursor material can be further stabilized.

[0058] In some embodiments of the present invention, in step S20:

[0059] The solvent is ethylene glycol, and the mass ratio of the precursor material, the ethylene glycol, the lithium supplement agent, the second dispersant, and the initiator is 100:(10-30):(5-10):(1-3):(1-5); within the above range, the precursor material is mixed with the lithium supplement agent. Among them, for example, the precursor material contains aluminum chloride, that is, ALCl 3 + 2OH - + Li + → LiAlO 2 + HCl, and at the same time Li 6 CoO 4 → Li + + LiCoO 2 + O 2 , thereby obtaining a mixture of two lithium salts. The combination of these two substances, lithium aluminate (LiAlO 2 ), improves the high energy density and conductivity, while lithium cobalt oxide (LiCoO 2)(It) enhances the structural stability and thermal stability. Combining the two can achieve a synergistic effect in performance. As the main lithium ion conductor, it provides an efficient ion migration path and improves the electrochemical performance.

[0060] Furthermore, during the use of ethylene glycol, ethylene glycol needs to be added to N-methylpyrrolidone (NMP) to prepare a 1wt% solution for use, which can improve solubility, reduce viscosity, improve electrochemical performance, promote dispersion and control reaction conditions.

[0061] In some embodiments of the present invention, the lithium supplementing agent includes Li 5 FeO 4 , Li 6 CoO 4 and Li 2 NiO 2 at least one of them, which is mainly used to supplement lithium ions, increase the number of lithium ions, improve the rate performance, and at the same time can also generate a lithium salt mixture to further improve the conductivity.

[0062] In some embodiments of the present invention, the second dispersant includes at least one of polyoxyethylene alkylphenol ether, stearyl trimethyl ammonium chloride, triethylhexyl phosphate and methyl pentanol, which is mainly used to disperse the mixed solution, helps to make each raw material uniform, and improves the preparation efficiency.

[0063] In some embodiments of the present invention, the initiator includes at least one of diacyl peroxide, benzoyl peroxide, peroxide ester, peroxydicarbonate, ketone peroxide and monoperoxycarbonate. Using any of the above initiators to initiate the polymerization reaction to form a polymer, and subsequent carbonization can form amorphous carbon, which can inhibit the decomposition of the functional layer in a high-temperature environment and extend the cycle life.

[0064] In some embodiments of the present invention, the steps of the second heat treatment include heating and reacting at 50~100°C for 1~3h. Within the above range, not only can the chemical reaction proceed completely, but also maintaining an appropriate sintering temperature can make the material form an ideal crystal structure, which is beneficial to the rapid conduction of ions.

[0065] The carbonization step includes: sintering at 800~1200°C for 1~6h. Within the above range, a stable carbon structure can be formed, the conductivity can be improved, the pore structure can be optimized, the heat resistance and chemical stability can be enhanced, the impurity content can be reduced, and the morphology of the material can be controlled.

[0066] The present invention also provides a secondary battery, including the fast ion conductor composite material as described in any one of the above.

[0067] The present invention also provides an electrical device, including the battery as described above. By way of example, the electrical devices proposed in this application include, but are not limited to: mobile phones, portable devices, laptop computers, and so on.

[0068] Both the above-mentioned battery and the electrical device contain the fast ion conductor composite material of the present invention, and thus have all the above beneficial effects, which will not be elaborated one by one here.

[0069] The technical solution of the present invention will be further described in detail below in conjunction with specific embodiments and the accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0070] Embodiment 1

[0071] A fast ion conductor composite material includes a core and a functional layer coated on the core;

[0072] Among them, the core includes graphite, and there are multiple functional layers. The coating composite layer includes a first functional layer and a second functional layer extending sequentially outward from the surface of the core. The material of the first functional layer includes porous alumina, and the material of the second functional layer includes a lithium salt mixture, that is, lithium aluminum oxide and lithium cobalt oxide; among them, the molar ratio of the lithium aluminum oxide to the lithium cobalt oxide is 4:1;

[0073] The specific surface area of the porous alumina is 50m 2 / g; the mass ratio of the graphite to the porous alumina is 100:5; the mass ratio of the graphite to the lithium salt mixture is 100:5; the thickness of the first functional layer is 300nm; the thickness of the second functional layer is 300nm.

[0074] Embodiment 2

[0075] Embodiment 2 is similar to Embodiment 1, the difference is that:

[0076] The molar ratio of the lithium aluminum oxide to the lithium cobalt oxide is 1:1;

[0077] The specific surface area of the porous alumina is 10m 2 / g; the mass ratio of the graphite to the porous alumina is 100:1; the mass ratio of the graphite to the lithium salt mixture is 100:1; the thickness of the first functional layer is 100nm; the thickness of the second functional layer is 100nm.

[0078] Embodiment 3

[0079] Embodiment 3 is similar to Embodiment 1, the difference is that:

[0080] The molar ratio of the lithium aluminum oxide to the lithium cobalt oxide is 5:1;

[0081] The specific surface area of the porous alumina is 100 m 2 / g; the mass ratio of the graphite to the porous alumina is 10:1; the mass ratio of the graphite to the lithium salt mixture is 10:1; the thickness of the first functional layer is 500 nm; the thickness of the second functional layer is 500 nm.

[0082] Example 4

[0083] A preparation method of a fast ion conductor-coated graphite composite material includes the following steps:

[0084] Step S10: Prepare a mixed solution by mixing 100 g of aluminum chloride, 5 g of glycerol, 800 g of an ammonia water solution with a mass concentration of 1 wt%, and 10 g of ZnO@Mg-MOF, then add 1000 g of artificial graphite to the mixed solution, and carry out a chemical reaction at a temperature of 80 °C for 2 h, filter, and vacuum dry at 80 °C for 24 h to obtain a precursor material;

[0085] Step S20: Add 20 g of polyvinyl alcohol to 2000 g of N-methylpyrrolidone to prepare a 1 wt% solution, then add 8 g of Li 5 FeO 4 、2 g of polyoxyethylene alkylphenol ether are dispersed evenly, 100 g of the precursor material is added and mixed evenly, and 3 g of diacyl peroxide is added and reacted at a temperature of 80 °C for 2 h, filtered, and the obtained filter residue is sintered at a high temperature of 1000 °C for 3 h to obtain a fast ion conductor composite material, wherein the molar ratio of the lithium aluminum oxide to the lithium cobalt oxide is 3.5:1.

[0086] Example 5

[0087] A preparation method of a fast ion conductor-coated graphite composite material includes the following steps:

[0088] Step S10: Prepare a mixed solution by mixing 100 g of zirconium tetrachloride, 1 g of polyvinylpyrrolidone, 500 g of a sodium hydroxide solution with a mass concentration of 1 wt%, and 5 g of Zn-MOF808, then add 1000 g of artificial graphite to the mixed solution, and carry out a chemical reaction at a temperature of 50 °C for 3 h, filter, and the obtained filter residue is vacuum dried at 80 °C for 24 h to obtain a precursor material;

[0089] Step S20: Add 10 g of polyvinyl alcohol to 1000 g of N-methylpyrrolidone to prepare a 1 wt% solution, then add 5 g of Li6CoO4 and 1 g of stearyl trimethyl ammonium chloride and disperse evenly, then add 100 g of the precursor material and mix evenly, and add 1 g of peroxide ester and react at a temperature of 50 °C for 3 h, filter, and the obtained filter residue is sintered at a high temperature of 800 °C for 6 h to obtain a fast ion conductor composite material.

[0090] Example 6

[0091] A preparation method of a fast ion conductor-coated graphite composite material, comprising the following steps:

[0092] Step S10: Prepare a mixed solution by mixing 100 g of niobium chloride, 10 g of polyethylene glycol, 1000 g of a potassium hydroxide solution with a mass concentration of 1 wt%, and 15 h of MOF-74(Zn). Then add 1000 g of artificial graphite and carry out a chemical reaction at a temperature of 100 °C for 1 h. Filter, and vacuum dry the obtained filter residue at 80 °C for 24 h to obtain a precursor material;

[0093] Step S20: Add 30 g of polyvinyl alcohol to 3000 g of N-methylpyrrolidone to prepare a 1 wt% solution. Then add 10 g of Li 2 NiO 2 , 3 g of methyl pentanol and disperse evenly. Then add 100 g of the precursor material and mix evenly. Add 5 g of dicarbonate peroxide and react at a temperature of 100 °C for 1 h. Filter, and sinter the obtained filter residue at a high temperature of 1200 °C for 1 h to obtain a fast ion conductor composite material.

[0094] Comparative Example 1

[0095] The difference between Comparative Example 1 and Example 4 is that no lithium supplement agent (Li 5 FeO 4 ) and the second dispersant (polyoxyethylene alkylphenol ether) are added, and the others are the same as in Example 4.

[0096] Comparative Example 2

[0097] The difference between Comparative Example 2 and Example 4 is that ZnO@Mg-MOF is not added, and the others are the same as in Example 4.

[0098] Comparative Example 3

[0099] The difference between Comparative Example 3 and Example 4 is that the mass ratio of the graphite to the metal oxide is 100:0.5, that is, 5 g of aluminum chloride is added, that is, there is only one lithium salt (lithium cobalt oxide), and the others are the same as in Example 4.

[0100] Comparative Example 4

[0101] The difference between Comparative Example 4 and Example 4 is that no aluminum chloride is added, that is, no porous oxide is formed, and the others are the same as in Example 4.

[0102] Comparative Example 5

[0103] The difference between Comparative Example 5 and Example 4 is that the molar ratio of the lithium aluminum oxide to the lithium cobalt oxide in Comparative Example 5 is 0.5:1, and the others are the same as in Example 4.

[0104] Performance Test

[0105] (1)SEM Test

[0106] The fast ion conductor-coated graphite composite prepared in Example 4 was subjected to SEM test, and the results are as Figure 1 shown. It can be seen from Figure 1 that the obtained composite material presents a secondary granular structure, with slight adhesion phenomenon, the particle size is between 10-15μm, and the size distribution is uniform.

[0107] (2)Button Cell Test

[0108] The fast ion conductor composites prepared in Examples 4-6 and the fast ion conductor composites of Comparative Examples 1-5 were assembled into button cells respectively according to the following method:

[0109] Binder, conductive agent and solvent were added to the fast ion conductor composite, stirred and mixed evenly to make the negative electrode slurry. The negative electrode slurry was coated on the copper foil, dried, rolled and cut to obtain the negative electrode sheet. The binder is polyvinylidene fluoride, the conductive agent is SP conductive agent, the solvent is NMP, and the weight ratio of the negative electrode material, SP conductive agent, polyvinylidene fluoride to NMP is 95:1:4:220. Using a metal lithium sheet as the counter electrode, a polyethylene (PE) membrane as the separator, and LiPF 6 / EC+DEC (the concentration of LiPF 6 is 1.3mol / L, and the volume ratio of EC to DEC is 1:1) as the electrolyte, the battery assembly was carried out in a glove box filled with argon.

[0110] The prepared button cells were respectively installed on a Wuhan Blue Electric CT2001A battery tester, charged and discharged at a rate of 0.1C, and the charge-discharge voltage range was 0.005V-2.0V. The first discharge capacity and the first discharge efficiency were measured. And the charging DCR (50% SOC) and the cycle performance (0.1C / 0.1C, 100 cycles) of the battery were tested.

[0111] The first discharge specific capacity, the first charge-discharge efficiency, the tap density, the specific surface area, the powder conductivity, the powder OI value, the DCR and the cycle performance of the above fast ion conductor composite materials were tested according to the national standard GB / T-24533-2019 "Graphite Anode Materials for Lithium-Ion Batteries". The test results are shown in Table 1:

[0112] Table 1

[0113]

[0114] As can be seen from Table 1, the discharge specific capacity and DCR of the fast ion conductor composites prepared in Examples 4-6 are significantly better than those in Comparative Examples 1-5. This is because the surface of the graphite material is coated with a porous metal alumina fast ion conductor containing lithium, which reduces its irreversible capacity and improves the lithium ion transport rate, enhancing the electronic and ionic conductivities of the material and its initial efficiency. At the same time, a mixture of lithium metaaluminate / lithium cobaltate or lithium iron phosphate is coated on the surface of the material to restrain the expansion of the inner core graphite and utilize the low expansion rate of MOF itself to improve the cycle performance.

[0115] Comparing Comparative Example 2 with Example 4, during the preparation of the battery, due to the lack of the framework support of MOFs and fewer porous structures, the pores in MOFs can not only provide an adsorption effect but also serve as catalytic active centers. When these structures are missing, the liquid retention performance of the material is reduced, and the cycle performance and ion transport rate are decreased, and the rate performance is also reduced. At the same time, the lack of MOF material causes an increase in the expansion of the material and a reduction in the cycle performance.

[0116] (3) Soft-pack battery test

[0117] Using the fast ion conductor composites prepared in Examples 4-6 and Comparative Examples 1-5 to prepare the negative electrode, using lithium iron phosphate as the positive electrode material to prepare the positive electrode, and using LiPF 6 (The solvent is EC+DEC, volume ratio 1:1, concentration 1.1mol / L) as the electrolyte, and celegard2400 as the separator to prepare a 2Ah soft-pack battery.

[0118] During the preparation of the negative electrode, a binder, a conductive agent, and a solvent are added to the negative electrode material, stirred and mixed evenly to make a negative electrode slurry. The negative electrode slurry is coated on the copper foil, dried, rolled, and cut to obtain a negative electrode sheet. The binder is LA132 binder, the conductive agent is SP conductive agent, the solvent is secondary distilled water, and the weight ratio of the negative electrode material, SP conductive agent, LA132 binder to secondary distilled water is 95:1:4:220.

[0119] 1) Rate performance test

[0120] The charge-discharge voltage range is 2.5~3.65V, the test temperature is 25±3.0℃, and the battery is charged at 1.0C, 2.0C, 3.0C, and 5.0C respectively and discharged at 1.0C to test the constant current ratio of the battery under different charging modes. The results are shown in Table 2:

[0121] Table 2

[0122]

[0123] As can be seen from Table 2, the rate charge performance of the packaged battery of the present invention is significantly better than that of the comparative example, and the charging time is shorter. This is because the materials of the examples have excellent powder conductivity and their low OI value improves the fast charging performance of the materials.

[0124] Compared with Comparative Example 1, since the examples added a lithium supplement agent (Li 5 FeO 4 ) and a second dispersant, the lithium supplement agent is uniformly attached to the surface of the first functional layer with two lithium salt mixtures, and an organic lithium salt layer can also be obtained, that is, a second functional layer is formed and superimposed on the surface of the first functional layer, greatly improving the conductivity. Therefore, the fast ion conductor composite material prepared in the examples has high powder conductivity and improves the constant current ratio of the material.

[0125] Compared with Comparative Example 2, since the comparative example lacks the framework support of MOFs and has fewer porous structures, the liquid retention performance of the material is reduced, resulting in a slower lithium ion transport rate during the charge and discharge process, and the rate performance is greatly reduced.

[0126] Compared with Comparative Example 3, due to the less aluminum chloride, lithium metaaluminate compounds cannot be formed, reducing the intercalation and deintercalation rate of lithium ions during its charge and discharge and reducing its rate performance.

[0127] Compared with Comparative Example 4, without a porous structure, the specific surface area is reduced, the diffusion coefficient of the material is reduced, and its rate performance is reduced.

[0128] Compared with Comparative Example 5, due to the relatively large content of lithium cobalt oxide, that is, the material has more lithium supplement agents, more lithium cobalt oxides are decomposed and formed, while fewer lithium ions form lithium aluminum oxides with aluminum chloride, and another part of the lithium will form dead lithium with amorphous carbon, resulting in a limited increase in the diffusion rate of lithium ions in the material, instead reducing the diffusion rate of lithium ions during charge and discharge and reducing its rate performance.

[0129] 2) Cycle performance test

[0130] The soft-pack batteries prepared from the fast ion conductor composite materials in Examples 4-6 and Comparative Examples 1-5 were subjected to the following experiments: at a charge and discharge rate of 2C / 2C and a voltage range of 2.5-3.65V, 100 and 500 charge and discharge cycles were carried out in sequence, and their capacity retention rates were tested. The results are shown in Table 3:

[0131] Table 3

[0132]

[0133] As can be seen from Table 3, the cycling performance of the lithium-ion battery prepared from the fast ion conductor composite material prepared by the present invention is superior to that of the comparative example. The reason is that the fast ion conductor composite material coated on the surface of graphite improves the structural stability of the material and its coated MOF material reduces expansion, thereby improving the cycling performance.

[0134] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the patent protection scope of the present invention.

Claims

1. A fast ion conductor composite material, characterized in that: The fast ion conductor composite material comprises: a core, the material of the core comprising graphite; and, A coating composite layer at least partially covers the inner core, the coating composite layer comprising a first functional layer and a second functional layer extending outward from the inner core surface in sequence, wherein the material of the first functional layer comprises porous oxide, MOF material, LiAlO2 and LiCoO2, and the material of the second functional layer comprises amorphous carbon; The method for preparing the fast ion conductor composite material comprises the following steps: S10, mixing a metal chloride, a first dispersant, an alkali solution, a MOF material and graphite to obtain a mixed liquid, performing a first heat treatment on the mixed liquid, and drying to obtain a precursor material; S20, mixing the precursor material of step S10 with a solvent, a lithium supplementing agent, a second dispersant and an initiator, performing a second heat treatment and carbonization to obtain a fast ion conductor composite material; The mass ratio of the metal chloride, the first dispersant, the alkali solution, the MOF material and the graphite is 100: (1-10): (500-1000): (5-15): 1000; The metal chloride comprises aluminum chloride; The lithium supplement comprises at least Li6CoO4; The porous oxide includes porous alumina.

2. The fast ion conductor composite material according to claim 1, characterized in that: The specific surface area of ​​the porous alumina is 10 to 100 m 2 / g, and / or, the porosity of the porous alumina is 50-80%; and / or, The MOF material includes at least one of ZnO@Mg-MOF, Zn-MOF808, MOF-818 and ZIF-8.

3. The fast ion conductor composite material according to claim 1, characterized in that: The thickness of the first functional layer is 10 nm to 500 nm; and / or, The thickness of the second functional layer is 100nm-500nm.

4. A method for preparing a fast ion conductor composite material as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: S10, mixing a metal chloride, a first dispersant, an alkali solution, a MOF material and graphite to obtain a mixed liquid, performing a first heat treatment on the mixed liquid, and drying to obtain a precursor material; S20, mixing the precursor material of step S10 with a solvent, a lithium supplement agent, a second dispersant and an initiator, performing a second heat treatment and carbonization to obtain a fast ion conductor composite material.

5. The method for preparing the fast ion conductor composite material according to claim 4, characterized in that: In step S10: The metal chloride comprises aluminum chloride; and / or, The first dispersant comprises at least one of glycerol, polyvinyl pyrrolidone and polyethylene glycol; and / or, The alkali solution includes at least one of aqueous ammonia, sodium hydroxide and potassium hydroxide; and / or, The first heat treatment step includes: heating the reaction at 50-100° C. for 1-3 hours.

6. The method for preparing the fast ion conductor composite material according to claim 4, characterized in that: In step S20: The solvent is ethylene glycol, and the mass ratio of the precursor material, the ethylene glycol, the lithium supplement agent, the second dispersant and the initiator is 100: (10-30): (5-10): (1-3): (1-5); and / or, The second dispersant comprises at least one of polyoxyethylene alkylphenol ether, stearyl trimethyl ammonium chloride, triethylhexyl phosphoric acid and methyl amyl alcohol; and / or, The initiator comprises at least one of diacyl peroxide, benzoyl peroxide, peroxyester, peroxydicarbonate, peroxyketal and monoperoxycarbonate; and / or, The second heat treatment step comprises heating the reaction at 50-100° C. for 1-3 hours; and / or, The carbonization step includes: sintering at 800-1200° C. for 1-6 hours.

7. A secondary battery, characterized in that: The fast ion conductor composite material comprises the fast ion conductor composite material as described in any one of claims 1 to 3 or the fast ion conductor composite material prepared by the preparation method of the fast ion conductor composite material as described in any one of claims 4 to 6.

8. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to claim 7.

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