Eutectic-coated composite solid electrolyte as well as preparation method and application thereof

Abstract

The invention relates to a eutectic-coated composite solid electrolyte as well as a preparation method and application thereof. The composite solid electrolyte comprises a fluorinated solid electrolyte and an eutectic coating layer coating the surface of the fluorinated solid electrolyte, the preparation method comprises the following steps: immersing a solid electrolyte material into a prepared fluorination treatment solution, and enabling dissociated F <-> in the fluorination treatment solution to be subjected to substitution reaction on unsaturated coordinated metal sites on the surface of the solid electrolyte material to form bonding of F <-> and metal elements, so as to obtain a fluorinated solid electrolyte; the preparation method comprises the following steps: mixing and ball-milling a fluorinated solid electrolyte and an eutectic liquid containing a cyano-Li < + > coordination cluster, and inducing to form an eutectic coating layer under the electrostatic attraction action between Li < + > in the cyano-Li < + > coordination cluster in the eutectic liquid and F <-> exposed on the surface of the fluorinated solid electrolyte, so as to obtain the eutectic-coated composite solid electrolyte, when the composite solid electrolyte is applied to the lithium battery, the electrochemical performance of the lithium battery can be improved.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte materials technology, and in particular to a eutectic-coated composite solid electrolyte, its preparation method, and its application. Background Technology

[0002] The current development of solid-state batteries is limited by the overall performance bottleneck of electrolyte materials. Although oxide ceramic electrolytes (such as LLZO and LATP) possess high ionic conductivity and thermal stability, their inherently high Young's modulus (>150 GPa) necessitates high-temperature sintering (>1000℃) and high-pressure molding (>600 MPa) during processing. Furthermore, the rigid interface results in poor contact with the electrode, leading to a huge interfacial impedance (>200 Ω·cm). 2 While sulfide and polymer electrolytes can be processed at low temperatures, they suffer from problems such as narrow electrochemical windows (<4V), easy penetration of lithium dendrites, and poor thermal stability.

[0003] Although existing studies have attempted to coat oxide particles with polymers to improve the interface, the coating layer of physical mixing is prone to detachment, and the traditional covalent bond anchoring process is complex and costly.

[0004] Therefore, there is an urgent need to develop a disruptive solid electrolyte structure that combines high ionic conductivity, wide electrochemical stability, low interfacial impedance, and low-temperature easy processing characteristics. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a eutectic-coated composite solid electrolyte, its preparation method, and its application.

[0006] The preparation method provided by this invention employs a "surface fluorination-lithium-ion bridging-eutectic coating" strategy, which significantly improves the overall performance of solid electrolyte materials. By immersing the solid electrolyte material in a fluorination treatment solution, the F-containing inorganic compound (e.g., NH4F) is dissociated in a low-carbon alcohol or aqueous solution. - O on unsaturated metal sites on the powder surface 2- or OH - Stable metal ions -F are formed on the surface. - This bond enables effective passivation and functionalization of the solid electrolyte material surface. Subsequently, the fluorinated solid electrolyte is combined with a cyano-Li bond... + Ball milling of eutectic solutions of coordination clusters, utilizing the Li in the clusters + With solid electrolyte surface F - The electrostatic attraction between them induces the formation of a uniform and continuous eutectic coating layer on the surface of solid electrolyte particles.

[0007] To achieve the above objectives, in a first aspect, the present invention provides a composite solid electrolyte with eutectic coating, the composite solid electrolyte comprising: a fluorinated solid electrolyte, and a eutectic coating layer covering the surface of the fluorinated solid electrolyte;

[0008] The fluorinated solid electrolyte is obtained by fluorinating a solid electrolyte material to a surface containing F. - Solid electrolyte materials;

[0009] The eutectic coating layer comprises a nitrile organic compound and a lithium salt: the eutectic coating layer is a cyano-Li formed by the nitrile organic compound and the lithium salt. + Li in coordination clusters + F exposed on the surface of the fluorinated solid electrolyte - The electrostatic attraction between them induces the formation.

[0010] Preferably, the particle size D of the fluorinated solid electrolyte is... 50 Between 5nm and 1μm;

[0011] The thickness of the eutectic coating layer is between 10 nm and 100 nm.

[0012] Preferably, the solid electrolyte material includes one or more of the following: oxide-based solid electrolyte material, sulfide-based solid electrolyte material, fluoride oxide-based solid electrolyte material, and solid polymer electrolyte;

[0013] The nitrile organic compounds include one or more of the following: succinic anionyl nitrile (SN), adiponitrile (ADN), glutaronitrile (GLN), methylsuccinic anionyl nitrile, and malononitrile (MDN);

[0014] The lithium salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethyl)sulfonyl)imide (LiTFSI), lithium bis(oxalateborate)borate (LiBOB), and lithium difluorooxalateborate (LiDFOB); the mass ratio of the nitrile organic compound to the lithium salt is 3-5:1-2.

[0015] More preferably, the oxide-based solid electrolyte material includes one or more of the following: garnet-type oxide solid electrolyte, perovskite-type oxide solid electrolyte, and NASICON-type oxide solid electrolyte;

[0016] The sulfide-based solid electrolyte material includes one or more of the following: silver sulfide germanite type solid electrolyte, LGPS type solid electrolyte, and Thio-LISICON type solid electrolyte;

[0017] The fluorine oxide-based solid electrolyte material includes one or more of the following: garnet-type fluorine oxide solid electrolyte, NASICON-type oxide solid electrolyte, layered fluorine oxide solid electrolyte, and disordered rock salt fluorine oxide solid electrolyte.

[0018] More preferably, the chemical formula of the garnet-type oxide solid electrolyte is: Li7Al3B12O 12 Where A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf;

[0019] The general chemical formula of the perovskite oxide solid electrolyte is: Li 3x A2 2 / 3-x B2O3, wherein 0.01≤x≤0.5, A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr;

[0020] The general chemical formula of the NASICON-type oxide solid electrolyte is: Li 1+y A3 y B3 2-y (PO4)3, wherein 0.01≤y≤0.5, A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf;

[0021] The general chemical formula of the sulfosilver germanite-type solid electrolyte is Li6PS5N, where N includes any one of Cl, Br, and I elements.

[0022] The general chemical formula of the LGPS type sulfide solid electrolyte is Li 11-z M 2-z P 1+z S 12 , where 0 < z < 2, and M includes any one of the elements Ge, Si, and Sn;

[0023] The Thio-LISICON type sulfide solid electrolyte includes: (100-u)Li₂S-uP₂S₅, (100-u)Li₂S-uSiS₂, Li 4-v Ge 1-v P v One or more of S4, where 0 < u < 100, 0 < v < 1;

[0024] The fluoride-based solid electrolyte material specifically includes: Li 1.5 Al 0.5 Ge 1.5 (PO4)2.9 F 0.1 Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Li₂VO₂F, Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Or with the general chemical formula Li m La n A a B b C c One or more of the fluoride oxide-based solid electrolytes of O6F; wherein A is a tetravalent cation, B is a pentavalent cation, and C is a hexavalent cation; 1 < m + 3n < 5, 0 < m ≤ 2, 1 / 3 < n < 5 / 3; 0 ≤ a ≤ 2, 0 ≤ b ≤ 2, 0 ≤ c ≤ 2, and a + b + c = 2.

[0025] This invention provides a method for preparing the composite solid electrolyte with eutectic coating as described in the first aspect, the method comprising:

[0026] Preparation of fluorination treatment solution;

[0027] The preparation of a fluorinated solid electrolyte includes: immersing a solid electrolyte material in the fluorination treatment solution, reacting it at a certain temperature, and providing F through the dissociation of fluorinated inorganic matter in the fluorination treatment solution. - Substitution reactions occur at unsaturated coordinated metal sites on the surface of solid electrolyte materials to form F. - The solid electrolyte material is fluorinated by bonding with metal elements. After fluorination, the solid electrolyte material is washed and dried to obtain fluorinated solid electrolyte.

[0028] The preparation of the eutectic solution includes: melting and mixing a nitrile organic compound with a lithium salt to form a homogeneous liquid phase, thereby obtaining a cyano-Li group. + Eutectic liquid of coordination clusters;

[0029] The preparation of a composite solid electrolyte with a eutectic coating includes: mixing the fluorinated solid electrolyte with the eutectic solution, ball milling the mixture under an inert atmosphere, and passing the cyano-Li in the eutectic solution through... + Li in coordination clusters + F exposed on the surface of fluorinated solid electrolyte - The electrostatic attraction between them induces the formation of a eutectic coating layer on the surface of the composite solid electrolyte, resulting in a composite solid electrolyte with eutectic coating.

[0030] Preferably, the preparation of the fluorination treatment solution specifically includes: adding fluorinated inorganic substances to a low-carbon alcohol solution or deionized water to prepare a fluorination treatment solution with a molar concentration of 0.1 mol / L to 1 mol / L;

[0031] The fluorine-containing inorganic compound includes one or more of NH4F, NaF, and KF; the low-carbon alcohol includes any one of methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, and glycerol.

[0032] The reaction at a certain temperature specifically includes reacting at 30℃ to 70℃ for 20 to 60 minutes.

[0033] Preferably, the nitrile organic compound includes one or more of the following: succinic anionyl nitrile (SN), adiponitrile (ADN), glutaronitrile (GLN), methylsuccinic anionyl nitrile, and malononitrile (MDN);

[0034] The lithium salt includes one or more of the following: lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethyl)sulfonyl)imide (LiTFSI), lithium bis(oxalateborate)borate (LiBOB), and lithium di(fluorooxalateborate)borate (LiDFOB);

[0035] The mass ratio of the nitrile organic compound to the lithium salt is 3-5:1-2;

[0036] The melting and mixing temperature is 50℃~80℃.

[0037] Preferably, the mass ratio of the fluorinated solid electrolyte to the eutectic solution is 50-70:30-50; the mixing ball milling specifically involves ball milling at a speed of 300-500 rpm for 2-5 hours under an inert atmosphere.

[0038] The inert atmosphere includes one or more combinations of nitrogen, helium, or argon atmospheres;

[0039] The grinding media in the ball mill are zirconia balls, and the material-to-ball ratio is 5:1 to 10:1.

[0040] The present invention provides a lithium battery, the lithium battery comprising the composite solid electrolyte with eutectic coating as described in the first aspect above, or comprising the composite solid electrolyte with eutectic coating prepared by the preparation method described in the second aspect above.

[0041] The present invention provides a eutectic-coated composite solid electrolyte, its preparation method, and its application, which have the following technical effects:

[0042] (1) This invention provides a method for preparing a eutectic-coated composite solid electrolyte, using a "fluorinated surface + Li" method. +The modification of solid electrolyte materials is achieved through "bridging + eutectic coating". Specifically, the solid electrolyte material is immersed in a pre-prepared fluorination solution, where F dissociates. - Substitution reactions occur at unsaturated coordinated metal sites on the surface of solid electrolyte materials to form F. - Bonding with metal elements yields fluorinated solid electrolytes; molten mixing of nitrile organic compounds with lithium salts yields cyano-Li-containing electrolytes. + Eutectic solution of coordination clusters; fluorinated solid electrolyte and eutectic solution are mixed and ball-milled, and the cyano-Li in the eutectic solution is detected. + Li in coordination clusters + F exposed on the surface of fluorinated solid electrolyte - The electrostatic attraction between the two elements induces the formation of a eutectic coating layer on the surface of the composite solid electrolyte, ultimately yielding a composite solid electrolyte with eutectic coating. This preparation method is simple to operate, the coating process does not require high-temperature sintering, and it consumes little energy and has low cost.

[0043] (2) The eutectic-coated composite solid electrolyte prepared by the method provided in this invention solves the problems of fragility and difficulty in processing caused by the high Young's modulus of traditional solid electrolytes. It also overcomes the problems of low ionic conductivity, poor electrochemical stability, and narrow operating temperature range of polymer solid electrolytes, while avoiding the defects of sulfide electrolytes such as sensitivity to water and oxygen and high cost. The resulting composite solid electrolyte material has high ionic conductivity, good interfacial stability, flexibility, and processability, making it suitable for practical applications of high-performance all-solid-state lithium batteries. It has good engineering feasibility and promotional value.

[0044] (3) When preparing a solid electrolyte membrane using the eutectic-coated composite solid electrolyte provided by the present invention, the lithium-ion bridging eutectic coating technology in the preparation process enables the composite solid electrolyte to be cold-pressed without sintering at a pressure of less than or equal to 500 MPa and at room temperature. Compared with the molding conditions of 600 MPa and 1000°C for traditional solid electrolytes, this solves the problem of the brittleness and difficulty in processing of existing traditional solid electrolyte materials.

[0045] (4) The solid electrolyte membrane prepared by the eutectic-coated composite solid electrolyte provided by the present invention is applied to lithium batteries, especially solid lithium batteries, because of the F--Li in the composite solid electrolyte. + Electrostatic anchoring of the interface reduces interfacial resistance, increases ionic conductivity and electrochemical window, and improves battery cycle performance; it can compress the interfacial resistance to less than 8 Ω·cm. 2 The cycle capacity retention rate of the full battery after 200 cycles is greater than 98%, improving the cycle stability of the full battery; at the same time, it is compatible with a wide temperature range of -10℃ to 180℃ and high-voltage battery systems, and can be adapted to various positive electrodes. Attached Figure Description

[0046] Figure 1 This is a flowchart illustrating the preparation method of a composite solid electrolyte with eutectic coating provided in an embodiment of the present invention. Detailed Implementation

[0047] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0049] The composite solid electrolyte with eutectic coating prepared by the above preparation method provided in this embodiment of the invention includes: a fluorinated solid electrolyte, and a eutectic coating layer coated on the surface of the fluorinated solid electrolyte.

[0050] Fluorinated solid electrolytes are obtained by fluorinating solid electrolyte materials to produce electrolytes with F-containing surfaces. - Solid electrolyte materials. Solid electrolyte materials include, but are not limited to, one or more of the following: oxide-based solid electrolyte materials, sulfide-based solid electrolyte materials, fluoride oxide-based solid electrolyte materials, and solid polymer electrolytes.

[0051] The eutectic coating layer comprises nitrile organic compounds and lithium salts: the eutectic coating layer is a cyano-Li formed by nitrile organic compounds and lithium salts. + Li in coordination clusters + F exposed on the surface of fluorinated solid electrolyte - Formation is induced by electrostatic attraction between the nitrile compounds. Nitrile organic compounds include one or more of the following: succinic anionyl nitrile (SN), adiponitrile (ADN), glutaronitrile (GLN), methylsuccinic anionyl nitrile, and malononitrile (MDN). Lithium salts include one or more of the following: lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiBOB), and lithium difluorooxalato)borate (LiDFOB); the mass ratio of nitrile organic compound to lithium salt is 3–5:1–2.

[0052] The aforementioned oxide-based solid electrolyte materials include one or more of the following: garnet-type oxide solid electrolytes, perovskite-type oxide solid electrolytes, and NASICON-type oxide solid electrolytes.

[0053] The general chemical formula of the garnet-type oxide solid electrolyte is: Li7Al3B12O 12 Where A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf. The general chemical formula of perovskite oxide solid electrolytes is: Li 3x A2 2 / 3-x B₂O₃, wherein 0.01 ≤ x ≤ 0.5, A₂ is one or more of La, Al, Mg, Fe, and Ta, and B₂ is one or more of Ti, Nb, Sr, and Pr. The general chemical formula of NASICON-type oxide solid electrolytes is: Li 1+ y A3 y B3 2-y (PO4)3, wherein 0.01≤y≤0.5, A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf.

[0054] Sulfide-based solid electrolyte materials include one or more of the following: sulfide-germanium sulfide-type solid electrolytes, LGPS-type solid electrolytes, and Thio-LISICON-type solid electrolytes. The general chemical formula of the sulfide-germanium sulfide-type solid electrolyte is Li₆PS₅N, where N includes any one of Cl, Br, and I elements. The general chemical formula of the LGPS-type sulfide solid electrolyte is Li₂... 11-z M 2-z P 1+z S 12 Where 0 < z < 2, and M includes any one of Ge, Si, and Sn. Thio-LISICON type sulfide solid electrolytes include: (100-u)Li₂S-uP₂S₅, (100-u)Li₂S-uSiS₂, Li 4-v Ge 1-v P v One or more of S4, where 0 < u < 100, 0 < v < 1.

[0055] Fluoride oxide-based solid electrolyte materials include one or more of the following: garnet-type fluoride oxide solid electrolytes, NASICON-type oxide solid electrolytes, layered fluoride oxide solid electrolytes, and disordered rock salt fluoride oxide solid electrolytes. Specifically, fluoride oxide-based solid electrolyte materials include: Li... 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Li 6.5 La3Zr 1.5 Ta 0.5 O11.5 F 0.5 Li₂VO₂F, Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Or with the general chemical formula Li m La n A a B b C c One or more of the fluorinated oxide-based solid electrolytes of O6F; wherein A is a tetravalent cation, B is a pentavalent cation, and C is a hexavalent cation; 1 < m + 3n < 5, 0 < m ≤ 2, 1 / 3 < n < 5 / 3; 0 ≤ a ≤ 2, 0 ≤ b ≤ 2, 0 ≤ c ≤ 2, a + b + c = 2. The particle size D of the above fluorinated solid electrolytes. 50 The particle size is between 5 nm and 1 μm; the thickness of the eutectic coating is between 10 nm and 100 nm. In this invention, the particle size D of the material is... 50 This refers to the median particle size of the material, which can be the median value sorted by volume, mass, or quantity. In the various embodiments of this invention, the median particle size sorted by quantity is specifically used, representing the particle size of the porous carbon matrix that accounts for 50% of the total particle size distribution. Particle size D 50 This is a meaning known in the art. The particle size D of the material provided in the embodiments of the present invention... 50 The particle size D can be determined using instruments and conventional methods known in the art. Specifically, a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK, was used to measure the particle size D. 50 Measurements were performed. This invention provides a method for preparing a composite solid electrolyte with eutectic coating, such as... Figure 1 As shown, the preparation method specifically includes the following steps.

[0056] Step 110: Add the fluorinated inorganic substance to a low-carbon alcohol solution or deionized water to prepare a fluorination treatment solution with a molar concentration of 0.1 mol / L to 1 mol / L.

[0057] Among them, fluorine-containing inorganic substances include one or more of NH4F, NaF, and KF; low-carbon alcohols include any one of methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, and glycerol.

[0058] The molar concentration of the fluorination treatment solution is 0.1 mol / L to 1 mol / L, and can be any value within this range, such as 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, etc., but is not limited to the listed values.

[0059] Step 120: Immerse the solid electrolyte material in the fluorination treatment solution and react at 30℃~70℃ for 20 minutes~60 minutes. The F provided by the dissociation of fluorinated inorganic matter in the fluorination treatment solution... - Substitution reactions occur at unsaturated coordinated metal sites on the surface of solid electrolyte materials to form F. - The solid electrolyte material is fluorinated by bonding with metal elements. After fluorination, the solid electrolyte material is washed and dried to obtain fluorinated solid electrolyte.

[0060] Specifically, solid electrolyte materials include, but are not limited to, one or more of the following: oxide-based solid electrolyte materials, sulfide-based solid electrolyte materials, fluoride oxide-based solid electrolyte materials, and solid polymer electrolytes.

[0061] Oxide-based solid electrolyte materials include one or more of the following: garnet-type oxide solid electrolytes, perovskite-type oxide solid electrolytes, and NASICON-type oxide solid electrolytes.

[0062] The general chemical formula of the garnet-type oxide solid electrolyte is: Li7Al3B12O 12 A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf.

[0063] The general chemical formula of perovskite oxide solid electrolytes is: Li 3x A2 2 / 3-x B2O3, wherein 0.01≤x≤0.5, A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr.

[0064] The general chemical formula of NASICON-type oxide solid electrolytes is: Li 1+y A3 y B3 2-y (PO4)3, wherein 0.01≤y≤0.5, A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf.

[0065] Sulfide-based solid electrolyte materials include one or more of the following: silver-germanium sulfide solid electrolyte, LGPS solid electrolyte, and Thio-LISICON solid electrolyte.

[0066] The general chemical formula of the sulfide-germanium ore type solid electrolyte is Li6PS5N, where N includes any one of Cl, Br, and I elements.

[0067] The general chemical formula of LGPS type sulfide solid electrolytes is Li 11-z M 2-z P 1+z S 12 , where 0 < z < 2, and M includes any one of the elements Ge, Si, and Sn.

[0068] Thio-LISICON type sulfide solid electrolytes include: (100-u)Li₂S-uP₂S₅, (100-u)Li₂S-uSiS₂, Li 4-v Ge 1-v P v One or more of S4, where 0 < u < 100, 0 < v < 1.

[0069] Fluoride oxide-based solid electrolyte materials include one or more of the following: garnet-type fluoride oxide solid electrolytes, NASICON-type oxide solid electrolytes, layered fluoride oxide solid electrolytes, and disordered rock salt fluoride oxide solid electrolytes. Specifically, fluoride oxide-based solid electrolyte materials include: Li... 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Li₂VO₂F, Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Or with the general chemical formula Li m La n A a B b C c One or more of the fluoride oxide-based solid electrolytes of O6F; wherein A is a tetravalent cation, B is a pentavalent cation, and C is a hexavalent cation; 1 < m + 3n < 5, 0 < m ≤ 2, 1 / 3 < n < 5 / 3; 0 ≤ a ≤ 2, 0 ≤ b ≤ 2, 0 ≤ c ≤ 2, and a + b + c = 2.

[0070] The washing and drying in this step are conventional and known methods; for example, washing can be done by repeatedly rinsing the fluorinated solid electrolyte material with deionized water at least 3 times; drying involves placing the washed product in a vacuum drying oven and drying it at 80°C to 100°C for 30 minutes to 24 hours.

[0071] Step 130: The nitrile organic compound is melt-mixed with the lithium salt to form a homogeneous liquid phase, yielding a cyano-Li group. + Eutectic liquid of coordination clusters.

[0072] Among them, nitrile organic compounds include one or more of the following: succinic anionyl nitrile (SN), adiponitrile (ADN), glutaronitrile (GLN), methylsuccinic anionyl nitrile, and malononitrile (MDN).

[0073] Lithium salts include one or more of the following: lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalateborate)borate (LiBOB), and lithium di(fluorooxalateborate)borate (LiDFOB).

[0074] The mass ratio of nitrile organic compounds to lithium salts is 3 to 5: 1 to 2, and can be any ratio within this range, such as 3: 1, 3: 2, 4: 1, 4: 2, 5: 1, 5: 2, etc., but is not limited to the listed ratios.

[0075] The melting and mixing temperature is 50℃~80℃. Within this temperature range, nitrile organic compounds melt, and lithium salts are uniformly distributed in the molten liquid phase of nitrile organic compounds.

[0076] Step 140: Mix the fluorinated solid electrolyte and the eutectic solution at a mass ratio of 50–70:30–50, and ball mill the mixture under an inert atmosphere. Pass the cyano-Li in the eutectic solution through... + Li in coordination clusters + F exposed on the surface of fluorinated solid electrolyte - The electrostatic attraction between them induces the formation of a eutectic coating layer on the surface of the composite solid electrolyte, resulting in a composite solid electrolyte with eutectic coating.

[0077] The fluorinated solid electrolyte and the eutectic solution are in a mass ratio of 50 to 70:30 to 50, which can be any ratio within this range, such as 50:30, 50:40, 50:50, 60:30, 60:40, 60:50, 70:30, 70:40, 70:50, etc., but are not limited to the listed ratios.

[0078] The equipment used for ball milling is conventional equipment, such as a ball mill. The specific process of ball milling is as follows: ball milling at a speed of 300 rpm to 500 rpm for 2 to 5 hours under an inert atmosphere.

[0079] Inert atmospheres include one or more combinations of nitrogen, helium, or argon atmospheres.

[0080] The grinding media in the ball mill are zirconia balls, and the material-to-ball ratio is 5:1 to 10:1.

[0081] The solid electrolyte material used in the embodiments of the present invention is preferably Li m La n A a B b C c The O6F fluoride oxide-based solid electrolyte, wherein A can be one or more elements selected from Zr, Ti, Hf, Si, Ge, and Sn; B can be one or more elements selected from Nb, Sb, Bi, V, and Ta; and C can be one or more elements selected from W, Cr, Mo, and Mn. Due to its inherent high density, high purity, high volumetric energy density, low internal resistance, and excellent ion conductivity, the fluoride oxide-based solid electrolyte, after being bridged with a eutectic coating layer, exhibits even better processability and electrochemical performance.

[0082] The principle of fluorination treatment of solid electrolyte materials in the preparation method provided in this embodiment of the invention is as follows: the solid electrolyte material is immersed in a fluorination treatment solution, and the fluorinated inorganic substances in the fluorination treatment solution dissociate. Taking NH4F and ethanol solution as an example, NH4F dissociates in ethanol solution to obtain F. - and NH4 + (The chemical equation is:) The exposed metal sites on the surface of the solid electrolyte material contain unsaturated coordinated oxygen anion groups (-O). - Solid electrolyte materials are immersed in a fluorination treatment solution containing hydroxyl groups (-OH) and / or hydroxyl groups (-OH). - Attacking metal points replaces weakly bonded -O - And / or -OH groups, thereby fluorinating solid electrolyte materials with the general chemical formula Li. m La n A a B b C c Taking O6F as an example of a fluoride-based solid electrolyte, F - Attack on the solid electrolyte with La 3+ The weakly bonded -OH group at the metal site makes F - with La 3+ Bonding (chemical reaction formula is La) 3+ -OH+F - →La 3+ -F - +OH - ), the Li m La n A a B b C c Other metal sites in the O6F solid electrolyte can also undergo similar substitution reactions to obtain fluorinated solid electrolytes.

[0083] In the preparation method provided in this embodiment of the invention, a nitrile organic compound and a lithium salt are melt-mixed to form a homogeneous liquid phase, and the cyano group (-C≡N) in the nitrile organic compound coordinates the lithium ion (Li). + This process forms cyano-lithium ion clusters, resulting in a eutectic solution. The fluorinated solid electrolyte is then ball-milled and mixed with the eutectic solution. The fluoride ions (F) on the surface of the fluorinated solid electrolyte... - The lithium ions (Li) in the cyano-lithium ion clusters of the eutectic solution + Li forms strong ionic bonds through electrostatic attraction. + Bridging allows the surface of the fluorinated solid electrolyte to be coated with a eutectic, ultimately resulting in a composite solid electrolyte with a eutectic coating.

[0084] The composite solid electrolyte with eutectic coating provided by the present invention can be used in lithium batteries, especially solid lithium batteries.

[0085] Specifically, the composite solid electrolyte of this invention is cold-pressed at 100 MPa to 500 MPa and room temperature for 10 to 60 minutes to form a dense composite solid electrolyte membrane for use in solid-state lithium-ion batteries. This is because the composite solid electrolyte provided by this invention contains F--Li... + Electrostatic anchoring interfaces can reduce interface resistance, increase ionic conductivity and electrochemical window, thereby improving the cycle performance of solid-state lithium batteries.

[0086] Example 1

[0087] This invention provides a method for preparing a composite solid electrolyte with eutectic coating, which specifically includes the following steps.

[0088] (1) First, prepare the fluorine oxide-based solid electrolyte Li 1.25 La 0.58 Nb₂O₆F (abbreviated as LLNOF) was prepared by mixing Li₂CO₃, La₂O₃, Nb₂O₅, and LiF in a molar ratio of 0.625:0.29:1:1. The mixture was then placed in a tube furnace, and nitrogen gas was introduced into the furnace at a flow rate of 1.5 L / min. Under the nitrogen atmosphere, the temperature was increased to 1000 °C at a rate of 2 °C / min and held for 6 hours to obtain the fluoride solid electrolyte Li. 1.25 La 0.58 Nb2O6F.

[0089] (2) Add NH4F to an ethanol solution (75% ethanol aqueous solution by mass) to prepare a fluorination treatment solution with a molar concentration of 0.5 mol / L.

[0090] (3) 500g of fluorine oxide-based solid electrolyte Li1.25 La 0.58 Nb₂O₆F is immersed in 1 kg of a fluorination treatment solution with a molar concentration of 0.5 mol / L and reacted at 50 °C for 60 minutes. The F provided by the dissociation of fluorinated inorganic matter in the fluorination treatment solution is then utilized. - Substitution reactions occur at unsaturated coordinated metal sites on the surface of the solid electrolyte material LLNOF to form F. - The solid electrolyte material is fluorinated by bonding with metal elements. After fluorination, the solid electrolyte material is washed and dried to obtain fluorinated solid electrolyte.

[0091] (4) 300g of succinic anionylene and 100g of lithium bis(trifluoromethanesulfonyl)imide were melt-mixed at 60°C to form a homogeneous liquid phase, yielding a cyano-Li-containing product. + Eutectic liquid of coordination clusters.

[0092] (5) Mix 500g of fluorinated solid electrolyte with 300g of eutectic solution, and ball mill at 500rpm for 3 hours under nitrogen atmosphere. The material-to-ball ratio is 5:1. The cyano-Li in the eutectic solution... + Li in coordination clusters + F exposed on the surface of fluorinated solid electrolyte - The electrostatic attraction between them induces the formation of a eutectic coating layer on the surface of the composite solid electrolyte, resulting in a composite solid electrolyte with eutectic coating.

[0093] (6) The composite solid electrolyte with eutectic coating prepared in this embodiment is cold-pressed at 200 MPa and room temperature for 10 minutes to form a dense composite solid electrolyte membrane.

[0094] Example 2

[0095] This invention provides a method for preparing a composite solid electrolyte with eutectic coating, which differs from Example 1 in that the solid electrolyte material is different, and specifically includes the following steps.

[0096] (1) First, prepare the fluorine oxide-based solid electrolyte Li 1.25 La 0.58 Ta₂O₆F (abbreviated as LLTOF) is prepared by mixing Li₂CO₃, La₂O₃, Ta₂O₅, and LiF in a molar ratio of 0.625:0.29:1:1. The mixture is placed in a tube furnace, and nitrogen gas is introduced into the furnace at a flow rate of 1.5 L / min. Under the nitrogen atmosphere, the temperature is increased to 1000 °C at a rate of 2 °C / min and held for 6 hours to obtain the fluoride solid electrolyte Li. 1.25 La 0.58 Nb2O6F.

[0097] (2) Add NH4F to an ethanol solution (75% ethanol aqueous solution by mass) to prepare a fluorination treatment solution with a molar concentration of 0.5 mol / L.

[0098] (3) 500g of fluorine oxide-based solid electrolyte Li 1.25 La 0.58 Ta₂O₆F was immersed in 1 kg of a fluorination treatment solution with a molar concentration of 0.5 mol / L and reacted at 50 °C for 60 minutes. The F provided by the dissociation of fluorinated inorganic substances in the fluorination treatment solution was then observed. - Substitution reactions occur at unsaturated coordinated metal sites of LLTOF on the surface of solid electrolyte materials to form F. - The solid electrolyte material is fluorinated by bonding with metal elements. After fluorination, the solid electrolyte material is washed and dried to obtain fluorinated solid electrolyte.

[0099] (4) 300g of succinic anionylene and 100g of lithium bis(trifluoromethanesulfonyl)imide were melt-mixed at 60°C to form a homogeneous liquid phase, yielding a cyano-Li-containing product. + Eutectic liquid of coordination clusters.

[0100] (5) Mix 500g of fluorinated solid electrolyte with 300g of eutectic solution, and ball mill at 500rpm for 3 hours under nitrogen atmosphere. The material-to-ball ratio is 5:1. The cyano-Li in the eutectic solution... + Li in coordination clusters + F exposed on the surface of fluorinated solid electrolyte - The electrostatic attraction between them induces the formation of a eutectic coating layer on the surface of the composite solid electrolyte, resulting in a composite solid electrolyte with eutectic coating.

[0101] (6) The composite solid electrolyte with eutectic coating prepared in this embodiment is cold-pressed at 200 MPa and room temperature for 10 minutes to form a dense composite solid electrolyte membrane.

[0102] Example 3

[0103] This invention provides a method for preparing a composite solid electrolyte with eutectic coating. The difference from Example 1 is the molar concentration of the fluorination solution in steps (2) and (3). Step (2) involves adding NH4F to an ethanol solution (an aqueous ethanol solution with a mass concentration of 75%) to prepare a fluorination solution with a molar concentration of 1 mol / L. The other preparation processes are the same as in Example 1.

[0104] Example 4

[0105] This invention provides a method for preparing a composite solid electrolyte with eutectic coating. The difference from Example 1 is that the mass ratio of succinic acid to lithium bis(trifluoromethanesulfonyl)imide in step (4) is different. In step (4), 400g of succinic acid and 100g of lithium bis(trifluoromethanesulfonyl)imide are melt-mixed at 60°C to form a homogeneous liquid phase, resulting in a cyano-Li-containing electrolyte. + Eutectic solution of coordination clusters. Other preparation procedures are the same as in Example 1.

[0106] Example 5

[0107] This invention provides a method for preparing a composite solid electrolyte with eutectic coating. The difference from Example 1 is in step (5), where 700g of fluorinated solid electrolyte is mixed with 400g of eutectic liquid and ball-milled at 500rpm for 4 hours under a nitrogen atmosphere, with a material-to-ball ratio of 6:1. The other preparation steps are the same as in Example 1.

[0108] Example 6

[0109] This invention provides a method for preparing a composite solid electrolyte with eutectic coating. The difference from Example 1 is that the pressure value of cold pressing is different. In this example, the composite solid electrolyte with eutectic coating prepared in step (6) of Example 1 is cold pressed at 150 MPa for 10 minutes to form a dense composite solid electrolyte membrane.

[0110] Example 7

[0111] This invention provides a method for preparing a composite solid electrolyte with eutectic coating, which differs from Example 1 in that it directly uses commercially available Li... 1.3 Al 0.3 Ti 1.7 The (PO4)3(LATP) solid electrolyte was eutectic coated, and the specific process is as follows:

[0112] (1) Add NH4F to an ethanol solution (75% ethanol aqueous solution by mass) to prepare a fluorination treatment solution with a molar concentration of 0.5 mol / L.

[0113] (2) Immerse 500g of LATP in 1kg of fluorination solution with a molar concentration of 0.5mol / L and react at 50℃ for 60 minutes. The F provided by the dissociation of fluorinated inorganic matter in the fluorination solution is then utilized. - Substitution reactions occur at unsaturated coordinated metal sites on the surface of the solid electrolyte material LATP to form F. - The solid electrolyte material is fluorinated by bonding with metal elements. After fluorination, the solid electrolyte material is washed and dried to obtain fluorinated solid electrolyte.

[0114] (3) 300g of succinic anionylene and 100g of lithium bis(trifluoromethanesulfonyl)imide were melt-mixed at 60°C to form a homogeneous liquid phase, yielding a cyano-Li-containing product. + Eutectic liquid of coordination clusters.

[0115] (4) Mix 500g of fluorinated solid electrolyte with 300g of eutectic solution, and ball mill at 500rpm for 3 hours under nitrogen atmosphere. The material-to-ball ratio is 5:1. The cyano-Li in the eutectic solution... + Li in coordination clusters + F exposed on the surface of fluorinated solid electrolyte - The electrostatic attraction between them induces the formation of a eutectic coating layer on the surface of the composite solid electrolyte, resulting in a composite solid electrolyte with eutectic coating.

[0116] (5) The composite solid electrolyte with eutectic coating prepared in this embodiment is cold-pressed at 200 MPa and room temperature for 10 minutes to form a dense composite solid electrolyte membrane.

[0117] Example 8

[0118] This invention provides a method for preparing a composite solid electrolyte with eutectic coating, which differs from Example 1 in that it directly uses commercially available sulfide-based solid electrolyte material Li7La3Zr2O. 12 (LLZO) is eutectic coated with the following process:

[0119] (1) Add NH4F to an ethanol solution (75% ethanol aqueous solution by mass) to prepare a fluorination treatment solution with a molar concentration of 0.5 mol / L.

[0120] (2) Immerse 500g of Li6PS5N in 1kg of a fluorination treatment solution with a molar concentration of 0.5mol / L, and react at 50℃ for 60 minutes. The F provided by the dissociation of fluorinated inorganic matter in the fluorination treatment solution is achieved. - Substitution reactions occur at unsaturated coordinated metal sites on the surface of the solid electrolyte material LLZO to form F. - The solid electrolyte material is fluorinated by bonding with metal elements. After fluorination, the solid electrolyte material is washed and dried to obtain fluorinated solid electrolyte.

[0121] (3) 300g of succinic anionylene and 100g of lithium bis(trifluoromethanesulfonyl)imide were melt-mixed at 60°C to form a homogeneous liquid phase, yielding a cyano-Li-containing product. + Eutectic liquid of coordination clusters.

[0122] (4) Mix 500g of fluorinated solid electrolyte with 300g of eutectic solution, and ball mill at 500rpm for 3 hours under nitrogen atmosphere. The material-to-ball ratio is 5:1. The cyano-Li in the eutectic solution... + Li in coordination clusters + F exposed on the surface of fluorinated solid electrolyte - The electrostatic attraction between them induces the formation of a eutectic coating layer on the surface of the composite solid electrolyte, resulting in a composite solid electrolyte with eutectic coating.

[0123] (5) The composite solid electrolyte with eutectic coating prepared in this embodiment is cold-pressed at 200 MPa and room temperature for 10 minutes to form a dense composite solid electrolyte membrane.

[0124] Example 9

[0125] This invention provides a method for preparing a composite solid electrolyte with eutectic coating. The difference from Example 1 is that it directly uses commercially available sulfide-based solid electrolyte material Li. 0.33 La 0.56 TiO3(LLTO) was coated with a eutectic layer, and the specific process is as follows:

[0126] (1) Add NH4F to an ethanol solution (75% ethanol aqueous solution by mass) to prepare a fluorination treatment solution with a molar concentration of 0.5 mol / L.

[0127] (2) Immerse 500g of Li6PS5N in 1kg of a fluorination treatment solution with a molar concentration of 0.5mol / L, and react at 50℃ for 60 minutes. The F provided by the dissociation of fluorinated inorganic matter in the fluorination treatment solution is achieved. - Substitution reactions occur at unsaturated coordinated metal sites on the surface of the solid electrolyte material LLTO to form F. - The solid electrolyte material is fluorinated by bonding with metal elements. After fluorination, the solid electrolyte material is washed and dried to obtain fluorinated solid electrolyte.

[0128] (3) 300g of succinic anionylene and 100g of lithium bis(trifluoromethanesulfonyl)imide were melt-mixed at 60°C to form a homogeneous liquid phase, yielding a cyano-Li-containing product. + Eutectic liquid of coordination clusters.

[0129] (4) Mix 500g of fluorinated solid electrolyte with 300g of eutectic solution, and ball mill at 500rpm for 3 hours under nitrogen atmosphere. The material-to-ball ratio is 5:1. The cyano-Li in the eutectic solution... + Li in coordination clusters + F exposed on the surface of fluorinated solid electrolyte -The electrostatic attraction between them induces the formation of a eutectic coating layer on the surface of the composite solid electrolyte, resulting in a composite solid electrolyte with eutectic coating.

[0130] (5) The composite solid electrolyte with eutectic coating prepared in this embodiment is cold-pressed at 200 MPa and room temperature for 10 minutes to form a dense composite solid electrolyte membrane.

[0131] Comparative Example 1

[0132] This comparative example uses the fluoride-based solid electrolyte Li prepared in step (1) of Example 1. 1.25 La 0.58 Nb2O6F was directly cold-pressed at 200 MPa and room temperature for 10 minutes to form a dense LLNOF solid electrolyte membrane.

[0133] Comparative Example 2

[0134] The difference between this comparative example and Example 1 is that the solid electrolyte material is not fluorinated, i.e., steps (2) and (3) are omitted, and 500g of the fluoride-based solid electrolyte Li is directly added. 1.25 La 0.58 Nb₂O₆F was mixed with 300g of eutectic solution and ball-milled at 500rpm for 3 hours under a nitrogen atmosphere. The material-to-ball ratio was 5:1. The cyano-Li groups in the eutectic solution were then analyzed. + Li in coordination clusters + F exposed on the surface of fluorinated solid electrolyte - The electrostatic attraction between them induces the formation of a eutectic coating layer on the surface of the composite solid electrolyte, resulting in a composite solid electrolyte with eutectic coating.

[0135] Comparative Example 3

[0136] In this comparative example, the LATP from Example 7 was directly cold-pressed at 200 MPa and room temperature for 10 minutes to form a dense LATP solid electrolyte membrane.

[0137] Comparative Example 4

[0138] In this comparative example, the LLZO from Example 8 was directly cold-pressed at 200 MPa and room temperature for 10 minutes to form a dense LLZO solid electrolyte membrane.

[0139] Comparative Example 5

[0140] In this comparative example, the LLTO from Example 9 was directly cold-pressed at 200 MPa and room temperature for 10 minutes to form a dense LLTO solid electrolyte membrane.

[0141] The performance of the composite solid electrolyte membranes of Examples 1-9 and the solid electrolyte membranes of Comparative Examples 1-5 were tested as follows.

[0142] 1. Ionic conductivity and surface resistivity tests are as follows.

[0143] (1) Ionic conductivity was tested using electrochemical impedance spectroscopy (EIS) on an electrochemical workstation. Specifically, the composite solid electrolyte membranes of Examples 1-9 and the solid electrolyte membranes of Comparative Examples 1-5 were first cut into circular pieces with a diameter of 17 mm. These pieces were then sandwiched between two stainless steel (SS) inert electrodes and inserted into a battery for testing. To ensure the accuracy of the test, the test battery was placed in a constant temperature chamber for temperature control. In the EIS test, the frequency range was set from 0.01 Hz to 1 MHz, and the amplitude voltage was set to 10 mV to accurately measure the resistance of the electrolyte. Next, by analyzing the Nyquist impedance spectrum, the ionic conductivity of the electrolyte could be calculated using the following formula: In the determination of ionic conductivity, d in the formula represents the thickness of the electrolyte, R is the impedance value of the electrolyte read from the Nyquist impedance diagram of EIS, and S represents the effective contact area between the solid electrolyte membrane and the stainless steel inert electrode. To ensure the accuracy of the measurement, when testing the ionic conductivity at different temperatures, the constant temperature chamber needs to be set to the target temperature and maintained for half an hour to allow the test battery to reach thermal equilibrium. This step ensures the stability of the test environment, thereby allowing for accurate measurement of the ionic conductivity of the solid electrolyte at various temperatures. The ionic conductivity tests of this invention were all conducted at 25±2℃ and humidity less than 50%. Detailed test data are shown in Table 1.

[0144] (2) Calculate the surface resistance. The formula is: Surface resistance = impedance value R × area S of solid electrolyte membrane.

[0145] 2. Electrochemical window testing: Lithium metal sheets were used as both the reference and counter electrodes, while stainless steel (SS) sheets were used as the working electrode. During the test, a lithium / stainless steel (Li|SS) battery was assembled inside a glove box, and then linear sweep voltammetry (LSV) was performed in a constant-temperature oven at room temperature. The scan rate was set to 1 millivolt-second (mV / s), scanning from the open-circuit voltage to 6V. The test results are detailed in Table 1.

[0146] 3. Cyclic performance testing: To test the cycle stability of the full battery composed of the electrolyte, lithium iron phosphate (LFP) was used as the positive electrode active material to prepare the LFP positive electrode, and graphite was used as the negative electrode active material to prepare the graphite negative electrode. The solid electrolyte membranes used were the composite solid electrolyte membranes of Examples 1-9 and the solid electrolyte membranes of Comparative Examples 1-5, respectively. A "LFP positive electrode | solid electrolyte membrane | graphite negative electrode" pouch battery was assembled using conventional methods. A Blue Electricity tester was used to perform 200 cycles at a 3C current density, and the capacity retention rate was calculated and recorded. The test results are detailed in Table 1.

[0147] Table 1 summarizes the test data for Examples 1-9 and Comparative Examples 1-5.

[0148]

[0149]

[0150] Table 1

[0151] As can be seen from the data in Table 1, the ionic conductivity of Examples 1-6 is much higher than that of Comparative Examples 1-2, the sheet resistivity of Examples 1-6 is significantly lower than that of Comparative Examples 1-2, the electrochemical window of Examples 1-6 is significantly higher than that of Comparative Examples 1-2, and the capacity retention of Examples 1-6 is significantly higher than that of Comparative Examples 1-2. This is because Comparative Example 1 does not undergo eutectic coating, has a high Young's modulus, and voids exist between particles under cold pressing, which seriously affects the bulk conduction of ions. Therefore, the ionic conductivity, sheet resistivity, and electrochemical window of Comparative Example 1 are all very low, and it is difficult to form a film. The assembled full cell cannot operate, and the capacity retention after 200 cycles is 0. On the other hand, Comparative Example 2 does not use fluorination treatment. After the eutectic is melted, it is mixed with the solid electrolyte material by ball milling. Although it is coated on the surface of the solid electrolyte material, there is no bonding effect, and it is easy to fall off, thus affecting its electrochemical performance.

[0152] Compared with Comparative Example 3, Example 7 showed significantly higher ionic conductivity, electrochemical window, and cycle capacity retention than Comparative Example 3, while its sheet resistance was much lower. This is because the solid electrolyte material of Comparative Example 3, which was not coated with eutectic coating, had a high Young's modulus and was brittle. Under cold pressing, there were voids between the particles, which severely affected the bulk conduction of ions. Therefore, Comparative Example 3 had very low ionic conductivity, sheet resistance, and electrochemical window, and it was also difficult to form a film. The assembled full cell could not operate, and the capacity retention after 200 cycles was 0.

[0153] The ionic conductivity, electrochemical window, and cycle capacity retention of Example 8 are much higher than those of Comparative Example 4, while the sheet resistance is much lower. This is because the solid electrolyte material of Comparative Example 4, which was not coated with eutectic coating, has a high Young's modulus and is brittle. Under cold pressing, there are voids between the particles, which seriously affect the bulk conduction of ions. Therefore, the ionic conductivity, sheet resistance, and electrochemical window of Comparative Example 4 are very low. At the same time, it is difficult to form a film, and the assembled full cell cannot operate. The capacity retention after 200 cycles is 0.

[0154] The ionic conductivity, electrochemical window, and cycle capacity retention of Example 9 are much higher than those of Comparative Example 5, while the sheet resistance is much lower. This is because the solid electrolyte material of Comparative Example 5, which was not coated with eutectic coating, has a high Young's modulus and is brittle. Under cold pressing, there are voids between the particles, which seriously affect the bulk conduction of ions. Therefore, the ionic conductivity, sheet resistance, and electrochemical window of Comparative Example 5 are very low. At the same time, it is difficult to form a film, and the assembled full cell cannot operate. The capacity retention after 200 cycles is 0.

[0155] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composite solid electrolyte with eutectic coating, characterized in that, The composite solid electrolyte includes: a fluorinated solid electrolyte, and a eutectic coating layer covering the surface of the fluorinated solid electrolyte; The fluorinated solid electrolyte is obtained by fluorinating a solid electrolyte material to a surface containing F. - Solid electrolyte materials; The eutectic coating layer comprises a nitrile organic compound and a lithium salt: the eutectic coating layer is a cyano-Li formed by the nitrile organic compound and the lithium salt. + Li in coordination clusters + F exposed on the surface of the fluorinated solid electrolyte - The electrostatic attraction between them induces the formation.

2. The composite solid electrolyte according to claim 1, characterized in that, The particle size D of the fluorinated solid electrolyte 50 Between 5nm and 1μm; The thickness of the eutectic coating layer is between 10 nm and 100 nm.

3. The composite solid electrolyte according to claim 1, characterized in that, The solid electrolyte material includes one or more of the following: oxide-based solid electrolyte material, sulfide-based solid electrolyte material, fluoride oxide-based solid electrolyte material, and solid polymer electrolyte. The nitrile organic compounds include one or more of the following: succinic anionyl nitrile (SN), adiponitrile (ADN), glutaronitrile (GLN), methylsuccinic anionyl nitrile, and malononitrile (MDN); The lithium salt includes one or more of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethyl)sulfonyl)imide (LiTFSI), lithium bis(oxalateborate)borate (LiBOB), and lithium difluorooxalateborate (LiDFOB); the mass ratio of the nitrile organic compound to the lithium salt is 3-5:1-2.

4. The composite solid electrolyte according to claim 3, characterized in that, The oxide-based solid electrolyte material includes one or more of the following: garnet-type oxide solid electrolyte, perovskite-type oxide solid electrolyte, and NASICON-type oxide solid electrolyte; The sulfide-based solid electrolyte material includes one or more of the following: silver sulfide germanite type solid electrolyte, LGPS type solid electrolyte, and Thio-LISICON type solid electrolyte; The fluorine oxide-based solid electrolyte material includes one or more of the following: garnet-type fluorine oxide solid electrolyte, NASICON-type oxide solid electrolyte, layered fluorine oxide solid electrolyte, and disordered rock salt fluorine oxide solid electrolyte.

5. The composite solid electrolyte according to claim 4, characterized in that, The general chemical formula of the garnet-type oxide solid electrolyte is: Li7Al3B12O 12 Where A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf; The general chemical formula of the perovskite oxide solid electrolyte is: Li 3x A2 2 / 3-x B2O3, wherein 0.01≤x≤0.5, A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr; The general chemical formula of the NASICON-type oxide solid electrolyte is: Li 1+y A3 y B3 2-y (PO4)3, wherein 0.01≤y≤0.5, A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf; The general chemical formula of the sulfosilver germanite-type solid electrolyte is Li6PS5N, where N includes any one of Cl, Br, and I elements. The general chemical formula of the LGPS type sulfide solid electrolyte is Li 11-z M 2-z P 1+z S 12 , where 0 < z < 2, and M includes any one of the elements Ge, Si, and Sn; The Thio-LISICON type sulfide solid electrolyte includes: (100-u)Li₂S-uP₂S₅, (100-u)Li₂S-uSiS₂, Li 4-v Ge 1-v P v One or more of S4, where 0 < u < 100, 0 < v < 1; The fluoride-based solid electrolyte material specifically includes: Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 Li₂VO₂F, Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 Or with the general chemical formula Li m La n A a B b C c One or more of the fluoride oxide-based solid electrolytes of O6F; wherein A is a tetravalent cation, B is a pentavalent cation, and C is a hexavalent cation; 1 < m + 3n < 5, 0 < m ≤ 2, 1 / 3 < n < 5 / 3; 0 ≤ a ≤ 2, 0 ≤ b ≤ 2, 0 ≤ c ≤ 2, and a + b + c = 2.

6. A method for preparing a composite solid electrolyte with eutectic coating as described in any one of claims 1-5, characterized in that, The preparation method includes: Preparation of fluorination treatment solution; The preparation of a fluorinated solid electrolyte includes: immersing a solid electrolyte material in the fluorination treatment solution, reacting it at a certain temperature, and providing F through the dissociation of fluorinated inorganic matter in the fluorination treatment solution. - Substitution reactions occur at unsaturated coordinated metal sites on the surface of solid electrolyte materials to form F. - The solid electrolyte material is fluorinated by bonding with metal elements. After fluorination, the solid electrolyte material is washed and dried to obtain fluorinated solid electrolyte. The preparation of the eutectic solution includes: melting and mixing a nitrile organic compound with a lithium salt to form a homogeneous liquid phase, thereby obtaining a cyano-Li group. + Eutectic liquid of coordination clusters; The preparation of a composite solid electrolyte with a eutectic coating includes: mixing the fluorinated solid electrolyte with the eutectic solution, ball milling the mixture under an inert atmosphere, and passing the cyano-Li in the eutectic solution through... + Li in coordination clusters + F exposed on the surface of fluorinated solid electrolyte - The electrostatic attraction between them induces the formation of a eutectic coating layer on the surface of the composite solid electrolyte, resulting in a composite solid electrolyte with eutectic coating.

7. The preparation method according to claim 6, characterized in that, The preparation of the fluorination treatment solution specifically includes: adding fluorinated inorganic substances to a low-carbon alcohol solution or deionized water to prepare a fluorination treatment solution with a molar concentration of 0.1 mol / L to 1 mol / L; The fluorine-containing inorganic compound includes one or more of NH4F, NaF, and KF; the low-carbon alcohol includes any one of methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, and glycerol. The reaction at a certain temperature specifically includes reacting at 30℃ to 70℃ for 20 to 60 minutes.

8. The preparation method according to claim 6, characterized in that, The nitrile organic compounds include one or more of the following: succinic anionyl nitrile (SN), adiponitrile (ADN), glutaronitrile (GLN), methylsuccinic anionyl nitrile, and malononitrile (MDN); The lithium salt includes one or more of the following: lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethyl)sulfonyl)imide (LiTFSI), lithium bis(oxalateborate)borate (LiBOB), and lithium di(fluorooxalateborate)borate (LiDFOB); The mass ratio of the nitrile organic compound to the lithium salt is 3-5:1-2; The melting and mixing temperature is 50℃~80℃.

9. The preparation method according to claim 6, characterized in that, The mass ratio of the fluorinated solid electrolyte to the eutectic solution is 50-70:30-50; the mixing and ball milling specifically involves ball milling at a speed of 300-500 rpm for 2-5 hours under an inert atmosphere. The inert atmosphere includes one or more combinations of nitrogen, helium, or argon atmospheres; The grinding media in the ball mill are zirconia balls, and the material-to-ball ratio is 5:1 to 10:

1.

10. A lithium battery, characterized in that, The lithium battery includes the composite solid electrolyte with eutectic coating as described in any one of claims 1-5, or the composite solid electrolyte with eutectic coating prepared by the preparation method described in any one of claims 6-9.

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