Composite solid electrolyte and preparation method and application thereof

Abstract

The invention relates to the field of solid-state lithium batteries, and discloses a composite solid-state electrolyte and a preparation method and application thereof.The composite solid-state electrolyte contains lithium salt polymer ionic gel and ceramic oxide, the ceramic oxide is selected from at least one of substances with the chemical formula being Li < 7-3x-y + z > A < x > La < 3 > Zr < 2-y > B < y > O < 12 + z > / 2 or Li < 7-3x-2k + z > A < x > La < 3 > Zr < 2-k > C < k > O < 12 + z > / 2, A is a trivalent metal element, y is a metal element, and z is a metal element; b is a pentavalent metal element, C is a hexavalent metal element, 0 < = x < = 0.4, 0 < = y < = 1, 0 < = k < = 0.7, and 0 < = z < = 1.4; the lithium salt polymer ionic gel is obtained by carrying out in-situ cross-linking polymerization on lithium salt, ionic liquid, a polymer monomer, a cross-linking agent and an initiator. The diaphragm provided by the invention has relatively good comprehensive performance, and particularly has high ionic conductivity at room temperature and good thermal stability and electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the field of solid-state lithium batteries, and in particular to a composite solid-state electrolyte and a preparation method and application thereof. Background Art

[0002] All-solid-state lithium batteries replace flammable organic electrolytes with non-flammable solid electrolytes. They have the advantages of high safety and high energy density, and are considered to be the preferred direction for the next generation of new power batteries and energy storage batteries.

[0003] According to the different synthetic materials, solid electrolytes can be roughly divided into inorganic solid electrolytes, polymer solid electrolytes and composite solid electrolytes. Among them, it is difficult to balance the mechanical properties and electrochemical properties of inorganic solid electrolytes; and polymer solid electrolytes need to be improved in terms of ionic conductivity and thermal stability. Therefore, in order to make the best use of strengths and avoid weaknesses, people have proposed the concept of composite solid electrolytes. Composite solid electrolytes can make up for the defects of a single material, so that the electrolyte has the excellent properties of various materials at the same time. The selection of composite materials and the determination of their synthesis methods have become the main problems that need to be solved for this type of electrolyte.

[0004] Many different types of composite solid electrolytes have been reported, such as tetragonal Li7La3Zr2O doped in polymer matrix PEO. 12 The ionic conductivity of the electrolyte is only 4.42×10 -4 S / cm, the room temperature conductivity is still not high enough, the preparation method is cumbersome, and the interface impedance between the electrode is high, and the conductivity cannot meet the ideal requirements for application in lithium batteries.

[0005] Therefore, there is an urgent need to provide a solid electrolyte with high room temperature ionic conductivity for the safe and effective application of lithium batteries. Summary of the invention

[0006] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a simple and readily available composite solid electrolyte with high room temperature ionic conductivity.

[0007] In order to achieve the above object, the present invention provides a composite solid electrolyte in the first aspect, which contains a lithium salt polymer ion gel and a ceramic oxide, wherein the ceramic oxide is selected from the group consisting of 7-3x-y+ z A x Ln3Z 2-y B y O 12+z / 2 or Li 7-3x-2k+z A x Ln3Z 2-k Ck O 12+z / 2 At least one of the substances, A is a trivalent metal element, B is a pentavalent metal element, C is a hexavalent metal element, 0≤x≤0.4, 0≤y≤1, 0≤k≤0.7, 0≤z≤1.4; the lithium salt polymer ion gel is obtained by in-situ crosslinking polymerization of lithium salt, ionic liquid, polymer monomer, crosslinking agent and initiator.

[0008] A second aspect of the present invention provides a method for preparing the aforementioned composite solid electrolyte, the method comprising:

[0009] (1) first mixing a lithium salt and an ionic liquid to obtain an ionic liquid precursor I;

[0010] (2) performing a second mixing of the polymer monomer, the crosslinking agent and the initiator to obtain a polymer precursor II;

[0011] (3) The ceramic oxide, the ionic liquid precursor I and the polymer precursor II are mixed for a third time, and then subjected to a cross-linking polymerization reaction to obtain the composite solid electrolyte.

[0012] The third aspect of the present invention provides the use of the aforementioned composite solid electrolyte in a solid-state lithium-ion battery.

[0013] Compared with the prior art, the composite solid electrolyte provided by the present invention has high ionic conductivity at room temperature, which can meet the application requirements of existing solid-state lithium-ion batteries. At the same time, the composite solid electrolyte provided by the present invention also has good thermal stability and electrochemical properties, and has excellent comprehensive performance.

[0014] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0015] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0016] As mentioned above, the first aspect of the present invention provides a composite solid electrolyte, the composite solid electrolyte comprising a lithium salt polymer ion gel and a ceramic oxide, wherein the ceramic oxide is selected from the group consisting of 7-3x-y+z A x Ln3Z 2- y B y O 12+z / 2 or Li7-3x-2k+z A x Ln3Z 2-k C k O 12+z / 2 At least one of the substances, A is a trivalent metal element, B is a pentavalent metal element, C is a hexavalent metal element, 0≤x≤0.4, 0≤y≤1, 0≤k≤0.7, 0≤z≤1.4; the lithium salt polymer ion gel is obtained by in-situ crosslinking polymerization of lithium salt, ionic liquid, polymer monomer, crosslinking agent and initiator.

[0017] In the present invention, the ceramic oxide is uniformly dispersed in the cross-linked polymer scaffold of the lithium salt polymer ion gel and interacts chemically with the polymer scaffold, for example, by chemical bonding. Specifically, in the presence of an initiator and a cross-linking agent, the polymer monomer undergoes an in-situ cross-linking polymerization reaction with the lithium salt, the ionic liquid and the ceramic oxide, the polymer monomer forms a cross-linked polymer scaffold structure, and the ceramic oxide is uniformly chemically fixed in the cross-linked polymer scaffold in the presence of the ionic liquid. At the same time, the lithium salt, the ionic liquid and the cross-linked polymer scaffold form a super-concentrated ion gel, namely the lithium salt polymer ion gel.

[0018] In the present invention, preferably, the molar ratio of the ceramic oxide to the lithium salt polymer ion gel is 1:0.1-2, more preferably 1:0.5-2, and the contents of the ceramic oxide and the lithium salt polymer ion gel are calculated based on the lithium element contained therein.

[0019] Preferably, the average particle size of the ceramic oxide is 50-200 μm, more preferably 50-150 μm.

[0020] Preferably, the chemical formula Li 7-3xy+z A x Ln3Z 2-y B y O 12+z / 2 or Li 7-3x-2k+z A x Ln3Z 2-k C k O 12+z / 2 In the above, A is Al and / or Ga, B is at least one selected from Ta, Nb and Sb, and C is W and / or Te.

[0021] Preferably, the ceramic oxide is selected from Li 6.4 Ln3Z 1.4 Ta 0.6 O 12 , Li 6.5 Ln3Z 1.75 Te 0.25 O 12 , Li 6.75 Ln3Z1.75 Nb 0.25 O 12 , Li 6.6 Ln3Z 1.6 Sb 0.4 O 12 , Li 6.4 Ln3Z 1.7 W 0.3 O 12 , Li 6.15 Al 0.2 Ln3Z 1.75 Ta 0.25 O 12 , Li 6.15 Ln3Z 1.75 Ta 0.25 Ga 0.2 O 12 , Li 6.5 Ln3Z 1.5 Ta 0.5 O 12 and Li 6.15 Ln3Z 1.75 Ta 0.25 Al 0.2 O 12 At least one of .

[0022] Preferably, the lithium salt is selected from at least one of lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perfluoroethanesulfonylimide and perfluoromethylsulfonylmethyl lithium; more preferably, the lithium salt is selected from at least one of lithium difluorooxalatoborate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide.

[0023] Preferably, the ionic liquid is selected from 1-ethyl-3-methylimidazolium bisfluorosulfonyl imide salt, 1-propyl-3-methylimidazolium bisfluorosulfonyl imide salt, 1-butyl-3-methylimidazolium bisfluorosulfonyl imide salt, N-propyl-N-methylpyridine bisfluorosulfonyl imide salt, 1-ethyl-1-methylpyrrolidine bisfluorosulfonyl imide salt, 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide salt, 1-propyl-3-methylimidazolium bistrifluoromethanesulfonyl imide salt, 1-butyl-3-methylimidazolium bistrifluoromethanesulfonyl imide salt, N- Propyl-N-methylpyridine bis trifluoromethanesulfonyl imide salt, 1-ethyl-1-methylpyrrolidine bis trifluoromethanesulfonyl imide salt, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-propyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, N-propyl-N-methylpyridine tetrafluoroborate, 1-ethyl-1-methylpyrrolidine tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-propyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluoro Phosphate, N-propyl-N-methylpyridinium hexafluorophosphate, 1-ethyl-1-methylpyrrolidine hexafluorophosphate, 1-ethyl-3-methylimidazolium difluorophosphate, 1-propyl-3-methylimidazolium difluorophosphate, 1-butyl-3-methylimidazolium difluorophosphate, N-propyl-N-methylpyridinium difluorophosphate, 1-ethyl-1-methylpyrrolidine difluorophosphate; more preferably, the ionic liquid is selected from 1-ethyl-3-methylimidazolium bis trifluoromethanesulfonyl imide, 1-propyl-3-methylimidazolium difluorophosphate, At least one of 1-ethyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide salt, 1-butyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide salt, 1-ethyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide salt, 1-propyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide salt, 1-butyl-3-methylimidazolium bis-fluoromethanesulfonyl imide salt, N-methyl, propyl pyrrole bis-trifluoromethanesulfonyl imide salt, N-methyl, butyl pyrrole bis-trifluoromethanesulfonyl imide salt, N-methyl, propyl pyrrole bis-trifluoromethanesulfonyl imide salt and N-methyl and butyl pyrrole bis-trifluoromethanesulfonyl imide salt. According to a more preferred embodiment of the present invention, the ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide, 1-butyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide and 1-ethyl-3-methylimidazolium bis-trifluoromethanesulfonyl imide. The inventors of the present invention have found that when the ionic liquid is particularly selected from at least one of 1-ethyl-3-methylimidazolium bis(fluoromethanesulfonyl imide), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide), the room temperature ionic conductivity of the obtained composite solid electrolyte material is better.

[0024] Preferably, the polymer monomer is selected from at least one of methyl methacrylate, methacrylic acid, acrylonitrile and acrylamide; more preferably, methyl methacrylate.

[0025] Preferably, the cross-linking agent is selected from at least one of polyethylene glycol dimethacrylate, polyethylene glycol diacrylate and polyethylene glycol methacrylate, more preferably polyethylene glycol dimethacrylate.

[0026] Preferably, the initiator is selected from one of azobisisobutyronitrile, dibenzoyl peroxide, sodium persulfate, ammonium persulfate and potassium persulfate; more preferably azobisisobutyronitrile.

[0027] Preferably, the room temperature ionic conductivity of the composite solid electrolyte is 0.8-3 mS / cm, more preferably 1-2 mS / cm; the thermal shrinkage is <5%, more preferably <3%.

[0028] As mentioned above, the second aspect of the present invention provides a method for preparing the aforementioned composite solid electrolyte, the method comprising:

[0029] (1) first mixing a lithium salt and an ionic liquid to obtain an ionic liquid precursor I;

[0030] (2) performing a second mixing of the polymer monomer, the crosslinking agent and the initiator to obtain a polymer precursor II;

[0031] (3) The ceramic oxide, the ionic liquid precursor I and the polymer precursor II are mixed for a third time, and then subjected to a cross-linking polymerization reaction to obtain the composite solid electrolyte.

[0032] Preferably, the first mixing, the second mixing and the third mixing are all carried out under anhydrous and oxygen-free conditions, with a water content of less than 0.1 ppm, an oxygen content of less than 0.1 ppm, and a mixing temperature of 10-100° C. independently of each other. According to the present invention, in the anhydrous and oxygen-free conditions, the water content is preferably less than 0.1 ppm, and the oxygen content is preferably less than 0.1 ppm. In order to obtain anhydrous and oxygen-free conditions, the method described in the second aspect of the present invention is carried out in a glove box, and the oxygen content is controlled by filling a sufficient amount of an inert gas such as argon.

[0033] Preferably, in step (3), the conditions for the cross-linking polymerization reaction include: temperature 50-100° C., time 8-24 h.

[0034] Preferably, in step (1), the weight ratio of the lithium salt to the ionic liquid is 1:0.5-5.

[0035] Preferably, in step (2), the weight ratio of the polymer monomer to the cross-linking agent and the initiator is 100:1-15:0.1-5.

[0036] Preferably, in step (3), the weight ratio of the ceramic oxide to the ionic liquid precursor I and the polymer precursor II is 1:0.05-5:0.05-5.

[0037] According to a preferred embodiment of the present invention, the method further comprises preparing the ceramic oxide by the following method:

[0038] The lithium source, the lanthanum source, the zirconium source, the first dopant containing the element A, and the second dopant containing the element B or the element C are sintered.

[0039] Preferably, the sintering conditions include: a temperature of 600-1200° C. and a time of 6-24 hours.

[0040] Preferably, the method comprises the steps of crushing the sintered product, first screening, ball milling and then second screening, and the ball milling conditions include: rotation speed 100-500 rpm, time 4-18 hours. According to the present invention, the ball milling operation is performed in a planetary ball mill, for example.

[0041] Preferably, the mesh sizes of the first sieve and the second sieve are preferably 50-200 meshes.

[0042] Preferably, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium chloride, lithium nitrate and lithium sulfate.

[0043] Preferably, the lanthanum source is selected from at least one of lanthanum carbonate, lanthanum hydroxide and lanthanum oxide.

[0044] Preferably, the zirconium source is selected from at least one of zirconium oxide, zirconium chloride and zirconium nitrate, more preferably zirconium oxide.

[0045] Preferably, the first dopant is selected from at least one of an oxide containing element A and a hydroxide containing element A, and is more preferably an oxide, such as aluminum oxide, gallium oxide, and the like.

[0046] Preferably, the second dopant is selected from at least one of an oxide containing element B or element C and a hydroxide containing element B or element C, more preferably a hydroxide, such as tantalum oxide, niobium oxide, antimony oxide, tungsten oxide, tellurium oxide, etc.

[0047] According to the present invention, the lithium source, the lanthanum source, the zirconium source, the first dopant containing element A, and the second dopant containing element B or element C are used in amounts such that the chemical formula of the obtained ceramic oxide is Li 7-3x-y+ z A x Ln3Z 2-y B y O 12+z / 2 or Li 7-3x-2k+z Ax Ln3Z 2-k C k O 12+z / 2 A is a trivalent metal element, B is a pentavalent metal element, C is a hexavalent metal element, 0≤x≤0.4, 0≤y≤1, 0≤k≤0.7, 0≤z≤1.4. At the same time, according to the present invention, in order to prevent lithium loss during the sintering process, the raw material containing the Li element, i.e., the lithium source, is usually weighed in excess of about 10-15% according to the stoichiometric ratio during the preparation process.

[0048] As mentioned above, the third aspect of the present invention provides the use of the aforementioned composite solid electrolyte in a solid-state lithium-ion battery.

[0049] In the present invention, unless otherwise specified, pressure refers to gauge pressure and room temperature refers to 25±2°C.

[0050] The present invention will be described in detail below through examples.

[0051] In the following examples, unless otherwise specified, all raw materials used are commercially available products.

[0052] The ionic liquids used in the following examples were purchased from TCI.

[0053] Example 1

[0054] (1) Preparation of ceramic oxide, whose chemical formula is Li 6.5 Ln3Z 1.5 Ta 0.5 O 12 (B=Ta, x=0, y=0.5, z=0)

[0055] According to the stoichiometric ratio, 26.18g of LiOH·H2O (purity of 99%), 45.62g of La(OH)3 (purity of 99.9%), 14.80g of ZrO2 (99.9%), and 8.83g of Ta2O5 (purity of 99.9%) were weighed, wherein the raw material containing the Li element was 10% in excess when weighed according to the stoichiometric ratio. The raw materials were mixed evenly and sieved through 100 mesh to obtain a mixture; the obtained mixture was placed in a platinum crucible, placed in a muffle furnace, heated to 900°C, pre-calcined for 12h, cooled, and the sintered product was crushed and sieved through 100 mesh. The powder was subjected to planetary ball milling at a speed of 200rpm for 12h, and then sieved through 100 mesh to obtain ceramic oxide particles with an average particle size of 100μm;

[0056] (2) Preparation of ionic liquid precursor I

[0057] In an argon-filled glove box (water content less than 0.1 ppm), 2.87 g of lithium bis(trifluoromethanesulfonyl)imide was dissolved in 3.91 g of 1-ethyl-3-methylimidazolium bis(fluoromethanesulfonyl)imide ionic liquid at 25° C., and the mixture was stirred and mixed until the lithium salt was completely dissolved to obtain ionic liquid precursor I;

[0058] (3) Preparation of polymer precursor II

[0059] In a glove box filled with argon (water content less than 0.1 ppm), 9.5 g of methyl methacrylate, 0.47 g of cross-linking agent polyethylene glycol dimethacrylate, and 0.02 g of initiator azobisisobutyronitrile were stirred and mixed at 50° C. to obtain a polymer precursor II;

[0060] (4) In an argon-filled glove box (water content less than 0.1 ppm), 5 g of ceramic oxide particles, 2.5 g of ionic liquid precursor I and 2.5 g of polymer precursor II were mixed and stirred at 60° C., and reacted at 60° C. for 12 hours to complete the cross-linking polymerization reaction to obtain a solid electrolyte with a thickness of 25 μm.

[0061] Example 2

[0062] (1) Preparation of ceramic oxide, chemical formula Li 6.15 Al 0.2 Ln3Z 1.75 Ta 0.25 O 12 (A=Al, x=0.2; B=Ta, y=0.25, z=0)

[0063] According to the stoichiometric ratio, 22.94g of LiOH·H2O (purity of 99%), 1.25g of Al(OH)3 (purity of 99.99%), 45.62g of La(OH)3 (purity of 99.9%), 17.27g of ZrO2 (99.9%), and 4.42g of Ta2O5 (purity of 99.9%) were weighed, wherein the raw material containing the Li element was 10% in excess when weighed according to the stoichiometric ratio. The raw materials were mixed evenly and sieved through 100 mesh to obtain a mixture; the obtained mixture was placed in a platinum crucible, placed in a muffle furnace, heated to 900°C, pre-burned for 8h, cooled, and the sintered product was crushed and sieved through 100 mesh. The powder was subjected to planetary ball milling at a speed of 200rpm for 5h, and then sieved through 100 mesh to obtain ceramic oxide particles with an average particle size of 100μm;

[0064] (2) Preparation of ionic liquid precursor I

[0065] In an argon-filled glove box (water content less than 0.1 ppm), 1.9 g of lithium bis(trifluoromethanesulfonyl)imide was dissolved in 4.2 g of 1-butyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide ionic liquid at 25° C., and the mixture was stirred and mixed until the lithium salt was completely dissolved to obtain ionic liquid precursor I;

[0066] (3) Preparation of polymer precursor II

[0067] In a glove box filled with argon (water content less than 0.1 ppm), 9.3 g of methyl methacrylate, 0.65 g of crosslinking agent polyethylene glycol dimethacrylate, and 0.05 g of initiator azobisisobutyronitrile were stirred and mixed at 60° C. to obtain a polymer precursor II;

[0068] (4) In an argon-filled glove box (water content less than 0.1 ppm), 5 g of ceramic oxide particles, 3 g of ionic liquid precursor I and 2 g of polymer precursor II were mixed and stirred at 60 ° C. and reacted at 70 ° C for 15 hours to complete the cross-linking polymerization reaction to obtain a solid electrolyte with a thickness of 25 μm.

[0069] Example 3

[0070] (1) Preparation of ceramic oxide, chemical formula Li 6.5 Ln3Z 1.75 Te 0.25 O 12 (x=0, C=Te, k=0.25, z=0)

[0071] According to the stoichiometric ratio, 22.94g of LiOH·H2O (purity of 99%), 45.62g of La(OH)3 (purity of 99.9%), 17.27g of ZrO2 (99.9%), and 1.59g of Te2O5 (purity of 99.9%) were weighed, wherein the raw material containing the Li element was 10% in excess when weighed according to the stoichiometric ratio. The raw materials were mixed evenly and sieved through 100 mesh to obtain a mixture; the obtained mixture was placed in a platinum crucible, placed in a muffle furnace, heated to 950°C, pre-calcined for 12h, cooled, and the sintered product was crushed and sieved through 100 mesh. The powder was subjected to planetary ball milling at a speed of 300rpm for 8h, and then sieved through 100 mesh to obtain ceramic oxide particles with an average particle size of 100μm;

[0072] (2) Preparation of ionic liquid precursor I

[0073] In an argon-filled glove box (water content less than 0.1 ppm), 2.87 g of lithium bis(trifluoromethanesulfonyl)imide was dissolved in 3.91 g of 1-ethyl-3-methylimidazole bis(trifluoromethanesulfonyl)imide ionic liquid at 25° C., and the mixture was stirred and mixed until the lithium salt was completely dissolved to obtain ionic liquid precursor I;

[0074] (3) Preparation of polymer precursor II

[0075] In a glove box filled with argon (water content less than 0.1 ppm), 9.6 g of methyl methacrylate, 0.39 g of crosslinking agent polyethylene glycol dimethacrylate, and 0.02 g of initiator azobisisobutyronitrile were stirred and mixed at 25° C. to obtain a polymer precursor II;

[0076] (4) In an argon-filled glove box (water content less than 0.1 ppm), 5 g of ceramic oxide particles, 2 g of ionic liquid precursor I and 3 g of polymer precursor II were mixed and stirred at 60 ° C. and reacted at 80 ° C for 8 hours to complete the cross-linking polymerization reaction to obtain a solid electrolyte with a thickness of 25 μm.

[0077] Example 4

[0078] A solid electrolyte was obtained in a manner similar to that of Example 1, except that the polymerization monomer in step (4) was methacrylic acid of equal mass, and the rest was the same as that of Example 1.

[0079] Example 5

[0080] A solid electrolyte was obtained in a manner similar to that of Example 1, except that the initiator in step (4) was an equal mass of sodium persulfate, and the rest was the same as that of Example 1.

[0081] Example 6

[0082] A solid electrolyte was obtained in a manner similar to that of Example 1, except that an equal mass of N-methylpropylpyrrole bistrifluoromethanesulfonyl imide salt was used in step (2) to replace 1-ethyl-3-methylimidazole bistrifluoromethanesulfonyl imide in Example 1, and the rest was the same as that of Example 1.

[0083] Comparative Example 1

[0084] (1) The same as step (1) of Example 3, a ceramic oxide having the chemical formula Li 6.5 Ln3Z 1.75 Te 0.25 O 12 (C = Te, z = 0.25);

[0085] (2) Preparation of ionic liquid precursor I

[0086] In an argon-filled glove box (water content less than 0.1 ppm), 2.8708 g of lithium bis(trifluoromethanesulfonyl)imide was dissolved in 13.9 g of N-methyl-propylpyrrolidine bis(trifluoromethanesulfonyl)imide ionic liquid, and the mixture was stirred and mixed until the lithium salt was completely dissolved to obtain ionic liquid precursor I;

[0087] (3) Weigh 1 g of ceramic oxide particles and 0.25 g of ionic liquid precursor I into a ball mill, seal the ball mill, and ball mill for 4 h at a speed of 300 rpm to obtain a composite electrolyte.

[0088] Comparative Example 2

[0089] A similar method to Example 3 is used, except that steps (3) and (4) are not performed. Instead, 5 g of the ceramic oxide particles obtained in step (1) and 5 g of the ionic liquid precursor I obtained in step (2) are directly placed in a ball mill and mixed, and ball milled for 4 h at a rotation speed of 300 rpm to obtain a composite electrolyte.

[0090] Test Case

[0091] 1. The following properties of the solid electrolytes obtained in the above embodiments and comparative examples were tested. The test results are shown in Table 1 below.

[0092] (1) Ionic conductivity: The ionic conductivity of the diaphragm was measured using an electrochemical workstation. The test frequency range was 0.001 Hz to 10 5 Hz, the test temperature is room temperature (25℃), and then the conductivity (σ) is calculated according to the formula. The specific results are shown in the table below:

[0093]

[0094] Where, σ is the ionic conductivity of the membrane (S / cm), d is the thickness of the membrane (cm), R b is the bulk resistance of the diaphragm (Ω), A is the effective contact area between the diaphragm and the electrode (cm 2 ).

[0095] (2) Thermal stability evaluation: Thermogravimetric analysis (TGA, Netzsch TG209) was performed in a N2 atmosphere from room temperature to 500°C at a heating rate of 10°C / min, and the mass loss at 400°C was recorded.

[0096] (3) Thermal shrinkage: The thermal shrinkage of the dimensions was measured in an oven. The sample was heat treated at 150°C for 1 h, and then the thermal shrinkage (δ) was calculated according to the formula:

[0097]

[0098] Among them, S1 and S2 are the areas of the diaphragm before and after heat treatment;

[0099] Table 1

[0100] Examples Thickness / μm Ion conductivity / mS / cm Thermal decomposition at 400℃ Thermal shrinkage Example 1 25 1.5 <0.5wt% ＜3％ Example 2 25 1.3 <0.5wt% ＜3％ Example 3 25 1.3 <0.5wt% ＜3％ Example 4 25 0.9 <0.5wt% ＜3％ Example 5 25 1.05 <0.5wt% ＜3％ Example 6 25 1.1 <0.5wt% ＜3％ Comparative Example 1 25 0.35 <0.5wt% ＜3％ Comparative Example 2 25 0.6 <0.5wt% ＜3％

[0101] 2. The solid electrolytes obtained in the above embodiments and comparative examples were assembled into solid-state lithium batteries, and the following performances of the batteries were tested. The test results are shown in Table 2 below.

[0102] Preparation of solid-state lithium batteries:

[0103] The positive electrode formula is lithium iron phosphate: conductive carbon black: binder (PVDF) = 80:10:10, the negative electrode is lithium metal, and the battery is assembled in the order of negative electrode shell, lithium metal negative electrode, solid electrolyte, positive electrode, and positive electrode shell.

[0104] Solid-state lithium batteries are charged and discharged at a rate of 1C in the range of 2.8-4.2V.

[0105] Table 2

[0106]

[0107]

[0108] In summary, the composite solid electrolyte provided by the present invention has high ionic conductivity at room temperature, which can meet the application requirements of existing solid-state lithium-ion batteries. At the same time, the composite solid electrolyte provided by the present invention also has good thermal stability and electrochemical properties, and has excellent comprehensive performance.

[0109] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A composite solid electrolyte, characterized in that: The composite solid electrolyte contains a lithium salt polymer ion gel and a ceramic oxide, wherein the ceramic oxide is selected from the group consisting of 7-3x-y+z A x LqCy 2-y B y O 12+z / 2 or Li 7-3x-2k+ z A x LqCy 2-k C k O 12+z / 2 At least one of the substances, A is a trivalent metal element, B is a pentavalent metal element, C is a hexavalent metal element, 0≤x≤0.4, 0≤y≤1, 0≤k≤0.7, 0≤z≤1.4; the lithium salt polymer ion gel is obtained by in-situ crosslinking polymerization of lithium salt, ionic liquid, polymer monomer, crosslinking agent and initiator.

2. The composite solid electrolyte according to claim 1, wherein A is Al and / or Ga, B is at least one selected from Ta, Nb and Sb, and C is W and / or Te; Preferably, the ceramic oxide is selected from Li 6.5 LqCy 1.5 Ta 0.5 O 12 , Li 6.4 LqCy 1.4 Ta 0.6 O 12 , Li 6.75 LqCy 1.75 Nb 0.25 O 12 , Li 6.6 LqCy 1.6 Sb 0.4 O 12 , Li 6.5 LqCy 1.75 Te 0.25 O 12 , Li 6.4 LqCy 1.7 W 0.3 O 12 , Li 6.15 Al 0.2 LqCy 1.75 Ta 0.25 O 12 , Li 6.15 LqCy 1.75 Ta 0.25 Ga 0.2 O 12 and Li 6.15 LqCy 1.75 Ta 0.25 Al 0.2 O 12 At least one of; Preferably, the average particle size of the ceramic oxide is 50-150 μm; Preferably, based on the lithium element contained, the molar ratio of the ceramic oxide to the lithium salt polymer ion gel is 1:0.1-2.

3. The composite solid electrolyte according to claim 1 or 2, wherein: The lithium salt is selected from at least one of lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)amide, lithium bis(fluorosulfonyl)imide, lithium perfluoroethanesulfonylimide and lithium perfluoromethylsulfonylmethyl; Preferably, the lithium salt is selected from at least one of lithium difluorooxalatoborate, lithium trifluoromethanesulfonate, lithium bistrifluoromethanesulfonimide and lithium bis(trifluoromethanesulfonyl)imide.

4. The composite solid electrolyte according to any one of claims 1 to 3, wherein: The ionic liquid is selected from 1-ethyl-3-methylimidazolium bisfluorosulfonyl imide, 1-propyl-3-methylimidazolium bisfluorosulfonyl imide, 1-butyl-3-methylimidazolium bisfluorosulfonyl imide, N-propyl-N-methylpyridine bisfluorosulfonyl imide, 1-ethyl-1-methylpyrrolidine bisfluorosulfonyl imide, 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, 1-propyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, 1-butyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, N-propyl-N-methylpyridine bistrifluoromethanesulfonyl imide, 1-ethyl-1-methylpyrrolidine bistrifluoromethanesulfonyl imide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-propyl-3-methylimidazolium bistrifluoromethanesulfonyl imide, at least one of 1-ethyl-1-methylpyrrolidine tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-propyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, N-propyl-N-methylpyrrolidine hexafluorophosphate, 1-ethyl-1-methylpyrrolidine hexafluorophosphate, 1-ethyl-3-methylimidazolium difluorophosphate, 1-propyl-3-methylimidazolium difluorophosphate, 1-butyl-3-methylimidazolium difluorophosphate, N-propyl-N-methylpyrrolidine difluorophosphate, and 1-ethyl-1-methylpyrrolidine difluorophosphate; Preferably, the ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide), 1-propyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl imide), 1-ethyl-3-methylimidazolium bis(fluoromethanesulfonyl imide), 1-propyl-3-methylimidazolium bis(fluoromethanesulfonyl imide), 1-butyl-3-methylimidazolium bis(fluoromethanesulfonyl imide), N-methyl, propylpyrrole bis(trifluoromethanesulfonyl imide), N-methyl, butylpyrrole bis(trifluoromethanesulfonyl imide), N-methyl, propylpyrrole bis(fluoromethanesulfonyl imide) and N-methyl and butylpyrrole bis(fluoromethanesulfonyl imide); More preferably, the ionic liquid is selected from at least one of 1-ethyl-3-methylimidazolium bis(fluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

5. The composite solid electrolyte according to any one of claims 1 to 4, wherein: The polymer monomer is selected from at least one of methyl methacrylate, methacrylic acid, acrylonitrile and acrylamide; preferably methyl methacrylate; And / or, the cross-linking agent is selected from at least one of polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, and polyethylene glycol methacrylate, more preferably polyethylene glycol dimethacrylate; And / or, the initiator is selected from one of azobisisobutyronitrile, dibenzoyl peroxide, sodium persulfate, ammonium persulfate and potassium persulfate; more preferably azobisisobutyronitrile.

6. The composite solid electrolyte according to any one of claims 1 to 4, wherein: The room temperature ionic conductivity of the composite solid electrolyte is 0.8-3 mS / cm, preferably 1-2 mS / cm; the thermal shrinkage is less than 5%, preferably less than 3%.

7. A method for preparing the composite solid electrolyte according to any one of claims 1 to 6, characterized in that: The method includes: (1) first mixing a lithium salt and an ionic liquid to obtain an ionic liquid precursor I; (2) performing a second mixing of the polymer monomer, the crosslinking agent and the initiator to obtain a polymer precursor II; (3) The ceramic oxide, the ionic liquid precursor I and the polymer precursor II are mixed for a third time, and then subjected to a cross-linking polymerization reaction to obtain the composite solid electrolyte.

8. The method according to claim 7, wherein: The first mixing, the second mixing and the third mixing are all carried out under anhydrous and oxygen-free conditions, with a water content of less than 0.1 ppm, an oxygen content of less than 0.1 ppm, and a mixing temperature independently selected from 10-100° C.; And / or, in step (3), the conditions of the cross-linking polymerization reaction include: temperature 50-100° C., time 8-24 h.

9. The method according to claim 7 or 8, wherein: In step (1), the weight ratio of the lithium salt to the ionic liquid is 1:0.5-5; and / or, in step (2), the weight ratio of the polymer monomer to the cross-linking agent and the initiator is 100:1-15:0.1-5; And / or, in step (3), the weight ratio of the ceramic oxide to the ionic liquid precursor I and the polymer precursor II is 1:0.05-5:0.05-5.

10. The method according to any one of claims 7 to 9, wherein: The method also includes preparing the ceramic oxide by the following steps: Sintering a lithium source, a lanthanum source, a zirconium source, a first dopant containing element A, and a second dopant containing element B or element C; Preferably, the sintering conditions include: a temperature of 600-1200° C. and a time of 6-24 h; Preferably, the method further comprises the step of ball milling the sintered product, and the conditions of the ball milling include: a rotation speed of 100-500 rpm and a time of 4-18 hours.

11. Use of the composite solid electrolyte according to any one of claims 1 to 6 in a solid-state lithium-ion battery.

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