Electrolyte composition, solid electrolyte membrane, composite electrolyte membrane, method for preparing same, and battery

Abstract

An embodiment of the present application provides an electrolyte composition, a solid electrolyte membrane, a composite electrolyte membrane, a preparation method thereof, and a battery. The electrolyte composition includes an inorganic electrolyte. The inorganic electrolyte includes a first inorganic electrolyte and a second inorganic electrolyte. The average particle size of the first inorganic electrolyte is 300 nm to 800 nm. The average particle size of the second inorganic electrolyte is 1 μm to 10 μm. In the inorganic electrolyte, the mass percentage of the first inorganic electrolyte is 60% to 80%, and the mass percentage of the second inorganic electrolyte is 20% to 40%. In this way, the first inorganic electrolyte and the second inorganic electrolyte cooperate with each other in a suitable mass percentage, that is, the mass percentage of the first inorganic electrolyte is greater than that of the second inorganic electrolyte, which improves the ionic conductivity of the electrolyte membrane, helps the rapid migration of lithium ions, and reduces the risk of cracks or even fractures in the electrolyte during use, thereby improving the cycling performance of the solid-state lithium battery.

Description

Technical Field

[0001] The present application relates to the technical field of electrolytes, and particularly relates to an electrolyte composition, a solid electrolyte membrane, a composite electrolyte membrane, a preparation method thereof, and a battery. Background Art

[0002] Solid-state lithium batteries have been widely used in various portable electronic devices. The rise of new energy vehicles has further promoted remarkable progress in lithium battery technology. Considering the current range anxiety of new energy vehicles, it is of great significance to develop the next generation of batteries with high energy density and high safety.

[0003] Currently, how to improve the cycling performance of solid-state lithium batteries is a problem to be solved. Summary of the Invention

[0004] In view of this, embodiments of the present application provide an electrolyte composition, a solid electrolyte membrane, a composite electrolyte membrane, a preparation method thereof, and a battery, which can ensure the ionic conductivity and mechanical properties of the solid electrolyte membrane prepared from the electrolyte composition, thereby improving the cycling performance of solid-state lithium batteries.

[0005] To achieve the object of the present application, according to the first aspect of the embodiments of the present application, an electrolyte composition is provided. The electrolyte composition includes an inorganic electrolyte. The inorganic electrolyte includes a first inorganic electrolyte and a second inorganic electrolyte. The average particle size of the first inorganic electrolyte is 300 nm to 800 nm. The average particle size of the second inorganic electrolyte is 1 μm to 10 μm. In the inorganic electrolyte, the mass percentage of the first inorganic electrolyte is 60% to 80%, and the mass percentage of the second inorganic electrolyte is 20% to 40%.

[0006] According to the second aspect of the embodiments of the present application, a solid electrolyte membrane is provided. The solid electrolyte membrane includes the electrolyte composition described in the first aspect.

[0007] According to the third aspect of the embodiments of the present application, a composite electrolyte membrane is provided. The composite electrolyte membrane includes the solid electrolyte membrane described in the second aspect and a polymer electrolyte membrane, and the polymer electrolyte membrane and the solid electrolyte membrane are stacked.

[0008] According to the fourth aspect of the embodiments of the present application, a preparation method of the composite electrolyte membrane described in the third aspect is provided, including:

[0009] Forming a solid electrolyte membrane;

[0010] Forming a polymer electrolyte membrane;

[0011] Stacking the solid electrolyte membrane and the polymer electrolyte membrane to obtain the composite electrolyte membrane.

[0012] According to a fifth aspect of the embodiments of the present application, a battery is provided. The battery includes a positive electrode, a negative electrode, and the composite electrolyte membrane as described in the third aspect. The composite electrolyte membrane is located between the positive electrode and the negative electrode, and the polymer electrolyte membrane is located between the solid electrolyte membrane and the negative electrode.

[0013] In the electrolyte composition, solid electrolyte membrane, composite electrolyte membrane, and their preparation methods, and batteries of some embodiments of the present application, the average particle size of the first inorganic electrolyte is 300 nm to 800 nm, so that the average particle size of the first inorganic electrolyte is relatively small, and more of the first inorganic electrolyte can increase the number of ion transport surfaces inside the electrolyte membrane and increase the ion transport paths. The average particle size of the second inorganic electrolyte is 1 μm to 10 μm, so that the average particle size of the second inorganic electrolyte is relatively large, and it can form a better network structure in the polymer matrix, which helps the rapid migration of lithium ions and improves the film-forming property and mechanical properties of the electrolyte membrane. Among the inorganic electrolytes, the first inorganic electrolyte and the second inorganic electrolyte cooperate with each other in a suitable mass percentage, that is, the mass percentage of the first inorganic electrolyte is greater than that of the second inorganic electrolyte, which improves the ionic conductivity of the electrolyte membrane, helps the rapid migration of ions, and reduces the risk of cracks or even fractures in the electrolyte during use, thereby improving the cycle performance of the solid-state lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic structural diagram of a solid electrolyte membrane provided by some embodiments of the present application;

[0015] Figure 2 A schematic structural diagram of a composite electrolyte membrane provided by some embodiments of the present application;

[0016] Figure 3 A schematic structural diagram of another composite electrolyte membrane provided by some embodiments of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present application.

[0018] In a first aspect, an embodiment of the present application provides an electrolyte composition. The electrolyte composition includes an inorganic electrolyte. The inorganic electrolyte includes a first inorganic electrolyte and a second inorganic electrolyte. The average particle size of the first inorganic electrolyte is 300 nm to 800 nm. The average particle size of the second inorganic electrolyte is 1 μm to 10 μm. In the inorganic electrolyte, the mass percentage of the first inorganic electrolyte is 60% to 80%, and the mass percentage of the second inorganic electrolyte is 20% to 40%.

[0019] The average particle size of the first inorganic electrolyte is 300 nm to 800 nm, so that the average particle size of the first inorganic electrolyte is relatively small. More of the first inorganic electrolyte can increase the number of ion transport surfaces inside the electrolyte membrane and increase the ion transport paths. The average particle size of the second inorganic electrolyte is 1 μm to 10 μm, so that the average particle size of the second inorganic electrolyte is relatively large. It can form a better network structure in the polymer matrix, contribute to the rapid migration of ions, and improve the film-forming property and mechanical properties of the electrolyte membrane. In the inorganic electrolyte, the first inorganic electrolyte and the second inorganic electrolyte cooperate with each other in a suitable mass percentage, that is, the mass percentage of the first inorganic electrolyte is greater than that of the second inorganic electrolyte, which can improve the ionic conductivity of the electrolyte membrane, contribute to the rapid migration of ions, and reduce the risk of cracks or even fractures in the electrolyte during use, thereby improving the cycle performance of the solid-state lithium battery.

[0020] It should be noted that the average particle size of the inorganic electrolyte is measured by any one of a laser particle size analyzer and a scanning electron microscope. Exemplarily, the average particle size of the inorganic electrolyte can be measured by a laser particle size analyzer.

[0021] In some embodiments, the average particle size of the first inorganic electrolyte is 400 nm to 700 nm, and the average particle size of the second inorganic electrolyte is 4 μm to 8 μm, so as to optimize the average particle sizes of the first inorganic electrolyte and the second inorganic electrolyte, further improve the ionic conductivity of the electrolyte membrane, contribute to the rapid migration of ions, and reduce the risk of cracks or even fractures in the electrolyte during use, thereby improving the cycle performance of the solid-state lithium battery.

[0022] In some embodiments, the average particle size of the first inorganic electrolyte is 500 nm to 800 nm, and the average particle size of the second inorganic electrolyte is 4 μm to 10 μm.

[0023] It is understandable that the average particle size of the first inorganic electrolyte can take one or more values in the range of 300 nm to 800 nm, such as 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, or 800 nm. The average particle size of the second inorganic electrolyte can take one or more values in the range of 1 μm to 10 μm, such as 4 μm, 5 μm, 6 μm, 7 μm, or 8 μm.

[0024] In some embodiments, in the inorganic electrolyte, the mass percentage of the first inorganic electrolyte is 65% - 75%, and the mass percentage of the second inorganic electrolyte is 25% - 35%, so as to optimize the mass percentages of the first inorganic electrolyte and the second inorganic electrolyte, further improve the ionic conductivity of the electrolyte membrane, and thus further enhance the cycling performance of the solid-state lithium battery.

[0025] In some embodiments, in the inorganic electrolyte, the mass percentage of the first inorganic electrolyte is 70% - 80%, and the mass percentage of the second inorganic electrolyte is 20% - 30%, so as to optimize the mass percentages of the first inorganic electrolyte and the second inorganic electrolyte, further improve the ionic conductivity of the electrolyte membrane, and thus further enhance the cycling performance of the solid-state lithium battery.

[0026] It is understandable that the mass percentage of the first inorganic electrolyte can take any value between 60% and 80%, such as 60%, 65%, 70%, 75%, or 80%; the mass percentage of the second inorganic electrolyte can take any value between 20% and 40%, such as 20%, 25%, 30%, 35%, or 40%.

[0027] In some embodiments, the inorganic electrolyte includes an inorganic oxide electrolyte, and the inorganic oxide electrolyte includes one or several of perovskite-type materials, NASICON-type materials, and garnet-type materials. In this way, it is ensured that the inorganic electrolyte has advantages such as high ionic conductivity, a wide electrochemical stability window, and excellent lithium stability.

[0028] In some embodiments, the perovskite-type material includes Li a La b Ti c A d O e , where 0 < a ≤0.5, 0 < b <0.6, 0.9 < c ≤1, 0≤ d ≤0.25, 2 < e ≤3, and A includes one or several of Ba, Sr, and Al.

[0029] In some embodiments, the perovskite-type material includes Li 0.5 La 0.5 TiO3, Li 0.29 La 0.57 TiO3, Li 0.30 La 0.57 TiO3, Li 0.33 La 0.56 TiO3, Li 0.34 La 0.51 TiO 2.94 、Li 0.30 La 0.567 TiO3, Li 0.36 Sr 0.04 La 0.523 TiO3, Li 0.33 Ba 0.25 La 0.39 TiO3 and (Li 0.33 La 0.56 ) 1.005 Ti 0.99 Al 0.01 O3, or one or more of them.

[0030] In some embodiments, the NASICON-type material includes Li f B g P h O 12 , where 1 ≤ f ≤ 3, 0 < g ≤ 4, 1 ≤ h ≤ 3, and B includes one or more of Al, Zr, Ti, Ge, and Si.

[0031] In some embodiments, the NASICON-type material includes LiZr2(PO4)3, LiTi2(PO4)3, and LiGe2(PO4)3, Li 1.3 Al 0.3 Ti 1.7 (PO4)3 (LATP), Li 1.5 Al 0.5 Ge 1.5 (PO4)3 (LAGP), Li3Zr2Si2PO 12 、Li 1.5 Al 0.5 Ge 1.5 (PO4)3, Li 1.4 Al 0.4 Ti 1.6 (PO4)3, Li 1.5 Al 0.5 Ti 1.5 (PO4)3, and Li1.4 Ti2Si 0.4 P 2.6 O 12 One or more of -AIPO4.

[0032] In some embodiments, the garnet-type material includes Li i La j Zr k M l O 12 , where 5 ≤ i ≤ 7, 2 ≤ j ≤ 3, 1 ≤ k ≤ 2, 0 ≤ l ≤ 1, and M is selected from any one of Ta, Nb, Hf, Al, Si, Ga, Sc, Ti, V, Y, and Sn.

[0033] In some embodiments, the garnet-type material includes Li 6.4 La3Zr 1.4 Ta 0.6 O 12 、Li7La3Zr2O 12 (LLZO)、Li 6.5 La3Zr 1.5 Nb 0.5 O 12 、Li 6.5 La3Zr 1.5 Ta 0.5 O 12 、Li 6.375 La3Zr 1.375 Nb 0.625 O 12 、Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 、Li 5.9 Al 0.2 La3Zr 1.75 W 0.25 O 12 And Li7La 2.75 Ca 0.25 Zr 1.75 Nb 0.25 O 12 One or more of.

[0034] In some embodiments, the electrolyte composition further includes an ionic liquid. The ionic liquid includes at least one of a first ionic liquid and a second ionic liquid. The first ionic liquid includes 1-benzyl-3-methylimidazolium cations. The second ionic liquid includes 1-ethyl-3-methylimidazolium cations. The 1-benzyl-3-methylimidazolium cations, due to their larger volume and more complex molecular structure, can provide more transport paths for lithium ions, and these transport paths ensure smoother transport of lithium ions in the inorganic electrolyte. The 1-ethyl-3-methylimidazolium cations have a relatively high ionic conductivity for lithium ions.

[0035] In some embodiments, the ionic liquid includes a first ionic liquid and a second ionic liquid. The mass ratio of the inorganic electrolyte, the first ionic liquid, and the second ionic liquid is (80~90):(0.6~0.9):(0.6~0.9). Thus, in the electrolyte composition, the 1-benzyl-3-methylimidazolium cations, the 1-ethyl-3-methylimidazolium cations, and the inorganic electrolyte are compounded in a suitable ratio in the electrolyte membrane, which can improve the transport performance of lithium ions in the inorganic electrolyte, thereby enhancing the cycling performance of the battery.

[0036] In some embodiments, the mass ratio of the inorganic electrolyte, the first ionic liquid, and the second ionic liquid is (80~90):(0.65~0.85):(0.65~0.85).

[0037] In some embodiments, the molar ratio of the cations of the first ionic liquid to the cations of the second ionic liquid is greater than or equal to 0.8 and less than 1. Thus, the cations of the second ionic liquid and the cations of the first ionic liquid in the electrolyte membrane have a suitable molar ratio, and the content of the cations of the second ionic liquid is higher, which can improve the ionic conductivity of lithium ions in the inorganic electrolyte, improve the transport performance of lithium ions in the inorganic electrolyte, and thereby enhance the cycling performance of the battery.

[0038] In some embodiments, the anions of the first ionic liquid and the anions of the second ionic liquid are each independently selected from one or more of bis(trifluoromethanesulfonyl)imide (NTf2), bis(fluorosulfonyl)imide, bis(trifluoromethylsulfonate), and trifluoromethylsulfonate (TFO). Thus, the fluorine element in the anions of the first ionic liquid and the anions of the second ionic liquid can react with the lithium element at the negative electrode, promote the formation of a solid electrolyte interface including LiF, effectively inhibit the formation of lithium dendrites, and further enhance the stability of the negative electrode of the solid-state lithium battery.

[0039] In some embodiments, the first ionic liquid may include 1-benzyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BzmimTFSI) (CAS No.: 433337-24-7). Thus, it ensures that the first ionic liquid provides more transport paths for lithium ions and promotes the formation of a solid electrolyte interface including LiF.

[0040] In some embodiments, the second ionic liquid may be selected from one or more of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt (CAS No.: 174899-82-2), 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide salt (CAS No.: 35789-75-0), and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (CAS No.: 145022-44-2). Thus, it ensures that the second ionic liquid has a higher ionic conductivity for lithium ions and promotes the formation of a solid electrolyte interface including LiF.

[0041] In some embodiments, the electrolyte composition may further include a first lithium salt. The first lithium salt includes a fluorine-containing lithium salt. Thus, the fluorine-containing lithium salt promotes the formation of a solid electrolyte interface including LiF, and further effectively inhibits the formation of lithium dendrites, enhancing the stability of the negative electrode of the solid-state lithium battery.

[0042] In some embodiments, the fluorine-containing lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalate borate, and lithium hexafluorophosphate. Optionally, the fluorine-containing lithium salt includes lithium bis(fluorosulfonyl)imide, such that the first lithium salt has a higher ionic conductivity in the electrolyte, which helps to improve the charge and discharge rate and overall performance of the battery. Moreover, the first lithium salt has good thermal stability.

[0043] In some embodiments, the mass ratio of the fluorine-containing lithium salt to the inorganic electrolyte is 1:(80 - 90). Thus, the fluorine-containing lithium salt and the inorganic electrolyte cooperate with a suitable ratio, ensuring the ionic conductivity of the solid electrolyte for lithium ions while promoting the fluorine element in the fluorine-containing lithium salt to promote the formation of a solid electrolyte interface including LiF, and further effectively inhibiting the formation of lithium dendrites, enhancing the stability of the negative electrode of the solid-state lithium battery.

[0044] In some embodiments, the electrolyte composition may further include a fluorinated ester compound. The fluorine element of the fluorinated ester compound promotes the formation of a solid electrolyte interface including LiF, further effectively inhibits the formation of lithium dendrites, and improves the stability of the negative electrode. The fluorine atoms of the fluorinated ester compound have an electron-withdrawing effect, which can promote the dissociation of the first lithium salt, construct an ion transport pathway in the electrolyte, promote the transport of lithium ions, effectively increase the voltage range of the electrolyte membrane, and improve the ionic conductivity of the electrolyte membrane. Moreover, the fluorinated ester compound is an organic substance, has good flexibility and good affinity with the electrode, can reduce the impedance of lithium ions at the electrode interface, strengthen the close contact between the electrolyte membrane and the electrode, and improve the cycle stability of the battery. In addition, the fluorinated ester compound also has high thermal stability, a wide electrochemical stability window and low viscosity properties, which can further improve the performance and safety of the battery.

[0045] In some embodiments, the mass ratio of the fluorinated ester compound to the inorganic electrolyte is (1.5~2.5):(80~90). In this way, the fluorinated ester compound and the inorganic electrolyte cooperate with each other in a suitable ratio to effectively inhibit the formation of lithium dendrites and improve the stability of the negative electrode.

[0046] In some embodiments, the fluorinated ester compound includes hexafluorobutyl methacrylate.

[0047] The electrolyte composition further includes a binder. The binder connects the particles of the inorganic electrolyte and enhances the compactness between the particles of the inorganic electrolyte. In some embodiments, the binder includes at least one of polyethylene oxide and fluoropolymer.

[0048] In some embodiments, the binder includes polyethylene oxide and fluoropolymer. The fluoropolymer has good mechanical properties, chemical stability and thermal stability, and can reduce the interfacial impedance between the electrolyte and the electrode. Polyethylene oxide has a relatively high ionic conductivity for lithium ions. When polyethylene oxide and fluoropolymer are compounded, they penetrate each other to form a three-dimensional network polymer. The three-dimensional network polymer better connects multiple particles of the inorganic electrolyte, enhances the structural stability and compactness of the inorganic electrolyte. Moreover, the compounding of polyethylene oxide and fluoropolymer can also increase the ionic conductivity of the electrolyte.

[0049] In some embodiments, the mass ratio of the inorganic electrolyte, polyethylene oxide and fluoropolymer is (80~90):(0.1~2):(5~9). In this way, the inorganic electrolyte, polyethylene oxide and fluoropolymer cooperate with each other in a suitable ratio to enhance the structural stability and compactness of the inorganic electrolyte, and at the same time improve the ionic conductivity of the inorganic electrolyte to lithium ions. Moreover, the mass of the fluoropolymer is greater than the mass of polyethylene oxide, which improves the mechanical properties and stability of the inorganic electrolyte.

[0050] In some embodiments, the mass ratio of the inorganic electrolyte, polyethylene oxide, and fluoropolymer is (80-90):(1-2):(6-8). Thus, the inorganic electrolyte, polyethylene oxide, and fluoropolymer cooperate with each other in a suitable ratio to enhance the structural stability and compactness of the inorganic electrolyte, while improving the ionic conductivity of the inorganic electrolyte to lithium ions. Moreover, the mass of the fluoropolymer is greater than that of the polyethylene oxide, enhancing the mechanical properties and stability of the inorganic electrolyte.

[0051] In some embodiments, the mass ratio of the inorganic electrolyte, polyethylene oxide, and fluoropolymer is (80-90):(1-2):(6.5-7.5).

[0052] In some embodiments, the fluoropolymer includes polyvinylidene fluoride. The fluoropolymer is selected from one or more of polyvinylidene fluoride, poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE), and poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) P(VDF-TrFE-CFE). Optionally, the fluoropolymer includes poly(vinylidene fluoride-trifluoroethylene).

[0053] In some embodiments, when the fluoropolymer includes poly(vinylidene fluoride-trifluoroethylene), in poly(vinylidene fluoride-trifluoroethylene), the molar ratio of vinylidene fluoride to trifluoroethylene is (75-85):(15-25). Thus, the mechanical strength and thermal stability of poly(vinylidene fluoride-trifluoroethylene) are improved, and the interfacial properties between the electrolyte membrane and the electrode are improved.

[0054] In some embodiments, the weight-average molecular weight of the fluoropolymer is 450,000-1,100,000. Optionally, the weight-average molecular weight of the fluoropolymer is 500,000-1,000,000.

[0055] In some embodiments, the relative molecular weight of polyethylene oxide is 7,500,000-8,500,000.

[0056] In a second aspect, as Figure 1 shown, an embodiment of the present application further provides a solid electrolyte membrane 10, including the above electrolyte composition. The first inorganic electrolyte and the second inorganic electrolyte with different particle sizes cooperate with each other in a suitable mass percentage, that is, the mass percentage of the first inorganic electrolyte is greater than that of the second inorganic electrolyte, improving the ionic conductivity of the electrolyte membrane, facilitating the rapid migration of lithium ions, and reducing the risk of cracks or even fractures in the electrolyte during use.

[0057] In a third aspect, as Figure 2As shown, the embodiment of the present application also provides a composite electrolyte membrane 100, which includes the above-mentioned solid electrolyte membrane 10 and polymer electrolyte membrane 20. The polymer electrolyte membrane 20 is stacked with the solid electrolyte membrane 10. Compared with the solid electrolyte membrane, the polymer electrolyte membrane 20 has good flexibility and can effectively construct a stable negative electrode-electrolyte interface, while the solid electrolyte membrane 10 corresponds to the positive electrode of the battery. Since the voltage window of the solid electrolyte membrane 10 is high, the deterioration of the positive electrode interface under the high voltage of the positive electrode can be effectively alleviated. Therefore, the composite electrolyte membrane formed by combining the polymer electrolyte membrane and the solid electrolyte membrane helps to improve the cycle stability of the solid-state battery.

[0058] Furthermore, the design of the above-mentioned solid electrolyte membrane 10 ensures that the solid electrolyte membrane 10 has good mechanical strength and structural stability, while improving the transport characteristics of lithium ions in the solid electrolyte membrane, thereby inhibiting the growth of lithium dendrites, and further improving the cycle performance and safety performance of the battery.

[0059] In some embodiments, the thickness of the solid electrolyte membrane 10 is 5 micrometers to 40 micrometers.

[0060] In some embodiments, the thickness of the polymer electrolyte membrane 20 is 10 micrometers to 15 micrometers.

[0061] In some embodiments, the polymer electrolyte membrane 20 further includes a polymer electrolyte and a second lithium salt. The mass ratio of the polymer electrolyte to the second lithium salt is (1.5-2.5):1, ensuring that the polymer electrolyte and the second lithium salt have a suitable ratio, so that the polymer electrolyte membrane has good flexibility to effectively construct a stable negative electrode-electrolyte interface, and also has high ionic conductivity for lithium ions.

[0062] In some embodiments, the polymer electrolyte includes, but is not limited to, polymers such as polyvinylidene fluoride.

[0063] In some embodiments, Figure 3 As shown, the composite electrolyte membrane 100 may further include a top solid electrolyte membrane 40 and a bottom solid electrolyte membrane 30. The bottom solid electrolyte membrane 30 is located between the polymer electrolyte membrane 20 and the solid electrolyte membrane 10. The top solid electrolyte membrane 40 is located on the side of the solid electrolyte membrane 10 away from the polymer electrolyte membrane 20. Therefore, the solid electrolyte membrane 10 is an intermediate solid electrolyte membrane between the top solid electrolyte membrane 40 and the bottom solid electrolyte membrane 30.

[0064] In some embodiments, the top solid electrolyte film 40 includes a third inorganic electrolyte, and the average particle size of the third inorganic electrolyte is less than or equal to the average particle size of the first inorganic electrolyte. Thus, the average particle size of the third inorganic electrolyte in the top solid electrolyte film 40 is small, which is conducive to reducing the surface defects of the top solid electrolyte film 40, thereby reducing the interfacial defects between the composite electrolyte film 100 and the electrode, and improving the cycling performance of the battery.

[0065] In some embodiments, the average particle size of the third inorganic electrolyte is equal to the average particle size of the first inorganic electrolyte. Thus, the third inorganic electrolyte and the first inorganic electrolyte can be prepared by the same preparation process, simplifying the formation process of the electrolyte film.

[0066] In some embodiments, the average particle size of the third inorganic electrolyte is less than the average particle size of the first inorganic electrolyte. Thus, the interfacial defects between the top solid electrolyte film 40 and the electrode are further reduced, improving the cycling performance of the battery.

[0067] In some embodiments, the average particle size of the third inorganic electrolyte is 100 nm to 800 nm. Optionally, the average particle size of the third inorganic electrolyte is 100 nm to 500 nm.

[0068] In some embodiments, the top solid electrolyte film 40 further includes an adhesive. The adhesive may include one or more of polyethylene oxide, polyurethane rubber, polyvinylidene fluoride, poly(vinylidene fluoride-trifluoroethylene), poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene), polyvinylidene fluoride hexafluoropropylene, polyarylene, polycaprolactone, and polyvinyl butyral. Exemplarily, the adhesive of the top solid electrolyte film includes poly(vinylidene fluoride-trifluoroethylene).

[0069] In some embodiments, the top solid electrolyte film 40 further includes a third lithium salt. In some embodiments, the third lithium salt may be the same as the first lithium salt, simplifying the preparation process of the composite electrolyte film.

[0070] In some embodiments, the third lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalate borate, and lithium hexafluorophosphate.

[0071] In some embodiments, the thickness of the top solid electrolyte film 40 is less than the thickness of the solid electrolyte film 10. When the thicknesses of the top solid electrolyte film 40, the solid electrolyte film 10, and the bottom solid electrolyte film 30 are fixed, the thickness of the solid electrolyte film 10 is thicker, which plays a major role in improving the lithium ion transport performance and thus the cycling performance of the solid state lithium battery, while the top solid electrolyte film 40 plays an auxiliary role in reducing the interfacial defects between the composite electrolyte film 100 and the electrode and thus improving the cycling performance of the solid state lithium battery.

[0072] In some embodiments, in the top solid electrolyte membrane, the mass ratio of the third inorganic electrolyte, the binder, and the third lithium salt is (80-90):(8-15):(1-5).

[0073] In some embodiments, the mass proportion of the third lithium salt in the top solid electrolyte membrane 40 is greater than the mass proportion of the first lithium salt in the solid electrolyte membrane 10. Thus, it is beneficial to improve the ionic conductivity of the top solid electrolyte membrane 40 to lithium ions.

[0074] In some embodiments, the thickness of the top solid electrolyte membrane 40 is 5 μm to 8 μm.

[0075] In some embodiments, the bottom solid electrolyte membrane 30 includes a fourth inorganic electrolyte, and the average particle size of the fourth inorganic electrolyte is greater than or equal to the average particle size of the second inorganic electrolyte. Thus, the average particle size of the fourth inorganic electrolyte in the bottom solid electrolyte membrane 30 is relatively large, and the bottom solid electrolyte membrane 30 has good mechanical strength. Moreover, since the bottom solid electrolyte membrane 30 is located between the polymer electrolyte membrane 20 and the solid electrolyte membrane 10, the bottom solid electrolyte membrane 30 provides good support for the polymer electrolyte membrane 20, the solid electrolyte membrane 10, and the top solid electrolyte membrane 40, further enhancing the mechanical strength of the entire electrolyte membrane.

[0076] In some embodiments, the average particle size of the fourth inorganic electrolyte can be 1 μm to 20 μm.

[0077] In some embodiments, the average particle size of the fourth inorganic electrolyte can be equal to the average particle size of the second inorganic electrolyte. At this time, the average particle size of the fourth inorganic electrolyte can be 1 μm to 10 μm.

[0078] In some embodiments, the average particle size of the fourth inorganic electrolyte can be greater than the average particle size of the second inorganic electrolyte, further improving the mechanical properties of the bottom solid electrolyte membrane 30. At this time, the average particle size of the fourth inorganic electrolyte can be 10 μm to 20 μm.

[0079] It should be noted that in the case where the average particle size of the third inorganic electrolyte is smaller than the average particle size of the first inorganic electrolyte, and the average particle size of the fourth inorganic electrolyte is greater than the average particle size of the second inorganic electrolyte, from the top solid electrolyte membrane 40 to the bottom solid electrolyte membrane 30, the particle size of the inorganic electrolyte shows an increasing trend, which also helps to improve the overall density of the electrolyte membrane.

[0080] In some embodiments, the bottom solid electrolyte membrane 30 further includes an adhesive. The adhesive may include one or more of polyethylene oxide, polyurethane rubber, polyvinylidene fluoride, poly(vinylidene fluoride-trifluoroethylene), poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene), polyvinylidene fluoride hexafluoropropylene, polyarylene, polycaprolactone, and polyvinyl butyral. Exemplarily, the adhesive of the top solid electrolyte membrane includes poly(vinylidene fluoride-trifluoroethylene).

[0081] In some embodiments, the bottom solid electrolyte membrane 30 further includes a fourth lithium salt. In some embodiments, the fourth lithium salt may be the same as the first lithium salt, which simplifies the preparation process of the composite electrolyte membrane.

[0082] In some embodiments, the fourth lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalate borate, and lithium hexafluorophosphate.

[0083] In some embodiments, the thickness of the bottom solid electrolyte membrane 30 may be greater than the thickness of the solid electrolyte membrane 10. Thus, the bottom solid electrolyte membrane 30 can better improve the mechanical strength of the electrolyte.

[0084] In some other embodiments, the thickness of the bottom solid electrolyte membrane 30 may be less than the thickness of the solid electrolyte membrane 10 and greater than the thickness of the top solid electrolyte membrane 40. Thus, when the thicknesses of the top solid electrolyte membrane 40, the solid electrolyte membrane 10, and the bottom solid electrolyte membrane 30 are fixed, the thickness of the solid electrolyte membrane 10 is thicker, which plays a major role in improving the cycling performance of the solid-state lithium battery, and the bottom solid electrolyte membrane 30 and the top solid electrolyte membrane 40 play an auxiliary role in improving the cycling performance of the solid-state lithium battery.

[0085] In some embodiments, the thickness of the bottom solid electrolyte membrane 30 is 12 microns to 15 microns.

[0086] In some embodiments, in the bottom solid electrolyte membrane 30, the mass ratio of the fourth inorganic electrolyte, the binder, and the fourth lithium salt is (80 - 90):(8 - 15):(1 - 5).

[0087] In some embodiments, the mass proportion of the fourth lithium salt in the bottom solid electrolyte membrane 30 is greater than the mass proportion of the first lithium salt in the solid electrolyte membrane 10. Thus, it is beneficial to improve the ionic conductivity of the bottom solid electrolyte membrane 30 to lithium ions.

[0088] In some embodiments, the bottom solid electrolyte membrane 30 and the top solid electrolyte membrane 40 can be formed on the opposite side of the solid electrolyte membrane 10 by a casting film-forming process.

[0089] Fourthly, the embodiments of the present application further provide a method for preparing a composite electrolyte membrane, including:

[0090] Forming a solid electrolyte membrane;

[0091] Forming a polymer electrolyte membrane;

[0092] Stacking the solid electrolyte membrane and the polymer electrolyte membrane to obtain a composite electrolyte membrane.

[0093] In some embodiments, forming the solid electrolyte membrane includes:

[0094] Providing the above electrolyte composition and a first solvent;

[0095] Dissolving the components of the electrolyte composition in the first solvent to obtain a first slurry;

[0096] Using the first slurry to form an initial solid electrolyte membrane and removing the first solvent to obtain the solid electrolyte membrane.

[0097] In some embodiments of the present application, the wet method is used to prepare the solid electrolyte membrane, which improves the dispersion uniformity of the components in the electrolyte composition and the performance uniformity of the solid electrolyte membrane.

[0098] In some embodiments, the initial solid electrolyte membrane can be formed on a release film, and after removing the first solvent, the solid electrolyte membrane is obtained.

[0099] In some embodiments, providing the electrolyte composition includes:

[0100] Providing an initial inorganic electrolyte;

[0101] Putting the initial inorganic electrolyte and a dispersant into a ball milling tank and performing a first ball milling treatment to obtain a second inorganic electrolyte;

[0102] Taking out a part of the second inorganic electrolyte and performing a second ball milling treatment on the remaining second inorganic electrolyte to obtain a first inorganic electrolyte;

[0103] Mixing the part of the second inorganic electrolyte and the first inorganic electrolyte evenly to obtain an inorganic electrolyte.

[0104] In some embodiments, the conditions of the first ball milling treatment include: the rotation speed is 400 r / min to 600 r / min, and the time is 12 h to 20 h.

[0105] In some embodiments, the conditions of the second ball milling treatment include: the rotation speed is 400 r / min to 600 r / min, and the time is 30 h to 34 h.

[0106] In some embodiments, the dispersant includes, but is not limited to, alcohol solvents, and the alcohol solvents include, but are not limited to, isopropyl alcohol.

[0107] In some embodiments, the first solvent includes amide compounds. The amide compounds include at least one of N,N-dimethylformamide, N-methylpyrrolidone, caprolactam, and N-ethylpyrrolidone. Exemplarily, the first solvent includes N,N-dimethylformamide.

[0108] In some embodiments, the electrolyte composition further includes a first lithium salt, an ionic liquid, a binder, and a fluorinated ester compound.

[0109] In some embodiments, dissolving the components of the electrolyte composition in the first solvent includes: dissolving an inorganic electrolyte, an ionic liquid, a first lithium salt, a binder, and a fluorinated ester compound in the first solvent.

[0110] In some embodiments, forming a polymer electrolyte membrane includes:

[0111] providing a polymer electrolyte, a second lithium salt, and a second solvent;

[0112] dissolving the polymer electrolyte and the second lithium salt in the second solvent to obtain a second slurry;

[0113] forming an initial polymer electrolyte membrane using the second slurry and removing the second solvent to obtain the polymer electrolyte membrane.

[0114] Some embodiments of the present application use a wet method to prepare a polymer electrolyte membrane, improving the dispersion uniformity of the components in the polymer electrolyte and the performance uniformity of the solid electrolyte membrane.

[0115] In some embodiments, the mass ratio of the polymer electrolyte to the second lithium salt is (1.5~2.5):1, ensuring a suitable ratio between the polymer electrolyte and the second lithium salt, so that the polymer electrolyte membrane has good flexibility and high ionic conductivity for lithium ions.

[0116] In some embodiments, the mass ratio of the polymer electrolyte to the second solvent is (1.5~2.5):(8~12). In this way, it is ensured that the polymer electrolyte can be fully dissolved in the second solvent.

[0117] In some embodiments, the polymer electrolyte includes, but is not limited to, polymers such as polyvinylidene fluoride.

[0118] In some embodiments, the second lithium salt can be the same as the first lithium salt, simplifying the preparation process of the composite electrolyte membrane.

[0119] In some embodiments, the second lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalate borate, and lithium hexafluorophosphate.

[0120] In some embodiments, the second solvent includes amide compounds. The amide compounds include but are not limited to at least one of N,N-dimethylformamide, N-methylpyrrolidone, caprolactam, and N-ethylpyrrolidone. Exemplarily, the first solvent includes N,N-dimethylformamide.

[0121] In some embodiments, the method for preparing the composite electrolyte membrane further includes:

[0122] Dissolve a third inorganic electrolyte, a third lithium salt, and a binder in a third solvent, mix uniformly to obtain a third slurry;

[0123] Form an initial top-layer solid electrolyte membrane using the third slurry, and remove the third solvent to obtain the top-layer solid electrolyte membrane.

[0124] In some embodiments, after forming the solid electrolyte membrane, the initial top-layer solid electrolyte membrane can be formed on the solid electrolyte membrane. Thus, during the process of forming the third slurry on the solid electrolyte membrane, the third inorganic electrolyte in the third slurry at least fills some of the gaps on the surface of the solid electrolyte membrane, so that the top-layer solid electrolyte membrane is stacked on the solid electrolyte membrane, while improving the density of the solid electrolyte membrane.

[0125] In some embodiments, the method for preparing the composite electrolyte membrane further includes:

[0126] Dissolve a fourth inorganic electrolyte, a fourth lithium salt, and a binder in a fourth solvent, mix uniformly to obtain a fourth slurry;

[0127] Form an initial bottom-layer solid electrolyte membrane using the fourth slurry, and remove the fourth solvent to obtain the bottom-layer solid electrolyte membrane.

[0128] In some embodiments, the initial bottom-layer solid electrolyte membrane can be formed on a release layer.

[0129] In some embodiments, after forming the bottom-layer solid electrolyte membrane, the initial solid electrolyte membrane can be formed on the bottom-layer solid electrolyte membrane. Thus, during the process of forming the first slurry on the bottom-layer solid electrolyte membrane, the first inorganic electrolyte in the first slurry can at least fill the gaps on the surface of the bottom-layer solid electrolyte membrane, so that the solid electrolyte membrane is stacked on the bottom-layer solid electrolyte membrane, while improving the density of the bottom-layer solid electrolyte membrane.

[0130] Fifth aspect, an embodiment of the present application further provides a battery. The battery includes a positive electrode, a negative electrode, and the above-mentioned composite electrolyte membrane. The composite electrolyte membrane is located between the positive electrode and the negative electrode. The polymer electrolyte membrane is located between the solid electrolyte membrane and the negative electrode.

[0131] In some embodiments, the material of the positive electrode includes one or more of lithium nickel manganese oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, and lithium nickel cobalt manganese oxide.

[0132] In some embodiments, the negative electrode includes one or more of a metallic lithium negative electrode, a metallic lithium alloy negative electrode, a graphite negative electrode, a silicon-based negative electrode, a silicon-graphite composite negative electrode, and a copper foil lithium-free negative electrode.

[0133] The following is a detailed description in conjunction with specific embodiments.

[0134] In the following embodiments, polyethylene oxide (PEO) (relative molecular weight of 7900000) was purchased from Macklin's P888666, and P(VDF-TrFE) was purchased from Gadell (molar ratio of VDF-TrFE was 80:20, product number JD200721095524), and other raw materials were all commercially available.

[0135] Example 1

[0136] This embodiment provides a preparation method of a solid electrolyte membrane. The preparation method includes preparing an inorganic electrolyte and a solid electrolyte membrane, and the specific methods of the two are as follows.

[0137] (1) Preparation of inorganic electrolyte

[0138] Weigh an appropriate amount of Li7La3Zr2O 12 (LLZO) powder with an original particle size of 100 μm and isopropanol (dispersant) and put them into a ball mill jar. The mass ratio of LLZO, isopropanol, and the ball mill beads in the ball mill jar is 2:3:10;

[0139] Ball mill the Li7La3Zr2O with an original particle size of 100 μm 12 at a rotation speed of 500 r for 18 h to obtain a second inorganic electrolyte with an average particle size of 1 μm to 10 μm;

[0140] Ball mill the second inorganic electrolyte with a particle size of 1 μm to 10 μm at a rotation speed of 500 r for 36 h to obtain a first inorganic electrolyte with an average particle size of 300 nm to 800 nm;

[0141] Mix the first inorganic electrolyte and the second inorganic electrolyte evenly according to a mass ratio of 8:2 to obtain an inorganic electrolyte.

[0142] (2) Preparation of solid electrolyte membrane

[0143] Add the above 5.22 g (87%) of the uniformly mixed inorganic electrolyte, 0.06 g (1%) of lithium bis(fluorosulfonyl)imide (LiFSI), 0.045 g (0.75%) of 1-benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt (BzmimTFSI), and 0.045 g (0.75%) of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt ([EMIM][TFSI]) to 9 g of N,N-dimethylformamide (DMF), and stir with a blender at 1500 r for 10 minutes to completely disperse the inorganic electrolyte, obtaining a first mixture;

[0144] Next, add 0.12 g (2%) of hexafluorobutyl methacrylate (TFBMA) to the above first mixture, and stir with a blender at 1500 r for 10 minutes to completely disperse it, obtaining a second mixture;

[0145] Then, add 0.09 g (1.5%) of polyethylene oxide (PEO) to the above second mixture, and stir with a blender at 1500 r for 10 minutes to completely disperse it, obtaining a third mixture;

[0146] After that, add 0.42 g (7%) of poly(vinylidene fluoride-trifluoroethylene) copolymer P(VDF-TrFE) to the above third mixture, stir with a blender at 1500 r for 10 minutes, and defoam with a defoamer for 2 minutes to obtain a first slurry;

[0147] Finally, scrape the first slurry on a PET release film with a 250-μm doctor blade to form an initial solid electrolyte membrane, and after vacuum drying, obtain a solid electrolyte membrane with a thickness of 30 μm.

[0148] Example 2

[0149] This example provides a method for preparing a solid electrolyte membrane. Example 2 is basically similar to Example 1, except that in the process of preparing the inorganic electrolyte, the first inorganic electrolyte and the second inorganic electrolyte are mixed evenly at a mass ratio of 7:3.

[0150] Example 3

[0151] This example provides a method for preparing a solid electrolyte membrane. Example 3 is basically similar to Example 1, except that in the process of preparing the inorganic electrolyte, the first inorganic electrolyte and the second inorganic electrolyte are mixed evenly at a mass ratio of 6:4.

[0152] Example 4

[0153] This embodiment provides a method for preparing a solid electrolyte membrane. Embodiment 4 is basically similar to Embodiment 1, except that in the process of preparing the solid electrolyte membrane, "0.045 g of 1-benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 0.045 g of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide" is replaced with 0.09 g (1.5%) of 1-benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0154] Embodiment 5

[0155] This embodiment provides a method for preparing a solid electrolyte membrane. Embodiment 5 is basically similar to Embodiment 1, except that in the process of preparing the solid electrolyte membrane, "0.045 g of 1-benzyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 0.045 g of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide" is replaced with 0.09 g (1.5%) of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide.

[0156] Embodiment 6

[0157] This embodiment provides a method for preparing a solid electrolyte membrane. Embodiment 6 is basically similar to Embodiment 1, except that in the process of preparing the solid electrolyte membrane, the step of "adding 0.12 g (2%) of hexafluorobutyl methacrylate to the above first mixture" is omitted.

[0158] Embodiment 7

[0159] This embodiment provides a method for preparing a solid electrolyte membrane. Embodiment 7 is basically similar to Embodiment 1, except that in the process of preparing the solid electrolyte membrane, "adding 0.09 g (1.5%) of polyethylene oxide (PEO) to the above second mixture and adding 0.42 g (7%) of PVDF-TrEE binder to the above third mixture" is replaced with "adding 0.51 g (8.5%) of PVDF-TrFE binder".

[0160] Embodiment 8

[0161] This embodiment provides a method for preparing a solid electrolyte membrane. Embodiment 8 is basically similar to Embodiment 1, except that in the process of preparing the solid electrolyte membrane, "adding 0.09 g (1.5%) of polyethylene oxide (PEO) to the above second mixture and adding 0.42 g (7%) of PVDF-TrFE binder to the above third mixture" is replaced with "adding 0.03 g (0.5%) of polyethylene oxide (PEO) to the above second mixture and adding 0.48 g (8%) of PVDF-TrFE binder to the above third mixture".

[0162] Comparative Example 1

[0163] Comparative Example 1 is basically similar to Example 1, except that in preparing the solid electrolyte membrane in Example 1, "5.22 g of inorganic electrolyte" is replaced with "5.22 g of first inorganic electrolyte".

[0164] Comparative Example 2

[0165] Comparative Example 2 is basically similar to Example 1, except that in preparing the solid electrolyte membrane in Example 1, "5.22 g of inorganic electrolyte" is replaced with "5.22 g of second inorganic electrolyte".

[0166] Comparative Example 3

[0167] Comparative Example 3 is basically similar to Example 1, except that in Example 1, "mixing the first inorganic electrolyte and the second inorganic electrolyte evenly in a mass ratio of 8:2" is replaced with "mixing the first inorganic electrolyte and the second inorganic electrolyte evenly in a mass ratio of 4:6".

[0168] The ionic conductivities of Examples 1 to 8 and Comparative Examples 1 to 3 were measured respectively, and the film-forming properties of the solid electrolyte membranes in Examples 1 to 8 and Comparative Examples 1 to 3 were observed. The results are shown in Table 1.

[0169] The ionic conductivity was obtained by cutting the solid electrolyte membrane into discs with a diameter of 16 mm respectively, assembling a symmetric cell by sandwiching the discs between two stainless steel gaskets, then connecting an electrochemical workstation and performing impedance testing to obtain the bulk impedance value of the sample to be tested.

[0170] According to the formula σ = l / (AR), the ionic conductivity was calculated, with the unit of S / cm; l is the thickness of the solid electrolyte membrane, with the unit of cm; A is the area of the solid electrolyte membrane, with the unit of cm 2 ; R is the bulk impedance of the sample to be tested, with the unit of Ω.

[0171] Table 1

[0172]

[0173] Combined with Table 1, it can be seen that the solid electrolyte membranes of Examples 1 to 8 have good film-forming properties and no cracks, and also have high ionic conductivity. Therefore, in the electrolyte composition provided by the embodiments of the present application, the first inorganic electrolyte with an average particle size of 300 nm to 800 nm and the second inorganic electrolyte with an average particle size of 1 μm to 10 μm are compounded in a suitable mass percentage, which not only improves the ionic conductivity of the electrolyte membrane, but also solves the problems of poor film-forming properties and cracks during the formation of the electrolyte.

[0174] Moreover, the solid electrolyte membrane of Comparative Example 1 has poor film-forming property and many cracks. The main reason is that all the inorganic electrolytes in Comparative Example 1 are the first inorganic electrolytes with a relatively small average particle size, and the first inorganic electrolytes with a relatively small average particle size are not conducive to film formation. The ionic conductivity of the solid electrolyte membrane of Comparative Example 2 is relatively small. The main reason is that all the inorganic electrolytes in Comparative Example 2 are the second inorganic electrolytes with a relatively large average particle size, and the second inorganic electrolytes with a relatively large average particle size are not conducive to improving the ionic conductivity. The ionic conductivity of the solid electrolyte membrane of Comparative Example 3 is relatively small. The main reason is that the mass ratio of the second inorganic electrolyte in Comparative Example 3 is greater than that of the first inorganic electrolyte, and the second inorganic electrolyte is not conducive to improving the ionic conductivity.

[0175] In addition, it can be seen from Examples 1 to 3 that as the mass ratio of the first inorganic electrolyte with a relatively small average particle size in the inorganic electrolyte increases, the ionic conductivity of the solid electrolyte membrane increases.

[0176] It can be seen from Example 1, Example 4 and Example 5 that the ionic conductivity of the solid electrolyte membrane in Example 1 is greater than that of the solid electrolyte membranes in Example 4 and Example 5. Therefore, the 1-benzyl-3-methylimidazolium cation of the first ionic liquid and the 1-ethyl-3-methylimidazolium cation of the second ionic liquid are compounded in a suitable ratio, which can improve the ionic conductivity of the solid electrolyte membrane.

[0177] It can be seen from Example 1 and Example 6 that the ionic conductivity of the solid electrolyte membrane in Example 1 is greater than that of the solid electrolyte membrane in Example 6. Therefore, introducing hexafluorobutyl methacrylate into the solid electrolyte can improve the ionic conductivity of the solid electrolyte membrane.

[0178] It can be seen from Example 1, Example 7 and Example 8 that the ionic conductivities of the solid electrolyte membranes in Example 1 and Example 8 are greater than that of the solid electrolyte membrane in Example 7. Therefore, polyethylene oxide and trifluoroethyl acetate-modified polyvinylidene fluoride are compounded in a suitable ratio, which can improve the ionic conductivity of the solid electrolyte membrane.

[0179] Application Example 1

[0180] This application example provides a composite electrolyte membrane and a battery, and the preparation method is as follows:

[0181] Dissolve 0.5 g of the second lithium salt LiFSI and 1.0 g of the polymer electrolyte PVDF in 10 g of the second solvent DMF, stir at room temperature for 12 h to obtain a second mixed solution, and through the solution casting-drying method, use a 250-μm doctor blade to scrape on a glass plate and dry at 80 °C to obtain a polymer electrolyte membrane with a thickness of 10 μm;

[0182] Align and stack the solid electrolyte membrane of Example 1 and the polymer electrolyte membrane of this example to obtain a composite electrolyte membrane;

[0183] Under the inert atmosphere of a glove box, the positive electrode, composite electrolyte membrane and negative electrode were assembled in sequence. The solid electrolyte membrane of the composite electrolyte membrane was arranged close to the positive electrode, and the polymer electrolyte membrane was arranged close to the negative electrode. The assembly was completed by pressing at 800 kPa for 5 s to obtain a Li||NMC811 battery.

[0184] Application Examples 2 to 8

[0185] Application Examples 2 to 8 are basically the same as Application Example 1, except that the solid electrolyte membrane of Example 1 is replaced by the solid electrolyte membrane of Examples 2 to 8 in Application Examples 2 to 8, respectively. Among them, the solid electrolyte in Application Example 2 is the solid electrolyte membrane of Example 2. The solid electrolyte in Application Example 3 is the solid electrolyte membrane of Example 3. The solid electrolyte in Application Example 4 is the solid electrolyte membrane of Example 4. The solid electrolyte in Application Example 5 is the solid electrolyte membrane of Example 5. The solid electrolyte in Application Example 6 is the solid electrolyte membrane of Example 6. The solid electrolyte in Application Example 7 is the solid electrolyte membrane of Example 7. The solid electrolyte in Application Example 8 is the solid electrolyte membrane of Example 8.

[0186] Application Example 9

[0187] The application example is basically the same as the application example 1, except that the composite electrolyte membrane in the application example 9 further includes a top solid electrolyte membrane and a bottom solid electrolyte membrane. The bottom solid electrolyte membrane is located between the polymer electrolyte membrane and the solid electrolyte membrane. The top solid electrolyte membrane is located on the side of the solid electrolyte membrane away from the polymer electrolyte membrane. In addition, the thickness of the solid electrolyte membrane is 10 microns.

[0188] The preparation method of the top solid electrolyte membrane is as follows:

[0189] 5.4 g (90%) of the third inorganic electrolyte with an average particle size of 300 nm to 800 nm obtained by grinding in Example 1, 0.12 g (2%) of the third lithium salt LiFSI and 0.48 g (8%) of the PVDF-TrFE binder were dissolved in 10 g of the third solvent DMF, mixed evenly, and then a 7-micron top solid electrolyte membrane was formed on the solid electrolyte membrane by a tape casting film forming technology.

[0190] The preparation method of the bottom solid electrolyte membrane is as follows:

[0191] 5.4 g (90%) of the fourth inorganic electrolyte with an average particle size of 1 μm to 10 μm ground in Example 1, 0.12 g (2%) of the fourth lithium salt LiFSI, and 0.48 g (8%) of the PVDF-TrFE binder were dissolved in 10 g of the fourth solvent DMF. After mixing evenly, a 15-μm bottom solid electrolyte membrane was formed on the solid electrolyte membrane by the casting film-forming technique.

[0192] Applied Comparative Examples 1 to 3

[0193] Applied Comparative Examples 1 to 3 were basically the same as Applied Example 1, except that in Applied Comparative Examples 1 to 3, the solid electrolyte membranes of Example 1 were replaced with the solid electrolyte membranes of Comparative Examples 1 to 3, respectively. Among them, the solid electrolyte in Applied Comparative Example 1 was the solid electrolyte membrane of Comparative Example 1. The solid electrolyte in Applied Comparative Example 2 was the solid electrolyte membrane of Comparative Example 2. The solid electrolyte in Applied Comparative Example 3 was the solid electrolyte membrane of Comparative Example 3.

[0194] The ionic conductivities of the composite electrolyte membranes of Applied Examples 1 to 9 and Applied Comparative Examples 1 to 3 were respectively tested, as well as the cycle life and capacity retention rate of the batteries. The data results are shown in Table 2.

[0195] Among them, the test methods for the cycle life and capacity retention rate (cycle curve) were as follows: The battery was charged at a constant current and constant voltage of 0.33C to 4.2V at 25°C, and then discharged at a constant current of 0.5C to 3.0V. This was one cycle. The remaining capacity was the capacity retention rate, and the cycle numbers or capacity retention rates of each battery were compared.

[0196] Table 2

[0197]

[0198] Combined with Table 2, it can be seen that compared with the composite electrolyte membranes of Applied Comparative Example 2 and Applied Comparative Example 3, the composite electrolyte membranes of Applied Examples 1 to 9 have high ionic conductivity. Moreover, compared with the batteries of Applied Comparative Examples 1 to 3, the cycle life of the batteries of Applied Examples 1 to 9 has not only been significantly improved, but also the capacity retention rate can still be maintained at 80% after 89 or more charge-discharge cycles. Therefore, the electrolyte composition provided by the embodiments of the present application can improve the ionic conductivity of the composite electrolyte membrane and enhance and improve the cycle life and capacity retention rate of the battery.

[0199] The description of the above embodiments is only used to help understand the technical solution and its core idea of the present application; those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An electrolyte composition, characterized in that include: An inorganic electrolyte, the inorganic electrolyte comprising a first inorganic electrolyte and a second inorganic electrolyte, the first inorganic electrolyte having an average particle size of 300 nm to 800 nm; the second inorganic electrolyte having an average particle size of 1 μm to 10 μm; wherein, in the inorganic electrolyte, the mass percentage of the first inorganic electrolyte is 60% to 80%, and the mass percentage of the second inorganic electrolyte is 20% to 40%; and An ionic liquid includes a first ionic liquid and a second ionic liquid, wherein the first ionic liquid includes a 1-benzyl-3-methylimidazolium cation, the second ionic liquid includes a 1-ethyl-3-methylimidazolium cation, and the mass ratio of the inorganic electrolyte, the first ionic liquid and the second ionic liquid is (80~90):(0.6~0.9):(0.6~0.9).

2. The electrolyte composition according to claim 1, characterized in that The mass ratio of the inorganic electrolyte, the first ionic liquid and the second ionic liquid is (80-90): (0.65-0.85): (0.65-0.85); the molar ratio of the cations of the first ionic liquid to the cations of the second ionic liquid is greater than or equal to 0.8 and less than 1; and / or, The mass percentage of the first inorganic electrolyte is 65% to 75%, and the mass percentage of the second inorganic electrolyte is 25% to 35%.

3. The electrolyte composition according to claim 1, characterized in that The anion of the first ionic liquid and the anion of the second ionic liquid are each independently selected from one or more of bis(trifluoromethylsulfonyl)imide, bis(fluorosulfonyl)imide, bistrifluoromethylsulfonate and trifluoromethylsulfonate.

4. The electrolyte composition according to claim 1, characterized in that The electrolyte composition further includes a first lithium salt, wherein the first lithium salt includes a fluorine-containing lithium salt, and the mass ratio of the fluorine-containing lithium salt to the inorganic electrolyte is 1:(80-90); and / or, The electrolyte composition further comprises a fluorine-containing ester compound, and the mass ratio of the fluorine-containing ester compound to the inorganic electrolyte is (1.5-2.5):(80-90).

5. The electrolyte composition according to claim 4, characterized in that The fluorine-containing ester compound includes hexafluorobutyl methacrylate; and / or, The fluorine-containing lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium difluorooxalatoborate and lithium hexafluorophosphate.

6. The electrolyte composition according to claim 1, characterized in that It also includes a binder, which includes polyethylene oxide and a fluorine-containing polymer. The mass ratio of the inorganic electrolyte, the polyethylene oxide and the fluorine-containing polymer is (80-90): (1-2): (6-8).

7. The electrolyte composition according to claim 6, characterized in that The fluorine-containing polymer is selected from one or more of polyvinylidene fluoride, poly(vinylidene fluoride-trifluoroethylene) and poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene); and / or, The weight average molecular weight of the fluorine-containing polymer is 450,000 to 1,100,000; and / or The weight average molecular weight of the polyethylene oxide is 7,500,000-8,500,000.

8. The electrolyte composition according to claim 1, characterized in that The inorganic electrolyte includes one or more of a perovskite-type material, a NASICON-type material, and a garnet-type material.

9. A solid electrolyte membrane, characterized in that: The electrolyte composition comprises the electrolyte composition according to any one of claims 1 to 8.

10. A composite electrolyte membrane, characterized in that: The invention comprises the solid electrolyte membrane and a polymer electrolyte membrane as claimed in claim 9, wherein the polymer electrolyte membrane is stacked with the solid electrolyte membrane, wherein the polymer electrolyte membrane comprises a polymer electrolyte.

11. A method for preparing a composite electrolyte membrane as claimed in claim 10, characterized in that: include: forming a solid electrolyte membrane; forming a polymer electrolyte membrane; The solid electrolyte membrane and the polymer electrolyte membrane are stacked to obtain the composite electrolyte membrane.

12. The method for preparing a composite electrolyte membrane according to claim 11, characterized in that: The forming of the solid electrolyte membrane comprises: Providing an electrolyte composition according to any one of claims 1 to 8 and a first solvent; dissolving each component of the electrolyte composition in the first solvent to obtain a first slurry; The first slurry is used to form an initial solid electrolyte membrane, and the first solvent is removed to obtain the solid electrolyte membrane.

13. The method for preparing a composite electrolyte membrane according to claim 11, characterized in that: The forming of the polymer electrolyte membrane comprises: providing a polymer electrolyte, a second lithium salt, and a second solvent; dissolving the polymer electrolyte and the second lithium salt in the second solvent to obtain a second slurry; The second slurry is used to form an initial polymer electrolyte membrane, and the second solvent is removed to obtain the polymer electrolyte membrane.

14. A battery, characterized in that: include: positive electrode; negative electrode; as well as The composite electrolyte membrane according to claim 10, wherein the composite electrolyte membrane is located between the positive electrode and the negative electrode, and the polymer electrolyte membrane is located between the solid electrolyte membrane and the negative electrode.

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