Sulfide electrolyte membrane, preparation method thereof, sulfide electrolyte slurry and solid-state battery

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a sulfide electrolyte membrane, a preparation method thereof, sulfide electrolyte slurry and a solid-state battery. Compared with the prior art, the rate capability and the safety performance of the battery are improved by comprehensively controlling the ionic conductivity and the relative dielectric constant of the solid electrolytic film.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and particularly relates to a sulfide electrolyte film, a preparation method thereof, a sulfide electrolyte slurry and a solid-state battery. BACKGROUND

[0002] According to the mass percentage content of the liquid electrolyte in the battery, the lithium battery can be divided into a liquid battery, a semi-solid battery, a quasi-solid battery and a full-solid battery, wherein the semi-solid, quasi-solid and full-solid three are collectively referred to as a solid-state battery. The solid-state battery and the liquid battery follow the same charging and discharging principle, and the solid-state electrolyte replaces the liquid electrolyte and the separator in the liquid battery, eliminates the safety hazard of flammable leakage, and significantly improves the battery energy density, becoming the focus of research in the academic and industrial fields.

[0003] The solid-state electrolyte is a crucial part in the full-solid-state battery. At present, the electrolyte in the full-solid-state battery mainly includes oxide solid-state electrolyte, sulfide solid-state electrolyte and polymer solid-state electrolyte. However, in the solid-state battery, the solid-state electrolyte and the positive and negative electrode sheets belong to solid-solid contact. The solid-solid contact will cause the increase of the resistance, block the transmission rate of lithium ions, and affect the fast charging performance of the battery. In the process of lithium ion transmission, the electrolyte plays a very important transition role. Although the sulfide electrolyte has a relatively good lithium ion transmission rate compared with oxide and polymer electrolytes, the ion transmission performance of the sulfide electrolyte film is affected after being prepared. How to improve the ion transmission performance of the sulfide electrolyte film is a technical problem to be solved. SUMMARY

[0004] Therefore, the present application aims to provide a sulfide electrolyte film with good uniformity and ion conductivity, a preparation method thereof, a sulfide electrolyte slurry and a solid-state battery.

[0005] The present application provides a sulfide electrolyte film, which comprises a sulfide solid-state electrolyte; the ion conductivity of the sulfide electrolyte film is 0.2-3 mS / cm; and the relative dielectric constant of the sulfide electrolyte film is 18-25.

[0006] Preferably, the ion conductivity of the sulfide electrolyte film is 1-2.5 mS / cm.

[0007] Preferably, the relative dielectric constant of the sulfide electrolyte film is 20-25.

[0008] Preferably, the sulfide solid-state electrolyte is selected from one or more of lithium phosphorus sulfide chloride, lithium germanium phosphorus sulfide, a lithium phosphorus sulfide chloride derivative and a lithium germanium phosphorus sulfide derivative.

[0009] Preferably, it further includes an adhesive; the adhesive is selected from one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, hydrogenated styrene copolymer, hydrogenated styrene-butadiene rubber, hydrogenated butadiene rubber and hydrogenated polyisobutylene.

[0010] Preferably, the adhesive is selected from one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, hydrogenated styrene copolymer, hydrogenated styrene-butadiene rubber and hydrogenated butadiene rubber, and hydrogenated polyisobutylene;

[0011] The mass ratio of one or more of the polyvinylidene fluoride-hexafluoropropylene copolymer, hydrogenated styrene copolymer, hydrogenated styrene-butadiene rubber and hydrogenated butadiene rubber to hydrogenated polyisobutylene is (9:1):(1:9).

[0012] Preferably, the hydrogenated styrene copolymer is selected from one or more of hydrogenated styrene-butadiene copolymer, hydrogenated styrene-isoprene-styrene copolymer, and styrene-ethylene-ethylene-propylene-styrene copolymer.

[0013] Preferably, the adhesive is selected from one or more of hydrogenated styrene-ethylene-ethylene-propylene-styrene copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated styrene-butadiene rubber and hydrogenated butadiene rubber, and hydrogenated polyisobutylene;

[0014] The mass ratio of one or more of the hydrogenated styrene-ethylene-ethylene-propylene-styrene copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated styrene-butadiene rubber and hydrogenated butadiene rubber to hydrogenated polyisobutylene is (9:1):(1:9).

[0015] Preferably, the mass ratio of the sulfide solid electrolyte to the binder is (93-99):(7-1).

[0016] Preferably, the thickness of the sulfide electrolyte membrane is 5–50 μm;

[0017] And / or, the areal density of the sulfide electrolyte membrane is 30–50 g / m³. 2 .

[0018] The present invention also provides a method for preparing the above-mentioned sulfide electrolyte membrane, comprising the following steps:

[0019] S1) The sulfide solid electrolyte, binder and organic solvent are mixed to obtain sulfide electrolyte slurry; the relative permittivity of the organic solvent is less than 10;

[0020] S2) The sulfide electrolyte slurry is coated onto a release film and dried to form a film, thereby obtaining a sulfide electrolyte membrane.

[0021] Preferably, the mass of the binder is 0.4% to 5% of the mass of the sulfide electrolyte slurry;

[0022] And / or, the organic solvent is 40% to 70% of the mass of the sulfide electrolyte slurry.

[0023] Preferably, the adhesive is selected from one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, hydrogenated styrene copolymer, hydrogenated styrene-butadiene rubber, hydrogenated butadiene rubber, and hydrogenated polyisobutylene;

[0024] And / or, the organic solvent is selected from one or more of C5-C8 haloalkanes, substituted benzene solvents and ester solvents; the number of halogen atoms in the haloalkyl group is greater than or equal to 1; the substituents in the substituted benzene solvent are selected from C1-C4 alkyl groups and / or halogen atoms, and the number of substituents in the substituted benzene solvent is greater than or equal to 2.

[0025] The ester solvent is formed by an acid group and a hydroxyl group, wherein the acid group has 4 to 10 carbon atoms and the hydroxyl group has 5 to 8 carbon atoms.

[0026] Preferably, the organic solvent is selected from one or more of the following: bromoisooctane, 1,6-dichlorohexane, 1-iodooctane, 1-fluoro-9-chlorononane, 1,4-diethylbenzene, 2-bromo-p-xylene, dichlorobenzene, octyl butyrate, hexyl hexanoate, and butyl valerate.

[0027] The present invention also provides a sulfide electrolyte slurry, comprising a sulfide solid electrolyte, a binder and an organic solvent; wherein the relative permittivity of the organic solvent is less than 10.

[0028] Preferably, the viscosity of the sulfide electrolyte slurry is 1000-10000 mPa·s.

[0029] The present invention also provides a solid-state battery, comprising the above-mentioned sulfide electrolyte membrane, positive electrode and negative electrode.

[0030] Preferably, the positive electrode sheet includes a positive electrode active material; the positive electrode active material is selected from one or more of lithium cobalt oxide, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium manganese oxide, lithium iron phosphate, lithium nickel manganese oxide, and lithium manganese iron phosphate.

[0031] And / or, the negative electrode sheet includes a negative electrode active material; the negative electrode active material is selected from one or more of carbon materials, silicon-based materials and lithium titanate.

[0032] Preferably, the positive electrode active material is selected from nickel-cobalt-manganese ternary materials Li. a Ni b Co c Mn dMO2; wherein 0.75≤a≤1.2, 0.7≤b<1, 0<c<1, 0<d<1, b+c+d=1; M is selected from at least one of B, Zr, Ti, Si, Mo, La, Ce, Te, Nb, Ta, Si, Al, W, Sr, V, Y, Mg, Co and Li;

[0033] The ionic conductivity of the sulfide electrolyte membrane is 0.5–3 mS / cm; the relative permittivity of the sulfide electrolyte membrane is 20–25.

[0034] Preferably, the positive electrode active material comprises single crystal particles and / or polycrystalline particles; the particle size of the single crystal particles is 0.5 to 5 μm; and the particle size of the polycrystalline particles is 5 to 15 μm.

[0035] Preferably, the negative electrode active material comprises a silicon-based material; the silicon-based material comprises a silicon-carbon material.

[0036] The ionic conductivity of the sulfide electrolyte membrane is 0.5–3 mS / cm; the relative permittivity of the sulfide electrolyte membrane is 20–25.

[0037] This invention improves the rate performance and safety performance of batteries by comprehensively controlling the ionic conductivity and relative permittivity of solid electrolyte membranes. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] The ionic conductivity of an electrolyte membrane refers to its ability to conduct ions under an electric field, and it is one of the important parameters for evaluating the performance of an electrolyte membrane. The level of ionic conductivity directly affects the charge / discharge rate, cycle durability, and safety of the battery.

[0040] The present invention provides a sulfide electrolyte membrane comprising a sulfide solid electrolyte; the ionic conductivity of the sulfide electrolyte membrane is 0.2-3 mS / cm; and the relative permittivity of the sulfide electrolyte membrane is 18-25.

[0041] Higher ionic conductivity of the electrolyte membrane results in lower internal resistance and better cycle life and rate capability. However, improving ionic conductivity often requires reducing the amount of binders in the electrolyte membrane, which reduces its flexibility. During charging and discharging, lithium ion transport impacts the electrolyte membrane, increasing the risk of breakage. Insufficient binder dosage can also lead to inadequate adhesion between electrolyte molecules, poor bonding, and increased susceptibility to short circuits, posing significant safety risks. By comprehensively controlling the ionic conductivity and dielectric constant of the sulfide electrolyte membrane, it is possible to reduce the directional movement of lithium ions on the negative electrode surface, decrease lithium dendrite formation, and thus reduce the risk of lithium dendrites piercing the separator and causing short circuits within the battery.

[0042] By controlling the ionic conductivity of the electrolyte membrane, the migration rate of lithium ions within the membrane layer can be improved, enhancing the lithium ion transport capacity between the positive and negative electrodes and improving the battery's fast-charging performance. Furthermore, by controlling the relative permittivity of the electrolyte membrane, the directional movement of lithium ions on the negative electrode surface can be reduced, decreasing the formation of lithium dendrites and mitigating the risk of internal short circuits. Therefore, by comprehensively controlling both the ionic conductivity and relative permittivity of the electrolyte membrane, both lithium-ion transport performance and battery safety can be comprehensively improved.

[0043] In one specific embodiment of the present invention, the sulfide solid electrolyte can be any sulfide solid electrolyte well known to those skilled in the art, and there are no special limitations. Preferably, it is one or more selected from lithium phosphorus-sulfur-chloride, lithium germanium-phosphorus-sulfide, lithium phosphorus-sulfur-chloride derivatives, and lithium germanium-phosphorus-sulfur derivatives. The preferred structural formula of the lithium phosphorus-sulfur-chloride is Li. 6-x1 PS 5-x1 Cl 1+x1 Where 0 ≤ x1 < 1; the preferred structural formula of the lithium germanium phosphorus sulfur is Li 10+x2 Ge 1-x2 P2S 12 ; 0 ≤ x2 ≤ 1; the lithium phosphorus sulfur chloride derivative is preferably oxygen-doped and / or halogen-doped; the preferred structural formula of the oxygen-doped lithium phosphorus sulfur chloride derivative is Li6PS 5-x3 O x3 Cl, where 0 < x3 < 1; the preferred structural formula of the halogen-doped lithium phosphorus sulfide chlorine derivative is Li6PS5M. 1-x M′ x4 Where 0 < x4 < 1, M and M′ are independently Cl, Br, or I, and are not the same; the lithium germanium phosphorus sulfide derivative is preferably one or more of element-doped lithium germanium phosphorus sulfide, element-substituted lithium germanium phosphorus sulfide, oxygen-doped lithium germanium phosphorus sulfide, and halogen-doped lithium germanium phosphorus sulfide; the structural formula of the element-doped lithium germanium phosphorus sulfide is preferably Li 10+x5 Ge 1- x5 M″ x5 P2S12 0≤x5<1, M″ is preferably one or more of La, Ce, Pr, Nd, Bi and Re; the structural formula of the element-substituted lithium germanium phosphorus sulfur is preferably Li 10 AP2S 12 A is preferably Sn and / or Si; the oxygen-doped lithium germanium phosphorus sulfur structure is preferably Li 9.54 Ge 1.74 P2S 11.7 O 0.3 The preferred structural formula for the halogen-doped lithium germanium phosphorus sulfur is Li. 9.6 GeP2S 11.4 A′ 0.6 A′ is preferably Br and / or Cl.

[0044] In a specific embodiment of the present invention, the sulfide solid electrolyte is preferably lithium phosphorus sulfur chloride; the preferred structural formula of the lithium phosphorus sulfur chloride is Li 6-x1 PS 5-x Cl 1+x1 x = 0 or 0.5; that is, the preferred structural formula of the lithium phosphorus sulfur chlorine is Li6PS5Cl and / or Li 5.5 PS 5.4 Cl 1.5 It can make the ionic conductivity of the obtained sulfide electrolyte membrane higher.

[0045] In one specific embodiment of the present invention, the structural formula of the lithium germanium phosphorus sulfur is Li 10 GeP2S 12 .

[0046] In one specific embodiment provided by the present invention, the structural formula of the lithium germanium phosphorus sulfur derivative is Li 10.5 Ge 0.5 La 0.5 P2S 12 .

[0047] In one specific embodiment of the present invention, the average particle size of the sulfide solid electrolyte is preferably 0.5 to 15 μm; optionally, the average particle size of the sulfide solid electrolyte is 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or any two of the above values.

[0048] The thickness and areal density of the electrolyte membrane affect the lithium-ion transport path, and thus the lithium-ion transport between the positive and negative electrodes and the electrolyte membrane. Controlling the thickness and areal density of the electrolyte membrane makes lithium-ion transport smoother, thereby improving the rate performance of the battery. In a specific embodiment of the present invention, the thickness of the sulfide electrolyte membrane is preferably 5-50 μm; optionally, the thickness of the sulfide electrolyte membrane is 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any two of the above values; the areal density of the sulfide electrolyte membrane is preferably 30-50 g / m³. 2 Optionally, the areal density of the sulfide electrolyte membrane is 30 g / m³. 2 32g / m 2 34g / m 2 36g / m 2 38g / m 2 40g / m 2 42g / m 2 44g / m 2 46g / m 2 48g / m 2 50g / m 2 Or the range between any two of the above values.

[0049] In this invention, the impedance spectrum of the sulfide electrolyte membrane can be measured using an electrochemical workstation, the resistance can be extracted by fitting a Nyquist plot, and then the ionic conductivity can be calculated using the following formula:

[0050]

[0051] Where σ is the ionic conductivity, in S / cm; L is the electrolyte membrane thickness, in cm; R is the measured resistance, in Ω; and A is the electrode area, in cm². 2 ; 1S / cm = 1000mS / cm.

[0052] In one specific embodiment of the present invention, optionally, the ionic conductivity of the sulfide electrolyte membrane is 0.2 mS / cm to 3 mS / cm, specifically 0.2 mS / cm, 0.5 mS / cm, 0.8 mS / cm, 1 mS / cm, 1.5 mS / cm, 1.8 mS / cm, 2 mS / cm, 12.2 mS / cm, 2.5 mS / cm, 2.8 mS / cm, 3 mS / cm, or any two of the above values; more specifically, the ionic conductivity of the sulfide electrolyte membrane is preferably 1 to 2.5 mS / cm.

[0053] In this invention, the relative permittivity of the sulfide electrolyte membrane can be tested by broadband dielectric spectroscopy. Specifically, it can be carried out as follows: after pressurizing the sulfide electrolyte membrane, the test is performed using a broadband dielectric spectrometer at a test frequency of 0.1 Hz to 10 MHz and a temperature of 25°C. The pressure of the pressurization is preferably 400 MPa.

[0054] In one specific embodiment of the present invention, the relative permittivity of the sulfide electrolyte membrane is preferably 20 to 25; optionally, the relative permittivity of the sulfide electrolyte membrane is 19, 20, 21, 22, 23, 24, 25, or any two of the above values. By further controlling the relative permittivity of the sulfide electrolyte membrane, the risk of lithium dendrite formation and internal short circuits in the battery is further reduced.

[0055] In one specific embodiment of the present invention, the relative permittivity of the sulfide electrolyte membrane can be adjusted by the type of binder, the proportion of binder, etc.; the ionic conductivity of the sulfide electrolyte membrane can be adjusted by the type of electrolyte, the size of the electrolyte, the selection of solvent, the solvent content, etc.

[0056] In one specific embodiment of the present invention, the sulfide electrolyte membrane further includes a binder, which binds the sulfide solid electrolyte to form a film. The binder is preferably one or more of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), hydrogenated styrene copolymers, hydrogenated styrene-butadiene rubber, hydrogenated butadiene rubber, and hydrogenated polyisobutylene. The hydrogenated styrene copolymers are preferably one or more of hydrogenated styrene-butadiene copolymer (SEBS), hydrogenated styrene-isoprene-styrene copolymer (SEPS), and hydrogenated styrene-ethylene-ethylene-propylene-styrene copolymer (SEEPS). The PS bonds in the sulfide electrolyte are extremely unstable and easily broken by polar groups, leading to structural changes and performance deterioration. These binders, whose main structure is CH, have very low polarity and low reactivity with the electrolyte, making them less likely to break the PS bonds and thus less likely to damage the electrolyte structure, which is beneficial for ionic conductivity.

[0057] Furthermore, in a specific embodiment provided by the present invention, the adhesive is preferably one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, hydrogenated styrene copolymer, hydrogenated styrene-butadiene rubber, and hydrogenated butadiene rubber, and hydrogenated polyisobutylene. The connection between hydrogenated polyisobutylene and the electrolyte is a point-like connection, covering a small surface area of ​​the electrolyte, thereby improving the ionic conductivity of the electrolyte membrane; while other types of adhesives have stronger adhesion and can be used to improve the bonding strength with the electrolyte. The preferred mass ratio of one or more of the polyvinylidene fluoride-hexafluoropropylene copolymer, hydrogenated styrene copolymer, hydrogenated styrene-butadiene rubber, and hydrogenated butadiene rubber to hydrogenated polyisobutylene is (9:1):(1:9). Optionally, the mass ratio of one or more of the polyvinylidene fluoride-hexafluoropropylene copolymer, hydrogenated styrene copolymer, hydrogenated styrene-butadiene rubber, and hydrogenated butadiene rubber to hydrogenated polyisobutylene is 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9, or any two of the above ratios. Specifically, the preferred mass ratio of one or more of the polyvinylidene fluoride-hexafluoropropylene copolymer, hydrogenated styrene copolymer, hydrogenated styrene-butadiene rubber, and hydrogenated butadiene rubber to hydrogenated polyisobutylene is (4:6):(1:9). When the adhesive contains multiple components other than hydrogenated polyisobutylene, their mass ratios can be the same or different. In the embodiments provided by this invention, the same mass ratio is used as an example for explanation.

[0058] Furthermore, the adhesive is preferably one or more of hydrogenated styrene-ethylene-ethylene-propylene-styrene copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated styrene-butadiene rubber, and hydrogenated butadiene rubber, and hydrogenated polyisobutylene; the mass ratio of one or more of the hydrogenated styrene-ethylene-ethylene-propylene-styrene copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated styrene-butadiene rubber, and hydrogenated butadiene rubber to hydrogenated polyisobutylene is preferably (9:1):(1:9); optionally, the mass ratio of one or more of the hydrogenated styrene-ethylene-ethylene-propylene-styrene copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated styrene-butadiene rubber, and hydrogenated butadiene rubber to hydrogenated polyisobutylene is 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9, or any two of the above ratios. Specifically, the preferred mass ratio of one or more of the hydrogenated styrene-ethylene-ethylene-propylene-styrene copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated styrene-butadiene rubber, and hydrogenated butadiene rubber to hydrogenated polyisobutylene is (4:6):(1:9). When the adhesive contains multiple components other than hydrogenated polyisobutylene, their mass ratios can be the same or different. In the embodiments provided by this invention, the same mass ratio is used as an example for explanation.

[0059] In one specific embodiment of the invention, the weight-average molecular weight of the SEEPS is preferably 5W to 20W; optionally, the weight-average molecular weight of the SEEPS is 5W, 8W, 10W, 12W, 15W, 18W, 20W or any two of the above values.

[0060] In one specific embodiment of the invention, the weight-average molecular weight of the PVDF-HFP is preferably 10W to 100W; optionally, the weight-average molecular weight of the PVDF-HFP is 10W, 20W, 30W, 40W, 50W, 60W, 70W, 80W, 90W, 100W or any two of the above values.

[0061] In one specific embodiment of the invention, the molar content of HFP in the PVDF-HFP is preferably 10% to 30%; optionally, the molar content of HFP in the PVDF-HFP is 10%, 15%, 20%, 25%, 30%, or any two of the above values.

[0062] In one specific embodiment of the present invention, the weight-average molecular weight of the hydrogenated polyisobutylene is preferably 50 to 500 W; optionally, the weight-average molecular weight of the hydrogenated polyisobutylene is 50 W, 100 W, 150 W, 200 W, 250 W, 300 W, 350 W, 400 W, 450 W, 500 W, or any two of the above values.

[0063] In one specific embodiment of the present invention, the weight-average molecular weight of the hydrogenated styrene-butadiene rubber is preferably 5W to 100W; optionally, the weight-average molecular weight of the hydrogenated styrene-butadiene rubber is 5W, 10W, 20W, 25W, 28W, 30W, 40W, 50W, 60W, 70W, 80W, 90W, 100W or any two of the above values.

[0064] In one specific embodiment of the present invention, the weight-average molecular weight of the hydrogenated butadiene rubber is preferably 5W to 100W; optionally, the weight-average molecular weight of the hydrogenated butadiene rubber is 5W, 10W, 20W, 25W, 30W, 40W, 50W, 60W, 70W, 80W, 90W, 100W or any two of the above values.

[0065] In one specific embodiment of the present invention, the weight-average molecular weight of the hydrogenated styrene-butadiene copolymer is preferably 5W to 100W; optionally, the weight-average molecular weight of the hydrogenated styrene-butadiene copolymer is 5W, 10W, 20W, 25W, 30W, 40W, 50W, 60W, 70W, 80W, 90W, 100W or any two of the above values.

[0066] In one specific embodiment of the present invention, the weight-average molecular weight of the hydrogenated styrene-isoprene-styrene copolymer is preferably 5W to 100W; optionally, the weight-average molecular weight of the hydrogenated styrene-isoprene-styrene copolymer is 5W, 10W, 20W, 25W, 30W, 40W, 50W, 60W, 70W, 80W, 90W, 100W, or any two of the above values.

[0067] The content of binder in the sulfide electrolyte membrane directly affects its conductivity and the electrochemical performance of the electrolyte. Therefore, in a specific embodiment of the present invention, the mass ratio of the sulfide solid electrolyte to the binder is preferably (93-99):(7-1), more preferably (95-99):(1-5); in some embodiments of the present invention, the mass ratio of the sulfide solid electrolyte to the binder is specifically 45:5, 35:5, 59:1, 47:3 or 58:2.

[0068] The sulfide electrolyte membrane provided by this invention is prepared by a wet film-forming process. Therefore, the sulfide electrolyte membrane also contains residual organic solvents. The residual amount of organic solvents is at the ppm level. The relative permittivity of the organic solvents is preferably less than 10. The range of permittivity is further controlled to reduce the risk of short circuit between the positive and negative electrodes. In addition, a large permittivity also avoids the situation where the solvent polarity is relatively large, resulting in a large side reaction with the electrolyte.

[0069] The present invention also provides a method for preparing the above-mentioned sulfide electrolyte membrane, comprising the following steps: S1) mixing a sulfide solid electrolyte, a binder and an organic solvent to obtain a sulfide electrolyte slurry; wherein the relative permittivity of the organic solvent is less than 10; wherein the binder is selected from one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene copolymer, hydrogenated styrene copolymer, styrene-butadiene rubber, butadiene rubber and polyisobutylene; S2) drying the sulfide electrolyte slurry on a release film to form a film, thereby obtaining a sulfide electrolyte membrane.

[0070] In this invention, there are no special restrictions on the source of any raw materials; commercially available materials are acceptable. The types of sulfide solid electrolyte and binder are the same as those described above and will not be repeated here.

[0071] A sulfide solid electrolyte, a binder, and an organic solvent are mixed to obtain a sulfide electrolyte slurry. The binder is preferably 1% to 7% of the mass of the sulfide electrolyte slurry. Optionally, the binder is 1%, 2%, 3%, 4%, 5%, 6%, or 7% of the mass of the sulfide electrolyte slurry, or any two of the above values. The organic solvent is preferably 40% to 70% of the mass of the sulfide electrolyte slurry. Optionally, the organic solvent is 40%, 45%, 50%, 55%, 60%, 65%, or 70% of the mass of the sulfide electrolyte slurry, or any two of the above values.

[0072] In one specific embodiment of the present invention, the relative permittivity of the organic solvent is preferably less than 10; further controlling the range of the permittivity reduces the risk of short circuit between the positive and negative electrodes; in addition, it also avoids a large permittivity, which would result in relatively high solvent polarity and large side reactions with the electrolyte.

[0073] As the carbon chain length increases, the substance changes from gas to liquid to solid. The polarity of the organic solvent decreases with increasing carbon chain length. Therefore, the selection of the specific organic solvent needs to consider its similarity and miscibility with the binder, good solubility, and high ionic conductivity to reduce its impact on the ionic conductivity of the sulfide electrolyte membrane. Furthermore, coating safety must also be considered. Therefore, in a specific embodiment of this invention, the organic solvent is preferably one or more of C5-C8 haloalkanes, substituted benzene solvents, and ester solvents. The haloalkanes have a main chain carbon number of 5-8, ensuring coating safety. Simultaneously, by substituting halogen atoms, their flash point is adjusted to the range of 60℃-120℃, reducing safety issues during electrolyte membrane processing. The haloalkyl group contains at least one halogen atom. Similarly, the benzene solvent adjusts its flash point by selecting the type and number of substituents. The substituents in the substituted benzene solvent are selected from C1-C4 alkyl groups and / or halogen atoms, and the number of substituents in the substituted benzene solvent is at least two. The ester solvent is formed by acid groups and hydroxyl groups. The longer the carbon chain of the ester solvent, the lower the polarity, the higher the flash point, and the greater the energy consumption. Conversely, the shorter the carbon chain, the greater the side reaction with the electrolyte. Considering the appropriate flash point, reducing polarity and side reactions with the electrolyte, the preferred carbon number of the acid group is 4 to 10, and the preferred carbon number of the hydroxyl group is 5 to 8.

[0074] In a specific embodiment of the present invention, the organic solvent is preferably one or more selected from the following: bromoisooctane, 1,6-dichlorohexane, 1-iodooctane, 1-fluoro-9-chlorononane, 1,4-diethylbenzene, 2-bromo-p-xylene, dichlorobenzene, octyl butyrate, hexyl hexanoate, and butyl valerate. These solvents have weak polar bond energies and low levels of side reactions with the electrolyte, allowing the sulfide electrolyte membrane to maintain good ionic conductivity. Furthermore, their moderate flash point of 60°C to 120°C makes industrial coating processes relatively safe.

[0075] In one specific embodiment of the present invention, it is preferable to first mix the adhesive with an organic solvent to obtain a slurry, and then mix the slurry with a sulfide solid electrolyte to obtain a sulfide electrolyte slurry.

[0076] In another specific embodiment of the present invention, it is preferable to first mix the sulfide solid electrolyte with the binder, and then add the organic solvent step by step for mixing and dispersion to form a sulfide electrolyte slurry. The electrolyte and binder dry powders are evenly dispersed and mixed, a small amount of solvent is added, and the mixture is stirred until it reaches a dough-like state. The stirring process creates the best shearing effect, which is more conducive to particle dispersion. Finally, more solvent is added to disperse the mixture into the finished slurry.

[0077] In a specific embodiment of the present invention, the mixing speed is preferably 1000–9000 rpm; optionally, the mixing speed is 1000 rpm, 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, 6000 rpm, 7000 rpm, 8000 rpm, 9000 rpm, or any two of the above values; the mixing linear velocity is preferably 10–23 m / s; optionally, the mixing linear velocity is 10 m / s, 12 m / s, 14 m / s, 16 m / s, 18 m / s, 20 m / s, 23 m / s, or any two of the above values; the mixing time is preferably 60–180 min; optionally, the mixing time is 60 min, 80 min, 100 min, 120 min, 140 min, 160 min, 180 min, or any two of the above values.

[0078] In a specific embodiment of the present invention, at 25°C, the viscosity of the sulfide electrolyte slurry is preferably 1000–10000 mPa·s; optionally, the viscosity of the sulfide electrolyte slurry is 1000 mPa·s, 2000 mPa·s, 3000 mPa·s, 4000 mPa·s, 5000 mPa·s, 6000 mPa·s, 7000 mPa·s, 8000 mPa·s, 9000 mPa·s, 10000 mPa·s, or a range between any two of the above values. This sulfide electrolyte slurry can be readily processed and coated into a film.

[0079] In this invention, the stability of the slurry can be tested and demonstrated under the following conditions: at room temperature (25°C), the slurry is placed in a sealed container and left to stand. Samples are taken at intervals of 6h, 12h, 24h, and 48h, and the viscosity, upper solid content, and lower solid content of the slurry are tested respectively. The viscosity change rate is calculated as slurry viscosity at 48h / initial viscosity at 0h × 100%. The difference in solid content between the upper and lower layers is calculated as lower solid content - upper solid content. The difference in solid content between the upper and lower layers can characterize the stability of the slurry and whether the solid content has settled. Generally, the solid density of the slurry is greater than the solvent density, and the slurry system has poor suspension ability. As time is left to stand, the upper solid will settle, resulting in changes in solid content.

[0080] In one specific embodiment of the present invention, the viscosity stability of the sulfide electrolyte slurry changes by less than 20% over 48 hours, and the solid content difference between the upper and lower layers is less than 0.5%.

[0081] In one specific embodiment of the present invention, the viscosity stability of the sulfide electrolyte slurry changes by less than 15% over 48 hours, and the solid content difference between the upper and lower layers is less than 0.2%.

[0082] In one specific embodiment of the present invention, the viscosity stability of the sulfide electrolyte slurry changes by 10.4% over 48 hours, and the solid content difference between the upper and lower layers is 0.1%.

[0083] The sulfide electrolyte slurry is coated onto a release film and dried to form a film, thereby obtaining a sulfide electrolyte membrane; specifically, the sulfide electrolyte slurry is coated onto a PET release film, dried to form a film, and then peeled off to obtain a sulfide electrolyte membrane.

[0084] The present invention also provides a solid-state battery comprising the above-described sulfide electrolyte membrane.

[0085] In a specific embodiment of the present invention, the solid-state battery further includes a positive electrode sheet; the positive electrode sheet includes a positive electrode active layer; the positive electrode active layer includes a positive electrode active material; the positive electrode active material can be any solid-state battery positive electrode active material known to those skilled in the art, and there are no special limitations. In the present invention, it is preferably one or more of lithium cobalt oxide (LCO), ternary materials, lithium manganese oxide (LiMn2O4), lithium iron phosphate (LFP), lithium nickel manganese oxide (LNMO), and lithium manganese iron phosphate (LMFP), and more preferably one or more of lithium cobalt oxide (LCO), nickel cobalt manganese ternary materials (NCM), nickel cobalt aluminum ternary materials (NCA), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LFP), lithium nickel manganese oxide (LNMO), and lithium manganese iron phosphate (LMFP).

[0086] In a specific embodiment provided by the present invention, the ternary material satisfies the general formula Li a1 Ni b1 Co c1 M1 d1 M2 e1 O f1 R g1 Wherein, 0.75≤a1≤1.2, 0<b1<1, 0<c1<1, 0<d1<1, b1+c1+d1=1, 0≤e1≤0.2, 1≤f1≤2.5, 0≤g1≤1, f1+g1≤3; M1 can be Mn and / or Al; M2 is selected from one or more of B, Zr, Ti, Si, Mo, La, Ce, Te, Nb, Ta, Si, Al, W, Sr, V, Y, Mg, Co and Li; R includes, but is not limited to, at least one of N, F, S and Cl.

[0087] Lithium nickel manganese oxide (LNMO) is a positive electrode active material with a spinel structure and high voltage characteristics. Its preferred general formula is Li 1+a2 Ni b2 M c2 Mn 2-a2-b2-c2 O 4-d2 -0.1≤a2≤0.2, 0.4≤b2≤0.6, 0≤c2≤0.2, 0≤d2≤0.1, M is a doping element, M includes but is not limited to one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Al and Ti.

[0088] Lithium manganese iron phosphate is a positive electrode active material with an olivine structure and a hexagonal close-packed structure. The chemical formula of lithium manganese iron phosphate is: Li a3 Ni b3 Fe c3 Mn d3 M 1-c3-d3 P 1-mQ m O 4-n R n In the formula, a3 is 0.9 to 1.1, b3 is 0 to 0.1, c3 is 0.001 to 0.999, d3 is 0.001 to 0.999, 1-c3-d3 is 0 to 0.1, m is 0 to 0.1, and n is 0 to 0.1. In the formula, M represents the doping element at the manganese and / or iron sites of lithium manganese iron phosphate, and M includes, but is not limited to, one or more of Co, Mg, Zn, Ca, Ti, V, Ni, and Cr; P represents the doping element at the lithium site of lithium manganese iron phosphate, and P includes, but is not limited to, one or more of Zn, Al, Na, K, Mg, Nb, Mo, and W; Q represents the doping element at the phosphorus site of lithium manganese iron phosphate, and Q includes, but is not limited to, one or more of B, S, Si, and N; R represents the doping element at the oxygen site of lithium manganese iron phosphate, and R includes, but is not limited to, one or more of S, F, Cl, and Br.

[0089] Lithium iron phosphate (LFP) is a cathode active material with an olivine-type crystal structure, offering advantages such as low cost and high safety. The general chemical formula for lithium iron phosphate is LiFe. 1-a4 M a4 PO b4 Q c4 Where a4≤0.1, 3.85≤b4≤4, 0≤c4≤0.05, and the doping element M includes, but is not limited to, one or more of Mn, Ni, Co, Cr, Cu, Bi, and Sb.

[0090] In one specific embodiment of the present invention, the positive electrode active material is preferably a nickel-cobalt-manganese ternary material Li. a5 Ni b5 Co c5 Mn d5 MO2; wherein 0.75≤a5≤1.2, 0.7≤b5<1, 0<c5<1, 0<d5<1, b5+c5+d5=1; M is selected from at least one of B, Zr, Ti, Si, Mo, La, Ce, Te, Nb, Ta, Si, Al, W, Sr, V, Y, Mg, Co, and Li; this allows the solid-state battery to have a high specific capacity; in this case, the ionic conductivity of the sulfide electrolyte membrane is preferably 0.5~3mS / cm; the relative permittivity of the sulfide electrolyte membrane is preferably 20~25. By selecting a nickel-cobalt-based ternary material as the positive electrode and controlling the sulfide electrolyte membrane within this range, the ion transport performance of the electrolyte membrane can be further improved, thereby improving the rate performance of the battery using nickel-cobalt-based ternary material as the positive electrode material.

[0091] In a specific embodiment of the present invention, the positive electrode active material preferably comprises single-crystal particles and / or polycrystalline particles; the particle size of the single-crystal particles is preferably 5-15 μm; optionally, the particle size of the single-crystal particles is 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm or any two of the above values; the particle size of the polycrystalline particles is preferably 0.5-5 μm; optionally, the particle size of the polycrystalline particles is 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm or any two of the above values.

[0092] In one specific embodiment of the present invention, the positive electrode active layer further includes a positive electrode binder and a positive electrode conductive agent; the positive electrode binder includes, but is not limited to, one or more of the binders polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), and polyacrylonitrile (PAN); the mass of the positive electrode binder is preferably 1% to 5% of the mass of the positive electrode active layer; optionally, the mass of the positive electrode binder is 1%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, or 4% of the mass of the positive electrode active layer. The positive electrode conductive agent comprises, but is not limited to, at least one of superconducting carbon (SP), acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the mass of the positive electrode conductive agent is preferably 0.5% to 5% of the mass of the positive electrode active layer; optionally, the mass of the positive electrode conductive agent is 0.5%, 1%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0% of the mass of the positive electrode active layer, or a range between any two of the above values.

[0093] In one specific embodiment of the present invention, the positive electrode sheet further includes a positive electrode current collector; the positive electrode active layer is disposed on at least one surface of the positive electrode current collector; the positive electrode current collector includes, but is not limited to, aluminum metal, aluminum alloy, carbon-coated aluminum foil, etc.

[0094] In a specific embodiment of the present invention, the solid-state battery further includes a negative electrode sheet; the negative electrode sheet includes a negative electrode active layer; the negative electrode active layer includes a negative electrode active material; the negative electrode active material can be any negative electrode active material of solid-state batteries known to those skilled in the art, and there are no special limitations. In the present invention, carbon materials, silicon-based materials, and lithium titanate (Li4Ti5O) are preferred. 12 One or more of the following.

[0095] In a specific embodiment of the present invention, the negative electrode active material is preferably a silicon-based material; the silicon-based material includes silicon-carbon material, i.e., porous carbon with deposited silicon; in this case, the ionic conductivity of the sulfide electrolyte membrane is preferably 0.5 to 3 mS / cm; and the relative permittivity of the sulfide electrolyte membrane is preferably 20 to 25.

[0096] In one specific embodiment of the present invention, the negative electrode active layer further includes a negative electrode binder and a negative electrode conductive agent; the negative electrode binder includes, but is not limited to, one or more of the binders polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyacrylonitrile (PAN), and sodium carboxymethyl cellulose (CMC); the mass of the negative electrode binder is preferably 1% to 5% of the mass of the negative electrode active layer; optionally, the mass of the negative electrode binder is 1%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5% of the mass of the positive electrode active layer. The negative electrode conductive agent comprises, but is not limited to, at least one of superconducting carbon (SP), acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the mass of the negative electrode conductive agent is preferably 0.5% to 5% of the mass of the negative electrode active layer; optionally, the mass of the negative electrode conductive agent is 0.5%, 1%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0% of the mass of the negative electrode active layer, or a range between any two of the above values.

[0097] In one specific embodiment of the present invention, the negative electrode sheet further includes a negative electrode current collector; the negative electrode active layer is disposed on at least one surface of the negative electrode current collector; the negative electrode current collector includes, but is not limited to, copper metal, copper alloy, carbon-coated copper foil, nickel-plated copper foil, etc.

[0098] In this invention, the solid-state battery can be prepared according to methods well known to those skilled in the art, without any particular limitations. Specifically, it can be prepared by sequentially stacking a positive electrode, a sulfide electrolyte membrane, and a negative electrode, pressing them together, and encapsulating them to obtain a solid-state battery. The pressing pressure can be 300–800 MPa; optionally, the pressure can be 300 MPa, 400 MPa, 500 MPa, 600 MPa, 700 MPa, 800 MPa, or any two of the above values.

[0099] The present invention also provides a sulfide electrolyte slurry, comprising a sulfide solid electrolyte, a binder, and an organic solvent; wherein the relative permittivity of the organic solvent is less than 10; and wherein the binder is selected from one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene copolymer, hydrogenated styrene copolymer, styrene-butadiene rubber, butadiene rubber, and polyisobutylene.

[0100] The types and amounts of the sulfide solid electrolyte, binder, and organic solvent are the same as described above, and will not be repeated here.

[0101] This invention achieves low side reactions between organic solvents and binders and sulfide solid electrolytes through multiple matching selections of organic solvents, binders, and sulfide solid electrolytes. This results in sulfide electrolyte membranes with good ionic conductivity while maintaining rate performance and internal battery safety. It also enables the slurry to have high coating performance and stability, thus solving the problem of industrial manufacturing of wet-process sulfide electrolyte membranes.

[0102] To further illustrate the present invention, the following describes in detail, in conjunction with embodiments, a sulfide electrolyte membrane, its preparation method, sulfide electrolyte slurry, and a solid-state battery provided by the present invention.

[0103] All reagents used in the following examples are commercially available; the weight-average molecular weight of the adhesive SEEPS used in the examples is 10W, the weight-average molecular weight of PVDF-HFP (20% HFP) is 40W, the weight-average molecular weight of HNBR is 28W, the weight-average molecular weight of hydrogenated polyisobutylene is 200W, the weight-average molecular weight of hydrogenated styrene-butadiene rubber (HSBR) is 28W, the weight-average molecular weight of hydrogenated butadiene rubber is 20W, and the weight-average molecular weight of hydrogenated styrene-butadiene copolymer (SEBS) is 20W.

[0104] Examples 1-18 and Comparative Examples 1-5

[0105] 1) Preparation method of sulfide electrolyte slurry: According to the formula in Table 1, the binder and organic solvent are mixed to obtain a slurry, and then the sulfide solid electrolyte Li6PS5Cl and lithium germanium phosphorus sulfide Li are added. 10 GeP2S 12 or lithium germanium phosphorus sulfur derivative Li 10.5 Ge 0.5 La 0.5 P2S 12 After being dispersed at a speed of 5000 rpm and a linear velocity of 18 m / s for 120 min until uniformly dispersed, a sulfide electrolyte slurry is obtained.

[0106] 2) Preparation method of sulfide solid electrolyte membrane: The prepared electrolyte slurry is coated onto a PET release film, dried at 100℃ for 5 min to form a film sheet, and then peeled off to obtain an electrolyte membrane with a thickness of 30 μm and an areal density of 45 g / cm³. 2 .

[0107] 3) Preparation of the positive electrode:

[0108] Positive electrode active materials (types shown in Table 1): PVDF binder and SP conductive agent are mixed evenly in a mass ratio of 97%:2%:1% and dispersed in NMP to obtain a positive electrode slurry. This positive electrode slurry is coated onto aluminum foil, baked at high temperature to remove solvents and moisture, then rolled and cut to obtain a positive electrode sheet with an areal density of 597 g / m². 2 Compacted density 3.4 g / cm³ 3 ;

[0109] 4) Negative electrode preparation: Artificial graphite + silicon carbide material, conductive agent SP, binder CMC, and binder SBR are dispersed in deionized water at a mass ratio of 97%:2%:0.5% and 0.5% respectively to obtain a negative electrode slurry; the negative electrode slurry is coated on copper foil, baked to remove moisture, rolled and cut to obtain a negative electrode sheet with an areal density of 196 g / m³. 2 The compacted density is 1.44 g / cm³. 3 The mass ratio of silicon-carbon material to artificial graphite is 5:95.

[0110] 5) Solid-state battery preparation: The cut positive electrode sheet, negative electrode sheet and electrolyte membrane are stacked according to requirements, further pressed (pressure 600MPa), packaged and formed, and tested to obtain the battery.

[0111] Methods for testing the ionic conductivity of sulfide electrolyte membranes:

[0112] 1. Discharge the battery at 0.33C to the lower limit voltage of 2.5V, then disassemble it and remove the electrolyte membrane;

[0113] 2. Use blocking electrodes at both ends;

[0114] 3. Use an electrochemical workstation to measure impedance spectroscopy;

[0115] 4. Extract resistance by fitting a Nyquist plot;

[0116] 5. Calculate the ionic conductivity using the formula.

[0117]

[0118] Where σ is the ionic conductivity, in S / cm; L is the electrolyte membrane thickness, in cm; R is the measured resistance, in Ω; and A is the electrode area, in cm². 2 .

[0119] Resistance extraction method:

[0120] Take an electrolyte membrane and press it into a sheet using a fixed-area stamping die. Remove the die, change the tooling, apply pressure, and conduct a test using a frequency scan-potential control mode. Test conditions: frequency scan range 10Hz~1MHz. Extract the real resistance value when the imaginary part is 0 from the spectrum to obtain the resistance R. Substitute the R value into the formula to calculate the ionic conductivity.

[0121] Methods for testing the relative permittivity of sulfide electrolyte membranes:

[0122] The sulfide click-inhibiting diaphragm was cut into discs and pressed at 400 MPa. The discs were then placed in a mold and the relative permittivity was recorded using a broadband dielectric spectrometer with a test frequency of 0.1 Hz to 10 MHz and a temperature of 25 °C.

[0123] 25℃ Magnification Test:

[0124] After formation and capacitance testing, lithium ions are charged at a constant current of 0.1C to the upper limit voltage, then charged at a constant voltage to the cutoff current of 0.05C, and then discharged at 0.1C to the lower limit voltage of 2.5V. The discharge capacity C0 is recorded. Then, the battery is charged at 0.33C to 4.25V, with a cutoff current of 0.05C, and then discharged at 0.33C to the lower limit voltage of 2.5V. The discharge capacity C1 is recorded. The rate test result of the battery at 25℃ is calculated as C1 / C0×100%.

[0125] The charging voltage is determined by the system. For lithium iron phosphate, the upper limit is 3.65V and the lower limit is 2.5V; for nickel-cobalt-manganese ternary lithium batteries, the upper limit is 4.25V and the lower limit is 2.5V.

[0126] Internal short circuit test of battery cell:

[0127] After formation, the lithium-ion battery is charged at a constant current of 0.33C to the upper limit voltage, and then charged at a constant voltage to 0.05C to stop charging; the positive and negative tabs of the battery cell are connected, and the voltage between the positive and negative tabs is tested.

[0128] The charging voltage is determined by the system. For lithium iron phosphate, the upper limit is 3.65V and the lower limit is 2.5V; for nickel-cobalt-manganese ternary lithium batteries, the upper limit is 4.25V and the lower limit is 2.5V.

[0129] For nickel-cobalt-manganese ternary batteries, if the voltage between the positive and negative electrodes is between 4.2-4.3V, it indicates that the voltage between the positive and negative electrodes is normal; if the voltage between the positive and negative electrodes is between 3.8V-4.2V (less than), it indicates a minor short circuit; if the voltage between the positive and negative electrodes is less than 1V, it indicates a short circuit between the positive and negative electrodes.

[0130] For lithium iron phosphate batteries, if the voltage between the positive and negative electrodes is measured to be between 3.5 and 3.7V, it indicates that the voltage between the positive and negative electrodes is normal; if the voltage between the positive and negative electrodes is measured to be between 3.0V and 3.5V, it indicates a minor short circuit; if the voltage between the positive and negative electrodes is less than 1V, it indicates that a short circuit has occurred between the positive and negative electrodes.

[0131] Table 1. Slurry formulation composition and battery performance test results

[0132]

[0133]

[0134]

[0135] Examples 1-12, 14-18, and Comparative Examples 1-5 show that when the sulfide electrolyte membrane has an ionic conductivity of 0.2-3 mS / cm and a relative permittivity of 18-25, the nickel-manganese battery has a rate performance greater than 77.9% and a voltage greater than or equal to 3.8V, which meets the requirements for normal battery use. When the sulfide electrolyte membrane does not meet the ionic conductivity range of 0.2-3 or the relative permittivity, the battery's rate performance is less than or equal to 72.4%, and / or the voltage between the positive and negative electrodes is less than 1V, posing a risk of short circuit.

[0136] As can be seen from Examples 5 to 10, when the ionic conductivity is further controlled at 1.02 to 2.5 mS / cm and the dielectric constant is further controlled at 20 to 25, the rate performance of the battery is improved to over 89.3%, and the voltage between the positive and negative electrodes is between 4.2 and 4.3V, indicating good battery safety performance.

[0137] As can be seen from Examples 15-18, when hydrogenated polyisobutylene or hydrogenated polyisobutylene is used as the binder in combination with other types, the rate performance of the battery can be improved to over 97.5%, and the voltage between the positive and negative electrodes of the battery is between 4.2 and 4.3V, resulting in good battery safety performance.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A sulfide electrolyte membrane, characterized in that, It includes a sulfide solid electrolyte; the ionic conductivity of the sulfide electrolyte membrane is 0.2 to 3 mS / cm; and the relative permittivity of the sulfide electrolyte membrane is 18 to 25.

2. The sulfide electrolyte membrane according to claim 1, characterized in that, The ionic conductivity of the sulfide electrolyte membrane is 1–2.5 mS / cm; And / or, the relative permittivity of the sulfide electrolyte membrane is 20 to 25; And / or, the sulfide solid electrolyte is selected from one or more of lithium phosphorus-sulfur-chloride, lithium germanium-phosphorus-sulfide, lithium phosphorus-sulfur-chloride derivatives and lithium germanium-phosphorus-sulfide derivatives.

3. The sulfide electrolyte membrane according to claim 1, characterized in that, It also includes an adhesive; the adhesive is selected from one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, hydrogenated styrene copolymer, hydrogenated styrene-butadiene rubber, hydrogenated butadiene rubber and hydrogenated polyisobutylene.

4. The sulfide electrolyte membrane according to claim 3, characterized in that, The adhesive is selected from one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, hydrogenated styrene copolymer, hydrogenated styrene-butadiene rubber and hydrogenated butadiene rubber, and hydrogenated polyisobutylene; The mass ratio of one or more of the polyvinylidene fluoride-hexafluoropropylene copolymer, hydrogenated styrene copolymer, hydrogenated styrene-butadiene rubber and hydrogenated butadiene rubber to hydrogenated polyisobutylene is (9:1):(1:9).

5. The sulfide electrolyte membrane according to claim 4, characterized in that, The hydrogenated styrene copolymer is selected from one or more of hydrogenated styrene-butadiene copolymer, hydrogenated styrene-isoprene-styrene copolymer, and styrene-ethylene-ethylene-propylene-styrene copolymer.

6. The sulfide electrolyte membrane according to claim 5, characterized in that, The adhesive is selected from one or more of hydrogenated styrene-ethylene-ethylene-propylene-styrene copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated styrene-butadiene rubber and hydrogenated butadiene rubber, and hydrogenated polyisobutylene; The mass ratio of one or more of the hydrogenated styrene-ethylene-ethylene-propylene-styrene copolymer, hydrogenated styrene-butadiene copolymer, hydrogenated styrene-butadiene rubber and hydrogenated butadiene rubber to hydrogenated polyisobutylene is (9:1):(1:9).

7. The sulfide electrolyte membrane according to claim 3, characterized in that, The mass ratio of the sulfide solid electrolyte to the binder is (93-99):(7-1).

8. The sulfide electrolyte membrane according to any one of claims 1 to 7, characterized in that, The thickness of the sulfide electrolyte membrane is 5–50 μm; And / or, the areal density of the sulfide electrolyte membrane is 30–50 g / m³. 2 .

9. A method for preparing the sulfide electrolyte membrane according to claim 1, characterized in that, Includes the following steps: S1) The sulfide solid electrolyte, binder and organic solvent are mixed to obtain sulfide electrolyte slurry; the relative permittivity of the organic solvent is less than 10; S2) The sulfide electrolyte slurry is coated onto a release film and dried to form a film, thereby obtaining a sulfide electrolyte membrane.

10. The preparation method according to claim 9, characterized in that, The mass of the binder is 0.4% to 5% of the mass of the sulfide electrolyte slurry; And / or, the organic solvent is 40% to 70% of the mass of the sulfide electrolyte slurry.

11. The preparation method according to claim 9, characterized in that, The adhesive is selected from one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, hydrogenated styrene copolymer, hydrogenated styrene-butadiene rubber, hydrogenated butadiene rubber and hydrogenated polyisobutylene; And / or, the organic solvent is selected from one or more of C5-C8 haloalkanes, substituted benzene solvents and ester solvents; the number of halogen atoms in the haloalkyl group is greater than or equal to 1; the substituents in the substituted benzene solvent are selected from C1-C4 alkyl groups and / or halogen atoms, and the number of substituents in the substituted benzene solvent is greater than or equal to 2. The ester solvent is formed by an acid group and a hydroxyl group, wherein the acid group has 4 to 10 carbon atoms and the hydroxyl group has 5 to 8 carbon atoms.

12. The preparation method according to claim 11, characterized in that, The organic solvent is selected from one or more of the following: bromoisooctane, 1,6-dichlorohexane, 1-iodooctane, 1-fluoro-9-chlorononane, 1,4-diethylbenzene, 2-bromo-p-xylene, dichlorobenzene, octyl butyrate, hexyl hexanoate, and butyl valerate.

13. A sulfide electrolyte slurry, characterized in that, It includes a sulfide solid electrolyte, a binder, and an organic solvent; the relative permittivity of the organic solvent is less than 10.

14. The sulfide electrolyte slurry according to claim 13, characterized in that, The viscosity of the sulfide electrolyte slurry is 1000–10000 mPa·s.

15. A solid-state battery, characterized in that, It includes the sulfide electrolyte membrane according to any one of claims 1 to 8 or the sulfide electrolyte membrane, positive electrode and negative electrode prepared by the preparation method according to any one of claims 9 to 12.

16. The solid-state battery according to claim 15, characterized in that, The positive electrode sheet includes a positive electrode active material; the positive electrode active material is selected from one or more of lithium cobalt oxide, nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium manganese oxide, lithium iron phosphate, lithium nickel manganese oxide, and lithium manganese iron phosphate; And / or, the negative electrode sheet includes a negative electrode active material; the negative electrode active material is selected from one or more of carbon materials, silicon-based materials and lithium titanate.

17. The solid-state battery according to claim 16, characterized in that, The positive electrode active material is selected from nickel-cobalt-manganese ternary material Li. a Ni b Co c Mn d MO2; wherein 0.75≤a≤1.2, 0.7≤b<1, 0<c<1, 0<d<1, b+c+d=1; M is selected from at least one of B, Zr, Ti, Si, Mo, La, Ce, Te, Nb, Ta, Si, Al, W, Sr, V, Y, Mg, Co and Li; The ionic conductivity of the sulfide electrolyte membrane is 0.5–3 mS / cm; the relative permittivity of the sulfide electrolyte membrane is 20–25.

18. The solid-state battery according to claim 16 or 17, characterized in that, The positive electrode active material includes single crystal particles and / or polycrystalline particles; the particle size of the single crystal particles is 0.5 to 5 μm; the particle size of the polycrystalline particles is 5 to 15 μm.

19. The solid-state battery according to claim 15 or 16, characterized in that, The negative electrode active material includes silicon-based materials; the silicon-based materials include silicon-carbon materials. The ionic conductivity of the sulfide electrolyte membrane is 0.5–3 mS / cm; the relative permittivity of the sulfide electrolyte membrane is 20–25.

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