Positive electrode sheet and preparation method therefor, solid-state battery and preparation method therefor, and electrical apparatus

Abstract

A positive electrode sheet and a preparation method therefor, a solid-state battery and a preparation method therefor, and an electrical apparatus, relating to the technical field of solid-state batteries. The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer formed on a surface of the positive electrode current collector. The positive electrode film layer comprises a positive electrode active material, a conductive agent, a sulfide solid-state electrolyte, and a lithium-containing solid-state electrolyte interface film. The delithiation potential of the positive electrode active material is higher than the oxidation potential of the sulfide solid-state electrolyte. The lithium-containing solid-state electrolyte interface film coats surfaces of the positive electrode active material, the conductive agent, and the sulfide solid-state electrolyte. The solid-state battery achieves both high initial Coulombic efficiency and a long cycle life.

Description

Positive electrode sheet and its preparation method, solid-state battery and its preparation method and electrical device

[0001] Cross-referencing

[0002] This application claims priority to Chinese Patent Application No. 202510224238.0, filed on February 27, 2025, entitled “Positive electrode sheet and method for preparation thereof, solid-state battery and method for preparation thereof and electrical device,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of solid-state battery technology, and in particular to a positive electrode sheet and its preparation method, a solid-state battery and its preparation method, and an electrical device. Background Technology

[0004] Sulfide solid electrolytes have advantages such as good processing performance, low interfacial impedance and ionic conductivity that is closer to that of liquid organic electrolytes, and have good prospects for industrialization. However, solid batteries with sulfide electrolytes in the positive electrode have problems with poor charge / discharge specific capacity and cycle stability in actual use. Summary of the Invention

[0005] This application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode sheet and a method for preparing the same, a solid-state battery and a method for preparing the same, and an electrical device, so as to improve the poor coulombic efficiency and cycle stability of solid-state batteries with positive electrode sheets containing sulfide electrolytes.

[0006] The first aspect of this application provides a solid-state battery, which includes a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer formed on the surface of the positive current collector, the positive electrode film layer including a positive electrode active material, a conductive agent, a sulfide solid electrolyte and a lithium-containing solid electrolyte interface film, the delithiation potential of the positive electrode active material being higher than the oxidation potential of the sulfide solid electrolyte, and the lithium-containing solid electrolyte interface film coating the surface of the positive electrode active material, the conductive agent and the sulfide solid electrolyte.

[0007] Therefore, the solid-state battery provided in this application utilizes a lithium-containing solid electrolyte interface film to coat the surface of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte. This effectively physically isolates the sulfide solid electrolyte from direct contact with other components: the positive electrode active material, the conductive agent, and the positive electrode current collector. It inhibits the degradation of the sulfide solid electrolyte caused by direct contact with other components, improves capacity decay, and suppresses the occurrence of side reactions caused by contact, thereby improving the initial coulombic efficiency and cycle life of the solid-state battery.

[0008] In any embodiment, the lithium-containing solid electrolyte interface film comprises an inorganic material formed by at least one of the elements P, S, Si, and F with Li.

[0009] The inorganic substances formed by the interaction of at least one of the elements P, S, Si and F with Li in the lithium-containing solid electrolyte interface film are beneficial to improving the ionic conductivity of the lithium-containing solid electrolyte interface film and improving the interfacial contact resistance between the positive electrode active material and the sulfide electrolyte.

[0010] In any embodiment, the thickness of the lithium-containing solid electrolyte interface film is 1 μm - 2 μm.

[0011] Controlling the thickness of the lithium-containing solid electrolyte interface film within the above range provides excellent isolation for the positive electrode active material, conductive agent, and sulfide solid electrolyte, while also achieving low DCR.

[0012] A second aspect of this application also provides a method for preparing a solid-state battery, comprising:

[0013] A solid-state battery to be formed is obtained. The solid-state battery to be formed includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer formed on the surface of the positive current collector. The positive electrode film layer includes a positive active material, a conductive agent, a sulfide solid electrolyte, a binder, and an additive. The additive is coated on the surface of the positive active material, the conductive agent, and the sulfide solid electrolyte. The delithiation potential of the positive active material is higher than the oxidation potential of the sulfide solid electrolyte. The additive includes a positive film-forming additive and an organic lithium salt. The HOMO energy level of the positive film-forming additive is higher than the HOMO energy level of the sulfide solid electrolyte.

[0014] The solid-state battery is formed by transforming the material into a solid-state battery.

[0015] In summary, the solid-state battery preparation method provided in this application adds an additive, including a positive electrode film-forming additive and an organic lithium salt, to the positive electrode film layer. The HOMO energy level of the positive electrode film-forming additive is higher than that of the HOMO energy level of the sulfide solid electrolyte. During formation, the additive preferentially decomposes before the sulfide solid electrolyte, reacting with the organic lithium salt to form a lithium-containing solid electrolyte interface film that coats the surfaces of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte. On the one hand, the formed lithium-containing solid electrolyte interface film can suppress the degradation of the sulfide solid electrolyte during cycling due to direct contact between the sulfide solid electrolyte and other components (positive electrode active material, conductive agent, and positive electrode current collector), improving battery capacity decay, suppressing side reactions caused by contact, and increasing the initial coulombic efficiency and cycle life of the solid-state battery. On the other hand, the method is simple to operate and has low preparation cost.

[0016] In any embodiment, the mass percentage of the additive in the positive electrode film layer is 0.01%-2%.

[0017] Since the higher the amount of positive electrode film-forming agent added, the better the film-forming effect, but the thicker the film, the greater the impedance, controlling the mass ratio of the additive in the positive electrode film layer within the above range is beneficial to obtaining a thinner lithium-containing solid electrolyte interface film with lower impedance, which is beneficial to improving the coulombic efficiency and cycle life of solid-state batteries.

[0018] In any embodiment, the mass percentage of the additive in the positive electrode film layer is 0.5%-2%.

[0019] Controlling the mass percentage of additives in the positive electrode film layer within the above range is beneficial to further improve the coulombic efficiency and cycle life of solid-state batteries.

[0020] In any embodiment, the positive electrode film-forming additive accounts for 10%-15% of the mass of the additives;

[0021] And / or, the organic lithium salt accounts for 85%-90% of the mass of the additive.

[0022] Controlling the mass ratio of cathode film-forming additives and / or organic lithium salts in the additives within the above range is beneficial for forming a lithium-containing solid electrolyte interface film with good coating effect and low DCR, which is beneficial for improving the first coulombic efficiency and cycle life of solid-state batteries.

[0023] In any embodiment, the positive electrode film-forming additive includes at least one of siloxane compounds, phosphate ester compounds, sulfate ester compounds, and fluoroethylene carbonate.

[0024] The aforementioned positive electrode film-forming additive has a high HOMO energy level. When combined with organic lithium salts, it readily reacts to form a lithium-containing solid electrolyte interface film rich in inorganic lithium salts, thereby improving the ion transport rate and enhancing the stability of the positive electrode under high voltage. This effectively delays the consumption of sulfide solid electrolytes and extends the service life of solid-state batteries.

[0025] In any embodiment, the organic lithium salt includes an electrolyte salt comprising at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0026] The aforementioned organic lithium salts can effectively regulate the ionic conductivity of the lithium-containing solid electrolyte interface membrane to a better range, which is beneficial to improving the cycle life and coulombic efficiency of solid-state batteries.

[0027] In any embodiment, the sulfide solid electrolyte includes Li 10 GeP2S 12Li7P3S 11 Li 5.5 PS 4.5 Cl 1.5 At least one of Li3PS4 and Li6PS5X, wherein X includes at least one of Cl, Br and I.

[0028] In any embodiment, the positive electrode film layer includes an adhesive, which includes at least one of polytetrafluoroethylene, hydrogenated polyethylene block copolymer, nitrile rubber, styrene-butadiene rubber, polyvinylidene fluoride, and polyisobutylene.

[0029] The aforementioned suitable binder can improve the adhesion between the positive electrode active material and the sulfide solid electrolyte, ultimately improving the cycle stability of the solid-state battery.

[0030] A third aspect of this application also provides an electrical device comprising a solid-state battery provided in the first aspect of this application or a solid-state battery prepared by the preparation method provided in the second aspect of this application.

[0031] The fourth aspect of this application provides a positive electrode sheet for a solid-state battery, which includes a positive current collector and a positive electrode film layer formed on the surface of the positive current collector. The positive electrode film layer includes a positive active material, a conductive agent, a sulfide solid electrolyte, a binder, and an additive, with the additive coating the surface of the positive active material, the conductive agent, and the sulfide solid electrolyte.

[0032] The delithiation potential of the positive electrode active material is higher than the oxidation potential of the sulfide solid electrolyte.

[0033] The additives include positive electrode film-forming additives and organic lithium salts. The HOMO energy level of the positive electrode film-forming additives is higher than that of the HOMO energy level of the sulfide solid electrolyte.

[0034] Therefore, the positive electrode sheet containing sulfide solid electrolyte provided in this application, by adding an additive including a positive electrode film-forming additive and an organic lithium salt to the positive electrode film layer, utilizes the fact that the HOMO energy level of the positive electrode film-forming additive is higher than that of the HOMO energy level of the sulfide solid electrolyte. As a result, during formation, the additive will preferentially decompose before the sulfide solid electrolyte, thereby reacting with the organic lithium salt to form a lithium-containing solid electrolyte interface film that coats the surfaces of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte. The formed lithium-containing solid electrolyte interface film can suppress the degradation of the sulfide solid electrolyte caused by direct contact between the sulfide solid electrolyte and other components: the positive electrode active material, the conductive agent, and the positive electrode current collector during cycling, improve the capacity decay of the solid battery, and suppress the occurrence of side reactions caused by contact, ultimately improving the first coulombic efficiency and cycle life of the solid battery.

[0035] The fifth aspect of this application provides a method for preparing a positive electrode sheet, comprising:

[0036] A positive electrode active material, a conductive agent, a sulfide solid electrolyte, a binder, an additive, and a non-polar solvent are mixed to disperse the additive on the surface of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte, respectively, to obtain a positive electrode slurry.

[0037] The positive electrode slurry is coated onto the surface of the positive electrode current collector, dried, and then cold-pressed.

[0038] The additives include positive electrode film-forming additives and organic lithium salts. The HOMO energy level of the positive electrode film-forming additives is higher than that of the HOMO energy level of the sulfide solid electrolyte.

[0039] The preparation method provided in this application is simple to operate and has low preparation cost. By adding an additive, including a positive electrode film-forming additive and an organic lithium salt, to the positive electrode slurry, the HOMO energy level of the positive electrode film-forming additive is higher than that of the HOMO energy level of the sulfide solid electrolyte. As a result, during the formation of the positive electrode sheet, the additive will preferentially decompose before the sulfide solid electrolyte, thereby reacting with the organic lithium salt to form a lithium-containing solid electrolyte interface film that coats the surfaces of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte. The formed lithium-containing solid electrolyte interface film can inhibit the degradation of the sulfide solid electrolyte caused by direct contact between the sulfide solid electrolyte and other components: the positive electrode active material, the conductive agent, and the positive electrode current collector during cycling. This reduces the occurrence of side reactions during cycling and improves the battery capacity decay, thereby improving the first coulombic efficiency and cycle life of the solid-state battery.

[0040] In any embodiment, the nonpolar solvent includes at least one of isopentane, n-pentane, cyclohexane, isooctane, cyclopentane, n-hexane, n-heptane, tetrahydrofuran, toluene, xylene, ethyl acetate, isobutyl isobutyrate, dichloromethane, and chloroform.

[0041] Choosing a suitable non-polar solvent can not only suppress side reactions between the sulfide solid electrolyte and the solvent, but also ensure that the additives, positive electrode active material, conductive agent and sulfide solid electrolyte are mixed evenly, which is beneficial for the additives to be dispersed on the surface of the positive electrode active material, conductive agent and sulfide solid electrolyte respectively. Attached Figure Description

[0042] Figure 1 is a schematic diagram of a battery module according to one embodiment of this application.

[0043] Figure 2 is an exploded view of a battery pack according to an embodiment of this application.

[0044] Explanation of reference numerals in the attached figures:

[0045] 1-Battery pack; 2-Upper housing; 3-Lower housing; 4-Battery module; 5-Battery cell. Embodiments of the present invention

[0046] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode sheet and its preparation method, the solid-state battery and its preparation method, and the electrical device thereof. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0047] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0049] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0050] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0051] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0052] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0053] Sulfide solid electrolytes possess advantages such as good processability, low interfacial impedance, and ionic conductivity closer to that of liquid organic electrolytes, indicating promising industrialization prospects. However, sulfide electrolytes have a relatively low electrochemical window (2.5V vs. Li). + When the voltage is high, sulfide solid electrolytes undergo continuous oxidative decomposition reactions during charging, producing a series of side reactions that lead to severe irreversible capacity loss in the battery. Furthermore, side reactions also occur between the sulfide electrolyte and electrode materials, conductive agents, and current collectors, especially with high-voltage oxide cathode materials (e.g., lithium cobalt oxide, lithium nickel manganese oxide) and the sulfide electrolyte. These side reactions are more severe, producing insulating substances such as S and P2S5 that impede Li ion transport, resulting in a significant increase in electrode impedance and deteriorating the charge / discharge specific capacity and cycle stability of the solid-state battery.

[0054] Based on this, the first aspect of this application provides a solid-state battery, which includes a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer formed on the surface of the positive current collector, the positive electrode film layer including a positive electrode active material, a conductive agent, a sulfide solid electrolyte and a lithium-containing solid electrolyte interface film, the delithiation potential of the positive electrode active material being higher than the oxidation potential of the sulfide solid electrolyte, and the lithium-containing solid electrolyte interface film coating the surface of the positive electrode active material, the conductive agent and the sulfide solid electrolyte.

[0055] Solid-state batteries are batteries that use solid electrodes and solid electrolytes. It can be understood that solid-state batteries include all-solid-state batteries and semi-solid-state batteries.

[0056] It is understandable that, since the delithiation potential of the positive electrode active material is higher than the oxidation potential of the sulfide solid electrolyte, if a lithium-containing solid electrolyte interface film is not formed, the formation and operating potential of the solid battery will be higher than the oxidation potential of the sulfide solid electrolyte in actual use. At this time, the sulfide solid electrolyte will continue to undergo oxidation and decomposition reactions during charging, producing a series of side reactions.

[0057] Since the solid-state battery provided in this application contains a lithium-containing solid electrolyte interface film, and the lithium-containing solid electrolyte interface film coats the surface of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte, the lithium-containing solid electrolyte interface film can not only physically isolate the positive electrode active material, the conductive agent, the sulfide solid electrolyte, and the positive electrode current collector from contacting each other, but also has good ion conductivity. Therefore, the above-mentioned arrangement can also improve the interfacial contact resistance between the positive electrode active material and the sulfide electrolyte to a certain extent.

[0058] Therefore, the solid-state battery provided in this application utilizes a lithium-containing solid electrolyte interface film to coat the surface of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte. This effectively physically isolates the sulfide solid electrolyte from direct contact with other components: the positive electrode active material, the conductive agent, and the positive electrode current collector. This inhibits the degradation of the sulfide solid electrolyte caused by direct contact with other components, improves capacity decay, and suppresses the occurrence of side reactions caused by contact, thereby improving the initial coulombic efficiency and cycle life of the solid-state battery.

[0059] In some embodiments, the lithium-containing solid electrolyte interface film comprises an inorganic material formed by at least one of the elements P, S, Si, and F with Li.

[0060] The testing methods for the composition of lithium-containing solid electrolyte interface membranes include: preparing the electrode into a test sample using the argon ion polishing (CP) method; obtaining an image of the lithium-containing solid electrolyte interface membrane in the CP cross-section of the test sample using a scanning electron microscope (SEM); and performing EDS elemental analysis on the lithium-containing solid electrolyte interface membrane.

[0061] The inorganic substances formed by the interaction of at least one of the elements P, S, Si and F with Li in the lithium-containing solid electrolyte interface film are beneficial to improving the ionic conductivity of the lithium-containing solid electrolyte interface film and improving the interfacial contact resistance between the positive electrode active material and the sulfide electrolyte.

[0062] In some embodiments, the thickness of the lithium-containing solid electrolyte interface film is 1 μm to 2 μm.

[0063] The method for testing the thickness of the lithium-containing solid electrolyte interface film includes: preparing the electrode into a test sample using the argon ion polishing (CP) method; obtaining an image of the lithium-containing solid electrolyte interface film in the CP cross-section of the test sample using a scanning electron microscope (SEM); for example, randomly selecting 20-50 locations in the image to measure the thickness of the lithium-containing solid electrolyte interface film, and using the average thickness as the thickness of the lithium-containing solid electrolyte interface film.

[0064] Controlling the thickness of the lithium-containing solid electrolyte interface film within the above range can not only effectively isolate the positive electrode active material, conductive agent, and sulfide solid electrolyte from contact with each other, but also achieve low DCR.

[0065] For example, the thickness of the lithium-containing solid electrolyte interface film is any value of 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm or between any two values.

[0066] A second aspect of this application provides a method for preparing a solid-state battery, comprising:

[0067] A solid-state battery to be formed is obtained. The solid-state battery to be formed includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer formed on the surface of the positive current collector. The positive electrode film layer includes a positive active material, a conductive agent, a sulfide solid electrolyte, a binder, and additives. The additives are coated on the surfaces of the positive active material, the conductive agent, and the sulfide solid electrolyte. The delithiation potential of the positive active material is higher than the oxidation potential of the sulfide solid electrolyte. The additives include a positive film-forming additive and an organic lithium salt. The HOMO energy level of the positive film-forming additive is higher than the HOMO energy level of the sulfide solid electrolyte.

[0068] The solid-state battery is formed by transforming the material into a solid-state battery.

[0069] The HOMO is the highest occupied orbital for electrons. The higher the HOMO energy level, the lower the ionization energy, and the easier it is to lose electrons.

[0070] It is understandable that, since the delithiation potential of the positive electrode active material is higher than the oxidation potential of the sulfide solid electrolyte, if no treatment is carried out, such as without adding additives, the formation and operating potential of the solid battery will be higher than the oxidation potential of the sulfide solid electrolyte in actual use. At this time, the sulfide solid electrolyte will continue to undergo oxidation and decomposition reactions during charging, producing a series of side reactions.

[0071] In this application, an additive is introduced into the positive electrode film layer. Since the additive includes a positive electrode film-forming additive and an organic lithium salt, and the HOMO energy level of the positive electrode film-forming additive is higher than that of the HOMO energy level of the sulfide solid electrolyte, the positive electrode film-forming additive can preferentially decompose before the sulfide solid electrolyte during the first charge and cooperate with the organic lithium salt to form a lithium-containing solid electrolyte interface film with excellent lithium ion conduction.

[0072] Because the additives are coated on the surfaces of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte, the lithium-containing solid electrolyte interface film formed during formation can be coated on the surfaces of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte in one step. The coating is easy and inexpensive, and it effectively isolates the positive electrode active material, the conductive agent, the sulfide solid electrolyte, and the positive electrode current collector from contact with each other. This inhibits the degradation of the sulfide solid electrolyte caused by direct contact between the sulfide solid electrolyte and other components (positive electrode active material, conductive agent, and positive electrode current collector) during cycling, reduces the occurrence of side reactions during cycling, and can improve the interfacial contact resistance between the positive electrode active material and the sulfide electrolyte to a certain extent.

[0073] In summary, the solid-state battery preparation method provided in this application adds an additive, including a positive electrode film-forming additive and an organic lithium salt, to the positive electrode film layer. The HOMO energy level of the positive electrode film-forming additive is higher than that of the HOMO energy level of the sulfide solid electrolyte. During formation, the additive preferentially decomposes before the sulfide solid electrolyte, reacting with the organic lithium salt to form a lithium-containing solid electrolyte interface film that coats the surfaces of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte. On the one hand, the formed lithium-containing solid electrolyte interface film can suppress the degradation of the sulfide solid electrolyte caused by direct contact with other components (positive electrode active material, conductive agent, and positive electrode current collector) during cycling, thus improving battery capacity decay, suppressing side reactions caused by contact, and improving the initial coulombic efficiency and cycle life of the solid-state battery. On the other hand, the method is simple to operate and has low preparation cost.

[0074] In some implementations, the mass percentage of the additive in the positive electrode film is 0.01%-2%.

[0075] Since the higher the amount of positive electrode film-forming agent added, the better the film-forming effect, but the thicker the film, the greater the impedance, controlling the mass ratio of the additive in the positive electrode film layer within the above range is beneficial to obtaining a thinner lithium-containing solid electrolyte interface film with lower impedance, which is beneficial to improving the coulombic efficiency and cycle life of solid-state batteries.

[0076] For example, the mass percentage of the additive in the positive electrode film layer is any one of 0.01%, 0.05%, 0.1%, 0.3%, 0.5%, 0.7%, 1.0%, 1.2%, 1.5%, 1.7%, or 2%, or between any two of these values.

[0077] Furthermore, the mass percentage of the additives in the positive electrode film layer is 0.5%-2%.

[0078] Controlling the mass ratio of additives in the positive electrode film layer within the above range is beneficial to forming a lithium-containing solid electrolyte interface film with good coating effect and low DCR, which is conducive to further improving the first coulombic efficiency and cycle life of solid-state batteries.

[0079] In some embodiments, the positive electrode film-forming additive accounts for 10%-15% of the mass of the additives;

[0080] And / or, the organic lithium salt accounts for 85%-90% of the mass of the additive.

[0081] Controlling the mass ratio of cathode film-forming additives and / or organic lithium salts in the additives within the above range is beneficial for forming a lithium-containing solid electrolyte interface film with good coating effect and low DCR, which is beneficial for improving the first coulombic efficiency and cycle life of solid-state batteries.

[0082] For example, the mass percentage of the positive electrode film-forming additive in the auxiliary agent is any one of 10%, 11%, 12%, 13%, 14%, or 15%, or between any two of these values.

[0083] For example, the mass percentage of the organic lithium salt in the additive is any one of 85%, 86%, 87%, 88%, 89%, or 90%, or between any two of these values.

[0084] In some embodiments, the cathode film-forming additive includes at least one of siloxane compounds, phosphate ester compounds, sulfate ester compounds, and fluoroethylene carbonate.

[0085] The aforementioned positive electrode film-forming additive has a high HOMO energy level. When combined with organic lithium salts, it readily reacts to form a lithium-containing solid electrolyte interface film rich in inorganic lithium salts, thereby improving the ion transport rate and enhancing the stability of the positive electrode under high voltage. This effectively delays the consumption of sulfide solid electrolytes and extends the service life of solid-state batteries.

[0086] For example, siloxane compounds include, but are not limited to, one or more of the following: polymethyltrifluoropropylsiloxane, aminoethylaminopropylpolydimethylsiloxane, side-chain phosphate-grafted polydimethylsiloxane, polymethylchloropropylsiloxane, polydimethylsiloxane, cyclopentapolydimethylsiloxane, dimethyldimethoxysilane, 2,4,6,8-tetramethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, cyclic polymethylvinylsiloxane, hexadecylcyclooctasiloxane, tetradecylcycloheptasiloxane, and cyclic polydimethylsiloxane.

[0087] For example, phosphate ester compounds include R4, R5, and R6 are independently selected from any one of hydrogen, alkane group, haloalkane group, olefin group, alkyne group, aromatic group, and haloaromatic group.

[0088] For example, sulfate compounds include, but are not limited to, at least one of dimethyl sulfate, diethyl sulfate, or cyclic sulfates, wherein cyclic sulfates include monocyclic or polycyclic cyclic sulfates, as can be found in related technologies, but are not limited herein.

[0089] In some embodiments, the organic lithium salt includes an electrolyte salt comprising at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0090] The aforementioned organic lithium salts can effectively regulate the ionic conductivity of the lithium-containing solid electrolyte interface membrane to a better range, which is beneficial to improving the cycle life and coulombic efficiency of solid-state batteries.

[0091] In some embodiments, the sulfide solid electrolyte includes Li 10 GeP2S 12 Li7P3S 11 Li 5.5 PS 4.5 Cl 1.5 At least one of Li3PS4 and Li6PS5X, wherein X includes at least one of Cl, Br and I.

[0092] In some embodiments, the binder includes at least one of polytetrafluoroethylene (PTFE), hydrogenated polyethylene block copolymer (HSBC), nitrile rubber (NBR), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), and polyisobutylene (PIB).

[0093] The aforementioned suitable binder can improve the adhesion between the positive electrode active material and the sulfide solid electrolyte, ultimately improving the cycle stability of the solid-state battery.

[0094] A third aspect of this application provides an electrical device comprising a solid-state battery provided in the first aspect of this application, or a solid-state battery prepared by the preparation method provided in the second aspect of this application.

[0095] The fourth aspect of this application provides a positive electrode sheet for a solid-state battery, which includes a positive current collector and a positive electrode film layer formed on the surface of the positive current collector. The positive electrode film layer includes a positive active material, a conductive agent, a sulfide solid electrolyte, a binder, and an additive, with the additive coating the surface of the positive active material, the conductive agent, and the sulfide solid electrolyte.

[0096] The delithiation potential of the positive electrode active material is higher than the oxidation potential of the sulfide solid electrolyte;

[0097] The additives include positive electrode film-forming additives and organic lithium salts. The HOMO energy level of the positive electrode film-forming additives is higher than that of the HOMO energy level of the sulfide solid electrolyte.

[0098] It is understandable that the positive electrode plate here refers to the positive electrode plate before it is formed.

[0099] It is understandable that, since the delithiation potential of the positive electrode active material is higher than the oxidation potential of the sulfide solid electrolyte, if no treatment is carried out, such as without adding additives, the formation and operating potential of the solid battery will be higher than the oxidation potential of the sulfide solid electrolyte in actual use. At this time, the sulfide solid electrolyte will continue to undergo oxidation and decomposition reactions during charging, producing a series of side reactions.

[0100] The positive electrode sheet containing sulfide solid electrolyte provided in this application adds an additive, including a positive electrode film-forming additive and an organic lithium salt, to the positive electrode film layer. The HOMO energy level of the positive electrode film-forming additive is higher than that of the HOMO energy level of the sulfide solid electrolyte. During formation, the additive preferentially decomposes before the sulfide solid electrolyte, thereby reacting with the organic lithium salt to form a lithium-containing solid electrolyte interface film that coats the surfaces of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte. This lithium-containing solid electrolyte interface film can suppress the degradation of the sulfide solid electrolyte during cycling due to direct contact between the sulfide solid electrolyte and other components (positive electrode active material, conductive agent, and positive electrode current collector). This reduces the occurrence of side reactions during cycling and improves battery capacity decay, thereby increasing the initial coulombic efficiency and cycle life of the solid-state battery.

[0101] The fifth aspect of this application provides a method for preparing a positive electrode sheet, comprising:

[0102] A positive electrode active material, a conductive agent, a sulfide solid electrolyte, a binder, an additive, and a non-polar solvent are mixed to disperse the additive on the surface of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte, respectively, to obtain a positive electrode slurry.

[0103] The positive electrode slurry is coated onto the surface of the positive electrode current collector, dried, and then cold-pressed.

[0104] The additives include positive electrode film-forming additives and organic lithium salts. The HOMO energy level of the positive electrode film-forming additives is higher than that of the HOMO energy level of the sulfide solid electrolyte.

[0105] It is understandable that non-polar solvents are mainly used to dissolve binders and disperse positive electrode active materials, sulfide solid electrolytes, conductive agents, etc., and non-polar solvents do not react with solid electrolytes.

[0106] The preparation method provided in this application is simple to operate and has low preparation cost. By adding an additive, including a positive electrode film-forming additive and an organic lithium salt, to the positive electrode slurry, the HOMO energy level of the positive electrode film-forming additive is higher than that of the HOMO energy level of the sulfide solid electrolyte. As a result, during the formation of the positive electrode sheet, the additive will preferentially decompose before the sulfide solid electrolyte, thereby reacting with the organic lithium salt to form a lithium-containing solid electrolyte interface film that coats the surfaces of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte. The formed lithium-containing solid electrolyte interface film can inhibit the degradation of the sulfide solid electrolyte caused by direct contact between the sulfide solid electrolyte and other components: the positive electrode active material, the conductive agent, and the positive electrode current collector during cycling. This reduces the occurrence of side reactions during cycling and improves the battery capacity decay, thereby improving the first coulombic efficiency and cycle life of the solid-state battery.

[0107] In some embodiments, the fourth aspect of this application provides a method for preparing a positive electrode sheet that yields the positive electrode sheet provided in the third aspect of this application.

[0108] In some embodiments, the nonpolar solvent includes at least one of isopentane, n-pentane, cyclohexane, isooctane, cyclopentane, n-hexane, n-heptane, tetrahydrofuran, toluene, xylene, ethyl acetate, isobutyl isobutyrate, dichloromethane, and chloroform.

[0109] Choosing a suitable non-polar solvent can not only suppress side reactions between the sulfide solid electrolyte and the solvent, but also ensure that the additives, positive electrode active material, conductive agent and sulfide solid electrolyte are mixed evenly, which is beneficial for the additives to be dispersed on the surface of the positive electrode active material, conductive agent and sulfide solid electrolyte respectively.

[0110] It should be noted that the amount of non-polar solvent added can be selected according to the solid content requirements, as long as the relevant requirements are met, and there is no limitation here.

[0111] In addition, the solid-state battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0112] Solid-state batteries

[0113] A second aspect of this application provides a solid-state battery. This application does not particularly limit the type of solid-state battery; for example, the solid-state battery can be a lithium-ion battery.

[0114] Typically, solid-state batteries are manufactured using a stacking process, consisting of a positive electrode, a negative electrode, and a solid electrolyte membrane. The solid electrolyte membrane is positioned between the positive and negative electrodes. During the charging and discharging process, active ions repeatedly insert and extract between the positive and negative electrodes. The solid electrolyte membrane serves to conduct ions and prevent short circuits between the positive and negative electrodes.

[0115] [Positive electrode plate]

[0116] The positive electrode is as provided in the third aspect of this application. The positive electrode includes a positive current collector and a positive electrode film layer formed on the surface of the positive current collector.

[0117] It is understandable that the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on one or both of the two opposite surfaces of the positive current collector.

[0118] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0119] The positive electrode active material in the positive electrode film can be any positive electrode active material known in the art for lithium-ion batteries. There are no particular limitations on the positive electrode active material, as long as it is a lithium composite oxide material capable of reversibly inserting and removing lithium ions. For example, it can include one or more of a composite oxide of cobalt, manganese, nickel, iron, or combinations thereof, and lithium.

[0120] In some embodiments, as examples, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0121] In some embodiments, to further improve the energy density of secondary batteries, the positive electrode active material for lithium-ion batteries may include materials with the general formula Li. a Ni b Co c M d O e A fone or more of lithium transition metal oxides and modified compounds thereof. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A is selected from one or more of N, F, S and Cl.

[0122] In some embodiments, by way of example, the positive active material for a lithium-ion battery may include one or more of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O2, LiFePO4 and LiMnPO4.

[0123] In the present application, the modified compound of each of the above positive active materials may be doping modification and / or surface coating modification performed on the positive active material.

[0124] During charging and discharging of the battery, it is accompanied by deintercalation and consumption of Li. When the battery is discharged to different states, the molar content of Li is different. In the enumeration of positive active materials in the present application, the molar content of Li refers to that in the initial state of the material, that is, the state before feeding. After the positive material is applied to a battery system and subjected to charge-discharge cycles, the molar content of Li will change.

[0125] In the enumeration of positive active materials in the present application, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O may fluctuate.

[0126] In some embodiments, by way of example, the conductive agent in the positive electrode sheet may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0127] [Negative electrode sheet]

[0128] In some embodiments, the negative electrode includes a negative current collector and metallic lithium disposed on at least one surface of the negative current collector. That is, the solid-state battery in this case is a lithium metal solid-state battery.

[0129] In some embodiments, the solid-state battery can be a lithium-ion solid-state battery, in which case the negative electrode includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector.

[0130] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0131] As an example, the negative electrode film layer includes a negative electrode active material. The negative electrode active material may be any negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0132] As an example, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0133] As an example, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0134] As an example, the negative electrode film may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0135] It is understood that, in some embodiments of both lithium-ion solid-state batteries and lithium metal solid-state batteries, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0136] [Solid electrolyte membrane]

[0137] A solid electrolyte membrane is disposed between the positive electrode and the negative electrode.

[0138] Solid electrolyte membranes may include, for example, sulfide solid electrolytes. It should be noted that the sulfide solid electrolyte in the solid electrolyte membrane may be the same as or different from the sulfide solid electrolyte contained in the positive electrode.

[0139] In some embodiments, the solid electrolyte membrane also includes, for example, an adhesive. The adhesive included in the solid electrolyte membrane can be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene, or any other adhesive used in the art. The adhesive of the solid electrolyte membrane can be the same as or different from the adhesives used for the positive and negative electrode layers.

[0140] In this application, a solid-state battery can refer to a single battery cell, or it can refer to a single physical module comprising multiple battery cells to provide higher voltage and capacity, and it can take the form of a battery pack, battery module, etc.

[0141] A typical battery cell includes a casing and an electrode assembly. The casing has an inner cavity, within which the electrode assembly is housed. The electrode assembly is manufactured using a stacking process, consisting of a positive electrode, a negative electrode, and a solid electrolyte membrane, with the solid electrolyte membrane positioned between the positive and negative electrodes. The positive electrode contains the solid electrolyte.

[0142] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0143] Figure 1 shows a battery module 4 as an example. Referring to Figure 1, in the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple battery cells 5 can be fixed in place using fasteners.

[0144] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0145] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0146] Figure 2 shows a battery pack 1 as an example. Referring to Figure 2, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0147] In addition, this application also provides an electrical device, which includes a secondary battery (at least one of a battery cell, battery module, or battery pack) provided in this application. The secondary battery can be used as a power source for the electrical device or as an energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0148] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0149] For example, the electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this electrical device, a battery pack or battery module can be used.

[0150] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0151] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0152] Example 1

[0153] Preparation of the positive electrode sheet

[0154] In the glove box, the positive electrode active material LiNi is placed 0.8 Co 0.1 Mn 0.1 O2, sulfide solid electrolyte Li6PS5Cl, conductive agent VGCF, binder PVDF, and additives are mixed in a weight ratio of (80-n):15:3:2:n, added to ethyl acetate, and stirred thoroughly to obtain a positive electrode slurry with a solid content of 70%. Here, n=0.5, meaning the additives account for 0.5% of the mass of the positive electrode film.

[0155] The positive electrode slurry is coated on both sides of an aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet.

[0156] The positive electrode sheet includes an aluminum foil serving as a current collector and a positive electrode film layer disposed on both surfaces of the current collector, wherein the thickness of the positive electrode film layer on one side is 100 μm.

[0157] The additives are FEC and LiPF6, with FEC accounting for 13% of the additives by mass and LiPF6 accounting for 87% of the additives by mass.

[0158] Preparation of the negative electrode sheet

[0159] A 25μm thick lithium metal is attached to the surface of a copper foil current collector for the negative electrode, and then sliced ​​to obtain the negative electrode sheet.

[0160] Solid electrolyte membrane

[0161] In a glove box, the sulfide solid electrolyte Li6PS5Cl was pressed at 100℃ and 250MPa for 2 min to obtain a solid electrolyte membrane with a thickness of 50μm.

[0162] Solid-state battery fabrication

[0163] The positive electrode, solid electrolyte membrane, and negative electrode are aligned and stacked in sequence. They are then cold-pressed at room temperature and 250 MPa for 2 minutes to obtain an electrode assembly. The single-layer electrode assembly is then cold-pressed and placed in a packaging shell for encapsulation to obtain a solid-state lithium metal battery.

[0164] Examples 2-8 and Comparative Examples 1-2

[0165] The only difference between Example 2 and Example 1 is that the mass content of the additive in the positive electrode film layer is 1%.

[0166] The only difference between Example 3 and Example 1 is that the mass content of the additive in the positive electrode film layer is 1.5%.

[0167] The only difference between Example 4 and Example 1 is that the mass content of the additive in the positive electrode film layer is 2%.

[0168] The only difference between Example 5 and Example 1 is that the sulfide solid electrolyte is Li3PS4.

[0169] The only difference between Example 6 and Example 1 is that dimethyl sulfate is used instead of FEC.

[0170] The only difference between Comparative Example 1 and Example 1 is that no additives are added.

[0171] The only difference between Comparative Example 2 and Example 5 is that no additives are added.

[0172] The differences between the various embodiments and comparative examples are shown in Table 1.

[0173] The solid-state lithium metal batteries provided in each embodiment and comparative example were tested, including:

[0174] The charge / discharge operating voltage range of the solid-state lithium metal battery is set to 2.5V to 4.25V. Cyclic testing is conducted using a constant current charge / discharge method, with a test current of 0.1C (current density of approximately 0.12 mA / cm2) and a test temperature of 25℃.

[0175] (1) First week specific capacity: The first week discharge specific capacity of the battery was tested at a charge and discharge current of 0.1C.

[0176] (2) First-week coulombic efficiency: The first-week coulombic efficiency of the battery is tested at a charge and discharge current of 0.1C; the first-week coulombic efficiency of the battery = first-week discharge specific capacity / first-week charge specific capacity × 100%.

[0177] (3) Cycling test: After cycling the battery for 200 cycles, test the battery capacity retention rate. Capacity retention rate = 200-cycle discharge specific capacity / first-cycle discharge specific capacity × 100%.

[0178] The test results are shown in Table 1 below:

[0179] Table 1. Differences and Test Results

[0180]

[0181] As can be seen from Table 1, the solid-state battery provided in this application balances high initial coulombic efficiency and high cycle life, while the first-cycle discharge specific capacity is also in a relatively high range.

[0182] As shown in Examples 1-4 and Comparative Example 1, the addition of additives to the positive electrode film layer is beneficial to improving the first coulombic efficiency and cycle life of solid-state batteries. Furthermore, as shown in Examples 1-4, the mass content of additives in the positive electrode film layer affects the first coulombic efficiency and cycle life of solid-state batteries. When the mass percentage of additives in the positive electrode film layer is in the range of 0.5%-2%, the solid-state battery can achieve both high first coulombic efficiency and long cycle life.

[0183] As can be seen from Examples 1 and 5 and Comparative Example 2, the addition of additives to the positive electrode film layer of sulfide solid electrolytes, whether Li6PS5X (X includes at least one of Cl, Br and I) or Li3PS4, is beneficial to improving the first coulombic efficiency and cycle life of solid batteries.

[0184] As can be seen from Examples 1 and 6, regardless of whether the positive electrode film-forming additive is a sulfate ester compound or a fluoroethylene carbonate, adding the positive electrode film-forming additive as an auxiliary agent to the positive electrode film layer is beneficial to improving the first coulombic efficiency and cycle life of solid-state batteries.

[0185] As can be seen from Examples 1 and 7-8, by controlling the mass ratio of the positive electrode film-forming additive in the additive to be 10%-15% and the mass ratio of the organic lithium salt in the additive to be within the range of 85%-90%, the solid-state battery can achieve both high initial coulombic efficiency and long cycle life.

[0186] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A solid-state battery, wherein, The device includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer formed on the surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, a conductive agent, a sulfide solid electrolyte, and a lithium-containing solid electrolyte interface film. The delithiation potential of the positive electrode active material is higher than the oxidation potential of the sulfide solid electrolyte. The lithium-containing solid electrolyte interface film coats the surfaces of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte.

2. The solid-state battery according to claim 1, wherein, The lithium-containing solid electrolyte interface film comprises an inorganic material formed by at least one of the elements P, S, Si, and F with the element Li.

3. The solid-state battery according to claim 1 or 2, wherein, The thickness of the lithium-containing solid electrolyte interface film is 1 μm - 2 μm.

4. A method for preparing a solid-state battery, wherein, include: A solid-state battery to be formed is obtained. The solid-state battery to be formed includes a positive electrode sheet, the positive electrode sheet includes a positive current collector and a positive electrode film layer formed on the surface of the positive current collector, the positive electrode film layer includes a positive electrode active material, a conductive agent, a sulfide solid electrolyte, a binder and an additive, the additive is coated on the surface of the positive electrode active material, the conductive agent and the sulfide solid electrolyte, the delithiation potential of the positive electrode active material is higher than the oxidation potential of the sulfide solid electrolyte, the additive includes a positive electrode film-forming additive and an organic lithium salt, the HOMO energy level of the positive electrode film-forming additive is higher than the HOMO energy level of the sulfide solid electrolyte; The solid-state battery to be formed is obtained by forming the solid-state battery.

5. The preparation method according to claim 4, wherein, The mass percentage of the additive in the positive electrode film is 0.01%-2%.

6. The preparation method according to claim 5, wherein, The additive accounts for 0.5%-2% of the mass of the positive electrode film.

7. The preparation method according to any one of claims 4-6, wherein, The positive electrode film-forming additive accounts for 10%-15% of the mass of the additives; And / or, the organic lithium salt accounts for 85%-90% of the mass of the additive.

8. The preparation method according to any one of claims 4-7, wherein, The positive electrode film-forming additive includes at least one of siloxane compounds, phosphate ester compounds, sulfate ester compounds, and fluoroethylene carbonate.

9. The preparation method according to any one of claims 4-8, wherein, The organic lithium salt includes electrolyte salts including at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

10. The preparation method according to any one of claims 4-9, wherein, The sulfide solid electrolyte includes Li 10 GeP2S 12 Li7P3S 11 Li 5.5 PS 4.5 Cl 1.5 At least one of Li3PS4 and Li6PS5X, wherein X includes at least one of Cl, Br and I.

11. The preparation method according to any one of claims 4-10, wherein, The positive electrode film layer includes an adhesive, which includes at least one of polytetrafluoroethylene, hydrogenated polyethylene block copolymer, nitrile rubber, styrene-butadiene rubber, polyvinylidene fluoride, and polyisobutylene.

12. An electrical appliance, wherein, This includes the solid-state battery as described in any one of claims 1-3, or the solid-state battery prepared by the preparation method as described in any one of claims 4-11.

13. A positive electrode for a solid-state battery, wherein, The device includes a positive current collector and a positive electrode film layer formed on the surface of the positive current collector. The positive electrode film layer includes a positive electrode active material, a conductive agent, a sulfide solid electrolyte, a binder, and an additive. The additive is coated on the surface of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte. The delithiation potential of the positive electrode active material is higher than the oxidation potential of the sulfide solid electrolyte; The additives include a positive electrode film-forming additive and an organic lithium salt, wherein the HOMO energy level of the positive electrode film-forming additive is higher than that of the HOMO energy level of the sulfide solid electrolyte.

14. A method for preparing a positive electrode sheet, wherein, include: A positive electrode active material, a conductive agent, a sulfide solid electrolyte, a binder, an additive, and a non-polar solvent are mixed to disperse the additive on the surface of the positive electrode active material, the conductive agent, and the sulfide solid electrolyte, respectively, to obtain a positive electrode slurry. The positive electrode slurry is coated onto the surface of the positive electrode current collector, dried, and cold-pressed. The additives include a positive electrode film-forming additive and an organic lithium salt, wherein the HOMO energy level of the positive electrode film-forming additive is higher than that of the sulfide solid electrolyte.

15. The preparation method according to claim 14, wherein, The nonpolar solvent includes at least one of isopentane, n-pentane, cyclohexane, isooctane, cyclopentane, n-hexane, n-heptane, tetrahydrofuran, toluene, xylene, ethyl acetate, isobutyl isobutyrate, dichloromethane, and trichloromethane.

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