Diaphragm-free solid-state battery, preparation method thereof, and electrical equipment

Abstract

The present invention relates to the field of battery technology, and in particular to a diaphragm-free solid-state battery, a preparation method thereof, and electrical equipment. The diaphragm-free solid-state battery comprises a composite positive electrode sheet and a composite negative electrode sheet; the composite positive electrode sheet comprises a positive electrode sheet and a cationic polymer electrolyte layer, and the cationic polymer electrolyte layer covers at least one surface of the positive electrode sheet; the composite negative electrode sheet comprises a negative electrode sheet and an anionic polymer electrolyte layer, and the anionic polymer electrolyte layer covers at least one surface of the negative electrode sheet. In the diaphragm-free solid-state battery of the present invention, after the composite positive electrode sheet and the composite negative electrode sheet are stacked, an ion-crosslinked interface layer will be formed at the interface through strong electrostatic interaction, which significantly improves the insulation stability between the positive and negative electrodes; and the ion-crosslinked interface layer has good high-temperature resistance, which improves the safety performance of the battery.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a diaphragm-free solid-state battery, a preparation method thereof, and electrical equipment. Background Art

[0002] With the rapid development and widespread application of lithium-ion battery technology, the market has placed increasingly stringent demands on its energy density and safety. Improving lithium-ion battery energy density often relies on employing cathode and anode material systems with higher intrinsic risks, such as high-nickel cathode materials, silicon-based anode materials, or metallic lithium anodes. The use of these materials inevitably brings safety challenges. Traditional lithium-ion batteries primarily consist of a cathode, anode, electrolyte, and separator. Current electrolyte systems, containing large amounts of flammable organic solvents, present the greatest safety hazard for lithium-ion batteries.

[0003] The use of solid-state electrolytes is one of the effective ways to improve the safety performance of lithium batteries. Current solid-state electrolyte systems can be mainly divided into three categories: oxide solid electrolytes, sulfide solid electrolytes, and polymer solid electrolytes. Although oxide and sulfide solid electrolytes have high ionic conductivity, the rigidity and brittleness of oxide solid electrolytes lead to poor interfacial contact with electrode materials. Sulfide solid electrolytes have poor stability and high preparation costs. In contrast, polymer solid electrolytes have attracted much attention due to their advantages such as good interfacial compatibility, high flexibility, and low cost.

[0004] Furthermore, while traditional separators (such as polyethylene, polypropylene, or glass fiber-based materials) can provide mechanical support and precisely control battery thickness, they are inherently inert components that cannot conduct lithium ions. This not only increases battery weight and volume, but also limits further increases in energy density. Therefore, the development of separator-free all-solid-state battery systems has become an important direction for the current development of solid-state battery technology.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] An object of the present invention is to overcome at least one defect in the prior art and provide a membrane-free solid-state battery.

[0007] Another object of the present invention is to provide a method for preparing a diaphragm-free solid-state battery.

[0008] Another object of the present invention is to provide a device including a separator-free solid-state battery.

[0009] In order to achieve the above-mentioned object of the present invention, the first aspect of the present invention provides a diaphragm-free solid-state battery, comprising a composite positive electrode sheet and a composite negative electrode sheet;

[0010] The composite positive electrode plate comprises a positive electrode plate and a cationic polymer electrolyte layer, wherein the cationic polymer electrolyte layer covers at least one surface of the positive electrode plate;

[0011] The composite negative electrode plate includes a negative electrode plate and an anionic polymer electrolyte layer, and the anionic polymer electrolyte layer covers at least one surface of the negative electrode plate.

[0012] In a specific embodiment of the present invention, the cationic polymer electrolyte layer includes a first metal salt, a first ionic liquid, and a cationic polymer. Furthermore, the cationic polymer electrolyte layer includes, by mass percentage, 20% to 60% of the first metal salt, 5% to 15% of the first ionic liquid, and 30% to 70% of the cationic polymer.

[0013] In a specific embodiment of the present invention, the first metal salt includes a metal salt X1Y1 and a metal salt X2Y2; the cation X1 of the metal salt X1Y1 + For Li + , the cation X2 of the metal salt X2Y2 + Selected from K + 、Ru + 、Cs + Any one of the metal salt X1Y1 anion Y1 - and the anion Y2 of the metal salt X2Y2 - One of them is a bistrifluoromethanesulfonyl imide anion, and the other is a bisfluorosulfonyl imide anion.

[0014] In a specific embodiment of the present invention, the mass ratio of the metal salt X1Y1 to the metal salt X2Y2 is (1-4):1.

[0015] In a specific embodiment of the present invention, the oxidation potential of the cation of the first ionic liquid is ≥2.0 V vs. SHE.

[0016] In a specific embodiment of the present invention, the first ionic liquid includes at least one of tributylmethylammonium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0017] In a specific embodiment of the present invention, the cationic polymer includes at least one of polyhexamethylene biguanidine hydrochloride and polyhexamethylene guanidine hydrochloride.

[0018] In a specific embodiment of the present invention, the thickness of the cationic polymer electrolyte layer is 1 to 10 μm, preferably 2 to 8 μm.

[0019] In a specific embodiment of the present invention, the anionic polymer electrolyte layer includes a second metal salt, a second ionic liquid, and an anionic polymer. Furthermore, the anionic polymer electrolyte layer includes, by mass percentage, 20% to 60% of the second metal salt, 5% to 15% of the second ionic liquid, and 30% to 70% of the anionic polymer.

[0020] In a specific embodiment of the present invention, the second metal salt includes a metal salt X3Y3 and a metal salt X4Y4; the cation X3 + For Li + , the cation X4 of the metal salt X4Y4 + Selected from K + 、Ru + 、Cs + Any one of the metal salt X3Y3 anion Y3 - and the anion Y4 of the metal salt X4Y4 - One of them is a bistrifluoromethanesulfonyl imide anion, and the other is a bisfluorosulfonyl imide anion.

[0021] In a specific embodiment of the present invention, the mass ratio of the metal salt X3Y3 to the metal salt X4Y4 is (1-4):1.

[0022] In a specific embodiment of the present invention, the reduction potential of the cation of the second ionic liquid is ≤-3.04 V vs. SHE.

[0023] In a specific embodiment of the present invention, the second ionic liquid includes at least one of N-methyl-N-butylpyrrolidine bis(trifluoromethanesulfonyl)imide and N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide.

[0024] In a specific embodiment of the present invention, the anionic polymer includes at least one of sodium polyacrylate, sodium polymethacrylate, potassium poly-2-acrylamido-2-methylpropanesulfonate and sodium phytate.

[0025] In a specific embodiment of the present invention, the thickness of the anionic polymer electrolyte layer is 1 to 10 μm, preferably 2 to 8 μm.

[0026] In a specific embodiment of the present invention, the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, and the cationic polymer electrolyte layer covers the surface of the positive electrode active material layer.

[0027] In a specific embodiment of the present invention, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the anionic polymer electrolyte layer covers the surface of the negative electrode active material layer.

[0028] A second aspect of the present invention provides a method for preparing a diaphragm-free solid-state battery, comprising the following steps:

[0029] (a) forming a cationic polymer electrolyte layer on the surface of the positive electrode to obtain a composite positive electrode, and forming an anionic polymer electrolyte layer on the surface of the negative electrode to obtain a composite negative electrode;

[0030] (b) laminating, assembling, hot pressing, forming, and dividing the capacity of the composite positive electrode sheet and the composite negative electrode sheet to obtain a diaphragm-free solid-state battery.

[0031] A third aspect of the present invention provides an electrical device, comprising any one of the diaphragm-free solid-state batteries provided in the first aspect of the present invention.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The membrane-free solid-state battery of the present invention uses a composite positive electrode sheet having a cationic polymer electrolyte layer and a composite negative electrode sheet having an anionic polymer electrolyte layer. After the composite positive electrode sheet and the composite negative electrode sheet are stacked, the cationic polymer electrolyte layer and the anionic polymer electrolyte layer at the interface form an ion-crosslinked interface layer through strong electrostatic interaction, which significantly improves the insulation stability between the positive and negative electrodes; and the ion-crosslinked interface layer has good high-temperature resistance, which can effectively avoid the short-circuit failure problem caused by thermal shrinkage of the insulation layer under high temperature conditions, thereby improving the safety performance of the battery;

[0034] (2) The membrane-free solid-state battery of the present invention further regulates the types of metal salts in the cationic polymer electrolyte layer and the anionic polymer electrolyte layer. Under the competitive coordination of different anions and cations, the melting point is lowered, the ionic conductivity is significantly improved, and the interface impedance is reduced.

[0035] (3) The membrane-free solid-state battery of the present invention does not contain liquid electrolyte, but only contains a small amount of non-flammable ionic liquid, which significantly inhibits the side reaction between the electrolyte and the electrodes in the battery, and can effectively improve the safety performance and cycle performance of the battery. DETAILED DESCRIPTION

[0036] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0037] In the description of the present invention, it should be noted that terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" to indicate positions or relationships are used solely to facilitate description and simplify the present invention. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific manner. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0038] A first aspect of the present invention provides a diaphragm-free solid-state battery, comprising a composite positive electrode sheet and a composite negative electrode sheet;

[0039] The composite positive electrode plate comprises a positive electrode plate and a cationic polymer electrolyte layer, wherein the cationic polymer electrolyte layer covers at least one surface of the positive electrode plate;

[0040] The composite negative electrode plate comprises a negative electrode plate and an anionic polymer electrolyte layer, wherein the anionic polymer electrolyte layer covers at least one surface of the negative electrode plate.

[0041] The membrane-free solid-state battery of the present invention adopts a composite positive electrode plate having a cationic polymer electrolyte layer and a composite negative electrode plate having an anionic polymer electrolyte layer. After the composite positive electrode plate and the composite negative electrode plate are stacked, the cationic polymer electrolyte layer and the anionic polymer electrolyte layer at the interface form an ion-crosslinked interface layer through strong electrostatic interaction, which significantly improves the insulation stability between the positive and negative electrodes; and the ion-crosslinked interface layer has good high-temperature resistance, which can effectively avoid the short-circuit failure problem caused by thermal shrinkage of the insulating layer under high temperature conditions, thereby improving the safety performance of the battery.

[0042] In a specific embodiment of the present invention, the cationic polymer electrolyte layer covers the surface of the positive electrode plate and partially fills the pores of the positive electrode plate; the anionic polymer electrolyte layer covers the surface of the negative electrode plate and partially fills the pores of the negative electrode plate.

[0043] In a specific embodiment of the present invention, the cationic polymer electrolyte layer includes a first metal salt, a first ionic liquid, and a cationic polymer. Furthermore, the cationic polymer electrolyte layer includes, by mass percentage, 20% to 60% of the first metal salt, 5% to 15% of the first ionic liquid, and 30% to 70% of the cationic polymer.

[0044] For example, in various embodiments, the amount of the first metal salt in the cationic polymer electrolyte layer can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any two thereof, by weight; the amount of the first ionic liquid can be 5%, 8%, 10%, 12%, 15%, or any two thereof; and the amount of the cationic polymer can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any two thereof. Regulating the amounts of each component in the cationic polymer electrolyte layer within the above ranges helps to balance improving the insulation stability between the positive and negative electrodes and the ionic conductivity.

[0045] In a specific embodiment of the present invention, the first metal salt includes a metal salt X1Y1 and a metal salt X2Y2; the cation X1 of the metal salt X1Y1 + For Li + , cation X2 of metal salt X2Y2 + Selected from K + 、Ru + 、Cs + Any one of; anion Y1 of metal salt X1Y1 - and the anion Y2 of the metal salt X2Y2 - One of the anions is bis(trifluoromethanesulfonyl)imide (TFSI - ), and the other is a bis(fluorosulfonyl)imide anion (FSI - ).

[0046] For example, the metal salt X1Y1 may include any of LiFSI and LiTFSI, and the metal salt X2Y2 may include any of KFSI, KTFSI, RuFSI, RuTFSI, CsFSI, and CsTFSI. Combinations of the first metal salt include, but are not limited to, LiFSI + KTFSI, LiFSI + RuTFSI, LiFSI + CsTFSI, LiTFSI + KFSI, LiTFSI + RuFSI, and LiTFSI + CsFSI. Using a first metal salt that meets the above conditions in the cationic polymer electrolyte layer can effectively enhance ionic conductivity and improve interfacial stability.

[0047] In specific embodiments of the present invention, the mass ratio of the metal salt X1Y1 to the metal salt X2Y2 is (1-4):1, such as 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, or any combination thereof. Adjusting the amounts of the metal salts X1Y1 and X2Y2 to meet this range helps achieve both enhanced ionic conductivity and improved interfacial stability.

[0048] In a specific embodiment of the present invention, the oxidation potential of the cation of the first ionic liquid is ≥2.0 V vs. SHE. The potential on the positive electrode side is higher. The first ionic liquid that meets the above conditions is more resistant to oxidation and is not easily oxidized and decomposed on the positive electrode side.

[0049] In a specific embodiment of the present invention, the first ionic liquid includes at least one of tributylmethylammonium bis(trifluoromethanesulfonylimide) ([3B1MN][TFSI]), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonylimide) ([EMIm][TFSI]), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonylimide) ([BMIm][TFSI]), and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonylimide) ([HMIm][TFSI]).

[0050] In a specific embodiment of the present invention, the cationic polymer includes at least one of polyhexamethylene biguanidine hydrochloride (PHMB) and polyhexamethylene guanidine hydrochloride (PHMG).

[0051] In a specific embodiment of the present invention, the thickness of the cationic polymer electrolyte layer is 1 to 10 μm, preferably 2 to 8 μm. For example, in different embodiments, the thickness of the cationic polymer electrolyte layer can be 1 μm, 2 μm, 3 μm, 5 μm, 6 μm, 8 μm, 10 μm, or a range consisting of any two thereof. A thickness of the cationic polymer electrolyte layer within the above range is more conducive to improving the energy density of the battery while ensuring mechanical properties and reducing ion transport impedance.

[0052] In a specific embodiment of the present invention, the anionic polymer electrolyte layer includes a second metal salt, a second ionic liquid, and an anionic polymer. Furthermore, the anionic polymer electrolyte layer includes, by mass percentage, 20% to 60% of the second metal salt, 5% to 15% of the second ionic liquid, and 30% to 70% of the anionic polymer.

[0053] For example, in various embodiments, the amount of the second metal salt in the anionic polymer electrolyte layer, measured by mass percentage, can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any combination thereof; the amount of the second ionic liquid can be 5%, 8%, 10%, 12%, 15%, or any combination thereof; and the amount of the anionic polymer can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any combination thereof. Regulating the amounts of each component in the anionic polymer electrolyte layer within the aforementioned ranges helps to balance improving the insulation stability between the positive and negative electrodes and the ionic conductivity.

[0054] In a specific embodiment of the present invention, the second metal salt includes a metal salt X3Y3 and a metal salt X4Y4; the cation X3 of the metal salt X3Y3 + For Li + , cation X4 of metal salt X4Y4 + Selected from K + 、Ru + 、Cs + Any one of; anion Y3 of metal salt X3Y3 - and the anion Y4 of the metal salt X4Y4 - One of the anions is bis(trifluoromethanesulfonyl)imide (TFSI - ), and the other is a bis(fluorosulfonyl)imide anion (FSI - ).

[0055] For example, the metal salt X3Y3 may include any of LiFSI and LiTFSI, and the metal salt X4Y4 may include any of KFSI, KTFSI, RuFSI, RuTFSI, CsFSI, or CsTFSI. Combinations of the second metal salt include, but are not limited to, LiFSI + KTFSI, LiFSI + RuTFSI, LiFSI + CsTFSI, LiTFSI + KFSI, LiTFSI + RuFSI, and LiTFSI + CsFSI. Using a second metal salt that meets these requirements in the anionic polymer electrolyte layer can effectively enhance ionic conductivity and improve interfacial stability.

[0056] In specific embodiments of the present invention, the mass ratio of the metal salt X3Y3 to the metal salt X4Y4 is (1-4):1, such as 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, or any combination thereof. Adjusting the amounts of the metal salts X3Y3 and X4Y4 to meet this range helps achieve both enhanced ionic conductivity and improved interfacial stability.

[0057] In a specific embodiment of the present invention, the reduction potential of the cation of the second ionic liquid is ≤-3.04 V vs. SHE. The potential on the negative electrode side is low. The second ionic liquid that meets the above conditions is more resistant to reduction and is not easily decomposed by reduction on the negative electrode side.

[0058] In a specific embodiment of the present invention, the second ionic liquid includes at least one of N-methyl-N-butylpyrrolidinobis(trifluoromethanesulfonyl)imide ([MBPy][TFSI]) and N-methyl-N-propylpiperidiniumbis(trifluoromethanesulfonyl)imide ([MPPp][TFSI]).

[0059] In a specific embodiment of the present invention, the anionic polymer includes at least one of sodium polyacrylate (PAAS), sodium polymethacrylate (PMAAS), potassium poly-2-acrylamido-2-methylpropanesulfonate (PAMPSK) and sodium phytate (PAS).

[0060] In a specific embodiment of the present invention, the thickness of the anionic polymer electrolyte layer is 1 to 10 μm, preferably 2 to 8 μm. For example, in different embodiments, the thickness of the anionic polymer electrolyte layer can be 1 μm, 2 μm, 3 μm, 5 μm, 6 μm, 8 μm, 10 μm, or a range consisting of any two thereof. An anionic polymer electrolyte layer thickness within the above range is more conducive to improving the energy density of the battery while ensuring mechanical properties and reducing ion transfer impedance.

[0061] In a specific embodiment of the present invention, the diaphragm-free solid-state battery of the present invention includes an ion-crosslinked interface layer formed in situ between the composite positive electrode sheet and the composite negative electrode sheet.

[0062] In a specific embodiment of the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, and the cationic polymer electrolyte layer covers the surface of the positive electrode active material layer. Specifically, the cationic polymer electrolyte layer covers the surface of the positive electrode active material layer and partially fills the pores of the positive electrode active material layer.

[0063] In a specific embodiment of the present invention, the positive electrode active material layer includes a positive electrode active material, an optional conductive agent, and an optional binder. The diaphragm-free solid-state battery of the present invention is applicable to various types of positive electrode active material layers, and the types of positive electrode active material, conductive agent, and binder used in the positive electrode active material layer are not limited.

[0064] The positive electrode active material includes but is not limited to LiMn x Fe 1-x PO4 material (0≤x≤1), chemical formula is LiNi m1 Co m2 Mn m3At least one of the ternary cathode materials and modified materials of O2 (0<m1<1, 0<m2<1, 0<m3<1, and m1+m2+m3=1, specifically including but not limited to NCM333, NCM523, NCM211, NCM622, NCM811, etc.), with the chemical formula of LiNi n1 Co n2 Al n3 At least one of the ternary cathode materials and modified materials of O2 (0<n1<1, 0<n2<1, 0<n3<1, and n1+n2+n3=1, specifically including but not limited to LiNi 0.85 Co 0.15 Al 0.05 O2、LiNi 0.5 Co 0.25 Al 0.25 O2、LiNi 0.6 Co 0.2 Al 0.2 O2, etc.).

[0065] The conductive agent includes, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder includes, but is not limited to, at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0066] In a specific embodiment of the present invention, the positive electrode 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 material base layer and a metal layer formed on at least one surface of the polymer material base layer.

[0067] In a specific embodiment of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the anionic polymer electrolyte layer covers the surface of the negative electrode active material layer. Specifically, the anionic polymer electrolyte layer covers the surface of the negative electrode active material layer and partially fills the pores of the negative electrode active material layer.

[0068] In a specific embodiment of the present invention, the negative electrode active material layer includes a negative electrode active material, an optional conductive agent, and an optional binder. The diaphragm-free solid-state battery of the present invention is applicable to various negative electrode active material layers, and the types of negative electrode active material, conductive agent, and binder used in the negative electrode active material layer are not limited.

[0069] Negative electrode active materials include, but are not limited to, artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials can be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon complexes, silicon-nitrogen complexes, and silicon alloys. Tin-based materials can be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. These negative electrode active materials may be used singly or in combination.

[0070] The conductive agent includes, but is not limited to, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder includes, but is not limited to, 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 cellulose (CMC).

[0071] In a specific embodiment of the present invention, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.

[0072] The membrane-free solid-state battery of the present invention does not include a liquid electrolyte and a membrane.

[0073] A second aspect of the present invention provides a method for preparing a diaphragm-free solid-state battery, comprising the following steps:

[0074] (a) forming a cationic polymer electrolyte layer on the surface of the positive electrode to obtain a composite positive electrode, and forming an anionic polymer electrolyte layer on the surface of the negative electrode to obtain a composite negative electrode;

[0075] (b) The composite positive electrode sheet and the composite negative electrode sheet are stacked, assembled, hot-pressed, formed, and capacity-divided to obtain a diaphragm-free solid-state battery.

[0076] The composite positive electrode sheet and the composite negative electrode sheet are laminated together using a lamination process, with the cationic polymer electrolyte layer and the anionic polymer electrolyte layer sandwiched between the sheets. Through hot pressing, an ionically cross-linked interface layer is formed between the composite positive electrode sheet and the composite negative electrode sheet.

[0077] In a specific embodiment of the present invention, the hot pressing conditions include: temperature of 85-95° C., pressure of 1.1-1.3 MPa, and time of 15-25 seconds.

[0078] In a specific embodiment of the present invention, a method for forming a cationic polymer electrolyte layer includes: applying a material containing a cationic polymer electrolyte to the surface of a positive electrode plate, performing an immersion treatment at 40 to 70°C, and then cooling the temperature to room temperature. For example, in different embodiments, the immersion treatment temperature may be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, or a range of any two thereof; and the immersion treatment time is 1 to 3 hours.

[0079] In a specific embodiment of the present invention, a method for forming an anionic polymer electrolyte layer includes applying a material containing an anionic polymer electrolyte to the surface of a negative electrode plate, performing an infiltration treatment at 40 to 70°C, and then cooling to room temperature. For example, in different embodiments, the infiltration treatment temperature may be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, or any combination thereof; and the infiltration treatment time is 1 to 3 hours.

[0080] In the preparation of the cationic polymer electrolyte layer and the anionic polymer electrolyte layer, after the infiltration treatment, during the process of cooling to room temperature, the polymer electrolyte is precipitated on the surface and inside the pores of the positive electrode sheet / negative electrode sheet.

[0081] In a specific embodiment of the present invention, the preparation of the material containing the cationic polymer electrolyte includes: weighing a first metal salt, a first ionic liquid and a cationic polymer according to the composition of the cationic polymer electrolyte layer, mixing and heating to 80° C., stirring the mixture until it is in a molten state and uniformly stirring.

[0082] In a specific embodiment of the present invention, the preparation of the material containing anionic polymer electrolyte includes: weighing the second metal salt, the second ionic liquid and the anionic polymer according to the composition of the anionic polymer electrolyte layer, mixing and heating to 80° C., stirring the mixture until it is in a molten state and uniformly stirring.

[0083] In a specific embodiment of the present invention, the positive electrode current collector has two opposing surfaces in its thickness direction, the positive electrode active material layer is disposed on the two opposing surfaces of the positive electrode current collector; and the cationic polymer electrolyte layer covers the surface of the positive electrode active material layer. Accordingly, the negative electrode current collector has two opposing surfaces in its thickness direction, the negative electrode active material layer is disposed on the two opposing surfaces of the negative electrode current collector; and the anionic polymer electrolyte layer covers the surface of the negative electrode active material layer.

[0084] In a specific embodiment of the present invention, the preparation of the positive electrode sheet includes: coating a material containing a positive electrode active substance on the surface of a positive electrode current collector, drying, and obtaining a positive electrode sheet; the preparation of the negative electrode sheet includes: coating a material containing a negative electrode active substance on the surface of a negative electrode current collector, drying, and obtaining a negative electrode sheet.

[0085] A third aspect of the present invention provides an electrical device, comprising any one of the diaphragm-free solid-state batteries provided in the first aspect of the present invention.

[0086] Example 1

[0087] This embodiment provides a method for preparing a diaphragm-free solid-state battery, comprising the following steps:

[0088] (1) Preparation of composite positive electrode sheets

[0089] S1: The positive electrode ternary active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) were mixed in a weight ratio of 90:5:5, and an appropriate amount of N-methylpyrrolidone (NMP) was added as a solvent and stirred to disperse evenly to obtain a positive electrode slurry. The positive electrode slurry was scraped onto both sides of aluminum foil and dried at 90°C to obtain a surface density of 20 mg / cm 2 The positive electrode is spare.

[0090] S2: Weigh 20g LiFSI, 10g CsTFSI, 10g [3B1MN][TFSI], and 60g PHMB, mix them, heat to 80°C, and stir evenly to obtain a molten cationic polymer electrolyte material. Cool the cationic polymer electrolyte material to 60°C and apply it to the surface of the positive electrode obtained in S1. Maintain it at 60°C for 2 hours to allow it to fully penetrate, then cool it to room temperature to obtain a composite positive electrode sheet.

[0091] (2) Preparation of composite negative electrode sheets

[0092] S3: Graphite, silicon carbon, conductive carbon black (Super P), hydroxymethyl cellulose binder, and styrene-butadiene rubber latex binder were mixed in a mass ratio of 92:3:2:3, and an appropriate amount of deionized water was added as a sol. The mixture was stirred and dispersed evenly to obtain a negative electrode slurry. The negative electrode slurry was scraped onto both sides of the copper foil and dried at 70°C to obtain a surface density of 13 mg / cm 2 The negative electrode is spare.

[0093] S4: Weigh 30g LiTFSI, 10g CsFSI, 10g [MBPy][TFSI], and 50g PAAS, mix them, heat to 80°C, and stir evenly to obtain a molten anionic polymer electrolyte material. Cool the anionic polymer electrolyte material to 50°C and apply it to the surface of the negative electrode obtained in S3. Maintain it at 50°C for 2 hours to allow it to be fully infiltrated, and then cool it to room temperature to obtain a composite negative electrode sheet.

[0094] (3) Separator-free solid-state battery

[0095] S5: The prepared composite positive electrode and composite negative electrode sheets are subjected to the following steps: slitting, lamination, assembly, baking, hot pressing, formation, and capacity division to obtain a diaphragm-free solid-state battery. The hot pressing conditions are: 90°C, 1.2 MPa, and 20 seconds.

[0096] Example 2

[0097] This embodiment refers to the preparation method of the membrane-free solid-state battery of Example 1, with the only difference being that the raw material compositions of the molten cationic polymer electrolyte material in S2 and the molten anionic polymer electrolyte material in S4 are different. The specific differences are as follows:

[0098] The raw materials of the molten cationic polymer electrolyte material in S2 of this embodiment are: 30g LiTFSI, 10g KFSI, 10g [BMIm][TFSI], 50g PHMG;

[0099] The raw materials of the molten anionic polymer electrolyte material in S4 of this embodiment are: 20 g LiFSI, 10 g KTFSI, 10 g [MPPp][TFSI], and 60 g PAMPSK.

[0100] Example 3

[0101] This embodiment refers to the preparation method of the membrane-free solid-state battery of Example 1, with the only difference being that the raw material compositions of the molten cationic polymer electrolyte material in S2 and the molten anionic polymer electrolyte material in S4 are different. The specific differences are as follows:

[0102] The raw materials of the molten cationic polymer electrolyte material in S2 of this embodiment are: 15g LiFSI, 5g CsTFSI, 10g [3B1MN][TFSI], 70g PHMB;

[0103] The raw materials of the molten anionic polymer electrolyte material in S4 of this embodiment are: 15 g LiTFSI, 5 g CsFSI, 10 g [MBPy][TFSI], and 70 g PAAS.

[0104] Example 4

[0105] This embodiment refers to the preparation method of the membrane-free solid-state battery of Example 1, with the only difference being that the raw material compositions of the molten cationic polymer electrolyte material in S2 and the molten anionic polymer electrolyte material in S4 are different. The specific differences are as follows:

[0106] The raw materials of the molten cationic polymer electrolyte material in S2 of this embodiment are: 40g LiFSI, 20g CsTFSI, 10g [3B1MN][TFSI], and 30g PHMB;

[0107] The raw materials of the molten anionic polymer electrolyte material in S4 of this embodiment are: 40 g LiTFSI, 20 g CsFSI, 10 g [MBPy][TFSI], and 30 g PAAS.

[0108] Example 5

[0109] This embodiment refers to the preparation method of the membrane-free solid-state battery of Example 1, with the only difference being that the raw material compositions of the molten cationic polymer electrolyte material in S2 and the molten anionic polymer electrolyte material in S4 are different. The specific differences are as follows:

[0110] The raw materials of the molten cationic polymer electrolyte material in S2 of this embodiment are: 30g LiFSI, 10g [3B1MN] [TFSI], 60g PHMB;

[0111] The raw materials of the molten anionic polymer electrolyte material in S4 of this embodiment are: 40 g LiTFSI, 10 g [MBPy] [TFSI], and 50 g PAAS.

[0112] Example 6

[0113] This embodiment refers to the preparation method of the membrane-free solid-state battery of Example 1, with the only difference being that the raw material compositions of the molten cationic polymer electrolyte material in S2 and the molten anionic polymer electrolyte material in S4 are different. The specific differences are as follows:

[0114] The raw materials of the molten cationic polymer electrolyte material in S2 of this embodiment are: 15g LiFSI, 15g CsTFSI, 10g [3B1MN][TFSI], and 60g PHMB;

[0115] The raw materials of the molten anionic polymer electrolyte material in S4 of this embodiment are: 20 g LiTFSI, 20 g CsFSI, 10 g [MBPy][TFSI], and 50 g PAAS.

[0116] Example 7

[0117] This embodiment refers to the preparation method of the membrane-free solid-state battery of Example 1, with the only difference being that the raw material compositions of the molten cationic polymer electrolyte material in S2 and the molten anionic polymer electrolyte material in S4 are different. The specific differences are as follows:

[0118] The raw materials of the molten cationic polymer electrolyte material in S2 of this embodiment are: 24g LiFSI, 6g CsTFSI, 10g [3B1MN][TFSI], and 60g PHMB;

[0119] The raw materials of the molten anionic polymer electrolyte material in S4 of this embodiment are: 32 g LiTFSI, 8 g CsFSI, 10 g [MBPy][TFSI], and 50 g PAAS.

[0120] Example 8

[0121] This embodiment refers to the preparation method of the membrane-free solid-state battery of Example 1, with the only difference being that the raw material compositions of the molten cationic polymer electrolyte material in S2 and the molten anionic polymer electrolyte material in S4 are different. The specific differences are as follows:

[0122] The raw materials of the molten cationic polymer electrolyte material in S2 of this embodiment are: 10g LiFSI, 20g CsTFSI, 10g [3B1MN][TFSI], and 60g PHMB;

[0123] The raw materials of the molten anionic polymer electrolyte material in S4 of this embodiment are: 15 g LiTFSI, 25 g CsFSI, 10 g [MBPy][TFSI], and 50 g PAAS.

[0124] Example 9

[0125] This embodiment refers to the preparation method of the membrane-free solid-state battery of Example 1, with the only difference being that the raw material compositions of the molten cationic polymer electrolyte material in S2 and the molten anionic polymer electrolyte material in S4 are different. The specific differences are as follows:

[0126] The raw materials of the molten cationic polymer electrolyte material in S2 of this embodiment are: 25g LiFSI, 5g CsTFSI, 10g [3B1MN][TFSI], and 60g PHMB;

[0127] The raw materials of the molten anionic polymer electrolyte material in S4 of this embodiment are: 35 g LiTFSI, 5 g CsFSI, 10 g [MBPy][TFSI], and 50 g PAAS.

[0128] Example 10

[0129] This embodiment refers to the preparation method of the membrane-free solid-state battery of Example 1, with the only difference being that the raw material compositions of the molten cationic polymer electrolyte material in S2 and the molten anionic polymer electrolyte material in S4 are different. The specific differences are as follows:

[0130] The raw materials of the molten cationic polymer electrolyte material in S2 of this embodiment are: 30g LiFSI, 10g LiTFSI, 10g [3B1MN][TFSI], and 60g PHMB;

[0131] The raw materials of the molten anionic polymer electrolyte material in S4 of this embodiment are: 30 g LiTFSI, 10 g CsTFSI, 10 g [MBPy][TFSI], and 50 g PAAS.

[0132] Example 11

[0133] This embodiment refers to the preparation method of the membrane-free solid-state battery of Example 1, with the only difference being that the raw material compositions of the molten cationic polymer electrolyte material in S2 and the molten anionic polymer electrolyte material in S4 are different. The specific differences are as follows:

[0134] The raw materials of the molten cationic polymer electrolyte material in S2 of this embodiment are: 30g LiFSI, 10g CsFSI, 10g [3B1MN][TFSI], and 60g PHMB;

[0135] The raw materials of the molten anionic polymer electrolyte material in S4 of this embodiment are: 30 g LiTFSI, 10 g LiFSI, 10 g [MBPy][TFSI], and 50 g PAAS.

[0136] Comparative Example 1

[0137] Comparative Example 1 refers to the preparation method of the membrane-free solid-state battery of Example 1, with the only difference being that the raw material composition of the molten anionic polymer electrolyte material in S4 is different, and the specific differences are as follows:

[0138] The raw materials of the molten anionic polymer electrolyte material in S4 of this comparative example are: 30 g LiTFSI, 10 g CsFSI, 10 g [MBPy][TFSI], and 50 g PHMG.

[0139] Comparative Example 2

[0140] Comparative Example 2 provides a method for preparing a conventional liquid battery, comprising the following steps:

[0141] (1) Prepare the positive electrode sheet by referring to S1 of Example 1.

[0142] (2) Prepare the negative electrode sheet by referring to S3 in Example 1.

[0143] (3) A polyethylene (PE) diaphragm with a thickness of 12 μm was selected and a Z-shaped lamination method was adopted. The positive and negative electrodes were placed on both sides of the diaphragm, and the diaphragm was placed between the electrodes. After lamination, the tabs were welded and then placed in an aluminum-plastic film. The top and side seals were performed, and a conventional liquid electrolyte (1M LiPF6, the solvent is EC and DEC with a volume ratio of 3:7, containing 5wt% FEC) was injected. The conventional liquid battery was obtained by the following steps: encapsulation, room temperature immersion, formation, and capacity separation.

[0144] Experimental example

[0145] 1. Determination of ionic conductivity

[0146] The molten cationic polymer electrolyte material and the molten anionic polymer electrolyte material in each embodiment and comparative example were coated on the surface of a stainless steel sheet (diameter 16 mm), and the surfaces of the stainless steel sheet coated with the cationic polymer electrolyte and the anionic polymer electrolyte were arranged opposite to each other to form a blocking cell. Then, an electrochemical workstation was used to measure the resistance at different temperatures by AC impedance, and then the ionic conductivity of the polymer electrolyte at different temperatures was calculated by formula (1);

[0147] σ=t / (R×S)(1)

[0148] Where: σ is the ionic conductivity (S / cm), t is the thickness of the polymer electrolyte membrane (the total thickness of the cationic polymer electrolyte layer and the anionic polymer electrolyte layer) (cm), R is the in-plane resistance perpendicular to the membrane surface (Ω), and S is the effective membrane area (cm 2 ).

[0149] 2. Cycle performance test

[0150] The lithium batteries prepared in each embodiment and comparative example were subjected to cycle testing on a Xinwei test system. The batteries adopted constant current-constant potential charge / constant current discharge (CC-CV / DC) mode. The charge and discharge cut-off voltages were 4.2V and 2.8V, respectively. The cut-off current of the constant potential was 0.05C. The battery was allowed to stand for 5 minutes between each cycle of charge and discharge. The battery was cycled at a charge and discharge rate of 0.2 / 0.5C at 25°C.

[0151] 3. Battery hot box test

[0152] The lithium batteries prepared in each embodiment and comparative example were fully charged and placed in an oven. They were first kept at 25°C for 120 minutes, then heated to 100°C and kept for 30 minutes to observe whether the battery failed. If the battery did not fail, the temperature was continued to be increased by 5°C each time and kept at this temperature for 30 minutes until the battery failed. The battery failure temperature and time were recorded.

[0153] Table 1 shows the ionic conductivity test results, and Table 2 shows the battery performance test results.

[0154] Table 1 Ionic conductivity of different embodiments and comparative examples

[0155]

[0156] Table 2 Battery performance test results of different embodiments and comparative examples

[0157]

[0158] It can be seen from the above test results that the solid electrolyte of the present invention has a relatively high electrical conductivity, and the diaphragm-free solid-state battery of the present invention has excellent cycle performance and high safety.

[0159] According to the test results of Example 1 and Comparative Example 1, the polymer electrolyte layers of the composite positive electrode sheet and the composite negative electrode sheet of Comparative Example 1 are both cationic polymer electrolytes. There is a strong electrostatic repulsion between the two at the interface, which is not conducive to interface bonding and has high interface impedance. As a result, the formed polymer electrolyte not only has low ionic conductivity, but also poor interface stability, and exhibits extremely poor cycle life and safety performance.

[0160] According to the test results of the embodiment and comparative example 2, the battery of comparative example 2 uses a conventional liquid electrolyte, the proportion of flammable carbonate solvent is high, and the thermal safety of the battery is extremely poor.

[0161] According to the test results of Examples 1 and 5, 10 to 11, by regulating the types of metal salts in the cationic polymer electrolyte layer and the anionic polymer electrolyte layer, the melting point is lowered under the competitive coordination of different anions and cations, which is beneficial to the improvement of ion pair conductivity; in Examples 8 and 9, the cationic polymer electrolyte uses a metal salt with the same cation or anion, and the anionic polymer electrolyte uses a metal salt with the same anion or cation, which is not easy to form a low eutectic, the ionic conductivity is reduced, and the cycle performance is affected.

[0162] According to the test results of Example 1 and Examples 6 to 9, when two metal salts are used in the cationic polymer electrolyte layer and the anionic polymer electrolyte layer, when the dosage of the two metal salts meets certain conditions, it is more conducive to the formation of a low eutectic, thereby improving the ionic conductivity and the cycle performance.

[0163] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A diaphragm-free solid-state battery, characterized in that: Including a composite positive electrode sheet and a composite negative electrode sheet; The composite positive electrode plate comprises a positive electrode plate and a cationic polymer electrolyte layer, wherein the cationic polymer electrolyte layer covers at least one surface of the positive electrode plate; The composite negative electrode plate comprises a negative electrode plate and an anionic polymer electrolyte layer, wherein the anionic polymer electrolyte layer covers at least one surface of the negative electrode plate; The cationic polymer electrolyte layer includes a first metal salt, a first ionic liquid and a cationic polymer; The first metal salt includes a metal salt X1Y1 and a metal salt X2Y2; the cation X1 of the metal salt X1Y1 + For Li + , the cation X2 of the metal salt X2Y2 + Selected from K + 、Ru + 、Cs + Any one of the metal salt X1Y1 anion Y1 - and the anion Y2 of the metal salt X2Y2 - One of them is a bis(trifluoromethanesulfonyl)imide anion, and the other is a bis(fluorosulfonyl)imide anion; The mass ratio of the metal salt X1Y1 to the metal salt X2Y2 is (1-4):1; The cationic polymer includes at least one of polyhexamethylene biguanidine hydrochloride and polyhexamethylene guanidine hydrochloride; The anionic polymer electrolyte layer includes a second metal salt, a second ionic liquid and an anionic polymer; The second metal salt includes a metal salt X3Y3 and a metal salt X4Y4; the cation X3 of the metal salt X3Y3 + For Li + , the cation X4 of the metal salt X4Y4 + Selected from K + 、Ru + 、Cs + Any one of the metal salt X3Y3 anion Y3 - and the anion Y4 of the metal salt X4Y4 - One of them is a bis(trifluoromethanesulfonyl)imide anion, and the other is a bis(fluorosulfonyl)imide anion; The mass ratio of the metal salt X3Y3 to the metal salt X4Y4 is (1-4):1; The anionic polymer includes at least one of sodium polyacrylate, sodium polymethacrylate, potassium poly-2-acrylamido-2-methylpropanesulfonate and sodium phytate.

2. The membrane-free solid-state battery according to claim 1, characterized in that: The cationic polymer electrolyte layer comprises, by mass percentage, 20% to 60% of the first metal salt, 5% to 15% of the first ionic liquid, and 30% to 70% of the cationic polymer.

3. The membrane-free solid-state battery according to claim 2, characterized in that: Has at least one of the following characteristics: (1) The oxidation potential of the cation of the first ionic liquid is ≥ 2.0 V vs. SHE; (2) the first ionic liquid includes at least one of tributylmethylammonium bis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide; (3) The thickness of the cationic polymer electrolyte layer is 1 to 10 μm.

4. The membrane-free solid-state battery according to claim 1, characterized in that: The anionic polymer electrolyte layer comprises, by mass percentage, 20% to 60% of the second metal salt, 5% to 15% of the second ionic liquid, and 30% to 70% of the anionic polymer.

5. The membrane-free solid-state battery according to claim 4, characterized in that: Has at least one of the following characteristics: (1) The reduction potential of the cation of the second ionic liquid is ≤ -3.04 V vs. SHE; (2) the second ionic liquid comprises at least one of N-methyl-N-butylpyrrolidine bis(trifluoromethanesulfonyl)imide and N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide; (3) The thickness of the anionic polymer electrolyte layer is 1 to 10 μm.

6. The membrane-free solid-state battery according to claim 1, characterized in that: Has at least one of the following characteristics: (1) The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, and the cationic polymer electrolyte layer covers the surface of the positive electrode active material layer; (2) The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the anionic polymer electrolyte layer covers the surface of the negative electrode active material layer.

7. The method for preparing a diaphragm-free solid-state battery according to any one of claims 1 to 6, characterized in that: The steps include: (a) forming a cationic polymer electrolyte layer on the surface of the positive electrode to obtain a composite positive electrode, and forming an anionic polymer electrolyte layer on the surface of the negative electrode to obtain a composite negative electrode; (b) laminating, assembling, hot pressing, forming, and dividing the capacity of the composite positive electrode sheet and the composite negative electrode sheet to obtain a diaphragm-free solid-state battery.

8. An electrical device, characterized in that: The invention comprises the membrane-free solid-state battery according to any one of claims 1 to 6.

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