Solid-state battery and method of manufacturing the same

Abstract

The application provides a solid-state battery and a preparation method thereof, and belongs to the technical field of secondary batteries.The solid-state battery comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode active material layer, the positive electrode active material layer comprises a sulfide electrolyte, and the average particle size D50 of the sulfide electrolyte satisfies 50 nm <= D50 < 1 mu m.The solid-state battery of the application nanocrystallizes the modified sulfide electrolyte in the positive electrode active material layer, thereby forming a closely distributed ion transmission network and a stable electrode / electrolyte interface in the positive electrode active material layer, achieving good conductive cycling of the battery by adding less sulfide electrolyte in the positive electrode active material layer, and improving the energy density and cycle life of the battery; meanwhile, the nanocrystallized sulfide electrolyte in the positive electrode active material layer has higher structural strength, can avoid cracking and pulverization of itself in the charging and discharging cycle process, and further improves the storage and cycle life of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a solid-state battery and a preparation method thereof. BACKGROUND

[0002] All-solid-state lithium batteries are potential candidates for large-scale energy storage applications such as electric vehicles and smart grids. Solid-state electrolytes have excellent electrochemical stability and thermal stability, making them suitable for lithium ion transport at high voltage and / or high temperature.

[0003] Sulfide solid-state electrolytes are widely used in the manufacture of all-solid-state lithium batteries due to their high conductivity (10 -2 ~ 10 -4 S / cm 2 ) and good mechanical properties. Generally, all-solid-state lithium batteries based on sulfide solid electrolytes can only be manufactured by cold pressing, and the addition of solid-state electrolytes in the positive active material layer of the battery can improve the ion and electron conduction performance of the active material.

[0004] Currently, due to the large size of the solid-state electrolyte particles added to the positive active material layer, it is often necessary to add 30-50wt% of solid-state electrolyte to the positive active material layer to ensure that it has good ion transport channels and low interface electrode / electrolyte resistance. However, the addition of such a large amount of solid-state electrolyte in the positive active material layer greatly reduces the energy density of the battery, and the large particle size of the electrolyte particles is easily affected by the internal stress and strain of the battery, resulting in particle pulverization and rupture, thereby increasing the risk of lithium dendrite penetrating the electrolyte layer and causing further degradation of the battery cycle performance.

[0005] Therefore, it is necessary to design a solid-state battery and a preparation method thereof to solve the above problems. SUMMARY

[0006] In view of the above shortcomings of the prior art, the present application provides a solid-state battery and a preparation method thereof to solve the technical problem that the positive active material layer with added sulfide electrolyte in the existing solid-state battery cannot balance the energy density and conductivity performance.

[0007] To achieve the above object and other related objects, the present application provides a solid-state battery, which comprises a positive electrode sheet, wherein the positive electrode sheet comprises a positive active material layer, the positive active material layer comprises a sulfide electrolyte, and the average particle size D50 of the sulfide electrolyte satisfies 50nm≤D50<1μm; wherein the sulfide electrolyte comprises Li a P 1-b M b S c O d X eand Li f P 1-g E g S w O y Q z one or more of Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Zn, Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb, one or more of Cl, Br, I, 5 < a < 6, 0 < b < 1, 1.5 < c < 5, 0 < d < 2.5, 4 < c + d < 5, 1 < e < 2, 5 < f < 10, 0 < g < 1, 3 < w < 6, 4 < w + y < 6, 0 < z < 2, M comprises at least one of Al, Ga, In, Ti, Sc, As, Sb, Bi, As, V, Nb, X comprises at least one of Cl, Br, I, E comprises at least one of Mg, Ca, Sr, Ba, Zn, Cr, Sn, Pb, Q comprises at least one of Cl, Br, I.

[0008] In an example of the present application, in the sulfide electrolyte, 0 < b ≤ 0.1, and M comprises at least one of Sb, In and Bi; and / or, 0.01 ≤ g ≤ 0.1, and E comprises at least Mg or Ca.

[0009] In an example of the present application, in the sulfide electrolyte, X comprises at least Cl, and Q comprises at least Cl.

[0010] In an example of the present application, the sulfide electrolyte has an average particle size D50 of 50 nm to 500 nm.

[0011] In an example of the present application, the positive electrode active material layer comprises a positive electrode active material, the mass content of the positive electrode active material in the positive electrode active material layer is 50% to 97%, and the mass content of the sulfide electrolyte in the positive electrode active material layer is 1% to 50%.

[0012] The present application also provides a preparation method of the solid-state battery of any one of the examples, the preparation method comprising: providing a positive electrode sheet, a solid-state electrolyte film and a negative electrode sheet; assembling the positive electrode sheet, the solid-state electrolyte film and the negative electrode sheet into an electric core, and packaging the electric core to obtain a solid-state battery.

[0013] The preparation method of the positive electrode sheet comprises:

[0014] preparing a sulfide electrolyte; adding a positive electrode raw material comprising a positive electrode active material, a positive electrode conductive agent and the sulfide electrolyte, and a dispersant into a solvent to obtain a mixed solution; the solvent comprises a protic solvent and an aprotic solvent, and the mass ratio of the protic solvent to the aprotic solvent is 1:(1-10); removing the solvent in the mixed solution to obtain a composite positive electrode raw material; mixing a positive electrode adhesive with the composite positive electrode raw material to prepare a positive electrode coating, and coating the positive electrode coating on a positive electrode current collector to obtain a positive electrode sheet.

[0015] In an example of the present application, the mass ratio of the composite cathode raw material to the solvent is 1:(1-20).

[0016] In an example of the present application, the protic solvent includes at least one of ethanol and methanol, and the aprotic solvent includes at least one of toluene, xylene, benzene, acetonitrile, diethyl ether, and carbon tetrachloride.

[0017] In an example of the present application, the dispersant includes at least one of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, cetyltrimethylammonium sulfonate, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium octyl sulfonate, polyethylene glycol octanol ether, polysorbate, polyoxyethylene stearyl alcohol ether, sodium cocoate, sodium palmitate, sodium olive oil acid, sodium dodecyl sulfonate, and sodium polyacrylate; the mass content of the dispersant relative to the cathode raw material is 0.01%-0.5%.

[0018] In an example of the present application, the sulfide electrolyte includes Li a P 1-b M b S c O d X e and Li f P 1-g E g S w O y Q z , 5<f<10, 0<g<1, 3<w<6, 4<w+y<6, 0<z<2, M includes at least one of Al, Ga, In, Ti, Sc, As, Sb, Bi, As, V, Nb, X includes at least one of Cl, Br, I, E includes at least one of Mg, Ca, Sr, Ba, Zn, Cr, Sn, Pb, and Q includes at least one of Cl, Br, I.

[0019] In an example of the present application, the preparation method of Li a P 1-b M b S c O d X e includes: mixing and sintering a lithium source, a phosphorus source, a M source, a sulfur source, an oxygen source, and an X source according to a preset stoichiometric ratio, to obtain Li a P 1-b M b S c O d X e ; and / or, the preparation method of Li f P 1-g E g Sw O y Q z The preparation method of the lithium ion battery positive electrode active material includes the following steps: mixing and sintering a lithium source, a phosphorus source, an E source, a sulfur source, an oxygen source and a Q source according to a preset stoichiometric ratio, so as to obtain Li f P 1-g E g S w O y Q z .

[0020] The solid-state battery nanocrystallizes the doped modified sulfide electrolyte in the positive electrode active material layer, so as to form a closely distributed ion transmission network and a stable electrode / electrolyte interface in the positive electrode active material layer, realizes that the battery can be well conducted and cycled by adding less sulfide electrolyte in the positive electrode active material layer, improves the energy density and cycle life of the battery; meanwhile, the nanocrystallized sulfide electrolyte in the positive electrode active material layer has higher structural strength, can avoid cracking and pulverization of itself in the charging and discharging cycle process, and further improves the storage and cycle life of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only some embodiments of the present application, and for those skilled in the art, other embodiments can be obtained without creative labor on the basis of these drawings.

[0022] Figure 1 It is a flowchart of the preparation method of the positive electrode sheet in an embodiment of the present application.

[0023] Figure 2 It is a 1C / 1C cycle test curve of the lithium ion battery in embodiment 3 of the present application. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0025] In the present application, it should be noted that the terms "first", "second" only appear for the purpose of description and distinction, and cannot be understood as indicating or implying relative importance.

[0026] In the present invention, a protic solution refers to a solution containing protons (i.e., hydrogen ions, H + ) in the solution. Such a solution is usually acidic because protons are the main component of acidic substances. A protic solution can be generated by the ionization of an acid or other chemical reactions.

[0027] In the present invention, an aprotic solution refers to a solution not containing protons in the solution. Such a solution can be neutral, basic, or of other properties. The main component in an aprotic solution can be an anion (such as a hydroxide ion, OH - ) or other compounds.

[0028] In one aspect, the present invention provides a solid-state battery, wherein the positive electrode active material layer is nano-sized by doping modification of the sulfide electrolyte to form a closely distributed ion transport path between the positive electrode active material in the positive electrode active material layer and a stable electrode / electrolyte interface, which realizes good conductive cycling of the battery with less sulfide electrolyte added in the positive electrode active material layer, improves the energy density and cycle life of the battery; at the same time, the nano-sized sulfide electrolyte in the positive electrode active material layer has higher structural strength, which can avoid its own cracking and pulverization during the charging and discharging cycle, further improving the storage and cycle life of the battery.

[0029] The above-mentioned solid-state battery is a solid-state lithium ion secondary battery, which comprises a positive electrode sheet, a negative electrode sheet, and a solid-state electrolyte film. The solid-state electrolyte film is arranged between the positive electrode sheet and the negative electrode sheet to isolate the positive electrode sheet and the negative electrode sheet and serve as a lithium ion conductor between the positive electrode sheet and the negative electrode sheet.

[0030] The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer coated on at least one side of the positive electrode current collector. The positive electrode active material layer comprises a positive electrode active material, a positive electrode binder, a positive electrode conductive agent, and a sulfide electrolyte.

[0031] The average particle size D50 of the sulfide electrolyte satisfies 50 nm≤D50<1 μm, for example, the average particle size D50 of the sulfide electrolyte can be 50 nm, 80 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm or 900 nm. Alternatively, in some embodiments, the average particle size D50 of the sulfide electrolyte is 50 nm-500 nm, for example, can be 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or 500 nm. The nano-sized sulfide electrolyte can be uniformly distributed in the positive electrode active material layer and increase the contact area of itself with the positive electrode active material in the positive electrode active material layer, form a good ion transport network in the positive electrode active material layer and a low electrode / electrolyte interface resistance, achieve a good conductive effect by adding less sulfide electrolyte in the positive electrode active material layer, effectively improve the proportion of the positive electrode active material in the positive electrode and improve the energy density and cycle life of the solid-state battery. At the same time, the nano-sized sulfide electrolyte has better mechanical strength and can better resist the strain influence caused by stress in the positive electrode active material layer, thereby reducing the risk of sulfide electrolyte particle pulverization and rupture, further improving the cycle life of the solid-state battery. It should be noted that the average particle size D50 refers to the particle size corresponding to the cumulative particle size distribution percentage of 50% of a sample, also known as the median diameter or median particle size. The average particle size D50 of the sulfide electrolyte can be obtained by dry method testing using a HELOS-RODOS type dry method laser particle size analyzer.

[0032] The sulfide electrolyte is selected from one or more of the compounds Li a P 1-b M b S c O d X e and the compound Li f P 1-g E g S w O y Q z of formula II, wherein 5

[0033] In the compound of formula I, M, X represent doping elements, the M and X elements can be any one or a combination of multiple of the above listed elements, for example, the M element can be Al, Ga, In, Ti, Sc, As, Sb, Bi, As, V or Nb, or co-doping of Sb and In, or co-doping of Sb and Ti, or co-doping of Sb and Bi, or co-doping of In and Bi, or co-doping of Ti and Nb, or co-doping of Sb, Nb and V, or co-doping of Sb, In and Bi, etc.; the X element can be Cl, Br or I, or co-doping of Cl and Br, or co-doping of Cl and I, or co-doping of Br and I, or co-doping of Cl, Br and I. Among them, b represents the doping amount of the M element, for example, b can be 0.01, 0.05, 0.1, 0.2, 0.5 or 0.8, etc.; e represents the doping amount of the X element, for example, e can be 1.1, 1.3, 1.5, 1.7 or 1.9.

[0034] In the compound of formula II, E, Q represent doping elements, the E and Q elements can be any one or a combination of multiple of the above listed elements, for example, the E element can be Mg, Ca, Sr, Ba, Zn, Cr, Sn or Pb, or co-doping of Mg and Ca, or co-doping of Mg and Zn, or co-doping of Mg and Sn, or co-doping of Ca and Ba, or co-doping of Zn and Cr, or co-doping of Mg, Ca and Sn, or co-doping of Mg, Ca and Zn, etc.; the Q element can be Cl, Br or I, or co-doping of Cl and Br, or co-doping of Cl and I, or co-doping of Br and I, or co-doping of Cl, Br and I. Among them, g represents the doping amount of the E element, for example, g can be 0.01, 0.05, 0.1, 0.2, 0.5 or 0.8, etc.; z represents the doping amount of the Q element, for example, z can be 1.1, 1.3, 1.5, 1.7 or 1.9.

[0035] Compared with the sulfide electrolyte without doping modification, the sulfide electrolyte doped with metal elements and halogen elements has relatively stable chemical properties and higher ionic conductivity, can form a stable electrode / electrolyte interface in the positive active material layer, thereby reducing the probability of lithium dendrite formation in the charging and discharging process. Even at the nanometer size, the sulfide electrolyte can still inhibit the formation of lithium dendrites in the positive active material layer during the charging and discharging cycle process, effectively reduces the risk of short circuit of the battery during the charging and discharging cycle, and improves the cycle life of the battery.

[0036] In some embodiments, in the sulfide electrolyte of the compound of formula I, the X element at least includes Cl, for example, the X element can be Cl, or co-doping of Cl and Br, or co-doping of Cl and I, or co-doping of Cl, Br and I.

[0037] In some embodiments, in the sulfide electrolyte of the compound of formula I, the M element is selected from at least one of Sb, In and Bi, i.e. the M element can be any one of the above-mentioned elements, for example can be Sb, In or Bi, or the M element can be a combination of any two or more of the above-mentioned elements, for example co-doping of Sb and In, or co-doping of Sb and Bi, or co-doping of In and Bi, or co-doping of Sb, In and Bi. Among them, the doping elements Sb, Bi and In are combined with O to form firm M-S bonds and P-O bonds in the sulfide electrolyte, which effectively enhances the structural stability of the sulfide electrolyte, inhibits the reaction of the sulfide electrolyte with water, and improves its oxidation resistance and hydrolysis resistance in air environment; at the same time, the doping elements Sb, Bi and In can increase the lattice distortion of the ion conductor by replacing P in the sulfide electrolyte, widen the transmission channel of lithium ions, reduce the activation energy of lithium ions, and improve the ionic conductivity of the sulfide electrolyte. Optionally, the M element at least includes Sb, and the doping element Sb can form a Li-Sb alloy layer on the surface of the sulfide electrolyte in addition to the above-mentioned improvement effect on the sulfide electrolyte, which can effectively hinder the growth of lithium dendrites during the cycle process.

[0038] In some embodiments, in the sulfide electrolyte of the compound of formula I, the doping amount b of the M element satisfies 0 < b < 0.1, for example the doping amount b of the M element can be 0.01, 0.02, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1. Optionally, when the M element is a +5 valence element, the doping amount b of the M element can be 0.04; when the M element is a +3 valence element, the doping amount b of the M element can be 0.02.

[0039] In some embodiments, in the sulfide electrolyte of the compound of formula II, the Q element at least includes Cl, for example the Q element can be Cl, or co-doping of Cl and Br, or co-doping of Cl and I, or co-doping of Cl, Br and I.

[0040] In some embodiments, in the sulfide electrolyte of the compound of formula II, the element E at least includes Mg or Ca, for example, the element E can be Mg or Ca, or co-doping of Mg and Ca, or co-doping of Mg and Ba, or co-doping of Mg and Sn, or co-doping of Mg and Zn, or co-doping of Ca and Ba, or co-doping of Ca and Sn, or co-doping of Ca and Zn, or co-doping of Mg, Ca and Cr. Among them, the doping elements Mg and Ca are combined with O to form firm E-S bonds and P-O bonds in the sulfide electrolyte, which effectively enhances the structural stability of the sulfide electrolyte, inhibits the reaction of the sulfide electrolyte with water, and improves its oxidation resistance and hydrolysis resistance in the air environment; at the same time, the doping elements Mg and Ca can replace P in the sulfide electrolyte to increase the lattice distortion of the ion conductor, widen the transmission channel of lithium ions, reduce the activation energy of lithium ions, and improve the ionic conductivity of the sulfide electrolyte.

[0041] In some embodiments, in the sulfide electrolyte of the compound of formula II, the doping amount g of the element E satisfies 0.01≤g≤0.1, for example, the doping amount g of the element E can be 0.01, 0.02, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1. Alternatively, the doping amount g of the element E can be 0.02.

[0042] In some embodiments, the positive electrode active material layer includes a positive electrode active material, and the mass content of the positive electrode active material in the positive electrode active material layer is 50% to 97%, for example, it can be 50%, 60%, 70%, 80%, 90%, 95% or 97%; the mass content of the sulfide electrolyte in the positive electrode active material layer is 1% to 50%, for example, it can be 1%, 3%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%. Based on the nanoscale characteristics of the sulfide electrolyte, the positive electrode active material layer can still achieve good ion transmission effect when a small amount of sulfide electrolyte is added, thereby effectively improving the proportion of the positive electrode active material in the positive electrode sheet and improving the energy density of the solid-state battery.

[0043] In some embodiments, the positive electrode active material layer includes a positive electrode active material, a sulfide electrolyte, a positive electrode binder, a positive electrode conductive agent, and a dispersant, and the mass ratio of the positive electrode active material, the sulfide electrolyte, the positive electrode binder, and the positive electrode conductive agent can be (50-97):(1-50):(0-3):(1-3):(0.01-0.5). The positive electrode active material is, for example, selected from one or more combinations of lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium-rich manganese-based oxide (LRMO), and lithium-containing phosphates. The positive electrode binder is, for example, selected from one or more combinations of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyurethane, polyvinyl alcohol (PVA), sodium alginate (Alg), ethylene-propylene-diene monomer, styrene-butadiene rubber, polyvinylidene fluoride, fluoro rubber, beta-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinylidene fluoride-trifluorochloroethylene copolymer. The positive electrode conductive agent is, for example, selected from one or more combinations of carbon black, ketjen black, acetylene black, graphene, carbon nanotubes, carbon nanofibers, porous carbon, and the like. In an example, the positive electrode conductive agent includes carbon black and carbon nanofibers, and the mass ratio of the carbon black and the carbon nanofibers is 1:(0.2-1.5).

[0044] In some embodiments, the negative electrode tab can be a metal lithium tab, a metal indium tab, a lithium-containing alloy tab (such as a lithium-tin-indium alloy tab, a lithium-silicon alloy tab, a lithium-tin alloy tab, a lithium-aluminum alloy tab). For example, in an example, the negative electrode tab is selected from a metal lithium tab.

[0045] In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode active material layer coated on at least one side of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, a sulfide electrolyte, a negative electrode binder, and a negative electrode conductive agent. The mass ratio of the negative electrode active material, the solid-state electrolyte, the negative electrode binder, and the negative electrode conductive agent can be (50-97):(1-50):(0-3):(1-10). The negative electrode active material can be selected from one or more of tin, artificial graphite (single-crystal graphite, polycrystal graphite, pyrolytic graphite, graphite fiber, etc.), natural graphite (block graphite, flake graphite, earthy graphite, etc.), soft carbon, hard carbon, pure silicon (crystalline silicon, amorphous silicon, or organic silicon), silicon oxide compounds, silicon carbon compounds, and nano metal oxides (Fe2O3, CuO, SnO2, Mn3O4 nanoparticles). The negative electrode binder can be selected from one or more of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyurethane, polyvinyl alcohol (PVA), sodium alginate (Alg), ethylene-propylene-diene monomer, styrene-butadiene rubber, polyvinylidene fluoride, fluoro rubber, beta-cyclodextrin polymer (beta-CDp), polypropylene emulsion (LA132), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinylidene fluoride-trifluorochloroethylene copolymer. The negative electrode conductive agent can be selected from one or more of graphite, carbon black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers.

[0046] In another aspect, the present application also provides a method for preparing a solid-state battery, the method including: providing a positive electrode tab, a solid-state electrolyte film, and a negative electrode tab; assembling the positive electrode tab, the solid-state electrolyte film, and the negative electrode tab into an electric core, and packaging the electric core to obtain a solid-state battery.

[0047] It should be noted that the negative electrode tab, the solid-state electrolyte film, and the solid-state battery assembly process in the solid-state battery can be prepared by conventional methods in the art.

[0048] In some embodiments, the negative electrode tab is prepared as follows: the negative electrode material, solid-state electrolyte, negative electrode binder, and negative electrode conductive agent are mixed in a mass ratio of (50-97):(1-50):(0-3):(1-10), deionized water is added, the solid content of the slurry is adjusted to 55%, and then the negative electrode slurry is obtained by fully stirring and mixing under the action of a vacuum stirrer; the negative electrode slurry is uniformly coated on an 8 μm negative electrode current collector copper foil; after drying at room temperature, it is transferred to an oven for drying, and then subjected to cold pressing, slitting and other processes to obtain the negative electrode tab. The negative electrode active material is selected from one or more of tin, artificial graphite (single crystal graphite, polycrystalline graphite, pyrolytic graphite, graphite fibers, etc.), natural graphite (block graphite, flake graphite, earthy graphite, etc.), soft carbon, hard carbon, pure silicon (crystalline silicon, amorphous silicon or organic silicon), silicon oxide compounds, silicon carbon compounds, and nano metal oxides (Fe2O3, CuO, SnO2, Mn3O4 nanoparticles). The negative electrode binder is selected from one or more of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylpyrrolidone (PVP), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyurethane, polyvinyl alcohol (PVA), sodium alginate (Alg), ethylene-propylene-diene monomer, styrene-butadiene rubber, polyvinylidene fluoride, fluororubber, β-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinylidene fluoride-trifluorochloroethylene copolymer. The negative electrode conductive agent is selected from one or more of graphite, carbon black, acetylene black, graphene, carbon nanotubes, and carbon nanofibers.

[0049] In other embodiments, a metal lithium sheet, a metal indium sheet, or a lithium-containing alloy sheet (such as a lithium-tin-indium alloy sheet, a lithium-silicon alloy sheet, a lithium-tin alloy sheet, or a lithium-aluminum alloy sheet) is used as the negative electrode tab.

[0050] In some embodiments, the solid-state electrolyte film is prepared as follows: the sulfide electrolyte is cold-pressed at a pressure of 300 MPa to 400 MPa to obtain a solid-state electrolyte film.

[0051] The assembly method of the solid-state battery is described as follows: one side of the solid-state electrolyte film is integrated with a positive electrode sheet, for example, the solid-state electrolyte film is placed on the positive active material layer of the positive electrode sheet, and the solid-state electrolyte film and the positive electrode sheet are pressed into one body at a pressure of 300 MPa; then the other side of the solid-state electrolyte film is integrated with a negative electrode sheet, for example, the negative electrode sheet is placed on the other side of the solid-state electrolyte film, so that the negative active material layer of the negative electrode sheet is in contact with the solid-state electrolyte film, and the negative electrode sheet, the solid-state electrolyte film and the positive electrode sheet are pressed into one body at a pressure of 300 MPa; the pressed battery is sealed and packaged in a vacuum or inert atmosphere, and a solid-state lithium ion battery is obtained.

[0052] The solid-state battery assembled by using the composite positive electrode with nanosulfide electrolyte has a stable cycle number increased by more than 5 times at a 1C / 1C current rate.

[0053] As shown in Figure 1 , the preparation method of the positive electrode sheet in the above solid-state battery includes the following steps:

[0054] S1, preparing a sulfide electrolyte;

[0055] S2, adding a positive electrode raw material containing a positive active material, a positive conductive agent and the sulfide electrolyte, and a dispersant to a solvent to obtain a mixed solution; the solvent includes a protic solvent and an aprotic solvent, and the mass ratio of the protic solvent to the aprotic solvent is 1:(1-10);

[0056] S3, removing the solvent in the mixed solution to obtain a composite positive electrode raw material;

[0057] S4, mixing a positive electrode adhesive with the composite positive electrode raw material to prepare a positive electrode coating, and coating the positive electrode coating on a positive current collector to obtain a positive electrode sheet.

[0058] In the preparation method, the protic & aprotic solvent is used to dissolve and reprecipitate the mixed sulfide electrolyte in the positive electrode raw material. The dispersant dissolved in the mixed solution can adsorb sulfide electrolyte molecules in the nucleation and particle formation process of the sulfide electrolyte to avoid excessive aggregation of the sulfide electrolyte during the desolvation process, so as to effectively limit the particle size of the precipitated sulfide electrolyte in the composite positive electrode raw material, and make the nanosulfide electrolyte uniformly adhere to the surface of the positive active material particles when precipitated, and then form a dense and uniform ion transmission network around the positive active material particles in the subsequently prepared positive active material layer.

[0059] In step S1, the prepared sulfide electrolyte includes Li a P 1-b M b S c O dX e and Li f P 1-g E g S w O y Q z one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, As, V, Nb, at least one of Cl, Br, I, at least one of Mg, Ca, Sr, Ba, Zn, Cr, Sn, Pb, and at least one of Cl, Br, I.

[0060] In some embodiments, the sulfide electrolyte has Li a P 1-b M b S c O d X e A method for preparing the sulfide electrolyte Li a P 1-b M b S c O d X e includes the following steps: mixing a lithium source, a phosphorus source, a M source, a sulfur source, an oxygen source, and an X source in a predetermined stoichiometric ratio under a protective atmosphere and placing them in a ball milling jar for ball milling treatment; and then sintering the mixture after ball milling to obtain the sulfide electrolyte Li a P 1-b M b S c O d X e .

[0061] In some embodiments, the sulfide electrolyte has Li f P 1-g E g S w O y Q z A method for preparing the sulfide electrolyte Li f P 1-g E g S w O y Q z .

[0062] In the above embodiments, the lithium source can be selected from lithium-containing compounds, and further, the lithium source is selected from one or more of LiCl, LiBr, Lil, Li2S, for example, the lithium source is selected from Li2S, or LiCl, or a combination of Li2S and LiCl, and the like.

[0063] The phosphorus source is selected from phosphorus-containing compounds, and further, the phosphorus source is selected from one or more of P2S5, P2O5, and specifically can be P2S5, or P2O5, or a combination of P2S5 and P2O5, and the like.

[0064] The sulfur source is selected from sulfur-containing compounds, and further, the sulfur source is selected from at least one of S, Li2S, P2S5, soft acid metal oxides, and specifically can be S, or Li2S, or P2S5, or a combination of Li2S and P2S5, and the like.

[0065] The oxygen source is selected from oxygen-containing compounds, and further, the oxygen source is selected from at least one of Li2O, LiOH, P2O5, soft acid metal oxides, and specifically can be Li2O, or LiOH, or P2O5, or a combination of Li2O and LiOH, and the like.

[0066] The M source is selected from M element-containing compounds, and further, the M source is selected from at least one of M element-containing halides, M element-containing sulfides, and M element-containing metal oxides.

[0067] The E source is selected from E element-containing compounds, and further, the E source is selected from at least one of E element-containing halides, E element-containing sulfides, and E element-containing metal oxides.

[0068] The X source and the Q source are selected from at least one of LiCl, LiBr, and LiI, and for example, the X source and the Q source can be LiCl, or LiBr, or LiI, or a combination of LiCl and LiBr, or a combination of LiBr and LiI, or a combination of LiCl, LiBr, and LiI, and the like.

[0069] In some embodiments, the ball milling treatment of the sulfide electrolyte raw materials in step S1 can obtain particles with uniform particle size and small size. Specifically, after the raw materials are uniformly mixed according to the stoichiometric ratio, they are added into a ball milling tank for ball milling treatment. During ball milling, the ball-to-material ratio and the amount of solvent added will affect the effect of wet ball milling. The larger the ball-to-material ratio, the higher the grinding efficiency and the finer the material particle size; the ball-to-material ratio can be determined according to the properties of the raw materials and the process requirements. For relatively hard raw materials, a higher ball-to-material ratio can be selected to improve the grinding effect; and for relatively soft raw materials, a lower ball-to-material ratio can be selected. In an embodiment, the ball-to-material mass ratio in the ball milling tank is (1-30):1, for example, the ball-to-material ratio can be 1:1, 10:1, 20:1, or 30:1, and the like; the ball milling time is 5-20h, for example, it can be 5h, 10h, 15h, or 20h, and the like. The ball milling speed is 1-1000rpm, and further, the ball milling speed is 100-800rpm, for example, the ball milling speed can be 300rpm, 500rpm, or 800rpm, and the like.

[0070] In some embodiments, the sintering treatment temperature of the raw material in step S1 is 200-600°C, for example, it can be 200°C, 300°C, 400°C, 500°C or 600°C. The sintering treatment time is 0.1-24h, further can be 5-20h, for example, it can be 5h, 10h, 15h or 20h, etc.

[0071] Step S2 specifically includes: mixing the positive active material, the sulfide electrolyte and the positive conductive agent in the positive electrode raw material into the solvent according to the mass ratio of (50-97):(1-50):(0.05-10); after the sulfide electrolyte is completely dissolved in the solvent, continue to add the dispersant in the solvent to obtain a mixed solution. The mass ratio of the protic solvent and the aprotic solvent is any value in the range of 1:(1-10), for example, it can be 1:1, 1:2, 1:4, 1:5, 1:6, 1:8 or 1:10. The protic solvent in the solvent plays a role of dissolving the sulfide electrolyte, and the aprotic solvent plays a role of surfactant, inducing the precipitation of the nanoscale sulfide electrolyte particles on the surface of the positive active material. Limiting the mass ratio of the protic solvent and the aprotic solvent in the solvent to any value in the appropriate range of 1:(1-10) can take into account the nanocrystallization and uniform precipitation of the sulfide electrolyte in the composite positive electrode raw material. If the content of the protic solvent is too high (the mass ratio of the protic solvent to the aprotic solvent is greater than 1:1), the sulfide electrolyte cannot be completely precipitated during the precipitation process, thereby affecting the conductivity of the positive electrode plate. When the content of the protic solvent is too low (the mass ratio of the protic solvent to the aprotic solvent is less than 1:10), the solvent cannot fully dissolve the sulfide electrolyte, thereby making part of the sulfide electrolyte unable to be nanocrystallized.

[0072] In some embodiments, in the mixed solution, the mass ratio of the finally precipitated composite positive electrode raw material to the solvent is 1:(1-20), for example, it can be 1:1, 1:2, 1:3, 1:5, 1:8, 1:10, 1:15 or 1:20. The composite positive electrode raw material includes the positive active material, the sulfide electrolyte, the positive conductive agent and the dispersant.

[0073] In some embodiments, the protic solvent includes at least one of ethanol and methanol, and optionally, the protic solvent can be ethanol; the aprotic solvent includes at least one of toluene, xylene, benzene, acetonitrile, diethyl ether and carbon tetrachloride, and optionally, the aprotic solvent is selected from at least one of acetonitrile and carbon tetrachloride, for example, the aprotic solvent can be acetonitrile, or carbon tetrachloride, or a mixture of acetonitrile and carbon tetrachloride in any ratio.

[0074] In some embodiments, the dispersant includes at least one of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, cetyltrimethylammonium sulfonate, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium octyl sulfonate, polyethylene glycol octanol ether, polysorbate, polyoxyethylene stearyl alcohol ether, sodium cocoate, sodium palmitate, sodium olive oil acid, sodium dodecyl sulfonate, and sodium polyacrylate. The mass content of the dispersant in the positive electrode raw material is 0.01% to 0.5%, for example, the mass content of the dispersant can be 0.01%, 0.05%, 0.2%, 0.3%, 0.4%, or 0.5%.

[0075] Step S3 specifically includes homogenizing the mixed solution using a shaker, and then heating the homogenized mixed solution under a vacuum environment until the solvent in the mixed solution is completely removed, thereby obtaining the re-precipitated composite positive electrode raw material, and the average particle size D50 of the sulfide electrolyte in the composite positive electrode raw material satisfies 50 nm≤D50<1 μm. In the re-precipitation process, the dissolved sulfide electrolyte in the mixed solution cannot aggregate to form large-size particles due to the effect of the dispersant, and then uniformly precipitates in the composite positive electrode raw material in the form of nano-sized small-size particles; meanwhile, the sulfide electrolyte is also affected by the aprotic solvent during the precipitation process, and then uniformly adheres to the surface of the positive electrode active material particles activated by the aprotic solvent, and finally forms a dense and uniform ion transport network around the positive electrode active material particles in the positive electrode active material layer formed subsequently.

[0076] In some embodiments, the vacuum drying temperature for the mixed solution is any value in the range of 25 to 200°C, for example, it can be 25°C, 30°C, 40°C, 50°C, 75°C, 100°C, 120°C, 140°C, 150°C, 180°C, or 200°C. The vacuum drying time for the mixed solution is any value in the range of 0.1 to 24 h, for example, it can be 0.1 h, 0.5 h, 1 h, 2 h, 5 h, 8 h, 10 h, 13 h, 15 h, 20 h, or 24 h.

[0077] In step S4, the composite positive electrode raw material is uniformly mixed with the positive electrode binder at a mass ratio of 100:(1-3) to obtain a positive electrode coating, and the positive electrode coating is coated on the positive electrode current collector to obtain a positive electrode sheet after drying, cold pressing, and cutting.

[0078] The technical solutions of the present application are described in detail below through several specific examples and comparative examples. Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by conventional methods in the art.

[0079] Example 1

[0080] This example provides a positive electrode sheet, and the preparation method of the positive electrode sheet is as follows:

[0081] S1, under argon atmosphere, 2 mol Li2S, 1.5 mol LiCl, 0.48 mol P2S5, 0.02 mol Sb2O5 raw materials were added into a ball mill tank, ball to material ratio 30:1, rotation speed 500 rpm, ball milling for 20 h; then the precursor powder obtained by ball milling was sintered at 500°C for 10 h to obtain sulfide electrolyte Li 5.5 P 0.96 Sb 0.04 S 4.40 O 0.10 Cl 1.5 .

[0082] S2, 2g of positive electrode raw material was weighed and added to 10g of solvent, after the sulfide electrolyte in the positive electrode raw material was completely dissolved, 0.01% of the dispersant polyethylene glycol octanol ether based on the mass of the positive electrode raw material was continuously added to the solvent to obtain a mixed solution; wherein the positive electrode raw material includes 93wt% of positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 5wt% of sulfide electrolyte Li 5.5 P 0.96 Sb 0.04 S 4.40 O 0.10 Cl 1.5 , 2wt% of positive electrode conductive agent (mass ratio of super-P and VGCF 1:1); the solvent includes protic solvent ethanol and aprotic solvent acetonitrile, and the mass ratio of the protic solvent to the aprotic solvent is 1:9.

[0083] S3, the mixed solution was homogenized using a shaking bed, and then the mixed solution was placed in a vacuum oven and dried at 80°C for 12h to remove the solvent in the mixed solution, to obtain a composite positive electrode raw material with nano-sulfide electrolyte;

[0084] S4, the composite positive electrode raw material and the positive electrode binder were mixed in a mass ratio of 100:1 to prepare a positive electrode coating, and the positive electrode coating was coated on the positive electrode current collector aluminum foil, and after drying, cold pressing and cutting, a positive electrode sheet with a diameter of 10mm was obtained.

[0085] Example 2

[0086] The positive electrode sheet of the same component system as in Example 1 was prepared in this example. The difference between this example and Example 1 is that in step S2, 0.05% of the dispersant polyethylene glycol octanol ether based on the mass of the positive electrode raw material was added to the solvent.

[0087] Example 3

[0088] The positive electrode sheet of the same component system as Example 1 was prepared in this example. The difference between this example and Example 1 is that in Step S2, 0.1% of the dispersant polyethylene glycol octanol ether by mass of the positive electrode raw material was added to the solvent.

[0089] Example 4

[0090] The positive electrode sheet of the same component system as Example 1 was prepared in this example. The difference between this example and Example 1 is that in Step S2, 0.2% of the dispersant polyethylene glycol octanol ether by mass of the positive electrode raw material was added to the solvent.

[0091] Example 5

[0092] The positive electrode sheet of the same component system as Example 1 was prepared in this example. The difference between this example and Example 1 is that in Step S2, 0.5% of the dispersant polyethylene glycol octanol ether by mass of the positive electrode raw material was added to the solvent.

[0093] Example 6

[0094] The positive electrode sheet of the same component system as Example 1 was prepared in this example. The difference between this example and Example 1 is that in Step S2, the positive electrode raw material included 50wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 48wt% of the sulfide electrolyte Li 5.5 P 0.96 Sb 0.04 S 4.40 O 0.10 Cl 1.5 , 2wt% of the positive electrode conductive agent (super-P and VGCF at a mass ratio of 1:1).

[0095] Example 7

[0096] The positive electrode sheet of the same component system as Example 1 was prepared in this example. The difference between this example and Example 1 is that in Step S2, the positive electrode raw material included 70wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 28wt% of the sulfide electrolyte Li 5.5 P 0.96 Sb 0.04 S 4.40 O 0.10 Cl 1.5 , 2wt% of the positive electrode conductive agent (super-P and VGCF at a mass ratio of 1:1).

[0097] Example 8

[0098] The positive electrode sheet of the same component system as Example 1 was prepared. The difference between this example and Example 1 is that in Step S2, the positive electrode raw material includes 90wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 8wt% of the sulfide electrolyte Li 5.5 P 0.96 Sb 0.04 S 4.40 O 0.10 Cl 1.5 , 2wt% of the positive electrode conductive agent (super-P and VGCF at a mass ratio of 1:1).

[0099] Example 9

[0100] The positive electrode sheet of the same component system as Example 1 was prepared. The difference between this example and Example 1 is that in Step S2, the positive electrode raw material includes 97wt% of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, 1wt% of the sulfide electrolyte Li 5.5 P 0.96 Sb 0.04 S 4.40 O 0.10 Cl 1.5 , 2wt% of the positive electrode conductive agent (super-P and VGCF at a mass ratio of 1:1).

[0101] Example 10

[0102] The positive electrode sheet of the same component system as Example 3 was prepared. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte prepared from 2mol Li2S, 1.5mol LiCl, 0.495mol P2S5, 0.005mol Sb2O5raw materials has the chemical formula of Li 5.5 P 0.99 Sb 0.01 S 4.475 O 0.025 Cl 1.5 .

[0103] Example 11

[0104] The positive electrode sheet of the same component system as Example 3 was prepared. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte prepared from 2mol Li2S, 1.5mol LiCl, 0.47mol P2S5, 0.03mol Sb2O5raw materials has the chemical formula of Li 5.5 P 0.94 Sb0.06 S 4.35 O 0.15 Cl 1.5 .

[0105] Example 12

[0106] The positive electrode sheet of the same component system as Example 3 was prepared in this example. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2 mol of Li2S, 1.5 mol of LiCl, 0.45 mol of P2S5, and 0.05 mol of Sb2O5 raw materials, and the chemical formula of the sulfide electrolyte was Li 5.5 P 0.9 Sb 0.1 S 4.25 O 0.25 Cl 1.5 .

[0107] Example 13

[0108] The positive electrode sheet of the same component system as Example 3 was prepared in this example. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2 mol of Li2S, 1.3 mol of LiCl, 0.1 mol of LiBr, 0.1 mol of LiI, 0.48 mol of P2S5, and 0.02 mol of Sb2O5 raw materials, and the chemical formula of the sulfide electrolyte was Li 5.5 P 0.96 Sb 0.04 S 4.4 O 0.1 Cl 1.3 Br 0.1 I 0.1 .

[0109] Example 14

[0110] The positive electrode sheet of the same component system as Example 3 was prepared in this example. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2.4 mol of Li2S, 1.1 mol of LiCl, 0.48 mol of P2S5, and 0.02 mol of Sb2O5 raw materials, and the chemical formula of the sulfide electrolyte was Li 5.9 P 0.96 Sb 0.04 S 4.8 O 0.10 Cl 1.1

[0111] Example 15

[0112] A positive electrode sheet was prepared with the same component system as in Example 3. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 1.6 mol Li2S, 1.9 mol LiCl, 0.48 mol P2S5, and 0.02 mol Sb2O5 raw materials. 5.1 P 0.96 Sb 0.04 S4O 0.10 Cl 1.9

[0113] Example 16

[0114] A positive electrode sheet was prepared with the same component system as in Example 3. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2.01 mol Li2S, 1.5 mol LiCl, 0.495 mol P2S5, and 0.005 mol In2O3 raw materials. 5.52 P 0.99 In 0.01 S 4.485 O 0.015 Cl 1.5 .

[0115] Example 17

[0116] A positive electrode sheet was prepared with the same component system as in Example 3. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2.02 mol Li2S, 1.5 mol LiCl, 0.49 mol P2S5, and 0.01 mol In2O3 raw materials. 5.54 P 0.98 In 0.02 S 4.47 O 0.03 Cl 1.5 .

[0117] Example 18

[0118] A positive electrode sheet was prepared with the same component system as in Example 3. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2.06 mol Li2S, 1.5 mol LiCl, 0.47 mol P2S5, and 0.03 mol In2O3 raw materials. 5.62 P 0.94 In 0.06 S 4.41 O 0.09 Cl 1.5 .

[0119] Example 19

[0120] This example produces a positive electrode sheet of the same component system as Example 3. This example differs from Example 3 in that in Step S1, a sulfide electrolyte with the chemical formula Li 5.7 P 0.9 In 0.1 S 4.35 O 0.15 Cl 1.5 .

[0121] Example 20

[0122] This example produces a positive electrode sheet of the same component system as Example 3. This example differs from Example 3 in that in Step S1, a sulfide electrolyte with the chemical formula Li 5.54 P 0.98 In 0.02 S 4.47 O 0.03 Cl 1.3 Br 0. 1I 0.1 .

[0123] Example 21

[0124] This example produces a positive electrode sheet of the same component system as Example 3. This example differs from Example 3 in that in Step S1, a sulfide electrolyte with the chemical formula Li 5.52 P 0.99 Bi 0.01 S 4.485 O 0.015 Cl 1.5 .

[0125] Example 22

[0126] This example produces a positive electrode sheet of the same component system as Example 3. This example differs from Example 3 in that in Step S1, a sulfide electrolyte with the chemical formula Li 5.54 P 0.98 Bi0.02 S 4.47 O 0.03 Cl 1.5 .

[0127] Example 23

[0128] The positive electrode sheet of the same component system as Example 3 was prepared in this example. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2.06 mol of Li2S, 1.5 mol of LiCl, 0.47 mol of P2S5, and 0.03 mol of Bi2O3 raw materials, and the chemical formula of the sulfide electrolyte was Li 5.62 P 0.94 Bi 0.06 S 4.41 O 0.09 Cl 1.5 .

[0129] Example 24

[0130] The positive electrode sheet of the same component system as Example 3 was prepared in this example. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2.1 mol of Li2S, 1.5 mol of LiCl, 0.45 mol of P2S5, and 0.05 mol of Bi2O3 raw materials, and the chemical formula of the sulfide electrolyte was Li 5.7 P 0.9 Bi 0.1 S 4.35 O 0.15 Cl 1.5 .

[0131] Example 25

[0132] The positive electrode sheet of the same component system as Example 3 was prepared in this example. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2.02 mol of Li2S, 1.3 mol of LiCl, 0.1 mol of LiBr, 0.1 mol of LiI, 0.49 mol of P2S5, and 0.01 mol of Bi2O3 raw materials, and the chemical formula of the sulfide electrolyte was Li 5.54 P 0.98 Bi 0.02 S 4.47 O 0.03 Cl 1.3 Br 0. 1I 0.1 .

[0133] Example 26

[0134] A positive electrode sheet was prepared with the same component system as in Example 3. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2.015 mol Li2S, 1.5 mol LiCl, 0.495 mol P2S5, and 0.01 mol MgO raw materials. 5.53 P 0.99 Mg 0.01 S 4.49 O 0.01 Cl 1.5 .

[0135] Example 27

[0136] A positive electrode sheet was prepared with the same component system as in Example 3. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2.03 mol Li2S, 1.5 mol LiCl, 0.49 mol P2S5, and 0.02 mol MgO raw materials. 5.56 P 0.98 Mg 0.02 S 4.48 O 0.02 Cl 1.5 .

[0137] Example 28

[0138] A positive electrode sheet was prepared with the same component system as in Example 3. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2.09 mol Li2S, 1.5 mol LiCl, 0.47 mol P2S5, and 0.06 mol MgO raw materials. 5.68 P 0.94 Mg 0.06 S 4.44 O 0.06 Cl 1.5 .

[0139] Example 29

[0140] A positive electrode sheet was prepared with the same component system as in Example 3. The difference between this example and Example 3 is that in Step S1, the sulfide electrolyte was prepared from 2.15 mol Li2S, 1.5 mol LiCl, 0.45 mol P2S5, and 0.1 mol MgO raw materials. 5.8 P 0.9 Mg 0.1 S 4.48 O 0.1 Cl 1.5 .

[0141] Example 30

[0142] This example produces a positive electrode sheet of the same component system as Example 3. This example differs from Example 3 in that in Step S1, a sulfide electrolyte of the formula Li 5.56 P 0.98 Mg 0.02 S 4.48 O 0.02 Cl 1.3 Br 0.1 I0 .1 .

[0143] Example 31

[0144] This example produces a positive electrode sheet of the same component system as Example 3. This example differs from Example 3 in that in Step S1, a sulfide electrolyte of the formula Li 6.96 P 0.98 Mg 0.02 S 5.88 O 0.02 Cl 0.1 .

[0145] Example 32

[0146] This example produces a positive electrode sheet of the same component system as Example 3. This example differs from Example 3 in that in Step S1, a sulfide electrolyte of the formula Li 5.16 P 0.98 Mg 0.02 S 4.08 O 0.02 Cl 1.9 .

[0147] Example 33

[0148] This example produces a positive electrode sheet of the same component system as Example 3. This example differs from Example 3 in that in Step S1, a sulfide electrolyte of the formula Li 5.56 P 0.98 Ca0.02 S 4.48 O 0.02 Cl 1.5 .

[0149] Example 34

[0150] The positive electrode sheet of the same component system as that of Example 3 was prepared in this example. The difference between this example and Example 3 is that a mixed solvent including a protic solvent methanol and an aprotic solvent acetonitrile was used as the solvent in Step S2, and the mass ratio of the protic solvent methanol to the aprotic solvent acetonitrile was 1:9.

[0151] Example 35

[0152] The positive electrode sheet of the same component system as that of Example 3 was prepared in this example. The difference between this example and Example 3 is that a mixed solvent including a protic solvent ethanol and an aprotic solvent toluene was used as the solvent in Step S2, and the mass ratio of the protic solvent ethanol to the aprotic solvent toluene was 1:9.

[0153] Example 36

[0154] The positive electrode sheet of the same component system as that of Example 3 was prepared in this example. The difference between this example and Example 3 is that a mixed solvent including a protic solvent ethanol and an aprotic solvent carbon tetrachloride was used as the solvent in Step S2, and the mass ratio of the protic solvent ethanol to the aprotic solvent carbon tetrachloride was 1:9.

[0155] Comparative Example 1

[0156] The positive electrode sheet of the same component system as that of Example 3 was prepared in this example. The difference between this example and Example 3 is that a mixed solvent including a protic solvent methanol and an aprotic solvent acetonitrile was used as the solvent in Step S2, and the mass ratio of the protic solvent methanol to the aprotic solvent acetonitrile was 1:9. 5.5 PS 4.5 Cl 1.5 .

[0157] Comparative Example 2

[0158] The positive electrode sheet of the same component system as that of Example 3 was prepared in this example. The difference between this example and Example 3 is that a mixed solvent including a protic solvent methanol and an aprotic solvent acetonitrile was used as the solvent in Step S2, and the mass ratio of the protic solvent methanol to the aprotic solvent acetonitrile was 1:9.

[0159] S1, under an argon atmosphere, 2 mol Li2S, 1.5 mol LiCl, 0.48 mol P2S5, 0.02 mol Sb2O5 raw materials were added into a ball milling tank, the ball-to-material ratio was 30:1, the rotation speed was 500 rpm, and the ball milling was performed for 20 h; then the precursor powder obtained by ball milling was sintered at a temperature of 500°C for 10 h to obtain a sulfide electrolyte Li 5.5P 0.96 Sb 0.04 S 4.40 O 0.10 Cl 1.5 , and the sulfide electrolyte with a particle size of 10 μm was screened out as a raw material for preparing the positive electrode;

[0160] S2, the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, the sulfide electrolyte Li 5.5 P 0.96 Sb 0.04 S 4.40 O 0.10 Cl 1.5 , and the positive electrode conductive agent (super-P and VGCF with a mass ratio of 1:1) were mixed in a mass ratio of 93:5:2 to obtain a composite positive electrode raw material; the composite positive electrode raw material and the positive electrode adhesive PTFE were mixed in a mass ratio of 100:1 to obtain a positive electrode coating; the positive electrode coating was coated on the positive electrode current collector aluminum foil, and after drying, cold pressing and cutting, a positive electrode tab with a diameter of 10 mm was obtained.

[0161] Comparative Example 3

[0162] The present comparative example provides a positive electrode tab with the same component system as that of Comparative Example 2, and the difference between the present comparative example and Comparative Example 2 is that in step S1, the Li 5.5 P 0.96 Sb 0.04 S 4.40 O 0.10 Cl 1.5 with a particle size of 20 μm was screened out as the sulfide electrolyte raw material.

[0163] To further verify the efficacy of the present application, the positive electrode tabs prepared from Examples 1 to 36 and Comparative Examples 1 to 3 were assembled into solid-state batteries, and the solid-state batteries assembled from Examples 1 to 36 and Comparative Examples 1 to 3 were subjected to cycle performance tests. The test results of the positive electrode tab parameters and the assembled solid-state batteries are shown in Table 1.

[0164] The solid-state battery was prepared as follows: 0.2 g of sulfide electrolyte powder was placed in a solid-state battery mold and pressed at a pressure of 300 MPa for 5 minutes to obtain a solid-state electrolyte film. The solid-state electrolyte film was integrated on one side of the positive electrode tab provided with a positive electrode active material layer, and was pressed at a pressure of 300 MPa to be integrated; a lithium metal sheet was used as a negative electrode tab, the negative electrode tab was integrated on the side of the solid-state electrolyte sheet away from the positive electrode tab, and was pressed at a pressure of 300 MPa to be integrated, to obtain an electric core; the electric core was subjected to heat packaging, and then was subjected to processes such as standing, hot and cold pressing, formation, clamping and capacity distribution, to obtain a solid-state battery.

[0165] Cycle performance test of the solid-state battery: at room temperature of 25°C, the solid-state battery was charged and discharged in turn at a test voltage interval of 2.5V (discharge cut-off voltage) to 4.3V (charge cut-off voltage) with a charge-discharge current ratio of 1C / 1C, and when the discharge capacity of the solid-state battery reached 80% of the discharge capacity of the first cycle (80% State of Health, 80% SOH), the test was stopped, and the number of cycles at room temperature was recorded.

[0166] Table 1: Parameters for preparing the positive electrode sheet of Examples 1 to 36 and Comparative Examples 1 to 3 and cycle performance test results of assembling the solid-state battery

[0167]

[0168]

[0169] By comparing the test results of Examples 1 to 36 and Comparative Examples 1, it can be seen that the same nanosized sulfide electrolyte, but when the sulfide electrolyte in the positive electrode sheet is not doped with relevant metal elements (such as Sb, In, Bi, Mg), the solid-state battery assembled with the corresponding positive electrode has almost no cycle performance, and the nanosized sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 Lithium dendrites are easily formed during charging and discharging, which leads to short circuit of the solid-state battery after cycling.

[0170] By comparing the test results of Examples 1 to 9, Examples 33 to 34 and Comparative Examples 2 to 3, it can be seen that the sulfide electrolyte in the positive electrode sheet can be nanosized by the action of the protic / non-protic solvent and the dispersing agent, so that when a small amount of sulfide electrolyte is added to the positive electrode sheet, the solid-state battery can still be normally charged and discharged, thereby eliminating the limitation of excessive use of sulfide electrolyte in the positive electrode sheet on the energy density, and ensuring the capacity and cycle performance of the solid-state battery. In contrast, in Comparative Examples 2 and 3, a small amount of large particle size sulfide electrolyte is added to the positive electrode sheet, which cannot guarantee the normal charge and discharge cycle of the solid-state battery, and the capacity of the solid-state battery decreases sharply after about 50 cycles.

[0171] By comparing the test results of Examples 1 to 5, it can be seen that, in the preparation process of the positive electrode sheet, as the addition amount of the dispersing agent increases, the particle size of the sulfide electrolyte in the positive electrode sheet becomes smaller and smaller, and the cycle performance of the solid-state battery presents a trend of gradually increasing first and then gradually decreasing as the particle size of the sulfide electrolyte decreases. This is because, when the particle size of the sulfide electrolyte decreases from micron level to nanometer level, the specific surface area of the sulfide electrolyte increases, thereby constructing a more dense ion transport network in the positive active material layer; but when the particle size of the sulfide electrolyte is too small, the conductivity of the sulfide electrolyte will be seriously reduced, thereby affecting the cycle performance of the solid-state battery.

[0172] By comparing the test results of Examples 3, 6 to 9, it can be seen that, as the mass proportion of the positive active material in the positive electrode sheet increases, the capacity density of the positive electrode sheet increases accordingly, but the cycle performance of the solid-state battery decreases correspondingly. In order to balance the needs of energy density and cycle performance, Example 3 can be the preferred proportion.

[0173] By comparing the test results of Examples 3, 33, 34 and 35, it can be seen that the positive electrode sheet prepared by using the solvent combination of ethanol: acetonitrile = 1:9 can achieve better cycle performance, which is mainly due to the fact that ethanol can act as a hydrogen bond donor and acceptor, while acetonitrile mainly acts as a hydrogen bond acceptor. This combination can better meet the hydrogen bond needs of different solutes, improve the solubility and reaction efficiency. Other combinations are insufficient in this respect: the hydrogen bond donor ability of methanol is too strong, and carbon tetrachloride and toluene lack hydrogen bond action. In addition, the boiling points of ethanol and acetonitrile are moderate, which is easy to evaporate and precipitate the sample after dissolution.

[0174] The present application provides a kind of solid-state battery and preparation method thereof, the solid-state battery will be modified sulfide electrolyte nanocrystallization in positive active material layer, thereby forming the ion transport network of close distribution and stable electrode / electrolyte interface in positive active material layer, it is realized in positive active material layer to join less sulfide electrolyte can make battery good conductive cycle, improve the energy density and cycle life of battery;While nanocrystallization sulfide electrolyte in positive active material layer has higher structural strength, can avoid itself in the process of charge and discharge cycle cracking and pulverization, further improve the storage and cycle life of battery.

[0175] The above examples are only illustrative of the principles and effects of the present application, and are not intended to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.

Claims

1. A solid-state battery, characterized in that, It includes a positive electrode plate, the positive electrode plate includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material and a sulfide electrolyte, the mass content of the sulfide electrolyte in the positive electrode active material layer is 1% - 8%, and the average particle size D50 of the sulfide electrolyte satisfies 50nm ≤ D50 < 1μm; The sulfide electrolyte includes Li a P 1-b M b S c O d X e and Li f P 1-g E g S w O y Q z One or more of the following; In the Li a P 1-b M b S c O d X e where 5 < a < 6, 0 < b < 1, 1.5 < c < 5, 0 < d < 2.5, 4 < c + d < 5, 1 < e < 2, M includes at least one of Al, Ga, In, Ti, Sc, As, Sb, Bi, As, V, Nb, and X includes Cl; In the Li f P 1-g E g S w O y Q z , 5 < f < 10, 0 < g < 1, 3 < w < 6, 4 < w + y < 6, 0 < z < 2, E includes at least one of Mg, Ca, Sr, Ba, Zn, Cr, Sn, Pb, and Q includes Cl.

2. The solid-state battery according to claim 1, characterized in that, In the sulfide electrolyte, 0 < b ≤ 0.1, and M includes at least one of Sb, In, and Bi; and / or, 0.01 ≤ g ≤ 0.1, and E at least includes Mg or Ca.

3. The solid-state battery according to claim 1, characterized in that, The average particle size D50 of the sulfide electrolyte is 50nm - 500nm.

4. The solid-state battery according to claim 1, characterized in that, The mass content of the positive electrode active material in the positive electrode active material layer is 90% - 97%.

5. A method for preparing a solid-state battery according to any one of claims 1 to 4, characterized in that, It includes: Providing a positive electrode plate, a solid electrolyte membrane, and a negative electrode plate; Pressing the positive electrode plate, the solid electrolyte membrane, and the negative electrode plate into an electrode assembly, and encapsulating to obtain a solid-state battery; Among them, the preparation method of the positive electrode plate includes: Preparing a sulfide electrolyte; Adding a positive electrode raw material containing a positive electrode active material, a positive electrode conductive agent, and the sulfide electrolyte and a dispersant into a solvent to obtain a mixed solution; the solvent includes a proton solvent and a non-proton solvent, and the mass ratio of the proton solvent to the non-proton solvent is 1:(1 - 10); Removing the solvent from the mixed solution to obtain a composite positive electrode raw material; Mixing a positive electrode binder with the composite positive electrode raw material to prepare a positive electrode coating, and coating the positive electrode coating on a positive electrode current collector to obtain a positive electrode plate.

6. The preparation method according to claim 5, characterized in that, In the mixed solution, the mass ratio of the composite positive electrode raw material to the solvent is 1:(1 - 20).

7. The preparation method according to claim 5, characterized in that, The proton solvent includes at least one of ethanol and methanol, and the non-proton solvent includes at least one of toluene, xylene, benzene, acetonitrile, ether, and carbon tetrachloride.

8. The preparation method according to claim 5, characterized in that, The dispersant includes at least one of cetyltrimethylammonium bromide, cetyltrimethylammonium chloride, cetyltrimethylammonium sulfonate, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium octylsulfonate, polyoxyethylene octyl alcohol ether, polysorbate, polyoxyethylene stearyl alcohol ether, sodium cocoate, sodium palmitate, sodium oleate, sodium dodecylsulfonate, and sodium polyacrylate; the mass content of the dispersant relative to the positive electrode raw material is 0.01% - 0.5%.

9. The preparation method according to claim 5, characterized in that, The sulfide electrolyte includes Li a P 1-b M b S c O d X e and Li f P 1-g E g S w O y Q z One or more of them, In the Li a P 1-b M b S c O d X e where 5 < a < 6, 0 < b < 1, 1.5 < c < 5, 0 < d < 2.5, 4 < c + d < 5, 1 < e < 2, M includes at least one of Al, Ga, In, Ti, Sc, As, Sb, Bi, As, V, Nb, and X includes Cl; In the Li f P 1-g E g S w O y Q z where 5 < f < 10, 0 < g < 1, 3 < w < 6, 4 < w + y < 6, 0 < z < 2, E includes at least one of Mg, Ca, Sr, Ba, Zn, Cr, Sn, Pb, and Q includes Cl; Among them, Li in the sulfide electrolyte a P 1-b M b S c O d X e The preparation method includes: mixing and sintering lithium source, phosphorus source, M source, sulfur source, oxygen source, and X source according to a preset stoichiometric ratio to obtain Li a P 1-b M b S c O d X e ; and / or, Li in sulfide electrolyte f P 1-g E g S w O y Q z The preparation method includes: mixing and sintering a lithium source, a phosphorus source, an E source, a sulfur source, an oxygen source, and a Q source according to a preset stoichiometric ratio to obtain Li f P 1-g E g S w O y Q z .

Images