All-solid-state battery positive electrode, preparation method thereof and all-solid-state battery

Abstract

The embodiment of the invention discloses an all-solid-state battery positive electrode, a preparation method thereof and an all-solid-state battery, and the all-solid-state battery positive electrode comprises a positive electrode active material, a halide solid electrolyte and a liquid additive, the liquid additive is subjected to decomposition reaction in a working voltage interval of the positive electrode active material to generate a barrier layer in situ, and the barrier layer coats the surface of the positive electrode active material to isolate direct contact between the positive electrode active material and the halide solid electrolyte; the side reaction between the positive electrode active material and the halide solid electrolyte is inhibited, and the cycle performance of the battery is effectively improved. And lithium ion transmission between the positive electrode active material and the halide solid electrolyte is improved, so that the positive electrode capacity is favorably exerted, and the capacity of the battery and the rate capability are favorably improved.

Description

TECHNICAL FIELD

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

[0002] In a full-solid-state battery, lithium ion transmission between the positive electrode and the negative electrode relies on a solid-state electrolyte film, and a solid-state electrolyte needs to be additionally added to the electrode to construct a lithium ion transmission channel. On the one hand, the transmission speed of lithium ions in the positive electrode is mostly dependent on the ionic conductivity of the solid-state electrolyte, and high ionic conductivity of the solid-state electrolyte is conducive to improving the rate performance of the battery. The ionic conductivity of the halide solid-state electrolyte is higher than that of other traditional inorganic solid-state electrolytes, but it is prone to side reactions with the positive electrode active material, causing the stability of the positive electrode to decrease, and the cycle performance of the battery prepared therefrom to deteriorate, which cannot balance the cycle performance and rate performance of the battery. On the other hand, the introduction of inorganic solid-state electrolyte into the positive electrode inevitably brings about the problem of poor contact between solid-state particles, large interface impedance and blocked ion transmission, which will affect the capacity of the battery to some extent, especially the poor stability of the halide solid-state electrolyte with most solvents, which cannot be prepared by a wet method, so that this problem is magnified.

[0003] Therefore, there is an urgent need for a positive electrode to solve the problems of poor stability of the positive electrode after introducing the halide solid-state electrolyte into the positive electrode and poor capacity after preparing the positive electrode by a dry method. SUMMARY

[0004] The present application aims to at least solve one of the problems in the prior art. To this end, the present application provides a full-solid-state battery positive electrode, a preparation method thereof and a full-solid-state battery, to solve the problems of poor stability of the battery, poor cycle performance and capacity reduction of the battery caused by the side reactions between the positive electrode active material and the halide solid-state electrolyte after adding the halide solid-state electrolyte into the positive electrode in the current full-solid-state battery positive electrode, and the relatively poor contact between the positive electrode active material and the halide solid-state electrolyte.

[0005] In a first aspect, the present application provides a full-solid-state battery positive electrode, comprising: a positive electrode active material, a halide solid-state electrolyte and a liquid additive. The liquid additive generates a barrier layer in situ by decomposition within the working voltage range of the positive electrode active material; and the barrier layer is coated on the surface of the positive electrode active material to isolate the direct contact between the positive electrode active material and the halide solid-state electrolyte.

[0006] In some embodiments of the above full-solid-state battery positive electrode, the decomposition voltage U of the liquid additive satisfies 2.5V≤U≤4.7V.

[0007] In some embodiments of the all-solid-state battery cathode described above, the halide solid-state electrolyte does not react with the liquid additive under the working environment of the all-solid-state battery.

[0008] Further, the liquid additive includes at least one of tris(trimethylsilyl)borate, tris(2,2,2-trifluoroethyl)borate, and tris(hexafluoroisopropyl)borate.

[0009] In some embodiments of the all-solid-state battery cathode described above, the mass ratio of the liquid additive in the all-solid-state battery cathode is 2.5% to 15%.

[0010] In some preferred embodiments, the mass ratio of the liquid additive in the all-solid-state battery cathode is 5% to 10%.

[0011] In some embodiments of the all-solid-state battery cathode described above, the thickness of the barrier layer is 5 to 10 nm.

[0012] In some embodiments of the all-solid-state battery cathode described above, the all-solid-state battery cathode further includes a conductive agent and a binder.

[0013] In a second aspect, the present application further provides a preparation method of the all-solid-state battery cathode according to any one of the first aspect, the method comprising: mixing the cathode active material, the halide electrolyte, and the liquid additive to obtain a composite cathode powder; mixing the composite cathode powder and the binder, and grinding and hot-rolling to form the all-solid-state battery cathode.

[0014] In a third aspect, the present application further provides an all-solid-state battery, comprising a negative electrode, a solid-state electrolyte film, and the all-solid-state battery cathode according to any one of the first aspect.

[0015] The above one or more embodiments of the present application have at least one or more of the following beneficial effects: The addition of the halide electrolyte and the liquid additive in the cathode causes the decomposition of the liquid additive in situ on the surface of the cathode active material to form a barrier layer, effectively isolating the direct contact between the cathode active material and the halide solid-state electrolyte, inhibiting the side reaction between the cathode active material and the halide solid-state electrolyte, and effectively improving the cycle performance of the battery. Moreover, the addition of the liquid additive effectively improves the contact between the cathode active material particles and the halide solid-state electrolyte particles, and the lithium ion transmission between the cathode active material and the halide solid-state electrolyte is improved, which is conducive to the capacity of the cathode and the improvement of the capacity and rate performance of the battery.

[0016] Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or can be learned by practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0017] The disclosure of the application will become more fully understood from the detailed description given herein and the accompanying drawings. It is understood that these drawings are only for purposes of illustration and are not intended to limit the scope of the application. Like numbers refer to like elements throughout. Figure 1 is a high-resolution transmission electron microscope (HR-TEM) image of the positive electrode of the all-solid-state battery provided by Example 1 of the application; Figure 2 is a high-resolution transmission electron microscope (HR-TEM) image of the positive electrode of the all-solid-state battery provided by Comparative Example 1 of the application. DETAILED DESCRIPTION

[0018] Some embodiments of the application will now be described with reference to the accompanying drawings. It will be appreciated by persons skilled in the art that these embodiments are only for the purpose of illustrating the technical principles of the application and are not intended to limit the scope of the application.

[0019] As described in the background, in order to improve the transmission efficiency of lithium ions in the all-solid-state battery, it is necessary to add solid-state electrolyte inside the electrode to build a lithium ion transmission channel. The existing solid-state electrolyte can be roughly divided into oxide solid-state electrolyte, sulfide solid-state electrolyte, halide solid-state electrolyte and polymer solid-state electrolyte. Among them, the ionic conductivity of oxide solid-state electrolyte and polymer solid-state electrolyte is low, the air stability of sulfide solid-state electrolyte is poor and it is easy to decompose, which is not conducive to commercial development. Relatively speaking, the ionic conductivity of halide electrolyte is higher, the commercial application prospect is better, and it is conducive to building an efficient lithium ion transmission channel and helping to exert the performance of the battery. However, the halide solid-state electrolyte is prone to side reactions with the positive active material, and has poor stability, which is not conducive to the cycle performance of the battery.

[0020] On the other hand, the introduction of inorganic solid-state electrolyte into the positive electrode inevitably brings the problem of poor contact between solid-state particles, large interface impedance and blocked ion transmission, which will affect the capacity exertion of the battery to some extent, especially the poor stability of halide solid-state electrolyte with most solvents, which cannot be prepared by wet method, so that this problem is magnified.

[0021] Therefore, there is an urgent need for a positive electrode to solve the problems of poor stability of the positive electrode after introducing halide solid-state electrolyte into the positive electrode and poor capacity exertion caused by dry preparation of the positive electrode.

[0022] To solve the above problems, the application creatively proposes a full solid-state battery positive electrode and a preparation method thereof and a full solid-state battery, wherein a halide electrolyte and a liquid additive are added in the positive electrode, the liquid additive decomposes to generate a barrier layer in situ, which effectively isolates the direct contact between the positive active material and the halide solid-state electrolyte, inhibits the side reaction between the positive active material and the halide solid-state electrolyte, and effectively improves the contact between the positive active material particles and the halide solid-state electrolyte particles, thereby effectively ensuring the capacity of the positive electrode.

[0023] The application will be specifically described below through specific examples.

[0024] Specifically, the application provides a full solid-state battery positive electrode, which comprises a positive active material, a halide solid-state electrolyte and a liquid additive; wherein the liquid additive decomposes to generate a barrier layer in situ within the working voltage range of the positive active material, and the barrier layer is coated on the surface of the positive active material to isolate the direct contact between the positive active material and the halide solid-state electrolyte.

[0025] The halide electrolyte and the liquid additive are added in the positive electrode, the liquid additive decomposes to generate a barrier layer in situ on the surface of the positive active material, which effectively isolates the direct contact between the positive active material and the halide solid-state electrolyte, inhibits the side reaction between the positive active material and the halide solid-state electrolyte, and effectively improves the cycle performance of the battery. Moreover, through the addition of the liquid additive, the contact between the positive active material particles and the halide solid-state electrolyte particles during the dry preparation process is effectively improved, the lithium ion transmission between the positive active material and the halide solid-state electrolyte is improved, which is conducive to the capacity of the positive electrode and the improvement of the capacity and the rate performance of the battery.

[0026] The positive active material can embed or de-embed metal ions such as lithium ions. Exemplarily, some suitable but non-limiting positive active materials can include but are not limited to lithium-containing transition metal oxides, transition metal fluorides, polyanion materials, fluorinated polyanion materials, transition metal sulfides, transition metal oxyfluorides, transition metal oxysulfides or transition metal oxynitrides. Exemplary lithium-containing transition metal oxides can be Li(NiCoAl)O2 or LiCoO2.

[0027] The working voltage range of the positive active material is 3.0V-4.8V.

[0028] The type of the positive active material is not limited in the application. Exemplarily, the positive active material includes LiMn2O4, LiCoO2, LiNi x Co y Mn zO2(x+y+z=1), xLi2MnO3·(1-x)LiMO2(M is a metal element), LiNi 0.5 Mn 1.5 O4, LiFePO4, LiFe a Mn 1-a PO4(0

[0029] The working voltage range of LiMn2O4 is 3.0-4.2V, the working voltage range of LiCoO2 is 3.0-4.2V, the working voltage range of LiNi 0.8 Co 0.1 Mn 0.1 O2 is about 3.0-4.2V, and the working voltage range of LiFePO4 is 2.7-3.5V.

[0030] In some embodiments, in the positive electrode of the all-solid-state battery, the mass percentage of the positive electrode active material is 50%-85%.

[0031] In some embodiments, the halide solid-state electrolyte has a general formula of Li x MX y N z , wherein 1≤x≤4, 4≤y+nz≤8, and n is the absolute value of the valence of N. The metal element M includes at least one of V, Cr, Mn, Zn, Cd, Fe, Pb, In, Y, Al, Sc, La, Lu, Ga, Zr, or Hf, and M further includes a doping metal element, which is used in combination with the aforementioned base metal element, such as one or more of Nb, Ta, Al, La, Mg, Ca, Ba, Ag. X includes at least one of halogen elements F, Cl, Br, or I. N is at least one of non-metal elements O or S. Exemplarily, the halide solid-state electrolyte includes Li3InBr 6-m1 Cl m1 (0≤m1≤6), LiInX4, Li3YX6, Li3ErX6, Li3ScX6, Li3LaX6, Li 3-m2 Er 1-m2 Zr m2 Cl6(m2≤0.6), Li 3-m3 Y 1-m3 Zr m3 Cl6(m3≤0.6), Li3Y 1-m4 In m4 Cl6(0 m5 O m6 (0 m7 Sm8 A mixture of one or more of the following (0<m8≤1,m7+m8=6).

[0032] For example, halide solid electrolytes include Li₂ZrCl₆, Li 2.5-y ZrCl 5.5-y O 0.5 One or more of the following: (0 < y < 0.75), Li2HfCl6, Li3InCl6, Li3YCl6, Li3ScCl6, Li3ScBr6, and Li3YCl3Br3.

[0033] The above-mentioned halide solid electrolytes can be in particulate form, for example, prepared by methods such as mechanical ball milling (e.g., weighing reactants according to stoichiometry and then ball milling in an inert atmosphere (e.g., Ar / He), followed by annealing), high-temperature melt quenching (e.g., heating a mixture of reactants to a melt in an inert atmosphere, then rapidly cooling the solution and annealing), solution processing (e.g., dissolving the reaction precursor in an organic solvent, slowly evaporating the solvent in an inert atmosphere, then sintering to remove residual solvent and crystallizing), chemical vapor deposition (e.g., depositing a thin film on a heated substrate using vaporized feedstock and then annealing at low temperature), and solid-state reaction (e.g., uniformly mixing powdered reactants, pressing them into sheets, heating and holding them in an inert atmosphere, followed by rapid cooling). This application does not impose any specific limitations.

[0034] In some embodiments, the halide solid electrolyte accounts for 10% to 40% of the mass of the positive electrode in an all-solid-state battery. Optionally, the mass percentage of the halide solid electrolyte in the positive electrode of an all-solid-state battery can be 10%, 15%, 20%, 23%, 27%, 30%, 34%, 38%, 40%, or any value within the above range. In some embodiments, the decomposition voltage U of the liquid additive satisfies 2.5V ≤ U ≤ 4.7V. Optionally, the decomposition voltage U of the liquid additive can be 2.5V, 2.7V, 2.9V, 3.1V, 3.5V, 3.7V, 3.9V, 4.0V, 4.2V, 4.5V, 4.7V, or any value within the above voltage range.

[0035] The decomposition voltage U of the liquid additive satisfies 2.5V≤U≤4.7V in the working voltage interval of the positive electrode active material, so as to ensure that the liquid additive can be electrochemically decomposed in situ to form a barrier layer during battery charging. If the decomposition voltage of the liquid additive is too low, it will decompose prematurely during battery assembly or initial cycling, resulting in the inability to stably form a barrier layer, which cannot effectively coat the positive electrode active material to inhibit the side reaction of the positive electrode active material and the halide solid electrolyte directly contacting. If the decomposition voltage of the liquid additive is too high, it cannot be decomposed at the normal charging voltage of the battery, and the barrier layer cannot be formed.

[0036] In some embodiments, the halide solid electrolyte and the liquid additive do not react under the working environment of the all-solid-state battery. It is ensured that the components are stably present during preparation.

[0037] The liquid additive does not react with the halide solid electrolyte, which can be specifically judged by soaking the halide solid electrolyte in the liquid additive and observing whether the structure of the halide solid electrolyte changes before and after soaking. In this application, whether the structure of the halide solid electrolyte changes is judged by XRD characterization and infrared spectrum characterization of the halide solid electrolyte before and after soaking, respectively.

[0038] In some preferred embodiments, the liquid additive includes at least one of tris(trimethylsilyl)borate, tris(2,2,2-trifluoroethyl)borate, and tris(hexafluoroisopropyl)borate. Tris(trimethylsilyl)borate, tris(2,2,2-trifluoroethyl)borate, and tris(hexafluoroisopropyl)borate can all decompose under a battery environment with a voltage of ≤4.2V, forming a uniform barrier layer on the contact interface between the positive electrode active material and the halide solid electrolyte, mainly on the surface of the positive electrode active material. It can stably and effectively isolate the high-activity positive electrode active material particles and the halide solid electrolyte particles, thereby inhibiting the side reaction between the positive electrode active material and the halide solid electrolyte. Further, the formed barrier layer has the advantages of excellent chemical stability, excellent lithium ion conductivity, and good elasticity, and can stably exist on the surface of the positive electrode active material, ensuring efficient transmission of lithium ions in the positive electrode, so that the battery has good cycle performance and rate performance, and can also improve the contact between the halide solid electrolyte and the positive electrode active material, effectively buffer the volume change of the positive electrode active material particles during charging and discharging, and ensure the capacity of the battery and prevent the cycle performance of the battery from deteriorating. Moreover, tris(trimethylsilyl)borate, tris(2,2,2-trifluoroethyl)borate, and tris(hexafluoroisopropyl)borate exhibit good chemical compatibility with the halide solid electrolyte, and do not react with the electrolyte during storage or positive electrode preparation, thereby ensuring the stability and initial performance of the all-solid-state battery during the manufacturing process.

[0039] In some embodiments, the mass percentage of the liquid additive in the all-solid-state battery cathode is 2.5% to 15%. Optionally, the mass percentage of the liquid additive in the all-solid-state battery cathode can be 2.5%, 4.0%, 5.3%, 6.5%, 7.1%, 8.6%, 9.2%, 10.5%, 11.7%, 12.0%, 13.6%, 14.9%, 15%, or any point value within the above mass percentage range.

[0040] If the amount of the liquid additive is too low, the barrier layer cannot completely cover all the positive active material particles, and the barrier layer is not completely covered, part of the positive active material will directly contact the halide solid electrolyte and cause side reactions, affecting the cycle performance of the battery.

[0041] When the mass percentage of the liquid additive in the all-solid-state battery cathode is within the above range, the addition of the liquid additive increases, which is beneficial to the formation of a barrier layer with appropriate thickness, ensuring the insulation effect of the positive active material and the halide solid electrolyte. When the content of the liquid additive continues to increase, the surface of the positive active material is completely wrapped by the barrier layer, and the liquid additive will not decompose any more, and the improvement of the performance of the battery is limited. At the same time, a relatively high mass percentage of the liquid additive also reduces the mass percentage of the functional components such as the positive active material and the halide solid electrolyte, directly leading to a decrease in the area capacity and energy density of the battery. It should be noted that as the amount of the liquid additive increases, the liquid additive may not be completely decomposed, but the appropriate excess of the liquid additive can compensate for the newly formed barrier interface during the cycle of the all-solid-state battery.

[0042] In some preferred embodiments, the mass percentage of the liquid additive in the all-solid-state battery cathode is 5% to 10%, for example, 5%, 5.3%, 6.0%, 6.7%, 7.0%, 7.5%, 8.0%, 8.1%, 9.0%, 9.8%, 10.0%, etc. When the mass percentage of the liquid additive in the all-solid-state battery cathode is within this range, a barrier layer with good performance can be obtained on the surface of the positive active material, and the amount of the liquid additive in the cathode can be controlled to avoid excessive liquid additive, which can reduce the energy density of the battery.

[0043] In some embodiments, the thickness of the barrier layer is 5 to 10 nm. Optionally, the thickness of the barrier layer can be 5.0 nm, 5.3 nm, 6.0 nm, 6.5 nm, 7.0 nm, 7.2 nm, 8.0 nm, 8.4 nm, 9.0 nm, 9.7 nm, 10.0 nm, or any point value within the above thickness range.

[0044] The barrier layer is too thin to completely cover the surface of the positive active material, and cannot achieve complete blocking of the positive active material and the halide solid-state electrolyte. Moreover, the mechanical strength of the barrier layer is low, and the barrier layer may crack and fall off during the charging and discharging process of the battery due to the volume change of the positive active material, losing the ability to continuously block protection.

[0045] The barrier layer is too thick to occupy the volume and mass of the positive electrode, resulting in a decrease in the energy density of the battery. Of course, due to the performance of the liquid additive, when the positive active material is completely covered by the barrier layer, the liquid additive will not continue to decompose, i.e., the thickness of the barrier layer will not continue to increase.

[0046] In some embodiments, the all-solid-state battery positive electrode further comprises a conductive agent, thereby imparting electrical conductivity to the electrode. The conductive agent can include any conductive material as long as it does not cause chemical changes.

[0047] The type of conductive agent is not limited in the present application. For example, the conductive agent includes any one or a combination of at least two of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers. The above are common conductive agents in the art and are only examples and are not limiting.

[0048] In some embodiments, the mass fraction of the conductive agent in the all-solid-state battery positive electrode is 0.1% to 10%. Alternatively, the mass fraction of the conductive agent in the all-solid-state battery positive electrode can be 0.1%, 1%, 2.3%, 3.5%, 4.1%, 5.6%, 6.4%, 7.8%, 8.2%, 9.3%, 10%, or any point value within the above mass fraction range.

[0049] In some embodiments, the all-solid-state battery positive electrode further comprises a binder, which improves the binding between the positive active material particles and also improves the binding between the positive electrode layer and the positive electrode current collector.

[0050] The binder includes a fibrous binder, for example, the fibrous binder includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride hexafluoropropylene, polypropylene, polyethylene, and polyimide.

[0051] In some embodiments, to further improve the binding ability of the binder to the positive electrode, the binder further comprises at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, nylon, etc.

[0052] In some embodiments, the mass percentage of the binder in the all-solid-state battery cathode is 0.1% to 10%. Optionally, the mass percentage of the binder in the all-solid-state battery cathode can be 0.1%, 1.2%, 2.5%, 3.3%, 4.5%, 5.1%, 6.3%, 7.4%, 8.7%, 9.2%, 10%, or any value within the above range.

[0053] In some embodiments, the all-solid-state battery cathode further comprises a cathode current collector comprising an electron-conducting metal material, for example, the cathode current collector comprises at least one of aluminum, nickel, tin, copper, and stainless steel.

[0054] In a second aspect, the embodiments of the present application further provide a method for preparing the all-solid-state battery cathode as described in any one of the above embodiments, the method comprising: S1, mixing the cathode active material, the halide electrolyte, and the liquid additive to obtain a composite cathode powder.

[0055] S2, mixing the composite cathode powder and the binder, and grinding and hot-rolling to obtain the all-solid-state battery cathode.

[0056] The liquid additive can act as a temporary liquid medium in the dry preparation mixing and grinding process, helping the cathode active material and the halide solid-state electrolyte to better contact and disperse, forming a more uniform cathode structure, and ensuring the formation of an effective barrier layer.

[0057] In some embodiments, the mixing method in step S1 is grinding.

[0058] In some embodiments, in step S2, the grinding time is 10 to 50 min, and the rolling temperature is 80 to 100°C.

[0059] In some embodiments, the all-solid-state battery cathode further comprises a conductive agent and a binder, and the composite cathode powder is obtained by mixing the cathode active material, the halide electrolyte, the liquid additive, and the conductive agent.

[0060] The embodiments of the present application further provide an all-solid-state battery comprising a negative electrode, a solid-state electrolyte film, and the all-solid-state battery cathode as described in any one of the above embodiments.

[0061] In some embodiments, the negative electrode comprises a negative electrode active material, which is a material containing metal ions capable of intercalating or deintercalating lithium ions, for example, a metal material (such as Li, Ag, Al, Bi, Cu, Ga, Ge, In, Ni, Pb, Sb, Si, Sn, Sr, Zn, etc., or an alloy or compound of the above metals, such as Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, TiO2-Li4Ti5O12 , Li-Al alloy, Ag-C alloy, etc.), carbon materials (such as graphite including natural graphite / artificial graphite, carbon fiber, soft carbon, hard carbon, crystalline carbon, amorphous carbon, etc.), silicon compounds (such as silicon, silicon-carbon composite), etc. In some embodiments, the negative electrode can be a lithium-based negative electrode. For example, the negative electrode can be a lithium metal negative electrode. Alternatively, the negative electrode can also be a silicon-based negative electrode. For example, the negative electrode is made of a carbon-silicon composite, coated on a copper foil as a negative electrode current collector to form a negative electrode sheet.

[0062] In some embodiments, the negative electrode includes a negative electrode layer and a negative electrode current collector, and the negative electrode layer includes a negative electrode active material.

[0063] In some embodiments, the mass percentage of the negative electrode active material contained in the negative electrode layer can be 80%-99%, for example, 80%, 85%, 90%, 95%, 97%, 99%, etc., preferably 95%-97%.

[0064] In some embodiments, the negative electrode can be an anode-free lithium metal solid-state battery, and the negative electrode can be made of an Ag-C alloy, coated on a copper foil as a negative electrode current collector to form a negative electrode sheet (or a negative electrode side structure).

[0065] In some embodiments, the negative electrode layer can also contain a binder. Non-limiting examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, butadiene-styrene rubber, acrylated butadiene-styrene rubber, epoxy resin, nylon, etc. The present application is not limited thereto.

[0066] In some embodiments, the negative electrode can also contain a conductive aid, for example, carbon-based materials such as graphite (natural graphite or artificial graphite, etc.), carbon black (acetylene black or ketjen black, etc.), carbon nanotubes, graphene, etc., metal-based materials such as metal powder (aluminum powder, nickel powder, etc.), metal oxide (titanium oxide, etc.), metal whisker (aluminum oxide, etc.), etc., conductive polymers such as polyaniline, polypyrrole, polythiophene, etc., conductive fibers such as carbon fiber, metal fiber, metal compound fiber, polymer type fiber, etc. The conductive aid can also be one of the above or a mixture of the above.

[0067] In some embodiments, the solid-state electrolyte film includes an inorganic solid-state electrolyte and / or a polymer solid-state electrolyte.

[0068] In some embodiments, the inorganic solid-state electrolyte can include one or a combination of halide solid-state electrolyte material, sulfide solid-state electrolyte. The halide solid-state electrolyte material can be the same material as the halide solid-state electrolyte in the positive electrode of the all-solid-state battery provided in the present application, or can be a different material from the halide solid-state electrolyte in the positive electrode of the all-solid-state battery provided in the present application, which is not specifically limited in the present application.

[0069] In some embodiments, the halide solid-state electrolyte has a general formula of Li x MX y N z wherein 1≤x≤4, 4≤y+nz≤8, n is the absolute value of the valence of N. The metal element M includes at least one of V, Cr, Mn, Zn, Cd, Fe, Pb, In, Y, Al, Sc, La, Lu, Ga, Zr or Hf, and M further includes a doped metal element, which is used in combination with the aforementioned base metal elements, such as one or more of Nb, Ta, Al, La, Mg, Ca, Ba, Ag. X includes at least one of halogen elements F, Cl, Br, I. N is at least one of non-metal elements O, S. Exemplarily, the halide solid-state electrolyte includes Li3InBr 6-m1 Cl m1 (0≤m1≤6), LiInX4, Li3YX6, Li3ErX6, Li3ScX6, Li3LaX6, Li 3-m2 Er 1-m2 Zr m2 Cl6(m2≤0.6), Li 3-m3 Y 1-m3 Zr m3 Cl6(m3≤0.6), Li3Y 1-m4 In m4 Cl6(0<m4<1), Li2ZrX6, Li2ZrX m5 O m6 (0<m6≤1, m5+m6=6), Li2ZrX m7 S m8 (0<m8≤1, m7+m8=6).

[0070] Exemplarily, the halide solid-state electrolyte includes Li2ZrCl6, Li 2.5-y ZrCl 5.5-y O 0.5 (0<y<0.75), Li2HfCl6, Li3InCl6, Li3YCl6, Li3ScCl6, Li3ScBr6, Li3YCl3Br3.

[0071] In some embodiments, the sulfide solid-state electrolyte can include, but is not limited to, Li2S-P2S5, Li2S-P2S5-MS x (M = Si, Ge, Sn, 0 < x < 2), Li 9.6 P3S 12 , Li7P3S 11 , Li7P2S8I, Li 10 SnP2S 12 , Li 10 SiP2S 12 , Li9P3S9O3, LGPS (Li 10 GeP2S 12 ), Thio-LISICON (Li 3.25 Ge 0.25 P 0.75 S4), Li6PS5X (X = Cl, Br, I), Li3PS 4-X (X = Cl, Br, I), Li4SnS 4-X (X = Cl, Br), Li 3.25 Ge 0.25 P 0.75 S4, Li 3.4 Si 0.4 P 0.6 S4, Li 10 GeP2S 11.7 O 0.3 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 10.35 Ge 1.35 P 1.65 S 12 , Li 10.35 Si 1.35 P 1.65 S 12 , Li 9.81 Sn 0.81 P 2.19 S 12 , Li 10 (Si 0.5 Ge 0.5 )P2S 12 , Li 10 (Ge 0.5 Sn 0.5 )P2S 12 , Li 10 (Si 0.5 Sn 0.5 )P2S 12 , Li6(PS5) 0.7(GeS4) 0.3 Cl, Li 7.5 P 2.5 Sn 0.5 S 10.5 Cl 1.5 , Li6PS5Cl 0.5 Br 0.5 , Li6PS5I 0.2 Cl 0.8 , Li5SnS2Cl3, Li 10 P3S 12 C l2 , Li7P2S 8.5 Cl 0.5 and / or any combination or related materials.

[0072] In some embodiments, the inorganic solid-state electrolyte can also be an oxide solid-state electrolyte material, a nitride solid-state electrolyte, a hydride solid-state electrolyte, a borate solid-state electrolyte, and the like. Illustratively, the oxide solid-state electrolyte can include, but is not limited to, NASICON-type solid electrolytes such as LiTi2(PO4)3, LiGeTi(PO4)3, LiGe2(PO4)3, LiHf2(PO4)3, Li 1+x Al x Ge 2-x (PO4)3(LAGP, where 0≤x≤2), Li 1+x Al x Ti 2-x (PO4)3(LATP, where 0≤x≤2), Li 1+x Y x Zr 2-x (PO4)3(LYZP, where 0≤x≤2), Li 1.3 Al 0.3 Ti 1.7 (PO4)3and the like, perovskite-type solid electrolytes such as Li 3x La (2 / 3-x) TiO3(LLTO, where 0 1.65 Z r1.3 Ta 1.7 O9, Li 2x-y Sr 1-x Ta y Zr 1-y O3(where x=0.75y and 0.60 14 ZnGe4O 16 , Li4SiO4, LiGeO4and the like, garnet-type solid electrolytes such as Li7La3Zr2O12 Li 6.5 La3Zr 1.75 Te 0.25 O 12 Li 6.2 Ga 0.3 La 2.95 Rb 0.05 Zr2O 12 Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 Li 6.25 Al 0.25 La3Zr2O 12 Li 6.75 La3Zr 1.75 Nb 0.25 O 12 Li 6.75 La3Zr 1.75 Nb 0.25 O 12 Derivatives produced by doping or coating with materials such as, etc., or any combination thereof or related materials.

[0073] In some embodiments, the nitride solid electrolyte may include, but is not limited to, Li3N, Li7PN4, LiSi2N3, Li9N2Cl3, etc.

[0074] In some embodiments, the hydride solid electrolyte may include, but is not limited to, LiBH4, LiBH4-Li X (X = Cl, Br or I), LiNH2, Li2NH, LiBH4-LiNH2, Li3AlH6, etc.

[0075] In some embodiments, the borate solid electrolyte may include, but is not limited to, Li₂B₄O₇, Li 2O -B₂O₃-P₂O₅, Li₂B 10 H 10 -Li2B 12 H 12 Li7N2I -0.5 LiOH, etc. Derivatives of the above electrolytes obtained through substitution, doping, modification, or compositing can also be used as inorganic solid electrolytes in this application. For example, bromine (Br)-substituted or partially substituted Li₂ZrCl₆, such as Li₂ZrCl₆-xBrx; rare earth metals such as lanthanum or yttrium-doped Li₆PS₅Br; and LLZO deposited on an indium (In) surface, etc. It should be noted that the above examples are for illustrative purposes only and are not intended to limit this application.

[0076] It is understood that the material of the solid electrolyte membrane in this application is not required to be selected from any one of the above-mentioned materials, but may be selected from one or more of the above-mentioned solid electrolyte materials, such as a mixture of a sulfide solid electrolyte material and a halide solid electrolyte material, or a mixture of an oxide and two halide materials; without departing from the inventive concept of this application, the use of known conventional solid electrolytes should be considered within the scope of protection of this application.

[0077] The present application will be further described in detail below with reference to embodiments. It should be noted that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection claimed in this application.

[0078] Example 1: Preparation of the positive electrode: The positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, halide solid electrolyte Li 1.75 ZrCl 4.75 O 0.5 The conductive agent, conductive carbon, and liquid additive tris(trimethylsilane)borate TMSB were ground and mixed in a certain mass ratio to obtain composite positive electrode powder. Polytetrafluoroethylene (PTFE) powder, a binder, is added to the well-mixed composite cathode powder. The mixture is then ground and hot-rolled to form a composite cathode film. The cathode active material is LiNi. 0.8 Co 0.1 Mn 0.1 O2, halide solid electrolyte Li 1.75 ZrCl 4.75 O 0.5 The mass ratio of conductive carbon (conductive agent), tris(trimethylsilane)borate TMSB (liquid additive), and polytetrafluoroethylene powder (binder) is 60:37:3:5.27:0.4. The liquid additive accounts for 5% of the mass of the composite positive electrode film.

[0079] Preparation of solid electrolyte membrane: Solid electrolyte Li 1.75 ZrCl 4.75 O 0.5 The powder is cold-pressed in a mold to prepare a solid electrolyte membrane.

[0080] Battery fabrication: A composite positive electrode film and Li6PS5Cl powder were cold-pressed onto both sides of a solid electrolyte film. Subsequently, a Li-In alloy negative electrode was stacked on one side of the Li6PS5Cl layer and cold-pressed to form a cell unit. After demolding, the cell unit was encapsulated in a coin cell casing to fabricate a coin cell all-solid-state lithium-ion battery.

[0081] Example 2: The difference between this example and Example 1 is that in this example, the mass percentage of the liquid additive in the composite positive electrode film is 2.5%.

[0082] Example 3: The difference between this example and Example 1 is that in this example, the mass percentage of the liquid additive in the composite positive electrode film is 15%.

[0083] Example 4: The difference between this example and Example 1 is that in this example, the mass percentage of the liquid additive in the composite positive electrode film is 10%.

[0084] Example 5: The difference between this example and Example 1 is that in this example, the mass percentage of the liquid additive in the composite positive electrode film is 2%.

[0085] Example 6: The difference between this example and Example 1 is that in this example, the mass percentage of the liquid additive in the composite positive electrode film is 20%.

[0086] Example 7: The difference between this example and Example 1 is that in this example, the liquid additive is tris(2,2,2-trifluoroethyl) borate TTEB.

[0087] Comparative Example 1: In this comparative example, the difference from Example 1 is that no liquid additive is used.

[0088] Comparative Example 2: In this comparative example, the difference from Example 1 is that fluoroethylene carbonate FEC is used instead of the liquid additive.

[0089] The liquid additives used in the above examples and comparative examples and the thickness of the barrier layer formed by decomposition of the liquid additive are shown in Table 1: Table 1 The all-solid-state batteries provided by the above examples and comparative examples were subjected to performance tests, and the following is the test method: 1) Cycle performance test: At a temperature of 25°C, charge to a charge cut-off voltage of 4.2V at a current of 0.1C, then charge to a charge cut-off current of 0.05C at a voltage of 4.2V, stand for 10min, then discharge to a discharge cut-off voltage of 3.0V at a current of 0.1C, stand for 10min. This is one charge-discharge cycle, and the cycle retention rate = discharge capacity of the 500th cycle / discharge capacity of the 1st cycle 100%.

[0090] 2) 0.1C first cycle discharge capacity test: At a temperature of 25°C, discharge the prepared battery to a discharge cut-off voltage of 3.0V at a current of 0.1C, and record the discharge capacity of the battery.

[0091] 3) Rate performance test: The full battery was discharged at a current of 0.1C to a discharge cut-off voltage of 3.0V at an ambient temperature of 25°C, and the discharge capacity Co of the battery was recorded.

[0092] The full battery was discharged at a current of 1C to a discharge cut-off voltage of 3.0V at an ambient temperature of 25°C, and the discharge capacity C1 of the battery was recorded.

[0093] Rate capability = C1 / C0 100%.

[0094] 4) TEM test: The prepared positive electrode was taken to prepare a sample, and an image was obtained by TEM.

[0095] The test results are shown in Table 2: Table 2 Referring to Figure 1 It can be seen that the surface of the positive active material particles to which the liquid additive is added is uniformly covered with a barrier layer CEI layer with a thickness of about 6nm, while the surface of the positive active material particles in the comparative example 1 does not have a barrier layer CEI layer. It can also be seen from the TEM image that the barrier layer is mainly composed of amorphous components, corresponding to the organic phase oligomer, and the barrier layer has excellent chemical stability, lithium conductivity and elasticity, and can effectively buffer the volume change of the particles during charging and discharging to prevent the barrier layer from being broken. Figure 2 Referring to Table 1, it can be seen that when the amount of the liquid additive exceeds 15% of the mass of the positive electrode, the filling amount of the liquid additive in the gap is relatively large, but the surface of the positive active material particles has been wrapped by the formed film, and the remaining liquid additive will not continue to react until a new interface is exposed during cycling to generate a film. Fluoroethylene carbonate FEC will react with the halide solid-state electrolyte and cannot form a barrier layer on the surface of the positive active material.

[0096] Referring to Table 1 and Table 2, it can be seen that too little liquid additive will not have a significant effect on the improvement of the cycle and capacity of the battery, and too much liquid additive will be beneficial to the cycle of the battery but will not significantly improve the capacity of the battery. Only by adding the liquid additive within the mass range defined in the present application can the cycle performance and capacity of the battery be considered. However, the use of a liquid additive that can react with the halide solid-state electrolyte will consume the halide solid-state electrolyte, resulting in the battery being unable to cycle normally.

[0097]

[0098] ​The present application has been described in relation to particular embodiments, which will be apparent to those of ordinary skill in the art and it is to be understood that many modifications and improvements can be made to the attached claims. It is also to be understood that such modifications and improvements are deemed minimally descriptive of the spirit and scope of the embodiments according to the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation, as it should be understood that the application is not limited to the embodiments described herein, but is capable of considerable modification, its scope being indicated and limited only by the appended claims.

[0099] Also, certain terminology can also be used in the description for the sake of clarity only. For example, the terms "one" or "the one" or "some" and / or "one or more" and / or "at least one" and / or "one or more of the following" employed in the description, either explicitly or implicitly, should be taken to mean any one, some, or each of the indicated term or feature, possibly in a multiple dependent fashion. As used herein, the term "exemplary" is used to mean "an example of." As used herein, the term "another" is used to mean "any one or more other than the one or more already named." As used herein, the term "at least one" is used to mean "one or more" of the indicated term. As used herein, the term "or" is used to mean "and / or," unless explicitly stated otherwise. As used herein, the term "about" is used to allow for variations from the nominal or desired value as would be recognized by one of ordinary skill in the art, and is not to be considered limiting but rather as a manner of describing particular embodiments. As used herein, the term "and / or" means "and" or "or," and / or "and" and "or." As used herein, the term "if" can be construed to mean "when" or "upon" or "in response to determining" or "in response to detecting," or even "if and when." As used herein, the term "user" can mean a person or a device, or a combination thereof.

[0100] As such, it should be understood that every maximum numerical limitation given throughout this patent application will include every lower numerical limitation, as if such lower numerical limitations were expressly written herein. Every minimum numerical limitation given throughout this patent application will include every higher numerical limitation, as if such higher numerical limitations were expressly written herein. Every numerical range given throughout this patent application will include every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.

[0101] Finally, it should be understood that the embodiments described herein are merely exemplary of the application. Other variations of the embodiments can be devised by those skilled in the art without departing from the spirit and scope of the application. Accordingly, the embodiments described herein are intended to be illustrative only and are not limiting of the scope of the application.

Claims

1. A positive electrode for an all-solid-state battery, characterized in that, include: Positive electrode active materials, halide solid electrolytes and liquid additives; The liquid additive decomposes in situ within the operating voltage range of the positive electrode active material to generate a barrier layer. The barrier layer is coated on the surface of the positive electrode active material to prevent the positive electrode active material from directly contacting the halide solid electrolyte.

2. The all-solid-state battery cathode according to claim 1, characterized in that, The decomposition voltage U of the liquid additive satisfies 2.5V≤U≤4.7V.

3. The all-solid-state battery cathode according to claim 1 or 2, characterized in that, The halide solid electrolyte and the liquid additive do not react under the operating environment of an all-solid-state battery.

4. The all-solid-state battery cathode according to claim 3, characterized in that, The liquid additive includes at least one of tris(trimethylsilane)borate, tris(2,2,2-trifluoroethyl)borate, and tris(hexafluoroisopropyl)borate.

5. The all-solid-state battery cathode according to claim 1, characterized in that, In the positive electrode of the all-solid-state battery, the liquid additive accounts for 2.5% to 15% of the total mass.

6. The all-solid-state battery cathode according to claim 5, characterized in that, In the positive electrode of the all-solid-state battery, the liquid additive accounts for 5% to 10% of the mass.

7. The all-solid-state battery positive electrode according to claim 1, characterized in that, The thickness of the barrier layer is 5~10nm.

8. The all-solid-state battery positive electrode according to claim 1, characterized in that, The positive electrode of the all-solid-state battery also includes a conductive agent and a binder.

9. A method for preparing an all-solid-state battery cathode as described in any one of claims 1-8, characterized in that, The method includes: Composite cathode powder is obtained by mixing positive electrode active material, halide electrolyte and liquid additive; The composite cathode powder is mixed with a binder, ground, and then hot-rolled into a solid-state battery cathode.

10. An all-solid-state battery, characterized in that, It includes a negative electrode, a solid electrolyte membrane, and an all-solid-state battery positive electrode as described in any one of claims 1-8, which are stacked in sequence.

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