A Li-doped oxide nanosheet material, including its composite electrolyte membrane and preparation method.

Abstract

This invention provides a composite electrolyte membrane comprising Li-doped oxide nanosheet materials and a method for preparing the same. The Li-doped oxide nanosheet materials comprise sheet-like structural units, each sheet-like structural unit having channels; the specific surface area of ​​the sheet-like structural units is 1-10 m². 2 / g; the sheet-like structural unit comprises oxide nanoparticles and Li oxides, with the Li oxides doped into the oxide lattice. This invention utilizes the unique structure of the prepared Li-doped oxide nanosheet material to improve the ionic conductivity, electrochemical window, cycle performance, and energy density of polymer electrolytes and solid-state lithium batteries.

Description

Technical Field

[0001] This invention belongs to the field of solid-state lithium battery technology, and relates to a Li-doped oxide nanosheet material and its preparation method, a composite electrolyte membrane including the Li-doped oxide nanosheet material and its preparation method, and a solid-state lithium battery including the composite electrolyte membrane. Background Technology

[0002] Lithium-ion batteries (LIBs) have dominated the development of commercial energy storage technology due to their high energy density. Although the liquid electrolytes currently used give LIBs high ionic conductivity, their flammability still poses a significant safety hazard. Solid-state lithium batteries, fabricated using non-flammable all-solid-state electrolytes instead of liquid electrolytes, can effectively improve their safety performance and energy density. Past research has identified various types of solid electrolyte materials, mainly falling into three categories: sulfides, oxides, and polymers. Specifically, sulfide and oxide electrolytes typically exhibit excellent ionic conductivity, but due to the rigidity of solids, they cannot fully contact the electrode materials, resulting in batteries with high electrolyte / electrode interface resistance. In contrast, polymer electrolytes can be easily fabricated into thin films and have good physical contact with the electrodes, thus improving battery interfacial compatibility. However, the low ionic conductivity and narrow electrochemical window of polymer electrolytes at room temperature limit their application in solid-state lithium metal batteries.

[0003] Introducing inorganic fillers (including inert and active fillers) into polymers to prepare organic / inorganic composite electrolytes is considered an important strategy for solving the aforementioned problems of polymer electrolytes. Compared with isolated inorganic particles, active filler nanosheets or nanowires with large surface areas not only increase surface interactions but also provide additional long-range lithium-ion transport channels. Furthermore, introducing oxygen vacancies into metal oxides (inorganic fillers) can improve ion transport properties; however, this research is still in its early stages, with complex preparation processes and an unclear relationship between the number of oxygen vacancies and the improvement in ionic conductivity.

[0004] Therefore, how to construct polymer electrolytes with high ionic conductivity and wide electrochemical window to further improve the cycle performance and energy density of solid-state lithium batteries is a complex problem that urgently needs to be solved. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a Li-doped oxide nanosheet material and its preparation method, a composite electrolyte membrane including the Li-doped oxide nanosheet material and its preparation method, and a solid-state lithium battery including the composite electrolyte membrane. This invention utilizes the unique structure of the prepared Li-doped oxide nanosheet material to improve the ionic conductivity, electrochemical window, cycle performance, and energy density of the polymer electrolyte and the solid-state lithium battery.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a Li-doped oxide nanosheet material for use in electrolytes, the Li-doped oxide nanosheet material comprising sheet-like structural units having channels with a channel size of 50-200 nm; the specific surface area of ​​the sheet-like structural units is 1-10 m². 2 / g; The sheet-like structural unit includes oxide nanoparticles and Li oxide, and the Li oxide is doped into the lattice of the oxide. The oxide includes any one or a combination of at least two of ZnO, SiO2, SnO, Sb2O3, CuO, and Cu2O. The mass fraction of Li doping is 0-13 wt% of the total mass of the Li-doped oxide nanosheet material, excluding 0, preferably 3.2 wt%.

[0008] Secondly, the present invention provides a method for preparing the aforementioned Li-doped oxide nanosheet material, the method comprising the following steps:

[0009] (1) A solution containing an oxide source, a lithium source, a catalyst, an adhesive, and a solvent is prepared into a fibrous precursor by electrospinning.

[0010] (2) The fibrous precursor in step (1) is calcined under a protective atmosphere to prepare Li-doped oxide nanosheet material.

[0011] As a preferred embodiment of the present invention, the oxide source includes any one or a combination of at least two of Zn salt, Si salt, Sn salt, Sb salt or Cu salt.

[0012] As a preferred embodiment of the present invention, the Zn salt includes any one or a combination of at least two of zinc nitrate, zinc sulfate, zinc acetate, zinc borate, or zinc phosphate.

[0013] As a preferred embodiment of the present invention, the Si salt includes any one or a combination of at least two of silicon dioxide, silicon suboxide, or silicon acetate.

[0014] As a preferred embodiment of the present invention, the Sn salt includes any one or a combination of at least two of stannous sulfate, stannous oxalate, stannous fluorophosphate, or stannous fluoroborate.

[0015] As a preferred embodiment of the present invention, the Sb salt includes any one or a combination of at least two of antimony acetate, antimony ethanol, antimony sodium tartrate, or antimony pentoxide.

[0016] As a preferred embodiment of the present invention, the Cu salt includes any one or a combination of at least two of copper nitrate, copper sulfate, copper acetate, copper borate, or copper phosphate.

[0017] As a preferred embodiment of the present invention, the lithium source includes any one or a combination of at least two of lithium acetate, lithium phosphate, lithium oxalate, or lithium tetraborate.

[0018] As a preferred embodiment of the present invention, the catalyst comprises any one or a combination of at least two of cobalt nitrate, nickel nitrate, cobalt acetate, or ferric nitrate.

[0019] As a preferred embodiment of the present invention, the adhesive comprises any one or a combination of at least two of polyvinylpyrrolidone (PVP), polytetrafluoroethylene, styrene-butadiene rubber, nitrile rubber, or hydroxymethyl cellulose.

[0020] As a preferred embodiment of the present invention, the solvent includes water.

[0021] As a preferred embodiment of the present invention, the amount of oxide source used is such that the oxide content in the solution is 0.1-2 mol / L.

[0022] As a preferred embodiment of the present invention, the amount of lithium source used is such that the lithium source content in the solution is 0.1-2 mol / L.

[0023] As a preferred embodiment of the present invention, the amount of catalyst used is such that the content of catalyst in the solution is 0.01-0.05 mol / L.

[0024] As a preferred embodiment of the present invention, the amount of adhesive used is such that the content of adhesive in the solution is 0.01-1 g / L.

[0025] As a preferred embodiment of the present invention, in step (1), the electrospinning pressure is a positive high voltage of 10-25 kV; the distance between the electrospinning needle and the receiver is 10-20 cm; and the spinning solution flow rate is 0.1-1 mL·h. -1 The continuous spinning time is 1-5 hours.

[0026] As a preferred embodiment of the present invention, the protective atmosphere in step (2) is argon.

[0027] As a preferred embodiment of the present invention, the calcination temperature in step (2) is 300-500℃ and the calcination time is 0.5-12h.

[0028] Thirdly, the present invention provides a composite electrolyte membrane for solid-state lithium batteries, the composite electrolyte membrane comprising: an ion-conducting polymer, an alkali metal salt, and the aforementioned Li-doped oxide nanosheet material; wherein the amount of alkali metal salt is 5wt%-50wt% of the total mass of the ion-conducting polymer, and the amount of Li-doped oxide nanosheet material is 0.5wt%-10wt% of the total mass of the ion-conducting polymer.

[0029] As a preferred embodiment of the present invention, the ion-conducting polymer is polyethylene oxide (PEO) with a molecular weight range of 30w-80w, preferably 60w.

[0030] As a preferred embodiment of the present invention, the alkali metal salt includes any one or a combination of at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxaborate, and lithium perchlorate.

[0031] As a preferred embodiment of the present invention, the amount of the alkali metal salt is 25wt%-35wt% of the total mass of the ion-conducting polymer.

[0032] As a preferred embodiment of the present invention, the amount of the Li-doped oxide nanosheet material is 2wt%-5wt% of the total mass of the ion-conducting polymer.

[0033] Fourthly, the present invention provides a method for preparing the aforementioned composite electrolyte membrane, the method comprising the following steps:

[0034] (1) Dissolve the ion-conducting polymer and the alkali metal salt in a solvent according to the dosage ratio to obtain a mixed solution;

[0035] (2) Dissolve the Li-doped oxide nanosheet material in the mixed solution of step (1) according to the dosage ratio to obtain a suspension;

[0036] (3) The suspension obtained in step (2) is coated on the substrate and allowed to stand and dry to obtain a composite electrolyte membrane.

[0037] As a preferred embodiment of the present invention, step (1) is carried out in an environment with a relative humidity of <0.1wt%.

[0038] As a preferred embodiment of the present invention, the solvent in step (1) includes any one or a combination of at least two of anhydrous acetonitrile, N-methylpyrrolidone, anisole or isopropanol.

[0039] As a preferred embodiment of the present invention, step (2) is carried out in an environment with a relative humidity of <0.1wt%.

[0040] As a preferred embodiment of the present invention, the coating in step (3) is blade coating, wherein the blade slit width is 50μm to 500μm.

[0041] As a preferred embodiment of the present invention, the substrate in step (3) includes a polytetrafluoroethylene substrate.

[0042] As a preferred embodiment of the present invention, the temperature for static drying in step (3) is 50-70°C and the time is 3-24h.

[0043] Fifthly, the present invention provides a solid-state lithium battery, the solid-state lithium battery comprising: an anode, a cathode and the aforementioned composite electrolyte membrane, wherein the composite electrolyte membrane is disposed between the anode and the cathode.

[0044] As a preferred embodiment of the present invention, the anode material is a high-nickel ternary cathode material, wherein the percentage of nickel moles in the anode material is greater than 80% of the total number of moles of metal cations other than lithium ions; the cathode material is a lithium metal strip or a lithium-copper composite strip, wherein the lithium layer thickness is 20μm-200μm, preferably 50μm-100μm.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] This invention introduces low-cost Li-doped oxide nanosheets into ion-conducting polymers. By increasing the number of oxygen vacancies on the surface of the Li-doped oxide nanosheets, the movement of anions in the lithium salt is effectively restricted, thereby increasing the concentration of transportable lithium ions. Simultaneously, the unique nanosheet structure endows the oxide nanosheet material with a large specific surface area, effectively enhancing the ceramic / polymer interface interaction and providing a long-range ordered transport channel for lithium ions.

[0047] The composite electrolyte membrane optimized by adding Li-doped oxide nanosheets exhibits high ionic conductivity (up to 3.3 × 10⁻⁶). -4 The optimized composite electrolyte membrane exhibits excellent performance in terms of S / cm, a wide electrochemical stability window (up to 5.2V), and superior ability to suppress lithium dendrite growth. The resulting solid-state lithium battery can sustain stable cycling for 1500 cycles. Attached Figure Description

[0048] Figure 1 SEM images of LZO nanosheets and their combinations prepared in Example 1 of this invention;

[0049] Figure 2 TEM and SAED images of LZO nanosheets and their combinations prepared in Example 1 of this invention;

[0050] Figure 3 The XRD patterns of LZO nanosheets and their combinations with different Li doping in Examples 1, 2 and 3 of this invention are shown.

[0051] Figure 4 This is a SEM image of the composite electrolyte membrane in group a of Example 4 of the present invention;

[0052] Figure 5 The XRD patterns of the composite electrolyte membranes of groups a, b, and c in Example 4 of this invention are shown.

[0053] Figure 6This is an Arrhenius curve diagram of the composite electrolyte membranes of groups a, b, and c in Example 4 of the present invention;

[0054] Figure 7 This is a schematic diagram illustrating the stability of the composite electrolyte membranes of groups a, b, and c in Example 4 of the present invention to the lithium anode under different current densities.

[0055] Figure 8 This is a cycle curve diagram of the all-solid-state lithium iron phosphate button battery in Embodiment 5 of the present invention;

[0056] Figure 9 This is a cycle curve diagram of the all-solid-state lithium iron phosphate button battery in Embodiment 6 of the present invention. Detailed Implementation

[0057] To better illustrate the present invention and facilitate understanding of its technical solutions, the present invention will be further described in detail below. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0058] The present invention provides a Li-doped oxide nanosheet material for use in electrolytes. The Li-doped oxide nanosheet material comprises sheet-like structural units, each sheet-like structural unit having channels with a channel size of 50-200 nm, such as 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, or 200 nm, but not limited to the listed values; other unlisted values ​​within this range are also applicable. The specific surface area of ​​the sheet-like structural unit is 1-10 m². 2 / g, for example, 1m 2 / g、2m 2 / g、3m 2 / g、4m 2 / g、5m 2 / g、6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g or 10m 2 / g, etc., but not limited to the listed values; other unlisted values ​​within this range also apply; the sheet-like structural unit includes oxide nanoparticles and Li oxide, and the Li oxide is doped into the oxide lattice. The oxide includes any one or a combination of at least two of ZnO, SiO2, SnO, Sb2O3, CuO, or Cu2O. The mass fraction of Li doping is 0-13 wt% of the total mass of the Li-doped oxide nanosheet material, excluding 0, for example, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, or 13 wt%, but not limited to the listed values; other unlisted values ​​within this range also apply, preferably 3.2 wt%.

[0059] In this invention, the electrolyte is primarily used for preparing solid-state lithium batteries. As those skilled in the art will understand, the Li-doped oxide nanosheet material described in this invention is not used as a single sheet-like structural unit, but rather as an aggregate of sheet-like structural units, i.e., a nanosheet material.

[0060] In this invention, the oxide is chosen so that it can be alloyed with Li, thereby providing a long-range and ordered transport channel for lithium ions.

[0061] In this invention, the Li doping content in the Li-doped oxide nanosheet material has a significant impact on the performance of the electrolyte membrane and solid-state lithium battery subsequently fabricated. If the Li doping content is too low, it is not conducive to the dissociation of lithium salt, resulting in low ionic conductivity. If the Li doping content is too high, it affects the number of oxygen vacancies on the nanosheet surface, limits the concentration of mobile lithium, and also causes a decrease in ionic conductivity.

[0062] The specific embodiments of this invention also provide a method for preparing the aforementioned Li-doped oxide nanosheet material, the method comprising the following steps:

[0063] (1) A solution containing an oxide source, a lithium source, a catalyst, an adhesive, and a solvent is prepared into a fibrous precursor by electrospinning.

[0064] (2) The fibrous precursor in step (1) is calcined under a protective atmosphere to prepare Li-doped oxide nanosheet material.

[0065] In this invention, during the preparation of Li-doped oxide nanosheet materials, the catalyst promotes lithium doping, and the adhesive is beneficial to improving the film strength and consistency.

[0066] As a preferred embodiment of the present invention, the oxide source includes any one or a combination of at least two of Zn salt, Si salt, Sn salt, Sb salt or Cu salt. Typical but non-limiting examples of the combination include: a combination of Zn salt and Si salt, a combination of Sn salt and Sb salt, a combination of Sb salt and Cu salt, a combination of Zn salt, Si salt and Sn salt, a combination of Sn salt, Sb salt and Cu salt, etc.

[0067] As a preferred embodiment of the present invention, the Zn salt includes any one or a combination of at least two of zinc nitrate, zinc sulfate, zinc acetate, zinc borate, or zinc phosphate. Typical but non-limiting examples of such combinations include: combinations of zinc nitrate and zinc sulfate, combinations of zinc sulfate and zinc acetate, combinations of zinc borate and zinc phosphate, combinations of zinc nitrate, zinc sulfate, and zinc acetate, and combinations of zinc acetate, zinc borate, and zinc phosphate, etc.

[0068] As a preferred embodiment of the present invention, the Si salt includes any one or a combination of at least two of silicon dioxide, silicon suboxide, or silicon acetate. Typical but non-limiting examples of such combinations include: a combination of silicon dioxide and silicon suboxide, a combination of silicon suboxide and silicon acetate, a combination of silicon dioxide, silicon suboxide, and silicon acetate, etc.

[0069] As a preferred embodiment of the present invention, the Sn salt includes any one or a combination of at least two of stannous sulfate, stannous oxalate, stannous fluorophosphate, or stannous fluoroborate. Typical but non-limiting examples of such combinations include: a combination of stannous sulfate and stannous oxalate, a combination of stannous oxalate and stannous fluorophosphate, a combination of stannous fluorophosphate and stannous fluoroborate, etc.

[0070] As a preferred embodiment of the present invention, the Sb salt includes any one or a combination of at least two of antimony acetate, antimony ethanol, antimony sodium tartrate, or antimony pentoxide. Typical but non-limiting examples of such combinations include: a combination of antimony acetate and antimony ethanol, a combination of antimony ethanol and antimony sodium tartrate, a combination of antimony sodium tartrate and antimony pentoxide, a combination of antimony acetate, antimony ethanol, and antimony sodium tartrate, etc.

[0071] As a preferred embodiment of the present invention, the Cu salt includes any one or a combination of at least two of copper nitrate, copper sulfate, copper acetate, copper borate, or copper phosphate. Typical but non-limiting examples of such combinations include: a combination of copper nitrate and copper sulfate, a combination of copper sulfate and copper acetate, a combination of copper acetate, copper borate, and copper phosphate, etc.

[0072] As a preferred embodiment of the present invention, the lithium source includes any one or a combination of at least two of lithium acetate, lithium phosphate, lithium oxalate, or lithium tetraborate. Typical but non-limiting examples of such combinations include: combinations of lithium acetate and lithium phosphate, combinations of lithium phosphate and lithium oxalate, combinations of lithium oxalate and lithium tetraborate, combinations of lithium acetate, lithium phosphate, and lithium oxalate, and combinations of lithium acetate, lithium phosphate, lithium oxalate, and lithium tetraborate, etc.

[0073] As a preferred embodiment of the present invention, the catalyst comprises any one or a combination of at least two of cobalt nitrate, nickel nitrate, cobalt acetate, or ferric nitrate. Typical but non-limiting examples of such combinations include: a combination of cobalt nitrate and nickel nitrate, a combination of nickel nitrate and cobalt acetate, a combination of cobalt acetate and ferric nitrate, a combination of cobalt nitrate, nickel nitrate, and ferric nitrate, etc.

[0074] As a preferred embodiment of the present invention, the adhesive comprises any one or a combination of at least two of polyvinylpyrrolidone (PVP), polytetrafluoroethylene, styrene-butadiene rubber, nitrile rubber, or carboxymethyl cellulose. Typical but non-limiting examples of such combinations include: a combination of polyvinylpyrrolidone and polytetrafluoroethylene, a combination of styrene-butadiene rubber and nitrile rubber, a combination of nitrile rubber and carboxymethyl cellulose, a combination of polyvinylpyrrolidone, polytetrafluoroethylene, and styrene-butadiene rubber, etc.

[0075] As a preferred embodiment of the present invention, the solvent includes water.

[0076] As a preferred embodiment of the present invention, the amount of oxide source used is such that the oxide content in the solution is 0.1-2 mol / L, for example, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L or 2 mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0077] As a preferred embodiment of the present invention, the amount of lithium source used is such that the lithium source content in the solution is 0.1-2 mol / L, for example, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.7 mol / L, 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L or 2 mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0078] As a preferred embodiment of the present invention, the amount of catalyst used is such that the content of catalyst in the solution is 0.01-0.05 mol / L, for example 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L or 0.05 mol / L, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0079] As a preferred embodiment of the present invention, the amount of adhesive used is such that the content of adhesive in the solution is 0.01-1 g / L, for example, 0.01 g / L, 0.03 g / L, 0.05 g / L, 0.07 g / L, 0.1 g / L, 0.2 g / L, 0.4 g / L, 0.6 g / L, 0.8 g / L or 1 g / L, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0080] As a preferred embodiment of the present invention, the electrospinning pressure in step (1) is a positive high voltage of 10-25kV, such as 10kV, 13kV, 15kV, 17kV, 20kV, 23kV, or 25kV, but not limited to the listed values; other unlisted values ​​within this range are also applicable. The distance between the electrospinning needle and the receiver is 10-20cm, such as 10cm, 11cm, 12cm, 13cm, 14cm, 15cm, 16cm, 17cm, 18cm, 19cm, or 20cm, but not limited to the listed values; other unlisted values ​​within this range are also applicable. The spinning solution flow rate is 0.1-1mL·h. -1 For example, 0.1 mL·h -1 0.2 mL·h -1 0.3 mL·h -1 0.4 mL·h -1 0.5 mL·h -1 0.6 mL·h -1 0.7 mL·h -1 0.8 mL·h -1 0.9 mL·h -1 or 1 mL·h -1 The values ​​are not limited to those listed; other unlisted values ​​within the range also apply. The continuous spinning time is 1-5 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, or 5 hours, but is not limited to those listed; other unlisted values ​​within the range also apply.

[0081] As a preferred embodiment of the present invention, the protective atmosphere in step (2) is argon.

[0082] As a preferred embodiment of the present invention, the calcination temperature in step (2) is 300-500℃, such as 300℃, 350℃, 400℃, 450℃ or 500℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable. The calcination time is 0.5-12h, such as 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h or 12h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0083] This invention provides a composite electrolyte membrane for solid-state lithium batteries, comprising: an ion-conducting polymer, an alkali metal salt, and the aforementioned Li-doped oxide nanosheet material. The alkali metal salt is used in an amount of 5wt%-50wt% of the total mass of the ion-conducting polymer, for example, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, or 50wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. The Li-doped oxide nanosheet material is used in an amount of 0.5wt%-10wt% of the total mass of the ion-conducting polymer, for example, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, or 10wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0084] As a preferred embodiment of the present invention, the ion-conducting polymer is polyethylene oxide (PEO) with a molecular weight range of 30w-80w, such as 30w, 35w, 40w, 55w, 60w, 65w, 70w, 75w or 80w, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, with 60w being the preferred value.

[0085] As a preferred embodiment of the present invention, the alkali metal salt includes any one or a combination of at least two of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium dioxolane-borate, and lithium perchlorate. Typical but non-limiting examples of such combinations include: combinations of lithium bis(trifluoromethanesulfonyl)imide and lithium bis(fluorosulfonyl)imide, combinations of lithium bis(fluorosulfonyl)imide and lithium dioxolane-borate, combinations of lithium dioxolane-borate and lithium perchlorate, and combinations of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium dioxolane-borate, etc.

[0086] As a preferred embodiment of the present invention, the amount of the alkali metal salt is 25wt%-35wt% of the total mass of the ion-conducting polymer.

[0087] As a preferred embodiment of the present invention, the amount of Li-doped oxide nanosheet material is 2wt%-5wt% of the total mass of the ion-conducting polymer.

[0088] In this invention, the amount of Li-doped oxide nanosheet material used will affect the physicochemical properties of the composite electrolyte membrane. Too much of it will cause particle agglomeration, affecting the consistency of the membrane and thus reducing the ionic conductivity. Too little of it will reduce the strength of the composite membrane and cause its ionic conductivity to be low due to the lack of sufficient active filler.

[0089] The specific embodiments section of this invention provides a method for preparing the aforementioned composite electrolyte membrane, the method comprising the following steps:

[0090] (1) Dissolve the ion-conducting polymer and the alkali metal salt in a solvent according to the dosage ratio to obtain a mixed solution;

[0091] (2) Dissolve the Li-doped oxide nanosheet material in the mixed solution of step (1) according to the dosage ratio to obtain a suspension;

[0092] (3) The suspension obtained in step (2) is coated on the substrate and allowed to stand and dry to obtain a composite electrolyte membrane.

[0093] As a preferred embodiment of the present invention, step (1) is carried out in an environment with a relative humidity of <0.1wt%.

[0094] As a preferred embodiment of the present invention, the solvent in step (1) includes any one or a combination of at least two of anhydrous acetonitrile, N-methylpyrrolidone, anisole, or isopropanol.

[0095] As a preferred embodiment of the present invention, step (2) is carried out in an environment with a relative humidity of <0.1wt%.

[0096] As a preferred embodiment of the present invention, the coating in step (3) is blade coating, wherein the blade slit width is 50μm to 500μm, for example 50μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm or 500μm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0097] As a preferred embodiment of the present invention, the substrate in step (3) includes a polytetrafluoroethylene substrate.

[0098] As a preferred embodiment of the present invention, the temperature for static drying in step (3) is 50-70℃, such as 50℃, 55℃, 60℃, 65℃ or 70℃, but not limited to the listed values. Other unlisted values ​​within this range are also applicable. The time is 3-24h, such as 3h, 5h, 7h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0099] A specific embodiment of the present invention provides a solid-state lithium battery, which includes an anode, a cathode, and the aforementioned composite electrolyte membrane, wherein the composite electrolyte membrane is disposed between the anode and the cathode.

[0100] As a preferred embodiment of the present invention, the anode material is a high-nickel ternary cathode material, wherein the percentage of nickel moles in the anode material relative to the total number of metal cations other than lithium ions is >80%, such as 82%, 85%, 87%, 90%, 93%, 95%, or 97%, etc., but not limited to the listed values; other unlisted values ​​within this range are also applicable. The cathode material is a lithium metal strip or a lithium-copper composite strip, wherein the lithium layer thickness is 20μm-200μm, such as 20μm, 30μm, 50μm, 70μm, 100μm, 130μm, 150μm, 170μm, or 200μm, etc., but not limited to the listed values; other unlisted values ​​within this range are also applicable, preferably 50μm-100μm.

[0101] The following are typical but non-limiting embodiments of the present invention:

[0102] Example 1:

[0103] This embodiment provides a Li-doped oxide nanosheet material for use in electrolytes. The Li-doped oxide nanosheet material comprises sheet-like structural units, each sheet-like structural unit having channels with a channel size of 100 nm. The specific surface area of ​​the sheet-like structural units is 4 m². 2 / g, the sheet-like structural unit includes oxide nanoparticles and Li oxide, and the Li oxide is doped into the lattice of the oxide, the oxide being ZnO, and the mass fraction of Li doping is 3.2wt% of the total mass of the Li-doped oxide nanosheet material.

[0104] The preparation method of the Li-doped oxide nanosheet material includes the following steps:

[0105] (1) Zinc nitrate, cobalt nitrate, lithium acetate and PVP were mixed in water at a mass ratio of 10:0.32:1:0.05 to form a solution and then electrospun into a fibrous precursor. The electrospinning voltage was 20kV, the distance between the needle and the receiver was 15cm, the flow rate was 0.5mL·h-1, and the electrospinning was continuous for 1h.

[0106] (2) The fibrous precursor in step (1) was calcined at 400°C for 6 hours under an argon atmosphere to prepare Li-doped ZnO nanosheet material.

[0107] The microstructure of the Li-doped ZnO nanosheet material prepared in this embodiment is as follows: Figure 1 and Figure 2 As shown, a clear layered structure with micropores can be observed. XRD characterization of it is performed, as shown... Figure 3 As shown.

[0108] Example 2:

[0109] This invention provides a Li-doped oxide nanosheet material for use in electrolytes. Except for the mass fraction of Li doping being 0.8 wt%, the other parameters and preparation method of the Li-doped oxide nanosheet material are the same as those in Example 1.

[0110] Example 3:

[0111] This invention provides a Li-doped oxide nanosheet material for use in electrolytes. Except for the Li doping mass fraction of 12.8 wt%, the other parameters and preparation method of the Li-doped oxide nanosheet material are the same as those in Example 1.

[0112] The Li-doped ZnO nanosheets in Examples 1, 2, and 3 were characterized by XRD, as shown below. Figure 3 As shown, all diffraction peaks of the lithium-doped LZO nanosheets match well with those of hexagonal wurtzite zinc oxide (JCPDS card number 36-1451). Compared to pure zinc oxide nanosheets, the three peaks of the lithium-doped LZO nanosheets at (1 0 0), (0 0 2), and (1 0 1) are slightly lower. According to Bragg's law, the decrease in diffraction angle (θ) indicates an increase in the interplanar spacing (d(hkl)), i.e., the lattice parameter of zinc oxide. Therefore, it can be concluded that Li has been successfully doped into the lattice of zinc oxide.

[0113] Example 4:

[0114] This embodiment provides three sets of composite electrolyte membranes for solid-state lithium batteries, namely sets a, b, and c. The difference between each set is that they use the Li-doped ZnO nanosheet material from Examples 1, 2, and 3, respectively, while other parameters are the same. Specifically, the composite electrolyte membrane includes: an ion-conducting polymer, an alkali metal salt, and Li-doped ZnO nanosheet material. The ion-conducting polymer is polyethylene oxide with a molecular weight range of 60 wt%, the alkali metal salt is lithium bis(trifluoromethanesulfonyl)imide, and its amount is 30 wt% of the total mass of the ion-conducting polymer. The amount of Li-doped ZnO nanosheet material is 3 wt% of the total mass of the ion-conducting polymer.

[0115] The structure of the composite electrolyte membrane prepared using the Li-doped ZnO nanosheet material in Example 1 is as follows: Figure 4 As shown.

[0116] The composite electrolyte membranes in groups a, b, and c were characterized by XRD, as follows: Figure 5As shown, the pure PEO / LiTFSI electrolyte exhibits two distinct characteristic peaks at 19.3° and 23.6°, indicating the presence of a crystalline state within the polymer. Furthermore, with increasing lithium doping in the LZO nanosheets, the intensity of the crystalline peak in the PEO polymer gradually decreases. This suggests that lithium doping increases the oxygen vacancy content on the LZO nanosheet surface, which promotes the interaction between the nanosheets and the polymer. This effectively increases the content of the amorphous phase in the composite electrolyte and accelerates the migration of lithium ions along the PEO polymer molecular chains.

[0117] The Arrhenius curves of the composite electrolyte membranes in groups a, b, and c are shown below. Figure 6 As shown, the ionic conductivity of all CPE-LZO composite electrolytes is significantly higher than that of pure PEO / LiTFSI electrolytes in the temperature range of 30-70℃. Furthermore, the ionic conductivity of the composite electrolytes gradually increases with increasing lithium doping concentration, reaching a maximum value of 3.3 × 10⁻⁴ S·cm at a doping concentration of 3.2 wt%. -1 .

[0118] The stability of the composite electrolyte membrane to the lithium anode in group A under different current densities, such as... Figure 7 As shown, the test battery using the CPE-3.2LZO composite electrolyte membrane exhibits excellent long-cycle stability at different current densities of 0.2 mA·cm, 0.4 mA·cm, 0.6 mA·cm, 0.8 mA·cm, and 1 mA·cm, especially when the current density increases from 1 mA·cm. -2 Return to 0.4mA·cm -2 At that time, the battery can still cycle stably for 1200 hours without short circuit, and the polarization voltage does not increase significantly throughout the cycle.

[0119] Example 5:

[0120] This embodiment provides an all-solid-state lithium iron phosphate button battery, which includes an anode, a cathode, and the composite electrolyte membrane in group a of embodiment 4. The anode is made of phosphoric acid, the cathode is made of lithium metal strip, and the lithium layer thickness is 300 μm.

[0121] Performance tests were conducted on the all-solid-state lithium iron phosphate button battery. The test conditions were: charge / discharge voltage range of 2.5-3.8V; constant current charge / discharge; and charge / discharge current density of 0.1 mA·cm⁻¹ every 10 cycles for the first 30 cycles. -2 0.2mA·cm -2 0.4mA·cm -2 The current density then returned to 0.2 mA·cm. -2 The test results are as follows Figure 8 As shown.

[0122] Example 6:

[0123] This embodiment provides an all-solid-state ternary button battery, which includes an anode, a cathode, and the composite electrolyte membrane in group a of Example 4. The anode material is high-nickel NCM811 material, the cathode material is lithium metal strip, and the lithium layer thickness is 300μm.

[0124] Performance tests were conducted on the all-solid-state ternary button cell battery. The test conditions were: charge / discharge voltage range of 2.8-4.2V; constant current charge / discharge, with a charge / discharge current density of 0.05 mA·cm⁻¹ every 10 cycles for the first 30 cycles. -2 0.1mA·cm -2 0.2mA·cm -2 0.1mA·cm -2 The current density then returned to 0.1 mA·cm. -2 The test results are as follows Figure 9 As shown.

[0125] Comparative Example 1:

[0126] This comparative example provides an undoped ZnO nanosheet material, whose structure and preparation method are the same as those in Example 1, except that Li doping is not performed.

[0127] The composite electrolyte membrane prepared using this comparative example was tested under the same conditions as in Example 4. Figure 6 As shown, although the ionic conductivity of the 0% lithium-doped ZnO composite electrolyte membrane is improved compared to the undoped electrolyte membrane, its ionic conductivity is lower than that of the lithium-doped ZnO composite membrane.

[0128] All-solid-state lithium iron phosphate button batteries were prepared using the composite electrolyte membrane of this comparative example, and tested under the same conditions as in Example 5. Figure 8 As shown, the battery using the comparative film has poor cycle performance, with a capacity decay of more than 20% after 50 cycles.

[0129] Comparative Example 2:

[0130] This comparative example provides a Li-doped ZnO nanosheet material, whose structure and preparation method are the same as those in Example 1, except that the mass fraction of Li doping in the Li-doped ZnO nanosheet material is 14 wt%.

[0131] The composite electrolyte membrane prepared using this comparative example was tested under the same conditions as in Example 4. It was found that the ionic conductivity of the membrane was further reduced.

[0132] All-solid-state lithium iron phosphate button batteries were prepared using the composite electrolyte membrane of this comparative example and tested under the same conditions as in Example 5. Compared with Comparative Example 1, the button batteries using this membrane showed slightly improved cycle performance, but the number of cycles was less than 1000 and below 1500.

[0133] Comparative Example 3:

[0134] This comparative example provides a composite electrolyte membrane prepared using the Li-doped ZnO nanosheet material from Example 1. The material dosage and preparation process are the same as in Example 4, except that the amount of Li-doped ZnO nanosheet material is 15 wt% of the total mass of the ion-conducting polymer.

[0135] All-solid-state lithium iron phosphate button batteries were prepared using the composite electrolyte membrane of this comparative example and tested under the same conditions as in Example 5. The cycle performance of the button batteries using this membrane was further reduced, with the number of cycles being less than 500.

[0136] Example 7:

[0137] This embodiment provides a Li-doped oxide nanosheet material for use in electrolytes. The Li-doped oxide nanosheet material comprises sheet-like structural units, each sheet-like structural unit having channels with a channel size of 100 nm; the specific surface area of ​​the sheet-like structural units is 4 m². 2 / g, the sheet-like structural unit includes oxide nanoparticles and Li oxide, and the Li oxide is doped into the lattice of the oxide, the oxide being SiO2, and the mass fraction of Li doping is 5wt% of the total mass of the Li-doped SiO2 nanosheet material.

[0138] The preparation method of the Li-doped SiO2 nanosheet material is the same as that in Example 1.

[0139] A composite electrolyte membrane was prepared using the Li-doped SiO2 nanosheet material in this embodiment, with the same dosage ratio and preparation process as in Example 4. The prepared composite electrolyte membrane was tested, and its ionic conductivity was found to be 10. -4 S / cm, while the ionic conductivity of the composite electrolyte membrane prepared from undoped SiO2 nanosheets is 2×10 -5 S / cm.

[0140] All-solid-state lithium iron phosphate button batteries were prepared using the composite electrolyte membrane made from Li-doped SiO2 nanosheets in this embodiment. The amount of materials and the preparation process were the same as in Example 5. The battery performance was tested, and the results showed that the button battery using the composite electrolyte membrane had a significantly improved cycle performance compared to the undoped electrolyte membrane, but the number of cycles was less than 500, far below 1500.

[0141] Example 8:

[0142] This embodiment provides a Li-doped SnO nanosheet material for electrolytes, with a structure similar to that in Example 1, except that the pore size is 200 nm and the specific surface area of ​​the sheet-like structural units is 2 m². 2 / g, where the Li doping mass fraction is 5wt% of the total mass of the Li-doped SnO nanosheet material.

[0143] The preparation method of the Li-doped SnO nanosheet material is the same as that in Example 1.

[0144] A composite electrolyte membrane was prepared using the Li-doped SnO nanosheet material in this embodiment. The dosage ratio and preparation process were the same as in Example 4. The obtained composite electrolyte membrane was tested, and its ionic conductivity was found to be 2.5 × 10⁻⁶. - 4 S / cm, while the ionic conductivity of the composite electrolyte membrane prepared from undoped SnO nanosheets is 3×10 -5 S / cm.

[0145] All-solid-state lithium iron phosphate button batteries were prepared using the composite electrolyte membrane made from Li-doped SnO nanosheets in this embodiment. The amount of materials and the preparation process were the same as in Example 5. The battery performance was tested, and the results showed that the button battery using the composite electrolyte membrane had a significantly improved cycle performance compared to the undoped electrolyte membrane, but the number of cycles was less than 600, far below 1500.

[0146] Example 9:

[0147] This embodiment provides a Li-doped oxide nanosheet material for electrolytes, comprising sheet-like structural units with channels having a channel size of 60 nm and a specific surface area of ​​8 m². 2 / g, the sheet-like structural unit includes oxide nanoparticles and Li oxide, and the Li oxide is doped into the oxide lattice. The oxide is ZnO, and the mass fraction of Li doping is 3.2wt% of the total mass of the Li-doped oxide nanosheet material.

[0148] The preparation method of the Li-doped oxide nanosheet material is the same as that in Example 1, except that: in step (1), the Zn salt is zinc phosphate, the Li salt is lithium phosphate, the catalyst is nickel nitrate, and the adhesive is polytetrafluoroethylene, and the amounts of zinc phosphate, lithium phosphate, nickel nitrate, and polytetrafluoroethylene are 10:1.5:0.5:0.1; in step (2), the calcination temperature is 500℃ and the calcination time is 3h.

[0149] A composite electrolyte membrane was prepared using the Li-doped ZnO nanosheet material in this embodiment, with the same dosage ratio and preparation process as in Example 4. The prepared composite electrolyte membrane was tested, and its ionic conductivity was found to be 2 × 10⁻⁶. -4 The ionic conductivity of the composite electrolyte membrane prepared from undoped SiO2 nanosheets is 1.5 × 10⁻⁶ S / cm, while that of the undoped SiO₂ nanosheets is 1.5 × 10⁻⁶ S / cm. -5 S / cm.

[0150] All-solid-state lithium iron phosphate button batteries were prepared using the composite electrolyte membrane made from Li-doped ZnO nanosheets in this embodiment. The amount of materials and the preparation process were the same as in Example 5. The battery performance was tested, and the results showed that the button battery using the composite electrolyte membrane had a significantly improved cycle performance compared to the undoped electrolyte membrane, but the number of cycles was less than 800, far below 1500.

[0151] The applicant declares that the detailed process equipment and process flow of this invention are illustrated through the above embodiments, but this invention is not limited to the above detailed process equipment and process flow, that is, it does not mean that this invention must rely on the above detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the products of this invention, additions of auxiliary components, and selection of specific methods, all fall within the protection scope and disclosure scope of this invention.

Claims

1. A Li-doped oxide nanosheet material for electrolyte, characterized in that, The Li-doped oxide nanosheet material comprises a sheet-shaped structural unit, the sheet-shaped structural unit has a pore channel thereon, the pore channel has a size of 50-200 nm; the specific surface area of the sheet-shaped structural unit is 1-10 m 2 / g; the sheet-shaped structural unit comprises oxide nanoparticles and an oxide of Li, and the oxide of Li is doped into the crystal lattice of the oxide, the oxide comprises any one or a combination of at least two of ZnO, SiO2, SnO, Sb2O3, CuO or Cu2O, and the mass fraction of the Li doping is 0-13wt% and not including 0 of the total mass of the Li-doped oxide nanosheet material.

2. The method for preparing the Li-doped oxide nanosheet material as claimed in claim 1, characterized in that, The method comprises the following steps: (1) configuring an oxide source, a lithium source, a catalyst, an adhesive and a solvent into a solution to prepare a fibrous precursor by electrospinning; (2) calcining the fibrous precursor in step (1) to prepare a Li-doped oxide nanosheet material under a protective atmosphere; The amount of the lithium source is such that the content of the lithium source in the solution is 0.1-2 mol / L.

3. The production method according to claim 2, characterized by, The oxide source comprises any one or a combination of at least two of a Zn salt, a Si salt, a Sn salt, a Sb salt or a Cu salt.

4. The production method according to claim 3, characterized by, The Zn salt comprises any one or a combination of at least two of zinc nitrate, zinc sulfate, zinc acetate, zinc borate or zinc phosphate.

5. The preparation method according to claim 3, characterized in that, The Si salt comprises any one or a combination of at least two of silicon dioxide, silicon monoxide or silicon acetate.

6. The preparation method according to claim 3, characterized in that, The Sn salt comprises any one or a combination of at least two of stannous sulfate, stannous oxalate, stannous fluorophosphate or stannous fluoroborate.

7. The preparation method according to claim 3, characterized in that, The Sb salt comprises any one or a combination of at least two of antimony acetate, antimony ethylate, sodium antimony tartrate or antimony pentoxide.

8. The preparation method according to claim 3, characterized in that, The Cu salt comprises any one or a combination of at least two of copper nitrate, copper sulfate, copper acetate, copper borate or copper phosphate.

9. The preparation method according to claim 2, characterized in that, The lithium source comprises any one or a combination of at least two of lithium acetate, lithium phosphate, lithium oxalate or lithium tetraborate.

10. The method of claim 2, wherein, The catalyst comprises any one or a combination of at least two of cobalt nitrate, nickel nitrate, cobalt acetate or iron nitrate.

11. The method of claim 2, wherein, The adhesive comprises any one or a combination of at least two of polyvinylpyrrolidone, polytetrafluoroethylene, butadiene styrene rubber, butyl nitrile rubber or hydroxymethyl cellulose.

12. The method of claim 2, wherein, The solvent comprises water.

13. The preparation method according to claim 2, characterized in that, The amount of the oxide source is such that the content of the oxide in the solution is 0.1-2 mol / L.

14. The method of claim 2, wherein, The amount of the catalyst is such that the content of the catalyst in the solution is 0.01-0.05 mol / L.

15. The preparation method according to claim 2, characterized in that, The amount of the adhesive is such that the content of the adhesive in the solution is 0.01-1 g / L.

16. The method of claim 2, wherein, The pressure of electrospinning in step (1) is positive high pressure of 10-25 kV; the distance between the electrospinning needle and the receiver is 10-20 cm; the flow rate of the spinning solution is 0.1-1 mL·h -1 ; and the continuous spinning time is 1-5 h.

17. The method of claim 2, wherein, The protective atmosphere in step (2) is argon.

18. The method of claim 2, wherein, The calcination temperature in step (2) is 300-500 DEG C, and the calcination time is 0.5-12 h.

19. A composite electrolyte membrane for a solid-state lithium battery, characterized by, The composite electrolyte membrane comprises an ion-conducting polymer, an alkali metal salt and the Li-doped oxide nanosheet material in claim 1; wherein the amount of the alkali metal salt is 5wt%-50wt% of the total mass of the ion-conducting polymer, and the amount of the Li-doped oxide nanosheet material is 0.5wt%-10wt% of the total mass of the ion-conducting polymer.

20. The composite electrolyte film of claim 19, wherein, The ion-conducting polymer is polyethylene oxide, and the molecular weight range is 30w-80w.

21. The composite electrolyte film of claim 20, wherein, The molecular weight range of the ion-conducting polymer is 60w.

22. The composite electrolyte film of claim 19, wherein, The alkali metal salt comprises any one or a combination of at least two of lithium bis(trifluoromethylsulfonyl)imide, lithium bisfluorosulfonylimide, lithium bis(oxalato)borate or lithium perchlorate.

23. The composite electrolyte film of claim 19, wherein, The amount of the alkali metal salt is 25wt%-35wt% of the total mass of the ion-conducting polymer.

24. The composite electrolyte film of claim 19, wherein, The amount of the Li-doped oxide nanosheet material is 2wt%-5wt% of the total mass of the ion-conducting polymer.

25. A method of making the composite electrolyte film of claim 19, wherein, The preparation method comprises the following steps: (1) dissolving the ion-conducting polymer and the alkali metal salt in a solvent according to the amount ratio to obtain a mixed solution; (2) The Li-doped oxide nanosheet material is dissolved in the mixed solution in step (1) according to the amount ratio to obtain a suspension; (3) The suspension obtained in step (2) is coated on a substrate and left to dry to obtain a composite electrolyte film.

26. The method of claim 25, wherein, Step (1) is performed in an environment with a relative humidity < 0.1wt%.

27. The preparation method according to claim 25, characterized in that, The solvent in step (1) includes any one or a combination of at least two of anhydrous acetonitrile, N-methyl pyrrolidone, anisole or isopropyl alcohol.

28. The preparation method according to claim 25, characterized in that, Step (2) is performed in an environment with a relative humidity < 0.1wt%.

29. The method of claim 25, wherein, The coating in step (3) is a doctor blade coating, and the doctor blade coating has a doctor blade slit width of 50-500μm.

30. The method of claim 25, wherein, The substrate in step (3) includes a polytetrafluoroethylene substrate.

31. The method of claim 25, wherein, The temperature for the standing and drying in step (3) is 50-70℃, and the time is 3-24h.

32. A solid-state lithium battery, characterized by, The solid-state lithium battery includes an anode, a cathode and the composite electrolyte film as claimed in claim 19, and the composite electrolyte film is arranged between the anode and the cathode.

33. The solid-state lithium battery of claim 32, wherein, The material of the anode is a high-nickel ternary positive electrode material, wherein the percentage of the number of moles of nickel in the total number of moles of metal cations in the anode material excluding lithium ions is > 80%; the material of the cathode is a lithium metal strip or a lithium-copper composite strip, wherein the thickness of the lithium layer is 20-200μm.

34. The solid-state lithium battery of claim 33, wherein, The thickness of the lithium layer is 50-100μm.

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