Inorganic / organic composite thin film solid electrolyte based on porous ceramic solid electrolyte and preparation method and application thereof

Abstract

The present application relates to a kind of inorganic / organic composite thin film solid electrolyte based on porous ceramic solid electrolyte and its preparation method and application.The inorganic / organic composite thin film solid electrolyte based on porous ceramic solid electrolyte includes: porous ceramic solid electrolyte, and organic electrolyte filled in the pore structure of porous ceramic solid electrolyte;The organic electrolyte is obtained by in-situ photoinitiation after the precursor solution of uniform mixture of acrylate compound, photoinitiator, lithium salt and small molecule solvent is subjected to polymerization.

Description

TECHNICAL FIELD

[0001] The present application relates to an inorganic / organic composite thin film solid-state electrolyte based on a porous ceramic solid-state electrolyte and a preparation method thereof, and application of the composite electrolyte in a lithium metal battery, belonging to the technical field of solid-state lithium batteries. BACKGROUND

[0002] Commercially available rechargeable lithium-ion batteries have been widely used in various fields due to their long cycle life and high energy density. The booming development of portable electronic devices, electric vehicles and power grids for energy storage makes the next generation of rechargeable lithium batteries with higher energy density and better safety a new focus. However, the limited capacity provided by intercalation anodes (graphite <400 mAh·g -1 ) and the thermal runaway problem caused by organic electrolyte make it difficult for current lithium-ion batteries to meet future needs. To solve this problem, all-solid-state lithium metal batteries composed of solid-state electrolytes with good thermal stability and lithium metal anodes with ultra-high specific capacity (3860 mAh·g -1 ), the lowest reduction potential (-3.04 V compared with the standard hydrogen electrode) have become an important development direction for the next generation of energy storage devices (Adv. Mater. 2020, 32, 1905517). Among them, ultra-thin solid-state electrolyte with excellent performance is a key component of all-solid-state lithium metal batteries.

[0003] Solid-state electrolytes include inorganic ceramic electrolytes, organic polymer electrolytes and organic-inorganic composite electrolytes. Among them, oxide inorganic ceramic electrolytes have good thermal stability, high lithium ion conductivity and high Young's modulus. However, due to the traditional powder pressing and sintering process of ceramic electrolytes and the inherent brittleness and low toughness of ceramics, it is difficult to reduce the thickness of the electrolyte while producing large-size electrolyte films (the thickness after sintering is usually greater than 500 microns for oxide electrolytes), which limits the energy density of the battery system. In contrast, polymer electrolytes usually have better processability, making it easier to obtain large-size and thin solid electrolyte films (~50 microns). At the same time, polymer electrolytes have good interface compatibility with electrodes. However, the low Li +Transfer number and lithium dendrite growth hinder their practical application. Organic-inorganic composite electrolytes can effectively compensate for the shortcomings of the above two types of electrolytes. By mixing LLZO ceramic powder as an active filler with polymers, not only can the mechanical properties of the electrolyte be improved, but the lithium-ion conductivity can also be increased, and the growth of lithium dendrites can be suppressed (J. Am. Chem. Soc. 2017, 139, 13779-13785). In addition, the thickness of the electrolyte has a very critical impact on the performance of solid-state batteries, especially the energy density. Some studies have shown that in order to achieve an energy density greater than 400 Wh / kg in solid-state batteries, the thickness of the electrolyte needs to be less than 25 μm (Energy Environ. Sci., 2021, 14, 12–36). Simply mixing ceramic powder with polymers can reduce the thickness of the electrolyte to some extent (Adv. Energy Mater. 2019, 9, 1900611). However, when the powder content is high, agglomeration and sedimentation will adversely affect the mechanical properties of the electrolyte, making it difficult to obtain very thin solid electrolytes. Introducing a support, such as a PP separator, into the polymer electrolyte can effectively reduce the electrolyte thickness (Energy Storage Materials, 2020, 29, 361–366). However, the introduction of the inert PP separator, which cannot transport lithium ions, will adversely affect lithium ion transport in the electrolyte. Therefore, reducing the thickness of the electrolyte while avoiding powder agglomeration is crucial for improving the energy density of the battery. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide an inorganic / organic composite thin-film solid electrolyte based on a porous ceramic solid electrolyte and its preparation method, as well as a lithium metal battery assembled with this composite electrolyte. The porous ceramic solid electrolyte phase in this composite electrolyte can prevent the agglomeration of inorganic powders within the composite electrolyte and can also promote lithium-ion transport, thereby improving the electrochemical performance of the battery. The polymer phase obtained through in-situ UV curing can effectively improve the interfacial contact between the positive and negative electrodes, while suppressing the volatilization of small molecule solvents. Furthermore, it can ensure the integrity of the composite electrolyte structure, forming an integrated structure. Finally, the lithium metal battery assembled with this composite electrolyte can effectively reduce the mass and volume ratio of the electrolyte in the battery system, thereby increasing the energy density.

[0005] In a first aspect, the present invention provides an inorganic / organic composite thin-film solid electrolyte based on a porous ceramic solid electrolyte, comprising: a porous ceramic solid electrolyte, and an organic electrolyte filling the pore structure of the porous ceramic solid electrolyte; the organic electrolyte is obtained by uniformly mixing a precursor solution containing acrylate compounds, a photoinitiator, a lithium salt, and a small molecule solvent, followed by in-situ photoinitiation to polymerize the acrylate compounds. The sufficient synergistic effect between the organic and inorganic components effectively improves the electrochemical performance of the electrolyte.

[0006] Preferably, the porous ceramic solid electrolyte is made of at least one of the following: lithium garnet type solid electrolyte, LISICON type solid electrolyte, NASICON type solid electrolyte, and perovskite type solid electrolyte.

[0007] Preferably, the lithium garnet-type solid electrolyte is selected from at least one of the following:

[0008] 1)Li 7-3a La3Zr2L a O 12 Where L = Al, Ga, or Fe, and 0 < a < 0.33;

[0009] 2)Li7La 3-b Zr2M b O 12 Where M = Bi or Y, and 0 < b < 1;

[0010] 3)Li 7-c La3(Zr 2-c N c )O 12 Wherein, N = at least one of In, Si, Ge, Sn, Sb, Sc, Ti, Hf, V, W, Te, Nb, Ta, Al, Ga, Fe, Bi, Y, Mg, and Ca, and 0 < c < 1;

[0011] Preferably, the LISICON type solid electrolyte is Li 14 Zn(GeO4)4;

[0012] Preferably, the NASICON-type solid electrolyte is Li (1+x) Al x Ti (2-x) P3O 12 and Li (1+y) Al y Ge (2-y) P3O 12 At least one of the following, where 0 ≤ x ≤ 2, 0 ≤ y ≤ 2;

[0013] Preferably, the perovskite-type solid electrolyte is Li 3z La 2 / 3-z TiO3, where 0≤z≤2 / 3.

[0014] Preferably, the porous ceramic solid electrolyte has a pore size distribution range of about 100 nm to 8 μm and a porosity of 30% to 70%.

[0015] Preferably, the thickness of the porous ceramic solid electrolyte is 5 to 200 micrometers.

[0016] Preferably, the acrylate compounds include diethylene glycol dimethacrylate (DEGDMA), triethylene glycol dimethacrylate (TEGDA), triethylene glycol dimethacrylate (TEGDMA), tetraethylene glycol dimethacrylate (TTEGDA), glycidyl methacrylate, polyethylene glycol diacrylate (PEGDA), polypropylene glycol diacrylate (PPGDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), diacrylate diol (DDA), and dimethacrylate diol (DDMA). The precursor solution contains at least one of the following: ethoxylated trimethylolpropane triacrylate (ETPTA), acrylate-functionalized ethylene oxide, butanediol dimethacrylate, propoxylated neopentyl glycol diacrylate (NPPOGDA), trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), pentaerythritol triacrylate (PETA), propoxylated glycerol triacrylate, and dipentaerythritol pentaacrylate (DPEPA); the content of the acrylate compound in the precursor solution is 1 wt.% to 50 wt.%.

[0017] Preferably, the photoinitiator is at least one selected from 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and methyl benzoylbenzoate; the content of the photoinitiator is 0 wt.% to 5 wt.% of the acrylate compound.

[0018] Preferably, the lithium salt is at least one selected from lithium hexafluorophosphate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, and lithium bis(oxalateborate); the lithium salt concentration in the precursor solution is 0.1–15 M.

[0019] Preferably, the small molecule solvent is at least one selected from fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate (PC), dioxolane (DOL), tetrahydrofuran, dimethyl tetrahydrofuran, ethylene glycol dimethyl ether, and dimethyl sulfoxide.

[0020] Preferably, the in-situ photoinitiation method is ultraviolet irradiation treatment; the parameters of the ultraviolet irradiation treatment include: ultraviolet light intensity of 10–200 μW / cm². 2 The ultraviolet wavelength is 200–400 nm, and the ultraviolet irradiation time is 2–60 minutes.

[0021] Secondly, the present invention provides a method for preparing an inorganic / organic composite thin-film solid electrolyte based on a porous ceramic solid electrolyte, comprising:

[0022] (1) The ceramic solid electrolyte ceramic powder, binder, plasticizer, dispersant, pore-forming agent and solvent are mixed to obtain a mixed slurry;

[0023] (2) The mixed slurry is cast onto a porous or dense matrix material by casting, and after drying, a ceramic blank is obtained. Then, after sintering, a porous ceramic solid electrolyte is obtained.

[0024] (3) Mix the acrylate compound, photoinitiator, lithium salt, and small molecule solvent evenly to obtain a precursor solution.

[0025] (4) The obtained precursor solution is added to the porous ceramic solid electrolyte to fill the internal pores, and then in-situ photoinitiation is performed to polymerize the acrylate compounds to obtain an inorganic / organic composite thin film solid electrolyte.

[0026] Preferably, the binder is at least one selected from vinyl, acrylic, polyvinyl alcohol, acrylic emulsion, ammonium polyacrylate, polymethyl acrylate, polymethyl methacrylate, ethyl cellulose, and polyvinyl butyral; the binder content in the mixed slurry is 1 wt.% to 10 wt.%.

[0027] Preferably, the plasticizer is at least one selected from polyethylene glycol, ethylene glycol, and butyl benzyl phthalate, and the content of the plasticizer in the mixed slurry is 0.1 wt.% to 10 wt.%.

[0028] Preferably, the dispersant includes at least one of trioleic acid glyceride, phosphate ester, ethoxylated compound and herring oil, polyethylene glycol, and castor oil, and the content of the dispersant in the mixed slurry is 0 wt.% to 5 wt.%.

[0029] Preferably, the pore-forming agent includes at least one of starch, graphite, carbon fiber, and polymer material, wherein the polymer material is at least one of polymethyl methacrylate, polystyrene, and polypropylene, and the pore-forming agent in the mixed slurry is 0 wt.% to 50 wt.% of the ceramic solid electrolyte ceramic powder.

[0030] Preferably, the solvent includes at least one selected from water, butanone, n-acetone, acetone, cyclohexanone, butyl acetate, butanol, methanol, ethanol, isopropanol, methyl ethyl ketone, trichloroethylene, toluene, and xylene, and the solvent content in the mixed slurry is 30 wt.% to 70 wt.%.

[0031] Preferably, the porous or dense matrix material includes bacterial cellulose, PI membrane, nonwoven fabric, PE membrane, PP membrane, nylon mesh, PET polyester film, or aluminum foil. In this invention, the extended substrate includes porous matrix materials, such as PI membranes, nonwoven fabrics, etc. These porous matrix materials can serve as supports for the green body or as pore-forming components during sintering.

[0032] Preferably, the sintering temperature is 900–1300℃ (preferably 1000–1200℃), and the time is 1–120 minutes; the thickness of the ceramic green body is 10–400 μm; and the thickness of the porous ceramic solid electrolyte is 5–200 μm. If the sintering temperature is too low (900℃), the ceramic is difficult to porcelainize and cannot form a self-supporting structure. If the temperature is too high (1300℃), the ceramic will be severely overheated, resulting in bending deformation and the transformation of interconnected pores into closed pores.

[0033] Thirdly, the present invention provides a solid-state lithium battery, comprising: a positive electrode, a negative electrode, and the aforementioned inorganic / organic composite thin-film solid electrolyte based on a porous ceramic solid electrolyte located between the positive electrode and the negative electrode.

[0034] Preferably, the negative electrode is one of lithium foil, lithium alloy, graphite, silicon and its composites.

[0035] Preferably, the positive electrode comprises LiFePO4, LiCoO2, or LiNi. b Co c Mn 1-b-c O2(0≤b≤1,0≤c≤1), LiNi 0.8 Co 0.15 Al 0.05 One or more of the following: LiMn2O4, lithium-rich phase aLi2MnO3·(1-a)LiMO2 (M=Mn、Ni、Co,0≤a≤1), S、Li2S、O2.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The thickness of the porous ceramic solid electrolyte in the composite electrolyte can be reduced to about 10 micrometers, which can effectively reduce the thickness of the composite electrolyte. At the same time, the casting method can be used to produce large-size products.

[0038] (2) Compared with the usual use of ceramic powder and polymer composite, this invention can effectively avoid the problem of uneven distribution of ceramic powder in polymer, avoid powder agglomeration blocking lithium ion transport channels, and the porous ceramic solid electrolyte itself has lithium ion transport performance. In addition, the rich and continuous two-phase interface between it and the organic phase can also promote the rapid transport of lithium ions.

[0039] (3) The high modulus of porous ceramic solid electrolyte and the relatively soft properties of polymer can be combined to form a structure with both rigidity and flexibility, which can improve the interfacial contact and enhance the ability to suppress dendrite growth. At the same time, the use of acrylate compounds containing double bonds for in-situ curing can effectively ensure the integrity of the composite electrolyte structure and suppress the volatilization of small molecule solvents to ensure the high lithium-ion conductivity of the electrolyte.

[0040] (4) The continuous phase porous ceramic solid electrolyte is combined with polymer. The ceramic phase has excellent thermal stability, which is beneficial to improving the safety performance of the composite electrolyte. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the process for preparing the composite electrolyte in Example 1 of the present invention;

[0042] Figure 2 This is a photograph of the green blank obtained after casting in Example 1 of this invention;

[0043] Figure 3 This is a photograph of the ceramic blank in Example 2 of this invention;

[0044] Figure 4 The XRD results of ceramics obtained by sintering in Examples 1, 3, and 4 of this invention are shown.

[0045] Figure 5 These are actual ceramic images obtained by sintering in Comparative Examples 1 and 2 of this invention;

[0046] Figure 6 These are SEM images of the ceramic surface and cross-section obtained during sintering in Example 1 of this invention.

[0047] Figure 7 The images show actual photographs and toughness of the ceramic obtained by sintering in Example 1 of this invention.

[0048] Figure 8 The images show cross-sectional SEM images and EDS results of the composite electrolyte in Example 1 of this invention.

[0049] Figure 9 The impedance results are for the lithium symmetric batteries assembled in Examples 1, 5, and 6 of this invention.

[0050] Figure 10The results of ionic conductivity tests of the composite electrolyte at different temperatures in Example 1 of this invention are shown.

[0051] Figure 11 The lithium-ion transference number results are shown for the lithium symmetric batteries assembled in Examples 1, 3, and 4 of this invention, where the horizontal axis represents time (Time) / s and the vertical axis represents current (Current) / μA.

[0052] Figure 12 The CCD results of the lithium symmetric batteries assembled in Examples 1, 3, and 4 of this invention are shown, where the horizontal axis is time (Time) / s and the vertical axis is voltage (V).

[0053] Figure 13 The results of long-cycle testing of the lithium symmetric batteries assembled in Examples 1, 3, and 4 of this invention are shown, where the horizontal axis represents cycle time (h) and the vertical axis represents voltage (V).

[0054] Figure 14 This is a charge-discharge cycle diagram and discharge curve of the full battery assembled in Example 1 of this invention, where A represents the number of cycles on the horizontal axis and the specific capacity (mAh·g) on ​​the vertical axis. -1 In B, the horizontal axis represents the specific capacity (mAh·g). -1 The vertical axis represents voltage (V). Detailed Implementation

[0055] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0056] This invention provides an inorganic / organic composite thin-film solid electrolyte based on a porous ceramic solid electrolyte and its preparation method. A precursor slurry is prepared by mixing a binder, plasticizer, dispersant, pore-forming agent, and ceramic powder in a solvent. After uniform mixing, the slurry is cast onto a porous or dense substrate using a casting method. After drying, a ceramic film preform is obtained, followed by high-temperature calcination to obtain a porous ceramic solid electrolyte matrix. Finally, a precursor solution containing acrylate compounds is cast into the porous ceramic solid electrolyte for in-situ photocuring to obtain the composite thin-film solid electrolyte. On one hand, the presence of the ceramic matrix effectively reduces the electrolyte thickness, and the non-inert porous ceramic solid electrolyte can also facilitate lithium-ion transport. On the other hand, the polymer phase formed by the in-situ curing of acrylate compounds effectively improves the interfacial contact between the positive and negative electrodes. Simultaneously, the polymer filling the continuous pores can efficiently transport lithium ions, improving lithium-ion conductivity. Furthermore, the in-situ cured polymer maintains the relative integrity of the electrolyte structure, forming a three-dimensional interconnected integrated structure with the ceramic matrix.

[0057] This invention uses a casting process to obtain a ceramic thin film. However, due to insufficient mechanical properties, direct battery assembly is difficult. Therefore, this invention creatively employs in-situ UV curing to obtain a composite electrolyte, utilizing the synergistic effect between the polymer and ceramic to ensure normal battery operation. The core of this method lies in adding a precursor solution containing an acrylate compound with unsaturated double bonds to a porous ceramic solid electrolyte film matrix, followed by UV curing to obtain an integrated inorganic / organic composite thin-film solid electrolyte. The detailed process of preparing this composite electrolyte is illustrated below.

[0058] Step 1: Preparation process of porous ceramic solid electrolyte.

[0059] First, the binder, plasticizer, dispersant, pore-forming agent, ceramic powder, and solvent are mixed. The mixing method can be ball milling, magnetic stirring, or other mechanical mixing methods. For example, the dispersant, ceramic powder, pore-forming agent, and binder can be added to a solution and magnetically stirred at 60°C for 24 hours. After cooling to room temperature, the plasticizer is added, and stirring continues for another 24 hours. Then, the mixture is cast onto a matrix material. The doctor blade height can be controlled according to the required thickness, ranging from 10 micrometers to 1000 micrometers. The dried green body is then hot-pressed to prevent deformation during sintering, and finally sintered. The ceramic powder is a lithium garnet-type solid electrolyte (e.g., Li). 7-3a La3Zr2L a O 12 Where L = Al, Ga, or Fe, and 0 <a<0.33;Li7La 3-b Zr2M b O 12, where M = Bi or Y, and 0 < b < 1; Li 7-c La3(Zr 2-c ,N c )O 12 , where N = In, Si, Ge, Sn, Sb, Sc, Ti, Hf, V, W, Te, Nb, Ta, Al, Ga, Fe, Bi, Y, Mg, Ca or a combination thereof, and 0 < c < 1); LISICON-type solid electrolyte (e.g., Li 14 Zn(GeO4)4, etc.); NASICON-type solid electrolyte (e.g., Li (1+x) Al x Ti (2-x) P3O 12 , where 0 ≤ x ≤ 2; Li (1+y) Al y Ge (2-y) P3O 12 , where 0 ≤ y ≤ 2); perovskite-type solid electrolyte (e.g., Li 3z La 2 / 3- z TiO3, where 0 ≤ z ≤ 2 / 3) or at least one of a mixture of one or more of them; the binder is at least one of vinyl, propenyl, polyvinyl alcohol, acrylic emulsion, ammonium polyacrylate, polymethyl acrylate, polymethyl methacrylate, ethyl cellulose and polyvinyl butyral ester, with a content of 1 wt.% - 10 wt.%; the plasticizer is at least one of polyethylene glycol, ethylene glycol, butyl benzyl phthalate, with a content of 0.1 wt.% - 10 wt.%; the dispersant includes but is not limited to at least one of glyceryl trioleate, phosphate ester, ethoxylate and herring oil, polyethylene glycol, castor oil, with a content of 0 wt.% - 5 wt.%; the pore-forming agent includes but is not limited to at least one of starch, graphite, carbon fiber, polymers such as polymethyl methacrylate, etc., with a content of 0 wt.% - 50 wt.% of the powder mass fraction; the solvent includes but is not limited to at least one of water, methyl ethyl ketone, n-acetone, acetone, cyclohexanone, butyl acetate, butanol, methanol, ethanol, isopropanol, methyl ethyl ketone, trichloroethylene, toluene, xylene, 30 wt.% - 70 wt.%; the porous or dense matrix material includes but is not limited to bacterial cellulose, PI membrane, non-woven fabric, PE membrane, PP membrane, nylon mesh, PET polyester film, aluminum foil, etc.; the sintering temperature is 600 - 1400 °C.

[0060] Step Two: Preparation of the composite film solid electrolyte.

[0061] An acrylate compound, photoinitiator, lithium salt, and small molecule solvent are uniformly mixed and added to a porous ceramic solid electrolyte to fill the internal pores. Photoinitiation is then performed to cause the acrylate compound to undergo cross-linking polymerization, thereby obtaining an organic-inorganic composite thin-film solid electrolyte. The acrylate compound includes, but is not limited to, diethylene glycol dimethacrylate (DEGDMA), triethylene glycol dimethacrylate (TEGDA), triethylene glycol dimethacrylate (TEGDMA), tetraethylene glycol dimethacrylate (TTEGDA), glycidyl methacrylate, polyethylene glycol diacrylate (PEGDA), polypropylene glycol diacrylate (PPGDA), dipropylene glycol diacrylate (DPGDA), tripropylene glycol diacrylate (TPGDA), diacrylate diol (DDA), dimethacrylate diol (DDMA), ethoxylated trimethylolpropane triacrylate (ETPTA), acrylate-functionalized ethylene oxide, butanediol dimethacrylate, and propoxylated neopentyl glycol diacrylate. The precursor solution contains 1 wt.% to 50 wt.% of the following: NPPOGDA, trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), pentaerythritol triacrylate (PETA), propoxylated glycerol triacrylate, dipentaerythritol pentaacrylate (DPEPA), ditrimethylolpropane tetraacrylate (DTMPTTA), etc.; the photoinitiator is at least one of 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and methyl phthalate, and its content is 0 wt.% to 5 wt.% of the acrylate compound content; the parameters of the ultraviolet irradiation treatment include: ultraviolet light intensity of 10–200 μW / cm². 2 The ultraviolet wavelength is 200–400 nm, and the ultraviolet irradiation time is 2–60 minutes; the lithium salt is at least one of lithium hexafluorophosphate, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, and lithium bis(oxalate-borate), and the lithium salt concentration is 0.1–10 M; the small molecule solvent is at least one of fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), ethylene carbonate (EC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), propylene carbonate (PC), dioxolane (DOL), tetrahydrofuran, dimethyl tetrahydrofuran, ethylene glycol dimethyl ether, and dimethyl sulfoxide.

[0062] Assembly of solid-state lithium metal batteries. The positive electrode is placed at the bottom, and a certain amount of electrolyte is added according to the load to construct an ion-conducting network inside the positive electrode. Then, using a lithium sheet as a substrate, a porous ceramic solid electrolyte is placed on its surface. A precursor solution containing acrylate compounds is cast, and after UV curing to form a whole, the lithium sheet and electrolyte are attached together to the positive electrode sheet, completing the assembly of the solid-state lithium metal battery. The positive electrode materials include LiFePO4, LiCoO2, and LiNi. b Co c Mn 1-b-c O2(0≤b≤1,0≤c≤1), LiNi 0.8 Co 0.15 Al 0.05 The cathode material is one or a mixture of various positive electrode materials such as LiMn2O4, lithium-rich phase aLi2MnO3·(1-a)LiMO2 (M=Mn,Ni,Co,0≤a≤1), S, Li2S, and O2; the negative electrode material includes lithium or lithium alloy.

[0063] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0064] Example 1:

[0065] (1) Li ceramic powder 6.5 La3Zr 1.5 Ta 0.5 O 12 The content of the first compound is 33.48%; the dispersant fish oil 0.91wt% is added to a mixed solvent of toluene and isopropanol, where the content of toluene and isopropanol is 26.86wt% each. The mixed solution is placed in a water bath at 60℃ and magnetically stirred for 12h. Then, the binder polyvinyl butyral ester (PVB) with a content of 5.81wt% is added, and magnetic stirring is continued for 12h. After cooling to room temperature, the plasticizer butyl benzyl phthalate (BBP) with a content of 5.08wt% is added, and magnetic stirring is continued for 12h. Then, the mixture is cast using PET polyester film as the substrate. The doctor blade height is 30 micrometers. After casting, the mixture is dried at room temperature for 24h, then cut to the required size, hot-pressed at 120℃ for 6h, and finally sintered. A crucible made of magnesium oxide is used for sintering, and the bottom of the crucible is filled with powder to ensure a lithium oxide atmosphere. The heating and cooling rates during sintering are both 5℃ / min, and the holding temperature is 1100℃ for 5min.

[0066] (2) After sintering, the porous ceramic solid electrolyte film obtained is quickly transferred to a glove box to avoid the formation of lithium carbonate. Then, a precursor solution containing acrylate compounds is prepared in the glove box. Ethoxylated trimethylolpropane triacrylate (ETPTA) at 15 wt%; photoinitiator phenylacetone (HMPP) at 0.5 wt% (mass fraction of acrylate compounds); and LB014 electrolyte (1.0 M LiPF6 in EC:DMC:DEC = 1:1:1 Vol%) at 85 wt% are magnetically stirred for 4 hours. The precursor solution is then pipetted into the porous ceramic solid electrolyte, filling the pores completely. UV curing is then performed at an UV intensity of 100 μW / cm². 2 A composite thin-film solid electrolyte can be obtained by using an ultraviolet light with a wavelength of 365nm and an ultraviolet irradiation time of 10 minutes.

[0067] (3) Place the NCM83 positive electrode at the bottom, add a certain amount of electrolyte according to the load to build an ion-conducting network inside the positive electrode, then use the lithium sheet as the substrate, place a porous ceramic solid electrolyte on its upper surface, cast a precursor solution containing acrylate compounds, and after UV curing to form a whole, attach the lithium sheet and electrolyte together to the positive electrode to complete the solid lithium metal battery assembly.

[0068] Example 2:

[0069] Except for the addition of 5% starch powder as a pore-forming agent to the casting slurry, the other conditions were the same as in Example 1. The porous ceramic solid electrolyte obtained in Example 2 has a pore size distribution range of approximately 100 nm to 4 μm, a porosity of 60%, and a thickness of 12 μm.

[0070] Example 3:

[0071] Except for the sintering temperature, the conditions were the same as in Example 1. The sintering temperature was 1130℃. The porous ceramic solid electrolyte obtained in Example 2 has a pore size distribution range of approximately 100 nm to 2 μm, a porosity of 53%, and a thickness of 11 μm.

[0072] Example 4:

[0073] Except for the sintering temperature, the conditions were the same as in Example 1. The sintering temperature was 1150℃. The porous ceramic solid electrolyte obtained in Example 2 has a pore size distribution range of approximately 100nm to 2μm, a porosity of 51%, and a thickness of 11μm.

[0074] Example 5:

[0075] Except for the concentration of acrylate compounds, which differs from that in Example 1, the other conditions are the same as in Example 1, with the concentration of acrylate compounds being 30%.

[0076] Example 6:

[0077] Except for the concentration of acrylate compounds, which differs from that in Example 1, the other conditions are the same as in Example 1, with the concentration of acrylate compounds being 50%.

[0078] Example 7:

[0079] Except for the acrylate compound, which is different from that in Example 1, the other conditions are the same as in Example 1. The acrylate compound is PEGMEMA. However, it was found in the experiment that because the PEGMEMA monomer contains only one carbon-carbon double bond, it has a linear structure after polymerization and poor strength, making it difficult to peel the composite electrolyte completely off the substrate.

[0080] Comparative Example 1:

[0081] Except for the sintering temperature, the conditions were the same as in Example 1. The sintering temperature was 900℃.

[0082] Comparative Example 2:

[0083] Except for the sintering temperature, the conditions were the same as in Example 1. The sintering temperature was 1300℃.

[0084] Comparative Example 3:

[0085] The precursor solution containing acrylate compounds from Example 1 was directly dropped onto the surface of the lithium sheet and solidified in situ to form a polymer electrolyte composed only of ETPTA. Then, the other side of the lithium sheet or positive electrode material was attached to assemble the battery.

[0086] Comparative Example 4:

[0087] In Example 1, 40% by mass of Li was added to the precursor solution containing acrylate compounds. 6.5 La3Zr 1.5 Ta 0.5 O 12 After the ceramic powder is mixed evenly, the precursor solution is added to the surface of the lithium sheet and solidified in situ to form a composite electrolyte composed of ETPTA and LLZO ceramic powder. Then, the lithium sheet or positive electrode material on the other side is attached to assemble the battery.

[0088] Sample analysis:

[0089] Figure 1This is a schematic diagram of the preparation process of the porous ceramic solid electrolyte and the composite electrolyte in Example 1. The ceramic blank is obtained by casting, and then the porous LLZO ceramic is obtained by sintering. Subsequently, the precursor solution containing lithium salt and acrylate compound is poured into the porous ceramic solid electrolyte and cured by ultraviolet initiation to obtain a composite thin film solid electrolyte integrating porous ceramic solid electrolyte and polymer.

[0090] Figure 2 This is a picture of the green blank obtained by casting in Example 1 of the present invention. The surface of the green blank is flat and smooth, with no obvious bubbles.

[0091] Figure 3 The image shown is a physical picture of the ceramic green body in Example 2 of this invention. The results show that the addition of starch as a pore-forming agent does not affect the film-forming characteristics of the green body, and the obtained green body can be completely peeled off from the substrate for subsequent experiments.

[0092] Figure 4 The XRD results are for porous ceramic solid electrolytes obtained at different sintering temperatures in Examples 1, 3, and 4 of this invention. The results show that a pure LLZO cubic phase structure can be obtained at all three temperatures, which has a high lithium-ion conductivity.

[0093] Figure 5 Comparative Example 1 in this invention Figure 5 Example A), Comparative Example 2 ( Figure 5 (B) Photographs of the samples after sintering. The results show that in Comparative Example 1, due to the low sintering temperature, the ceramic could not be vitrified and could not form a self-supporting structure, making it extremely fragile and opaque; in Comparative Example 2, due to the high sintering temperature, the ceramic would bend and deform.

[0094] Figure 6 The images show the surface and cross-sectional SEM images of the porous ceramic solid electrolyte obtained by sintering in Example 1 of this invention. First, the surface SEM results show that there are a large number of inwardly extending pore structures on the ceramic surface. At the same time, the ceramic grains are tightly bonded, which can ensure the transport of lithium ions. The cross-sectional SEM results show that the thickness of the porous ceramic solid electrolyte is about 12 micrometers, and the internal pores are all interconnected pores (pore size distribution range is about 100nm to 3μm, porosity is 57%), which is conducive to the composite with polymer electrolyte to form an integrated structure.

[0095] Figure 7The image shows a photograph of the large-sized LLZO porous ceramic solid electrolyte film prepared in Example 1, which measures approximately 6cm × 4cm. Due to its thickness of only 10–15 micrometers, it exhibits a certain degree of transparency. The inset at the top left shows a test of its mechanical properties. As can be seen from the image, the porous ceramic solid electrolyte has a certain degree of toughness and can undergo some bending deformation without breaking. This non-rigid structure is also beneficial for maintaining the relative integrity of its structure during the subsequent polymer composite process.

[0096] Figure 8 The results show the cross-sectional SEM and EDS results of the composite electrolyte in Example 1. The results show that the thickness of the composite electrolyte is about 12 micrometers. The EDS results show that the components are uniformly distributed and the ceramic phase and polymer phase form a three-dimensional interconnected integrated structure.

[0097] Figure 9 The impedance test results of the lithium symmetric batteries assembled in Examples 1, 5, and 6 of this invention show that as the concentration of acrylate compounds decreases, the interfacial impedance between the composite electrolyte and metallic lithium gradually decreases, mainly due to the increase in the content of small molecule solvents in the precursor solution. The reduced interfacial impedance also facilitates the rapid transport of lithium ions at the interface.

[0098] Figure 10 The results of lithium-ion conductivity tests of the composite electrolyte in Example 1 of this invention at different temperatures show that its lithium-ion conductivity can reach 1.19 mS / cm at 25°C, which is high. At the same time, due to its thinness, the lithium-ion transport path is greatly shortened, thus greatly reducing the impedance generated by ion diffusion in the electrolyte, and lithium ions can diffuse rapidly between the positive and negative electrodes.

[0099] To further illustrate the superior performance of this composite electrolyte structure, the single polymer electrolyte ETPTA and the ceramic powder composite polymer electrolyte LLZO Powder@ETPTA were selected as control samples for electrochemical performance comparison. Figure 11 The results show the lithium-ion transference number (LTN) test results of the lithium symmetric batteries assembled in Examples 1, 3, and 4. The results show that the composite electrolyte (Porous-LLZO@ETPTA) of this structure can achieve a LTN of 0.78, which is much higher than the two comparative samples. This is mainly because LLZO, as a single-ion conductor, can effectively increase the LTN of the composite electrolyte. At the same time, the rich and continuous two-phase interface also provides a fast transport channel for lithium-ion migration. The higher LTN is beneficial to reduce concentration polarization during actual battery operation and reduce the tendency of dendrite growth.

[0100] likeFigure 12 The results show the critical current density (CCD) test results of the lithium symmetric batteries assembled in Examples 1, 3, and 4 (the critical current density test can reflect the electrolyte's resistance to lithium dendrites). The results show that the CCD of this composite electrolyte can reach 1.2 mA / cm². 2 The results were significantly higher than those of the two control samples. This was mainly due to the efficient lithium-ion transport and the fact that ceramics, as a rigid material, could resist dendrite formation to a certain extent. In addition, the use of porous ceramic solid electrolytes combined with polymers made the structure of the composite electrolyte more uniform, thus avoiding uneven local current.

[0101] like Figure 13 The figures show the long-cycle performance tests of the lithium symmetric batteries assembled in Examples 1, 3, and 4. The results indicate that the composite electrolyte (Porous-LLZO@ETPTA) of this structure can achieve a high current density of 0.4 mA / cm². 2 The composite electrolyte exhibits good long-term cycling stability, exceeding 500 hours, while the control sample is prone to short-circuit failure. Therefore, the long-cycle test results further verify the superior performance of this composite electrolyte.

[0102] Figure 14 The diagram shows the charge-discharge cycle diagram and cycle curve of the full battery assembled in Example 1 of this invention. The test temperature was 25°C, the charge-discharge voltage range was 2.8–4.2V, the rate was 0.5C, and the active material loading was approximately 2.5 mg / cm³. 2 Test results show that after three cycles of activation at 0.2C, the discharge specific capacity of the first cycle at 0.5C can reach 163.1 mAh / g, and the capacity retention rate after 100 cycles is 93%, with an average coulombic efficiency of more than 99%, indicating good cycle stability.

[0103] This invention can effectively reduce the thickness of the electrolyte while avoiding the agglomeration of inorganic powders in the composite electrolyte, thus improving the electrochemical performance of the battery. In addition, the polymer phase obtained by UV curing can effectively improve the interfacial contact between the positive and negative electrodes while ensuring the integrity of the composite electrolyte structure. The lithium metal battery assembled with this composite electrolyte has excellent long-cycle stability.

Claims

1. An inorganic / organic composite thin-film solid-state electrolyte based on a porous ceramic solid-state electrolyte, characterized by, The application relates to a porous ceramic solid electrolyte prepared by a flow-casting-sintering method and an organic electrolyte filled in the pore structure of the porous ceramic solid electrolyte. The flow-casting-sintering method refers to that mixed slurry is cast on a porous base material or a dense base material by a flow-casting method, a ceramic blank is obtained after drying, and a porous ceramic solid electrolyte is obtained after sintering. The material of the porous ceramic solid electrolyte comprises at least one of a lithium garnet type solid electrolyte, a LISICON type solid electrolyte, a NASICON type solid electrolyte and a perovskite type solid electrolyte. The organic electrolyte is obtained by polymerization of a precursor solution which is uniformly mixed with an acrylate compound, a photoinitiator, a lithium salt and a small molecule solvent, and then in-situ ultraviolet light initiation; wherein the photoinitiator is at least one of 1-hydroxy-cyclohexyl-phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone and methyl o-benzoylbenzoate; the small molecule solvent is at least one of fluorinated ethylene carbonate, dimethyl carbonate, ethylene carbonate, methyl ethyl carbonate, diethyl carbonate, propylene carbonate, dioxolane, tetrahydrofuran, dimethyl tetrahydrofuran, ethylene glycol dimethyl ether and dimethyl sulfoxide; the content of the acrylate compound in the precursor solution is 15wt.%-50wt.%; the content of the photoinitiator is 0.5wt.%-5wt.% of the acrylate compound. The porosity of the porous ceramic solid electrolyte is 51%-60%, and the pore size distribution range is 100nm-4mu m; the thickness of the porous ceramic solid electrolyte is 11-12mu m. The lithium garnet type solid electrolyte is selected from at least one of the following:

2. The inorganic / organic composite thin film solid state electrolyte based on a porous ceramic solid state electrolyte according to claim 1, characterized by, The acrylate compound comprises at least one of diethylene glycol dimethyl acrylate, triethylene glycol diacrylate, triethylene glycol dimethyl acrylate, tetraethylene glycol diacrylate, glycidyl methacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, butanediol dimethyl acrylate, propoxylated neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, propoxylated glycerol triacrylate and dipentaerythritol pentaacrylate. 1) Li 7-3a La3Zr2L a O 12 wherein L = Al, Ga or Fe, and 0 < a < 0.33; 2) Li7La 3-b Zr2M b O 12 where M = Bi or Y, and 0 < b < 1. 3) Li 7-c La3(Zr 2-c N c )O 12 wherein N = at least one of In, Si, Ge, Sn, Sb, Sc, Ti, Hf, V, W, Te, Nb, Ta, Al, Ga, Fe, Bi, Y, Mg, Ca, and 0 < c < 1.

3. The inorganic / organic composite thin film solid state electrolyte based on a porous ceramic solid state electrolyte according to claim 1, characterized by, The LISICON-type solid electrolyte is Li 14 Zn(GeO4)4.

4. The inorganic / organic composite thin film solid state electrolyte based on a porous ceramic solid state electrolyte according to claim 1, characterized by, The NASICON-type solid electrolyte is Li (1+x) Al x Ti (2-x) P3O 12 and Li (1+y) Al y Ge (2-y) P3O 12 wherein 0≤x≤2, 0≤y≤2.

5. The inorganic / organic composite thin film solid state electrolyte based on porous ceramic solid state electrolyte according to claim 1, characterized by, The perovskite-type solid electrolyte is Li 3z La 2 / 3-z TiO3, wherein 0≤z≤2 / 3.

6. The inorganic / organic composite thin film solid state electrolyte based on a porous ceramic solid state electrolyte according to claim 1, characterized by, The lithium salt is at least one of lithium hexafluorophosphate, lithium perchlorate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium tetrafluoroborate and lithium bisoxalate borate; the lithium salt concentration in the precursor solution is 0.1-15M.

7. The inorganic / organic composite thin film solid state electrolyte based on porous ceramic solid state electrolyte according to claim 1, characterized in that, The application also relates to a preparation method of the porous ceramic solid electrolyte.

8. The inorganic / organic composite thin film solid state electrolyte based on porous ceramic solid state electrolyte according to claim 1, characterized by, The in-situ UV light initiation mode is UV light irradiation treatment; the parameters of the UV light irradiation treatment include: UV light intensity is 10-200 μW / cm 2 , UV wavelength is 200-400 nm, and UV irradiation time is 2-60 minutes.

9. A method for producing the inorganic / organic composite thin-film solid-state electrolyte based on the porous ceramic solid-state electrolyte according to any one of claims 1 to 8, characterized by, ​ (1) mixing ceramic solid electrolyte ceramic powder, binder, plasticizer, dispersant, pore-forming agent and solvent to obtain a mixed slurry; the pore-forming agent comprises at least one of starch, carbon fiber and polymer, the polymer is at least one of polymethyl methacrylate, polystyrene and polypropylene, the content of the pore-forming agent in the mixed slurry is 0wt.%-50wt.% of the mass of the ceramic solid electrolyte ceramic powder; the binder is at least one of polyvinyl alcohol, acrylic emulsion, polyacrylate ammonium salt, polymethyl acrylate, polymethyl methacrylate, ethyl cellulose and polyvinyl butyral ester; the content of the binder in the mixed slurry is 1wt.%-10wt.%; the plasticizer is at least one of polyethylene glycol, ethylene glycol and butyl benzyl phthalate, the content of the plasticizer in the mixed slurry is 0.1wt.%-10wt.%; the dispersant comprises at least one of glyceryl trioleate, phosphate ester, ethoxylated compound, herring oil, polyethylene glycol and castor oil, the content of the dispersant in the mixed slurry is 0wt.%-5wt.%; (2) casting the mixed slurry on a porous matrix material or a dense matrix material by a flow casting method, drying to obtain a ceramic green body, and sintering to obtain a porous ceramic solid electrolyte; the sintering temperature is 900-1300℃, and the sintering time is 1-120 minutes; the thickness of the ceramic green body is 10-400μm; the thickness of the porous ceramic solid electrolyte is 11-12μm; (3) uniformly mixing an acrylate compound, a photoinitiator, a lithium salt and a small molecule solvent to obtain a precursor solution; (4) adding the obtained precursor solution into the porous ceramic solid electrolyte to fill the internal voids, and then performing in-situ photoinitiation to make the acrylate compound polymerize, to obtain an inorganic / organic composite thin film solid electrolyte.

10. The production method according to claim 9, characterized by, The solvent comprises at least one of water, butanone, n-propanone, acetone, cyclohexanone, butyl acetate, butanol, methanol, ethanol, isopropyl alcohol, methyl ethyl ketone, trichloroethylene, toluene and xylene, and the content of the solvent in the mixed slurry is 30wt.%-70wt.%.

11. The preparation method according to claim 9, characterized in that, The porous matrix material or the dense matrix material comprises bacterial cellulose, a PI separator, a non-woven fabric, a PE separator, a PP separator, a nylon net, a PET polyester film or an aluminum foil.

12. A solid-state lithium battery comprising: A positive electrode sheet, a negative electrode sheet and an inorganic / organic composite thin film solid electrolyte based on a porous ceramic solid electrolyte between the positive electrode sheet and the negative electrode sheet, as claimed in any one of claims 1-8.

13. The solid-state lithium battery of claim 12, wherein, The negative electrode sheet is one of a metal lithium foil, a lithium alloy, graphite, silicon and a composite thereof. LiFePO4, LiCoO2, LiNi b Co c Mn 1-b-c O2, 0≤b≤1, 0≤c≤1, LiNi 0.8 Co 0.15 Al 0.05 , LiMn2O4, S, Li2S one or more.

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