Interface modified phosphate ceramic solid electrolyte, battery and preparation method

Abstract

The invention relates to the technical field of solid-state batteries, and particularly discloses an interface-modified phosphate ceramic solid-state electrolyte, a battery and a preparation method.The method comprises the steps that an adhesive and lithium salt are stirred and mixed in an organic solution, and a uniformly-dispersed first mixed solution is obtained; adding LATP ceramic powder into the first mixed solution, carrying out ultrasonic treatment and stirring to obtain a second mixed solution, and drying the second mixed solution to obtain the LATP solid electrolytic film with a stable structure; and compounding the prepared gel electrolyte precursor with the LATP solid electrolyte membrane, heating for a period of time at constant temperature, and completing the curing process to obtain the LATP-based composite solid electrolyte. The gel electrolyte is used as an interface layer to be combined with the LATP electrolyte membrane to stabilize an LATP / Li interface, a firm cross-linked network is formed through in-situ polymerization, basic mechanical stability is provided, good compatibility with lithium metal is achieved, the ionic conductivity is improved, and the transference number of lithium ions is increased.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, specifically to an interface-modified phosphate ceramic solid electrolyte, a battery, and a preparation method thereof. Background Technology

[0002] Liquid lithium-ion batteries, due to serious safety concerns, can no longer meet the high demand for energy. Solid-state batteries, which use solid electrolytes instead of liquid electrolytes, offer high safety and significantly improved energy density, making them the optimal choice for electric vehicles and large-scale energy storage systems. Therefore, the development of solid-state electrolytes is of paramount importance.

[0003] Typical solid electrolytes are classified into sulfide, oxide, halide, and polymer electrolytes. Among them, oxide electrolytes have significant advantages in terms of safety due to their high ionic conductivity and flame retardancy. However, they still have shortcomings such as poor interfacial stability with the electrode and high interfacial impedance at room temperature, which can lead to the failure of solid-state lithium-ion batteries.

[0004] Therefore, developing a solid electrolyte with good contact with the battery negative electrode interface, which allows lithium ions to pass through quickly while effectively reducing high interfacial impedance, is essential for achieving high-performance solid-state batteries.

[0005] Constructing composite solid electrolytes can significantly improve the instability of the solid electrolyte-electrode interface. Polymer electrolytes, with their flexibility, good stability, and ease of functionalization, have become a key research focus. Specifically, taking the oxide electrolyte LATP as an example, it possesses high ionic conductivity (10⁻⁶ Ω·cm). -4 ~10 -3 S cm -1 It has been extensively studied due to its wide electrochemical window and excellent thermal stability.

[0006] However, LATP undergoes interfacial side reactions with the lithium metal anode, leading to the continuous decomposition of the LATP / Li interface. Furthermore, the high impedance generated between LATP and the electrode significantly hinders lithium-ion transport.

[0007] Since solid electrolytes with different interface modulations have different effects on battery performance, developing solid electrolyte interfaces modified with gel electrolytes is of great significance and value. Summary of the Invention

[0008] The purpose of this invention is to provide an interface-modified phosphate ceramic solid electrolyte, a battery, and a preparation method thereof, which can not only improve ionic conductivity and ion transference number, but also act as a promoter for Li +This method is a novel approach to interface-controlled LATP solid-state electrolytes. It is an efficient accelerator for ion conduction and also possesses good interfacial stability. Furthermore, the in-situ co-grown Li3N-rich and LiF-rich double protective layers of the constructed gel electrolyte layer protect the P-LATP interface and generate a good interfacial stabilization layer during charge and discharge. This enables the development of high-performance solid-state batteries.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for preparing an interface-modified phosphate ceramic solid electrolyte, comprising the following steps: Step (1) Mix the adhesive and lithium salt in an organic solution to obtain a uniformly dispersed first mixed solution.

[0010] Step (2) Add LATP ceramic powder to the first mixed solution, stir by ultrasound to obtain the second mixed solution, and then dry the second mixed solution to obtain a structurally stable LATP solid electrolyte membrane; Step (3) The prepared gel electrolyte precursor is combined with the LATP solid electrolyte membrane and heated at a constant temperature for a period of time to complete the curing process and obtain the LATP-based composite solid electrolyte.

[0011] The method of this invention can not only improve ionic conductivity and ion transference number, but also act as a promoter of Li + It is an efficient accelerator for ion conduction and also has good interfacial stability. Moreover, the in-situ co-grown Li3N-rich and LiF-rich double protective layer of the constructed gel electrolyte layer protects the interface of the LATP electrolyte membrane.

[0012] As a preferred option, in step (1), the mass ratio of adhesive to lithium salt is 3~4:2~3.

[0013] As a preferred embodiment, the LATP ceramic powder is prepared in step (2) as follows: Weigh out an appropriate amount of Li2CO3:Al2O3:TiO2:NH4H2PO4, then add an appropriate amount of alcohol solution, put it into a ball mill, and ball mill at 300~500 rpm for 4~8 h to obtain LATP precursor; The molar ratio of Li2CO3:Al2O3:TiO2:NH4H2PO4 is 2~3:1~2:6~7:18~20, and the solid-liquid ratio is 1:1~3. The obtained LATP precursor was sintered into LATP ceramic sheets using a solid-state method. The sintering temperature was 700~900℃, the holding time was 2~6h, and the heating rate to the calcination temperature was 5~10℃ / min. The LATP ceramic powder was obtained by thorough grinding.

[0014] Based on inorganic ceramic LATP powder, the inherent anion immobilization function of LATP is utilized, effectively promoting uniform ion distribution, reducing the concentration gradient, and contributing to the Li + Uniform ion deposition. A good interfacial protective layer is also generated during charge and discharge. Solid-state lithium iron phosphate batteries assembled with this novel electrolyte exhibit good capacity retention, thus enabling the development of high-performance solid-state batteries.

[0015] As a preferred embodiment, in step (2), the amount of LATP ceramic powder added is 9.5~10.5wt%, the ultrasonic time is 50~60 min, and the reaction temperature is 50~60℃.

[0016] Different LATP powder contents lead to different electrochemical performance of the composite electrolyte; an addition of around 10 wt% is more beneficial to Li + Migration, but the added amount of LATP powder is prone to agglomeration, and conventional physical mixing cannot improve it well. Therefore, the mixed solution after adding LATP powder is first ultrasonicated and then physically mixed within the above range.

[0017] As a preferred embodiment, in step (2), drying the second mixed solution specifically involves pouring the second mixed solution into a PTFE mold and then heating it to evaporate the solvent, thereby forming a dense monolithic P-LATP membrane.

[0018] Improving the dispersibility of LATP particles through solution casting film formation can simultaneously enhance the mechanical strength and thermal stability of LATP composite solid electrolytes, thereby increasing the safety and reliability of battery systems.

[0019] As a preferred embodiment, the preparation method of the gel electrolyte precursor in step (3) is as follows: Using polyethylene glycol diacrylate as a crosslinking agent to polymerize monomers, polyethylene glycol diacrylate: acrylonitrile: lithium hexafluorophosphide electrolyte are mixed in a mass ratio of 1~2:3~4:7~8, and then fluorinated additives with a mass percentage of 1~2wt% are added to obtain a mixed solution. The mixed solution is stirred at 25~30℃ for 0.5~1h to obtain the gel electrolyte precursor for battery assembly.

[0020] LATP solid electrolyte modified with gel electrolyte can improve ionic conductivity and ion transference number, inhibit dendrite growth, limit anion transport, match lithium iron phosphate solid batteries, and realize the development of solid batteries.

[0021] As a preferred option, in step (3), the gel electrolyte precursor and the LATP solid electrolyte membrane are polymerized in situ at a polymerization temperature of 60~70 ℃ and a polymerization time of 2~3 h.

[0022] Polymerization temperatures that are too low or too high may cause the polymer's cross-linked network structure and its physicochemical properties to deteriorate.

[0023] The gel electrolyte, formed through in-situ polymerization, forms a robust cross-linked network that provides not only fundamental mechanical stability but also excellent compatibility with lithium metal. This facilitates rapid and uniform Li+ plating / stripping while isolating direct contact between LATP / Li, reducing side-reactive active sites.

[0024] Secondly, the present invention also provides an interface-modified phosphate ceramic solid electrolyte, which is prepared by the above-described method for preparing phosphate ceramic solid electrolyte.

[0025] The ionic conductivity of the obtained composite solid electrolyte is 5.9 × 10⁻⁶. ~4 S cm −1 The ion mobility number is 0.74, and the voltage window is 4.82V.

[0026] Thirdly, the present invention also provides a lithium-ion battery comprising the above-described interface-modified phosphate ceramic solid electrolyte.

[0027] The interface-modified LATP-based solid electrolyte can improve ionic conductivity and ion transference number, inhibit dendrite growth, limit anion transport, match lithium iron phosphate solid batteries, and realize the development of solid batteries. Attached Figure Description

[0028] Figure 1 The infrared spectrum of the LATP-based electrolyte in Example 1 is shown below. Figure 2 This is a scanning electron microscope image of the LATP-based electrolyte from Example 1; Figure 3 The nitrogen adsorption-desorption curve of the LATP-based electrolyte in Example 1 is shown. Figure 4 The ionic conductivity diagram of the LATP-based electrolyte in Example 1 is shown. Figure 5 This is an electrochemical window diagram of the LATP-based electrolyte in Example 1; Figure 6 This is a ion transport number diagram of the LATP-based electrolyte in Example 1; Figure 7 The image shows the XRD pattern of the LATP solid electrolyte membrane and the crystal structure of LATP in Example 1. Figure 8The cycle performance of the lithium symmetric battery prepared using the LATP-based electrolyte in Example 1 is shown. Figure 9 The rate performance of the solid-state battery prepared by matching the LATP-based electrolyte with the lithium iron phosphate cathode in Example 1 is shown. Figure 10 The image shows the charge-discharge curves of the solid-state battery prepared by matching the LATP-based electrolyte with the lithium iron phosphate cathode in Example 1 at different rates. Figure 11 The cycle performance of the solid-state battery prepared by matching the LATP-based electrolyte with the lithium iron phosphate cathode in Example 1 is shown. Figure 12 The conductivity test results for P-LATP electrolyte membranes with different LATP contents are shown in the figure. Figure 13 The rate performance diagrams for P-LATP electrolyte membranes with different LATP contents are shown. Figure 14 The graph shows the long-term cycling performance of P-LATP electrolyte membranes with different LATP contents. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased.

[0030] Unless otherwise stated, all percentages in this invention represent mass fractions. Ratios are mass percentages, and concentrations are mass concentrations.

[0031] LATP has high ionic conductivity (10) -4 ~10 -3 S cm -1 It has been extensively studied due to its wide electrochemical window and excellent thermal stability.

[0032] However, LATP and lithium metal anodes are affected by Ti 4 ⁺ / Ti 3 The redox reaction of ⁺ causes Li / Li + During ion conversion, interfacial side reactions occur, leading to the continuous decomposition of the LATP / Li interface. Furthermore, the high impedance generated by the solid-solid contact between LATP and the electrode significantly hinders lithium-ion transport.

[0033] Therefore, adjusting the ion conduction behavior and charge distribution at the electrolyte / electrode interface to allow for rapid and uniform Li + Transfer is an essential area of ​​in-depth research for achieving high-performance lithium metal batteries. Combined with gel electrolytes, the thermal stability of the composite solid electrolyte ensures that it maintains its structural integrity and functional efficacy over a wide temperature range and in the presence of various electrochemically active materials. Since different interface-modified solid electrolytes have varying effects on battery performance, developing gel electrolyte-modified solid electrolyte interfaces is of significant importance and value to both academia and industry.

[0034] In a first aspect, embodiments of the present invention provide a method for preparing an interface-modified phosphate ceramic solid electrolyte, comprising the following steps: Step (1) Mix the adhesive and lithium salt in an organic solution to obtain a uniformly dispersed first mixed solution.

[0035] Step (2) Add LATP ceramic powder to the first mixed solution, and stir by ultrasound to obtain a second mixed solution. Then dry the second mixed solution to obtain a structurally stable LATP solid electrolytic membrane; thereby forming a continuous channel to enhance ion conduction.

[0036] Step (3) The prepared gel electrolyte precursor is combined with the LATP solid electrolyte membrane and heated at a constant temperature for a period of time to complete the curing process and obtain the LATP-based composite solid electrolyte.

[0037] This invention provides a strategy for creating a composite solid electrolyte by introducing a gel electrolyte as an interface modification. The gel electrolyte is combined with an LATP electrolyte membrane as an interface layer to stabilize the LATP / Li interface. Through in-situ polymerization, the gel electrolyte forms a robust cross-linked network, providing not only basic mechanical stability but also good compatibility with lithium metal. This promotes rapid and uniform Li... + The plating / stripping process isolates the direct contact between LATP / Li, reducing side reaction active sites. This improves ionic conductivity while the electron-rich environment effectively repels anion migration, increasing the lithium-ion transference number. The high ionic conductivity addresses a key challenge of solid-state electrolytes, promoting the application of high-performance solid-state batteries.

[0038] This invention not only improves ionic conductivity and ion transference number, but also acts as a promoter of Li + It is an efficient accelerator for ion conduction and also has good interfacial stability. Moreover, the in-situ co-grown Li3N-rich and LiF-rich double protective layer of the constructed gel electrolyte layer protects the interface of the LATP electrolyte membrane.

[0039] In one embodiment, in step (1), the mass ratio of the binder to the lithium salt is 3~4:2~3. The lithium salt can be bis(trifluoromethanesulfonyl)imide, LiFSI, or other lithium salts with similar properties. The organic solution can be N,N-dimethylformamide solution or other organic solutions with similar properties. In preparing the composite electrolyte membrane, the organic solvent DMF can help disperse the lithium salt and the inorganic ceramic powder LATP. The binder is polyvinylidene fluoride or other binders with similar properties. PVDF is a classic polymer electrolyte binder, and it itself provides good mechanical properties and electrochemical stability.

[0040] In one embodiment, the LATP ceramic powder is prepared in step (2) as follows: Weigh out an appropriate amount of Li2CO3:Al2O3:TiO2:NH4H2PO4, then add an appropriate amount of alcohol solution, place in a ball mill, and ball mill at 300~500 rpm for 4~8 h to obtain the LATP precursor. The molar ratio of Li2CO3:Al2O3:TiO2:NH4H2PO4 is 2~3:1~2:6~7:18~20, and the solid-liquid ratio is 1:1~3. The obtained LATP precursor was sintered into LATP ceramic sheets using a solid-state method. The sintering temperature was 700~900℃, the holding time was 2~6h, and the heating rate to the calcination temperature was 5~10℃ / min. The LATP ceramic powder was obtained by thorough grinding.

[0041] The inorganic ceramic lithium titanium phosphate (LiAl) prepared in this embodiment of the invention is an aluminum titanium phosphate. 1.3 Al 0.3 Ti 1.7 (PO4)3 Based on inorganic ceramic LATP powder, the inherent anion immobilization function of LATP is utilized, effectively promoting uniform ion distribution, reducing the concentration gradient, and contributing to the Li + Uniform ion deposition. A good interfacial protective layer is also generated during charge and discharge. Solid-state lithium iron phosphate batteries assembled with this novel electrolyte exhibit good capacity retention, thus enabling the development of high-performance solid-state batteries. Li2CO3, Al2O3, TiO2, and NH4H2PO4 raw materials are inexpensive, stable, and suitable for mechanical ball milling.

[0042] In one embodiment, in step (2), the amount of LATP ceramic powder added is 9.5~10.5wt%, the ultrasonic time is 50~60 min, the reaction temperature is 50~60℃, and the drying temperature can be 50~60℃.

[0043] Different LATP powder contents lead to different electrochemical performance of the composite electrolyte; an addition of around 10 wt% is more beneficial to Li + Migration, but the added amount of LATP powder is prone to agglomeration, and conventional physical mixing cannot improve it well. Therefore, the mixed solution after adding LATP powder is first ultrasonicated and then physically mixed within the above range.

[0044] In one embodiment, in step (2), drying the second mixed solution specifically involves pouring the second mixed solution into a PTFE mold and then heating it to evaporate the solvent, thereby forming a dense monolithic P-LATP membrane.

[0045] Improving the dispersibility of LATP particles through solution casting film formation can simultaneously enhance the mechanical strength and thermal stability of LATP composite solid electrolytes, thereby increasing the safety and reliability of battery systems.

[0046] In one embodiment, the preparation method of the gel electrolyte precursor in step (3) is as follows: Using polyethylene glycol diacrylate as a crosslinking agent to polymerize monomers, polyethylene glycol diacrylate: acrylonitrile: lithium hexafluorophosphide electrolyte are mixed in a mass ratio of 1~2:3~4:7~8, and then fluorinated additives with a mass percentage of 1~2wt% are added to obtain a mixed solution. The mixed solution is stirred at 25-30°C for 0.5-1 h to obtain the gel electrolyte precursor for battery assembly. The fluorinated additive can be a polyfluoropolymer.

[0047] LATP electrolytes exhibit high interfacial impedance and side reactions. Therefore, we discovered that introducing a PEGDA-based gel electrolyte as an interfacial layer optimizes interfacial contact while preventing side reactions. We introduced a polyethylene glycol diacrylate (PEGDA)-based gel electrolyte as an interfacial layer, combining it with the LATP electrolyte membrane as an interfacial modification to stabilize the LATP / Li interface. The gel electrolyte-modified LATP solid-state electrolyte improves ionic conductivity and ion transference number, inhibits dendrite growth, and restricts anion transport, making it suitable for lithium iron phosphate solid-state batteries and enabling the development of solid-state batteries.

[0048] In one embodiment, in step (3), the gel electrolyte precursor and the LATP solid electrolyte membrane are polymerized in situ at a polymerization temperature of 60-70 °C and a polymerization time of 2-3 h.

[0049] The gel electrolyte, formed through in-situ polymerization, possesses a robust cross-linked network, providing not only fundamental mechanical stability but also excellent compatibility with lithium metal. This facilitates rapid and uniform Li+ plating / stripping while isolating direct contact between LATP and Li, reducing side-reaction active sites. The in-situ co-grown Li3N-rich and LiF-rich dual protective layers of the constructed gel electrolyte layer protect the LATP electrolyte membrane interface. The inherent anion immobilization function of LATP is utilized, effectively promoting uniform ion distribution, reducing the concentration gradient, and contributing to Li+ absorption. + Uniform deposition of ions.

[0050] The thermal polymerization of this invention does not form a film outside the battery, but directly forms an electrolyte film inside the battery. The assembled battery can be placed in an oven at the above temperature and kept warm for the above time.

[0051] Secondly, embodiments of the present invention also provide an interface-modified phosphate ceramic solid electrolyte, which is prepared by the above-described method for preparing phosphate ceramic solid electrolytes.

[0052] The ionic conductivity of the obtained composite solid electrolyte is 5.9 × 10⁻⁶. -4 S cm −1 The ion mobility number is 0.74, and the voltage window is 4.82V.

[0053] Thirdly, embodiments of the present invention also provide a lithium-ion battery, comprising the above-described interface-modified phosphate ceramic solid electrolyte.

[0054] In this embodiment of the invention, the positive electrode of the assembled battery is commercial lithium iron phosphate, and the negative electrode is high-capacity lithium metal.

[0055] The battery assembly process of this invention involves a positive electrode, a composite solid electrolyte, and a lithium metal negative electrode, eliminating the need for commercially available separators and electrolytes, thus improving battery safety and energy density. Battery testing was conducted at room temperature.

[0056] If the present invention does not impose any special limitations on the application method or testing method, any method well known to those skilled in the art can be used.

[0057] The following detailed description, in conjunction with embodiments, illustrates an interface-modified phosphate ceramic solid electrolyte, battery, and preparation method provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0058] Example 1 The method for preparing the interface-modified phosphate ceramic solid electrolyte in this embodiment includes the following steps: Step (1) Polyvinylidene fluoride (PVDF) and bis(trifluoromethanesulfonyl)imide salt are stirred and mixed in N,N-dimethylformamide solution to obtain a uniformly dispersed first mixed solution. The mass ratio of PVDF to bis(trifluoromethanesulfonyl)imide salt is 3:2.

[0059] Step (2) First, prepare LATP ceramic powder: Weigh out appropriate amounts of Li2CO3, Al2O3, TiO2, and NH4H2PO4, then add an appropriate amount of anhydrous ethanol solution, place in a ball mill, and ball mill at 400 rpm for 6 h.

[0060] The molar ratio of Li2CO3:Al2O3:TiO2:NH4H2PO4 is 3:1:6:18.

[0061] The solid-liquid ratio was 1:1.5. The obtained LATP precursor was sintered into LATP ceramic sheets using a solid-state method at a temperature of 800℃ and a holding time of 4h. The heating rate to the calcination temperature was 8℃ / min. The LATP ceramic powder was obtained by thorough grinding.

[0062] LATP ceramic powder is added to the first mixed solution at a rate of 10 wt%, which is 10% of the total mass. The mixture is sonicated for 60 minutes at a reaction temperature of 55°C and stirred to obtain a second mixed solution. The second mixed solution is then poured into a PTFE mold and heated to evaporate the solvent, forming a dense, integral P-LATP membrane, which is a structurally stable LATP solid electrolyte membrane (P-LATP). This forms a continuous channel that enhances ion conduction.

[0063] Step (3) Preparation of gel electrolyte precursor: Polyethylene glycol diacrylate was used as a crosslinking agent to polymerize monomers. Polyethylene glycol diacrylate, acrylonitrile, and lithium hexafluorophosphide electrolyte were mixed in a mass ratio of 1:3:7, and then 1.5 wt% of a fluorinated additive was added to obtain a mixed solution. The fluorinated additive was a polyfluorinated crosslinking agent, 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane (OFHDODA).

[0064] The mixed solution was stirred at 25°C for 0.5 h to obtain the gel electrolyte precursor for battery assembly.

[0065] The prepared gel electrolyte precursor was composited with an LATP solid electrolyte membrane and polymerized at 60°C for 2 hours to complete the curing process and obtain an LATP-based composite solid electrolyte.

[0066] Example 2 The method for preparing the interface-modified phosphate ceramic solid electrolyte in this embodiment includes the following steps: Step (1) Polyvinylidene fluoride (PVDF) and bis(trifluoromethanesulfonyl)imide salt are stirred and mixed in N,N-dimethylformamide solution to obtain a uniformly dispersed first mixed solution. The mass ratio of PVDF to bis(trifluoromethanesulfonyl)imide salt is 4:3.

[0067] Step (2) First, prepare LATP ceramic powder: Weigh out appropriate amounts of Li2CO3, Al2O3, TiO2, and NH4H2PO4, then add an appropriate amount of anhydrous ethanol solution, place in a ball mill, and ball mill at 300 rpm for 8 hours.

[0068] The molar ratio of Li2CO3:Al2O3:TiO2:NH4H2PO4 is 3:2:7:20.

[0069] The solid-liquid ratio was 1:2. The obtained LATP precursor was sintered into LATP ceramic sheets using a solid-state method at a temperature of 900℃ and a holding time of 4 hours. The heating rate to the calcination temperature was 5℃ / min. The LATP ceramic powder was obtained by thorough grinding.

[0070] LATP ceramic powder was added to the first mixed solution at an amount of 9.8 wt%, which is 9.8% of the total mass. The mixture was sonicated for 55 minutes at a reaction temperature of 58°C and stirred to obtain a second mixed solution. The second mixed solution was then poured into a PTFE mold and heated to evaporate the solvent, forming a dense, integral P-LATP membrane, which is a structurally stable LATP solid electrolyte membrane (P-LATP). This creates continuous channels that enhance ion conduction.

[0071] Step (3) Preparation of gel electrolyte precursor: Polyethylene glycol diacrylate was used as a crosslinking agent to polymerize monomers. Polyethylene glycol diacrylate, acrylonitrile, and lithium hexafluorophosphide electrolyte were mixed in a mass ratio of 2:4:7, and then 1.2 wt% of a fluorinated additive was added to obtain a mixed solution. The fluorinated additive was a polyfluorinated crosslinking agent, 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane (OFHDODA).

[0072] The mixed solution was stirred at 28°C for 50 min to obtain the gel electrolyte precursor for battery assembly.

[0073] The prepared gel electrolyte precursor was composited with an LATP solid electrolyte membrane and heated at 65°C for 1.5 h to complete the curing process and obtain an LATP-based composite solid electrolyte.

[0074] Example 3 The method for preparing the interface-modified phosphate ceramic solid electrolyte in this embodiment includes the following steps: Step (1) Polyvinylidene fluoride (PVDF) and bis(trifluoromethanesulfonyl)imide salt are stirred and mixed in N,N-dimethylformamide solution to obtain a uniformly dispersed first mixed solution. The mass ratio of PVDF to bis(trifluoromethanesulfonyl)imide salt is 3:2.5.

[0075] Step (2) First, prepare LATP ceramic powder: Weigh out appropriate amounts of Li2CO3, Al2O3, TiO2, and NH4H2PO4, then add an appropriate amount of anhydrous ethanol solution, place in a ball mill, and ball mill at 450 rpm for 5 hours.

[0076] The molar ratio of Li2CO3:Al2O3:TiO2:NH4H2PO4 is 2:1:7:18.

[0077] The solid-liquid ratio was 1:1.5. The obtained LATP precursor was sintered into LATP ceramic sheets using a solid-state method at a temperature of 800℃ and a holding time of 4h. The heating rate to the calcination temperature was 8℃ / min. The LATP ceramic powder was obtained by thorough grinding.

[0078] LATP ceramic powder was added to the first mixed solution at an amount of 10.5 wt%, which is 10.5% of the total mass. The mixture was sonicated for 60 minutes at a reaction temperature of 58°C and stirred to obtain a second mixed solution. The second mixed solution was then poured into a PTFE mold and heated to evaporate the solvent, forming a dense, integral P-LATP membrane, which is a structurally stable LATP solid electrolyte membrane (P-LATP). This creates continuous channels that enhance ion conduction.

[0079] Step (3) Preparation of gel electrolyte precursor: Polyethylene glycol diacrylate (PEG) was used as the crosslinking agent and monomer. PEG, acrylonitrile, and lithium hexafluorophosphide electrolyte were mixed in a mass ratio of 2:3:8, and then 1.8 wt% fluorinated additive was added to obtain a mixed solution. In this embodiment, the fluorinated additive was the polyfluorinated crosslinking agent 1,6-bis(acryloyloxy)-2,2,3,3,4,4,5,5-octafluorohexane (OFHDODA).

[0080] The mixed solution was stirred at 25°C for 0.5 h to obtain the gel electrolyte precursor for battery assembly.

[0081] The prepared gel electrolyte precursor was composited with an LATP solid electrolyte membrane and heated at 58°C for 2 hours to complete the curing process and obtain an LATP-based composite solid electrolyte.

[0082] Comparative Example 1 In step (2), the obtained LATP precursor (which is obtained by ball milling Li2CO3: Al2O3: TiO2: NH4H2PO4 in proportion) is sintered into ceramic LATP sheets by solid-state method. The sintering temperature is 1000℃ and the holding time is 4h. The rest is the same as in Example 1.

[0083] Comparative Example 2 In step (3), polyethylene glycol diacrylate is used as a crosslinking agent to polymerize monomers. Polyethylene glycol diacrylate, acrylonitrile, and lithium hexafluorophosphate electrolyte are mixed in a mass ratio of 1:3:7 without adding fluorinated additives to obtain a mixed solution. The rest is the same as in Example 1.

[0084] Tests and Results This application tests the LATP-based composite solid electrolyte of Example 1 according to IEC60086-4 standard, and the test temperature in this application is 30°C. The results are as follows: like Figure 1 As shown, the wavenumber at 1200 in the infrared spectrum is a COC bond, indicating that this GEL layer has successfully complexed with LATP.

[0085] like Figure 2 As shown, SEM analysis of the electrolyte membrane reveals a smooth surface, which is beneficial for interfacial contact. Figure 3 As shown, the nitrogen adsorption-desorption curve of LATP powder has a surface area of ​​1.34 m. 2 A specific surface area of ​​ / g is beneficial for the adsorption and migration of lithium ions.

[0086] Impedance testing was performed on the interface-modified LATP composite solid electrolyte, such as... Figure 4 As shown, the ionic conductivity of this electrolyte is calculated using the formula for ionic conductivity, based on the impedance magnitude. The ionic conductivity of the donor-acceptor electrolyte is 5.9 × 10⁻⁶. -4 S cm −1 It has high ionic conductivity. For example... Figure 5 The image shows the electrochemical window test of this electrolyte, with a voltage window of 4.82V, indicating high antioxidant capacity. Figure 6 As shown, this electrolyte exhibits a high ion transference number (0.74) and selectivity. The interface-modified LATP composite solid-state electrolyte significantly improves ionic conductivity, ion transference number, and broadens the electrochemical reaction window, thus promoting the development of high-performance solid-state batteries.

[0087] Figure 7 XRD images of the LATP solid electrolyte membrane and the crystal structure of LATP are shown. Figure 7It can be seen that the LATP electrolyte membrane has high purity and no impurity phase is generated. The illustration shows that LATP is a NASICON-type ionic conductor with a typical rhombic structure.

[0088] Determination of LATP content A series of membranes were prepared by incorporating different amounts of LATP particles into a PVDF matrix to determine the optimal LATP content and obtain a structurally stable LATP solid electrolytic membrane, thereby forming a continuous channel to enhance ion conduction.

[0089] To determine the optimal LATP content, we used a gradient increase in LATP powder content. We then tested the conductivity of P-LATP electrolyte membranes with different LATP contents (0 wt%, 5 wt%, 7.5 wt%, 10 wt%, 12.5 wt%). Figure 12 As shown, the ionic conductivity of P-LATP10 at 30℃ is 0.76 mS / cm. −1 Superior to other P-LATP contents. Direct comparison of their ionic conductivity differences shows that the high ionic conductivity and low interfacial impedance of P-LATP10 jointly promote efficient lithium-ion migration and stable cycling. Too low a content cannot form an effective lithium-ion transport network, resulting in limited performance improvement; too high a content results in insufficient polymer binder to encapsulate all particles, leading to insufficient film toughness and poor processing performance.

[0090] Furthermore, the rate performance and long-term cycling performance of P-LATP electrolyte membranes with different LATP contents were tested. The P-LATP10 electrolyte membrane provided higher specific capacity at all current densities, such as... Figure 13 As shown, the differences in discharge capacity between LATP electrolyte membranes with different contents are even more pronounced at higher current densities.

[0091] Figure 14 P-LATP10 was confirmed to have better cycling performance than PVDF, P-LATP5, P-LATP7.5, and P-LATP12.5. After 100 cycles at 1C, P-LATP10 retained 90.4% of its capacity. These electrochemical properties indicate that P-LATP10 is more favorable for Li... + Migration. Therefore, an LATP content of around 10 wt% is appropriate.

[0092] Test Example 1 The interface-modified LATP composite solid electrolyte obtained in Example 1 was used to assemble a lithium-lithium symmetric coin cell, and constant current charge-discharge stability cycling tests were performed. The coin cell fabrication process is as follows: 1. Preparation of electrode materials A slurry was prepared by mixing lithium iron phosphate (LFP) (Kolute, battery grade), conductive carbon black (Ketjen Black, model XC-72), and PVDF-NMP (2 g PVDF (Exploration Platform, YP-50F purity) dissolved in 60 g NMP (Adamas Reagents, AR purity), with PVDF acting as a binder for the positive electrode material) at a weight ratio of 9:0.5:0.5. To avoid the slurry becoming too concentrated, an appropriate amount of NMP solution was added for dilution. The prepared slurry was placed in a homogenizer and stirred at 2000 rpm for 20 min, repeated 3 times. After the slurry was thoroughly mixed, it was evenly coated onto aluminum foil with a spatula, and then the aluminum foil was placed in an 80 ℃ vacuum drying oven to dry for 12 hours to remove the NMP solvent. After drying, the positive electrode material was rolled and cut to the required size. The electrode sheet was dried in a 110 ℃ vacuum drying oven for 2 hours to remove residual moisture and then transferred to a glove box for later use. The negative electrode material is lithium foil (Kelode, pure battery grade).

[0093] 2. Battery assembly The battery assembly sequence is as follows: positive electrode shell - positive electrode sheet - LATP-based composite solid electrolyte of Example 1 - negative electrode sheet - pad - spring sheet - negative electrode shell.

[0094] Battery assembly: Place a 0.5mm steel sheet, a negative lithium electrode sheet, an electrolyte membrane, a lithium sheet, and a steel sheet in sequence, and apply a pressure of 9.5MPa to press them into a symmetrical battery.

[0095] For the battery at 0.5 mA cm –2 and 0.5 mAh cm –2 Under the conditions of conducting transverse current charge and discharge tests, such as... Figure 8 As shown, the symmetric cell remained stable after 400 h of cycling, demonstrating long-term cycling stability of lithium-ion intercalation / deintercalation and effectiveness in suppressing lithium dendrites at the interface.

[0096] Test Example 2 The manufacturing process of lithium iron phosphate solid-state batteries is as follows: Preparation method of the positive electrode: Commercial lithium iron phosphate (LFP) powder, carbon black (Super P), and polyvinylidene fluoride (PVDF) are mixed together in a mass ratio of 90:5:5. Then, an appropriate amount of N-methylpyrrolidone (NMP) solvent is added to form a uniform slurry. After coating with aluminum foil, it is dried in an oven at 80°C for 10 hours. Then, it is pressed into a disc (Φ=14.0mm). The negative electrode material is lithium sheet (Kelode, pure battery grade). Assembly process: Sequentially place the positive electrode lithium iron phosphate electrode (preferably with a loading of 3.8 mg / cm³). 2The process involved first, then the LATP composite solid electrolyte from Example 1, and finally a lithium sheet, which was pressed into a solid-state battery under a pressure of 9.5 MPa.

[0097] like Figure 9 and Figure 10 As shown, the specific capacity and charge-discharge curves of the solid-state battery at different rates (0.1C, 0.2C, 0.5C, 1C, and 2C) provide a more intuitive view of the fact that the GEL@P-LATP composite electrolyte still retains 120mAh g⁻¹ at a high rate of 2C. –1 The specific capacity is approximately [value missing]. The battery is tested under constant current charge-discharge conditions at a current density of 1C, such as... Figure 11 As shown, the battery's initial discharge specific capacity at 1 C is 140.67 mAh g. –1 The discharge specific capacity is 113.53 mAh g. –1 After 200 cycles, the capacity retention rate can still reach 80.7%, indicating that the battery has high coulombic efficiency and high capacity retention.

[0098] The test results of the examples and comparative examples are shown in Table 1: Table 1 The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an interface-modified phosphate ceramic solid electrolyte, characterized in that, Includes the following steps: Step (1) The adhesive and lithium salt are stirred and mixed in an organic solution to obtain a first mixed solution that is evenly dispersed; Step (2) Add LATP ceramic powder to the first mixed solution, stir by ultrasound to obtain the second mixed solution, and then dry the second mixed solution to obtain a structurally stable LATP solid electrolyte membrane; Step (3) The prepared gel electrolyte precursor is combined with the LATP solid electrolyte membrane and heated at a constant temperature for a period of time to complete the curing process and obtain the LATP-based composite solid electrolyte.

2. The method for preparing phosphate ceramic solid electrolyte according to claim 1, characterized in that, In step (1), the mass ratio of adhesive to lithium salt is 3~4:2~3.

3. The method for preparing phosphate ceramic solid electrolyte according to claim 1, characterized in that, In step (2), the LATP ceramic powder is prepared as follows: Weigh out an appropriate amount of Li2CO3:Al2O3:TiO2:NH4H2PO4, then add an appropriate amount of alcohol solution, put it into a ball mill, and ball mill at 300~500 rpm for 4~8 h to obtain LATP precursor; The molar ratio of Li2CO3:Al2O3:TiO2:NH4H2PO4 is 2~3:1~2:6~7:18~20, and the solid-liquid ratio is 1:1~3. The obtained LATP precursor was sintered into LATP ceramic sheets using a solid-state method. The sintering temperature was 700~900℃, the holding time was 2~6h, and the heating rate to the calcination temperature was 5~10℃ / min. The LATP ceramic powder was obtained by thorough grinding.

4. The method for preparing phosphate ceramic solid electrolyte according to claim 1, characterized in that, In step (2), the amount of LATP ceramic powder added is 9.5~10.5wt%, the ultrasonic time is 50~60 min, and the reaction temperature is 50~60℃.

5. The method for preparing phosphate ceramic solid electrolyte according to claim 1, characterized in that, In step (2), drying the second mixed solution specifically involves pouring the second mixed solution into a PTFE mold and then heating it to evaporate the solvent, forming a dense monolithic P-LATP membrane.

6. The method for preparing phosphate ceramic solid electrolyte according to claim 1, characterized in that, In step (3), the preparation method of the gel electrolyte precursor is as follows: Using polyethylene glycol diacrylate as a crosslinking agent to polymerize monomers, polyethylene glycol diacrylate: acrylonitrile: lithium hexafluorophosphide electrolyte are mixed in a mass ratio of 1~2:3~4:7~8, and then fluorinated additives with a mass percentage of 1~2wt% are added to obtain a mixed solution. The mixed solution is stirred at 25~30℃ for 0.5~1h to obtain the gel electrolyte precursor for battery assembly.

7. The method for preparing phosphate ceramic solid electrolyte according to claim 1, characterized in that, In step (3), the gel electrolyte precursor and LATP solid electrolyte membrane are polymerized in situ at a temperature of 60-70°C for 2-3 hours.

8. An interface-modified phosphate ceramic solid electrolyte, characterized in that: It is prepared by the method for preparing phosphate ceramic solid electrolyte according to any one of claims 1 to 7.

9. A lithium-ion battery, characterized in that: Includes the interface-modified phosphate ceramic solid electrolyte as described in claim 8.

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