CN115799608A - A method for improving the interface between inorganic phase filler and polymer in composite solid electrolyte and its application - Google Patents

Abstract

The invention discloses a method for improving an interface between an inorganic phase and a polymer in a composite solid electrolyte and application thereof, belonging to the field of lithium battery solid electrolytes. The preparation method comprises the steps of preparing a precursor solution containing the silane coupling agent, standing, and dispersing an inorganic phase in the precursor solution for modification. And dissolving the modified inorganic phase, the polymer and the lithium salt in anhydrous acetonitrile, and fully and uniformly stirring. And dripping the uniformly mixed slurry into a die, drying until the solvent is completely volatilized, and punching the die into a wafer serving as a composite electrolyte membrane. The invention takes the solid composite electrolyte membrane as the diaphragm to assemble the battery. The modification layer is formed on the surface of the inorganic phase, so that the interface between the inorganic phase and the polymer in the composite solid electrolyte is effectively improved, the transmission path of lithium ions is increased, the electrochemical window of the electrolyte membrane is widened, the electrochemical performance of the solid battery assembled by the composite electrolyte is improved, and a new idea is provided for the research of the composite solid electrolyte.

Description

A method for improving the interface between inorganic phase filler and polymer in composite solid electrolyte and its application

technical field

The invention belongs to the technical field of solid electrolytes and relates to a method for improving the interface between an inorganic phase filler and a polymer in a composite solid electrolyte.

Background technique

Over the past few decades, advanced lithium battery devices have been widely used in portable electronic products, electric vehicles and even large power grids, playing an irreplaceable role in modern society. However, with the increasing demand for energy storage, traditional liquid lithium-ion batteries can no longer meet the needs of social development for energy density, safety, cost, and lifespan. In traditional battery systems, the pursuit of energy density has reached its limit. At the same time, the complexity of the composition of the liquid electrolyte and the instability of the lithium anode make the safety of the liquid battery particularly significant. In line with the demands of both energy density and safety, solid-state electrolytes, as the best candidates to replace traditional organic electrolytes, have gradually become a research hotspot.

Solid electrolytes are roughly divided into three types: inorganic solid electrolytes, polymer electrolytes, and composite solid electrolytes. Among them, the inorganic solid electrolyte has high ionic conductivity and high mechanical strength, but the solid contact with the electrode interface makes the interface resistance high and the assembly is difficult; the polymer electrolyte has strong flexibility and good interface contact, but the polymer ion The conductivity is low, which cannot meet the actual use requirements of the battery. Composite solid electrolytes combine the advantages of both. While retaining the flexibility of polymer membranes, they improve the ionic conductivity and electrochemical window of composite electrolytes. They are currently the most promising solid electrolytes. However, due to the small particle size of the inorganic filler introduced into the polymer matrix, there is a huge difference in the surface energy of the polymer, and it is easy to spontaneously agglomerate, which is not conducive to the rapid transport of lithium ions inside the electrolyte.

There are a large number of interfaces between the inorganic filler and the polymer matrix in the composite solid electrolyte, and a good interface is very important for the transport and migration of lithium ions in the electrolyte. The introduction of materials with good interfaces with both the inorganic filler and the polymer matrix can significantly reduce the energy barrier required for lithium ions to migrate from the inorganic filler to the polymer, thereby improving the ionic conductivity and lithium transfer number of the composite electrolyte membrane, and correspondingly enabling The electrochemical performance and stability of the final assembled solid-state battery have also been greatly improved. At present, there is still a lot of room for improvement in the existing technology. Only by further improving the interface performance between the inorganic filler and the polymer matrix can it meet the industrial needs of higher quality and higher performance lithium battery devices.

Contents of the invention

The purpose of the present invention is to improve the interface between the inorganic phase filler and the polymer in the composite solid electrolyte, so as to solve the problems of particle agglomeration and lithium ion transmission path discontinuity caused by the difference in the surface energy of the inorganic filler in the current composite solid electrolyte. The invention provides a method for improving the interface between inorganic phase fillers and polymers in a composite solid electrolyte and its application. The composite solid electrolyte containing inorganic fillers of the present invention includes surface-modified inorganic fillers, polymers and lithium salts. The present invention adopts Modification of the silane coupling agent on the surface of the inorganic phase effectively improves the interface problem, reduces the migration barrier between the two phases, increases the electrochemical window of the electrolyte, and improves the electrochemical performance of the solid-state battery.

In order to realize the foregoing invention object, the present invention adopts following technical scheme:

A method for improving the interface between an inorganic phase filler and a polymer in a composite solid electrolyte, comprising the following steps:

(1) heating the precursor solution containing the silane coupling agent in a water bath to obtain a uniform precursor solution;

(2) dispersing the inorganic phase in the precursor solution obtained in the step (1), and stirring to obtain the inorganic phase filler dispersion;

(3) collecting the inorganic phase material in the inorganic phase filler dispersion obtained in the step (2), washing with ethanol solution, and centrifuging at least twice to obtain the inorganic phase material;

(4) Washing, centrifuging, and drying the inorganic phase material to obtain inorganic phase particles and collect them in a centrifuge tube; the collected product inorganic phase particles are modified inorganic phase fillers;

(5) Mix the polymer and the lithium salt in sample bottle A, add anhydrous acetonitrile as a solvent, and stir at a constant temperature on a heating platform until the solution is completely uniform;

(6) Mix the inorganic phase filler modified in the step (4) with polyethylene glycol (PEG) in sample bottle B, add anhydrous acetonitrile as a solvent, and stir at a constant temperature on a heating platform until the solution is completely Uniform;

(7) Pour the solution obtained in the sample bottle B in the step (6) into the sample bottle A in the step (5), fully stir to obtain a uniform slurry;

(8) drip-coat the homogeneous slurry obtained in the step (7) onto the mold, and dry, fully remove the organic solvent, form a dry film on the mold, and then cut it into discs of required size, as Solid composite electrolyte membrane;

(9) Make the positive electrode material into the battery positive electrode sheet, use lithium metal as the negative electrode, use the solid composite electrolyte membrane prepared in the step (8) as the diaphragm, assemble the button battery, and then assemble the solid state battery The electrochemical performance was tested, and a solid-state battery with an improved interface between the inorganic phase filler and the polymer in the composite solid electrolyte was obtained.

Preferably, in the step (1), the silane coupling agent adopts methacrylpropyltrimethoxysilane (KH570), γ-(2,3-glycidyloxy)propyltrimethoxysilane ( KH560), at least one of 3-chloropropyltrimethoxysilane; the heating temperature is 50-80°C; the standing time is 1.0-3.0h.

Preferably, in the step (2), the mass of the inorganic phase particles treated each time is 1.0-5.0 g; each time the stirring treatment is different, and the total time of the stirring treatment is 3.0-12.0 h; the inorganic phase is garnet At least one of type, perovskite type, sulfide, sodium fast ion conductor, lithium fast ion conductor. Further preferably, the inorganic phase is at least one of Li _6.4 La ₃ Zr _1.4 Ta _0.6 O ₁₂ , La _0.56 Li _0.33 TiO ₃ , and Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ .

Preferably, in the step (4), the drying condition adopted is 80-180° C. for 0.5-5.0 hours.

Preferably, in the step (5), the polymer is at least one of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), and polyacrylonitrile (PAN); the lithium salt is bistrifluoro At least one of lithium methanesulfonimide (LiTFSI), lithium bisfluorosulfonimide (LiFSI), lithium perchlorate (LiClO ₄ ); the molar ratio of polymer to lithium salt is 15:1~5 : 1; Control the heating temperature at 50-90°C and the stirring time at 0.5-5.0h.

Preferably, in the step (6), the added content of the modified inorganic phase is 5 to 30 wt% of the sum of the mass of the polymer and the lithium salt; the mass ratio of polyethylene glycol (PEG) to the polymer The ratio is 1:5~1:2; the heating temperature is controlled at 60~80°C, and the stirring time is 1.0~3.0h.

Preferably, in the step (7), the stirring time is controlled to be 6.0-9.0 h.

Preferably, in the step (8), the mold material is at least one of polytetrafluoroethylene (PTFE), release paper (PET) and glass plate.

Preferably, in the step (9), the positive electrode sheet includes a positive electrode active material, a conductive agent, and a binder, and the mass fractions of the positive electrode active material, the conductive agent, and the binder in the positive electrode sheet are 70 to 70% respectively. 85%, 10-20%, 5-15%; the conductive agent is at least one of acetylene black, super carbon black or carbon nanotubes; the binder is PVDF or PTFE; the positive active material is At least one of lithium iron phosphate (LFP) and NCM811.

Preferably, in the step (9), the upper limit of the cut-off voltage of the electrochemical charging and discharging of the solid-state battery is 3.5-4.3V, and the lower limit is 2.2-2.8V.

An application of a composite electrolyte that improves the interface between the inorganic phase and the polymer by the above-mentioned method of the present invention in a solid-state lithium battery, using the solid composite electrolyte membrane prepared by improving the interface between the inorganic phase filler and the polymer in the composite solid electrolyte as a diaphragm, Preparation of solid-state batteries.

Mechanism of the present invention is:

In composite solid-state electrolytes, special attention needs to be paid to the large number of interfaces existing inside the electrolyte to reduce the energy barrier for ion transport at the interface and increase the migration number of lithium ions. Using the hydrolysis reaction of the coupling agent to modify the surface of the inorganic phase particles can improve the interfacial contact between the inorganic phase filler and the polymer matrix and form a continuous lithium ion migration path inside the electrolyte. The composite film prepared by the modified inorganic phase and polymer has high ion conductivity and large electrochemical window. The solid-state battery assembled with lithium metal as the negative electrode and lithium iron phosphate (LFP) and NCM811 as the positive electrode has a small interface resistance and excellent electrochemical performance. The present invention modifies the silane coupling agent on the surface of the inorganic filler, improves the interface between it and the polymer matrix, improves the ionic conductivity of the composite solid electrolyte, increases the electrochemical window of the electrolyte, and enables it to be matched with a high-voltage positive electrode and Run a long loop test.

Compared with the prior art, the technical solution of the present invention has the following obvious outstanding substantive features and significant advantages:

1. The preparation method of the composite solid electrolyte containing inorganic fillers of the present invention uses a silane coupling agent to treat the inorganic ceramic powder, which effectively reduces the surface energy and solves the problem of agglomeration of small particle size particles caused by surface energy differences;

2. The present invention utilizes coupling agents, polymers, and inorganic fillers to form bonds through chemical reactions, and constructs a continuous lithium ion transmission path of filler-coupling agent-polymer, and the assembled solid-state battery has excellent cycle performance and rate performance.

Description of drawings

Fig. 1 is the X-ray diffraction pattern of the LLZTO powder prepared in Examples 1-4 and Comparative Example 1.

2 is a scanning electron microscope (SEM) image of the surface of the composite solid electrolyte membrane prepared in Example 2 and Comparative Example 1.

3 is an EIS impedance test diagram of the composite electrolyte membranes prepared in Example 2 and Comparative Example 1.

Fig. 4 is the LSV electrochemical test diagram of the composite electrolyte membrane prepared in Example 2 and Comparative Example 1.

Fig. 5 is a cycle capacity performance diagram of a full battery assembled with the composite membrane prepared in Example 2 and Comparative Example 1 as the electrolyte and lithium iron phosphate (LFP) as the positive electrode.

6 is a rate performance diagram of a solid-state battery prepared in Example 2 with lithium iron phosphate (LFP) as the positive electrode.

Fig. 7 is a cycle capacity performance diagram of a full battery assembled with the composite membrane prepared in Example 2 as the electrolyte and NCM811 as the positive electrode.

Detailed ways

The present invention will be described in further detail below in conjunction with the examples and drawings, but the implementation of the present invention is not limited thereto. Based on the embodiments of the present invention, other embodiments obtained by persons of ordinary skill in the art without making creative efforts all belong to the protection scope of the present invention.

Example 1:

A method for improving the interface between an inorganic phase filler and a polymer in a solid composite electrolyte, comprising the following steps:

(1) Measure 36mL of absolute ethanol, 2mL of water, and 1mL of coupling agent in a beaker, add acetic acid dropwise to adjust the pH of the precursor solution between 3.5 and 5.0, and let it stand for 1.0h under heating in a water bath at 70°C;

(2) Weigh 1.0 g of LLZTO inorganic phase and disperse it in the precursor solution, and treat it for 3.0 h, so that the coupling agent is modified on the surface of the inorganic phase ceramic particle LLZTO;

(3) Wash the treated inorganic particles with absolute ethanol and centrifuge them for 5 times, transfer them to a blast drying oven at 80°C for 2 hours to evaporate the remaining solvent to dryness, and collect the dried inorganic particles into a centrifuge tube for use;

(4) Weigh 0.44gPEO and 0.36gLiTFSI into sample bottle A and add anhydrous acetonitrile solvent to fully stir to dissolve;

(5) Weigh 0.22g PEG and 0.08g modified LLZTO into sample bottle B and add anhydrous acetonitrile solvent to fully stir to dissolve;

(6) Pour the solution in sample bottle B into sample bottle A and continue to stir for 6.0h;

(7) Take the uniformly mixed slurry and drop-coat it on a polytetrafluoroethylene mold, then place the mold on a heating table at 60°C and bake for 48 hours. The dried composite film was cut into discs with a diameter of 19 mm for use.

Example 2:

A method for improving the interface between an inorganic phase filler and a polymer in a solid composite electrolyte, comprising the following steps:

(1) Measure 36mL of absolute ethanol, 2mL of water, and 1mL of coupling agent in a beaker, add acetic acid dropwise to adjust the pH of the precursor solution between 3.5 and 5.0, and let it stand for 1.0h under heating in a water bath at 70°C;

(2) Weigh 1.0 g of LLZTO inorganic phase and disperse it in the precursor solution, and treat it for 6.0 h, so that the coupling agent is modified on the surface of the inorganic phase ceramic particle LLZTO;

(3) Wash the treated inorganic particles with absolute ethanol and centrifuge them for 5 times, transfer them to a blast drying oven at 80°C for 2.0 hours to dry the remaining solvent, and collect the dried inorganic particles into a centrifuge tube for use;

(4) Weigh 0.44gPEO and 0.36gLiTFSI into sample bottle A and add anhydrous acetonitrile solvent to fully stir to dissolve;

(5) Weigh 0.22g PEG and 0.08g modified LLZTO into sample bottle B and add anhydrous acetonitrile solvent to fully stir to dissolve;

(6) Pour the solution in sample bottle B into sample bottle A and continue to stir for 6.0h;

(7) Take the uniformly mixed slurry and drop-coat it on a polytetrafluoroethylene mold, then place the mold on a heating table at 60°C and bake for 48 hours.

The dried composite film was cut into discs with a diameter of 19 mm for use.

Example 3:

A method for improving the interface between an inorganic phase filler and a polymer in a solid composite electrolyte, comprising the following steps:

(1) Measure 36mL of absolute ethanol, 2mL of water, and 1mL of coupling agent in a beaker, add acetic acid dropwise to adjust the pH of the precursor solution between 3.5 and 5.0, and let it stand for 1.0h under heating in a water bath at 70°C;

(2) Weigh 1.0 g of LLZTO inorganic phase and disperse it in the precursor solution, and treat it for 9.0 h, so that the coupling agent is modified on the surface of the inorganic phase ceramic particle LLZTO;

(3) Wash the treated inorganic particles with absolute ethanol and centrifuge them for 5 times, transfer them to a blast drying oven at 80°C for 2.0 hours to dry the remaining solvent, and collect the dried inorganic particles into a centrifuge tube for use;

(4) Weigh 0.44gPEO and 0.36gLiTFSI into sample bottle A and add anhydrous acetonitrile solvent to fully stir to dissolve;

(5) Weigh 0.22g PEG and 0.08g modified LLZTO into sample bottle B and add anhydrous acetonitrile solvent to fully stir to dissolve;

(6) Pour the solution in sample bottle B into sample bottle A and continue to stir for 6.0h;

(7) Take the uniformly mixed slurry and drop-coat it on a polytetrafluoroethylene mold, then place the mold on a heating table at 60°C and bake for 48 hours.

The dried composite film was cut into discs with a diameter of 19 mm for use.

Example 4:

A method for improving the interface between an inorganic phase filler and a polymer in a solid composite electrolyte, comprising the following steps:

(1) Measure 36mL of absolute ethanol, 2mL of water, and 1mL of coupling agent in a beaker, add acetic acid dropwise to adjust the pH of the precursor solution between 3.5 and 5.0, and let it stand for 1.0h under heating in a water bath at 70°C;

(2) Weigh 1.0 g of LLZTO inorganic phase and disperse it in the precursor solution, and treat it for 12 hours, so that the coupling agent is modified on the surface of the inorganic phase ceramic particle LLZTO;

(3) Wash the treated inorganic particles with absolute ethanol and centrifuge them for 5 times, transfer them to a blast drying oven at 80°C for 2.0 hours to dry the remaining solvent, and collect the dried inorganic particles into a centrifuge tube for use;

(4) Weigh 0.44gPEO and 0.36gLiTFSI into sample bottle A and add anhydrous acetonitrile solvent to fully stir to dissolve;

(5) Weigh 0.22g PEG and 0.08g modified LLZTO into sample bottle B and add anhydrous acetonitrile solvent to fully stir to dissolve;

(6) Pour the solution in sample bottle B into sample bottle A and continue to stir for 6.0h;

(7) Take the uniformly mixed slurry and drop-coat it on a polytetrafluoroethylene mold, then place the mold on a heating table at 60°C and bake for 48 hours.

The dried composite film was cut into discs with a diameter of 19 mm for use.

Comparative example 1:

A method for preparing a solid composite electrolyte, comprising the following steps:

(1) Weigh 0.44gPEO, 0.36gLiTFSI and 0.08gLLZTO into a sample bottle and add anhydrous acetonitrile solvent to fully stir to dissolve;

(2) Take the uniformly mixed slurry and drop-coat it on a polytetrafluoroethylene mold, then place the mold on a heating table at 60°C and bake for 48 hours.

The dried composite film was cut into discs with a diameter of 19 mm for use.

Experimental test analysis:

Full battery assembly: Slurry and coat lithium iron phosphate (LFP)/NCM811 with acetylene black and PVDF at a mass ratio of 8:1:1, and cut them into pole pieces with a diameter of 12mm with a slicer after drying. Metal lithium was used as the negative electrode, and the composite solid electrolyte membrane prepared in Examples 1-4 and Comparative Example 1 was used as the electrolyte of the battery, and a full battery was assembled in an argon glove box.

Charge and discharge test: the voltage range of charge and discharge of the button battery is 2.5~3.8V (the positive electrode is lithium iron phosphate) and 2.8~4.3V (the positive electrode is NCM811). The magnification test range is 0.2 ~ 2C. All electrochemical performance tests were performed at 60 °C.

Fig. 1 is the X-ray diffraction pattern of the LLZTO powder prepared in Examples 1-4 and Comparative Example 1. It can be seen from the figure that the phase composition of the LLZTO surface will not be changed after modification, and the modified LLZTO phase is the same as the original particle regardless of the treatment time.

2 is a scanning electron microscope (SEM) image of the surface of the composite solid electrolyte membrane prepared in Example 2 and Comparative Example 1. It can be seen from the figure that modification on the surface of LLZTO particles can effectively improve the phenomenon of spontaneous aggregation of nanoparticles in the polymer matrix. The treated LLZTO is uniformly dispersed in the PEO matrix, which can provide fast lithium ion transport channels.

Fig. 3 is the EIS impedance test diagram of the composite electrolyte membrane prepared in Example 2 and Comparative Example 1, as can be seen from the figure, the coupling agent has effectively modified the interface between the inorganic phase and the polymer, reducing the lithium ion migration barrier, thereby improving the ionic conductivity of the composite solid electrolyte membrane.

Fig. 4 is the LSV electrochemical test diagram of the composite electrolyte membrane prepared in Example 2 and Comparative Example 1. It can be seen from the figure that the modified electrolyte membrane exhibits an electrochemical window as high as 5.2V, which is improved compared with the original electrolyte membrane.

Fig. 5 is a cycle capacity performance diagram of a full battery assembled with the composite membrane prepared in Example 2 and Comparative Example 1 as the electrolyte and lithium iron phosphate (LFP) as the positive electrode. It can be seen from the figure that after modifying the LLZTO inorganic powder with a coupling agent, the contact interface between the inorganic phase and the polymer was successfully improved, and the cycle performance of Example 2 was greatly improved compared with Comparative Example 1. The first cycle discharge capacity of Example 2 was 156.7mAh·g ^-1 , and the first cycle discharge capacity of Comparative Example 1 was 85mAh·g ^-1 . After 100 cycles, the capacity of Example 2 is 153.3 mAh·g ^-1 , and the capacity retention rate is 97.83%. In comparison, Comparative Example 1 was severely overcharged after 63 cycles, and no longer had the ability to charge and discharge normally. It can be seen that the modification of the coupling agent on the surface of the inorganic phase LLZTO can effectively solve the interface problem existing in the electrolyte itself, and significantly improve the electrochemical performance of the composite solid electrolyte membrane.

6 is a rate performance diagram of a solid-state battery prepared in Example 2 with lithium iron phosphate (LFP) as the positive electrode. In the rate change of 0.2-2C, the modified solid-state batteries all have good charge-discharge performance. When the rate is returned from 2C to 0.2C, the discharge capacity can still be maintained at the initial level, indicating that the modified solid-state battery has excellent rate performance.

Fig. 7 is a cycle capacity performance diagram of a full battery assembled with the composite membrane prepared in Example 2 as the electrolyte and NCM811 as the positive electrode. It can be seen from the figure that the capacity of the first cycle is 165.2mAh·g ^-1 , and after 100 cycles, the battery capacity is 91.8mAh·g ^-1 . The good match with the high-voltage cathode confirms that the modified composite electrolyte membrane has a wider electrochemical window.

The above-mentioned embodiments of the present invention improve the method and application of the interface between the inorganic phase and the polymer in the composite solid electrolyte. The method of the present invention first prepares a precursor solution containing a silane coupling agent and stands still. Then the inorganic phase is dispersed in the precursor solution for modification. Dissolve the modified inorganic phase, polymer, and lithium salt in anhydrous acetonitrile and stir well in a sample bottle. The uniformly mixed slurry is drip-coated into a mold and dried until the solvent is completely evaporated, and then punched into a disc with the mold as a composite electrolyte membrane. The final assembled button battery uses lithium iron phosphate or NCM811 as the positive electrode, lithium metal as the negative electrode, and the modified composite membrane as the electrolyte. The method of the above embodiment forms a modified layer on the surface of the inorganic phase, which effectively improves the interface between the inorganic phase and the polymer inside the composite solid electrolyte, increases the transmission path of lithium ions, widens the electrochemical window of the electrolyte membrane, and improves the The electrochemical performance of solid-state batteries assembled from composite electrolytes provides a new idea for the research of composite solid-state electrolytes.

The technical features of the above-mentioned embodiments can be combined arbitrarily, and all possible combinations of the technical features of the above-mentioned embodiments are not described for concise description. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope of the description.

The above-mentioned embodiments only express several implementations of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the scope of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the appended claims.

Claims (10)

1. A method for improving the interface between an inorganic phase filler and a polymer in a composite solid electrolyte, comprising the steps of:

(1) Heating and standing a precursor solution containing a silane coupling agent in a water bath to obtain a uniform precursor solution;

(2) Dispersing an inorganic phase in the precursor solution obtained in the step (1), and stirring to obtain an inorganic phase filler dispersion liquid;

(3) Collecting the inorganic phase material in the inorganic phase filler dispersion liquid obtained in the step (2), washing with an ethanol solution, and centrifuging at least twice to obtain an inorganic phase material;

(4) Washing, centrifuging and drying the inorganic phase material to obtain inorganic phase particles, and collecting the inorganic phase particles in a centrifugal tube; the collected product inorganic phase particles are the modified inorganic phase filler;

(5) Mixing a polymer and lithium salt in a sample bottle A, adding anhydrous acetonitrile serving as a solvent, and stirring on a heating table at constant temperature until the solution is completely uniform;

(6) Mixing the inorganic phase filler modified in the step (4) with polyethylene glycol (PEG) in a sample bottle B, adding anhydrous acetonitrile serving as a solvent, and stirring on a heating table at constant temperature until the solution is completely uniform;

(7) Pouring the solution obtained in the sample bottle B in the step (6) into the sample bottle A in the step (5), and fully and uniformly stirring to obtain uniform slurry;

(8) Dripping the uniform slurry obtained in the step (7) on a mould, drying, fully removing the organic solvent, forming a dry film on the mould, and cutting into a wafer with a required size as a solid composite electrolyte film;

(9) And (3) preparing a positive electrode plate of the battery from the positive electrode material, assembling the button battery by using lithium metal as a negative electrode and the solid composite electrolyte membrane prepared in the step (8) as a diaphragm, and then testing the electrochemical performance of the assembled solid battery to obtain the solid battery with the interface between the inorganic phase filler and the polymer in the composite solid electrolyte improved.

2. The method for improving the interface of an inorganic phase filler with a polymer in a solid composite electrolyte according to claim 1, wherein in the step (1), the silane coupling agent employs at least one of methacryloxypropyltrimethoxysilane (KH 570), γ - (2, 3-glycidoxy) propyltrimethoxysilane (KH 560), 3-chloropropyltrimethoxysilane; the heating temperature is 50-80 ℃; the standing time is 1.0-3.0 h.

3. The method for improving the inorganic phase filler to polymer interface in the composite solid electrolyte according to claim 1, wherein in the step (2), the inorganic phase particle mass per treatment is 1.0 to 5.0g; stirring for different time each time, wherein the total stirring time is 3.0-12.0 h; the inorganic phase is at least one of garnet type, perovskite type, sulfide, sodium fast ion conductor and lithium fast ion conductor.

4. The method for improving the interface between the inorganic phase filler and the polymer in the composite solid electrolyte according to claim 1, wherein the drying in the step (4) is performed at 80 to 180 ℃ for 0.5 to 5.0 hours.

5. The method for improving the interface between the inorganic phase filler and the polymer in the composite solid electrolyte according to claim 1, wherein in the step (5), the polymer is at least one of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN); the lithium salt is bis (trifluoromethyl) sulfonyl imide Lithium (LiTFSI), bis (fluoro) sulfonyl imide lithium salt (LiFSI), and lithium perchlorate (LiClO) ₄ ) At least one of (a); the molar ratio of polymer to lithium salt is 15:1 to 5:1; the heating temperature is controlled to be 50-90 ℃, and the stirring time is 0.5-5.0 h.

6. The method for improving the interface between the inorganic phase filler and the polymer in the composite solid electrolyte according to claim 1, wherein in the step (6), the modified inorganic phase is added in an amount of 5 to 30wt% based on the sum of the polymer and the lithium salt; the mass ratio of polyethylene glycol (PEG) to polymer is 1:5 to 1:2; the heating temperature is controlled to be 60-80 ℃, and the stirring time is 1.0-3.0 h.

7. The method for improving the interface between the inorganic phase filler and the polymer in the composite solid electrolyte according to claim 1, wherein in the step (7), the stirring time is controlled to be 6.0 to 9.0 hours.

8. The method for improving the interface between the inorganic phase filler and the polymer in the composite solid electrolyte according to claim 1, wherein in the step (8), the mold material is at least one of Polytetrafluoroethylene (PTFE), release Paper (PET), and glass plate.

9. The method for improving the interface between the inorganic phase filler and the polymer in the composite solid electrolyte according to claim 1, wherein in the locking step (9), the positive electrode plate comprises a positive active material, a conductive agent and a binder, and the mass fractions of the positive active material, the conductive agent and the binder in the positive electrode plate are 70-85%, 10-20% and 5-15%, respectively; the conductive agent is at least one of acetylene black, super carbon black or carbon nano tubes; the binder is PVDF or PTFE; the positive active material is at least one of lithium iron phosphate (LFP) and NCM 811;

in the step (9), the upper limit of the voltage cut-off for electrochemical charging and discharging of the solid-state battery is 3.5 to 4.3V, and the lower limit thereof is 2.2 to 2.8V.

10. Use of a method according to claim 1 for improving the interface between an inorganic phase filler and a polymer in a composite solid electrolyte, characterized in that: the solid composite electrolyte membrane prepared by the method for improving the interface between the inorganic phase filler and the polymer in the composite solid electrolyte is used as a diaphragm to prepare the solid battery.

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