Polypyrrole coated solid electrolyte and preparation method thereof

Abstract

The invention provides a polypyrrole coated solid electrolyte and a preparation method thereof, the preparation method comprises a reactant preparation step and a polymerization reaction step, in the reactant preparation step, a pyrrole monomer and a solid electrolyte are respectively dissolved in an anhydrous organic solvent A, and a mixed reaction system is prepared. Adding a catalyst into the anhydrous organic solvent A, and uniformly mixing to obtain the catalytic system. In the polymerization reaction step, a catalytic system is dropwise added into a mixed reaction system, an oxidative polymerization reaction is initiated through an oxidizing agent under anhydrous and anaerobic conditions, pyrrole monomers are polymerized on the surfaces of solid electrolyte particles, a polypyrrole coating layer is formed, and the polypyrrole-coated solid electrolyte is prepared. The method has the advantages of simple preparation process, good controllability, no use of aqueous solution in the preparation process and the like. The polypyrrole coated solid electrolyte has the advantages that the interface performance is improved, the low-temperature resistance is improved, the overall performance of a battery is improved, and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a polypyrrole-coated solid electrolyte and a preparation method thereof. Background Art

[0002] With the growing global demand for high-energy-density, high-safety batteries, solid-state battery technology has garnered widespread attention. Solid-state lithium-ion batteries, which use solid electrolytes instead of traditional liquid or gel electrolytes, are expected to fundamentally address safety issues associated with liquid electrolytes, such as leakage, flammability, and explosion. They can also potentially accommodate higher-energy-density cathode and anode materials, thereby improving the battery's energy density and cycle life.

[0003] Among various solid electrolyte materials, inorganic solid electrolytes such as garnet type (LLZO), NASICON type (such as LATP-Li 1+x Al x Ti 2-x (PO4)3), sulfide type, etc. have attracted much attention due to their high bulk ionic conductivity. Among them, NASICON type phosphate solid electrolytes (such as LATP) have the advantages of stable structure, relatively easy synthesis, and wide electrochemical window, and are considered to be a promising solid electrolyte material. However, inorganic solid electrolytes still face some challenges in practical applications, especially in the construction of high-performance solid-state batteries: (1) Interface problems: There is usually a large interface impedance between inorganic solid electrolytes and electrode materials (especially positive high-voltage materials and negative metal lithium). It is difficult for hard inorganic particles to form a close and stable contact with the electrode active material particles, resulting in the obstruction of lithium ion transmission at the interface, affecting the battery's rate performance and cycle stability. (2) Brittleness: Inorganic solid electrolytes are usually brittle. During the battery charging and discharging process, due to volume changes or internal stress, they may cause cracking, destroying the ion transmission path. (3) Low temperature performance: Although some solid electrolytes have high ionic conductivity at room temperature, their ionic conductivity will drop significantly at lower temperatures, limiting the application of solid-state batteries in cold environments. (4) Preparation challenges: The preparation of pure inorganic solid electrolyte films or dense layers with high ionic conductivity and good mechanical properties usually requires complex processes such as high-temperature sintering. Summary of the Invention

[0004] In light of this, the present invention provides a polypyrrole-coated solid electrolyte to address the problems of poor interfacial contact between existing solid electrolytes and electrode materials, high interfacial impedance, and severe attenuation of ionic conductivity at low temperatures. The present invention also provides a method for preparing a polypyrrole-coated solid electrolyte. This method avoids the use of aqueous solutions throughout the entire preparation process, preventing moisture-sensitive solid electrolytes from experiencing performance degradation or introducing side reactions upon contact with water during the preparation process. It also addresses existing solid electrolyte preparation processes, including process engineering, the use of hazardous solvents, and difficulty achieving uniform coating.

[0005] In a first aspect, the present invention provides a method for preparing a polypyrrole-coated solid electrolyte, comprising the following steps, in parts by mass: Reactant preparation: 1 to 5 parts of pyrrole monomer, 100 parts of solid electrolyte, 2 to 10 parts of catalyst, and anhydrous organic solvent A are provided. The solid electrolyte and the pyrrole monomer are sequentially added to a portion of the anhydrous organic solvent A and mixed uniformly to obtain a mixed reaction system. The catalyst is then added to the remaining anhydrous organic solvent A and mixed uniformly to obtain a catalytic system. Polymerization reaction: Inert gas is introduced into the mixed reaction system, the temperature of the mixed reaction system is adjusted to below 20°C, and the catalyst system is added dropwise to the mixed reaction system while stirring the mixed reaction system. After the addition is completed, the stirring reaction is continued for more than 1 hour to obtain a crude product. The crude product is washed and dried to obtain a polypyrrole-coated solid electrolyte.

[0006] The preparation method of the polypyrrole coated solid electrolyte of the present invention includes two steps, namely, a reactant preparation step and a polymerization reaction step, in which pyrrole monomer and solid electrolyte are dissolved in anhydrous organic solvent A respectively to obtain a mixed reaction system. Catalyst is added to the anhydrous organic solvent A and mixed uniformly to obtain a catalytic system. In the polymerization reaction step, the catalytic system is added dropwise to the mixed reaction system, and under anhydrous and anaerobic conditions, an oxidative polymerization reaction is initiated by an oxidant, and pyrrole monomer is polymerized on the surface of solid electrolyte particles to form a polypyrrole coating layer to obtain a polypyrrole coated solid electrolyte. The preparation method of the polypyrrole coated solid electrolyte of the present invention has the advantages of simple preparation process, good controllability, and no aqueous solution in the preparation process, and is particularly suitable for coating a solid electrolyte that is sensitive to moisture, and avoids causing material performance degradation or introducing side reactions after contact with water. The core advantages of the preparation method of the polypyrrole-coated solid electrolyte of the present invention are: an anhydrous system, low temperature control and oxidant catalysis, which can achieve uniform and controllable growth of polypyrrole on the particle surface and avoid the formation of large amounts of agglomerates or free polymers.

[0007] Preferably, in the reactant preparation step, the solid electrolyte is at least one of LATP, LLZO, LZG, LOC, LLTO and LiPON, the catalyst is ferric chloride or ammonium persulfate, and the anhydrous organic solvent A is at least one of anhydrous acetonitrile, anhydrous ethanol, anhydrous methanol and anhydrous dimethyl sulfoxide. Inorganic solid electrolytes, such as NASICON-type phosphate solid electrolytes, have advantages such as stable structure, relatively easy synthesis, and a wide electrochemical window, but such solid electrolytes have poor interface contact with electrode materials and high interface impedance, which restricts the power performance and cycle life of the battery. By coating polypyrrole on the surface of such solid electrolytes using the preparation method of the polypyrrole-coated solid electrolyte of the present invention, the interface impedance between the solid electrolyte and the electrode material can be effectively reduced, the ion transfer efficiency can be improved, the ionic conductivity of the solid electrolyte at low temperatures can be improved, and the requirements of low-temperature applications can be met.

[0008] More preferably, the solid electrolyte is Li 1+x Al x Ti 2-x (PO4)3, with an X value of 0.1 to 0.5; the catalyst is ferric chloride, and the anhydrous organic solvent A is anhydrous acetonitrile. Anhydrous acetonitrile has good solubility or dispersibility for pyrrole, ferric chloride, and the solid electrolyte lithium aluminum titanium phosphate (LATP). Through this in-situ polymerization coating method under anhydrous conditions, a uniform and dense polypyrrole coating with controllable thickness can be obtained on the surface of the solid electrolyte particles.

[0009] Preferably, in the reactant preparation step, the pyrrole monomer and the solid electrolyte are first dissolved separately in an anhydrous organic solvent A to produce a pyrrole monomer solution and a solid electrolyte solution, which are then uniformly mixed to form a mixed reaction system. The mass fraction of the pyrrole monomer solution is 0.1% to 2.5%, and the mass fraction of the solid electrolyte solution is 10% to 67%. Dissolving the pyrrole monomer and the solid electrolyte separately in an anhydrous organic solvent A to produce a pyrrole monomer solution and a solid electrolyte solution, and then mixing the pyrrole monomer solution and the solid electrolyte solution, effectively promotes uniform mixing and contact between the pyrrole monomer and the solid electrolyte, thereby improving the uniformity of the polypyrrole coating.

[0010] More preferably, the volume of anhydrous organic solvent A is 500 ml; the pyrrole monomer is dissolved in 200 ml of anhydrous organic solvent A to prepare a pyrrole monomer solution; the solid electrolyte is dissolved in 200 ml of anhydrous organic solvent A to prepare a solid electrolyte solution; and the catalyst is dissolved in 100 ml of anhydrous organic solvent A to prepare a catalytic system. Selecting appropriate concentrations of the pyrrole monomer solution, solid electrolyte solution, and catalytic system can effectively promote uniform mixing and contact between the pyrrole monomer and the solid electrolyte, thereby improving the uniformity of the polypyrrole coating.

[0011] Preferably, in the reactant preparation step, the pyrrole monomer is first dissolved in an anhydrous organic solvent A to obtain a pyrrole monomer solution, and then the solid electrolyte is added to the pyrrole monomer solution, and mixed to obtain a mixed reaction system. The solid electrolyte is directly added to the pyrrole monomer solution for dissolution and mixing, thereby reducing the step of mixing the reaction raw materials. In other embodiments, the solid electrolyte can also be first dissolved in an anhydrous organic solvent A to obtain a solid electrolyte solution, and then the pyrrole monomer is added to the solid electrolyte solution, and mixed to obtain a mixed reaction system.

[0012] Preferably, in the polymerization reaction step, an inert gas is first introduced into the mixed reaction system, and then the temperature of the mixed reaction system is adjusted to below 10°C; the inert gas is nitrogen, argon or helium, and the time for introducing the inert gas is at least 10 minutes. In other embodiments, the temperature of the mixed reaction system can be adjusted to below 10°C first, and then an inert gas is introduced into the mixed reaction system to ensure that the reaction system discharges oxygen from the system before adding the catalyst for oxidative polymerization and ensures that the system temperature is below 10°C. Oxygen-free and low-temperature conditions help control the polymerization rate of pyrrole, promote uniform nucleation and growth of polypyrrole on the surface of solid electrolyte particles, and avoid the generation of a large amount of free polypyrrole precipitation.

[0013] Preferably, during the polymerization reaction step, the catalyst system is added dropwise at a rate of 0.5-2 ml / min, and the reaction is continued for 4 hours after the addition is completed. Under conditions of continuous stirring and temperature control (e.g., an ice bath), the oxidant solution is slowly added dropwise to the reaction system containing the solid electrolyte particles and pyrrole monomer to control the polymerization rate. After the addition is completed, the reaction is stirred for a predetermined period of time until the pyrrole monomer is fully polymerized.

[0014] Preferably, in the polymerization step, the crude product is allowed to stand, and after particles are precipitated, the supernatant is removed. The precipitated particles are washed with an anhydrous organic solvent B and collected by centrifugation. The washing and centrifugation steps are repeated 1 to 3 times, and the precipitate is then transferred to a vacuum drying oven for drying to obtain a polypyrrole-coated solid electrolyte. The anhydrous organic solvent B is at least one of anhydrous acetonitrile, anhydrous ethanol, anhydrous methanol, and anhydrous dimethyl sulfoxide. Washing and centrifuging the precipitate can remove unreacted monomers, oxidants, byproducts, and free polypyrrole. The washed solid product is then dried under vacuum conditions to completely remove the solvent.

[0015] In a second aspect, the present invention further provides a polypyrrole-coated solid electrolyte, which is prepared by the preparation method of the polypyrrole-coated solid electrolyte described in the first aspect.

[0016] The polypyrrole-coated solid electrolyte of the present invention has the following advantages: (1) Improved interface performance. The polypyrrole coating significantly improves the interface contact between the inorganic solid electrolyte particles and the electrode material, reduces the interface impedance, and is beneficial to improving the power performance of the battery. (2) Improved low-temperature resistance. The polypyrrole coating may help maintain the ion transmission efficiency at low temperatures, so that the battery using the modified material can still show excellent charge and discharge performance in a low-temperature environment. The battery using the polypyrrole-coated solid electrolyte of the present application has a discharge energy efficiency of up to 93.45% at 5°C, which is much higher than the national standard requirement of 80%. Even after exposure to -30°C, the room temperature performance recovery rate is very high. (3) Improved overall battery performance. The battery using the material system of the present invention not only has outstanding low-temperature performance, but also performs well in basic capacity, internal resistance, rate discharge, high-temperature adaptability, storage performance, cycle life and various safety performance (over-discharge, overcharge, drop, puncture, extrusion, short circuit) and meets relevant standards, which indirectly proves the contribution of the modified material to the overall performance of the battery.

[0017] Advantages of the present invention will be partially set forth in the following description, and some will be obvious from the description, or may be learned through practice of the embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To more clearly illustrate the content of the present invention, it is described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Figure 1 Characteristic X-ray energy spectrum of the polypyrrole-coated solid electrolyte particles prepared in Example 1 ( Figure 1 The scale bars in all images are 2 μm); Figure 2 is the powder X-ray diffraction spectrum; Figure 3 is the infrared spectrum; Figure 4 is the Raman spectrum; Figure 5 These are the charge and discharge curves at 45°C (the curve on the upper right side is the charge curve of the No. 12 battery, and the curve on the upper right side is the charge curve of the No. 11 battery; the curve on the lower right side is the discharge curve of the No. 12 battery, and the curve on the lower right side is the discharge curve of the No. 11 battery). DETAILED DESCRIPTION

[0020] The following is a preferred embodiment of the present invention. It should be noted that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

[0021] The following describes in detail the preparation method of the polypyrrole-coated solid electrolyte and the prepared polypyrrole-coated solid electrolyte through specific examples. Example 1

[0022] A method for preparing a polypyrrole-coated solid electrolyte comprises the following steps.

[0023] Reactant preparation steps: provide 0.75 g pyrrole monomer, 50 g lithium aluminum titanium phosphate powder (Li 1+x Al x Ti 2-x (PO4)3, X equals 0.1), 2.42 g of anhydrous ferric chloride, and 500 ml of anhydrous acetonitrile (393 g). First, add pyrrole monomer to 200 ml of anhydrous acetonitrile and dissolve under stirring at 100 rpm to obtain a pyrrole monomer solution. Then, add lithium aluminum titanium phosphate powder to 200 ml of anhydrous acetonitrile and dissolve under stirring at 100 rpm to obtain a solid electrolyte solution. Finally, add ferric chloride to 100 ml of anhydrous acetonitrile and dissolve under stirring at 100 rpm to obtain a catalytic system. After mixing the pyrrole monomer solution and solid electrolyte solution, pour them into a four-necked jacketed reaction flask to obtain a mixed reaction system.

[0024] Polymerization reaction steps: Turn on the stirring mechanism of the four-necked jacketed reaction flask at 100 rpm and connect it to a cold water circulation system to keep the temperature of the mixed reaction system below 20°C. Continuously flow dry nitrogen into the four-necked jacketed reaction flask for 10 minutes to remove oxygen and moisture. Under continuous stirring and cooling, slowly add the catalyst system dropwise to the four-necked jacketed reaction flask at a rate of 1 ml / min. After the addition is complete, continue stirring under cold water circulation for 4 hours. After the reaction is complete, stop stirring and allow the solid to settle. Carefully decant the supernatant. Transfer the precipitate to a centrifuge tube, add an appropriate amount of anhydrous acetonitrile, centrifuge, and then decant the supernatant. Repeat this washing process twice. The washed solid product is dried in a vacuum oven at 65°C to obtain polypyrrole-coated solid electrolyte particles. Example 2

[0025] A method for preparing a polypyrrole-coated solid electrolyte comprises the following steps.

[0026] Reactant preparation steps: provide 5 g pyrrole monomer, 100 g lithium aluminum titanium phosphate powder (Li 1+x Al x Ti 2-x(PO4)3, X equals 0.5), 10 g of anhydrous ferric chloride, and 500 ml of anhydrous acetonitrile (393 g). First, add pyrrole monomer to 400 ml of anhydrous acetonitrile and dissolve under stirring at 150 rpm to obtain a pyrrole monomer solution. Then, add lithium aluminum titanium phosphate powder to a four-necked jacketed reaction flask. Finally, pour the pyrrole monomer solution into the four-necked jacketed reaction flask containing solid electrolyte particles and stir at 150 rpm to obtain a mixed reaction system. Finally, add ferric chloride to 100 ml of anhydrous acetonitrile and dissolve under stirring at 150 rpm to obtain the catalyst system.

[0027] Polymerization reaction steps: Turn on the stirring mechanism of the four-necked jacketed reaction flask at 150 rpm and place the four-necked jacketed reaction flask in an ice-water bath to keep the temperature of the mixed reaction system below 10°C. Continuously flow dry helium into the four-necked jacketed reaction flask for 10 minutes to remove oxygen and moisture. While stirring and cooling in an ice bath, slowly add the catalyst system dropwise to the four-necked jacketed reaction flask at a rate of 1 ml / min. After the addition is complete, continue stirring in the ice bath for 6 hours. After the reaction is complete, stop stirring and allow the solid to settle. Carefully decant the supernatant. Transfer the precipitate to a centrifuge tube, add an appropriate amount of anhydrous acetonitrile, centrifuge, and then decant the supernatant. Repeat this washing process twice. The washed solid product is dried in a vacuum oven at 65°C to obtain polypyrrole-coated solid electrolyte particles. Example 3

[0028] A method for preparing a polypyrrole-coated solid electrolyte comprises the following steps.

[0029] Reactant preparation steps: provide 2.5 g pyrrole monomer, 100 g lithium aluminum titanium phosphate powder (Li 1+x Al x Ti 2-x (PO4)3, where x is 0.2), 5 g of ammonium persulfate, and 500 ml of anhydrous dimethyl sulfoxide. First, add lithium aluminum titanium phosphate powder to 400 ml of anhydrous dimethyl sulfoxide and dissolve under stirring at 150 rpm to obtain a solid electrolyte solution. Then, add pyrrole monomer to a four-necked jacketed reaction flask. Finally, pour the solid electrolyte solution into the four-necked jacketed reaction flask containing pyrrole monomer and stir at 150 rpm to obtain a mixed reaction system. Finally, add ammonium persulfate to 100 ml of anhydrous dimethyl sulfoxide and dissolve under stirring at 150 rpm to obtain a catalytic system.

[0030] Polymerization reaction steps: Turn on the stirring mechanism of the four-necked jacketed reaction flask at 150 rpm and place the four-necked jacketed reaction flask in an ice-water bath to keep the temperature of the mixed reaction system below 10°C. Continuously flow dry argon gas into the four-necked jacketed reaction flask for 10 minutes to remove oxygen and moisture. While stirring and cooling in an ice bath, slowly add the catalyst system dropwise to the four-necked jacketed reaction flask at a rate of 0.5 ml / min. After the addition is complete, continue stirring in the ice bath for 4 hours. After the reaction is complete, stop stirring and allow the solid to settle. Carefully decant the supernatant. Transfer the precipitate to a centrifuge tube, add an appropriate amount of anhydrous acetonitrile, centrifuge, and then decant the supernatant. Repeat this washing process twice. The washed solid product is dried in a vacuum oven at 60°C to obtain polypyrrole-coated solid electrolyte particles. Example 4

[0031] A method for preparing a polypyrrole-coated solid electrolyte comprises the following steps.

[0032] Reactant preparation steps: Prepare 1 g of pyrrole monomer, 50 g of perovskite-type solid electrolyte (LLTO), 4 g of anhydrous ferric chloride, and 500 ml of anhydrous methanol. First, add the pyrrole monomer to 200 ml of anhydrous methanol and dissolve it at 150 rpm to obtain a pyrrole monomer solution. Then, add the perovskite-type solid electrolyte to 200 ml of anhydrous methanol and dissolve it at 150 rpm to obtain a solid electrolyte solution. Finally, add ferric chloride to 100 ml of anhydrous methanol and dissolve it at 150 rpm to obtain a catalytic system. After mixing the pyrrole monomer solution and solid electrolyte solution, pour them into a four-necked jacketed reaction flask to obtain a mixed reaction system.

[0033] Polymerization reaction steps: Turn on the stirring mechanism of the four-necked jacketed reaction flask at 150 rpm and connect a cold water circulation system to keep the temperature of the mixed reaction system below 10°C. Continuously flow dry argon gas into the four-necked jacketed reaction flask for 20 minutes to exclude oxygen and moisture. Under continuous stirring and cooling, slowly add the catalyst system dropwise to the four-necked jacketed reaction flask at a rate of 2 ml / min. After the addition is complete, continue stirring under cold water circulation for 8 hours. After the reaction is complete, stop stirring and allow the solid to settle. Carefully decant the supernatant. Transfer the precipitate to a centrifuge tube, add an appropriate amount of anhydrous ethanol, centrifuge, and then decant the supernatant. Repeat this washing process once. Dry the washed solid product in a vacuum oven at 55°C to obtain polypyrrole-coated solid electrolyte particles. Example 5

[0034] A method for preparing a polypyrrole-coated solid electrolyte comprises the following steps.

[0035] Reactant preparation steps: Prepare 2.5 g of pyrrole monomer, 50 g of garnet-type solid electrolyte (LLZO), 2 g of anhydrous ammonium persulfate, and 500 ml of anhydrous ethanol. First, add the pyrrole monomer to 400 ml of anhydrous ethanol and dissolve under stirring to obtain a pyrrole monomer solution. Then, add the garnet-type solid electrolyte to a four-necked jacketed reaction flask. Finally, pour the pyrrole monomer solution into the four-necked jacketed reaction flask containing the solid electrolyte particles and stir at 50 rpm to obtain a mixed reaction system. Finally, add the ammonium persulfate to 100 ml of anhydrous ethanol and dissolve under stirring to obtain the prepared catalytic system.

[0036] Polymerization reaction steps: Turn on the stirring mechanism of the four-necked jacketed reaction flask at 50 rpm and place the four-necked jacketed reaction flask in an ice-water bath to keep the temperature of the mixed reaction system below 10°C. Continuously flow dry nitrogen gas into the four-necked jacketed reaction flask for 10 minutes to remove oxygen and moisture. While stirring and cooling in an ice bath, slowly add the catalyst system dropwise to the four-necked jacketed reaction flask at a rate of 0.5 ml / min. After the addition is complete, continue stirring in the ice bath for 6 hours. After the reaction is complete, stop stirring and allow the solid to settle. Carefully decant the supernatant. Transfer the precipitate to a centrifuge tube, add an appropriate amount of anhydrous dimethyl sulfoxide, centrifuge, and then decant the supernatant. Repeat this washing process twice. The washed solid product is dried in a vacuum oven at 65°C to obtain polypyrrole-coated solid electrolyte particles. Example 6

[0037] A method for preparing a solid electrolyte modified electrode, comprising the following steps: The polypyrrole-coated solid electrolyte particles prepared in Example 1 were first dispersed in 200 ml of N-methylpyrrolidone solution and ball-milled for 12 hours to obtain a nanosized solid electrolyte solution. The active material, conductive agent, and binder were then added to the N-methylpyrrolidone solution in a ratio of 95:2:3 and stirred to mix thoroughly. Subsequently, 2% of the total weight of the solid electrolyte solution was added and stirred for 24 hours until a uniform mixture with no obvious particles formed was obtained. Finally, the mixed slurry was coated on aluminum foil and dried at 100 degrees Celsius for 12 hours to obtain a solid electrolyte-modified electrode.

[0038] Effect Example 1: Energy Spectrum Detection The polypyrrole-coated solid electrolyte particles prepared in Example 1 were subjected to energy spectrum detection. Figure 1As shown, a thin film is present on the surface of the lithium aluminum titanium phosphate after polypyrrole coating. Energy spectrum analysis reveals that in addition to oxygen, aluminum, phosphorus, and titanium elements uniformly distributed throughout the entire detection range, carbon and nitrogen elements are also detected, suggesting that the polypyrrole is uniformly coated on the lithium aluminum titanium phosphate surface. The energy spectrum analysis results indicate that the preparation method of the polypyrrole-coated solid electrolyte successfully produces a polypyrrole-coated solid electrolyte.

[0039] Effect Example 2: Powder X-ray diffraction detection Lithium aluminum titanium phosphate powder (Li 1+x Al x Ti 2-x (PO4)3, X is equal to 0.1, that is, uncoated lithium aluminum titanium phosphate), polypyrrole and the polypyrrole-coated solid electrolyte particles prepared in Example 1 were characterized by powder X-ray diffraction. Figure 2 As shown, lithium aluminum titanium phosphate without polypyrrole coating shows a series of clear and sharp diffraction peaks. These sharp peaks are typical characteristics of crystalline materials, which indicates that lithium aluminum titanium phosphate is a material with good crystallinity. Polypyrrole shows a broad and diffuse peak, and the overall intensity is relatively low. This broad peak is a typical characteristic of amorphous or semi-crystalline materials, indicating that polypyrrole presents an amorphous or low-crystallinity structure here. Combining the characteristics of the first two materials, the spectrum of the polypyrrole-coated solid electrolyte particles prepared in Example 1 shows consistent sharp diffraction peak positions, which indicates that in the composite material, lithium aluminum titanium phosphate still exists in its original crystal structure. At the same time, since polypyrrole exists in its amorphous or semi-crystalline state, the diffraction peak intensity of the crystalline lithium aluminum titanium phosphate is reduced, which confirms that polypyrrole successfully coats lithium aluminum titanium phosphate and its crystal structure is not seriously damaged.

[0040] Effect Example 3: Infrared Detection Lithium aluminum titanium phosphate powder (Li 1+x Al x Ti 2-x (PO4)3, X is equal to 0.1, that is, uncoated lithium aluminum titanium phosphate), polypyrrole and the polypyrrole-coated solid electrolyte particles prepared in Example 1 were subjected to infrared detection. Figure 3 As shown, for uncoated lithium aluminum titanium phosphate, the phosphate groups (PO4 3- ) may have a characteristic peak at 1000-1100 cm -1 The main absorption peak of polypyrrole as a conductive polymer may be around 1550 cm -1 (C=C stretching vibration), 1450 cm -1 (CN stretching vibration), and 1300 cm -1 and 1200 cm -1The CH in-plane bending vibration near the polypyrrole is observed. In the spectrum of the polypyrrole-coated lithium titanium aluminum phosphate, characteristic peaks of lithium titanium aluminum phosphate and polypyrrole appear simultaneously. The results show that Example 1 successfully prepared polypyrrole and successfully coated lithium titanium aluminum phosphate.

[0041] Effect Example 4: Raman spectroscopy detection Raman spectroscopy was performed on the polypyrrole-coated solid electrolyte particles prepared in Example 1. Figure 4 As shown in Figure 2, the Raman spectrum successfully shows the characteristic vibration modes of the two main components in the lithium aluminum titanium phosphate-polypyrrole composite material. On the one hand, the characteristic peaks of lithium aluminum titanium phosphate (symmetric PO4 3- , PO stretching vibration) indicates that the phosphate component was successfully introduced and retained in the composite material. Furthermore, the characteristic peaks of polypyrrole (CN, D peak, and G peak) were also present, indicating that the polypyrrole component was also present in the composite material. These results demonstrate that Example 1 successfully prepared a polypyrrole-coated solid electrolyte.

[0042] Effect Example 5: Charge and Discharge Performance Test Lithium aluminum titanium phosphate powder (Li 1+x Al x Ti 2-x (PO4)3, X is equal to 0.1, that is, uncoated lithium aluminum titanium phosphate) and the polypyrrole-coated solid electrolyte particles prepared in Example 1 assembled batteries, and the battery charge and discharge performance tests were carried out. The battery using lithium aluminum titanium phosphate powder corresponds to No. 12, and the battery using the polypyrrole-coated solid electrolyte particles prepared in Example 1 corresponds to No. 11. The results are as follows Figure 5 As shown, the discharge energy of battery No. 11 at 45°C reaches 275.14 Wh. In comparison, the discharge energy of battery No. 12 at 45°C reaches 268.39 Wh, indicating that the polypyrrole-coated solid electrolyte prepared in Example 1 can improve the overall energy density of the battery.

[0043] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing a polypyrrole-coated solid electrolyte, characterized in that: The following steps are included by mass: Reactant preparation: providing 1 to 5 parts of pyrrole monomer, 100 parts of solid electrolyte, 2 to 10 parts of catalyst, and anhydrous organic solvent A; sequentially adding the solid electrolyte and the pyrrole monomer to a portion of the anhydrous organic solvent A and mixing uniformly to obtain a mixed reaction system; then adding the catalyst to the remaining anhydrous organic solvent A and mixing uniformly to obtain a catalytic system; Polymerization reaction: Inert gas is introduced into the mixed reaction system, the temperature of the mixed reaction system is adjusted to below 20°C, and the catalytic system is added dropwise to the mixed reaction system while stirring the mixed reaction system. After the addition is completed, the stirring reaction is continued for more than 1 hour to obtain a crude product. The crude product is washed and dried to obtain a polypyrrole-coated solid electrolyte.

2. The method for preparing a polypyrrole-coated solid electrolyte according to claim 1, wherein: In the reactant preparation step, the solid electrolyte is at least one of LATP, LLZO, LZG, LOC, LLTO and LiPON, the catalyst is ferric chloride or ammonium persulfate, and the anhydrous organic solvent A is at least one of anhydrous acetonitrile, anhydrous ethanol, anhydrous methanol and anhydrous dimethyl sulfoxide.

3. The method for preparing a polypyrrole-coated solid electrolyte according to claim 2, wherein: The solid electrolyte is Li 1+x Al x Ti 2-x (PO4)3, the X value is 0.1-0.5; the catalyst is ferric chloride, and the anhydrous organic solvent A is anhydrous acetonitrile.

4. The method for preparing a polypyrrole-coated solid electrolyte according to claim 1, wherein: In the reactant preparation step, the pyrrole monomer and the solid electrolyte are first dissolved in an anhydrous organic solvent A to prepare a pyrrole monomer solution and a solid electrolyte solution, and then the pyrrole monomer solution and the solid electrolyte solution are mixed uniformly to obtain a mixed reaction system; The mass fraction of the pyrrole monomer solution is 0.1% to 2.5%, and the mass fraction of the solid electrolyte solution is 10% to 67%.

5. The method for preparing a polypyrrole-coated solid electrolyte according to claim 4, wherein: The volume of the anhydrous organic solvent A is 500 ml; The pyrrole monomer was dissolved in 200 ml of anhydrous organic solvent A to prepare a pyrrole monomer solution; the solid electrolyte was dissolved in 200 ml of anhydrous organic solvent A to prepare a solid electrolyte solution; and the catalyst was dissolved in 100 ml of anhydrous organic solvent A to prepare a catalytic system.

6. The method for preparing a polypyrrole-coated solid electrolyte according to claim 1, wherein: In the reactant preparation step, the pyrrole monomer is first dissolved in an anhydrous organic solvent A to prepare a pyrrole monomer solution, and then the solid electrolyte is added to the pyrrole monomer solution and mixed evenly to obtain a mixed reaction system.

7. The method for preparing a polypyrrole-coated solid electrolyte according to claim 1, wherein: In the polymerization step, an inert gas is first introduced into the mixed reaction system, and then the temperature of the mixed reaction system is adjusted to below 10° C.; The inert gas is nitrogen, argon or helium, and the time for passing the inert gas is at least 10 minutes.

8. The method for preparing a polypyrrole-coated solid electrolyte according to claim 1, wherein: In the polymerization reaction step, the rate of adding the catalyst system dropwise is 0.5-2 ml / min, and the reaction is continued for 4 hours after the addition is completed.

9. The method for preparing a polypyrrole-coated solid electrolyte according to claim 1, wherein: In the polymerization reaction step, the crude product is allowed to stand, and after particles are precipitated, the supernatant is removed, the particle precipitate is washed with an anhydrous organic solvent B, and the precipitate is collected by centrifugation, and the washing and centrifugation steps are repeated 1 to 3 times, and the precipitate is transferred to a vacuum drying oven for drying to obtain a polypyrrole-coated solid electrolyte; The anhydrous organic solvent B is at least one of anhydrous acetonitrile, anhydrous ethanol, anhydrous methanol and anhydrous dimethyl sulfoxide.

10. A polypyrrole-coated solid electrolyte, characterized in that: The polypyrrole-coated solid electrolyte is prepared by the preparation method of the polypyrrole-coated solid electrolyte according to any one of claims 1 to 9.

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