A polypyrrole-coated solid-state electrolyte and a preparation method thereof

Abstract

The application provides a polypyrrole-coated solid electrolyte and a preparation method thereof, wherein the preparation method comprises a reactant preparation step and a polymerization step; in the reactant preparation step, a pyrrole monomer and a solid electrolyte are respectively dissolved into anhydrous organic solvent A to prepare a mixed reaction system; a catalyst is added into the anhydrous organic solvent A and uniformly mixed to obtain a catalytic system; in the polymerization step, the catalytic system is added dropwise into the mixed reaction system, and an oxidizing agent is used to initiate an oxidative polymerization reaction under anhydrous and anaerobic conditions; the pyrrole monomer is polymerized on the surface of the solid electrolyte particles to form a polypyrrole coating layer, and the polypyrrole-coated solid electrolyte is prepared. The method has the advantages of simple preparation process, good controllability and the like, and water solution is not used in the preparation process. The polypyrrole-coated solid electrolyte has the advantages of improved interface performance, improved low-temperature resistance and improved overall performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a polypyrrole-coated solid electrolyte and its preparation method. Background Technology

[0002] With the increasing global demand for high-energy-density and high-safety batteries, solid-state battery technology has attracted widespread attention. Solid-state lithium-ion batteries use solid electrolytes to replace traditional liquid or gel electrolytes, which is expected to fundamentally solve the safety problems of liquid electrolytes, such as leakage, flammability, and explosion. They may also be able to be matched with positive and negative electrode materials with higher energy density, thereby improving the energy density and cycle life of the battery.

[0003] Among various solid electrolyte materials, inorganic solid electrolytes such as garnet-type (LLZO) and NASICON-type (such as LATP-Li) are important. 1+x Al x Ti 2-x (PO4)3), sulfide-type and other types have attracted much attention due to their high bulk ionic conductivity. Among them, NASICON-type phosphate solid electrolytes (such as LATP) have advantages such as structural stability, 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 batteries: (1) Interface problem: There is usually a large interfacial impedance between inorganic solid electrolytes and electrode materials (especially high-voltage positive electrode materials and negative electrode metallic lithium). Hard inorganic particles are difficult to form a tight and stable contact with electrode active material particles, which leads to the obstruction of lithium ion transport at the interface, affecting the rate performance and cycle stability of the battery. (2) Brittleness: Inorganic solid electrolytes are usually brittle. During the charging and discharging process of the battery, volume changes or internal stress may cause cracking, which will destroy the ion transport pathway. (3) Low temperature performance: Although some solid electrolytes have high ionic conductivity at room temperature, their ionic conductivity will decrease significantly at low temperatures, which limits the application of solid 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 view of this, the present invention provides a polypyrrole-coated solid electrolyte to solve 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 provides a method for preparing the polypyrrole-coated solid electrolyte, which does not use aqueous solutions throughout the entire preparation process. This avoids the degradation of material performance or the introduction of side reactions when the moisture-sensitive solid electrolyte comes into contact with water during preparation. It also solves the problems of existing solid electrolyte preparation processes, such as process limitations, use of harmful solvents, and difficulty in 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 by weight: Reactant preparation: Provide 1-5 parts of pyrrole monomer, 100 parts of solid electrolyte, 2-10 parts of catalyst and anhydrous organic solvent A. Add the solid electrolyte and the pyrrole monomer to a portion of the anhydrous organic solvent A and mix evenly to obtain a mixed reaction system. Then add the catalyst to the remaining anhydrous organic solvent A and mix evenly to obtain a catalytic system. Polymerization reaction: Inert gas is introduced into the mixed reaction system, and the temperature of the mixed reaction system is adjusted to below 20°C. While stirring the mixed reaction system, the catalyst system is added dropwise to the mixed reaction system. After the addition is completed, the stirring reaction continues 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 this invention includes two steps: a reactant preparation step and a polymerization reaction step. In the reactant preparation step, pyrrole monomers and solid electrolytes are dissolved in anhydrous organic solvent A to obtain a mixed reaction system. A catalyst is added to anhydrous organic solvent A and mixed evenly to obtain a catalytic system. In the polymerization reaction step, the catalytic system is added dropwise to the mixed reaction system. Under anhydrous and oxygen-free conditions, an oxidative polymerization reaction is initiated by an oxidant, and the pyrrole monomers polymerize on the surface of the solid electrolyte particles to form a polypyrrole coating layer, thus obtaining the polypyrrole-coated solid electrolyte. The preparation method of the polypyrrole-coated solid electrolyte of this invention has the advantages of simple preparation process, good controllability, and no use of aqueous solution in the preparation process. It is particularly suitable for coating solid electrolytes that are sensitive to moisture, avoiding the degradation of material performance or the introduction of side reactions after contact with water. The core advantage of the preparation method of polypyrrole-coated solid electrolyte of the present invention lies in the fact that the anhydrous system, low temperature control and oxidant catalysis can achieve uniform and controllable growth of polypyrrole on the particle surface, avoiding the formation of a large number of agglomerates or free polymers.

[0007] Preferably, in the reactant preparation step, the solid electrolyte is at least one selected from 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 selected from anhydrous acetonitrile, anhydrous ethanol, anhydrous methanol, and anhydrous dimethyl sulfoxide. Inorganic solid electrolytes, such as NASICON-type phosphate solid electrolytes, have advantages such as structural stability, relatively easy synthesis, and a wide electrochemical window. However, these solid electrolytes suffer from poor interfacial contact with electrode materials and high interfacial impedance, which limits the power performance and cycle life of the battery. The polypyrrole-coated solid electrolyte preparation method of this invention coats the surface of such solid electrolytes with polypyrrole, effectively reducing the interfacial impedance between the solid electrolyte and electrode materials, improving ion transport efficiency, and enhancing the ionic conductivity of the solid electrolyte at low temperatures, thus meeting the requirements of low-temperature applications.

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

[0009] Preferably, in the reactant preparation step, the pyrrole monomer and the solid electrolyte are first dissolved separately in anhydrous organic solvent A to obtain a pyrrole monomer solution and a solid electrolyte solution, respectively. 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%–2.5%, and the mass fraction of the solid electrolyte solution is 10%–67%. First, dissolving the pyrrole monomer and the solid electrolyte separately in anhydrous organic solvent A to obtain the pyrrole monomer solution and the solid electrolyte solution, and then mixing the pyrrole monomer solution and the solid electrolyte solution, can effectively promote the uniform mixing and contact of the pyrrole monomer and the solid electrolyte, improving the uniformity of the polypyrrole coating layer.

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

[0011] Preferably, in the reactant preparation step, the pyrrole monomer is first dissolved in anhydrous organic solvent A to obtain 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. Directly adding the solid electrolyte to the pyrrole monomer solution for dissolution and mixing reduces the steps involved in mixing the reactants. In other embodiments, the solid electrolyte may also be first dissolved in anhydrous organic solvent A to obtain a solid electrolyte solution, and then the pyrrole monomer may be added to the solid electrolyte solution and mixed evenly 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 inert gas is introduced for at least 10 minutes. In other embodiments, the temperature of the mixed reaction system can also be adjusted to below 10°C first, and then an inert gas is introduced into the mixed reaction system to ensure that oxygen in the system is removed before the catalyst is added for oxidative polymerization and to ensure that the system temperature is below 10°C. Anaerobic and low-temperature conditions help control the polymerization rate of pyrrole, promote the uniform nucleation and growth of polypyrrole on the surface of solid electrolyte particles, and avoid the formation of a large amount of free polypyrrole precipitate.

[0013] Preferably, in the polymerization reaction step, the rate of adding the catalyst system is 0.5–2 ml / min, and the reaction continues for 4 hours after the addition is completed. Under continuous stirring and temperature control (e.g., ice bath), the oxidant solution is slowly added dropwise to the reaction system containing solid electrolyte particles and pyrrole monomers to control the polymerization rate. After the addition is completed, the reaction is stirred continuously for a certain period of time until the pyrrole monomers are fully polymerized.

[0014] Preferably, in the polymerization reaction step, the crude product is allowed to stand until the particles precipitate, then the supernatant is removed. The precipitate is washed with anhydrous organic solvent B, and the precipitate is collected by centrifugation. This washing and centrifugation process is repeated 1-3 times. 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 centrifugation remove unreacted monomers, oxidants, byproducts, and free polypyrrole. The washed solid product is dried under vacuum to completely remove the solvent.

[0015] Secondly, the present invention also provides a polypyrrole-coated solid electrolyte, which is prepared by the method for preparing polypyrrole-coated solid electrolyte described in the first aspect.

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

[0017] The advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of the embodiments thereof. Attached Figure Description

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

[0019] Figure 1 The characteristic X-ray energy spectrum of the polypyrrole-coated solid electrolyte particles prepared in Example 1 ( Figure 1 (The scale bar for all images in this document is 2 micrometers). Figure 2 Powder X-ray diffraction pattern; Figure 3 This is an infrared spectrum; Figure 4 Raman spectrum; Figure 5 The curves are the charge and discharge curves at 45℃ (the curve on the upper right left is the charging curve of battery 12, and the curve on the upper right right is the charging curve of battery 11; the curve on the lower right left is the discharging curve of battery 12, and the curve on the lower right right is the discharging curve of battery 11). Detailed Implementation

[0020] The following describes preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

[0021] The following detailed embodiments illustrate the preparation method of the polypyrrole-coated solid electrolyte of this application and the obtained polypyrrole-coated solid electrolyte. Example 1

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

[0023] Reactant preparation steps: Provide 0.75 g of pyrrole monomer and 50 g of 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, the pyrrole monomer was added to 200 ml of anhydrous acetonitrile and dissolved under stirring at 100 r / min to obtain a pyrrole monomer solution. Then, lithium aluminum titanium phosphate powder was added to 200 ml of anhydrous acetonitrile and dissolved under stirring at 100 r / min to obtain a solid electrolyte solution. Finally, ferric chloride was added to 100 ml of anhydrous acetonitrile and dissolved under stirring at 100 r / min to obtain the prepared catalytic system. The pyrrole monomer solution and the solid electrolyte solution were mixed thoroughly and poured into a four-necked jacketed reaction flask to obtain a mixed reaction system.

[0024] Polymerization reaction steps: Turn on the stirrer of the four-necked jacketed reaction flask at 100 r / min, and connect the cooling water circulation device to keep the temperature of the mixed reaction system in the four-necked jacketed reaction flask below 20℃. Continuously purge dry nitrogen gas 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 for 4 hours under cooling water circulation. After the reaction is complete, stop stirring and wait for the solid to precipitate. Carefully decant to remove the supernatant. Transfer the precipitate to a centrifuge tube, add an appropriate amount of anhydrous acetonitrile, centrifuge, and then decant to remove the supernatant. Repeat this washing operation twice. Dry the washed solid product in a vacuum oven at 65℃ to obtain polypyrrole-coated solid electrolyte particles. Example 2

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

[0026] Reactant preparation steps: Provide 5 g of pyrrole monomer and 100 g of lithium aluminum titanium phosphate powder (Li 1+x Al x Ti 2-xThe reaction mixture consisted of (PO4)3 (X = 0.5 g), 10 g of anhydrous ferric chloride, and 500 ml of anhydrous acetonitrile (393 g). First, the pyrrole monomer was added to 400 ml of anhydrous acetonitrile and dissolved under stirring at 150 r / min to obtain a pyrrole monomer solution. Then, lithium aluminum titanium phosphate powder was added to a four-necked jacketed reaction flask. Finally, the pyrrole monomer solution was poured into a four-necked jacketed reaction flask containing solid electrolyte particles, and stirring was started at 150 r / min to obtain a mixed reaction system. Finally, ferric chloride was added to 100 ml of anhydrous acetonitrile and dissolved under stirring at 150 r / min to obtain the prepared catalytic system.

[0027] Polymerization reaction steps: Turn on the stirrer of the four-necked jacketed reaction flask at 150 r / min and place the flask in an ice-water bath to keep the temperature of the mixed reaction system below 10°C. Continuously purge the four-necked jacketed reaction flask with dry helium gas for 10 minutes to remove oxygen and moisture. Under continuous stirring and ice-bath 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 ice-bath conditions for 6 hours. After the reaction is complete, stop stirring and allow the solid to precipitate. Carefully decant to remove the supernatant. Transfer the precipitate to a centrifuge tube, add an appropriate amount of anhydrous acetonitrile, centrifuge, and then decant to remove the supernatant. Repeat this washing operation twice. Dry the washed solid product 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 includes the following steps.

[0029] Reactant preparation steps: Provide 2.5 g of pyrrole monomer and 100 g of lithium aluminum titanium phosphate powder (Li). 1+x Al x Ti 2-x The reaction mixture consisted of (PO4)3 (X = 0.2), 5 g of ammonium persulfate, and 500 ml of anhydrous dimethyl sulfoxide. First, lithium aluminum titanium phosphate powder was added to 400 ml of anhydrous dimethyl sulfoxide and dissolved under stirring at 150 r / min to obtain a solid electrolyte solution. Then, pyrrole monomer was added to a four-necked jacketed reaction flask. Finally, the solid electrolyte solution was poured into the four-necked jacketed reaction flask containing the pyrrole monomer, and stirring was started at 150 r / min to obtain a mixed reaction system. Finally, ammonium persulfate was added to 100 ml of anhydrous dimethyl sulfoxide and dissolved under stirring at 150 r / min to obtain the prepared catalytic system.

[0030] Polymerization reaction steps: Turn on the stirrer of the four-necked jacketed reaction flask at 150 r / min and place the flask in an ice-water bath to keep the temperature of the mixed reaction system below 10°C. Continuously purge the four-necked jacketed reaction flask with dry argon gas for 10 minutes to remove oxygen and moisture. Under continuous stirring and ice-bath cooling, 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 under ice-bath conditions for 4 hours. After the reaction is complete, stop stirring and allow the solid to precipitate. Carefully decant to remove the supernatant. Transfer the precipitate to a centrifuge tube, add an appropriate amount of anhydrous acetonitrile, centrifuge, and then decant to remove the supernatant. Repeat this washing operation twice. Dry the washed solid product 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 includes the following steps.

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

[0033] Polymerization reaction steps: Turn on the stirrer of the four-necked jacketed reaction flask at 150 r / min, and connect the cooling water circulation device to keep the temperature of the mixed reaction system in the four-necked jacketed reaction flask below 10℃. Continuously purge dry argon gas into the four-necked jacketed reaction flask for 20 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 2 ml / min. After the addition is complete, continue stirring for 8 hours under cooling water circulation. After the reaction is complete, stop stirring and wait for the solid to precipitate. Carefully decant to remove the supernatant. Transfer the precipitate to a centrifuge tube, add an appropriate amount of anhydrous ethanol, centrifuge, and then decant to remove the supernatant. Repeat this washing operation once. Dry the washed solid product in a vacuum oven at 55℃ to obtain polypyrrole-coated solid electrolyte particles. Example 5

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

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

[0036] Polymerization reaction steps: Turn on the stirrer of the four-necked jacketed reaction flask at 50 r / min and place the flask in an ice-water bath to keep the temperature of the mixed reaction system below 10°C. Continuously purge the four-necked jacketed reaction flask with dry nitrogen gas for 10 minutes to remove oxygen and moisture. Under continuous stirring and ice-bath cooling, 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 under ice-bath conditions for 6 hours. After the reaction is complete, stop stirring and allow the solid to precipitate. Carefully decant to remove the supernatant. Transfer the precipitate to a centrifuge tube, add an appropriate amount of anhydrous dimethyl sulfoxide, centrifuge, and then decant to remove the supernatant. Repeat this washing operation twice. Dry the washed solid product 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 includes the following processes: 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 nano-sized solid electrolyte solution. Then, the active material, conductive agent, and binder were added to the N-methylpyrrolidone solution in a ratio of 95:2:3 and stirred until homogeneous. Next, 2% (by mass) of the solid electrolyte solution was added, and the mixture was stirred continuously for 24 hours until homogeneous and free of obvious particles, yielding a slurry. Finally, the slurry was coated onto aluminum foil and dried at 100°C for 12 hours to obtain a solid electrolyte-modified electrode.

[0038] Example 1: Energy Spectroscopy Detection Energy dispersive spectroscopy (EDS) was performed on the polypyrrole-coated solid electrolyte particles prepared in Example 1. Figure 1As shown, a thin film exists on the surface of lithium titanium aluminum phosphate after polypyrrole coating. Energy dispersive spectroscopy (EDS) analysis revealed that oxygen, aluminum, phosphorus, and titanium elements are uniformly distributed throughout the detection range, and carbon and nitrogen elements were also detected, indicating that polypyrrole is uniformly coated on the surface of lithium titanium aluminum phosphate. The EDS results demonstrate that the method for preparing polypyrrole-coated solid electrolytes in this application successfully produces polypyrrole-coated solid electrolytes.

[0039] Example 2: Powder X-ray diffraction detection Lithium titanium aluminum phosphate powder (Li 1+x Al x Ti 2-x (PO4)3, X equals 0.1, i.e., uncoated lithium titanium aluminum phosphate), polypyrrole, and the polypyrrole-coated solid electrolyte particles prepared in Example 1 were characterized by powder X-ray diffraction. Figure 2 As shown, uncoated lithium titanium aluminum phosphate exhibits a series of clear and sharp diffraction peaks, a typical characteristic of crystalline materials, indicating that lithium titanium aluminum phosphate is a material with good crystallinity. Polypyrrole, on the other hand, shows a broad and diffuse peak with relatively low overall intensity. This broad peak is typical of amorphous or semi-crystalline materials, indicating that polypyrrole here presents an amorphous or low-crystallinity structure. Combining the characteristics of the first two materials, the polypyrrole-coated solid electrolyte particles prepared in Example 1 exhibit consistent sharp diffraction peak positions. This indicates that lithium titanium aluminum phosphate still exists in its original crystalline structure in the composite material. Simultaneously, the presence of polypyrrole in its amorphous or semi-crystalline state reduces the diffraction peak intensity of crystalline lithium titanium aluminum phosphate. This confirms that polypyrrole successfully coats lithium titanium aluminum phosphate without severely damaging its crystal structure.

[0040] Example 3: Infrared Detection Lithium titanium aluminum phosphate powder (Li 1+x Al x Ti 2-x (PO4)3, X equals 0.1, i.e., uncoated lithium titanium aluminum phosphate), polypyrrole, and polypyrrole-coated solid electrolyte particles prepared in Example 1 were subjected to infrared detection. Figure 3 As shown, for uncoated lithium titanium aluminum phosphate, the phosphate groups (PO4) 3- The characteristic peak may be in the range of 1000-1100 cm⁻¹. -1 The left and right corresponding to the stretching vibration of PO and the bending vibration of OPO. As a conductive polymer, polypyrrole's main absorption peak is likely around 1550 cm⁻¹. -1 (C=C stretching vibration), 1450 cm -1 (CN stretching vibration), and 1300 cm -1 and 1200 cm -1Nearby CH-plane in-plane bending vibrations were observed. Characteristic peaks of both lithium titanium aluminum phosphate and polypyrrole were simultaneously observed in the spectrum of polypyrrole-coated lithium titanium aluminum phosphate. The results indicate that Example 1 successfully prepared polypyrrole-coated lithium titanium aluminum phosphate.

[0041] Example 4: Raman spectroscopy detection Raman spectroscopy was performed on the polypyrrole-coated solid electrolyte particles prepared in Example 1. Figure 4 As shown, the Raman spectrum successfully revealed the characteristic vibrational modes of the two main components in the lithium aluminum titanium phosphate-polypyrrole composite material. On the one hand, the characteristic peak of lithium aluminum titanium phosphate (symmetric PO4)... 3- The presence of PO stretching vibrations indicates that the phosphate component was successfully introduced and retained in the composite material; on the other hand, the characteristic peaks of polypyrrole (CN, D, and G peaks) were also observed, 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] Example 5: Charge and Discharge Performance Test Lithium titanium aluminum phosphate powder (Li) was used respectively 1+x Al x Ti 2-x (PO4)3, X equals 0.1, i.e., uncoated lithium titanium aluminum phosphate) and the polypyrrole-coated solid electrolyte particles prepared in Example 1 were used to assemble batteries. The charge-discharge performance of the batteries was tested. The battery using lithium titanium aluminum phosphate powder corresponds to size 12, and the battery using the polypyrrole-coated solid electrolyte particles prepared in Example 1 corresponds to size 11. The results are as follows: Figure 5 As shown, battery No. 11 achieved a discharge energy of 275.14 Wh at 45°C, while battery No. 12 achieved a discharge energy of 268.39 Wh at 45°C. This indicates that the polypyrrole-coated solid electrolyte prepared in Example 1 can improve the overall energy density of the battery.

[0043] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a polypyrrole-coated solid electrolyte, characterized in that, The steps included when calculating by weight are as follows: Reactant preparation: Provide 1-5 parts of pyrrole monomer, 100 parts of solid electrolyte, 2-10 parts of catalyst and anhydrous organic solvent A. Add the solid electrolyte and the pyrrole monomer to a portion of the anhydrous organic solvent A and mix evenly to obtain a mixed reaction system. Then add the catalyst to the remaining anhydrous organic solvent A and mix evenly to obtain a catalytic system. Polymerization reaction: Inert gas is introduced into the mixed reaction system, and the temperature of the mixed reaction system is adjusted to below 20°C. While stirring the mixed reaction system under anaerobic conditions, the catalyst system is added dropwise to the mixed reaction system. After the addition is completed, the reaction is stirred for more than 1 hour to obtain a crude product. The crude product is washed and dried to obtain a polypyrrole-coated solid electrolyte. The catalyst is ferric chloride or ammonium persulfate.

2. The method for preparing the polypyrrole-coated solid electrolyte as described in claim 1, characterized in that, In the reactant preparation step, the solid electrolyte is at least one of LATP, LLZO, LZG, LOC, LLTO, and LiPON, 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 the polypyrrole-coated solid electrolyte as described in claim 2, characterized in that, The solid electrolyte is Li1₊ x Al x Ti2₋ x (PO4)3, wherein the X value is 0.1 to 0.5; the catalyst is ferric chloride; and the anhydrous organic solvent A is anhydrous acetonitrile.

4. The method for preparing the polypyrrole-coated solid electrolyte as described in claim 1, characterized in that, In the reactant preparation step, the pyrrole monomer and the solid electrolyte are first dissolved in anhydrous organic solvent A to obtain a pyrrole monomer solution and a solid electrolyte solution, and then the pyrrole monomer solution and the solid electrolyte solution are mixed evenly to obtain a mixed reaction system. The pyrrole monomer solution contains 0.1% to 2.5% by mass, and the solid electrolyte solution contains 10% to 67% by mass.

5. The method for preparing the polypyrrole-coated solid electrolyte as described in claim 4, characterized in that, 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 obtain a pyrrole monomer solution; the solid electrolyte was dissolved in 200 ml of anhydrous organic solvent A to obtain a solid electrolyte solution; the catalyst was dissolved in 100 ml of anhydrous organic solvent A to obtain a catalytic system.

6. The method for preparing the polypyrrole-coated solid electrolyte as described in claim 1, characterized in that, In the reactant preparation step, the pyrrole monomer is first dissolved in anhydrous organic solvent A to obtain 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 the polypyrrole-coated solid electrolyte as described in claim 1, characterized in that, 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 inert gas is introduced for at least 10 minutes.

8. The method for preparing the polypyrrole-coated solid electrolyte as described in claim 1, characterized in that, During the polymerization reaction, the rate of adding the catalytic system was 0.5–2 ml / min, and the reaction continued for 4 hours after the addition was completed.

9. The method for preparing the polypyrrole-coated solid electrolyte as described in claim 1, characterized in that, In the polymerization reaction step, the crude product is allowed to stand until the particles precipitate. The supernatant is then removed. The precipitated particles are washed with anhydrous organic solvent B and collected by centrifugation. The washing and centrifugation steps are repeated 1 to 3 times. The precipitate is then transferred to a vacuum drying oven for drying to obtain 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 method for preparing polypyrrole-coated solid electrolyte according to any one of claims 1-9.

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