Composite solid electrolyte membrane rich in hydrogen bond network as well as preparation method and application of composite solid electrolyte membrane

Abstract

The invention relates to the technical field of lithium metal solid electrolyte modification, in particular to a composite solid electrolyte membrane rich in a hydrogen bond network and a preparation method and application thereof. The lithium lanthanum zirconium aluminum oxide particles coated with the lithium carboxymethyl cellulose and the polydopamine are added into the PVDF-HFP matrix, so that the density and the mechanical strength are improved, the interface stability with a lithium metal electrode is enhanced, and the cycle life of the lithium metal electrode is prolonged. The addition of the carboxymethyl cellulose lithium promotes the volatilization of the second solvent, and improves the performance of the composite solid electrolyte membrane. The prepared composite solid electrolyte membrane shows excellent electrochemical performance and mechanical performance, growth of lithium dendrites is effectively inhibited, and the cycle life of a battery is remarkably prolonged. The capacity retention ratio of the composite solid electrolyte membrane is still greater than 95% after 200 cycles under 2C multiplying power, and the composite solid electrolyte membrane shows excellent electrochemical stability and mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of modification of lithium metal solid electrolytes, and particularly relates to a composite solid electrolyte membrane rich in hydrogen bond networks, a preparation method thereof, and applications thereof. Background Art

[0002] With the rapid development of lithium-ion battery technology, in order to meet the continuously increasing requirements for high energy density, fast charging, long cycle life, and safety, the development of high-performance lithium metal solid electrolyte membranes has become a key technical issue.

[0003] Solid electrolytes mainly include organic polymer solid electrolytes, inorganic solid electrolytes, and organic-inorganic composite solid electrolytes. Organic polymer solid electrolytes have good flexibility and processability, but their mechanical strength is low, and their ionic conductivity at room temperature is also low. Inorganic solid electrolytes have high ionic conductivity and sufficient mechanical strength, but they have poor thermal stability, poor interfacial contact, and lack flexibility. In contrast, inorganic-organic composite solid electrolytes can combine the advantages of both, but in practical applications, attention needs to be paid to the compatibility between the organic matter and the inorganic filler and the processability of the electrolyte membrane.

[0004] Currently, the practical application of composite solid electrolytes still faces many challenges. The low lithium ion conductivity of solid electrolytes significantly affects the cycle life and performance of batteries; at the same time, it is difficult to balance the mechanical strength and flexibility of solid electrolytes, which makes it a difficult problem to maintain stable contact between the electrolyte and the electrode during battery assembly. In addition, the formation of lithium dendrites, the decomposition of electrolytes, and the increase in interfacial impedance seriously affect the cycle stability and safety of solid-state batteries.

[0005] PVDF-HFP, the full English name is Poly(vinylidene fluoride-co-hexafluoropropylene), and the Chinese name is polyvinylidene fluoride-hexafluoropropylene copolymer. In the PVDF-HFP-based composite solid electrolyte system, the solvent and the lithium salt will undergo a complexation reaction to form a specific solvation structure, which may affect the solubility and conductivity of the lithium salt. Although the residual solvent can improve the conductivity to a certain extent, there are also a series of potential negative effects. For example, the excess solvent may act as a plasticizer, which can improve the conductivity in the short term, but will induce side reactions with lithium metal, thus seriously affecting the cycle performance of the battery.

[0006] In addition, during the solvent evaporation process of the PVDF-HFP-based composite solid electrolyte, phase separation occurs, and its microstructure forms spherical crystals one by one, generating many voids. The void defects and mechanical strength of the PVDF-HFP-based composite solid electrolyte significantly affect the growth of lithium dendrites. Void defects lead to a decrease in the uniformity of lithium metal during deposition, thereby promoting the formation of irregular lithium dendrites. The mechanical stress during the growth of lithium dendrites further exacerbates the damage of the electrolyte, resulting in an increase in the local current density and promoting the formation of more lithium dendrites. Summary of the Invention

[0007] To solve the above problems, the present invention provides a composite solid electrolyte membrane rich in hydrogen bond network, a preparation method thereof, and an application.

[0008] To achieve the above object, the technical solution of the present invention is as follows.

[0009] In a first aspect of the present invention, a preparation method of a composite solid electrolyte membrane rich in hydrogen bond network is provided, including the following steps: Disperse lithium lanthanum zirconium aluminum oxide particles in a first solvent, and mix and react with dopamine hydrochloride at pH = 8.0 - 8.5 to obtain lithium lanthanum zirconium aluminum oxide particles coated with polydopamine; disperse lithium bis(trifluoromethanesulfonyl)imide, lithium carboxymethyl cellulose, and lithium lanthanum zirconium aluminum oxide particles coated with polydopamine into a second solvent, and carry out a film-forming reaction with poly(vinylidene fluoride-hexafluoropropylene) copolymer, and dry to obtain a composite solid electrolyte membrane rich in hydrogen bond network; the mass ratio of poly(vinylidene fluoride-hexafluoropropylene) copolymer, lithium bis(trifluoromethanesulfonyl)imide, lithium carboxymethyl cellulose, and lithium lanthanum zirconium aluminum oxide particles coated with polydopamine is 1:0.8:0.07:0.2.

[0010] The present invention uses lithium carboxymethyl cellulose as a hydrogen bond regulator, which can improve the density of the composite solid electrolyte membrane, promote the evaporation of the second solvent, and inhibit the side reaction between the second solvent and lithium metal.

[0011] The present invention constructs a dual-functional composite particle with both electron conduction and ion conduction by in-situ self-polymerization of dopamine to modify the surface of lithium lanthanum zirconium aluminum oxide particles. The present invention synchronously optimizes the electrochemical stability and mechanical properties through the three-dimensional hydrogen bond network and blend phase structure among poly(vinylidene fluoride-hexafluoropropylene) copolymer, lithium carboxymethyl cellulose, and lithium lanthanum zirconium aluminum oxide particles coated with polydopamine.

[0012] Preferably, the mass ratio of lithium lanthanum zirconium aluminum oxide particles to polydopamine is 1:0.02 - 0.03.

[0013] Preferably, the first solvent is methanol, and the second solvent is N,N-dimethylacetamide.

[0014] Preferably, the mass ratio of the polyvinylidene fluoride - hexafluoropropylene copolymer to the second solvent is 1:8 - 16.

[0015] Preferably, the mass ratio of the lithium lanthanum zirconium aluminum oxide particles to the first solvent is 1:20 - 30.

[0016] Preferably, the degree of substitution of lithium carboxymethyl cellulose is 8 - 10; the average particle size of the polydopamine - coated lithium lanthanum zirconium aluminum oxide particles is 200 nm; the weight - average molecular weight of the polyvinylidene fluoride - hexafluoropropylene copolymer is 400000.

[0017] Preferably, the temperature of the film - forming reaction is 60°C ± 5°C, and the time is 12 h - 14 h.

[0018] Preferably, the drying temperature is 60°C, and the time is 12 h - 14 h.

[0019] Preferably, the specific operation of dispersing the lithium lanthanum zirconium aluminum oxide particles in the first solvent is as follows: Mix and stir the lithium lanthanum zirconium aluminum oxide particles and the first solvent for 1 h - 2 h, and then ultrasonicate for 10 min - 20 min.

[0020] Preferably, when the mixing reaction is carried out at pH = 8.0 - 8.5, the pH is adjusted to 8.0 - 8.5 using Tris buffer. Among them, the mass ratio of the lithium lanthanum zirconium aluminum oxide particles to the Tris buffer is 1:0.01 - 0.02. The mixing reaction time is 12 h - 24 h. After the reaction, centrifuge and wash 3 times, and vacuum - dry at 80°C - 90°C for 24 h - 30 h.

[0021] In the second aspect of the present invention, a composite solid - state electrolyte membrane rich in a hydrogen - bond network is provided, which is prepared by using the preparation method of the composite solid - state electrolyte membrane rich in a hydrogen - bond network described in the first aspect.

[0022] In the third aspect of the present invention, an application of the composite solid - state electrolyte membrane rich in a hydrogen - bond network described in the first aspect as a lithium - battery electrolyte membrane is provided.

[0023] The beneficial effects of the present invention: 1. In the present invention, the rich hydroxyl groups in lithium carboxymethyl cellulose disrupt the regular arrangement of the crystalline phase of the polyvinylidene fluoride - hexafluoropropylene copolymer through hydrogen - bond interactions. The hydroxyl and amino groups on the surface of the polydopamine - coated lithium lanthanum zirconium aluminum oxide particles further form a three - dimensional hydrogen - bond network with lithium carboxymethyl cellulose and the polyvinylidene fluoride - hexafluoropropylene copolymer, so as to improve the density and mechanical strength of the composite solid - state electrolyte membrane.

[0024] 2. After coating lithium lanthanum zirconium aluminum oxide particles with polydopamine, the present invention uses the polydopamine-coated lithium lanthanum zirconium aluminum oxide particles as inorganic fillers, and the interfacial compatibility between the inorganic fillers and the polyvinylidene fluoride-hexafluoropropylene copolymer is significantly enhanced, and the particle dispersion uniformity is improved.

[0025] 3. The lithium lanthanum zirconium aluminum oxide particles of the present invention are used as inorganic fast ion conductor fillers to form a continuous ion transport channel with the flexible polymer matrix of polyvinylidene fluoride-hexafluoropropylene copolymer / lithium carboxymethyl cellulose.

[0026] 4. The composite solid electrolyte membrane rich in hydrogen bond network prepared by the present invention can assemble a lithium battery that exhibits excellent electrochemical stability and mechanical properties in the charge and discharge cycle test. The capacity retention rate is ≥99% after 200 cycles at 0.5C rate, and the capacity retention rate is still greater than 95% after 200 cycles at 2C rate. Moreover, the interfacial reaction rate between the composite solid electrolyte membrane of the present invention and the lithium metal electrode is significantly reduced, effectively inhibiting the nucleation and growth of lithium dendrites. Description of the Drawings

[0027] Figure 1 It is the characterization images of PDA@LLZAO particles and LLZAO particles prepared in Example 1. Among them, (a1) is the transmission electron microscope image of PDA@LLZAO particles prepared in Example 1; (a2) is the transmission electron microscope image of LLZAO particles; (b1) is the scanning electron microscope image of PDA@LLZAO particles prepared in Example 1; (b2) is the surface scan image of Zr; (b3) is the surface scan image of N element; (c) is the Fourier transform infrared spectrum image of PDA@LLZAO particles and LLZAO particles prepared in Example 1.

[0028] Figure 2 It is the electrochemical impedance spectroscopy images of the steel symmetric batteries assembled in Application Example 3 and Application Comparative Examples 7-9. Among them, Zre (ohms) represents the real part of the impedance, and the unit is ohm; Zim (ohms) represents the imaginary part of the impedance, and the unit is ohm.

[0029] Figure 3 It is the rate performance diagram of the lithium iron phosphate batteries assembled in Application Example 1 and Application Comparative Examples 1 and 2.

[0030] Figure 4 It is the long cycle performance and Coulomb efficiency diagram of the lithium iron phosphate batteries assembled in Application Example 1 and Application Comparative Examples 1 and 2 at 2C rate.

[0031] Figure 5Long cycle performance and Coulombic efficiency graphs at 0.5C rate for the lithium iron phosphate batteries assembled with Application Example 1, Application Comparative Example 1, and Application Comparative Example 2.

[0032] Figure 6 Scanning electron microscope images of the composite solid electrolyte membrane prepared in Example 1 and the solid electrolyte membrane prepared in Comparative Example 1. Among them, (a) is the scanning electron microscope image of the solid electrolyte membrane prepared in Comparative Example 1; (b) is the scanning electron microscope image of the composite solid electrolyte membrane prepared in Example 1.

[0033] Figure 7 Voltage vs. time curves of the lithium symmetric batteries assembled with Application Example 2, Application Comparative Example 4, and Application Comparative Example 5 at room temperature and a constant current density of 0.1 mA•cm -2 ².

[0034] Figure 8 Voltage vs. time curves of the lithium symmetric batteries assembled with Application Example 2, Application Comparative Example 4, and Application Comparative Example 5 at room temperature and different current densities.

[0035] Figure 9 Scanning electron microscope images of the lithium metal sheets after cycling for the lithium symmetric batteries assembled with Application Example 2 and Application Comparative Example 4. Among them, (a) is the scanning electron microscope image of the lithium metal sheet before cycling of the lithium symmetric battery; (b) is the scanning electron microscope image of the lithium metal sheet after cycling of the lithium symmetric battery assembled with Application Comparative Example 4; (c) is the scanning electron microscope image of the lithium metal sheet after cycling of the lithium symmetric battery assembled with Application Example 2.

[0036] Figure 10 Stress-strain curves of the composite solid electrolyte membrane prepared in Example 1 and the solid electrolyte membrane prepared in Comparative Example 1. Detailed implementation manners

[0037] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0038] All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0039] In the following embodiments of the present invention, the full English name of lithium carboxymethyl cellulose is CarboxymethylCellulose Lithium, abbreviated as CMC-Li.

[0040] The full English name of polydopamine is Polydopamine, abbreviated as PDA. The full English name of lithium bis(trifluoromethanesulfonyl)imide is Lithium bis(trifluoromethanesulfonyl)imide, abbreviated as LiTFSI.

[0041] The Chinese name of Tris buffer is tris(hydroxymethyl)aminomethane buffer. The full English name of DMAc is N,N-Dimethylacetamide, and its Chinese name is N,N-dimethylacetamide.

[0042] The full English name of NMP is N-Methylpyrrolidone, and its Chinese name is N-methylpyrrolidone.

[0043] PVDF-HFP, the full English name is Poly(vinylidene fluoride-co-hexafluoropropylene), and the Chinese name is poly(vinylidene fluoride-hexafluoropropylene) copolymer; PVDF is polyvinylidene fluoride.

[0044] High mechanical strength can effectively maintain the integrity of the composite solid electrolyte membrane, reduce the formation of voids and cracks, thereby inhibiting the penetration and growth of lithium dendrites, and improving the overall performance of lithium metal batteries. Based on this, the present invention aims to develop a hydrogen bond interconnected PVDF-HFP-based composite solid electrolyte membrane with high density, high mechanical strength, high compatibility between polymer and inorganic filler, and good compatibility with the substrate, while balancing the amount of residual solvent.

[0045] In the present invention, lithium carboxymethyl cellulose is added to the PVDF-HFP matrix to improve the density of the composite solid electrolyte membrane. Lithium carboxymethyl cellulose can not only be uniformly dispersed in the PVDF-HFP matrix, but also form a tight network structure, thereby increasing the density of the composite solid electrolyte membrane. However, after adding lithium carboxymethyl cellulose, the conductivity of the composite solid electrolyte membrane decreases, probably because lithium carboxymethyl cellulose promotes solvent volatilization. The hydrophilic groups and hydrophobic main chains in lithium carboxymethyl cellulose molecules may form an interfacial adsorption layer in the solvent, reducing the surface tension of the solution. The reduction of surface tension makes it easier for solvent molecules to overcome the energy barrier and escape from the liquid surface.

[0046] Therefore, on this basis, the present invention adds LLZAO particles coated with polydopamine. The Chinese name of LLZAO is lithium lanthanum zirconium aluminum oxide, and the chemical formula is Li 6.28 La3Zr2Al 0.24 O 12The LLZAO particles coated with polydopamine can improve the compatibility with the substrate, reduce the interfacial impedance, and promote the adhesion between the substrate and the composite solid electrolyte membrane. At the same time, the polydopamine coating layer can effectively prevent side reactions between the LLZAO particles and the substrate, further enhancing the compatibility. More importantly, lithium carboxymethyl cellulose and the LLZAO particles coated with polydopamine form an interconnected network structure through hydrogen bonding, which not only improves the conductivity of the composite solid electrolyte membrane but also significantly enhances its mechanical strength. The formation of this structure ensures the stability and flexibility of the composite solid electrolyte membrane, enabling it to be stably applied in lithium metal batteries for a long time.

[0047] The composite solid electrolyte membrane prepared by the present invention has excellent density and mechanical properties, thereby being able to effectively inhibit the growth of lithium dendrites in lithium metal batteries and improving the cycle capacity and service life of lithium metal batteries. Experimental tests show that the lithium metal battery using the composite solid electrolyte membrane of the present invention exhibits higher stability and longer cycle life.

[0048] The technical solution of the present invention will be further described below through specific examples.

[0049] In the following examples, unless otherwise specified, the methods are all conventional methods; the reagents and materials, unless otherwise specified, can be purchased on the market.

[0050] Determine the optimal value of the mass percentage of CMC-Li in PVDF-HFP. The specific method is as follows: S1. Prepare a mixed solution of CMC-Li, PVDF-HFP, LiTFSI, and DMAc: Add CMC-Li and LiTFSI to DMAc, stir at 60 °C for 12 hours, then add PVDF-HFP, and then stir at 60 °C with a stirring speed of 500 r / s for 12 h to obtain a mixed solution of CMC-Li, PVDF-HFP, LiTFSI, and DMAc. Among them, the mass percentage of CMC-Li in PVDF-HFP is 6% - 8%; the mass ratio of PVDF-HFP to LiTFSI is 1:0.8; the mass of DMAc is 800 wt% of the mass of PVDF-HFP.

[0051] S2. Use ultrasonic means to fully stir and disperse the mixed solution of CMC-Li, PVDF-HFP, LiTFSI, and DMAc, and then pour it into a polytetrafluoroethylene mold. Place the polytetrafluoroethylene mold in a vacuum oven and dry it at 60 °C for 12 h, and then place it in a glove box and dry it at 60 °C for 12 h to ensure the drying of the mixed solution and form a PVDF-HFP composite electrolyte film.

[0052] By adjusting the mass percentages of CMC-Li in PVDF-HFP to 6%, 7%, and 8% respectively, the densification of the obtained PVDF-HFP composite electrolyte films was tested and recorded. The densification of the PVDF-HFP composite electrolyte films was analyzed using a scanning electron microscope to determine the mass percentage of CMC-Li in PVDF-HFP when the densification of the PVDF-HFP composite electrolyte films reached the optimum, which was used as the optimal content of CMC-Li.

[0053] Table 1 Densification of PVDF-HFP Composite Electrolyte Films

[0054] The results showed that the mass percentage of CMC-Li in PVDF-HFP when the densification of the PVDF-HFP composite electrolyte films reached the optimum was 7%, which was used as the optimal content of CMC-Li.

[0055] Example 1 A method for preparing a composite solid electrolyte membrane rich in a hydrogen bond network, comprising the following steps: Step 1, Preparation of polydopamine-coated LLZAO particles: 0.5 g of LLZAO particles were mixed and stirred with 12 g of anhydrous methanol for 1 hour, sonicated for 10 minutes, then 12 mg of dopamine hydrochloride and 6 mg of Tris buffer were added to maintain the reaction pH at 8.0 - 8.5; mixed and stirred for 5 hours, then centrifuged and washed three times, and dried under vacuum drying conditions at 80 °C for 24 hours to obtain dry polydopamine-coated LLZAO particles, abbreviated as PDA@LLZAO particles. After sufficient grinding, they were placed in a glove box for standby.

[0056] Step 2, Preparation of the composite solid electrolyte membrane: The molecular weight of PVDF-HFP was about 400000; each raw material was weighed according to the mass ratio of PVDF-HFP, LITFSi, CMC-Li, and PDA@LLZAO of 1:0.8:0.07:0.2; DMAc was used as the solvent, and the mass of DMAc was 800 wt% of the mass of PVDF-HFP.

[0057] LITFSi, CMC-Li, and PDA@LLZAO were added to DMAc, stirred at 60 °C for 12 hours, then PVDF-HFP was added, and then stirred at 60 °C. The stirring speed was 500 r / s and the time was 12 hours to obtain a mixed solution. The mixed solution was poured into a polytetrafluoroethylene mold and dried in a vacuum oven at 60 °C for 12 h to obtain a composite solid electrolyte membrane, denoted as PVDF-HFP / CMC-Li / PDA@LLZAO.

[0058] Comparative Example 1 A preparation method of a solid electrolyte membrane, which is different from that of Example 1 in that PDA@LLZAO and CMC-Li are not added. The specific preparation method includes the following steps: The molecular weight of PVDF-HFP is about 400,000; each raw material is weighed according to the mass ratio of PVDF-HFP to LITFSi of 1:0.8; DMAc is used as the solvent, and the mass of DMAc is 800 wt% of the mass of PVDF-HFP.

[0059] LITFSi is added to DMAc, and after stirring at 60 °C for 12 hours, PVDF-HFP is added, and then stirred at 60 °C. The stirring speed is 500 r / s and the time is 12 hours to obtain a mixed solution. The mixed solution is poured into a polytetrafluoroethylene mold and dried in a vacuum oven at 60 °C for 12 h to obtain a solid electrolyte membrane, denoted as PVDF-HFP.

[0060] Comparative Example 2 A preparation method of a solid electrolyte membrane, which is different from that of Example 1 in that LLZAO particles are used to replace the polydopamine-coated LLZAO particles of Example 1. The specific preparation method includes the following steps: The molecular weight of PVDF-HFP is about 400,000; each raw material is weighed according to the mass ratio of PVDF-HFP, LITFSi, CMC-Li and LLZAO particles of 1:0.8:0.07:0.1; DMAc is used as the solvent, and the mass of DMAc is 800 wt% of the mass of PVDF-HFP.

[0061] LITFSi, CMC-Li and LLZAO particles are added to DMAc, and after stirring at 60 °C for 12 hours, PVDF-HFP is added, and then stirred at 60 °C. The stirring speed is 500 r / s and the time is 12 hours to obtain a mixed solution. The mixed solution is poured into a polytetrafluoroethylene mold and dried in a vacuum oven at 60 °C for 12 h to obtain a solid electrolyte membrane, denoted as PVDF-HFP / CMC-Li / LLZAO.

[0062] Comparative Example 3 A preparation method of a solid electrolyte membrane includes the following steps: The molecular weight of PVDF-HFP is about 400,000; each raw material is weighed according to the mass ratio of PVDF-HFP, LITFSi and CMC-Li of 1:0.8:0.07; DMAc is used as the solvent, and the mass of DMAc is 800 wt% of the mass of PVDF-HFP.

[0063] LITFSi and CMC-Li were added to DMAc. After stirring at 60 °C for 12 hours, PVDF-HFP was added, and then stirring was carried out at 60 °C. The stirring speed was 500 r / s and the time was 12 hours to obtain a mixed solution. The mixed solution was poured into a polytetrafluoroethylene mold and dried in a vacuum oven at 60 °C for 12 h to obtain a solid electrolyte membrane, denoted as PVDF-HFP / CMC-Li.

[0064] Table 2 Comparison of the solid electrolyte membranes of Example 1 and Comparative Examples 1 to 3

[0065] Application Example 1 A lithium iron phosphate battery was prepared using the composite solid electrolyte membrane prepared in Example 1. The preparation method of the lithium iron phosphate battery is as follows: PVDF and N-methylpyrrolidone were mixed evenly to obtain an N-methylpyrrolidone solution containing PVDF, which was reserved; among them, the mass percentage of PVDF in the N-methylpyrrolidone solution containing PVDF was 5%.

[0066] Lithium iron phosphate, conductive carbon black SuperP and the N-methylpyrrolidone solution containing PVDF were evenly mixed according to a mass ratio of 8:1:20; dried under vacuum conditions at 60 °C for 12 hours to obtain a lithium iron phosphate positive electrode. The dried lithium iron phosphate positive electrode was cut into a circle with a diameter of 14 mm and reserved.

[0067] The composite solid electrolyte membrane prepared in Example 1 was cut into a circle with a diameter of 16 mm in a glove box; then a button-type lithium iron phosphate battery was assembled in a glove box filled with argon. Using a 2032 type positive and negative battery case, it was assembled using a hydraulic press in the order of the positive electrode case, gasket, lithium iron phosphate positive electrode, composite solid electrolyte membrane, lithium sheet, gasket, spring sheet and negative electrode case.

[0068] Application Comparative Example 1 According to the preparation method of the lithium iron phosphate battery in Application Example 1, a lithium iron phosphate battery was prepared using the solid electrolyte membrane prepared in Comparative Example 1.

[0069] Application Comparative Example 2 According to the preparation method of the lithium iron phosphate battery in Application Example 1, a lithium iron phosphate battery was prepared using the solid electrolyte membrane prepared in Comparative Example 2.

[0070] Application Comparative Example 3 According to the preparation method of the lithium iron phosphate battery in Application Example 1, a lithium iron phosphate battery was prepared using the solid electrolyte membrane prepared in Comparative Example 3.

[0071] Application Example 2 Prepare a lithium symmetric battery using the composite solid electrolyte membrane prepared in Example 1. The preparation method of the lithium symmetric battery is as follows: Use the positive and negative electrode battery cases of model 2032, and assemble them using a hydraulic press in the order of the positive electrode case, gasket, lithium sheet, electrolyte, lithium sheet, gasket, spring sheet, and negative electrode case.

[0072] Apply Comparative Example 4 According to the preparation method of the lithium symmetric battery in Application Example 2, prepare a lithium symmetric battery using the solid electrolyte membrane prepared in Comparative Example 1.

[0073] Apply Comparative Example 5 According to the preparation method of the lithium symmetric battery in Application Example 2, prepare a lithium symmetric battery using the solid electrolyte membrane prepared in Comparative Example 2.

[0074] Apply Comparative Example 6 According to the preparation method of the lithium symmetric battery in Application Example 2, prepare a lithium symmetric battery using the solid electrolyte membrane prepared in Comparative Example 3.

[0075] Apply Application Example 3 Prepare a steel symmetric battery using the composite solid electrolyte membrane prepared in Example 1. The preparation method of the steel symmetric battery is as follows: Use the positive and negative electrode battery cases of model 2025, and assemble them using a hydraulic press in the order of the positive electrode case, steel sheet, composite solid electrolyte, steel sheet, spring sheet, and negative electrode case.

[0076] Apply Comparative Example 7 According to the preparation method of the steel symmetric battery in Application Example 3, prepare a steel symmetric battery using the solid electrolyte membrane prepared in Comparative Example 1.

[0077] Apply Comparative Example 8 According to the preparation method of the steel symmetric battery in Application Example 3, prepare a steel symmetric battery using the solid electrolyte membrane prepared in Comparative Example 2.

[0078] Apply Comparative Example 9 According to the preparation method of the steel symmetric battery in Application Example 3, prepare a steel symmetric battery using the solid electrolyte membrane prepared in Comparative Example 3.

[0079] Test 1: Characterization and analysis of PDA@LLZAO particles and LLZAO particles.

[0080] As Figure 1 shown, the particle size of the PDA@LLZAO particles prepared in Example 1 is approximately 200 μm. It can be seen from Figure 1 Figures (a1) and (a2) that the LLZAO particles have a darker color in the middle, and the PDA has a lighter color around. Combining Figure 1It can be seen from Figures (b1) to (b3) that the presence of Zr and N elements further proves that PDA is coated onto LLZAO particles.

[0081] From Figure 1 Figure (c), it can be seen that the range of 3600 cm -1 to 3100 cm -1 is attributed to the stretching vibration of N-H / O-H in polydopamine, and the peak intensity increases. The peak at 1658 cm -1 is attributed to the C=C resonance in the aromatic ring of PDA. In addition, the peak at 1674 cm -1 is attributed to the stretching vibration of conjugated C=O; the peak at 1507 cm -1 is attributed to the N-H shear vibration; the peak at 1400 cm -1 is attributed to the stretching vibration of C-OH; these peaks respectively represent the quinone, aromatic nitrogen and phenolic hydroxyl structures in the PDA molecule. This proves that PDA is successfully coated onto LLZAO particles.

[0082] Test 2: Electrochemical impedance spectroscopy analysis of steel symmetric batteries.

[0083] Steel symmetric batteries were assembled respectively using the composite solid electrolyte membrane prepared in Example 1 and the solid electrolyte membranes prepared in Comparative Examples 1 to 3, and electrochemical impedance spectroscopy tests were carried out. Assembly of the steel symmetric battery: Use 2025-type positive and negative battery cases, and assemble them using a hydraulic press in the order of the positive electrode case, steel sheet, composite solid electrolyte, steel sheet, spring sheet and negative electrode case.

[0084] As Figure 2 shown, the conductivity of the steel symmetric battery assembled with the solid electrolyte membrane of Comparative Example 3 is the lowest. It may be that after adding CMC-Li, the volatilization of the solvent N,N-dimethylacetamide is promoted. However, the conductivity of the steel symmetric battery assembled with the composite solid electrolyte membrane of Example 1 is the highest, reaching 0.4 mS•cm −1 , which is attributed to the multi-level hydrogen bond network structure, improved filler compatibility and ion conduction synergistic mechanism of the composite solid electrolyte membrane prepared in Example 1.

[0085] Test 3: Rate performance analysis of lithium iron phosphate batteries.

[0086] As Figure 3 shown, the discharge specific capacities of the lithium iron phosphate battery assembled with the composite solid electrolyte membrane prepared in Example 1 at 0.1C, 0.2C, 0.5C, 1C and 2C rate cycles are 153 mAh•g -1 , 148 mAh•g -1 , 140 mAh•g -1 , 130 mAh•g -1 and 110 mAh•g -1When the magnification is restored to 0.1C, the discharge specific capacity rapidly increases to 153 mAh•g again. -1 As mentioned above, it shows that the stability of the lithium iron phosphate battery in Application Example 1 is very high.

[0087] For the lithium iron phosphate batteries assembled with the solid electrolyte membranes prepared in Comparative Example 1 and Comparative Example 2, when cycled at different magnifications, their discharge specific capacities decay rapidly. The penetration depth of lithium dendrites increases with the increase of the charging magnification. The growth of lithium dendrites is the main reason for the loss of active lithium ions. The loss of active lithium ions reduces the available capacity and performance of the battery.

[0088] By performing magnification cycling on different solid electrolyte membranes, it can be seen that the lithium iron phosphate battery assembled with the composite solid electrolyte membrane prepared in Example 1 has good magnification performance and can effectively inhibit the growth of lithium dendrites.

[0089] Test 4: Long cycle performance of the lithium iron phosphate battery.

[0090] The long cycle performance and Coulomb efficiency of the lithium iron phosphate batteries assembled with Application Example 1, Application Comparative Example 1, and Application Comparative Example 2 at 2C and 0.5C magnifications are as Figure 4 and Figure 5 shown.

[0091] As Figure 4 shown, after 200 cycles at 2C magnification, the discharge specific capacity of the lithium iron phosphate battery assembled with Application Example 1 remains at 95%; after 300 cycles, the retention rate of its discharge specific capacity remains at 84%. For the lithium iron phosphate batteries assembled with Application Comparative Example 1 and Application Comparative Example 2, their discharge specific capacities are lower and decay faster.

[0092] As Figure 5 shown, when the lithium iron phosphate battery assembled with Application Example 1 is cycled 100 times at 0.5C magnification, its discharge specific capacity decreases from 149.46 mAh•g -1 to 147.3 mAh•g -1 , and its capacity retention rate is 99%. For the lithium iron phosphate battery assembled with Application Comparative Example 1, its discharge specific capacity decreases from 129.8 mAh•g -1 to 116.4 mAh•g -1 , and its capacity retention rate is 89%. For the lithium iron phosphate battery assembled with Application Comparative Example 2, its discharge specific capacity decreases from 140.1 mAh•g -1 to 139.5 mAh•g -1 , and the capacity retention rate is 99%, but its discharge specific capacity is lower.

[0093] Test 5: Scanning electron microscope analysis of the composite solid electrolyte membrane.

[0094] AsFigure 6 Compared with the solid electrolyte membrane of Comparative Example 1, the composite solid electrolyte membrane of Example 1 has fewer pores, and its density is significantly improved, which is beneficial to the uniform deposition of lithium dendrites.

[0095] Test 6: Cyclic stability of lithium symmetric battery.

[0096] As Figure 7 shown, the lithium symmetric battery assembled with Example 2 can stably cycle at 0.1 mA•cm -2 current at room temperature for 1400 hours, and has a polarization voltage of less than 80 mV. The lithium symmetric battery assembled with Comparative Example 4 shorted when stably cycling at 0.1 mA•cm -2 current at room temperature for 600 hours, and the polarization voltage suddenly increased at 300 hours. The lithium symmetric battery assembled with Comparative Example 5 only stably cycled for 600 hours at 0.1 mA•cm -2 current at room temperature. It can be proved that, compared with Comparative Examples 1 and 2, the service life of the lithium symmetric battery assembled with the composite solid electrolyte prepared in Example 1 has been greatly improved.

[0097] Test 7: Critical current density test of lithium symmetric battery.

[0098] The critical current density tests were carried out on the lithium symmetric batteries assembled with Example 2, Comparative Example 4 and Comparative Example 5, and the results are as Figure 8 shown.

[0099] As Figure 8 shown, for the lithium symmetric battery assembled with the composite solid electrolyte membrane of Example 1, its critical current density is 0.55 mA•cm -2 . For the lithium symmetric batteries assembled with the solid electrolyte membranes of Comparative Example 1 and Comparative Example 2, their critical current densities are 0.45 mA•cm -2 and 0.5 mA•cm -2 respectively. It can be proved that the electrolyte membrane prepared in Example 1 can effectively inhibit lithium dendrites.

[0100] Test 8: Scanning electron microscope analysis of lithium foil after cycling of lithium symmetric battery.

[0101] Lithium symmetric batteries were assembled with the composite solid electrolyte membrane prepared in Example 1 and the solid electrolyte membrane prepared in Comparative Example 1 respectively. After cycling 200 times at a current density of 0.1 mA•cm -2 , scanning electron microscope analysis was carried out on the lithium foil, and the results are as Figure 9 shown.

[0102] From Figure 9 Figure (a), it can be seen that the surface of the lithium foil before cycling of the lithium symmetric battery is flat and smooth.

[0103] As can be seen from Figure 9 Figure (b) of Comparative Example 1, after 200 cycles of the lithium symmetric battery assembled with the solid electrolyte membrane prepared in Comparative Example 1, the surface of the lithium sheet is rough, with a large number of lithium dendrites and uneven deposition.

[0104] As can be seen from Figure 9 Figure (c) of Example 1, after 200 cycles of the lithium symmetric battery assembled with the composite solid electrolyte membrane prepared in Example 1, the morphology of the lithium sheet is improved. This shows that the composite solid electrolyte membrane prepared in Example 1 promotes the uniform deposition of lithium and helps to achieve more stable and uniform deposition and stripping of lithium ions.

[0105] Test 9: Tensile property test of the composite solid electrolyte membrane.

[0106] The composite solid electrolyte membrane prepared in Example 1 and the solid electrolyte membrane prepared in Comparative Example 1 were subjected to a tensile property test, and the results are as Figure 10 shown.

[0107] As can be seen from Figure 10 it that the tensile strength of the composite solid electrolyte membrane prepared in Example 1 is 5.1 MPa and the elongation at break is greater than 250%. While the tensile strength of the solid electrolyte membrane prepared in Comparative Example 1 is only 3.5 MPa. This can prove that the composite solid electrolyte membrane prepared in Example 1 has enhanced mechanical properties due to the formed multi-level hydrogen bond network structure.

[0108] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite solid electrolyte membrane rich in a hydrogen bond network, characterized in that, It includes the following steps: Disperse lithium lanthanum zirconium aluminum oxide particles in the first solvent, and mix and react with dopamine hydrochloride at pH = 8.0 - 8.5 to obtain lithium lanthanum zirconium aluminum oxide particles coated with polydopamine; Disperse lithium bis(trifluoromethanesulfonyl)imide, lithium carboxymethyl cellulose and lithium lanthanum zirconium aluminum oxide particles coated with polydopamine into the second solvent, and carry out a film-forming reaction with poly(vinylidene fluoride - hexafluoropropylene) copolymer, and dry to obtain a composite solid electrolyte membrane rich in hydrogen bond network; The mass ratio of poly(vinylidene fluoride - hexafluoropropylene) copolymer, lithium bis(trifluoromethanesulfonyl)imide, lithium carboxymethyl cellulose and lithium lanthanum zirconium aluminum oxide particles coated with polydopamine is 1:0.8:0.07:0.

2.

2. The preparation method of the composite solid electrolyte membrane rich in hydrogen bond network according to claim 1, characterized in that The mass ratio of lithium lanthanum zirconium aluminum oxide particles to polydopamine is 1:0.02 - 0.

03.

3. The preparation method of the composite solid electrolyte membrane rich in hydrogen bond network according to claim 1, wherein, The first solvent is methanol, and the second solvent is N,N - dimethylacetamide.

4. The preparation method of the composite solid electrolyte membrane rich in hydrogen bond network according to claim 1, characterized in that, The mass ratio of poly(vinylidene fluoride - hexafluoropropylene) copolymer to the second solvent is 1:8 - 16.

5. The preparation method of the composite solid electrolyte membrane rich in hydrogen bond network according to claim 1, characterized in that, The mass ratio of lithium lanthanum zirconium aluminum oxide particles to the first solvent is 1:20 - 30.

6. The preparation method of the composite solid electrolyte membrane rich in hydrogen bond network according to claim 1, characterized in that, The degree of substitution of lithium carboxymethyl cellulose is 8 - 10; The average particle size of lithium lanthanum zirconium aluminum oxide particles coated with polydopamine is 200 nm; The weight-average molecular weight of poly(vinylidene fluoride - hexafluoropropylene) copolymer is 400000.

7. The preparation method of the composite solid electrolyte membrane rich in hydrogen bond network according to claim 1, wherein The temperature of the film-forming reaction is 60°C ± 5°C, and the time is 12 h - 14 h.

8. A composite solid electrolyte membrane rich in a hydrogen bond network, characterized in that, It is prepared by using the preparation method of the composite solid electrolyte membrane rich in hydrogen bond network described in any one of claims 1 - 7.

9. Application of a composite solid electrolyte membrane rich in a hydrogen bond network as a lithium battery electrolyte membrane, characterized in that, The composite solid electrolyte membrane rich in hydrogen bond network is the composite solid electrolyte membrane rich in hydrogen bond network described in claim 8.

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