Composite solid electrolyte containing oxygen-vacancy-rich filler and preparation method of composite solid electrolyte

Abstract

The invention discloses a composite solid electrolyte containing oxygen-vacancy-rich fillers and a preparation method thereof, the oxygen-vacancy-rich fillers (LnMCoxFe2-xO5 + delta, 0 < = x < = 2) and (Ln2-xMxNiO4 + delta, 0 < = x < = 2) are prepared by a sol-gel method, Ln comprises but is not limited to Pr, Gd, Sm, Tb, Dy, Ho and La; m is Ba, Sr or the like. The preparation method of the composite solid electrolyte comprises the following steps: mixing a basic polymer, a lithium salt and the oxygen vacancy-enriched perovskite powder filler, using anhydrous acetonitrile as a solvent, uniformly stirring, and pouring to form a film. In addition, the invention also relates to an all-solid-state lithium metal battery which contains the composite solid electrolyte, and an active substance of a positive electrode material is one of nickel cobalt manganese (NCM, Ni > = 0.8) or a lithium iron phosphate (LiFePO4) material. The composite solid electrolyte prepared by the method has high ionic conductivity, good interface stability and thermal stability, and is suitable for a wide-temperature-range all-solid-state lithium metal battery with rate capability and long service life.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state lithium metal batteries, and in particular to a method for preparing an oxygen-rich vacancy filler for a composite solid-state electrolyte. Background Art

[0002] With the growing global demand for clean energy and sustainable development, the markets for new energy vehicles and smart devices are experiencing rapid expansion. The development of these industries poses unprecedented challenges to battery technology, particularly in terms of energy density, safety, and lifespan. All-solid-state lithium batteries, due to their exceptional performance in these areas, have garnered industry attention. With its high energy density, exceptional safety, and ultra-long cycle life, this battery technology is considered a revolutionary direction for future power battery technology.

[0003] Compared with traditional liquid electrolyte lithium-ion batteries, all-solid-state batteries abandon flammable and toxic organic solvents and use solid electrolytes instead. This shift not only significantly improves the safety of batteries in the face of potential thermal runaway risks, but also greatly increases the energy density of batteries, which is expected to reach 500Wh / kg. -1 From a practical application perspective, the development of all-solid-state battery technology is of great significance for improving battery safety, extending service life, and increasing energy efficiency. It not only meets the demands of modern electronic devices for smaller size and longer battery life, but also provides a safer and more reliable energy solution for applications with stringent endurance requirements, such as electric vehicles. Furthermore, breakthroughs in all-solid-state battery technology will drive advances in related materials science, interface science, and manufacturing technologies, profoundly impacting the future development of the entire new energy industry. As these technologies continue to mature and be applied, we can expect a cleaner, more efficient, and more sustainable energy future.

[0004] In all-solid-state lithium metal batteries, all-solid electrolytes (SSEs) are an important component, which can be classified into polymer solid electrolytes (SPEs), inorganic solid electrolytes (ISEs), and composite solid electrolytes (CSEs) according to their components. Among them, composite solid electrolytes better combine the flexibility of polymers and the high mechanical strength of inorganic materials, and can have high ionic conductivity while retaining the flexibility of membrane materials. In addition, the preparation process of CSEs is simple and efficient, and can be well compatible with existing production processes, and has great potential for commercial application. However, CSEs still have many practical problems: the inter-ionic interaction in the solid electrolyte is strong, and the ion migration energy barrier is high, so the ionic conductivity is low; in addition, the solid-solid interface stability problem involves the compatibility between the electrolyte and the high-energy electrode material, as well as the physical and chemical stability during the charge and discharge process, which has become an obstacle to the further development of high-energy-density all-solid-state lithium batteries. Therefore, optimizing the solid-solid contact interface problem of all-solid-state lithium batteries and improving ionic conductivity and electrochemical stability are major challenges facing the development of high-energy all-solid-state lithium batteries. Existing patents have made some optimizations and improvements:

[0005] A Chinese invention patent (CN 118336087 A) discloses a method for preparing and applying a composite solid electrolyte with polyethylene oxide (PEO) as a matrix and basalt as a filler. A PEO-based basalt composite solid electrolyte was successfully prepared by mixing and pouring basalt turbidity with PEO dispersed in an organic solvent. This method improves the mechanical strength of CSEs and reduces the risk of lithium dendrite puncture, thereby enhancing battery safety. However, the inorganic components used in this patent are complex, and it may be difficult to ensure the consistency of the electrolyte membrane properties and adapt to the needs of mass production, which limits its potential in large-scale commercial applications. Maintaining the consistency of the electrolyte membrane properties at the same time limits its use.

[0006] A Chinese invention patent (CN 118738524 A) proposes a method for preparing a high-dielectric composite solid electrolyte and an integrated all-solid-state battery. This method incorporates dielectric ceramic fillers into a mixed electrolyte solution and combines this with an electrospinning process to produce the composite solid electrolyte. While the optimized CSEs material effectively reduces the interfacial impedance between the cathode and electrolyte, it still faces challenges such as low ionic conductivity and scalable production.

[0007] The Chinese invention patent (CN 202411104378.6) uses polyimidazole salts and modified mesoporous molecular sieves as additives for solid electrolyte membranes. Through the synergistic effect with the pore structure of the modified mesoporous molecular sieve, the mechanical strength of the solid polymer electrolyte is enhanced, and the ionic conductivity and cycle stability of the lithium-ion battery are improved. However, the controlled synthesis process of the polyimidazole salts and mesoporous molecular sieves is complex and easily generates by-products.

[0008] A Chinese invention patent (CN 118448710 A) reports the use of a specific dielectric glass material as a sintering aid. After sintering, it fills the gaps between solid electrolyte grains, enabling interconnectivity between the grains and improving the ionic conductivity, air stability, and mechanical strength of CSEs. However, this patent does not address the issue of poor solid-solid interface contact, a significant obstacle to the development of high-energy-density all-solid-state lithium batteries.

[0009] While the optimization strategies for CSEs proposed in the aforementioned patents address certain issues with solid-state electrolytes to a certain extent, they fail to fully address practicality and overlook the limitations of the process flow. These limitations restrict the feasibility of large-scale production and also present difficulties in practical application at room temperature. Therefore, in order to promote the development of high-energy all-solid-state lithium batteries, it is necessary to further optimize the solid-solid contact interface in CSEs and improve ionic conductivity and electrochemical stability, which is a major challenge currently faced. Summary of the Invention

[0010] Solid-state electrolytes directly contact the cathode active material and the lithium metal anode, and the microscopic characteristics of their solid-solid interface are closely related to the electrochemical performance. Furthermore, the composition of CSEs determines their inherent properties, including ionic conductivity, electrochemical stability, and compatibility with high-voltage cathode materials. These properties directly affect the chemical reactions during the charge and discharge process of all-solid-state batteries at different temperatures, significantly affecting the battery's cycling stability.

[0011] To overcome the limitations of the existing technology, the present invention innovatively develops a high-performance composite solid electrolyte containing a perovskite filler rich in oxygen vacancies and applies it to all-solid-state lithium metal batteries. This oxygen-vacancy-rich perovskite filler has a unique ferromagnetic effect. By carefully designing its surface properties and combining it with a charge compensation mechanism, the oxygen vacancy concentration can be effectively controlled. This method not only enables the preparation of low-cost, high-performance composite solid electrolytes, but also significantly improves battery safety, extends its service life, and improves energy efficiency. This not only enables it to meet the needs of modern electronic devices for smaller size and longer battery life, but also provides a safer and more reliable solution for applications such as electric vehicles that have strict requirements for battery life.

[0012] To achieve the above object, the present invention adopts the following technical solutions:

[0013] The present invention adds LnMCo to the polymer-based solid electrolyte x Fe 2-x O 5+δ Type and Ln 2-x M x NiO 4+δThe use of oxygen-rich vacancy fillers as fillers significantly improves the ionic conductivity and electrochemical stability of CSEs and optimizes the solid-solid contact interface of all-solid-state lithium batteries. The base polymer includes lithium salts including but not limited to LiClO4, LiAsF4, LiPF6, LiBF4, etc.

[0014] Furthermore, the polymer matrix is ​​one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA).

[0015] Furthermore, filler LnMCo x Fe 2-x O 5+δ and Ln 2-x M x NiO 4+δ Where Ln is Pr, Gd, Sm, Tb, Dy, Ho, La, etc., and M is Ba, Sr, etc.

[0016] Furthermore, LnMCo x Fe 2-x O 5+δ and Ln 2-x M x NiO 4+δ In the equation ( ), 0≤x≤2.

[0017] Furthermore, the addition amount of the oxygen-rich vacancy filler accounts for 1–30 wt.% of the total mass of the composite solid electrolyte.

[0018] The present invention also provides a method for preparing the composite solid electrolyte as described above, comprising thoroughly mixing a base polymer, a lithium salt, and the oxygen-vacancy-rich perovskite powder filler in an anhydrous acetonitrile solvent, stirring the mixture, and casting the mixture into a film to obtain the composite solid electrolyte.

[0019] The present invention also provides an all-solid-state lithium metal battery, characterized in that the all-solid-state battery uses the composite solid electrolyte as described above.

[0020] Furthermore, the positive electrode active material used is NCM (Ni≥0.8) nickel-cobalt-manganese ternary material or lithium iron phosphate (LiFePO4) material with a loading of 2-10 mg cm -2 .

[0021] Compared with the prior art, the present invention has the following obvious outstanding substantial features and significant advantages:

[0022] 1. Provides a preparation scheme for a composite solid electrolyte containing oxygen-rich vacancy fillers, using polymer solid electrolyte as the matrix, by introducing a series of LnMCo x Fe 2-x O5+δ Type and Ln 2-x M x NiO 4+δ type oxygen-rich vacancy filler to construct a composite solid electrolyte system.

[0023] 2.LnMCo x Fe 2-x O 5+δ The oxygen-rich vacancy filler is adjusted by adjusting the concentration gradient of Ln element, Co and Fe; Ln 2- x M x NiO 4+δ The oxygen-rich vacancy filler is prepared by gradient adjustment of Ln and M elements. Diversified oxygen-rich vacancy fillers with different oxygen vacancy contents and ferromagnetic effects are prepared. At the same time, the special distribution of this oxygen-rich vacancy filler provides a channel for the rapid migration of lithium ions in the material, thereby greatly promoting the diffusion of ions in the composite electrolyte phase and providing more surface active sites required for the reaction.

[0024] 3. The polarization-induced effect of the oxygen-rich vacancy filler under the action of the electric field can interact with the polymer chain and the lithium salt anion, promoting the dissociation of the lithium salt, thereby improving the ionic conductivity and the battery's rate performance and charge and discharge capacity at room temperature.

[0025] 4. This method of designing specific oxygen-rich vacancy fillers and introducing composite solid electrolytes into all-solid-state lithium metal batteries has extremely high potential application value in other types of energy storage systems or energy catalysis.

[0026] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of the oxygen-rich vacancy filler of the present invention;

[0028] Figure 2 The oxygen-rich vacancy filler PrBaFe2O prepared in Example 1 of the present invention 5+δ X-ray diffraction (XRD) pattern of powder;

[0029] Figure 3 It is PrBaFe2O in Example 1 of the present invention. 5+δ Cross-sectional scanning electron microscopy (SEM) image of the composite solid electrolyte prepared with oxygen-rich vacancy fillers;

[0030] Figure 4 This is an electrochemical stability window test of the Li||SS symmetrical battery assembled in Example 1 of the present invention;

[0031] Figure 5 This is the EIS impedance curve of the SS||SS symmetrical battery assembled in Example 2 of the present invention at 30°C;

[0032] Figure 6 The long cycle performance of the Li||Li symmetrical battery assembled in Example 2 of the present invention;

[0033] Figure 7 The long cycle performance of the Li||LFP full battery assembled in Example 2 of the present invention at 30°C;

[0034] Figure 8 The rate performance of the Li||Li symmetrical battery assembled in Example 3 of the present invention;

[0035] Figure 9 The long cycle performance of the Li||NCM full battery assembled in Example 3 of the present invention;

[0036] Figure 10 This is the long cycle performance of the Li||Li symmetrical battery assembled in Example 4 of the present invention at 30°C.

[0037] Figure 11 The Ln-containing 2-x M x NiO 4+δ X-ray diffraction (XRD) patterns of composite solid electrolytes containing oxygen vacancy-rich filler powders;

[0038] Figure 12 This is a cross-sectional scanning electron microscope (SEM) image of the composite solid electrolyte in Example 5 of the present invention;

[0039] Figure 13 This is the EIS impedance curve of the SS||SS symmetrical battery assembled in Example 5 of the present invention at 30°C;

[0040] Figure 14 This is an electrochemical stability window test of the Li||SS symmetrical battery assembled in Example 5 of the present invention;

[0041] Figure 15 The long cycle performance of the Li||Li symmetrical battery assembled in Example 6 of the present invention;

[0042] Figure 16 This is the long cycle performance of the Li||LFP all-solid-state battery assembled in Example 6 of the present invention at 60°C and 0.5C conditions. DETAILED DESCRIPTION

[0043] The following describes several preferred embodiments of the present invention with reference to the accompanying drawings to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the scope of protection of the present invention is not limited to the limited embodiments mentioned herein.

[0044] Comparative Example:

[0045] 1. Weigh 0.88 g of polyethylene oxide (PEO) and 0.72 g of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) into sample bottle A, add 20 mL of anhydrous acetonitrile solvent and stir thoroughly for 6 h.

[0046] 2. Pour the mixed slurry A onto a release paper (PET) sheet and apply it with a doctor blade. Then, place the PET sheet on a 60°C heating plate to dry for 48 hours. Cut the dried solid electrolyte membrane into 19 mm diameter discs for subsequent use.

[0047] 3. Assemble the battery from bottom to top in the following order: a 2032 stainless steel positive electrode battery case, a stainless steel gasket, a lithium metal disc (or a positive electrode sheet, a stainless steel sheet - SS), the solid electrolyte membrane, a second lithium metal sheet, a stainless steel current collector and spring, and a negative electrode battery case. The battery is packaged on a press to obtain an all-solid-state lithium metal battery. The assembled battery is activated in a 60°C oven for 12 hours before testing.

[0048] 4. Use the Princeton electrochemical workstation and LAND battery testing system to conduct comprehensive electrochemical performance tests on the assembled all-solid-state lithium battery at different temperatures (30-80°C), and set the test parameters as needed.

[0049] Example 1:

[0050] 1. Preparation of composite solid electrolyte I:

[0051] (a) First, oxygen vacancy-rich powder fillers (PrBaFe2O 5+δ ), 9.27 g, 5.57 g and 12.21 g of praseodymium nitrate, barium nitrate and ferric nitrate were weighed and dissolved in 100 mL of deionized water, 24.90 g of chelating agent EDTA and 26.86 g of citric acid were added and stirred evenly, and then the pH of the solution was adjusted to about 10 with ammonia water. After stirring and evaporation to form a gel, it was placed in a 140 ° C oven for thermal expansion, and then transferred to a 400 ° C muffle furnace for 6 hours to remove organic matter. The above product was ground and sintered at 1100 ° C for 12 hours to obtain the oxygen vacancy-rich powder filler (PrBaFe2O 5+δ ).

[0052] (b) The ingredients and preparation method in sample bottle A were the same as those in the comparative example, except that 150 mg of the above-mentioned filler powder and 10 mL of anhydrous acetonitrile were added to sample bottle B and stirred for 4 h. A and B were mixed into slurry C and stirred for another 3 h. All components in the composite solid electrolyte precursor slurry C were well dispersed.

[0053] (c) The casting, coating, drying and cutting of the composite solid electrolyte I are the same as those in the comparative example.

[0054] 2. The assembly method and materials used for the all-solid-state lithium battery are the same as those in the comparative example, except that the electrolyte membrane used is the composite solid electrolyte I prepared in step 1.

[0055] 3. The battery test conditions and ambient temperature are the same as those of the comparative example.

[0056] Example 2:

[0057] 1. Preparation of Composite Solid Electrolyte II: The method is basically the same as that in Example 1, except that the oxygen vacancy powder filler is PrBaCoFeO 5+δ 9.14 g, 5.50 g, 6.12 g and 8.49 g of praseodymium nitrate, barium nitrate, cobalt nitrate and ferric nitrate were weighed and dissolved in 100 mL of deionized water, respectively. The weights of the complexing agents EDTA and citric acid were 24.60 g and 26.48 g, respectively. In addition, the muffle furnace sintering temperature was 1000 ° C, and the mass of the filler powder in the composite solid electrolyte was 225 mg.

[0058] 2. The assembly method and materials used for the all-solid-state lithium battery are the same as those in the comparative example, except that the electrolyte membrane used is the composite solid electrolyte II prepared in step 1.

[0059] 3. The battery performance test steps are basically the same as those in Example 1.

[0060] Example 3:

[0061] 1. Preparation of Composite Solid Electrolyte III: The method is basically the same as that in Example 2, except that the oxygen-rich vacancy powder filler is PrBaCo2O 5+δ The mass of cobalt nitrate weighed is 12.24g.

[0062] 2. The assembly method and materials used for the all-solid-state lithium battery are the same as those in the comparative example, except that the electrolyte membrane used is the composite solid electrolyte III prepared in step 1.

[0063] 3. The battery performance test steps are consistent with those in Example 1.

[0064] Example 4:

[0065] 1. Preparation of composite solid electrolyte IV. The preparation method is basically the same as that of Example 1, except that the oxygen vacancy powder filler component is LaSrCo2O 5+δ .

[0066] 2. The assembly method and materials used for the all-solid-state lithium battery are the same as those in the comparative example, except that the electrolyte membrane used is the composite solid electrolyte IV prepared in step 1.

[0067] 3. The battery performance test steps are basically the same as those in Example 1.

[0068] Example 5:

[0069] 1. Preparation of Composite Solid Electrolyte V. The difference from Example 1 is that the raw materials used are Pr(NO3)3.6H2O and Ni(NO3)2.6H2O, and the calcination time is 5h to obtain the desired oxygen-rich vacancy Pr2NiO 4+δ Phase-forming powder.

[0070] 2. The assembly method and materials used for the all-solid-state lithium battery are the same as those in the comparative example, except that the electrolyte membrane used is the composite solid electrolyte V prepared in step 1.

[0071] 3. The battery performance test steps are basically the same as those in Example 1.

[0072] Example 6:

[0073] 1. Preparation of Composite Solid Electrolyte VI. The difference from Example 5 is that the raw materials used are Pr(NO3)3·6H2O, Sr(NO3)2 and Ni(NO3)2·6H2O. The calcination time is 5h to obtain the required oxygen-rich vacancy Pr 0.5 Sr 1.5 NiO 4+δ Phase-forming powder.

[0074] 2. The assembly method and materials used for the all-solid-state lithium battery are the same as those of the comparative example, except that the electrolyte membrane used is the composite solid electrolyte VI prepared in step 1.

[0075] 3. The battery performance test steps are basically the same as those in Example 1.

[0076] Evaluation and analysis of test results

[0077] Figure 1 The schematic diagram of the double-layer perovskite structure. The A-site elements of the double perovskite material are highly ordered. 3+ and M 2+They occupy the A-site lattice in an orderly manner and form alternating layers along the c-axis, and the oxygen vacancies are completely concentrated in the rare earth ion layer. The ideal structure of this type of compound is [CoO2][MO][FeO 2-δ ][LnO δ ]……are stacked sequentially, and in [LnO δ The oxygen vacancies in the layer also show a strong, ordered trend. This special distribution of oxygen vacancies in the layered perovskite provides channels for the rapid migration of oxygen ions in the material, thereby greatly promoting the diffusion of oxygen ions in the material and potentially providing more surface active sites required for reactions.

[0078] Figure 2 For the PrBaFe2O 5+δ From the XRD pattern of the oxygen-rich vacancy powder, it can be found that the characteristic diffraction peaks of the prepared oxygen-rich vacancy material completely correspond to those of the standard card, indicating that pure double perovskite crystal powder has been obtained.

[0079] Figure 3 The PrBaFe2O 5+δ From the cross-sectional SEM image of the composite solid electrolyte prepared with oxygen-rich vacancy powder, it can be found that its thickness is about 90 microns, and the added oxygen-rich vacancy powder filler is dispersed in it.

[0080] Figure 4 The composite solid electrolyte I prepared in Example 1 was assembled into a Li||SS battery. The electrochemical stability window was tested using a Princeton electrochemical workstation. It was found that Example 1 had an electrochemical stability potential expanded to 5.3 V, which was approximately 0.5 V higher than that of the comparative example, indicating that the introduction of oxygen-rich vacancy powder filler improved the high-voltage tolerance of the composite solid electrolyte.

[0081] Figure 5 The EIS impedance data of the SS||SS battery assembled with the composite solid electrolyte II prepared in Example 2 was tested at 30°C, from which the ionic conductivity of the solid electrolyte membrane (negatively correlated with the impedance value) can be calculated. As can be seen from the figure, under the same test conditions, the impedance value corresponding to the semicircle in the electrochemical impedance spectrum of Example 2 is about 7 times smaller than that of the comparative example, indicating that its lithium ion conductivity has been greatly improved.

[0082] Figure 6 The Li||Li battery assembled using the composite solid electrolyte II prepared in Example 2 was heated at 60°C with a current density of 0.1 mA cm –2 Under the test conditions, Example 2 can stably cycle for more than 3000 hours, while the comparative example can only work for 260 hours, indicating that the composite solid electrolyte has excellent electrochemical stability.

[0083] Figure 7 The long cycle performance of the Li||LFP full battery assembled using the composite solid electrolyte II prepared in Example 2 was tested at a current density of 0.5C in a 30°C environment. It can be seen that after 500 cycles, Example 2 still maintained a specific capacity of about 125 mAh per gram, with a retention rate of about 90%. At the same time, the average coulombic efficiency was 99.9%, while the capacity of the comparative example decayed rapidly and the coulombic efficiency was low, indicating that the composite solid electrolyte has a positive effect on improving the room temperature cycle performance of the battery and the interface compatibility with the positive electrode material.

[0084] Figure 8 The rate performance of the Li||Li symmetrical battery assembled using the composite solid electrolyte III prepared in Example 3 is shown. It can be seen that the rate performance of the Li||Li symmetrical battery is significantly improved when the current density is increased from 0.05 to 0.3 mA cm –2 During the continuous improvement of the battery capacity, the battery can still maintain a stable cycle, which shows that the solid electrolyte has excellent high current tolerance and excellent electrochemical stability.

[0085] Figure 9 The long cycle performance of the Li||NCM full battery assembled using the composite solid electrolyte III prepared in Example 3 is shown. Under 60°C conditions, in the voltage range of 3.0-4.3V, the coulombic efficiency of the battery is stable, and after 200 cycles, it can still provide a specific capacity of about 110 mAh per gram, indicating that the composite solid electrolyte has good high-voltage positive electrode matching characteristics, which is of positive significance for achieving higher energy density.

[0086] Figure 10 The long cycle performance of the assembled Li||Li symmetric battery at 30°C is shown in Figure 2. –2 At a current density of , the Li||Li symmetric battery in Example 4 can maintain a low polarization voltage and stably cycle for more than 500 hours, while the comparative example short-circuit occurs in less than 50 hours of operation, indicating that the composite electrolyte improves lithium ion transfer at lower temperatures and the ion transfer process has a lower energy barrier.

[0087] Figure 11 The Ln-containing 2-x M x NiO 4+δ From the X-ray diffraction (XRD) pattern of the composite solid electrolyte of the oxygen vacancy filler powder, it can be found that the characteristic peaks of the composite solid electrolyte completely correspond to the characteristic diffraction peaks of the standard card of the raw materials contained, indicating that the modified composite solid electrolyte has been successfully prepared.

[0088] Figure 12This is a cross-sectional scanning electron microscope (SEM) image of the composite solid electrolyte in Example 5 of the present invention. It can be found that its thickness is about 107 microns, and the added oxygen vacancy-rich perovskite powder filler is uniformly distributed in the polymer phase.

[0089] Figure 13 This is the EIS impedance curve of the SS||SS symmetrical battery assembled in Example 5 of the present invention at 30°C. The composite solid electrolyte obtained in Example 5 exhibits significantly reduced resistance, indicating that its ionic conductivity has been improved.

[0090] Figure 14 The electrochemical stability window test of the Li||SS symmetric battery assembled in Example 5 of the present invention shows that Example 5 has an electrochemical stability potential extended to 5.1V, which indicates that the introduction of oxygen vacancy-rich powder filler improves the stability of the composite solid electrolyte at high voltage and prevents its decomposition trend;

[0091] Figure 15 The long-cycle performance of the Li||Li symmetrical battery assembled in Example 6 of the present invention is shown. At a current density of 0.1 milliamperes per square centimeter, the composite solid electrolyte prepared in Example 6 can maintain a low polarization voltage and operate stably for more than 900 hours, which is much higher than the 150 hours of the comparative example, demonstrating excellent cycle stability.

[0092] Figure 16 The long cycle performance of the Li||LFP all-solid-state battery assembled in Example 6 of the present invention at 60°C and 0.5C conditions can be seen from the figure. After 100 cycles, the solid-state battery using the composite solid electrolyte in Comparative Example 6 still maintains 135 mAh g -1 In sharp contrast, the control group shows a lower initial discharge specific capacity, and the capacity decays rapidly to the point where it cannot maintain normal operation after about 20 cycles, which shows that the modified composite solid electrolyte has excellent advantages in improving battery capacity and cycle stability.

[0093] According to the comparison of Examples 1-6 and the comparative example presented above, it can be found that the composite solid electrolytes prepared by double perovskite fillers of different components or mass ratios have the effect of improving electrochemical stability and widening the electrochemical window. Under various test conditions, not only high ionic conductivity is achieved, but also good coulombic efficiency and stable cycle are exhibited, which proves the effectiveness of this series of double perovskite fillers in improving the electrochemical performance of all-solid-state lithium metal batteries.

[0094] Beneficial effects of the present invention

[0095] In summary, in terms of mechanism of action, the LnBaCo xFe 2-x O 5+δ (0≤x≤2) and Ln 2-x M x NiO 4+δ The polarization effect of the (0≤x≤2) oxygen-rich vacancy filler can interact with the polyethylene oxide (PEO) in the composite solid electrolyte to form an intermolecular interaction, adjust the microstructure of the electrolyte, reduce the coordination of lithium ions with PEO, and promote the dissociation of lithium ions. By forming a specific microstructure (fast ion transport channel) to promote ion transport, the double perovskite filler makes the composite solid electrolyte have higher ionic conductivity, and the optimized ion transport path improves the charge and discharge rate and cycle performance of the battery. At the same time, the interfacial potential difference between the composite solid electrolyte and the positive electrode active material is reduced, and the solid-solid interface contact is good. The rigid double perovskite powder filler also improves the electrochemical window of the electrolyte, making it stable over a wider voltage range and the enhanced mechanical properties are particularly important for preventing physical damage to the battery during long-term use.

[0096] The innovation of the present invention is that the LnBaCo x Fe 2-x O 5+δ (0≤x≤2) and Ln 2-x M x NiO 4+δ A method for preparing a composite solid electrolyte with (0≤x≤2) oxygen-vacancy fillers is described. A ferromagnetic double perovskite powder rich in oxygen vacancies is added as a functional filler to a polymer solid electrolyte, achieving efficient lithium ion transport through intermolecular interactions. The polarization-induced effect reduces the solid-solid interface impedance, enabling room-temperature operation of an all-solid-state lithium battery with a polymer-based composite electrolyte, with a capacity retention greater than 90% after 500 cycles. By utilizing the interaction between the oxygen-vacancy filler and the polymer, the high-voltage stability and Young's modulus of the composite solid electrolyte are improved, achieving a 5.3V electrochemical window and stable cycling of the all-solid-state lithium battery at 4.3V. The preparation method of this composite solid electrolyte is low-cost. The technological advancements and application prospects of this patent provide key improvements to all-solid-state lithium metal batteries and an effective solution for promoting large-scale applications.

[0097] The above describes in detail the preferred embodiments of the present invention. It should be emphasized that the above description is not intended to limit the present invention, and those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be obtained through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and on the basis of the existing technology, and any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention, shall be within the scope of protection determined by the claims.

Claims

1. A composite solid electrolyte comprising an oxygen-rich vacancy filler, characterized in that include: LnMc x Fe 2-x O 5+δ Type and Ln 2-x M x NiO 4+δ The invention relates to a composite material comprising a type oxygen-rich vacancy filler having a content of y wt.%; the base polymer used includes one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA); and further comprising a lithium salt having a content of z wt.%; wherein 0≤y≤30, 5≤z≤50.

2. The composite solid electrolyte according to claim 1, wherein The solvent for the base polymer was anhydrous acetonitrile.

3. The composite solid electrolyte according to claim 1, wherein The lithium salt is LiTFSI, LiClO4, LiAsF4, LiPF6, or LiBF4.

4. The composite solid electrolyte according to claim 1, wherein Ln is Pr, Gd, Tb, Dy, Ho or La; M is Ba or Sr.

5. The composite solid electrolyte according to claim 1, wherein 0≤x≤2。 6. A method for preparing the composite solid electrolyte as claimed in claim 1, characterized in that The following steps are involved: (a) LnMCo synthesized as needed x Fe 2-x O 5+δ and Ln 2-x M x NiO 4+δ Chemical formula, weigh the nitrate or sulfate of the corresponding metal ion according to the stoichiometric ratio, mix, add deionized water and stir to dissolve, to obtain solution A; (b) heating and stirring the above solution A on a magnetic stirrer at a temperature of 60 to 100° C. and adding a complexing agent, ethylenediaminetetraacetic acid (EDTA) and citric acid monohydrate, at a molar ratio of 1:1:1.5 to the total metal ion to obtain solution B; (c) adding aqueous ammonia to the above solution B to adjust its pH to 7-10, evaporating the water until gel C is formed, drying the gel in an oven at 150-180°C for 12-24 hours, and calcining the gel at 350-500°C in air for 4-10 hours to remove organic matter and obtain residue D; (d) grinding the residue D in a mortar and calcining at 800-1300° C. for 8-12 h to obtain an oxygen vacancy-rich powder filler; (e) mixing a base polymer and a lithium salt in a fixed ratio in a sample bottle A, wherein the molar ratio of the base polymer and the lithium salt is 3:1 to 20:1; placing an oxygen-rich vacancy powder filler in a desired ratio in a sample bottle B, and using anhydrous acetonitrile as the solvent in the sample bottles A and B, and stirring at a constant temperature until the solution is completely uniform, wherein the heating temperature is 40 to 90° C. and the stirring time is 1 to 6 hours; (f) Mixing the sample solutions A and B and continuing to stir thoroughly to obtain sample C, with the stirring time controlled to be 4 to 10 hours; (g) The sample C is cast on a high-molecular-weight PET plate or a glass plate and dried naturally to form a film with a film thickness of 20-200 μm.

7. An all-solid-state lithium metal battery, characterized in that: The all-solid-state battery contains the composite solid electrolyte according to any one of claims 1 to 5.

8. The all-solid-state lithium metal full battery according to claim 7, wherein: The active material of the cathode material used is one of nickel cobalt manganese (NCM, Ni ≥ 0.8) or lithium iron phosphate (LiFePO4) materials, with a loading of 2-10 mg cm -2 .

Images