Composite solid-state electrolyte with dielectric filler induced phase transition and mixed phase interface method

Abstract

The application discloses a method for composite solid electrolyte and dielectric filler induced phase transition and mixed phase interface, wherein the preparation method of the composite solid electrolyte comprises the following steps: W1, adding the dielectric filler into a grinding container containing a trace amount of solvent dimethylformamide, and obtaining a white suspension after grinding; W2, dissolving polyvinylidene fluoride and lithium bisfluorosulfonylimide salt by using dimethylformamide, and stirring for 2-6 hours to obtain a uniform transparent solution; W3, adding the white suspension obtained in the step W1 into the uniform transparent solution, and stirring for 6-12 hours to obtain a uniform precursor solution A; and W4, pouring the precursor solution A into a glass container, and then drying in a drying device for 20-24 hours to obtain the composite solid electrolyte. The method can improve the ionic conductivity of the composite solid electrolyte, realize high ionic transport flux, and inhibit the growth of lithium dendrites to realize high surface capacity operation of the solid-state battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and specifically to a method for inducing phase transition and mixing phase interfaces between a composite solid electrolyte and a dielectric filler. Background Technology

[0002] With the development of new energy vehicles, the requirements for battery energy density are becoming increasingly stringent. Matching a high-capacity, high-nickel ternary cathode (NCM811) with a lithium metal anode can achieve high energy density. However, when using liquid electrolytes, safety issues such as gas release and thermal runaway occur in NCM811 / Li batteries. Compared to liquid electrolytes, solid-state electrolytes (SSEs) can address these challenges due to their high safety and electrochemical stability. Among various SSEs, solid polymer electrolytes (SPEs) are considered the most likely candidates for commercial solid-state batteries due to their good interfacial compatibility, flexibility, and large-scale fabrication capabilities. However, the low room-temperature ionic conductivity and poor mechanical properties of SPEs severely hinder their practical application. In contrast to SPEs, composite solid electrolytes (CSEs), which combine polymers and inorganic ceramics, can achieve high ionic conductivity and high mechanical strength, and are considered the most promising candidates for the practical application of solid-state batteries. Currently, various fillers are used to improve the ionic conductivity and mechanical strength of composite solid electrolytes, thereby enhancing the electrochemical performance of solid-state batteries. However, when using high areal capacity cathodes to increase the energy density of solid-state batteries, the batteries fail quickly. Generally, high areal capacity cathodes require a solid electrolyte interphase (SEI) at the electrolyte-electrode interface to meet high ion transport flux. However, current conventional SEIs, due to their low ionic conductivity, poor kinetic performance, and low mechanical strength, are difficult to meet the requirements for achieving high ion transport flux, which affects battery energy density and causes lithium dendrite growth and uneven lithium deposition. Summary of the Invention

[0003] To address the problem that traditional solid electrolyte interface layers struggle to achieve high ion transport flux, thus affecting the energy density of solid-state batteries in practical applications, this invention proposes a method for inducing phase transition and mixing phase interfaces using composite solid electrolytes and dielectric fillers.

[0004] The technical problem of this invention is solved by the following technical solution:

[0005] A method for preparing a composite solid electrolyte, comprising the following steps:

[0006] W1: Add the dielectric filler to a grinding container containing a trace amount of dimethylformamide solvent, and grind to obtain a white suspension;

[0007] W2: Polyvinylidene fluoride and lithium bis(fluorosulfonyl)imide were dissolved in dimethylformamide and stirred for 2-6 hours to obtain a uniform and transparent solution.

[0008] W3: Add the white suspension to the uniform transparent solution and stir for 6-12 hours to obtain a uniform precursor solution A;

[0009] W4: Pour the precursor solution A into a glass container and then dry it in a drying device for 20-24 hours to obtain a composite solid electrolyte.

[0010] In some embodiments, the dielectric filler in step W1 is prepared by the following steps:

[0011] Step S1: Niobium pentoxide is added to sodium hydroxide solution at a predetermined molar ratio and stirred for 3-6 hours to obtain precursor solution B;

[0012] Step S2: Place the precursor solution B into a 50-100 mL high-pressure reaction vessel and react at 150-180°C for 4-8 hours to obtain precipitate A;

[0013] Step S3: Wash the precipitate A with deionized water several times until the supernatant of the solution is neutral to obtain precipitate B;

[0014] Step S4: Dry the precipitate B in a vacuum environment at 60-80°C for 12-24 hours to remove moisture and obtain dielectric filler.

[0015] In some embodiments, the dielectric filler is sodium niobate, which contains hydroxyl groups. The hydroxyl groups in the sodium niobate can form hydrogen bonds with the polyvinylidene fluoride chains in the composite solid electrolyte, inducing the formation of β-phase polyvinylidene fluoride.

[0016] In some embodiments, in step S1, the predetermined molar ratio is 15.6:1 to 15.7:1.

[0017] In some embodiments, in step W1, the grinding container is a ball mill jar, and the white suspension obtained after grinding is specifically obtained by ball milling at 400-500 r for 3-6 h.

[0018] The present invention also proposes a composite solid electrolyte, which is prepared using the composite solid electrolyte preparation method described above. The mass ratio of the components of the composite solid electrolyte is: polyvinylidene fluoride: lithium bis(fluorosulfonyl)imide: dimethylformamide: dielectric filler = 400:267:90:20.

[0019] In some embodiments, the dielectric filler is formed by filling the composite solid electrolyte as described above, participating in the construction of the solid electrolyte interface of the mixed phase to accelerate ion transport flux and induce phase transformation of the polymer matrix polyvinylidene fluoride to promote lithium salt dissociation and improve room temperature ionic conductivity.

[0020] In some embodiments, when the dielectric filler induces a mixed interface, the dielectric filler may undergo lithium-sodium displacement during battery cycling. The displaced sodium ions participate in the construction of the solid electrolyte interface, generating a lithium-sodium mixed fluorinated interface layer.

[0021] In some embodiments, when the dielectric filler induces a phase transition, the polymer matrix is ​​polyvinylidene fluoride and is in a composite solid electrolyte, and the dielectric filler can induce the polyvinylidene fluoride polymer in the composite solid electrolyte to transform into β-phase polyvinylidene fluoride.

[0022] The present invention also proposes a battery comprising a composite solid electrolyte as described above, a negative electrode composed of lithium metal, and a positive electrode composed of high-capacity nickel-cobalt-manganese oxide.

[0023] The beneficial effects of this invention include:

[0024] This invention proposes a composite solid electrolyte and its preparation method, which involves filling the composite solid electrolyte with a dielectric filler that can induce phase transition and mixed phase interface. The preparation method of the composite solid electrolyte is simple and efficient, and can effectively reduce production costs. The composite solid electrolyte prepared in this way has high dielectric constant, high lithium salt dissociation degree and high ionic conductivity, and can be matched with high areal capacity high nickel ternary cathode materials to improve the energy density of the battery. It has good market prospects and obvious technical and cost advantages.

[0025] This invention also proposes a method for inducing phase transformation and mixed phase interface with dielectric filler. The dielectric filler is formed by filling a prepared composite solid electrolyte. During electrochemical cycling, it participates in the construction of a mixed phase solid electrolyte interface to accelerate ion transport and increase the transport flux. It induces phase transformation of the polymer matrix polyvinylidene fluoride to promote lithium salt dissociation and improve room temperature ionic conductivity. It also inhibits the growth of lithium dendrites to achieve high-capacity operation of solid-state batteries.

[0026] The battery proposed in this invention can stably cycle 2200 times at 2C rate at room temperature with a capacity retention of 60%, and is matched with a high-load positive electrode of 10mg cm⁻¹. -2It can run stably for 150 cycles, and it has great potential for practical application.

[0027] In addition, some embodiments also have the following beneficial effects:

[0028] This dielectric filler contains hydroxyl groups, which can induce phase transitions in the polymer matrix, promote lithium salt dissociation, improve room temperature ionic conductivity, and homogenize lithium deposition to achieve large-capacity lithium deposition and stripping.

[0029] Other beneficial effects of the embodiments of the present invention will be further described below. Attached Figure Description

[0030] Figure 1 This is a flowchart of the steps in the preparation method of the composite solid electrolyte in this embodiment of the invention.

[0031] Figure 2 This is a flowchart of the steps in the preparation method of dielectric filler in an embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram illustrating the principle of sodium niobate, a dielectric filler, participating in the construction of a hybrid interface in an embodiment of the present invention.

[0033] Figure 4 This is a schematic diagram illustrating the principle of sodium niobate, a dielectric filler, inducing the phase transformation of polyvinylidene fluoride in an embodiment of the present invention.

[0034] Figure 5 This is the XRD pattern of sodium niobate, the dielectric filler prepared in the embodiments of the present invention.

[0035] Figure 6 This is a SEM image of sodium niobate, the dielectric filler prepared in the embodiments of the present invention.

[0036] Figure 7 This is the XRD pattern of the composite solid electrolyte prepared in the embodiments of the present invention.

[0037] Figure 8 This is a SEM image of the composite solid electrolyte prepared in the embodiments of the present invention.

[0038] Figure 9 This is a SEM image of the cross-section of the composite solid electrolyte obtained in the embodiments of the present invention.

[0039] Figure 10 This is a hysteresis curve obtained by piezoelectric force microscopy of the composite solid electrolyte prepared in the embodiments of the present invention.

[0040] Figure 11 This is a schematic diagram of the room temperature electrochemical performance of the composite solid electrolyte assembled coin cell obtained in the embodiments of the present invention.

[0041] Figure 12This is a schematic diagram of the room temperature electrochemical performance of the composite solid electrolyte assembled coin cell with high areal capacity obtained in the embodiments of the present invention. Detailed Implementation

[0042] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0044] This invention proposes a composite solid-state electrolyte, its preparation method, and a method for inducing phase transformation and mixed-phase interfaces using dielectric fillers. The dielectric filler in the composite solid-state electrolyte prepared in this invention is sodium niobate (NaNbO3), which can induce the formation of highly polar β-phase PVDF (in the crystal structure of PVDF, there are two morphologies: α-phase and β-phase. Among them, β-phase PVDF has higher polarity and is therefore more advantageous as an electrolyte material in solid-state lithium metal batteries). The highly polar β-phase PVDF promotes lithium salt dissociation, generating more free lithium ions and improving ionic conductivity. Simultaneously, during battery cycling, the dielectric filler sodium niobate (NaNbO3) can undergo lithium-sodium substitution (i.e., lithium ions can replace sodium ions in the NaNbO3 lattice). The substituted sodium ions participate in the construction of the solid-state electrolyte interface, generating a mixed interface rich in lithium fluoride and sodium fluoride, improving the interfacial ion transport rate, and enhancing the performance of solid-state batteries at high areal capacities in practical applications. Furthermore, the improved mixed interface composition can effectively address the shortcomings of traditional SEIs, such as poor kinetic performance and low mechanical strength.

[0045] like Figure 1 The diagram shown is a flowchart of the steps in the preparation method of the composite solid electrolyte in an embodiment of the present invention. As can be seen, this embodiment of the present invention proposes a method for preparing a composite solid electrolyte filled with dielectric filler, comprising the following steps:

[0046] W1: Sodium niobate (NaNbO3), which induces the phase transformation of polyvinylidene fluoride (PVDF) and mixes the interfacial dielectric filler, is added to a grinding container containing a trace amount of dimethylformamide (DMF). After grinding, a white suspension is obtained.

[0047] W2: Dissolve PVDF and lithium difluorosulfonamide in DMF and stir at room temperature for 2-6 hours to obtain a uniform, transparent solution;

[0048] W3: Add a certain amount of the white suspension obtained in step W1 to the uniform transparent solution and stir at room temperature for 6 to 12 hours to obtain a uniform precursor solution A;

[0049] W4: Pour the precursor solution A into a glass container and then dry it in a drying device for 20-24 hours to obtain a composite solid electrolyte.

[0050] Preferably, in step W1, the grinding container is a ball mill jar, and the white suspension obtained after grinding is obtained by ball milling at 400-500 r for 3-6 h. At the same time, the method for preparing the composite solid electrolyte may also include W5: punching the composite solid electrolyte membrane prepared in step W4 into round pieces of suitable size and storing them in a dry atmosphere for later use.

[0051] like Figure 2 The diagram shows a flowchart of the dielectric filler preparation method in an embodiment of the present invention. It can be seen that the dielectric filler in step W1 is prepared by the following steps:

[0052] Step S1: Niobium pentoxide is added to sodium hydroxide solution at a predetermined molar ratio and stirred at room temperature for 3-6 hours to obtain precursor solution B, wherein the predetermined molar ratio is 15.6:1 to 15.7:1.

[0053] Step S2: Place the precursor solution B into a 50-100 mL high-pressure reaction vessel and react at 150-180 °C for 4-8 h to obtain precipitate A.

[0054] Step S3: Wash the precipitate A with deionized water several times until the supernatant of the solution is neutral (pH=7), and the precipitate B is obtained.

[0055] Step S4: Dry precipitate B in a vacuum environment at 60-80℃ for 12-24 hours to remove moisture and obtain dielectric filler.

[0056] Preferably, the dielectric filler is sodium niobate, which contains abundant hydroxyl groups. The hydroxyl groups in the sodium niobate can form hydrogen bonds with the polyvinylidene fluoride chains in the composite solid electrolyte, inducing the formation of β-phase polyvinylidene fluoride. Step S2 is used to react and generate NaNbO3, step S3 is used to remove the alkaline environment in the preparation process, and step S4 is used to dry the sample to obtain a dry sample.

[0057] In this embodiment of the invention, the composite solid electrolyte prepared by the above-described composite solid electrolyte preparation method has the following composition mass ratio: vinylidene fluoride: lithium bis(fluorosulfonyl)imide: dimethylformamide: dielectric filler = 400: 267: 90: 20, and a thickness of 100-120 μm; it can be matched with high areal capacity high-nickel ternary cathode materials to improve energy density.

[0058] In this embodiment of the invention, lithium metal is used as the negative electrode, and a high-capacity nickel-cobalt-manganese oxide (LiNi) is employed. 0.8 Co 0.1 Mn 0.1 O2, NCM811; LiNi 0.9 Co 0.05 Mn 0.05 Using O2 and Ni90 as the positive electrode active material, this composite solid electrolyte is assembled to obtain a solid lithium metal battery. Due to the mixed phase interface rich in lithium fluoride and sodium fluoride constructed in situ between the electrolyte and lithium metal, and the high polarity β-phase PVDF promoting lithium salt dissociation and improving the ionic conductivity of the composite solid electrolyte, the cycling stability of the lithium metal battery matched with a high areal capacity positive electrode at room temperature can be significantly enhanced.

[0059] like Figure 3 The diagram illustrates the principle of sodium niobate, a dielectric filler, participating in the construction of a hybrid interface in an embodiment of the present invention. It shows that sodium niobate can undergo lithium-sodium substitution, and the substituted sodium and lithium ions react with bis(fluorosulfonyl)imide ions (FSI) at the interface. - The reaction produces lithium fluoride and sodium fluoride; for example... Figure 4The diagram illustrates the principle of sodium niobate-induced phase transition of vinylidene fluoride (PVDF) in an embodiment of the present invention. It shows that hydrogen bonds are formed between the hydroxyl groups on the surface of sodium niobate and the PVDF chains, inducing the formation of β-phase PVDF. Unlike existing research on fillers, this embodiment focuses on their role in interfacial reactions and regulation. To further improve the energy density of solid-state batteries, dielectric fillers are used to construct an SEI with rapid kinetic performance and high mechanical strength to achieve high ion transport flux. Based on the characteristics of sodium niobate in this embodiment of the invention—participating in the construction of a mixed-phase (rich in lithium fluoride and sodium fluoride) solid-state electrolyte interface during battery charge-discharge cycles and inducing phase transitions in the polymer matrix to promote lithium salt dissociation and improve room-temperature ionic conductivity—this embodiment of the present invention aims to propose a new method for designing fillers in composite solid-state electrolytes, and to provide a method for preparing a composite solid-state electrolyte with high interfacial stability and high ionic conductivity, and its application in the battery field. In this invention, sodium niobate, a dielectric filler, was found to participate in the construction of a high Young's modulus SEI layer rich in lithium fluoride (LiF) and sodium fluoride (NaF), accelerating ion transport at the interface and achieving high ion transport flux. Furthermore, this sodium niobate dielectric filler can induce a phase transition in the PVDF polymer matrix, generating a large amount of highly polar β-phase PVDF, promoting lithium salt dissociation and increasing room-temperature ionic conductivity. The method of using sodium niobate as a dielectric filler to construct a stable interface and enhance ion transport is simple to operate, low in cost, and easy to mass-produce. Moreover, the method proposed in this invention for in-situ construction of an interface layer and enhanced ion transport in composite solid-state electrolytes using low-cost sodium niobate dielectric filler has universality, enabling stable operation of solid-state batteries at high areal capacities, and will promote the industrialization of solid-state batteries.

[0060] Specifically, this invention proposes a composite solid electrolyte and its preparation method based on the design of filling a composite solid electrolyte with an induced mixed-phase interface dielectric filler. This significantly improves the cycle stability of high areal capacity in practical solid-state lithium metal batteries. The preparation process is simple and low-cost, making it suitable for large-scale production applications. Using this method, a composite solid electrolyte capable of in-situ construction of an interface layer and enhanced ion transport can be prepared by coupling a polymer matrix PVDF. The sodium niobate dielectric filler undergoes lithium-sodium substitution during cycling to generate Li. 0.025 Na 0.975 NbO3 (new substance), the Na that is displaced +It participates in the construction of the solid electrolyte layer (SEI), generating a mixed SEI rich in LiF and NaF in situ, accelerating lithium-ion transport at the interface to achieve high ion transport flux. Furthermore, the hydroxyl groups on the surface of the dielectric filler sodium niobate induce the formation of a high-dielectric β-phase PVDF, promoting lithium salt dissociation and improving the ionic conductivity of the composite solid electrolyte. This composite solid electrolyte enables lithium-lithium symmetric batteries to achieve high conductivity at 3 mAh / cm². -2 It can operate stably for 600 hours at its areal capacity. A solid-state battery assembled with an NCM811 cathode can operate stably for 2200 cycles at 2C. (The last sentence appears to be incomplete and possibly refers to a specific type of battery or technology.) -2 Under certain conditions, it can be stably cycled 150 times, which significantly improves the electrochemical performance of PVDF-based solid-state batteries at high areal capacity and will promote the industrialization of solid-state batteries.

[0061] like Figure 5 The image shown is the XRD (X-ray Diffraction) pattern of sodium niobate, a dielectric filler prepared in an embodiment of the present invention. It can be seen that sodium niobate, a dielectric filler, can be obtained through its preparation method.

[0062] like Figure 6 The image shown is an SEM (Scanning Electron Microscope) image of the dielectric filler sodium niobate prepared in the embodiment of the present invention. It can be seen that the particle size of the dielectric filler sodium niobate obtained by the preparation method is 0.5 to 1.5 μm.

[0063] like Figure 7 The image shown is the XRD pattern of the composite solid electrolyte prepared in the embodiments of the present invention. It can be seen that the NaNbO3 in the composite solid electrolyte prepared in the embodiments of the present invention (specifically, Experimental Example 2) affects the PVDF and LiFSI (… Lithium difluorosulfonylimide Salt DMF is very stable and does not cause side reactions.

[0064] like Figure 8 The image shown is a SEM image of the composite solid electrolyte prepared in the embodiment of the present invention. It can be seen that the composite solid electrolyte prepared in the embodiment of the present invention (specifically Experimental Example 2) is very dense, which is beneficial to suppressing the growth of lithium dendrites.

[0065] like Figure 9 The image shown is a SEM image of the cross-section of the composite solid electrolyte prepared in the embodiment of the present invention. It can be seen that the thickness of the composite solid electrolyte prepared in the embodiment of the present invention (specifically, Experimental Example 2) is 100-120 μm.

[0066] like Figure 10The figure shown is a hysteresis curve obtained by piezoelectric response force microscopy of the composite solid electrolyte prepared in the embodiment of the present invention. It can be seen that the composite solid electrolyte prepared in the embodiment of the present invention (specifically Experimental Example 2) is rich in β-phase PVDF.

[0067] This invention also proposes a method for inducing phase transition and mixed-phase interface using dielectric fillers. The composite solid electrolyte is prepared as described above. During battery cycling, the dielectric filler used to induce the mixed-phase interface in the composite solid electrolyte participates in constructing the mixed-phase solid electrolyte interface to accelerate ion transport flux and induces phase transition in the polymer matrix, promoting lithium salt dissociation and improving room-temperature ionic conductivity. Preferably, during battery cycling, the dielectric filler (sodium niobate) can undergo lithium-sodium substitution, with the displaced sodium ions participating in the construction of the solid electrolyte interface to generate a lithium-sodium mixed fluorinated interface layer. Preferably, the polymer matrix is ​​vinylidene fluoride and is located within the composite solid electrolyte; the dielectric filler can induce the PVDF polymer in the composite solid electrolyte to transform into β-phase PVDF.

[0068] This invention also proposes a battery comprising a composite solid electrolyte prepared as described above, a negative electrode composed of lithium metal, and a positive electrode composed of high-capacity nickel-cobalt-manganese oxide.

[0069] The advantages of the battery prepared in the embodiments of the present invention will be illustrated below through a comparison of Experiment 1 and Experiment 2:

[0070] Experimental Example 1

[0071] This experimental example 1 provides a method for preparing a PVDF solid electrolyte and assembling a full cell, which includes at least the following steps:

[0072] Step 1: Weigh 100mg PVDF (binder), 100mg SuperP (conductive carbon black), and 800mg NCM811 active material and grind them in a mortar for 20 minutes (this process needs to be carried out under infrared irradiation to reduce the influence of moisture in the air). After the three are thoroughly mixed, add 2.4mL NMP (N-methyl-2-pyrrolidone) and stir at room temperature for more than 6 hours.

[0073] Step 2: Coat the positive electrode slurry obtained in Step 1 onto aluminum foil, dry it at 60°C for more than 6 hours, cut it into appropriately sized round pieces to obtain the NCM811 positive electrode, and place it in a vacuum oven to dry and store it.

[0074] Step 3: First, weigh 267 mg of LiFSI under an inert atmosphere. Lithium difluorosulfonylimidePlace the mixture in a stirred flask, add 15 mL of DMF (dimethylformamide) and 400 mg of PVDF, and stir at room temperature for more than 2 hours on a small stirrer until LiFSI and PVDF are completely dissolved to obtain a uniform and transparent solution.

[0075] Step 4: Pour the solution obtained in Step 3 into a glass petri dish and dry it in a 55°C forced-air oven for 24 hours to remove excess DMF solvent, thereby obtaining an electrolyte membrane. Cut the membrane to the appropriate size, dry it under an inert atmosphere, and store it for later use.

[0076] Step 5: Assemble the NCM811 cathode, PVDF polymer electrolyte, and lithium metal into a full cell according to the battery assembly process.

[0077] Experiment Example 2

[0078] This experimental example 2 provides a method for preparing a composite solid electrolyte and assembling a full cell, which includes at least the following steps:

[0079] Step 1: Weigh 100mg PVDF (binder), 100mg SuperP (conductive carbon black), and 800mg NCM811 active material and grind them in a mortar for 20 minutes (this process needs to be carried out under infrared irradiation to reduce the influence of moisture in the air). After the three are fully mixed, add 2.4mL NMP and stir at room temperature for more than 6 hours.

[0080] Step 2: Coat the positive electrode slurry obtained in Step 1 onto aluminum foil, dry it at 60°C for more than 6 hours, cut it into appropriately sized round pieces to obtain the NCM811 positive electrode, and place it in a vacuum oven to dry and store it.

[0081] Step 3: First, weigh 267 mg of LiFSI under an inert atmosphere, place it in a stirred flask, add 15 mL of DMF and 400 mg of PVDF, and stir at room temperature for more than 2 hours with a small stirrer until LiFSI and PVDF are completely dissolved to obtain a uniform transparent solution.

[0082] Step four: Niobium pentoxide (Nb₂O₅) was added to a sodium hydroxide (NaOH) solution of a certain concentration according to the molar ratio, and stirred at room temperature for 3 hours to obtain precursor solution B. Precursor solution B was then placed in a 100 mL high-pressure reactor and reacted at 180 °C for 8 hours. The resulting precipitate was then washed several times with deionized water until the supernatant was neutral. Finally, the precipitate was dried in a vacuum oven at 80 °C for 12 hours to remove moisture, yielding NaNbO₃.

[0083] Step 5: Add NaNbO3 to the ball mill jar and ball mill at 400 rpm for 3 hours to obtain a white suspension.

[0084] Step six: Add 20 mg of NaNbO3 obtained in step five to the solution obtained in step three, stir at room temperature for more than 6 hours to obtain a uniform white suspension.

[0085] Step 7: Pour the solution obtained in Step 6 into a glass petri dish and dry it in a 55°C forced-air oven for 24 hours to remove excess DMF solvent, thereby obtaining an electrolyte membrane. Cut the membrane to the appropriate size, dry it under an inert atmosphere, and store it for later use.

[0086] Step 8: Assemble the NCM811 cathode, composite solid electrolyte, and lithium metal into a full battery according to the battery assembly process.

[0087] like Figure 11 The diagram shows the room-temperature electrochemical performance of a coin cell assembled with the composite solid electrolyte obtained in this embodiment of the invention (dark color represents the composite solid electrolyte, light color represents the PVDF polymer electrolyte). The comparison clearly shows that the battery assembled with the composite solid electrolyte exhibits long-cycle stability; simultaneously... Figure 12 The diagram shows the room-temperature electrochemical performance of the composite solid electrolyte assembled coin cells at high areal capacity in the embodiments of the present invention (dark color represents the composite solid electrolyte, light color represents the PVDF polymer electrolyte). The battery prepared in Example 1 exhibits rapid capacity decay after 200 cycles at 2C, while the battery prepared in Example 2 retains 60% of its capacity after 2200 cycles at 2C, and can maintain a high areal capacity of 10 mg / cm³. -2 After 150 stable cycles, the comparison shows that the battery assembled with this composite solid electrolyte can achieve high surface capacity operation.

[0088] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A method for preparing a composite solid electrolyte, characterized in that, The preparation of a composite solid electrolyte filled with dielectric filler includes the following steps: W1: Add the dielectric filler to a grinding container containing a trace amount of dimethylformamide solvent, and grind to obtain a white suspension; W2: Polyvinylidene fluoride and lithium bis(fluorosulfonyl)imide were dissolved in dimethylformamide and stirred for 2-6 h to obtain a uniform and transparent solution; W3: Add the white suspension to the uniform transparent solution and stir for 6-12 h to obtain a uniform precursor solution A; W4: Pour the precursor solution A into a glass container and then dry it in a drying device for 20-24 h to obtain a composite solid electrolyte; The dielectric filler is sodium niobate, which contains hydroxyl groups. The hydroxyl groups in the sodium niobate form hydrogen bonds with the polyvinylidene fluoride chains in the composite solid electrolyte, inducing the formation of β-phase polyvinylidene fluoride. During battery cycling, the dielectric filler undergoes lithium-sodium displacement, and the displaced sodium ions participate in the construction of the solid electrolyte interface, generating a lithium-sodium mixed fluorinated interface layer.

2. The method for preparing the composite solid electrolyte as described in claim 1, characterized in that, The dielectric filler in step W1 is prepared by the following steps: Step S1: Niobium pentoxide is added to sodium hydroxide solution at a predetermined molar ratio and stirred for 3-6 h to obtain precursor solution B; Step S2: Place the precursor solution B into a 50-100 mL high-pressure reaction vessel and react at 150-180 ℃ for 4-8 h to obtain precipitate A; Step S3: Wash the precipitate A with deionized water several times until the supernatant of the solution is neutral to obtain precipitate B; Step S4: Dry the precipitate B in a vacuum environment at 60~80 ℃ for 12~24 h to remove moisture and obtain dielectric filler.

3. The method for preparing the composite solid electrolyte as described in claim 2, characterized in that, In step S1, the predetermined molar ratio is 15.6:1 to 15.7:

1.

4. The method for preparing the composite solid electrolyte as described in claim 1, characterized in that, In step W1, the grinding container is a ball mill jar, and the white suspension obtained after grinding is specifically obtained by ball milling at 400~500 r for 3~6 h.

5. A composite solid electrolyte, characterized in that, The composite solid electrolyte is prepared using the method described in any one of claims 1-4, wherein the mass ratio of the components of the composite solid electrolyte is: polyvinylidene fluoride: lithium bis(fluorosulfonyl)imide: dimethylformamide: dielectric filler = 400:267:90:

20.

6. A method for inducing phase transformation and mixed phase interface using dielectric fillers, characterized in that, The dielectric filler is formed by filling the composite solid electrolyte as described in claim 5, participating in the construction of the solid electrolyte interface of the mixed phase to accelerate ion transport flux and induce phase transformation of the polymer matrix polyvinylidene fluoride to promote lithium salt dissociation and improve room temperature ionic conductivity.

7. The method for inducing phase transformation and mixed phase interface with dielectric filler as described in claim 6, characterized in that, When the dielectric filler induces a phase transition, the polymer matrix is ​​polyvinylidene fluoride and is in a composite solid electrolyte. The dielectric filler induces the polyvinylidene fluoride polymer in the composite solid electrolyte to transform into β-phase polyvinylidene fluoride.

8. A battery, characterized in that, The battery comprises a negative electrode consisting of a composite solid electrolyte as described in claim 5 and lithium metal, and a positive electrode consisting of a high-capacity nickel-cobalt-manganese oxide.

Images