Preparation method of high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte
By adding ferroelectric ceramic lithium tantalate to polymer electrolyte to regulate lithium deposition and enhance ion conduction, a high-ferroelectric polyvinylidene fluoride-lithium tantalate composite solid electrolyte was prepared, which solved the problems of poor interface stability and electrochemical performance of solid electrolytes and realized a solid battery with high safety and long cycle performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- TSINGHUA SHENZHEN INTERNATIONAL GRADUATE SCHOOL
- Filing Date
- 2023-05-30
- Publication Date
- 2026-07-31
AI Technical Summary
The poor stability of the interface between existing solid electrolytes and positive and negative electrodes, as well as their poor room-temperature electrochemical performance, lead to lithium dendrite growth and battery safety issues.
A high-ferroelectric polyvinylidene fluoride-lithium tantalate composite solid electrolyte was prepared by introducing lithium tantalate (LiTaO3) ceramic filler, which has both ferroelectric properties and ionic conductivity, into a polymer electrolyte. The lithium deposition was regulated by polarization and an additional ion conduction pathway was provided.
It significantly improves the stability of the electrolyte-electrode interface and room-temperature electrochemical performance, suppresses lithium dendrite growth, enhances battery safety and cycle performance, and is suitable for large-scale production.
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Figure CN116565300B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium metal solid-state battery technology, and in particular to a method for preparing a high-speed iron-electric polyvinylidene fluoride-lithium tantalate composite solid electrolyte. Background Technology
[0002] Since their commercialization, lithium-ion batteries (LIBs) have been widely used as key components in electronic devices such as smartphones, laptops, electric vehicles, and energy storage power stations. With the further development of information technology and mobility, higher demands are being placed on the safety performance and capacity of LIBs. This is due to the use of high-nickel ternary cathode materials (such as LiNi...) 0.8 Co 0.1 Mn 0.1 O2 and lithium metal anodes have high specific capacity, making the development of high-nickel ternary materials to match lithium metal batteries a major development direction for next-generation high-safety, high-capacity lithium batteries. However, lithium metal is highly reactive and readily undergoes a series of side reactions with traditional flammable organic electrolytes during cycling, leading to safety issues such as battery thermal runaway and explosions. In contrast, using solid-state electrolytes (SSEs) with high mechanical properties, good thermal stability, and electrochemical stability can effectively solve problems such as electrolyte-lithium metal reactions, increasing battery safety while improving battery energy density.
[0003] Solid-state electrolytes mainly include inorganic solid-state electrolytes, polymer electrolytes, and organic-inorganic composite solid-state electrolytes. From a cost and process perspective, polymer electrolytes are more valuable due to their flexibility, ease of preparation, and good contact with electrodes. However, the slow chain segment movement of polymer electrolytes at room temperature leads to poor room-temperature ionic conductivity, and the unstable interfacial chemistry easily forms lithium dendrites, which greatly limits the application development of polymer electrolytes. Typically, adding inorganic fillers to polymer electrolytes to form composite solid-state electrolytes can improve the ionic conductivity of composite electrolytes. Inorganic fillers can effectively reduce the crystallinity of polymers and increase the chain segment movement rate, thereby improving ionic conductivity at room temperature. However, while the addition of traditional fillers improves ionic conductivity, it does not improve the stability of the electrolyte-electrode interface. In particular, the uneven deposition of lithium ions at the negative electrode interface easily leads to the formation of lithium dendrites, and the strength of polymer electrolytes is insufficient to resist the penetration of lithium dendrites, resulting in internal short circuits between the positive and negative electrodes of the battery. Therefore, enhancing the stability of the polymer electrolyte-lithium metal interface while promoting efficient ion transport is an important way to achieve good operation of solid-state batteries at room temperature. Summary of the Invention
[0004] To address the technical problems of poor stability at the interface between existing solid electrolytes and positive and negative electrodes, as well as poor electrochemical performance at room temperature, the primary objective of this invention is to provide a method for preparing a high-iron electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte.
[0005] Another object of the present invention is to provide a polyvinylidene fluoride-lithium tantalate composite solid electrolyte prepared by the above preparation method.
[0006] Another object of the present invention is to provide a solid-state battery comprising the above-mentioned high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid-state electrolyte.
[0007] The technical problem of this invention is solved by the following technical solution:
[0008] A method for preparing a high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte includes the following steps:
[0009] S1. Dissolve polyvinylidene fluoride and inorganic lithium salt in a solvent at a certain mass ratio and stir at room temperature to obtain a uniform and transparent solution.
[0010] S2. Add lithium tantalate to the uniform transparent solution obtained in step S1 and stir ultrasonically to obtain a uniform white suspension.
[0011] S3. Pour the uniform white suspension obtained in step S2 into a container and place it in an oven to dry, removing excess solvent, and obtain a polyvinylidene fluoride-lithium tantalate composite solid electrolyte membrane.
[0012] S4. The polyvinylidene fluoride-lithium tantalate solid electrolyte membrane obtained in step S3 is punched and then dried and stored in an inert atmosphere to obtain the high-speed ferroelectric polyvinylidene fluoride-lithium tantalate composite solid electrolyte.
[0013] In some embodiments, in step S1, the inorganic lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethyl)sulfonyl)imide (LiTFSI); the mass ratio of the polyvinylidene fluoride (PVDF) to the inorganic lithium salt is (2-4):2.
[0014] In some embodiments, in step S1, the solvent is selected from N,N-dimethylformamide (DMF) solution; the amount of solvent added is 15-20 mL.
[0015] In some embodiments, in step S1, the room temperature for stirring is 20–27°C; the stirring time is 1–3 hours; and the stirring speed is 400–650 rpm.
[0016] In some embodiments, in step S2, the amount of lithium tantalate (LTO) added is 10-20 wt% of the uniform transparent solution.
[0017] In some embodiments, in step S3, the ultrasonic time is 1 to 3 hours and the ultrasonic speed is 90 to 110 kHz; the stirring time is 4 to 6 hours and the stirring speed is 400 to 650 rpm.
[0018] In some embodiments, in step S3, the container is selected as a glass petri dish; the oven is selected as a forced-air oven; and the drying time is 20-24 hours.
[0019] In some embodiments, in step S4, the diameter of the punching is 16-19 mm; the inert atmosphere is argon.
[0020] The present invention also proposes a high-speed electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte, which is prepared by the above-mentioned preparation method of the high-speed electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte.
[0021] The present invention also proposes a solid-state battery, comprising the above-mentioned high-speed iron-electric polyvinylidene fluoride-lithium tantalate composite solid electrolyte, as well as lithium nickel manganese cobalt oxide NCM811 positive electrode and lithium metal negative electrode.
[0022] The beneficial effects of this invention compared to the prior art include:
[0023] This invention involves dissolving polyvinylidene fluoride (PVDF) and inorganic lithium salt at a specific mass ratio and stirring at room temperature. Then, a specific amount of lithium tantalate (LTO) is added as a ferroelectric ceramic and ultrasonically stirred at room temperature. The mixture is poured into a container, dried, cut, and then dried and stored under an inert atmosphere to obtain a high-ferroelectric PVDF-lithium tantalate composite solid electrolyte, P-LTO. The stability of the P-LTO at the interface with the positive and negative electrodes and its room-temperature electrochemical performance are significantly improved. Furthermore, this preparation method is simple, low-cost, and suitable for large-scale production in lithium battery manufacturers, the new energy vehicle industry, and consumer electronics industries such as mobile phones.
[0024] Other beneficial effects of the embodiments of the present invention will be further described below. Attached Figure Description
[0025] Figure 1 This is a flowchart of the preparation method of the high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte proposed in the embodiments of the present invention;
[0026] Figure 2 These are scanning electron microscope images of the surface of the high-iron electro-polyvinylidene fluoride-lithium tantalate composite solid electrolyte prepared in the embodiments of the present invention;
[0027] Figure 3 This is a cross-sectional scanning electron microscope image of the high-iron electro-polyvinylidene fluoride-lithium tantalate composite solid electrolyte prepared in the embodiments of the present invention;
[0028] Figure 4 This is a schematic diagram illustrating the regulation principle of lithium ferroelectric ceramic tantalate in polyvinylidene fluoride electrolyte in a comparative example of the present invention.
[0029] Figure 5a This is a schematic diagram of the ferroelectric response of the high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte in an embodiment of the present invention;
[0030] Figure 5b This is a schematic diagram of the ferroelectric response of the polyvinylidene fluoride solid electrolyte in the comparative example;
[0031] Figure 6 This is a schematic diagram of the electrochemical performance of the lithium nickel manganese cobalt oxide NCM811 / high-speed iron-polyvinylidene fluoride-lithium tantalate composite solid electrolyte P-LTO / Li and lithium nickel manganese cobalt oxide NCM811 / polyvinylidene fluoride electrolyte PVDF / Li coin cells prepared in the embodiments of the present invention. Detailed Implementation
[0032] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.
[0033] It should be noted that the directional terms such as left, right, up, down, top, and bottom used in this embodiment are only relative concepts or are based on the normal use of the product, and should not be considered as restrictive.
[0034] Studies have shown that lithium tantalate (LTO), as a typical ferroelectric ceramic, exhibits the characteristics of ferroelectric materials. Under an applied electric field, the positive and negative charges inside the ceramic deviate, generating polarization. The polarization direction is opposite to the direction of the applied electric field, effectively homogenizing the local potential at the negative electrode interface and reducing the local current density, thereby regulating lithium-ion deposition and inhibiting lithium dendrite growth. Simultaneously, as a ceramic filler with ionic conductivity, it can provide additional ion conduction pathways in composite solid electrolytes, enhancing their ion transport capacity. The method of using fillers with both ferroelectric properties and ionic conductivity to regulate lithium deposition and improve ionic conductivity is simple, low-cost, and yields a safe composite solid electrolyte with excellent cycle performance, making it highly suitable for large-scale production. Furthermore, the synergistic mechanism for regulating interfacial lithium deposition and enhancing ion transport proposed in this patent has strong universality.
[0035] To address the technical problems of poor stability at the interface between existing solid electrolytes and positive and negative electrodes, as well as poor room-temperature electrochemical performance, this invention proposes a polyvinylidene fluoride-lithium tantalate (P-LTO)-based high-ferroelectric composite solid electrolyte and its preparation method. This electrolyte exhibits both high ferroelectricity and high ionic conductivity, long-cycle stability, and high safety at the positive and negative electrode interfaces. Specifically, it utilizes a common strategy of controlling lithium deposition at the interface between the polymer electrolyte and the lithium metal anode using ceramic fillers that combine ferroelectric properties and ionic conductivity. The main approach involves combining a polymer electrolyte with a filler that integrates both ferroelectric and ion-conducting properties, thereby significantly improving electrolyte performance. Existing technologies typically only add ion-conducting or dielectric materials to the electrolyte, resulting in limited improvement in the overall room-temperature ionic conductivity of the solid electrolyte. This solid electrolyte not only possesses high ionic conductivity but also achieves uniform lithium-ion concentration on the lithium metal anode side through the ferroelectric effect of the filler, promoting uniform lithium-ion deposition and suppressing lithium dendrite growth. This solves the problem that conventional composite electrolytes cannot simultaneously achieve high ionic conductivity, uniform electric field, and suppression of lithium dendrites. Furthermore, the inorganic filler used does not require special treatment, significantly reducing production costs. Meanwhile, the performance of the solid electrolyte is greatly improved, demonstrating clear technological and cost advantages.
[0036] Specifically, ferroelectric ceramic LiTaO3 (LTO, lithium tantalate) is introduced into the PVDF electrolyte. The ferroelectricity of LTO is polarized under an applied electric field, generating a polarization electric field in the opposite direction, thereby offsetting the local potential and reducing the local current density, thus regulating lithium deposition at the negative electrode interface and inhibiting lithium dendrite growth.
[0037] On the other hand, while the ferroelectric ceramic LTO undergoes polarization, the positive and negative charges inside the ferroelectric ceramic shift towards their respective ends, thereby attracting oppositely charged ions, regulating the lithium-ion flow, and affecting the composition of the negative electrode interface. The specific operation is as follows:
[0038] LTO ceramic was added as a filler to PVDF, and after being dissolved with lithium bis(fluorosulfonyl)imide (LIFSI) in N,N-dimethylformamide (DMF) solution, it was cast and dried to prepare a polyvinylidene fluoride-lithium tantalate (P-LTO) composite solid electrolyte. This was matched with PVDF polymer as the positive electrode binder, and LiNi... 0.8 Co 0.1 Mn 0.1A lithium metal solid-state battery was assembled using O2 (NCM811, lithium nickel manganese cobalt oxide) as the active material, conductive carbon black as the conductive agent to prepare the positive electrode, and lithium metal as the negative electrode. The ferroelectric properties of LTO played a role in regulating lithium deposition, significantly suppressing the growth of lithium dendrites in the solid-state battery and reducing unnecessary side reactions. Furthermore, the ionic conductivity of the LTO ceramic itself provided an additional ion conduction pathway for the P-LTO electrolyte, greatly improving the ionic conductivity and lithium-ion transference number of the composite solid-state electrolyte. The synergistic effect of these two factors significantly enhanced the safety and long-cycle performance of the solid-state battery at room temperature.
[0039] The present invention employs a simple and low-cost method for regulating lithium deposition and improving ionic conductivity using fillers that combine ferroelectric properties and ionic conductivity. The resulting composite solid electrolyte is safe, exhibits excellent cycle performance, and is highly suitable for large-scale production. Furthermore, the synergistic mechanism for regulating interfacial lithium deposition and enhancing ion transport proposed in this invention has strong universality and is expected to advance the industrialization of solid electrolytes.
[0040] This invention proposes an active filler for a functional electrolyte, wherein the inorganic filler is lithium tantalate (LTO), which has both high ferroelectric properties and ionic conductivity, thereby improving ion transport efficiency while regulating lithium deposition at the electrolyte-anode interface.
[0041] This invention also proposes a high-ferroelectric polyvinylidene fluoride-lithium tantalate composite solid electrolyte prepared using the above-mentioned active filler. This composite solid electrolyte exhibits a strong ferroelectric response, can effectively control lithium deposition, and has high room-temperature ionic conductivity, allowing for stable matching with high-voltage cathodes such as LiNi. 0.8 Co 0.1 Mn 0.1 O2 (NCM811).
[0042] In LTO inorganic filler, under an applied electric field, the positive and negative charges inside the ceramic deviate, resulting in polarization. The polarization direction is opposite to the direction of the applied electric field. This effectively homogenizes the internal electric field at the negative electrode interface, reducing the local current density and thus controlling lithium deposition to form a uniform solid electrolyte layer. Furthermore, the inherent ionic conductivity of the polymer electrolyte provides additional ion transport paths, thereby improving the ionic conductivity of the solid electrolyte.
[0043] The preparation method of the above-mentioned high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte is as follows: Figure 1 As shown, it includes the following steps:
[0044] S1. Dissolve polyvinylidene fluoride and inorganic lithium salt in a solvent at a certain mass ratio and stir at room temperature to obtain a uniform and transparent solution.
[0045] The inorganic lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethyl)sulfonyl)imide (LiTFSI); the mass ratio of polyvinylidene fluoride (PVDF) to inorganic lithium salt is (2–4):2. The solvent is selected from N,N-dimethylformamide (DMF) solution; the amount of solvent added is 15–20 mL. The room temperature for stirring is 20–27 °C; the stirring time is 1–3 h, and the stirring speed is 400–650 rpm.
[0046] S2. Add lithium tantalate to the uniform transparent solution obtained in step S1, and ultrasonically stir at room temperature to obtain a uniform white suspension.
[0047] The amount of lithium tantalate (LTO) added is 10–20 wt% of the uniform transparent solution.
[0048] S3. Pour the uniform white suspension obtained in step S2 into a container and place it in an oven to dry, removing excess solvent, and obtain a polyvinylidene fluoride-lithium tantalate composite solid electrolyte membrane.
[0049] The ultrasonic treatment time was 1–3 hours at a speed of 90–110 kHz; the stirring time was 4–6 hours at a speed of 400–650 rpm. Glass petri dishes were used as containers; a forced-air drying oven was used; and the drying time was 20–24 hours.
[0050] S4. The polyvinylidene fluoride-lithium tantalate solid electrolyte membrane obtained in step S3 is punched and then dried and stored in an inert atmosphere to obtain the high-speed ferroelectric polyvinylidene fluoride-lithium tantalate composite solid electrolyte.
[0051] The diameter of the punching is 16-19 mm; the inert atmosphere is argon.
[0052] This invention also proposes a polyvinylidene fluoride-lithium tantalate composite solid electrolyte, which is prepared by the above-described method for preparing the high-speed ferroelectric polyvinylidene fluoride-lithium tantalate composite solid electrolyte.
[0053] This invention also proposes a solid-state battery, comprising the above-mentioned high-speed iron-electric polyvinylidene fluoride-lithium tantalate composite solid electrolyte, as well as lithium nickel manganese cobalt oxide NCM811 positive electrode and lithium metal negative electrode.
[0054] The prepared composite solid electrolyte has a room temperature ionic conductivity of 3.94 × 10⁻⁶. -4 S·cm -1 This enables solid-state batteries to operate at room temperature. Furthermore, when assembled with an NCM811 cathode and a lithium metal anode, the solid-state battery can stably cycle 1400 times at room temperature and a 1C current density, retaining 70% of its capacity.
[0055] The composite solid electrolyte obtained in this invention can uniformly distribute the ion concentration on the lithium metal anode side, forming a dense solid electrolyte layer. Furthermore, the solid-state battery prepared using the above-mentioned solid electrolyte exhibits higher room-temperature performance than existing similar methods.
[0056] The embodiments of the present invention have the following advantages:
[0057] This invention proposes a general method for enhancing the interface stability and transport capacity of PVDF-based solid electrolytes at the anode using LTO filler, which possesses both ferroelectric properties and ionic conductivity. This method is simple, low-cost, and suitable for large-scale production. A highly safe and stable P-LTO composite solid electrolyte is prepared using this method. As a ceramic filler with ionic conductivity, it provides additional ion conduction pathways in the composite solid electrolyte, enhancing its ion transport capacity. Details are as follows:
[0058] Compared to traditional PVDF polymer electrolytes, the P-LTO composite solid electrolyte exhibits a room-temperature ionic conductivity of 2.11 × 10⁻⁶. -4 Scm -1 Increased to 3.94 × 10⁻⁴ S cm -1 The lithium-ion transference number increased from 0.21 to 0.45. Piezoelectric force microscopy (PFM) testing showed that the P-LTO composite solid electrolyte exhibited a strong ferroelectric response compared to the PVDF polymer electrolyte. This is due to the polarization of the ferroelectric ceramic LTO under an electric field, generating an opposite polarization electric field. This effectively homogenizes the local potential at the negative electrode interface, reduces the local current density, thereby regulating lithium-ion deposition, inhibiting lithium dendrite growth, and improving interface stability. Using lithium sheets as both positive and negative electrodes, a lithium-lithium symmetric battery was assembled at room temperature with a current density of 0.1 mA / cm². -2 The first method achieved stable cycling for 4000 hours with a polarization voltage of approximately 50mV, while a battery matched with a PVDF polymer electrolyte experienced a short circuit after only 380 hours of cycling. A lithium metal solid-state battery was assembled using a positive electrode prepared with PVDF5130 as the positive electrode binder, NCM811 as the active material, and conductive carbon black (SuperP) as the conductive agent, along with a lithium metal negative electrode. This battery achieved stable cycling for 1400 cycles at 1C current density at room temperature with 70% capacity retention. In contrast, a battery assembled with a PVDF polymer electrolyte and negative electrode without LTO ceramic short-circuited after less than 250 cycles at 1C current density. This method of enhancing the stability and transport capacity of the polymer electrolyte at the negative electrode interface is simple to operate, low in cost, and produces a safe and highly efficient composite solid-state electrolyte, making it ideal for large-scale production.
[0059] Example 1:
[0060] This embodiment provides a method for preparing a PVDF solid electrolyte and assembling a full cell, which includes at least the following steps:
[0061] S1. First, weigh 100 mg of PVDF (binder) and place it in a stirring flask. Add 1 mL of NMP (N-methylpyrrolidone) and stir on a small stirrer for 1 hour until the PVDF is completely dissolved. Then add 100 mg of SuperP (conductive carbon black) and 1 mL of NMP, stir at room temperature for 1 hour, add 800 mg of NCM811 active material and 1.5 mL of NMP, and stir at room temperature for at least 6 hours.
[0062] S2. Coat the positive electrode slurry obtained in step S2 onto aluminum foil, dry it at 80°C for more than 6 hours, cut it into a suitable size to obtain NCM811 positive electrode, and place it in a vacuum oven to dry and store it.
[0063] S3. First, weigh 267 mg of LiFSI under an inert atmosphere and place it in a stirred flask. Add 15 mg of LDM and 400 mg of PVDF and stir on a small stirrer. Stir at room temperature for more than 2 hours until LiFSI and PVDF are completely dissolved to obtain a uniform and transparent solution.
[0064] S4. Pour the solution obtained in step S3 into a glass petri dish, place it in a 55°C forced-air oven to dry for 24 hours to remove excess solvent DMF, obtain an electrolyte membrane, cut it to a suitable size, dry it under an inert atmosphere and store it for later use.
[0065] Then, following the battery assembly process, the NCM811 cathode, PVDF polymer electrolyte, and lithium metal were combined and assembled into a full cell.
[0066] The assembly process for button cell (CR2032) is as follows:
[0067] 1. Material preparation: Cut the NCM811 positive electrode prepared in steps S1 and S2 into φ12mm round pieces; the lithium sheet is φ15.6mm in size; cut the electrolyte prepared in steps S3 and S4 into φ19mm round pieces.
[0068] 2. Assembly sequence: From bottom to top, the order is: negative electrode shell - spring sheet - gasket - lithium metal - solid electrolyte - NCM811 positive electrode - gasket - positive electrode shell. The above steps are carried out in a glove box filled with argon gas.
[0069] 3. Press the assembled battery using a tablet press at a pressure of 50 kg / cm². -2 .
[0070] Example 2:
[0071] This embodiment provides a method for preparing a P-LTO solid electrolyte and assembling a full cell, which includes at least the following steps:
[0072] First, weigh 100 mg of PVDF (binder) and place it in a stirring flask. Add 1 mL of NMP (N-methylpyrrolidone) and stir on a small stirrer for 1 hour until the PVDF is completely dissolved. Then add 100 mg of SuperP (conductive carbon black) and 1 mL of NMP, stir at room temperature for 1 hour, add 800 mg of NCM811 active material and 1.5 mL of NMP, and stir at room temperature for at least 6 hours.
[0073] The positive electrode slurry obtained in the above steps is coated onto aluminum foil, dried at 80°C for more than 6 hours, cut into appropriate sizes, and then placed in a vacuum oven to dry and store.
[0074] S1. First, weigh 267 mg of LiFSI under an inert atmosphere, place it in a stirred flask, add 15 mg of LDM and 400 mg of PVDF, stir on a small stirrer, stir at room temperature for more than 2 hours, and the LiFSI and PVDF will be completely dissolved to obtain a uniform transparent solution.
[0075] S2. Add 60 mg of LTO ceramic particles to the solution obtained in step S3, sonicate for 2 h, stir at room temperature for 6 h to obtain a uniform white suspension.
[0076] S3. Pour the solution obtained in step four into a glass petri dish and dry it in a 55°C forced-air oven for 24 hours to remove excess solvent DMF and obtain an electrolyte membrane.
[0077] S4. Cut to the appropriate size, dry in an inert atmosphere and store for later use.
[0078] Then, following the battery assembly process, the NCM811 cathode, P-LTO polymer electrolyte, and lithium metal were combined and assembled into a full cell.
[0079] The high-iron electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte prepared in the embodiments of the present invention is as follows: Figure 2 and Figure 3 As shown, the addition of ceramics to the polymer electrolyte makes the membrane surface denser and significantly reduces porosity. Figure 3 As shown, the thickness of the P-LTO electrolyte membrane prepared in this embodiment of the invention is 92 μm, which is an increase in thickness compared to the traditional PVDF electrolyte (88 μm), but it is still within a controllable range, and the thickness has little impact on the experimental results.
[0080] In the embodiments of the present invention, the high-speed iron electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte is as follows: Figure 4As shown, the ferroelectric ceramic lithium tantalate is polarized under the action of an external electric field. The positive and negative charges inside the ceramic move to both ends, attracting cations and anions, generating a polarized electric field opposite to the applied electric field, uniformizing the internal potential, reducing the local current density, thereby regulating lithium deposition, and forming a dense solid electrolyte layer (SEI) on the surface of the lithium metal anode.
[0081] In this embodiment of the invention, the ferroelectric response of the high-speed ferroelectric polyvinylidene fluoride-lithium tantalate solid electrolyte is as follows: Figure 5a As shown, the ferroelectric response of the polyvinylidene fluoride solid electrolyte in the comparative example is as follows: Figure 5b As shown. Figure 5a As shown, PFM testing specifically demonstrates that the amplitude of the P-LTO electrolyte exhibits a distinct butterfly-shaped curve, while the phase shows a broad leaf-like pattern, indicating that the P-LTO electrolyte possesses a strong ferroelectric response. In contrast, the amplitude and phase curves of the PVDF electrolyte both show a closed state. Figure 5b As shown, there is almost no ferroelectric response, and this strong ferroelectric response result is mainly due to the addition of the ferroelectric ceramic LTO.
[0082] The electrochemical performance of the lithium nickel manganese cobalt oxide NCM811 / high-iron electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte P-LTO / Li and the lithium nickel manganese cobalt oxide NCM811 / polyvinylidene fluoride electrolyte PVDF / Li coin cells prepared in the embodiments of the present invention are as follows: Figure 6 The performance curves of the electrolyte-matched NCM811 positive electrode and lithium metal negative electrode under conditions of 1C current density and 25°C are shown. The inclusion of the comparative example PVDF electrolyte highlights the performance advantages of P-LTO. The lithium nickel manganese cobalt oxide NCM811 / polyvinylidene fluoride electrolyte PVDF / Li coin cell in the comparative example short-circuited and failed after 250 cycles, while the lithium nickel manganese cobalt oxide NCM811 / polyvinylidene fluoride-lithium tantalate composite solid electrolyte P-LTO / Li coin cell prepared in this embodiment of the invention maintained a capacity retention of 70% after 1400 cycles.
[0083] The high-speed ferroelectric polyvinylidene fluoride-lithium tantalate (P-LTO) based composite solid electrolyte proposed in this invention can be used to prepare high-performance, high-safety solid-state batteries. It is expected to be applied in lithium battery manufacturing, the new energy vehicle industry, and consumer electronics industries such as mobile phones.
[0084] 1) The composite solid electrolyte proposed in this embodiment is prepared using the same method as conventional solid electrolytes. This embodiment adds lithium tantalate (LiTaO3), a ceramic electrolyte possessing both ion conductivity and ferroelectric properties, to the PVDF polymer electrolyte. The composite solid electrolyte proposed in this embodiment exhibits superior room-temperature electrochemical performance at a similar cost.
[0085] 2) The composite solid electrolyte proposed in this invention not only possesses extremely high room-temperature ionic conductivity, but also simultaneously solves the problems of uneven lithium deposition at the electrolyte / anode interface and lithium dendrite growth on the anode side. Conventional composite electrolytes cannot simultaneously address the issues of ionic conductivity, uniform electric field, and suppression of lithium dendrites.
[0086] 3) The high-performance solid-state battery proposed in this invention can solve the safety problems such as fire and explosion caused by conventional electrolyte batteries, and has great research value and application prospects.
[0087] The composite solid electrolyte proposed in this invention can be applied to the fields of batteries and electric vehicles in the future, reducing the risk of spontaneous combustion in electric vehicles and electronic products.
[0088] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several equivalent substitutions or obvious modifications can be made without departing from the concept of the present invention, and all such modifications, achieving the same performance or purpose, should be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a high ferroelectric polyvinylidene fluoride-lithium tantalate composite solid-state electrolyte, characterized by, Includes the following steps: S1. Dissolve polyvinylidene fluoride and inorganic lithium salt in a solvent at a certain mass ratio and stir at room temperature to obtain a uniform and transparent solution. S2. Add lithium tantalate to the uniform transparent solution obtained in step S1, and ultrasonically stir at room temperature to obtain a uniform white suspension. S3. Pour the uniform white suspension obtained in step S2 into a container and place it in an oven to dry, removing excess solvent, and obtain a polyvinylidene fluoride-lithium tantalate composite solid electrolyte membrane. S4. The polyvinylidene fluoride-lithium tantalate solid electrolyte membrane obtained in step S3 is punched and then dried and stored in an inert atmosphere to obtain the high-speed ferroelectric polyvinylidene fluoride-lithium tantalate composite solid electrolyte.
2. The preparation method of the high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte as described in claim 1, characterized in that, In step S1, the inorganic lithium salt is selected from one or more of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethyl)sulfonyl)imide (LiTFSI); the mass ratio of the polyvinylidene fluoride (PVDF) to the inorganic lithium salt is (2-4):
2.
3. The preparation method of the high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte as described in claim 1, characterized in that, In step S1, the solvent is selected from N,N-dimethylformamide (DMF) solution; the amount of solvent added is 15-20 mL.
4. The preparation method of the high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte as described in claim 1, characterized in that, In step S1, the room temperature for stirring is 20-27°C; the stirring time is 1-3 hours; and the stirring speed is 400-650 rpm.
5. The preparation method of the high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte as described in claim 1, characterized in that, In step S2, the amount of lithium tantalate (LTO) added is 10-20 wt% of the uniform transparent solution.
6. The preparation method of the high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte as described in claim 5, characterized in that, In step S3, the room temperature for ultrasonic stirring is 20–27°C; the ultrasonic time is 1–3 h; the ultrasonic speed is 90–110 kHz; the stirring time is 4–6 h; and the stirring speed is 400–650 rpm.
7. The preparation method of the high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte as described in claim 1, characterized in that, In step S3, the container is selected as a glass petri dish; the oven is selected as a forced-air oven; and the drying time is 20-24 hours.
8. The preparation method of the high-speed rail electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte as described in claim 1, characterized in that, In step S4, the diameter of the punching is 16-19 mm; the inert atmosphere is argon.
9. A high ferroelectric polyvinylidene fluoride-lithium tantalate composite solid-state electrolyte, characterized by, It is prepared by the method for preparing high-speed iron electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte according to any one of claims 1 to 8.
10. A solid state battery, characterized by, It includes the high-speed iron electrolytic polyvinylidene fluoride-lithium tantalate composite solid electrolyte as described in claim 9, as well as the lithium nickel manganese cobalt oxide NCM811 positive electrode and the lithium metal negative electrode.