Difunctional filler synergistically enhanced polymer solid electrolyte and solid-state battery

Abstract

The invention discloses a difunctional filler synergistically enhanced polymer solid electrolyte and a solid-state battery, and belongs to the field of solid-state batteries. The electrolyte adopts a polymer matrix, a lithium salt and two functional fillers: the first filler has a high dielectric constant, and can accelerate dissociation of the lithium salt, fix negative ions of the lithium salt and improve the transference number of lithium ions under the action of self polarization; and the second filler has high electrochemical window and ionic conductivity, can inhibit high-voltage decomposition, and is adaptive to a high-voltage positive electrode material. Through cooperation and balance design of the two kinds of filler, ion transmission, interface stability and high-pressure compatibility can be considered at the same time. In addition, the invention further designs a composite negative pole piece, the surface of the negative pole piece is coated with the solid electrolyte, and the ion transmission kinetics in the pole piece can be remarkably improved. On the basis, the invention develops a high-performance solid-state battery which is excellent in electrochemical performance and can play an important role in the fields of consumer electronics, electric automobiles, energy storage systems, low-altitude flight and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid electrolytes, and particularly relates to a polymer solid electrolyte and a solid-state battery synergistically enhanced by dual-functional fillers. Technical Background

[0002] Traditional polymer-based solid electrolytes are limited in their application in high-voltage and high-energy-density solid-state batteries due to problems such as low room-temperature ionic conductivity, narrow electrochemical window, and lithium dendrite growth. In the prior art, single filler doping is difficult to meet multiple performance requirements, such as ionic conductivity, electrochemical window, interfacial compatibility, etc. In addition, under high-quality loading, the internal dynamics of the electrode sheet are poor, the interfacial impedance between the solid electrolyte and the electrode sheet is large, and the cycling performance is severely limited. Summary of the Invention

[0003] To solve the above problems, the present application provides a polymer solid electrolyte and a solid-state battery synergistically enhanced by dual-functional fillers.

[0004] In a first aspect, the present application provides a polymer solid electrolyte synergistically enhanced by dual-functional fillers, comprising the following components:

[0005] Polymer matrix: 50 - 90 wt%;

[0006] Lithium salt: 5 - 30 wt%;

[0007] Functional filler: 5 - 20 wt%;

[0008] The functional filler includes a first filler and a second filler;

[0009] The first filler includes at least one of titanium dioxide (TiO2), zirconium oxide (ZrO2), tantalum pentoxide (Ta2O5), barium titanate (BTO), strontium barium titanate (BST), and strontium titanate (STO);

[0010] The second filler includes at least one of LLZTO, LLZO, or LATP, and is used to expand the electrochemical window and ionic conductivity of the electrolyte;

[0011] The mass of the first filler is X1 and the mass of the second filler is X2, and it is required that 0.5 ≤ X1 / X2 ≤ 2;

[0012] First, the introduction of the first filler, by virtue of its high dielectric constant, can weaken the interaction between the cations and anions of the lithium salt, accelerate the dissociation of the lithium salt, and fix the anions in the lithium salt by means of the Lewis acid effect, significantly increasing the free lithium ion transference number and enhancing the ionic conductivity. Secondly, the introduction of the second filler, by virtue of its high electrochemical window and ionic conductivity, can significantly increase the electrochemical window of the polymer solid electrolyte and be compatible with high-voltage cathode materials. Finally, by reasonably regulating the ratio of the first filler to the second filler, high lithium ion transference number, high ionic conductivity, and wide electrochemical window can be achieved simultaneously, thus significantly improving the battery performance.

[0013] In some exemplary embodiments, the polymer matrix includes at least one of polyethylene oxide (PEO), polytetrafluoroethylene (PVDF), poly(vinylidene fluoride - hexafluoropropylene) (PVDF - HFP), and polymethyl methacrylate (PMMA);

[0014] In some exemplary embodiments, the lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide.

[0015] In some exemplary embodiments, the dielectric constant of the first filler at 10 Hz is greater than or equal to 30, the particle size is 10 - 500 nm, and its average specific surface area is 100 - 1500 m 2 g -1 .

[0016] In some exemplary embodiments, the second filler has an electrochemical window greater than or equal to 4.5 V, an ionic conductivity higher than 10 -4 S / cm at 25 °C, and a particle size of 10 - 500 nm.

[0017] In a second aspect, the present application provides a method for preparing a dual-functional filler polymer solid electrolyte membrane, including the following steps:

[0018] Filler mixing: Mix the nanoscale first filler and the second filler evenly to ensure sufficient contact between the first filler and the second filler. Combining the advantages of both, the first filler promotes the dissociation of the lithium salt to form free lithium ions, which are rapidly transported along the interface and within the bulk phase of the second filler.

[0019] Film-forming treatment: Dissolve the polymer and the lithium salt in an organic solvent in a certain proportion, mix and disperse them evenly, then add the evenly mixed filler, and finally coat it on the surface of an aluminum foil or a PTFE film. After drying, the film can be easily peeled off.

[0020] Calendering treatment: Perform calendering treatment on the solid electrolyte membrane to control the thickness of the solid electrolyte membrane and balance the processing performance and electrochemical performance.

[0021] In some exemplary embodiments, the organic solvent includes at least one of methanol, ethanol, isopropanol, acetonitrile, N,N-dimethylformamide, N,N-dimethylpyrrolidone, dimethyl sulfoxide, dimethyl carbonate, diethyl carbonate, and ethylene carbonate.

[0022] The solid electrolyte membrane can be applied to electrochemical devices such as liquid lithium-ion batteries, solid-state batteries, and lithium metal batteries, and will play an important role in fields such as consumer electronics, electric vehicles, energy storage systems, and low-altitude flight.

[0023] In a third aspect, the present application also provides a solid-state battery, including a composite negative electrode sheet, a positive electrode sheet, and a polymer solid electrolyte (the solid electrolyte membrane located between the positive electrode and the negative electrode), and the solid electrolyte membrane is the above-mentioned bifunctional filler polymer solid electrolyte membrane. The preparation of the composite negative electrode sheet includes the following steps:

[0024] Preparation of solid electrolyte slurry: Mix PEO, a lithium salt, a plasticizer, and the second filler in proportion and dissolve them in an organic solvent to form a uniform slurry;

[0025] Coating treatment: Coat the slurry on the surface of the negative electrode sheet and form a dense coating after drying and hot pressing.

[0026] In some exemplary embodiments, the plasticizer includes at least one of polyethylene glycol (PEG), ethylene carbonate (EC), or succinonitrile (SN), and the mass ratio of PEO to the plasticizer is 1:0.01 - 0.2.

[0027] In some exemplary embodiments, the mass percentage of the second filler in the PEO-based solid electrolyte coating is 10% - 40%.

[0028] In some exemplary embodiments, for the hot pressing process, the temperature is 80 - 120°C and the pressure is 5 - 20 MPa.

[0029] Compared with the prior art, the beneficial effects of the invention are as follows: The present application discloses a solid electrolyte with synergistic dual-functional fillers. First, the first filler has a high dielectric constant. Under its own polarization effect, it can accelerate the dissociation of lithium salts, fix lithium salt anions, and increase the lithium ion transference number. The second filler has a high electrochemical window and ionic conductivity, can inhibit high-voltage decomposition, and is compatible with high-voltage cathode materials. Secondly, through the synergy and concentration design of the two fillers, ion transport, interface stability, and high-voltage compatibility can be taken into account. In addition, the present application has also developed a high-performance negative electrode sheet. A high-performance PEO-based solid electrolyte is coated on the surface of the negative electrode sheet. PEO can penetrate into the pores of the negative electrode sheet, significantly improving the ionic conductivity of the negative electrode sheet and improving the interface compatibility between the solid electrolyte and the negative electrode sheet. Based on this, through the synergistic innovation of the solid electrolyte material and the composite negative electrode material, the present invention breaks through the performance bottleneck of single components, significantly improves the cycle life and energy density of solid-state batteries, has excellent electrochemical performance, and can play an important role in the fields of consumer electronics, electric vehicles, energy storage systems, and low-altitude flight. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects, and advantages of the present invention will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0031] Figure 1 are the cross-sectional and planar SEM diagrams of the original negative electrode sheet and the composite negative electrode sheet disclosed in the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The present invention will be further described in detail below through embodiments. The embodiments are only used to illustrate the present invention and do not limit the scope of the present invention.

[0033] In a first aspect, the present application provides a polymer solid electrolyte with synergistic enhancement of dual-functional fillers, including a polymer matrix, a lithium salt, and functional fillers, wherein:

[0034] Polymer matrix: 50 - 90 wt%;

[0035] Lithium salt: 5 - 30 wt%;

[0036] Functional fillers: 5 - 20 wt%;

[0037] The functional fillers include a first filler and a second filler;

[0038] The first filler includes at least one of titanium dioxide (TiO2), zirconium oxide (ZrO2), tantalum pentoxide (Ta2O5), barium titanate (BTO), strontium barium titanate (BST), and strontium titanate (STO);

[0039] The second filler includes at least one of lithium lanthanum zirconium tantalum oxide (LLZTO), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLTO), lithium aluminum titanium phosphate (LATP), lithium germanium aluminum phosphate (LAGP), and halide electrolytes, and is used to expand the electrochemical window of the electrolyte;

[0040] The mass of the first filler is X1 and the mass of the second filler is X2, and it is required that 0.5 ≤ X1 / X2 ≤ 2;

[0041] The polymer matrix includes at least one of polyethylene oxide (PEO), polytetrafluoroethylene (PVDF), polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), polyethylene glycol methacrylate (PEGMA), polydioxolane (P-DOL), polysiloxane (PS), and polymethyl methacrylate (PMMA);

[0042] The lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, and lithium bis(oxalato)borate;

[0043] The dielectric constant of the first filler at 10 Hz needs to be greater than or equal to 30, and the particle size is 10 - 500 nm, and its average specific surface area is 100 - 1500 m 2 g -1 。

[0044] The second filler has an electrochemical window greater than or equal to 4.5 V, an ionic conductivity higher than 10 -4 S / cm at 25 °C, and the particle size is 10 - 500 nm.

[0045] First, the introduction of the first filler, by virtue of its high dielectric constant, can weaken the interaction between the cations and anions of the lithium salt, accelerate the dissociation of the lithium salt, and fix the lithium salt anions through the Lewis acid effect, increasing the free lithium ion transference number and enhancing the ionic conductivity. Secondly, the introduction of the second filler, by virtue of its high electrochemical window and ionic conductivity, can significantly increase the electrochemical window of the polymer solid electrolyte and be compatible with high-voltage cathode materials. Finally, reasonably regulating the ratio of the first filler and the second filler can take into account high lithium ion transference number, high ionic conductivity, and wide electrochemical window, thus significantly improving the battery performance.

[0046] Second, the present application provides a method for preparing a polymer solid electrolyte membrane synergistically enhanced by bifunctional fillers.

[0047] Including the following steps:

[0048] S1. Mix the first filler and the second filler and load them into a ball milling jar, and ball mill at 400 r / min for 1 h to mix evenly.

[0049] S2. Mix the polymer matrix and the lithium salt in proportion and dissolve them in an organic solvent to form a homogeneous slurry. Subsequently, add the uniformly mixed filler in S1 to the above slurry in proportion and stir to form a homogeneous slurry.

[0050] S3. Form a solid electrolyte membrane by a casting method or a hot pressing method, with a thickness of 10 - 100 μm.

[0051] In some exemplary embodiments, the organic solvent includes at least one of methanol, ethanol, isopropanol, acetonitrile, N,N - dimethylformamide, N,N - dimethylpyrrolidone, dimethyl sulfoxide, dimethyl carbonate, diethyl carbonate, and ethylene carbonate.

[0052] First, the first filler and the second filler are nanoscale. Mix the nanoscale first filler and the second filler uniformly to ensure sufficient contact between the first filler and the second filler. Combining the advantages of both, the first filler promotes the dissociation of the lithium salt to form free lithium ions, which rapidly transport along the interface and the bulk interior of the second filler. Secondly, after mixing the polymer matrix and the lithium salt uniformly, add the filler. Finally, prepare the solid electrolyte membrane by a casting method or a hot pressing method, and control the thickness of the solid electrolyte membrane to balance the processing performance and the electrochemical performance.

[0053] The solid electrolyte membrane can be applied to electrochemical devices such as liquid lithium - ion batteries, solid - state batteries, and lithium - metal batteries, and will play an important role in fields such as consumer electronics, electric vehicles, energy storage systems, and low - altitude flight.

[0054] In a third aspect, the present application also provides a solid - state battery, including a composite negative electrode sheet, a positive electrode sheet, and a polymer solid electrolyte. The polymer solid electrolyte is a solid electrolyte membrane located between the positive electrode and the negative electrode, and the solid electrolyte membrane is a polymer solid electrolyte membrane synergistically enhanced by dual - functional fillers. The preparation method includes the following steps: S1. Prepare the positive electrode sheet: Dissolve the positive electrode material lithium iron phosphate, the conductive agent Super P, the binder polyvinylidene fluoride, and the second filler in N - methylpyrrolidone according to a mass ratio of 94.5:1.5:2:2, mix uniformly and coat on an aluminum foil, dry and roll it into a positive electrode sheet with a compaction density of 2 g / cm 3 The positive electrode sheet includes a positive electrode material, a conductive agent, a binder, and the second filler, wherein the mass ratio of the second filler is 1% - 5%.

[0055] S2. The preparation method of the composite negative electrode sheet includes the following steps:

[0056] First, mix the negative electrode material artificial graphite, the conductive agent Super P, the binder styrene - butadiene rubber, and the thickener sodium carboxymethyl cellulose in a mass ratio of 95:1:2:2 and dissolve them in deionized water. After mixing uniformly, coat on a copper foil, dry and roll it into a 1.55 g / cm3 The negative electrode plate with compacted density.

[0057] Then, PEO, lithium salt, plasticizer and the second filler are mixed in proportion and dissolved in an organic solvent to form a uniform slurry; finally, the slurry is directly coated on the surface of the above-mentioned negative electrode plate, and after drying, it is hot-pressed to form a dense coating with a thickness of 0.1 - 5 μm;

[0058] The organic solvent includes at least one of methanol, ethanol, isopropanol, acetonitrile, N,N-dimethylformamide, N,N-dimethylpyrrolidone, dimethyl sulfoxide, dimethyl carbonate, diethyl carbonate, ethylene carbonate;

[0059] The plasticizer includes at least one of polyethylene glycol (PEG), ethylene carbonate (EC) or succinonitrile (SN), and the mass ratio of PEO to the plasticizer is 1:0.01 - 0.2.

[0060] The mass proportion of the second filler in the PEO-based solid electrolyte coating is 10% - 40%.

[0061] The PEO-based solid electrolyte coating is formed by the doctor blade method and a dense negative electrode - electrolyte interface is formed through a hot-pressing process. For the hot-pressing process, the temperature is 80 - 120 °C and the pressure is 5 - 20 MPa.

[0062] S3. Prepare the solid electrolyte membrane: See the following examples for the specific scheme;

[0063] S4. Battery assembly: Stack the positive electrode, the solid electrolyte membrane and the negative electrode, and use the above-mentioned solid electrolyte membrane for the solid electrolyte membrane;

[0064] The ion conductivity test, electrochemical window, electrochemical performance and thermal conductivity test include the following steps:

[0065] S1. Ion conductivity test: Using the alternating current impedance method, sandwich the solid electrolyte membrane between two stainless steel circular wafers and assemble it into a button cell. Heat-treat it at 60 °C for 2 h in advance to improve the interface contact between the electrolyte and the electrode. Then connect the electrochemical workstation, apply a voltage amplitude of 10 mV, the test frequency range is 1 MHz - 1 Hz, measure the response current, and the corresponding impedance value R can be obtained. Use a micrometer to measure the thickness H at more than 10 different positions of the solid electrolyte membrane and take the average value. Using the area of the stainless steel sheet as S, according to the formula σ = H / (R*S), the ion conductivity of the solid electrolyte membrane can be obtained.

[0066] S2. Electrochemical window test: Test by linear sweep voltammetry, the scanning voltage range is 2 - 6 V, and the scanning rate is 5 mV s -1 , and evaluate the electrochemical stability window of the solid electrolyte membrane.

[0067] S3. Lithium ion transference number test: The steady-state current method is used to test the lithium ion transference number. The EIS curve of the test battery before polarization is measured to obtain the interfacial impedance R0 before polarization. Then, a constant potential ΔV of 10 mV is set for constant potential polarization test, the test time is 12,000 s, the initial polarization current value I0 and the steady-state current value Iss are recorded. After the polarization test, the EIS test of the test battery is carried out to obtain the interfacial impedance Rss after polarization. According to the formula tLi+ = Iss*(ΔV - I0*R0) / [I0*(ΔV - Iss*Rss)], the lithium ion transference number of the solid electrolyte membrane can be obtained.

[0068] S4. Electrochemical performance test: Using a Neware test system, at room temperature of 25 °C and low temperature of 0 °C, the assembled battery is charged and discharged at a constant current density of 0.5C to test its cycling performance, and the number of cycles at 80% discharge capacity retention rate is recorded.

[0069] Now, exemplary embodiments according to the present application will be described in more detail with reference.

[0070] The present application discloses a polymer solid electrolyte and a solid battery synergistically enhanced by dual-functional fillers. In the first aspect, a polymer solid electrolyte synergistically enhanced by dual-functional fillers is provided. For details, see Figure 1 The present invention discloses a polymer solid electrolyte and a solid battery synergistically enhanced by dual-functional fillers, belonging to the field of solid batteries. The electrolyte uses a polymer matrix, a lithium salt and two functional fillers: the first filler has a high dielectric constant, and under its own polarization effect, it can accelerate the dissociation of the lithium salt and fix the lithium salt anions, improving the lithium ion transference number. The second filler has a high electrochemical window and ionic conductivity, can inhibit high-voltage decomposition, and is compatible with high-voltage cathode materials. Through the synergy and concentration design of the two fillers, ion transport, interfacial stability and high-voltage compatibility can be taken into account. Based on this, the present application has developed a high-performance solid battery with excellent electrochemical performance, which can play an important role in the fields of consumer electronics, electric vehicles, energy storage systems and low-altitude flight.

[0071] Example 1

[0072] Preparation of polymer solid electrolyte membrane:

[0073] S1. Mix the first filler (titanium dioxide) and the second filler (lithium lanthanum zirconium tantalum oxide) and load them into a ball mill jar, and ball mill at 400 r / min for 1 h to mix evenly.

[0074] S2. Dissolve polyvinylidene fluoride - hexafluoropropylene and lithium bis(fluorosulfonyl)imide in N,N - dimethylformamide in proportion to form a homogeneous slurry, and mix and disperse them evenly. Subsequently, add the evenly - mixed filler in S1 to the above - mentioned slurry in proportion and stir to form a homogeneous slurry. Among them, the mass ratio of the polymer matrix, lithium salt, first filler, and second filler is 60:25:7.5:7.5 (X1 / X2 = 1).

[0075] S3. Cast it on a PTFE mold by the casting method to prepare a polymer solid electrolyte membrane. Finally, through a hot - pressing process (temperature: 120°C, pressure: 10 MPa, time: 10 min), control the thickness of the solid electrolyte membrane, and the thickness is 20 - 30 μm.

[0076] Prepare a solid - state battery:

[0077] S1. Prepare a positive electrode sheet: Dissolve the positive electrode material NCM811, conductive agent Super P, binder polyvinylidene fluoride, and lithium lanthanum zirconium tantalum oxide in N - methylpyrrolidone according to a mass ratio of 94.5:1.5:2:2, mix them evenly, coat them on an aluminum foil, dry, and roll them into a positive electrode sheet with a compaction density of 2 g / cm 3 compaction density.

[0078] S2. Prepare a composite negative electrode sheet: Mix the negative electrode material artificial graphite, conductive agent Super P, binder styrene - butadiene rubber, and thickening agent sodium carboxymethyl cellulose in a mass ratio of 95:1:2:2, dissolve them in deionized water, mix them evenly, coat them on a copper foil, dry, and roll them into a negative electrode sheet with a compaction density of 1.55 g / cm 3 compaction density. Mix PEO, lithium bis(trifluoromethanesulfonyl)imide, succinonitrile, and lithium lanthanum zirconium tantalum oxide in a ratio of 5:2:1:2, dissolve them in anhydrous acetonitrile to form a homogeneous slurry; finally, directly scrape - coat the slurry on the surface of the graphite negative electrode sheet, dry it at room temperature for 1 h, then dry it at a high temperature, and finally hot - press it to form a dense coating, with the thickness controlled at 0.5 - 1 μm (temperature: 120°C, pressure: 10 MPa, time: 10 min).

[0079] S3. Battery assembly: Stack the positive electrode, polymer solid electrolyte membrane, and composite negative electrode sheet, and use the above - mentioned solid electrolyte membrane for the solid electrolyte membrane;

[0080] The polymer solid electrolyte and solid - state battery enhanced by the synergistic effect of the bifunctional filler can be applied to fields such as consumer electronics, electric vehicles, energy storage systems, and low - altitude flight.

[0081] Example 2

[0082] The main differences from Example 1 include: The mass ratio of the polymer matrix, lithium salt, first filler, and second filler is 60:25:5:10, and the corresponding X1 / X2 = 0.5.

[0083] Example 3

[0084] The differences from Example 1 mainly include: the mass ratios of the polymer matrix, lithium salt, first filler, and second filler are 60:25:10:5, corresponding to X 1 / X2 = 2.

[0085] Example 4

[0086] The differences from Example 3 mainly include: the polymer matrix is replaced with polymethyl methacrylate, the first filler is barium titanate, and the second filler is lithium germanium phosphate.

[0087] Comparative Example 1

[0088] The differences from Example 1 mainly include: the mass ratios of the polymer matrix, lithium salt, and first filler are 60:25:15.

[0089] Comparative Example 2

[0090] The differences from Example 1 mainly include: the mass ratios of the polymer matrix, lithium salt, and second filler are 60:25:15.

[0091] Comparative Example 3

[0092] The differences from Example 1 mainly include: the mass ratios of the polymer matrix, lithium salt, first filler, and second filler are 60:25:12:3, corresponding to X1 / X2 = 4.

[0093] Comparative Example 4

[0094] The differences from Comparative Example 3 mainly include: the negative electrode sheet does not contain a PEO-based modified solid electrolyte coating.

[0095] From the results of the above Examples 1 - 4 and Comparative Examples 1 - 4, it can be seen that

[0096] In the polymer electrolyte system, the entanglement and interaction between polymer molecular chains are strong. The lithium ions in the lithium salt are tightly entangled by anions and polymer chains, resulting in a small number of free lithium ions and a small lithium ion transference number. Secondly, the lithium ion transport generally can only move slowly along the long-range polymer chains, and the ionic conductivity is low. In addition, the polymer electrolyte has a narrow electrochemical window, is easily oxidized at high voltages, has poor chemical stability, and poor cycling performance.

[0097] When a polymer electrolyte is compounded with inorganic fillers, the lithium-ion transference number and the electrochemical window of the polymer electrolyte can be improved. When compounded with the first filler, which has a high dielectric constant itself, the interaction between cations and anions of the lithium salt can be weakened, the dissociation of the lithium salt can be accelerated, and the lithium salt anions can be fixed by the Lewis acid effect, significantly improving the transference number of free lithium ions. However, most of the lithium-ion transport still relies on slow long-range polymer chains, resulting in low ionic conductivity and limited performance improvement. When compounded with the second filler, which has a high electrochemical window and ionic conductivity, the electrochemical window of the polymer solid electrolyte can be significantly improved, compatible with high-voltage cathode materials. However, its ability to dissociate lithium salts is weak, the transference number of free lithium ions is low, and the improvement of cycle performance is limited.

[0098] Furthermore, when the first filler and the second filler are compounded, the electrochemical performance is further improved. The compounding of the two fillers can not only broaden the transference number of free lithium ions in the polymer electrolyte but also improve the electrochemical window and ionic conductivity. When there is too much of the first filler, the transference number of dissociated free lithium ions is large, but most lithium ions can only slowly transport along the polymer chains, and only a few can transport along the filler-polymer interface, resulting in low ionic conductivity. When there is too much of the second filler, the ability to dissociate lithium salts is poor, the available lithium ions are few, and the electrochemical performance is limited. When the mass X1 of the first filler and the mass X2 of the second filler satisfy 0.5 ≤ X1 / X2 ≤ 2, it can not only promote the dissociation of the lithium salt but also allow the dissociated lithium ions to rapidly transport along the polymer-filler interface, taking into account high lithium-ion transference number, high ionic conductivity, and wide electrochemical window, thus significantly improving the battery performance.

[0099] In addition, when matching high-loading positive and negative electrode sheets, the kinetic performance inside the electrode sheets is also a key factor affecting the battery performance. This application also discloses a composite negative electrode sheet, on which a modified PEO-based solid electrolyte coating is coated on the surface of the negative electrode sheet. The high flexibility of PEO can effectively reduce the interfacial voids inside the electrode sheet, forming a continuous and stable solid-solid contact interface. The high mechanical strength of PEO can limit the uneven deposition of lithium metal, and its uniform distribution can alleviate the lithium dendrite problem caused by excessive local current. The modified PEO-based solid electrolyte coating can also reduce the interfacial impedance between the negative electrode and the electrolyte, significantly improving the ionic conductivity of the graphite negative electrode and alleviating the kinetic problems under high loading.

[0100] Finally, under the dual strategies of the polymer solid electrolyte synergistically enhanced by bifunctional fillers and the composite negative electrode sheet, the electrochemical performance of the solid-state battery is significantly improved. Table 1 shows the performance test results of the solid electrolyte membranes and solid-state batteries of the examples and comparative examples.

[0101]

[0102] Table 1

[0103] The present application discloses a polymer solid electrolyte and a solid-state battery synergistically enhanced by dual-functional fillers. In a first aspect, a polymer solid electrolyte synergistically enhanced by dual-functional fillers is provided. The electrolyte employs a polymer matrix, a lithium salt, and two functional fillers: the first filler has a high dielectric constant, and under its own polarization effect, it can accelerate the dissociation of the lithium salt, fix the lithium salt anions, and increase the lithium ion transference number. The second filler has a high electrochemical window and ionic conductivity, can inhibit high-voltage decomposition, and is compatible with high-voltage cathode materials. Through the synergy and gradient design of the two fillers, ion transport, interface stability, and high-voltage compatibility can be taken into account. In addition, the present application also designs a composite negative electrode sheet by coating a modified PEO-based solid electrolyte coating on the surface of the negative electrode sheet. The high flexibility of the PEO electrolyte can effectively reduce the interface voids inside the electrode sheet, form a continuous and stable solid-solid contact interface, and the high ionic conductivity can significantly improve the ionic conductivity of the negative electrode sheet and alleviate the kinetic problems under high loading. Based on the polymer solid electrolyte and the composite negative electrode sheet, the high-performance solid-state battery developed in the present application has excellent electrochemical performance and can play an important role in fields such as consumer electronics, electric vehicles, energy storage systems, and low-altitude flight. Table 1 shows the performance test results of the solid electrolyte membranes and solid-state batteries of the examples and comparative examples of the present application.

[0104] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that this is only an example, and the protection scope of the present invention is defined by the appended claims. Without departing from the principles and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A polymer solid electrolyte synergistically enhanced by dual-functional fillers, comprising a polymer matrix, a lithium salt, and functional fillers, wherein: Polymer matrix: 50 - 90 wt%; Lithium salt: 5 - 30 wt%; Functional fillers: 5 - 20 wt%; The functional fillers include a first filler and a second filler; The first filler includes at least one of titanium dioxide, zirconium oxide, tantalum pentoxide, barium titanate, strontium barium titanate, and strontium titanate; The second filler includes at least one of lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium aluminum titanium phosphate, lithium germanium aluminum phosphate, and halide electrolytes; The mass percentage of the first filler is X1 and the mass percentage of the second filler is X2, which need to satisfy 0.5 ≤ X1 / X2 ≤ 2.

2. The polymer solid electrolyte synergistically enhanced by dual-functional fillers according to claim 1, wherein The polymer matrix includes at least one of polyethylene oxide, polytetrafluoroethylene, polyvinylidene fluoride hexafluoropropylene, polyethylene glycol methacrylate, poly(dioxolane), polysiloxane, and polymethyl methacrylate; The lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium tetrafluoroborate, and lithium bis(oxalato)borate.

3. The polymer solid electrolyte synergistically enhanced by dual-functional fillers according to claim 2, wherein The first filler has a dielectric constant greater than or equal to 30 at 10 Hz and a particle size of 10 - 500 nm; The second filler has an electrochemical window ≥ 4.5 V, an ionic conductivity higher than 10 -4 S / cm at 25°C, and a particle size of 10 - 500 nm.

4. The polymer solid electrolyte synergistically enhanced by the bifunctional filler according to any one of claims 1-3, characterized in that, The preparation method of the polymer solid electrolyte membrane synergistically enhanced by dual-functional fillers includes the following steps: S1. Ball-mill the first filler and the second filler for a certain time and mix them evenly; S2. Mix the polymer and the lithium salt in proportion and dissolve them in an organic solvent to form a uniform slurry; subsequently, add the fillers mixed evenly in S1 to the above slurry in proportion and stir to form a uniform slurry; S3. Form a solid electrolyte membrane by the casting method or the hot pressing method, with a thickness of 10 - 100 μm.

5. A solid-state battery comprising a polymer solid electrolyte synergistically reinforced with the bifunctional filler according to any one of claims 1-4, characterized in that It includes a composite negative electrode sheet, a positive electrode sheet, and a polymer solid electrolyte.

6. The solid-state battery according to claim 5, characterized in that, The composite negative electrode sheet includes a lithium metal negative electrode or a graphite negative electrode, and a modified PEO-based solid electrolyte coating coated on the surface of the lithium metal negative electrode or the graphite negative electrode, with a coating thickness of 0.1 - 5 μm.

7. The solid-state battery according to claim 6, characterized in that, The PEO-based solid electrolyte coating contains PEO, a lithium salt, a plasticizer, and the second filler, wherein the mass ratio of the second filler is 10% - 40%.

8. The solid-state battery according to claim 7, characterized in that, The plasticizer is at least one of polyethylene glycol (PEG), ethylene carbonate, or succinonitrile, and the mass ratio of PEO to the plasticizer is 1:0.01 - 0.

2.

9. The solid-state battery according to claim 8, wherein The PEO-based solid electrolyte coating is formed by the doctor blade method and a dense negative electrode - electrolyte interface is formed through a hot pressing process; For the hot pressing process, the temperature is 80 - 120 °C and the pressure is 5 - 20 MPa.

10. The solid-state battery according to claim 9, characterized in that, The positive electrode sheet includes a positive electrode material, a conductive agent, a binder, and the second filler, wherein the mass ratio of the second filler is 1% - 5%.

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