Hierarchical porous ceramic-polymer electrolytes, their preparation methods and applications

Abstract

This invention belongs to the field of solid-state electrolyte and solid-state lithium metal battery engineering technology, specifically relating to a ceramic-polymer electrolyte with a hierarchical porous structure, its preparation method, and its application. It includes: a ceramic framework with a hierarchical porous structure and a polymer electrolyte filling the pores of the ceramic framework. The ceramic framework comprises a relatively dense layer and a porous framework layer. The relatively dense layer is positioned towards the positive electrode side to reduce direct contact between the polymer electrolyte and the positive electrode. The porous framework layer fuses with the diffusely permeated polymer electrolyte to form a continuous ceramic-polymer interface transition region. Compared with existing technologies, this invention effectively solves the problems of high-pressure decomposition of polymer-based electrolytes, low lithium-ion transfer numbers, and solid-solid interface contact issues of LLZTO electrolytes by incorporating a PEO / PVDF polymer electrolyte into a hierarchical porous LLZTO framework, providing a practical approach to achieving high-performance and safe solid-state lithium batteries.

Description

Technical Field

[0001] This invention belongs to the field of solid electrolyte development technology, specifically relating to ceramic-polymer electrolytes with hierarchical pore structures, their preparation methods, and applications. Background Technology

[0002] The global energy transition to renewable energy requires technological breakthroughs in the efficiency and safety of energy storage systems. Polymer-based solid electrolytes (PSEs) are considered promising candidates for solid-state lithium batteries due to their inherent safety, mechanical flexibility, and compatibility with lithium metal anodes. However, their practical application in conjunction with high-voltage cathodes is limited by their low lithium-ion transference number and relatively narrow electrochemical stability window. Polyethylene glycol (PEO) / polyvinylidene fluoride (PVDF)-based polymer electrolytes have been extensively studied, but the high crystallinity of polyethylene glycol and the poor lithium-ion transport capacity of PVDF itself hinder the continuous and rapid migration of lithium ions. Furthermore, the limited anion confinement capacity of the PEO / PVDF matrix results in a low lithium-ion transference number, which exacerbates local interfacial polarization during operation. This polarization further accelerates the oxidative decomposition of the electrolyte at the cathode under high-voltage conditions, thus limiting the electrochemical stability window and restricting the application of practical batteries.

[0003] To improve lithium-ion transference numbers and broaden the electrochemical stability window of polymer electrolytes, inorganic ceramic electrolyte particles (such as LLZO) are often incorporated as active fillers to enhance anion adsorption and interfacial interactions. Although some ceramic electrolytes are not thermodynamically fully compatible with highly delithiated high-voltage cathodes, with appropriate interfacial engineering, their interfacial reactions may be kinetically restricted or passivation layers may form, thus achieving stable cycling at room temperature. However, directly adding ceramic fillers is insufficient to effectively separate the polymer from the cathode, leading to oxidative decomposition under high-voltage conditions and compromising interfacial stability. Dense inorganic electrolyte sheets can effectively separate the polymer electrolyte from the cathode, but their fully laminated structure often lacks sufficient interfacial interpenetration and a gradual phase transition with the polymer, thus disrupting continuous lithium-ion transport and exacerbating local interfacial polarization. For polymer electrolytes, the rational design of inorganic-organic topologies remains a significant challenge, as it must simultaneously meet requirements such as continuous ion transport, low polarization, high lithium-ion transference numbers, and a wide electrochemical stability window. Therefore, achieving high lithium-ion transfer number, low polarization, and a wide electrochemical stability window simultaneously in polymer electrolytes remains a significant challenge. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a ceramic-polymer electrolyte with a hierarchical pore structure, its preparation method, and its application.

[0005] The adopted technical solution is as follows: a ceramic-polymer electrolyte with a hierarchical pore structure, comprising: a ceramic framework with a hierarchical pore structure and a polymer electrolyte filling the pores of the ceramic framework. The ceramic framework comprises a relatively dense layer and a porous framework layer, wherein the porosity of the relatively dense layer is lower than that of the porous framework layer. The relatively dense layer is positioned towards the positive electrode side to reduce direct contact between the polymer electrolyte and the positive electrode; the porous framework layer fuses with the diffusely permeated polymer electrolyte to form a continuous ceramic-polymer interface transition region.

[0006] Preferably, the ceramic framework is an LLZTO ceramic framework with the following chemical composition: .

[0007] Preferably, the relatively dense layer contains interconnected residual pores, which serve as permeation channels to improve the interfacial wettability on the positive electrode side.

[0008] Preferably, the polymer electrolyte diffuses into the porous framework layer and forms a bicontinuous phase structure therewith.

[0009] Preferably, the polymer electrolyte is a PEO / PVDF polymer electrolyte.

[0010] A method for preparing a ceramic-polymer electrolyte with a hierarchical porous structure, used to prepare the ceramic-polymer electrolyte with a hierarchical porous structure as described in this invention, includes the following steps: S1. Preparation of ceramic slurry containing pore-forming agent and ceramic slurry without pore-forming agent; S2. Ceramic slurry containing pore-forming agent and ceramic slurry without pore-forming agent are cast and coated onto a transfer film, and then pressed, dried and sintered to obtain a ceramic skeleton with a hierarchical pore structure. S3. Apply the polymer electrolyte solution to the porous framework layer of the ceramic skeleton, allowing the polymer solution to penetrate into the pores of the porous framework layer. After drying to remove the solvent, the ceramic-polymer electrolyte with hierarchical pore structure is obtained, referred to as P-LLZTOP electrolyte membrane.

[0011] Preferably, in step S2, the ceramic slurry containing a pore-forming agent and the ceramic slurry without a pore-forming agent are respectively cast and coated onto the transfer membrane. Pressure is applied to mechanically press the two membranes together while the surfaces of the two slurries are in a semi-solid state. The sedimentation effect of ceramic particles and the double-layer pressing effect are used to form a dense intermediate zone. After static drying, the membrane is sintered at high temperature in a lithium-rich atmosphere to obtain the ceramic skeleton.

[0012] Preferably, in step S1, the ceramic slurry is prepared by mixing LLZTO pre-formed powder with a solvent, dispersant, plasticizer, and binder to obtain a mixed slurry, wherein the LLZTO pre-formed powder is composed of LiOH. , and Raw materials It is obtained by calcining after mixing in stoichiometric proportions.

[0013] Application of ceramic-polymer electrolytes with hierarchical pore structures as described in this invention in solid-state lithium batteries.

[0014] A solid-state lithium battery includes a positive electrode, a negative electrode, and a ceramic-polymer electrolyte with a hierarchical porous structure as described in this invention, wherein the relatively dense layer is disposed toward the positive electrode side, and the porous framework layer of the composite polymer electrolyte is disposed toward the negative electrode side.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By incorporating PEO / PVDF polymer electrolyte into the hierarchical porous LLZTO framework, replacing the mechanically dispersed LLZTO filler and the composite of PEO / PVDF polymer, a progressive inorganic-organic lithium-ion transport pathway is formed, avoiding local current unevenness caused by filler agglomeration.

[0016] 2. The relatively dense LLZTO layer serves as an enriched region on the positive electrode side, reducing the direct contact between the polymer phase and the high-voltage positive electrode and improving the high-voltage stability of the electrolyte.

[0017] 3. The porous framework region of LLZTO facilitates the penetration and diffusion of viscous polymer electrolytes, forming a continuous ceramic-polymer interface transition region, providing a continuous ion transport path, thereby increasing the lithium-ion transference number and reducing interfacial impedance and local polarization.

[0018] 4. The P-LLZOP electrolyte achieves an ionic conductivity of [value missing] at 30°C. The lithium-ion transference number reaches 0.69, and the electrochemical stability window is approximately 4.7V. Symmetrical cells It can be stably cycled for over 2000 hours, with a critical current density reaching [value missing]. .

[0019] 5. Using P-LLZTOP and The (LFP) cathode-paired full cell retained 87.4% of its initial capacity after 600 cycles. The P-LLZTOP cathode-paired full cell can undergo long cycles at high voltages.

[0020] In summary, by incorporating a PEO / PVDF polymer electrolyte into a hierarchical porous LLZTO framework, this invention effectively solves the problems of high-pressure decomposition of polymer-based electrolytes, low lithium-ion transfer number, and solid-solid interface contact of LLZTO electrolytes, providing a practical approach to achieving high-performance and safe solid-state lithium batteries. Attached Figure Description

[0021] Figure 1 These are cross-sectional SEM images of polymer electrolytes and composite electrolytes.

[0022] Figure 2 This is an overview diagram of the structure, morphology, and lithium-ion transport advantages of the composite electrolyte in this invention.

[0023] Figure 3 This is a cross-sectional SEM image of the graded porosity LLZTO in this invention.

[0024] Figure 4 This is a SEM image of the relatively dense layer in the graded porosity LLZTO of this invention.

[0025] Figure 5 This is a SEM image of the porous framework layer in the graded porosity LLZTO of this invention.

[0026] Figure 6 This is an optical photograph of the P-LLZTOP composite electrolyte membrane in this invention.

[0027] Figure 7 This is a high-magnification SEM image of the PEO / PVDF side of the P-LLZTOP composite electrolyte membrane in this invention.

[0028] Figure 8 This is an elemental distribution diagram of Zr, La, F and S in the P-LLZTOP composite electrolyte membrane of this invention.

[0029] Figure 9 These are the FT-IR spectra of P-LLZTOP and LLZTO in this invention.

[0030] Figure 10 These are the Raman spectra of PEO / PVDF and P-LLZTOP in this invention.

[0031] Figure 11 This is the thermogravimetric analysis (TGA) diagram of PEO / PVDF and P-LLZTOP in this invention.

[0032] Figure 12 These are the 7Liss NMR spectra of different electrolytes at 25°C in this invention.

[0033] Figure 13DSC test diagrams of PEO / PVDF and P-LLZTOP in this invention.

[0034] Figure 14 These are XRD test images of PEO / PVDF, LLZTO, and P-LLZTOP in this invention.

[0035] Figure 15 This is the Arrhenius diagram of PEO / PVDF and P-LLZTOP in this invention.

[0036] Figure 16 This is the timing current measurement curve of F-LLZTOP under a 10mV potential step in this invention.

[0037] Figure 17 This is the timing current measurement curve of P-LLZTOP in this invention at a potential step of 10mV.

[0038] Figure 18 This is a bar chart comparing the performance of the present invention with that of previously reported electrolytes in terms of lithium-ion transference number.

[0039] Figure 19 It is a P-LLZTOP symmetric cell in the range of 0.01 to Voltage curves within the current density range.

[0040] Figure 20 These are the Tafel curves for PEO / PVDF, F-LLZTOP, and P-LLZTOP electrolytes.

[0041] Figure 21 It is a P-LLZTOP symmetric cell in Cyclic performance at current density.

[0042] Figure 22 It is a P-LLZTOP symmetric cell in Cyclic performance at current density.

[0043] Figure 23 This is a rate performance graph for Li / P-LLZTOP / LFP batteries.

[0044] Figure 24 This is a charge-discharge curve of a Li / P-LLZTOP / LFP battery at different rates.

[0045] Figure 25 It is Li / P-LLZTOP / LFP in Cyclic performance at current density.

[0046] Figure 26 This is the LSV curve of PEO / PVDF, F-LLZTOP and P-LLZTOP electrolytes.

[0047] Figure 27 This is a charge-discharge curve of a Li / P-LLZTOP / NCM811 battery at different rates.

[0048] Figure 28 This is a graph showing the cycling performance of Li / P-LLZTOP / NCM811 at a charge / discharge rate of 0.3C.

[0049] Figure 29 This is a SEM image of the surface of the P-LLZTOP electrolyte after cycling.

[0050] Figure 30 This is a SEM image of the lithium anode surface in a cycled P-LLZTOP symmetric cell.

[0051] Figure 31 This is a SEM image of the lithium anode surface in a cycled F-LLZTOP symmetric cell.

[0052] Figure 32 This is a model diagram of the early stage of reaction in the PEO / PVDF structure.

[0053] Figure 33 This is a model diagram of the PEO / PVDF structure reaction in the last frame.

[0054] Figure 34 During the reaction process and TFSI - Diffusion coefficient diagram in PEO / LLZTO.

[0055] Figure 35 During the reaction process and TFSI - The quantity distribution in PEO / LLZTO for the last frame.

[0056] Figure 36 This is a graph showing the MSD calculation results of each component at the PEO / LLZTO interface.

[0057] Figure 37 This is a calculation plot of g(r)RDF for Li-OTFSI, La-OTFSI, and Zr-OTFSI at the PEO / LLZTO interface.

[0058] Figure 38 This is a CN(r)RDF calculation diagram of Li-OTFSI, La-OTFSI, and Zr-OTFSI at the PEO / LLZTO interface. Detailed Implementation

[0059] To facilitate understanding of the present invention, it will be described in more detail below with reference to the accompanying drawings and specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0060] The composite electrolyte of this invention comprises: a ceramic framework with a hierarchical pore structure and a polymer electrolyte filling the pores of the ceramic framework. The ceramic framework includes a relatively dense layer and a porous framework layer. The porosity of the relatively dense layer is lower than that of the porous framework layer. The relatively dense layer is disposed towards the positive electrode side to reduce direct contact between the polymer electrolyte and the positive electrode. The porous framework layer fuses with the diffusely permeated polymer electrolyte to form a continuous ceramic-polymer interface transition region. (Refer to...) Figure 2 It is understood that relatively dense regions correspond to relatively dense layers, while highly porous regions correspond to porous framework layers.

[0061] The relatively dense layer provides mechanical integrity for processing and assembly. Retaining some residual porosity rather than being completely dense, the interconnected pores act as open permeation channels, suppressing incomplete permeation, air gaps, and voids. It also facilitates cathode-side coupling via liquid electrolytes or ionic liquids, thereby improving interfacial wettability, reducing interfacial resistance, and mitigating local current inhomogeneity. This layer's main surface faces the cathode side, reducing direct contact between the polymer phase and the high-voltage cathode surface, providing a high-voltage stable interface. The porous framework layer facilitates the permeation and diffusion of the viscous polymer electrolyte. The looser regions fuse with the polymer electrolyte, forming a continuous ceramic-polymer interfacial transition zone, providing a continuous ion transport path, reducing interfacial impedance and local polarization.

[0062] In one embodiment, the ceramic framework is an LLZTO ceramic framework with the following chemical composition: .

[0063] In one embodiment, the polymer electrolyte diffuses into the porous framework layer and forms a bicontinuous phase structure therewith.

[0064] In one embodiment, the polymer electrolyte is a PEO / PVDF polymer electrolyte, comprising: polyethylene glycol (PEO), polyvinylidene fluoride (PVDF), and lithium salt LiTFSI, wherein the mass ratio of PEO to PVDF is 1:1, and the mass ratio of EO to PVDF is 1:1. The molar ratio is 20:1.

[0065] The preparation of the above-mentioned composite electrolyte includes the following steps: S1. Preparation of ceramic slurry containing pore-forming agent and ceramic slurry without pore-forming agent; S2. Ceramic slurry containing pore-forming agent and ceramic slurry without pore-forming agent are cast and coated onto a transfer film, and then pressed, dried and sintered to obtain a ceramic skeleton with a hierarchical pore structure; wherein the sintering temperature is 1000-1100℃ and the sintering time is 1-5h. S3. Apply the polymer electrolyte solution to the porous framework layer of the ceramic skeleton, allowing the polymer solution to penetrate into the pores of the porous framework layer. After drying to remove the solvent, the ceramic-polymer electrolyte with hierarchical pore structure is obtained, referred to as P-LLZTOP electrolyte membrane.

[0066] In one embodiment, in step S2, the ceramic slurry containing a pore-forming agent and the ceramic slurry without a pore-forming agent are respectively cast and coated onto a transfer membrane. Pressure is applied to mechanically press the two membranes together while the surfaces of the two slurries are in a semi-solid state. The sedimentation effect of ceramic particles and the double-layer pressing effect are used to form an intermediate dense region. After static drying, the membrane is sintered at high temperature in a lithium-rich atmosphere to obtain the ceramic skeleton. The porosity of the intermediate dense region is lower than that of the relatively dense layer.

[0067] In one embodiment, in step S1, the ceramic slurry is prepared by mixing LLZTO pre-formed powder with a solvent, dispersant, plasticizer, and binder to obtain a mixed slurry. The LLZTO pre-formed powder is made from LiOH. , and Raw materials It is obtained by calcining after mixing in stoichiometric proportions.

[0068] In one embodiment, the polymer electrolyte solution is prepared by dissolving PEO, PVDF, and lithium salt in an NMP-acetonitrile mixed solvent and stirring continuously until a homogeneous mixture is obtained; wherein the mass ratio of PEO:PVDF is 0.9-1.1:1, and the mass ratio of EO:PVDF is 1:1. The molar ratio is 20:1.

[0069] In one embodiment, the pore-forming agent is chosen to be completely burned off during the subsequent sintering process, leaving pores. It can be PMMA or PS microspheres.

[0070] The application of the ceramic-polymer electrolyte with hierarchical pore structure described in this invention in solid-state lithium batteries.

[0071] A solid-state lithium battery includes a positive electrode, a negative electrode, and a ceramic-polymer electrolyte with a hierarchical porous structure as described in this application, wherein the relatively dense layer is disposed towards the positive electrode side, and the porous framework layer of the composite polymer electrolyte is disposed towards the negative electrode side.

[0072] Example 1: Preparation method of graded porosity LLZTO composite polymer-based electrolyte, the steps are as follows: S1. Solvent preparation: Methylpyrrolidone (NMP) and acetonitrile are mixed to obtain an NMP-acetonitrile mixed solvent; S2, PEO / PVDF electrolyte preparation: First, PEO (MW~600,000) and LiTFSI (EO: The polymer electrolyte solution was dissolved in an acetonitrile-NMP mixed solvent (PEO:PVDF = 20:1), followed by the addition of PVDF (PEO:PVDF mass ratio 1:1). The mixture was continuously stirred until the polymer was completely dissolved to obtain a homogeneous solution (in a glove box), which is the polymer electrolyte solution. The resulting homogeneous mixture was coated onto a PTFE plate using a solution casting method and dried in a vacuum oven at 60°C for 8 hours, then transferred to a glove box for 12 hours to remove residual solvent.

[0073] S3. Preparation of graded porosity LLZTO electrolyte membrane: according to Weigh out LiOH in stoichiometric proportions. , and The raw material powder, with a 10 mol% excess of lithium, was used to compensate for lithium loss during the subsequent electrolyte membrane preparation process. The powder was impregnated with IPA and ball-milled for 10 hours, ensuring air isolation during mixing. The solvent was evaporated in a vacuum drying oven, and the raw material was pulverized again and calcined in a muffle furnace at 920°C for 10 hours. The calcined pre-formed powder was mixed with TOL, IPA, and fish oil at a weight ratio of 40:25:20:0.5 and ball-milled for 5 hours to ensure uniform dispersion of the powder under the influence of the fish oil. Subsequently, BBP and PVB were added at a mass ratio of 8.5:6, and the mixture was ground for 6 hours to form a slurry. Half of the slurry was mixed with PMMA pore-forming agent and ball-milled for 1 hour. Vacuum treatment for 2 minutes was performed to remove air bubbles from the slurry, taking care to avoid surface solidification, which could affect subsequent casting. The two slurries were then cast and coated onto a polyethylene terephthalate (PET) film. After the surfaces of the two slurries have slightly solidified, pressure is applied to mechanically press the two films together. Due to the LLZTO settling effect and the double-layer pressing effect, the middle region becomes denser. After complete static drying, the LLZTO film to be sintered is sandwiched in an alumina plate, and pre-prepared powder is laid around it to provide a lithium-rich atmosphere during sintering. Sintering is carried out in a muffle furnace at 1050°C for 2 hours to obtain a graded porous LLZTO ceramic framework with binder removed.

[0074] Preparation of S4 and P-LLZTOP electrolyte membranes: Using a polytetrafluoroethylene plate as a support, the PEO / PVDF polymer solution obtained in S2 was uniformly coated on the high porosity side of the hierarchical porosity LLZTOP skeleton obtained in S3, allowing the polymer solution to penetrate into the high porosity region and locally penetrate into the residual pores of the relatively dense layer. The membrane was vacuum dried at 60°C for 10 hours, and then transferred to a glove box to air dry for 12 hours to completely remove residual solvent.

[0075] Note: Toluene (TOL) is used as a solvent for dissolution; isopropanol (IPA) acts as a co-solvent to regulate the evaporation rate and prevent surface crusting; fish oil is used as a dispersant to prevent particle agglomeration and ensure uniform dispersion; butyl benzyl phthalate (BBP) is used as a plasticizer to increase the flexibility of the green body, facilitating pressing; polyvinyl butyral (PVB) is used as a binder to provide mechanical strength to the green body and maintain its shape. All of the above materials volatilize during subsequent processing or decompose during the sintering process. All are commercially available.

[0076] Comparative Example: To illustrate the difference between the hierarchical porosity framework structure of this invention and the traditional filler composite strategy, LLZTO powder prepared in S2 was directly added as a filler to the PEO / PVDF precursor solution obtained in S2. After stirring, dispersion, casting, and drying, an F-LLZTOP electrolyte membrane was obtained. In this comparative sample, LLZTO was randomly dispersed in the polymer matrix as particulate filler and could not form a continuous hierarchical porosity ceramic framework.

[0077] Battery assembly, assembly In symmetrical cell assembly, the polymer side of P-LLZTOP is brought into contact with the lithium metal anode. or In a full cell configuration, the relatively dense LLZTO layer faces the positive electrode, while the polymer side faces the lithium metal negative electrode.

[0078] Test method: The surface and cross-section of the prepared electrolyte sheet were characterized using scanning electron microscopy (Thermofisher Sciencetific Apero S Hivac, 5kV), including the morphology, grain size, and elemental distribution of the sample. Raman spectroscopy (HORIBA France SAS, 532nm) and X-ray diffraction (Bruker, 5kV) were also used. The surface information and phase structure of the samples were characterized using X-ray photoelectron spectroscopy (FTIR, Agilent Cary 630) and Fourier transform infrared spectroscopy (FTIR, Agilent Cary 630). The interfacial structure of the electrolyte and lithium anode before and after cycling was characterized, and all peaks were calibrated with reference to the C-C bond at 284.8 eV.

[0079] Electrochemical measurements were performed on symmetrical Li / CPEs / Li batteries assembled with lithium-ion electrodes at different current densities. EIS tests were conducted at an AC voltage of 10 mV within the range of 1 MHz to 0.1 Hz, and the resistance of the symmetrical cells was measured to calculate the ionic conductivity. The ionic conductivity of the polymer electrolyte was calculated using the formula: σ = L / R∙S, where L is the thickness of the polymer electrolyte film, R is the bulk ohmic resistance, and S represents the contact area between the stainless steel (SS) and the polymer electrolyte film.

[0080] Using a symmetrical lithium-ion battery, EIS testing was conducted at an AC voltage of 10 mV within the range of 1 MHz to 0.1 Hz to measure the ionic conductivity of the symmetrical battery. The ionic conductivity of the polymer electrolyte was calculated using the following formula: σ = L / R∙S, where L is the thickness of the polymer electrolyte film, R is the volume ohmic resistance, and S represents the contact area between the lithium metal and the polymer electrolyte film. The lithium-ion transfer number (LTL) of the polymer electrolyte was investigated using a symmetrical lithium-ion battery by combining AC impedance and DC polarization methods. ). The value is calculated according to the Bruce-Vincent Evans equation: ΔV is the applied DC polarization voltage of 10 mV. I0 and Is are present, representing the DC currents before and after polarization, respectively. R0 and Rs represent the initial and final charge transfer resistances during the polarization process. The electrochemical stability of the electrolyte was measured by linear sweep frequency voltammetry (LSV) on an SS / SPEs / lithium asymmetric cell at a scan rate of 1 mV / s. To assess the compatibility of the electrolyte with lithium metal, galvanostatic cycling tests were performed in a symmetric Li / SPE / Li cell, including repeated charge-discharge cycles of 40 minutes.

[0081] The electrochemical stability of the electrolyte was studied by linear sweep voltammetry (LSV) at a scan rate of 1 mV / s on an SS / CPEs / Li asymmetric cell.

[0082] To evaluate the compatibility of the electrolyte with lithium metal, constant-current cycling measurements consisting of repeated 40-minute charge / discharge cycles were performed in a symmetrical Li / SPEs / Li battery. The prepared LFP cathode material was assembled into a complete battery with an electrolyte diameter of 9 mm. All batteries were assembled in an argon-filled glove box. and The charge-discharge performance and electrochemical performance of the assembled battery were recorded using an LH-TCS-300L / CT3004A testing system and a CHI760E electrochemical workstation, respectively.

[0083] Test result description: Figure 1-2This paper presents SEM images and schematic diagrams of our designed stepped porous ceramic / polymer composite electrolyte. The electrochemical performance of traditional PEOVDF polymer electrolytes is mainly limited by their high crystallinity, leading to slow ion transport, low ion conductivity, and low lithium-ion transfer number. Although LLZTO in the filler-composite F-LLZTOP electrolyte can interact with the polymer matrix at the interface to enhance ion transport, the filler exhibits uneven dispersion and agglomeration within the polymer matrix, resulting in localized high current density and uneven charge distribution leading to dendrite growth, and it does not solve the problem of high-pressure decomposition. In contrast, the stepped porous LLZTO exhibits a more compact central structure due to particle sedimentation and bilayer compression effects, resulting in a complete and continuous framework structure. This framework can undergo interfacial composite with the polymer matrix while isolating the polymer from the positive electrode, homogenizing the electric field, and establishing continuous lithium-ion transport channels for faster lithium-ion conduction. Furthermore, the porous LLZTO framework can achieve anion adsorption and maintain the local migration rate of anions within the pores, thereby reducing polarization. The synthesized electrolyte achieves a high lithium-ion transfer number of approximately 0.69 at room temperature, significantly superior to the traditional PEOVDF electrolyte and LLZTO filler composite electrolyte. Simultaneously, the porous LLZTO prevents polymer decomposition under high voltage, giving the electrolyte a wide electrochemical window of 4.7V. Furthermore, after adding a small amount of ester electrolyte to the positive electrode side and mechanically pressing, stable cycling of full cells matched with LFP and NCM811 positive electrodes is achieved.

[0084] Figure 3-5 The morphological characterization of the porous LLZTO cross-section is shown. We designed the porous LLZTO to have a hierarchical porous morphology, dividing it into a high-porosity side (porosity framework layer, also known as the porous side) and a relatively dense side (relatively dense layer, also known as the dense region). On the polymer side, the LLZTO exhibits a rounded porous structure, allowing it to bond tightly with the polymer. The dense region faces the positive electrode side, avoiding side reactions at the electrolyte-positive electrode interface caused by contact between the polymer and the high-voltage positive electrode material.

[0085] Figure 6-7 The image shows the morphological characterization of the P-LLZTOP composite electrolyte. Among them, Figure 6 The morphology of the P-LLZTOP composite electrolyte is shown. This composite electrolyte membrane was fabricated by uniformly coating a PEO / PVDF precursor solution onto an LLZTO membrane, supporting it with a PTFE substrate, and then drying it under an argon atmosphere. Scanning electron microscopy (SEM) was used to image the surface and cross-sectional morphology of both the positive and negative electrodes of the P-LLZTOP electrolyte. The results show that the positive electrode LLZTO surface exhibits a uniform, rounded, porous structure, while the negative electrode polymer surface is pore-free. Figure 7This unique structural design can overcome the incompatibility between LLZTO and lithium metal anodes in a solid-solid manner, and the positive electrode LLZTO can suppress polymer decomposition under high pressure.

[0086] Figure 8-11 This indicates that the Lewis acidic sites on the LLZTO surface bind with the polymer, forming a nanoconfinement effect. Elemental mapping of the p-LLZTOP electrolyte shows that some polymer is embedded in the porous LLZTO structure, generating a nanoconfinement effect. Figure 8 FTIR spectra obtained from the porous side of the P-LLZTOP electrolyte ceramic show the ether-oxygen (COC) bonds in PEO and the CF bonds in PVDF. Figure 9 Compared to pure PEO / PVDF electrolyte, the vibrational frequencies of the COC bonds changed significantly. This indicates that the polymer successfully penetrated into the porous LLZTO framework and interacted with the Lewis acid sites on the framework surface. Raman spectroscopy was performed... The location belongs to PEO / PVDF. The characteristic peaks of stretching vibrations further validated the polymer's permeation in porous structures. Figure 10 Thermogravimetric analysis showed that approximately 60% of the final residue of P-LLZTOP electrolyte was composed of the LLZTO backbone, and compared to pure polymer electrolytes, its decomposition temperature was increased, and its thermal stability was significantly enhanced. Figure 11 ).

[0087] Figure 12-14 This indicates that the LLZTO crystal structure remains intact, forming a bicontinuous phase with the polymer. Firstly, to further elucidate the lithium-ion transport mechanism, we conducted [analysis / testing] on the P-LLZTOP electrolyte. Solid-state nuclear magnetic resonance testing ( Figure 12 The spectrum shows two separate resonance peaks, whose chemical shifts precisely correspond to the characteristic peak positions of pure LLZTO and pure PEO / PVDF electrolytes, respectively. This confirms the formation of a clear bicontinuous phase structure in the composite material: lithium ions exhibit distinctly different coordination environments in the rapid conduction pathway of the porous LLZTO framework and the nano-confined polymer phase. Based on this structure, lithium ions can preferentially migrate long distances through the highly conductive LLZTO framework, while the confined polymer phase provides a stable negative electrode interface and effectively immobilizes anions, thereby synergistically constructing a continuous lithium ion transport channel. Secondly, to verify the effect of the porous LLZTO composite on the polymer crystallinity, DSC tests were performed on PEO / PVDF and P-LLZTOP electrolytes. Figure 13The results showed that, compared to the PEO / PVDF system, the glass transition temperature of the P-LLZTOP electrolyte decreased from -55°C to -57°C, while the enthalpy of melting significantly decreased to 34.5 J / g. This indicates that the nano-confinement effect of the polymer within the LLZTO channels enhanced local chain segment movement and inhibited crystallization behavior. Finally, XRD analysis confirmed this. Figure 14 The porous P-LLZTOP composite electrolyte consists of two phases: crystalline LLZTO and a polymer phase. No impurity crystalline phases (such as...) were detected. This indicates that the polymer has fully impregnated the porous LLZTO structure while the LLZTO crystal framework remains intact, thus providing a stable channel for the rapid migration of lithium ions.

[0088] Figure 15-20 This demonstrates that the porous LLZTO composite structure can improve the electrochemical performance of the electrolyte. Arrhenius curves ( Figure 15 This indicates that the ionic conductivity of the P-LLZTOP electrolyte is significantly higher than that of the PEO / PVDF system, reaching [value missing] at 30°C. And further increased to 60°C To further investigate lithium-ion migration behavior, we conducted combined chronoamperometry and electrochemical impedance spectroscopy measurements on symmetric cells assembled with different electrolytes. The results showed that the lithium-ion transference number of the F-LLZTOP electrolyte was 0.43 (…). Figure 16 The value was significantly higher than the 0.22 of the pure PEO / PVDF matrix. This improvement is mainly attributed to the enhanced interfacial interaction between the LLZTO filler particles and the polymer matrix, which improves lithium-ion transport. However, due to problems such as uneven filler dispersion and easy agglomeration, it is difficult to form a continuous and efficient lithium-ion conduction pathway.

[0089] In comparison, the P-LLZTOP electrolyte exhibits superior performance, with a lithium-ion transference number of 0.69 ( Figure 17 This is thanks to the porous LLZTO framework's ability to homogenize lithium-ion flux and establish continuous, rapid lithium-ion transport channels, thereby significantly improving overall migration efficiency. Based on its unique porous structure, this LLZTO framework achieves a lithium-ion transference number of 0.69, superior to most reported ceramic electrolyte systems. Figure 18 The critical current density of P-LLZTOP electrolyte is... ( Figure 19 This significantly exceeds that of traditional polymer electrolytes. The exchange current density measured in the PPL-L symmetric cell is... In P-LLZTOP symmetric cells, this value is significantly increased to ( Figure 20This indicates that the porous LLZTO structure reduces the charge transfer activation energy, giving the battery superior fast-charging capability and cycle stability. These performance improvements can be attributed to the multiple functions of the porous LLZTO framework in homogenizing lithium-ion flux, providing mechanical support, and constructing continuous lithium-ion transport pathways.

[0090] Figure 21 and Figure 22 The performance of a symmetric battery assembled with a P-LLZTOP composite electrolyte was demonstrated. The battery using the P-LLZTOP electrolyte exhibited… Maintaining lithium plating / stripping stability for over 2000 hours (see...) Figure 21 The F-LLZTOP electrolyte, due to the aggregation of LLZTO filler leading to uneven interfacial charge, resulted in increased interfacial impedance and dendrite growth, causing a short circuit after approximately 700 hours. To further evaluate high current density cycling performance, a symmetric cell containing P-LLZTOP electrolyte was tested... The cycle showed 600 hours of stable operation without short circuits (see...). Figure 22 The porous LLZTO structure demonstrates excellent interfacial stability achieved through homogenized current. Furthermore, the high compatibility of the polymer electrolyte with lithium metal at the negative electrode avoids the defects of solid-solid interface point contact, enabling stable cycling of the symmetrical battery through this unique structural design.

[0091] Figure 23-25 The performance of the LFP full cell assembled with P-LLZTOP electrolyte is demonstrated. First, to systematically evaluate the electrochemical performance of the Li / P-LLZTOP / LFP full cell, we tested its rate performance and long-term cycling stability. Rate test results ( Figure 23 The results show that the reversible specific capacities of the battery at charge / discharge rates of 0.05, 0.1, 0.3, 0.5, 1, and 2C are 159.7, 157.8, 142.0, 125.3, 97.7, and 62.9, respectively. It exhibits excellent high-rate adaptability; when the current density recovers to 0.1C, the capacity rapidly rebounds to 157.6. This demonstrates excellent capacity recovery capability and structural reversibility. Secondly, by observing the charge-discharge curves at different rates ( Figure 24 It was found that the electrode exhibited a stable voltage plateau at different charge-discharge rates, further demonstrating the high stability of the electrode reaction. Finally, by using 0.38... Long-term cycling of the full cell at current density ( Figure 25The battery exhibited excellent long-cycle durability, retaining 87.4% of its initial capacity after 600 cycles, with an average coulombic efficiency of 99.4%. This result fully demonstrates the effective stabilizing effect of the P-LLZTOP electrolyte on the electrode / electrolyte interface and the homogenization of lithium-ion current transport during cycling, thereby suppressing side reactions and ensuring continuous and efficient lithium-ion transport and deposition / stripping processes.

[0092] Figure 26-28 The electrochemical performance of P-LLZTOP electrolyte at high voltage was demonstrated. First, the electrochemical stability window of the electrolyte was tested using linear sweep voltammetry. Figure 26 The P-LLZTOP electrolyte remained stable below 4.7V without a significant increase in oxidation current, indicating that LLZTO, as the positive electrode component in the composite electrolyte, effectively suppressed the high-voltage decomposition of the polymer electrolyte. Secondly, to systematically evaluate the electrochemical performance of the Li / P-LLZTOP / NCM811 high-voltage full cell, we tested its rate performance and long-cycle stability. Rate test results ( Figure 27 The results show that the reversible specific capacities of the battery at charge / discharge rates of 0.1, 0.2, 0.3, and 0.5C are 180.7, 171.1, 138.7, and 111.2, respectively. It exhibits excellent high-rate adaptability under high-voltage cycling; when the current density recovers to 0.1C, the capacity rapidly rebounds to 174.3. This demonstrates its excellent capacity recovery capability and structural reversibility under high voltage. Figure 28 This study demonstrates the long-term cycling performance of a Li / P-LLZTOP / NCM811 high-voltage full cell at a current density of 0.3C. The full cell achieves stable cycling for 150 cycles at a high voltage of 3-4.3V with 90% capacity retention. The stable long-term cycling performance under high voltage is primarily attributed to the unique structural design of the composite electrolyte, which suppresses the decomposition of the polymer electrolyte under high voltage conditions. Furthermore, the LLZTOP electrolyte at the positive electrode end is compatible with ester-based electrolytes, enabling the long-term cycling of the NCM811 high-voltage full cell.

[0093] Figures 29-31 The microstructure of the electrolyte-lithium anode interface after cycling was investigated. SEM analysis of the lithium metal anode and electrolyte surfaces after 100 cycles of the full cell revealed that the P-LLZTOP electrolyte interface remained smooth and intact, with only slight undulations caused by cycling. Figure 29 In contrast, the lithium metal anode in P-LLZTOP batteries exhibits a uniform spherical lithium deposition morphology. Figure 30 The control group F-LLZTOP battery, on the other hand, exhibited an irregular, loose, moss-like structure. Figure 31These results demonstrate that the porous LLZTO framework can homogenize lithium-ion flux, and the internal nano-confined polymer layer further restricts lithium-ion diffusion and surface migration, causing the deposited lithium to reduce surface energy, thereby forming a dense and stable spherical morphology.

[0094] Figure 32-36 We investigated how the porous LLZTO structure improves the lithium-ion transfer number using mean square displacement (MSD) calculations. Since the PVDF in the PEOVDF structure does not participate in lithium-ion transport by the polymer electrolyte and only serves as structural support, we first constructed a model for lithium-ion transport in the PEO polymer and porous LLZTO composite system. Figure 32 and Figure 33 In the diagram, gray represents Li ions, blue represents TFSI ions, green represents PEO, and yellow represents LLZTO. In the early stages of the PEOVDF reaction, TFSI- ions are uniformly distributed in the polymer electrolyte. However, in the final frame of the reaction, TFSI- ions aggregate at the PEO / LLZTO interface and the polymer anode interface. This indicates that the porous LLZTO framework blocks the passage of anions, allowing Li ions to pass through. + The LLZTO phase alone can increase the lithium-ion transference number of the electrolyte, and the aggregates at the negative electrode are due to the reversible space charge effect caused by charge-discharge cycles during cycling. To more intuitively reflect the role of porous LLZTO as an anion barrier in the lithium-ion transport process, the reaction process... and The diffusion coefficient and the reaction at the last frame and The distribution quantity at different locations is calculated. Figure 34 and Figure 35 The diffusion coefficient results show... and The fact that the diffusion coefficients are essentially the same in the polymer layer indicates that the two types of ions are uniformly distributed and have the same mobility within the polymer, and that no concentration polarization occurs. However, after diffusing into the porous LLZTO layer, the LLZTO attracts anion adsorption, resulting in only allowing... This achieved a uniform and rapid lithium-ion channel, increasing the lithium-ion transfer rate. In the last frame of the reaction, Atoms mainly aggregate at the LLZTO-polymer and polymer-anode interfaces, indicating that LLZTO acts as an anion barrier and forms a dynamically reversible cycle with charge-discharge cycling, suppressing polarization. To reveal the lithium-ion transport mechanism at the PEO / LLZTO interface, we calculated the diffusion coefficients of various ions in the interfacial region (…). Figure 36 The average diffusion coefficient of lithium ions in the interface region (TotalLi) is 1.6 × 10⁻⁶. Among them, lithium ions from the LLZTO framework (LLZTOLi) exhibited the highest diffusion coefficient, reflecting the intrinsic properties of LLZTO as a fast ion conductor. TFSI - The diffusion coefficient of anions in the interfacial region (TFSICOM) is as high as 1.47 × 10⁻⁶. The concentration is comparable to that of lithium ions. This indicates that anions are not fixed at the interface, but rather possess a certain degree of local mobility, which greatly alleviates the polarization phenomenon caused by anion adsorption.

[0095] Figure 37 and Figure 38 The radial distribution function (RDF) was used to investigate the cation pairing on porous LLZTO surfaces. The strength of adsorption capacity. The results show that due to... A stable first adsorption layer forms on the LLZTO surface, causing all surface cations to be in < A distinct g(r) peak appeared within the range; due to The inability to penetrate the interior of LLZTO effectively enhances the selective transport capability of lithium ions, resulting in RDF of all subsurface cations being < No characteristic peaks were found within the range. Furthermore, in... Subsequently, g(r) still exhibits a broad peak, and further analysis of the coordination number CN(r) indicates that... A certain degree of localized motion capability is maintained at the LLZTO / polymer interface. This localized dynamic behavior helps to quickly balance the interface charge, thereby effectively suppressing polarization.

[0096] This invention effectively solves the dendrite problem caused by localized high current density by introducing a porous LLZTO framework into a PEO / PVDF electrolyte matrix, thus establishing a continuous... The introduction of porous LLZTO enables the homogenization of lithium-ion flux and the construction of continuous lithium-ion transport channels. Its synergistic effect with the polymer under nano-confined conditions forms a highly efficient dual-continuous transport structure, thereby achieving a lithium-ion flux of 3.9 × 10⁻⁶ at room temperature. The high ionic conductivity and excellent lithium-ion transference number of 0.69, combined with the stable interface layer formed by the polymer on the negative electrode side and the rigid framework of LLZTO, enable the critical current density of the symmetric cell to reach 2.0. And at 0.3 Stable cycle time exceeds 2000 hours. (Matching) The positive electrode of the full cell is at 3.8. After 600 cycles at the specified current density, the capacity retention was 87.4%. Simultaneously, the electrolyte exhibited an electrochemical window of 4.7 V, and the full cell matched with the NCM811 cathode maintained a capacity of 0.15 V. After 300 cycles at the current density, the capacity retention rate was 80%. The developed electrolyte membrane combines the flexibility of polymer-like materials (elongation 210%) with the rigidity imparted by LLZTO (tensile strength 6 MPa), achieving an ideal balance between mechanical strength, flexibility, and processability. The electrolyte interface composite strategy proposed in this study simultaneously solves the high-pressure decomposition problem of polymer electrolytes and the solid-solid interface challenge of LLZTO, providing valuable reference for the rational design and widespread application of next-generation composite solid-state lithium battery energy storage systems.

[0097] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A ceramic-polymer electrolyte with a hierarchical porous structure, characterized in that, include: A ceramic framework with a hierarchical pore structure and a polymer electrolyte filling the pores of the ceramic framework. The ceramic framework comprises a relatively dense layer and a porous framework layer, wherein the porosity of the relatively dense layer is lower than that of the porous framework layer. The relatively dense layer is positioned towards the positive electrode side to reduce direct contact between the polymer electrolyte and the positive electrode; the porous framework layer fuses with the diffusely permeated polymer electrolyte to form a continuous ceramic-polymer interface transition region.

2. The ceramic-polymer electrolyte with a hierarchical porous structure according to claim 1, characterized in that, The ceramic framework is an LLZTO ceramic framework, and its chemical composition is as follows: .

3. The ceramic-polymer electrolyte with a hierarchical porous structure according to claim 1, characterized in that, The relatively dense layer contains interconnected residual pores, which serve as permeation channels to improve the interfacial wettability on the positive electrode side.

4. The ceramic-polymer electrolyte with a hierarchical porous structure according to claim 1, characterized in that, The polymer electrolyte diffuses and permeates into the porous framework layer, forming a bicontinuous phase structure therewith.

5. The ceramic-polymer electrolyte with a hierarchical porous structure according to claim 1, characterized in that, The polymer electrolyte is a PEO / PVDF polymer electrolyte.

6. A method for preparing a ceramic-polymer electrolyte with a hierarchical porous structure, used to prepare a ceramic-polymer electrolyte with a hierarchical porous structure as described in any one of claims 1-5, characterized in that, Includes the following steps: S1. Preparation of ceramic slurry containing pore-forming agent and ceramic slurry without pore-forming agent; S2. Ceramic slurry containing pore-forming agent and ceramic slurry without pore-forming agent are cast and coated onto a transfer film, and then pressed, dried and sintered to obtain a ceramic skeleton with a hierarchical pore structure. S3. Apply the polymer electrolyte solution to the porous framework layer of the ceramic skeleton, allowing the polymer solution to penetrate into the pores of the porous framework layer. After drying to remove the solvent, the ceramic-polymer electrolyte with hierarchical pore structure is obtained, referred to as P-LLZTOP electrolyte membrane.

7. The method for preparing the ceramic-polymer electrolyte according to claim 6, characterized in that, In step S2, the ceramic slurry containing a pore-forming agent and the ceramic slurry without a pore-forming agent are respectively cast and coated onto the transfer membrane. Pressure is applied to mechanically press the two membranes together while the surfaces of the two slurries are in a semi-solid state. The sedimentation effect of ceramic particles and the double-layer pressing effect are used to form a dense intermediate zone. After static drying, the membrane is sintered at high temperature in a lithium-rich atmosphere to obtain the ceramic skeleton.

8. The method for preparing the ceramic-polymer electrolyte according to claim 6, characterized in that, In step S1, the ceramic slurry is prepared by mixing LLZTO pre-formed powder with solvent, dispersant, plasticizer, and binder to obtain a mixed slurry. The LLZTO pre-formed powder is made from LiOH. , and Raw materials It is obtained by calcining after mixing in stoichiometric proportions.

9. The application of a ceramic-polymer electrolyte with a hierarchical pore structure as described in any one of claims 1-5 in a solid-state lithium battery.

10. A solid-state lithium battery, characterized in that, The invention comprises a positive electrode, a negative electrode, and a ceramic-polymer electrolyte with a hierarchical porous structure as described in any one of claims 1-5, wherein the relatively dense layer is disposed toward the positive electrode side, and the porous framework layer of the composite polymer electrolyte is disposed toward the negative electrode side.

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