Solid electrolyte interface composite buffer layer based on fiber-cross-linked network, solid-state battery and preparation method of solid-state battery

Abstract

The invention discloses a solid electrolyte interface composite buffer layer based on a fiber-cross-linked network, a solid-state battery and a preparation method of the solid-state battery. The composite buffer layer consists of a polymer fiber skeleton and a polymer network which is filled in pores of the polymer fiber skeleton and is formed by curing and cross-linking a polymer matrix and a solvated ionic liquid. The solid-state battery is formed by covering the composite buffer layer with the same area on the surface of a solid-state electrolyte and then assembling the composite buffer layer with corresponding positive and negative electrode materials. The composite buffer layer has good flexibility and energy dissipation capability, can adapt to electrode volume fluctuation and restrain the interface mechanical failure problem of the solid electrolyte and the metal negative electrode, the internal solvated ionic liquid can achieve high ionic conductivity, the stability of the solid-state battery is improved, and the service life of the solid-state battery is prolonged. Wide application prospects are realized in the field of solid-state batteries.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery fabrication technology, specifically relating to a solid electrolyte interface composite buffer layer based on a fiber-crosslinked network, and a solid-state battery containing the composite buffer layer. This invention also relates to methods for fabricating the interface buffer layer and the solid-state battery. Background Technology

[0002] Traditional lithium-ion rechargeable batteries (with cathodes such as lithium iron phosphate / lithium cobalt oxide and anodes such as graphite carbon) rely on organic liquid electrolytes. These electrolytes have narrow voltage windows, poor electrochemical stability, and are prone to decomposition during battery cycling. This not only reduces electrochemical activity but also increases interfacial impedance due to the accumulation of decomposition products, and the generated gases can easily lead to battery bulging. More seriously, organic electrolytes also carry the risks of transition metal dissolution, high-temperature failure, and even short circuits and explosions. In contrast, solid-state electrolytes, with their superior chemical stability, wide electrochemical window, high mechanical strength, and non-flammability, fundamentally eliminate the flammability and explosion hazards of organic electrolytes, significantly improving the intrinsic safety of batteries.

[0003] However, the use of solid-state electrolytes still faces numerous challenges. Oxide solid-state electrolytes, with their high safety and ion conductivity advantages, have become an ideal choice for high-energy-density batteries. However, a fundamental contradiction exists between their interface and the lithium metal anode: the enormous local stress generated during lithium deposition far exceeds the mechanical strength of the electrolyte, inevitably leading to structural fracture and dendrite penetration. Simultaneously, the drastic volume fluctuations of the electrode during electric cycling cause periodic interface separation, resulting in a continuous surge in interface impedance and electrical contact failure. While sulfide solid-state electrolytes possess higher ion conductivity, their insufficient chemical stability leads to interfacial side reactions and safety risks, severely hindering industrialization. Currently, mainstream interface optimization strategies for solid-state electrolytes all have significant drawbacks: polymer buffer layers, due to insufficient mechanical strength, cannot effectively dissipate dendrite growth stress; inorganic coatings, while improving interfacial wettability, are inherently brittle and cannot adapt to changes in electrode volume, resulting in cracks after cycling that accelerate failure; lithium-loving metal layers only improve the initial contact state and are ineffective against long-term stress accumulation. These interface optimization strategies have failed to overcome the dual technical bottlenecks of "stress dissipation" and "dynamic contact maintenance," resulting in the critical current density and cycle life of solid-state batteries failing to meet practical application requirements for a long time.

[0004] In summary, the key to current research on solid-state batteries is to prepare a composite buffer layer with good flexibility and energy dissipation capacity using a universal, low-tech, and simple method to adapt to electrode volume fluctuations and suppress interfacial mechanical failure between the solid electrolyte and the metal anode, thereby comprehensively improving the stability and electrochemical performance of solid-state batteries. Summary of the Invention

[0005] Based on the above, the purpose of this invention is to provide a solid electrolyte interface composite buffer layer based on a fiber-crosslinked network and its preparation method, so as to maintain the interfacial contact between the electrode and the solid electrolyte, reduce the interfacial impedance and delay the mechanical failure of the solid electrolyte; wherein the highly elastic polymer fiber has good flexibility and stress dissipation ability, and the internal solvated ionic liquid can maintain ionic conductivity. Using the composite buffer layer at the electrode-solid electrolyte interface can improve the stability of the solid battery.

[0006] To achieve its objective, the technical solution adopted by this invention is as follows: This invention provides a method for preparing a solid electrolyte interface composite buffer layer based on a fiber-crosslinked network. Specifically, the method involves cutting a polymer fiber membrane according to the area of ​​the solid electrolyte. Then, it is placed in an equimolar amount of polymer matrix and ionic liquid, and photocured to form a cross-linked network to obtain the composite buffer layer.

[0007] Furthermore, the polymer matrix is ​​selected from either polymethyl methacrylate (PMMA) or polyethylene glycol diacrylate (PEGDA). This selection is based on the following considerations: PMMA and PEGDA, as photocurable oligomers, can construct flexible, cross-linked three-dimensional networks; the mechanical properties and ion transport channels of the final cured network can be controlled to adapt to the application requirements of different environments.

[0008] Furthermore, the ionic liquid is one of tetraethylene glycol dimethyl ether, 1,2-dioxapentane, or triethylene glycol dimethyl ether. This selection is based on the fact that tetraethylene glycol dimethyl ether, 1,2-dioxapentane, or triethylene glycol dimethyl ether possess high polarity, excellent ionic solubility, and electrochemical stability, while also exhibiting good compatibility with the aforementioned polymer matrix, making them suitable as the continuous phase for the final solid-state ionic conductor. More importantly, they have low volatility and a wide electrochemical window, which helps improve the safety, environmental adaptability, and long-term cycling stability of the composite material in electrochemical devices such as batteries.

[0009] The polymer matrix is ​​uniformly dissolved in a selected ionic liquid to form a homogeneous, flowable precursor solution. Photo-initiated polymerization and cross-linking reactions occur in the polymer matrix, forming a three-dimensional polymer network in situ within the fiber pores. During this process, the ionic liquid is encapsulated and immobilized by the in-situ formed cross-linked polymer network, creating continuous ion transport channels throughout the pores. Ultimately, the polymer fiber membrane serves as a mechanical support framework, while its pores form a composite ionicly conductive phase composed of the cross-linked polymer network and the ionic liquid.

[0010] Furthermore, the polymer fiber membrane is selected from one of polyacrylonitrile, polyimide, or polyvinylidene fluoride.

[0011] Furthermore, the solid electrolyte is a lithium lanthanum zirconium oxide electrolyte, a lithium aluminum titanium phosphate electrolyte, or a Li... 10 GeP2S 12 One or more of the following types of electrolytes.

[0012] The above method can be used to prepare a solid electrolyte interface composite buffer layer.

[0013] The present invention also provides a solid-state battery comprising the above-mentioned composite buffer layer, wherein the solid-state battery is formed by coating the surface of a solid electrolyte with the composite buffer layer of the same area and then assembling it with corresponding positive and negative electrode materials.

[0014] Furthermore, the positive electrode material is one or more of lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, or lithium nickel cobalt manganese oxide.

[0015] Furthermore, the negative electrode material is one or more of lithium metal, lithium alloy, graphite carbon, silicon, or silicon-carbon composite material.

[0016] By adopting the above technical solution, the present invention has the following beneficial effects: (1) The preparation method of the present invention is simple and applicable to a variety of solid electrolytes and a variety of positive and negative electrode materials; (2) It has low technical difficulty, low cost, and can be applied on a large scale; (3) The composite buffer layer of the present invention is composed of a polymer fiber skeleton and a polymer network formed by the solidification and cross-linking of a polymer matrix and a solvated ionic liquid filling its pores. The composite buffer layer prepared by the method of the present invention has good ion transport capability, can maintain ion transport at the solid electrolyte interface, and reduce interface impedance; its flexibility and energy dissipation capability can adapt to electrode volume fluctuations, suppress the interfacial mechanical failure problem between the solid electrolyte and the metal anode, and the solvated ionic liquid inside can maintain ionic conductivity, improve the stability of the solid battery, and thus improve the cycle life of the solid battery, and has broad application prospects in the field of solid batteries. Attached Figure Description

[0017] Figure 1 The image shows a scanning electron microscope (SEM) image of the composite buffer layer prepared using the method described in Example 1 of this invention. Figure 2 Example 1 of the present invention is at 0.1 mA cm -2 Scanning electron microscope (SEM) image of lithium lanthanum zirconium oxide solid electrolyte after 50 cycles at current density; Figure 3 Example 1 of the present invention is at 0.1 mA cm -2 Cross-sectional SEM image of lithium lanthanum zirconium oxide solid electrolyte after 50 cycles at current density; Figure 4 Compared to Example 1, without the addition of a composite buffer layer with high energy dissipation capability as an intermediate layer, the solid-state battery achieves a voltage of 0.1 mA cm⁻¹. -2 SEM images of lithium lanthanum zirconium oxide solid electrolyte after 20 cycles at current density; Figure 5 A comparison chart of the cycle performance of batteries with and without a composite buffer layer in Embodiment 1 of the present invention; Figure 6 The image shows a scanning electron microscope (SEM) image of the composite buffer layer prepared using the method described in Example 2 of this invention. Figure 7 To use the method in Embodiment 2 of the present invention at 0.1 mA cm -2 SEM image of the cross section of lithium lanthanum zirconium oxide solid electrolyte after 50 cycles at current density; Figure 8 Compared to Example 2, without the composite buffer layer as the intermediate layer, the solid-state battery at 0.1 mA cm⁻¹ -2 SEM images of lithium lanthanum zirconium oxide solid electrolyte after 20 cycles at current density; Figure 9 The image shows a scanning electron microscope (SEM) image of the composite buffer layer prepared using the method described in Example 3 of this invention. Figure 10 To use the method in Embodiment 3 of the present invention at 0.1 mA cm -2 SEM image of the cross section of lithium lanthanum zirconium oxide solid electrolyte after 50 cycles at current density; Figure 11 The image shows a scanning electron microscope (SEM) image of the composite buffer layer prepared using the method described in Example 4 of this invention. Detailed Implementation

[0018] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the claims. All inventions utilizing the concept of the present invention are within its protection scope.

[0019] Example 1 A method for preparing a solid electrolyte interface composite buffer layer based on a fiber-crosslinked network is disclosed. The specific process of the method is as follows: using lithium lanthanum zirconium oxide (LLZO) as the solid electrolyte, a polyacrylonitrile film is cut according to its area, and then placed in tetraethylene glycol dimethyl ether (10 mmol) and polymethyl methacrylate (10 mmol), and cured into a crosslinked network under 365 nm ultraviolet light irradiation to obtain the composite buffer layer.

[0020] The aforementioned composite buffer layer was coated onto the surface of the LLZO solid electrolyte, and finally assembled with a lithium metal anode and a lithium iron phosphate cathode to form a solid-state battery. Its performance characterization diagram is shown below. Figure 1-5 .

[0021] in, Figure 1 The image shows a scanning electron microscope image of the composite buffer layer; the results in the image show that tetraethylene glycol dimethyl ether and polymethyl methacrylate were successfully and uniformly cured in polyacrylonitrile fibers.

[0022] Figure 2 For 0.1 mA cm -2 Scanning electron microscope image of lithium lanthanum zirconium oxide solid electrolyte after 50 cycles at current density; the results show that the LLZO surface is smooth and free of cracks.

[0023] Figure 3 For 0.1 mA cm -2 SEM image of the cross section of lithium lanthanum zirconium oxide solid electrolyte after 50 cycles at current density; the results in the image show that no dendrite growth penetrates the interior of LLZO.

[0024] Figure 4 Compared to Example 1, without the addition of a composite buffer layer with high energy dissipation capability as an intermediate layer, the solid-state battery achieves a voltage of 0.1 mA cm⁻¹. -2 SEM images of the lithium lanthanum zirconium oxide solid electrolyte (LLZO) after 20 cycles at the current density are shown. The results indicate that without the composite buffer layer, significant lithium deposition occurs within the LLZO after only 20 cycles. This generates substantial localized stress within the hard LLZO grains or along grain boundaries, leading to microcracks within the LLZO electrolyte. Once these cracks propagate, they provide easier pathways for subsequent lithium deposition, ultimately causing mechanical fracture of the solid electrolyte.

[0025] Figure 5 The graph shows a comparison of the cycle performance of batteries with and without the composite buffer layer in Example 1. The results in the graph show that the cycle life of the battery without the composite buffer layer is about 100 cycles, while the cycle life of the battery with the composite buffer layer in this example can reach more than 270 cycles, indicating that the use of the interface composite buffer layer significantly extends the cycle life of the solid-state battery.

[0026] Example 2 A method for preparing a solid electrolyte interface composite buffer layer based on a fiber-crosslinked network is described. The specific process of the method is as follows: using lithium lanthanum zirconium oxide as a solid electrolyte, cutting a polyimide fiber film according to its area, and then placing it in tetraethylene glycol dimethyl ether (10 mmol) and polyethylene glycol diacrylate (10 mmol), and curing it into a crosslinked network under 365 nm ultraviolet light irradiation to obtain the composite buffer layer. The aforementioned composite buffer layer was coated onto the surface of lithium lanthanum zirconium oxide, and finally assembled with a lithium metal anode and a lithium nickel cobalt manganese oxide cathode to form a solid-state battery. Its performance characterization diagram is shown below. Figure 6-8 .

[0027] in, Figure 6 The image shows a scanning electron microscope (SEM) image of the composite buffer layer. The results in the image show that tetraethylene glycol dimethyl ether and polyethylene glycol diacrylate were successfully and uniformly cured in polyimide fibers, and the composition of the interfacial composite buffer layer was uniform.

[0028] Figure 7 For 0.1 mA cm -2 SEM image of the cross-section of the lithium lanthanum zirconium oxide solid electrolyte in this embodiment after 50 cycles at current density; the results in the image show that there are no dendrites penetrating inside the LLZO.

[0029] Figure 8 For the battery without a buffer layer, at 0.1 mA cm -2 SEM image of the cross section of lithium lanthanum zirconium oxide solid electrolyte after 20 cycles at current density; the results in the image show that obvious dendrite growth occurs inside LLZO, and the dendrite growth will eventually penetrate the electrolyte layer and cause a short circuit inside the battery.

[0030] Example 3 A method for preparing a solid electrolyte interface composite buffer layer based on a fiber-crosslinked network is disclosed. The specific process of the method is as follows: using lithium aluminum titanium phosphate as the solid electrolyte, a polyacrylonitrile film is cut according to its area, and then placed in 1,2-dioxane (11 mmol) and polyethylene glycol diacrylate (11 mmol), and cured into a crosslinked network under 365 nm ultraviolet light irradiation to obtain the composite buffer layer.

[0031] The aforementioned composite buffer layer was coated onto the surface of lithium lanthanum zirconium oxide, and finally assembled with a silicon-carbon anode and a lithium nickel cobalt-manganese cathode to form a solid-state battery.

[0032] in, Figure 9 The image shows a scanning electron microscope image of the composite buffer layer. The results in the image show that 1,2-dioxane and polyethylene glycol diacrylate were successfully and uniformly cured in polyacrylonitrile fibers, and the surface of the buffer layer was smooth.

[0033] Figure 10 For 0.1 mA cm -2 SEM images of the cross-section of lithium lanthanum zirconium oxide solid electrolyte (LLZO) after 50 cycles at current density; the results show that there is no crack propagation or dendrite growth inside LLZO.

[0034] Example 4 A method for preparing a solid electrolyte interface composite buffer layer based on a fiber-crosslinked network is disclosed. The specific process of the method is as follows: using lithium lanthanum titanate as a solid electrolyte, a polyvinylidene fluoride membrane is cut according to its area, and then placed in triethylene glycol dimethyl ether (10 mmol) and polymethyl methacrylate (10 mmol), and cured into a crosslinked network under 365 nm ultraviolet light irradiation to obtain the composite buffer layer.

[0035] The aforementioned composite buffer layer was coated onto the surface of lithium lanthanum titanate, and finally assembled with a lithium metal anode and a lithium cobalt oxide cathode to form a solid-state battery.

[0036] The scanning electron microscope (SEM) image of the composite buffer layer is shown below. Figure 11 As shown. Figure 11 The results showed that triethylene glycol dimethyl ether and polymethyl methacrylate were successfully and uniformly cured in polyvinylidene fluoride fibers, and the surface of the buffer layer was smooth and uniform.

Claims

1. A method for preparing a fiber-crosslinked network based solid-state electrolyte interface composite buffer layer, characterized by, The polymer fiber film is cut according to the area of the solid electrolyte, and then placed in equal molar amounts of a polymer matrix and an ionic liquid to form a cross-linked network by light curing to obtain the composite buffer layer.

2. The method of claim 1, wherein the fiber-crosslinked network-based solid-state electrolyte interfacial composite buffer layer is prepared by the steps of: The polymer matrix is selected from one of polymethyl methacrylate (PMMA) or polyethylene glycol diacrylate (PEGDA).

3. The method for preparing a solid electrolyte interface composite buffer layer based on a fiber-crosslinked network as described in claim 2, characterized in that, The ionic liquid is one of tetraglycol dimethyl ether, 1,2-dioxolane or triethylene glycol dimethyl ether.

4. The method for preparing a solid electrolyte interface composite buffer layer based on a fiber-crosslinked network as described in claim 3, characterized in that, The polymer fiber film is selected from one of polyacrylonitrile, polyimide or polyvinylidene fluoride.

5. The method for preparing a solid electrolyte interface composite buffer layer based on a fiber-crosslinked network as described in claim 1, characterized in that, The solid-state electrolyte is one of a lithium lanthanum zirconium oxide type electrolyte, an aluminum titanium lithium phosphate type electrolyte, or Li 10 GeP2S 12 type electrolyte.

6. The composite buffer layer prepared by the method of any one of claims 1-5.

7. A solid-state battery comprising a solid-state electrolyte, characterized by, The solid electrolyte interface is provided with the composite buffer layer of claim 6.

8. A method of producing a solid state battery as claimed in claim 7, wherein, The solid-state battery is assembled by covering the composite buffer layer of the same area size on the surface of the solid electrolyte.

9. A method of producing a solid state battery according to claim 8, wherein The positive electrode material is one or more of lithium iron phosphate, lithium cobaltate, lithium manganate or nickel cobalt manganate.

10. A method of producing a solid-state battery according to claim 8 or 9, characterized in that, The negative electrode material is one or more of metallic lithium, lithium alloy, graphite carbon, silicon or carbon-silicon composite material.

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