Preparation method of functional diaphragm for solid-state battery

Abstract

The invention relates to the field of solid-state batteries, in particular to a preparation method of a functional diaphragm for a solid-state battery. The preparation method comprises the following steps: taking a ceramic solid electrolyte and a nano material as active fillers, compounding with a fluorine-containing polymer, stirring for a certain time at a certain temperature, coating on a diaphragm, and drying to prepare the composite solid electrolyte membrane. The invention provides a new view angle for realizing high ionic conductivity and good mechanical property through room-temperature processing. The permanent dipole of the nano material with high dielectric property can reduce the interface resistance between the polymer electrolyte and the electrode, adjust the Li < + > migration kinetics, and form a stable and effective intermediate layer between the cathode and the electrolyte. The spontaneous polarization can generate electrification at two ends, and negative charges at the upper end can attract Li < + >, so that the distribution and gradient of the Li < + > are favorably adjusted, and uniform lithium deposition is realized. And lithium salt dissociation can be effectively promoted by compounding with a fluorine-containing polymer. The battery using the composite solid electrolyte membrane shows stronger cycle performance in the aspects of capacity and stability.

Description

Technical Field

[0001] The present invention relates to the field of solid-state batteries, and particularly to a method for preparing a functionalized separator for a solid-state battery. Background Art

[0002] Due to the advantages of rapid conversion between chemical energy and electrical energy, high conversion efficiency, and no gas emissions, rechargeable batteries have been widely used in the energy storage field. In particular, lithium-ion batteries have characteristics such as high energy density, high power density, long life cycle, low self-discharge rate, and wide operating temperature range, and are widely used in fields such as portable electronic devices and electric vehicles. However, an obvious drawback is that lithium-ion batteries are prone to uneven lithium deposition / stripping during the redox reaction process, resulting in uncontrolled growth of lithium dendrites. Worse still, lithium dendrites can pierce the separator, causing the battery to short-circuit and even leading to fire or explosion, which hinders the development of lithium-metal batteries. A separator is a thin microporous membrane that allows lithium ions (Li + +) to be transported through the interface and electrolyte, and plays a crucial role in maintaining the stable performance and safety of lithium batteries. The microstructure characteristics and chemical composition of the separator significantly affect the safety, capacity, internal resistance, and long-term cycling performance of the battery. How to design and prepare a separator that can improve the cycling stability while simultaneously suppressing lithium dendrites remains a difficult problem.

[0003] Generally speaking, a battery separator consists of a porous membrane and several polymer matrices, and is immersed in different electrolyte solutions (lithium salts mixed in organic solvents). Liquid electrolytes are flammable and prone to short-circuiting, and efforts have been made to replace these separators with solid electrolytes. However, current solid electrolytes have obvious drawbacks, including low ionic conductivity and low electrode interface, which are the main obstacles to obtaining solid-state batteries with excellent cycling performance at room temperature. Summary of the Invention

[0004] Aiming at the problems in the background art, a method for preparing a functionalized separator for a solid-state battery is proposed. The method steps include using a ceramic solid electrolyte and a nanomaterial as active fillers, compounding them with a fluoropolymer, stirring for a certain time at a certain temperature, and coating and drying on the separator to prepare a composite solid electrolyte membrane.

[0005] Preferably, the ceramic solid electrolyte includes one or more of cerium oxide, zirconium oxide, LLZO, LATP, LGPS, LSPSC, or NZSP.

[0006] Preferably, the nanomaterial includes one or more of titanium dioxide nanometer, barium titanate nanometer, silicon dioxide nanometer, carbon nanotube, or aramid nanofiber.

[0007] Preferably, the fluoropolymer includes one or more of polytetrafluoroethylene, polytrifluorochloroethylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, ethylene-trifluorochloroethylene copolymer, or polyvinyl fluoride.

[0008] Preferably, the stirring temperature is 20°C - 80°C.

[0009] Preferably, the stirring time is 2h - 48h.

[0010] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention incorporates ceramic solid electrolyte and nanomaterials with high dielectric properties into the separator. The ceramic solid electrolyte has high ionic conductivity and good atmospheric chemical stability at room temperature. This material also has a high oxidation electrochemical window and is widely used as a coating material. Due to the volume change of the electrode material, the brittle characteristics of the ceramic solid electrolyte are not conducive to the physical contact of the solid electrolyte / electrode interface. In contrast, fluoropolymers have great flexibility and good electrode compatibility, but poor ionic conductivity. The composite solid electrolyte combining ceramic solid electrolyte and polymer electrolyte provides a new perspective for achieving high ionic conductivity and good mechanical properties through room-temperature processing. Nanomaterials with high dielectric properties are widely used in piezoelectric materials. Their permanent dipoles can reduce the interfacial resistance between the polymer electrolyte and the electrode, regulate Li + migration kinetics, and form a stable and effective intermediate layer between the cathode and the electrolyte. Their spontaneous polarization will generate charges at both ends, where the negative charges at the upper end will attract Li + +, which is beneficial to adjusting the distribution and gradient of Li + + and achieving uniform lithium deposition. When compounded with fluoropolymers, it can effectively promote the dissociation of lithium salts, balance the uneven charge distribution caused by concentration polarization, and stabilize the cathode electrolyte interface layer. The battery using the composite solid electrolyte membrane shows stronger cycling performance in terms of capacity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 X-ray diffraction patterns of different types of separators Figure 2 Comparison chart of voltage windows between commercial separators and functionalized separators Figure 3 Comparison chart of rate performance between commercial separators and functionalized separators Figure 4 Comparison chart of cycling performance between commercial separators and functionalized separators DETAILED DESCRIPTION OF THE INVENTION

[0012] Example 1. The present invention provides a method for preparing a functionalized separator for a solid-state battery. The method steps include using a ceramic solid electrolyte and a nanomaterial with high dielectric properties as active fillers, respectively, compounding them with a fluoropolymer, stirring for a certain time at a certain temperature, coating on a commercial separator, and drying to prepare a composite solid electrolyte membrane.

[0013] It should be further noted that the ceramic solid electrolyte includes one or more of cerium oxide, zirconium oxide, LLZO, LATP, LGPS, LSPSC, NZSP, etc.

[0014] It should be further noted that the nanomaterial with high dielectric properties includes one or more of nanometer titanium dioxide, barium titanate nanometer, nanometer silicon dioxide, carbon nanotubes, aramid nanofibers, etc.

[0015] It should be further noted that the fluoropolymer includes one or more of polytetrafluoroethylene, polytrifluorochloroethylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, ethylene-trifluorochloroethylene copolymer, polyvinyl fluoride, etc.

[0016] It should be further noted that the stirring temperature is 2°C.

[0017] It should be further noted that the stirring time is 2 h.

[0018] Example 2. The present invention provides a method for preparing a functionalized separator for a solid-state battery. The method steps include using a ceramic solid electrolyte and a nanomaterial with high dielectric properties as active fillers, respectively, compounding them with a fluoropolymer, stirring for a certain time at a certain temperature, coating on a commercial separator, and drying to prepare a composite solid electrolyte membrane.

[0019] It should be further noted that the ceramic solid electrolyte includes one or more of cerium oxide, zirconium oxide, LLZO, LATP, LGPS, LSPSC, NZSP, etc.

[0020] It should be further noted that the nanomaterial with high dielectric properties includes one or more of nanometer titanium dioxide, barium titanate nanometer, nanometer silicon dioxide, carbon nanotubes, aramid nanofibers, etc.

[0021] It should be further noted that the fluoropolymer includes one or more of polytetrafluoroethylene, polytrifluorochloroethylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, ethylene-trifluorochloroethylene copolymer, polyvinyl fluoride, etc.

[0022] It should be further noted that the stirring temperature is 80°C.

[0023] It should be further noted that the stirring time is 48 h.

[0024] Example 3. The present invention provides a method for preparing a functionalized separator for a solid-state battery. The method steps include using a ceramic solid electrolyte and a nanomaterial with high dielectric properties as active fillers respectively, compounding them with a fluoropolymer, stirring at a certain temperature for a certain time, coating on a commercial separator and drying to prepare a composite solid electrolyte membrane.

[0025] It should be further noted that the ceramic solid electrolyte includes one or more of cerium oxide, zirconium oxide, LLZO, LATP, LGPS, LSPSC, NZSP, etc.

[0026] It should be further noted that the nanomaterial with high dielectric properties includes one or more of nanometer titanium dioxide, barium titanate nanometer, silicon dioxide nanometer, carbon nanotubes, aramid nanofibers, etc.

[0027] It should be further noted that the fluoropolymer includes one or more of polytetrafluoroethylene, polytrifluorochloroethylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, ethylene-trifluorochloroethylene copolymer, polyvinyl fluoride, etc.

[0028] It should be further noted that the stirring temperature is 40 °C.

[0029] It should be further noted that the stirring time is 20 h.

[0030] This technical solution innovatively introduces a composite system of a ceramic solid electrolyte and a high-dielectric nanomaterial into the battery separator system. Among them, the ceramic electrolyte component has excellent room-temperature ion transport ability (>1 mS / cm), a wide electrochemical stability window (>4.5 V vs. Li + / Li) and excellent environmental stability, and has been widely used in the field of electrode interface modification. However, its intrinsic brittleness leads to easy interfacial contact failure problems when the electrode volume changes. Complementary to this, although the fluoropolymer matrix exhibits excellent mechanical flexibility and interfacial adaptability, it has the defect of insufficient ionic conductivity. By constructing a ceramic-polymer composite electrolyte system, we have successfully achieved the synergistic optimization of room-temperature processability, high ionic conductivity and excellent mechanical properties. The specially introduced high-dielectric nanomaterials (such as BaTiO3, etc.) have the following multiple functions: Reducing the interfacial transfer resistance (Rct) through the permanent dipole moment effect and optimizing the lithium-ion migration energy barrier; Constructing a stable buffer layer with gradient characteristics at the positive electrode / electrolyte interface; Using the surface charge (negative terminal potential) generated by spontaneous polarization to guide the directional distribution of lithium ions and promoting uniform deposition; Synergize with fluoropolymers to enhance the dissociation degree of lithium salts (the dissociation rate is increased by >30%) and effectively inhibit the concentration polarization phenomenon.

[0031] The above has described the embodiments of the present invention in detail, but the present invention is not limited thereto. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the gist of the present invention.

Claims

1. A preparation method of a functional separator for a solid-state battery, characterized in that, The method steps include using a ceramic solid electrolyte and a nanomaterial as active fillers, compounding them with a fluoropolymer, stirring for a certain time at a certain temperature, and coating and drying on a separator to prepare a composite solid electrolyte membrane.

2. The preparation method of the functionalized separator for a solid-state battery according to claim 1, wherein The ceramic solid electrolyte includes one or more of cerium oxide, zirconium oxide, LLZO, LATP, LGPS, LSPSC, or NZSP.

3. The preparation method of the functionalized separator for a solid-state battery according to claim 1, wherein The nanomaterial includes one or more of nanometer titanium dioxide, barium titanate nanometer, nanometer silicon dioxide, carbon nanotubes, or aramid nanofibers.

4. The preparation method of the functionalized separator for solid-state batteries according to claim 1, characterized in that, The fluoropolymer includes one or more of polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, or polyvinyl fluoride.

5. The preparation method of the functionalized separator for solid-state batteries according to claim 1, characterized in that, The stirring temperature is 20°C - 80°C.

6. The preparation method of the functionalized separator for solid-state batteries according to claim 1, wherein The stirring time is 2h - 48h.

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