## 1 Introduction  
Despite rapid scientific and technological development, the world is facing an increasing demand for energy and the need to control the resulting environmental pollution, which makes the development of new green industries an urgent priority. Lithium-ion batteries are commonly used in many fields, such as electronic devices and the aerospace industry, because of their many advantages, such as high energy density, low power consumption, recyclability, and low carbon emissions. The diaphragm is a key component of the lithium-ion battery and largely determines its performance [1; 2; 3]. The film properties of lithium-ion batteries determine the capacity, cycling stability, and other important battery characteristics, and therefore the diaphragm must have an adequate thickness, ionic conductivity, high porosity, and both thermal and electrochemical stability [4; 5; 6]. Currently, commercial diaphragms are microporous membranes based on polypropylene (PP), polyethylene (PE), and their composites. These diaphragms have low porosity and liquid absorption rates and poor thermal stability due to the hydrophobic properties of the constituent materials. This makes the electrochemical performance of lithium-ion battery diaphragms poor, and commercial diaphragms are susceptible to shrinkage when heated, which is not conducive to maintaining the long-term stable operation of lithium-ion batteries, especially after repeated charging and discharging: the diaphragm is heated, which can easily cause a short circuit inside the battery. Additionally, their cumbersome preparation process, difficult equipment control, and high-cost limit their application in electric vehicles and energy storage systems. These problems can be solved by using different types of polymer diaphragms and by using different diaphragm manufacturing techniques [7; 8]. To replace the traditional polyolefin microporous membrane,high-performance lithium-ion battery diaphragms have been prepared at the laboratory scale using dry and wet spinning, electrostatic spinning, and centrifugal spinning methods. [PERSON] et al. [9] prepared polypropylene/polyethylene (PP/PE) composite diaphragms with a shut-off function by dry biaxial stretching. When the temperature rises to 135 \({}^{\circ}\)C, the PE inside the diaphragm melts, blocking the channels for lithium-ion transport. [PERSON] et al. [10] used a wet spinning process to prepare a polysulfone/polyvinylpyrrolidone fiber diaphragm. However, the wide range of pore sizes of the polyolefin microporous diaphragm prepared by the wet and dry spinning method resulted in a localized diaphragm with a resistance that was too high. Unlike the dry-wet method, the fiber diaphragms prepared by this method usually have high porosity, liquid absorption, and thermal stability due to the specificity of the electrostatic spinning process. [PERSON] et al. [11] prepared polyacrylonitrile/polyimide (PAN/PI) composite films by electrostatic spinning, and their composite films had good thermal stability and exhibited better mechanical properties than the original PAN films. [PERSON] et al. [12] improved the wettability and ionic conductivity of the diaphragm by the electrostatic spinning of polyacrylamide(PAN) and polymethyl methacrylate (PMMA) to produce lithium-ion battery diaphragms with embedded graphene nanoflakes. [PERSON] et al. [13] successfully modified 3D nanofiber-structured polyurethane (PU) into a novel PU-coated diaphragm using an electrostatic spinning process. Its fiber morphology was better, and its average pore size was lower than that of commercial PP diaphragms, but its porosity (63.7%), liquid absorption(371%), and ionic conductivity were greatly improved compared with commercial diaphragms, and it had a lower interfacial resistance and good multiplicative properties.