# Application of a New Polymer Particle Adhesive for Lithium Battery Separators
## 1 Introduction  
Recently, with the rapid development of the economy, the subsequent environmental pollution problems have become more and more prominent, and the view of carbon neutrality has constantly been a cause for concern around the world. Therefore, the need to vigorously develop electric vehicles has become the consensus around the world [1, 2, 3]. The development of electric vehicles has also become the focus of many large enterprises [4]. The safety performance of electric vehicles has attracted the attention of consumers, especially the lithium batteries used in electric vehicles. Lithium batteries are mainly composed of positive and negative electrode sheets, a battery separator and a battery electrolyte. In lithium batteries, the safety performance of the battery separator affects the performance of the lithium battery [5, 6]. As a key part placed between the positive and negative electrode sheets of the lithium battery, the battery separator is mainly used as a carrier for effective transmission of lithium ions between the positive and negative electrode sheets. It can also prevent short circuit caused by direct contact between the positive and negative electrode sheets [7, 8, 9]. Therefore, the battery separator must have chemical/electrochemical stability and sufficient mechanical strength to avoid damage during the assembly of the lithium battery [10, 11, 12, 13, 14]. The battery separator used in lithium batteries is made of polyolefin resin, including polyethylene (PE), polypropylene (PP) and their blends, which can be obtained by dry and wet processes [15, 16, 17, 18, 19]. However, the polyolefin separator sold in the market has a series of problems, and it is difficult to use directly in lithium batteries. The polyolefin separator is made of an inert material, which is not well wetted by organic electrolyte solutions in lithium batteries. Additionally, it has a poor ability to hold the electrolyte during charge-discharge cycles of the lithium battery. The polyolefin separator is also a flexible material that cannot meet the requirements of a lithium battery for the thermal stability of the battery separator. Therefore, the polyolefin separator must be modified to meet the requirements of lithium batteries. [PERSON] et al. dispersed aluminum trioxide (Al\({}_{2}\)O\({}_{3}\)) nanoparticles and polyvinylidene fluoride (PVDF) in deionized water to prepare an aqueous suspension containing Al\({}_{2}\)O\({}_{3}\) and PVDF, which was coated on a polyolefin separator surface. The mechanical properties and puncture resistance of the polyolefin separator were enhanced, and the heat resistance improved. This can also cause the polyolefin separator to have an affinity with the battery electrolyte after modification, thereby improving the safety and cycling performance of the lithium battery [20]. Previous studies reported [21] that polyimide (PI), polyetherimide (PEI) or polyacrylonitrile (PAN) was coated on the surface of the polyolefin separator to enhance its affinity to the battery electrolyte. [PERSON] et al. grafted vinyltrimethoxysilane (VTMS) on the surface of PE film with electron beam (EB) irradiation. The VTMS particles were hydrolyzed and silica was introduced, and, thus, the thermal stability of the PE film was improved [22]. On the one hand, in the lithium battery manufacturing industry, surface coating of polyolefin separators has become more convenient with the widespread use of large gravure coaters. Without affecting the air permeability of the polyolefin separator, coating Al\({}_{2}\)O\({}_{3}\) nanoparticles with a certain thickness on the surface of the polyolefin separator is beneficial to improve the thermal resistance of the polyolefin separator, reduce its thermal contractility and increase its affinity for the battery electrolyte. This method is widely used in the preparation of lithium battery separators.