The main chain of raw rubber molecule of silicone rubber (SR) is composed of Si-O bond and the side group is mainly methyl. Depending on the type of silicone rubber, some methyl groups or atoms can also be substituted by vinyl, phenyl or fluorine. The terminal group may be methyl or hydroxyl. The structure of silicone rubber is as follows:

Among them, n, m and P are the number of segments of different Si-O chains. There are many ways to classify silicone rubber. Four kinds of classifications are listed here.

1. According to the vulcanization temperature, it can be divided into room temperature vulcanized silicone rubber and high temperature vulcanized silicone rubber.

2. According to the morphology before curing, it can be divided into solid silicone rubber and liquid silicone rubber (which is also the focus of this paper).

3. According to the difference of monomers used, it can be divided into methyl vinyl silicone rubber, methyl phenyl vinyl silicone rubber, fluorosilicone, nitrile silicone rubber, etc.

4. According to the different properties and uses of silicone rubber, it can also be divided into general type, ultra-low temperature type, ultra-high temperature type, high strength type, oil-resistant type, medical type and so on.

Liquid silicone rubber (LSR) is an elastomer which vulcanizes and crosslinks in the atmosphere or under heating condition with a small amount of water as initiator or platinum as catalyst. It can be divided into two groups according to the packaging form: single component and two component (multi-component). According to the reaction type, LSR can be divided into condensation type or moulded liquid silicone rubber. Liquid silicone rubber does not contain any stabilizer, plasticizer or accelerator. As a cross-linking material, it can withstand very high temperature without thermal aging, and can maintain its mechanical properties and elasticity. By changing some of its side groups, the material can be modified to meet specific functions or requirements. LSR has excellent chemical stability, oil resistance and weathering resistance. It can be stabilized in the temperature range of 50 to 180 degrees C. It can be stabilized at temperatures higher than 250 degrees C after adding stabilizers, and has low temperature flexibility at - 60 degrees C. LSR is usually transparent, can be added to other pigments as needed, and very easy to color. It is widely used in electronic components sealing, pipeline sealing, medical devices, keyboards and baby related products. The application of liquid silicone rubber in the fields of 3D printing, waterproofing, painting, food contact silicone rubber and wearable parts has great development potential. Of course, the application in the automotive industry also achieves all-round coverage, such as connectors in the automotive industry, battery seals for electric vehicles, engine washers, headlamp seals and shock absorbers, etc., which become the preferred materials to provide sealing, heat insulation and internal application solutions.

Rapid technological trends in the electric vehicle manufacturing industry are prompting silicone manufacturers to adopt innovative methods to produce customized products. The solutions of liquid silicone rubber for new energy vehicles are mainly applied in four aspects: sealing and waterproof, safety protection, structural heat conduction and lightweight.  Liquid silicone elastomer is the most prominent product in the electric vehicle market. Its growth can be attributed to its wide application, such as seals, enclosures and gaskets. It is used for insulation of various components, such as connector seals, radiators, etc. It forms a heat shield around the battery pack to protect the battery unit from overheating or overcooling. In addition, customized design can insulate or help heat dissipation to ensure the best working temperature. In order to adapt to harsh space, silica gel is designed to withstand severe vibration. Short circuit and overcurrent are the main causes of battery failure in electric vehicles. The dielectric properties of silicone rubber can protect and isolate key components, protect batteries and buses from surge and help prevent battery fire.

Application of Liquid Silicone Rubber in Lithium Ion Battery Board

In new energy vehicles, liquid silica gel sealant is mainly used in the Pack link of lithium battery, which plays the role of heat dissipation, flame retardant, insulation and waterproof, and greatly improves the power safety of new energy vehicles. Lithium batteries are sensitive to water, and their sealing directly affects the working safety of battery system and the use safety of electric vehicles. From the point of view of development history, silicone has experienced one-component gasket-free rubber, foam forming seal ring and on-line foam silica gel product upgrade in sealing and waterproofing. However, liquid silica gel encapsulation gel has a large proportion, which will increase the weight of battery pack, reduce the energy ratio per unit volume, and ultimately affect the energy density. How to realize the lightweight of liquid silica gel is an urgent problem for silicone enterprises. At present, on-line foamed silica gel is very popular in the new energy automotive industry. It is suitable for the application scenarios of sealing and waterproofing of power battery, shock absorption protection of soft-packed cores, thermal insulation and lightweight of battery packs.