Core categories and functional analysis of battery accessories

Polar ear: a conductive component that connects a battery cell to an external circuit, usually made of copper (negative electrode), aluminum (positive electrode), or copper aluminum composite material, and requires low resistance and high oxidation resistance. The current mainstream technology direction is "ultra-thin pole ear+integrated design", which can reduce energy loss and adapt to high rate charging needs. ​

Current collector: A metal foil material (copper foil/aluminum foil) used to carry active substances, whose thickness and flatness directly affect the energy density and cycle life of the battery cell. For example, power batteries have begun to use 6 μ m ultra-thin copper foil, which can increase energy density by about 5% compared to traditional 12 μ m copper foil. ​

Battery protection board (BMS accessory): It includes components such as chips, resistors, capacitors, etc., which can monitor battery voltage, current, and temperature in real time. When overcharge, overdischarge, short circuit, etc. occur, the circuit will be immediately cut off. In new energy vehicles, the protective board also needs to have a "balanced charging" function to ensure consistency among multiple battery cells. ​

Explosion proof valve/explosion-proof plate: installed on the top of the battery housing, it can quickly release pressure when the internal pressure of the battery cell is too high (such as in the early stage of thermal runaway), avoiding battery explosion. At present, the mainstream materials are aluminum alloy or polymer composite film, which need to meet the dual requirements of "low opening pressure+high sealing". ​

Diaphragm: An insulating material located between the positive and negative electrodes, which prevents direct contact and short circuits between the positive and negative electrodes, while allowing lithium ions to pass through. According to the material, it can be divided into dry diaphragm and wet diaphragm. Among them, wet diaphragm is more suitable for power batteries due to its stronger temperature resistance (able to withstand high temperatures above 150 ℃), accounting for over 70%. ​

Battery shell: divided into hard shell (aluminum alloy/stainless steel, used for power batteries and energy storage batteries) and soft package (aluminum-plastic film, used for consumer batteries). Hard shells need to have impact resistance and corrosion resistance. For example, the shell of a new energy vehicle power battery needs to pass rigorous tests such as "1-meter drop test" and "squeeze test"; The soft pack focuses on lightweight design, with a thickness as thin as 0.3mm, suitable for the miniaturization needs of mobile phones and smart wearable devices. ​

Connectors/wiring terminals: used for connecting battery modules with external devices, requiring high conductivity and vibration resistance. In energy storage systems, connectors also need to support high current (such as 500A or above) transmission. Currently, the mainstream material used is silver plated copper, which can reduce contact resistance. ​

Electrolyte injection port and sealing plug: The injection port needs to accurately control the amount of electrolyte injected, while the sealing plug needs to prevent electrolyte leakage and moisture from entering (electrolyte is sensitive to moisture and the moisture content should be below 20ppm). At present, automated liquid injection equipment has achieved the integration of "liquid injection sealing", with an accuracy of ± 0.1ml

Electrolyte adsorption membrane: used to adsorb excess electrolyte and avoid local concentration unevenness caused by electrolyte flow. It is commonly used in cylindrical and square batteries, and is mostly made of polypropylene (PP) non-woven fabric.