Main functions of the cover
1) Fixing/sealing function: The top cover is laser welded with the aluminum shell to wrap and fix the bare battery cell and achieve sealing;
2) Current conduction function (pole): In the battery, the top cover pole, adapter and battery cell tab are welded and connected to ensure the current conduction of the battery cell; in the module, the top cover pole is laser welded and bolted to the busbar to form a series/parallel connection;
3) Pressure relief function (explosion-proof plate): When the battery is abnormal and the internal air pressure increases to a certain value, the top cover explosion-proof valve will open to relieve pressure , reducing the risk of explosion;
4) Fuse protection function (flip sheet): When the battery is abnormal, the internal air pressure increases to a certain value, the top cover flip sheet pushes up and contacts the negative electrode riveting block, causing the positive and negative electrodes of the top cover to short-circuit directly, and the aluminum connecting piece Fuse melts at the same time, quickly cutting off the current;
5) Reduce electrical corrosion: The plastic on the positive electrode uses conductive PPS to ensure that there is a certain resistance between the positive electrode column and the top cover plate, reduce the potential difference between the positive electrode column and the aluminum shell, prevent the top cover plate/aluminum shell from electrical corrosion, and thus improve product quality and service life
Cover plate components
1) Explosion-proof plate: Generally, the top cover of lithium iron phosphate system batteries adopts a single explosion-proof valve design, and the explosion-proof valve opening pressure is generally 0.4~0.8MPa. When the internal pressure increases and exceeds the opening pressure of the explosion-proof valve, the explosion-proof valve will rupture from the notch and open to release pressure;
2) Flip plate: In addition to the explosion-proof valve, the ternary system battery will also superimpose the SSD flip plate combination design. The explosion-proof valve opening pressure and SSD flip pressure are generally 0.75~1.05MPa and 0.45~0.5MPa respectively. When the internal pressure of the battery increases to the SSD flip pressure, the flip plate pushes up and quickly cuts off the current;
3) Pole: It mainly plays the role of current conduction. Usually, the positive electrode uses an aluminum pole and the negative electrode uses a copper-aluminum composite pole.
