Summarize the working principle of lithium battery cap

Summarize the working principle of lithium battery cap

1、 The function and principle of battery cap
(1) Positive or negative terminal (2) Temperature protection function: PTC (sudden increase in resistance, cutting off current) (3) Power off protection function: CID current disconnection device (internal pressure rise → Vent flip → CID solder joint breakage) (4) Pressure relief protection function: Vent (internal pressure rise → Vent flip → CID solder joint breakage → continuous pressure rise → Vent rupture) (5) Sealing function: waterproof, gas invasion, and electrolyte evaporation prevention

3、 Cap pressure design
(1) Internal pressure drives vent flipping
(2) Vent flipping breaks CID solder joint (3) Control points: (1) Vent flipping pressure, (2) CID solder joint tension CID breaking pressure=Vent flipping pressure+equivalent pressure of CID solder joint tension CID solder joint tension converted to equivalent pressure: equivalent pressure of CID solder joint tension (MPa)=CID solder joint tension (N)/78.5

5、 The relationship between cap breakage and flipping
2.1 Is it better to have a smaller CID welding tension?
Small impact on Vent flipping
2.2 Possible problems with welding tension that is too low?
The vibration caused the CID solder joint to break, however, the weight of CID is about 0.1g, and the 0.1N welding tension can resist 100G vibration, so we can ignore its influence.
6、 The influence of welding tension on CID
The experimental data shows that the welding tension is [16N, 32N], and the corresponding CID breaking pressure is [0.2MPa, 0.4MPa]. The influence of welding tension on CID disconnection is relatively small, and CID disconnection is mainly related to Vent flipping pressure.
7、 Key points of cap design
(1) Reduce the height of the cap (2) Optimize the double-sided scoring of Vent to single-sided scoring, which improves the consistency of Vent’s explosive flipping. (3) Utilize hard aluminum CID application, which makes Vent scoring less prone to stretching and deformation, resulting in better explosive consistency