Comparison of current interrupt device and vent design for 18650 format lithium-ion battery caps: New findings

Abstract

The CID and vent mechanism are designed in 18650 format lithium-ion cells to activate at a given internal pressure in order to electrically isolate the cell from the external circuit and to relieve internal pressure, respectively. In prior work, the CID- and vent-activation pressures were measured experimentally for two commercial lithium-ion battery caps (MTI 18650 and LG MJ1). The cap structure was then analyzed with high resolution CT scanning and finite element modeling (FEM) simulations were conducted to simulate the vent-activation pressure. In the present study, two additional vent cap assemblies from commercial lithium-ion cells (K2 18650E and LG M36) were analyzed. The experimentally measured CID-activation pressures of K2 and LG M36 caps were 0.997 ± 0.292 and 1.393 ± 0.113 MPa at ambient temperature and 0.834 ± 0.057 and 1.083 ± 0.077 MPa at 100 °C. The experimentally measured vent-activation pressures of the K2 and LG M36 caps were 2.190 ± 0.372 and 2.363 ± 0.199 MPa at ambient temperature and 1.781 ± 0.355 and 1.799 ± 0.284 MPa at 100 °C. In prior work, an FEM procedure was introduced to simulate the vent-activation pressure. In the present study, the vent-activation simulations were conducted on the new caps; additionally, the FEM procedure was extended to simulate CID-activation pressure and to conduct a sensitivity analysis on geometric parameters of the vent mechanism. At ambient temperature, the FEM simulated CID-activation pressure of the K2 and LG M36 caps were 1.207 and 1.428 MPa, respectively. The FEM simulated vent-activation pressure of the K2 and LG M36 caps at the ambient temperature were 2.241 and 2.379 MPa, respectively. Simulated CID- and vent-activation pressures for the K2 and LG M36 caps were in good agreement with experiments. The FEM procedure for simulating vent-activation pressure, and the newly-developed method for simulating CID-activation pressure, may be used in the future to design new vent cap assemblies and to develop temperature-dependent activation pressure functions for use in abuse simulations.