Lithium-ion batteries used for IT, automobiles, and industrial energy-storage devices have battery management systems (BMS) to protect the battery from abnormal voltage, current, and temperature environments, as well as safety devices like, current interruption device (CID), fuse, and vent to obtain positive temperature coefficient (PTC). Nonetheless, there are harmful to human health and property and damage the brand image of the manufacturer because of smoke, fire, and explosion of lithium battery packs. In this paper, we propose a systematic protection algorithm combining battery temperature, over-current, and interconnection between protection elements to prevent copper deposition, internal short circuit, and separator shrinkage due to frequent and instantaneous over-current discharges. The parameters of the proposed algorithm are suggested to utilize the experimental data in consideration of battery pack operating conditions and malicious conditions.

In this study, the effect of Nb2O5 and sintering time on the positive temperature of coefficient of resistivity (PTCR) behavior of lead free Ba0.99(Bi0.5Na0.5)0.01TiO3 (BBNT) ceramics were investigated in order to fabricate a PTC thermistor with high Tc temperature more than 140℃. In particular, BBNT ceramic doped with 0.1mol% Nb2O5 and sintered at 1350℃ for 4 h has significantly increased Curie temperature (Tc) of about 200℃, showed good PTCR behavior of room-temperature resistivity (ρrt) of 40 Ω·㎝, a high ρmax/ρmin ratio of 43.78×103 and a large resistivity temperature factor (α) of 16.1%/℃. With increasing addition of Nb2O5 content, the ρrt decreased to a minimum value of 40 Ω·㎝ at 0.1mol% Nb2O5 and the ρrt increased for x value over 0.1 mol%.