Lithium-ion batteries for hearing aid applications II. Pulse discharge andsafety tests

Rechargeable lithium-ion batteries were designed to meet the power requirem ents of hearing aid devices (HADs). The batteries were designed in a 312-bu tton cell size, compatible with existing hearing aids. The batteries were t ested to evaluate the design and the electrochemical performance, as they r elate to a typical hearing aid application. The present report covers the p ulse capabilities, cycle life and preliminary safety tests. The results are compared with other battery chemistries: secondary lithium-alloy and nicke l-metal hydride batteries and primary Zn-air batteries. The cell AC impedan ce was stable over the frequency range between 1 and 50 kHz, ranging betwee n 5 Omega at the higher frequency and 12 Omega at the lower extreme. Pulse tests were consistent with these values, as the cells were capable of provi ding a series of 100 mA pulses of 10-s duration. The safety tests suggest t hat the design is intrinsically safe with respect to the most common types of abuse conditions. (C) 2000 Elsevier Science S.A. All rights reserved.