Investigating the High-Rate Discharge Capability of 18650-Type Li-Ion Cells

Abstract : The high-rate discharge capability of 18650-type lithium-ion cells has been investigated using two commercial cells from Canon battery (A&TB Cells) and Sony, and one space-grade lithium-ion cell. All cells exhibit good voltage stability at various states of charge during pulse application, with Canon (A&TB) cells having the largest drop in voltage. These Canon (A&TB) cells also show the greatest sensitivity to aging with respect to pulse performance, exhibiting irregular voltage signature due to aging. The voltage drop during the pulse load is found to be independent of the pulse rate for all the cells. The voltage drop for the space-grade lithium-ion cell is also independent of the state of charge, exhibiting similar loss at different voltages. The two commercial cells exhibit a higher loss of voltage due to pulse load at lower states of charge. This data indicates that voltage loss at high rates needs to be tested at the lowest state of charge for an intended application. This finding is in contrast with silver-zinc cells, which typically do not have a strong dependence on states of charge.