Scalable Bath Cell Method for Reversible Lithium Management towards Near Zero Volt Tolerance in Lithium-Ion Cells

Abstract

Near zero-volt storage is a promising concept to controllably ensure the safety of user-inactive lithium-ion cells during storage or transit. An advantageous method to enable lithium-ion cells to tolerate near zero volt conditions is to manage the amount of reversible lithium ions in a cell such that during near zero volt storage, the potential of each electrode is maintained outside of its damage range. Unlike current commercial methods, this method can be applied to lithium-ion cells in a full range of cell designs (i.e. high power, high energy density) using current state of the art active materials, electrolytes, and current collectors. In the present work, a scalable reversible lithium management technique using a bath cell is demonstrated for the fabrication of a zero-volt tolerant 225 mAh LiNiCoAlO2/MCMB pouch cell. An electrode asymptotic potential (EAP, the potential at which the electrodes asymptote to when the cell is in a near zero volt state) of 2.2 V vs. Li/Li+ was achieved in the final pouch cell as a result of the bath-cell reversible lithium management step. The constructed pouch cell demonstrated ~100% discharge capacity and voltage retention after 14 days at a near zero volt state maintained by an applied resistor. Thus, the bath-cell reversible lithium management method can successfully fabricate reversible lithium managed lithium-ion cells that are highly tolerant to a prolonged (> 1 day) zero volt state.