Improved Zero-Charge Storage Performance of LiCoO/Mesocarbon Microbead Lithium-Ion Batteries by LiFeO Cathode Additive.

Discharging lithium-ion batteries to zero-charge state is one of the most reliable ways to avoid the thermal runaway during their transportation and storage. However, the zero-charge state causes the degradation or even complete failure of lithium-ion batteries. Specialized solutions are required to endow lithium-ion batteries with improved zero-charge storage performance, namely, the ability to tolerate zero-charge state for a long time without unacceptable capacity loss. Here, we report that a LiFeO cathode additive can improve the zero-charge storage performance of LiCoO/mesocarbon microbead (MCMB) batteries. The irreversible charge capacity of the LiFeO additive results in the downregulation of anode and cathode potentials when the battery is at zero-charge state. More importantly, the LiFeO additive offers a small discharge plateau below 2.9 V versus Li/Li, which can hold the anode potential at zero-charge battery state (APZBS) in a potential range of 2.4∼2.5 V versus Li/Li during storage for 10 days. Such a precise control on APZBS not only suppresses the decomposition of the solid electrolyte interface film on the MCMB anode and inhibits the dissolution of the copper current collector occurring at high potentials but also avoids the excessive decrease of the cathode potential at the zero-charge battery state and consequently protects the LiCoO cathode from overlithiation occurring at low potentials. As a result, the LiFeO additive with a charge capacity percentage of 23% in the cathode increases the capacity recovery ratio of the LiCoO/MCMB battery from 37.6 to 95.5% after being stored at the zero-charge state for 10 days.