Stable and high-rate overcharge protection for rechargeable lithium batteries

Rechargeable lithium or lithium-ion cells can be overcharge-protected by an electroactive polymer composite separator. The use of non-woven fibrous membranes instead of conventional microporous membranes as the composite substrates allowed better distribution of the electroactive polymer, which led to improved utilization and a 40-fold increase in sustainable current density. For the first time, stable overcharge protection for hundreds of cycles was demonstrated in several cell chemistries, including LiNi1/3Co1/3Mn1/3O2, LiFePO4, and spinel Li1.05Mn1.95O4 half-cells. Protection at a charging rate as high as 5 C was achieved at a steady state cell potential below 4.85 V.