Advanced poly(vinyl alcohol) porous separator with overcharge protection function for lithium-ion batteries

The separator plays a key role in improving the safety and charge-discharge property of lithium-ion batteries. Herein, a home-made polyvinyl alcohol porous separator with three-dimensional porous structure is used as the substrate to allow a perfect distribution of the inexpensive electroactive polymer polytriphenylamine. The electroactive polymer exhibits a reversible electrochemical reaction belonging to doping and dedoping process between 3.0 and 4.5 V, which provides potential overcharge protection function for the functionalized composite separator. Due to maximum preservation of the original porous structure of the polyvinyl alcohol separator, the composite separator likewise possesses excellent electrolyte affinity and ionic conductivity. A blocking cell assembled with the composite separator still has a certain voltage clamp function even if the current density increases to 5.0 mA cm(-2). Moreover, a half-cell (LiFePO4-Li) assembled with the composite separator exhibits a reversible voltage-regulated current shunt even after 50 overcharge cycles. At a high current density rate of 4.0 C, the half-cell can still provide a discharge capacity of 94 mAh g(-1) and an effective overcharging shunting at 4.0 V.