Multifunctional separators with high safety and regulated ion transport for lithium-ion batteries

Poor electrolyte wettability, nasty heat shrinkage and severe dendrite-growth issues of commonly used polyolefin separators significantly hamper further application and improvement of energy-density for lithium-ion batteries (LIBs). Hence, designing and constructing advanced separator materials with good wettability, robust mechanical strength and satisfied fire-thermal safety is critical for next-generation LIBs. In this study, novel separators consisted of bacterial cellulose (BC) and the prelithiated halloysite nanotubes (Li-HNTs), denoted Li-HNTs@BC separator, are designed and prepared via vacuum-assisted strategy. Compared with conventional Celgard separator, the obtained Li-HNTs@BC separators deliver good thermal stability, high porosity (62.99 %) and electrolyte uptake (497 %), and excellent thermal dimensional stability (almost no shrinkage at 300 °C for 30 min). In addition, Li-HNTs could provide extra lithium ions source and expedite lithium ion's migration, thus decreasing the concentration polarization and uneven lithium deposition during the battery cycling. As a result, the assembled Li//LiFePO₄ cell using Li-HNTs@BC separator displays obviously improved charging-discharging reversibility and excellent rate capability. More importantly, the separator endows the battery with excellent thermal safety, which could also well-process at 150 °C.