Low heat yielding electrospun phosphenanthrene oxide loaded polyacrylonitrile composite separators for safer high energy density lithium-ion batteries

Battery-induced fire scenarios are on the rise globally. The severity of battery fires is directly linked to the combustion behavior of battery components such as the separator and electrolyte which constitute the main combustible materials in the battery. To achieve safer batteries, components with a low combustibility must be employed in the new lithium-ion batteries. In this work, aiming to alleviate the battery separator's combustibility and preserve the electrochemical performance of lithium-ion batteries, we designed a novel low heat releasing composite separator by incorporating 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) into the polyacrylonitrile (PAN) matrix via electrospinning technique. Notably, the membranes containing DOPO remarkably exhibited a decreased peak heat release rate (pHRR) which was evidenced by a 33% and 49% decrease for PAN-15DOPO and PAN-20D0P0 samples respectively, evaluated using a microscale-combustion calorimeter (MCC). Furthermore, compared to pristine PAN based cells having an initial discharge capacity of 117 mAhg(-1) at a C-rate of 0.6C, the PAN-15DOPO based cells showed a superior initial discharge capacity of 131 mAhg(-1) and a capacity retention of 83% at a C-rate of 0.6C after 100 cycles. This strategy of electrospinning PAN with DOPO, provides a feasible design for fabricating batteries with simultaneously improved electrochemical properties and safety. (C) 2020 Elsevier Ltd. All rights reserved.