Magnetron sputtering deposition of silicon nitride on polyimide separator for high-temperature lithium-ion batteries

To date, lithium-ion batteries are becoming increasingly significant in the application of portable devices and electrical vehicles, and revolutionary progress in theoretical research and industrial application has been achieved. However, the commercial polyolefin separators with unsatisfying electrolytes affinity and poor thermal stability have extremely restricted the further application of lithium-ion batteries, especially in the high-temperature fields. In this work, magnetron sputtering deposition technique is employed to modify the commercial polyimide separator by coating silicon nitride on both sides. Magnetron sputtering deposition modified polyimide (MSD-PI) composite separator shows high thermal stability and ionic conductivity. More importantly, compared with the cells using Celgard separator, the cells with MSD-PI separator exhibit superior electrochemical performance, especially long-term cycle performance under high temperature environment, owing to the high thermal conductivity of surface Si₃N₄ particles. Hence, lithium-ion batteries with MSD-PI separator are capable of improving thermal safety and capacity retention, which demonstrates that magnetron sputtering deposition technique could be regarded as a promising strategy to develop advanced organic/inorganic composite separators for high-temperature lithium-ion batteries.