Improvement of low-temperature performance by adopting polydimethylsiloxane-g-polyacrylate and lithium-modified silica nanosalt as electrolyte additives in lithium-ion batteries

In this work, poly[dimethylsiloxane-co-(siloxane-g-acrylate)] (PDMS-A) and lithium-modified silica nanosalt (Li202) are used together as low-temperature electrolyte additives in lithium-ion batteries (LIBs), taking advantage of the electrochemical and interfacial stabilities due to their surface functional groups. Using these additives together improves the electrochemical stability and ionic conductivity of liquid electrolyte solution to over 5.5 V and 4 × 10^-4 S cm^-1 at -20 °C, respectively. The room-temperature electrochemical performance of a conventional LIB (LiCoO₂/graphite) is improved by the addition (e.g., initial discharge capacity of 95.9 mAh g^-1 obtained after charging at 1.0 C-rate and consequent discharging at 5.0 C-rate). The low-temperature performance is also enhanced, achieving a capacity retention ratio of 63.4% after 50 cycles at -20 °C, compared to 38.7% without the additives. It is also notable that the PDMS unit commonly existing in both additives may be the main cause of the synergistic effects on the electrochemical performance due to the compatibility between PDMS-A and Li202.