Alternative Pulse Current Charging Reinforcing the Cathode–Electrolyte Interphase to Inhibit the Aluminum Corrosion of LiFSI-Based Batteries at High Temperatures

Lithium difluorooxalate borate (LiDFOB) can preferentially oxidize and form a passivation layer to resist the corrosion of an aluminum (Al) current collector in lithium difluorosulfonyl imide (LiFSI)-based batteries at room temperature. However, such a protective effect turns out to be a failure at high temperatures. The fundamental reason is that the LiDFOB-derived cathode–electrolyte interphase (CEI) formed during the traditional constant current (CC) charging protocol is not sufficiently stable, whereby its continuous dissolution and regeneration and eventual rupture struggle to prevent the mutual diffusion of FSI– anions and Al3+, ultimately triggering drastic Al corrosion. Herein, we apply an alternative pulse current (APC) charging protocol to the LiDFOB oxidation potential to drive the full decomposition of LiDFOB, thereby forming a reinforced CEI characteristic of richness in inorganics, thickness and smoothness, higher rigidity, and lower resistance. Attributed to the intrinsic chemical–mechanical stability of this APC-reinforced CEI, the Al corrosion at high temperatures is greatly inhibited, which has been proved by electrochemical tests and morphology characterizations. Consequently, the LiFSI-based LiFePO4/Li battery exhibits superior long-term cycle stability (after 300 cycles at 50 °C and 0.5C, 91.8% capacity retention) and rate performances (50 °C, 2C, 151.3 mAh g–1) at high temperatures, far exceeding the data currently reported. This study, therefore, develops an effective strategy to expand the application of imide-based batteries in high-temperature scenarios.