Temperature-insensitive fast anion intercalation kinetics in graphite electrodes for aluminum-ion batteries

Lithium-ion batteries (LIBs) rule today's energy storage market owing to their overall high performance, which, however, deteriorate severely at temperatures below -10°C. Emerging aluminum-ion batteries (AIBs), unlike LIBs, can deliver higher reversible capacities at low temperatures down to even -30°C. Here, we perform a systematic electrochemical characterization of the AIBs using classical electroanalytical methods at five temperatures selected between -20°C and room temperature, to assess the fundamental kinetics. With a generalized model, we obtained diffusion coefficients in the range of 10⁻⁹ – 10⁻⁷ cm² s⁻¹, and the rate-limiting mechanism shifts from mixed-control at room temperature to diffusion-control at -20°C. Further independent impedance analysis reveals a much less severe increase in the impedance in AIBs than those in LIBs, at low temperatures. The temperature-insensitive fast kinetics can be attributed to the high availability and easy access of active species at the inner Helmholtz plane near the electrode surface. The results here shed light on the governing mechanisms facilitating the high performance of AIBs in a wide temperature range and demonstrate the necessity of electrolyte optimization with a focus on the inner Helmholtz plane of the electric double layer structure to ensure high-rate electrode performance at low temperatures.