Understanding the limitations of lithium ion batteries at high rates

Commercial lithium ion cells with different power: energy ratios were disassembled, to allow the electrochemical performance of their electrodes to be evaluated. Tests on coin cell half cells included rate tests (continuous and pulsed), resistance measurements, and extended pulse tests. Pulse power tests at high rates typically showed three limiting processes within a 10 s pulse; an instantaneous resistance increase, a solid state diffusion limited stage, and then electrolyte depletion/saturation. On anodes, the third process can also be lithium plating. Most of the cells were rated for a 10 C continuous discharge, and the cathode charging voltage at 10 C was around 4.2 V. For anodes, the maximum charge current to avoid a negative voltage was 3–5 C. Negative anode voltages do not necessarily mean that lithium plating has occurred. However, lithium deposits were observed on all the anodes after 5000 pulse sequences with 10 s pulses at ± 20 C. •Harvested electrodes are tested at high discharge and charge rates.•Several limiting processes were observed within a single 10 s pulse.•In 10s pulses, the cathodes could be charged at 10C and stay below the 4.2 V limit.•The anodes voltages went negative at 5C, but the limiting process was diffusion.•Repeated pulsing with 20C, 10s pulses lead to lithium plating on the anodes.