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 be evaluated. Tests on coin cell half included rate tests (continuous and pulsed), resistance measurements, extended pulse tests. Pulse power at high rates typically showed three limiting processes within a 10 s pulse; an instantaneous increase, solid state diffusion limited stage, then electrolyte depletion/saturation. On anodes, third process can also plating. Most rated for C continuous discharge, cathode charging voltage was around 4.2 V. For maximum charge current avoid negative 3–5 C. Negative anode voltages do not necessarily mean that plating has occurred. However, deposits observed all anodes after 5000 sequences pulses ± 20