Battery Degradation and Performance

Float Current (Constant Voltage) Measurement of SEI Growth and Electrolyte Oxidation Float current measurements combined with voltage slippage analysis deconvolutes reductive/oxidative electrolyte/interface reactions at both electrodes.

Quantitative analysis of measured currents during repeat voltage holds (Ifloat) on Samsung Gr|NCA cell at varying voltages and temperatures combining voltage slippage analysis, ICP-OES and EIS to deconvolute float current as SEI current (ISEI growth)and electrolyte oxidation current (ICL). Li-ion battery capacity loss occurs from LLI due to SEI growth, while Li inventory and capacity increases due to electrolyte oxidation. Voltage slippage is the drift of anode and cathode potentials with ageing. It is a crucial analysis for quantitative current splitting. ISEI growth dominates ICL; both increase with high voltage and temperature This technique is broadly applicable for Li-ion batteries with slippage analysis increasing in complexity for next generation batteries (e.g. silicon anodes with hysteresis, stress potential coupling etc.)

Source: M. Azzam, A. Aydin, C. Endisch, D-U. Sauer, M. Lewrenz

FLOAT TESTING PROTOCOL

FLOAT TEST CURRENT MEASUREMENTS AT VARYING VOLTAGE AND TEMPERATURES

SEI growth current

Cathode lithiation current

Capacity loss current

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