Electrochimica Acta, Vol.178, 525-532, 2015
Optimization of Charging Strategy by Prevention of Lithium Deposition on Anodes in high-energy Lithium-ion Batteries - Electrochemical Experiments
The study evaluates the capacity fade of commercial 3.25 Ah 18650-type cells with NCA cathodes and graphite anodes quantitatively for different temperatures and charging strategies. For standard constant current/constant voltage (CC-CV) charging, the aging rate for cells cycled at 0.5C is increased with decreasing temperature in the range of 25 degrees C to 0 degrees C. Interestingly, no accelerated aging is observed for CC-CV charging in the temperature range of 25 degrees C to 60 degrees C at 0.5C. The observed behavior indicates lithium deposition on anodes for temperatures up to similar to 25 degrees C and is further investigated by reconstruction of anode and cathode from the commercial 18650-type cells into full cells with an additional lithium metal reference electrode. The reconstruction method is scrutinized regarding its validity. Measurements with the reconstructed cells at 25 degrees C reveal the quantitative dependency of the anode potential vs. Li/Li+ from the charge C-rate and cell voltage. This allows deriving charging strategies involving strictly positive anode potentials to avoid lithium deposition and preventing the corresponding capacity fade. (C) 2015 Published by Elsevier Ltd.
Keywords:Lithium-ion batteries;charging procedure;battery aging;reconstruction;lithium deposition;lithium reference electrode;operating conditions