Effects of water contamination on the electrical properties of 18650 lithium-ion batteries

Effects of water on the voltage, internal resistance, initial capacity and cycling behavior of 18650-type lithium-ion batteries are studied. The voltage curves of the first charging can be used to judge whether cells are contaminated by water, because the voltage growth rates of cells are obviously different (>100 mV) between water-free batteries and containing water batteries at the first charging period of 10–50 min. The self-discharging performances of water contamination cells are also larger, because water-related side effects happen continuously during aging at high voltage of 4.2 V. Besides, HF corrosion on the cathode materials and Co ion dissolved out from lithium nickel cobalt manganese oxides lead to rapid capacity fading from >90% (100 cycles) to <80% (300 cycles, 0.5 C charging/0.5 C discharging).