>I've always wondered what the degradation is like, because it dictates what secondary applications are viable. All of the above. Internal resistance increases

>I've always wondered what the degradation is like, because it dictates what secondary applications are viable. All of the above. Internal resistance increases as the SEI layer (boundary between electrolyte material and the anode) gets thicker and thicker. Eventually it reaches a point where internal resistance is so high that it becomes dangerous to even charge, and at that point the battery basically has to be completely disassembled and recycled. There's essentially no way to safely reuse a whole cell because of the wildly different charge/discharge profiles each one may have been exposed to, which affects the discharge curve accordingly. https://arxiv.org/ftp/arxiv/papers/1210/1210.3672.pdf https://arxiv.org/ftp/arxiv/papers/1210/1210.3672.pdf