Red Phosphorus Flags Lithium Dendrites

James Tour and his lab at Rice University have made battery cells with a coat of red phosphorus on the separator that keeps the anode and cathode electrodes apart. The phosphorus alerts management systems used to charge and monitor batteries by detecting the formation of lithium dendrites. Lithium metal anodes charge much faster and hold about 10 times more energy by volume than common lithium-ion anodes used in just about every electronic device on the market, including cellphones and electric cars, writes But charging lithium-infused anodes forms dendrites that, if they reach the cathode, cause a short circuit and possibly a fire or explosion. By using a red phosphorus-coated separator, the battery’s charging voltage changes when a dendrite reaches the separator. That tells the battery management system to stop charging.

Unlike other proposed dendrite detectors, the Rice strategy doesn’t require a third electrode. “Manufacturing batteries with a third electrode is very hard,” Tour said. “We propose a static layer that gives a spike in the voltage while the battery is charging. That spike is a signal to shut it down.” The research appears in Advanced Materials.