High‐Efficiency Cryo‐Thermocells Assembled with Anisotropic Holey Graphene Aerogel Electrodes and a Eutectic Redox Electrolyte

, respectively. Moreover, assembled thermocells in series packaging substantially enhance the voltage of the open-circuit, i.e., from 140 mV (1-cylinder thermocell) to 2.1 V (15-cylinder thermocells).