Monolithic integration of mesoporous germanium: A step toward high-performance on-chip anode

Advanced energy storage systems are one of the essential pillars for accelerating development of the cutting-edge technologies, including Internet of things and grid energy storage. Microbatteries with high power and energy density levels are then required and germanium, despite its relatively high cost, is an attractive candidate in this field due to its high specific capacity. This study is the first report of a monolithic mesoporous germanium (mpGe) and graphene-coated mesoporous germanium nanocomposite (GPGNC) as anodes for Li-ion battery within an on-chip architecture. In this configuration, the sample substrate is used as the current collector while the porous part acts as the active material. GPGNC exhibits an outstanding electrochemical performance at high areal capacity (1 mAh cm−2) and offers a high capacity retention at slow (C/5) and medium (2C) discharge rates. Moreover, no capacity fading is observed during 1000 cycles at C/5 rate with Coulombic efficiency of 98.9 %. High rate capacity application has also been investigated and a 4000 cycle lifetime at 5 mA cm−2 discharge current during 1 min was demonstrated. Our findings evidenced superior performance of on-chip anodes based on mesoporous Ge at high energy and high power density regimes.