Flexible ReS2 nanosheets/N-doped carbon nanofibers-based paper as a universal anode for alkali (Li, Na, K) ion battery

Alkali (Li, Na, K) ion battery have practically or potentially been widely used as a power source for portable electronic devices and electric vehicles. However, lack of universal anodes for these three alkali ion battery are restricting their development, especially for Na-ion battery and K-ion battery. Rhenium disulfide (ReS2), with large interlayer space and weak van der Waals interaction between layers, can afford massive alkali (lithium, sodium, and potassium) ions to diffuse easily between the layers. However, its low electronic conductivity and large volume changes in the conversion reaction significantly compromise the cycle life. To address this issue, here, we anchor ReS2 nanosheets onto nitrogen doped carbon nanofibers (N-CNF) which forms a flexible ReS2/N-CNFs paper for alkali (Li, Na, and K) ion battery anodes. The carbon nanofibers (CNFs) can improve the conductivity and the doped nitrogen can absorb sulfur and polysulfide generated by the conversion reaction. As a result, the ReS2/N-CNFs composite anode maintains a reversible capacity of 430 mAh/g after 400 cycles at 100 mA/g in LIBs, 245 mAh/g after 800 cycles at 100 mA/g in NIBs, and 253 mAh/g after 100 cycles at 50 mA/g in KIBs. This performance is one of the best among all ReS2 reported up to date. In addition, the solid electrolyte interface formation on ReS2 and the coulombic efficiency in different alkali ion batteries are also systemically investigated.