Peanut shell derived hard carbon as ultralong cycling anodes for lithium and sodium batteries

The peanut shells derived porous hard carbons (PSDHCs) by pyrolysis have been investigated as anodes of lithium/sodium batteries (LIBs/NIBs). Directly from the starting peanut shells, 600°C is found to be the favorable pyrolysis temperature for preparation of the PSDHC sample (PSDHC-600) with the best electrochemical performances for LIB applications. Furthermore, from the activated peanut shells in KOH solution, the produced PSDHC-600A by pyrolysis at 600°C is observed to offer greatly enhanced Li+/Na+ ion storages. For LIB applications, PSDHC-600A delivers a retained capacity of 474 mAhg−1 after 400 cycles at 1 Ag−1, larger than 314 mAhg−1 of PSDHC-600. At a high current rate of 5 Ag−1, PSDHC-600A sustains over 10000 cycles with no obvious sign of fade in capacity, and a capacity of 310 mAhg−1 is still retained. For NIB applications, a capacity of 193 mAh g−1 is retained after 400 cycles at 0.25 Ag−1, higher than 130 mAhg−1 of PSDHC-600. Even at 1 Ag−1, PSDHC-600A can be stably cycled over 3000 cycles, and a capacity of 129 mAhg−1 is still retained. In comparison to PSDHC-600, the enhanced electrochemical properties of PSDHC-600A can be attributed to the finer porous structure with the increased percentage of nanoscale pores of diameter less than 2 nm and the larger specific surface area.