Bismuth nanorod networks confined in a robust carbon matrix as long-cycling and high-rate potassium-ion battery anodes

Bismuth (Bi) is a promising alloy-type material for potassium-ion batteries (KIBs). However, its large volume variation during the cycling process remains a great challenge to its practical application. Here, a one-step approach was developed to synthesize a novel Bi-based composite structure comprising Bi nanorod networks confined in a N, S co-doped carbon matrix (Bi∈NS-C). As an anode, the Bi∈NS-C structure successfully integrated the merits of the micro-sized N, S co-doped carbon matrix, which functioned concurrently as a conductive framework and a robust buffer for large volume variation, and the network structure of Bi nanorods which enhanced the reaction kinetics and accommodated the large strain originating from the alloying/dealloying process. As a result, the Bi∈NS-C electrodes exhibited an excellent overall performance, i.e., high rate capabilities of 338 mA h g^-1 and 289 mA h g^-1 at current densities of 0.5 and 6 A g^-1, respectively, and outstanding long-term cycling stability with 91% capacity retention at 5 A g^-1 after 1000 cycles. Furthermore, a full KIB with hexacyanoferrate as the cathode and Bi∈NSC as the anode was assembled, which was demonstrated to be able to deliver a decent energy density of 295 W h kg^-1 and superior cycling stability with 83% capacity retention after 800 cycles.