Highly active cobalt-doped nickel sulfide porous nanocones for high-performance quasi-solid-state zinc-ion batteries

Flexible quasi-solid zinc-ion batteries (ZIBs) have large potential in power applications due to the low price, wearable nature, safety, and high capacity. However, the use of transition metal sulfide cathodes in ZIBs has not been studied extensively and the underlying mechanism and theoretical basis of this type of batteries are not well understood. Herein, a highly active cobalt-doped Ni₃S₂ porous nanocone framework (C12NS) is designed and demonstrated as a zinc-ion battery electrode. First-principles calculation and experiments reveal that the cobalt dopant improves the battery properties greatly. The assembled flexible zinc-ion battery exhibits a high specific capacity of 453.3 mAh g⁻¹ at a current density of 0.4 A g⁻¹ in as well as excellent cycling stability as manifested by a capacity retention ratio of 89.5% at a current density of 4 A g⁻¹ after 5000 cycles. The peak energy density of 553.9 Wh kg⁻¹ is also superior to those of most recently reported NiCo-based zinc-ion batteries. More importantly, the flexible battery can be operated under severe mechanical bending and even continues to work after physical puncturing without showing leakage. These exciting results not only reveal a novel design of cathode materials for zinc-based batteries, but also suggest their immense commercial potential in portable and wearable electronics.