Strong magnetic field-dual-assisted fabrication of heterogeneous sulfide-based hollow nanochain electrodes for high-rate supercapacitors

Abstract

Many sulfide-based supercapacitors suffer from the problem of large capacity and energy attenuation at high rates. To tackle this problem, a strong magnetic field (SMF) was exerted twice during new material synthesis and electrode fabrication. Here, one-dimensional (1D) hetero-Zn_0.76Co_0.24S/Co₃S₄/β-CoS_1.097 hollow sphere nanochains (CZ₅₅S^6T) were first prepared via a one-step anion-exchange reaction under SMF. The SMF-induced directional growth of paramagnetic Zn_0.76Co_0.24S in the outer shell contributed to the directional assembly of the simultaneously hollowing-out spheres into 1D nanochains based on the Kirkendall effect accelerated by SMF. Physicochemical investigations revealed that SMF endowed CZ₅₅S^6T with a larger surface area and reduced the loss of active components, especially Zn. The unique 1D hollow nanochain nanostructures contributed to a remarkable rate performance. An oriented CZ₅₅S^6T nanochains/graphene flake capacitive electrode (CZ₅₅S^6T/G) with high loading (∼8 mg cm⁻²) was further fabricated using SMF to reduce the path tortuosity. The CZ₅₅S^6T/G electrode exhibited strikingly enhanced rate capability with 80% capacitance retention (863.8 F g⁻¹) and cycling capacitance (705 F g⁻¹ after 5000 cycles) at a high rate of 20 A g⁻¹. Furthermore, the CZ₅₅S^6T/G-based asymmetric supercapacitor delivered remarkable energy density of 51.5 W h kg⁻¹ at a large power density of 6811 W kg⁻¹.