Nickel cobalt selenides on black phosphorene with fast electron transport for high-energy density sodium-ion half/full batteries

Abstract

Herein, in situ chemical anchoring of nickel cobalt selenide (Ni₃Se₄/CoSe₂) on two-dimensional (2D) black phosphorene is creatively proposed via a facile approach. The introduction of 2D black phosphorene brings abundant interfacial effects and provides fully exposed active sites. The construction of such a heterogeneous structure (BP@Ni₃Se₄/CoSe₂) effectively buffers the volume expansion effect caused by Na ion insertion and promotes electron/ion transfer during cycling. Therefore, the BP@Ni₃Se₄/CoSe₂ electrode exhibits superior sodium storage properties in half cells, such as a high stable discharge specific capacity (about 358.8 mA h g⁻¹ at 1 A g⁻¹ after 100 cycles), excellent cycling stability (up to 2500 cycles, the capacity retention rate close to 82%) and high rate performance (from the initial 0.2 A g⁻¹ to the final 20 A g⁻¹ and the total capacity retention rate is about 76%). In addition, BP@Ni₃Se₄/CoSe₂ achieved a high energy density of 163.7 W h kg⁻¹ at the power density of 136.4 W kg⁻¹ in the sodium-ion battery full battery test. Such high performance of BP@Ni₃Se₄/CoSe₂ is attributed to its excellent reaction kinetic characteristics. The investigation of the sodium storage mechanism of BP@Ni₃Se₄/CoSe₂ is conducted in detail.