Confining MoS2 nanodots in compact layered graphene blocks for high volumetric capacity, fast, and stable sodium storage

Abstract

Sodium storage materials have gained increasing attention as next-generation power sources. However, realizing high volumetric capacity, high rate performance, and long-term stability remains challenging. Herein, we report a novel strategy for the confined growth of MoS₂ nanodots between densely nitrogen-doped graphene layers (DNG/MoS₂) assisted by electrostatic attraction between Mo₇O_24⁻ anions and polyaniline coated graphene oxide nanosheets. The interlayer confined structure provides sufficient space for fast ion transport and accommodates the volume change of MoS₂. The large contact area and strong interfacial Mo–N bonds between MoS₂ nanodots and nitrogen-doped graphene not only improve the electrical conductivity and charge-transfer kinetics, but also ensure good structural stability. Based on the above merits, DNG/MoS₂ delivers high gravimetric and volumetric capacities (514 mA h g⁻¹/1439 mA h cm⁻³ at 0.1 A g⁻¹), remarkable rate performance (290 mA h g⁻¹/811 mA h cm⁻³ at 10 A g⁻¹), and outstanding cycle stability (capacity retention of 82.4% over 2000 cycles at 1 A g⁻¹). The assembled sodium ion capacitor exhibits the high energy densities of 129 W h kg⁻¹ at 79 W kg⁻¹, as well as long-term cycle stability. Our work may provide new thoughts for designing high density advanced electrode materials.