Hollow Ni3Se4 with High Tap Density as a Carbon-Free Sulfur Immobilizer to Realize High Volumetric and Gravimetric Capacity for Lithium-Sulfur Batteries

Despite that the practical gravimetric energy density of lithium sulfur batteries has exceeded that of the traditional lithium-ion battery, the volumetric energy density still pales due to the low density of carbonaceous materials. Herein, hollow polar nickel selenide (Ni3Se4) with various architectures was designed and employed as a carbon-free sulfur immobilizer. Among them, hollow sea urchins like Ni3Se4 with high porosity (0.39 cm 3 g(-1)) and large specific surface area (82.7 m(2) g(-1)) exhibit abundant adsorptive and electrocatalytic sites, which pledge excellent electrochemical performances of the Li-S battery. Correspondingly, the Ni3Se4 based sulfur electrode presents excellent rate endurability (581 mAh g(-composite)(-1) at 2.0 C) and superior cycle stability (ultralow fading rate of 0.042% per cycle during the 1000 cycles at 1.0 C). More importantly, thanks to the higher tap density (Ni3Se4/S: 1.57 g cm(-3) vs super P/S: 0.7 g cm(-3)), the volumetric specific capacity of Ni3Se4-based cathodes is as high as 1699 mAh cm(-composite)(-3) at 0.1 C, which is almost 2.8 times that of the carbonaceous electrode. Hence, rational transition metal selenide architecture design with synergistic function of good conductivity, well-defined catalyst and adsorption, as well as high tap density provide a promising route toward high gravimetric and volumetric energy density of Li-S batteries.

Automated summary

In this study, hollow polar nickel selenide (Ni3Se4) with abundant adsorptive and electrocatalytic sites was designed and employed as a carbon-free sulfur immobilizer to enhance the volumetric energy density of lithium sulfur batteries. The Ni3Se4-based sulfur electrode exhibited excellent rate endurability and cycle stability, with a nearly 2.8 times higher volumetric specific capacity compared to carbonaceous electrodes.