The Interfacial Electronic Engineering in Binary Sulfiphilic Cobalt Boride Heterostructure Nanosheets for Upgrading Energy Density and Longevity of Lithium-Sulfur Batteries.

High gravimetric, areal and volumetric capacities together with long lifetime are key indexes for the applications of lithium-sulfur (Li-S) batteries in compact space. The sulfur host materials play pivotal roles in the practical deployment. Herein, one type of new heterostructure nanosheets composed of cobalt boride (CoB) on nitrogen, boron-codoped porous carbon (NBC), which is constructed through molten salt-assisted strategy using ZIF-67-encapsulated ZIF-8 as precursors is reported on. Benefiting from strong interfacial electronic interactions between binary sulfiphilic CoB and porous NBC, the CoB/NBC-S electrode exhibits the excellent cycling stability with low average capacity decay of 0.013% in ultralong 1500 cycles at high rate of 5 C. Remarkably, the electrode with high sulfur content of 82 wt% and high sulfur loading of 5.8 mg cm-2 delivers gravimetric capacity of 1309 mA h g-1 , areal capacity of 7.59 mA h cm-2 , and volumetric capacity of 1355 mA h cm-3 at 0.1 C. The favorable electrochemical performance can rival with the state-of-the-art of those in the reported nanosheets-based sulfur cathodes. This study provides new methodology for the design of heterostructure nanosheets of metal borides to achieve energy density and longevity of Li-S batteries.