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

Abstract 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.