Selective Nitridation Crafted a High‐Density, Carbon‐Free Heterostructure Host with Built‐In Electric Field for Enhanced Energy Density Li–S Batteries

Abstract

To achieve both high gravimetric and volumetric energy densities of lithium-sulfur (Li-S) batteries, it is essential yet challenging to develop low-porosity dense electrodes along with diminishment of the electrolyte and other lightweight inactive components. Herein, a compact TiO₂ @VN heterostructure with high true density (5.01 g cm^-3 ) is proposed crafted by ingenious selective nitridation, serving as carbon-free dual-capable hosts for both sulfur and lithium. As a heavy S host, the interface-engineered heterostructure integrates adsorptive TiO₂ with high conductive VN and concurrently yields a built-in electric field for charge-redistribution at the TiO₂ /VN interfaces with enlarged active locations for trapping-migration-conversion of polysulfides. Thus-fabricated TiO₂ @VN-S composite harnessing high tap-density favors constructing dense cathodes (≈1.7 g cm^-3 ) with low porosity (<30 vol%), exhibiting dual-boosted cathode-level peak volumetric-/gravimetric-energy-densities nearly 1700 Wh L^-1 _cathode /1000 Wh kg^-1 _cathode at sulfur loading of 4.2 mg cm^-2 and prominent areal capacity (6.7 mAh cm^-2 ) at 7.6 mg cm^-2 with reduced electrolyte (<10 µL mg^-1 _sulfur ). Particular lithiophilicity of the TiO₂ @VN is demonstrated as Li host to uniformly tune Li nucleation with restrained dendrite growth, consequently bestowing the assembled full-cell with high electrode-level volumetric/gravimetric-energy-density beyond 950 Wh L^-1 _{cathode+anode} /560 Wh kg^-1 _{cathode+anode} at 3.6 mg cm^-2 sulfur loading alongside limited lithium excess (≈50%).