A strategy to achieve high loading and high energy density Li-S batteries

Abstract Lithium-sulfur (Li-S) batteries are one of the most promising rechargeable storage devices due to the high theoretical energy density. However, the low areal sulfur loading impedes their commercial development. Herein, a 3D free-standing sulfur cathode scaffold is rationally designed and fabricated by coaxially coating polar Ti3C2Tx flakes on sulfur-impregnated carbon cloth (Ti3C2Tx@S/CC) to achieve high loading and high energy density Li-S batteries, in which, the flexible CC substrate with highly porous structure can accommodate large amounts of sulfur and ensure fast electron transfer, while the outer-coated Ti3C2Tx can serve as a polar and conductive protective layer to further promote the conductivity of the whole electrode, achieve physical blocking and chemical anchoring of lithium-polysulfides as well as catalyze their conversion. Due to these advantages, at a sulfur loading of 4 mg cm−2, Li-S cells with Ti3C2Tx@S/CC cathodes can deliver outstanding cycling stability (746.1 mAh g−1 after 200 cycles at 1 C), superb rate performance (866.8 mAh g−1 up to 2 C) and a high specific energy density (564.2 Wh kg−1 after 100 cycles at 0.5 C). More significantly, they also show the commercial potential that can compete with current lithium-ion batteries due to the high areal capacity of 6.7 mAh cm−2 at the increased loading of 8 mg cm−2.