Cross-linking Cu-TCPP@CNT-OH-S as high sulfur loading cathode for Li-S batteries

Abstract

To obtain high theoretical energy density, lithium–sulfur batteries (LiSBs) with high sulfur loading are urgently required. Herein, sulfur was effectively immobilized on hydroxylated carbon nanotubes (CNT-OH) through chemical reaction deposition strategy to obtain CNT-OH-S, then combining with 2D Cu-TCPP nanosheets (TCPP = tetrakis (4-carboxyphenyl) porphyrin) successfully fabricated a 3D cross-linking Cu-TCPP@CNT-OH-S network, where CNT-OH-S carries the effective polar bond confirmed by FTIR, XPS and SAED tests, and Cu-TCPP promises the inhibition of LiPSs shuttle and promotes kinetics for sulfur conversion explored by UV–vis, symmetrical electrodes tests and XRD in suit. The fast diffusion of Li+ was calculated through CV, and the low electrochemical polarization was demonstrated by GITT, Tafel, GCD, etc., ensuring a high S utilization under practical conditions of high loading. As a consequence, the Cu-TCPP@CNT-OH-S@S cathode with 92.8 wt% sulfur content delivers a high specific capacity of 1448 mAh g−1 at 0.2C, and stabilize at 820 mAh g−1 after 900 cycles. In Li–S pouch cell, a 4.3 mAh cm−2 reversible areal capacity with 10.04 mg cm−2 sulfur loading was obtained at 2C after 100 cycles, which is in the top class among reported porphyrin-based, MOFs-based and nanocarbons-based cathode host.