The Metal–Organic Frameworks Derived Co₃O₄/TiO₂ Heterojunction as a High‐Efficiency Sulfur Carrier for Lithium–Sulfur Batteries

Abstract

Lithium–sulfur batteries, due to their various advantages such as their unique theoretical capacity, inexpensive, and environmental friendliness, have become one of the new‐generation energy storage systems. However, during the commercial development of lithium–sulfur batteries, they are limited by obstacles such as the volume expansion, shuttle effect, and low conductivity of S, which eventually lead to slow system reaction kinetics and poor cycling stability. Herein, heterostructured metal–organic framework‐derived Co3O4/TiO2 hybrids have been designed. The hollow structure of the Co3O4 is coupled with TiO2 on the surface to form a heterojunction to construct an internal electric field, which can promote charge transfer and improve reaction kinetics. Meanwhile, Co3O4/TiO2 has excellent trapping ability for lithium polysulfide, reducing the shuttle effect and alleviating volume expansion. As the cathode material, the initial discharge capacity of S@Co3O4/TiO2 at 0.1C is 1152.7 mAh g−1. Meanwhile, it has an initial specific capacity of 657 mAh g−1 at 1C, a capacity retention rate of 63.7% after 500 charge/discharge cycles, and an effective cycling stability with a decay rate of 0.072% in each cycle. This indicates that the construction of heterojunctions between materials has some enhancement on the performance of Li–S batteries.

Graphene/Heterojunction Composite Prepared by Carbon Thermal Reduction as a Sulfur Host for Lithium-Sulfur Batteries

“…The electrochemical performance of rGO and CC@rGO cells was compared at a scan rate of 0.1 mv/s and a voltage window of 1.7-2.8 V. The two typical reduction peaks (2.25 V, 2.01 V) characterized by CC@rGO correspond to the reduction of S to soluble polysulfide (Li 2 S x , 4 ≤ x ≤ 8) and the reduction of soluble polysulfide to insoluble polysulfide (Li 2 S 2 , Li 2 S) during discharge, respectively [50]. Compared with rGO, the CC@rGO has a smaller electrochemical polarization with a higher peak after the introduction of the heterostructure, implying that the composite has better kinetic catalytic performance as well as charge and discharge capacity [51].…”