Constructing high gravimetric and volumetric capacity sulfur cathode with LiCoO2 nanofibers as carbon-free sulfur host for lithium-sulfur battery

Although the gravimetric energy density of lithium-sulfur battery is very encouraging, the volumetric energy density still remains a challenge for the practical application. To achieve the high volumetric energy density of battery, much attention should be paid to the sulfur cathode. Herein, we introduce heavy lithium cobalt oxide (LiCoO2) nanofibers as sulfur host to enhance the volumetric capacity of cathode, maintaining the high gravimetric capacity simutaneously. With the high tap density of 2.26 g cm−3, LiCoO2 nanofibers can be used to fabricate a really compact sulfur cathode, with a density and porosity of 0.85 g cm−3 and 61.2%, respectively. More importantly, LiCoO2 nanofibers could act as an efficient electrocatalyst for enhancing the redox kinetics of sulfur species, ensuring the cathode electroactivity and alleviating the shuttle effect of polysulfides. Therefore, a balance between compact structure and high electrochemical activity is obtained for the sulfur cathode. At the sulfur loading of 5.1 mg cm−2, high volumetric and gravimetric capacities of 724 mA h cm−3cathode and 848 mA h g−1cathode could be achieved based on the cathode volume and weight, respectively. Moreover, with this efficient S/LiCoO2 cathode, the lithium corrosion by polysulfides is supressed, leading to a more stable lithium anode.