Researchers at Beihang University in Beijing have developed a new Li-sulfur battery using honeycomb-like sulfur copolymer uniformly distributed onto 3D graphene (3D cpS-G) networks for a cathode material and a 3D lithiated Si-G network as anode.
In a paper published in the RSC journal Energy & Environmental Science, they reported that the full cell exhibits superior electrochemical performances in term of a high reversible capacity of 620 mAh g-1, ultrahigh energy density of 1147 Wh kg−1 (based on the total mass of cathode and anode), good high-rate capability and excellent cycle performance over 500 cycles (0.028% capacity loss per cycle).
Lithium-sulfur (Li-S) batteries are of great interest as next-generation energy storage solutions, especially for electric vehicles, due to their high energy density, low production cost and environmental friendliness.
A number of challenges—in both sulfur cathode and lithium-metal anode—are retarding their commercialization, however. On the cathode side, the inherent insulation of sulfur (5×10-30 S cm-1) and high solubility of polysulfide intermediates commonly cause large active-material loss and poor cycle performance.
A number of approaches have been taken to address these cathode issues, including embedding sulfur into various porous carbons such as activated carbons, macroporous, mesoporous and microporous carbons, generating sulfur-carbon hybrids with well-designed nanostructures.
While this has improved overall electric conductivity and inhibited loss of active materials, restricted pore volumes still limit the contents of sulfur and polysulfides.
Another cathode strategy has involved the use of sulfur copolymer; this has shown good inhibition of polysulfide dissolution, but needs improved electric conductivity.
On the anode side, the lithium-metal anode reacts with the commonly used organic electrolytes forms lithium dendrites during cycling, resulting in short life and sever safety issues.
Alloy-type anodes are potential alternatives because of similar voltage plateaus to lithium. A number of approaches have been proposed, including the use of Si nanowires and lithiated Si/SiOx nanospheres.
Thus, a new type of silicon-sulfur battery built from silicon-based anode and sulfur-based cathode is becoming one of next-generation Li-S batteries to overcome their severe cyclability and safety problems. However, the researches of emerging silicon-sulfur battery including the configurations, design and fabrication of appropriate and mutual matching anodes and cathodes are still in the infancy.
Herein, we develop a new configured lithiated silicon-sulfur battery with well-designed three-dimensional (3D) sulfur co- polymer cathode and lithiated silicon anode onto graphene networks. Our 3D sulfur copolymer cathode is synthesized through the thermal copolymerization of sulfur with 1, 3- diisopropenylbenzene (DIB) onto 3D graphene (3D G) network, which can significantly improve the electric conductivity of sulfur copolymer-based cathode. Remarkably enough, the re- sultant sulfur copolymer is anchored closely onto graphene skeleton in the state of separated and individual honeycombs with multi-sized pores, which not only facilitate the easy access of electrolyte, but also can efficiently restrain the dissolution of polysulfides and accommodate their large volume change during lithiation-delithiation processes. Coupled with our 3D lithiated silicon-graphene network as anode, a full lithiated silicon-sulfur battery with a high stability reversible capacity of 620 mAh g-1 based on the total mass of both cathode and anode, good high-rate capability, ultrahigh energy density (1147 Wh kg−1 based on the total mass of both cathode and anode) and excellent cycle performance (0.028% capacity loss per cycle over 500 cycles) is achieved, providing the best reported electrochemical performances for lithiated silicon-sulfur batteries to date.—Li et al.
Bin Li, Songmei Li, Jingjing Xu and Shubin Yang (2016) “A new configured lithiated silicon-sulfur battery built on 3D graphene with superior electrochemical performances” Energy Environ. Sci. doi: 10.1039/C6EE01019A