Electrochemical characteristics of sulfur composite cathode for reversible lithium storage

Abstract

The electrochemical characteristics of the sulfur composite cathode for reversible lithium storage were investigated. The sulfur composites showed novel electrochemical characteristics as well as high specific capacity and good cycleability. The sulfur composite presented the average discharge voltage of 1.9 V, which was just the half of conventional LiCoO 2 cathode materials, indicating that the double cells in series presented the same working voltage as conventional LiCoO 2 cells and meaning that the sulfur composite cells will have good interchangeability with conventional LiCoO 2 cells. The overcharge test showed that the sulfur composite cell cannot be charged over 5.0 V, indicating that the sulfur composite cell presented the intrinsic safety for overcharge. Overcharge can cause serious problems for the conventional Li ion cells. The overcharge test also showed that the sulfur composite cell was destroyed when the cell was charged over 4.0 V, resulting in that the cell cannot normally be discharged again. It is found, however, that the sulfur composite cell can be discharged again at very low current density of a 0.002-C rate after the cell was overcharged. Being much safer than lithium metal anode, the graphite anode was used to fabricate sulfur composite/graphite lithium ion cells with a prelithiated sulfur composite cathode, which was produced by electrochemical lithiation. The charge/ discharge and cycling characteristics of the sulfur composite/ graphite cell was investigated. The result showed that the sulfur composite/graphite cells can be normally cycled and showed the different voltages from that of the cell with the lithium metal anode. This paves the effective way to fabricate safer sulfur composite/graphite lithium ion cells.

Progress in Mechanistic Understanding and Characterization Techniques of Li‐S Batteries

“…[ 30 ] In spite of their instability with the presence of polysulfi de anions, carbonate-based electrolytes have proven to be safe with cathode composites in which sulfur was either physically confi ned within micro-sized pores of a carbon structure, which avoided polysulfi de dissolution to the electrolyte, or covalently immobilized in polymeric composites. [ 38,46,165,170,177,[179][180][181] For example, Wang et al demonstrated this effect with sulfur in a microporous-mesoporous carbon material, [ 46 ] and Xin et al did the same with metastable small sulfur molecules of S 2-4 in a microporous carbon matrix. [ 38 ] At present, the preferred ether solvents in Li-S cells are dimethyl ether (DME), [ 24,72,161 ] tetra(ethylene glycol) dimethyl ether (TEGDME), [ 70,72,80,123,169 ] polyethylene glycol dimethyl ether (PEGDME), and 1,3-dioxolane (DOL), [ 69,85,161,171,[182][183][184] with lithium bis(trifl uoromethanesulfonyl)imide (LiTFSI) as the Li + ion carrier.…”

Structural Design of Cathodes for Li‐S Batteries

“…[ 75,83 ] In fact, it was recently demonstrated that an all carbon-based Li-ion system can be assembled from S-PAN cathodes and graphite, an anode that requires the carbonate-based electrolyte for optimal function. [ 104 ] However, there are no convenient and scalable methods for pre-lithiating these electrode materials. This remains a challenge that must be addressed in order to replace lower capacity Li-ion battery cathodes.…”

Understanding of Sulfurized Polyacrylonitrile for Superior Performance Lithium/Sulfur Battery

“…The reported advantages of the SPAN over elemental sulfur include: (1) it offers very stable specific capacity close to or even higher than the theoretical value of elemental sulfur; (2) it completely avoids the dissolution of long-chain lithium polysulfide (PS) in organic electrolyte, as well as the resulting redox shuttle and parasitic reactions with lithium anode; (3) it is chemically compatible with the LiPF 6 -carbonate based electrolytes widely used in the state-of-art Li-ion batteries; (4) it suits for the cathode with high active material loading; and (5) the Li/SPAN cell after activation has nearly 100% coulombic efficiency (CE) and extremely low self-discharge rate. Moreover, He et al have successfully demonstrated a proof-of-concept "all carbon" Li-ion battery by electrochemically pre-lithiating a graphite anode and then coupling the pre-lithiated graphite anode with a SPAN cathode [6]. The dream to fabricate safe and low cost metal-free Li-ion batteries will become true once a viable process for the pre-lithiation of either SPAN cathode or carbonaceous (or others such as silicon, tin, and their relative alloys) anode can be successfully developed.…”