Lithium Sulfur Battery Chemistry Introduction

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Lithium Sulfur batteries is one of the promising battery chemistry of the future. This battery chemistry is particularly suitable in the Energy storage systems due to superior theoretical capacity, cost effectiveness and eco friendliness.

  • Theoretical Specific Capacity: 1675 mAh/g
  • Energy Density 2600 Wh/kg

Today the LI-Ion batteries Cathode is made of various chemistries NMC (Nickel Manganese Cobalt) one of the popular ones. Sulfur as Cathode is a much cheaper option as Sulfur is widely available.

As compared to Lithium Ion Chemistry, Energy density for Li-S is 10 times theoretically. (2600Wh/kg vs 260/270 Wh/kg).

Below Infographic shows current status of Lithium Sulfur (Li-S) batteries vs Solid State and Lithium Ion Batteries.

What happens inside a Lithium Sulfur Battery?

  • Anode: Lithium Metal Anode
  • Cathode: Sulfur Composite Cathode
  • Electrolyte: Organic Electrolyte

Source: Reprinted with permission from A. Manthiram, Y. Z. Fu and Y. S. Su, Acc. Chem. Res., 2013, 46, 1125–1134. Copyright 2013 American Chemical Society.

Working Principle of Li-S Battery

The Oxidation and reduction chemistry reaction is given above in the infographic. The Cathode Sulfur Reduction is very complex. Sulfur combines with Lithium Ion and electron and then forms a number of intermediate Polysulfides until the final Polysulfide Li2S is formed. Sulfur is non polar whereas L2S is polar. The Intermediate polysulfides are of intermediate polarity and quite soluble into the electrolyte. This leads to fading of capacity as active material is lost and dissolved into the electrolyte. Another problem is this polysulfides can travel to the anode and insulate the anode which again leads to capacity loss due to increase in impedance.

These are the major drawbacks of Lithium Sulfide Chemistry and where majority of research is currently focused on. The Research focus Areas are improved Separator in the electrolyte to stop the flow of Polysulfides or improved cathode to reduce the dissolvement of polysulfides into electrolyte.

Challenges and limitations for Li-S battery chemistry.

  • Resistance of Sulfur is very High 5 x 10-30
  • Unstable Electrochemical contact within the electrode during cycling due to intermediate product Li2Sx
  • Rapid Fading of capacity due to shuttle effect as polysulfide causes loss of active materials. Polysulfide get dissolved into the electrode and cause corrosion. Cathode can get pulverised which severely reduces the capacity and contacts between electrodes and collectors. This happens due to volume expansion of cathode which can reach upto 80%.
  • Dendrite formation in the lithium metal anode can lead to short circuits or fire. Thus it is a safety concern.
  • Insulated Li2S which forms on the surface of the cathode increases the impedance of the electrode which again leads to capacity loss or poor cyclability.

Future Developments:

  • Battery Report 2022 from Volta Foundation. Read Pages 59,60,61 for recent developments and companies involved in Li-S Battery development.
  • University of Michigan Develops 1,000-Cycle Lithium-Sulfur Battery That Could Quintuple Electric Vehicle Ranges.
  • Development of Lithium Sulfur Batteries for High Energy Applications. Authors: Hong Wang, James Dong, Kevin Schelkun, Shay Penski, Chris Silkowski, Michael Wixom, Les Alexander.
  • Research to reduce Polysulfide Shuttling: Lee, BJ., Zhao, C., Yu, JH. et al. Development of high-energy non-aqueous lithium-sulfur batteries via redox-active interlayer strategy. Nat Commun 13, 4629 (2022). https://doi.org/10.1038/s41467-022-31943-8
    • “we propose a polar and redox-active interlayer concept for high-energy and long-cycling Li-S batteries, in which sulfur is embedded into a polar platelet ordered mesoporous silica to form an interlayer. Interestingly, sulfur storage/trapping occur at the polar silica while electron transfer at conducting agent in pOMS/Sx IL during charge-discharge. During the electrochemical processes, this interlayer not only fulfils the role of effectively preventing the shuttling of long-chain polysulfides, but also contributes to enhance the areal capacity to the cell. The cell with optimal interlayer delivers an areal capacity of >10 mAh cm−2 with the benefit of high sulfur loading of >10 mg cm−2 and stable cyclability for 700 cycles, even under high specific current cycling and low electrolyte/sulfur ratio. These attributes can increase the practical specific energy of Li-S batteries.“

this Article is live as I update more details on this topic.

References:

  1. A review of recent developments in rechargeable lithium–sulfur batteries. Authors: Weimin Kang, Nanping Deng, Jingge Ju, Quanxiang Li, Dayong Wu, Xiaomin Ma, Lei Li, Minoo Naebe and Bowen Cheng. Aug 2026
  2. Recent Progress in Quasi/All-Solid-State Electrolytes for Lithium–Sulfur Batteries, AUTHOR=Yang Shichun, Zhang Zhengjie, Lin Jiayuan, Zhang Lisheng, Wang Lijing, Chen Siyan, Zhang Cheng, Liu Xinhua. July 2022
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