Description:

Introduction: Lithium-sulphur batteries, which are lighter and cheaper than most of the present models, may be the next generation of power cells that can be used in electric cars or mobile phones. Lithium-sulphur batteries have the potential to become the energy storage devices of the future, if they overcome some limitations.

The main benefit is that they can store much more energy than a similar battery using current lithium-ion (Li-ion) technology. That means they can last substantially longer on a single charge. They can also be manufactured in plants where Li-ion batteries are made.

Advantages:

• Lithium-sulphur batteries need little maintenance compared to other batteries, such as lithium-ion batteries. These are known to be the most resilient batteries that are not easily damaged in harsh environments and last a few years longer.
• Self-discharge is one of the most important issues that many batteries offer. They automatically discharge even if they are not connected to any devices.

Limitations:

• Transportation of lithium-sulphur batteries is one of the major limitations. Because of the chemicals used in them, nearly every airline company restricts lithium sulphur batteries to carry in the aircraft.
• Lithium-sulphur batteries, relative to other batteries, are expensive.

Process: The lithium-sulphur batteries are promising because of the high energy density, low cost, and natural abundance of sulphur material. However, these advantages can be achieved only when the battery uses elemental sulphur as the cathode active material and the sulphur approaches the theoretical capacity with a low process cost.

Lithium-sulphur batteries are fundamentally a liquid electrochemical system, in which elemental sulphur must dissolve into the liquid electrolyte in the form of long-chain Polysulphide (PS) and serve as the liquid catholyte. Dissolution of PS in the liquid electrolyte, on the one hand, facilitates the electrochemical reactions of insulating sulphur species, and on the other hand, causes severe redox shuttle and parasitic reactions with the Li anode. Therefore, following improvements can be made to balance the various positive and negative effects of the PS dissolution:

1. Sulphur cathode: To meet the requirements of low cost and high energy density, elemental sulphur should be preferentially considered as the cathode active material, and the cathode should contain at least 70% sulphur and have a sulphur-loading of not lower than 2 mg/cm2. Furthermore, the cathode structure should be tolerant enough to stand the large volume expansion and contraction incurred by the discharging and charging of sulphur active material.
2. Anode material: When metallic Li is used as the anode material, it is essential to develop an effective and cost-acceptable approach for the protection of the Li anode from reactions with the dissolved PS and from the growth of Li dendrites. To completely solve the problem of Li dendrites, developing an alternative anode material free of Li metal is essential for the safety of Li–S batteries. In this case, a facile and cost-acceptable lithiation technique should be explored either for the anode or for the sulphur cathode.
3. Electrolyte: Electrolyte is the key to determining the operation temperature range of lithium-sulphur batteries, and affecting the dissolution and chemical stability of PS. The PS in the electrolyte will spontaneously disproportionate into low soluble or insoluble short-chain PS and elemental sulphur, which could precipitate out of the liquid electrolyte and clog the pores of the separator. Therefore, in view of the sulphur utilization and reaction kinetics, a liquid electrolyte that can well dissolve and stabilize the PS is highly demanded; however, this promotes the redox shuttle of PS. Electrolyte also affects the coulombic efficiency of the Li anode and the formation of a passivation layer on the Li surface.

The battery design plays a crucial role in affecting the cycling performance of lithium-sulphur batteries. As suggested by the fundamental chemistry of the lithium-sulphur battery, the dissolution of PS in the liquid electrolyte is essential to enable the electrochemical reactions to insulate sulphur species; however, it meanwhile causes severe redox shuttle and Li corrosion.

Commercialization:

• As of 2021,  few companies had been able to commercialize the technology on an industrial scale. Companies such as Sion Power have partnered with Airbus Defence and Space to test their lithium sulphur battery technology.
• Sony, which also commercialized the first lithium-ion battery, planned to introduce lithium–sulphur batteries to the market in 2020, but has provided no updates since the initial announcement in 2015.
• Monash University’s Department of Mechanical and Aerospace Engineering in Melbourne, Australia developed an ultra-high capacity Li-S battery that has been manufactured by partners at the Fraunhofer Institute for Material and Beam Technology in Germany. It is claimed the battery can provide power to a smartphone for five days.