Recently, researchers at the University of Texas at Austin have developed a new type of electrolyte additive. The research team led by Professor Arumugam Manthiram found that the use of phosphorus pentasulfide (P2S5) as an electrolyte additive can directly use commercialized Li2S particles as high-capacity cathode materials for lithium-sulfur batteries without the need for complex synthesis Or use a rechargeable termination voltage (which will reduce the stability and safety of the electrolyte).

The large-scale use of commercialized particles can greatly reduce the production cost of lithium-sulfur batteries that use lithium-sulfur as anion*. The paper was published in the Journal of Physical Chemistry Letters of the American Chemical Society. Researchers pointed out in the paper that the discovery is of great significance to the safe use of Li2S as a battery cathode material and the manufacture of low-cost, lithium-free lithium-sulfur batteries.

The theoretical capacity of lithium-sulfur batteries is very high, reaching ～2500 Wh kg-1, requiring the use of lithium metal as a positive electrode, but lithium metal will gradually degrade in the battery positive electrode and affect the safety and performance of the battery. An alternative method is to connect lithium-free battery anodes* (such as tin and silicon) and lithium sulfide cathodes (~1166 mAh g-1)* together.

Researchers have confirmed through research that the use of lithium sulfide in the initial charging stage has great difficulties and is related to the build-up of new polysulfide compounds.

The voltage barrier can be solved by using the termination voltage in the early stage of charging, but it will cause the instability of the commonly used ether-based electrolyte and the deterioration of the electrochemical performance of the battery.

Researchers compared the performance of lithium sulfur anion* in electrolyte and P2S5 in CR2032 button battery. After comparison, the reversible discharge capacity of lithium sulfur anion is ~800mAh g-1, and the capacity can still be as high as 83% after 80 cycles of charging and discharging, and the coulombic efficiency is still close to 100%.

The researchers concluded that: the interaction of P2S5 and Li2S will cause the cell resistance to decrease, accelerate the oxidation of Li2S into polysulfur compounds, and greatly reduce the voltage plateau of the initial charge.

The researchers added that when the molar ratio of Li2S to P2S5 is 7:1, an electrochemical reaction will occur before a thick solid electrolyte is formed on the surface of Li2S. Because the P2S5 core structure is activated, the micron-level Li2S will be retained when the activation occurs, and the activation is only a surface effect.