Liquid Electrolytes and Additives for Lithium-ion Batteries

A series of propylene carbonate (PC) analogue solvents with increasing length of linear alkyl substitutes were synthesized and used as co-solvents with PC for graphite-based lithium-ion half cells. A graphite anode reaches a capacity of around 310 mAh/g in PC and its analogue co-solvents, with CE similar to the values obtained with standard electrolytes.

Electrolyte interaction with the graphite anode and subsequent decomposition determines the graphite anode performance. Solvents with longer alkyl chains are able to prevent graphite exfoliation when used as co-solvents with PC. 

Reference

Zhao, H.;  Park, S. J.;  Shi, F. F.;  Fu, Y. B.;  Battaglia, V.;  Ross, P. N.; Liu, G., Propylene Carbonate (PC)-Based Electrolytes with High Coulombic Efficiency for Lithium-Ion Batteries. J. Electrochem. Soc. 2014, 161 (1), A194-A200.

Fluorinated Electrolyte Additives

The electrolyte additives and formulations can prevent sulfur dissolution, promote smooth lithium deposition and enhance high voltage stabilities. 

  Reference

Zhao, Y. Z.;  Fang, C.;  Zhang, G. Z.;  Hubble, D.;  Nallapaneni, A.;  Zhu, C. H.;  Zhao, Z. W.;  Liu, Z. M.;  Lau, J.;  Fu, Y. B.; Liu, G., A Micelle Electrolyte Enabled by Fluorinated Ether Additives for Polysulfide Suppression and Li Metal Stabilization in Li-S Battery. Front. Chem. 2020, 8, 9.

Electrolytes for Low Temperature Li-ion Batteries

Lithium-ion batteries often function poorly at sub-zero temperatures, with corresponding voltage and capacity losses becoming most notable around -20°C. However, many emerging applications require robust energy storage under such conditions; for instance, an electric vehicle must deliver similar driving range in both the winter and summer. Accordingly, the US Department of Energy has set a target of >70% usable energy (compared to room temperature) available at -20°C and C/3 discharge rate for electric vehicle battery packs.We are working to meet this goal through rational engineering of electrolyte composition (additives, solvents, and salts), which has been shown to largely influence lithium-ion behavior at low temperature. By careful study of electrolyte effects on internal resistance via charge transfer, interfacial chemistry, and bulk ion transport, we hope to uncover new insight into low-temperature performance characteristics and develop novel materials strategies to optimize the usable energy of cells.

Reference

Hubble, D.;  Brown, D. E.;  Zhao, Y. Z.;  Fang, C.;  Lau, J.;  McCloskey, B. D.; Liu, G., Liquid electrolyte development for low-temperature lithium-ion batteries. Energy Environ. Sci. 2022, 15 (2), 550-578.