We have shown different strategies^{1, 2} for improving capacity retention and reducing impedance rise of layered oxide cathodes using novel additives. Examples include in situ electrolyte additives to synthesize the beneficial lithium tetrafluorophosphate components^{3, 4} or dual-salt electrolytes¹ for reducing cathode impedance rise.

The cathodes we have tested have a LiNiO₂ structure with a low amount of Co/Mn. An improved structural stability compared to that of LiNiO₂ can be achieved while maintaining the high Ni content and high specific capacity. Using an optimal ratio of Ni/Mn/Co of 90/5/5 for a LiNi_0.9Mn_0.05Co_0.05O₂ cathodes,⁵ we here report the reduced reactivity of electrolytes using a combinatorial approach of reducing EC and introducing effective additives, targeting both a more robust SEI formation and a less resistive cathode electrolyte interface.

Multifaceted post-test analytical methods were used to understand the failure mechanism of the baseline cells and how additives/solvents approaches help the performance. For example, the new electrolytes prevent the transesterification reactions on anode surface, form a stable cathode interface, and mitigate structural damage on the cathode surface. Further analysis also investigated how electrolytes protect the cathode bulk structure.

[1] J. Yang, M.-T. Fonseca Rodrigues, S.-B. Son, J. C. Garcia, K. Liu, J. Gim, H. Iddir, D. P. Abraham, Z. Zhang and C. Liao, ACS Applied Materials & Interfaces, 2021.

[2] J. Yang, I. Shkrob, K. Liu, J. Connell, N. L. Dietz Rago, Z. Zhang and C. Liao, Journal of The Electrochemical Society, 2020, 167, 070533.

[3] J. Yang, I. Shkrob, Q. Liu, N. L. Dietz Rago, Y. Liu, K. Liu, Z. Zhang and C. Liao, Journal of Power Sources, 2019, 438, 227039.

[4] I. A. Shkrob, B. Han, R. Sahore, A. P. Tornheim, L. Zhang, D. P. Abraham, F. Dogan, Z. Zhang and C. Liao, Chemistry of Materials, 2019, 31, 2459-2468.

[5] C. S. Yoon, M. H. Choi, B.-B. Lim, E.-J. Lee and Y.-K. Sun, Journal of The Electrochemical Society, 2015, 162, A2483-A2489.