High voltage Li-ion batteries have been expected a forward technology designed for vehicles, marines and other high power and energy density applications ^1–3. Among high voltage cathodes, LiNi_0.5Mn_1.5O₄ is considered a promising cathode to reduce the battery cost as well as environmental hazard issues^4,5. However, a high operation potential and Mn dissolution brings the most critical challenges for achieving the long cycle-life of Li-ion cell^6,7.

In this study, we report a rational design of nonflammable electrolyte based on LiBF₄ and sulfolane (TMS) mixed with a dimethyl carbonate (DMC) as co-solvent to enhance conductivity. Among different molar ratios, the electrolyte LiBF₄: TMS: DMC =1:2:1 in mol. exhibited the highest electrochemical stability (~ 6.1 V vs. Li⁺/Li) and ionic conductivity up to 1.57 mS.cm^-1 at 30 ^oC. Cycling performance of LNMO/Li half-cell and LNMO/graphite full-cell cycled were carried out using the optimized electrolyte. While half-cells LNMO//Li display a high initial capacity of 118 mAh.g^-1 and remain 56.48 % of initial value after 100 cycles, a full cell LNMO//Graphite with an areal loading of 1.0 mAh.cm^-2 and low N/P ratio (~1.2) exhibited a better cycling stability than the one using commercial electrolyte 1M LiPF₆/EC-DMC, 1:1 in vol (with initial capacity of 87 mAh.g^-1 and capacity retention of 18% after 100 cycles⁸).

References

1. Goodenough JB, Kim Y. Challenges for Rechargeable Li Batteries. Chem Mater. 2010;22(3):587-603.
2. Etacheri V, Marom R, Elazari R, Salitra G, Aurbach D. Challenges in the development of advanced Li-ion batteries: a review. Energy Environ Sci. 2011;4(9):3243.
3. Amine K, Kanno R, Tzeng Y. Rechargeable lithium batteries and beyond: Progress, challenges, and future directions. MRS Bull. 2014;39(5):395-401.
4. Kim J-H, Myung S-T, Sun Y-K. Molten salt synthesis of LiNi_0.5Mn_1.5O₄ spinel for 5 V class cathode material of Li-ion secondary battery. Electrochim Acta. 2004;49(2):219-227.
5. Patoux S, Daniel L, Bourbon C. High voltage spinel oxides for Li-ion batteries: From the material research to the application. J Power Sources. 2009;189(1):344-352.
6. Jang DH, Shin YJ, Oh SM. Dissolution of Spinel Oxides and Capacity Losses in 4 V Li / Li_xMn₂O₄ Cells. J Electrochem Soc. 1996;143(7):2204-2211.
7. Du Pasquier A, Blyr A, Courjal P. Mechanism for Limited 55°C Storage Performance of Li_1.05Mn_1.95 O ₄ Electrodes. J Electrochem Soc. 1999;146(2):428-436.
8. Wang J, Yamada Y, Sodeyama K, Chiang CH, Tateyama Y, Yamada A. Superconcentrated electrolytes for a high-voltage lithium-ion battery. Nat Commun. 2016;7(1):12032.

Acknowledgement

This work is supported by Ho Chi Minh city - Department of Science and Technology (DOST) under grant number 54/2020/HĐ-QPTKHCN.