The lithium-ion battery has been widely employed in mobile applications because of its advantages, such as high energy density, insignificant self-discharge rate, and reasonable price. While it is also the most promising candidate power source for advanced automobiles, it needs further development to meet the specifications of electric vehicles^1,2. For example, the driving distance of an electric vehicle on a single charge is becoming more and more important, which requires batteries with ever higher energy density. One of the main strategies to enhance the energy density is to raise the average potential and specific capacity of the cathode materials³. For this purpose, Ni rich lithium transition metal oxides have been developed for promising cathode materials^4,5. Nevertheless, there are several limitations that need to be surmounted before the mass production of high energy density batteries containing Ni rich lithium transition metal oxides. In particular, significant capacity fading has been observed with lithium ion battery using Ni rich lithium transition metal oxides^6,7.

In this study, we found that cathode (Ni-rich LiNi_0.8Co_0.1Mn_0.1O₂) surface modification – phase transformation from a layered structure to a cubic phase – exerted a significant influence on battery performance. Such cubic phase hindered ionic and electronic conductivity of cathode particles. The kind of the cubic phase was different by changing the composition of the electrolyte. As a result, the resistance of the cylindrical cells after 300 cycles using different electrolyte showed a large gap, especially on cathode side.

[1] B. Scrosati, J. Garche, J. Power Sources, 2010, 195, 2419

[2] M. Armand, J.-M. Tarascon, Nature, 2008, 451, 652

[3] J. B. Goodenough, Y. Kim, Chem. Mater., 2010, 22, 587

[4] W. Liu et al, Angew. Chem. Int. Ed. Engl. 2015, 54, 4440

[5] A. Manthiram et al, Adv. Energy Mater, 2016, 6, 1501010

[6] D.P. Abraham et al, Electrochem. Comm., 2002, 4, 620

[7] S. Watanabe et al, J. Power Sources, 2014, 258, 210