Lithium-ion batteries (LIBs) are considered to be the most promising power sources for electric vehicles (EVs) because of their high energy densities and long cycle lives. However, major impediments for general public acceptance of EVs are their cost, durability, and driving range.^1,2 Following the successful application of the hybrid scheme to the NCM cathodes,^3-6 we developed a core–shell with concentration gradient Li[Ni_0.865Co_0.120Al_0.015]O₂ cathode material (CSG NCA) with a Ni-rich core to maximize the discharge capacity and a Co-rich particle surface to provide structural and chemical stability. Compared to the conventional NCA cathode with a uniform composition, the gradient NCA cathode exhibits improved capacity retention and better thermal stability. Even more remarkably, the gradient NCA cathode maintains 90% of its initial capacity after 100 cycles when cycled at 60 °C, whereas the conventional cathode exhibits poor capacity retention and suffers severe structural deterioration. The superior cycling stability of the gradient NCA cathode largely stemmed from the gradient structure combines with the Co-rich surface, which provides chemical stability against electrolyte attack and reduces the inherent internal strain observed in all Ni-rich layered cathodes in their charged state, thus providing structural stability against the repeated anisotropic volume changes during cycling. The high discharge capacity of the proposed gradient NCA cathode extends the driving range of electric vehicles and reduces battery costs. Furthermore, its excellent capacity retention guarantees a long battery life. Therefore, gradient NCA cathodes represent one of the best classes of cathode materials for electric vehicle applications that should satisfy the demands of future electric vehicles.

References

1. U.S. Department of Energy, EV Everywhere Grand Challenge Blueprint, 31 January 2013.
2. S.-T. Myung, F. Maglia, K.-J. Park, C. S. Yoon, P. Lamp, S.-J. Kim, Y.-K. Sun, ACS Energy Lett. 2017, 2, 196.
3. Y.-K. Sun, S.-T. Myung, B.-C. Park, J. Prakash, I. Belharouak, K. Amine, Nat. Mater. 2009, 8, 320.
4. Y.-K. Sun, Z. Chen, H.-J. Noh, D.-J. Lee, H.-G. Jung, Y. Ren, S. Wang, C. S. Yoon, S.-T. Myung, K. Amine, Nat. Mater. 2012, 11, 942.
5. B.-B. Lim, S.-J. Yoon, K.-J. Park, C. S. Yoon, S.-J. Kim, J. J. Lee, Y.-K. Sun, Adv. Funct. Mater. 2015, 25, 4673.
6. 6. D.-W. Jun, C. S. Yoon, U.-H. Kim, Y.-K. Sun, Chem. Mater. 2017, 29, 5048.