Microstructure Modified Ni-Rich Cathode Material By Microscale Concentration Gradient for High Energy Density Li-Ion Batteries

A concentration gradient (CG) Li[Ni0.9Co0.05Mn0.05]O2 cathode in which Li[Ni0.94Co0.038Mn0.022]O2 at the particle core is encapsulated by a 1.5-μm-thick CG shell with the outer surface composition Li[Ni0.841Co0.077Mn0.082]O2 is synthesized using a differential co-precipitation process. The CG at the microscale combined with the radial texturing of the refined primary particles in the CG shell layer protracts the detrimental H2 → H3 phase transition1,2, providing with the rise to sharp changes in the unit cell dimensions. This protraction, confirmed by in-situ X-ray diffraction and transmission electron microscopy, allows effective dissipation of the internal strain generated upon the H2 → H3 phase transition, markedly improving cycling performance and thermochemical stability as compared to those of the conventional without CG Li[Ni0.9Co0.05Mn0.05]O2 cathode3-6. The compositionally partitioned cathode delivers a specific capacity of 229 mAh g-1 and exhibits capacity retentions of 88% after 1,000 cycles in a pouch-type full cell (cf. 68% for the conventional cathode). Thus, the proposed cathode material provides an opportunity for the rational design and development of a wide range of multi-functional cathodes, especially for Ni-rich NCM cathodes, by compositionally partitioning the cathode particles and thus optimizing the microstructural response to the internal strain produced in the 100% depth of discharge state. Reference U.-H. Kim, S.-T. Myung, C. S. Yoon and Y.-K. Sun ACS Energy Lett. 2017, 2, 1848-1854. H.-H. Ryu, K.-J. Park, C. S. Yoon and Y.-K. Sun Chem. Mater. 2018, 30, 1155. Y.-K. Sun, S.-T. Myung, B.-C. Park, J. Prakash, I. Belharouak and K. Amine. Nat. Mater. 2009, 8, 320. U.‐H. Kim, E.‐J. Lee, C. S. Yoon, S.‐T. Myung and Yang‐Kook Sun Adv. Energy Mater. 2016, 6, 1601417. D.-W. Jun, C. S. Yoon, U.-H. Kim and Y.-K. Sun Chem. Mater. 2017, 29, 5048. U.-H. Kim, S.-T. Myung, C. S. Yoon and Yang-Kook Sun ACS Energy Lett. 2017, 2, 1848.