Robust Concentration Gradient Co-Free Ni-Rich Cathodes Enable Long-Life and Safe Operations in High-Voltage Li-Ion Batteries

Co-free Ni-rich cathodes are the most cost-competitive for high-energy-density Li-ion batteries (LIBs), but their commercial applications are hindered by structural instability and severe interface side reactions compared to those of Co-contained cathodes. Herein, we successfully construct a concentration-gradient LiNi0.753Mn0.247O2 cathode that consists of the elongated and radially aligned primary particles through Mo–Ti–Mg doping. The microcracks and Li/Ni disorder are greatly inhibited with high structural stability. The Co-free Ni-rich cathodes also exhibit a low Li-ion diffusion energy barrier with enhanced reaction kinetics. Besides, the lattice oxygen loss is also reduced due to the stronger Mo–O and Ti–O bonds, further alleviating the undesirable surface parasitic reactions with the electrolyte. As a consequence, a high reversible specific capacity of 212.2 mA h g–1 is achieved at 0.1 C and maintains 94.1 mA h g–1 even at 10 C. Impressively, it displays exceptional high-voltage cycling stability with a capacity retention of 81.1% after 1000 cycles in a pouch full cell at 1 C within 2.7–4.5 V, significantly accelerating the development of Co-free Ni-rich cathodes.