| Institution: | 1. Department of Physics and Astronomy, University of California, 92697 Irvine, CA, USA
These authors contributed equally to this work.;2. Department of Physics and Astronomy, University of California, 92697 Irvine, CA, USA;3. Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 94025 Menlo Park, CA, USA;4. X-Ray Science Division, Argonne National Laboratory, 60439 Lemont, IL, USA |
| Abstract: | Deep sodium extraction/insertion of sodium cathodes usually causes undesired Jahn–Teller distortion and phase transition, both of which will reduce structural stability and lead to poor long-cycle reliability. Here we report a zero-strain P2- Na2/3Li1/6Co1/6Mn2/3O2 cathode, in which the lithium/cobalt substitution contributes to reinforcing the host structure by reducing the Mn3+/Mn4+ redox, mitigating the Jahn–Teller distortion, and minimizing the lattice change. 94.5 % of Na+ in the unit structure can be reversibly cycled with a charge cut-off voltage of 4.5 V (vs. Na+/Na). Impressively, a solid-solution reaction without phase transitions is realized upon deep sodium (de)intercalation, which poses a minimal volume deviation of 0.53 %. It attains a high discharge capacity of 178 mAh g−1, a high energy density of 534 Wh kg−1, and excellent capacity retention of 95.8 % at 1 C after 250 cycles. |
