O3-type layer-structured Na0.8[Ni1/5Fe1/5Co1/5Mn1/5Ti1/5]O2 as long life and high power cathode material for sodium-ion batteries

O3-type layer-structured Na0.8[Ni1/5Fe1/5Co1/5Mn1/5Ti1/5]O2 (denoted as N0.8NFCMTO) has been investigated as a new cathode material for Na-ion batteries. The N0.8NFCMTO cathode delivers an initial discharge capacity of 107 mAhg−1 with excellent cycling stability of over 90% capacity retention after 100 cycles. This material delivers comparable capacity to that of previously reported layered cathode materials with multi-transition metal elements while showing an excellent rate capability and stable long cycle life. Synchrotron-based in situ X-ray diffraction and ex situ X-ray absorption spectroscopy investigations combined with quantitative refinement analysis reveal the reversible structural changes and charge compensation mechanism during sodium extraction/insertion, which is associated with the excellent cycling stability of the N0.8NFCMTO electrode.