Efficient Stabilization of Na Storage Reversibility by Ti Integration into O′3-Type NaMnO ₂

Abstract

The development of an energy storage system with abundant elements is a key challenge for a sustainable society, and the interest of Na intercalation chemistry is extending throughout the research community. Herein, the impact of Ti integration into NaMnO2 in a binary system of x NaMnO2–(1–x) TiO2 (0.5≤x≤1) is systematically examined for rechargeable Na battery applications. Stoichiometric NaMnO2, which is classified as an in-plane distorted O′3-type layered structure, delivers a large initial discharge capacity of approximately 200 mAh g-1, but insufficient capacity retention is observed, most probably associated with dissolution of Mn ions on electrochemical cycles. Ti-substituted samples show highly improved electrode performance as electrode materials. However, the appearance of a sodium-deficient phase, Na4Mn4Ti5O18 with a tunnel-type structure, is observed for Ti-rich phases. Among the samples in this binary system, Na0.8Mn0.8Ti0.2O2 (x=0.8), which is a mixture of a partially Ti-substituted O′3-type layered oxide (Na0.88Mn0.88Ti0.12O2) and tunnel-type Na4Mn4Ti5O18 as a minor phase elucidated by Rietveld analysis on both neutron and X-ray diffraction patterns, shows good electrode performance on the basis of energy density and cyclability. Both phases are electrochemically active as evidenced by in situ X-ray diffraction study, and the improvement of reversibility originates from the suppression of Mn dissolution on electrochemical cycles. From these results, the feasibility of Mn-based electrode materials for high-energy rechargeable Na batteries made from only abundant elements is discussed in detail.

Controllable MOF-Derived Hierarchical Hollow CoNiSe2 with Enhanced Mechanics and Kinetics for Extraordinary Rate Performance and Durable Anode of Sodium-Ion Batteries

“…The higher strength and the higher elastic modulus reveal the improvement of mic-mechanical properties compared with Co 0.85 Se/C and NiSe/C. The enhanced mic-mechanical performance is ascribed to the optimization of the electronic structure from Ni and Co, which provided more potential to resist the impact in the repeated sodiation/desodiation process, thereby holding the integrity topography. , …”

Origin of Fast Capacity Decay in Fe‐Mn Based Sodium Layered Oxides

“…As the discharge goes deeper, O3 phase partially transforms into the monoclinic O'3 phase (space group C2/m ) after a short period of solid‐solution process, which is generally related to the synergistic Jahn–Teller distortion of Mn 3+ . [ 33 ] During the second cycle of charging, O'3 phase is transformed back into O3 phase. However, with the further extraction of sodium ions, the material fails to undergo an obvious O3‐P3 phase transition, while only a few weak diffraction peaks of P3 phase emerge before the transformation into “X” phase.…”

W‐Doping Induced Efficient Tunnel‐to‐Layered Structure Transformation of Na0.44Mn1‐xWxO2: Phase Evolution, Sodium‐Storage Properties, and Moisture Stability

“…[4][5][6][7] However, the cathode materials suitable for practical application are still under controversy. A wide range of cathode materials have been investigated, including transition metal oxides, [8][9][10][11] polyanion compounds, [12][13][14][15][16] and Prussian blues analogues. [17][18][19][20] Among them, the layered transition metal oxides (Na x TmO 2 , with Tm = Mn, Ni, Co, Cr, Fe, etc.)…”