Phosphoric acid and thermal treatments reveal the peculiar role of surface oxygen anions in lithium and manganese-rich layered oxides

Abstract

Reversible oxygen redox during electrochemical cycling makes layered Li-rich oxides appealing cathodes for state-of-the-art lithium-ion batteries. However, it remains challenging as the origin of lattice oxygen activity is not yet...

Li+/Na+ Ion Exchange in Layered Na2/3(Ni0.25Mn0.75)O2: A Simple and Fast Way to Synthesize O3/O2-Type Layered Oxides

“…Figure a,b presents the charge–discharge voltage profiles of Li/NNMO-P3 and Li/NNMO-P2 cells for different cycle numbers (namely, 1, 2, 3, 5, 10, 20, 30, 40, and 50) between 2.0 and 4.8 V; the corresponding differential capacity versus voltage (d Q /d V ) curves are displayed in Figure S6. The initial charge curve of a Li/NNMO-P3 cell exhibits a monotonic region below 4.5 V and a voltage plateau at approximately 4.5 V versus Li + /Li, which is similar to the electrochemical behaviors of LMLO cathode materials with the O3 structure . The high-voltage functionality was believed to be related to the anionic oxygen activity in LMLOs. , Inspiringly, the voltage plateau and the d Q /d V peak at about 4.5 V is still visible in the Li/NNMO-P3 cell during the discharge process, whereas these features cannot be observed in the Li/LMLO batteries .…”

“…As shown in Figure S15, the fully lithiated O2-type phase converts to a disordered Li-containing rock-salt intermediate ( Fm m ) at about 550 °C and then transforms to a layered O3-type Li­(TM)­O 2 ( R m ) and an orthorhombic Li 2 (TM)­O 2 ( Immm ) phase at higher temperatures above 650 °C. These results reveal the thermal instability of the O2-type layered structure, in contrast to that of the O3-type layered structure …”

“…The initial charge curve of a Li/NNMO-P3 cell exhibits a monotonic region below 4.5 V and a voltage plateau at approximately 4.5 V versus Li + /Li, which is similar to the electrochemical behaviors of LMLO cathode materials with the O3 structure. 42 The high-voltage functionality was believed to be related to the anionic oxygen activity in LMLOs. 27,43 Inspiringly, the voltage plateau and the dQ/dV peak at about 4.5 V is still visible in the Li/NNMO-P3 cell during the discharge process, whereas these features cannot be observed in the Li/LMLO batteries.…”

Facilitating Reversible Cation Migration and Suppressing O2 Escape for High Performance Li‐Rich Oxide Cathodes

“…Vo in the surface of the oxide is introduced by soaking the Li-rich oxides into hydrazine hydrate, and P doping is fulfilled by introducing P element into the precursor. Since P and O have a close electronegativity (O: 3.44, P: 2.19), the introduction of P [32][33][34] can enhance the covalency between cations and anions, thus making up for the instability caused by oxygen defects. The existences of V O and P doping in LMNPO-V O could be probed from electron paramagnetic resonance (EPR) in Figure S1, Supporting Information and X-ray photoelectron spectroscopy (XPS) in Figure S2, Supporting Information.…”

Optimizing the Electrolyte Systems for Na3(VO1‐xPO4)2F1+2x (0≤x≤1) Cathode and Understanding their Interfacial Chemistries Towards High‐Rate Sodium‐Ion Batteries

“…[8,9] Since the cathode material mainly determines and limits the specific capacity of SIBs in the full-cell configuration, developing high-voltage cathodes is expected to further boost the overall energy density of SIBs. Currently, main cathode materials for SIBs can be categorized into P2 or O3 transition metal oxides, [10,11] polyanionic compounds, [12][13][14][15][16] Prussian blue analogues, [17] and organic compounds, [18][19][20] among others. P2 or O3-structure transition oxides suffer from fast capacity decay during the long-term cycling at high-voltage, [21] while Prussian blue analogues deliver a low coulombic efficiency (CE) and inferior cycle stability due to the coordinated lattice-water.…”