Stacking Faults Hinder Lithium Insertion in Li₂RuO₃

Abstract

Both the lithium-stoichiometric transition metal (TM) layered oxides (LiTMO 2) and the Li-rich layered oxides (Li 1+x TM 1−x O 2) cathode materials are promising highenergy cathode materials but suffer from severe initial capacity losses. [2] In addition to the electrolyte decomposition, the irreversible TM migration into the Li layer is the most commonly blamed origin for the capacity loss. It results in surface densification and triggers the layered to rock-salt structural degradation in the nickel-rich LiTMO 2 [3] or the (sub)surface deterioration such as layered to spinel(-like) structural transition [4] and a cation-mixed layered structure in Li 1+x TM 1−x O 2. [5] The anions (O 2−) are oxidized to compensate for the lost charges when more than half of the lithium ions are extracted from the layered LiTMO 2 [6] or when the Lirich Mn-based layered oxides are charged to 4.5 V (vs. Li + /Li) or above. [7] A moderate anionic redox can induce TM migration and deteriorate the lithiation dynamics of the Li-rich layered oxides, [8] whereas an immoderate one may result in oxygen loss and severe structural degradation. [9] For Layered transition metal (TM) oxides have aroused enormous interest in both fundamental and applied cathode material research in the context of high energydensity batteries. Although various mechanisms have been proposed to explain their significant initial capacity losses, the effect of the local structural defects on performance has been largely ignored. Herein, the stacking faults are visualized and their presence is correlated with the incomplete phase transition in Li 2 RuO 3 to understand the significant abnormal capacity loss in the first cycle. The comprehensive performance evaluation, physical characterization and theoretical calculations indicate that the two types of stacking faults, the [100]//[110] boundaries and the [110]//[110] boundaries, lead to sluggish lithium diffusion and increasing stacking faults deteriorates the lithium insertion dynamics. These findings are helpful to understand the performance degradation of the layer-structured oxides in which the anionic redox or the transition metal migration is not involved in electrochemical reactions. It is hoped that this research will also inspire new ideas for designing novel cathode materials and for improving the performance of existing materials by tuning the local structures or minimizing the local structural defects.

Highly reversible Li2RuO3 cathodes in sulfide-based all solid-state lithium batteries

“…40 Subsequently, two transitions ( R 3̄ phase and Li deficient C 2/ c phase) were observed with further discharging to 2.0 V (point e) and the second cycle (point f, g). 40 As expected, these results with multiple phase transitions of LRO during ASSLBs charging and discharging could be analogous to the LIBs system reported in literature, 39,48 indicating that changes in electrolyte composition have little effect on the structural evolution of LRO. Replacing the liquid electrolyte with SEs, the most direct impact on the cell originates from the interface, suggesting that the interface features between LRO and LPSCl have a crucial role in maintaining the ultra-long cycle stability.…”

“…Many researchers have used LRO as a model to investigate the composition-structure–electrochemical properties relationship, electrochemical reaction mechanism, and tuning the reversibility of oxygen redox, achieving fruitful research results. 37,44–48…”

Mechanism of Na-Ion Conduction in the Highly Efficient Layered Battery Material Na2Mn3O7

“…Similar types of diffraction patterns with a combination of sharp and broad peaks are reported for several layered compounds and such features in the diffraction patterns are explained by stacking faults of the layered crystal structures. [51][52][53][54] The stacking faults are planar defects that can be described as stacking of different layer types. Besides, (2-12), ( 102) and (012) Bragg peak positions are shifted as compared to the pattern for the stacking fault free structure.…”

“…Similar results i.e., the enhancement of the conductivity with the reduction of the stacking faults are reported for the other layered compound Li2RuO3. 54 Therefore, the present work would be useful as a reference to tune ionic conductivity of a material by varying the synthesis condition.…”

Boosting the Electrochemical Performance of Li- and Mn-Rich Cathodes by a Three-in-One Strategy

“…Nevertheless, the incorporated doping of inactive elements usually reduces the reversible capacity. On the other hand, some previous works have implied that introducing defects into the LMR cathode materials, like the planar defects of stacking faults, can accommodate strain and stress in the layered crystal grains [ 16 – 20 ]. These defects in the LMR cathodes have been confirmed as active sites during charge and discharge processes, which means that the introduction of appropriate defects in LMR cathode can compensate the capacity loss caused by elemental doping [ 15 ].…”