Revisiting the Role of Hydrogen in Lithium‐Rich Antiperovskite Solid Electrolytes: New Insight in Lithium Ion and Hydrogen Dynamics

Abstract

Li2OHX (X = Cl or Br) with an antiperovskite structure possess the advantages of low melting point, low cost, and ease of scaling‐up, which show great promise for applications in all‐solid‐state Li metal batteries (ASSLMBs). However, Li‐ion transport mechanisms in Li2OHX are still debated and the influence of H on the electrochemical performance of Li2OHX is yet to be explored. Herein, combining the theoretical calculations and experimental measurements, it is found that H affects Li‐ion transport, crystal stability, electrochemical stability, and electronic conductivity of Li2OHX. Compared with H‐free Li3OCl, although H helps to generate vacancy‐like defects, the electrostatic repulsive force between H and Li‐ion leads to an increase in both the activation energy and the diffusion length (space compensation effect), resulting in special Li ion transport trajectories along the Li‐O plane. Decreasing H content reduces the electronic conductivity and enhances the reduction‐resistant ability of Li2OHX, promoting the cycling stability and rate performance of Li∣Li2OHX∣Li symmetric cells and the ASSLMBs. This work delivers a new insight into the role of H in antiperovskite Li2OHX and can serve as guidance for solid electrolyte design.

Enhanced Moisture Stability of Lithium‐Rich Antiperovskites for Sustainable All‐Solid‐State Lithium Batteries

“…But in cubic phase, hydrogen rotates more freely as the reduced halogen site radius, which increases the number of accessible positions for Li‐ions and results in enhanced ionic conductivity. [ 22 ] To evaluate the effect of hygroscopicity suppression, as shown in Figure 4c, the TG curve of Li 3− x (OH x )Cl 0.9 F 0.1 displayed a much smaller water content than Li 3− x (OH x )Cl, which was only 0.27 wt% for the pellet and 0.93 wt% for the powder. The room‐temperature ionic conductivity of the pristine Li 3− x (OH x )Cl 0.9 F 0.1 increased to 9.0 × 10 −6 S cm −1 due to the transformation from orthorhombic or tetragonal to cubic structure.…”

Strain engineering of antiperovskite materials for solid-state Li batteries: a computation-guided substitution approach

“…10(b) shows the cycle performance of Li/Li 2 OHCl 0.921 I 0.079 /LiFePO 4 full cell at 0.3C and 383 K. The capacity retention of this cell after 274 cycles is 50%, which is much better than the value measured for Li/Li 2 OHCl/LiFePO 4 battery (34.2% capacity retention after 60 cycles under 393 K). 26 The significantly improved cycling performance is mainly attributed to the increased σ Li + of the solid electrolyte after substitution.…”

“…The cell exhibits excellent Li stripping/plating performance with a stabilized polarization voltage of 0.043 V vs. Li/Li + aer 800 h. 50%, which is much better than the value measured for Li/Li 2 -OHCl/LiFePO 4 battery (34.2% capacity retention aer 60 cycles under 393 K). 26 The signicantly improved cycling performance is mainly attributed to the increased s Li + of the solid electrolyte aer substitution.…”

Ternary Rotational Polyanion Coupling Enables Fast Li Ion Dynamics in Tetrafluoroborate Ion Doped Antiperovskite Li2OHCl Solid Electrolyte

“…[14,[36][37] Another correlation effect, so-called paddlewheel effect, involves rotational or re-orientational movements of polyanions (also known as molecular anions, clusters or complex anions, e.g. OH À , [32,[38][39][40] BH 4…”

“…Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 ), [19] NASICON (e.g., Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 ), [20] garnet (e.g., Li 7 La 3 Zr 2 O 12 ), [21–22] perovskite (e.g., Li 0.5 La 0.5 TiO 3 ), [23] halides, [24–25] oxyhalides [26–27] and Li rich anti‐perovskites (LiRAPs, e.g., Li 3 OCl) [28–30] have been widely investigated. Among them, the LiRAPs represent a typical family of SEs with high ionic conductivity, low activation energy, good reduction resistance, low cost, and being easy for mass production [29,31–32] . Nevertheless, efforts for improving their electrochemical performance are still required to advance their practical applications.…”