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The development of rechargeable Ca metal batteries (RCMBs) is hindered by the Ca2+ passivating solid electrolyte interphases (SEIs). The cation solvation structure dictated by electrolyte chemistry plays a critical role in the SEIs properties. While a relatively weak cation‐solvent binding is preferred in Li metal anodes to promote anion‐derived SEIs, we demonstrate an enhanced Ca deposition/stripping reversibility under a strong cation‐solvent interaction, which is materialized in strongly‐solvating solvent and highly‐dissociated salt combinations. Such electrolyte formulations benefit the formation of solvent‐occupied solvation structure and minimize the anion reduction, resulting in organic‐rich/CaF2‐poor SEIs for reversible Ca metal anodes. Furthermore, RCMBs paired with an organic cathode using the optimized electrolytes are demonstrated as a proof‐of‐concept. Our work reveals the paradigm shift in SEIs design for Ca metal anodes, opening up new opportunities for emerging RCMBs. [ABSTRACT FROM AUTHOR]

Metallic Zn is a preferred anode material for rechargeable aqueous batteries towards a smart grid and renewable energy storage. Understanding how the metal nucleates and grows at the aqueous Zn anode is a critical and challenging step to achieve full reversibility of Zn battery chemistry, especially under fast‐charging conditions. Here, by combining in situ optical imaging and theoretical modeling, we uncover the critical parameters governing the electrodeposition stability of the metallic Zn electrode, that is, the competition among crystallographic thermodynamics, kinetics, and Zn2+‐ion diffusion. Moreover, steady‐state Zn metal plating/stripping with Coulombic efficiency above 99 % is achieved at 10–100 mA cm−2 in a reasonably high concentration (3 M) ZnSO4 electrolyte. Significantly, a long‐term cycling‐stable Zn metal electrode is realized with a depth of discharge of 66.7 % under 50 mA cm−2 in both Zn||Zn symmetrical cells and MnO2||Zn full cells. [ABSTRACT FROM AUTHOR]

• Sea urchins-like TiNb 2 O 7 with hierarchical structure are synthesized. • The obtained materials exhibit a specific capacity of 220 mAh g−1. • Pouch-type full cell exhibits stable fast-charging cycling performance at 15 C. • The hierarchical structure accelerates the kinetics of electrochemical reactions. • Smaller particles organized into larger ones would help to improve energy density. Novel sea urchins-like TiNb 2 O 7 anode materials with hierarchical structure are synthesized through simple spray drying route combined to subsequent calcination process. The obtained anode materials exhibit a specific capacity of 220 mAh g−1 after 500 cycling at 0.5C with the capacity retention of 88%. Further, the pouch-type full cell (TiNb 2 O 7 vs. LiCoO 2) exhibits stable cycling performance of 600 cycles with ~90% capacity retention at 15 C. [ABSTRACT FROM AUTHOR]