Currently, the application of calcium metal anodes is challenged by rapidly degenerated plating/stripping electrochemistry without suitable solid electrolyte interphases (SEIs) capable of fast Ca2+ transport kinetics and superior ability to resist anion oxidation. Here, through in situ evolved Na/Ca hybrid SEIs, symmetrical Ca//Ca batteries readily remain stable for more than 1000 h deposition–dissolution cycles (versus less than 60 h for those with pure Ca SEIs under the same condition). Coupled with a specially designed freestanding lattice‐expanded graphitic carbon fiber membrane and tailored operation voltages, the proof‐of‐concept Ca‐metal batteries reversibly run for almost 1900 cycles with ≈83% capacity retention and a high average discharge voltage of 3.16 V. The good performance not only benefits from the stable SEIs at the Ca metal surface which affords free Ca2+ transports and prohibits out‐of‐control fluridation of Ca (forming CaF2 ion‐/electron‐insulating layer) but is also attributed to reversible relay insertion/extraction electrochemistry in the cathode. This work sheds new light on durable metal battery technology.

A solid electrolyte interphase (SEI)‐free surface and fully reversible conversion are simultaneously realized in the Li‐ion storage of a specially designed ZnO porous nanocomposite with in situ surfaces/interfaces organic encapsulation for the first time. The built‐in oxygen‐ and/or moisture‐isolating organic layer of subangstrom thickness not only avoids the SEI formation, but also guarantees monodisperse and ultrasmall dimensions of ZnO nanocrystals, which are crucial for the high initial Coulombic efficiency (ICE) and fully reversible conversion. Benefiting from the high ICE up to 91.4%, stable long‐term cyclibility (95% capacity retention at 1 A g−1 after 1400 cycles), and no sacrificing Li‐ion storage capability (868 mAh g−1 at 0.1 A g−1), the ZnO nanocomposite demonstrates the highest initial Li‐ion utilization efficiency (ILUE, ≈85.4%) among previous transition metal oxide–based full cells.

Calcium metal batteries, as one of the promising alternatives beyond Li‐metal technology, is held back by the lack of suitable cathodes of considerable energy storage capability, and Ca anodes of long‐term stability and lower polarization potentials for Ca‐plating/stripping. Here, by recycling cellulose waste paper, feasible cathodes for Ca‐metal batteries of good high‐voltage and wide‐window‐voltage adaptability (0.005–4.9 V versus Ca/Ca2+), and impressive energy density (≈517.5 Wh kg−1 at 0.1 A g−1) are developed. Meanwhile, through tailorable Ca‐plating/stripping potentials (∆V ≈ 0.65 V) realized by a modified electrolyte of Li+, Ca2+, BF4−, and PF6− multi‐ions system, the proof‐of‐concept Ca‐metal batteries not only delivered enhanced storage capability (101 mAh g−1 versus 51 mAh g−1 at 0.1 A g−1 in the window voltage of 2.0–4.7 V) and cycling stability (≈77% capacity retention for 100 cycles), but also simultaneously show a high output average working voltage of ≈3.2 V. The work provides a hint that mixed metal deposition under multi‐ions electrolyte system may address the challenging issues faced by single alkali or alkaline‐earth metal batteries.

Morphology reshaping or reconfiguration, a concept widely used in plastic surgery, energy harvesting, and reconfigurable robots, is introduced for the first time to construct densified electrodes and realize compact Li-ion storage desirable for high specific energy storage field. Hausmannite-based hybrid materials, as a proof-of-concept prototype, engineered by 1-methyl-2-pyrrolidinone-soluble surface/interface organic encapsulation, which is crucial in reshaping, exhibit a remarkable increase in the volumetric capacity of more than five times after this process (≈1889 Ah L −1 vs ≈322 Ah L −1 ). With the simultaneous maintenance of the intrinsic nature, good contact, and no collapsed/agglomerated unit structures of the materials in electrodes, the design affords a maximal increase in the packing compactness and manifests no sacrifice of the reversible ion storage capability (1150 mAh g −1 at 40 mA g −1 ), stable cycling (≈100% capacity retention), high rate performance (185 mAh g −1 at 10 A g −1 ), and long lifespan (1000 cycles with 108% capacity retention, ≈455 mAh g −1 at 3 A g −1 ) for relatively highly loaded electrodes (active materials: 1.20-5.34 mg cm −2 ). The concept may not only shed new light on fabricating advanced Si-based and other high capacity-related densified Li storage electrodes but also inject fresh vitality into the field of highdensity power sources.

Theoretically, Cu2O delivers a poor Li storage capacity ∼373.9 mA h g–1 based on a so-called conversion reaction (Cu2O + 2Li → 2Cu + Li2O). Herein, we broke through the bottleneck and acquired an impressive lithium storage capability (1122 mA h g–1) tripled more than the theoretical one by an in situ surface/interface engineering process for the first time. The surface/interface modification enabled us to fabricate ultrasmall nanocrystals of Cu2O with Cu vacancies (VCu) of high concentration, somewhat like monovalent anion doping. Except for the conversion reaction-type capacity, VCu enhancing intercalation pesudocapacitance in Cu2O and its reduction product-Cu also contributed a lot to the Li-storage capability. First-principles calculation substantiated that intercalation energy of Li was severely lowered for both Cu vacancy-rich Cu2O and Cu comparing with their stoichiometric counterparts. Another important factor for the enhancement was the surface/interface organic species themselves which could reversibly store Li by redox reactions. The surface/interface modification for vacancies, vacancy inheritance from metal oxide to single metal, and vacancy-enhancing Li-storage capability in metal oxide and single metal all will inspire us a lot in fabricating new-generation advanced electrodes for rechargeable batteries.