A stable anode‐free all‐solid‐state battery (AF‐ASSB) with sulfide‐based solid‐electrolyte (SE) (argyrodite Li6PS5Cl) is achieved by tuning wetting of lithium metal on “empty” copper current‐collector. Lithiophilic 1 µm Li2Te is synthesized by exposing the collector to tellurium vapor, followed by in situ Li activation during the first charge. The Li2Te significantly reduces the electrodeposition/electrodissolution overpotentials and improves Coulombic efficiency (CE). During continuous electrodeposition experiments using half‐cells (1 mA cm−2), the accumulated thickness of electrodeposited Li on Li2Te–Cu is more than 70 µm, which is the thickness of the Li foil counter‐electrode. Full AF‐ASSB with NMC811 cathode delivers an initial CE of 83% at 0.2C, with a cycling CE above 99%. Cryogenic focused ion beam (Cryo‐FIB) sectioning demonstrates uniform electrodeposited metal microstructure, with no signs of voids or dendrites at the collector‐SE interface. Electrodissolution is uniform and complete, with Li2Te remaining structurally stable and adherent. By contrast, an unmodified Cu current‐collector promotes inhomogeneous Li electrodeposition/electrodissolution, electrochemically inactive “dead metal,” dendrites that extend into SE, and thick non‐uniform solid electrolyte interphase (SEI) interspersed with pores. Density functional theory (DFT) and mesoscale calculations provide complementary insight regarding nucleation‐growth behavior. Unlike conventional liquid‐electrolyte metal batteries, the role of current collector/support lithiophilicity has not been explored for emerging AF‐ASSBs.

We fabricated sulfur and nitrogen codoped cyanoethyl cellulose-derived carbons (SNCCs) with state-of-the-art electrochemical performance for potassium ion battery (PIB) and potassium ion capacitor (PIC) anodes. At 0.2, 0.5, 1, 2, 5, and 10 A g −1 , the SNCC shows reversible capacities of 369, 328, 249, 208, 150, and 121 mA h g −1 , respectively. Due to a high packing density of 1.01 g cm −3 , the volumetric capacities are also uniquely favorable, being 373, 331, 251, 210, 151, and 122 mA h cm −3 at these currents, respectively. SNCC also shows promising initial Coulombic efficiency of 69.0% and extended cycling stability with 99.8% capacity retention after 1000 cycles. As proof of principle, an SNCC-based PIC is fabricated and tested, achieving 94.3 Wh kg −1 at 237.5 W kg −1 and sustaining over 6000 cycles at 30 A g −1 with 84.5% retention. The internal structure of S and N codoped SNCC is based on highly dilated and defective graphene sheets arranged into nanometer-scale walls. Using a baseline S-free carbon for comparison (termed NCC), the role of S doping and the resultant dilated structure was elucidated. According to galvanostatic intermittent titration technique and electrochemical impedance spectroscopy analyses, as well as COMSOL simulations, this structure promotes rapid solid-state diffusion of potassium ions and a solid electrolyte interphase that is stable during cycling. X-ray diffraction was used to probe the ion storage mechanisms in SNCC, establishing the role of reversible potassium intercalation and the presence of KC 36 , KC 24, and KC 8 phases at low voltages.

A new concentrated ternary salt ether-based electrolyte enables stable cycling of lithium metal battery (LMB) cells with high-mass-loading (13.8 mg cm −2 , 2.5 mAh cm −2 ) NMC622 (LiNi 0.6 Co 0.2 Mn 0.2 O 2 ) cathodes and 50 μm Li anodes.Termed "CETHER-3," this electrolyte is based on LiTFSI, LiDFOB, and LiBF 4 with 5 vol% fluorinated ethylene carbonate in 1,2-dimethoxyethane. Commercial carbonate and state-of-the-art binary salt ether electrolytes were also tested as baselines. With CETHER-3, the electrochemical performance of the full-cell battery is among the most favorably reported in terms of high-voltage cycling stability. For example, LiNi x Mn y Co 1-x-y O 2 (NMC)-Li metal cells retain 80% capacity at 430 cycles with a 4.4 V cut-off and 83% capacity at 100 cycles with a 4.5 V cut-off (charge at C/5, discharge at C/2). According to simulation by density functional theory and molecular dynamics, this favorable performance is an outcome of enhanced coordination between Li + and the solvent/salt molecules. Combining advanced microscopy (high-resolution transmission electron microscopy, scanning electron microscopy) and surface Carbon Energy.

Sodiophilic micro‐composite films of sodium‐chalcogenide intermetallics (Na2Te and Na2S) and Cu particles are fabricated onto commercial copper foam current collectors (Na2Te@CF and Na2S@CF). For the first time a controllable capacity thermal infusion process is demonstrated. Enhanced wetting by the metal electrodeposition leads to state‐of‐the‐art electrochemical performance. For example, Na2Te@CF‐based half‐cells demonstrate stable cycling at 6 mA cm−2 and 6 mAh cm−2, corresponding to 54 µm of Na electrodeposited/electrodissolved by geometric area. Sodium metal batteries with Na3V2 (PO4)3 cathodes are stable at 30C (7 mA cm−2) and for 10 000 cycles at 5C and 10C. Cross‐sectional cryogenic focused ion beam (cryo‐FIB) microscopy details deposited and remnant dissolved microstructures. Sodium metal electrodeposition onto Na2Te@CF is dense, smooth, and free of dendrites or pores. On unmodified copper foam, sodium grows in a filament‐like manner, not requiring cycling to achieve this geometry. Substrate–metal interaction critically affects the metal–electrolyte interface, namely the thickness and morphology of the solid electrolyte interphase. Density functional theory and mesoscale simulations provide insight into support‐adatom energetics, nucleation response, and early‐stage morphological evolution. On Na2Te sodium atomic dispersion is thermodynamically more stable than isolated clusters, leading to conformal adatom coverage of the surface.

Front cover image: Lithium metal battery matched with high nickel cathode is a promising energy storage scheme. However, developing an electrolyte that can simultaneously match the robust oxidizing cathode and the reducing lithium metal anode is challenging. In article number https://doi.org/10.1002/cey2.275, Yang et al. developed a new high‐concentration ternary lithium salt ether‐based electrolyte to make commercial high‐mass loading high‐nickel NMC (LiNi0.6Co0.2Mn0.2O2) cathode and thin anode lithium metal battery stable cycling at 4.5V. The optimization mechanism is analyzed from solvent sheath structure, solid electrolyte interface (SEI), and cathode lattice transition. This work provides new insight into high‐voltage lithium metal battery electrolyte.