Anode‐free designs can obtain the ultimate energy density of lithium metal batteries. However, without a continuous Li supply from the anode side, it is much more challenging to achieve high capacity retention with a competitive energy density. Here, the lifespan of an anode‐free Li metal battery is prolonged by applying an epitaxial induced plating current‐collector (E‐Cu). The functional layer on E‐Cu initiates Li storage by an alloying approach, forming an epitaxial induce layer, which exhibits speedy surface diffusion for of Li‐ions, resulting in the block like epitaxial growth of Li. Moreover, this alloying process also promotes the formation of a LiF‐rich solid electrolyte interphase (SEI), which is very useful for uniform Li plating. Due to the benefits of epitaxial Li plating and LiF‐rich SEI, the initial coulombic efficiency of the E‐Cu/Li asymmetric cell increases from 93.24 to 98.24%, and the capacity retention of anode‐free NCM811/E‐Cu pouch cell increases from 66 to 84% with a remarkable energy density of 420 Wh kg−1 in the condition of limited electrolyte addition (E/C ratio of 2 g Ah−1). This strategy is promising in the development of high energy batteries in extending their lifespans.

Amorphous Si (a-Si) shows potential advantages over crystalline Si (c-Si) in lithium-ion batteries, owing to its high lithiation potential and good tolerance to intrinsic strain/stress. Herein, porous a-Si has been synthesized by a simple process, without the uses of dangerous or expensive reagents, sophisticated equipment, and strong acids that potential cause environment risks. These porous a-Si particles exhibit excellent electrochemical performances, owing to their porous structure, amorphous nature, and surface modification. They deliver a capacity of 1025 mAh g at 3 A g after 700 cycles. Moreover, the reversible capacity after electrochemical activation, is quite stable throughout the cycling, resulting in a capacity retention about around 88 %. The direct comparison between a-Si and c-Si anodes clearly supports the advantages of a-Si in lithium-ion batteries.

Mass dissolution is one main problems for cathodes in aqueous electrolytes due to the strong polarity of water molecules. In principle, mass dissolution is a thermodynamically favorable process as determined by the Gibbs free energy. However, in real situations, dissolution kinetics, which include viscosity, dissolving mass mobility, and interface properties, are also a critical factor influencing the dissolution rate. Both thermodynamic and kinetic dissolving factors can be regulated by the ratio of salt to solvent in the electrolyte. In this study, concentration‐controlled cathode dissolution is investigated in a susceptible Na3V2(PO4)3 cathode whose time‐, cycle‐, and state‐of‐charge‐dependent dissolubility are evaluated by multiple electrochemical and chemical methods. It is verified that the super‐highly concentrated water‐in‐salt electrolyte has a high viscosity, low vanadium ion diffusion, low polarity of solvated water, and scarce solute−water dissolving surfaces. These factors significantly lower the thermodynamic‐controlled solubility and the dissolving kinetics via time and physical space local mass interfacial confinement, thereby inducing a new mechanism of interface concentrated‐confinement which improves the cycling stability in real aqueous rechargeable sodium‐ion batteries.

Anode-free lithium metal batteries can maximizethe energy density at the cell level. However,w ithout the Li compensation from the anode side,i tf aces muchm ore challenging to achieve al ong cycling life with ac ompetitive energy density than Li metal-based batteries.Here,weprolong the lifespan of an anode-free Li metal battery by introducing Li-rich Li 2 [Ni 0.8 Co 0.1 Mn 0.1 ]O 2 into the cathode as aL i-ions extender.T he Li 2 [Ni 0.8 Co 0.1 Mn 0.1 ]O 2 can release al arge amount of Li-ions during the first charging process to supplement the Li loss in the anode,then convert into NCM811, thus extending the lifespan of the battery without the introduction of inactive elements.B yt he benefit of Li-rich cathode and high reversibility of Li metal on Cu foil, the anode-free pouchcells enable to achieve 447 Wh kg À1 energy density and 84 % capacity retention after 100 cycles in the condition of limited electrolyte addition (E/C ratio of 2gAh À1).