The unstable electrode/electrolyte interface with inhomogeneous Zn deposition and side reactions plagues the practical application of aqueous Zn-ion batteries. Herein, L-carnitine (L-CN) is proposed to stabilize both electrodes and extend the lifespan as an efficient additive. Simultaneous quaternary ammonium cations, COO⁻ anions and hydroxyl groups in a trace amount of added L-CN have a huge synergy in manipulating the behaviors of Zn²⁺ electrochemical deposition/insertion and water molecule activity. Specifically, to accommodate the negative charge on electrodes driven by the electric field, the cationic portion in L-CN automatically orients toward the corresponding electrode surfaces (anode for charging and cathode for discharging), occupying active water sites and realizing reversible adsorption interfaces. The carboxyl anion provides a prominent interaction with Zn²⁺, regulating the Zn²⁺ flux to ensure uniform and fast charge transfer kinetics. Hydroxyl groups effectively capture free-water and coordinated-water through hydrogen bond fixation, thus suppressing side reactions and the cathode dissolution. Noticeably, a trace amount of L-CN additive actualizes ultralong life in the symmetric cell with an 87-fold improvement in cycle life (over 6000 h, 1 mA cm⁻²/1 mA h cm⁻²) for dendrite-free Zn plating/stripping and enables the Zn//V₂O₅ full cell to achieve 3500 cycles with a high capacity retention.

Two-step redox reactions (Mn( ii ) ions ⇌ ZnMn ₂ O ₄ spinel ⇌ layered Zn-birnessite) during the charge–discharge process.

The in situ formed AgZn ₃ alloy on the Zn@Ag anode can facilitate uniform zinc deposition and enhance the electrochemical performance of ZIBs.

High energy density lithium metal batteries (LMBs) are promising next‐generation energy storage devices. However, the uncontrollable dendrite growth and huge volume change limit their practical applications. Here, a new Mg doped Li–LiB alloy with in situ formed lithiophilic 3D LiB skeleton (hereinafter called Li–B–Mg composite) is presented to suppress Li dendrite and mitigate volume change. The LiB skeleton exhibits superior lithiophilic and conductive characteristics, which contributes to the reduction of the local current density and homogenization of incoming Li⁺ flux. With the introduction of Mg, the composite achieves an ultralong lithium deposition/dissolution lifespan (500 h, at 0.5 mA cm⁻²) without short circuit in the symmetrical battery. In addition, the electrochemical performance is superior in full batteries assembled with LiCoO₂ cathode and the manufactured composite. The currently proposed 3D Li–B–Mg composite anode may significantly propel the advancement of LMB technology from laboratory research to industrial commercialization.