Alleviating Side Reactions on Zn Anodes for Aqueous Batteries by a Cell Membrane Derived Phosphorylcholine Zwitterionic Protective Layer

Aqueous zinc (Zn) ion batteries are attractive for next generation batteries with high safety, yet their applications are still hindered by the uncontrollable dendrite formation and side reactions on Zn anode. Here, a polyzwitterion protective layer (PZIL) was engineered by polymerizing 2-methacryloyloxyethyl phosphorylcholine (MPC) in carboxymethyl chitosan (CMCS), which renders the following merits: the choline groups of MPC can preferentially adsorb onto Zn metal to avoid side reactions; the charged phosphate groups chelate with Zn2+ to regulate the solvation structure, further improving side reaction inhibition; the Hofmeister effect between ZnSO4 and CMCS can enhance the interfacial contact during electrochemical characterization. Consequently, the symmetrical Zn battery with PZIL can keep stable for more than 1000 hours under the ultra-high current density of 40 mA cm-2 . The PZIL confers the Zn/MnO2 full battery and Zn/active carbon (AC) capacitor with stable cycling performance under high current density.

Electrocrystallization Regulation Enabled Stacked Hexagonal Platelet Growth toward Highly Reversible Zinc Anodes

Realizing durative flattened and dendrite-free zinc (Zn) metal configuration is the key to resolving premature battery failure caused by the internal short circuit, which is highly determined by the crystal growth in the electrocrystallization process. Herein, we report that regulating the molecular structure of the inner Helmholtz plane (HIP) can effectively convert the deposition into activation control by weakening the solvated ion adsorption at the interface. The moderated electrochemical reaction kinetics lower than the adatom self-diffusion rate steers conformal stratiform Zn growth and dominant Zn (0001) texture, achieving crystallographic optimization. Through in situ mediation of electrolyte engineering, orientational plating and stripping behaviors at edge-sites and tailored solvation structure immensely improve the utilization efficiency and total charge passed of Zn metal, even under extreme conditions, including high areal capacity (3 mAh cm^-2 ) and wide temperature range (-40-60 °C).

Realizing Textured Zinc Metal Anodes through Regulating Electrodeposition Current for Aqueous Zinc Batteries

Crystallography modulation of zinc (Zn) metal anode is promising to promote Zn reversibility in aqueous electrolytes, but efficiently constructing Zn with specific crystallographic texture remains challenging. Herein, we report a current-controlled electrodeposition strategy to texture the Zn electrodeposits in conventional aqueous electrolytes. Using the electrolytic cell with low-cost Zn(CH₃ COO)₂ electrolyte and Cu substrate as a model system, the texture of as-deposited Zn gradually transforms from (101) to (002) crystal plane as increasing the current density from 20 to 80 mA cm^-2 . Moreover, the high current accelerates the Zn nucleation rate with abundant nuclei, enabling uniform deposition. The (002) texture permits stronger resistance to dendrite growth and interfacial side reactions than the (101) texture. The resultant (002)-textured Zn electrode achieves deep cycling stability and supports the stable operation of full batteries with conventional V/Mn-based oxide cathodes.

Synchronous Dual Electrolyte Additive Sustains Zn Metal Anode with 5600 h Lifespan

Despite conspicuous merits of Zn metal anodes, the commercialization is still handicapped by rampant dendrite formation and notorious side reaction. Manipulating the nucleation mode and deposition orientation of Zn is a key to rendering stabilized Zn anodes. Here, a dual electrolyte additive strategy is put forward via the direct cooperation of xylitol (XY) and graphene oxide (GO) species into typical zinc sulfate electrolyte. As verified by molecular dynamics simulations, the incorporated XY molecules could regulate the solvation structure of Zn²⁺ , thus inhibiting hydrogen evolution and side reactions. The self-assembled GO layer is in favor of facilitating the desolvation process to accelerate reaction kinetics. Progressive nucleation and orientational deposition can be realized under the synergistic modulation, enabling a dense and uniform Zn deposition. Consequently, symmetric cell based on dual additives harvests a highly reversible cycling of 5600 h at 1.0 mA cm^-2 /1.0 mAh cm^-2 .

Empowering Zn Electrode Current Capability Along Interfacial Stability by Optimizing Intrinsic Safe Organic Electrolytes

Metallic Zn is one of the most promising anodes, but its practical application has been hindered by dendritic growth and serious interfacial reactions in conventional electrolytes. Herein, ionic liquids are adopted to prepare intrinsically safe electrolytes via combining with TEP or TMP solvents. With this synergy effect, the blends of TEP/TMP with an IL fraction of ≈25 wt% are found to be promising electrolytes, with ionic conductivities comparable to those of standard phosphate-based electrolytes while electrochemical stabilities are considerably improved; over 1000 h at 2.0 mA cm^-2 and ≈350 h at 5.0 mA cm^-2 with a large areal capacity of 10 mAh cm^-2 . The use of functionalized IL turns out to be a key factor in enhancing the Zn²⁺ transport due to the interaction of Zn²⁺ ions with IL-zincophilic sites resulting in reduced interfacial resistance between the electrodes and electrolyte upon cycling leading to spongy-like highly porous, homogeneous, and dendrite-free zinc as an anode material.