RESUMO
Aqueous zinc-ion batteries are promising due to inherent safety, low cost, low toxicity, and high volumetric capacity. However, issues of dendrites and side reactions between zinc metal anode and the electrolyte need to be solved for extended storage and cycle life. Here, we proposed that an electrolyte additive with an intermediate chelation strength of zinc ion-strong enough to exclude water molecules from the zinc metal-electrolyte interface and not too strong to cause a significant energy barrier for zinc ion dissociation-can benefit the electrochemical stability by suppressing hydrogen evolution reaction, overpotential growth, and dendrite formation. Penta-sodium diethylene-triaminepentaacetic acid salt was selected for such a purpose. It has a suitable chelating ability in aqueous solutions to adjust solvation sheath and can be readily polarized under electrical loading conditions to further improve the passivation. Zn||Zn symmetric cells can be stably operated over 3500 h at 1 mA cm-2. Zn||NH4V4O10 full cells with the additive show great cycling stability with 84.6% capacity retention after 500 cycles at 1 A g-1. Since the additive not only reduces H2 evolution and corrosion but also modifies Zn2+ diffusion and deposition, highlyreversible Zn electrodes can be achieved as verified by the experimental results. Our work offers a practical approach to the logical design of reliable electrolytes for high-performance aqueous batteries.
RESUMO
Garnet oxides such as Li6.4 La3 Zr1.4 Ta0.6 O12 (LLZTO) are promising solid electrolyte materials for all-solid-state lithium-metal batteries because of high ionic conductivity, low electronic leakage, and wide electrochemical stability window. While LLZTO has been frequently discussed to be stable against lithium metal anode, it is challenging to achieve and maintain good solid-on-solid wetting at the metal/ceramic interface in both processing and extended electrochemical cycling. Here we address the challenge by a powder-form magnesium nitride additive, which reacts with the lithium metal anode to produce well-dispersed lithium nitride. The in situ formed lithium nitride promotes reactive wetting at the Li/LLZTO interface, which lowers interfacial resistance, increases critical current density (CCD), and improves cycling stability of the electrochemical cells. The additive recipe has been diversified to titanium nitride, zirconium nitride, tantalum nitride, and niobium nitride, thus supporting the general concept of reactive dispersion-plus-wetting. Such a design can be extended to other solid-state devices for better functioning and extended cycle life.
RESUMO
Garnet-type Li6.4 La3 Zr1.4 Ta0.6 O12 (LLZTO) electrolyte is considered as a promising solid electrolyte because of its relatively high ionic conductivity and excellent electrochemical stability. The surface contamination layer and poor Li/LLZTO interface contact cause large interfacial resistance and quick Li dendrite growth. In this paper, a porous hard carbon layer is introduced by the carbonization of a mixed layer of phenolic resin and polyvinyl butyral on the LLZTO surface to improve Li/garnet interfacial wettability. The multi-level pore structure of the hard carbon interlayer provides capillary force and large specific surface area, which, together with the chemical activity of the carbon material with Li, promote the molten Li infiltration with garnet electrolyte. The Li/LLZTO interface delivers a low interfacial resistance of 4.7 Ωâcm2 at 40 °C and a higher critical current density, which can achieve stable Li+ conduction for over 800 h under current densities of 0.1 and 0.2 mAâcm-2 . The solid-state battery coupled with Li and LiFePO4 exhibits excellent rate and cycling performance, demonstrating the application feasibility of the hard carbon interlayer for a solid state Li metal battery.