Xiaoke Wang,Xixi Zhang,Gang Zhao,Hu Hong,Zijie Tang,Xijin Xu,Hongfei Li,Chunyi Zhi,Cuiping Han
Magnesium ion batteries have potential for large-scale energy storage. However, the high charge density of Mg2+ ions establishes a strong intercalation energy barrier in host materials, causing sluggish diffusion kinetics and structural degradation. Here, we report that the kinetic and dissolution issues connected to cathode materials can be resolved simultaneously using a tetraethylene glycol dimethyl ether (TEGDME)–water hybrid electrolyte. The lubricating and shielding effect of water solvent could boost the swift transport of Mg2+, contributing to a high diffusion coefficient within the sodium vanadate (NaV8O20·nH2O) cathode. Meanwhile, the organic TEGDME component can coordinate with water to diminish its activity, thus providing the hybrid electrolyte with a broad electrochemical window of 3.9 V. More importantly, the TEGDME preferentially amassed at the interface, leading to a robust cathode electrolyte interface layer that suppresses the dissolution of vanadium species. Consequently, the NaV8O20·nH2O cathode achieved a specific capacity of 351 mAh g–1 at 0.3 A g–1 and a long cycle life of 1000 cycles in this hybrid electrolyte. A mechanism study revealed the reversible interaction of Mg2+ during cycles. This organic water hybrid electrolyte is effective for overcoming the difficulty of multivalent ion storage.
Lifan Wang,Guicheng Liu,Rui Wang,Xindong Wang,Liguang Wang,Zhenpeng Yao,Chun Zhan,Jun Lu
Ultrahigh-Ni layered oxides are proposed as promising cathodes to fulfill the range demand of electric vehicles; yet, they are still haunted by compromised cyclability and thermal robustness. State-of-the-art surface coating has been applied to solve the instability via blocking the physical contact between the electrolyte and the highly active Ni 4+ ions on the cathode surface, but it falls short in handling the chemo–physical mobility of the oxidized lattice oxygen ions in the cathode. Herein, a direct regulation strategy is proposed to accommodate the highly active anionic redox within the solid phase. By leveraging the stable oxygen vacancies/interstitials in a lithium and oxygen dual-ion conductor (layered perovskite La 4 NiLiO 8 ) coating layer, the reactivity of the surface lattice oxygen ion is dramatically restrained. As a result, the oxygen release from the lattice is suppressed, as well as the undesired irreversible phase transition and intergranular mechanical cracking. Meanwhile, the introduced dual-ion conductor can also facilitate lithium-ion diffusion kinetics and electronic conductivity on the particle surface. This work demonstrates that accommodating the anionic redox chemistry by dual-ion conductors is an effective strategy for capacity versus stability juggling of the high-energy cathodes.
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