The conventional aqueous electrolyte in Zn batteries often induces a chain of interconnected marvels including dendrites, passivation and hydrogen evolution leading to catastrophic battery failures. Herein, we propose a new organic electrolyte comprising of mixed solvents {trimethyl phosphate (TMP), N-methyl formamide (NMF)} and Zn(OTf)2 salt, which not only enables highly reversible and dendrite-free Zn anode but ensures excellent non-flammability endorsing battery safety. The enhanced electrolyte-electrode (Zn) interactions and changes in solvation structure of electrolyte due to NMF incorporation in TMP, assisted uniform Zn deposition free from dendrites. Consequently, Zn anode exhibited long cycling of over 1200 hat high current densities of 3.0 and 5.0 mA cm-2 with high average Coulombic efficiency (CE)99.83% and affords promising areal capacity of 20.0 mAh cm-2. Much stronger TMPNMF-Zn2+ and NMF-Zn surface interactions revealed by molecular simulations provided insights to the beneficial role of NMF as co-solvent in stabilizing Zn anode. Moreover, Zn/NaV3O8 full battery delivered remarkable capacity retention and cycling stability in TMPNMF electrolyte. The present research work proposes promising route for designing new electrolyte systems for sustainable and safe non-aqueous Zn batteries.

Zn metal has been proved to be a promising anode material in aqueous secondary Zn-ion batteries. However, the uncontrollable dendrite growth on Zn anode deriving from uneven Zn deposition during cycling seriously impairs its reliability and limits the service life. Achieving uniform Zn deposition is the key to overcoming the dendritic issue and accelerating the commercial application of aqueous Zn-ion batteries. Herein, a polymer coating with semi-interpenetrating network (s-IPN) structure is designed for the protection of Zn anode in aqueous Zn-ion batteries. Benefiting from the hydrophilic and robust polymer network, uniform Zn deposition and excellent dendrite growth resistance could be realized for the s-IPN polymer coated Zn (s-IPN@Zn) anode. As a consequence, the symmetric cell with s-IPN@Zn shows an ultra-long cycle life of 2370 h at 0.5 mA cm-2, which exhibits significant improvement compared with the unmodified bare Zn anode. Furthermore, the Zn//MnO2 rechargeable aqueous battery with s-IPN@Zn anode shows more excellent long-cycle stability compared with bare Zn, revealing the effectiveness of this unique s-IPN polymer coating design.

Layered ammonium vanadate materials exhibit significant mass‐specific capacity and ion transport rate due to their small molecular weight and large ionic radius. However, the strong electrostatic interactions of Zn 2+ and V–O bonds and the fragile ionic bonding of N‐H … O bonds hinder their development. Therefore, this work reports Mg 2+ doping NH 4 V 4 O 10 materials accompanied by flower‐like morphology to lower the migration energy barrier and inhibit amine dissolution. Owing to the 3D‐flower‐like morphology and the combined impact of Mg 2+ and structural water, the binding of Zn 2+ … V‐O is significantly enhanced and additional ion channels were constructed. Pre‐intercalated Mg 2+ enhances the structural integrity and prevents irreversible deammoniation from obtaining excellent cyclic stability. Density functional theory (DFT) calculations show that MNVO provides a smoother Zn 2+ diffusion path with a lower migration barrier. Benefited from these advantages, the MNVO cathode exhibits a high specific capacity of 410 mAh g −1 at 0.1 A g −1 , satisfactory cyclic stability (90.2 % capacity retention at 10 A g −1 after 5000 cycles), and capable rate ability (118 mAh g −1 at 25 A g −1 ) within 0.4‐1.5 V. Furthermore, the zinc ion storage mechanism in the MNVO cathode is investigated through multiple analyses.

Nickel-rich LiNi0.8Co0.15Al0.015O2 (NCA) with excellent energy density is considered one of the most promising cathodes for lithium-ion batteries. Nevertheless, the stress concentration caused by Li+/Ni2+ mixing and oxygen vacancies leads to the structural collapse and obvious capacity degradation of NCA. Herein, a facile codoping of anion (F-)-cation (Mg2+) strategy is proposed to address these problems. Benefiting from the synergistic effect of F- and Mg2+, the codoped material exhibits alleviated Li+/Ni2+ mixing and demonstrates enhanced electrochemical performance at high voltage (≥4.5 V), outperformed the pristine and F-/Mg2+ single-doped counterparts. Combined experimental and theoretical studies reveal that Mg2+ and F- codoping decreases the Li+ diffusion energy barrier and enhances the Li+ transport kinetics. In particular, the codoping synergistically suppresses the Li+/Ni2+ mixing and lattice oxygen escape, and alleviates the stress-strain accumulation, thereby inhibiting crack propagation and improving the electrochemical performance of the NCA. As a consequence, the designed Li0.99Mg0.01Ni0.8Co0.15Al0.05O0.98F0.02 (Mg1+F2) demonstrates a much higher capacity retention of 82.65% than NCA (55.69%) even after 200 cycles at 2.8-4.5 V under 1 C. Furthermore, the capacity retention rate of the Mg1+F2||graphite pouch cell after 500 cycles is 89.6% compared to that of the NCA (only 79.4%).

Nickel-rich cathode materials are widely used for electronic devices because of their high capacity and rate performance. However, structural deterioration after long-term cycling leads to a significant decline in capacity and cycle life. In this work, the effects of three different cations doping on the structural stability and electrochemical performance of Ni-rich cathode materials were investigated. XRD characterization reveals that doped cation leads to broadening of the distance between Li layers and inhibiting Li+/Ni2+ mixing arrangement. Compared with Na+ and K+, the high valence Mg2+ provides a stronger Mg-O bond, which can effectively restrain the undesired phase transition and sustain the ordered structure. Electrochemical tests demonstrate that NCA with Mg doping has better cycle stability and rate performance than Na and K. The capacity retention rate of NCA with 1% Mg doping is 87.7% after 200 cycles at 1C, and it can still provide a specific capacity of 146.8 mAh g-1 at a high rate of 5C.

Aqueous rechargeable Zn batteries have gathered supreme significance and importance in the recent times as promising energy storage devices. Zn batteries possess prodigious potential for safer and large-scale energy storage applications. However, the critical challenges associated with both Zn anode and cathode adversely affects their widespread commercialization that needs urgent methodologies to tackle these issues governed by thermodynamic instability of Zn anode in traditional aqueous electrolytes. The water induced unwanted side reactions include Zn dendrites, corrosion, shape change, passivation, H2 evolution that leads to poor Zn utilization and reversibility. Surface engineering of Zn anode through artificial protective layers/coatings is an emerging and promising research direction towards stabilization of Zn metal anodes. In this review, we summarize briefly the critical issues of Zn anode in aqueous environment and then switching to the up-to-date developments in surface coatings for Zn anode, with comprehensive explanations of their working principles. This review will provide latest and summarized literature for Zn battery community assisting them to design novel Zn anode protective approaches.

Aqueous zinc ion battery (AZIBs) has become a research hotspot because of its advantages of low cost, high safety and environmental protection. However, AZIBs still face challenges in achieving excellent rate performance, long service life, and wide temperature range due to slow Zn2+ diffusion kinetics. In this work, we developed a nonstoichiometric Na-0.3(NH4)(0.6)V4O10 center dot 0.4H(2)O(NVO-Na) cathode material for AZIBs. The combined effects of pre-intercalated Na+ and structural water in NVO enhance the diffusion kinetic, reduce the electrostatic repulsion of Zn2+ (de)intercalation and keep the layer structure stable. The results show that NVO-Na cathode delivers an impressive specific capacity of 400.2 mAh g(-1) at a current density of 0.1 Ag-1 and an excellent capacity retention of 97.2 % after 2000 cycles at 10 A g(-1). In addition, the reversible intercalation mechanism of zinc ions in NVO-Na was investigated through ex-situ XRD and XPS analysis. The combined effect of pre-intercalated Na+, structural H2O molecules and remaining NH4+ keeps the layer structure stable during the reversible Zn2+ (de) intercalation reaction. This modification method provides a promising direction for the preparation of high-performance AZIBs cathode materials.