Enhanced Electrochemical Performance of Zn/VOx Batteries by a Carbon-Encapsulation Strategy

Chitosan-induced NH4V4O10 hierarchical hybrids as high-capacity cathode for aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) have been widely investigated due to their characteristics of convenient operation and intrinsic safety. However, there are several issues to be addressed in AZIBs, such as slow diffusion kinetics of Zn2+, cathode material dissolution and the dendrite formation of zinc anodes. Thus, it is challenging to prepare a high-performance cathode material. In this work, we prepare NH4V4O10 flower-like structures by a facile hydrothermal route. The introduction of chitosan significantly enlarges the layer spacing of the (001) crystal plane. The assembled Zn//NVO-0.15C batteries deliver a specific capacity of 520.54 mA h g-1 at a current density of 0.2 A g-1. Furthermore, they maintain 91% of the retention rate at 5.0 A g-1 after 1000 times cycling. It demonstrates the excellent zinc ion storage behavior of ammonium vanadate electrode materials for AZIBs.

Anti-Freezing Electrolytes in Aqueous Multivalent Metal-Ion Batteries: Progress, Challenges, and Optimization Strategies

Aqueous rechargeable multivalent metal-ion batteries (ARMMBs) have attracted considerable attention due to their high capacity, high energy density, and low cost. However, their performance is often limited by low temperature operation, which requires the development of anti-freezing electrolytes. In this review, we summarize the anti-freezing mechanisms and optimization strategies of anti-freezing electrolytes for aqueous batteries (especially for Zn-ion batteries). Besides, we investigate the possible interactions and side reactions between electrolytes and electrodes. We also analyze the problems between electrolytes and electrodes at low temperature, and propose possible solutions. The research progress in the field of low temperature energy storage for aqueous Mg-ion, Ca-ion, and Al-ion batteries, and the challenges faced in their anti-freezing electrolytes are investigated in detail. Last but not least, the outlook on the energy storage applications of ARMMBs is provided to guide the future research.

W-doped VO2 for high-performance aqueous Zn-ion batteries

Aqueous Zn-ion batteries (AZIBs) have become one of the most promising energy storage devices due to their high safety and low cost. However, the development of stable cathodes with fast kinetics and high energy density is the key to achieving large-scale application of AZIBs. In this work, W-doped VO2 (W-VO2) is developed by a one-step hydrothermal method. Benefiting from the pre-insertion of W6+ and the introduction of the W-O bond, accomplishing an expanded lattice spacing and a stable structure, both improved kinetics and long cycle life are achieved. The W-VO2 delivers a specific capacity of 340.2 mA h g-1 at 0.2 A g-1, an excellent high-rate capability with a discharge capacity of 186.9 mA h g-1 at 10 A g-1, and long-term cycling stability with a capacity retention of 76.5% after 2000 cycles. The electrochemical performance of the W-VO2 has been greatly improved, compared with the pure VO2. The W doping strategy proposed here also presents an encouraging pathway for developing other high-energy and stable cathodes.

V2O3@C Microspheres as the High-Performance Cathode Materials for Advanced Aqueous Zinc-Ion Storage

Vanadium oxides attract increasing research interests for constructing the cathode of aqueous zinc-ion batteries (ZIBs) because of high theoretical capacity, but the low intrinsic conductivity and unstable phase changes during the charge/discharge process pose great challenges for their adoption. In this work, V₂O₃@C microspheres were developed to achieve enhanced conductivity and improved stability of phase changes. Compounding vanadium oxides and conductive carbon through the in-situ carbonization led to significant improvement of the cathode materials. ZIBs prepared with V₂O₃@C cathodes produce a specific capacity of 420 mA h g^-1 at 0.2 A g^-1. A reversible capacity of 132 mA h g^-1 was achieved at 21.0 A g^-1. After 2000 cycles, the electrode could still deliver a capacity of 202 mA h g^-1 at the current of 5.0 A g^-1. Besides, the energy density of batteries constructed with the thus-prepared electrodes was about 294 W h kg^-1 at 148 W kg^-1 power. The in-situ compounding of V₂O₃ and carbon resulted in a microstructure that facilitated the stable phase transformation of Zn_xV₂O_5-a·nH₂O (ZnVOH), which provided more Zn²⁺ storage activity than the original phase before electrochemical activation. Moreover, the in-situ compositing strategy presents a simple route to the development of ZIB cathodes with promising performance.

Vanadium Oxides with Amorphous-Crystalline Heterointerface Network for Aqueous Zinc-Ion Batteries

Rechargeable aqueous Zn-VO_x batteries are attracting attention in large scale energy storage applications. Yet, the sluggish Zn²⁺ diffusion kinetics and ambiguous structure-property relationship are always challenging to fulfil the great potential of the batteries. Here we electrodeposit vanadium oxide nanobelts (VO-E) with highly disordered structure. The electrode achieves high capacities (e.g., ≈5 mAh cm^-2 , 516 mAh g^-1 ), good rate and cycling performances. Detailed structure analysis indicates VO-E is composed of integrated amorphous-crystalline nanoscale domains, forming an efficient heterointerface network in the bulk electrode, which accounts for the good electrochemical properties. Theoretical calculations indicate that the amorphous-crystalline heterostructure exhibits the favorable cation adsorption and lower ion diffusion energy barriers compared to the amorphous and crystalline counterparts, thus accelerating charge carrier mobility and electrochemical activity of the electrode.

Bio-Template Synthesis of V2O3@Carbonized Dictyophora Composites for Advanced Aqueous Zinc-Ion Batteries

In terms of new-generation energy-storing devices, aqueous zinc-ion batteries (AZIBs) are becoming the prime candidates because of their inexpensive nature, inherent safety, environmental benignity and abundant resources. Nevertheless, due to a restrained selection of cathodes, AZIBs often perform unsatisfactorily under long-life cycling and high-rate conditions. Consequently, we propose a facile evaporation-induced self-assembly technique for preparing V₂O₃@carbonized dictyophora (V₂O₃@CD) composites, utilizing economical and easily available biomass dictyophora as carbon sources and NH₄VO₃ as metal sources. When assembled in AZIBs, the V₂O₃@CD exhibits a high initial discharge capacity of 281.9 mAh g^-1 at 50 mA g^-1. The discharge capacity is still up to 151.9 mAh g^-1 after 1000 cycles at 1 A g^-1, showing excellent long-cycle durability. The extraordinary high electrochemical effectiveness of V₂O₃@CD could be mainly attributed to the formation of porous carbonized dictyophora frame. The formed porous carbon skeleton can ensure efficient electron transport and prevent V₂O₃ from losing electrical contact due to volume changes caused by Zn²⁺ intercalation/deintercalation. The strategy of metal-oxide-filled carbonized biomass material may provide insights into developing high-performance AZIBs and other potential energy storage devices, with a wide application range.

Recent Advances of Transition Metal Chalcogenides as Cathode Materials for Aqueous Zinc-Ion Batteries

In recent years, advances in lithium-ion batteries (LIBs) have pushed the research of other metal-ion batteries to the forefront. Aqueous zinc ion batteries (AZIBs) have attracted much attention owing to their low cost, high capacity and non-toxic characteristics. Among various cathodes, transition metal chalcogenides (TMCs) with a layered structure are considered as suitable electrode materials. The large layer spacing facilitates the intercalation/de-intercalation of Zn²⁺ between the layers. In this mini-review, we summarize a variety of design strategies for the modification of TMCs. Then, we specifically emphasize the zinc storage capacity of the optimized electrodes. Finally, we propose the challenges and future prospects of cathode materials for high-energy AZIBs.

High performance aqueous zinc battery enabled by potassium ion stabilization

Aqueous zinc ion batteries (AZIBs) are highly competitive in the energy storage systems due to their feature with operation safety and environmental friendliness. However, the sluggish diffusion kinetics of Zn²⁺ and inferior cathode circulation hinder their widespread application. Herein, we assemble a highly durable zinc ion battery by intercalating K⁺ into V₂O₅ nanolayers. The K⁺ pre-intercalation can buffer the lattice expansion of the electrode materials and reduce the internal stress. In addition, the stable K⁺ acts as a "pillar" to protect the layered structure of V₂O₅ materials from collapse during operation cycling. It delivers a reversible capacity of 479.8 mAh g^-1 at 0.2 A g^-1 and achieves excellent cyclic stability with a retention rate of 91.3% (10 A g^-1) after 3000 cycles. The cell still maintains excellent specific capacity at high work temperature.

A Review on Electrode Materials of Fast-Charging Lithium-Ion batteries

In recent years, the driving range of electric vehicles (EVs) has been dramatically improved. But the large-scale adoption of EVs still is hindered by long charging time. The high-energy LIBs are unable to be safely fast-charged due to their electrode materials with unsatisfactory rate performance. Thus it is necessary to summarize the properties of cathode and anode materials of fast-charging LIBs. In this review, we summarize the background, the fundamentals, electrode materials and future development of fast-charging LIBs. First, we introduce the research background and the physicochemical basics for fast-charging LIBs. Second, typical cathode materials of LIBs and the method to enhancing their fast-charging properties are discussed. Third, the anode materials of LIBs and the strategies for improving their fast-charging performance are analyzed. Finally, the future development of the cathode materials in fast-charging LIBs is prospected.

The Synthesis of Manganese Hydroxide Nanowire Arrays for a High-Performance Zinc-Ion Battery

The morphology, microstructure as well as the orientation of cathodic materials are the key issues when preparing high-performance aqueous zinc-ion batteries (ZIBs). In this paper, binder-free electrode Mn(OH)₂ nanowire arrays were facilely synthesized via electrodeposition. The nanowires were aligned vertically on a carbon cloth. The as-prepared Mn(OH)₂ nanowire arrays were used as cathode to fabricate rechargeable ZIBs. The vertically aligned configuration is beneficial to electron transport and the free space between the nanowires can provide more ion-diffusion pathways. As a result, Mn(OH)₂ nanowire arrays yield a high specific capacitance of 146.3 Ma h g⁻¹ at a current density of 0.5 A g⁻¹. They also demonstrates ultra-high diffusion coefficients of 4.5 × 10⁻⁸~1.0 × 10⁻⁹ cm² s⁻¹ during charging and 1.0 × 10⁻⁹~2.7 × 10⁻¹¹ cm⁻² s⁻¹ during discharging processes, which are one or two orders of magnitude higher than what is reported in the studies. Furthermore, the rechargeable Zn//Mn(OH)₂ battery presents a good capacity retention of 61.1% of the initial value after 400 cycles. This study opens a new avenue to boost the electrochemical kinetics for high-performance aqueous ZIBs.

Toward Long-Life Aqueous Zinc Ion Batteries by Constructing Stable Zinc Anodes

Aqueous zinc-ion batteries (AZIBs) with high safety and low cost are considered to be one of the alternatives to Li-ion batteries. In recent years, AZIBs have become a research hotspot, mainly focusing on the research of cathode, anode and electrolyte. Although many efforts have been made in cathode materials, their low specific capacity and poor cycle life remain unsolved. In fact, side reactions of zinc metal anodes, such as dendrite growth, zinc corrosion, and hydrogen evolution reactions (HER), are also the main factors restricting the electrochemical performance of AZIBs. In this review, we first discuss the fundamental of these adverse reactions. Then, the various solution strategies are summarized based on advanced materials and structural design. It includes surface modification and the internal structure optimization of Zn electrodes, the regulation of electrolytes and separators. Finally, we propose the future challenges and development prospects of zinc anode.

Boosted H+ Intercalation Enables Ultrahigh Rate Performance of the δ-MnO2 Cathode for Aqueous Zinc Batteries

H+ intercalation, as a critical battery chemistry, enables electrodes' high rate performance due to the fast diffusion kinetics of H+. In this work, more water molecules are introduced into δ-MnO2 by the protonation of δ-MnO2 with abundant oxygen vacancies. Benefiting from the structure with a close arrangement of water molecules in interlayers, the Grotthuss transport of proton is achieved in the energy storage of the δ-MnO2 cathode. As a result, the δ-MnO2 cathode exhibits an ultrahigh rate performance with a capacity of 368.1 mAh g-1 at 0.5 A g-1 and 83.4 mAh g-1 at 50 A g-1, which has a capacity retention of 73% after 1100 cycles at 10 A g-1. The study of the storage mechanism reveals that the Grotthuss intercalation of proton predominates the storage process, which empowers the cathode with high rate performance.

Ammonium vanadate electrode materials with stable layered structures for rechargeable zinc ion battery

As electricity demand grows, it is important to develop some energy storage systems with long cycle life and high specific capacity. Aqueous Zn ion batteries (AZIBs) are emerging storage energy...