Opportunities and Challenges of Zinc Anodes in Rechargeable Aqueous Batteries

Aqueous rechargeable zinc-ion batteries (ZIBs) have recently attracted increasing research interests due to their high safety, low cost, abundant resources, and eco-friendliness compared with commercial lithium-ion batteries. However, problems of zinc anodes in ZIBs such as zinc dendrites and side reactions severely shorten the cycling lifetime and restrict the practical application of ZIBs. In this review, the fundamental understanding of existing issues including dendrite formation, corrosion, and hydrogen evolution are mainly revealed, the current existing strategies on the protection of the zinc electrode and electrolyte engineering in the aqueous electrolyte are discussed. In addition, the existing techniques applied on analyzing the interaction between anodes and electrolytes are summarized. Furthermore, perspectives and suggestions are provided to design highly stable zinc anodes

MoS2/NiS core-shell structures for improved electrocatalytic process of hydrogen evolution

It is important to develop a low-cost and easy-prepared electrocatalyst for hydrogen evolution reaction. In this work, MoS2/NiS hierarchical nanostructures (HHs) were fabricated on Ni foam by a simple one-step hydrothermal reaction using Ni foam as raw materials directly. Owing to the unique synthetic strategy that provide uniform MoS2/NiS HHs structure on the porous Ni foam, generate abundant active surfaces, small resistance, furthermore it is beneficial for carrier migration and contributing to a large number of active sites. Excellent electrocatalytic performances are obtained such as an overpotential of only ~ 84.1 mV to reach the current density of 10 mA cm-2, a Tafel slope of 76.9 mV dec-1 and a small inherent resistance of 6.33 Ω. More importantly, a quick current response under multistep potentials is realized and an excellent stability retained after 3000 cycles of CV test. Besides, a DC power to supply a device (MnMoO4//MoS2/NiS HHs B) under 1.6 V can generate a current density of 21 mA cm-2, demonstrating its practical application

Design of nanostructures and hybrids of transition metal derivatives for energy storage applications

The research for high-performance energy storage devices, such as supercapacitors, Li-ion batteries, is continuing apace. These devices can store energy via electrochemical processes. However, further increases of capacity and stability of these devices to meet practical requirements remain a challenge. By using nanostructured electrode materials, several strategies were proposed in this thesis based on transition metals and their derivatives. The binder-free strategy was used across the entire project, which could increase the utilization and avoid “dead volume” of active materials. To improve the commonly reported electrochemical performance in aqueous of transition metal hybrids, such as nickel, cobalt or tungsten materials, bimetal nanostructured electrodes were proposed. Ni foam supported NiWO4 and CoWO4 electrodes were synthesized and increased the capacity and rate performance because of an increased electrical conductivity. Other methods for enhancing energy storage performance by means of increased electrical conductivities were found to be the sulfide or nitride counterparts of the corresponding oxide. To further improve the specific capacity and clarify the blurred energy storage mechanism of nickel or cobalt-based electrode materials, nickel cobalt sulfide nanostructures within sulfur and nitrogen-doped graphene frameworks were produced. Importantly, the redox reactions between materials and OH- groups were demonstrated as diffusion-controlled processes. In addition, the solid-state devices and properties of oxygen reduction were explored. Pseudocapacitor electrodes are attractive by bridging the power density and energy density between the electro-double layer capacitor and batteries. W2N@C core-shell structures on carbon cloth was synthesized by chemical vapour deposition via an ammoniation process and evaluated for supercapacitor performance. Combining with electrochemical analysis, in-situ electrical measurements and simulation, the merits of W2N materials were determined. The interesting nanostructured electrodes could be utilized in Li-ion batteries. Illuminated by above stratigies and considering the stable structures, capacity contribution and Li intercalation, a highly stable V2O5-based cathodes were developed

A shear-thickening colloidal electrolyte for aqueous zinc-ion batteries with resistance on impact

A conventional aqueous electrolyte is a crucial component of zinc-ion batteries providing an ion conductive medium. However, the monofunction of a liquid electrolyte cannot bear any external load. With regard to applications in electric vehicles and stationary energy storage devices, complicated battery packing materials are required to improve the mechanical properties, resulting in reduced energy or power densities from the perspective of the entire device. In this work, an electrolyte suspension combining both fluid-like and solid-like performances was developed for rechargeable zinc-ion batteries. Cornstarch water suspension is utilized in the electrolyte design forming a shear-thickening electrolyte with impact resistance ability. The formed electrolyte becomes rigid at a high shear rate. In other words, under a sudden impact, a battery with this shear-thickening electrolyte could offer additional load bearing avoiding short-circuiting and improving safety. Although an additional functionality, namely impact resistance, was added to the electrolyte, the as-prepared electrolyte still performs with comparable electrochemical performances for which it exhibits a superior ionic conductivity of 3.9 × 10−3 S cm−1 and Zn2+ transference number. This electrolyte even suppresses side-effects on the zinc anode, exhibiting a lower voltage gap in the symmetric cell compared to the aqueous electrolyte. The integrated full cell also delivered a specific capacity of 255 mA h g−1 with commercial MnO2 as the cathode at a current density of 0.1 A g−1

Pseudohexagonal Nb2O5 Anodes for Fast-Charging Potassium-Ion Batteries

High-rate batteries will play a vital role in future energy storage systems, yet while good progress is being made in the development of high-rate lithium-ion batteries, there is less progress with post-lithium-ion chemistry. In this study, we demonstrate that pseudohexagonal Nb2O5(TT-Nb2O5) can offer a high specific capacity (179 mAh g-1 ∼ 0.3C), good lifetime, and an excellent rate performance (72 mAh g-1 at ∼15C) in potassium-ion batteries (KIBs), when it is composited with a highly conductive carbon framework; this is the first reported investigation of TT-Nb2O5 for KIBs. Specifically, multiwalled carbon nanotubes are strongly tethered to Nb2O5 via glucose-derived carbon (Nb2O5@CNT) by a one-step hydrothermal method, which results in highly conductive and porous needle-like structures. This work therefore offers a route for the scalable production of a viable KIB anode material and hence improves the feasibility of fast-charging KIBs for future applications

Pseudohexagonal Nb2O5-Decorated Carbon Nanotubes as a High-Performance Composite Anode for Sodium Ion Batteries

Pseudohexagonal Nb2O5 (TT-Nb2O5) has been applied in sodium ion batteries (SIBs) for the first time. Lower synthesis temperatures, improved conductivity and stability were achieved by the introduction of a designed carbon framework. The TT-Nb2O5/carbon nanotube composite exhibits high specific capacity (135 mAh g−1 at 0.2 A g−1) in long cycles and good rate capability (53 mAh g−1 at high current density of 5 A g−1). The outstanding electrochemical performance is attributed to the superior electrical conductivity and connectivity, optimal mass transport conditions and the mechanical strength and durability established by the strongly linked TT-Nb2O5 and MWCNT network. This study provides a cost-effective route to the application of Nb2O5 in SIBs

Biochar for supercapacitor electrodes: Mechanisms in aqueous electrolytes

The utilization of biomass materials that contain abundant carbon–oxygen/nitrogen functional groups as precursors for the synthesis of carbon materials presents a promising approach for energy storage and conversion applications. Porous carbon materials derived from biomass are commonly employed as electric‐double‐layer capacitors in aqueous electrolytes. However, there is a lack of detailed discussion and clarification regarding the kinetics analysis and energy storage mechanisms associated with these materials. This study focuses on the modification of starch powders through the KOH activation process, resulting in the production of porous carbon with tunable nitrogen/oxygen functional groups. The kinetics and energy storage mechanism of this particular material in both acid and alkaline aqueous electrolytes are investigated using in situ attenuated total reflectance‐infrared in a three‐electrode configuration

Strategies for pH regulation in aqueous zinc ion batteries

Aqueous zinc ions batteries (AZIBs), which use non-organic electrolytes, have garnered sustained interest as a future energy storage technology, primarily due to their low cost, environmental friendliness, and intrinsic safety. However, zinc ion batteries suffer from a series of serious challenges, including hydrogen evolution reaction (HER) at the anode, surface passivation, dendrite formation, as well as limited operating voltage and comparatively low energy density. These factors are all influenced by the concentration of H+ in the electrolyte (i.e. the pH), and its fluctuations during the cycling process. To date, there remains a lack of systematic evaluation of the correlation between the pH value of electrolyte and the challenges faced by AZIBs, a focused review of how pH influences the electrochemical performance of AZIBs, or any focused discussion of strategies that can be used to improve cell efficiency. In this review we emphasize the strong correlation between electrolyte pH and AZIBs challenges and detail the research progress made in recent years relating to electrolyte additives, separator modification, interfacial protective layers, and battery system design, with a particular focus on the regulatory mechanisms associated with pH control. On this basis, we propose future research focuses and make suggestions for the onward development of AZIBs

Robust Bioinspired MXene–Hemicellulose Composite Films with Excellent Electrical Conductivity for Multifunctional Electrode Applications

MXene-based structural materials with high mechanical robustness and excellent electrical conductivity are highly desirable for multifunctional applications. The incorporation of macromolecular polymers has been verified to be beneficial to alleviate the mechanical brittleness of pristine MXene films. However, the intercalation of a large amount of insulating macromolecules inevitably compromises their electrical conductivity. Inspired by wood, short-chained hemicellulose (xylo-oligosaccharide) acts as a molecular binder to bind adjacent MXene nanosheets together; this work shows that this can significantly enhance the mechanical properties without introducing a large number of insulating phases. As a result, MXene–hemicellulose films can integrate a high electrical conductivity (64,300 S m–1) and a high mechanical strength (125 MPa) simultaneously, making them capable of being high-performance electrode materials for supercapacitors and humidity sensors. This work proposes an alternative method to manufacture robust MXene-based structural materials for multifunctional applications