Review of the use of transition-metal-oxide and conducting polymer-based fibres for high-performance supercapacitors

Heteroatom doped graphene engineering for energy storage and conversion

Rocking-chair based lithium-ion batteries (LIBs) have extensively applied to consumer electronics and electric vehicles (EVs) for solving the present worldwide issues of fossil fuel exhaustion and environmental pollution. However, due to the growing unprecedented demand of LIBs for commercialization in EVs and grid-scale energy storage stations, and a shortage of lithium and cobalt, the increasing cost gives impetus to exploit low-cost rechargeable battery systems. Dual-ion batteries (DIBs), in which both cations and anions are involved in the electrochemical redox reaction, are one of the most promising candidates to meet the low-cost requirements of commercial applications, because of their high working voltage, excellent safety, and environmental friendliness compared to conventional rocking-chair based LIBs. However, DIB technologies are only at the stage of fundamental research and considerable effort is required to improve the energy density and cycle life further. We review the development history and current situation, and discuss the reaction kinetics involved in DIBs, including various anionic intercalation mechanism of cathodes, and the reactions at the anodes including intercalation and alloying to explore promising strategies towards low-cost DIBs with high performance.

Strategies towards Low-Cost Dual-Ion Batteries with High Performance.

Mechanically stable and foldable air cathodes with exceptional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities are key components of wearable metal-air batteries Herein, a directional freeze-casting and annealing approach is reported for the construction of a 3D honeycomb nanostructured, N,P-doped carbon aerogel incorporating in situ grown FeP/Fe2 O3 nanoparticles as the cathode in a flexible Zn-air battery (ZAB) The aqueous rechargeable Zn-air batteries assembled with this carbon aerogel exhibit a remarkable specific capacity of 648 mAh g-1 at a current density of 20 mA cm-2 with a good long-term durability, outperforming those assembled with commercial Pt/C+RuO2 catalyst Furthermore, such a foldable carbon aerogel with directional channels can serve as a freestanding air cathode for flexible solid-state Zn-air batteries without the use of carbon paper/cloth and additives, giving a specific capacity of 676 mAh g-1 and an energy density of 517 Wh kg-1 at 5 mA cm-2 together with good cycling stability This work offers a new strategy to design and synthesize highly effective bifunctional air cathodes to be applied in electrochemical energy devices

An Iron-Decorated Carbon Aerogel for Rechargeable Flow and Flexible Zn-Air Batteries.

As one of the most promising alternatives for future energy systems, the rechargeable Zn–air battery (ZAB) has attracted extensive attention due to its extraordinarily high theoretical specific energy density. However, several obstacles restrict its practical application. One challenge is the sluggish kinetics of oxygen-reduction reaction (ORR) and oxygen-evolution reaction (OER) in the discharging and charging processes of ZABs. In addition, when using unifunctional ORR or OER electrocatalysts as air electrodes, like noble metal catalysts (Pt/C or Ru/IrO2), there are the disadvantages of high cost and poor stability. Therefore, rational design of non-noble metal bifunctional ORR/OER electrocatalysts with high activity and stability is essential for the development of ZABs. In this review, we discuss the latest developments of non-noble metal bifunctional ORR/OER electrocatalysts for ZABs. Firstly, the related reaction mechanisms of ORR and OER are introduced. Then, the latest developments of bifunctional ORR/OER materials for ZABs are discussed in detail from three aspects: (i) MOF-based catalysts, including pristine MOFs and their derivatives; (ii) metal-free-based carbon catalysts, including heteroatom-doped carbon and defective carbon; (iii) metal-based catalysts, including metal–nitrogen–carbon materials (such as metals/alloys, single-atom) and metal compound materials. Finally, some challenges and outlooks for the optimal design of bifunctional air electrodes for rechargeable ZABs with high activity and ultra-long lifetime are put forward.

Bifunctional electrocatalysts for Zn–air batteries: recent developments and future perspectives

Regulation of Lamellar Structure of Vanadium Oxide via Polyaniline Intercalation for High-Performance Aqueous Zinc-Ion Battery

Lithium metal is considered as the most promising anode material due to its high theoretical specific capacity and the low electrochemical reduction potential. However, severe dendrite problems have to be addressed for fabricating stable and rechargeable batteries (e.g., lithium-iodine batteries). To fabricate a high-performance lithium-iodine (Li-I2 ) battery, a 3D stable lithium metal anode is prepared by loading of molten lithium on carbon cloth doped with nitrogen and phosphorous. Experimental observations and theoretical calculation reveal that the N,P codoping greatly improves the lithiophilicity of the carbon cloth, which not only enables the uniform loading of molten lithium but also facilitates reversible lithium stripping and plating. Dendrites formation can thus be significantly suppressed at a 3D lithium electrode, leading to stable voltage profiles over 600 h at a current density of 3 mA cm-2 . A fuel cell with such an electrode and a lithium-iodine cathode shows impressive long-term stability with a capacity retention of around 100% over 4000 cycles and enhanced high-rate capability. These results demonstrate the promising applications of 3D stable lithium metal anodes in next-generation rechargeable batteries.

A 3D and Stable Lithium Anode for High-Performance Lithium-Iodine Batteries.

Cobalt nitride embedded holey N-doped graphene as advanced bifunctional electrocatalysts for Zn-Air batteries and overall water splitting

Exploring efficient bifunctional oxygen electrocatalysts is beneficial to promote the practical applications for rechargeable Zn-air batteries. Herein, a high-efficiency one-pot method is developed to synthesize porous carbon with N, S doping and embedded hollow cobalt oxide nanoparticles. The coordination of polyethyleneimine molecules with cobalt ions enables the formation of organic-inorganic precursors via the co-precipitation with lignosulfonate because of the electrostatic interaction. Under thermal treatment, the hollow cobalt oxide nanoparticles can be well dispersed among the carbon matrix codoped with N, S. The as-prepared composite catalysts exhibit efficient bifunctional activity for electrochemical reduction and evolution reactions of oxygen, thanks to the N, S codoping nature and the hollow cobalt oxide with abundant oxygen vacancies. The bifunctional catalytic activity renders the assembly of high-performance Zn-air battery in an aqueous electrolyte with a specific capacity of 745 mA h gZn-1 and good cycling stability for over 100 h. More importantly, the all-solid-state Zn-air battery is assembled with a polymer-based electrolyte, also exhibiting good cycling stability and flexibility under various bending status.

Song Chen

Papers

Regulation of Lamellar Structure of Vanadium Oxide via Polyaniline Intercalation for High-Performance Aqueous Zinc-Ion Battery

A 3D and Stable Lithium Anode for High-Performance Lithium-Iodine Batteries.

Cobalt nitride embedded holey N-doped graphene as advanced bifunctional electrocatalysts for Zn-Air batteries and overall water splitting

Bifunctional Oxygen Electrocatalysis of N, S-Codoped Porous Carbon with Interspersed Hollow CoO Nanoparticles for Rechargeable Zn-Air Batteries.

A flexible solid-state supercapacitor based on graphene/polyaniline paper electrodes