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Abstract The rapidly increasing adoption of electric vehicles (EVs) worldwide is causing high demand for production of lithium‐ion batteries (LIBs). Tremendous efforts have been made to develop different components of LIBs in addition to design of battery pack architectures as well as manufacturing processes to make better batteries with affordable prices. Nonetheless, sustainable use of LIBs relies on the availability and cost of rare metals, which are naturally concentrated in a few countries. In addition, toxic electrolytes used in LIBs pose concerns on environmental impacts if LIBs are not handled properly after decommissioned from EVs. Therefore, it is paramount to realize effective utilization of spent LIBs, where their remaining capacities can be reused in less demanding applications. Finally, electrode materials and other valuable components of LIBs can be recovered via recycling, completing their circular life cycle. In this review, available options of LIBs after their retirement from EV applications, including battery second use, repair of electrode materials by direct regeneration, and material recovery by hydrometallurgical or pyrometallurgical processes are discussed. Throughout the review, the discussion is based around current available technologies, their environmental impacts, and economic feasibility as well as provided examples of pilot and industrial scale adoption of the processes.

Its high nominal voltage, thermal stability, and low toxicity render LiMn2O4 a highly promising cathode material for lithium ion batteries, but capacity fading due to unwanted side reactions during cycling remains an issue. Here, the authors show that carbon-coating a LiMn2O4 cathode reduces side reactions such as manganese dissolution and manganese oxide formation, thereby improving battery cycling stability.

Abstract Scalable aqueous-based supercapacitors are ideal as future energy storage technologies due to their great safety, low cost, and environmental friendliness. However, the corrosion of metal current collectors e.g., aluminium (Al) foil in aqueous solutions limits their practical applications. In this work, we demonstrate a low-cost, scalable, and simple method to prepare an anti-corrosion current collector using a concept of hydrophobicity by coating the hydrophobic graphite passivation layer on the Al foil via a roll-to-roll coating technology at the semi-automation scale of production pilot plant of 18,650 cylindrical supercapacitor cells. All qualities of materials, electrodes, and production process are therefore in the quality control as the same level of commercial supercapacitors. In addition, the effects of the graphite coating layer have been fundamentally evaluated. We have found that the graphite-coated layer can improve the interfacial contact without air void space between the activated carbon active material layer and the Al foil current collector. Importantly, it can suppress the corrosion and the formation of resistive oxide film resulting in better rate capability and excellent cycling stability without capacitance loss after long cycling. The scalable supercapacitor prototypes here in this work may pave the way to practical 18,650 supercapacitors for sustainable energy storage systems in the future.

In order to bridge the gap between academia and industry in the development of cathode active material for high-energy lithium-ion batteries (LIBs), several experimental factors reflecting commercial use need to be considered. Herein, based on a thick commercial level NMC811 electrode, we simply demonstrated the effect of charging protocols on the rate performance, cycling stability, and Li storage mechanism. A constant current charge/discharge, typically used in most publications, was found to exhibit worse rate capability and cycling stability compared to the constant current constant voltage (CCCV) mode of charge, used in commercial LIB cells due to the less uniform Li concentration gradient between the surface and bulk of the material. In operando XRD also revealed that there was no negative impact from the rapid change in lattice parameters towards cycling performance. We also found that the major degradation mechanism of Ni-rich NMC811 showing poor cycling performance across literature, can be mainly ascribed to the thick cathode electrolyte interphase (CEI) resistive layer, hindering Li intercalation at high rate and also lead to lower accessible capacity in each cycle. This work illustrates a simple example of the gaps between research in academic and industry that need to be narrowed for the development of practical high energy materials.

Zero-emission hydrogen and oxygen production are critical for the UK to reach net-zero greenhouse gasses by 2050. Electrochemical techniques such as water splitting (electrolysis) coupled with renewables energy can provide a unique approach to achieving zero emissions. Many studies exploring electrocatalysts need to “electrically wire” to their material to measure their performance, which usually involves immobilization upon a solid electrode. We demonstrate that significant differences in the calculated onset potential for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) can be observed when using screen-printed electrodes (SPEs) of differing connection lengths which are immobilized with a range of electrocatalysts. This can lead to false improvements in the reported performance of different electrocatalysts and poor comparisons between the literature. Through the use of electrochemical impedance spectroscopy, uncompensated ohmic resistance can be overcome providing more accurate Tafel analysis.

Abstract Although Nickel–Cadmium (NiCd) and Nickel–metal hydride (NiMH) batteries have been widely used, their drawbacks including toxic Cd and expensive La alloy at the negative electrodes, low energy density (40–60 Wh/kg for NiCd and 140–300 Wh/L for NiMH), low power density (150 W/kg for NiCd and 1000 W/kg for NiMH), and low working potential (1.2 V) limit their applications. In this work, Cd and La alloy were replaced with N-doped reduced graphene oxide aerogel (N-rGOae) providing a hybrid energy storage (HES) having the battery and supercapacitor effects. The HES of Ni(OH)2-coated N-rGOae//N-rGOae provides 1.5 V, a specific energy of 146 Wh/kg, a maximum specific power of 7705 W/kg, and high capacity retention over 84.6% after 5000 cycles. The mass change at the positive electrode during charging/discharging is 8.5 µg cm−2 owing to the insertion/desertion of solvated OH− into the α-Ni(OH)2-coated N-rGOae. At the negative electrode, the mass change of the solvated K+, physically adsorbed/desorbed to the N-rGOae, is 7.5 μg cm−2. In situ X-ray absorption spectroscopy (XAS) shows highly reversible redox reaction of α-Ni(OH)2. The as-fabricated device without using toxic Cd and expensive La alloy has a potential as a candidate of NiCd and NiMH.

Although metal-organic frameworks (MOFs) or porous coordination polymers have been widely studied, their antimicrobial activities have not yet been fully investigated. In this work, antifungal activity of copper-based benzene-tricarboxylate MOF (Cu-BTC MOF), which is water stable and industrially interesting, is investigated against Candida albicans, Aspergillus niger, Aspergillus oryzae and Fusarium oxysporum. The Cu-BTC MOF can effectively inhibit the growth rate of C. albicans and remarkably inhibit the spore growth of A. niger, A. oryzae and F. oxysporum. This finding shows the potential of using Cu-BTC MOF as a strong biocidal material against representative yeasts and moulds that are commonly found in the food and agricultural industries.

Herein, highly dispersed 10-nm lithiophilic silver nanoparticles (AgNPs) were synthesized and decorated on 3D graphene aerogel supporting materials. The prelithiated AgNPs/3D graphene aerogel exhibits a high specific capacity of 1589 mAh/g at 0.1 A/g with a high initial coulombic efficiency (ICE) of ca. 93% and a long cycling stability over 500 cycles. A Li-ion battery cell using the prelithiated AgNPs/3D graphene aerogel with a finely tuned Ag content of 0.52 at.% as the anode and the Ni-rich LiNi0.88Co0.09Al0.03O2 as the cathode exhibits a high energy density of -290 Wh/kg at 0.1 C. This new anode material may be a useful high-energy anode for next-generation Li-ion batteries. [ABSTRACT FROM AUTHOR]

The specific cell capacitance, equivalent series resistance (ESR) and equivalent distributed resistance (EDR) of porous carbon-based supercapacitors linearly depend on the cationic molecular length of room-temperature ionic liquids. [ABSTRACT FROM AUTHOR]

A thin-film Ni0.07Co2.93O4 p-type semiconductor finely tuned with better electronic conductivity and electrochemical activity than NiO and Co3O4 is proposed as a new photoelectrode of single asymmetric hybrid energy conversion and storage cell (HECS). Photoactive Ni0.07Co2.93O4 and N-doped reduced graphene oxide aerogel (N-rGOAE) were used as positive and negative electrodes of the HECS. Under light illumination, the Ni0.07Co2.93O4 can generate a hole (photogenerated carrier, Ni0.07Co2.93O4 +) at the valence band (VB) and a photoelectron at the conduction band (CB) via the photoelectric effect. During charging, the active hole (Ni0.07Co2.93O4 +) of the positive electrode can chemically react with OH- and H2O forming CoO(OH) and NiO(OH). This process can enhance the redox mechanism leading to the charge storage performance of the Ni0.07Co2.93O4 electrode since OH- can easily react with the active Ni0.07Co2.93O4 + hole having the lower energy level of the VB when compared with the electrode under the dark condition. The changes in the oxidation state of Ni and Co in Ni0.07Co2.93O4 were fundamentally investigated by an in situ electrochemical X-ray absorption spectroscopy. The electrochemical performance of Ni0.07Co2.93O4//N-rGOAE HECS can be enhanced under light illumination about 1.9-fold higher than that under dark condition. The HECS device may be useful for renewable energy applications. [ABSTRACT FROM AUTHOR]

The bifunctional electrocatalytic activities of birnessite-type layered manganese oxide with lithium ion as an intercalated cation (Li-bir) and its composite with reduced graphene oxide (Li-bir/rGO) toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were investigated. The enhanced catalytic activity of the Li-bir/rGO composite can be ascribed to the elevated electrical conductivity of the birnessite suggested via a lower charge transfer resistance obtained from the electrochemical impedance spectroscopy.Moreover, the local oxidation states of Mn in the Li-bir/rGO were investigated by in situ X-ray absorption spectroscopy during the ORR and OER processes. Interestingly, the generated oxygen gas from the OER process observed via the in situ gas chromatography of the Li-bir/rGO is 5.44 mmol g-1 which is higher than that of the pristine Li-bir (4.98 mmol g-1). These results suggest that the Li-bir/rGO can be further utilized as a bifunctional electrocatalyst for high-performance metal-air batteries. [ABSTRACT FROM AUTHOR]

To enhance the specific energy of electrochemical capacitors, several methods have been introduced including complex electrode modification as well as asymmetric cell development. Herein, an alternative approach to enhance both specific energy and power of N-doped reduced graphene oxide aerogel electrochemical capacitor via the introduction of hybrid redox electrolyte is proposed. The electrochemical properties of the hybrid electrolyte composing of 1-butyl-1-methylpyrrolidinium dicyanamide ionic liquid with 100mMferrocenemethanol redox additive were studied via cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The combination between a unique nanostructure of N-doped reduced graphene oxide aerogel and novel hybrid electrolyte results in an excellent specific capacitance and specific energy of 112.1 F g-1 and 34.2 Wh kg-1, respectively, as compared to 76.7 F g-1 and 23.5 Wh kg-1 of the neat 1-butyl-1-methylpyrrolidinium dicyanamide electrolyte. The remarkable improvements can be explained by the emerging of the Faradaic-redox activity of the ferrocene methanol at the electrode-electrolyte interface. This simple approach could demonstrate another feasible route to improve the performance of ionic liquid-based electrochemical capacitors. [ABSTRACT FROM AUTHOR]

Nitrogen-doped graphene aerogel (NGae) with a three-dimensional (3D) interconnected structure with ca. 3.5 at% of nitrogen content was synthesized by a hydrothermal reduction of graphene oxide with hydrazine and a following freezing-dry method. The 3D morphology of conductive NGae provides fast ion diffusion leading to nearly steady specific capacitances (ca. 450 F g-1) when increasing scan rates (10-100 mV-1) or applied currents (0.5-2.5 A g-1). Not only can the nitrogen-containing groups improve the electrical conductivity of NGae but also they can store charges via their reversible surface redox reactions. The as-fabricated symmetric supercapacitor of NGae in 1 M H2SO4 electrolyte provides a maximum specific energy and power of 42 Wh kg-1 and 2077 W kg-1, respectively. In addition, incorporating pseudocapacitor materials i.e., MnO2 and polyaniline to NGae structure can also provide higher specific energy owing to surface redox reactions. The as-fabricated supercapacitors in this work may be practically used in high energy and power applications. [ABSTRACT FROM AUTHOR]