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Thanks to low cost, high safety, and large energy density, aqueous zinc-ion batteries have attracted tremendous interest worldwide. However, it remains a challenge to develop high-performance cathode materials with an appropriate method that is easy to realize massive production. Herein, we use a molten salt method to synthesize nanostructured manganese oxides. The crystalline phases of the manganese oxides can be tuned by changing the amount of reduced graphene oxide added to the reactant mixture. It is found that the α-MnO2/Mn2O3 nanocomposite with the largest mass ratio of Mn2O3 delivers the best electrochemical performances among all the products. And its rate capability and cyclability can be significantly improved by modifying the Zn anode with carbon black coating and nanocellulose binder. In this situation, the nanocomposite can deliver high discharging capacities of 322.1 and 213.6 mAh g–1 at 0.2 and 3 A g–1, respectively. After 1000 cycles, it can retain 86.2% of the capacity at the 2nd cycle. Thus, this nanocomposite holds great promise for practical applications.

Due to their low cost, high safety, environmental friendliness, and impressive electrochemical performances, aqueous zinc-ion batteries are considered promising alternative technologies to lithium-ion batteries for use in large-scale applications. However, existing aqueous zinc-ion batteries usually suffer from poor cyclability and cannot operate at subzero temperatures. Herein, to solve these problems, the electrolyte in aqueous zinc-ion batterie is optimized by adding the appropriate amounts of diethyl ether and ethylene glycol. Results show that the addition of 1% diethyl ether contributes to the best cyclability at 25 °C. Furthermore, the addition of 30% ethylene glycol results in the best electrochemical performances at 0 and − 10 °C. This significant performance improvement at low temperatures is ascribed to the high ionic conductivity of the modified electrolyte and the low charge transfer impedance of the battery with the modified electrolyte at 0 and −10 °C. It is also shown that the modified electrolyte can decrease the nucleation overpotential of zinc plating, enhance the interfacial stability between the zinc metal and electrolyte, suppress the zinc dendritic growth and side reactions, and decrease the self-corrosion rate of the zinc anode. This work offers a facile strategy to realize aqueous zinc-ion batteries with excellent cyclability and antifreezing ability and may inspire research on other aqueous energy storage systems.

It is urgent to develop high-performance cathode materials for the emerging aqueous zinc-ion batteries with a facile strategy and optimize the related components. Herein, a Ca0.23V2O5·0.95H2O nanobelt cathode material with a rather large interlayer spacing of 13.0 A is prepared via a one-step hydrothermal approach. The battery with this cathode material and 3 M Zn(CF3SO3)2 electrolyte displays high specific capacity (355.2 mAh g−1 at 0.2 A g−1), great rate capability (240.8 mAh g−1 at 5 A g−1), and excellent cyclability (97.7% capacity retention over 2000 cycles). Such superior performances are ascribed to fast electrochemical kinetics, outstanding electrode/electrolyte interface stability, and nearly dendrite-free characteristic. Instead, when ZnSO4 or Zn(ClO4)2 is used to replace Zn(CF3SO3)2, the electrochemical performances become much inferior, due to the slow electrochemical kinetics, inhomogeneous Zn stripping/plating process, and the formation of large dendrites and byproducts. This work not only discloses a high-performance cathode material for aqueous zinc-ion batteries but also offers a reference for the choice of electrolyte salt.

Aqueous zinc-ion batteries have received significant attention due to their low cost and high safety. However, the unsatisfactory cycling performances caused by the dendritic growth on the Zn anode limit their practical applications. Herein, we propose to modify the conventional Zn foil anode by using carbon black coating and nanofibrillated cellulose binder. The carbon black can form an electrically conductive network, thus greatly enlarging the electroactive surface area, while the nanofibrillated cellulose can act as an electrolyte reservoir to facilitate charge transports. Thanks to that, the modified anode can significantly eliminate the dendritic growth and side reactions, therefore ensuring excellent interface stability with the electrolyte even at a commercial-level areal capacity of 5 mAh g-1. With the modified anode, the Zn-MnO2 battery gives a high capacity retention of 87.4% after 1000 cycles, much higher than that with the unmodified Zn foil (42.6%). This study discloses a facile, scalable, and cost-effective strategy to achieve dendrite-free metal electrodes towards great cyclability.

In this study, label-free quantitative proteomics was used to investigate the biological functions of M. oleifera seed proteins, which resulted in the identification of milk-clotting proteases. In total, 921 proteins were identified, and proteins within the molecular weight range of 30–50 kDa were abundant. The identified proteins were mainly involved in catalytic activity and metabolic processes associated with carbohydrate and protein metabolism, among which, proteases in the observed molecular weight range could possibly be responsible for the previously reported milk-clotting activity. An aspartic-type endopeptidase with molecular mass of 45,517 Da was purified from M. oleifera seeds using ammonium sulfate precipitation, ultrafiltration, and preparative high performance liquid chromatography, and was characterized using liquid chromatography-mass spectrometry (LC-MS)/MS. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the purified protease exhibited hydrolase activity and was involved in several metabolic pathways, which further confirmed that proteomic analysis can assist in the purification of the milk-clotting protease. The optimal temperature and pH required for protease activity were 60 °C and 5.0, respectively. The high thermal stability and good pH stability of the protease indicated that it can be used in the dairy industry.

Flexible aqueous zinc-ion batteries (AZIBs) are promising to satisfy the emerging wearable electronics. However, conventional hydrogel electrolytes are unable to work at subzero temperatures because they inevitably freeze. In this work, a borax-crosslinked polyvinyl alcohol (PVA)/glycerol gel electrolyte is developed, in which glycerol can strongly interact with PVA chains, thus effectively prohibiting the formation of ice crystals within the whole gel network. Thanks to this, the freezing point of this gel electrolyte is below −60 °C, which allows it to work in extremely cold environments. Even at −35 °C, it still exhibits a high ionic conductivity of 10.1 mS cm−1 and great mechanical properties. On the basis of this anti-freezing gel electrolyte, a flexible quasi-solid-state aqueous Zn–MnO2 battery is assembled and realizes an impressive energy density of 46.8 mW h cm−3 (1330 μW h cm−2) at a power density of 96 mW cm−3 (2.7 mW cm−2) at 25 °C, outperforming nearly all the reported AZIBs. More importantly, when the temperature is reduced to −35 °C, a rather high energy density (25.8 mW h cm−3, 732 μW h cm−2) can still be achieved, and 53.3% of that value can be retained when the power density is increased to about 10-fold. This battery also shows excellent cycling durability (around 90% capacity retention over 2000 cycles) and great tolerance to various extreme conditions even when the temperature is down to −35 °C. These findings provide valuable insights into designing aqueous batteries/supercapacitors that can work in cold climates and high-altitude areas.

Aqueous zinc-ion batteries (AZIBs) are promising due to their intrinsic safety and low cost. However, the unsatisfactory cathode materials with low mass loading (

With the booming development of wearable electronics, flexible zinc-based batteries are attracting significant attention due to their high safety, low cost, environmental benignity, and relatively large energy/power densities. However, in a conventional segregated configuration, the electrodes could be easily detached from the separator when the battery is subjected to bending strain, which would dramatically depress electrochemical performances. Moreover, severe zinc dendrite growth and parasitic side reactions at the anode are extremely detrimental to the durability and the reliability of zinc-based batteries. Herein, a flexible self-standing composite film anode consisting of zinc microspheres, carbon nanotubes, and nanocellulose is constructed to replace the conventional Zn foil. It is found that the use of this anode can effectively inhibit the dendrites and side reactions, thereby substantially improving the cyclability. In addition, a layer-by-layer vacuum filtration method is used to integrate the composite film anode with a cellulose separator and a MnO2-based composite film cathode into a single matrix. The unique integrated battery realizes great rate capability and cycling stability, and more importantly, superior affordability to bending deformations. Besides, the commonly used thick, heavy, and expensive current collectors are no longer required in the integrated configuration, therefore enabling the battery to be smarter and cheaper. This study not only opens a new option for building dendrite-free zinc anodes but also discloses a facile strategy to achieve integrated configuration for energy storage devices.

The present study aimed to investigate the biological functions of germinated M. oleifera seed proteins and to identify the identity of milk-clotting proteases. A total of 963 proteins were identified, and those with molecular weights between 10 and 30 kDa were most abundant. The identified proteins were mainly involved in energy-associated catalytic activity and metabolic processes, and carbohydrate and protein metabolisms. The numbers of proteins associated with the hydrolytic and catalytic activities were higher than the matured dry M. oleifera seeds reported previously. Of the identified proteins, proteases were mainly involved in the milk-clotting activity. Especially, a cysteine peptidase with a molecular mass of 17.727 kDa exhibiting hydrolase and peptidase activities was purified and identified. The identified cysteine peptidase was hydrophilic, and its secondary structure consisted of 27.60% alpha helix, 9.20% beta fold, and 63.20% irregular curl; its tertiary structure was also constructed using M. oleifera seed 2S protein as the protein template. The optimal pH and temperature of the purified protease were pH 4.0 and 60 °C, respectively. The protease had high acidic stability and good thermostability, thus could potentially be applied in the dairy industry.

With the advantages of intrinsic safety, low price, high output potential, and acceptable energy density, aqueous rechargeable Zn-MnO2 batteries are gradually emerging as promising energy storage devices in recent years. Unfortunately, the structural instability and poor electrical conductivity of manganese dioxides still hinder their further applications. To tackle these issues, we demonstrate a high-performance cathode material for Zn-MnO2 batteries by hybridizing lignin-derived porous carbon with δ-MnO2 (denoted as LPC/δ-MnO2). Benefiting from the high electrical conductivity of porous carbon, the LPC/δ-MnO2 cathode material can offer high discharge capacity of 332.3 mAh g–1 at 0.2 A g–1 and excellent high-rate capability (196.1 mAh g–1 at 5 A g–1). Meanwhile, the assembled Zn-MnO2 battery displays good long-term cycling stability (82% capacity retention after 1000 cycles). Such superior performances are attributed to the synergetic effect of nanostructured δ-MnO2 and porous carbon scaffold, which is in favor of rapid Zn2+ ion diffusion and large contribution ratio of pseudocapacitive Zn2+ ion intercalation. The results of this study show great prospects of hybridizing biomass-derived carbon framework with electrochemically active materials towards advanced energy storage materials.

Rechargeable aqueous zinc-ion batteries based on Mn-based cathode materials are of considerable interest for large-scale energy storage. However, the intrinsic low electronic conductivity and the dissolution issue of Mn-based cathode materials result in slow reaction kinetics and fast capacity fading. Herein, a facile and scalable strategy combining molten salt synthesis and self-initiated polymerization is developed to in-situ generate a thin layer of polypyrrole onto the surface of MnO2/Mn2O3 nanocomposite, aiming to resolve the problems mentioned above. The obtained product provides large specific capacity (289.8 mAh g−1 at 0.2 A g−1), remarkable rate capability (199.8 mAh g−1 at 3 A g−1), and excellent cycling stability (96.7% after 1000 cycles at 1 A g−1, compared to the 2nd cycle). The cyclability remains good when Mn2+ ions are not pre-added into the electrolyte. Also, the obtained product exhibits slight electrochemical polarization, low charge transfer impedance after cycling, high capacitive contribution, and large electrolyte ion diffusion coefficient. All these performances and properties are significantly superior to that of MnO2/Mn2O3 nanocomposite without polypyrrole coating. This work opens a new path towards long-life and fast-discharging electrode materials.

Flexible aqueous zinc-ion batteries are promising to satisfy the booming wearable electronics. Herein, a facile, scalable, and cost-effective method (one-step electrodeposition) is developed to grow MnO2 nanoflakes onto carbon nanotube (CNT) film. The binder-free self-supporting CNT@MnO2 film can take advantages of highly conductive CNT scaffold and nanostructure of MnO2, thus leading to facilitated electrochemical kinetics. Based on the CNT@MnO2 film, a flexible quasi-solid-state Zn-MnO2 battery is assembled and achieves high reversible capacity of 292.7 mAh g−1 (corresponding to 16.5 mWh cm−3) at 0.2 mA cm−2, great rate capability (105.6 mAh g−1 at 3 mA cm−2), and excellent cycling stability (no capacity fading after 1000 cycles). The quasi-solid-state Zn-MnO2 battery also shows high tolerance to mechanical bending. With these merits, the CNT@MnO2 film holds great potential for Zn-MnO2 batteries to power wearable electronics.