No abstract

Among the aqueous rechargeable batteries, Zn 2+ -based batteries exhibit a series of unique attributes for large-scale energy storage: (i) feasibility of using low-cost Zn metal anode with a high theoretical specific capacity of 819 mA h g −1 ; (ii) replacement of the traditional alkaline electrolytes by mild neutral electrolytes, mitigating the environmental disruption and recycling costs; and (iii) low redox potential of Zn/Zn 2+ (−0.76 V vs standard hydrogen electrode) and two-electron transfer mechanism during cycling responsible for the high energy density. [6,22,23] However, the zinc system also has long-standing challenges, such as the unstable cathode and anode structures in the aqueous environment. On the cathode side, the cycling stability is related to how zinc ions and the electrolyte react with the cathode materials, which is much more complex as compared to the lithium-ion systems. An initial attempt on the hexacyanoferrate system delivered a limited capacity (≈60 mA h g −1 ), although a high operation voltage of ≈1.7 V was achieved. [23][24][25][26][27][28] Recently, Pan et al. demonstrated that the manganese oxide cathode goes through a chemical conversion reaction with the zinc species and H 2 O rather than the simple intercalation process, delivering a high capacity of ≈285 mA h g −1 and an operating voltage of ≈1.44 V. [29] Nazar's group developed a Zn 0.25 V 2 O 5 ·nH 2 O cathode material, which displayed a specific energy of ≈250 Wh kg −1 (based on cathode) and a high capacity of 220 mA h g −1 at 15 C (1 C = 300 mA g −1 ). [30] During cycling, the structural water in Zn 0.25 V 2 O 5 ·nH 2 O was revealed to exchange with Zn 2+ reversibly, thus resulting in good kinetics and rate performance. Furthermore, some other studies have also suggested the importance of H 2 O in metal ion intercalation. [23,31] During cycling, the solvating H 2 O works as a charge shield for the metal ions (Al 3+ , Mg 2+ , Li + , etc.), reducing their effective charges and hence their interactions with the host frameworks. [32,33] This strategy has been investigated to enhance the capacity and rate capability of Li + , Na + , and Mg 2+ batteries. [34][35][36][37][38][39] In this paper, we present a systematic and detailed study of the role of H 2 O in bilayer V 2 O 5 ·nH 2 O (n ≥ 1) as a prototype cathode material for zinc batteries. By coupling the electrochemical measurements, thermogravimetric/differential BatteriesLarge-scale energy storage systems are critical for the integration of renewable energy and electric energy infrastructures. [1][2][3] Among numerous candidates, lithium-ion batteries with organic electrolytes are one of the most attractive options due to their high energy density [4][5][6][7][8][9][10] and mature markets. [11,12] However, for grid scale energy storage, the cost of lithium-ion batteries is still too high, [13,14] and the use of the flammable organic electrolyte in large format batteries poses a severe safety and environmental concern. [15] As an alternative, low-cost aqueous batteries wi...

With the rapid development of energy storage devices, aqueous battery with noncombustion properties and instinct safe features has received great attentions and Zn anode is investigated intensively due to its high theoretical capacity (820 mAh g−1), and low negative potential (−0.762 V vs SHE). However, the unavoidable gas evolution hinders the cyclability and the application in the commercial field. Herein, the atomic layer deposition of TiO2 coating is first demonstrated as the protection layer of metallic zinc anode. The corrosion of zinc plate is significantly suppressed, leading to less gas evolution and Zn(OH)2 byproduct formation. The reduced gas generation on the outer surface of the zinc plate will maintain the effective contact area between the electrolyte and anode and leads to an improved coulombic efficiency. In this way, the Zn anode with 100 ALD cycles TiO2 protection shows reduced overpotential (72.5 mV) at 1 mA cm−2 for Zn–Zn symmetrical battery and additionally, the protection of TiO2 extended the Zn–MnO2 battery cycling performance up to 1000 cycles with the capacity retention of 85% at current density of 3 mA cm−2. The novel design of atomic layer deposition protected metal zinc anode brings in new opportunities to the realization of the ultrasafe aqueous zinc metal batteries.

Electrochemical energy storage technology is of critical importance for portable electronics, transportation and large-scale energy storage systems. There is a growing demand for energy storage devices with high energy and high power densities, long-term stability, safety and low cost. To achieve these requirements, novel design structures and high performance electrode materials are needed. Porous 1D nanomaterials which combine the advantages of 1D nanoarchitectures and porous structures have had a significant impact in the field of electrochemical energy storage. This review presents an overview of porous 1D nanostructure research, from the synthesis by bottom-up and top-down approaches with rational and controllable structures, to several important electrochemical energy storage applications including lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-oxygen batteries and supercapacitors. Highlights of porous 1D nanostructures are described throughout the review and directions for future research in the field are discussed at the end.

Carbon materials are generally preferred as anodes in supercapacitors; however, their low capacitance limits the attained energy density of supercapacitor devices with aqueous electrolytes. Here, we report a low-crystalline iron oxide hydroxide nanoparticle anode with comprehensive electrochemical performance at a wide potential window. The iron oxide hydroxide nanoparticles present capacitances of 1,066 and 716 F g−1 at mass loadings of 1.6 and 9.1 mg cm−2, respectively, a rate capability with 74.6% of capacitance retention at 30 A g−1, and cycling stability retaining 91% of capacitance after 10,000 cycles. The performance is attributed to a dominant capacitive charge-storage mechanism. An aqueous hybrid supercapacitor based on the iron oxide hydroxide anode shows stability during float voltage test for 450 h and an energy density of 104 Wh kg−1 at a power density of 1.27 kW kg−1. A packaged device delivers gravimetric and volumetric energy densities of 33.14 Wh kg−1 and 17.24 Wh l−1, respectively.

No abstract

Lithium-ion batteries have attracted enormous attention for large-scale and sustainable energy storage applications. Here we present a design of hierarchical Li3V2(PO4)3/C mesoporous nanowires via one-pot synthesis process. The mesoporous structure is directly in situ carbonized from the surfactants (CTAB and oxalic acid) along with the crystallization of Li3V2(PO4)3 without using any hard templates. As a cathode for lithium-ion battery, the Li3V2(PO4)3/C mesoporous nanowires exhibit outstanding high-rate and ultralong-life performance with capacity retention of 80.0% after 3000 cycles at 5 C in 3-4.3 V. Even at 10 C, it still delivers 88.0% of its theoretical capacity. The ability to provide this level of performance is attributed to the hierarchical mesoporous nanowires with bicontinuous electron/ion pathways, large electrode-electrolyte contact area, low charge transfer resistance, and robust structure stability upon prolonged cycling. Our work demonstrates that the unique mesoporous nanowires structure is favorable for improving the cyclability and rate capability in energy storage applications.

The V2O5·nH2O xerogel composed of thin acicular interconnected nanowire networks has been synthesized via a facile freeze-drying process and exhibits superior sodium storage capacity.