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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...

Formation of a new class of layered, microcrystalline polymers from a simple hydrolytic polycondensation of n-alkyltrichlorosilanes in water is demonstrated. The structure of the polymeric condensate, determined from a combination of spectroscopic, diffraction, and thermal analysis techniques, consists of highly uniform, pillared microcrystallites in which the inorganic siloxy backbones are present in periodic layers, each containing a monomolecular layer of intercalated water, separated by crystalline assemblies of alkyl chains. The alkyl-chain organization shows a remarkable resemblance to that in highly organized, self-assembled monolayers formed from the precursor silane molecules on hydrophilic substrates and this parallel lends support to the critical importance of water in monolayer self-assembly of silanes.