Abstract
A rechargeable hybrid aqueous battery (ReHAB) containing NASICON-type M3V2(PO4)3 (M = Li, Na) as the cathodes and Zinc metal as the anode, working in Li2SO4-ZnSO4 aqueous electrolyte, has been studied. Both of Li3V2(PO4)3 and Na3V2(PO4)3 cathodes can be reversibly charge/discharge with the initial discharge capacity of 128 mAh g−1 and 96 mAh g−1 at 0.2C, respectively, with high up to 84% of capacity retention ratio after 200 cycles. The electrochemical assisted ex-XRD confirm that Li3V2(PO4)3 and Na3V2(PO4)3 are relative stable in aqueous electrolyte, and Na3V2(PO4)3 showed more complicated electrochemical mechanism due to the co-insertion of Li+ and Na+. The effect of pH of aqueous electrolyte and the dendrite of Zn on the cycling performance of as designed MVP/Zn ReHABs were investigated, and weak acidic aqueous electrolyte with pH around 4.0–4.5 was optimized. The float current test confirmed that the designed batteries are stable in aqueous electrolytes. The MVP//Zn ReHABs could be a potential candidate for future rechargeable aqueous battery due to their high safety, fast dynamic speed and adaptable electrochemical window. Moreover, this hybrid battery broadens the scope of battery material research from single-ion-involving to double-ions -involving rechargeable batteries.
Highlights
rechargeable hybrid aqueous battery (ReHAB) could be a potential candidate for future rechargeable aqueous battery due to their high safety, fast dynamic speed and adaptable electrochemical window
The 4 V materials such as LiMn2O423,24, LiCoO225 or LiNi1/3Co1/3Mn1/3O226 were introduced into aqueous electrolyte batteries, their potential plateaus in aqueous media are close to water decomposition potential
Few cathodes are more possible in Li-containing ReHABs with possible good cycling performance in aqueous electrolytes, including Li3V2(PO4)[3] (LVP)[27,28,29,30], Na3V2(PO4)[3] (NVP)[31,32,33,34], LiFePO410, and MnO235,36
Summary
We designed a two-ions (Zn2+ and Li+) involving aqueous electrolyte rechargeable battery with MVP (M =Li, Na) as cathode and Zn foil as anode, respectively (Fig. 1a). With the charge depth increases from 0.8 V to 2.1 V, more sodium ions were extracted from the lattice of NVP, and the initial rhombohedral phase Na3V2(PO4)[3] disappeared, companying with other obvious different diffraction peaks appeared, which should be attributed to that of intermediates ( ) Na3−x+mLi(x−m) V2(PO4 process was complicated. In the case of NVP//Zn battery, owing to the complicated two-ions mixed insertion/extraction mechanism, the stabled charge/discharge profiles were obtained after 25 cycles with specific capacity of 86.7 mAh g−1 at 0.2 C after 200 cycles. The development of this ReHABs with MVP (M =Na, Li) as cathodes may have a significant impact on electrochemical energy storages owing to its low cost and safety. More work should be focused on improving the cycling performance, optimizing electrolyte and counter electrode, well as the dissolution and dendrites formation on the Zn anode in weak acidic electrolytes
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