Title: Design and Performance of Rechargeable Sodium Ion Batteries, and Symmetrical Li-Ion Batteries with Supercapacitor-Like Power Density Based upon Polyoxovanadates

Abstract:

The polyanion Li₇V₁₅O₃₆(CO₃) is a nanosized molecular cluster (≈1 nm in size), that has the potential to form an open host framework with a higher surface-to-bulk ratio than conventional transition metal oxide electrode materials. Herein, practical rechargeable Na-ion batteries and symmetric Li-ion batteries are demonstrated based on the polyoxovanadate Li₇V₁₅O₃₆(CO₃). The vanadium centers in {V₁₅O₃₆(CO₃)} do not all have the same V^IV/V redox potentials, which permits symmetric devices to be created from this material that exhibit battery-like energy density and supercapacitor-like power density. An ultrahigh specific power of 51.5 kW kg⁻¹ at 100 A g⁻¹ and a specific energy of 125 W h kg⁻¹ can be achieved, along with a long cycling life (>500 cycles). Moreover, electrochemical and theoretical studies reveal that {V₁₅O₃₆(CO₃)} also allows the transport of large cations, like Na⁺, and that it can serve as the cathode material for rechargeable Na-ion batteries with a high specific capacity of 240 mA h g⁻¹ and a specific energy of 390 W h kg⁻¹ for the full Na-ion battery. Finally, the polyoxometalate material from these electrochemical energy storage devices can be easily extracted from spent electrodes by simple treatment with water, providing a potential route to recycling of the redox active material.

Full-Link: http://onlinelibrary.wiley.com/doi/10.1002/aenm.201701021/full