A High Performance Hybrid Battery Based on Aluminum Anode and LiFePO4 Cathode

Abstract

The environmental concerns over the use of fossil fuels and their limited resources, combined with energy security concerns, have spurred great interest in energy harvesting from renewable sources such as wind and solar.[1] However, both solar and wind are intermittent, and hence, in order to effectively utilize these renewable energies, low-cost electric energy storage (EES) devices are needed. Among various EES technologies, lithium ion batteries have been dominant in the electronic markets such as cellular phones, laptop computers and electric vehicles, and therefore, they are also good candidates for and grid and stationary applications. However, one major issue is the high cost. As an alternative, cheap and naturally abundant elements based technologies such as sodium ion, magnesium ion and aluminum ion batteries have been intensively studied during the last few years. [2] Among these emerging technologies, aluminum batteries have distinct advantages because its three electron redox couple provides a high theoretical specific capacity of 2980 mAh g-1 and a high volumetric capacity of 8040 mAh cm-3. However, the development of rechargeable aluminum ion batteries faces major challenges from both electrolyte and cathode. Because of the low reduction potential of aluminum (-1.68 V vs. standard hydrogen electrode), aqueous electrolytes cannot be used as hydrogen will be generated before aluminum can be plated during the reduction process. So far, it has been shown that aluminum deposition/stripping is only possible in acidic ionic liquids based on mixtures of anhydrous AlCl3 with organic halide salts such as EMImCl and N-(1-butyl)pyridinium chloride etc. However, the strong acidic nature of the ionic liquids poses stringent requirement for the hardwares of the aluminum batteries, as it was shown that corrosion was readily occurred to stainless steels. On the other hand, the challenge facing the aluminum cathodes results from its own advantage, i.e. trivalent cation, which makes its intercalation/de-intercalation very difficult. Other challenges facing aluminum ion batteries are low cell voltage and poor cycling performance. Recently, two groups led by Dai and Jiao et al reported good cycling performance on high voltage rechargeable aluminum ion batteries utilizing three-dimensional graphitic-foam and carbon paper as the cathode, respectively.[2d, 3] Besides aluminum ion batteries, Chang et al. reported good cycling performance on an asymmetric capacitor based on Prussian blue and active carbon electrodes in an aqueous electrolyte. [4] However, the reported capacities for the aforementioned batteries and capacitors were low, i.e. below 100 mAh g-1. Herein we report a new rechargeable battery based on the hybrid chemistries of aluminum anode and lithium intercalation cathode LiFePO4, which exhibits a high capacity of 160 mAh g-1at a current rate of C/5. It also shows good rate capability and cycling performance. [5]