Amorphous iron phosphate: potential host for various charge carrier ions

Abstract

In response to the ever-increasing global demand for viable energy-storage systems, sodium and potassium batteries appear to be promising alternatives to lithium ion batteries because of the abundance, low cost and environmental benignity of sodium/ potassium. Electrical energy storage via ion-intercalation reactions in crystalline electrodes is critically dependent on the sizes of the guest ions. Herein, we report on the use of a porous amorphous iron phosphate synthesized using ambient temperature strategies as a potential host that stores electrical energy through the feasible insertion of mono-/di-/tri-valent ions. A combination of ex situ studies reveals the existence of a reversible amorphous-to-crystalline transition in this versatile electrode during electrochemical reactions with monovalent sodium, potassium and lithium. This reconstitutive reaction contributes to realizing specific capacities of 179 and 156 mAhg − 1 versus sodium and potassium at current densities of 10 and 5 mAg − 1 , respectively. This finding facilitates the feasible development of several amorphous electrodes with similar phase behavior for energy-storage applications. NPG Asia Materials (2014) 6, e138; doi:10.1038/am.2014.98; published online 17 October 2014 INTRODUCTIONSince 1990, the global demand for electricity has increased twice as much as the demand for energy overall, and the demand for electricity is expected to further increase by more than two-thirds over the next 20 years. Energy storage/conversion technologies have therefore become a crucial research topic as we seek to make society sustainable. In particular, electrical energy storage is critical not only for supporting electronic, vehicular and load-leveling applications but also for efficiently commercializing renewable solar and wind power. Rechargeable Li-ion batteries with an output energy exceeding 90% have emerged as one of the most effective electrochemical energystorage technologies, and these batteries power most modern-day electronic devices. 1 Despite substantial research to enhance Li-ion batteries for high-power applications, aspects such as their availability, cost and safety still remain to be fully addressed. 2 The controversies surrounding the accessible global lithium reserves and the anticipated energy demand may greatly impact the cost of Li-ion batteries in the long term. 3 Although advancing Li-ion battery technologies for electric vehicle applications is attractive, the quest for alternative energy sources for smart grid-scale storage applications has recently gained significant momentum. Rechargeable sodium and potassium batteries offer tremendous potential because they utilize inexpensive, abundant and environmentally benign sodium/potassium elements. [4][5][6][7][8][9] However,

Tailoring the shape of amorphous nanomaterials: recent developments and applications

“…Therefore, nanosized amorphous materials should have better cycling performance during the discharge/charge process than bulk crystalline ones. In addition, the high level of disorder in amorphous materials decreases charge transport resistance [10] and enhances the ability to host charge carrier ions [95], the latter of which is illustrated in Fig. 12.…”

Kinetically controlled formation of uniform FePO4 shells and their potential for use in high-performance sodium ion batteries

“…[6][7][8] Amorphous iron phosphates have been identified as a promising cathode material for SIBs in view of their unique properties. Compared with its crystalline counterpart, the amorphous framework of FePO 4 is defect free, can provide more available sites for Na ions and can exhibit less structural confinement to the reversible insertion/extraction for Na ions, [9][10][11] which ensure a much improved structural stability over long-term cycling. Unfortunately, iron phosphates themselves are well known for their poor electronic conductivity, 12,13 leading to sluggish electron transport during cycling, which becomes a critical issue in the consideration of FePO 4 as a practical cathode material.…”

Non-Aqueous K-Ion Battery Based on Layered K0.3MnO2and Hard Carbon/Carbon Black

“…18 From 2012 on, other studies reported the performance of different active materials (amorphous FePO 4 , FeSO 4 F, carbon nanofibers, organic electrode) in potassium-metal cells and with different organic electrolytes. [19][20][21][22] The use of K metal is not likely to be accepted for a practical application due to severe safety concerns, which are undoubtedly higher than for Li or even Na metal. For this reason, interest lies in finding suitable anode materials which can be applicable in K-ion full cells, thus reducing the risks associated with K metal.…”