Microwave synthesized TiP₂O₇ assisted by carbon‐coating as anode material for aqueous rechargeable lithium‐ion batteries

Abstract

TiP 2 O 7 and carbon-coated TiP 2 O 7 were successfully synthesized via a rapid microwave method and were electrochemically tested in 1 M Li 2 SO 4 aqueous electrolyte. Physical properties were characterized through X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy, and transmission electron microscopy. The relationship between processing parameters (graphite concentration, ball mill duration, microwave energy input, heating duration) and the final products' electrochemical performance was studied. Full cell tests with LiMn 2 O 4 cathode materials were also tested to obtain cycling stability and rate performance results. The highest specific capacity of C-TiP 2 O 7 was 109 mAh g-1 (90.1% of the theoretical capacity) from the cyclic voltammetry test with the scan rate of 0.3 mV s-1. After 200 cycles under the rate of 0.5C, the C-TiP 2 O 7 's capacity still maintained 92% of the initial capacity. These results suggested that the rapid microwave synthesis method is a promising process to synthesis the electrode materials with excellent electrochemical performances. K E Y W O R D S anode material, aqueous rechargeable lithium-ion batteries, energy storage, rapid processing technology 1 INTRODUCTION Lithium-ion batteries are playing a significant role in electronic products like smartphones, laptops, digital cameras, portable music players. [1] Rüetschi has come up with the "three E" criteria: Energy, Economics, and Environment, [2] in which batteries need to be designed to improve the wellness of the environment and to store energy with a safe, efficient, and convenient method. The Aqueous Rechargeable Lithium-ion Battery (ARLB) This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Regulating the PO4 and TiO6 Polyhedral Building Blocks in TiP2O7 Boosts the Potassium Ion Diffusion Kinetics

“…Potassium-ion batteries (PIB) have gained prominence for energy storage technology research owing to the abundant reserve and low cost of K. − Moreover, the lower desolvation energy and the smallest Stokes radius of K + (3.6 vs 4.8 Å for Li and 4.6 Å for Na) stand a good change of accelerating K + diffusion kinetics in organic electrolytes. − Unfortunately, the large radius of K + results in tremendous volume change and sluggish reaction kinetics, which incurs severe capacity degeneration and poor structural integrity over long-time cycling. ,, Particularly, layered anode materials usually suffer from huge volume changes on K + intercalation, while alloy conversion-type anodes even expand up to 200–400%, such as Bi, Sn, Sb, and P. − Therefore, it is meaningful and urgent to develop low-cost and durable anode materials with fast reaction kinetics. ,, …”

“…Compared with the aqueous batteries, chemical and electrochemical processes in organic electrolytes are more simple in nonaqueous electrolytes because of many side reactions from the O 2 and water involved in aqueous electrolytes . Moreover, owing to the rigid 3D open-framework structure of TiP 2 O 7 , all the proposed synthetic strategies are generally based on the reaction between phosphoric acid (H 3 PO 4 ) and TiO 2 precursor, which involves a complicated synthetic route stemming from the use of additives that ineluctably either sacrifice the desired crystal structure or undermine the surface reactivity, giving rise to bulk TiP 2 O 7 with atactic morphology and low purity. ,, Although the incorporation of the carbon matrix in heterostructure engineering can regulate the particle sizes and morphology of TiP 2 O 7 to some extent, it should be mentioned here that the density of the active material is extremely diluted when considering the low content of TiP 2 O 7 in the heterostructure, and the attained K + storage mechanism is greatly intervened by the dominant presence of conductive carbon. − More importantly, the exotic K + uptake will probably impair the configuration/connectivity of TiO 6 and PO 4 polyhedral building blocks owing to the intrinsic local distortions and defect of the constituent TiO 6 octahedra, which further exacerbates the collapse of structure and capacity fading during cell operation despite the delicate nanoengineering strategy that is otherwise accompanied by large irreversible capacities. , Precisely because of this, the detailed mechanism of K + diffusion (or hoping) kinetics in the TiP 2 O 7 skeleton is still elusive. As a matter of fact, atomic-scale control over the arrangement in building blocks of materials is essential for the creation of novel nanostructures with multifarious crystal structures and regulation of the K + migration path.…”