Phosphorus compounds, such as metal phosphides and phosphates have shown excellent performances and great potential in electrochemical energy storage, which are demonstrated by research works published in recent years. Some of these metal phosphides and phosphates and their hybrids compare favorably with transition metal oxides/hydroxides, which have been studied extensively as a class of electrode materials for supercapacitor applications, where they have limitations in terms of electrical and ion conductivity and device stability. To be specific, metal phosphides have both metalloid characteristics and good electric conductivity. For metal phosphates, the open-framework structures with large channels and cavities endow them with good ion conductivity and charge storage capacity. In this review, we present the recent progress on metal phosphides and phosphates, by focusing on their advantages/disadvantages and potential applications as a new class of electrode materials in supercapacitors. The synthesis methods to prepare these metal phosphides/phosphates are looked into, together with the scientific insights involved, as they strongly affect the electrochemical energy storage performance. Particular attentions are paid to those hybrid-type materials, where strong synergistic effects exist. In the summary, the future perspectives and challenges for the metal phosphides, phosphates and hybrid-types are proposed and discussed.

Metal Phosphides and Phosphates-based Electrodes for Electrochemical Supercapacitors.

Lithium cobalt oxide, LiCoO2, has been the most widely used cathode material in commercial lithium ion batteries. Nevertheless, cobalt has economic and environmen- tal problems that leave the door open to exploit alternative cathode materials, among which LiNixCoyMn1−x−yO2 may have improved performances, such as thermal stability, due to the synergistic effect of the three ions. Recently, intensive effort has been directed towards the development of LiNixCoyMn1−x−yO2 as a possible replacement for LiCoO2. Recent advances in layered LiNixCoyMn1−x−yO2 cathode materials are summarized in this paper. The preparation and the performance are reviewed, and the future promising cathode materials are also prospected.

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Recent advances in layered LiNixCoyMn1xyO2 cathode materials for lithium ion batteries

Currently, the application of new energy conversion and storage technologies is urgent in order to meet the increasing requirements for energy. Rechargeable batteries are universal devices, and among them, the use of lithium-ion batteries and sodium-ion batteries is particularly extensive, and they show great potential. Thus, it is necessary to find suitable anode materials that have the capability of playing a dual storage role in both lithium-ion batteries and sodium-ion batteries. This review summarizes and evaluates recent progress in the research on dual anode materials for lithium-ion batteries and sodium-ion batteries in detail. The morphologies, synthesis schemes, and electrochemical performances of these materials and future prospects in this field are also included.

Dual anode materials for lithium- and sodium-ion batteries

Carbon quantum dots from glucose oxidation as a highly competent anode material for lithium and sodium-ion batteries

Low-cost electrochemical energy storage systems (EESSs) are urgently needed to promote the application of renewable energy sources such as wind and solar energy. In analogy to lithium-ion batteries, the cost of EESSs depends mainly on charge-carrier ions and redox centers in electrodes, and their performance is limited by positive electrodes. In this context, this Minireview evaluates several EESS candidates and summarizes the known mixed polyanionic compounds (MPCs)-a family with robust frameworks and large channels for ion storage and migration. After comprehensive analysis, it is pointed out that a deeper exploration of MPCs may generate numerous novel crystallographically interesting compounds and excellent cathode materials for low-cost energy storage applications.

Mixed Polyanionic Compounds as Positive Electrodes for Low-Cost Electrochemical Energy Storage

Synthesis of One Dimensional Li2MoO4 Nanostructures and Their Electrochemical Performance as Anode Materials for Lithium-ion Batteries

Structural and electrochemical properties of Na2VMn2(PO4)3/C as cathode materials for sodium-ion batteries

Layered Li-rich vanadium phosphate Li 9 V 3 (P 2 O 7 ) 3 (PO 4 ) 2 : cathode and anode materials for lithium-ion batteries

A new alluaudite-type Na2VFe2(PO4)3 with carbon composite has been prepared for the first time via a simple sol-gel method using citric acid as an assistant agent and carbon source. The crystal structure and morphology of Na2VFe2(PO4)3/C composite are well characterized by X-ray diffraction, scan electron microscope, and energy-dispersive X-ray analysis. The experimental results show that a three-dimensional [VFe2(PO3)3]2− framework in this alluaudite structure provides two types of tunnels to enable the sodium-ion transporting which contributes to the electrochemical performance. When evaluated as a cathode for sodium-ion batteries, Na2VFe2(PO4)3/C composite delivers the first specific charge capacity of 66.7 mAh g−1 and discharge capacity of 65.8 mAh g−1 at 5 mA g−1 current density. After 100 cycles, the charge capacity (~52.2 mAh g−1at 5 mA g−1) shows a good capacity retention (~78%) compared to the first cycle. Cyclic voltammetric profiles confirm the activated multi-electron reactions including the Fe2+/Fe3+, V2+/V3+, and V3+/V4+ redox couples. Furthermore, the diffusion coefficient of sodium-ion (D
 Na
 +) in this structure is also calculated based on the result of electrochemical impedance spectroscopy.

Synthesis of alluaudite-type Na2VFe2(PO4)3/C and its electrochemical performance as cathode material for sodium-ion battery

Cheese-like bulk carbon with nanoholes has been successfully fabricated from egg white via a simple annealing method by using distilled water as a green clean “corrosive agent”. X-ray diffractions and SEM images show the decomposition product of boiled egg white after annealing is bulk carbon, containing NaCl and KCl with a trace amount of nitrogen doping. After ultrasonic washing and centrifugation, the distilled water removed the NaCl and KCl nanocrystals from the bulk carbon completely and retained empty spaces, which eventually leads to the formation of a cheese-like structured bulk carbon with nanoholes. Our electrochemical tests show this cheese-like bulk carbon with nanoholes has a high specific capacity and good cycling performance and rate stability when evaluated as an anode material for lithium-ion batteries. Meanwhile, the electrochemical performances as an anode material for a sodium-ion battery are also displayed for comparison.

Mingming Wen

Papers

Synthesis of One Dimensional Li2MoO4 Nanostructures and Their Electrochemical Performance as Anode Materials for Lithium-ion Batteries

Structural and electrochemical properties of Na2VMn2(PO4)3/C as cathode materials for sodium-ion batteries

Layered Li-rich vanadium phosphate Li 9 V 3 (P 2 O 7 ) 3 (PO 4 ) 2 : cathode and anode materials for lithium-ion batteries

Synthesis of alluaudite-type Na2VFe2(PO4)3/C and its electrochemical performance as cathode material for sodium-ion battery

Cheese-like bulk carbon with nanoholes prepared from egg white as an anode material for lithium and sodium ion batteries