Kezhu Jiang

Reversible anionic redox activity in Na3RuO4 cathodes: a prototype Na-rich layered oxide

Sodium-ion batteries are attractive for large-scale energy storage due to the abundance of sodium, but the deficient capacity achieved by cathode materials prevents their further applications. Chemical substitution of Na in transition metal layers is a promising solution to utilize both the cationic and anionic redox activities for boosting energy storage. Unfortunately, different from the classic Li-rich Li2MnO3, a pure prototype with anionic redox activity has not been found among the typical Na-rich cathodes. Herein, we originally design a Na-rich layered oxide prototype, namely Na3RuO4 (Ru5+), which delivers a partial reversible capacity solely via the participation of oxygen anions. More importantly, the anionic redox activity is validated by the in situ Raman observation of reversible peroxo-based O–O (de)bonding upon cycling. Our findings not only highlight the multiple electron-transfer strategy for capacity extension, but also broaden the horizon in designing Na-rich electrode materials for high-energy sodium-ion batteries.

An ultrafast rechargeable lithium metal battery

Rechargeable lithium metal batteries have been regarded as one of the most attractive high-energy-density batteries due to their large specific capacity and the lowest reduction potential of metallic lithium. However, the uncontrollable Li dendrite growth and the resulting unstable interfaces during repeated Li plating/stripping lead to severe safety issues and a short cycle life, which are aggravated especially at a high current density. Herein, we present an organic/inorganic composite protective layer via pretreating the lithium metal in an Mn(NO3)2-containing carbonate electrolyte, not only enabling stable lithium deposition and formation with a prolonged cycle life, but also providing a record high rate of 20 mA cm−2 with a minimized overpotential of 60 mV in a symmetric lithium cell. Results indicate that such an artificial protective film could effectively prolong the cycle life of Li|Cu cells, and greatly improve the comprehensive electrochemical performance of Li|LiMn2O4 cells. The pretreated-Li|LiMn2O4 cells show an outstanding cycling performance with 83% capacity retention over 200 cycles at a high rate of 2C and a high temperature of 55 °C, and exhibit robust recovery capabilities with a high capacity and coulombic efficiency after the cycles at 10C. These findings highlight the significance of a protective layer in stabilizing a Li metal anode and pave a new way for designing high-energy batteries for practical utilization.

Amorphous P2S5/C Composite as High-Performance Anode Materials for Sodium-Ion Batteries

We show a general method for achieving high-performance sodium storage materials via transforming crystalline P2S5 to amorphous P2S5 adhered to carbon matrix. The amorphous P2S5/C composite shows unique structural characteristics differing from the crystalline, which is identified by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscope (TEM) and so on. The amorphous P2S5/C composite exhibits a safe average potential of 0.82 V, a reversible capacity of 400 mA h g-1, a remarkable capacity retention of 89.4% over 4000 cycles as well as good rate capability. Our findings open up opportunities to design of advanced anodes for room-temperature sodium-ion batteries.