Qinzhi Lai

A High‐Energy‐Density Redox Flow Battery based on Zinc/Polyhalide Chemistry

Zn and the Art of Battery Development: A zinc/polyhalide redox flow battery employs Br(-) /ClBr(2-) and Zn/Zn(2+) redox couples in its positive and negative half-cells, respectively. The performance of the battery is evaluated by charge-discharge cycling tests and reveals a high energy efficiency of 81%, based on a Coulombic efficiency of 96% and voltage efficiency of 84%. The new battery technology can provide high performance and energy density at an acceptable cost.

Cage-Like Porous Carbon with Superhigh Activity and Br2-Complex-Entrapping Capability for Bromine-Based Flow Batteries

Bromine-based flow batteries receive wide attention in large-scale energy storage because of their attractive features, such as high energy density and low cost. However, the Br2 diffusion and relatively low activity of Br2 /Br- hinder their further application. Herein, a cage-like porous carbon (CPC) with specific pore structure combining superhigh activity and Br2 -complex-entrapping capability is designed and fabricated. According to the results of density functional theory (DFT) calculation, the pore size of the CPC (1.1 nm) is well designed between the size of Br- (4.83 Å), MEP+ (9.25 Å), and Br2 complex (MEPBr3 12.40 Å), wherein Br- is oxidized to Br2 , which forms a Br2 complex with the complexing agent immediately and is then entrapped in the cage via pore size exclusion. In addition, the active sites produced during the carbon dioxide activation process dramatically accelerate the reaction rate of Br2 /Br- . In this way, combining a high Br2 -entrapping-capability and high specific surface areas, the CPC shows very impressive performance. The zinc bromine flow battery assembled with the prepared CPC shows a Coulombic efficiency of 98% and an energy efficiency of 81% at the current density of 80 mA cm-2 , which are among the highest values ever reported.

Synthesis of a meso–macro hierarchical porous carbon material for improvement of O2 diffusivity in Li–O2 batteries

Meso–macro hierarchical porous carbon (HPC) is prepared and used as a cathode material in Li–O2 batteries. The O2 diffusivity has been largely improved due to the unblocked macropores. As a result, a better pore utilization and extremely high discharge capacity is achieved.

Relationship between activity and structure of carbon materials for Br2/Br− in zinc bromine flow batteries

Zinc bromine flow battery (ZBFB) is one of the highly efficient and low cost energy storage devices. However, the low operating current density hinders its progress. Developing high activity cathode materials is an efficient way to reduce cell electrochemical polarization and improve the operating current density. Thus, it is essential to study the relationship between the activity and structure of carbon materials to optimize the performance of ZBFB. The pore parameters and phase structure of four commercialized carbon materials were investigated by an N2 sorption isotherm experiment and X-ray diffraction (XRD), respectively. The electrochemical property of the four carbon materials was systematically studied by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) and the kinetic parameters and diffusion coefficients were calculated. The results indicate that specific surface area, pore size distribution and electrical conductivity are the main factors affecting the electrochemical activity of carbon materials. The carbon material with high surface area, suitable pore size distribution and excellent electrical conductivity shows high activity to the Br2/Br− redox couple in ZBFB. This study lays foundations for developing cathode materials of excellent activity for ZBFB, which can efficiently improve the power density, reduce the stack size of the ZBFB and boost its potential for commercial application.

Performance and potential problems of high power density zinc–nickel single flow batteries

High power density with high efficiency can facilitate rapid charge–discharge and reduce the cost of zinc–nickel single flow batteries, and therefore it is of significant technological importance. In this paper, the battery performance and potential problems have been investigated at high current density up to 300 mA cm−2, which is the highest current density that has ever been obtained. The results show that coulombic efficiency first increases and then decreases with the current density increasing due to the non-uniform distribution of electrode potential and side reactions. The positive electrode deeply discharges and zinc accumulates on the negative electrode at the end of the discharging process at a high current density. The morphologies of the deposited zinc vary from smooth, spongy to dendrite with the increasing current density. Moreover, the positive polarization is a critical obstacle to improve the performance of zinc–nickel single flow batteries at a high current density. Based on these findings, we point out the remaining issues and struggling directions enabling high power density ZNBs without the substantial loss of cycle life.