On charge percolation in slurry electrodes used in Vanadium Redox Flow Batteries

In vanadium redox flow battery systems porous carbon felts are commonly employed as electrodes inside the flow channel. Recently, slurry electrodes (or flow suspension electrodes) were introduced as a potentially viable electrode system. Such electrode systems are little understood so far. Mass, momentum and charge transfer phenomena co-occur, interactions with each other are nearly impossible to capture experimentally. We present a novel discrete model of the particulate phase combining theories from fluid dynamics, colloidal physics, and electrochemistry with a coupled CFD-DEM approach. The methodology allows to visualize local phenomena occurring during the charging of the battery and to compute the net current of the slurry electrode system. We demonstrate that an increasing particle volume fraction enables the formation of conducting networks in the flow electrode until a threshold is reached. Our study concludes, that the assumption of all particles participating in the charge transfer as assumed in pure CFD investigations is not necessarily valid.

Phosphorus and oxygen co-doped composite electrode with hierarchical electronic and ionic mixed conducting networks for vanadium redox flow batteries

The GF-TCN electrodes with excellent electrocatalytic activity and faster electron/ion conduction indicate outstanding rate capability and energy efficiency of VRFBs.

Graphene-Carbon Nanotubes-Modified LiFePO4 Cathode Materials for High-Performance Lithium-Ion Batteries

A nanocrystalline LiFePO4/graphene-carbon nanotubes (LFP-G-CNT) composite has been successfully synthesized by a hydrothermal method followed by heat-treatment. The microstructure and morphology of the LFP-G-CNTs composite were comparatively investigated with LiFePO4/graphene (LFP-G) and LiFePO4/carbon nanotubes (LFP-CNT) by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The LFP-G-CNTs nanoparticles were wrapped homogeneously and loosely within a 3D conducting network of graphene-carbon nanotubes. The conducting networks provided highly conductive pathways for electron transfer during the intercalation/deintercalation process, facilitated electron migration throughout the secondary particles, accelerated the penetration of the liquid electrolyte into the LFP-G-CNT composite in all directions and enhanced the diffusion of Li ions. The results indicate that the electrochemical activity of LFP-G-CNT composite may be enhanced significantly. The charge-discharge curves, cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS) results demonstrate that LFP-G-CNT composite performes better than LFP-G and LFP-CNT composites. In particular, LFP-G-CNT composite with a low content of graphene and carbon nanotubes exhibites a high initial discharge capacity of 168.4 mAh g−1 at 0.1 C and 103.7 mAh g−1 at 40 C and an excellent cycling stability.

Nanocellulose/polypyrrole aerogel electrodes with higher conductivity via adding vapor grown nano-carbon fibers as conducting networks for supercapacitor application

The electrochemical performances of nanocellulose-based electrode materials were improved via building nano-carbon conducting networks.