Initial Electrode Kinetics of Anion Intercalation and De‐intercalation in Nonaqueous Al‐Graphite Batteries^†

Abstract

Graphite electrode | Anion intercalation | Al battery | Electrochemical kinetics | Diffusion Graphitic materials with intercalated sites are considered as the mostly used positive electrode materials in nonaqueous Al batteries. Unlike the small-size cations, the intercalation/de-intercalation of large-size anions into/out of graphite would induce large volume expansion and micro-structure reconfiguration, leading to unexpected coulombic efficiency in the full cells (<95% within initial several cycles). For understanding the irreversible processes induced by anion intercalation/de-intercalation (AlCl 4-), here the kinetics of first two cycles for the Al-graphite batteries have been systematically studied. To study kinetics behaviors at representative states, a combined method upon galvanostatic intermittent titration technique and electrochemical impedance spectroscopy has been carried out. The achieved diffusion coefficients of the positive electrodes assembled with different graphite sizes suggest that size effect also plays a critical role in determining the electrochemical kinetics in the mass transport in both electrolyte and graphitic layers as well as in interface reaction. The morphologies and micro-structures of the post-cycled graphite electrodes have been also experimentally studied, which also well supports the irreversible intercalation/de-intercalation behaviors in graphite electrodes. The results offer a significant platform to well understand the essential factors in tailoring coulombic efficiency from a kinetic view, which would be helpful in promoting the graphite electrodes in Al batteries.

Nonaqueous Rechargeable Aluminum Batteries: Progresses, Challenges, and Perspectives

“…The experimental results also confirmed the practical diffusion coefficient of graphite electrode. The results indicate that the value could reach on the order of ∼10 –8 cm 2 s –1 in nonaqueous RABs, which would decrease with progressive AlCl 4 – anion intercalation …”

“…The results indicate that the value could reach on the order of ∼10 −8 cm 2 s −1 in nonaqueous RABs, which would decrease with progressive AlCl 4 − anion intercalation. 125 For 3D diffusion with geometry factor b of 6, the diffusion coefficient can be written as eq 32: 123…”

Design Strategies of High‐Performance Positive Materials for Nonaqueous Rechargeable Aluminum Batteries: From Crystal Control to Battery Configuration

“…Han et al. [ 66 ] determined that the selection of appropriate graphite powders could be an essential factor in influencing the electrochemical performance of Al‐graphite cells because the graphite size could fundamentally determine the kinetics of both mass transport in the electrolyte and diffusion ability in the graphitic layers.…”

Impact of Aluminium Electrode Potential during Charging on Aluminium‐Ion Battery Performance with TEA‐AlCl3 Electrolyte

“…À intercalation into the graphite matrix. [10,11] Han et al [12] compared the performance of four different graphite materials and concluded that graphite size affects the reversibility and kinetics of AlCl 4 À diffusion into graphite electrodes during intercalation/deintercalation processes. They claimed that graphite morphology influences the trapping, diffusion coefficient and mass transfer kinetics of AlCl 4 À intercalation/deintercalation into/from graphite.…”