High Rate Capability of Graphite Negative Electrodes for Lithium-Ion Batteries

Abstract

The rate capability of various lithium-ion half-cells was investigated. Our study focuses on the performance of the carbon negative electrode, which is composed of TIMREX SFG synthetic graphite material of varying particle size distribution. All cells showed high discharge and comparatively low charge rate capability. Up to the 20 C rate, discharge capacity retention of more than 96% was found for SFG6. The rate capability of the half-cells is a function of both the particle size distribution of the graphite material and the preparation method of the electrode. A transport limitation model is proposed to explain the restrictions of the high current performance of graphite electrodes. The key parameters found to influence the performance of a graphite negative electrode were the loading, the thickness, and the porosity of the electrode.Lithium-ion batteries have attracted considerable scientific and technological attention for more than a decade. Being already broadly available for small portable electronic devices like mobile phones, laptop computers, video camcorders, and personal digital assistants, the field of commercial applications of lithium-ion batteries is gradually extending to large battery systems. A particular field of growing importance is the transportation sector, where the lithium-ion battery technology is envisaged for traction batteries in overall electric vehicles and for onboard ͑42 V͒ batteries in conventional, hybrid, and fuel cell vehicles. For these purposes, the vehicle battery must deliver sufficient power. At the same time, the automotive industry imposes good cycle and calendar lifetime 1,2 for the systems used with moderate material costs. Therefore, high-ratecapable and comparatively cheap electroactive materials are required for the development of high-power lithium-ion batteries. [3][4][5] Graphite materials with a high degree of graphitization based on synthetic or natural sources are attractive candidates for negative electrodes of lithium-ion batteries due to the relatively high theoretical specific reversible charge of 372 mAh/g. The electrochemical insertion of lithium into graphite leads to an intercalation compound with a chemical composition of LiC 6 . It was generally believed that graphite negative electrodes have only a moderate rate capability. 6,7 Slow kinetics 8,9 and a solid-state diffusion limitation during charge and discharge reactions were suggested as rationalities of why the graphite electrode does not deliver high currents. 10-12 Arora et al. 13 suggested that one of the most important parameters that limits the performance of lithium-ion batteries at high rates is the transport of lithium ions in the electrolyte. The transport of lithium ions in the solid phase takes place mainly within single particles, where diffusion lengths are much shorter than the thickness of the whole electrode. 13,14 However, recently we demonstrated that graphitebased electrodes support a much higher current density than believed before. 15 There are also other studies that could s...

Room-temperature sodium-ion batteries: Improving the rate capability of carbon anode materials by templating strategies

“…An additional potentiostatic step at 1.6 V was added during Na-deinsertion until the current dropped below 2 Â 10 À3 mA to allow equilibration of the system. 19 The overall shape of the voltage profile was similar for all porous carbons, as illustrated by two samples with similar surface area (Timrex 300 and templated carbon, Fig. 2).…”

Experimental and Modeling Analysis of Graphite Electrodes with Various Thicknesses and Porosities for High-Energy-Density Li-Ion Batteries

“…However, the experimental curve lies in between the basecase simulation and that without electrolyte limitation (i.e., ∼middle of the light blue area), thereby attesting once again that the experimental utilization decrease of high-loading electrodes is ascribed to liquid-phase limitation in agreement with earlier literature reports. 12 At current densities above ca 5 mA cm −2 , experimental potential curves of all designs are jagged in the same way as in Figure 11d, resulting in experiment repeats that produced large ranges of final utilization (See error bars in Figs. 4a-4c).…”

Toward Low-Cost, High-Energy Density, and High-Power Density Lithium-Ion Batteries

“…Graphite anodes used in commercial LIBs can achieve a reversible capacity >360 mAh/g, close to the theoretical value of 372 mAh/g for LiC 6 . [84][85][86] By contrast, even the best commercial cathodes are limited to gravimetric capacities around 200 mAh/g. 85,87 The cell voltage is also limited by the choice of cathode.…”