Delamination behavior of lithium-ion battery anodes: Influence of drying temperature during electrode processing

Abstract

One essential process step during electrode processing for Li-ion batteries is the drying of the wet particulate electrode coating. The electrode film solidifies during evaporation of the solvent and a porous film is formed. In this study we focus on the influence of drying temperature on the internal electrode structure of the dry film. Anode slurries that consist of graphite and an aqueous binder system were coated and subsequently dried. To assure defined and controllable drying conditions, a laboratory set-up with a temperaturecontrolled substrate carrier and an impingement dryer was used. To facilitate a scale-up to continuously passed dryers the choice of experimental temperatures was based on a calculation of steady-state temperatures that result from gas temperatures that are commonly applied in industrial drying processes. The delamination behavior of the differently dried electrodes was investigated by means of a 90° peel test. The results show a strong dependency of electrode adhesion on drying temperature. A lower adhesion force at higher temperatures hints to a variation in binder content at the interface between the copper substrate and the coating layer. The formation of a consolidation Downloaded by [University of Manitoba Libraries] at 22:53 26 August 20152 layer at the air-film interface during drying is identified as a possible explanation and a criterion for consolidation layer formation is suggested.

Improvement of Lithium‐Ion Battery Performance by Two‐Layered Slot–Die Coating Operation

“…Baunach et al. found that, under high drying temperature conditions, the adhesion forces between the anode layer and substrate copper foil were relatively weak and the binder content in the region near the substrate was low . The present results on drying of cathodes at different temperatures appeared to be consistent with their observations.…”

“…The conventional method for drying the electrodes in LIBs is to use forced convection air drying. The drying temperature and air flow rate are the main parameters that control the dried electrode quality . Because the energy density requirement for LIBs used in EVs is much higher than that of 3C batteries, a thicker electrode containing more active material has to be used .…”

“…However, high‐temperature drying may also cause surface defects, uneven distribution of particles, binder migrations, and other heterogeneous structure problems. All of these factors may affect the electrochemical performance of the composite LIBs …”

Water‐Soluble Binders for Lithium‐Ion Battery Graphite Electrodes: Slurry Rheology, Coating Adhesion, and Electrochemical Performance

“…Baunach et al. reported that binder depletion at the current‐collector–coating interface compromised the adhesion properties if the drying rate was too fast and did not allow for back diffusion of the material . Furthermore, the rheological data on both the aqueous binder solutions and the electrode slurries indicates poorer particle bridging and networking with PAA‐Na.…”

Thermal characterization of Li-ion cell electrodes by photothermal deflection spectroscopy

“…The difference in absolute value may be attributed to (i) the intrinsic properties of the graphite particles and (ii) the thermal contact resistance between the particles, which is significantly influenced by the binder content and distribution. Additionally, the drying process and temperature impact the mechanical stability [43] and thus may influence the thermal resistances of anodes.…”