Heated Calendering of Cathodes for Lithium‐Ion Batteries with Varied Carbon Black and Binder Contents

Abstract

Electrodes are usually calendered to enhance the energy density and improve the electrochemical cell performance. However, low porosities can compromise these two important features. To achieve the optimum porosity, a comprehensive process control is of major interest. This study further develops a Heckel‐based compaction model considering the impact of the roll temperature and discusses the effect of the composition. Increasing the temperature of the roll linearly decreases the achievable coating porosity and the line load effort due to the rise of the elastic deformability of the thermoplastic binder PVDF. Reduced contents of simultaneously less‐distributed additives increase the achievable coating porosity. Furthermore, the poor distribution is the main factor for lower line load efforts with lower additive contents. Moreover, the adhesion strength of the coating improves with increasing the temperature of the rolls due to the thermal rising of the elasticity of the binder.

On the Use of Carbon Nanotubes in Prototyping the High Energy Density Li‐ion Batteries

“…It is known that a high compression rate of the electrode reduces its porosity resulting in poorer wettability by an electrolyte . At the same time, an increase in the roll temperature results in both better C‐rate performance and cycling stability, which may be associated with becoming PVDF more flexible at higher temperature and, as a result, improvement the adhesion strength and electrical interface between cathode layer and current collector . We determined that for the electrodes studied in the work, the most optimal compression rate is of 10% at a roll temperature of 100 °C.…”

Accelerating Battery Manufacturing Optimization by Combining Experiments, In Silico Electrodes Generation and Machine Learning

“…Our hybrid methodology was used to analyse the effect of the applied calender pressure (P) on the following electrode properties: (i) tortuosity (t) and electrolyte effective conductivity calendering, they occupy a higher fraction of the latter region, generating a more compact electrode. 46 On the other side, higher values output lower porosities after calendering, indicating that an initially more porous electrode would have more degrees of freedom to reorganize its structure upon an applied pressure, which leads to a more compact and interconnected solid phase network. This is of major importance for the electrode manufacturing process, as during the coating and drying stages the process parameters should be controlled to reach an optimal porosity.…”

Calendering of Li(Ni0.33Mn0.33Co0.33)O2‐Based Cathodes: Analyzing the Link Between Process Parameters and Electrode Properties by Advanced Statistics

“…As this property is related with the contacts between the particles and the binder adhesion, its low sensitivity in terms of the calendering conditions can be related to the low amount of polymer and carbon additive used for the electrode formulation. Besides us, few studies have dealt with the calendering impact on the electrode adhesion [23,32] . Non‐linear relations were also found on those studies and it was also concluded that the loss of particle contact sensitivity towards calendering when working with low binder/carbon additive electrodes.…”

“…The analysis of ϵ vs. calender pressure profiles is based on the Heckel equation [37] [Eq. (2)], which was adapted to analyze the compressibility of composite electrodes, [23] as shown in Eq. 2): …”

“…focused on developing empirical models for understanding the impact of calendering process parameters on the uncertainties and the key factors that condition the electrochemical performance upon reduction of the ϵ . Comprehensive research was also conducted to understand the impact of applied calender pressure, temperature and line speed (separately) over a range of properties such as pore size distribution, electrode mechanical features, coating density and rearrangement over different kind of electrodes, such as graphite, NMC and LMO [20–23] . Furthermore, we recently published a machine learning‐experimental hybrid approach to rationalize the impact of calendering pressure over the ϵ , the electronic and ionic conductivities, particles contact with the current collector and active material active surface area for NMC‐based cathodes in terms of the amount of active material used to prepare the electrodes [10] …”