Low Cost, Solvent-Free Lithium-Ion Battery Electrode Manufacturing Based on Electrostatic Dry Powder Coating
Authors: Chaves Juan Scott , Bree Gerard , John Low Chee Tong 
Published: November 2022

Conventional industrial processes for the manufacture of Lithium-Ion Battery (LIB) electrodes are costly and not environmentally friendly. The state-of-the-art slurry casting technique utilizes a large amount of toxic N-methly pyrollidinone (NMP), necessitating significant energy and capital costs associated with electrode drying and solvent recovery.

Electrostatic Dry Powder Deposition (EDPD) is well established in many industries as an effective method of achieving well-adhered and uniform coatings of controlled thickness & composition. Recently, a small number of studies have demonstrated the viability of EDPD in LIB electrode manufacture, achieving cell capacities similar to, or exceeding, those from slurry casting. Crucially, this approach eliminates the need for solvent usage. Nevertheless, several challenges remain before EDPD can be adopted within the LIB industry. In particular, achieving adequate dispersion of powder materials and a level of adhesion sufficient for use in standard roll-2-roll lines.

With the goal of developing & demonstrating the viability of the EDPD process, this work will present a solvent-free approach, coupled with innovative methods to improve adhesion and overall coating quality. The high voltage spinel cathode Lithium Nickel Manganese Oxide (LNMO) was utilized as a demonstrator material, as it can provide high energy density cells without the use of expensive and rare cobalt. Results will include: (a) development of EDPD equipment and appropriate process parameters, (b) optimization of coating formulation, (c) adhesion enhancement through through the use of in-situ heating and post-deposition treatments, (d) electrochemical analysis of EDPD electrodes and benefits compared with slurry casting, (e) full process cost analysis. The presentation will conclude with a discussion of the potential of this new manufacturing technique to disrupt the LIB industry.

Rechargeable lithium-ion batteries (LIBs) are ubiquitous in mostly every electronic device. However, the process of manufacturing LIBs is costly and not environmentally friendly. State of the art LIB electrode manufacturing is carried out using slurry casting. A mixture of active material (most commonly containing Cobalt), a binder and a conductive additive are mixed with a solvent and cast onto a substrate. This process is energy-intensive and requires significant capital for drying equipment and processes and the recovery of toxic solvents, such as N-methyl pyrrolidone (NMP).

Utilising an EDPD process with a Cobalt free active material such as LNMO in place of the slurry casting process would eliminate the need to use toxic solvents, thereby significantly reducing the manufacturing time and cost. Additionally, LNMO can work as a replacement for the next-generation lithium-ion battery Cobalt-free cathode materials due to its high lithiation/delithiation potential, > 4.5 V compared with 3 – 4 V in the case of more conventional cathode material.

The EDPD process presented has demonstrated that a reduction in cost of over 35% can be achieved when tested with LNMO, polyvinylidene fluoride (PVDF) as binder and Carbon Black (CB) as a conductive additive, by eliminating the use of NMP and Cobalt from the process. This is based on a comparison carried out with 1kg of active material mix. There are challenges associated with dry powder electro manufacture for LIBs, such as achieving good adhesion, tortuosity, and obtaining an even dispersion and thickness of the coating. This work addresses these challenges and develops an innovative dry powder deposition method assisted with a low power laser to improve adhesion in a scalable manner.

Using a combination of EDPD, low heat and low power laser as an enhancement for the adhesion process in electrode manufacture create an innovative opportunity to remove the toxic solvents to achieve good dry powder depositions making the process less energy demanding and more environmentally friendly. The present research will focus on how to produce dry electrodes with electrostatic coating manufacture, the process innovation of adding a Laser to improve the adhesion and electrochemical testing to quantify the LIB's performance when using this approach.

Early research has shown that the manufactured electrodes have similar capacity retention and improved rate capability in lithium-ion batteries when compared to the current state of the art of slurry casting. The simple process operation offers flexibility in scalable production and modularity for future development and commercial implementation.