Julian Kalhoff, Battery Business Development Manager
Electric vehicle (EV) batteries have played a crucial role in improving sustainability for the automotive industry and will continue to be a major tool as more people focus on reducing their environmental impact. However, battery production could soon be challenged as some EU-based governments have proposed chemical bans that include materials used in the battery manufacturing process. Knowing this, the EV market must commit to creating sustainable and innovative solutions that improve battery performance while also meeting any potential regulations. A key component to answering these challenges lies in water-based binders.
Water-based binders, such as Latex binders, are critical to enabling essential battery function, despite only making up less than 1% of the total weight in lithium-ion (Li-ion) batteries. In particular, styrene butadiene (SB) latex is a state-of-the-art binder technology used throughout graphite-based anode electrode manufacturing to support battery performance. SB binders are non-electrochemical active components; however, they can support electrochemical cell processes by affecting electrode porosity and acting as a part in electrical and ionic conductivity. Moreover, SB binders offer mechanical electrode stability—enabling functionality even throughout charging and discharging, as the graphite particle volume can grow or shrink by up to 10% during this process.
Potential Legislative Concerns
Environmental and human health remains a top concern, and governments around the world are prioritizing the topic when developing new regulations that include chemical restrictions. Earlier this year, some EU member states proposed legislation to the European Chemicals Agency to phase out the use of per- and polyfluorinated substances (PFAS) in the European Union due to their persistence as an environmental pollutant and their negative impact on human health. A potential ban on the use of this family of chemicals would affect a plethora of products, including electric vehicle (EV) batteries, as the organic solvent-based polyvinylidene fluoride (PVDF) is the state-of-the-art binder system for lithium-ion battery cathode electrodes and falls into the PFAS category.
Knowing this, cell manufacturers and material providers are looking for more sustainable battery chemistries that can replace this material in EVs without compromising performance. Among others, water-based chemistries, such as styrene acrylate (SA)- and polyacrylic acid (PAA)-based technologies are considered more sustainable cathode binder systems to replace PFAS-based chemistries, while meeting performance needs.
Looking at Alternative Cathode Manufacturing Processes
One method to improve the sustainability of batteries is to incorporate water-based processing for Li-ion battery cathodes, limiting the amount of hazardous chemicals used throughout the battery production process.
Battery manufacturers are showing an increased interest in this method, as water-based processing of cathodes removes the need to use N-Methyl-2-pyrrolidone (NMP) as a solvent—applied in combination with PVDF binders and a known potential hazard to human health—and creates a more sustainable cell manufacturing process. Removing the chemical also eliminates the need for NMP handling and recycling facilities, in turn benefiting CAPEX and OPEX procedures.
Market leaders have already started to implement water-based cathode coating processes—not only for LPF cathode chemistries but also for high Nickel-containing NMC cathode chemistries.
Introducing New Materials
A primary goal of improving batteries is to increase their energy and power density—adding mileage and fast-charging potential to EVs. Silicon (Si) can be used as an active anode material to help manufacturers meet this goal. However, with Si addition to the anode, binder requirements become more demanding.
Depending on the Si particle structure, this material is subject to a volume expansion of up to 300% upon battery charging. This mechanical stress can lead to particle cracking and electrode delamination, resulting in a rapid cell performance drop that hinders manufacturers from adding large amounts of Si into the anode electrode.
Today, up to 10% of Si can be added to the graphite anode with commercially available binder systems, but there is the potential to develop new solutions so that the binder becomes an enabler to increase the Si amount. That’s why Trinseo is proud to be partnering with Ferroglobe PLC to jointly develop Si-rich anode solutions. Together, the companies can push the limits of battery performance and introduce new binder chemistries that can support even higher levels of silicon.
By examining new and more sustainable electrode manufacturing methods and material options now, material providers and cell manufacturers can proactively team up to create solutions that meet the performance needs for more sustainable EV batteries.