Car manufacturers have questioned whether they will be able to keep up with the Government’s Zero Emission Vehicle targets, which will require 28% of all car sales to be fully electric in 2025 as part of a broader plan to phase out all new gasoline and diesel vehicles by 2030.
Many car manufacturers are skeptical that demand will continue to rise in line with ZEV targets, with consumers raising concerns over costs and charging point capacity. Car makers failing to meet ZEV targets face the prospect of fines and compliance costs. At the same time, the Government is under pressure to meet net zero goals in the global fight against climate change.
As car manufacturers contemplate how to produce efficiently-running EVs at a sustainable price point to help boost demand, it is vital that battery production costs are optimized. From a commercial standpoint, lithium-ion batteries are still the preferred renewable power option for most car manufacturers. Ensuring that a battery’s four functional components – the cathode, anode, separator and electrolyte – are free of contaminants is critical for achieving maximum operational and cost efficiencies.
Protecting vital Cathode Active Materials
Creating the cathode – the positive electrode – involves the most complex process in EV battery manufacturing and its composition can account for around 40% of the battery’s cost. This elemental part of the technology also affects the battery’s performance. To allow the battery to operate at an optimal level, these materials must be as pure as possible. Contaminants diminish performance.
Cathode active materials are typically composed of metal oxides that are ground and mixed into a water-based slurry and then coated onto an aluminum foil which is then compressed, to create the cathode electrode. The most common cathode materials used in lithium-ion batteries include lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and lithium nickel manganese cobalt oxide.
Manufacturers of CAM face challenges due to the presence of other chemicals and materials that need to be removed, and the requirement to meet specifications on particle size and levels of contaminants. They must also preserve the structure of crystals and control their surface area and porosity.
Solving the contamination dilemma
This is where high performance filtration systems are needed to achieve the requisite levels of purity. A range of coarse metallic strainers, 0.3-5µm depth filters, and regenerable filters can be used to achieve liquid, chemical and gas purity levels that make the final cathode electrode more efficient and stable.
Contamination in the CAM slurry mix will reduce the electrode’s effectiveness resulting in lower battery performance and shorter discharge life. With increased CAM purity, manufacturers can maximize performance but only if other complementary factors such as electrolyte cleanliness and polymeric separator materials are also of a high material standard.
The processes for creating the anode are similar, by mixing graphite with a binder (often polyvinylidene fluoride) and a solvent such as N-methyl-2-pyrrolidone. This anode slurry is coated onto a copper foil.
Mitigating electrolyte corrosion
Cleanliness of the electrolyte is necessary to facilitate the transfer of the ions between the anode and cathode. The solution of lithium salts and organic must be pure enough to enable ionic conductivity, chemical and electrochemical stability, and thermal stability.
Controlling water content is essential. Moisture in the electrolytes can result in the formation of hydrofluoric acid from fluoride lithium salts. As HF can corrode certain metals – such as those present in internal battery components – it is critical to prevent moisture from encountering the electrolytes.
Due to the high degree of acidity of the electrolyte, chemically-resistant filter materials and fluoropolymer-coated stainless steel filter vessels are recommended. Filters with fine particulate removal ratings (0.45µm-2µm) are appropriate to achieve high levels of electrolyte cleanliness.
Advanced filtration systems: Paving the way for a zero-emission automotive future
Although the transition to EVs is challenging, shifting to zero-emission transport is imperative to meet decarbonization goals. In addition to government investment in financial incentives and EV infrastructure, any technologies that can help EV manufacturers increase cost efficiencies and bolster consumer demand must be leveraged. Modern filtration systems play a pivotal role in maximizing the purity and performance of batteries as well as protecting equipment and reducing unnecessary downtime.
Anoop Suvarna, Global Battery Materials Manager for Energy Storage at Pall Corporation
