The Never Contented! How spray drying enables batteries to keep on keeping on.

The importance of batteries in the modern world cannot be ignored. There is a continual desire for longer-lasting, more efficient batteries capable of powering larger and larger devices. An increasing number of industries are turning to batteries to power their devices, from vacuum cleaners to cars and even electric aircraft. These developments are being driven by the need to reduce emissions, lower noise levels, and decrease operating costs. Always with an eye on the latest laboratory equipment and methods, I focus on the role spray drying plays in producing the electrode materials used in modern batteries.

My wife finally replaced her aging laptop that she bought new in 2010. The phrase “if it ain’t broke, don’t fix it” may well have been coined by my wife, who is always determined to keep things running as long as humanly possible. It is a tremendous attitude to have, especially these days, given the pervasive throw-away culture that exists. In this regard, I am not as good as my wife, as I am always enthralled by the latest technology. After receiving her new laptop, the main thing that impressed her was its incredible battery life compared to her old computer. Obviously, the battery life of her original laptop had deteriorated over time; it could barely stay on for 20 minutes without being plugged in before it was finally replaced. Regardless, the new laptop’s battery life far exceeded the original battery life of the old laptop, even when new. It is also likely that the battery’s cycle life in the new laptop will exceed the one she replaced, meaning she may use it even longer than the last one!

In a few cases, replacing and upgrading equipment may be the more sustainable long-term option. I recently wrote about the latest Supercritical Fluid Chromatography instruments that offer more sustainable solutions when compared to traditional HPLC instruments. Another example of this is vehicles. Replacing an internal combustion engine (ICE) vehicle with an electric one could have long-term environmental benefits. As someone always enthralled by the latest and greatest technology, I have watched the advancements in electric vehicles with wonder. Initially skeptical about the range of such vehicles and the charging times, I have been impressed by the achievements made in these areas. In fact, the electric car is not technically the latest technology as they predate ICE vehicles. Before the advent of the ICE-powered vehicle attributed to Karl Benz, electric vehicles were common. It was, in fact, an electric vehicle that first broke the 100km/h land speed record in 1899. The vehicle, born out of an ongoing rivalry to hold the land speed record, was dubbed “La Jamais Contente” (The Never Contented) and was powered by two 25-kilowatt electric motors and two 100-volt, 124-amp batteries. Due to readily available and relatively cheap gasoline, ICE-powered vehicles that could be filled quickly and cover greater distances replaced electric-powered vehicles for almost a century. However, battery makers who remain ‘never contented’ are paving the way for the return of electric transport.

So how are battery developers able to continue making such improvements to the life cycle and capacity of modern batteries? The advancements in these areas and numerous other innovations arise from the field of material science, specifically developments in advanced materials. The manufacturing process for advanced materials starts with the production of raw materials and subsequent powder conditioning. This is where spray drying plays a significant role. The last step of the process involves pressing the powder and shaping it. With regard to spray drying, there are two approaches:

The bottom-up approach

Starts with the wet chemical synthesis of particles that are transformed into granules by spray drying, resulting in high-purity powders and well-defined properties.

The top-down approach

Starts with the material being ground into fine particles by a milling process. This results in dry fine powders or suspensions of fine particles, which are subsequently transformed into granules by spray drying.

Advanced materials are used in the electro-medical space and are integral to several the technologies we use every day. One such area is battery research, as advanced materials play a fundamental role in the development of anodes and cathodes in Li-Ion batteries. When the Li-Ion battery came to market in 1991, the anode material was made from graphite and the positive electrode was made of the mixed metal oxide Lithium Cobalt Oxide (LiCoO2), though nowadays, cathode materials are also made from spinel and olivine structures.

Mixed oxides, spinel, and olivine structures are used for their unique properties that contribute to electrochemical performance, thermal stability, and safety. Mixed metal oxides such as LiCoO2, NMC, and NCA are widely used for their high specific capacity, high energy density, and good cycling performance. The combination of different metal ions in a crystal lattice allows for fine-tuning properties such as ionic conductivity, structural stability, and redox potential. Spinel cathode materials have a three-dimensional crystal structure with Lithium and transition metal ions occupying specific lattice sites. The structure has several benefits, including high ionic and electronic conductivity. Olivine structures, such as Lithium Iron Phosphate (LiFeO4), have a one-dimensional structure where Lithium ions reside in channels surrounded by a metal-oxygen network. The structure has high structural stability offering excellent cycling performance and excellent thermal stability. The use of non-toxic elements such as Iron and Phosphorus makes olivine structures a particularly environmentally friendly solution. The huge variety of possibilities offered by these structures has left plenty of room for developments and advances over the years.

Continual research and development with advanced materials and structures have led to the great improvements we have witnessed over the years and developments are still being made. The graphite that was traditionally used in the first Li-Ion batteries was insufficient to meet the demands of the anode materials being used and tested due to their low theoretical specific capacity. Graphite was replaced with graphene in 2004 as it was discovered to be an excellent substrate for active materials. Graphene was ideal as it has high electronic conductivity, a large surface area, and superior mechanical properties. Numerous graphene composites have been investigated and cycling performance and rate capability have increased as a consequence. These structures and composites are created using various spray drying techniques such as granulation and composite forming.

Granulation and controlled agglomeration refer to the process of forming granules out of fine particles. Mixing raw materials with binders and dispersants can achieve several µm granules by spray drying. It is necessary to agglomerate fine powders into larger granules as small particles have poor flowability.

Composite Forming is a process where a material is included in a matrix through spray drying. The matrix material envelopes the guest material forming a composite. This process can be used either introduce or reduce the properties of a material.

Many of the aforementioned battery applications require granulation by spray drying, whereby a suspension of primary particles, binder, and surfactant gets atomized into small droplets. These are injected into a stream of hot gas that causes the fluid to evaporate from the droplet surface. The droplets continuously shrink into almost spherical granules made up of fine particles. Tailor-made spray drying instruments are able to influence the morphology of granules in a number of ways. Several parameters can be adapted to influence solid loading, the rheology of the sprayed slurries, and the degree of flocculation within the slurries. Binders and plasticizers can also be introduced to help form solid particles. Different nozzles and nozzle tips can produce a wide range of particle sizes, and almost any liquid or even two immiscible liquids can be spray-dried at once. There are even solutions for drying solutions or suspensions in a fully closed system to maximize safety and minimize solvent waste. For the type of precision required for battery applications, a dehumidifier can be used for accurately conditioned drying air. Due to the adaptability of the spray drying equipment and the potential offered by the various structures discussed, spray drying battery applications are numerous. I for one, who can’t get enough of the latest and greatest, look forward to witnessing how optimized batteries can get and what possibilities lie ahead.

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