Battery Cell Formats and Chemistries

In the ever-evolving realm of energy storage solutions, the choice of battery cell formats and chemistries plays a pivotal role in determining the overall performance, safety, and cost-effectiveness of a battery system. At BOLD, we have a deep understanding of the intricate dynamics of formats, chemistries, and emerging technologies within the battery cell landscape. We carefully focus on cell selection to keep our products at the forefront of continuous innovation.

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Battery cell formats typically fall into three main categories:

  1. Cylindrical cells consist of sheet-like battery anode, cathode, and separator that are packed into a cylinder-shaped enclosure. This type of cell is one of the first to be mass-produced and is still very popular (specially in 18650 and 21700 formats). Typically, they have a capacity between 3 and 5Ah and possess good mechanical stability. This, coupled with thermal runaway mitigation components/designs such as a venting valve or current interruption method, makes them a truly safe format.
  2. Prismatic cells are an evolution of the cylindrical ones, being larger and having a more user-friendly format for assembly. They typically have a capacity ranging from 30 up to >300Ah, making them the preferred format for stationary applications and for most EV manufacturers. This format exhibits a safety level similar to that of the cylindrical cells.
  3. Pouch cells are flexible and utilise a sealed flexible foil as the cell container. The electrode and separator layers of a pouch cell are stacked. With a highly variable capacity ranging from a few Ah up to approximately 100Ah, the typical thin rectangular format makes them suitable for high energy density applications. However, this same simple format also renders these cells less safe.
Various cell designs a cylindrical b prismatic c pouch
Various cell designs: (a) cylindrical; (b) prismatic; (c) pouch. Image courtesy of Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering via https://www.researchgate.net

Formats aside, cell chemistries are the heart of battery technology, and is responsible for the performance and characteristics of energy storage devices. BOLD delves into key chemistries, such as Lithium Iron Phosphate (LFP), Nickel Manganese Cobalt (NMC), and Nickel Cobalt Aluminum (NCA), understanding their strengths and weaknesses. Notably, the integration of Silicon-Graphite anode technology is introduced as a strategic move to boost energy density, enhancing the overall capabilities of the batteries.

BOLDhp

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Each format comes with its own set of advantages and limitations, influencing factors such as energy density, thermal management, and overall efficiency. BOLD’s expertise in navigating through these formats allows us to tailor solutions according to customer needs. Currently, the cells that present a greater balance in terms of power/energy, safety and capacity are cylindrical cells which are utilised in our high-performance off-the-shelf battery product – BOLDhp, tailored for applications such as sports cars, defence, aerospace or any application requiring high specific power.

We have strategically chosen cells for BOLDhp to suit applications which need exceptional power (≈2,000 Wh/kg continuous and over 4,000 Wh/kg peak) while maintaining a superior energy density (> 240 Wh/kg).

BOLDair

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For BOLDair, a battery system developed for pure electric or hybrid aviation applications such as lightweight, fixed-wing aircrafts, eVTOLs, UAVs, BOLD has strategically opted for cells tailored to meet the demands of aviation, with an energy density exceeding 300Wh/kg.

The decision to employ a Silicon (Si) + graphite anode, with Si doping providing additional capacity, and a pouch cell format has proven essential to achieve higher energy densities. This format allows for a superior utilisation percentage in the final product, boasting 80%, as opposed to the 70-75% achievable in cylindrical cells.

BOLDhd

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BOLD’s heavy-duty battery system, BOLDhd, utilises high capacity (>100Ah) Lithium Iron Phosphate (LFP) prismatic cells. The use of these cells ensures long cycling life (>5,000 cycles), high safety and lower cost in comparison with other Li-ion chemistries.

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BOLD’s Market Knowledge and Strategic Cell Selection:

In developing solutions for clients, BOLD can be very strategic in selecting cells and is not linked to a single provider. Our cell selection process stands out due to its reliance on a robust market knowledge base. With over 50 identified cell suppliers and close collaborations with key players, we gain early access to next-gen cells. This strategic advantage is further reinforced by continuous market screening, allowing the company to stay informed about new developments and relevant players in the industry.

Our team perform detailed supplier data sheet and testing data analysis, before performing in-house testing. The final decision is based on a comprehensive evaluation, ensuring that the chosen cell aligns seamlessly with customer needs in terms of performance, safety, and price. Once the cell is selected, we have state of the art pack architecture meaning we can incorporate cells with varying capacities to achieve different system energy levels, providing flexibility in system design. This approach allows for cost optimisation when needed.

Next generation batteries from BOLD

As BOLD looks to the future, the company is actively working on the next generation of BOLDhp, aiming for higher energy with 4.5 to 5Ah cells in the same form factor and weight. Additionally, we are exploring the possibility of a 6Ah cell by the end of 2025. BOLD is also delving into super high-power cells (>100C) and conducting a thorough study on second-life cells, showcasing a commitment to continuous innovation and improvement.

In conclusion, BOLD’s approach to battery technology is not just about selecting cells but understanding the intricate dynamics of formats, chemistries, and emerging technologies. Through a combination of market insight, strategic partnerships, and a forward-thinking mindset, we position ourselves as a leader in the ever-evolving world of energy storage solutions.

If you want to learn more about our advanced energy storage solutions or to discover how BOLD’s innovative approach to battery technology and cell optimisation services can benefit your specific needs, please reach out to our team at sales@boldvaluable.tech.

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