Lithium batteries have revolutionized how we power our devices, from smartphones to electric vehicles. While the spotlight often shines on the high energy density and longevity of these batteries, another critical aspect plays a pivotal role in their performance: the cell design.

Among various cell configurations, we chose cylindrical cells as the preferred cell choice for building our 12v and 24v batteries, because they offer the following advantages over prismatic or pouch cells:
their compact design allows for efficient packing within battery modules Cylindrical cells exhibit better heat dissipation characteristics compared to prismatic or pouch cells, cylindrical cells have a lower risk of overheating, their robust metal casing is more resistant to physical damage and environmental stressors, cell production is very cost-effective, and streamlined, with consistent quality control, cylindrical cells are a reliable choice for large and durable battery packs, cylindrical cells perform better at high discharge rates, the cells’ geometry, containment within a rigid casing and ability to shed heat inhibits thermal runaway, cylindrical cells are also the cell choice of leading electronic vehicle manufacturers. In this blog, we expand on why we feel cylindrical cells are the superior option for our 12v and 24v lithium iron phosphate batteries.

 

Compact and Efficient Use of Space:
Cylindrical cells, resembling traditional AA batteries, possess a distinct advantage in terms of space utilization. Their inherently compact design allows for efficient packing within battery modules, allowing batteries to be shaped and leaving minimal wasted space.

Good Thermal Management:
Lithium batteries can generate substantial heat during charge and discharge cycles. Cylindrical cells exhibit better heat dissipation characteristics compared to prismatic or pouch cells due to their cylindrical geometry, allowing heat to be more evenly distributed.

 

This property lowers the risk of overheating, which extends battery life and further enhances safety, especially in high-demand applications.

Very Robust and Durable:
When it comes to durability, cylindrical cells take the lead with their robust metal casing. This casing provides a protective shield for the internal components, rendering the cells more resistant to physical damage and environmental stressors.

In contrast, prismatic and pouch cells, lacking the rigid casing, are more vulnerable to external pressures, potentially compromising their performance and safety.

High Quality and Consistent Manufacturing:
Cylindrical cells have been in production for decades, resulting in highly optimized manufacturing processes.

 

This experience has led to very consistent quality control, streamlined production and cost-effectiveness, making them a reliable choice for large and durable battery packs used in applications like EVs and energy storage systems.

Higher Discharge Rates:
Cylindrical cells generally exhibit better performance at high discharge rates, which is essential for applications demanding rapid power delivery while maintaining a small battery size.

Best Thermal Runaway Management:
A large safety concern for lithium batteries is that they can catch on fire in what is called a thermal runaway (a rare but severe safety concern). This concern is fueled by reports of fires caused by lithium-based chemistry, but not lithium iron phosphate (LiFePO4) specifically.

The internal chemistry of LiFePO4 cells is not considered an oxide-based lithium-ion chemistry, so LiFePO4 heat generation is not self-sustaining, and especially for cylindrical cells the cells’ geometry, containment within a rigid casing and ability to shed heat versus the reaction rate does not create enough heat to combust cells next to it. There is thus no “cascade” effect and thermal runaway is inhibited.

Choice of leaders in EV industry:
The Tesla Model 3 compact sedan, Lucid Air large sedan, and Rivian R1T pickup truck are all range and efficiency leaders in their respective classes. The three automakers have a key technology choice in common, beyond exclusively making battery electric vehicles: They each favor cylindrical batteries.

Tesla CEO Elon Musk called the probability of thermal runaway “dangerously high with large pouch cells,” and pointed to the physical challenges of cooling them.

Lucid CEO Peter Rawlinson explained that Lucid’s choice of cylindrical cells comes down to thermal attributes and the consistency and reliability of the cells themselves, as well as their predictable cost on the market. It also means not being bound to the design constraints of larger cells.

Overall, deciding on ideal cells is an engineering problem with different solutions depending on the vehicle and its use case, and how a company sees the tradeoffs. Yet there’s something to be said now, with the three American companies still seeing cylindrical as the near-term choice.