On October 31st, Li Auto made an official apology regarding a safety issue that occurred in its 2024 Li Auto MEGA model. The company admitted that a defect in the coolant liquid used in some of the vehicles from the same batch caused corrosion, which led to potential thermal runaway in the battery under extreme conditions. The incident once again highlighted the ongoing debate between NCM lithium battery packs (Nickel-Cobalt-Manganese) and LFP battery technology (Lithium Iron Phosphate).
While the argument has existed for years with each battery type carving out its own niche, this recent safety issue brought the conversation back into the spotlight. NCM batteries, known for their high energy density, long-range, and extreme performance, also come with higher risks, particularly thermal instability. Meanwhile, LFP batteries, which are praised for their safety and stability, often suffer from lower energy density. The question now arises: which is truly the safest option?
Battery thermal management is a critical aspect of electric vehicle (EV) safety. Both high voltage batteries and the electric motor require an efficient thermal management system to regulate temperature. This system uses coolant fluids to dissipate heat, ensuring optimal vehicle performance, safety, and longevity.
In the case of the Li Auto MEGA, a defect in the coolant used in certain batches led to a series of failures. The coolant’s poor anti-corrosion properties caused degradation of the aluminum plates in the battery’s cooling circuit. This eventually led to short-circuiting, which resulted in thermal runaway and fire hazards.
Coolant liquids are typically made from a mix of ethylene glycol and water, which is weakly acidic and can cause corrosion over time. Manufacturers add anti-corrosion additives such as silicates, phosphates, or organic acids to mitigate this effect. However, over time, the additives degrade, and oxidation leads to the formation of harmful by-products, such as oxalic acid and acetic acid, which further accelerate the corrosion process.
This corrosion is especially dangerous in electric vehicles, where coolant leakage can come into contact with high-voltage battery packs. If coolant touches the battery terminals, it can cause a short-circuit, which may lead to catastrophic thermal runaway.
From a chemical standpoint, NCM lithium-ion batteries are known for their higher energy density and superior performance, making them ideal for high-end electric vehicles. However, these batteries are less thermally stable compared to LFP cells. Studies have shown that NCM batteries can undergo severe degradation at temperatures above 200°C, potentially triggering a thermal runaway reaction that could lead to fires. Furthermore, this reaction releases oxygen, which can accelerate the fire.
In contrast, LFP batteries have a much higher thermal stability, with decomposition only occurring at temperatures of 500°C to 800°C. LFP batteries do not release oxygen during decomposition, giving them a much safer profile in case of thermal issues. For instance, LFP battery packs can withstand abuse better in crash scenarios or in extreme temperature fluctuations, making them particularly well-suited for applications where safety is paramount.
Testing has shown significant differences between NCM and LFP batteries when subjected to thermal abuse. For example, in puncture tests designed to simulate an internal short circuit, an NCM battery can reach temperatures of 400-600°C in as little as 10 seconds, while an LFP battery takes approximately 2 minutes to reach a peak temperature of 300°C. This extra minute can make the difference between a contained safety situation and a catastrophic event.
The future of lithium battery technology is undoubtedly tied to both NCM and LFP chemistries, but each has its own role in the market.
For high-end electric vehicles, NCM battery packs are an essential technology. The high energy density of NCM batteries allows automakers to design lighter and more efficient vehicles, offering longer driving ranges and superior performance. These advantages are crucial for high-performance, luxury EVs, such as those produced by companies like Tesla, BMW, and Mercedes-Benz.
Despite the potential safety concerns, NCM batteries are here to stay in the premium automotive segment due to their superior energy efficiency and performance. The industry is investing heavily in developing advanced thermal management systems and Battery Management Systems (BMS) to monitor and control the battery’s temperature and prevent thermal runaway incidents. While accidents still happen, technological advancements are improving the safety profile of NCM batteries, ensuring they remain the dominant choice for performance-oriented electric vehicles.
On the other hand, LFP batteries are becoming the preferred choice for mass-market EVs. They offer superior safety, cost efficiency, and adequate performance for most consumer applications. As LFP batteries are less expensive to produce and have a longer lifespan, they are ideal for vehicles aimed at consumers seeking a balance between performance, cost, and safety.
LFP batteries are also gaining traction in energy storage systems, where reliability and safety are critical. Many EV battery manufacturers are increasingly turning to LFP chemistry to meet demand from the mass-market segment and to provide consumers with affordable and safer options.
The future of battery technology will likely follow two parallel paths.
Currently, NCM batteries have taken a dominant position in emerging trillion-dollar industries such as low-altitude economy and robotics. Fields like eVTOL (electric vertical take-off and landing), often referred to as "flying cars," and high-end mechanical products such as robots demand extreme lightweight and energy density from batteries—every gram counts. Their performance requirements for batteries far exceed those of ground vehicles, yet they are less sensitive to cost, making them the perfect stage for ternary lithium batteries to showcase their advantages.
Meanwhile, LFP batteries will thrive in mass-market vehicles and energy storage applications, where safety, cost-effectiveness, and long lifespan are more critical.
Furthermore, the development of solid-state batteries may shift the landscape even further. Solid-state technology is expected to build upon the strengths of both NCM and LFP chemistries, offering high energy densities along with significantly improved safety characteristics. Both NCM and LFP materials are key components in the ongoing development of solid-state batteries, positioning them as essential technologies for the next generation of electric vehicles.
In conclusion, both NCM lithium battery packs and LFP batteries offer unique advantages and will coexist in the electric vehicle and energy storage markets. While NCM batteries are ideal for high-performance vehicles due to their higher energy density, LFP batteries provide a safer and more affordable solution for mass-market EVs and energy storage. As the industry continues to evolve, the collaboration between these two technologies will play a key role in shaping the future of electric mobility and energy management.
If you're a professional in the electric vehicle or energy storage sector, or an EV battery manufacturer looking to enhance your product offerings, don't hesitate to reach out. Let’s discuss how the right battery chemistry can elevate your projects and meet the growing demand for safe, efficient, and reliable solutions.
Contact Brogen to find the electric vehicle power solutions that best fits your business.
