Demand

　　Currently, lithium-ion batteries are primarily used in mobile phones, tablets, and other 3C electronic products. Among commercially available batteries, they have the highest energy density but still cannot meet people's needs. Why? In short, it's because larger battery cells cannot fit into the limited space. People have strict requirements for the size and weight of 3C products, so the space available for batteries is limited.

　　Performance

　　Although lithium-ion batteries are widely recognized as having the potential to dominate the market, they are still inferior to lead-acid batteries in at least two aspects. These two aspects are critical for automotive starter power supplies: low-temperature performance and high-current performance.

　　First, let's talk about low-temperature performance. Lead-acid batteries perform quite well in low-temperature environments. At -10°C, they can discharge at a 10C rate while maintaining a voltage above 10V for over 90 seconds, which is sufficient to handle the harsh conditions in most regions of China. In contrast, lithium-ion batteries have much poorer low-temperature performance, especially lithium iron phosphate (LiFePO4) batteries, which see a sharp decline in discharge performance at low temperatures. This makes them difficult to use in northeastern and northwestern regions of China, or far from practical application in such areas.

　　Safety

　　Starter power supplies are typically installed in the engine compartment of vehicles, which have relatively high levels of enclosure. Therefore, safety is critical. The heat and potential dangers from the instantaneous release of hundreds of amps of current are self-evident.

　　Lead-acid batteries are among the safest in current battery systems. First, their excellent high-current performance means they are less likely to fail. Second, even in the event of a failure, the positive and negative electrode materials are lead compounds, and the electrolyte is sulfuric acid solution. None of these materials are flammable, so they would only cause surrounding components to burn.

　　Lithium-ion batteries, on the other hand, use graphite as the negative electrode material, which is a type of carbon material and is flammable. The electrolyte is composed of ester solvents and lithium salts. Ester solvents are not only flammable but also highly volatile. In the event of a large heat release or a car collision, they can easily catch fire or even explode, escalating the severity of accidents. Additionally, lithium-ion batteries are prone to forming lithium dendrites on the negative electrode during high-current discharge, which can pierce the separator and cause an internal short circuit, leading to explosions. This is a well-known issue in the lithium battery industry.

　　There are many other issues, such as the stability of electrode materials when batteries are kept in a high state of charge (SOC) for long periods. Research on these issues is still limited, and many mechanisms remain unclear. The safety problems of lithium-ion batteries are numerous and cannot all be addressed here.

　　Cost

　　In terms of cost, lead-acid batteries are undoubtedly the cheapest. The cost of electrode materials, electrolytes, and assembly requirements are all far lower than those of lithium-ion batteries.

　　For electrode materials, lithium-ion batteries require complex preparation processes, including high-temperature heat treatment (graphitization above 2000°C for the negative electrode and 700–800°C for the positive electrode). The cost is generally between 15–20k RMB/ton, with graphite being slightly cheaper. In contrast, the lead oxide and lead sulfate used in lead-acid batteries are much less expensive.

　　For electrolytes, lithium-ion batteries use multiple ester solvents, which are expensive and require strict control of water content, usually within tens of ppm. The electrolyte salt, lithium hexafluorophosphate, is not only costly but also prone to decomposition, posing safety risks. One of its decomposition products is the highly dangerous HF (hydrofluoric acid), whose hazards can be easily found online. In comparison, lead-acid batteries use sulfuric acid solution, which needs no further explanation.

　　Environment

　　There is a common misconception that lead-acid batteries pollute the environment while lithium-ion batteries are environmentally friendly. This is not entirely true. In the past, many small lead-acid battery factories in southern China ignored environmental protection and discharged pollutants recklessly, leading to this perception. Additionally, the government's push to reduce the scale of lead-acid battery production and promote new energy sources has influenced media narratives. However, the reality is different.

　　Currently, lead-acid batteries have a well-established recycling mechanism compared to lithium-ion batteries. Lead-acid batteries are mainly used in electric bicycles and starter power supplies, both of which have strong recycling incentives. Users typically return old batteries to specialized stores for replacement because they can get a discount on new ones. These old batteries are then sent to specialized lead recycling plants for secondary processing to produce new electrode materials.

　　Have you ever seen specialized institutions recycling lithium-ion batteries for electrode material production? The reasons are as follows: First, lithium-ion batteries are used in a wide range of applications, making recycling difficult. Second, lithium-ion batteries are mostly small-sized, and people usually throw them away or sell them when their devices (like phones or MP3 players) are no longer in use. Ultimately, these batteries end up in landfills.

　　Although lithium-ion batteries contain fewer heavy metals (only cobalt in the positive electrode), the sheer number of users worldwide makes this a long-term issue. Overall, as long as proper environmental measures are taken during production, lead-acid batteries are not problematic. They are sealed and maintenance-free during use, and there is an effective recycling mechanism in place at the end of their lifecycle.

　　Conclusion

　　Lead-acid batteries are truly evergreen in the world of chemical power sources. Having been around for over a century, they remain irreplaceable in certain fields despite the rise of lithium-ion batteries. At least for the next three to five decades, replacement is unlikely.

　　We should adopt a forward-looking perspective. Research on lead-acid batteries continues to advance. In the field of automotive starter power supplies, they remain unparalleled. Lithium-ion batteries still have a long way to go and are young in comparison. Hopefully, more advanced batteries will emerge in the future to replace them!

　　Tianheng looks forward to extensive cooperation with clients from all sectors to share our products and successes.

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