Background
This article serves as a supplement to previous publications on low-temperature battery performance, providing readers with an intuitive understanding of how cathodes, anodes, and electrolytes influence low-temperature performance. More importantly, it reveals the root causes affecting low-temperature performance from an impedance analysis perspective.
It's crucial to avoid a common misconception: having capacity doesn't automatically mean a cell can deliver low-temperature discharge performance through simple modifications. Without inherent low-temperature capability or discharge ability, capacity alone is meaningless.
Introduction
Lithium-ion batteries face numerous challenges when operating in low-temperature environments, including lithium plating during charging and reduced discharge capacity. Below 0°C, both energy density and power density drop sharply. At -20°C, battery performance deteriorates significantly, and at -40°C, cells can only deliver 20-30% (or even less) of their rated capacity—particularly for lithium iron phosphate (LFP) batteries.
I frequently receive questions about improving LFP battery low-temperature performance through electrolyte modifications. Recently, someone claimed that the low discharge voltage plateau of LFP batteries at low temperatures is solely due to the electrolyte, and that improving the electrolyte would raise the voltage plateau.
Before accepting this conclusion, consider these questions:
- Does having capacity automatically mean having low-temperature performance or discharge capability?
- What factors cause voltage plateau reduction in normal cells?
- What components make up cell impedance, and what are their sources?
By breaking down these questions logically, you'll arrive at the answer. When troubleshooting issues—especially during failure analysis—it's essential to approach problems systematically and logically. Jumping to conclusions without proper analysis often leads to embarrassing mistakes (which ultimately stems from insufficient knowledge).