Energy Density and Volume:
The 18650 battery cell utilizes a cylindrical structure, boasting an energy density of up to 250Wh/kg. However, its bulk and fixed shape limit its lightweight and slim design. Polymer cells utilize an aluminum-plastic composite film package, allowing compression down to 0.5mm. These cells are 30% lighter than 18650 cells, offering greater flexibility in form factor and making them more suitable for thinner and lighter products.
Safety:
Due to their solid-state electrolyte, polymer cells offer better temperature control (within 60°C) during penetration tests and feature a more comprehensive overcharge protection circuit. The steel-cased structure of the 18650 cell poses a risk of short circuits, but newer generations have enhanced safety through technologies such as PTC fuses.
Low-Temperature Performance:
Polymer cells can experience a 40% drop in discharge efficiency at -10°C, while 18650 cells maintain a more stable low-temperature performance. ‌
Cycle Life:
Polymer cells have a longer cycle life (600-1000 cycles) than 18650 cells (500-800 cycles), but in actual use, both experience increased capacity degradation over time. ‌
Cost and Market Positioning:
Due to the cost advantages of a mature supply chain, 18650 cells still hold a 60% share of the low- and mid-range markets; polymer cells are primarily used in high-end products.