The energy density of lithium-sulfur (Li-S) batteries has a direct impact on their lifespan and cyclability, with key trade-offs stemming from the battery chemistry and associated challenges.
High Energy Density of Li-S Batteries
- Lithium-sulfur batteries offer significantly higher energy densities compared to traditional lithium-ion batteries. Theoretical gravimetric energy densities are around 2,510 Wh/kg based on sulfur capacity and average discharge voltage, while practical cells demonstrate specific energies in the range of 380–550 Wh/kg and volumetric energy densities around 540–550 Wh/L. This is roughly 2 to 3 times higher than typical lithium-ion batteries, which range from 150 to 260 Wh/kg specific energy.
Impact on Lifespan and Cyclability
- Despite the high energy density, Li-S batteries currently have a shorter lifespan and poorer cycle durability relative to lithium-ion cells. One of the primary limitations is the dissolution of intermediate lithium polysulfides into the electrolyte during cycling. This phenomenon, known as the shuttle effect, causes active material loss and corrosion of the lithium anode, leading to rapid capacity fade over time.
- Additionally, Li-S batteries face issues such as significant volume changes during charge-discharge cycles and poor electronic conductivity of sulfur and its discharge products, which further degrade cycle life.
- The trade-off is that while the high energy density promises longer run times or lighter batteries for a given capacity, maintaining that capacity over many cycles is challenging. Recent research and material innovations aim to mitigate these issues, with some advances extending cycle life beyond 1,000 cycles, but commercial-grade Li-S batteries still lag behind traditional lithium-ion cells in cycle durability.
Summary
| Feature | Lithium-Sulfur Battery | Lithium-Ion Battery |
|---|---|---|
| Specific Energy (Wh/kg) | ~380–550 practical; up to theoretical ~2,510 | ~150–260 |
| Volumetric Energy (Wh/L) | ~540–550 | Lower than Li-S |
| Lifespan (cycles) | Limited by polysulfide shuttle effect and volume expansion; recent advances >1,000 cycles | Typically 1,000–2,000+ cycles |
| Main lifespan challenge | Polysulfide dissolution and lithium anode corrosion | Electrode degradation, SEI formation |
In conclusion, the very high energy density of lithium-sulfur batteries comes with significant cyclability and lifespan challenges primarily due to polysulfide dissolution and volume change effects. Overcoming these challenges is the key to commercializing Li-S batteries that combine high energy density with acceptable cycle life.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-energy-density-of-lithium-sulfur-batteries-impact-their-lifespan-and-cyclability/
