Non-Destructive Method Reveals Insights into Lithium-Sulphur Battery Performance

Using a novel non-destructive method, researchers at HZB have investigated the practical lithium-sulphur pouch cells with a lean electrolyte for the first time. By employing operando neutron tomography, they were able to visualize in real-time how the liquid electrolyte distributes and wets the electrodes across multilayers during charging and discharging. This breakthrough offers valuable insights into cell failure mechanisms and is crucial for designing compact Li-S batteries with high energy density in formats relevant to industrial applications.

Key Takeaways:

• The team at HZB used a non-destructive method to investigate lithium-sulphur pouch cells with a lean electrolyte for the first time.
• Operando neutron tomography allowed the researchers to visualize the liquid electrolyte's distribution and wetting of electrodes in real-time.
• The findings provide valuable insights into cell failure mechanisms and are crucial for designing compact Li-S batteries with high energy density.
• Lithium-sulphur batteries have the potential to achieve ultrahigh gravimetric energy densities (above 700 Wh/kg) compared to state-of-the-art Li-ion batteries (~250 Wh/kg).
• The practical energy density of lithium-sulphur batteries is often constrained by the high weight fraction of inactive materials, such as the electrolyte.
• Reducing the amount of electrolyte in the battery cell is necessary to increase the energy density, but it also makes it more challenging to fully wet the electrodes.
• Incomplete wetting disrupts the electrochemical processes and causes the battery to age faster or even fail.
• The team observed unique "breath in" and "breath out" wetting behaviours in the electrolyte, which are periodic processes that correlate with the dissolution and precipitation of sulphur compounds.
• These findings offer insights into the mechanisms that lead to rapid ageing and failure of LI-S systems.

Statistics:

• Lithium-sulphur batteries can achieve ultrahigh gravimetric energy densities of above 700 Wh/kg.
• State-of-the-art Li-ion batteries have a gravimetric energy density of approximately 250 Wh/kg.
• The team observed that the discharge/charge processes significantly improve the homogeneity of the electrolyte and can promote the electrochemical activation of sulphur, leading to enhanced capacity of batteries.

Sources:

• [HZB Press Release, published online]
• [Institut Laue-Langevin, press release]
• [Batterie 2020 (SkaLiS) research program]