Faster Charging For Lithium–Sulfur Batteries

The nitrogen-doped carbon material helps lithium-sulfur batteries charge faster, hold more energy, and last longer, solving key problems for broader use.

A research team at Daegu Gyeongbuk Institute of Science and Technology (DGIST) has developed a new technology to boost lithium-sulfur batteries’ charging speed significantly. They achieved this by using a nitrogen-doped porous carbon material, addressing the slow charging issue that has hindered the commercialization of these batteries.

Lithium-sulfur batteries are considered promising alternatives to lithium-ion batteries due to their higher energy density and the low cost of sulfur. However, their commercialization has faced hurdles, such as poor sulfur utilization during fast charging, which reduces battery capacity. Another issue is the formation of lithium polysulfides during discharge, which migrate within the battery and degrade its performance.

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The team developed a highly graphitic, multiporous carbon material doped with nitrogen and applied it to the cathode of a lithium-sulfur battery. This approach enabled the battery to maintain high energy capacity even under rapid charging. 

The team synthesized the new carbon material using a thermal reduction method involving magnesium and ZIF-8, a metal-organic framework. Magnesium reacts with the nitrogen in ZIF-8 at high temperatures, stabilizing the carbon structure and creating a diverse pore network. This design supports higher sulfur loading and enhances contact between sulfur and the electrolyte, improving battery performance.

The lithium-sulfur battery in this study used this multifunctional carbon material, produced through the magnesium-assisted thermal reduction method, as a sulfur host. The battery demonstrated high performance, achieving a capacity of 705 mAh g⁻¹ even under rapid charging conditions with a full charge time of just 12 minutes—1.6 times better than conventional batteries.

Nitrogen doping on the carbon surface also played a critical role in suppressing the migration of lithium polysulfides. This feature allowed the battery to retain 82% of its capacity after 1,000 charge-discharge cycles, showing excellent long-term stability.

The analyses revealed that lithium sulfide (Li₂S) formed in a specific orientation within the carbon material’s layered structure. This confirmed that nitrogen doping and the porous design enhanced sulfur loading, while the graphitic properties of the carbon accelerated sulfur reactions, boosting charging speed.

Reference: Jeong-Hoon Yu et al, Tailoring-Orientated Deposition of Li2S for Extreme Fast-Charging Lithium–Sulfur Batteries, ACS Nano (2024). DOI: 10.1021/acsnano.4c09892