Synergistic CO2 etching and carbonization engineers closed-pore anodes for high-performance sodium batteries

Sodium-ion batteries (SIBs) offer a sustainable solution for energy storage but suffer from inadequate anode performance. While hard carbon is the premier anode candidate, precise control of its closed nanopores, critical for high-capacity sodium storage, remains a fundamental challenge.

A breakthrough study in Nano Research introduces a synergistic CO₂ etching-carbonization strategy that solves this problem. By first using CO₂ gas to create open nanopores in biomass precursors, then driving pore closure via controlled carbonization, researchers achieved unprecedented control over pore volume (0.163 cm³/g) and size (1.413 nm).

“Previous methods focused solely on pore creation or carbonization,” explained Huanlei Wang from Ocean University of China. “Our dual approach harnesses gas chemistry and thermal dynamics: CO₂ carves pore templates, while carbonization temperature dictates their transformation into sealed sodium reservoirs.”

The temperature-regulated carbonization step proved decisive:

• Increasing carbonization temperature from 1300℃ to 1700℃ tripled closed-pore volume (0.0465 → 0.163 cm³/g)
• Higher temperatures enhanced graphitic layer curvature, directly facilitating pore closure

The optimized anode (CH-800-1500) shattered benchmarks:

• 388.8 mAh/g capacity at 0.05 A/g
• 279.6 mAh/g from low-voltage plateau (<0.1 V)
• 83.8% capacity retention after 800 cycles at 0.5 A/g
• Full-cell energy density of 165.2 Wh/kg

In situ diagnostics revealed sodium ions forming quasi-metallic clusters within closed pores-accounting. “The pores act as nanoreactors where confinement enables unprecedented sodium storage,” noted Wang.

This synthesis strategy can be extended to a wide range of precursors. The results establish a clear correlation between precursor heteroatom chemistry, closed-pore architecture, and sodium-storage capacity, underscoring the pivotal role of precursor selection in optimizing carbon anodes for high-performance sodium-ion batteries.

This green process avoids toxic byproducts from traditional methods and demonstrates scalability through pouch-cell validation.

Other contributors include Wancheng Ren, Lei Yang, Xinyu Wang, Chenglong Qiu, Jing Shi, Jingwei Chen, Weiqian Tian and Minghua Huang from the Ocean University of China.

This work was supported by the National Natural Science Foundation of China (No. 22179123), the Taishan Scholar Program of Shandong Province, China (No. tsqn202211048), and the Major Basic Research Projects of Shandong Natural Science Foundation (ZR2024ZD37).

About Nano Research

Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.