Unconventional capacity increase kinetics of a chemically engineered SnO2 aerogel anode for long-term stable lithium-ion batteries

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2020-01, Vol.8 (17), p.8244-8254
• Main Authors: Jung, Sung Mi, Kim, Dong Won, Hyun Young Jung
• Format: Article
• Language: English
• Subjects: Aerogels; Anodes; Batteries; Carbon nanotubes; Chemical bonds; Conversion; Discharge; Electrochemistry; Electrodes; Electron transfer; Energy storage; Heat treatment; Heat treatments; Immersion coating; Interdiffusion; Ion storage; Lithium; Lithium oxides; Lithium-ion batteries; Nanoparticles; Porous media; Reaction kinetics; Rechargeable batteries; Size effects; Synergistic effect; Tin dioxide; Ultrafines
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d0ta02188a

Conversion-type materials are attractive candidates as anodes for next-generation batteries due to their high theoretical capacity. However, their irreversible conversion and excessive volume expansion during charge and discharge cycles present many limitations in practical applications. Here, we report a chemically engineered 3D SnO2 aerogel anode with significantly improved reversible capacity and excellent cyclic retention for Li-ion storage. Uniformly distributed SnO2 nanoparticles with sub-3 nm size are chemically bonded on 3D porous carbon nanotube networks through a facile dip coating method without heat treatment. The ultrafine SnO2 nanoparticles contribute significantly to capacity improvement by increasing the interdiffusion layer by the size effect. Also, the electrochemical synergistic effect between the SnO2 and carbon matrix and the open porous structures of the aerogel electrode facilitates significantly enhanced reversibility in the conversion between Li2O/Sn and SnO2 through rapid electron transfer and multidimensional Li-ion accessibility, respectively. Furthermore, the robust structure of the binder-free, freestanding aerogel electrode effectively buffers the massive volume expansion during the charge/discharge process through novel spatial confinement. As a result, the chemically engineered SnO2 anode delivers the highest reversible capacity of about 2031 mA h g−1 with a 200% capacity increase after the 600th cycle at 1C. Such an increased capacity is mainly driven by a rise of the conversion reaction activity where the capacity ratio of the conversion reaction to the dealloying reaction increases up to 2.6 fold. It also presents gradually increasing capacity up to 224 mA h g−1 at 10C and superior cyclability over 10 000 cycles under high C-rates without an evident capacity fading tendency. This study provides new insights into the practical design of highly reversible conversion-type electrodes and ultralight energy storage devices.