Ultrasmall Sn(OH)4 nanoparticles on the oxidized mesocarbon microbeads as lithium-ion battery anode with high capacity and stable performance

Highlights: • The Sn(OH)₄ are first employed as the anode materials for LIBs, showing higher capacity and longer cycle life. • Mesocarbon microbeads (MCMB) via air-oxidation treatment are acted as the carrier to anchor the ultra-small size Sn(OH)₄. • The discharge mechanisms of Sn(OH)₄ is first proposed according to the CV curves, TEM and XRD characterizations. • The LiOH and carbon can shorten the lithium ion diffusion pathway and buffer the volume expansion and aggregation of Sn. • This composite presents excellent cycling stability and large reversible capacity as an electrode material. -- Abstract: SnO₂-based composites have attracted considerable attention as anode for lithium-ion batteries due to their high theoretical capacity and cost-effectiveness. However, capacity fading often occurs due to the severe volume expansion and cracking during cycling. Herein, ultra-small Sn(OH)₄ nanoparticles have been deposited on the surface of mesocarbon microbeads (MCMB) via a low-temperature air-oxidation treatment. The in-situ oxygenated functional groups from beta-resin on the surface of MCMB lead to the high loading of Sn(OH)₄ nanoparticles with the sizes of 2–3 nm. Interestingly, compared to SnO₂, the as-prepared Sn(OH)₄ nanoparticles in the composite exhibits a higher reversible specific capacity of 850 mA h g⁻¹ after 50 cycles at a current density of 100 mA g⁻¹. This is because the small sizes of Sn(OH)₄ NPs buffer the large volume expansion and remain stable structure during cycling. The electrochemical reaction mechanism of Sn(OH)₄ is further clarified, in which the generated LiOH can effectively prevent the Sn agglomeration. LiOH also enables the composite to show low diffusion impedance and better electrochemical performance. Therefore, novel Sn(OH)₄/MCMB composite provides the possibility for practical energy storage devices.