Nitrogen-ion-irradiated defective tin oxyhydroxide nanoparticle anode for ultrafast and highly stable lithium-ion storage

High-performance lithium-ion batteries require high energy density, long cycle life, and fast (dis)chargeability. Despite several accomplishments in increasing capacity under normal operation, maintaining high capacity under fast charging and discharging remains a challenge. To achieve such performance, we have applied nitrogen-ion (N+) irradiation to an anode material comprising tin oxyhydroxide nanoparticles (Sn6O4(OH)4 NPs) active material, carbon black conducting agent, and polyvinylidene fluoride (PVDF) binder. Sn6O4(OH)4 NPs have high capacity and fair rate capability due to their layered structure with a large interlayer spacing of 0.455 nm and a small particle size of < 5 nm. N+ irradiation induces multiple defects including implanted N+ and oxygen vacancies in the anode material. The defects provide more Li-ion active sites in the Sn6O4(OH)4 NPs and lead to amorphization of carbon black as well as increasing the conductivities of Sn6O4(OH)4 NPs. Additionally, N+ irradiation brings about cross-linking of PVDF, enhancing the binding property. As a consequence, the N+-irradiated anode shows significantly improved performance: a capacity maintains 2306 mA h g−1 after 500 cycles at 0.5C and 1053 mA h g−1 after 300 cycles at 5C. Moreover, the anode exhibits outstanding rate capability even under ultrahigh-rate operation: 65.1 % capacity retention at 50C.