Charged-Particle-Irradiated Tin Oxyhydroxide Nanoparticle Anodes for Lithium-Ion Batteries

Abstract

Metal oxyhydroxides have been promising ceramic materials in miscellaneous electrochemical fields due to their multiple redox states, interlayer conductivity, and structural stability as well as electrocatalytic activity. When applied to anode active materials for secondary batteries, particularly lithium-ion batteries, metal oxyhydroxides have a much larger theoretical capacity than that of commercial graphite by conversion and/or alloying reactions with lithium ions rather than intercalation. However, the inevitable volume variation of metal oxyhydroxides during battery operation impinges other primary components in anode materials such as binders and conducting agents, leading to pulverizing the anode materials. Moreover, metal oxyhydroxides are not electrically conductive so much that electrochemical reactions cannot be facilitated efficiently during cycling. Accordingly, many efforts, for example, nanostructuring, constructing hierarchical configurations or hollow structures, and hybridization with carbonaceous materials, have been attempted to overcome the limitations of metal oxyhydroxide anode active materials. In addition, crystal defects in anode materials are greatly helpful to promote electrochemical activity by tuning electronic and chemical properties. Hydrogen annealing, plasma treatment, and chemical reduction method are common approaches to inducing a large number of defects in materials, but they are generally employed at high temperatures or under controlled-pressure circumstances. Therefore, we deploy charged particle irradiation to generate numerous defects in the metal oxyhydroxide anode materials. Incident charged particles interact with a lot of atoms in the anode materials, causing atomic displacement. As a result of the displacement, diverse kinds of defects are produced, which change the electronic and chemical structures of the anode materials. Charged particle irradiation introduces a high density of defects and selective defect types for short time at room temperature. Amorphization is also induced by charged particle irradiation, which is beneficial to improve the electrochemical performance of metal oxyhydroxide anode materials. Herein, we first synthesize tin oxyhydroxide nanoparticles (SnOOH NPs), one of the potential anode active materials using simple nanostructuring, via an electrochemical route, anodization. Anodization is a very fast and concise process to obtain nanostructured metal oxides as well as NPs. Electrodes with SnOOH NPs are irradiated with various charged particles including electrons, protons, helium ions, nitrogen ions, and argon ions, and the irradiation effects are investigated. SnOOH NP anodes irradiated with each type of charged particle show different electrochemical performances from each other, but all of the irradiated SnOOH NP anodes exhibit enhanced discharge capacity or cycle life compared with a pristine SnOOH NP anode. Plausible mechanisms of the irradiation effects depending on charged particles are also proposed. Charged particle irradiation can be utilized for not only metal oxyhydroxides but any kind of ceramic materials in diverse applications including lithium-ion batteries. Figure 1