Synergistically Tailoring the Electronic Structure and Ion Diffusion of Atomically Thin Co(OH)₂ Nanosheets Enable Fast Pseudocapacitive Sodium Ion Storage

The fast-growing development for high-capacity anodes is undermined by their unsatisfactory rate performance and cycling stability stemming from sluggish ion-migration speed, poor electronic conductivity, and mechanical degradation induced by the stress accumulation, which greatly hamper practical applications of Na-ion batteries. Here, a combined experimental and theoretical study on atomic-thickness (0.6 nm) Co(OH)₂ nanosheet with surface defects (2D-Co(OH)₂@D NSs) and large interplanar spacing (0.465 nm) is presented, in which fast ion/electron transport is permitted to boost battery reactions. The mechanical degradation on cycling can be well buffered via tailoring mesopores across the Co(OH)₂ nanosheet and an elastic solid–electrolyte interface is established by modulating the electronic structure of the Co(OH)₂ surface. The 2D-Co(OH)₂@D NSs exhibit high rate-capacity (>228 mAh g⁻¹ at 20 A g⁻¹) and superior cyclic stability with negligible decay during 1300 cycles. This study will shed light on the development of electrode materials at atomic-level design for high-power and long-lived performance.