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

Abstract 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.