TY - JOUR AU - Yang, Jinlin AU - Wang, Xiaowei AU - Dai, Wenrui AU - Lian, Xu AU - Cui, Xinhang AU - Zhang, Weichao AU - Zhang, Kexin AU - Lin, Ming AU - Zou, Ruqiang AU - Loh, Kian Ping AU - Yang, Quan‑Hong AU - Chen, Wei PY - 2021/03/30 Y2 - 2024/03/29 TI - From Micropores to Ultra-micropores inside Hard Carbon: Toward Enhanced Capacity in Room-/Low-Temperature Sodium-Ion Storage JF - Nano-Micro Letters JA - Nano-Micro Lett VL - 13 IS - SE - Articles DO - 10.1007/s40820-020-00587-y UR - https://nmlett.org/index.php/nml/article/view/864 SP - 98 AB - <p>Pore structure of hard carbon has a fundamental influence on the electrochemical properties in sodium-ion batteries (SIBs). Ultra-micropores (&lt; 0.5&nbsp;nm) of hard carbon can function as ionic sieves to reduce the diffusion of slovated Na<sup>+</sup> but allow the entrance of naked Na<sup>+</sup> into the pores, which can reduce the interficial contact between the electrolyte and the inner pores without sacrificing the fast diffusion kinetics. Herein, a molten diffusion–carbonization method is proposed to transform the micropores (&gt; 1&nbsp;nm) inside carbon into ultra-micropores (&lt; 0.5&nbsp;nm). Consequently, the designed carbon anode displays an enhanced capacity of 346 mAh&nbsp;g<sup>−1</sup> at 30&nbsp;mA&nbsp;g<sup>−1</sup> with a high ICE value of ~ 80.6% and most of the capacity (~ 90%) is below 1&nbsp;V. Moreover, the high-loading electrode (~ 19&nbsp;mg&nbsp;cm<sup>−2</sup>) exhibits a good temperature endurance with a high areal capacity of 6.14&nbsp;mAh&nbsp;cm<sup>−2</sup> at 25&nbsp;°C and 5.32 mAh cm<sup>−2</sup> at −&nbsp;20&nbsp;°C. Based on the in situ X-ray diffraction and ex situ solid-state nuclear magnetic resonance results, the designed ultra-micropores provide the extra Na<sup>+</sup> storage sites, which mainly contributes to the enhanced capacity. This proposed strategy shows a&nbsp;good potential for the development of high-performance SIBs.</p><p>Highlights:</p><p>1 Hard-carbon anode dominated with ultra-micropores (&lt; 0.5 nm) was synthesized for sodium-ion batteries via a molten diffusion–carbonization method.<br>2 The ultra-micropores dominated carbon anode displays an enhanced capacity, which originates from the extra sodium-ion storage sites of the designed ultra-micropores.<br>3 The thick electrode (~ 19 mg cm<sup>−2</sup>) with a high areal capacity of 6.14 mAh cm<sup>−2</sup> displays an ultrahigh cycling stability and an outstanding low-temperature performance.</p> ER -