1成果简介

　　锂离子电池（LIBs）和钠离子电池（SIBs）是具有广阔应用前景的关键电化学储能装置；然而，由于商业石墨的容量和倍率性能有限，无法满足日益增长的能源需求。本文，西南科技大学李劲超 副教授 、张亚萍 教授团队在《Journal of Power Sources》期刊发表名为“Waste banana bract-derived porous carbon as anode for lithium/sodium-ion batteries with hybrid adsorption-pore filling/insertion mechanism”的论文，研究针对废弃香蕉花苞的利用需求，采用简便的KOH活化及700°C-900°C碳化工艺，从废弃香蕉花苞制备多孔碳材料，用于LIBs和SIBs。其大比表面积与杂原子掺杂提供了丰富的储能位点，而多孔结构通过形成快速通道，促进了离子的储存与扩散。因此，香蕉花苞衍生的碳材料展现出高容量和长循环寿命。
　　LIBs在0.1 A g−1电流密度下展现出高达953.89mAh g−1的容量，经过1000次1 A g−1循环后仍保持320.41mAh g−1的容量。类似地，SIBs在0.1A g−1电流密度下展现出212.16mAh g−1的卓越容量，并在1000次循环后保持稳定容量。这些容量和倍率性能均优于传统石墨负极。此外，电化学研究（包括循环伏安法、原位X射线衍射和原位拉曼光谱）揭示了储能机制，证明了香蕉叶片衍生碳作为锂离子电池（LIBs）和硫离子电池（SIBs）负极材料的巨大潜力。
　　2图文导读 

　　图1. Flow chart for the preparation of banana bract-derived carbon materials.

　　图2. (a–c) SEM images of BBC-7, BBC-8 and BBC-9, respectively (the insets in the upper right corner show the respective detail enlargements), (d–f) TEM images of BBC-7, BBC-8 and BBC-9, respectively, (g) EDS mapped image of (h) C, (i) O and (j) N of BBC-8.

　　图3. Structural characterization of BBC-7, BBC-8 and BBC-9: (a) X-ray diffraction patterns, (b) Raman spectra, (c) N2 adsorption/desorption isotherms and (d–f) pore size distribution. High-resolution XPS spectra of BBC-8: (g) C 1s, (h) N 1s and (i) O 1s.

　　图4. Electrochemical performances of BBC-7, BBC-8 and BBC-9 as LIBs and SIBs: (a, g) rate performance diagrams, (b, h) Nyquist diagrams, (c, i) cycle performances at 100 mA g−1, (d, j) charge/discharge curves of BBC-8, (e, k) CV curves of BBC-8 at 0.1 mV s−1, (f, l) long-cycle performances at 1000 mA g−1 of BBC-8.

　　图5. Electrochemical performances characterization of BBC-8 in LIBs and SIBs. (a, e) CV curves at different scan rates (0.1–5.0 mV s−1), (b, f) peak current versus scan rate, (c, g) capacitance contribution at different scan rates and (d, h) capacitance contribution at 1.0 mV s−1. (I, k) GITT curves during the discharge process and (j, l) corresponding Li and Na diffusion coefficient. (m) ex-situ XRD, (n) Ex-situ Raman.++

　　图6. (a) Schematic representation of Li and Na full cell. Electrochemical performances of full cell, (b, c) charge/discharge curves, (d, e) cycling stability and demonstration of a full cell powering LED.++
　　3小结
　　综上所述，我们成功地从废弃香蕉花苞中合成了成本低廉的多孔碳材料。由于其独特的孔结构、高比表面积以及自掺杂的氮和氧原子，所得的BBC-8材料展现出卓越的电化学性能。此外，组装的完整电池展现出令人印象深刻的能量密度，锂离子电池（LIBs）为178.3 Wh kg−1，硫离子电池（SIBs）为111.1  Wh kg−1。我们初步提出吸附-孔隙填充/插层机制来解释其优异的储能性能。来源于其他香蕉废弃物的多孔碳材料也展现出卓越的电化学性能。因此，将生物废弃物转化为高性能电极材料是应对能源与环境挑战的关键策略。
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