1成果简介 

　　废旧塑料污染是当今全球最严峻的环境挑战之一。聚乙烯（PE）作为产量最大的塑料品种，广泛应用于包装、农膜、管材等领域，年产量超过1亿吨，但回收率极低，绝大部分被填埋或焚烧，造成严重的资源浪费和环境污染。如何将废旧聚乙烯高值化转化为功能性碳材料，实现"以废治废、变废为宝"，是塑料废弃物资源化利用的前沿方向。锌溴电池（ZBBs）凭借其高理论能量密度（~430 Wh kg⁻¹）、低成本锌/溴原料和长寿命等优势，在大规模静态储能领域极具潜力。然而，传统锌溴电池通常需要复杂的流动系统来抑制溴的穿梭效应，导致系统体积大、密封难、维护成本高。无流动锌溴电池（Flowless ZBBs）省去了泵和储液罐，结构简洁紧凑，但面临溴的严重穿梭效应——Br₂/Br₃⁻扩散至锌负极引发自放电和腐蚀，导致库伦效率低、循环寿命差。开发高效的正极催化材料来加速Br⁻/Br₂氧化还原动力学、抑制溴穿梭，是实现无流动锌溴电池长循环稳定性的关键。

　　本文，华南理工大学环境与能源学院程爽 副教授、陈燕 教授、西藏大学杨改秀 教授等团队在《Energy & Fuels》期刊发表名为"Upcycling Waste Polyethylene into Defect-Engineered CNTs via Pyrolysis-CVD for Ultrastable Flowless Zinc–Bromine Batteries"的论文。该研究报道了一种集热解与化学气相沉积（CVD）于一体的策略，用于将聚乙烯升级再利用为高价值的碳纳米管（CNTs）。这些碳纳米管被集成到碳毡（CCF）上，构建出一种用于无液锌-溴电池的高性能阴极。

　　所得器件表现出卓越的稳定性，在10 mA·cm–2和2 mAh·cm–2的条件下可维持1200次循环，且退化可忽略不计，同时平均库仑效率和能量效率分别达到98.12%和84.82%，可与最先进的器件媲美。这种卓越性能源于两个关键特征：(i) 介孔碳纳米管结构提高了活性位点密度，并加速了Br–/Br₂的氧化还原动力学；(ii) 丰富的碳缺陷能强力吸附并锚定多溴化物物种，从而有效抑制了穿梭效应。本研究为塑料废弃物的高价值回收提供了创新途径，并为碳基能源材料的理性设计提供了宝贵的见解。

　　2图文导读  

　　图1. (a) Schematic diagram of the CCF preparation process. (b) Schematic diagram of carbon nanotube growth on carbon felt via a chemical vapor deposition process. (c) Schematic diagram of the working principle and assembly of a zinc–bromine battery. (d) Actual assembly photograph of the pouch-type zinc–bromine battery.

　　图2. (a,b) SEM images of pristine CF. (c) SEM image of NiO–CF. (d–f) SEM images of CCF. (g) EDX elemental mapping image of Ni at the tip of carbon nanotubes in CCF. (h) TEM image of the top of carbon nanotubes. (i) TEM image of carbon nanotubes. (j) Interlayer spacing image of multiwalled carbon nanotubes.

　　图3. (a) Coulombic efficiency plots of Zn//CF and (b) Zn//CCF under the operating conditions of a charge capacity of 2 mAh·cm–2 and a charge–discharge current of 10 mA·cm–2. (c) Comparison plot of energy efficiency between Zn//CF and Zn//CCF. (d) Comparison plot of Coulombic efficiency of Zn//CF and Zn//CCF under different charge–discharge capacities. (e,f) Charge–discharge curves of Zn//CF and Zn//CCF under the operating conditions of a charge capacity of 6 mAh·cm–2 and a charge–discharge current of 10 mA·cm–2. (g) Comparison plot of Coulombic efficiency and energy efficiency between this work and previously reported literature.

　　图4. (a) Schematic diagram of the operando Raman setup, where 1, 2, and 3 denote the counter electrode, reference electrode, and working electrode, respectively. Operando Raman spectra of the (b) CCF and (c) CF cathodes during galvanostatic charging (0–30 min) and discharging (after 30 min) at 10 mA cm–2. (d) Photos of solution color changes caused by bromine species diffusion on CF and CCF during continuous charging at 10 mA cm–2.

　　图5. (a) Nitrogen adsorption–desorption isotherm of CF. (b) Nitrogen adsorption–desorption of isotherm CCF. (c) Pore size distribution curves of CF, NiO–CF, and CCF. (d,e) Contact angle test images of CF and CCF. (f) Raman spectra of CF and CCF.

　　图6. (a–d) AC-TEM images and carbon defect indication images of carbon nanotubes. (e) Pristine graphene model, simulating the surface of CF and graphene model with carbon vacancy, simulating the carbon defect structure on the CCF. (f) Comparison diagram of the adsorption energies of Br–, Br2, and Br3– on the two models. (g,h) Charge density difference map and Bader charge of Br2 when in contact with the graphene model and the graphene model with carbon vacancy, respectively.

　　3小结 

　　总而言之，本研究采用热解-CVD一体化策略，以废聚乙烯为原料，成功制备了碳纳米管改性碳毡（CCF）。所得CCF被应用于锌溴电池的阴极。基于CCF的电池展现出卓越的循环稳定性，在10 mA·cm–2的电流密度下可循环1200次，比容量达2 mAh·cm–2，平均库仑效率为98.12%，能量效率为84.82%，显著优于传统的碳毡（CF）基电池。原位拉曼光谱和光学成像直接证实，CCF阴极能有效富集电极表面的多溴化物物种（Br3–和Br5–），并显著抑制其向电解液内部的扩散，从而缓解了有害的穿梭效应。离线表征揭示，经碳纳米管（CNT）改性的结构使 CCF 的比表面积增加了 3 倍，并形成了分级介孔结构，这增强了电解质的可及性，并为 Br–/Br₂ 氧化还原反应提供了丰富的活性位点。此外，拉曼光谱和像差校正透射电子显微镜（TEM）证实了碳纳米管壁内存在高密度的碳缺陷。密度泛函理论（DFT）计算提供了原子级别的见解，表明碳空位缺陷显著增强了Br–、Br₂和Br₃–离子的吸附能力，同时促进了溴氧化还原过程中更高效的电子转移。结构、化学及界面优势的这种协同作用共同支撑了电池的卓越性能。本研究为将废弃塑料定向转化为高性能储能材料开辟了一条新途径，为先进能源系统提供了创新且可持续的策略。

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