1成果简介 

        硬碳负极因具有高比容量、合适的储钠电位和优异的循环稳定性，被认为是钠离子电池（SIBs）最具前景的负极材料。然而，如何通过闭孔工程精准调控硬碳中斜坡容量和平台容量的比例，以提升低电压平台区的储钠容量，仍是当前高性能硬碳负极研发面临的关键挑战，

        本文，四川大学材吴昊教授、武开鹏 副研究员、厦门理工学院庄树新教授等在《Advanced Energy Materials》期刊发表题为"Benzoxazine Chemistry-Directed Closed-Pore Engineering in Microspheric Hard Carbon toward Ultrafast Sodium Energy Storage"的研究论文。研究提出了一种基于苯并噁嗪化学定向交联的创新策略，以天然茶多酚（Tea Polyphenol）、谷氨酸（Glutamic Acid）和甲醛（Formaldehyde）为单体，通过聚合反应合成了聚苯并噁嗪基聚合物微球（G-FT），再经高温碳化制备了富含纳米闭孔的硬碳微球（G-FT-HC）。

        该策略的核心在于：具有双羧基-胺结构的谷氨酸通过多位点连接机制，同时触发了与茶多酚的原位Mannich反应和酯化反应，构建了高度交联的独特Mannich桥接框架。该框架在后续碳化过程中促进了石墨化微区的有序生长，在衍生的硬碳微球中形成了丰富的纳米闭孔结构。所制备的G-FT-HC展现出90.6%的高首次库仑效率、325.7 mAh g?1的高可逆容量（平台容量贡献68.2%），以及15 A g?1下仍保持78.9 mAh g?1的超快倍率性能（≈16秒满充放）。

        2图文导读  

        

        图1、Fabrication and multi-scale characterization of FT and G-FT precursors. (a) Schematic illustration of the preparation process of FT and G-FT. (b) 1H NMR spectra of FT intermediate and G-FT intermediate. (c) FTIR spectra of tea polyphenol, FT, and G-FT. (d) High-resolution XPS spectra of C 1s for the FT and G-FT samples. (e) FESEM image and particle size distribution of G-FT. (f) Free volume distribution from computational simulations of the FT and G-FT models.

        

        图2、Microstructural analysis of FT-HC and G-FT-HC. FESEM images of (a) FT-HC and (b) G-FT-HC. HRTEM images of (c) FT-HC and (d) G-FT-HC. (e) Schematic illustration of the microstructure difference between FT-HC and G-FT-HC. (f) XRD and (g) SAXS patterns with two-dimensional images of FT-HC and G-FT-HC. (h) Radar chart for comparing the pore structural parameters of FT-HC and G-FT-HC. (i) TG-DTG curves of FT and G-FT. Evolution of gaseous products with temperature via in situ FTIR spectra of (j) FT and (k) G-FT.

        

        图3、Electrochemical performance tests and sodium storage mechanism. (a) The first cycle of galvanostatic charge/discharge (GCD) curves at 0.05 A g?1 and (b) rate capacities at various current densities of FT-HC and G-FT-HC electrodes. (c) Comparison of rate performance in ether-based electrolytes of G-FT-HC with the typical HC anodes previously reported in literatures. (d) Discharge capacity contribution from the plateau region in the second cycle at different current densities of FT-HC and G-FT-HC electrodes. (e) Cycling performance at 2 A g?1 of FT-HC and G-FT-HC electrodes. (f) The ICE and cycling performance at different current densities of G-FT-HC compared with previously reported HC anodes. (g) In situ Raman spectra of G-FT-HC electrode and the corresponding variation of ID/IG value. (h) Ex situ SAXS patterns and (i) ex situ XPS Na 1s spectra of G-FT-HC electrodes. (j) Schematic diagram of the sodium storage stages of G-FT-HC electrode.

        

        图4、Na storage kinetics analysis for FT-HC and G-FT-HC. (a) In situ EIS of FT-HC and G-FT-HC electrodes during the initial discharge/charge process. (b) Corresponding DRT profiles from 0.2 to 0.01 V. (c) The Na diffusion coefficients calculated from the GITT curves of G-FT-HC and FT-HC. (d) DFT calculations of Na diffusion and adsorption in carbon interlayers: the diagrams of Na diffusion path, Na adsorption energy and corresponding DOS illustrations at the diffusion end point for the five models. (e) The calculated diffusion barrier energies of Na. (f) Schematic diagram of the distinct Na and electron diffusion behavior in the FT3 and GFT2 models. (g) Different adsorption models for Na clusters of FT3-Pore and GFT2-Pore models. HRTEM images and high-resolution XPS depth profiles of (h) FT-HC and (i) G-FT-HC electrodes after 100 cycles at 0.1 A g++++++?1.

        

        图5、Electrochemical performance of G-FT-HC||NVP full cells and evaluation of hard carbons derived from diverse amino acid-based precursors. (a) The typical GCD curves of NVP cathode, G-FT-HC anode, and G-FT-HC||NVP full cell. (b) Schematic illustration of the assembled G-FT-HC||NVP full cell. (c) The GCD curves of G-FT-HC||NVP full cell at different current densities. (d) Rate capability of G-FT-HC||NVP full cell at different current densities. (e) Cycling performance of G-FT-HC||NVP full cell at 10 C. (f) Eight representative amino acids selected for their distinct R-group properties. (g) Comparison of the ICE and specific capacity of HC derived from eight amino acids-based polymers.

        3小结 

        综上所述。本文开发了一种简便且可控的策略，通过在分子层面调控聚苯并噁嗪基聚合物前驱体，成功合成了用于固态锂电池（SIBs）的高性能碳氢化合物（HC）负极。依托引入含二羧胺的谷氨酸，结合苯并噁嗪化学导向聚合与原位酯基形成，在球形前驱体中形成了高度交联的内部结构。得益于聚苯并噁嗪聚合物前驱体的独特网络结构，有效抑制了热解过程中碳层的结构坍塌和过度无序化。这使得前驱体能够高效转化为均匀的碳氢微球，其具有氮掺杂的类石墨域、丰富的闭孔以及较低的缺陷浓度。因此，所制备的碳氢化合物负极实现了高平台容量（219.0 mAh g?1）、90.6%的优异初始容量（ICE）、卓越的高倍率性能（15 A g?1 时为 78.9 mAh g?1）以及持久的循环性能（2 A g?1 下循环 1000 次后容量保持率为 88.2%）。此外，组装后的整电池在10 C下循环500次后保持82.8%的容量，并在2375.4 W kg?1功率密度下展现出214.1 Wh kg?1的优异能量密度。本研究为设计具有高度交联网络的聚合物前驱体提供了指导策略，以开发适用于固态锂电池（SIBs）的经济高效、高性能碳氢化合物（HC）负极。

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