石墨烯屏蔽层助力锂离子电池实现耐氧石墨负极

1成果简介

高压阴极的氧气穿透是开发高能量密度锂离子电池面临的关键挑战，因为它会在石墨阳极引发寄生反应，并破坏固体电解质界面（SEI）的稳定性。本文，北京科技大学詹纯 教授、中国科学院物理研究所 王雪锋、华北电力大学 刘桂成 教授等在《Green Chem》期刊发表名为“Graphene shields enabling oxygen-durable graphite anode in high-energy lithium-ion batteries”的论文，研究通过在石墨负极上设计石墨烯屏蔽层来解决这一关键问题，该屏蔽层可阻隔氧气渗透，并在形成周期中强制排出氧气，这一效果已通过差分电化学质谱法（DEMS）得到验证。

低温透射电子显微镜（cryo-TEM）与原子力显微镜（AFM）揭示，石墨烯屏蔽层促进了富无机物的SEI形成，显著提升了其化学与机械强度（杨氏模量：17.63 GPa vs. 6.69 GPa基线值）。电化学评估表明，屏蔽阳极在4.8V全电池循环中实现了更优的初始库仑效率、更低的不可逆容量损耗及更强的容量保持能力。尤其值得注意的是，该氧气屏蔽方案在4.8V条件下经100次循环后，容量保持率达到原始石墨阳极的1.6倍。展望未来，该方法通过与阴极稳定化及电解液工程的协同整合，有望为高性能锂离子电池的商业化开辟可行路径：在实现突破性能量密度（超过400 Wh kg⁻¹）的同时，通过系统性界面工程优化显著延长循环寿命耐久性。

2图文导读

图1、Schematic illustration of SEI formation in Gr anode using rGO shields to modulate oxygen crossover.

图2、(a–d) SEM images of the pristine Gr and shielded Gr@xrGO (x = 1, 3, 5) samples. (e–h) TEM images and corresponding high-resolution magnified views of both the pristine sample and the graphene-modified sample. (i and g) TEM images of the wrinkled graphene film and its corresponding SAED pattern. (k) XRD patterns of rGO-shielded and the pristine samples. (l) Raman spectra of all the as-prepared samples.

图3、(a and b) Initial charge/discharge profiles of the assembled full cells and statistical chart of charging capacity contribution per battery. (c and d) Schematic diagram using two half-cells in reverse series to exclude the effect of oxygen crossover and the corresponding initial charge/discharge profiles. (e) Initial charge/discharge curves of LFP||Gr with different rGO content shields. XPS spectra of C 1s (f) and F 1s (g) from Gr and Gr@3rGO after formation stage. (h) The relative atomic ratio ofC–C, C–O, C=O, and ROCO2Li based on C 1s spectra and Li–F, and P–F based on F 1s spectra.

图4、(a) Cycling performance of the pristine and rGO-shielded full cells. Cryo-TEM images and Fourier transform patterns of SEI layers of Gr (b–d) and Gr@3rGO (e–g) after 100 cycles.

图5、 (a and b) Top-down SEM images of Gr (a) and Gr@3rGO (b). (c–f) Cross-sectional SEM images of Gr and Gr@3rGO after 100 and 200 cycles. (g and h) Relative atomic ratios of C–C, C–O,C=O,and ROCO2Li based on C 1s spectra as well as Li–F and P–F based on F 1s spectra.

图6、 (a and b) Nyquist plots of Gr||Ref (Li) in each system with three electrode set-up. (c) The RSEI value of Gr||Ref (Li) in each system with three electrode set-up. (d) Normalized current density vs. time curves of Gr||Li, measured by potentiostatic test for 110 h at 0.2 V. (e) Normalized capacity density vs. time curves Gr/Li, converted from the curves in d. (f) The growth rates of capacity loss of each half cell.

图7、AFM height images and Young's modulus mappings of Gr (a and b) and Gr@3rGO (c and d) anodes. (e) Force-displacement approaching curves for Gr and Gr@3rGO anodes.

3小结

综上所述，我们开发了一种基于rGO的理性设计氧气阻隔屏障，将其应用于石墨负极，有效缓解了LRMO全电池中氧气穿透引起的性能衰减。该rGO屏蔽层展现出三重功能：(1) 通过立体位阻实现选择性氧气阻隔（层间距：0.32–0.34 nm）；(2) 通过边缘缺陷维持锂离子渗透性；(3) 通过抑制寄生氧-电解质反应增强界面稳定性。与未涂覆阳极相比，rGO改性系统使氧气排出量提高30%，从而减少表面氧气积累。因此，采用rGO屏蔽阳极的全电池在1/3C循环100次后，容量保持率提升1.6倍，首充放电容量超过270 mAh g⁻¹，初始库仑效率达74.48%。此外，相较于原始样品，rGO屏蔽样品的RSEI值显著降低。这表明rGO屏蔽层能抑制氧气穿透引发的副反应，优化SEI层结构并增强界面稳定性。冷冻透射电子显微镜、X射线光电子能谱与原子力显微镜联合验证：屏蔽阳极形成富含LiF的薄层（约12纳米）SEI，其杨氏模量高达17.63GPa，显著区别于未涂覆样品中厚层有机主导的SEI。本研究强调了阳极侧界面工程在调控高电压正极系统氧行为中的关键作用。基于物理筛分与界面稳定化的rGO屏蔽概念，可广泛推广至其他产氧正极材料（如富锂锰氧化物、富镍层状氧化物）。展望未来，该方法若能与阴极稳定化及电解液工程协同整合，有望为实现能量密度突破400 Wh kg⁻¹且循环寿命更长的实用锂离子电池铺平道路。

文献：

• DOI
• https://doi.org/10.1039/D5GC04826E
• DOI
• https://doi.org/10.1039/D5GC04826

来源：材料分析与应用