物理化学学报

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基于混合溶剂有机电解液的超低温孔洞石墨烯超级电容

薄拯1,2, 孔竞1, 杨化超1,2, 郑周威1, 陈鹏鹏1, 严建华1, 岑可法1   

  1. 1 浙江大学能源清洁利用国家重点实验室, 能源工程学院, 杭州 310027;
    2 浙江大学杭州国际科创中心, 杭州 311215
  • 收稿日期:2020-05-21 修回日期:2020-06-16 录用日期:2020-07-01 发布日期:2020-07-03
  • 通讯作者: 杨化超 E-mail:huachao@zju.edu.cn
  • 基金资助:
    国家自然科学基金(51722604),浙江省自然科学基金(LR17E060002),浙江省重点研发项目(2019C01044),中国博士后科学基金(2019M662048)资助

Ultra-Low-Temperature Supercapacitor Based on Holey Graphene and Mixed-Solvent Organic Electrolyte

Zheng Bo1,2, Jing Kong1, Huachao Yang1,2, Zhouwei Zheng1, Pengpeng Chen1, Jianhua Yan1, Kefa Cen1   

  1. 1 State Key Laboratory of Clean Energy Utilization, College of Energy Engineering, Zhejiang University, Hangzhou 310027, China;
    2 Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou 311215, China
  • Received:2020-05-21 Revised:2020-06-16 Accepted:2020-07-01 Published:2020-07-03
  • Supported by:
    The project was supported by the National Natural Science Foundation of China (51722604), the Zhejiang Provincial Natural Science Foundation of China (LR17E060002), the Key R&D Program of Zhejiang Province, China (2019C01044) and the China Postdoctoral Science Foundation (2019M662048).

摘要: 适用于极低温环境的石墨烯超级电容具有广阔的应用前景。然而,由于片层间严重的堆叠团聚,目前石墨烯超级电容的低温储能性能并不理想。本文使用H2O2氧化刻蚀法制备了孔洞石墨烯(rHGO),将传统有机溶剂碳酸丙烯酯(PC)和低凝固点溶剂甲酸甲酯(MF)混合制备了混合溶剂有机电解液,组装获得了能够在-60℃极低温环境下稳定工作的超级电容。结果表明,该超级电容在-60℃下的比电容为106.2 F·g-1,相对于常温电容(150.5 F·g-1)的性能保持率高达70.6%,显著优于未做处理的石墨烯(52.3%)以及文献中的其他石墨烯材料。得益于孔洞化形貌中丰富的介孔和大孔所形成的离子传输通道和缩短的离子传输路径,孔洞石墨烯内的离子扩散阻抗远小于普通石墨烯,且受温度降低的影响更小。在-60℃的极低温条件下,该超级电容表现出26.9 Wh·kg-1的最大能量密度和18.7 kW·kg-1的最大功率密度,优于传统碳材料的低温超级电容性能。-60℃时在5 A·g-1电流密度下循环充放电10000次后电容保持率达89.1%,具有良好的低温循环稳定性。

关键词: 超级电容, 超低温, 孔洞石墨烯, 混合溶剂有机电解液, 电化学性能

Abstract: Supercapacitors that can withstand extremely low temperatures have become desirable in applications including portable electronic devices, hybrid electric vehicles, and renewable energy conversion systems. Graphene is considered as a promising electrode material for supercapacitors owing to its high specific surface area (up to 2675 m2·g-1) and electrical conductivity (approximately 2×102 S·m-1). However, the restacking of graphene sheets decreases the accessible surface area, reduces the ion diffusion rate and prolongs the ion transport pathways, thereby limiting the energy storage performance at low temperatures (typically <100 F·g-1 at sub-zero temperatures). Herein, we fabricate a supercapacitor based on holey graphene and mixed-solvent organic electrolyte for ultra-low-temperature applications (e.g., -60℃). Reduced holey graphene oxide (rHGO) was synthesized as the electrode material via an oxidative-etching process with H2O2. Methyl formate was mixed with propylene carbonate to improve the electrolyte conductivity at temperatures ranging from -60 to 25℃. The as-fabricated supercapacitor showed a high room-temperature capacitance of 150.5 F·g-1 at 1 A·g-1, which was almost 1.5 times greater than that of the supercapacitor using untreated reduced graphene oxide (rGO; 101.4 F·g-1). The improved capacitance could be attributed to the increased accessible surface rendered by the abundant mesopores and macropores on the holey surface. As the temperature decreased to -60℃, the rHGO supercapacitor still delivered a high capacitance of 106.2 F·g-1 with a retention of 70.6%, which was superior to other state-of-the-art graphene-based supercapacitors. Electrochemical impedance spectra tests revealed that the ion diffusion resistance in rHGO was significantly smaller than that in rGO and less influenced by temperature with a lower activation energy. This was because the holey morphology can provide transport pathways for ions and reduce the ion diffusion length during charging/discharging, consequently diminishing the diffusion resistance at low temperatures. Specifically, at -60℃, the energy density of supercapacitor reached up to 26.9 Wh·kg-1 at 1 A·g-1 with a maximum power density of 18.7 kW·kg-1 at 20 A·g-1, surpassing the low-temperature performance of conventional carbon-based supercapacitors. Moreover, after 10000 cycles at -60℃ with a current density of 5 A·g-1, 89.1% of capacitance was retained, suggesting the stable and reliable power output of the current supercapacitor at extremely low temperatures.

Key words: Supercapacitor, Ultra-low temperature, Holey graphene, Mixed-solvent organic electrolyte, Electrochemical performance

MSC2000: 

  • O646