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电化学(中英文) ›› 2020, Vol. 26 ›› Issue (5): 750-758.  doi: 10.13208/j.electrochem.200643

• 研究论文 • 上一篇    下一篇

基于钴酸锂载体构筑高体积比容量硫基复合材料

王璐, 高学平*()   

  1. 南开大学新能源材料化学研究所,天津 300350
  • 收稿日期:2020-06-15 修回日期:2020-07-15 出版日期:2020-10-28 发布日期:2020-07-21
  • 通讯作者: 高学平 E-mail:xpgao@nankai.edu.cn
  • 基金资助:
    国家自然科学基金项目(21935006)

LiCoO2 as Sulfur Host to Enhance Cathode Volumetric Capacity for Lithium-Sulfur Battery

WANG Lu, GAO Xue-ping*()   

  1. Institute of New Energy Material Chemistry, Nankai University, Tianjin 300350, China
  • Received:2020-06-15 Revised:2020-07-15 Published:2020-10-28 Online:2020-07-21
  • Contact: GAO Xue-ping E-mail:xpgao@nankai.edu.cn

摘要:

锂-硫电池具有高的理论质量/体积能量密度,因而成为最具发展潜力的高比能二次电池体系. 然而,由于硫载体通常采用轻质的碳纳米材料,导致硫基复合材料的振实密度和体积比容量均偏低,制约了电池体积能量密度的提升. 本文尝试采用具有高密度特征的钴酸锂(LiCoO2)作为硫的载体材料,以构筑高振实密度的硫基复合材料,进而提高硫正极的体积比容量. 研究显示,LiCoO2对可溶性多硫化物具有较强的吸附作用,能够促进硫的电化学转化,因而提高了硫的活性物质利用率和循环稳定性. 同时,由于具有高的振实密度(1.90 g·cm-3),S/LiCoO2复合材料的首周体积比容量高达1750.5 mAh·cm-3,是常规硫/碳复合材料的2.2倍. 因此,本文利用具有高密度特征的LiCoO2作为硫载体来提升硫复合材料的体积比容量,有助于实现锂-硫电池的高体积能量密度.

关键词: 锂-硫电池, 硫正极, 金属氧化物, 体积比容量

Abstract:

Lithium-sulfur battery is one of the most promising secondary battery systems due to its super high theoretical gravimetric and volumetric energy densities (2600 Wh·kg-1 and 2800 Wh·L-1, respectively). However, the practical volumetric capacity of sulfur cathode is still unsatisfied due to the overuse of low-density host materials, such as carbon nanomaterials. Herein, commercial LiCoO2 with the high tap density of 2.94 g·cm-3 was used as the host material to build high density sulfur-based composite and compact electrode for increasing the volumetric capacity. Obviously, the tap density of the as-prepared S/LiCoO2 composite was 1.90 g·cm-3, larger than that of the conventional S/carbon composite (0.89 g·cm-3). Correspondingly, the pressed electrode density could be increased to 2.60 g·cm-3 by using the S/LiCoO2 composite. In particular, LiCoO2 showed an effective adsorption and electrocatalytic conversion toward soluble intermediate polysulfides, and facilitied to achieve the high utilization of sulfur and cycle stability. As expected, the S/LiCoO2 composite exhibited larger capacity and slower capacity decay rate at 0.1 C rate as compared with the S/carbon composite. Meanwhile, the polarization in discharge-charge processes was smaller for the S/LiCoO2 composite, showing the enhanced reaction kinetics by adopting LiCoO2 host. Therefore, the S/LiCoO2 composite showed superior rate capability and cycle performance at large current density. By virtue of the high tap density, the S/LiCoO2 composite delivered a larger volumetric capacity (1750.5 mAh·cm-3-composite), almost 2.2 times of the S/carbon composite (811.4 mAh·cm-3-composite). Furthermore, the volumetric capacity of the pressed S/LiCoO2 electrode could reach 1676.8 mAh·cm-3-electrode based on the electrode level, almost 2.5 times of the S/carbon electrode (676.5 mAh·cm-3-electrode). This work provides a feasible strategy to achieve the high volumetric capacity and energy density of cathode based on LiCoO2 as sulfur host, which provides reference for further developing high volumetric energy density cathode materials for lithium-sulfur battery.

Key words: lithium-sulfur battery, sulfur cathode, metal oxides, volumetric capacity

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