【作者】 王莉；

【导师】 李志健； 吴海伟；

【作者基本信息】 陕西科技大学 ， 轻工技术与工程， 2021， 硕士

【摘要】 随着柔性可穿戴设备的兴起,锂离子电池发展趋向于开发高性能柔性的正极材料。富锂锰基材料和硫材料是目前研究比较热的两种正极材料,但仍存在一些问题需要解决,比如容量低、电压衰减快和机械性能不好等问题。针对这些问题本文采用氮掺杂的碳纳米层(NC)表面包覆改性提高富锂锰基正极的电化学问题,通过加入阔叶木纤维(HWF)和纳米纤维素纤维(CNF)分别对富锂锰基正极材料和硫正极材料实现柔性化。研究结果表明,NC能提高富锂锰基正极的放电比容量,同时加入的HWF和CNF不仅能实现正极材料的柔性化,还能缓解充放电过程中存在的一些电化学问题。具体工作如下:(1)富锂锰基正极材料Li1.2Mn0.54Ni0.13Co0.13O2(LNMC),主要通过一种氮掺杂的碳纳米层改性提高富锂锰基正极材料(NC@LNMC)的电化学性能,研究了表面包覆量对LNMC电性能的影响。研究结果表明:2%NC@LNMC具有最好的电化学性能,在0.1C下首次放电比容量为260 mAh/g,在1 C倍率下循环200次后,2%NC@LNMC放电比容量仍保持在180 mAh/g。(2)以富锂锰基为正极材料,主要通过用HWF、多壁碳纳米管(MWCNT)与LNMC正极材料复合制备柔性自支撑复合碳纸HWF/CNT/LNMC。研究结果表明,HWF能实现富锂锰基正极材料的柔性化,同时提高富锂锰基正极材料的电性能,在1 C倍率下循环200次后放电比容量仍可达225 mA h/g。(3)以硫为正极材料,主要通过真空抽滤法制备出MWCNT、MWCNT-CNF、MWCNT-CNF-NiCo2O4 和 MWCNT-CNF-NiCo2S4 等柔性自支撑复合纸电极,研究结果表明:CNF能实现硫正极材料的柔性化,同时可以改善提高硫正极材料的电性能。电性能测试结果表明,无论是在低倍率还是高倍率条件下,MWCNT-CNF-NiCo2S4复合纸的放电性能都要优于其他三种柔性自支撑复合纸,并且具有较好的循环稳定性(0.2C和1C下循环100次:比容量在880 mA h/g和811 mA h/g以上、库伦效率都在90%以上)。综上,本文提出采用纳米纤维素纤维和阔叶木纤维实现锂离子电池正极材料的柔性化,能改善并提高锂离子电池的电化学性能和机械性能,对于其它电池正极材料有很好的借鉴作用。更多还原

【Abstract】 With the rise of flexible wearable devices,the development of lithium-ion batteries tends to develop high-performance flexible cathode materials.Lithium-rich manganese-based materials and sulfur materials are currently two relatively hot cathode materials,but there are still some problems that need to be solved,such as low specific capacity,fast voltage decay,and poor mechanical properties.In response to these problems,this paper uses nitrogen-doped carbon nano-layer(NC)surface coating modification to improve the electrochemical problems of lithium-rich manganese-based cathodes.By adding hardwood fiber(HWF)and nano-fiber(CNF),respectively,the lithium-rich Manganese-based cathode materials and sulfur cathode materials realize flexibility.The research results show that NC can increase the specific discharge capacity of lithium-rich manganese-based cathodes,and the addition of HWF and CNF can not only realize the flexibility of cathode materials,but also alleviate some electrochemical problems in the charging and discharging process.The specific work is as follows:(1)The lithium-rich manganese-based cathode material Li1.2Mn0.54Ni0.13Co0.13O2(LNMC)is mainly modified by a nitrogen-doped carbon nano-layer to improve the electrochemical performance of the lithium-rich manganese-based cathode material(NC@LNMC).The influence of the amount of surface coating on the electrical properties of LNMC is discussed.The research results show that:2%NC@LNMC has the best electrochemical performance,the first discharge specific capacity at 0.1 C is 260 mAh/g,after 200 cycles at 1 C rate,the discharge specific capacity of 2%NC@LNMC is still Keep it at 180 mAh/g.(2)With lithium-rich manganese base as the cathode material,flexible self-supporting composite carbon paper HWF/CNT/LNMC is mainly prepared by using HWF,multi-walled carbon nanotube(MWCNT)and LNMC cathode material to compound.The research results show that HWF can realize the flexibility of lithium-rich manganese-based cathode materials and improve the electrical performance of lithium-rich manganese-based cathode materials.The discharge specific capacity can still reach 225 mA h/g after 200 cycles at 1 C rate.(3)Using sulfur as the cathode material,flexible self-supporting composite paper electrodes such as MWCNT,MWCNT-CNF,MWCNT-CNF-NiCo204 and MWCNT-CNF-NiCo2S4 were prepared mainly by vacuum filtration.Flexibility can improve the electrical performance of sulfur cathode materials at the same time.The electrical performance test results show that the discharge performance of MWCNT-CNF-NiCo2S4 composite paper is better than the other three flexible self-supporting composite papers,and it has better cycle stability(Cycle 100 times at 0.2 C and 1 C:the specific capacity is above 880 mA h/g and 811 mA h/g,and the coulombic efficiency is above 90%)In summary,this article proposes that the use of nano-cellulose fibers and hardwood fibers to realize the flexibility of lithium-ion battery cathode materials can improve and enhance the electrochemical and mechanical properties of lithium-ion batteries,which is a good reference for other battery cathode materials.更多还原