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Silicon-carbon anode materials

Time:2020/01/06 丨 source:未知 丨 visit count:

Important progress has been made in the research of silicon-carbon anode materials

Recently, professor Yingbin Lin, associate professor Jiaxin Li, Professor Zhigao Huang, associate professor Yangyang Li, and academician Jian Lu of the City University of Hong Kong have made significant progress in the research of silicon-carbon anode Materials: "Dramatic improvement enabled by incorporated thermal conductive TiN into Si-based electrodes for Lithium Batteries" , published in the International Journal of Materials, Energy Storage Materials; "A facile strategy to construct silver-modified, ZnO-incorporated and carbon-coated Silicon / porous-nanofibers with enhanced lithium storage" was published in the International Journal of Comprehensive Authority.
Introducing high thermal conductivity TiN to promote thermal balance to improve the performance of silicon-carbon anode.

[ research background ]
Due to its high specific capacity, suitable working potential and abundant reserves, Si based materials are considered as the first choice for the next generation of high energy density lithium-ion battery materials. However, the large volume change and low intrinsic conductivity of Si-based materials during charging and discharging hinder the industrialization process. In order to solve these two problems, the stable SEI film is also very important, besides the strategy of decreasing the volume expansion and improving the conductivity. However, due to the poor thermal conductivity and electrical conductivity of Si and binder in the electrode, the heat generated by electrochemical reaction can not be conducted rapidly, which will lead to the accumulation of heat in the electrode, the thermal decomposition of SEI film and the uneven growth of thickness, as a result, the structural stress and the volume phase crack of SEI film are increased, and the capacity decay is fast. At the same time, because of the macroscopical difference of active substance distribution and compaction density in the electrode, the difference of current distribution and heat production in the electrode is inevitable, which will have a significant influence on the dynamic diffusion of lithium ion and the evolution of SEI. Therefore, it is necessary to realize the uniform thermal distribution of Si-based electrode, to guarantee the stability of SEI film, and to improve the electrochemical performance of Si-based anode materials.
[ Introduction ]
A Silicon / graphene / TiN / Carbon Composite (Si / G@C / TiN) with high conductivity and thermal conductivity was designed, in order to solve the problem of SEI film stability caused by temperature and stress uneven distribution at high current and high temperature. The reversible capacity of the Si / G@C / TiN Electrode is 660mAh / G at 10A/g , and 776.5 mAh / G remains after 400 cycles of 5A / G, and 996 mAh / G remains after 200 cycles of 2A / G at 55 °C. The full cell with LiNi0.5Co0.2Mn0.3O2 cathode material can achieve an energy density of up to 476Wh / kg. At the same time, the relationship between thermal conductivity and SEI stability was analyzed by means of IR thermal imaging, DSC, XPS and AFM measurements, and the effect of high thermal conductivity on the electrochemical performance and SEI stability of SI-C anode was revealed.
[Graphic Guide]

Figure 1. The Composite Schematic Diagram of Si / G@C / TiN and the SEM, TEM and HR-TEM images of( a-f)Si / G@C / TiN. The Si / G@C / TiN anode can be prepared by a simple ultrasonic spraying method, and the Si / G@C / TiN Materials with micro / Nano composite structure can be prepared by ultrasonic spraying, tin Particles, silicon particles and graphite are uniformly coated with graphene and pyrolytic carbon, and have good interfacial contact and conductivity enhancement effects.

Figure 2. Electrochemical Properties of Si/G@C and Si/G@C/TiN at 25 °C and 55 °C. The reversible capacity of the Si / G@C / TiN electrode can reach 660mAh/g at 10A/g, and still maintain 776.5 mAh/g at 5A/g after 400 cycles, and 996 mAh/g at 55 °C and 200 cycles at 2A/g test Current.

Figure 3. The temperature distributions of Si/G@C and Si/G@C/TiN electrodes were measured by infrared thermal imaging at different time of thermal radiation and the results of DSC at different temperatures after cycling. The relationship between the thermal conductivity and the stability of Sei was analyzed by means of infrared thermal imaging technique, combined with DSC, XPS and AFM measurements, and the effect of high thermal conductivity on the electrochemical performance and SEI stability of Si-C anode was revealed, especially at high temperature, it promotes the stability of SEI, which makes the material have excellent battery performance.

Figure 4. Design and performance test demonstration of Si/G@C/TiN‖LiNi0.5Co0.2Mn0.3O2 full battery. Based on the total weight of the active material, the electrode material can provide 476 Whk/genergy density.
[ research conclusion ]
In this work, high conductivity and thermal conductivity TiN nanoparticle loaded lithium-ion battery composite anode materials were synthesized by vacuum and ultrasonic atomization techniques. The Tin load with high thermal conductivity improves the conductivity of the electrode, promotes the uniform distribution of heat in the electrode, improves the stability of SEI, and improves the electrochemical performance of the silicon-carbon anode at high temperature and high current, it provides a new design idea for the design of silicon-carbon anode.
Secondly, a silicon-carbon anode with lithium-storage-enhanced silver-modified, Zinc oxide-doped and carbon-protected was constructed

[ research background ]
Silicon Carbon is one of the most attractive anode materials to meet the increasing demand of high capacity and high cycle rate of lithium-ion battery. However, silicon-carbon materials still face the constraints of material nature and technology development: First, the volume effect of silicon materials is more than 300% in the cycle, and the related problems caused by it; Second, the poor conductivity of silicon materials due to its semiconductor properties seriously restricts the diffusion rate of lithium ions in silicon anode and limits its full performance. In addition, the poor interface compatibility between silicon-carbon anode material and electrolyte during battery cycle is also an important reason to limit the improvement of battery performance. Therefore, it is very important to prepare silicon-carbon anode materials which can overcome the volume expansion and poor conductivity of silicon and enhance the interface compatibility.
[ job description ]
In this work, the ZnO-Si@C-PCNFs composites were designed and synthesized by the traditional electrospinning method. The prepared ZnO-Si@C-PCNFs can obviously overcome the disadvantages of silicon bulk expansion and poor conductivity. As the anode of lithium battery, the ZnO-Si@C-PCNFs exhibits excellent cycle life and high rate performance. At the same time, ZnO-Si@C-PCNFs anode loaded with AG particles showed enhanced Lib performance. At 1.8 a / G current, the average capacity remained at 920mAh / G after 1000 cycles, and the loss of capacity was negligible The mechanism of the enhancement of electric chemical kinetics due to the doping and mismatching of zno is also revealed in detail. In addition, the assembly design of a simple soft-pack all-cell was introduced, and it was used to evaluate the performance of all-cell with the silicon-carbon anode. Using NCM523 as the positive electrode, the whole Cell Assembly of Ag / ZnO-Si@C-PCNFs was carried out. The energy density of the whole cell was 230 wh / kg, which was about 18% higher than that of commercial graphite / NCM523 flexible package whole cell.
[Graphic Guide]

Figure 1. Schematic diagram of Synthesis of ZnO-Si@C-PCNFs and AG / ZnO-Si@C-PCNFs.

Figure 2. A SEM and B TEM images of Ag / ZnO-Si@C-PCNFs, schematic diagram of c electron and Ion Transport, D cycle performance and test results and demonstration of e-g Ag / ZnO-Si@C-PCNFs / / NCM523 flexible battery. The AG / ZnO-Si@C-PCNFs electrode was prepared, and the average capacity of the electrode remained at 920mAh / G after 1000 cycles at the current of 1.8 a / G, provides an energy density of 230 wh / kg.

Figure 3. The surface SEM images of ZnO-Si@C-PCNFs and AG / ZnO-Si@C-PCNFs electrodes after 5 and 50 cycles and the corresponding XPS results, the SI@C-PCNFS and ZnO-Si@C-PCNFs with and without zinc oxide in m-n are shown. In view of the fact that the mechanism of improving the performance of silicon-carbon battery by modification of micro-zinc oxide is not clear, this work proves that the modification of micro-zinc oxide can inhibit the reaction of silicon particles with trace amount of hydrofluoric acid, the interface contact between silicon-carbon electrode material and electrolyte was stabilized, so as to improve the battery performance.

Figure 4. Photo of electrode and battery cell of a simple flexible battery pack, Engineering Test Platform of B Fujian Normal University lithium battery and display of finished battery. The research team of Fujian Normal University has a solid foundation and accumulated applied research, relying on the key laboratory of quantum control and new energy materials of Fujian Province and the research center of Solar Energy Conversion and energy storage engineering technology of Fujian Province, lithium-ion battery has a complete pilot plant, can manufacture and research and development of 18650 cylindrical batteries, 266990 square power batteries and 383450 flexible battery series commercialization.
[1] Jianming Tao, Lin Lu, Baoqi Wu, Xinyue Fan, Yanming Yang, Jiaxin Li*, Yingbin Lin*, Yang Yang Li*, Zhigao Huang, Jian Lu. Dramatic improvement enabled by incorporating thermal conductive TiN into Si-based anodes for lithium ion batteries. Energy Storage Mater.2019.DOI:10.1016/j.ensm.2019.12.025
[2] Jiaxin Li, Zebiao Li, Weijian Huang, Lan Chen, Fucong Lv, Mingzhong Zou, Feng Qian, Zhigao Huang*, Jian Lu*, Yang Yang Li*. A facile strategy to construct silver-modified, ZnO-incorporated and carbon-coated silicon/porous-carbon nanofibers with enhanced lithium storage. Small 2019,1900436, DOI:10.1002/smll.201900436

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