scholarly journals The Role of Silicon in Silicon-Graphite Composite Electrodes Regarding Specific Capacity, Cycle Stability, and Expansion

Author(s):  
Erfan Moyassari ◽  
Thomas Roth ◽  
Simon Kücher ◽  
C. C. Chang ◽  
Shang-Chieh Hou ◽  
...  

Abstract One promising way of compensating for the repeated volume expansion and contraction of silicon as an anode active material in lithium ion batteries (LIBs) is to embed silicon within a graphite matrix. Silicon-graphite (SiG) composites combine the advantageous properties of graphite, i.e., large electrical conductivity and high structural stability, with the advantageous properties of silicon, i.e., high theoretical capacity. Graphite has a much lower volume expansion upon lithiation (≈ 10%) than pure silicon (≈ 300%) and provides a mechanically stable matrix. Herein, we present an investigation into the electrochemical performance and thickness change behavior of porous SiG anode compositions with silicon contents ranging from 0 wt% to 20 wt%. The electrode composites were studied using two methods: in situ dilatometry for the thickness change investigation and conventional coin cells for the assessment of electrochemical performance. The measurements show that the initial thickness change of SiG electrodes increased significantly with the silicon content, but it leveled off during cycling for all compositions. There appears to be a correlation between silicon content and capacity loss, but no clear correlation between thickness change and capacity loss rate was found.

2021 ◽  
Vol 1036 ◽  
pp. 35-44
Author(s):  
Ling Fang Ruan ◽  
Jia Wei Wang ◽  
Shao Ming Ying

Silicon-based anode materials have been widely discussed by researchers because of its high theoretical capacity, abundant resources and low working voltage platform,which has been considered to be the most promising anode materials for lithium-ion batteries. However,there are some problems existing in the silicon-based anode materials greatly limit its wide application: during the process of charge/discharge, the materials are prone to about 300% volume expansion, which will resultin huge stress-strain and crushing or collapse on the anods; in the process of lithium removal, there is some reaction between active material and current collector, which creat an increase in the thickness of the solid phase electrolytic layer(SEI film); during charging and discharging, with the increase of cycle times, cracks will appear on the surface of silicon-based anode materials, which will cause the batteries life to decline. In order to solve these problems, firstly, we summarize the design of porous structure of nanometer sized silicon-based materials and focus on the construction of three-dimensional structural silicon-based materials, which using natural biomass, nanoporous carbon and metal organic framework as structural template. The three-dimensional structure not only increases the channel of lithium-ion intercalation and the rate of ion intercalation, but also makes the structure more stable than one-dimensional or two-dimensional. Secondly, the Si/C composite, SiOx composite and alloying treatment can improve the volume expansion effection, increase the rate of lithium-ion deblocking and optimize the electrochemical performance of the material. The composite materials are usually coated with elastic conductive materials on the surface to reduce the stress, increase the conductivity and improve the electrochemical performance. Finally, the future research direction of silicon-based anode materials is prospected.


Author(s):  
Yanping Dang ◽  
Wangyu Liu ◽  
Weigui Xie ◽  
Weiping Qiu

Abstract The anode and cathode pieces are vital components of lithium-ion batteries. The coating surface density of active material is a significant parameter involved during the fabrication of electrodes and has considerable impact on battery performance. In this paper, anode and cathode pieces are prepared with different surface densities within the allowable range. The anode and cathode pieces are first graded respectively and then matched up according to different surface density ranges. Afterward, the electrodes are assembled with commercial polypropylene separator in 18,650 cell case and infused with electrolyte. The cathode is constituted with a mixture of nickel cobalt manganese (NCM) ternary material and lithium manganese oxide coated on aluminum foil, while the anode is composed of graphite coated on copper foil. The electrochemical performance and safety properties were tested to investigate the influence of the coating surface density of electrodes and optimize the electrochemical performance by regulating the matching surface density of electrodes. The results indicate that larger surface density of both cathode and anode can provide better battery consistency, while smaller surface density can contribute to better specific capacity and smaller capacity loss after cycling. Modest cost and superior properties can be achieved for lithium-ion batteries by reasonably matching the surface density of anodes and cathodes pieces.


NANO ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. 2050149
Author(s):  
Xiangyu Shi ◽  
Jifei Liu ◽  
Jianfeng Dai ◽  
Yufeng Qi

Silicon carbon nanoparticles (SCNPs) coated with reduced graphene oxide (rGO) were fabricated by a hydrothermal method and subsequently by a simple heat treatment process. SCNPs/rGO exhibit excellent electrochemical performance which not only attributes the rGO layer to inhibit the volumetric expansion of silicon and reduce the impedance between the active material and lithium ions during the electrochemical process, but also improves the electrical conductivity of SCNPs/rGO. The as-prepared compound was cyclically tested at a current density of 150[Formula: see text]mA/g, with the first charge and discharge capacities of 3152.2[Formula: see text]mAh/g and 3342.7[Formula: see text]mAh/g, respectively. Moreover, the electrochemical performance of SCNPs/rGO was better than SCNPs. The [Formula: see text] values for fresh battery, after 1 cycle and 100 cycles, are 120.9[Formula: see text][Formula: see text], 120.5[Formula: see text][Formula: see text] and 104[Formula: see text][Formula: see text]. Thus, compared with SCNPs, SCNPs/rGO exhibited lower overall impedance values. These results indicate that the addition of graphene layer significantly improved the electrochemical performance of SCNPs electrodes and reduced the internal resistance of the battery.


Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3448
Author(s):  
Alexandra Meyer ◽  
Fabian Ball ◽  
Wilhelm Pfleging

To increase the specific capacity of anodes for lithium-ion cells, advanced active materials, such as silicon, can be utilized. Silicon has an order of magnitude higher specific capacity compared to the state-of-the-art anode material graphite; therefore, it is a promising candidate to achieve this target. In this study, different types of silicon nanopowders were introduced as active material for the manufacturing of composite silicon/graphite electrodes. The materials were selected from different suppliers providing different grades of purity and different grain sizes. The slurry preparation, including binder, additives, and active material, was established using a ball milling device and coating was performed via tape casting on a thin copper current collector foil. Composite electrodes with an areal capacity of approximately 1.70 mAh/cm² were deposited. Reference electrodes without silicon were prepared in the same manner, and they showed slightly lower areal capacities. High repetition rate, ultrafast laser ablation was applied to these high-power electrodes in order to introduce line structures with a periodicity of 200 µm. The electrochemical performance of the anodes was evaluated as rate capability and operational lifetime measurements including pouch cells with NMC 622 as counter electrodes. For the silicon/graphite composite electrodes with the best performance, up to 200 full cycles at a C-rate of 1C were achieved until end of life was reached at 80% relative capacity. Additionally, electrochemical impedance spectroscopies were conducted as a function of state of health to correlate the used silicon grade with solid electrolyte interface (SEI) formation and charge transfer resistance values.


2019 ◽  
Vol 807 ◽  
pp. 74-81
Author(s):  
Ying Wang ◽  
Wei Ruan ◽  
Ren Heng Tang ◽  
Fang Ming Xiao ◽  
Tai Sun ◽  
...  

In this study, Si@C/Graphite composite anodes were synthesized through spray drying and pyrolysis using silica, artificial graphite, and two kinds of organics (phenolic resin or pitch). The Si@PR-C/Graphite exhibits enhanced electrochemical performance for lithium-ion batteries. The first charge-discharge specific capacity is 512.8mAh/g and 621.8mAh/g, respectively, the initial coulombic efficiency is 82.5% at 100mA/g, and its capacity retention rate reached as high as 85.4% with the capacity fade rate of less than 0.18% per cycle after 85 cycles. The Si@PI-C/Graphite also presents excellent discharge specific capacity of 702.8mAh/g with the capacity retention rate of 76.9% after 30 cycles. Mechanisms for high electrochemical performances of the Si@C/Graphite composite anode are discussed. It found that the enhanced electrochemical performance due to the formation of core/shell microstructure. These encouraging experimental results suggest that proper organic carbon source has great potential for improvement of electrochemical properties of pure silicon as anode. Key words:lithium-ion batteries; anode; Si@C/Graphite composite; electrochemical performance


Author(s):  
Linghong Zhang ◽  
Sookyung Jeong ◽  
Nathan Reinsma ◽  
Kerui Sun ◽  
Derrick S Maxwell ◽  
...  

Abstract Compared to the graphite anode, Si and SiOx-containing anodes usually have a larger initial capacity loss (ICL) due to more parasitic reactions. The higher ICL of the anode can cause significant Li inventory loss in a full cell, leading to a compromised energy density. As one way to mitigate such Li inventory loss, Li2O2 can be used as the cathode prelithiation additive to provide additional lithium. However, an additional catalyst is usually needed to lower its decomposition potential. In this work, we investigate the use of Li2O2 as the cathode prelithiation additive without the addition of a catalyst. Li2O2 decomposition is first demonstrated in coin half-cells with a calculated capacity of 1180 mAh/g obtained from Li2O2 decomposition. We then further demonstrate successful Li2O2 decomposition in single-layer pouch (SLP) full cells and evaluate the initial electrochemical performance. Despite its moisture sensitivity, Li2O2 showed reasonable compatibility with dry-room handling. After dry-room handling, Li2O2 decomposition was observed with an onset potential of 4.29 V vs. SiOx anode in SLP cells. With Li2O2 addition, the utilization of the Li inventory from cathode active material was improved by 12.9%, and discharge DCR has reduced by 7% while the cells still deliver similar cell capacities.


2021 ◽  
Vol 10 (1) ◽  
pp. 210-220
Author(s):  
Fangfang Wang ◽  
Ruoyu Hong ◽  
Xuesong Lu ◽  
Huiyong Liu ◽  
Yuan Zhu ◽  
...  

Abstract The high-nickel cathode material of LiNi0.8Co0.15Al0.05O2 (LNCA) has a prospective application for lithium-ion batteries due to the high capacity and low cost. However, the side reaction between the electrolyte and the electrode seriously affects the cycling stability of lithium-ion batteries. In this work, Ni2+ preoxidation and the optimization of calcination temperature were carried out to reduce the cation mixing of LNCA, and solid-phase Al-doping improved the uniformity of element distribution and the orderliness of the layered structure. In addition, the surface of LNCA was homogeneously modified with ZnO coating by a facile wet-chemical route. Compared to the pristine LNCA, the optimized ZnO-coated LNCA showed excellent electrochemical performance with the first discharge-specific capacity of 187.5 mA h g−1, and the capacity retention of 91.3% at 0.2C after 100 cycles. The experiment demonstrated that the improved electrochemical performance of ZnO-coated LNCA is assigned to the surface coating of ZnO which protects LNCA from being corroded by the electrolyte during cycling.


2015 ◽  
Vol 167 ◽  
pp. 303-308 ◽  
Author(s):  
Hong-Qiang Wang ◽  
Guan-Hua Yang ◽  
You-Guo Huang ◽  
Xiao-Hui Zhang ◽  
Zhi-Xiong Yan ◽  
...  

RSC Advances ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 6660-6666 ◽  
Author(s):  
Jun Wang ◽  
Shengli Li ◽  
Yi Zhao ◽  
Juan Shi ◽  
Lili Lv ◽  
...  

With a high specific capacity (4200 mA h g−1), silicon based materials have become the most promising anode materials in lithium-ions batteries.


Nanoscale ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 3159-3165 ◽  
Author(s):  
Yucheng Dong ◽  
Shiliu Yang ◽  
Zhenyu Zhang ◽  
Jong-Min Lee ◽  
Juan Antonio Zapien

Antimony sulfide can be used as a promising anode material for lithium ion batteries due to its high theoretical specific capacity derived from sequential conversion and alloying lithium insertion reactions.


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