Beijing University of Chemical Technology JMCA: High-performance Lithium-ion battery with interface enhanced two-dimensional continuous carbon network silicon negative electrode
【Article information】
High-performance l-ion battery with interface enhanced two-dimensional continuous carbon network Silicon negative electrode
First author: Peng Jiaying
First author: Peng Jiaying
0 Corresponding author: Oxford*, Wang Feng*
Unit: Beijing University of Chemical Technology
[Research background]
Lithium-ion battery has become one of the necessities of human life since it was commercially applied in 1991. However, with the rapid development of portable electronic devices and new energy vehicles, commercial applications have higher requirements for the energy density, security, and life cycle life cycle life. Nowadays, graphite negative electrode theoretical specific capacity for commercial applications is very low, only 372 mAh g-1, cannot meet the growing energy density demand.
silicon-based anode has a high theoretical specific capacity (4200 mAh g-1) and suitable working potential . Replacing the traditional graphite negative electrode can greatly increase the energy density of lithium-ion batteries, and has been widely studied. However, the silicon-based anode will undergo huge volume expansion during the lithiation/delithation process, resulting in continuous side reactions between the active material and the electrolyte and the continuous thickening of the solid electrolyte interface (SEI), and the performance of electrochemical rapidly decays. Therefore, designing the structure of the silicon-based negative electrode is an important strategy to improve volume expansion and improve electrochemical performance.
[Article Introduction]
Recently, Professor Wang Feng from Beijing University of Chemical Technology and Oxford's associate professor team published an article titled "Interface-enhanced continuous 2D-carbon network enabling high performance Si anodes for Li-ion batteries" in the internationally renowned journal Journal of Materials Chemistry A. This article uses a two-dimensional continuous carbon network to coat silicon in situ, which not only improves the problem of volume expansion and poor conductivity of the silicon negative electrode, but also promotes ion and electron transport at the same time, forming a stable interface between the silicon negative electrode and the electrolyte, thus greatly improving the rate performance and cycling performance of the silicon-based negative electrode.
Figure 1. Three different ways of silicon-carbon composite modification (a) 3D carbon coating (b) 2D carbon load (c) 2D carbon network enhanced by continuous interface
[Big points of this article]
Key points 1: The morphology and structure characterization of the silicon negative electrode (Si@GCNS) enhanced by continuous interface
Traditional silicon-carbon two-dimensional composite materials usually use carbon nanosheets (for example, carbon or graphene synthesized by templates) as carriers to load or encapsulate silicon particles, which requires complex synthesis steps and a large number of additional additives. In addition, the interface contact between the carbon nanosheets and silicon particles is poor, and the improvement performance is not obvious. This paper selects gelatin as the precursor for interface-enhanced carbon networks. At the same time, a two-dimensional nanosheet structure was formed using water-soluble potassium chloride as the template. Through pyrolysis and water washing, a negative electrode material (called Si@GCNS) of silicon nanoparticles embedded in gelatin-derived carbon nanosheets was obtained. For comparison, gelatin was also used as the same carbon precursor to prepare silicon negative electrodes modified with three-dimensional carbon coated (called Si@GC) and two-dimensional carbon loading (called Si-GCNS).
Figure 2. Characterization of morphology and structure of Si@GCNS, Si@GC, Si-GCNS
Key points 2: The electrochemical performance characterization of the silicon negative electrode of the continuous interface enhanced two-dimensional carbon network (Si@GCNS)
Si@GCNS negative electrode exhibits a high charging specific capacity (2975 mAh g-1), and the first circle of Kulun efficiency reaches 83%. In addition to the high reversible capacity, Si@GCNS negative electrode also has excellent rate performance, and can still reach 1892 mAh at the current density of 5 A g-1 The charging capacity of g-1, these excellent electrochemical properties, are achieved through the continuous two-dimensional carbon network in the Si@GCNS anode.Due to the enhanced three-dimensional carbon coating of the Si@GC negative electrode, the Si@GC negative electrode has a higher capacity than the Si-GCNS negative electrode, but its block structure leads to its poor rate performance. This result further demonstrates the structural advantages of interface-enhanced two-dimensional carbon networks. The Si-GCNS negative electrode has the lowest reversible capacity due to poor contact between silicon and two-dimensional carbon sheets, and the worst cycle performance among all negative electrodes. Si@GCNS and LiFePO4 assembled for testing. After cycling for 300 cycles at a current density of 1 A g-1, the capacity retention rate reached 89.8%, and the energy density was as high as 460 Wh kg-1, which is higher than other related studies reported recently.
Figure 3. Characterization of electrochemical properties of Si@GCNS, Si@GC, Si-GCNS
Point 3: The important role of interface-enhanced two-dimensional carbon network in stabilizing silicon structure
In order to verify the modification mechanism of interface-enhanced two-dimensional carbon network, we used in situ Raman spectroscopy to study the structural transformation of Si@GCNS negative electrode during charging and discharging. During the lithiation process of Si@GCNS negative electrode, as the voltage decreases, the intensity of the silicon characteristic peak gradually weakens until it disappears in a fully lithiated state, indicating that the silicon has been completely converted to LixSi. During the subsequent detachment process, the silicon feature peak recovery indicates that the interface-enhanced two-dimensional carbon network imparts a higher reversibility to the Si@GCNS negative electrode. The mapping corresponding to the Si@GCNS negative electrode after 5 cycles shows that the C, N, O and F elements are well dispersed and covered with Si elements. This result verifies that interface-enhanced two-dimensional carbon networks facilitate stabilization and formation of uniform solid electrolyte interfaces (SEIs).
Figure 4. (a) In-situ Raman spectroscopy of Si@GCNS negative electrode during charging and discharging (b) TEM image and mapping image after Si@GCNS negative electrode cycle
Key points 4: GITT test and COMSOL simulation
using constant current intermittent titration technology (GITT) to evaluate the diffusion of lithium ion in lithium ion cationization process. The results show that the lithium ion diffusion coefficient of Si@GCNS is significantly higher than that of Si-GCNS and Si@GC. Due to the block structure of Si@GC, it exhibits the lowest lithium ion diffusion coefficient. The relationship between current density distribution and structural composition was further studied using COMSOL multiphysical simulation. Different models were established based on the structure and composition of silicon-carbon negative electrode. The current density distribution of Si@GCNS is significantly higher than that of Si-GCNS and Si@GC and is more uniform, due to Si@GCNS having faster ion electron conduction. The above results show that the interface-enhanced two-dimensional carbon network can accelerate the transport of lithium ions in the electrodes and make the silicon uniformly lithiate, thereby making the Si@GCNS negative electrode have good rate performance and high reversibility.
【Article link】
Interface-enhanced continued 2D-carbon network enabling high performance Si anodes for Li-ion batteryes
https://pubs.rsc.org/en/content/articlelanding/2022/ta/d2ta06859a
[ Corresponding Author Introduction]
Wang Feng, professor and doctoral supervisor , a fellow of the Royal Chemistry Society of England, graduated from Tokyo Metropolitan University in Japan in 2003 and received a doctorate degree in engineering engineering , and completed postdoctoral research at National Shinshu University in Japan from 2003 to 2006. He is currently the vice president of Beijing University of Chemical Technology and director of the Beijing Key Laboratory of Electrochemical Process and Technology of Materials, and also serves as the vice chairman of the 8th Board of the Beijing Surface Engineering Society, a member of the Energy Chemistry Professional Committee of the Chinese Chemical Society, and a member of the Materials Department of the Science and Technology Committee of the Ministry of Education. Mainly engaged in research in electrocatalytic materials, electrochemical energy storage materials, nanocarbon materials, and applied electrochemical engineering. In 2007, he was selected as the Ministry of Education’s New Century Outstanding Talent Support Program , and in 2011, he received the funding from the National Outstanding Youth Science Foundation.
has successively undertaken more than 10 scientific research projects, including the National Key R&D Program, the National Natural Science Foundation of China Key Project, the National Natural Science Foundation of China Joint Fund key support project, the Beijing Science and Technology Plan project and the enterprise commissioned project. It has been held in Chem. Soc. Rev., J. Am. Chem. Soc., Adv. Mater., Angew. Chem. Int. Ed., Adv. Energy Mater., Adv. Funct. Mater., Nano Energy, ACS Catal. and other international journals have published more than 190 SCI academic papers, compiled one English monograph, and obtained 48 national invention patents, 1 authorization each, 1 verified European and Japanese invention patents, and 1 verified first prize and 1 second prize each of provincial and ministerial science and technology awards.
Oxford, associate professor and master's supervisor , graduated from Beijing University of Chemical Technology in 2018 with a doctorate in engineering, visited and exchanged at the Massachusetts Institute of Technology in the United States from 2017 to 2018, and conducted postdoctoral research at Tokyo Metropolitan University in Japan from 2019 to 2020. Mainly engaged in electrochemical energy storage materials and their application research in supercapacitor , alkali metal ion secondary batteries, metal negative electrode secondary batteries, etc. In the past five years, he has published more than 20 papers included in SCI in journals such as Adv. Funct. Mater., Adv. Sci., Nano Energy, Energy Storage Mater., J. Mater. Chem. A, Chem. Eng. J. and other , and has compiled 1 English monograph and obtained 5 national invention patents.
