Super Performance Graphene Coated Silicon Oxide Anode Material
Although silicon oxide (SiO) has high capacity and long cycle life, its inherent conductivity and coulombic efficiency are low, so that it has not been able to be used in large-scale commercial applications. Researchers from the University of North Dakota used low-cost coal humic acid as a raw material to synthesize graphene-coated disproportionated silicon oxide anode material in situ by a simple method. Its first discharge capacity was 1937.6mAh g−1, and its first coulombic efficiency It is 78.2%, the reversible capacity at 2.0 A g-1 is 1023 mAh g-1, and the capacity retention rate after 500 cycles of cycling is 72.4%.
Silicon (Si) is considered to be a potential negative electrode material due to its high specific capacity. However, the volume of silicon expands severely during charging and discharging. This change causes the silicon particles to lose contact with the electrode, resulting in low battery cycle efficiency and rapid capacity loss. . Silicon oxide (SiO) has higher cycle stability and greater potential application value than elemental silicon. Silicon oxide can be synthesized by the vapor deposition reaction of Si and SiO2 at high temperature, and can be simulated as amorphous on the nanometer scale. A mixture of silicon and silicon dioxide. However, the inherent low conductivity and low first coulombic efficiency (ICE) of silicon oxide lead to a decrease in rate performance and an increase in capacity attenuation, hindering its practical application in lithium-ion batteries.
Graphene coating is one of the most effective methods to alleviate the challenges faced in the use of silicon oxide anodes. The coating layer can significantly improve the electronic conductivity and prevent the reaction of silicon oxide with the electrolyte. The multilayer graphene shell layer has Good elasticity and higher conductivity can effectively adjust the volume expansion of silicon oxide through the sliding process between adjacent layers without damaging the graphene shell layer. However, in the currently published reports of in-situ synthesis of graphene, metal catalysts are used, or the process is complicated and the technical cost is high.
In this work, researchers at the University of North Dakota used coal humic acid as a carbon source to develop a simple and low-cost method for in-situ synthesis of graphene-coated silicon oxide anodes. The resulting anode materials have excellent properties. Its cycle performance and coulombic efficiency, the preparation process is simple, and it has great commercial prospects. The related paper was published on Advanced Functional Materials with the title "InSitu Synthesis of Graphene-Coated Silicon Monoxide Anodes from Coal-Derived Humic Acid for High-Performance Lithium-Ion Batteries".
The author uses coal humic acid as a carbon source to develop a method for in-situ synthesis of graphene-coated silicon oxide anode. The rich functional groups of humic acid make it highly soluble in alkaline aqueous solutions. This makes it more effective to coat silicon oxide particles with humic acid than graphene or graphene oxide. In this experiment, humic acid is uniformly coated on the surface of amorphous silicon oxide (P-SiO@HA), and the subsequent heat treatment produces disproportionated silicon oxide. At the same time, the humic acid is converted into graphene coating in situ. The cladding is verified by physical and chemical characterization and electrochemical testing to verify the validity of the experimental design.
Figure 1a) Schematic diagram of the synthesis process of D-SiO@G anode material; b) Humic acid and its typical molecular model; c) SEM images of P-SiO and d) D-SiO@G; e) Hydrogen fluoride etching D- Backscattered electron micrographs of SiO@G particles; f) Raman spectra of P-SiO and D-SiO@G; g) XRD spectra of P-SiO, D-SiO and D-SiO@Gsamples
Figure 2a) XPS measurement spectra of P-SiO and D-SiO@G; b) fitting peak of silicon in D-SiO@G; c) fitting peak of carbon in D-SiO@G; d) D-SiO Fitted peak of oxygen in @G
Figure 3a,b) Low-magnification and high-magnification TEM images of D-SiO@G; c) Interplanar spacing of crystalline silicon and graphene layers corresponding to zone 1 and zone 2; d) SEM cross section of D-SiO@G particles Figure; e–h) Corresponding EDX element map
Figure 4a) P-SiO cycle performance, D-SiO@G cycle performance and Coulomb efficiency; b) D-SiO@G electrode charge and discharge curves under different cycles; c) P-SiO and D-SiO@G Rate performance; d) D-SiO@G charge-discharge curve at different current densities; e) D-SiO@G in the lithium-insertion graphic shows that the graphene layer can buffer the expansion of silicon oxide
Figure 5 After 50 weeks of cycling a) STXM images of P-SiO particles and c) D-SiO@G particles and (b, d) corresponding energy spectra; e) P-SiO particles, P-SiO particle surface, D- XANE spectra on the surface of SiO@G particles and D-SiO@G particles; f) STXM images and XANES spectra of D-SiO@G particles during cycling
Figure 6a) CV curves of P-SiO and b) D-SiO@G in the first three weeks; c) AC impedance diagram of P-SiO and D-SiO@G electrodes before cycling
Figure 7a) Charge and discharge curves of D-SiO@G//LFP full battery at different rates; b) Cycle performance and Coulomb efficiency of D-SiO@G//LFP full battery at 1 C; c) D-SiO@ G//LFP full battery successfully lights up the LED matrix
In summary, the author uses coal humic acid as a carbon source to develop a simple in-situ synthesis of high-performance lithium-ion battery silousite and graphene anode materials. The author uses various characterization methods to confirm the simultaneous occurrence of humic acid The conversion to graphene and the disproportionation reaction of silicon oxide, in which the well-coated graphene layer prevents the reaction between the electrolyte and the silicon oxide particles, and at the same time significantly improves the conductivity of the silicon oxide negative electrode. Therefore, the D-SiO@G anode material has excellent cycle performance and rate performance, and its reversible capacity at current densities of 2 A g−1 and 5 A g−1 are 1023 mAh g−1 and 774 mAh g−1, respectively 1. The first coulombic efficiency is 78.2%.
The in-situ graphene coating method can be easily adapted to the existing lithium-ion battery electrode material production process. No toxic reagents, expensive catalysts or harsh process conditions are used in the synthesis process. The method is simple and easy to implement. Therefore, this This simple process coupled with abundant and cheap raw materials shows its great potential for successful commercialization in the future.
Silicon (Si) is considered to be a potential negative electrode material due to its high specific capacity. However, the volume of silicon expands severely during charging and discharging. This change causes the silicon particles to lose contact with the electrode, resulting in low battery cycle efficiency and rapid capacity loss. . Silicon oxide (SiO) has higher cycle stability and greater potential application value than elemental silicon. Silicon oxide can be synthesized by the vapor deposition reaction of Si and SiO2 at high temperature, and can be simulated as amorphous on the nanometer scale. A mixture of silicon and silicon dioxide. However, the inherent low conductivity and low first coulombic efficiency (ICE) of silicon oxide lead to a decrease in rate performance and an increase in capacity attenuation, hindering its practical application in lithium-ion batteries.
Graphene coating is one of the most effective methods to alleviate the challenges faced in the use of silicon oxide anodes. The coating layer can significantly improve the electronic conductivity and prevent the reaction of silicon oxide with the electrolyte. The multilayer graphene shell layer has Good elasticity and higher conductivity can effectively adjust the volume expansion of silicon oxide through the sliding process between adjacent layers without damaging the graphene shell layer. However, in the currently published reports of in-situ synthesis of graphene, metal catalysts are used, or the process is complicated and the technical cost is high.
In this work, researchers at the University of North Dakota used coal humic acid as a carbon source to develop a simple and low-cost method for in-situ synthesis of graphene-coated silicon oxide anodes. The resulting anode materials have excellent properties. Its cycle performance and coulombic efficiency, the preparation process is simple, and it has great commercial prospects. The related paper was published on Advanced Functional Materials with the title "InSitu Synthesis of Graphene-Coated Silicon Monoxide Anodes from Coal-Derived Humic Acid for High-Performance Lithium-Ion Batteries".
The author uses coal humic acid as a carbon source to develop a method for in-situ synthesis of graphene-coated silicon oxide anode. The rich functional groups of humic acid make it highly soluble in alkaline aqueous solutions. This makes it more effective to coat silicon oxide particles with humic acid than graphene or graphene oxide. In this experiment, humic acid is uniformly coated on the surface of amorphous silicon oxide (P-SiO@HA), and the subsequent heat treatment produces disproportionated silicon oxide. At the same time, the humic acid is converted into graphene coating in situ. The cladding is verified by physical and chemical characterization and electrochemical testing to verify the validity of the experimental design.
Figure 1a) Schematic diagram of the synthesis process of D-SiO@G anode material; b) Humic acid and its typical molecular model; c) SEM images of P-SiO and d) D-SiO@G; e) Hydrogen fluoride etching D- Backscattered electron micrographs of SiO@G particles; f) Raman spectra of P-SiO and D-SiO@G; g) XRD spectra of P-SiO, D-SiO and D-SiO@Gsamples
Figure 2a) XPS measurement spectra of P-SiO and D-SiO@G; b) fitting peak of silicon in D-SiO@G; c) fitting peak of carbon in D-SiO@G; d) D-SiO Fitted peak of oxygen in @G
Figure 3a,b) Low-magnification and high-magnification TEM images of D-SiO@G; c) Interplanar spacing of crystalline silicon and graphene layers corresponding to zone 1 and zone 2; d) SEM cross section of D-SiO@G particles Figure; e–h) Corresponding EDX element map
Figure 4a) P-SiO cycle performance, D-SiO@G cycle performance and Coulomb efficiency; b) D-SiO@G electrode charge and discharge curves under different cycles; c) P-SiO and D-SiO@G Rate performance; d) D-SiO@G charge-discharge curve at different current densities; e) D-SiO@G in the lithium-insertion graphic shows that the graphene layer can buffer the expansion of silicon oxide
Figure 5 After 50 weeks of cycling a) STXM images of P-SiO particles and c) D-SiO@G particles and (b, d) corresponding energy spectra; e) P-SiO particles, P-SiO particle surface, D- XANE spectra on the surface of SiO@G particles and D-SiO@G particles; f) STXM images and XANES spectra of D-SiO@G particles during cycling
Figure 6a) CV curves of P-SiO and b) D-SiO@G in the first three weeks; c) AC impedance diagram of P-SiO and D-SiO@G electrodes before cycling
Figure 7a) Charge and discharge curves of D-SiO@G//LFP full battery at different rates; b) Cycle performance and Coulomb efficiency of D-SiO@G//LFP full battery at 1 C; c) D-SiO@ G//LFP full battery successfully lights up the LED matrix
In summary, the author uses coal humic acid as a carbon source to develop a simple in-situ synthesis of high-performance lithium-ion battery silousite and graphene anode materials. The author uses various characterization methods to confirm the simultaneous occurrence of humic acid The conversion to graphene and the disproportionation reaction of silicon oxide, in which the well-coated graphene layer prevents the reaction between the electrolyte and the silicon oxide particles, and at the same time significantly improves the conductivity of the silicon oxide negative electrode. Therefore, the D-SiO@G anode material has excellent cycle performance and rate performance, and its reversible capacity at current densities of 2 A g−1 and 5 A g−1 are 1023 mAh g−1 and 774 mAh g−1, respectively 1. The first coulombic efficiency is 78.2%.
The in-situ graphene coating method can be easily adapted to the existing lithium-ion battery electrode material production process. No toxic reagents, expensive catalysts or harsh process conditions are used in the synthesis process. The method is simple and easy to implement. Therefore, this This simple process coupled with abundant and cheap raw materials shows its great potential for successful commercialization in the future.
