| With the wide application of lithium ion batteries in the field of electric car and aerospace energy storage,higher requirements have been placed on the safety and energy density of lithium-ion batteries.Based on the supramolecular template method,single-handed helical silica and organic-inorganic hybrid silica nanomaterials were prepared,and their applications in lithium ion battery were explored.The main work is shown as following:The research of inorganic ionic gel electrolyte matrix materials is mainly focused on silica nanoparticles,the work related to the electrolyte of helical silica nanofibers has not been reported.In this paper,single-handed helical silica nanofibers were prepared in a mixed system of n-propanol and ammonia,using TEOS as the precursor and the self-assembly of the amphiphilic valine derivative D-18Val11PyBr as the template.The helical silica-based ionic gel electrolyte was firstly prepared by adsorbing lithium salt-ionic liquid solution.The experimental results show that:(1)The helical silica nanofibers existed in an amorphous form and had a large adsorption capacity as an inorganic framework,and their porous structure could provide a continuous transmission channel for lithium ions;(2)The ionic gel electrolyte possessed excellent thermal stability(thermal decomposition temperature is about 370?),good electrochemical stability(oxidative decomposition potential is about 5.2 V),and high ionic conductivity(3×10-3 S cm-1 at 25?),and could promote the uniform deposition of metallic lithium;(3)When using the helical silica film to replace the separator and using the helical silica-based ionic gel electrolyte to replace liquid electrolyte in LiFePO4/Li batteries,at a current density of 0.2 C and room temperature,the battery exhibited good eclectrochemical performances:discharge specific capacity maintained at 103.0 mA h g-1 after 80 cycles,Coulomb efficiency kept 92.1%.Secondly,single-handed helical 1,4-phenylene bridged organic-inorganic hybrid silicas nanotubes were obtain using LL-8Val11PyClO4 as the template and BTEB as the precursor through the permeation and diffusion of concentrated ammonia.Then helical Si/SiC/C composite nanotubes and SiC/C composite nanorods were obtained via magnesium thermal reduction and carbothermal reduction,respectively.The two composites were applied as anode materials for lithium ion batteries(LIBs).It was found that:(1)The carbon in the two composite materials was mainly amorphous.The carbon content in the Si/SiC/C composite nanotubes is 27.9 wt%,and that in the SiC/C composite nanorods is 6.9 wt%;(2)Si/SiC/C composite nanotubes had a specific surface area of 496.5 m2/g,and SiC/C composite nanorods had a specific surface area of 39.3 m2/g.The porous structure of the two materials could benefit the insertion and extraction of lithium ions;(3)The Si/SiC/C composite nanotubes electrode showed a discharge specific capacity of 1260.0 mA h g-1 after 750 cycles at a current density of 0.1 A g-1,which was much better than commercial graphite materials.The SiC/C composite nanorods electrode circulated at 275.8 mA h g-1 at the 500th cycle under a current density of 0.3 A g-1.Finally,single-handed helical 4,4-phenylene bridged organic-inorganic hybrid silicas tubular nanoribbons were synthesized with 12K as the template,BTSB as the precursor,and APTMS as the structural assistants.After carbonization followed by removing silica moiety,twisted carbonaceous nanoribbons were obtained and applied in LIBs.The results disclosed that:(1)The carbon in the carbonaceous nanoribbons was mainly amorphous;(2)The specific surface area of the carbonaceous nanoribbons were 1413 m2/g,and the microporous structure was conducive to the delivery of lithium ions;(3)The carbonaceous nanoribbons showed a discharge specific capacity of 921.1 mA h g-1 after 250 cycles at a current density of 0.1 A g-1,indicating that they are potential substitute of commercial graphite anodes. |
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