Huang, Qianye (2018) Development on high energy lithium-ion batteries based on silicon electrodes. PhD thesis, University of Warwick.

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Abstract

To develop a high-energy lithium-ion battery system based on the silicon (Si) anodes, a comprehensive investigation has been conducted through different approaches. These include optimising the composite formulation of the Si electrode, developing a robust binder system and identifying an appropriate electrolyte system to achieve high voltage in Si full cells.

These studies reveal that the carbon blends (a mixture of graphite, carbon black and few-layer graphene) is a more effective conductive system for Si electrodes, compared with the conventional carbon black. An optimised carbon mixture formulation has been identified and applied to other investigations in this project.

By incorporating few-layer graphene (FLG) as a combined active material, the cyclability of Si electrodes can be largely improved. An optimised formulation for the Si-FLG composite electrode has been identified, and the beneficial mechanism of FLG has been comprehensively studied. The optimised Si-FLG formulation has been further manufactured into electrodes with a scale-up battery pilot line, and fabricated into the full cells with the LiNi0.6Mn0.2Co0.2O2 (NMC622) cathode. Based on this full cell system, ethylene-carbonate (EC)-free electrolyte systems with different additives, have been systematically studied to improve the stability of the system under 4.4 V. The results indicate that, by excluding EC from the electrolyte, the cells could effectively avoid the large capacity loss that occurs during initial cycles due to the oxidation of EC. The optimal combination of electrolyte additives has been identified. The surface chemistries of electrodes, with different electrolytes, have been deeply analysed thoroughly.

The development of binder systems based on polyacrylic acid (PAA) has also been investigated, including partial neutralisation, the synthesis of binary cross-linked polymers and the design of a novel multi-level cross-linked polymer. Different levels of improvement for the cyclability of Si electrodes have been achieved. The multi-level cross-linked binder has delivered the best performance, due to the strong ionic interaction with the Si surface.

Item Type:	Thesis (PhD)
Subjects:	Q Science > QD Chemistry T Technology > TK Electrical engineering. Electronics Nuclear engineering
Library of Congress Subject Headings (LCSH):	Lithium ion batteries, Electrodes, Silicon, Anodes, Graphene, Crosslinked polymers
Official Date:	September 2018
Dates:	Date Event September 2018 UNSPECIFIED
Institution:	University of Warwick
Theses Department:	Warwick Manufacturing Group
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Bhagat, Rohit ; Loveridge, Melanie
Format of File:	pdf
Extent:	vii, viii, 141, 17 leaves : illustrations, charts
Language:	eng

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