Graphenised Lithium Iron Phosphate and Lithium Manganese Silicate Hybrid Cathode Systems for Lithium-Ion Batteries
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Date
2017
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University of the Western Cape
Abstract
This research was based on the development and characterization of graphenised lithium iron
phosphate-lithium manganese silicate (LiFePO4-Li2MnSiO4) hybrid cathode materials for use
in Li-ion batteries. Although previous studies have mainly focused on the use of a single
cathode material, recent works have shown that a combination of two or more cathode
materials provides better performances compared to a single cathode material. The LiFePO4-
Li2MnSiO4 hybrid cathode material is composed of LiFePO4 and Li2MnSiO4. The Li2MnSiO4
contributes its high working voltage ranging from 4.1 to 4.4 V and a specific capacity of 330
mA h g-1, which is twice that of the LiFePO4 which, in turn, offers its long cycle life, high
rate capacity as well as good electrochemical and thermal stability. The two cathode materials
complement each other's properties however they suffer from low electronic conductivities
which were suppressed by coating the hybrid material with graphene nanosheets. The
synthetic route entailed a separate preparation of the individual pristine cathode materials,
using a sol-gel protocol. Then, the graphenised LiFePO4-Li2MnSiO4 and LiFePO4-Li2MnSiO4
hybrid cathodes were obtained in two ways: the hand milling (HM) method where the pristine
cathodes were separately prepared and then mixed with graphene using a pestle and mortar,
and the in situ sol-gel (SG) approach where the Li2MnSiO4 and graphene were added into the
LiFePO4 sol, stirred and calcined together.
Description
Magister Scientiae - MSc (Chemistry)