THESIS
2015
xviii, 119 pages : illustrations ; 30 cm
Abstract
Li-ion batteries (LIBs) are widely used in portable electronic devices and electric vehicles.
LiFePO
4 (LFP) has been one of the most promising cathode materials for LIBs due to its high
theoretical specific capacity. This thesis aims at developing a causal table which summarizes the
effect of all particle quality factors on battery performance. A critical assessment was performed
to validate the causal table by measuring the particle qualities of commercial LFP. One of the LFP
sample with small particle size (0.15*0.4*0.6 μm), plate morphology, and around 2.5 wt% carbon
coating had the highest specific capacity (164.9 mAh g-1 at 0.1C) and rate capability (88.5% at 1.5
C). With the causal table, desired particles quality can be identified to enhance the battery
performance. The p...[
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Li-ion batteries (LIBs) are widely used in portable electronic devices and electric vehicles.
LiFePO
4 (LFP) has been one of the most promising cathode materials for LIBs due to its high
theoretical specific capacity. This thesis aims at developing a causal table which summarizes the
effect of all particle quality factors on battery performance. A critical assessment was performed
to validate the causal table by measuring the particle qualities of commercial LFP. One of the LFP
sample with small particle size (0.15*0.4*0.6 μm), plate morphology, and around 2.5 wt% carbon
coating had the highest specific capacity (164.9 mAh g-1 at 0.1C) and rate capability (88.5% at 1.5
C). With the causal table, desired particles quality can be identified to enhance the battery
performance. The particle synthesis methods and their operating conditions are then selected to
ensure particles with the desired attributes can be produced. The LFP particles should be designed
with a good particle quality to have a good electrochemical performance, including nano-size, rod-like
morphology, and uniform carbon coating. The optimal conditions for synthesis of nano-size
carbon coated LFP particle by polyol refluxing process is summarized, and the physical properties
of four different morphology LFP and the electrochemical performance are measured. The sample
with small particle size (140*40 nm), rod morphology, and around 2.9 wt. % carbon coating had
the best specific capacity (160.5 mAh g
-1 at 0.1C) and rate capability (77.1% at 1.5 C).
Recycling of spent LIBs receives increasing attention in recent years, and chemical precipitation
and solvent extraction have been widely applied in the recycling process of spent LIB. Solid-liquid
equilibrium (SLE) phase behavior governs the products to be recovered from the precipitation
process and can be used to guide and optimize the process. Case studies on the recycling of
LiFePO
4 and LiCo
xMn
1-xO
2 have been studied in this thesis to demonstrate how the SLE phase
behavior can be used to design the recovery process. The SLE phase behavior can be utilized to
determine the optimal operating conditions such as the amount of precipitant to be added to the
system. With the insights provided from the SLE phase behavior, new process alternative with
solvent extraction can be generated. Process alternative can be compared with the base case process
to come up with the optimal process for recycling metal salts from spent LIB.
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