Development of high-performance cathode materials for lithium-ion batteries
by Jiadong Li
THESIS
2019
M.Phil. Chemical and Biological Engineering
xv, 106 pages : illustrations (some color) ; 30 cm
Abstract
Cathode materials have been the bottleneck for the development of more advanced lithium-ion
batteries due to their lower specific capacity. Lithium-rich manganese-based layered oxides
(xLi2MnO3·1-xLiMO2, M=Ni, Co or Mn, 0 xMnyCozO2, x+y+z=1, x≥0.5) have gained significant attention due to their high specific
capacity and moderate cost. In this work, i) Li1+xMn0.54Co0.13Ni0.13O2 (0.12≤x≤0.28) and
LiNi0.5Mn0.3Co0.2O2 were synthesized via the co-precipitation and high-temperature sintering
method. Spherical transition metal carbonate precursor (Mn0.675Ni0.1625Co0.1625CO3) was
successfully obtained by a home-made continuous stirring tank reactor (CSTR) system. The
tailor-made precursors were used for the systematic study of the impacts of lithium to transition
metal ratio in Li1+xMn...[ Read more ]
Cathode materials have been the bottleneck for the development of more advanced lithium-ion
batteries due to their lower specific capacity. Lithium-rich manganese-based layered oxides
(xLi2MnO3·1-xLiMO2, M=Ni, Co or Mn, 0 xMnyCozO2, x+y+z=1, x≥0.5) have gained significant attention due to their high specific
capacity and moderate cost. In this work, i) Li1+xMn0.54Co0.13Ni0.13O2 (0.12≤x≤0.28) and
LiNi0.5Mn0.3Co0.2O2 were synthesized via the co-precipitation and high-temperature sintering
method. Spherical transition metal carbonate precursor (Mn0.675Ni0.1625Co0.1625CO3) was
successfully obtained by a home-made continuous stirring tank reactor (CSTR) system. The
tailor-made precursors were used for the systematic study of the impacts of lithium to transition
metal ratio in Li1+xMn0.54Co0.13Ni0.13O2 on electrochemical performance. The best performance
was achieved on Li1.12Mn0.54Co0.13Ni0.13O2. ii) Conventional coatings such as Al2O3 and carbon
may not be applicable to surface modification of LiNi0.85Mn0.05Co0.1O2. Reductive agents
should be avoided to prevent the reduction of transition metal cations which could lead to cation
disordering or even severe phase change. The oxidative chemical vapor deposition process was
shown as a promising method to coat a conductive polymer layer on LiNi0.85Mn0.05Co0.1O2. iii)
LiNi0.5Mn0.3Co0.2O2 materials with a high rate capacity was also synthesized. The
concentration of complexing agent, pH of synthesis solution, and temperature at different
stages of the co-precipitation process were tuned to fabricate flower-like precursors. The
specific capacity of the synthesized high-power LiNi0.5Mn0.3Co0.2O2 was 145.1 mAh/g at 5C,
which was 20% higher than that of commercial one. The unique porous structure of secondary
particle benefits high energy output at high rates as well as the cycling performance.
Post a Comment