Novel EXperimental & Theoretical Group for materials design
次世代材料設計研究群
Energy materials
Anode material in Lithium ion battery
Owing to the increasing demand for portable electronic products, electric vehicles (EVs), and the smart-grid for storage of electricity from wind and solar generation, the development and applications of energy storage technologies have drawn tremendous attentions. In particular, grid-scale energy storage is needed in conjunction with the deployment of solar, wind, and other renewable energy sources and their integration with the electrical grid. Lithium ion batteries and sodium ion batteries are ones of the most promising energy storage systems because they provide high capacity, high rate-capability and affordable price. Ab initio calculations based on the density functional theory (DFT) is a powerful approach for modern materials design and mechanistic studies.
Therefore, the goal of our research is to design and develop lithium ion batteries and sodium ion batteries with long lifetime, high safety, and low cost energy storage systems by integrating the ab initio calculations and experiment. We are working on several projects:
(1) The Li4Ti5O12 defect spinel is a promising anode material for lithium ion batteries because it transforms to/from Li7Ti5O12 with a negligible volume change during charging/discharging.
(2) The Li2MnO3•(1-x)LiM’O2 has very high theoretical capacity and has been regarded as the next-generation cathode material for lithium ion batteries.
(3) Hard carbon (disorder carbon) has much higher practical capacity than graphite. It has been investigated as the negative electrode in both lithium ion batteries and sodium ion batteries.
Figure 1. Unit cells of the (a) Li4Ti5O12 and (b) Li7Ti5O12 phases.
1.P.-C. Tsai, W.-D. Hsu and S.-K. Lin, “Atomistic structure and ab initio electrochemical properties of Li4Ti5O12 defect spinel for Li ion batteries”
J. Electrochem. Soc. 161, A439-A444 (2014).
Cathode material in Lithium ion battery
Energy crisis and environmental pollution were forced us to search a new material and technology for energy storage in this generation. Among the various types of energy storage, lithium ion batteries (LIBs) have many advantages of high capacity, high voltage and high stability. The lithium-rich oxide solid solution as xLi2MnO3•(1-x)LiM’O2 with layered structure has high capacity in cathode material. Because of the disadvantage like high initial irreversible capacity, quick capacity fading and low rate capability, it always obstructed the development and application in LIBs.
In this work, the density functional theory (DFT) calculations were applied to simulate the composite layered cathode material by doping. Through this method, it can hopefully to reduce the formation of the oxygen vacancy and avoid the transition metal to block the diffusion pathways for lithium ion during charging/discharging. With theoretical methods in this project, We hope that it can investigate and design a novel layered cathode material in LIBs.
Additives in Lithium ion battery
After first cycle of the lithium ion battery, the SEI film is formed. The properties of SEI film has a big influence the performance of battery, electrolyte additives are often added to enhance the properties of SEI film. However, understanding the mechanism of SEI film forming is important.
1,3 propane sultone is an SEI forming additive for anode. By means of Gaussian simulation, the details of SEI formation can be known, The plot shows the possible reaction of PS reduction.
Diffusion behavior of Li ion in the electrolytes of Lithium ion battery
Lithium-ion batteries compared to other secondary batteries have a higher energy density and better Power-to-weight ratio, has been widely applied to various energy storage product. In our research, the diffusion of lithium ions in electrolyte of lithium-lon battery was studied by geometry optimization and molecular dynamics simulations.In the geometry optimization analysis, lithium ions prefer attracting the dielectric molecule like EC than the DEC. We studied the diffusion of lithium ions in the elecrtrolyte. We checked the temperature effect and the electric field effect.
Solid electrolyte of Lithium ion battery
Within the solid state electrolyte, La2/3-xLi3x□1/3-2xTiO3 attracts the widest interest because of its highest ionic conductivity. However, the mechanism of its reaction with Li anode is still a riddle. Therefore, my research focus on how to simulate the most probable arrange order of La, Li and vacancies to make sure the mechanism.
