Engineering of electrode structure of automotive Li-ion batteries.

摘要

The present work aims to improve auto-motive level Lithium-ion battery performance and explore pilot battery design and fabrication. A brief survey about configuration and operation condition used in industry work and lab scale research is given to motivate our efforts to establish knowledge of intrinsic material property in an extended range and correlate it to macro level performance. Electrolyte ionic conductivity with extended salt concentrations under different temperatures are studied. The conductivity change trend is explained by 3 factors: the number of free ions, the viscosity of electrolyte and the dielectric constant. Later, solid diffusion coefficient measurement is studied with LS-GITT method. Without inputting phase change features, the method successfully extracts apparent solid diffusion coefficient at a reasonable magnitude level. Quantified accuracy is also given by root mean squares error values. Thus we approve the method is an efficient way deriving diffusion coefficients to reconstruct voltage profiles with good chemistry compatibility. Low temperature 18650 battery cell performance is investigated as our focus shifts to macro level. A comparison between PVDF and SBE/CMC binders shows superior performance of electrodes made with PVDF binder at low temperatures. Finally a pilot design and fabrication is demonstrated to build battery core for multifunctional composite PowerPanel. A 19Ah battery panel is successfully made and retains 79.3% capacity after 90 cycles.