Size effect on the thermal and mechanical performance of cylindrical lithium-ion batteries

Increasing the size of cylindrical lithium-ion batteries (LIBs) to achieve higher energy densities and faster charging represents one effective tactics in nowadays battery society. A systematic understanding on the size effect of energy density, thermal and mechanical performance of cylindrical LIBs is of compelling need. Taking the diameter D and height H of cylindrical LIBs as variables, we shed light on the energy densities, thermal and mechanical performance of cylindrical LIBs. The volumetric energy density increases with D , while the gravimetric energy density first increases with D , peaks at a certain diameter before dropping with further increasing D . The thermal performance of cylindrical LIBs could be better characterized by the diameter-to-height ratio: cells of identical capacity but with greater D / H show lower temperature rise and lower thermal gradient at high cycling rates. Mechanically, LIBs of greater D are prone to buckling on the jellyroll close to core, and may fracture under tension on outer jellyroll near the cell case. Those findings suggest the necessity to optimize D and H of cylindrical LIBs insomuch as the trade-offs between the thermal and mechanical performance.