Mechanical analysis and design of flexible beads-and-thread lithium-ion battery

Novel beads-and-thread structural designs have been applied in the new-generation flexible lithium-ion batteries (LIBs) to achieve high electrochemical performance and high flexibility simultaneously. However, to understand the mechanical degradation and to obtain the best performance of these flexible LIBs, the structural analysis and design of such LIBs are of crucial importance. Accordingly, it is necessary to establish detailed and systematic analytic and simulation models to describe the mechanical behavior of these LIBs. Here, the flexibility, energy density, and safety criterion of beads-and-thread LIBs are quantitatively discussed by an analytic finite deformation model and a finite element analysis (FEA) model. The trade-off between effective flexibility and relative energy density of LIBs has been discussed with the parametrical study of two key geometric parameters, length ratio and winding layer number of the structural element. Stress/strain analysis reveals the yield of the Al foil layer in unwound part could be a safe criterion for evaluating mechanical degradation of the battery. Rational design diagrams of flexibility and relative energy density are investigated for the battery designers, considering the balance of battery safety, mechanical and energy storage properties. This work is expected to provide the design guidelines for flexible beads-and-thread LIBs.