Under thermal abuse conditions

lithium-ion batteries are subject to multiple sources of uncertainty

which can potentially trigger thermal runaway. To enable reliable structural design under thermal safety constraints

this study proposes a reliability-based design optimization (RBDO) method for lithium-ion batteries based on critical venting prediction. First

an analytical model is developed that couples electrochemical reactions

heat conduction

gas dynamics

and nonlinear elasticity

enabling a comprehensive characterization of the thermogas-mechanical evolution

with the critical venting time adopted as the performance metric. Second

global sensitivity analysis using a variance-based decomposition method identifies high-sensitivity parameters for dimensionality reduction. Finally

an RBDO model with venting response probability as the constraint is formulated

and an efficient solution strategy is established by integrating the performance measure approach with a decoupled optimization frame-work to ensure computational efficiency and numerical stability. Experimental results show that the proposed model achieves prediction errors lower than 3% for temperature and critical response. Compared to existing methods

it achieves a superior balance between accuracy and efficiency

with RBDO solution time under two hours. The proposed approach demonstrates strong engineering applicability and extensibility

offering an effective tool for safety-oriented structural optimization of lithium-ion batteries.