Multimodal Large Language Model-Based Explainable Boosting Machine Analysis for Interpretation of State-of-Health Prediction of Lithium-Ion Batteries

Accurate prediction of the state of health (SOH) of lithium-ion batteries is essential for ensuring the safety and reliability of electric vehicles and energy storage systems. While machine learning (ML)-based models have demonstrated strong predictive performance, their limited interpretability remains a major challenge for deployment in safety-critical applications. Although explainable boosting machines (EBMs) provide an interpretable alternative through their additive structure, existing studies still rely on manual analysis of model outputs, which restricts scalability and reproducibility. To address this limitation, this study proposes a structured interpretation framework that integrates EBMs with multimodal large language models (MLLMs). The proposed framework employs EBMs to generate SOH predictions along with global feature importance and variable-level score-density visualizations. These outputs are subsequently processed by an MLLM to perform automated interpretation at both global and variable levels, followed by aggregation, cross-validation, and generation of a unified interpretation report. Experiments were conducted on a lithium-ion battery degradation dataset and the EBM achieved competitive predictive performance compared to baseline ML models. In addition, the quality of the generated interpretations was evaluated using both an MLLM-as-a-Judge and a user study. The evaluation results show that the generated interpretations consistently achieved high scores, with average ratings exceeding 4.5 out of 5 across key criteria such as interpretation accuracy and faithfulness, as assessed by both independent MLLMs and domain experts. These results demonstrate that the proposed framework enables reliable and scalable interpretation of battery SOH prediction models, providing a practical solution for explainable artificial intelligence in battery health management.