Electrochemical modeling of solid-state hydride-ion batteries based on a CeH₂ | 3CeH₃@BaH₂ | NaAlH₄ architecture

Hydride-ion batteries (HIBs) have recently emerged as a promising class of solid-state energy storage systems, offering high energy density, intrinsic safety, and access to abundant hydride-based materials. Yet their electrochemical behavior remains insufficiently understood, and predictive modeling tools are still lacking. This work presents the first comprehensive electrochemical model for a solid-state HIB based on the newly developed CeH₂ | 3CeH₃@BaH₂ | NaAlH₄ architecture (Cui et al., 2025). A one-dimensional finite-volume framework couples hydride transport, ionic/electronic potential distributions, and Butler-Volmer interfacial kinetics to simulate galvanostatic discharge and quantify the origin of voltage losses. The model successfully reproduces key operational features of HIBs, including plateau-like voltage-capacity curves, physically consistent activation and ohmic polarization, and electrolyte potential profiles. High-current and thick-electrolyte simulations generate hydride-concentration gradients exceeding 10 % across the solid electrolyte, confirming the onset of diffusion-limited regimes consistent with solid hydride conductors. The framework also captures how improved hydride transport, via higher diffusivity or reduced electrolyte thickness, sustains voltage at higher utilization, while limited transport accelerates polarization growth. A systematic sensitivity analysis demonstrates the expected kinetic ordering: increasing the interfacial exchange current density raises the discharge voltage and reduces activation losses. Aging multiphysics simulations further reveal monotonic interfacial-resistance growth and a corresponding decline in delivered capacity over 50 cycles, reproducing experimentally observed degradation phenomenology. Mesh-independence tests, analytical diffusion benchmarks, and normalized root-mean-square comparisons with synthetic experimental voltage–capacity data confirm the numerical robustness and the overall consistency of the model validation. Overall, the modeling framework provides a physically grounded and quantitatively coherent tool for diagnosing transport and kinetic limitations in HIBs. The results highlight actionable design levers, enhancing hydride-ion diffusivity, thinning the electrolyte, and strengthening interfacial kinetics, offering a predictive basis for the optimization of next-generation solid-state hydride-ion batteries. • First multidomain electrochemical model for solid-state hydride-ion batteries. • Hydride transport, interfacial kinetics, and aging effects quantified mechanistically. • Strong concentration gradients reveal diffusion-limited regimes under high load. • Mesh, analytical, and RMS benchmarks confirm numerical accuracy and stability. • Model identifies transport, thickness, and interfacial kinetics as key design levers.