Sodium vs Lithium: We Tested Both — Here's the Winner

We ran real electrochemical impedance spectroscopy (EIS) on a sodium-ion cell and a lithium-ion cell — same capacity, same conditions — using published physics models in PyBaMM, and let the two Nyquist curves settle it. The models: sodium = Chayambuka 2022 (hard carbon || NVPF, DOI 10.1016/j.electacta.2021.139764); lithium = Chen 2020 (graphite-Si || NMC811, LG M50, DOI 10.1149/1945-7111/ab9050). Both are full Doyle-Fuller-Newman models; EIS is computed with pybamm.EISSimulation (surface-form double-layer), 60 frequencies from 10 kHz to 0.02 Hz at 50% SOC, area-normalized to compare fairly (per cm²). The honest result: there's NO universal winner. Sodium actually has the LOWER ohmic resistance (its bigger, lower-charge-density ion carries a smaller solvated shell, so the electrolyte conducts a little better), while lithium wins the charge-transfer arc in this 2021 lab cell. In today's commercial cells total impedance is essentially tied (~16 mΩ each). Sodium wins cold-temperature power, cost (no Li/Co/Ni) and safety; lithium wins energy density. Different tools, for different jobs. Chapters: 0:00 The duel 0:26 What EIS actually is 1:17 The two cells, models & parameters (with refs) 2:24 Running live EIS on both 3:02 Overlay & compare (the surprise) 3:49 Analyse — ECM fit + DRT 4:41 Who wins & why (honest) 5:29 Recap Sodium isn't the loser the old textbooks imply — it's a different trade. ⏱ CHAPTERS 0:00 The duel 0:26 What EIS is 1:17 Models & parameters 2:24 Running live EIS 3:02 Overlay & compare 3:49 Analyse: ECM + DRT 4:41 Who wins & why 5:29 Recap 📌 What you'll learn: • What EIS / a Nyquist plot actually shows (R0, R_ct, Warburg) • How to compare two cells fairly (area-normalized, same capacity) • Why sodium's ohmic resistance can be LOWER than lithium's • What the charge-transfer arc and DRT peaks reveal • Who really wins on impedance, cold, cost, safety and energy density One battery curve, done justice. Subscribe to BATTXplore. #sodiumion #lithiumion #battery #EIS #nyquist #electrochemistry #pybamm #science #naion