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The effect of modulus and partial molar volume on curvature of bi-layer electrode in Li-ion battery is analyzed by using a finite bi-layer plate theory and in situ charging-discharging experiment. A new relationship among curvature (κ), Li concentration (C), modulus (M), partial molar volume (Ω) and state of charge (SOC) is derived. The modulus has significant effect on curvature in charging. If we simply consider the modulus as constant, the theoretical result of κ vs. SOC is almost twice as much with the experimental data. So we have reason to believe that modulus is dependent on lithium concentrations in the battery recycling. In fact, at this time the theoretical and experimental curves of κ vs. SOC agree well, only 5%-10% error. The reason why there is an error is we ignore the effect of partial molar volume. Combining with concentration-dependent modulus and experiment data, we get a more accurate experimental partial molar volume (ca. 3.2×10^-6m³/mol) in second charge. It is worth noting that in first charge the partial molar volume increases with SOC increasing and should be taken into consideration in modeling and numerical simulation.