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Caption : fig. s1 (a) voltage profile of the lfp electrode after charging at 0.1c for 5 h, demonstrating stable performance as a reference electrode. (b) schematic illustration of the three-electrode pouch cell.

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Caption : fig. s2 reproducibility test of graphite electrodes under identical conditions: (a) lithiation and (b) de-lithiation processes showing consistent potential profiles and diffusivity trends (deviation within 10 %).

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Caption : fig. s3 electrochemical performance of the si alloy anode. (a) initial voltage profile, (b) cycling performance, (c) coulombic efficiency, and (d) capacity retention.

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Caption : fig. s4 δv as a function of ocv during (a) lithiation and (b) de-lithiation.

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Caption : fig. s5 tafel plots of the graphite/si alloy anode at different states of charge (soc, from left to right: 10, 30, 50, 70, and 90 %).

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Caption : fig. s6 tafel plots of the graphite/si alloy anode at different depths of discharge (dod, from left to right: 10, 30, 50, 70, and 90 %).