Understanding the entropy change (ΔS) characteristics of Hard carbon ∣∣ Na3V2(PO4)3full cell is crucial for its long cycle life and high safety. This work investigated the thermodynamic data of sodium ion half/full cells based on Na3V2(PO4)3and hard carbon material. The results show that the trend of ΔSfor Na ∣∣ Na3V2(PO4)3exhibits great change at 0%–10% and 90%–100% SOCs (states of charge), and remains constant (≈−14.54 J·mol−1·k−1) in 10%–90% SOCs, which is consistent with the characteristics of two-phase reaction. Whereas the ΔSof Na ∣∣ hard carbon (HC) remains essentially constant (≈8.30 J·mol−1·k−1) in the most Na+concentration, fluctuating in the range of 3.17–11.71 J·mol−1·k−1. Notably, ΔSshows a negative value (−6.09 J·mol−1·k−1) at x= 0.3 (xin NaxC) and is close to 0 J·mol−1·k−1at x= 1.0. The HC ∣∣ Na3V2(PO4)3full cell entropy change is basically constant (≈−19.56 J·mol−1·k−1) in 10%–90% SOCs, and reaches a peak at 60% SOC (−10.75 J·mol−1·k−1), indicating the ΔSof full cell is mainly influenced by Na3V2(PO4)3electrode. Based on thermodynamic entropy change characteristics, this work aims to provide a reliable reference to the storage, transportation, thermal management, and safety boundary for batteries.