Entropy Change Characteristics for Sodium Ion Half/Full Cells Based on Na3V2(PO4)3 and Hard Carbon Materials. Issue 5 (1st May 2022)

• Record Type: Journal Article
• Authors: Wei, Fanglin; Li, Pengzhao; Zhang, Qiaoping; Shao, Guosheng; Mao, Jing
• Is Part Of: Journal of the Electrochemical Society. Volume 169:Issue 5(2022)
• Publication Date: 2022-05-01
• Subjects: Na3V2(PO4)3 -- hard carbon -- entropy change -- open-circuit voltage -- safety; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/1945-7111/ac6a14
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : Understanding the entropy change (Δ S ) characteristics of Hard carbon ∣∣ Na3 V2 (PO4 )3 full 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 Na3 V2 (PO4 )3 and hard carbon material. The results show that the trend of Δ S for Na ∣∣ Na3 V2 (PO4 )3 exhibits 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 Δ S of 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, Δ S shows a negative value (−6.09 J·mol −1 ·k −1 ) at x = 0.3 ( x in Na x C) and is close to 0 J·mol −1 ·k −1 at x = 1.0. The HC ∣∣ Na3 V2 (PO4 )3 full 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 Δ S of full cell is mainly influenced by Na3 V2 (PO4 )3 electrode. 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.