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Structural study on the development of high-voltage Na4Co3(PO4)2P2O7 cathode materials for sodium-ion batteries by in situ and time-resolved X-ray diffraction
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2022-07-28 , DOI: 10.1039/d2ta01561g
Dong Hyun Kim 1, 2 , Ji-Young Kim 3 , Min Kyung Cho 3 , Hyungseok Kim 1, 4 , Sang-Ok Kim 1, 4 , Kwang-Bum Kim 2 , Kyung Yoon Chung 1, 4
Affiliation  

As the demand for energy-storage systems grows, lithium sources may become scarce and alternative materials will be required. Sodium-ion batteries (SIBs) are low cost and safe alternatives to lithium-ion batteries (LIBs). Herein, in situ and time-resolved X-ray diffraction (TR-XRD) was used to investigate the structural changes and thermal safety of Na4Co3(PO4)2P2O7 cathode materials for high-voltage SIBs. A range of undesirable compounds (Na2Co2P2O7, alpha-NaCoPO4, Na4Co7(PO4)6, and beta-NaCoPO4) form during heating; therefore, an optimized heating temperature of 740 °C was used to obtain Na4Co3(PO4)2P2O7. The in situ XRD results showed the dependency of the lattice parameters of Na4Co3(PO4)2P2O7 on the Na content during charging and discharging. During the charging process from 4.41 to 4.47 V, lattice constant a showed a significant decrease and b showed a steep increase, whereas c showed a marginal increase. During the charging process from 4.47 to 4.7 V, lattice constant b continued to increase, whereas no significant changes were observed in a and c. The discharge process was evaluated in a reverse order. Na4Co3(PO4)2P2O7 exhibited a 6% volume reduction during charging and 4% volume expansion during discharging. The TR-XRD results revealed that the structure of desodiated Na4−xCo3(PO4)2P2O7 (x = 2) was decomposed to the Na2CoP2O7 phase at ∼215 °C during heating in the presence of an electrolyte, which was lower than that without electrolyte (∼230 °C). These results provide an in-depth understanding of Na4Co3(PO4)2P2O7 cathode materials and may serve as a basis for the development of high-performance Na4Co3(PO4)2P2O7 cathode materials for SIBs.

中文翻译:

原位和时间分辨X射线衍射法制备钠离子电池高压Na4Co3(PO4)2P2O7正极材料的结构研究

随着对储能系统需求的增长,锂资源可能会变得稀缺,需要替代材料。钠离子电池 (SIB) 是锂离子电池 (LIB) 的低成本且安全的替代品。在此,原位和时间分辨X射线衍射(TR-XRD)用于研究Na 4 Co 3 (PO 4 ) 2 P 2 O 7高压SIBs正极材料的结构变化和热安全性。一系列不良化合物(Na 2 Co 2 P 2 O 7、α-NaCoPO 4、Na 4 Co 7 (PO4 ) 6 , 和β-NaCoPO 4 ) 在加热过程中形成;因此,使用740℃的最佳加热温度来获得Na 4 Co 3 (PO 4 ) 2 P 2 O 7原位XRD结果表明Na 4 Co 3 (PO 4 ) 2 P 2 O 7的晶格参数在充放电过程中对Na含量的在 4.41 到 4.47 V 的充电过程中,晶格常数a显着降低, b显示出急剧增加,而c显示出边际增加。在从 4.47 到 4.7 V 的充电过程中,晶格常数b继续增加,而ac没有明显变化。以相反的顺序评估放电过程。Na 4 Co 3 (PO 4 ) 2 P 2 O 7在充电时体积减少6%,在放电时体积膨胀4%。TR-XRD结果表明,脱钠Na 4- x Co 3 (PO 4 ) 2 P 2的结构O 7 ( x = 2) 在有电解质存在的加热过程中在~215 °C 下分解为Na 2 CoP 2 O 7相,低于没有电解质(~230 °C)的温度。这些结果提供了对Na 4 Co 3 (PO 4 ) 2 P 2 O 7正极材料的深入理解,可作为开发高性能Na 4 Co 3 (PO 4 ) 2 P 2 O 7的基础。 SIBs的正极材料。
更新日期:2022-07-28
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