Effect of co-precipitation pH on the electrochemical properties of Prussian blue electrode materials for sodium-ion batteries

• Published in: Solid state ionics Vol. 336; pp. 120 - 128
• Main Authors: Zuo, Daxian, Wang, Cuiping, Wu, Junwei, Qiu, Huajun, Zhang, Jinbin, Han, Jiajia, Liu, Xingjun
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.08.2019; Elsevier BV
• Subjects: Batteries; Cathode materials; Cathodes; Chemical precipitation; Coprecipitation; Defects; Discharge; Electrochemical analysis; Electrochemical performances; Electrode materials; Electrodes; High voltages; Ion diffusion; Performance enhancement; Pigments; Prussian blue analogues; Rechargeable batteries; Sodium ion batteries; Stability; Water chemistry; Prussian blue analogues; Sodium ion batteries; Electrochemical performances; Cathode materials
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2019.03.014

Prussian blue analogues (PBA) are promising cathode materials because of their low-cost and wide diffusion tunnels for sodium ion batteries. However, several key challenges, such as low actual capacity and high voltage instability, restrain their further development. Here, we investigate the influence of pH value on the electrochemical performances of Na2MnFe(CN)6 cathodes during co-precipitation process. When the pH equals to 3.0, the sample shows the high content of sodium, low contents of interstitial water molecules and Fe(CN)6 defects, which achieves a high discharge capacity (~130.6 mAh g−1) and a capacity retention of 72% after 100 cycles at 1C. As the pH becomes 9.0, the sample exhibits an excellent high-rate capability, and the discharge capacity can still remain about 92% when the rate goes back to 0.1C from 5C. Besides, the sample also reveals capacity retention of about 80% after 100 cycles at 1C, which shows the best stability among all samples. The enhanced performances could be mainly ascribed to two aspects: on the one hand, the high content of Na+ contributes to high specific capacity; on the other hand, less Fe(CN)6 defects are beneficial to Na+ ion diffusion and stabilize the structure during the Na+ insertion/extraction process. [Display omitted] •The different PBM samples are successfully prepared by controlling pH value.•The effects of different pH value on the properties of PBM are discussed in detail.•The PBM-3 sample exhibits the highest content of sodium and discharge capacity.•The PBM-9 sample reveals capacity retention of about 80% after 100 cycles at 1C.