Enabling the Electrochemical Performance of Maricite-NaMnPO4 and Maricite-NaFePO4 Cathode Materials in Sodium-Ion Batteries

Abstract

NaMnPO4 and NaFePO4, polyanion cathode materials, exist in two different phases maricite/natrophilite and maricite/olivine, respectively. Both natrophilite NaMnPO4 and olivine NaFePO4 are electrochemically active and possess a one-dimensional tunnel for sodium-ion migration; however, these two phases are thermodynamically unstable. Therefore, they can be synthesized through an electrochemical route. On the contrary, maricite (m)-NaMnPO4 and maricite (m)-NaFePO4 are thermodynamically stable forms but have a huge activation energy of their diffusion pathways for sodium extraction and insertion in the crystal structure, which hinders electrochemical reactions. Therefore, the electrochemical behaviour of commercial m-NaMnPO4 and m-NaFePO4 has been studied to find a way for enabling them electrochemically. Ball milling and thermal/mechanical carbon coating are employed to reduce the particle size to enhance the electrochemical performance and shorten the diffusion pathway. Moreover, ball milling leads to defects and partial phase transformation. The electrochemical performance of milled-coated NaMnPO4 and NaFePO4 has been thoroughly investigated and compared. The phase transition of NaFePO4 is revealed by a differential scanning calorimeter. As a result, the achievable capacities of both cathode materials are significantly enhanced up to ∼50 mAh.g−1 via the particle size reduction as well as by carbon coating. However, the side reactions and agglomeration problems in such materials need to be minimized and must be considered to enable them for applications.

Marigold-like MoS2@MOF-Derived N-Doped Carbon as a Stable and High-Capacity Anode Material for Sodium-Ion Batteries

“…Understanding the nuances of nanomaterial synthesis has now led to the fabrication of a lot of materials that can handle the chemistry of larger size Na ions. These include Na 3 V 2 (PO 4 ) 2 F 3 , Na 4 Fe 7 (PO 4 ) 6 , NaFeMnO, etc. − The nominal voltage delivered by NIBs based on these materials is typically in the range of 2.0–4.0 V . In these batteries, mostly conventional carbon-based anodes are utilized, leading to specific capacity in the range of 80 to 300 mAh g –1 . − NIBs also exhibit suitable redox potential ( E o Na + /Na = 2.71 V versus the standard hydrogen electrode), which is close to that of lithium ( E o Li + /Li = 3.04 V) .…”

Investigation of Morphology, Optical and Electronic Ac Conduction of the Olivine Manganite Compound: NaMnPO4

“…[15][16][17] Numerous investigations have concentrated on the substance NaMnPO 4 , which has appealing properties. [18][19][20][21][22][23][24][25][26][27][28] The literature indicates that the crystalline NaMnPO 4 stabilizes in two types of polymorphs: maricite and olivine. The phosphate group framework is the same in both configurations (space group Pnma).…”

“…Numerous investigations have concentrated on the substance NaMnPO 4 , which has appealing properties [18–28] . The literature indicates that the crystalline NaMnPO 4 stabilizes in two types of polymorphs: maricite and olivine.…”