Prussian blue analogues (PBAs) are considered as an economical electrode material for sodium-ion batteries, which can be synthesized on a large scale through a simple and low-cost co-precipitation method. The physical parameters of PBAs have a significant impact on their electrochemical performance, among which sodium content is considered one of the key factors affecting electrochemical performance. In this study, PBAs with different sodium contents are prepared using sodium citrate-assisted co-precipitation method, and the influence of sodium content on the electrochemical performance is systematically investigated. Furthermore, the morphological and structural changes of cubic and monoclinic PBAs samples after cycling are studied to explore the intrinsic mechanism of how sodium content affects the electrochemical performance. The study reveals that when the sodium content exceeds 1.5, the structure of PBAs will transfer from cubic phase to monoclinic phase. In terms of electrochemical performance, compared to cubic phase, monoclinic phase samples exhibit higher initial capacity, but lower rate capability and cycling performance, and their cycling stability deteriorates more severely with increasing sodium content. The cubic phase exhibits a more stable crystal structure compared to the monoclinic phase after cycling. During the charge-discharge process, the de-intercalation of excessive sodium ions in monoclinic PBAs leads to structural distortion, triggering the phase transition and resulting in the destruction of the crystal structure, which is the fundamental reason for the influence of sodium content on the electrochemical performance.

普鲁士蓝类似物（PBA）被认为是一种经济的钠离子电池电极材料，可以通过简单且低成本的共沉淀法大规模合成。PBA的物理参数对其电化学性能有显着影响，其中钠含量被认为是影响电化学性能的关键因素之一。本研究采用柠檬酸钠辅助共沉淀法制备了不同钠含量的PBA，并系统研究了钠含量对电化学性能的影响。此外，研究了循环后立方和单斜PBA样品的形态和结构变化，以探索钠含量影响电化学性能的内在机制。研究表明，当钠含量超过1.5时，PBA的结构将从立方相转变为单斜相。在电化学性能方面，与立方相相比，单斜相样品表现出更高的初始容量，但倍率性能和循环性能较低，并且随着钠含量的增加，其循环稳定性恶化得更严重。循环后，与单斜相相比，立方相表现出更稳定的晶体结构。在充放电过程中，单斜晶系PBA中过量钠离子的脱嵌导致结构畸变，引发相变，导致晶体结构破坏，这是钠含量影响其性能的根本原因。电化学性能。