基于低含水量普鲁士蓝正极的准固态钠离子电池

Development of Quasi-solid-state Na-ion Battery Based on Water-minimal Prussian Blue Cathode

与锂离子电池相比,钠离子电池具有成本低、低温性能与安全性更佳等优势,在成本与可靠性敏感的应用领域备受瞩目。高容量、低成本的普鲁士蓝类材料(PBAs)是极具前景的钠离子电池正极材料,但结构中存在的结晶水导致电池性能快速衰减,是限制其应用的瓶颈。本研究提出了一种简便易行的热处理策略,以高效脱除PBAs正极材料中的结晶水,340次循环后的容量保持率由73%提升到88%。利用原位技术揭示了PBAs正极在充放电过程中,其晶体结构由三方向立方发生不可逆转变是造成首次库仑效率损失的机制,并针对性地提出在正极中添加Na_(2)C_(2)O_(4)钠补偿剂可以解决这一问题。在此基础上,采用高离子电导率、高电化学稳定性的聚乙二醇二丙烯酸酯(PEGDA)准固态电解质,匹配添加Na_(2)C_(2)O_(4)钠补偿剂的低含水量PBAs正极与硬碳(HC)负极,构建了高性能准固态钠离子电池。此类电池在20~500mA·g^(-1)电流密度下的比容量为58~105mAh·g^(-1),并可稳定循环超过200次。研究表明高效脱除结晶水,可以显著提高PBAs正极的稳定性与比容量。

In comparison to Li-ion batteries,Na-ion batteries offer the benefits of low cost,good low-temperature performance,and safety,attracting great attention in the cost-and reliability-sensitive applications.With high capacity and low cost,Prussian blue-like materials(PBAs)stand as promising cathode materials for Na-ion batteries.However,the presence of crystalline water within their structure induces fast performance decay of the battery,serving as a critical bottleneck limiting their application.This work reports a facile thermal treatment strategy to effectively remove crystalline water from PBAs cathode materials,improving capacity retention from 73%to 88%after 340 cycles.The in-situ analysis uncovers that the initial loss of Coulombic efficiency of PBAs cathode is a result of its irreversible transformation from a trigonal form to cubic phase during the charging and discharging process.This issue can be addressed by introducing of Na_(2)C_(2)O_(4)to compensate the irreversible Na loss in the cathode.On this basis,a high-performance quasi-solid-state Na-ion battery is built by pairing a low-water-content PBAs cathode with Na_(2)C_(2)O_(4)additive and a hard carbon(HC)anode within a poly(ethylene glycol)diacrylate(PEGDA)-based quasi-solid-state electrolyte with high ionic conductivity and electrochemical stability.This battery exhibits the specific capacities ranging from 58 to 105 mAh·g^(-1)at current densities from 20 to 500 mA·g^(-1),capable of sustaining stable cycling for over 200 cycles.This study underscores the significant improvement in stability and capacity of PBAs cathode materials by the efficient removal of crystalline water in them.