通过高价Nb掺杂提升Na_0.44MnO₂正极材料容量

Enhancing the Capacity of Na_0.44MnO₂ Cathode Material through High-Valence Nb Doping

摘要: 由于锂离子电池近年来由于原料价格急剧上涨、原料供应受限，使得人们开始寻找其替代方案。钠离子电池由于钠的化学性质与锂相似、储量丰富、安全性高，因而成为了热门的替代选项，其中，锰基钠氧化物Na_0.44MnO₂循环稳定性好、成本低廉、制备简单，成为了一种具有发展潜力的钠电池正极材料。但是，Na_0.44MnO₂的低理论比容量(120 mAh·g⁻¹)，成为了其投入实际生产应用的最大障碍。在本研究中，尝试将Nb⁵⁺引入Na_0.44MnO₂、使用固相法制得了Na_0.44Mn_0.98Nb_0.02O₂。结果表明，Na_0.44Mn_0.98Nb_0.02O₂结晶性相比于Na_0.44MnO₂有所提升，同时其中还出现了层状氧化物结构。以其为正极组装出的半电池在1 C下首周放电比容量达到了141.8 mAh·g⁻¹，能量密度达到369.2 Wh·kg⁻¹；100次循环后放电比容量保持在94.2 mAh·g⁻¹，证明其拥有高能量密度，为解决Na_0.44MnO₂体系的推广应用提供了有潜力的解决方案。

Abstract: In recent years, the sharp rise of price and limited supply of raw materials for lithium-ion batteries have spurred the search for alternative technologies. Sodium-ion batteries have emerged as a prominent candidate due to sodium’s chemical similarity to lithium, abundant natural reserves, and high safety profile. Among potential cathode materials for sodium-ion batteries, the manganese-based sodium oxide Na_0.44MnO₂ stands out for its excellent cycling stability, low cost, and facile synthesis, which make it become a promising option for practical applications. However, the low theoretical specific capacity (120 mAh·g⁻¹) strictly impede its practical application. In this study, we attempted to introduced Nb⁵⁺ into the Na_0.44MnO₂ lattice and successfully synthesized Na_0.44Mn_0.98Nb_0.02O₂ via solid-state method. Characterization results show that the crystallinity of Na_0.44Mn_0.98Nb_0.02O₂ is enhanced compared to the pristine Na_0.44MnO₂, structure of layered oxide appear in the material at the same time. Electrochemical tests reveal that the half-cell that used Na_0.44Mn_0.98Nb_0.02O₂ as cathode delivers an initial discharge specific capacity of 141.8 mAh·g⁻¹ at 1 C, corresponding to an energy density of 369.2 Wh·kg⁻¹. After 100 cycles at the same rate, the discharge specific capacity retains 94.2 mAh·g⁻¹, confirming the material’s high energy density and satisfactory cycling stability. This work provides a potential strategy to address the challenges associated with the practical application of Na_0.44MnO₂-based cathode materials.