Wang Siya, Bai Jin, Wang Peiyao, Mao Yunjie, Xiao Ke, Liu Yuanyuan, Qiu Shiyu, Zhu Xuebin, Zhao Bangchuan, Sun Yuping
Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei, 230031, P. R. China.
University of Science and Technology of China, Hefei, 230026, P. R. China.
Small. 2025 Mar;21(10):e2500566. doi: 10.1002/smll.202500566. Epub 2025 Jan 28.
Vanadium-based Na superionic conductor (NASICON) type materials (NaVM(PO), M = transition metals) have attracted extensive attention when used as sodium-ion batteries (SIBs) cathodes due to their stable structures and large Na diffusion channels. However, the materials have poor electrical conductivity and mediocre energy density, which hinder their practical applications. Activating the V/V redox couple (V/V≈4.1 V vs Na/Na) is an effective way to elevate the energy density of SIBs, whereas the irreversible phase transition of V/V and severe structural distortion will inevitably result in fast capacity fading and unsatisfactory rate capability. Herein, a high entropy regulation strategy is proposed to optimize the detailed crystal structure and improve the reversibility of crystalline phase transformation and electrical conductivity of the material. With the activated reversible V/V redox couple, stable structure, and fast electrochemical kinetics, the high entropy material NaVFeAlCrMnCu(PO) (NVMP-HE) exhibits an outstanding electrochemical performance with highly reversible specific capacity of 120.1 mAh g at 0.1 C and excellent cycling stability (92.4% retention after 1000 cycles at 20 C). Besides, the in situ X-ray diffraction (XRD) measurement reveals that a smooth three-phase transition reaction is involved in this high-entropy cathode and the existence of mesophase facilitates a fast phase transition.
钒基钠超离子导体（NASICON）型材料（NaVM(PO)，M = 过渡金属）因其稳定的结构和较大的钠离子扩散通道，在用作钠离子电池（SIBs）阴极时受到了广泛关注。然而，这些材料的电导率较差且能量密度一般，这阻碍了它们的实际应用。激活V/V氧化还原对（V/V≈4.1 V vs Na/Na）是提高钠离子电池能量密度的有效方法，然而V/V的不可逆相变和严重的结构畸变将不可避免地导致快速的容量衰减和不理想的倍率性能。在此，我们提出了一种高熵调控策略来优化材料的详细晶体结构，并提高晶相转变的可逆性和材料的电导率。凭借激活的可逆V/V氧化还原对、稳定的结构和快速的电化学动力学，高熵材料NaVFeAlCrMnCu(PO)（NVMP-HE）展现出优异的电化学性能，在0.1 C下具有120.1 mAh g的高度可逆比容量以及出色的循环稳定性（在20 C下1000次循环后容量保持率为92.4%）。此外，原位X射线衍射（XRD）测量表明，这种高熵阴极涉及一个平滑的三相转变反应，中间相的存在促进了快速的相转变。
