Gu Zhen-Yi, Guo Jin-Zhi, Cao Jun-Ming, Wang Xiao-Tong, Zhao Xin-Xin, Zheng Xue-Ying, Li Wen-Hao, Sun Zhong-Hui, Liang Hao-Jie, Wu Xing-Long
MOE Key Laboratory for UV Light-Emitting Materials and Technology, Northeast Normal University, Changchun, Jilin, 130024, P. R. China.
Department of Chemistry, Northeast Normal University, Changchun, Jilin, 130024, P. R. China.
Adv Mater. 2022 Apr;34(14):e2110108. doi: 10.1002/adma.202110108. Epub 2022 Feb 25.
Impossible voltage plateau regulation for the cathode materials with fixed active elemental center is a pressing issue hindering the development of Na-superionic-conductor (NASICON)-type Na V (PO ) F (NVPF) cathodes in sodium-ion batteries (SIBs). Herein, a high-entropy substitution strategy, to alter the detailed crystal structure of NVPF without changing the central active V atom, is pioneeringly utilized, achieving simultaneous electronic conductivity enhancement and diffusion barrier reduction for Na , according to theoretical calculations. The as-prepared carbon-free high-entropy Na V (Ca,Mg,Al,Cr,Mn) (PO ) F (HE-NVPF) cathode can deliver higher mean voltage of 3.81 V and more advantageous energy density up to 445.5 Wh kg , which is attributed by the diverse transition-metal elemental substitution in high-entropy crystalline. More importantly, high-entropy introduction can help realize disordered rearrangement of Na at Na(2) active sites, thereby to refrain from unfavorable discharging behaviors at low-voltage region, further lifting up the mean working voltage to realize a full Na-ion storage at the high voltage plateau. Coupling with a hard carbon (HC) anode, HE-NVPF//HC SIB full cells can deliver high specific energy density of 326.8 Wh kg at 5 C with the power density of 2178.9 W kg . This route means the unlikely potential regulation in NASICON-type crystal with unchangeable active center becomes possible, inspiring new ideas on elevating the mean working voltage for SIB cathodes.
对于具有固定活性元素中心的阴极材料而言，无法实现电压平台调控是阻碍钠离子电池（SIBs）中钠超离子导体（NASICON）型NaV(PO₄)₂F（NVPF）阴极发展的一个紧迫问题。在此，一种高熵取代策略被开创性地采用，即在不改变中心活性V原子的情况下改变NVPF的详细晶体结构，根据理论计算，这实现了Na⁺的电子传导率增强和扩散势垒降低。所制备的无碳高熵NaV(Ca,Mg,Al,Cr,Mn)(PO₄)₂F（HE-NVPF）阴极能够提供高达3.81 V的更高平均电压以及高达445.5 Wh kg⁻¹的更有利能量密度，这归因于高熵晶体中多种过渡金属元素的取代。更重要的是，高熵引入有助于在Na(2)活性位点实现Na⁺的无序重排，从而避免在低电压区域出现不利的放电行为，进一步提高平均工作电压以在高电压平台实现全钠离子存储。与硬碳（HC）阳极耦合，HE-NVPF//HC SIB全电池在5 C时能够提供326.8 Wh kg⁻¹的高比能量密度以及2178.9 W kg⁻¹的功率密度。这条途径意味着在具有不变活性中心的NASICON型晶体中实现不太可能的电位调控成为可能，为提高SIB阴极的平均工作电压带来了新思路。
