Cao Dongwei, Sha Quan, Wang Jiaxin, Li Jiaxin, Ren Jing, Shen Tianyang, Bai Sha, He Lei, Song Yu-Fei
State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, P. R. China.
ACS Appl Mater Interfaces. 2022 May 18;14(19):22186-22196. doi: 10.1021/acsami.2c04077. Epub 2022 May 5.
Polyoxometalates (POMs) have shown great potential in sodium-ion batteries (SIBs) due to their reversible multielectron redox property and high ionic conductivity. Currently, POM-based SIBs suffer from the irreversible trapping and sluggish transmission kinetics of Na. Herein, a series of POMs/metal-organic frameworks (MOFs)/graphene oxide (GO) (MOFs = MIL-101, MIL-53, and MIL-88B; POM = [PMoO], denoted as PMo) composites are developed as SIB anode materials for the first time. Unlike MIL-101 with large pore structures, the pores in flexible MIL-53 and MIL-88B swell spontaneously upon the accommodation of PMo. Particularly, the PMo/MIL-88B/GO composites deliver an excellent specific capacity of 214.2 mAh g for 600 cycles at 2.0 A g, with a high initial Coulombic efficiency (ICE) of 51.0%. The so-called "breathing effect" of flexible MOFs leads to the relatively tight confinement space for PMo, which greatly modulates its electronic structure, affects the adsorption energy of Na, and eventually reduces the trapping of sodium ions. Additionally, the straight and multidimensional channels in MIL-88B significantly accelerate ion diffusion, inducing favored energetic kinetics and thus generating high-rate performance.
多金属氧酸盐（POMs）由于其可逆的多电子氧化还原特性和高离子电导率，在钠离子电池（SIBs）中显示出巨大潜力。目前，基于POM的SIBs存在钠的不可逆捕获和缓慢传输动力学问题。在此，首次开发了一系列POMs/金属有机框架（MOFs）/氧化石墨烯（GO）（MOFs = MIL-101、MIL-53和MIL-88B；POM = [PMoO]，记为PMo）复合材料作为SIB负极材料。与具有大孔结构的MIL-101不同，柔性MIL-53和MIL-88B中的孔在容纳PMo时会自发膨胀。特别是，PMo/MIL-88B/GO复合材料在2.0 A g下循环600次时表现出214.2 mAh g的优异比容量，初始库仑效率（ICE）高达51.0%。柔性MOFs的所谓“呼吸效应”导致对PMo的限制空间相对紧密，这极大地调节了其电子结构，影响了Na的吸附能，并最终减少了钠离子的捕获。此外，MIL-88B中笔直的多维通道显著加速了离子扩散，引发了有利的能量动力学，从而产生了高倍率性能。
