Wang Jiaqi, Ni Youxuan, Liu Junxiang, Lu Yong, Zhang Kai, Niu Zhiqiang, Chen Jun
Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Renewable Energy Conversion and Storage Center (RECAST), College of Chemistry, Nankai University, Tianjin 310071, P.R. China.
ACS Cent Sci. 2020 Nov 25;6(11):1955-1963. doi: 10.1021/acscentsci.0c00849. Epub 2020 Oct 27.
Rechargeable Na-O batteries have been regarded as promising energy storage devices because of their high energy density, ultralow overpotential, and abundant resources. Unfortunately, conventional Na-O batteries with a liquid electrolyte often suffer from severe dendrite growth, electrolyte leakage, and potential HO contamination toward the Na metal anode. Here, we report a quasi-solid-state polymer electrolyte (QPE) composed of poly(vinylidene fluoride--hexafluoropropylene)-4% SiO-NaClO-tetraethylene glycol dimethyl ether for rechargeable Na-O batteries with high performance. Density functional theory calculations reveal that the fluorocarbon chains of QPE are beneficial for Na transfer, resulting in a high ionic conductivity of 1.0 mS cm. Finite element method simulations show that the unique nanopore structure and high dielectric constant of QPE can induce a uniform distribution of the electric field during charge/discharge processes, thus achieving a homogeneous deposition of Na without dendrites. Moreover, the nonthrough nanopore structure and hydrophobic behavior resulting from fluorocarbon chains of QPE could effectively protect Na anode from HO erosion. Therefore, the fabricated quasi-solid-state Na-O batteries exhibit an average Coulombic efficiency of up to 97% and negligible voltage decay during 80 cycles at a discharge capacity of 1000 mAh g. As a proof of concept, flexible pouch-type Na-O batteries were assembled, displaying stable electrochemical performance for ∼400 h after being bent from 0 to 360°. This work demonstrates the application of the quasi-solid-state electrolyte for high-performance flexible Na-O batteries.
可充电钠氧电池因其高能量密度、超低过电位和丰富的资源而被视为有前景的储能装置。不幸的是，具有液体电解质的传统钠氧电池经常遭受严重的枝晶生长、电解质泄漏以及对钠金属阳极潜在的氢氧根污染。在此，我们报道了一种由聚（偏二氟乙烯 - 六氟丙烯）-4% 二氧化硅 - 高氯酸钠 - 四乙二醇二甲醚组成的准固态聚合物电解质（QPE），用于高性能的可充电钠氧电池。密度泛函理论计算表明，QPE的碳氟链有利于钠离子转移，从而产生1.0 mS cm的高离子电导率。有限元方法模拟表明，QPE独特的纳米孔结构和高介电常数可在充放电过程中诱导电场均匀分布，从而实现钠的均匀沉积而无枝晶。此外，QPE的碳氟链产生的非贯穿纳米孔结构和疏水行为可有效保护钠阳极免受氢氧根侵蚀。因此，所制备的准固态钠氧电池在1000 mAh g的放电容量下，80次循环中平均库仑效率高达97%，电压衰减可忽略不计。作为概念验证，组装了柔性软包型钠氧电池，在从0°弯曲到360°后，显示出约400小时的稳定电化学性能。这项工作展示了准固态电解质在高性能柔性钠氧电池中的应用。
