超薄无序结构还原氧化石墨烯/锂金属复合箔材的制备及电化学性质

Preparation and electrochemical performance of ultra-thin reduced graphene oxide/lithium metal composite foils

超薄锂金属(≤50μm)是下一代高比能锂金属电池负极选择。然而纯锂质软、易脆,机械加工性较差,导致超薄锂箔的制备工艺复杂、成本高昂;此外相比于较厚的锂金属负极,超薄锂金属负极常呈现更差的电化学循环性能。本文提出一种“自下而上”的策略制备10~50μm厚度可控的超薄还原氧化石墨烯/锂金属(rGO/Li)复合箔材,其结构由大量无序随机的rGO片层非平行排列并均匀分散在锂金属内。首先将还原氧化石墨烯(rGO)粉片与熔融锂金属在200℃下搅拌复合,获得微米级的还原氧化石墨烯/锂复合粉片,之后将复合粉片作为原材料进一步通过反复辊压制备出结构均匀、超薄的复合箔材,该方法具有一定的规模化潜力。不同于其他所报道的rGO层状薄膜结构,在复合箔材中rGO片层随机无序分散形成三维网络,有利于实现锂的均匀沉积/剥离。所制50μm超薄无序结构rGO/Li复合箔材负极在对称电池中以1 mA cm^(-2)、1 mAh cm^(-2)条件在醚基电解液中可稳定循环1600 h以上,在与硫化聚丙烯腈(SPAN)正极组配全电池以0.2 C倍率循环220次后比容量高达~675 mAh g^(-1),优于使用同厚度纯锂负极的电池。

Ultra-thin(≤50μm)lithium metal anodes(LMAs)are highly desirable for high energy density lithium metal batteries(LMBs).However,their fabrication is complicated and costly due to the sticky and brittle nature of metallic Li,and they have a worse cycling stability than their thick counterparts.We report the fabrication of ultra-thin reduced graphene oxide/Li metal(rGO/Li)composite foils with thicknesses ranging from 10 to 50μm.During the fabrication,disordered rGO sheets and molten metallic Li were stirred at 200ºC to produce micrometer-size rGO/Li particles,which were rolled to form an ultra-thin uniform composite foil.The rGO sheets were randomly distributed in the composite to form a three-dimensional network,which is different from the laminated rGO structure previously reported,and supported stable Li plating/stripping behavior.As expected,a superior electrochemical performance was achieved using this composite sheet for the anode.A 50μm-thick rGO/Li composite foil electrode showed stable cycling for>1600 h at 1 mA cm^(-2) and 1 mAh cm^(-2) in symmetrical cells in an ether-based electrolyte.A full cell consisting of a 50μm-thick rGO/Li composite foil anode and a sulfurized polyacrylonitrile cathode had a high capacity retention of 675 mAh g^(-1) after 220 cycles at 0.2 C.