锂硫电池用LiPFSD/PVDF/SiO_2复合膜的研究

Research on LiPFSD/PVDF/SiO_2 composite membranes used in lithium-sulfur batteries

锂硫电池正极活性物质理论比容量高达1 675 m Ah/g,单质硫具有环境友好,资源丰富,价格低廉等优点,因此,锂硫电池最有希望成为下一代二次电池的有力竞争者。硝酸锂是抑制锂硫电池飞梭的常用添加剂,会随着电池循环不断被消耗。不断消耗的硝酸锂难以长期抑制硫负载量较高电池的飞梭。有研究表明锂离子选择透过性聚合物电解质膜能够有效抑制飞梭效应。将聚偏氟乙烯(PVDF)和SiO_2改性并与Celgard膜复合的全氟磺酸双氰胺锂(LiPFSD)单离子聚合物电解质膜应用于锂硫电池中,研究了电解液中无硝酸锂条件下,复合膜对电池性能的影响。膜的厚度为15μm,膜内添加20%PVDF和10%SiO_2,正极硫负载量3.5 mg/cm2的锂硫电池,其首次放电比容量为995 m Ah/g,0.1 C下50次循环后放电比容量为798 m Ah/g,库仑效率维持80%以上。

Lithium-sulfur batteries is highly promising for next generation of batteries due to their high theoretical specific energy of 1 675 mAh/g,abundant resources environment friendly and low cost.Lithium nitrate,commonly used as shuttle inhibitor in lithium sulfur cell,was continuously consumed during the charge-discharge process,especially in high-sulfur batteries.So lithium nitrate was unable to restrain shuttle for long circle times.Some researches work show that Li-ion selective polymer electrolytes for lithium-sulfur cells can restrain shuttle effect.The modification was carried out for perfluorinated ionomer electrolyte with lithium sulfonyl dicyanomethide functional groups by the SiO2 and PVDF.When the quality fraction of SiO2 and PVDF was 10%and 20%respectively.Lithium sulfur battery with a positive sulfur load of 3.5 mg/cm2 has a first discharge specific capacity of 995 mAh/g,798 mAh/g for the next 50 cycles at 0.1 C,and the coulomb efficiency maintains over 80%.