摘要：The development of high-performance solid polymer electrolytes is crucial for producing all-solid-state lithium metal batteries with high safety and high energy ***,the low ionic conductivity of solid polymer electrolytes and their unstable electrolyte/electrode interfaces have hindered their widespread *** address these critical challenges,a strong Lewis acid(aluminum fluoride(AIF_(3)))with dual functionality is introduced into poly(ethylene oxide)(PEO)-based polymer *** AlF;facilitates the dissociation of lithium salt,increasing the iontransfer efficiency due to the Lewis acid-base interaction;further the in-situ formation of lithium fluoride-rich interfacial layer is promoted,which suppresses the uneven lithium deposition and continuous undesired reactions between the Li metal and PEO *** from our rational design,the symmetric Li/Li battery with the modified electrolyte exhibits much longer cycling stability(over 3600 h)than that of the pure PEO/lithium bis(trifluoromethanesulfonyl)imide(LiTFSI)electrolyte(550 h).Furthermore,the all-solid-state LiFeP04 full cell with the composite electrolyte displays a much higher Coulombic efficiency(98.4%after 150 cycles)than that of the electrolyte without the AlF;additive(63.3%after 150 cycles)at a large voltage window of 2.4-4.2 V,demonstrating the improved interface and cycling stability of solid polymer lithium metal batteries.

摘要：合成气转化是实现煤、天然气、生物质、固体废弃物及CO_(2)等非石油含碳资源清洁高效利用的关键过程,可合成多种清洁液体燃料和高附加值化学品,如汽油、柴油、航空煤油、固体石蜡、烯烃、芳烃和含氧化合物等.其中,合成气直接制烯烃(STO)具有流程短、能耗低和经济性高等优点,备受学术界和工业界关注.近年来,合成气直接制烯烃取得了突破性进展,发展了基于氧化物-分子筛的双功能路线法以及改性费托路线法.然而,由于目前STO体系所使用的氧化物或者碳化物活性相同时也是水煤气变换(WGS)活性位点,导致反应过程产生30%-50%的CO_(2)副产物,造成较低的碳原子利用效率和烯烃收率,以及尾气产品分离能耗的增加.如何通过催化剂界面和局域环境的调控,创新反应路径,提高烯烃选择性和收率,降低C1副产物选择性已成为重大挑战.本文提出通过发展界面浸润性调控策略,将CoMnAl复合氧化物(CMA)衍生的CO_(2)C活性相与疏水SiO_(2)进行一定尺度的物理耦合,能够将CO_(2)选择性从47.8%降到16.8%,同时催化剂的活性提高30%,总产物中烯烃选择性也提高了~65%,体现出较高的碳效.FI-IR光谱和接触角测试结果表明,疏水基团成功引入到SiO_(2)载体上,并且通过粉末混合的方式获得了同样具备疏水特性的CoMnAl复合催化剂(CMASc).热重(TG-DTG)结果表明,即使样品经过300℃的高温处理,其疏水性仍然能得到保持.X射线衍射(XRD)和高分辨率透射电镜(HRTEM)表征结果表明,复合氧化物的活性中心仍是棱柱状Co_(2)C.进一步表征和探针实验解释了催化剂浸润性调变对Co_(2)C基催化剂FTO性能的影响.CO/H_(2)O-TPSR-MS实验表明,往体系中引入H_(2)O蒸气,CMASc催化剂产生的CO_(2)信号强度远低于单独CMA催化剂的.CO/H_(2)-TPSR-MS实验结果表明,在相同的温度下,CMASc催化剂上产生的H_(2)O信号强度高于CMA,而相应的CO_(2)信号强度则要低很多.在250-400℃,将产生的CO_(2)信号峰面积进行积分,发现CMA产生的CO_(2)浓度是CMASc的2.3倍.利用固定床开展CO/H_(2)和CO/H_(2)O探针切换实验,结果表明,在典型FTO反应条件下引入水蒸气到CMA催化剂体系后,CO转化率和尾气H_(2)/CO比大幅度提高,而CMASc上则出现相反趋势.这些实验证实了H_(2)O分子容易吸附在CMA上发生WGS反应,而在Co_(2)C活性位界面构建局域疏水环境有利于水分子快速转移,并防止其再次吸附.利用CO-DRIFTS和烯烃-H_(2)脉冲实验研究活性和烯烃选择性提高的原因.相比于CMA,CO更容易吸附在疏水CMASc上.H_(2)O的引入会导致CO在两个催化剂的强度变弱,但CMASc上吸附的CO强度仍要高于CMA.这说明活性位点存在水会阻碍CO的吸附,而CMASc上相对干燥的表面更有利于CO吸附及后续活化.调控H_(2)O分压探针实验也在宏观层面上验证了该结论,说明活性中心吸附的H_(2)O会抑制催化活性.丙烯加氢脉冲实验发现,浸润环境可以极大地影响烯烃的吸附和加氢能力.在H_(2)O存在的情况下,丙烯更容易在CMA上发生加氢生成丙烷,而疏水CMASc上丙烯更容易直接脱落,从而提高了烯烃选择性.综上,通过调控Co_(2)C活性位局域疏水环境,可以降低表面H_(2)O的吸附,抑制CO_(2)副产物生成,同时强化CO吸附和烯烃脱附,提高烯烃选择性和收率,这为高碳效Co_(2)C基催化剂的理性设计提供借鉴.