Inceoglu Sebnem, Rojas Adriana A, Devaux Didier, Chen X Chelsea, Stone Greg M, Balsara Nitash P
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
Joint Center for Energy Storage Research (JCESR), Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
ACS Macro Lett. 2014 Jun 17;3(6):510-514. doi: 10.1021/mz5001948. Epub 2014 May 15.
A significant limitation of rechargeable lithium-ion batteries arises because most of the ionic current is carried by the anion, the ion that does not participate in energy-producing reactions. Single-ion-conducting block copolymer electrolytes, wherein all of the current is carried by the lithium cations, have the potential to dramatically improve battery performance. The relationship between ionic conductivity and morphology of single-ion-conducting poly(ethylene oxide)--polystyrenesulfonyllithium(trifluoromethylsulfonyl)imide (PEO-PSLiTFSI) diblock copolymers was studied by small-angle X-ray scattering and ac impedance spectroscopy. At low temperatures, an ordered lamellar phase is obtained, and the "mobile" lithium ions are trapped in the form of ionic clusters in the glassy polystyrene-rich microphase. An increase in temperature results in a thermodynamic transition to a disordered phase. Above this transition temperature, the lithium ions are released from the clusters, and ionic conductivity increases by several orders of magnitude. This morphology-conductivity relationship is very different from all previously published data on published electrolytes. The ability to design electrolytes wherein most of the current is carried by the lithium ions, to sequester them in nonconducting domains and release them when necessary, has the potential to enable new strategies for controlling the charge-discharge characteristics of rechargeable lithium batteries.
可充电锂离子电池存在一个重大局限，这是因为大部分离子电流是由阴离子携带的，而阴离子并不参与产生能量的反应。单离子传导嵌段共聚物电解质中，所有电流均由锂阳离子携带，它有可能显著提升电池性能。通过小角X射线散射和交流阻抗谱研究了单离子传导聚环氧乙烷-聚苯乙烯磺酰锂（三氟甲基磺酰）亚胺（PEO-PSLiTFSI）二嵌段共聚物的离子电导率与形态之间的关系。在低温下，会形成有序的层状相，“可移动”的锂离子以离子簇的形式被困在富含聚苯乙烯的玻璃态微相中。温度升高会导致向无序相的热力学转变。高于此转变温度，锂离子从簇中释放出来，离子电导率增加几个数量级。这种形态-电导率关系与之前所有关于已发表电解质的数据都非常不同。设计大部分电流由锂离子携带、将它们隔离在非导电区域并在必要时释放它们的电解质的能力，有可能为控制可充电锂电池的充放电特性带来新策略。
