Although organic electrode materials have merits of abundant resources, diverse structures and environmental friendliness, their performance for electrochemical energy storage is far insufficient. In this work, a thiourea-based polyimide/reduced graphene oxide (PNTCSA/RGO) composite was synthesized via a condensation polymerization method. As a cathode material in lithium-ion batteries, excellent performance is demonstrated with high reversible capacity (144.2 mA h g⁻¹), high discharge voltage (∼2.5 V), and long cycling life (over 2000 cycles at 500 mA g⁻¹), which are comparable to those of other well documented in organic electrodes. Encouraging electrochemical performance is also demonstrated for sodium ion batteries (a cycling life of 800 cycles at 500 mA g⁻¹), while poor performance is delivered in potassium ion batteries. Theoretical studies reveal that the active sites are carbonyl groups for all alkali ions but one inserted alkali metal ion is shared by two carbonyl groups from the two neighbor units. More importantly, K ions have stronger interaction with S atoms than Li/Na ions, which may lead to poor structure reversibility and account for the poor cycling performance. Our findings provide a fundamental understanding of polyimide based polymer electrodes and help to design and develop high performance organic electrode materials for alkali metal ion batteries.

尽管有机电极材料具有资源丰富，结构多样和环境友好的优点，但是它们在电化学能量存储方面的性能仍然远远不够。在这项工作中，通过缩聚方法合成了硫脲基聚酰亚胺/还原氧化石墨烯（PNTCSA / RGO）复合材料。作为锂离子电池的正极材料，具有优异的性能，具有高可逆容量（144.2 mA hg ^-1），高放电电压（〜2.5 V）和长循环寿命（在500 mA g ^-1下超过2000次循环）），可与有机电极中其他有据可查的相比。钠离子电池还具有令人鼓舞的电化学性能（在500 mA g ^-1时的循环寿命为800个循环），而钾离子电池的性能却很差。理论研究表明，所有碱金属离子的活性位均为羰基，但一个插入的碱金属离子被两个相邻单元中的两个羰基共享。更重要的是，与Li / Na离子相比，K离子与S原子的相互作用更强，这可能导致结构可逆性较差，并解释了较差的循环性能。我们的发现为基于聚酰亚胺的聚合物电极提供了基础知识，并有助于设计和开发用于碱金属离子电池的高性能有机电极材料。