Han Cuiping, Li Hongfei, Li Yu, Zhu Jiaxiong, Zhi Chunyi
Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong, China.
Songshan Lake Materials Laboratory, Dongguan, Guangdong, China.
Nat Commun. 2021 Apr 23;12(1):2400. doi: 10.1038/s41467-021-22698-9.
Rechargeable calcium-ion batteries are intriguing alternatives for use as post-lithium-ion batteries. However, the high charge density of divalent Ca establishes a strong electrostatic interaction with the hosting lattice, which results in low-capacity Ca-ion storage. The ionic radius of Ca further leads to sluggish ionic diffusion, hindering high-rate capability performances. Here, we report 5,7,12,14-pentacenetetrone (PT) as an organic crystal electrode active material for aqueous Ca-ion storage. The weak π-π stacked layers of the PT molecules render a flexible and robust structure suitable for Ca-ion storage. In addition, the channels within the PT crystal provide efficient pathways for fast ionic diffusion. The PT anode exhibits large specific capacity (150.5 mAh g at 5 A g), high-rate capability (86.1 mAh g at 100 A g) and favorable low-temperature performances. A mechanistic study identifies proton-assisted uptake/removal of Ca in PT during cycling. First principle calculations suggest that the Ca ions tend to stay in the interstitial space of the PT channels and are stabilized by carbonyls from adjacent PT molecules. Finally, pairing with a high-voltage positive electrode, a full aqueous Ca-ion cell is assembled and tested.
可充电钙离子电池作为锂离子电池的替代方案备受关注。然而，二价钙离子的高电荷密度与主体晶格建立了强烈的静电相互作用，导致钙离子存储容量较低。钙离子的离子半径进一步导致离子扩散缓慢，阻碍了高倍率性能。在此，我们报道了5,7,12,14-并五苯四酮（PT）作为一种用于水性钙离子存储的有机晶体电极活性材料。PT分子的弱π-π堆积层呈现出一种灵活且坚固的结构，适合钙离子存储。此外，PT晶体内的通道为快速离子扩散提供了有效途径。PT负极表现出大的比容量（5 A g时为150.5 mAh g）、高倍率性能（100 A g时为86.1 mAh g）和良好的低温性能。机理研究确定了循环过程中PT中质子辅助的钙离子嵌入/脱嵌。第一性原理计算表明，钙离子倾向于留在PT通道的间隙空间中，并由相邻PT分子的羰基稳定。最后，与高压正极配对，组装并测试了全水性钙离子电池。
