多孔有機高分子應用至鋰金屬電池人工固態電解質介面層

Abstract

多孔有機高分子(Porous organic polymers, POPs)，是由輕量元素如碳、氫、氧、氮等共價鍵結形成，擁有高表面積、大量的官能基團、連續多孔微結構等優點。POP的拓樸形貌可藉由節點與邊緣單體的立體幾何構造與官能基種類及數量來進行調控，進而得到不同微結構與結晶特性之POP。本研究利用相同反應條件之一鍋法合成出兩種同樣具有imine連結官能基與拓樸設計但卻具有極大微結構差異的POP：一為以與先前文獻報導相同的單體組合1,3,5-tris(4-aminophenyl)benzene (TAPB,節點三胺基單體)與terephthalaldehyde (PDA,邊緣雙醛基單體)，合成出具有高度六方堆積結晶度的TAPB-PDA POP；另一POP則是以1,3,5-tris(4-formyl phenyl) benzene (TFPB, 節點三醛基單體) 與p-phenylenediamine (PPD,邊緣雙胺基單體)為單體,合成出片狀且無規整六角孔洞之層狀堆疊結構。為解釋將單體進行連結反應的醛基與胺基的位置對調而造成微結構上的巨大差異, 本研究利用imine鍵結機制與反應動力學提出一模型進行解釋。爾後此兩種POP進一步應用於鋰金屬電池之人工固態電解質介面(artificial solid electrolyte interphase, A-SEI)時，相對於無POP A-SEI之電池，POP A-SEI皆能使鋰離子均勻沉積/剝離於鋰金屬表面，抑制鋰枝晶生長，進而提升鋰金屬電池長期穩定性與安全性。有趣的是，相對於六方堆積TAPB-PDA POP，層狀TFPB-PPD POP擁有較高的導離子率、更穩定的鋰金屬介面與電池循環壽命。此結果與多數文獻認為高結晶度的六方堆積POP能提供鋰離子快速傳輸的通道以提升相關之電化學性質的論點相衝突。此篇論文也提出一對應的鋰離子傳輸機制以解釋層狀POP展現出較優異的電池表現的原因。

Porous Organic Polymers (POPs), constructed from light elements such as C, O, N, H via covalent bonding, possess advantages of high surface area with abundant functionalities and continuous porous microstructures. POPs are generally built by linking knot and/or edge monomers, and whose topography could be manipulated by employing monomers with functional groups at designated positions. The microstructure and the crystallinity of POPs are affected complicatedly by the topography and the reaction parameters. In this work, two imine linked POPs having identical topography design are prepared via the same one-pot chemistry from two different monomer combinations; interestingly, the resulting POPs exhibited different topography and very distinctive microstructures. The one using 1,3,5-tris(4-aminophenyl)benzene (TAPB, amine knot monomer) and terephthalaldehyde (PDA, aldehyde edge monomer), termed as TAPB-PDA POP, exhibits high crystallinity with hexagonal channels similar to those reported in previous literatures . Contrary, by switching the positions of the aldehyde and the amine groups in the knot/edge monomers, the POPs synthesized from 1,3,5-tris(4-formyl phenyl) benzene (TFPB, aldehyde knot monomer) and p-phenylenediamine (PPD, amine edge more) are layered stacking flakes without orderly hexagonal pores. We propose a model to explain the interesting differences in topography and microstructure based on the imine bonding formation mechanism and the associated kinetics. When these two POPs are applied as an artificial solid-electrolyte interphase (A-SEI) in lithium metal batteries, both POPs could facilitate homogeneous lithium ion deposition/stripping at lithium metal surface to suppress lithium dendrite formation comparing to the cell without POP based A-SEI, therefore improving long term stability and safety of LMBs. Interestingly, the layer stacked TFPB-PPD POP demonstrates a higher ion conductivity, more stable lithium metal surface and a longer life time in galvanostatic cycling with respect to the hexagonal packed TAPB-PDA POP. The observation is somewhat opposite to most literatures, which suggested that highly ordered hexagonal crystals in POPs serving as ion conducting channels could benefit fast lithium ion transport and improve the associate electrochemical properties. A corresponding mechanism is proposed in this thesis to address the superiority of layered POPs.