Charge-Delocalized Triptycene-Based Ionic Porous Organic Polymers as Quasi-Solid-State Electrolytes for Lithium Metal Batteries

• DOI: 10.1021/acsami.4c10123
• Publication Date: 2024-08-13T19:44:56Z
• Authors: Yufei Yuan; Dan-Dong Wang; Zhengyang Zhang; Ki-Taek Bang; Rui Wang; Huanhuan Chen; Yanming Wang; Yoonseob Kim
• Keywords: 050; Ionic polymers; Quasi-solid-state electrolytes; 540; Porous organic polymers; Chargedelocalization; Lithium metal batteries

Ideal solid electrolytes for lithium (Li) metal batteries should conduct Li+ rapidly with low activation energy, exhibit a high Li+ transference number, form a stable interface with the Li anode, and be electrochemically stable. However, the lack of solid electrolytes that meet all of these criteria has remained a considerable bottleneck in the advancement of lithium metal batteries. In this study, we present a design strategy combining all of those requirements in a balanced manner to realize quasi-solid-state electrolyte-enabled Li metal batteries (LMBs). We prepared Li+-coordinated triptycene-based ionic porous organic polymers (Li+@iPOPs). The Li+@iPOPs with imidazolates and phenoxides exhibited a high conductivity of 4.38 mS cm-1 at room temperature, a low activation energy of 0.627 eV, a high Li+ transference number of 0.95, a stable electrochemical window of up to 4.4 V, excellent compatibility with Li metal electrodes, and high stability during Li deposition/stripping cycles. The high performance is attributed to charge delocalization in the backbone, mimicking the concept of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), which facilitates the diffusion of coordinated Li+ through the porous space of the triptycene-based iPOPs. In addition, Li metal batteries assembled using Li+@Trp-Im-O-POPs as quasi-solid-state electrolytes and a LiFePO4 cathode showed an initial capacity of 114 mAh g-1 and 86.7% retention up to 200 cycles.