Electropolymerization Triggered in Situ Surface Modification of Electrode Interphases: Alleviating First-Cycle Lithium Loss in Silicon Anode Lithium-Ion Batteries
article
We report on interphase modification by in situ generated protons (H+) via electropolymerization. The protons are released from oxidative electropolymerization of indole-3-carboxylic acid (InAc) used as an additive in a LiNi0.8Co0.15Al0.05O2 (NCA) based cathode during cycling against lithium metal and silicon-graphite composite (Si-Gr) electrodes. Electrochemical data supported by ex situ NMR spectroscopy and X-ray photoelectron spectroscopy (XPS) prove that the H+ produced in the lithium metal cell are used for cathode interphase formation and thereby improve the Coulombic efficiency during cycling. With the help of Li3PO4, which scavenges H+ by the release of Li+, it can be established that H+ is reduced at the cathode at a potential of ∼3 V vs Li/Li+ to form H2 without large-capacity fade. The H+ have a more pronounced effect on the anode side when replacing lithium metal by Si-Gr. This is due to the facile H+ reduction at the anode during charge which modulates the solid electrolyte interphase (SEI) as well as the Si surface which is proven by ex situ XPS. The reduction of H+ at the anode is found to have a positive effect in mitigating the irreversible Li+ loss (10% capacity gain with 10% InAc) at the Si-Gr electrode, which was maintained over 100 cycles.
TNO Identifier
882131
Source
ACS Sustainable Chemistry and Engineering, 8(34), pp. 12788-12798.
Publisher
ACS
Pages
12788-12798
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