Electropolymerization Triggered in Situ Surface Modification of Electrode Interphases: Alleviating First-Cycle Lithium Loss in Silicon Anode Lithium-Ion Batteries

Abstract

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 LiNi 0.8 Co 0.15 Al 0.05 O 2 (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 Li 3 PO 4 , 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 H 2 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.

Production of high-energy Li-ion batteries comprising silicon-containing anodes and insertion-type cathodes

“…By virtue of its overwhelming attributes, Si has attracted increased attention from the academic and industrial research communities along with policymakers as a next-generation anode material 11 . Nevertheless, the practical application of pure Si-and/or high Si-containing anodes is currently impeded by the presence of multiple interrelated challenges: the enormous volume change (>280%) of Si upon full lithiation induces severe cracking and pulverisation of anodes (at both the active material and electrode levels), a much lower electronic conductivity (σ e < 10 −5 S cm −1 ) and Li + diffusion rate (D Li + , 10 −14 -10 −13 cm 2 s −1 ) in high-purity Si compared to that of carbon and graphite (σ e− , 10-10 4 S cm −1 ; D Li + , 10 −9 cm 2 s −1 ) [17][18][19] , unstable/dynamic solid electrolyte interphase (SEI) formation, electrode swelling and electrolyte drying 14 .…”

“…Si-based materials: Si-graphite blend/composite, Si-containing functional second phase. To mitigate the challenges linked to pure Si, coupling Si and Gr has been hailed as the most effective strategy towards the commercialisation of Si anode-based highenergy LIBs [17][18][19] . Adding Gr to Si materials buffers the volume change of the overall composite electrode (not individual Si particles) at a relatively low Si content (~20% Si) because the major portion of the reactive sites for SEI formation is provided by the graphite particles 20 .…”

A Study to Explore the Suitability of LiNi0.8Co0.15Al0.05O2/Silicon@Graphite Cells for High-Power Lithium-Ion Batteries

“…In addition, the highly stable performance for 50 charge–discharge cycles at the 5C rate is shown in Figure 5 b. For comparison, Table 2 shows the capacity values and cycling conditions of recent similar full cells [ 44 , 45 , 46 ].…”

Investigations of Intramolecular Hydrogen Bonding Effect of a Polymer Brush Modified Silicon in Lithium‐Ion Batteries

“…The marketing of electric vehicles is growing fast due to the restriction policy of using petrol such as Norway in 2025, [1] Netherlands/Germany in 2030 [2] and United Kingdom/France in 2040. [3] In addition, carbon emission becomes a big issue in air pollution, which significantly affects the natural environ-doping, [13] alloy composition, [14] aqueous binder, [15] morphology design, [16] surface modification, [17,18] and electrolyte control, [19] respectively. In addition, Si also suffers a high susceptibility to hydrolysis in aqueous slurry and generates H 2 as a byproduct.…”