Host–Guest Interlocked Complex Binder for Silicon–Graphite Composite Electrodes in Lithium Ion Batteries

Abstract

mileage of electric vehicles (EVs). Although the operating voltage of Si is only slightly higher than that of its commercial graphite (Gr) counterpart, the theoretical specific capacity of Si (above 3000 mAh g −1 ) is far greater than that of its bare Gr counterpart (≈372 mAh g −1 ). [1] Nevertheless, the massive volume change (as much as 300%) Si undergoes during each charge-discharge cycle, has long been recognized as the origin of wrecking the integrity of the Si electrode at both the particle and electrode level as well as destabilizing the electrodeelectrolyte interface by accelerating the decomposition of the electrolyte. [2] These failure mechanisms shorten the cycle life of a Si-based electrode drastically and place a critical obstacle in the way of increasing the Si content of the LIB anodes.A variety of approaches have been introduced thus far to address the problems caused by the volume expansion of Si: diverse Si nanostructures represented by nanowires, [3] nanotubes, [4] and porous materials [5] as well as Si alloys with foreign atoms such as iron (Fe), [6] manganese (Mn), [7] and nickel (Ni) [8] turned out to be effective in buffering the volume expansion of Si. Carbon materials such as Gr, [9] graphene, [10] carbon nanofibers, [11] and carbon nanotubes [12] were also acknowledged to play a crucial role in stabilizing the electrodes over long-term cycling while supplementing the electrical conductivity. Although the exclusive use of Si as the active material would be the most ideal in terms of the energy density, blending Si with Gr would be a more realistic option in the near future to manage the aforementioned failure modes of Si.In addition to the various approaches mentioned above, the polymeric binder has also been identified as a critical electrode component that has to be taken into account when addressing the issues associated with the volume expansion of Si. [13] In this regard, it would be desirable to design the binder such that it outperforms conventional binders, which include carboxymethyl cellulose (CMC)-styrene butadiene rubber (SBR) blends, poly(vinylidene difluoride) (PVDF), and poly(acrylic acid) (PAA) in terms of preserving the electrode integrity during cycling. Beyond these established binders, various unconventional concepts were recently divulged, which include covalent crosslinking, [14] noncovalent supramolecular interactions with self-healing ability, [15] 3D networks, [16] and high elasticity. [15c,17] Most of these approaches were validated in treating bare Si active Maximizing the energy density of a lithium-ion battery cell by increasing the silicon content in the silicon-graphite (Si-Gr) composite anode is an ongoing research topic that is receiving much attention. However, the paradoxical surface characteristics of Si and Gr make it challenging to uniformly distribute the electrode components and maintain their adhesion during cycling accompanied with the immense volume change of Si. Here, an amphiphilic, tightly interlocked host-guest complex binder composed ...

Design Criteria for Silicon‐Based Anode Binders in Half and Full Cells

“…In recently published works, the mechanism of action of binders in Si-based/C systems was further investigated. Kim et al [91] applied a host-guest binder, γ CDp/Py-PAA, to a Si-graphite system and designed pyrene into the binder structure. The structure of the binder and its mechanism of action in the silicon-graphite system are shown in Figure 30a.…”

“…However, in the full-cell, the limited Li source magnifies the problem of low coulombic efficiency for Reproduced with permission. [91] Copyright 2022, Wiley-VCH. b) The contact angle of Si, Si/C, and graphite with water.…”

“…Binders for Si-based/C materials. a) The molecular structure of γ CDp/Py-PAA binder and its mechanism of action in Si-graphite electrode.Reproduced with permission [91]. Copyright 2022, Wiley-VCH.…”

Eight‐Electron Redox Cyclohexanehexone Anode for High‐Rate High‐Capacity Lithium Storage

“…[5] However, these novel anode materials still face great challenges in terms of cycling durability and rate performance, mainly caused by drastic volume variation, severe mechanical pulverization, and cumulative growth of solid electrolyte interphase (SEI) layer upon cycling. [6,7] It should be noted that, in addition to the performance bottleneck, the high carbon emission caused by the high-energy synthesis route is also a serious issue that deserves more attention for inorganic anodes.Replacing inorganic anodes with organic electrode materials is an extremely attractive direction for future LIBs. Organic compounds offer significant merits, including structural diversity, processing compatibility, easy recycling/disposal, and low environmental footprint.…”

“…[5] However, these novel anode materials still face great challenges in terms of cycling durability and rate performance, mainly caused by drastic volume variation, severe mechanical pulverization, and cumulative growth of solid electrolyte interphase (SEI) layer upon cycling. [6,7] It should be noted that, in addition to the performance bottleneck, the high carbon emission caused by the high-energy synthesis route is also a serious issue that deserves more attention for inorganic anodes.…”