Self‐Repairable Silicon Anodes Using a Multifunctional Binder for High‐Performance Lithium‐Ion Batteries

Abstract

A currently commercialized graphitebased anode in LIBs cannot meet the increasing demand for high energy density because of the limited theoretical specific capacity of graphite (372 mAh g −1 ). [2] As an alternative to the graphite anode for highenergy anode materials, silicon has gained substantial attention due to its high theoretical specific capacity of 3579 mAh g −1 at room temperature (Li 15 Si 4 ), [3] low working potential (0.4 V vs Li + /Li), [4] nontoxicity, and natural abundance. [5] However, the massive volume change of Si (≈300%) during lithiation/delithiation processes causes various problems, including pulverization, delamination of electrodes, [6] and uncontrollable growth of the solidelectrolyte interface (SEI) layer, [7] resulting in a significant irreversible capacity and rapid capacity decay. [8] Furthermore, Si has low conductivity of ≈0.67 mS cm −1 , [9] leading to a relatively poor rate capability. To address aforementioned issues and enhance the cycle life of Si anodes, several approaches have been developed, including the design of nanostructured Si (porous, yolk-shell, nanowires, and nanomesh), [10][11][12] artificial SEI layer, [13] composites, [14,15] electrolytes, [16] and binders. [17,18] Proper design of binders is particularly crucial for Si anodes because binders affect the structural integrity and mechanical stability of Si anodes. Unfortunately, the most widely used polyvinylidene fluoride (PVDF) binder is unsuitable for Si anodes, showing fast capacity decay due to its insufficient mechanical properties and weak van der Waals interaction with Si. [19] Thus, other diverse polymeric binders have been explored, including poly(acrylic acid) (PAA), [20] sodium carboxymethoxy cellulose, [21] sodium alginate, [22] guar gum, [23] and other functionalized polymers for Si anodes. [24,25] These binders have polar functional groups interacting more closely with Si active materials, offering better adhesion and enhanced capacity retention compared with the PVDF binder. However, Si anodes with those binders were also gradually degraded over the repeated charge/discharge cycles because of the massive volume expansion of Si, resulting in significant capacity decay.A self-healing binder is especially desirable for Si anodes because of its capability to self-heal mechanical damages or cracks typically generated during cycling. For instance, selfhealing polymers with urea functional groups offer abundant hydrogen bonding sites and self-healing properties, which Despite of extremely high theoretical capacity of Si (3579 mAh g −1 ), Si anodes suffer from pulverization and delamination of the electrodes induced by large volume change during charge/discharge cycles. To address those issues, herein, self-healable and highly stretchable multifunctional binders, polydioxythiophene:polyacrylic acid:phytic acid (PEDOT:PAA: PA, PDPP) that provide Si anodes with self-healability and excellent structural integrity is designed. By utilizing the self-healing binder, Si anodes self-repair cracks and damages of...

N-Type Polyoxadiazole Conductive Polymer Binders Derived High-Performance Silicon Anodes Enabled by Crosslinking Metal Cations

“…The physical damage of M n + -PODs gels is achieved by self-healing at room temperature when the damaged interface is re-contacted. The M n + -POD healed gels can maintain the damage interface without fracture after stretching to a certain length, which confirms the excellent healing ability of the Si electrode based on the interaction of ionic and hydrogen bonds. , Among M n + -PODs/Si electrodes, the surface cracks of M 2+ -POD-binding Si anodes are significantly less severe than those of M + -PODs/Si electrodes, which makes the coordination effect of divalent ions stronger. The surface of the Ca-POD/Si anode has the least and shallowest cracks because the Ca-POD binder shows an outstanding balance between excellent strength and moderate elasticity, which endow the electrode with small volume fluctuations and displays excellent high-rate capability and superior cycle stability.…”

“…Figures f and S4 show the electrolyte contact angles of M n + -PODs and PAALi binders. The electrolyte contact angle characterizes the electrolyte wettability of the electrode, which is mainly related to the polar groups of the binders. , Due to the similar SD of M n + -PODs, their electrolyte contact angles are relatively close. Figure f shows that the contact angles of M n + -PODs are around 30°, with minor differences within the margin of error.…”

A Comprehensive Review of Current and Emerging Binder Technologies for Energy Storage Applications

“…To enhance battery energy density, multifunctional binder strategies have emerged, aiming to combine diverse benefits from individual polymers. − A multifunctional binder refers to a compound used in battery electrode fabrication that serves multiple purposes beyond the traditional role of binding active materials and additives. For instance, binders can also be used to form protective layers, which helps in mitigating side reactions between electrodes and electrolytes to improve battery performance.…”

A Cellulose Reinforced Multifunctional Binder for High-Performance Silicon Anodes

“…It is worth noting that the dissipation of mechanical stress is crucial for polymer binders in maintaining electrode integrity; thus, the addition of small, soft components to the rigid polymer framework can play a role in buffering and dissipating the stress. 24 Malik et al 25 reported a self-healing and stretchable multifunctional binder PEDOT:PAA:PA (PDPP), where PAA provides mechanical support as a polymer framework and PEDOT enhances the capacity and rate performance. The PA, PEDOT, and PAA interact with each other through dynamic hydrogen bonding and electrostatics, which further enhances the mechanical properties of Si electrodes.…”