β‐cyclodextrin as Lithium‐ion Diffusion Channel with Enhanced Kinetics for Stable Silicon Anode

Abstract

Silicon (Si) is regarded as a promising anode material for next‐generation lithium‐ion batteries due to its ultrahigh theoretical capacity. However, the drastic volume change and the continuous solid electrolyte interphase (SEI) formation during the lithiation/delithiation process seriously hinder its practical application as commercial anodes. Herein, macrocyclic beta‐cyclodextrin (β‐CD) has been designed as the diffusion channel for lithium ions at the molecular scale. The diameter of molecular channel is approximately comparable with the solvated lithium ions, which enables the transport of lithium ions and prevents the penetration of solvent molecules. Moreover, the addition of β‐CD changes the formation behavior of SEI layer and stabilizes the Si nanoparticles. The enhanced electrochemical performances in terms of fast kinetics and improved stability have been achieved. The Si anode with the particularly selected lithium‐ion diffusion channel and stabilized SEI layer exhibits a high reversible capability of 2 562 mAh g−1 after 50 cycles at the current density of 500 mA g−1, 1 944 mAh g−1 after 200 cycles at the current density of 1 A g−1, and high rate performance. The novel strategy of molecular channel for lithium‐ion diffusion offers new insights into the design of alloy‐typed anode electrodes with high capacity for lithium‐ion batteries.

Crosslinked Polymer Binder via Phthalic Acid for Stabilizing SiOx Anodes

“…[48,49] Over the past decade, multiple polymer binders have been researched, including carboxymethyl cellulose (CMC), [50,51] alginate sodium, [52] polyacrylic acid, [53] and polyvinyl alcohol. [54] Several new concepts of polymeric binders have been introduced such as self-healing binders, [55,56] conducting binders, [57] 3D network binders [58][59][60][61] and mussel-inspired adhesion binders. [42] Owing to their structural particularity, the active hydrogen bonding interaction and a few of covalent bonding interaction between different components of the whole electrode, these polymer binders possess excellent mechanical and electrochemical properties.…”

Tuning Inactive Phases in Si–Ti–B Ternary Alloy Anodes to Achieve Stable Cycling for High-Energy-Density Lithium-Ion Batteries

“…The dramatic development of consumer electronics and electric vehicles puts forward higher demands for the energy density of lithium-ion batteries (LIBs). − In the past few years, research on Sn and Si-based materials, with an alloying mechanism of lithium storage, has been in a blowout growth. − Among them, Si-alloy anodes could increase the energy density of LIBs by as much as 20% over conventional graphite electrodes, as Si shows a high theoretical capacity (3579 mAh g –1 , 2194 Ah L –1 ) and a moderate voltage (∼0.4 V). − However, the poor cyclability of the Si electrode hinders its commercialization due to the enormous volume change (∼280%) during Si alloying/dealloying with Li and a sudden crystallization of lithiated amorphous Li 15 Si 4 at a low lithiation voltage (∼50 mV). − In addition, its low electrical conductivity (∼10 –3 S/m) is another hurdle for applying Si as a lithium-ion anode …”

Combining ReaxFF Simulations and Experiments to Evaluate the Structure–Property Characteristics of Polymeric Binders in Si-Based Li-Ion Batteries

“…Appropriate iondiffusion channels in binders play a crucial role in improving ion-conduction. 36 Similarly, an ideal binder matrix also needs to have the capacity to conduct electrons, facilitating charge transport between the Si particles and the current collector. This usually requires the addition of carbon black into the binder matrix in the case of nonconductive polymers, but the use of electronically conductive binders can obviate the need for such an additive, potentially increasing the active material content and creating more efficient pathways for electron transport within the electrode matrix.…”

“…An elastic binder allows for more lithiation, whereas a stiffer binder constrains Si expansion and causes self-delithiation or lithium retardation. , Third, binders with high Li-ion conduction are essential, especially for high-power applications, to achieve fast kinetics and improved energy efficiencies. Appropriate ion-diffusion channels in binders play a crucial role in improving ion-conduction . Similarly, an ideal binder matrix also needs to have the capacity to conduct electrons, facilitating charge transport between the Si particles and the current collector.…”