Ambidextrous Polymeric Binder for Silicon Anodes in Lithium-Ion Batteries

Abstract

A new type of polyamide imidazole (PAID) polymer with two functional groups for tight binding with silicon (Si) particles and carbon black is investigated as a binder for the Si anode in lithium-ion batteries (LIBs). PAID is synthesized via three reaction phases. The first phase is polyamide polymerization (p-PAID), the second phase is formation of imide and imidazole rings (i-PAID), and the last phase is ring cyclization for the PAID structure. Among these stages, i-PAID shows ambidextrous binding characteristics for LIBs. The planar π-conjugated backbone in the i-PAID provides a strong π−π stacking interaction with carbon black, thus sustaining the electrical conduction pathway in the Si electrode during cycling. The amine and carboxylic acid functional group in the i-PAID have a strong interaction with Si particles, which efficiently suppresses the volume expansion of the Si electrode, confirmed by in situ electrochemical dilatometry and ex situ SEM observation. The Si anode with the bifunctional i-PAID binder shows not only a higher reversible capacity but also a greatly enhanced cycle performance over 200 cycles in comparison to the Si anode with a simple polyimide binder. This ambidextrous polymer binder offers a new opportunity to positively impact the development of a mechanically robust Si anode for lithium-ion batteries.

Structure‐Performance Relationship of Aromatic Polymer Binder for Silicon Anode in Lithium‐Ion Batteries

“…We anticipated that introducing 3,3′‐diaminobenzidine into the aromatic polyimides would serve dual functions. [ 46 ] First, the extra amines can provide strong binding with Si particles after imidization. Second, the remaining amines that do not bind with Si make fused aromatic rings after thermal imidazolation, which enhances the interactions with the conductive agent.…”

Recent achievements of free‐standing material and interface optimization in high‐energy‐density flexible lithium batteries

“…Meanwhile, the amino and carboxylic acid functional groups among the polymer binders are tightly combined with silicon particles to restrain the volume change of silicon electrodes during cycling. [50] Typically, the electron conducting polymers such as polyaniline (PANI), polythiophen, polypyrrole (PPY), polyacetylene, and poly (3,4-ethylenedioxythiophene) (PEDOT) are also widely applied in lithium-sulfur batteries and LiBs to alleviate the volume variation of electrodes during charge/discharge and ensure the integrity of the electrodes. [51,53,54] Fan's group has designed a flexible free-standing V 2 O 5 -based core-shell cathode by adding conductive polymers (PEDOT) to the active materials (Figure 3c,d).…”

“…Reproduced with permission: Copyright 2022, American Chemical Society. [ 50 ] (c) and (d) Schematic illustration of the 3D UGF@V 2 O 5 /PEDOT nanobelts, SEM image, and rate performance. Reproduced with permission: Copyright 2014, Wiley.…”

Superior Effect of Si Doping on Interfacial Reaction of LiPON Solid Electrolyte for the Silicon-Rich Oxide (SiO1/2) Anode in All-Solid-State Batteries: A First-Principles Prediction

“…In the view of electrode in LIBs, Si presents a very high theoretical capacity of 4200 mAh/g among all the known materials. − However, Si suffers from serious capacity fading with huge volumetric change (∼300%) in cycling processes. − The Si/LLZTa/Li ASSB cell was deposited and exhibited a high capacity of 2700 mAh/g for first cycle, while its delithiation capacity decreases to 1200 mAh/g after 100th cycles . Silicon oxide is considered as an alternative of silicon; SiO and Si 2 O were successfully applied in lithium batteries, which exhibit superior cycling stability and ion diffusion properties compared to silicon. , A composite was synthesized by embedding Si nanocrystallites in the SiO 2 matrix; the volume change of silicon was effectively limited. , Moreover, the oxygen content in SiO x also presented a significant impact on the performance of silicon oxide electrodes. , …”