Cross-Linked γ-Polyglutamic Acid as an Aqueous SiO_x Anode Binder for Long-Term Lithium-Ion Batteries

Abstract

Silicon oxide (SiO x ) has outstanding capacity and stable lithium-ion uptake/removal electrochemistry as a lithium-ion anode material; however, its practical massive commercialization is encumbered by unavoidable challenges, such as dynamic volume changes during cycling and inherently inferior ionic conductivities. Recent literature has offered a consensus that binders play a critical role in affecting the electrochemical performance of Si-based electrodes. Herein, we report an aqueous binder, γ-polyglutamic acid cross-linked by epichlorohydrin (PGA–ECH), that guarantees enhanced properties for SiO x anodes to implement long-term cycling stability. The abundant amide, carboxyl, and hydroxyl groups in the binder structure form strong interactions with the SiO x surface, which contribute strong interfacial adhesion. The robust covalent interactions and strong supramolecular interactions in the binder ensure mechanical strength and elasticity. Additionally, the interactions between lithium ions and oxygen (nitrogen) atoms of carboxylate (peptide) bonds, which serve as a Lewis base, facilitate the diffusion of lithium ions. A SiO x anode using this PGA–ECH binder exhibits an impressive initial discharge capacity of 1962 mA h g–1 and maintains a high capacity of 900 mA h g–1 after 500 cycles at 500 mA g–1. Meanwhile, the assembled SiO x ||LiNi0.6Co0.2MnO0.2 full cell shows a reversible capacity of 155 mA g–1 and displays 73% capacity retention after 100 cycles.

Engineering High-Performance SiOx Anode Materials with a Titanium Oxynitride Coating for Lithium-Ion Batteries

“…It is known that full-cell testing is an effective way to evaluate the practicability of an anode. − To further test the practical viability of SiO x -TiON-200, the SiO x -TiON-200||NCM622 full cells were assembled with a commercial LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) cathode. According to the tested specific capacities of the cathode and the anode, the anode/cathode capacity ratio is designed to be 1.15.…”

In Situ Prepared Three-Dimensional Covalent and Hydrogen Bond Synergistic Binder to Boost the Performance of SiOx Anodes for Lithium-Ion Batteries

“…All these problems lead to a decrease of electrochemical performance and reduce the service life of batteries. In order to ease the volume expansion of the silicon anode materials, it can be solved by the following three aspects: (1) the design and modification of the Si materials, mainly including nanocrystallization, carbon coverage, alloying, and SiO x ; − (2) the application of adapted electrolytes and electrode additives; − (3) the design and modification of binders . SiO x (0 < x < 2) is a promising anode material due to not only the higher capacity than graphite but also the lower volume change than silicon. , However, SiO x still has problems such as a large volume expansion, low initial Coulombic efficiency (ICE), and poor electrical conductivity during the cycling process. , One of the simple and low-cost ways to solve this problem is to design and modify the binders. − …”

Engineering of a newly isolated Bacillus tequilensis BL01 for poly-γ-glutamic acid production from citric acid

“…γ-PGA nanocomposite hydrogels are potentially applied for injectable tissue engineering hydrogels, tissue adhesives, and hemostatic materials [ 9 ]. The SiOx electrode using γ-PGA cross-linked by epichlorohydrin as the binder achieves high reversible capacity and outstanding cycle stability [ 10 ]. In agriculture, exogenous application of γ-PGA could significantly improve plant drought resistance by improving photosynthesis, and root development, and enriching plant growth-promoting bacteria [ 11 ].…”