Investigations of Intramolecular Hydrogen Bonding Effect of a Polymer Brush Modified Silicon in Lithium‐Ion Batteries

Abstract

Gradually eradicating petrolic use is therefore the correct direction for maintaining the environment of the earth. Developing energy storage and saving energy consumption is the key to maintaining a good life. Currently, the lithium-ion battery is one of the best choices for the use of vehicles. However, the energy density of the lithium-ion batteries on current developments is less than 300 Wh kg -1 , which is restricted by the capacity of electrode active materials.Si has the maximum theoretical capacity (4000 mAh g -1 ) compared with the graphite (372 mAh g -1 ) and Li 4 Ti 5 O 12 (175 mAh g -1 ). However, Si can only be used in small amounts as an additive (less than 10 wt%) in commercial battery owing to the problems of volume expansion [6,7] and electrochemical irreversibility. [8,9] In terms of previous discussions, the repeatable pulverization of Si during cycling is the key in decaying the performance. [10,11] With the volume expansion and the pulverization, the new surface area of Si is continuously generated and contacts electrolyte for more solid electrolyte interphase (SEI) formation, which increases the impedance and consumes lithium ions significantly. Moreover, 300-400% volume change of Si during cycling makes it difficult for battery design. Several researches have been investigated for solving those problems of Si such as carbon coating, [12] element Silicon (Si) has the maximum capacity compared with the conventional graphite, which can dramatically increase the energy density of the battery. However, due to some tremendous drawbacks of Si material such as electrochemical irreversibility and volume expansion on alloy reaction, pure Si cannot be used in large quantities in the anode electrode. In this research, a polymer brush core-shell structure (PBCS) on Si nanoparticle provides three significant functions because of the intramolecular effect of hydrogen bonding with PBCS and the binder delivers a good dispersion in the slurry, a mechanical protection during cycling, and excellent ionic conductivity for highrate tests. The carbonyl groups of polymer brush on Si surface are fabricated to enhance lithium-ion diffusion and the adjustment of attraction and repulsion by intramolecular hydrogen bonding effect with binder in between each Si particles. The PBCS-Si electrode shows the first coulombic efficiency is 87.1%; the retentions are 92.5% (0.1C/ 0.1C) for 200 cycles and 86.2% (0.5C/ 0.5C) for 400 cycles. Operando TXM displays that the PBCS structure significantly protects the nano Si from cracking owing to the high elastic function and intramolecular hydrogen bonding effect of the PBCS. With this novel PBCS-Si material, a high energy density lithium-ion battery can be expected.

Constructing a Stable Conductive Network for High-Performance Silicon-Based Anode in Lithium-Ion Batteries

“…The stronger peak of LiSiO x suggests a better structural stability of Si@(POH-AOCNTs). 49 The C and O contents of the cycled samples were further analyzed, as shown in Figure S12. For the cycled Si@(POH-AOCNTs) electrode, the SEI layer has a relatively low amount of Li 2 CO 3 , whereas the content of organic substances in the SEI layer increases with the decrease of Li 2 CO 3 , a high content of organic substances can enhance the elasticity of the SEI film, which, in turn, can have a better adaptation to the volume expansion and shrinkage of Si@(POH-AOCNTs) anode.…”

“…LiF-enriched SEI layer is beneficial to the structural stability of the anode, thus promoting the long-cycle performance. , As shown in the Si 2p XPS spectra (Figure S11), the peaks at 99.8 and 102.5 eV are attributed to Li x Si and LiSiO x . The stronger peak of LiSiO x suggests a better structural stability of Si@(POH-AOCNTs) . The C and O contents of the cycled samples were further analyzed, as shown in Figure S12.…”

Carbon-Coated Si Nanoparticles Anchored on Three-Dimensional Carbon Nanotube Matrix for High-Energy Stable Lithium-Ion Batteries

“…In addition, Si shows poor intrinsic electron conductivity, resulting in sluggish electrochemical kinetics and severely limiting the cycle life of the Sibased batteries [9,20]. To date, various strategies have been explored to develop the superior Si-based electrode materials, including the construction of Si nanostructures [21,22], porous Si [23][24][25], surface coating of protective layers [26][27][28], Si-based composites [17,[29][30][31], SiO xbased materials [32][33][34], and new electrode binders [35][36][37][38][39]. Of these, nano-Si materials have been shown to effectively relax the mechanical stress and strain on the electrode during volume fluctuation, avoiding cracking or pulverization of their structures, thereby significantly improving Coulombic efficiency and cyclability [30,40].…”