Silicon Composite Electrode with High Capacity and Long Cycle Life

Abstract

International audienceA nanosilicon-based composite electrode that can achieve more than 700 cycles at a high capacity of 960 mAh/g of electrode was prepared using aqueous processing in an acidic medium. The buffering of the aqueous solution is mandatory to promote covalent bonding between Si particles and the carboxymethyl cellulose (CMC) binder. The latter is claimed to allow the formation of mechanically stronger contacts within the composite electrode in addition to the CMC bridging of the Si and carbon black particles

Stable Li-ion battery anodes by in-situ polymerization of conducting hydrogel to conformally coat silicon nanoparticles

“…For example, phytic acid, a naturally occurring molecule consisting of six phosphoric acid groups, can be used as both the gelator and dopant to react with the aniline monomer by protonating the nitrogen groups on polyaniline (PANi), leading to the formation of a 3D interconnected network structure 38 . In this work, when SiNPs are mixed into the solution during polymerization, the phosphoric acid groups in the phytic acid molecules can potentially bind with the SiO 2 on the Si particle surfaces via hydrogen bonding, which was thought to contribute to the improved cycle lifetime for PAA, CMC and alginate binders with carboxylic acid groups [32][33][34]36 . This interaction can also result in the conformal coating of phytic acid molecules on the surface, which may further crosslink with aniline monomers during polymerization to generate a conformal conductive coating.…”

“…Various polymer binders other than traditional polyvinylidene difluoride (PVDF), including polyacrylic acid (PAA), carboxy-methyl cellulose (CMC), poly(9,9-dioctylfluorene-co-Suorenone-comethylbenzoic acid) (PFFOMB) and alginate, have been found to enhance the cycle life 14,15,[32][33][34][35][36] . The cycle life improvement when using PAA, CMC and alginate binders was attributed to the high polymer modulus values and the binding between the functional groups on the polymers with the surface oxide on the Si particles.…”

Recent Progress on Polymeric Binders for Silicon Anodes in Lithium-Ion Batteries

“…From these mechanisms, it is likely that at high pH values, the dominant interaction is the hydrogen bonding interaction between the CMC and the Si nanoparticle. Interestingly, Guyomard et al reported that an esterification reaction between Si-OH on the Si surface and the COOH of the CMC binder preferentially occurred at pH = 3 and that this covalent bonding could remarkably improve the cycling performance of nano-Si anodes [32]. Oh et al investigated a polyvinyl alcohol (PVA) linear-type polymer with many hydroxyl groups, showing that it can form hydrogen bonds with active materials and the current collector as a binder for Si/graphite composite anodes [33].…”

Revealing lithium–silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy

“…At these low voltages, the amorphous Li-silicides (a-Li x Si) formed on lithiation are converted to crystalline phases such as crystalline Li 3.75 Si (c-Li 3.75 Si) 5,12,[22][23][24][25][26][27] , a process that is associated with a large overpotential on delithiation. This approach differs from other practical strategies to improve capacity retention that limit the Si cycling regimes to B1,200-1,500 mAh g À 1 , cycling at higher potentials between different a-Li x Si compositions 3,28 . To utilize Si to its full potential using these very different cycling regimes, an understanding needs to be developed of the different structural processes that occur, the kinetics of the various transformations and how they correlate with capacity retention.…”