High capacity Li-ion battery anodes: Impact of crystallite size, surface chemistry and PEG-coating

SWNT Anchored with Carboxylated Polythiophene “Links” on High-Capacity Li-Ion Battery Anode Materials

“…Here, we introduce the use of carboxylated polythiophene to fabricate single-walled carbon nanotube (SWNT) electrical networks to anchor high-capacity active anode materials (Figure a). Water-soluble, carboxylate substituted polythiophenes, such as poly­[3-(potassium-4-butanoate) thiophene] (PPBT), have the potential to serve as a polymeric binder, or a physical/chemical linker to render electroactive particles and carbon additives well-connected through specific molecular interactions, thereby yielding stable, high-performance battery electrodes. − The PPBT has relatively high electronic conductivity of ∼10 –5 S cm –1 when compared with polyvinylidene fluoride (PVDF; ∼10 –8 S cm –1 ) and experiences electrochemical doping where the conjugated polymer undergoes reduction within the operating voltage of anode applications, enabling more rapid electron transport. , …”

“…Figure a presents scanning electron microscope (SEM) images of SWNT-sFe 3 O 4 , confirming that SWNTs are well-connected at the PEG-sFe 3 O 4 surface. Fourier transform infrared (FT-IR) spectroscopy (Figure b) provides strong evidence of the specific interactions between the PPBT carboxylate group and sFe 3 O 4 particles, namely, the formation of an Fe-carboxylate complex where PPBT carboxylate substituents were chemically bound to hydroxyl groups present on the metal oxide surface. − SWNT-sFe 3 O 4 presents a peak at ∼1716 cm –1 for CO stretching and a peak at ∼1520 cm –1 for O–C–O asymmetric stretching where the shoulder was split from ∼1558 cm –1 band, associated with the Fe–carboxylate bond. The X-ray photoelectron spectroscopy (XPS) spectra (Figures c and S1a) further substantiate the presence of such interactions.…”

“…Given that the PPBT binder provided stable electrodes, − improved cyclability was also anticipated. Contrary to that expectation, the SWNT-sFe 3 O 4 /PPBT binder electrode exhibited poor cycling (Figure d) and inferior rate capability (Figure S1f).…”

Active Material Interfacial Chemistry and Its Impact on Composite Magnetite Electrodes

“…Figure schematically illustrates the attachment strategies, whereby each synthetic route was designed to probe the role of distinct chemical characteristics that could be integral to creating high performing Fe 3 O 4 anodes. On the basis of prior studies, PEG aids in the dispersion of magnetite, providing for more uniform composites and possibly creating a highly ion conductive network at the electroactive material surface. − Thus, the PEG coated material served as a control. Benzoic acid functionalization has been shown to mitigate electrode pulverization due to volume expansion, and the aromatic acid may be expected to facilitate π–π stacking interactions with PPBT creating an electronically conductive network. , Alternatively, PPBT could be directly attached to the particle surface to create a flexible electronically conductive network that links with other particles in the electrode.…”

High performance polyurethane–polyacrylic acid polymer binders for silicon microparticle anodes in lithium-ion batteries

“…5,6 Therefore, new anode materials need to be developed. 7–11 Silicon has been considered to be one of the most promising anode materials, with a theoretical specific capacity as high as 4200 mA h g −1 (about ten times that of graphite). In addition, silicon has the advantages of abundant reserves, easy availability of raw materials and environmental friendliness, thus it has been widely studied.…”