Silicon is one of the most promising anode materials for high energy density lithium ion batteries (LIBs) due to its high theoretical capacity and natural abundance. Unfortunately, significant challenges arise due to the large volume change of silicon upon lithiation/delithiation which inhibit its broad commercialization. An advanced binder can, in principle, reversibly buffer the volume change, and maintain strong adhesion toward various components as well as the current collector. In this work, we present the first report on the applicability of polyvinyl butyral (PVB) polymer as a binder component for silicon nanoparticles-based LIBs. Characteristic binder properties of commercial PVB and polyacrylic acid (PAA) polymers are compared. The work focuses on polymer mixtures of PVB polymers with PAA, for an improved binder composition which incorporates their individual advantages. Different ratios of polymers are systematically studied to understand the effect of particular polymer chains, functional groups and mass fractions, on the electrochemical performance. We demonstrate a high-performance polymer mixture which exhibits good binder-particle interaction and strong adhesion to Cu-foil. PAA/PVB-based electrode with a Si loading of ∼1 mg/cm 2 tested between 0.01 and 1.2 V vs. Li/Li + demonstrate specific capacities as high as 2170 mAh/g after the first hundred cycles.

Silicon has great potential to be applied as an alternative anode in lithium-ion batteries. However, the electrochemical performance of silicon anodes in ether-based electrolytes, which is essential for better understanding the electrochemistry of sulfur/silicon full cells, has not been fully investigated. In this work, the effect of ether-based electrolytes on the cycling performance and surface chemistry of silicon electrodes containing microsized particles was systematically studied. In LiNO3-containing ether-based electrolyte, silicon electrode showed the fastest capacity fading and the shortest cycle life. Electrochemical impedance spectroscopy, scanning electron microscope, and X-ray photoelectron spectroscopy were employed to examine the solid electrolyte interphase (SEI) properties of silicon microparticles. An unfavorable SEI is responsible for poor cycling performance in ether-based electrolytes. Our results shed new light on the reason for short cycle life of most of the reported sulfur/silicon full cells.

Sodium polyacrylate (NaPA) in dilute aqueous solution at an ionic strength of [NaNO3] = 0.01M establishes a rich phase behavior in the presence of low amounts of silver cations, which were introduced at a few millimoles or less by replacing the corresponding amount of Na+ cations. Beyond an extremely low level of Ag+ cations, anionic PA chains aggregate. By increasing the concentration of Ag+, the aggregates become denser and keep on growing without limit. Once a certain range of [Ag+] is reached, the instantaneously formed dense aggregates remain stable. Irradiation of the PA aggregate solutions with UV-light induces formation of silver nanoparticles (Ag-Nps). Based on a combination of UV-vis spectroscopy, light scattering, transmission electron microscopy, and small angle neutron scattering, the mechanism of this NaPA assisted formation of Ag-Nps is studied. One focus of the study is lying on the effect of the two different solution states of dense aggregates, corresponding to the unstable growing AgPA aggregates and to the stable AgPA aggregates and another focus is aiming at the characterisation of the morphology of the generated hybrid particles composed of Ag-Nps and hosting PA chains.

Energy coverage In cover article ntls.20210105, Michael Bojdys et al. introduce a semi‐conducting porous organic polymer network, replacing all conventional additives in Si‐Li anodes and enabling the one‐pot production of moreperformant, flexible and thermally stable electrodes.

Silicon-based anodes with lithium ions as charge carriers have the highest predicted charge density of 3579 mA h g^-1 (for Li₁₅Si₄) while being comparatively safe. Contemporary electrodes do not achieve these theoretical values largely because production paradigms remained unchanged since their inception and rely on the mixing of weakly coordinated, multiple components. In this paper, we present the one-pot synthesis of high-performance anodes that reach the theoretical capacity of the fully lithiated state of silicon. Here, a semi-conductive triazine-based graphdiyne polymer network is grown around silicon nanoparticles directly on the current collector, a copper sheet. The current collector (Cu) acts as the catalyst for the formation of a semi-conductive triazine-based graphdiyne polymer network that grows around the inorganic, active material (Si). In comparison to established electrode assemblies, this process (i) omits any steps related to curing, drying, and annealing, (ii) does away with binders and conductivity-enhancing additives that decrease volumetric and gravimetric capacity, and (iii) cancels out the detrimental effects on performance, chemical and physical stability of conventional, three-component anodes (Si, binder, carbon black). This is because, the porous, semi-conducting organic framework (i) adheres to the current collector on which it grows <i>via</i> cooperative van der Waals interactions, (ii) acts effectively as conductor for electrical charges and binder of silicon nanoparticles <i>via</i> conjugated, covalent bonds, and (iii) enables selective transport of mass and charge-carriers (electrolyte and Li-ions) through pores of defined size. As a result, the anode shows extraordinarily high capacity at the theoretical limit of fully lithiated silicon, excellent performances in terms of cycling (exceeding 70% capacity retention after 100 cycles), and high mechanical and thermal stability. These high-performance anodes pave the way for use in flexible, wearable electronics and in environmentally demanding applications.