Silicon Nanoparticles with a Polymer-Derived Carbon Shell for Improved Lithium-Ion Batteries: Investigation into Volume Expansion, Gas Evolution, and Particle Fracture

Abstract

Silicon (Si) and composites thereof, preferably with carbon (C), show favorable lithium (Li) storage properties at low potential, and thus hold promise for application as anode active materials in the energy storage area. However, the high theoretical specific capacity of Si afforded by the alloying reaction with Li involves many challenges. In this article, we report the preparation of small-size Si particles with a turbostratic carbon shell from a polymer precoated powder material. Galvanostatic charge/discharge experiments conducted on electrodes with practical loadings resulted in much improved capacity retention and kinetics for the Si/C composite particles compared to physical mixtures of pristine Si particles and carbon black, emphasizing the positive effect that the core–shell-type morphology has on the cycling performance. Using in situ differential electrochemical mass spectrometry, pressure, and acoustic emission measurements, we gain insights into the gassing behavior, the bulk volume expansion, and the mechanical degradation of the Si/C composite-containing electrodes. Taken together, our research data demonstrate that some of the problems of high-content Si anodes can be mitigated by carbon coating. Nonetheless, continuous electrolyte decomposition, particle fracture, and electrode restructuring due to the large volume changes during battery operation (here, ∼170% in the voltage range of 600–30 mV vs Li + /Li) remain as serious hurdles toward practical implementation.

Chemical, Structural, and Electronic Aspects of Formation and Degradation Behavior on Different Length Scales of Ni‐Rich NCM and Li‐Rich HE‐NCM Cathode Materials in Li‐Ion Batteries

“…A custom setup for highthroughput in situ pressure analysis was demonstrated by Schiele et al [102] and is shown in Figure 12a. In fact, in situ pressure measurements have been performed on some anode and cathode materials in the past [102,103,212,213] (on an electrode level) to gain insights into 3D volume changes of practical electrodes. To probe the "true" gas evolution with cycling, usually the cell volume is determined first.…”

Phase Transformation Behavior and Stability of LiNiO2 Cathode Material for Li‐Ion Batteries Obtained from In Situ Gas Analysis and Operando X‐Ray Diffraction

“…[52][53][54] Ad etailedd escription of the setup used and the general working principle can be found in Ref. This methodw as already used to monitorL ip lating/stripping and the volume expansion/contraction of graphite and silicon anodes.…”

“…This methodw as already used to monitorL ip lating/stripping and the volume expansion/contraction of graphite and silicon anodes. [52][53][54] Ad etailedd escription of the setup used and the general working principle can be found in Ref. [52,54] as well as in Appendix SI 1a nd Figure S4.…”

Tailored Silicon/Carbon Compounds for Printed Li–Ion Anodes

“…The mass increase starting between 500 and 600°C can be assigned to SiO x formation in case of Si nanoparticles. [15] Since this SiO x formation appears in the case of Si/C composites after decomposition of the carbon shell as well, the mass difference at 800°C between both measure-ments is related to the total amount of carbon burnt. The mass increase at a later stage of Si and Si/C nanopowders can be ascribed to the formation of SiO 2 due to oxidation of silicon.…”