Active Buffer Matrix in Nanoparticle‐Based Silicon‐Rich Silicon Nitride Anodes Enables High Stability and Fast Charging of Lithium‐Ion Batteries

Abstract

first and foremost are defined by both anode and cathode material properties.Silicon is considered the most attractive high-capacity anode material for the next generation of LIBs, showing a low working potential and a high theoretical storage capacity of 3579 mAh g −1 . [1,2] Additional advantages include better rate performance compared to graphite, [3,4] high natural abundance, and low cost. [5][6][7] In spite of these clear advantages, the implementation of silicon-based anodes has not yet been accomplished, mainly due to two major challenges: the continuous solid electrolyte interphase (SEI) growth and the pulverization of the anode material. These challenges have their origin in the high capacity of Si and the alloying reaction with Li that inevitably leads to huge volume expansion of up to 300% in a fully lithiated state. [8] The volume changes during charging and discharging lead to mechanical instability of the anode, noticeable by severe cracking and eventually a loss of electrical contact of active material. [9,10] Thus, silicon-based electrodes show rapid degradation and failure after only a few cycles, while the application of nanomaterials, such as nanowires, nanoparticles, or thin films, have been shown to circumvent distinct mechanical failure. [11][12][13][14] Whereas nanostructures mitigate challenges related to, for example, fracturing and pulverization, they do promote irreversible capacity losses and capacity fading associated with excessive SEI build-up during cycling, owing to their usually A very promising way to improve the stability of silicon in lithium-ion battery (LIB) anodes is the use of nanostructured silicon-rich silicon nitride (SiN x ), known as a conversion-type anode material. To investigate the conversion mechanism in this material in detail, SiN 0.5 nanoparticles are synthesized and examined as LIB anodes using a combination of ex situ X-ray photoelectron spectroscopy and solid-state 7 Li MAS NMR measurements. During the initial cycle, the conversion of SiN 0.5 nanoparticles results in the formation of lithium silicides and a buffer matrix consisting of different lithium nitridosilicates and lithium nitride. These phases can be reversibly lithiated and contribute to the total reversible capacity of the silicon nitride active material. The structure of the material after conversion is best described by an amorphous solid solution. Further, it is shown that silicon-rich silicon nitrides possess improved rate capability because of the higher ionic conductivity of the buffer matrix compared to pure silicon, and very fine dispersion of silicon clusters throughout the buffer matrix. Thus, unlike most conversion materials, the silicon-rich silicon nitride exhibits an additional intrinsic active functionality of the buffer matrix that goes far beyond the mere reduction of electrolyte contact area and volume expansion.

Lithium-Ion Battery Anodes Based on Silicon Nitride Nanoparticles as Active Material and Vertically Aligned Carbon Nanotubes as Electrically Conductive Scaffolding

“…To put our work into perspective, Table S.2 is compiled to give an overview of results presented in the current literature on SiN x -based electrodes. − …”

Double Nitrogenation Layer Formed Using Nitric Oxide for Enhancing Li+ Storage Performance, Cycling Stability, and Safety of Si Electrodes

“…Inorganic Si functional composites such as Si oxides/oxycarbides (e.g., SiO, SiO x , SiO 2 , SiOC), [ 22 , 23 ] Si carbide (SiC), [ 24 , 25 ] and Si nitrides (e.g., Si 3 N 4 , SiN x ) [ 26 , 27 , 28 ] have attracted increasing attention because these Si‐containing ceramic materials efficiently increase electrode cycling stability. Among them, Si nitrides have received a lot of research interest.…”