Silicon in Hollow Carbon Nanospheres Assembled Microspheres Cross‐linked with N‐doped Carbon Fibers toward a Binder Free, High Performance, and Flexible Anode for Lithium‐Ion Batteries

Abstract

Silicon (Si), as the most promising anode material, has drawn tremendous attention to substitute commercially used graphite for lithium‐ion batteries (LIBs). However, recently, the insufficiently high structural stabilities and electron/ion conductivities of silicon‐based composites have become the main concerns, hindering the further progress of silicon as the anode material for LIBs. Herein, to cope with these concerns, a binder‐free and free‐standing type anode electrode paper is fabricated from self‐assembled microspheres and intertwined fabrics, in which a 3D interconnected nitrogen/carbon network connects hollow carbon nanospheres with uniformly distributed silicon nanodots (SHCM/NCF). The as‐prepared SHCM/NCF paper maintains a reversible capacity of 1442 mAh g−1 at 1 A g−1 for 800 cycles in lithium half‐cell, and 450 mAh g−1 at 0.5 A g−1 for 200 cycles in lithium full‐cell, respectively. The excellent battery performances are mainly attributed to the free‐standing paper electrode suppressing side reactions, nitrogen/carbon networks maintaining electrical contact, and silicon nanodots alleviating the harm caused by volume expansion. Furthermore, this excellent performance combined with the simplicity of the synthesis method and the saving of excess polymer binder, current collector and conducting additives, make the designed paper exhibit great potential in practical applications.

Nitrogen, Oxygen‐Codoped Vertical Graphene Arrays Coated 3D Flexible Carbon Nanofibers with High Silicon Content as an Ultrastable Anode for Superior Lithium Storage

“…The delithiation process is also confirmed by ex situ XRD, in which Si still exists in the amorphous form, suggesting crystalline Si peaks cannot be reformed, in conformity to the previous literatures. [21,37,47] Besides, the weak diffraction peaks of LiF as a component of SEI layer are observed at around 38.9°and 45.3°(JCPDS:001-1270), indicating the formation of crystalline LiF. [65] The formation of LiF arises from the SEI layer caused by the decomposition of electrolyte, corresponding to the cathodic peaks at around 0.90 V in the CV curves (Figure 5a).…”

“…To understand the influence of the Li + ion diffusion on the electrode kinetics, we investigated the diffusion coefficient of Li + ion using galvanostatic intermittent titration technique (GITT) methods (Figure 6f,g). The Li + ion diffusion coefficient (D Li + ) of VGAs@Si@CNFs-1 can be further calculated according to the simplified equations: [37,63]…”

“…The CV measurements at different sweep rates ranging from 0.1 to 2.0 mV s −1 are recorded to further analyze the Li + (de)intercalation kinetics of VGAs@Si@CNFs-1 anode (Figure 6a). Note that the current response (i) and the sweep rate (v) in a certain electrode can be described by the power-law equations: [37,63]…”

“…[34][35][36] Among these methods, carbon coating has been demonstrated as an attractive choice to accommodate the volume expansion and enhance kinetics of Si. Multifarious Si-C composite nanostructures, such as Si-amorphous carbon, Si-graphene, Si-carbon nanotubes, Si-graphite, and Sicarbon nanofibers, [37,38] have been reported recently. Despite their significantly improved electrochemical performance, most of the previous synthetic routes still face challenges such as: a) inhomogeneous coating of carbon from the common methods, including ball milling, solution mixing, and templating method, which result in rapid decay of electrochemical stability; b) the difficulty in tuning the thickness and compactness of carbon layers causes a terrible balance between electrons conduction and ions transporting; c) low Si content for the whole electrode severely leads to low energy density and weaken the capacity advantage of Si anode.…”

P‐Doped SiOx/Si/SiOx Sandwich Anode for Li‐Ion Batteries to Achieve High Initial Coulombic Efficiency and Low Capacity Decay

“…Si's poor intrinsic electron conductivity results in a low Li diffusion coefficient (10 −14 -10 −13 cm 2 s −1 ). [2] In addition to the above problems, a challenging new issue was recently raised regarding its low initial Coulombic efficiency (ICE) for practical application in battery systems. [3] The ICE defines the ability of anode materials to prevent irreversible reactions and loss of irreversible capacity, [4] and hence a key variable for available energy density in applications.…”