Understanding Excess Li Storage beyond LiC₆ in Reduced Dimensional Scale Graphene

Abstract

A phenomenon is observed in which the electrochemical performances of porous graphene electrodes show unexpectedly increasing capacities in the Li storage devices. However, despite many studies, the cause is still unclear. Here, we systematically present the reason for the capacity enhancements of the pristine graphene anode under functional group exclusion through morphological control and crystal structure transformation. The electrochemical synergy of both the edge effect and surface effect of the reduced dimensional scale graphene in an open-porous structure facilitates significantly enhanced capacity through multidimensional Li-ion accessibility and accumulation of Li atoms. Furthermore, the Stone–Wales defects boosted during Li insertion and extraction promote a capacity elevation beyond the theoretical capacity of the carbon electrode even after long-term cycles at high C-rates. As a result, the morphologically controlled graphene anode delivers the highest reversible capacity of 3074 mA h g–1 with a 163% capacity increase after 2000 cycles at 5 C. It also presents a gradually increasing capacity up to 1102 mA h g–1 even at 50 C without an evident capacity fading tendency. This study provides valuable information into the practical design of ultralight and high-rate energy storage devices.

Effects of Pre‐Electroplated Metal or/and Graphene on the Initial Coulombic Efficiency of Graphite Anode

“…By comparing the Coulombic efficiency data (Figure S3), it might be pointed out that the Sn and rGO in the composites can promote the formation of the SEI layer, which improves further the cycling stability. The slight increases of capacities of graphite/rGO and graphite/Sn/rGO composites are ascribed to the edge and surface effect of the surface coated graphene sheets [17] …”

Preparation of ZnS@N-doped-carbon composites via a ZnS-amine precursor vacuum pyrolysis route

“…Studies have shown that defect carbon can effectively improve the conductivity which is benecial to storing lithium ions. 51,52 As the temperature increases, it can be observed that the I D /I G ratio present a slight upward trend from ZnS@NC-L (0.96), ZnS@NC-M (0.97), to ZnS@NC-H (1.05), indicating that more defects generated. 45,46 X-ray photoelectron spectroscopy (XPS) analysis is used to further conrm the above result.…”

Chemically engineered alloy anode enabling fully reversible conversion reaction: design of a C–Sn-bonded aerofilm anode

“…Impedance measurements were obtained through an impedance analyzer (ZIVE, WonATech) at a sine wave amplitude of 5 mV between frequency 1 MHz to 0.01 Hz. The power-law calculation for the charge storage contribution is as follows: 20,21 log( i ) = b × log( v ) + log( a ) i ( V ) = k 1 v + k 2 v 0.5 , i ( V )/ v 0.5 = k 1 v 0.5 + k 2 where i denotes the anodic and cathodic peak currents, v denotes the scan rate, and a and b denote adjustable parameters. The constants k 1 and k 2 can be evaluated from the slope and intercept, respectively.…”

“…The Li + ion diffusivity was calculated according to the following equation, 21 where σ denotes the Warburg constant, ω denotes the angular frequency, D Li + denotes the diffusion coefficient, R denotes the gas constant, T denotes the absolute temperature, A denotes the electrode area, n denotes the number of electrons, F denotes the Faraday constant, and C denotes the concentration of Li-ions.…”