An Investigation of the Effect of Graphite Degradation on Irreversible Capacity in Lithium-ion Cells

Abstract

The effect of surface structural damage on graphitic anodes, commonly observed in tested Li-ion cells, was investigated. Similar surface structural disorder was artificially induced in Mag-10 synthetic graphite anodes using argon-ion sputtering. Raman microscopy, scanning electron microscopy (SEM) and Brunauer Emmett Teller (BET) measurements confirmed that Ar-ion sputtered Mag-10 electrodes display similar degree of surface degradation as the anodes from tested Li-ion cells. Artificially modified Mag-10 anodes showed double the irreversible charge capacity during the first formation cycle, compared to fresh un-altered anodes. Impedance spectroscopy and Fourier transform infrared (FTIR) spectroscopy on surface modified graphite anodes indicated the formation of a thicker and slightly more resistive SEI layer. Gas for the surface modified electrode with no evidence of elevated M w species for the unmodified electrode. The structural disorder induced in the graphite during long-term cycling maybe responsible for the slow and continuous SEI layer reformation, and consequently, the loss of reversible capacity due to the shift of lithium inventory in cycled Li-ion cells.3

High-temperature capacity fading mechanism for LiFePO4/graphite soft-packed cell without Fe dissolution

“…Additionally, this result is also support a view reported by Hardwick et al [22].They have shown that the surface disordering of the graphite may lead to the continuous reformation of SEI, resulting in a thicker SEI layer, and consequently higher interfacial resistance, as supported by our EIS data, and great consumption of active lithium [23].…”

“…three factors: ionic conductivity of the electrolyte, the charge transfer resistance between the active material and the electrolyte, and the double-layer capacitance [15][16][17][18][19]. It is can be clearly seen that R ct is increased with increase of temperature, which is due to the increase of interfacial resistance induced by the thicker SEI layer on the surface of graphite anode [20,21].…”

“…SEI layer is highly temperature sensitive. According to previous studies, operating temperature during cycling has a direct effect on the SEI morphology [30][31][32], composition [32,33] and thickness [31,23]. Due to this physical instability of SEI layer at higher temperature, the amount of active lithium will be reduced at each cycle, leading to fast and continuous reformation/repairing of this layer.…”

Insight into the mechanical integrity of few-layers graphene upon lithiation/delithiation via in situ monitoring of stress development

“…Even though considered fairly stable due to the moderate dimensional changes upon Li-intercalation compared to the potential metallic anode materials [1][2][3], structural degradation of graphitic carbon based anodes still contribute considerably towards the overall capacity fade of Li-ion batteries [4][5][6][7][8][9]. In fact, such structural degradation is possibly one of the major contributing factors towards the aging of Li-ion batteries because it leads to the continued formation of solid electrolyte interphase (SEI) layers at the 'freshly formed' graphitic carbon surfaces, which http://dx.doi.org/10.1016/j.carbon.2015.02.078 0008-6223/Ó 2015 Elsevier Ltd. All rights reserved.…”

Synthesis and Electrochemical Behavior of Nanostructured Copper Particles on Graphite for Application in Lithium Ion Batteries

“…During charge/discharge cycling or storage of LIBs, aging effects may occur [7]. Mechanical degradation like graphite exfoliation or surface structural disordering leads to loss of mobile lithium or self-discharge [8][9][10][11]. One of the main reasons for exfoliation is the cointercalation of solvated lithium ions.…”