Mechanisms for overcharging of carbon electrodes in lithium-ion/sodium-ion batteries analysed by operando solid-state NMR

Abstract

An in-depth investigation of the overlithiation/oversodiation and subsequent delithiation/desodiation of graphite and hard carbon electrodes in the first cycle was conducted using operando7Li/23Na solid-state NMR.

High-Capacity Reversible Lithium Storage in Defined Microporous Carbon Framework for All Solid-State Lithium Batteries

“…This temporary decrease in cell potential is associated with overcoming the overpotential for the nucleation of lithium metal on a substrates surface and is therefore assigned to the start of lithium metal plating. 23 The delithiation of the HCmicro-electrode exhibits a very long plateau region close to The two plateaus formed in delithiation of the carbons indicate the existence of two different delithiation mechanisms occurring in both carbons to different extent. The plateau up to 20 mV can be attributed to the stripping of metallic lithium from a 3D structured conducting material due to the small hysteresis between plating and stripping in the case of low current densities (0.05 mA cm -2 ).…”

“…There are two possible lithium species known from literature forming at potentials near and slightly below 0 Vlithium clusters and lithium metal. 23,31 For the interpretation of the ConVol measurements, it is important to state that the minimum potential of the cell in constant voltage step was at -0.5 mV slightly below the intended 0 V due to the precision of the measurement device. However, this is at least one order of magnitude smaller than the overpotential for lithium metal plating observed in CC experiments e.g.…”

“…Only recently, an operando 7 Li NMR study on HC and graphite half-cells has been published by Gotoh et al investigating overlithiation behavior of the lithium NMR signal in different carbon materials. 23 We envisioned carbide-derived carbons (CDCs) to offer an ideal microporous carbon framework for stabilizing lithium clusters due to their narrow pore size distribution, which can be precisely tuned. [24][25][26][27] However, their high porosity comprises pores that are accessible for small molecules like N2 or liquid electrolyte components as well as defect sites in the hexagonal carbon structure.…”

“…The latter, to the best of our knowledge have not been observed for lithiated carbon electrodes so far. 22,23,[29][30][31][32][33][34] Based on these findings, we propose a lithiation mechanism of HCmicro in the all solidstate system via the reversible formation of extended lithium clusters in the carbon framework.…”

MgO‐Template Synthesis of Extremely High Capacity Hard Carbon for Na‐Ion Battery

“…However, from magnified charge-discharge curves in Figure 4 d, we confirmed that the sodiation potential plateau is located around 0.05 V vs. Na and lower, which is higher than that of the post-heated activated carbon at 2100 8C in a Na cell [5a] and sucrose-derived low postHTT hard carbon in a Li cell. [3d] The 23 Na MAS NMR signal at the lower-frequency shift of 1030 ppm for sodiated HC600-1500(F50:50) also implies more ionic state of sodium atoms compared to those reported for the sucrose-derived hard carbon at the postHTT of 2000 8C (1114 ppm). [10c] Therefore, the potential risk of [25] Angewandte Chemie Zuschriften metal plating for HC600-1500(F50:50) is lower than high postHTT hard carbon as well as high-capacity low-postHTT hard carbon in a Li cell.…”