Origin of non-SEI related coulombic efficiency loss in carbons tested against Na and Li
- 14 October 2014
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of Materials Chemistry A
- Vol. 2 (46), 19685-19695
- https://doi.org/10.1039/c4ta04995k
Abstract
Partially ordered but not graphitized carbons are widely employed for sodium and lithium ion battery (NIB and LIB) anodes, either in their pure form or as a secondary supporting phase for oxides, sulfides and insertion electrodes. These “pseudographitic” materials ubiquitously display a poor initial coulombic efficiency (CE), which has been historically attributed to solid electrolyte interface (SEI) formation on their large surface areas (up to ∼2500 m2 g−1). Here we identify the other sources CE loss by examining a pseudographitic carbon with a state-of-the-art capacity (>350 mA h g−1 for NIB, >800 mA h g−1 for LIB), but with a purposely designed low surface area (14.5 m2 g−1) that disqualifies SEI from having a substantial role. During the initial several (<5) cycles both Na and Li are irreversibly trapped in the bulk, with the associated CE loss occurring at higher desodiation/delithiation voltages. We measure a progressively increasing graphene interlayer spacing and a progressively increasing Raman G band intensity, indicating that the charge carriers become trapped not only at the graphene defects but also between the graphene planes hence causing them to both dilate and order. For the case of Li, we also unambiguously detected irreversible metal underpotential deposition (“nanoplating”) within the nanopores at roughly below 0.2 V. It is expected that in conventional high surface area carbons these mechanisms will be a major contributor to CE loss in parallel to classic SEI formation. Key implications to emerge from these findings are that improvements in early cycling CE may be achieved by synthesizing pseudographitic carbons with lower levels of trapping defects, but that for LIBs the large cycle 1 CE loss may be unavoidable if highly porous structures are utilized.Keywords
This publication has 69 references indexed in Scilit:
- Ti3C2 MXene as a High Capacity Electrode Material for Metal (Li, Na, K, Ca) Ion BatteriesACS Applied Materials & Interfaces, 2014
- Reactivation of dissolved polysulfides in Li–S batteries based on atomic layer deposition of Al2O3 in nanoporous carbon clothNano Energy, 2013
- Carbon nanofibers derived from cellulose nanofibers as a long-life anode material for rechargeable sodium-ion batteriesJournal of Materials Chemistry A, 2013
- Room-temperature stationary sodium-ion batteries for large-scale electric energy storageEnergy & Environmental Science, 2013
- Update on Na-based battery materials. A growing research pathEnergy & Environmental Science, 2013
- High capacity hard carbon anodes for sodium ion batteries in additive free electrolyteElectrochemistry Communications, 2013
- Sodium‐Ion BatteriesAdvanced Functional Materials, 2012
- Electrochemical Na Insertion and Solid Electrolyte Interphase for Hard‐Carbon Electrodes and Application to Na‐Ion BatteriesAdvanced Functional Materials, 2011
- Stabilizing lithium–sulphur cathodes using polysulphide reservoirsNature Communications, 2011
- Is lithium the new gold?Nature Chemistry, 2010