The state of understanding of the lithium-ion-battery graphite solid electrolyte interphase (SEI) and its relationship to formation cycling

An, Seong Jin; Li, Jianlin; Daniel, Claus; Mohanty, Debasish; Nagpure, Shrikant C.; Wood, David L.

doi:10.1016/j.carbon.2016.04.008

Cited by 1,600 publications

(1,218 citation statements)

References 258 publications

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“…Figure 1 shows capacity-voltage profiles from the full cells with each graphite anode and NMC811 cathode during the first four cycles at C/10 rate (also known as formation cycles). 23 During the first lithiation of the graphite anode, electrolyte reduction occurs on the graphite surface forming a solid-electrolyte-interphase (SEI), which is ionically conductive but electronically insulating. The SEI acts as a protective layer to impede continuous electrolyte decomposition and solvent co-intercalation into graphitic layers during subsequent cycles.…”

Section: Resultsmentioning

confidence: 99%

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Mao

Wood

David

et al. 2018

J. Electrochem. Soc.

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Most lithium-ion batteries still rely on intercalation-type graphite materials for anodes, so it is important to consider their role in full cells for applications in electric vehicles. Here, we systematically evaluate the chemical and physical properties of six commerciallyavailable natural and synthetic graphites to establish which factors have the greatest impact on the cycling stability of full cells with nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. Electrochemical data and post-mortem characterization explain the origin of capacity fade. The NMC811 cathode shows large irreversible capacity loss and impedance growth, accounting for much of full cell degradation. However, six graphite anodes demonstrate significant differences with respect to structural change, surface area, impedance growth, and SEI chemistry, which impact overall capacity retention. We found long cycle life correlated most strongly with stable graphite crystallite size. In addition, graphites with lower surface area generally had higher coulombic efficiencies during formation cycles, which led to more stable long-term cycling. The best graphite screened here enables a capacity retention around 90% in full pouch cells over extensive long-term cycling compared to only 82% for cells with the lowest performing graphite. The results show that optimal graphite selection improves cycling stability of high energy lithium-ion cells. With the booming demands for electric vehicles and electronic devices, high energy density lithium-ion batteries with long cycle life are highly desired. Despite the recent progress in Si 1 and Li metal 2 as future anode materials, graphite still remains the active material of choice for the negative electrode. 3,4 Lithium ions can be intercalated into graphite sheets at various stages like Li x C 12 and Li x C 6 , providing a high specific capacity of 372 mAh/g (∼2.5 times higher than LiCoO 2 ) and high volumetric capacity (similar to LiCoO 2 ) corresponding to LiC 6 . 5,6 In addition to its low cost and non-toxicity, graphite has a lowest average voltage (150 mV vs. Li/Li + ) and the flat voltage profile, rendering a high overall cell voltage. 7 Graphite also displays a very low voltage hysteresis, which in turn results in high energy efficiency. 8 For applications in lithium-ion batteries, many properties of the graphite powders must be optimized including crystallinity, particle size, morphology, and surface chemistry. However, most research effort has been placed on the development and characterization of high performance cathodes, while the impact of the graphite anode on full cell performance has been largely unexplored.Compared to widely used battery cathodes such as LiCoO 2 (140 mAh/g), LiFePO 4 (160 mAh/g), LiNi 1/3 Mn 1/3 Co 1/3 O 2 (160 mAh/g), and LiNi 0.5 Mn 0.3 Co 0.2 O 2 (175 mAh/g), 9-11 nickel-rich LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) is delivers a higher specific capacity (180-220 mAh/g), which increases the battery life on a single charge. 12,13 The high capacity arises because Ni is the main red...

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Section: Resultsmentioning

confidence: 99%

Selecting the Best Graphite for Long-Life, High-Energy Li-Ion Batteries

Mao

Wood

David

et al. 2018

J. Electrochem. Soc.

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“…VC decomposes and precipitates (forms SEI) around 1.4 V versus Li/Li + . 46 Hence, during a charge cycle, VC precipitates first on the anode and becomes a part of the SEI structure followed by EC (or PC). The reduction potentials increase at an elevated temperature and vary depending on anode (graphite) surface chemistry (e.g., amount and kind of electron donor groups) and structure (e.g., basal plane surface or edge surface).…”

Section: Shortening Formation Periodmentioning

confidence: 99%

“…Electrode surface properties determine interactions between the electrodes and electrolytes, which impacts electrolyte wetting and reduction potentials and, eventually, SEI formation. 46,[51][52][53] There have been several studies on modifying graphite surfaces such as heat and acid treatment to control surface chemistry (e.g., oxygen and nitrogen). [54][55][56][57][58] Nitrogen or oxygen on graphite surfaces can interact more with Li + in electrolyte because their electron density is high.…”

Section: Shortening Formation Periodmentioning

confidence: 99%

Toward Low-Cost, High-Energy Density, and High-Power Density Lithium-Ion Batteries

Ruther

et al. 2017

JOM

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Reducing cost and increasing energy density are two barriers for widespread application of lithium-ion batteries in electric vehicles. Although the cost of electric vehicle batteries has been reduced by $70% from 2008 to 2015, the current battery pack cost ($268/kWh in 2015) is still >2 times what the USABC targets ($125/kWh). Even though many advancements in cell chemistry have been realized since the lithium-ion battery was first commercialized in 1991, few major breakthroughs have occurred in the past decade. Therefore, future cost reduction will rely on cell manufacturing and broader market acceptance. This article discusses three major aspects for cost reduction: (1) quality control to minimize scrap rate in cell manufacturing; (2) novel electrode processing and engineering to reduce processing cost and increase energy density and throughputs; and (3) material development and optimization for lithium-ion batteries with high-energy density. Insights on increasing energy and power densities of lithium-ion batteries are also addressed.

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“…5a. The peak at 2.02 V is only observed in the first discharge cycle, which comes from a solid SEI layer and the decomposition of the electrolyte [49][50][51]. In the subsequent CV steps, the main oxidation/reduction pair is 1.2/1.46 V, associating with the reaction of MoO 3 [52,53].…”

Section: Resultsmentioning

confidence: 96%