Phase formation and microstructure in lithium-carbon intercalation compounds during lithium uptake and release

Drüe, Martin; Seyring, Martin; Rettenmayr, Markus

doi:10.1016/j.jpowsour.2017.03.152

Cited by 42 publications

(26 citation statements)

References 48 publications

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“…A Drude model where the GIC’s optical conductivity depends only on the lithium concentration is overly simplistic 27 – the structure and organization of the lithium dopants must also be important. Since X-ray data has shown that the colors of lithium GICs indicate ordered staging, and the trajectory endpoints (fully intercalated and deintercalated) are well-ordered, the most reasonable deduction is that the greyish-gold colored lithium compounds observed during intercalation correspond to disordered, unstaged (or solid solution 3,26 ) GICs, at least on the ≳ 1 μ m length scales resolvable in this experiment. In the arguments that follow we adopt this assumption.…”

Section: Resultsmentioning

confidence: 71%

“…7 See Figure S2.) In the second and third frames the flake has changed color relative to its initial state with such speed that the subtle color boundaries (which we take to be indicative of phase boundaries 26,28 ) are difficult to note in the still images (see Movie S2 for a better perspective). However, the fourth frame clearly shows the co-existence of the blue, red, and gold phases.…”

Section: Resultsmentioning

confidence: 99%

“…(Three phase co-existence has been previously observed with optical methods. 23,24,26–29 ) Without this image, one might reasonably wonder whether the “slow” intercalation (i.e. failure to reach quasi-equilibrium) was caused by insufficient Li diffusion through the electrolyte to the micro-crystal edge.…”

Section: Resultsmentioning

confidence: 99%

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Irreversibility at macromolecular scales in the flake graphite of the lithium-ion battery anode

Lodico

Lai

Woodall

et al. 2019

Journal of Power Sources

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Charging a commercial lithium-ion battery intercalates lithium into the graphite-based anode, creating various lithium carbide structures. Despite their economic importance, these structures and the dynamics of their charging-discharging transitions are not well-understood. We have videoed single microcrystals of high-quality, natural graphite undergoing multiple lithiation-delithiation cycles. Because the equilibrium lithium-carbide compounds corresponding to full, half, and one-third charge are gold, red, and blue respectively, video observations give direct insight into both the macromolecular structures and the kinematics of charging and discharging. We find that the transport during the first lithiation is slow and orderly, and follows the core-shell or shrinking annuli model with phase boundaries moving at constant velocities (i.e. non-diffusively). Subsequent lithiations are markedly different, showing transport that is both faster and disorderly, which indicates that the initially pristine graphite is irreversibly and considerably altered during the first cycle. In all cases deintercalation is not the time-reverse of intercalation. These findings both illustrate how lithium enters nearly defect-free host material, and highlight the differences between the idealized case and an actual, cycling graphite anode.

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Section: Resultsmentioning

confidence: 71%

Section: Resultsmentioning

confidence: 99%

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Irreversibility at macromolecular scales in the flake graphite of the lithium-ion battery anode

Lodico

Lai

Woodall

et al. 2019

Journal of Power Sources

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“…We hypothesise that the experimentally observed OCV hysteresis between lithiation and delithiation in slow continuous galvanostatic measurements and in galvanostatic intermittant titration technique (GITT) experiments originates from different carbon stacking pathways during lithiation versus delithiation [11,6,27,28]. In-situ XRD suggests Stage I -Stage II coexistence for x ≥ 0.5 within an AAAA stacked host lattice in both cycling directions [9,8].…”

Section: Introductionmentioning

confidence: 94%

Voltage hysteresis during lithiation/delithiation of graphite associated with meta-stable carbon stackings

Mercer

Peng

Soares

et al. 2020

Preprint

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Cell voltage is a fundamental quantity used to monitor and control Li-ion batteries. The open circuit voltage (OCV) is of particular interest as it is believed to be a thermodynamic quantity, free of kinetic effects and history and, therefore, "simple" to interpret. Here we show that the OCV characteristics of graphite show hysteresis between charge and discharge that does not solely originate from Li dynamics and that the OCV is in fact history dependent. Combining First Principles calculations with temperature-controlled electrochemical measurements, we identify a residual hysteresis that persists even at elevated temperatures of greater than 50°C due to differences in the phase succession between charge and discharge. Experimental entropy profiling, as well as energies and volume changes determined from First Principles calculations, suggest that the residual hysteresis is associated with different host lattice stackings of carbon and is related to Li disorder across planes in stage II configurations.

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“…However, the layered structure of graphite causes lithium ions from the edge to embed between layers, creating a single lithium ion diffusion path and low lithium ion diffusion dynamics between the graphite layers and resulting in poor rate performance . The volume expansion caused by the lithium graphite intercalation compound (Li‐GIC) during the charging‐discharging process of the negative electrode and the stress concentration caused by Li intercalation all lead to the fracture and degradation of graphite, resulting in the attenuation of reversible capacity . In addition, its theoretical specific capacity (372 mAh g −1 ) cannot meet the requirements of electrode materials in the future …”

Section: Introductionmentioning

confidence: 99%

Effect of Microcracks on Graphite Anode Materials for Lithium‐Ion Batteries

Gao

et al. 2020

ChemistrySelect

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Modified graphite with microcracks was obtained by a combination of microwave heating and KOH activation. KOH enhanced the degree of order of the graphite, and K + increased the spacing of the graphite layer. Microwave heating caused microcracks on graphite and promoted doping of K + into the graphite. The microcracks could increase the contact area of electrode materials and electrolytes and decrease diffusion length. Furthermore, the uniform microcracks dis-persed the pressure of the electrode wetted by the electrolyte, relieved stress during lithium removal and increased the degree of order of the graphite. The modified graphite has a capacity of 449 mAh g À 1 at 0.1 C, 380 mAh g À 1 at 0.25 C and 367 mAh g À 1 at 0.5 C. In addition, the capacity retention rate was 96.1% after one hundred cycles at 0.25 C, and the average coulombic efficiency was 99.4%.[a] J.

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Phase formation and microstructure in lithium-carbon intercalation compounds during lithium uptake and release

Cited by 42 publications

References 48 publications

Irreversibility at macromolecular scales in the flake graphite of the lithium-ion battery anode

Irreversibility at macromolecular scales in the flake graphite of the lithium-ion battery anode

Voltage hysteresis during lithiation/delithiation of graphite associated with meta-stable carbon stackings

Effect of Microcracks on Graphite Anode Materials for Lithium‐Ion Batteries

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