Narrowing the Gap between Theoretical and Practical Capacities in Li‐Ion Layered Oxide Cathode Materials

Radin, Maxwell D.; Hy, Sunny; Sina, Mahsa; Fang, Chengcheng; Liu, Haodong; Vinckevičiūtė, Julija; Zhang, Minghao; Whittingham, M. Stanley; Meng, Ying Shirley; Ven, Anton Van der

doi:10.1002/aenm.201602888

Cited by 556 publications

(623 citation statements)

References 302 publications

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“…A close correlation between the loss in capacity and loss of cobalt has been observed 10 . Specifically, as lithium ion (Li + ) is removed from the bulk LCO, Cobalt(III) ion (Co 3+ ) is oxidized to Cobalt(IV) ion (Co 4+ ), which is an unstable oxidation state.…”

Section: Introductionmentioning

confidence: 61%

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Electrochemical surface passivation of LiCoO2 particles at ultrahigh voltage and its applications in lithium-based batteries

et al. 2018

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Lithium cobalt oxide, as a popular cathode in portable devices, delivers only half of its theoretical capacity in commercial lithium-ion batteries. When increasing the cut-off voltage to release more capacity, solubilization of cobalt in the electrolyte and structural disorders of lithium cobalt oxide particles are severe, leading to rapid capacity fading and limited cycle life. Here, we show a class of ternary lithium, aluminum, fluorine-modified lithium cobalt oxide with a stable and conductive layer using a facile and scalable hydrothermal-assisted, hybrid surface treatment. Such surface treatment hinders direct contact between liquid electrolytes and lithium cobalt oxide particles, which reduces the loss of active cobalt. It also forms a thin doping layer that consists of a lithium-aluminum-cobalt-oxide-fluorine solid solution, which suppresses the phase transition of lithium cobalt oxide when operated at voltages >4.55 V.

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Section: Introductionmentioning

confidence: 61%

“…Lithium-ion diffusivity decreases consequently, which leads to increased concentration gradients and huge internal strains. The irreversible phase transition degrades the mechanical properties of the bulk LCO crystallites greatly and limits the utilization of LCO particles 10,13 .…”

Section: Introductionmentioning

confidence: 99%

Electrochemical surface passivation of LiCoO2 particles at ultrahigh voltage and its applications in lithium-based batteries

et al. 2018

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“…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.…”

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confidence: 99%

“…12,13 The high capacity arises because Ni is the main redoxactive species in the NMC host structure. 14 While Ni-rich cathodes could reach an energy density that exceeds 700 Wh/kg, undesirable side-reactions like electrolyte oxidation 15 and cathode surface reconstruction 16,17 have been identified as major causes of capacity loss, due to the high reactivity of Ni 4+ .…”

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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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“…The continuing need for higher rate capability, especially during charge, and higher energy density, by increasing the upper limit of charge voltage, requires detailed understanding of lithium transport kinetics in battery electrodes at multiple length scales. 1 In a typical composite electrode, there are many possible rate-limiting transport paths; measurements of macroscopic electrodes can be especially difficult to deconvolute into processes occurring at smaller length scales. There exists a need for techniques that can probe electrochemical kinetics of battery electrode materials in a manner that allows separation of individual transport parameters, including their dependence on state-of-charge (SOC) and cycling.…”

Section: Introductionmentioning

confidence: 99%

Single-particle measurements of electrochemical kinetics in NMC and NCA cathodes for Li-ion batteries

Tsai

Wen

Wolfman

et al. 2018

Energy Environ. Sci.

266

229

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aThe electrochemical kinetics of battery electrodes at the single-particle scale are measured as a function of state-of-charge, and interpreted with the aid of concurrent transmission X-ray microscopy (TXM) of the evolving particle microstructure. An electrochemical cell operating with near-picoampere current resolution is used to characterize single secondary particles of two widely-used cathode compounds, NMC333 and NCA. Interfacial charge transfer kinetics are found to vary by two orders of magnitude with state-of-charge (SOC) in both materials, but the origin of the SOC dependence differs greatly. NCA behavior is dominated by electrochemically-induced microfracture, although thin binder coatings significantly ameliorate mechanical degradation, while NMC333 demonstrates strongly increasing interfacial reaction rates with SOC for chemical reasons. Micro-PITT is used to separate interfacial and bulk transport rates, and show that for commercially relevant particle sizes, interfacial transport is rate-limiting at low SOC, while mixed-control dominates at higher SOC. These results provide mechanistic insight into the mesoscale kinetics of ion intercalation compounds, which can guide the development of high performance rechargeable batteries. Broader contextThe performance of high performance Li-ion batteries, central to both electric transportation and grid scale storage, is ultimately reliant on the performance of critical components such as their cathode and anode compounds. For ease of manufacturing, the prevailing technological forms of these materials are secondary particles of nearly spherical morphology containing many nanocrystallites. The electrochemical kinetics at this critical length scale have been difficult to assess; particle-level behavior has primarily been deduced from macroscale cell measurements. Thus the microelectrode technique developed in this work, combined with state-of-the-art TXM imaging, allows for the first time the direct measurement of electrochemical kinetics of particles as they are charged and discharged. Surprising behavior is revealed -interfacial charge transfer kinetics are found to vary greatly with state-of-charge and cycling history, both for intrinsic chemical reasons (in NMC333) and because of massively damaging ''electrochemical shock'' (in NCA). Moreover, a thin coating of polymer binder is found to ameliorate fracture damage. These results, and the techniques demonstrated, provide a bridge between macroscopic battery function and microscale electrode kinetics as influenced by electrochemomechanical stress and charging history.

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Narrowing the Gap between Theoretical and Practical Capacities in Li‐Ion Layered Oxide Cathode Materials

Cited by 556 publications

References 302 publications

Electrochemical surface passivation of LiCoO2 particles at ultrahigh voltage and its applications in lithium-based batteries

Electrochemical surface passivation of LiCoO2 particles at ultrahigh voltage and its applications in lithium-based batteries

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

Single-particle measurements of electrochemical kinetics in NMC and NCA cathodes for Li-ion batteries

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