Interfacial Origin of Performance Improvement and Fade for 4.6 V LiNi0.5Co0.2Mn0.3O2 Battery Cathodes

Lee, Yu‐Mi; Nam, Kyoung-Mo; Hwang, Eui-Hyung; Kwon, Young‐Gil; Kang, Dong-Hyun; Kim, Sung‐Soo; Song, Seung‐Wan

doi:10.1021/jp501670g

Cited by 174 publications

(147 citation statements)

References 47 publications

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“…The results in Figure highlight an additional finding about the composition of the positive electrode interphase (PEI) layer of the aged electrode . Even after rinsing of the extracted aged electrode with dimethyl carbonate (DMC), the white surface layer of material seen in Figure b, and again in Figure a, was found to persist (with varying thickness) across most of the PEI region.…”

mentioning

confidence: 64%

Composition and Impedance Heterogeneity in Oxide Electrode Cross‐Sections Detected by Raman Spectroscopy

Gilbert

Maroni

Cui

et al. 2018

Adv Materials Inter

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the upper cutoff voltage (UCV) for cycling is increased. [4][5][6][7][8] The capacity fade in these cells mainly results from immobilization of Li + ions in the solid electrolyte interphase (SEI) of the graphite electrode; this immobilization is accelerated by the dissolution of TM ions from the positive electrode that deposit in the negative electrode SEI. [9,10] Cell impedance rise on aging arises mainly at the positive electrode. Contributing factors include the build-up of electrolyte decomposition products in the electrode, [11] crystal reconstruction at the oxide-particle surfaces, [12,13] increased separation of primary particles within the secondary particle agglomerates, [14,15] and intragranular cracking within the primary particles. [16] An interesting finding from our studies is the significant scatter in electrochemical performance data observed for cells cycled at a C/1 rate to an UCV > 4.3 V. [8] We attributed this nonuniform behavior to the fracture of sintered boundaries between the submicrometer-size primary particles, which occurs in an unpredictable and relatively random manner. Such "intergranular cracking" was also reported recently by Liu et al. [17] who obtained transmission X-ray tomograms on LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) oxide electrodes cycled in operando to a UCV = 4.5 V. These authors described heterogeneities in the oxide behavior noting the presence of "active" and "sluggish" populations in cells that displayed ≈20% capacity fade. This observation points to an impedance inhomogeneity within the oxide particle population that develops on extended cycling, wherein the active and sluggish particles can be described as having low impedance and high impedance, respectively.Inhomogeneous behavior in lithium battery electrodes has been the subject of many recent articles. [18][19][20][21][22][23][24][25][26] The presence of these heterogeneities has been revealed by both in situ and ex situ techniques, which include conventional X-ray diffraction (XRD), [17,19] energy dispersive X-ray diffraction, [20] X-ray tomography, [21] X-ray absorption spectroscopy, [22] transmission X-ray microscopy, [23] and transmission electron microscopy. [24][25][26] Another technique, Raman spectroscopy, offers an opportunity to probe local structure in a manner that complements data obtained by the X-ray and electron beam techniques. Whereas the latter techniques provide average information from all particles within the path of the X-ray or electron beam, Raman Lithium-bearing layered transition metal oxides are the materials of choice for positive electrodes in high energy lithium-ion cells being developed for electric vehicle applications. During electrochemical cycling, the loss of mobile lithium-ions due to undesirable side reactions and an increase in cell resistance leads to a decline in the energy and power performance of the cells. This performance loss is often nonuniform across multiple cells, especially for those cycled at high voltages or high C-rates. This nonuniformity results from inhomoge...

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mentioning

confidence: 64%

Composition and Impedance Heterogeneity in Oxide Electrode Cross‐Sections Detected by Raman Spectroscopy

Gilbert

Maroni

Cui

et al. 2018

Adv Materials Inter

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“…Extensive efforts have therefore been made to further improve the electrochemical performance of LIBs, and especially to search for high capacity cathode materials. Layered lithium transition metal (TM) oxides, which have the -NaFeO2 structure and the general chemical formula, LiNixMnyCozO2 (NMC) (x+y+z=1), are cathode materials that are currently under extensive studies with the high theoretical capacity of about 280 mAh g -1 [3][4][5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Transition-metal redox evolution in LiNi0.5Mn0.3Co0.2O2 electrodes at high potentials

Qiao

Kourtakis

et al. 2017

Journal of Power Sources

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The mixed transition-metal layered compound, LiNi0.5Mn0.3Co0.2O2 (NMC532), is a promising high-energy cathode material. However, the required high-voltage (>4.3 V) cycling is accompanied by a rapid capacity fade associated with a complex redox mechanism that has not been clarified. Here we report soft x-ray absorption spectroscopy of NMC532 electrodes, both pristine and those charged to 4.2, 4.35, or 4.5 V in graphite/NMC532 cells. A quantitative sXAS analysis shows that about 20% of the nickel exists as Ni 4+ in the as-synthesized NMC532. The experimental capacity of NMC532 electrodes obtained below 4.2 V is from the redox of both Ni and Co. However, Co redox reactions take place throughout the electrochemical cycling and are the only observed transition-metal redox reactions above 4.2 V. In contrast to the changing ratio of the well-defined Ni 2+ , Ni 3+ and Ni 4+ ions, Co always displays ill-defined intermediate valence states in the charged NMC532 electrodes. This indicates an itinerant electron system in NMC electrodes related to the improved rate performance through Co doping. Additionally, about 20% of Ni 2+ is found on the electrode surface at the high potential, which suggests that the electrode surface has either gone through surface reconstruction or reacted with the electrolyte at high voltage.

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“…Hence, it can be rationally concluded that the preformed SEI protector can suppress the electrolyte decomposition and stabilize the graphite cathode during the successive cycles, facilitating the PF 6 ‐ de‐/intercalation from/into graphene layers. Moreover, the low content of Li x PO y F z on SMG indicates the high possibility of PF 6 ‐ to occur the de‐/intercalation reactions rather than the decomposition on the surface of graphite electrode, which can enhance the reversible capacity of SMG . As a result, UMG delivers the obviously lower discharge capacity than SMG (Figure S11, Supporting Information), which is also probably due to the blocked anion migration path by the substantial direct deposition of electrolyte decomposition products on the surface of graphite electrode.…”

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confidence: 99%

Highly Improved Cycling Stability of Anion De‐/Intercalation in the Graphite Cathode for Dual‐Ion Batteries

et al. 2018

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electrochemical reactions in SCs, which can take advantage of the anions in electrolyte to achieve the energy storage. [3] However, SCs store ions only at the interfaces between electrodes and electrolyte, making their energy densities too low to power the high-energy devices ( Figure S1, Supporting Information). Although the recently proposed aluminium ion battery exhibits excellent cycling performance, [4] the relatively low energy density still needs to be addressed due to the low working voltage. Hence, it is highly urgent to develop the de-/intercalation reaction based dual-ion battery (DIB) with theoretically high energy density. [5] The first DIB with dual-graphite configuration was presented in 1989, in which graphite was used as both cathode and anode, realizing anion de-/intercalation in the cathodic graphite electrode. [6] In addition, the term of "dual-ion battery" was proposed for the first time by Winter and co-workers in 2012. [7] Different from the traditional Li/Na-ion batteries in which cationic charge carriers are initially originated from cathode materials, the electrolyte provides all charge carriers including anions and cations in the DIB. This means that the capacity delivered by DIB would not be limited by the usually low Coulombic efficiency (CE) of electrodes due to the sufficient supply of ions from electrolyte. [5b] However, the redox reactions of anion de-/intercalation on graphite cathode are usually taken place at a high potential, nearly or higher than 5.0 V versus Li + / Li, which exceeds the anodic stabile window of conventional carbonate electrolytes. As a result, such anion de-/intercalation processes usually suffer from severe side reactions, such as decomposition of electrolyte, [8] exfoliation of graphene layers, [9] and some unknown irreversible electrochemical reactions, leading to the very low CE (usually lower than 90%) during early cycling and hence poor cyclic stability. [10] In order to conquer these issues to improve the energystorage performance of DIB, there are four strategies proposed recently: 1) the utilization of ionic liquids with wider electrochemical stable window as the high-voltage electrolyte, which is hard to realize practicality due to the much expensive price; [11] 2) applying alloying metals (such as Al and Sn) with the higher redox potential to replace the metallic Li anode, greatly improving the cycle life of DIB to over 1500 cycles as Conventional ion batteries utilizing metallic ions as the single charge carriers are limited by the insufficient abundance of metal resources. Although supercapacitors apply both cations and anions to store energy through absorption and/or Faradic reactions occurring at the interfaces of the electrode/electrolyte, the inherent low energy density hinders its application. The graphite-cathodebased dual-ion battery possesses a higher energy density due to its high working potential of nearly 5 V. However, such a battery configuration suffers from severe electrolyte decomposition and exfoliation of the graphite cath...

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Interfacial Origin of Performance Improvement and Fade for 4.6 V LiNi_0.5Co_0.2Mn_0.3O₂ Battery Cathodes

Cited by 174 publications

References 47 publications

Composition and Impedance Heterogeneity in Oxide Electrode Cross‐Sections Detected by Raman Spectroscopy

Composition and Impedance Heterogeneity in Oxide Electrode Cross‐Sections Detected by Raman Spectroscopy

Transition-metal redox evolution in LiNi0.5Mn0.3Co0.2O2 electrodes at high potentials

Highly Improved Cycling Stability of Anion De‐/Intercalation in the Graphite Cathode for Dual‐Ion Batteries

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