Decrease in Capacity in Mn-Based/Graphite Commercial Lithium-Ion Batteries

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Solid electrolyte interphase (SEI) and Mn deposition formed on capacity-degraded graphite electrodes in commercially available Mn-based/Graphite lithium ion batteries were characterized using glow discharge-optical emission spectroscopy (GD-OES). The depth profile of the whole electrode showed a homogeneous distribution of Li and Mn except for the surface region at the initial state. With the progress of degradation, Li and Mn concentrations increased inhomogeneously in the depth-direction of the electrode; the Li and Mn concentrations were high in the outer layer and decreased with depth to the current collector in the degraded electrodes. The SEI layer deposited on the electrode surface was separately analyzed in detail. The GD-OES surface profile was explained by comparing to the XPS analysis results. The amount of Li deposited on the electrode surface was almost constant with the capacity degradation, though the Li concentration in the whole electrode increased along with the capacity degradation. In contrast, the amount of Mn deposition increased with the capacity degradation both in the surface deposition layer and in the whole electrode.Lithium ion batteries (LIBs) have been applied to portable power sources and then extensively to various uses of electric vehicles and stationary devices. An important subject related to LIBs is deterioration during long-term and high-temperature operations. The deterioration mechanism has been studied extensively to date. Solid electrolyte interphase (SEI) growth on the negative electrode is well known to contribute strongly to capacity fading during cycles. 1,2 Formation of the SEI layer on the negative electrode causes irreversible capacity loss in the first few cycles. Even in additional cycles, lithium is consumed continuously as a result of continuous reduction of the electrolyte on the electrode.Lithium manganese oxide spinel, LiMn 2 O 4 (LMO), has been regarded as a promising positive electrode material for large-scale commercial battery because of its low-cost and environmentally friendly characteristics. In the case of LMO cathode, manganese dissolution is a critical factor for deterioration, just as SEI growth is for it. 3,4 Manganese dissolution probably results from acid that is generated by oxidation of the solvent. The dissolved manganese is migrated to the negative electrode. Then it is reduced and deposited as Mn metal on the negative electrode. Finally, it presumably forms manganese compounds such as MnCO 3 . 5 The deposited manganese can enhance the electrolyte decomposition to accelerate SEI growth on the negative electrode. 6 These deposited manganese compounds and SEI growth promote lithium consumption and enhance cell resistance.Recently, capacity fading in commercially available Mnbased/Graphite (LiMn 2 O 4 /LiNi 0.8 Co 0.15 Al 0.05 O 2 mixed cathode and graphite anode) batteries was investigated by Kobayashi et al. 7,8 They performed long-term charge-discharge cycling at the operation temperature of 25 and 45 • C for the cells. They carefully disass...

Section: Sei Growth and Mn Deposition On Graphite Electrode Surface-supporting

confidence: 68%

Analysis of Solid Electrolyte Interphase in Mn-Based Cathode/Graphite Li-Ion Battery with Glow Discharge Optical Emission Spectroscopy

Takahara

Kobayashi

Shono

et al. 2014

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“…6 The loaded weight of the cathode without the aluminum current collector was 21 mgcm −2 . The counter anode was graphite, and the loaded weight of the anode without the copper current collector was 8 mgcm −2 .…”

Section: Methodsmentioning

confidence: 99%

Decrease in Capacity in Mn-Based/Graphite Commercial Lithium-Ion Batteries

Kobayashi

Shono

et al. 2013

Self Cite

A precise and simple temperature measurement technique during charge and discharge is applied to 5 Ah Al-laminated lithium-ion batteries (LiMn 2 O 4 /LiNi 0.8 Co 0.15 Al 0.05 O 2 cathode and graphite anode) using a quasi-adiabatic cell holder. The obtained temperature profiles are described in terms of the reactions of the anode and cathode. This technique is applied to a cycled cell, and the capacity fading mechanism is also indicated by the temperature profiles. From the comparison between the cell temperature profiles and the reaction heat flows of the half cells in each electrode obtained by an isothermal microcalorimeter, we find that the capacity fading of the cycled cell can be derived from the capacity fading of the cathode and also from the upward shift in the operated state of charge (SOC) of the cathode in the cell. The latter shift is derived from the irreversible loss of lithium at the anode, and it leads to the misalignment of the cathode and anode operation windows. The proposed temperature measurement technique has the potential to be applied to various types of large lithium-ion batteries during operation, thus providing a new approach to analyzing the degradation of lithium-ion batteries.The applications of lithium-ion batteries are now being extended from mobile use to hybrid, plug-in hybrid, and electric vehicles, and various stationary uses. In these systems, the lithium-ion batteries are required to have a larger capacity and a longer lifetime than those for mobile use. Determination of the degradation factor in cells is becoming essential for improving the lifetime of batteries. Postanalysis, such as analysis of the electrode structure, electrolyte composition, and solid electrolyte interface (SEI), is a conventional tool used to determine the degradation of materials in cells. However, a large number of samples are needed to determine the degradation process during the operation. Nondestructive analyzes, such as capacity retention, power fading, and AC impedance analysis, are other approaches to determining the degradation process during cell operation. However, using these approaches it is not easy to find a convincing relationship between capacity fading and the degradation of the materials and/or misalignment of the electrode-capacity window in the cathode and anode materials in a cell.Electrochemical calorimetry is a useful nondestructive approach to determining electrode reactions during the charge and discharge of lithium-ion cells. [1][2][3][4][5] This approach enables the reactions at each electrode to be separated by comparing the heat flow profiles of half cells. We previously reported its application to prismatic [graphite/LiMn 2 O 4 ] 2 and cylindrical 18650-type [graphite/LiCoO 2 ] 5 cells, determination of the thermal behavior of graphite and LiCoO 2 , and analysis of the degradation from heat flow profiles. However, the conductive-type microcalorimeter that was used had a size limitation (<50 mmφ), meaning that we could not apply it to larger cells. Therefore, a more versati...

“…One way to overcome this problem is not to consider the average surface capacity (in mAh/cm 2 ) of the samples, but to consider the average weight of the samples harvested from "fresh" electrodes before building coin-cells to calculate and compare the mass capacity (in mAh/g). Kobayashi 12 The residual capacity of cathodes harvested from cells after cycling or calendaric aging (converted in the cathode SOC in the discharge state) increased if compared with the value obtained for the fresh cell. 12 The authors demonstrated that there is a relationship between the capacity retention of the studied cell and the SOC of the cathode in the discharge state (identically with the open-circuitvoltage of the half coin-cell that deduces the state of lithiation of the electrode).…”

mentioning

confidence: 97%

“…Kobayashi 12 The residual capacity of cathodes harvested from cells after cycling or calendaric aging (converted in the cathode SOC in the discharge state) increased if compared with the value obtained for the fresh cell. 12 The authors demonstrated that there is a relationship between the capacity retention of the studied cell and the SOC of the cathode in the discharge state (identically with the open-circuitvoltage of the half coin-cell that deduces the state of lithiation of the electrode). 12 That suggests that Li ions are not only irreversibly stored on the anode side in the initial SEI formation cycle but also continuously accumulated during cycling or calendaric aging.…”

mentioning

confidence: 97%

See 1 more Smart Citation

Review—Post-Mortem Analysis of Aged Lithium-Ion Batteries: Disassembly Methodology and Physico-Chemical Analysis Techniques

Waldmann

Iturrondobeitia

Kasper

et al. 2016

249

149

Improvement of life-time is an important issue in the development of Li-ion batteries. Aging mechanisms limiting the life-time can efficiently be characterized by physico-chemical analysis of aged cells with a variety of complementary methods. This study reviews the state-of-the-art literature on Post-Mortem analysis of Li-ion cells, including disassembly methodology as well as physicochemical characterization methods for battery materials. A detailed scheme for Post-Mortem analysis is deduced from literature, including pre-inspection, conditions and safe environment for disassembly of cells, as well as separation and post-processing of components. Special attention is paid to the characterization of aged materials including anodes, cathodes, separators, and electrolyte. More specifically, microscopy, chemical methods sensitive to electrode surfaces or to electrode bulk, and electrolyte analysis are reviewed in detail. The techniques are complemented by electrochemical measurements using reconstruction methods for electrodes built into half and full cells with reference electrode. The changes happening to the materials during aging as well as abilities of the reviewed analysis methods to observe them are critically discussed. Li-ion batteries are currently used in everyday objects such as smart-phones, power tools and tablet computers as well as in the growing fields of light electric vehicles (LEVs), unmanned aerial vehicles (UAVs), battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). [1][2][3][4] Furthermore, the rise of renewable energy sources like wind and solar power, which are only intermittently available, demands reliable and highly flexible stationary energy storage solutions, which provide high capacities and predictable life-times. 2,5Aging of Li-ion batteries is a general problem for manufacturers as they have to guarantee long-term reliability of their products. For state-of-the-art cells, degradation effects on the material level lead to capacity fade and resistance increase on the cell level. The aging state of a battery is often characterized by the state-of-health (SOH) in % according to 3,16,22,[29][30][31] SO H(t) = discharge capacity (t) discharge capacity (t = 0)[1]where t represents the aging time. In general, one has to differentiate between cycling 7,16,18,21,[23][24][25]32 and calendar aging. 7,19,[21][22][23][24]27 Since commercial Li-ion cells can be subject to calendar aging in the time between manufacturing and delivery, it is good practice to measure the discharge capacity at t = 0 for each cell that undergoes an aging test. Since the discharge capacity depends mainly on temperature, depth-of-discharge (DOD), and discharge current, the SOH is usually monitored by regular check-ups with defined parameter sets, 7,16,21,23,24 which can vary depending on the application. Typically, a temperature of 25• C, 16,22,24 DOD of 100%, 16,21 and discharge rates of 1C 7,16,21,22,24 or lower 23 are used in check-ups. The performance dec...