Electrochemical Activation of Li2MnO3 Electrodes at 0 °C and Its Impact on the Subsequent Performance at Higher Temperatures (original) (raw)
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Effects of structural defects on the electrochemical activation of Li2MnO3
Nano Energy, 2015
Structural defects, e.g. Mn 3 + /oxygen non-stoichiometry, largely affect the electrochemical performance of both Li 2 MnO 3 and lithium-rich manganese-rich (LMR) layered oxides with Li 2 MnO 3 as one of the key components. Herein, Li 2 MnO 3 samples with different amount of structural defects of Mn 3 + /oxygen non-stoichiometry are prepared. The results clearly demonstrate that the annealed Li 2 MnO 3 (ALMO), quenched Li 2 MnO 3 (QLMO), and quenched Li 2 MnO 3 milled with Super P (MLMO) all show pure C2/m monoclinic phase with stacking faults. MLMO shows the largest amount of Mn 3 + , followed by the QLMO and then the ALMO. The increased amount of Mn 3 + in Li 2 MnO 3 (such as sample MLMO) facilitates the activation of Li 2 MnO 3 and leads to the highest initial discharge specific capacity of 167.7 mA h g À 1 among the samples investigated in this work. However, accelerated activation of Li 2 MnO 3 also results in faster structural transformation to spinel-like phase, leading to rapid capacity degradation. Therefore, the amount of Mn 3 + needs to be well controlled during synthesis of LMR cathode in http://dx.(J. Xiao), jiguang.zhang@pnnl.gov (J.-G. Zhang). Nano Energy 16, 143-151 order to reach a reasonable compromise between the initial activity and long-term cycling stability. The findings of this work could be widely applied to explain the effects of Mn 3 + on different kinds of LMR cathodes.
Study of the electrochemical behavior of the “inactive” Li2MnO3
Electrochimica Acta, 2012
In this work, we studied the cycling performance of initially inactive Li 2 MnO 3 electrodes prepared from micron-sized particles, at 30 • C and 60 • C and possible structural transitions that this material can undergo due to de-lithiation. It was found that being activated at elevated temperatures, Li 2 MnO 3 electrodes demonstrate a steady-state cycling behavior and reasonable capacity retention after aging at 60 • C. The main gases evolved during polarization of the Li 2 MnO 3 electrodes are O 2 evolved from the structure and CO 2 and CO that can be formed due the reaction of oxygen with carbon black. It was found that a transformation of the Li 2 MnO 3 layered structure into a spinel-like phase occurred during the initial charging of the Li 2 MnO 3 electrodes, which were characterized as possessing domains of both layered and spinel-like structures. The results of the structural studies of these electrodes obtained by the X-ray diffraction and transmission electron microscopy were found to be in agreement with their Raman spectroscopic responses. We suggest that the mechanism of the charge compensation during the extraction of lithium at 60 • C involves both oxygen removal from the Li 2 MnO 3 structure and the exchange between Li + and protons formed during the anodic oxidation of ethylene carbonate or dimethyl carbonate solvents in LiPF 6 solutions at high potentials (>4.5 V). It is assumed that the proton-containing structure Li 2−x H x−y MnO 3−0.5y is retained in a discharged state of the electrode and may decompose above 500 • C with the formation of Li 2 O and manganese oxides accompanied by the release of water and CO 2 .
tudy of the electrochemical behavior of the “ inactive ” Li 2 MnO 3
2012
In this work, we studied the cycling performance of initially inactive Li2MnO3 electrodes prepared from micron-sized particles, at 30 ◦C and 60 ◦C and possible structural transitions that this material can undergo due to de-lithiation. It was found that being activated at elevated temperatures, Li2MnO3 electrodes demonstrate a steady-state cycling behavior and reasonable capacity retention after aging at 60 ◦C. The main gases evolved during polarization of the Li2MnO3 electrodes are O2 evolved from the structure and CO2 and CO that can be formed due the reaction of oxygen with carbon black. It was found that a transformation of the Li2MnO3 layered structure into a spinel-like phase occurred during the initial charging of the Li2MnO3 electrodes, which were characterized as possessing domains of both layered and spinel-like structures. The results of the structural studies of these electrodes obtained by the X-ray diffraction and transmission electron microscopy were found to be in ag...
Synthesis and properties of Li2MnO3-based cathode materials for lithium-ion batteries
Journal of Alloys and Compounds, 2013
Lithium-ion batteries have been wildly used in various portable electronic devices and the application targets are currently moving from small-sized mobile devices to large-scale electric vehicles and grid energy storage. Therefore, lithium-ion batteries with higher energy densities are in urgent need. For high-energy cathodes, Li 2 MnO 3 -LiMO 2 layered-layered (M = Mn, Co, Ni) materials are of significant interest due to their high specific capacities over wide operating potential windows. Here, three Li 2 MnO 3based cathode materials with a-NaFeO 2 structure were prepared by a facile co-precipitation method and subsequent heat treatment. Among these three materials, 0.3Li 2 MnO 3 Á0.5LiMn 0.5 Ni 0.5 O 2 Á0.2LiCoO 2 shows the best lithium storage capability. This cathode material is composed of uniform nanosized particles with diameters ranging from 100 to 200 nm, and it could be charged to a high cutoff potential to extract more lithium, resulting in a high capacity of 178 mAh g À1 between 2.0 and 4.6 V with almost no capacity loss over 100 cycles.
Structural Changes in Li2 MnO 3 Cathode Material for Li- Ion Batteries
Advanced Energy Materials, 2014
Structural changes in Li 2 MnO 3 cathode material for rechargeable Li-ion batteries are investigated during the fi rst and 33 rd cycles. It is found that both the participation of oxygen anions in redox processes and Li + -H + exchange play an important role in the electrochemistry of Li 2 MnO 3 . During activation, oxygen removal from the material along with Li gives rise to the formation of a layered MnO 2 -type structure, while the presence of protons in the interslab region, as a result of electrolyte oxidation and Li + -H + exchange, alters the stacking sequence of oxygen layers. Li re-insertion by exchanging already present protons reverts the stacking sequence of oxygen layers. The re-lithiated structure closely resembles the parent Li 2 MnO 3 , except that it contains less Li and O. Mn 4+ ions remain electrochemically inactive at all times. Irreversible oxygen release occurs only during activation of the material in the fi rst cycle. During subsequent cycles, electrochemical processes seem to involve unusual redox processes of oxygen anions of active material along with the repetitive, irreversible oxidation of electrolyte species. The deteriorating electrochemical performance of Li 2 MnO 3 upon cycling is attributed to the structural degradation caused by repetitive shearing of oxygen layers.
Li Mn2O4 as a Li ion battery cathode
Eriksson, T. 2001. LiMn2O4 as a Li-Ion Battery Cathode. From Bulk to Electrolyte Interface. Acta Universitatis Upsaliensis. Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 651. 53 pp. Uppsala. ISBN 91-554-5100-4.
Lithiated manganese oxide Li0.33MnO2 as an electrode material for lithium batteries
Journal of Power Sources, 2006
Li 0.33 MnO 2 was prepared by solid-state reaction of CMD oxide and a lithium salt. The structure was studied by X-ray diffraction and Raman scattering during electrochemical discharging. The possibility of application as a positive electrode in rechargeable lithium batteries was investigated. The electrochemical properties of Li//Li 0.33 MnO 2 cells were studied as a function of temperature in the range 25-55 • C. The electrode material delivers an initial capacity of 194 mAh g −1 and shows good reversibility at room temperature. Finally, the lithium insertion mechanism was examined by the determination of the ion kinetics.
Chemistry of Materials, 2012
Investigation of the high-voltage Li-[Ni 0.5−x Mn 1.5+x ]O 4 (x = 0, 0.05, 0.08) spinels prepared at temperatures of T ≤ 900°C and given different thermal treatments has shown that the solubility limit for oxygen vacancies in the disordered spinel phase is small at 600°C. With x = 0, long-range ordering of Ni 2+ and Mn 4+ and elimination of all oxygen vacancies occurs after an anneal at 700°C. Above 700°C, a reversible transition from spinel to rock-salt is initiated, to accommodate oxygen loss. A sample quenched from 900°C into liquid nitrogen traps some rocksalt second phase; the volume fraction of rock-salt phase decreases with oxygen uptake to 600°C. However, upon slow cooling (1°C min −1 ) from 900°C, the particles have time to eliminate most of the rock-salt phase by 700°C; upon further cooling below 700°C, the spinel phase and the oxygen gain are retained. However, the spinel phase retains oxygen vacancies and attendant Mn 3+ with only short-range order of Ni and Mn. The rock-salt phase lowers sharply the electrochemical capacity of the quenched sample; but retention of Mn 3+ in the slow-cooled sample improves the electrochemical performance relative to that of an oxygen-stoichiometric spinel formed by annealing at 700°C. The Mn-rich Li[Ni 0.45 Mn 1.55 ]O 4 sample annealed at 700°C exhibits a segregation of a long-range-ordered spinel phase and a Ni-deficient spinel phase having a larger fraction near the particle surface. Removal of the Ni 4+ /Ni 2+ redox reactions from the surface stabilizes the electrochemical performance at 55°C, but the problem of Mn 2+ dissolution resulting from surface disproportionation of Mn 3+ to Mn 2+ and Mn 4+ remains.
Journal of Alloys and Compounds, 2017
In this work a series of Li-rich layered-layered solid solution of Li 2 MnO 3-LiMnO 2 [Li[Li (1Àx)/3 Mn (xþ2)/3 ]O 2 ; x ¼ 0.0, 0.1, 0.3 and 0.5] nanocomposite structure were successfully synthesized using sol-gel technique. All the synthesized compositions exhibit the main characteristics peaks of m-Li 2 MnO 3 and could be indexed to the C2/m space group except some weak diffraction peaks located around 20e30 which can be attributed to the superlattice structure originate due to the ordering of Mn ion into Li-Mn layers and are typically observed for Li-rich based materials. CV results show that pristine LMO possesses weak anodic peak around 4.7 V and no symmetric cathodic peak in the voltage window of 2.0e4.8 V. Among all the synthesized compositions, x ¼ 0.3 (LMO3) delivers highest specific discharge capacity and best rate and cycling performances at all values of current densities. The LMO3 composition delivers an initial discharge capacity of 177 ± 5 mAhg À1 at a current density of 10 mA/g in the voltage range of 2.0e4.8 V and holds nearly 97% of the initial discharge capacity after 120 charge/discharge cycles at the same current density.