Synthesis and Structural Aspects of LiMn2 O 4 ± δ as a Cathode for Rechargeable Lithium Batteries

Abstract

The phase diagram of LiMn2Q over a wide oxygen pressure-temperature region was determined, and the thermodynamics of the oxygen extraction (the heat of reaction, AH, etc.) were estimated using thermal analysis, x-ray diffraction, sample quenching, and a high pressure oxygen treatment. The oxygen stoichiometry, 8, in LiMn204_+a varied with the selection of treatment conditions. The extent of the cooperative Jahn-Teller effect in the LiMn204 8 and various kinds of spinel Mn oxides are discussed in terms of the Madelung potential and Mn valency using the DV-Xa calculation. The performance of coin-type cells containing cathodes of the synthesized spinel was investigated and compared to that of cells containing standard LiMn20~ spinel cathodes.

Systematic Studies on “Abundant” Battery Materials: Identification and Reaction Mechanisms

“…Figure 2 is the phase diagram of LiMn 2 O 4 in the temperatureoxygen partial pressure system (T-P O2 ) obtained by TG/DTA analysis. 2 The metastable samples of high-temperature phases were obtained by quenching from the corresponding temperatures in the regions B and C in Fig. 2.…”

“…4 In the lithium manganospinel system, LiMn 2 O 4 is of particular interest because it takes the threshold manganese valence, 3.5, where the cubic lattice is apt to exhibit JT distortion when the manganese valence is slightly reduced by lithium insertion 5 or oxygen extraction. 2 This situation led us to an investigation of the low temperature structure of LiMn 2 O 4 and the discovery of the unique Verwey-like chargeordering transition with large local JT distortion in the vicinity of T t = 280 K (Fig. 5).…”

“…Different from the lithium case, Na x FeO 2 satisfies the tolerance criterion for layered structure, r B /r A < 0.86, due to the larger ionic radius of Na + (r Na+ = 102 pm, r Li+ = 76 pm). To date, O3-type NaFeO 2 30 and P2-type Na Electrochemistry, 84(9), 654-661 (2016) been reported, both suffering from low operating potential even by using a Fe 4+ /Fe 3+ redox couple, and the stable reversible capacity is limited. In spite of the great success with olivine LiFePO 4 , the sodium analogue with the same structure has turned out to be unsuitable for an electrode.…”

Phase Transitions and Low-temperature Structure of Lithium Manganese Oxide Spinel

“…Three types of phases related to co-operative Jahn-Teller ordering were reported; (i) the tetragonal phase synthesized at high-temperatures and quenched to liq N 2 , (ii) the tetragonal phase appeared during lithium intercalation from LiMn 2 O 4 , and (iii) the low-temperature phase appeared around room temperature. The tetragonal phase (i) observed at high-temperature was stabilized at room temperature by quenching from 920 C. 3) Its structure has a cooperative ordered arrangement of trivalent manganese ions. 4,5) The tetragonal phase (ii) appeared during the lithium intercalation has been studied in detail to clarify the charge-discharge characteristics of the 3 V region.…”

Study of Mn Dissolution from LiMn[sub 2]O[sub 4] Spinel Electrodes Using Rotating Ring-Disk Collection Experiments

“…instability of the two-phase structure in the charged state leading to the loss of MnO and dissolution of Mn to a more stable single-phase structure, 4,8,9 (iv) formation of tetragonal Li 2 Mn 2 O 4 on the surface of the spinel and the associated Jahn-Teller distortion at the end of discharge, especially under high current density, nonequilibrium conditions, 5,10,11 (v) formation of oxygen-deficient spinels, 12 (vi) cation mixing between the lithium and manganese sites in the spinel lattice, 13 and (vii) loss of crystallinity during cycling. 14,15 Although many possible factors have been proposed to contribute to the capacity fading of the spinel LiMn 2 O 4 electrode, most of the evidence reported so far points to manganese dissolution at the top of charge as the major reason for the capacity fading.…”