Solid-State Lithium-Polymer Batteries Using Lithiated MnO[sub 2] Cathodes

Abstract

We have used a lithiated MnO 2 , Li 0.33 MnO 2 , with ordered alternating one-dimensional [1 ϫ 2] and [1 ϫ 1] channels as a cathode material in solid-state lithium/polymer cells. An optimized cell can operate at moderate temperatures (40-80ЊC). Li 0.33 MnO 2 delivers a rechargeable capacity of 160 mAh/g with a flat potential plateau at ca. 3.0 V vs. Li/Li ϩ at the C/3 rate and 65ЊC, corresponding to a specific energy of 450 Wh/kg of the pure oxide. Cells show good rate capability and excellent cyclability when cycled between 2.7 and 3.5 V at 80% depth of discharge, whereas a capacity decline was observed when cycled between 2.0 and 3.5 V. Capacity fading upon cycling is believed to be due to the formation of a thin layer of spinel phase (transformation to Li 0.5 MnO 2 from Li 0.33 MnO 2 ) on the particle surfaces, as well as to increased cell resistance during charge/discharge cycling. The cell self-discharge at high temperature and the thermal stability of Li 0.33 MnO 2 in contact with the polymer electrolyte are also discussed.

Thermal Lithiation of Manganese Dioxide: Effect of Low Lithium Concentration (x ≤ 0.3 in LixMnO2) on Structure and Electrochemical Performance

“…As mentioned in the Introduction, this material has been assigned to a single phase monoclinic (c2/m) structure incorporating an ordered alternation of (1 × 1) and (1 × 2) tunnels. [13][14][15]25 In the present work, Figure 1 indicates this structure is formed using lithium concentrations between x = 0.22 and 0.28.…”

“…12 However, neither of these proposals can account for the electrochemical performance or X-ray diffraction patterns of Li 0.33 MnO 2 . 10,12,13 These considerations prompted Li et al to propose the formation of a single Li 0.33 MnO 2 phase. 11 This proposal is supported by the work of Aurbach and coworkers who found good agreement between experimental data and a simulated XRD pattern for a single phase, tunneled, monoclinic Li 0.33 MnO 2 material using the Rietveld method.…”

Thermally Stable Gel Polymer Electrolytes

“…In the case of interfacial resistance, the progressive expansion of R i for PVdF-HFP indicates the continuous growth of a passivation layer on the Li metal surface. 19 This resistive layer is known to be caused by the reaction between aprotic solvents and Li metal electrode. It is supposed that the passivation layer is not uniform in composition and density across the layer and the middle frequency semicircle is usually depressed.…”

Rate Capabilities of Composite Gel Electrolytes Containing Fumed Silica Nanoparticles

“…7,8,[18][19][20] Figure 10 reports typical charge-discharge ͑third cycle͒ curves. The voltage during charge of the liquid electrolyte at C/15 presents a smoother behavior in time in comparison to that at C/2 ͑Fig.…”

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