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Ni-Cd and Ni-MH batteries [ 1 ] are classifi ed as the " fi rst-generation " because their voltages are limited as small as 1.2 V, mainly due to the narrow potential stability windows of aqueous-based electrolytes. Indeed Ni-MH batteries have yielded great commercial success as power sources for hybrid vehicles (HVs) since the release of the Prius in 1997, but their limited energy density has restricted their application for pure EVs that require more energy than HVs. The low energy densities of Ni-MH batteries was overcome by the " second-generation " lithium-ion batteries operating at ca. 4 V range using 4V-class cathodes such as LiCoO 2 , [ 2,3 ] LiMn 2 O 4 , [ 4 ] Li(Ni, Co, Al)O 2 , [ 5 ] or Li(Ni, Co, Mn)O 2 . [ 6 ] Their high-voltage is owed mainly to the wide potential stability windows of non-aqueous solvents such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC), etc., [ 7 ] in liquid electrolytes. [ 8 ] Although such 4V-class lithium-ion batteries are now going to be dominantly used as power sources for EVs, a strong demand to improve their driving range is awaiting the realization of the " third-generation " batteries operating at ca. 5 V range.To date, several kinds of 5V-class cathodes, [ 9 ] such as LiNi 0.5 Mn 1.5 O 4-δ , [ 10 ] Cr-doped LiNi 0.5 Mn 1.5 O 4 , [ 11 ] LiCoPO 4 , [ 12 ] Li 2 CoPO 4 F, [ 13 ] LiNiPO 4 , [ 14,15 ] Li 2 NiPO 4 F, [ 16,17 ] LiNiVO 4 , [ 18,19 ] etc. have been reported. However, when they are used with conventional liquid-based electrolytes, they face problems in terms of durability and cycle stability because they give rise to strong oxidation atmospheres against the electrolytes and decompose them. [ 20 ] Although the kinetics of such side-reactions can be slowed down by techniques like surface coating on cathode materials, [ 21 ] concentration-gradient cathodes, [ 22 ] and additives into the electrolyte, [ 23,24 ] etc., it should not be possible to suppress the side-reactions completely as long as liquid-based electrolytes are used. Such an underlying problem in the 5V-class batteries led us to utilize inorganic solid electrolytes [ 8 ] that generally possess wider electrochemical potential windows compared to conventional liquid-based electrolytes. The resultant 5V-class all-solid-state lithium batteries are expected to ensure not only better durability, but also improved safety because of the non-fl ammable properties of the solid electrolytes. [ 25,26 ] As an example of an inorganic solid electrolyte, in this work we used a lithium-oxynitride phosphate glass, Li 3.2 PO 3.8 N 0.2 (LiPON), that is reported to be stable up to 5.5 V (vs. Li/Li + ). [ 27 ] The LiPON was combined with 5V-class LiCr 0.05 Ni 0.45 Mn 1.5 O 4-δ (LNM) cathodes [ 11 ] with spinel structure whose charge/discharge capacities are predominantly given at around 4.8 V (vs. Li/Li + ) using the Ni 2+ Ni 4+ redox couple as well as small capacities at around 4.0 V (vs. Li/Li + ) using the Mn 3+ Mn 4+ redox couple. The as-prepared 5V-class Li/Li...

We derive a mathematical model for space-charge-layer formation in a solid electrolyte based on first principles only. Consistent with the second law of thermodynamics, we employ mass, momentum, and energy conservation, supplemented with constitutive assumptions in the form of a Helmholtz free-energy functional. The resulting system of differential equations is solved semianalytically for a stationary 1D case, and the parametric dependencies of the space-charge layers forming at the boundaries under the influence of an external voltage are studied. We present results for different applied potentials, dielectric susceptibilities, and other parameters and compare our results with experiments. The predicted space-charge layers at the boundaries are in general not symmetric due to the restricted mobility of the anion lattice. Their size is found to be approximately 1 order of magnitude larger compared with liquid electrolytes, even if all macroscopic properties like mass density, dielectric constant, etc. are the same. Depending strongly on the dielectric properties of the material, typical widths of space-charge layers in some glass ceramics with very high dielectric susceptibility are predicted to be as large as several hundreds of nanometers, in qualitative agreement with experimental results in literature.

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