Commercially available lithium-ion batteries (LiMn 2 O 4 /LiNi 0.8 Co 0.15 Al 0.05 O 2 mixed cathode and graphite anode) are disassembled to determine the reversible capacity of each electrode, the state of charge (SOC) in the operation range, and the lithium content in the graphite anode by inductively coupled plasma optical emission spectroscopy (ICP-OES) after a cycle or storage operation. The origin of the decrease in capacity of the battery is attributed to (i) the decrease in capacity of the cathode active material and (ii) the limited cathode operation range. This leads to a shift to a high SOC of the cathode owing to the irreversible loss of lithium at the anode. We quantitatively explain all degraded battery capacities using the above two factors. The shift in capacity is obtained by discharging from the constant disassembly conditions at a constant open-circuit voltage (OCV), which cannot be obtained by electrochemical analysis of the anode. The determined shift in capacity has a strong correlation with the amount of irreversibly accumulated lithium at the anode determined by ICP-OES.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 155.69.4.4 Downloaded on 2015-05-26 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 155.69.4.4 Downloaded on 2015-05-26 to IP

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...

The all solid-state lithium battery with polyether-based solid polymer electrolyte (SPE) is regarded as one of next-generation lithium batteries, and has potential for sufficient safety because of the flammable-electrolyte-free system. It has been believed that polyether-based SPE is oxidized at the polymer/electrode interface with 4 V class cathodes. Therefore, it has been used for electric devices such as organic transistor, and lithium battery under 3 V. We estimated decomposition reaction of polyether used as SPE of all solid-state lithium battery. We first identified the decomposed parts of polyether-based SPE and the conservation of most main chain framework, considering the results of SPE analysis after long cycle operations. The oxidation reaction was found to occur slightly at the ether bond in the main chain with the branched side chain. Moreover, we resolved the issue by introducing a self-sacrificing buffer layer at the interface. The introduction of sodium carboxymethyl cellulose (CMC) to the 4 V class cathode surface led to the suppression of SPE decomposition at the interface as a result of the preformation of a buffer layer from CMC, which was confirmed by the irreversible exothermic reaction during the first charge, using electrochemical calorimetry. The attained 1500 cycle operation is 1 order of magnitude longer than those of previously reported polymer systems, and compatible with those of reported commercial liquid systems. The above results indicate to proceed to an intensive research toward the realization of 4 V class "safe" lithium polymer batteries without flammable liquid electrolyte.

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