The mechanical flexibility of a cable‐type battery reaches levels far beyond what is possible with conventional designs. The hollow‐spiral (helical) multi‐helix anode architecture is critical to the robustness under mechanical stress and facilitates electrolyte wetting of the battery components. This design enables the battery to reliably power an LED screen or an MP3 player even under severe mechanical twisting and bending.

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The interfacial origin of performance improvement and fade of high-voltage cathodes of LiNi 0.5 Co 0.2 Mn 0.3 O 2 for high-energy lithium-ion batteries has been investigated. Performance improvement was achieved through interfacial stabilization using 5 wt % methyl (2,2,2-trifluoroethyl) carbonate (FEMC) of fluorinated linear carbonate as a new electrolyte additive. Cycling with the FEMC additive at 3.0−4.6 V versus Li/Li + results in the formation of a stable solid electrolyte interface (SEI) layer and effective passivation of cathode surface, leading to improved cycling performance delivering enhanced discharge capacities to 205−182 mAhg −1 and capacity retention of 84% over 50 cycles. The SEI layer notably includes plenty of metal fluorides and −CF-containing species formed by additive decomposition. On the contrary, the origin of performance fade in electrolyte only was ineffective surface passivation and dissolution of metal elements, which leads to oxygen loss, surface structural degradation and crack formation at the LiNi 0.5 Co 0.2 Mn 0.3 O 2 particles. The data provide a basic understanding of the interfacial stabilization mechanism on high-voltage layered oxide cathodes.

Systematic Mn 2p XPS and Mn K-edge XAS analyses together with the electrochemical measurement have been carried out for the spinel LiMn 2 O 4 prepared at various sintering temperatures in order to elucidate an origin of the dependence of electrochemical properties on synthetic conditions. From the comparative experiments, it becomes clear that a lowering of synthetic temperature gives rise to an increase of structural disorder and of the average oxidation state of manganese, which is more prominent on the surface than in the bulk. Such results suggest that the modification of surface property induced by a decrease of particle size is closely related to the electrochemical performance. The nanocrystalline LiMn 2 O 4 prepared at 250 °C shows excellent cyclability at the 3 V region compared to that of microcrystalline LiMn 2 O 4 prepared at 700 °C. For the purpose of examining the evolution of the chemical bonding nature of inserted lithium, 7 Li MAS NMR studies have been performed for both the spinel compounds before and after Li + intercalation. While the intercalation of 0.2 mol Li + does not induce any remarkable spectral change for the microcrystalline LiMn 2 O 4 , it leads to a dramatic suppression of the NMR signal for the nanocrystalline LiMn 2 O 4 , indicating that the process of grafting Li into the latter phase results in significant modifications of the chemical environment of lithium. On the basis of present experimental findings, it can be concluded that the lowering of synthetic temperature modifies the surface properties, which facilitates the grafting process of Li + ion and, thereby, enhances the electrochemical properties for the 3 V region corresponding to the Li insertion.