With the increasing importance of wireless microelectronic devices the need for on-board power supplies is evidently also increasing. Possible candidates for microenergy storage devices are planar all-solid-state Li-ion microbatteries, which are currently under development by several start-up companies. However, to increase the energy density of these microbatteries further and to ensure a high power delivery, three-dimensional (3D) designs are essential. Therefore, several concepts have been proposed for the design of 3D microbatteries and these are reviewed. In addition, an overview is given of the various electrode and electrolyte materials that are suitable for 3D all-solidstate microbatteries. Furthermore, methods are presented to produce fi lms of these materials on a nano-and microscale.www.MaterialsViews.com REVIEW www.advenergymat.de

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Kelvin probe monitoring of metal-organic framework coated electrodes is demonstrated as a route for ppb-level detection of alkyl phosphonates.

Like all rechargeable battery systems, conventional Li-ion batteries (LIB) inevitably suffer from capacity losses during operation. This also holds for all-solid-state LIB. In this contribution an in operando Neutron Depth Profiling (NDP) method is developed to investigate the degradation mechanism of all-solid-state, thin film Si-Li 3 PO 4 -LiCoO 2 batteries. Important aspects of the long-term degradation mechanisms are elucidated. It is found that the capacity losses in these thin film batteries are mainly related to lithium immobilization in the solid-state electrolyte, starting to grow at the anode/electrolyte interface during initial charging. The Li-immobilization layer in the electrolyte is induced by silicon penetration from the anode into the solid-state electrolyte and continues to grow at a lower rate during subsequent cycling. X-ray Photoelectron Spectroscopy (XPS) depth profiling and Transmission Electron Microscopy (TEM) analyses confirm the formation of such immobilization layer, which favorably functions as an ionic conductor for lithium ions. As a result of the immobilization process, the amount of free moveable lithium ions is reduced, leading to the pronounced storage capacity decay. Insights gained from this research shed interesting light on the degradation mechanisms of thin film, all-solid-state LIB and facilitate potential interfacial modifications which finally will lead to substantially improved battery performance.

In situ neutron depth profiling (NDP) offers the possibility to observe lithium transport inside micro‐batteries during battery operation. It is demonstrated that NDP results are consistent with the results of electrochemical measurements, and that the use of an enriched 6LiCoO2 cathode offers more insight in transport processes occurring inside all‐solid‐state thin‐film batteries.