Liquid-phase step-by-step growth of an iron cyanide coordination framework on LiCoO2 particle surfacesElectronic supplementary information (ESI) available: SEM images of the PBNL@LCO particles before and after immersion into the liquid electrolyte. See DOI: 10.1039/c5dt00968e

Surface modification of inorganic objects with metal-organic frameworks (MOFs) - organic-inorganic hybrid framework materials with infinite networks - opens wide windows for potential applications. In order to derive a target property, the key is the ability to fine tune the degree of modification. Solution-based step-by-step growth techniques provide excellent control of layer thickness which can be varied with the number of deposition cycles. Such techniques with MOFs have been mainly applied to flat substrates, but not to particle surfaces before. Here, we present the facile surface modification of inorganic particles with a framework compound under operationally simple ambient conditions. A solution-based sequential technique involving the alternate immersion of LiCoO 2 (LCO) - a positive electrode material for a lithium ion battery - into FeCl 2 ·4H 2 O and K 3 [Fe(CN) 6 ] solutions results in the formation of Prussian blue (PB) nanolayers on the surface of the LCO particles (PBNL@LCO). The PB growth is finely controlled by the number of immersion cycles. An electrochemical cell with PBNL@LCO as a positive electrode material exhibits a discharge capacity close to the specific capacity of LCO. The results open a new direction for creating suitable interfacial conditions between electrode materials and electrolytes in secondary battery materials. The facile surface modification of LiCoO 2 (LCO) - a positive electrode material for a lithium ion battery - with a framework compound, Prussian blue, in a step-by-step manner under operationally simple ambient conditions is described.