Today and for some years to come, the development of batteries with high performance and safety at a low cost is the key for the expansion of important industries and markets such as electric vehicles and renewable energies. Lithium-metal polymer battery (LMP) technology is the most attractive one. Lithium-metal as anode shows specific capacity more than ten times that of LiC6 anode used in the widespread lithium-ion battery and is considered as the best to complement the positive air (O2) or sulfur cathodes. However, solid polymer electrolyte must be operated at 80°C to provide sufficient ionic conductivity, so that mechanical properties are weak with a limited electrochemical stability window. Furthermore, as in liquids, the fraction of charge carried by lithium ions is small (transference number 1000) and with a very limited dendritic growth. To reach these objectives, we propose a multidisciplinary approach gathering different complementary skills to design groundbreaking single-ion nanohybrid electrolytes able to afford different antagonist properties (i.e. high ion transport at RT and high mechanical strength). These materials are composed of ionic functional nanofillers (NFs) and amorphous polymer based on poly(ethylene oxide) (PEO). SELPHy project therefore devotes to: • The functionalization of NFs from various families (POSS, colloidal silica, cellulose nanofibers) with amorphous PEO short chains and/or lithium salt. • The formulation of single-ion nanohybrid electrolytes by blending functionalized NFs with an ionic conductor matrix, i.e. a crosslinked PEO based polymer. • The depth-characterizations of nanohybrid electrolytes including NFs dispersion state, (macro)molecular dynamics and macroscospic properties (transport and mechanical properties) in the aim to establish the structure-composition-macroscopic properties relationships. • The assembly of LMP battery prototype to qualify the new single-ion nanohybrid electrolytes. We are totally confident that our proposed single-ion electrolytes will exhibit: i) transference number close to 1 since the Li+ counter-ions are covalently grafted to the NFs, ii) High ionic conductivity (i.e. 10-4 S/cm at RT) thank to the high mobility of the amorphous PEO short chains grafted to the NF surface and the use of high lithium dissociated salt iii) Sufficient mechanical properties to encounter dendrites growth provided by the crosslinked polymer network and the NFs reinforcing capacity iv) High electrochemical stability up to 5 V vs Li+/Li (required for the battery comprising high potential active material) due to the grafting of the anions. v) Enhanced thermal stability for the safety thank to the presence of NFs like POSS. SELPHy is a collaborative research project involving three academic partners and interdisciplinary as it gathers indispensable expertise in organic and polymer chemistries, nanocomposite materials, physical chemistry, electrochemistry and electrochemical storage.