NOVELTY - Preparing a phospho-olivine type compound (I) or (Ia) involves reacting a phospho-olivine type compound (II) with a metal compound (III), in presence of an acid scavenger adapted to at least solubilize the compounds (II) and (III), at a predetermined temperature, and adapted to be converted into a protic ionic liquid upon protonation.    USE - For preparing a phospho-olivine type compound useful in electrodes (claimed) for lithium batteries.    ADVANTAGE - The processes can be carried out at low temperature as opposed to processes of the prior art which require high temperatures generally greater than 800 degrees C. Also the process can be carried out in an organic solvent which is also an acid scavenger and it permit to keep the obtained compound under anhydrous conditions and avoid the presence of Fe3+ ions, which are contaminants detrimental for lithium batteries. Moreover, the process does not require costly reagents or comprise several steps.    DETAILED DESCRIPTION - Preparing a phospho-olivine type compound of formula AMPO4 (I) or AM'tM''1-tPO4 (Ia) involves reacting a phospho-olivine type compound of formula AH2PO4 (II) with a metal compound of formula MXn (III) in the presence of an acid scavenger adapted to at least solubilize the compounds (II) and (III), at a predetermined temperature, and adapted to be converted into a protic ionic liquid upon protonation.    A=H+, Li+, Na+, K+, or Cs    M, M' and M''=Be2, Mg2+, Ba2+, Ca2+, Sr2+, Fe2+, Co2+, Ni2+, Mn2+, Zn2+, Cu2+, or Mo2+;    X=F-, Cl-, Br-, I-, CN-, CH3COO-, CF3SO3-, NO3-, OCN-, SCN-, (CN)2N-, CO32-, ClO3-, CrO42-, BrO3-, Cr2O72-, S2O42-, S4O62-, S2O32-, SO42-, MnO4-, S2-, ClO-, or C2O42-;    n=1 or 2;and    t=0-1.    INDEPENDENT CLAIMS are included for the following:    (1) preparing an electrode involving: reacting the compound (II) with (III), in the presence of an acid scavenger adapted to at least solubilize the compounds (II) and (III), at a predetermined temperature, adapted to be converted into a protic ionic liquid upon protonation, thus obtaining a composition comprising (I) or (Ia), protonated acid scavenger, and optionally unprotonated acid scavenger; depositing the composition on a substrate; and annealing the composition deposited on the substrate so as to obtain the electrode;    (2) method of using a scavenger compound of formula (IV) involving using the compound as an acid scavenger in the preparation of a phospho-olivine type compound; and    (3) scavenging protons involving contacting the protons with the compound (IV).    R=H, 1-12C alkyl, 3-12C cycloalkyl, 1-12C heterocyclyl, 2-12C alkenyl, 2-12C alkynyl, 6-12C aryl, 6-20C aralkyl, 6-20C alkylaryl, or 1-12C heteroaryl.    R comprises a polymerizable moiety.