TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: (p2) have an average particle diameter of 5 - 100 nm. (p2) comprise carbon black. A molar ratio of carbon atoms in (p2) with respect to lithium atoms is 0.02 - 0.2.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Oxide: (A) has particles having an average particle diameter of 0.2 - 5 mum. (A) is expressed by a composition formula LiFe1-xMxPO4.M = Mn, Mg, Ni, Co, Cu, Zn or Ge (preferably Mn);x = 0.02 - 0.2 (preferably 0.05 - 0.15).Preferred Components: The lithium source is Li2CO3, iron source is FeC2O4.2H2O and phosphorus source is NH4H2PO4. LiH2PO4 acts as a source of lithium as well as phosphorus.Preferred Method: The calcining step is carried out in an inert or in a reducing atmosphere. EXAMPLE - Carbon-containing lithium-iron composite phosphorus oxides expressed by a ratio LiFe1-xMnxPO4:Cy (where x = 0.15 by mol and y was 0, 0.02, 0.05 or 0.1 by mol) was prepared. LiH2PO4 was used as the lithium source as well as the phosphorus source, FeC2O4.2H2O was used as iron source, MnCO3 was used as the substitution element source and carbon black having average particle size of 24 nm was used as the carbonaceous fine particles. Firstly FeC2O4.2H2O and MnCO3 were mixed so that the ratio of FeC2O4.2H2O:MnCO3 was 0.85:0.15 by molar ratio. To the mixture LiH2PO4 and carbon black were added so that the ratio of Li:(Fe+Mn):C was 1:1:0, 1:1:0.02, 1:1:0.05 or 1:1:0.1. All the mixtures were calcined at 650degreesC for 6 hours.    The resulting carbon-containing as well as carbon-free oxides were pulverized to powder form, which had an average particle diameter of 1 mum. The oxides were used to manufacture lithium secondary batteries, of which active material charge- and discharge capacities were measured.    The lithium-iron composite phosphorus oxides (carbon-containing/carbon-free) exhibited the initial active material discharge capacity (mAh/g) of 88/80 and showed a high capacity retention rate (%) of 84/77 after 500 cycles. Thus carbon-containing lithium-iron composite phosphorus oxides showed not only the higher active material discharge capacity initially but also the capacity lowered less.