A process for preparing a battery grade formulation comprising a carbon-deposited alkali metal phosphate of the formula C-A a M m (XO 4) x wherein C-A a M m (XO 4) x is composed of particles of a compound corresponding to the general formula A a M m (XO 4) x which have an olivine structure and which carry, on at least a portion of their surface, a film of carbon deposited by pyrolysis, the general formula A a M m (XO 4) x being such that: A represents Li, alone or partially replaced by at most 20% as atoms of Na and/or K, and 0 < a ≤ 8; M comprise at least 50% at. of Fe(ll) or Mn(ll) or mixture thereof, and m = 1; and • X0 4 represents PO 4, alone or partially replaced by at most 30 mol% of at least one group chosen from SO 4 and SiO 4, and 0 < x ≤ 3; wherein M, X, a, m and x are selected as to maintain electroneutrality of said compound, the process comprising the steps of providing carbon-deposited alkali metal phosphate C-A a M m (XO 4) x in the form of strong agglomerates which show a reduction of D 50 of no more than 50-fold when subjected to ultrasonic dispersion for 30 seconds at an ultrasonic power of 130W at a frequency of 20 kHz, wherein the strong agglomerates are obtained by a process comprising a dry high-energy ball milling of precursors of the carbon-deposited alkali metal phosphate C-A a M m (XO 4) x and performing a milling step of the carbon-deposited alkali metal phosphate C-A a M m (XO 4) x in the form of strong agglomerates, wherein said milling step is performed in the presence of a solvent used for battery electrode coating and wherein the process comprises the addition of at least one metal alkoxide during or after the milling step. A represents Li, alone or partially replaced by at most 20% as atoms of Na and/or K, and 0 < a ≤ 8; M comprise at least 50% at. of Fe(ll) or Mn(ll) or mixture thereof, and m = 1; and • X0 4 represents PO 4, alone or partially replaced by at most 30 mol% of at least one group chosen from SO 4 and SiO 4, and 0 < x ≤ 3; • X0 4 represents PO 4, alone or partially replaced by at most 30 mol% of at least one group chosen from SO 4 and SiO 4, and 0 < x ≤ 3; wherein M, X, a, m and x are selected as to maintain electroneutrality of said compound, the process comprising the steps of providing carbon-deposited alkali metal phosphate C-A a M m (XO 4) x in the form of strong agglomerates which show a reduction of D 50 of no more than 50-fold when subjected to ultrasonic dispersion for 30 seconds at an ultrasonic power of 130W at a frequency of 20 kHz, wherein the strong agglomerates are obtained by a process comprising a dry high-energy ball milling of precursors of the carbon-deposited alkali metal phosphate C-A a M m (XO 4) x and performing a milling step of the carbon-deposited alkali metal phosphate C-A a M m (XO 4) x in the form of strong agglomerates, wherein said milling step is performed in the presence of a solvent used for battery electrode coating and wherein the process comprises the addition of at least one metal alkoxide during or after the milling step. providing carbon-deposited alkali metal phosphate C-A a M m (XO 4) x in the form of strong agglomerates which show a reduction of D 50 of no more than 50-fold when subjected to ultrasonic dispersion for 30 seconds at an ultrasonic power of 130W at a frequency of 20 kHz, wherein the strong agglomerates are obtained by a process comprising a dry high-energy ball milling of precursors of the carbon-deposited alkali metal phosphate C-A a M m (XO 4) x and performing a milling step of the carbon-deposited alkali metal phosphate C-A a M m (XO 4) x in the form of strong agglomerates, wherein said milling step is performed in the presence of a solvent used for battery electrode coating and wherein the process comprises the addition of at least one metal alkoxide during or after the milling step.