A method for preparing non-agglomerated nanoparticles of a lithium lamellar oxide comprising one or more metal elements disposed in the form of layers of metal cations and lithium disposed in interlayers of lithium cations and optionally, partially, in the layers of metal cations, said interlayers ensuring the separation between said layers, said oxide corresponding to the following formula: Li (a+b) Ni c Mn d Co e M f O g wherein: *a represents the proportion of lithium comprised in the interlayers and being greater than 0 and less than or equal to 1; *b represents the proportion of lithium comprised in the layers of metal cations and being greater than or equal to 0 and less than or equal to (1/3); *c, d, e and f are comprised between 0 and 1, with the condition that b+c+d+e+f=1, so that the electroneutrality of the oxide of formula is respected; *g is comprised between 1.9 and 2.1; *when f is different from 0, M is at least one element selected from Al, Fe, Ti, Cr, V, Cu, Mg, Zn, Na, K, Ca, Sc and combinations thereof; said method comprising the following steps: a) a step of synthesising a mixed carbonate or a mixed hydroxide comprising the elements other than Li by contacting, with stirring, the elements other than Li in the form of cations with carbonate anions, when it comes to synthesising the mixed carbonate, or with hydroxide anions, when it comes to synthesising the mixed hydroxide; b) a step of reacting the mixed carbonate or the mixed hydroxide obtained in step a) with a lithium carbonate or lithium hydroxide, whereby the aforementioned lithium lamellar oxide of formula is formed, characterised in that step a) is carried out at a predetermined pH, which pH ranges from 8 to 9.5 when the synthesis step relates to a mixed carbonate or ranges from 11 to 12.5 when the synthesis step relates to a mixed hydroxide and in that step a) is carried out at a fixed stirring speed so as to obtain a power dissipated per unit volume which is at least greater than or equal to 1000 W/m 3. *a represents the proportion of lithium comprised in the interlayers and being greater than 0 and less than or equal to 1; *b represents the proportion of lithium comprised in the layers of metal cations and being greater than or equal to 0 and less than or equal to (1/3); *c, d, e and f are comprised between 0 and 1, with the condition that b+c+d+e+f=1, so that the electroneutrality of the oxide of formula is respected; *g is comprised between 1.9 and 2.1; *when f is different from 0, M is at least one element selected from Al, Fe, Ti, Cr, V, Cu, Mg, Zn, Na, K, Ca, Sc and combinations thereof; said method comprising the following steps: a) a step of synthesising a mixed carbonate or a mixed hydroxide comprising the elements other than Li by contacting, with stirring, the elements other than Li in the form of cations with carbonate anions, when it comes to synthesising the mixed carbonate, or with hydroxide anions, when it comes to synthesising the mixed hydroxide; b) a step of reacting the mixed carbonate or the mixed hydroxide obtained in step a) with a lithium carbonate or lithium hydroxide, whereby the aforementioned lithium lamellar oxide of formula is formed, a) a step of synthesising a mixed carbonate or a mixed hydroxide comprising the elements other than Li by contacting, with stirring, the elements other than Li in the form of cations with carbonate anions, when it comes to synthesising the mixed carbonate, or with hydroxide anions, when it comes to synthesising the mixed hydroxide; b) a step of reacting the mixed carbonate or the mixed hydroxide obtained in step a) with a lithium carbonate or lithium hydroxide, whereby the aforementioned lithium lamellar oxide of formula is formed, characterised in that step a) is carried out at a predetermined pH, which pH ranges from 8 to 9.5 when the synthesis step relates to a mixed carbonate or ranges from 11 to 12.5 when the synthesis step relates to a mixed hydroxide and in that step a) is carried out at a fixed stirring speed so as to obtain a power dissipated per unit volume which is at least greater than or equal to 1000 W/m 3.