A method of preparing a cathode material for a lithium-ion battery cell, comprising the steps of: 1) dissolving a combination of at least three of a salt of nickel, a salt of manganese, a salt of cobalt, and a salt of aluminium in water to obtain a first solution, wherein a total molar concentration of the metal elements in the first solution is from 0.1 mol/L to 3 mol/L; 2) dissolving a precipitating agent in water to form a second solution, wherein a concentration of the precipitating agent in the second solution is from 0.5 mol/L to: 6 mol/L; 3) pre-heating the first solution and the second solution to the same temperature from 30°C to 80 °C to obtain a pre-heated first solution and a pre-heated second solution respectively; 4) feeding the pre-heated first solution and the pre-heated second solution to a first inlet and a second inlet of a static mixer respectively to obtain a co-precipitating solution; 5) filtering a suspension eluted from an outlet of the static mixer to obtain a cathode material precursor, wherein the outlet of the static mixer is coupled to a pH controller for controlling the flow rate of the pre-heated first and second solutions; 6) washing the cathode material precursor with water; 7) drying the cathode material precursor at a temperature from 60 °C to 105 °C for a time period from 4 hours to 24 hours to obtain a dried cathode material precursor; 8) mixing the dried cathode material precursor with one or more lithium salts to obtain a solid mixture, wherein a molar ratio of the metal element lithium of the one or more lithium salts to the total amount of the metal elements selected from a combination of at least three of nickel, manganese, cobalt, and aluminium is from 1.5:1 to: 1:1, or from 1.03:1 to 1:1; and 9) calcinating the solid mixture in two stages to obtain the cathode material, wherein the first stage is conducted at a temperature from t 350 °C to 550 °C for a time period from: 2 hours to: 10 hours, and the second stage is conducted at a temperature from 750 °C to: 950 °C for a time period from: 6 hours to 15 hours, and wherein the cathode material comprises a lithium multi-metal composite oxide represented by xLi 2 MnO 3 •(1-x)LiNi a Mn b Co c Al( 1-a-b-c) O 2, wherein 0≤a<1, 0≤b<1, 0≤c<1, a+b+c≤1, and 0≤x<1; and the cathode material has a D90/D10 ratio from: 1.4 to 1.9. 1) dissolving a combination of at least three of a salt of nickel, a salt of manganese, a salt of cobalt, and a salt of aluminium in water to obtain a first solution, wherein a total molar concentration of the metal elements in the first solution is from 0.1 mol/L to 3 mol/L; 2) dissolving a precipitating agent in water to form a second solution, wherein a concentration of the precipitating agent in the second solution is from 0.5 mol/L to: 6 mol/L; 3) pre-heating the first solution and the second solution to the same temperature from 30°C to 80 °C to obtain a pre-heated first solution and a pre-heated second solution respectively; 4) feeding the pre-heated first solution and the pre-heated second solution to a first inlet and a second inlet of a static mixer respectively to obtain a co-precipitating solution; 5) filtering a suspension eluted from an outlet of the static mixer to obtain a cathode material precursor, wherein the outlet of the static mixer is coupled to a pH controller for controlling the flow rate of the pre-heated first and second solutions; 6) washing the cathode material precursor with water; 7) drying the cathode material precursor at a temperature from 60 °C to 105 °C for a time period from 4 hours to 24 hours to obtain a dried cathode material precursor; 8) mixing the dried cathode material precursor with one or more lithium salts to obtain a solid mixture, wherein a molar ratio of the metal element lithium of the one or more lithium salts to the total amount of the metal elements selected from a combination of at least three of nickel, manganese, cobalt, and aluminium is from 1.5:1 to: 1:1, or from 1.03:1 to 1:1; and 9) calcinating the solid mixture in two stages to obtain the cathode material, wherein the first stage is conducted at a temperature from t 350 °C to 550 °C for a time period from: 2 hours to: 10 hours, and the second stage is conducted at a temperature from 750 °C to: 950 °C for a time period from: 6 hours to 15 hours, and wherein the cathode material comprises a lithium multi-metal composite oxide represented by xLi 2 MnO 3 •(1-x)LiNi a Mn b Co c Al( 1-a-b-c) O 2, wherein 0≤a<1, 0≤b<1, 0≤c<1, a+b+c≤1, and 0≤x<1; and the cathode material has a D90/D10 ratio from: 1.4 to 1.9.