Abstract: The present invention provides a method for preparing a composite negative electrode material for a lithium ion battery. The method uses the p-toluenesulfonamide modified fatty acid as the carbon source, and uses the nitrogen and sulfur element as dopant. The nitrogen/sulfur doped graphitized ordered mesoporous carbon material is prepared after high temperature carbonization, annealing and strong alkali treatment. The nano silicon powder coated with the nitrogen and sulfur doped mesoporous graphite material. The nitrogen and sulfur doped mesoporous graphite material can prevent the silicon from directly contacting the electrolyte, effectively alleviate the large volume expansion of silicon during charge and discharge, maintain the stability of the material structure, prevent the continuous formation of the SEI film, and improve the first discharge efficiency.

Abstract: The present application provides a method for modifying lithium iron phosphate. According to the method for modifying lithium iron phosphate of the present application, lithium iron phosphate is modified by using a graphite oxide and a honeycomb carbon material with large specific area and big pore size, wherein, the graphite oxide is obtained by oxidizing graphite with concentrated nitric acid and concentrated phosphoric acid, the honeycomb carbon material is obtained by adjusting the temperature of a mixture consisting of lithium carbonate, sodium carbonate and potassium carbonate, injecting CO2, and controlling the current density of the electricity for electrolysis. The method for modifying lithium iron phosphate could improve the conductivity of lithium iron phosphate, shorten the migration path and increase the migration rate of lithium ions. The present application also provides a positive electrode using the modified lithium iron phosphate and a lithium ion battery including the positive electrode.

Abstract: A lithium iron phosphate power battery includes: a battery case; a battery cell in the battery case, including: a positive plate including a positive current collector and a positive active material formed thereon, the positive active material including lithium iron phosphate having a primary particle diameter of no more than 200 nm and a D50 of no more than 3 ?m, a mass content of the lithium iron phosphate in the positive active material being 93-96%, a solid content of the positive active material being 50-65%; a negative plate including a negative current collector and a negative active material formed thereon, the negative active material including a graphite having a D50 of 10-15 ?m, a mass content of the graphite in the negative active material being 92-95%, a solid content of the negative active material being 50-65%; a separator between the positive plate and the negative plate; and an electrolyte.