Positive electrode material of lithium ion battery and preparing method thereof

Abstract

The invention relates to a lithium titanate-carbon co-cladded lithium manganese iron phosphate positive electrode material. According to the invention, the characteristic of zero stress of a lithium titanate material is utilized for inhibition of deformation of a positive electrode during charging and discharging so as to improve cycle performance and resistance to over-charge and over-discharge of the positive electrode material, and conductivity and electrochemical properties of the positive electrode material are improved through co-cladding of the lithium titanate material and carbon; meanwhile, tap density of lithium titanate is as high as 1.68 g / cm<3>, which enables influence of carbon cladding on the tap density of the positive electrode material to be reduced. A preparation method for the positive electrode material provided by the invention is simple, is easy to operate and can easily realize industrial application.

Description

technical field [0001] The invention relates to the field of electrode material preparation, in particular, the invention relates to a lithium ion battery cathode material and a preparation method thereof. Background technique [0002] As a new type of energy storage device, lithium-ion batteries have the advantages of high working voltage, large specific energy, long cycle life, small self-discharge, wide working temperature range, good safety, no memory effect, and no pollution. Widely concerned, it has been widely used in mobile power sources for portable electronic devices and energy storage batteries for electric vehicles, and is considered to be the most promising new energy battery. [0003] The materials used to make the positive electrode of lithium-ion batteries are mainly LiCoO 2 , LiNiO 2 , LiMn 2 o 4 , nickel-cobalt-manganese ternary system and LiFePO 4 , where LiCoO 2 It has been commercialized and is currently the main cathode material for lithium-ion ba...

AI Technical Summary

Problems solved by technology

Carbon coating is an effective method to improve the electrical conductivity of materials, but due to the low tap density of carbon, carbon coating will reduce the tap density of materials while improving electrical conductivity, such as the patent of CN102364726A. In the "Method for preparing lithium iron manganese phosphate composite positive electrode materials for lithium ion batteries by carbon reduction", macromolecular organic matter is used as a carbon source, and the organic matter is decomposed into carbon and coated on the surface of lithium iron phosphate by high-temperature sintering. Although the conductivity is improved, The tap density reached 1.2g / cm 3 , but its tap density is still relatively low and needs to be further improved

[0005] In addition to carbon coating, in recent years, there have also been studies on the coating of lithium iron phosphate with metal salts or metal oxides, such as the patent of Chinese Patent Publication No. CN101859887A: "A lithium-ion battery composite positive electrode coated with transition metal phosphate In "Materials", the transition metal phosphate is used as the coating layer, which protects the lithium storage material, effectively prevents the electrolyte from dissolving and eroding the active material, and improves the cycle performance. However, compared with the uncoated material, the coated material The energy density of the material did not increase significantly, indicating that it did not play a significant role in improving the conductivity of the material.

Chinese Patent Publication No. CN102185141A patent "Modification Method for Improving High-temperature Cycle Performance and Ion Conductivity of Lithium Iron Phosphate Material" uses organic matter containing silicon, aluminum, and titanium to be mixed with lithium iron phosphate, and after a certain heat treatment, the carbon dioxide Silicon, alumina or titanium oxide is coated on the surface of lithium iron phosphate material, which improves the high-temperature cycle performance and high-rate performance of the material, but it cannot limit and reduce the deformation of the positive electrode material during charge and discharge.