Doped and surface coating co-modified anode material for lithium ion battery and preparation method thereof

Abstract

The invention discloses a doped and surface coating co-modified anode material for a lithium ion battery and a preparation method thereof. The anode material uses doped lithium cobalt oxide as a matrix, the surface of which is coated with Co3(PO4)2, AlPO4, Mn3(PO4)2, FePO4, Ni3(PO4)2, Mg3(PO4)2 and other phosphates, therefore, the electric conductivity, the circulating performance, the high temperature and high pressure resistance and other performances are improved. The preparation method has the advantages that the coating material is uniformly coated on the surface of the anode material to be beneficial to improving the electrochemical performance; the method is simple to operate, is green and environment-friendly and has industrial applicability.

Description

technical field [0001] The invention relates to the field of materials, in particular to a lithium ion battery positive electrode material co-modified by doping and surface coating and a method for doping and surface coating of the lithium ion battery positive electrode material. Background technique [0002] Currently, lithium-ion batteries are widely used in electronic equipment, mobile phones and electric vehicles. With the continuous improvement of people's requirements for equipment performance, higher requirements are also put forward for the energy density of lithium-ion batteries. However, when a Li-ion battery is charged to 4.2V, LiCoO 2 Lithium ions in Li are extracted to form Li 1-x CoO 2 (0≤x≤0.5), when the charging voltage increases above 4.4V, LiCoO 2 There will be more lithium ions out, resulting in LiCoO 2 The transformation from the hexagonal system to the monoclinic system no longer has the function of reversible intercalation and extraction of lithium...

AI Technical Summary

Problems solved by technology

However, when a Li-ion battery is charged to 4.2V, LiCoO 2 Lithium ions in Li are extracted to form Li 1-x CoO 2 (0≤x≤0.5), when the charging voltage increases above 4.4V, LiCoO 2 There will be more lithium ions out, resulting in LiCoO 2 The transformation from the hexagonal system to the monoclinic system no longer has the function of reversible intercalation and extraction of lithium ions; at the same time, this process is accompanied by the dissolution of cobalt in the electrolyte. Therefore, the actual lithium cobaltate lithium ion battery cathode material Capacity (150mAh·g -1 ) is much lower than its theoretical capacity (274mAh·g -1 )

[0003] In order to improve lithium cobalt oxide LiCoO 2 Cyclic stability at high voltage can be modified by doping or surface coating, such as Chinese patent CN201210461299.1 using a sol-gel method to prepare a surface-coated Al 2 o 3 -AlPO 4 Lithium cobalt oxide, this method only coats the positive electrode material of the lithium ion battery, but does not do doping and modification to the positive electrode material itself. Above, between 45°C and 3-4.5V, the charge-discharge cycle test was carried out at 0.7C / 0.7C. After 100 cycles, the capacity retention rate was 95%, but it did not study the electrochemical performance of the voltage above 4.6V. ; Jaephil Cho's research group (Control of AlPO 4 -nanoparticle coating on LiCoO 2 by using water or ethanol; Electrochimica Acta50 (2005) 4182-4187) discloses a method for coating the positive electrode material of lithium cobalt oxide with aluminum phosphate, and this method also only coats the positive electrode material with aluminum phosphate, but does not carry out the process on the positive electrode material itself. modified, and no other coating material was used to coat the positive electrode material, and it did not study the electrochemical performance of the prepared positive electrode material at a voltage above 4.6V; another example is Chinese patent CN102583585A, which discloses a The preparation process of spherical lithium cobaltate doped with Ti, Mg and Al, which adds any one of Ti, Mg or Al to lithium cobaltate to improve the anti-overcharge performance of lithium cobaltate, and its high-voltage cycle The performance has not been studied; and for example, Chinese patent CN102347470A discloses a lithium cobalt oxide composite material particle and its preparation method. The positive electrode material used is lithium cobalt oxide and doped lithium cobalt oxide, and the coating material is aluminum phosphate, but The preparation method or source of the doped lithium cobaltate used is not disclosed, nor is the positive electrode material coated with other coating materials

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