Lithium ion phosphate positive electrode material of nanometer core shell structure and preparation method thereof

Abstract

The invention discloses a lithium ion phosphate positive electrode material of a nanometer core shell structure. The positive electrode material is provided with an inner core active material and a conductive outer shell structure; a conductive agent is an outer shell material; the active material is of an inner core structure; and the structure formula of the inner core active material is LiFe[1-x]MxP[1-y]AyO4, wherein x is greater than or equal to 0, y is less than or equal to 0.1, M is a transition metal element, and A is silicon. Additionally, the invention also discloses a preparation method of the lithium ion phosphate positive electrode material. According to the preparation method in the invention, a porous material is adopted as a synthesis microreactor, and a lithium ion phosphate precursor is loaded and filled in holes, namely, the inner core active precursor reversely wraps a porous precursor so as to form a special nanometer core shell structure, thus the topography granularity of primary granule is controlled; and the lithium ion phosphate positive electrode material of the nanometer core shell structure is prepared by adopting a liquid phase mixed material and solid phase sintering technology. According to the invention, on the premise that the electrical performance of the positive electrode material is not influenced, a nanometer core shell structured active substance with uniform and controllable topography and granularity is synthesized; and the preparation method disclosed by the invention has lower technology, devices and control costs, which is beneficial to large-scale production.

Description

technical field [0001] The invention relates to a lithium ion secondary battery positive electrode material, which is used in the field of energy materials; in particular, it relates to a lithium iron phosphate positive electrode material with a nano-core-shell structure with controllable morphology and particle size; in addition, the invention also relates to the preparation of a porous material The invention relates to a lithium iron phosphate cathode material with a nano core-shell structure. Background technique [0002] The lithium iron phosphate material has outstanding characteristics such as environmental protection, excellent cycle performance and safety performance; the electrical conductivity of the lithium iron phosphate material after carbon coating, nanometerization, and ion doping modification is greatly improved [WO2007 / 0649934A2; CN101636861A; CN100517817C] , so that the stability and life of high-rate discharge are much higher than traditional mature lithiu...

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Problems solved by technology

[0003] However, lithium iron phosphate also has obvious deficiencies. The low theoretical density leads to a reduction in the tap density of the powder and the compaction density during powder processing, especially carbon coating and nanonization will lead to powder agglomeration and material Inhomogeneity and other problems reduce the processing and use effect of powder again; at the same time, the large-scale production of powder is also more difficult due to the problem of primary particle shape and particle size control, and faces the substantive problem of unstable product batches

[0004] For the stable control of the morphology and particle size of lithium iron phosphate particles, researchers usually use methods such as controlling the morphology and particle size of the precursor mixture, strengthening the mixing and grinding conditions of the precursor (such as multi-stage pulverization of powder), and optimizing the sintering system; using these method, the secondary morphology of the powder can be better controlled, but because it is difficult to ensure the stability of the primary particle and its polymerization state, it has little effect on the stability of the batch of products produced on a large scale [WO03 / 088383A1; CN1547273A; CN101150191A ], and will significantly increase the energy consumption cost of the preparation process; while using methods such as hydrothermal synthesis and liquid phase precipitation [CN101159328A; CN101327922A], the primary morphology is stable and controllable, but it is difficult to scale production, and the cost of equipment and process control are higher

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