Secondary sintering synthesis method for lithium iron phosphate

Abstract

The invention discloses a secondary sintering synthesis method for lithium iron phosphate, which comprises the following process steps of: 1, preparing materials in a molar ratio of lithium to iron to phosphorus element of (0.98-1.02): 1: 1, and mixing the materials uniformly; 2, heating the obtained mixture to between 350 and 550 DEG C, preserving the heat for 5 to 15 hours, then cooling the mixture along with a furnace to room temperature, and crushing the obtained material to obtain lithium iron phosphate powder; 3, mixing the obtained lithium iron phosphate powder, a carbon source and a solvent uniformly, drying the mixture and then heating the mixture to between 650 and 850 DEG C, preserving the heat for 10 to 20 hours, then cooling the mixture along with the furnace to room temperature, and crushing, screening and grading the mixture to obtain a screened product which is a lithium iron phosphate product produced by the method. The method is simple; the operation is convenient; the prepared lithium iron phosphate has high electric conductivity, good storage performance, good low-temperature performance and good batch consistency; and the method greatly improves the electric conductivity, low-temperature performance, storage performance and batch stability of the lithium iron phosphate. The method is suitable for industrialized production and can replace the conventional one-time high temperature sintering process.

Description

technical field [0001] The invention discloses a preparation method of lithium iron phosphate, a positive electrode material of a lithium ion power battery, in particular to a secondary sintering synthesis method of lithium iron phosphate, which belongs to the interdisciplinary technical field of electrochemistry, materials science and physics. Background technique [0002] Lithium-ion battery is a universal rechargeable battery, which is the latest generation of secondary battery products that emerged in the early 1990s, and there is no foreseeable alternative at present. Lithium-ion batteries have the advantages of high single-unit operating voltage, large mass and volume specific energy, small self-discharge, no memory effect, and long cycle life. Power tools, model aircraft and other portable electrical fields, and are gradually applied in large power fields, such as electric vehicles, mopeds, hybrid (pure) power vehicles, uninterruptible power supplies, large-scale comm...

AI Technical Summary

Problems solved by technology

The four methods have their own advantages. The first method has a simple process and is convenient for industrialization, but the synthesized lithium iron phosphate has poor processing performance and poor consistency; the second method has a simple process and the synthesized lithium iron phosphate The physical indicators are outstanding, the processing performance is good, but the rate performance is not ideal, and the consistency problem is poor; the third method is relatively simple, and the synthesized lithium iron phosphate has outstanding physical indicators and good rate performance, but it is difficult to solve the problem of lithium iron phosphate The problem of poor consistency of synthesis; the fourth method is complex in process, and the performance of the synthesized lithium iron phosphate is good, but there is also the problem of poor consistency

Moreover, the lithium iron phosphate prepared by the above four methods has a common defect, that is, the storage performance is poor, because the storage performance is closely related to the impurity phase in the lithium iron phosphate, and the high-temperature sintering synthesis cannot avoid producing more impurity phases , and these heterogeneous substances can interact with the electrolyte when the battery is in use, and the formed metal ions are easy to precipitate on the negative electrode, resulting in lithium intercalation, thus affecting the cycle performance of the battery

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