Positive pole lithium iron phosphate/carbon composite material for low-temperature battery and preparation method of composite material

Abstract

The invention discloses a preparation method of a positive pole lithium iron phosphate / carbon composite material for a low-temperature battery. The preparation method comprises the following steps: by adopting a ferrous compound as a raw material, and weighing the ferrous compound, a lithium compound and a phosphorus compound according to the mole ratio of Fe:Li:P=(0.98-1):(1-1.02):1; respectively dissolving or dispersing in deionized water; adding to a liquid-phase reducing agent with moderate volume according to a certain sequence; carrying out reflux reaction at specific temperature; carrying out solid-liquid separation to obtain lithium iron phosphate precursor; then calcining under the protection of inert gas to prepare the LiFePO4 / C composite positive pole material. Compared with other methods, the preparation method disclosed by the invention has the advantages of simple process equipment, moderation in condition, completeness in precursor crystallization, great shortening of high-temperature calcination time, great reduction of energy consumption, fine lithium iron phosphate particle diameter and more excellent normal-temperature discharge property and low-temperature charge-discharge property.

Description

technical field [0001] The invention relates to the field of cathode materials for lithium ion batteries, in particular to a method for preparing a cathode material lithium iron phosphate / carbon composite material for low-temperature lithium ion batteries. technical background [0002] With the emergence of new materials and improvements in battery design technology, the application range of lithium-ion batteries continues to expand. The civilian field has expanded from the information industry to energy transportation. In the field of national defense and military affairs, lithium-ion batteries cover many arms such as land, sea, air, and space. Among them, when military equipment needs to work in cold regions (such as below -40°C), the low-temperature electrochemical performance of lithium-ion batteries is extremely high. However, the charge-discharge performance of lithium-ion batteries in low-temperature environments below -20°C decays significantly. , greatly restricti...

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Problems solved by technology

The general steps of the mechanical method are to mix the basic raw materials and perform high-energy ball milling once or twice to increase the reaction area and then perform long-term calcination, as described in patent application numbers 201210155024.5 and 201310504706.7. The disadvantage is that a large amount of grinding equipment is required and can consumes a lot

The commonly used liquid-phase synthesis method is hydrothermal or solvothermal synthesis. As described in the authorized announcement number CN100454615C, this method not only needs to be carried out in high-pressure reaction equipment, but also has high requirements for reaction equipment, and the yield is low, which increases cost pressure. , the prepared uniformly dispersed lithium iron phosphate nanocrystals with an average particle size of 200-500nm have poor low-temperature discharge performance

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