Method for preparing lithium iron phosphate in batch-type high-vacuum dynamic sintering mode

Abstract

The invention discloses a method for preparing lithium iron phosphate in a batch-type high-vacuum dynamic sintering mode. The method includes: adopting a batch-type rotary furnace to heat a precursor of the lithium iron phosphate, performing sealing treatment on a furnace head and a rotary portion through a sealing pad and high-temperature-resisting vacuum fat, vacuumizing the rotary furnace during heating, and pumping oxidizing gases and steam generating in the sintering process quickly, wherein the vacuum degree is kept to be 10<2>-10<12> pa, the furnace body is rotated continuously, the heating temperature is 300-900 DEG C, the heating hour is 5-15h; stopping a vacuum pump and a pumping valve after heating is finished, leading in inert gases into the rotary furnace, and taking the product out after cooling. The prepared precursor of the lithium iron phosphate is fed into the batch-type rotary furnace for vacuum sintering, the high-vacuum state is kept by fast vacuumizing the furnace body through the multi-stage vacuum pump during the whole process, and powder materials rotate along with the furnace body to achieve the aim of dynamic sintering, so that the method for preparing lithium iron phosphate in the batch-type high-vacuum dynamic sintering mode is suitable for preparing lithium ion positive pole materials in industrial mode.

Description

technical field [0001] The invention discloses a method for preparing lithium iron phosphate, in particular a method for preparing lithium iron phosphate by intermittent high-vacuum dynamic sintering. Background technique [0002] As lithium-ion batteries are more and more widely used in people's lives, lithium-ion battery materials have also been greatly developed, especially for lithium iron phosphate battery cathode materials. Lithium iron phosphate cathode materials have a wide range of sources, cheap prices, thermal It has the advantages of good stability, environmental friendliness, no memory, etc., and its theoretical specific capacity is relatively high (170mAh / g), which can generate 3.4V (vs. Li / Li + ) voltage, it has good thermal stability and excellent charge-discharge cycle performance in the fully charged state, and the prepared battery has good safety performance. These outstanding advantages make lithium iron phosphate rapidly become the ideal developmen...

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Problems solved by technology

For example, the patent with the publication number CN102403500A discloses "a method for preparing lithium iron phosphate material in a static mixing tubular reactor": due to the use of static calcination, because of the accumulation of materials during the sintering process, it is easy to cause sandwiches, and the surface and inner layers are heated Unequal phenomenon, the oxidizing gas produced cannot be discharged in time, it is easy to oxidize the material at the dead corner of the furnace body, and the reaction time is long, the temperature rises slowly, and the product uniformity is low; and because it is sintered under an inert atmosphere, due to There are differences in gas purity and batches, which increase many uncontrollable factors

For example, the patent with the publication number CN1948134 discloses "a method for synthesizing lithium iron phosphate by vacuum carbothermal reduction method": the vacuum static sintering method is adopted, no inert gas is required, and the oxidizing gas produced can be extracted in time, but the furnace body is in a vacuum In the static sintering process, the heat conduction method is radiation heat transfer, and the heat transfer efficiency is low, which is more likely to cause uneven heating inside and outside the piled material. The temperature must be raised slowly to ensure temperature uniformity, and the cooling speed is slow and the amount of feed is small, resulting in low work efficiency

The patent with the publication number CN101186289A discloses "a process method for producing lithium iron phosphate material in a vacuum rotary kiln", which adopts a vacuum dynamic sintering method, and the material is turned by the rotation of the furnace body to improve the problem of uneven heating, and The sintering process operates under a certain vacuum state, but it adopts the method of continuous feeding and discharging, so it is impossible to maintain a high vacuum in the kiln body, and the vacuum degree in the kiln body can only be controlled at 10 -2 MPa, the oxidizing gas generated during the sintering process still cannot be discharged in time, which may easily cause some materials to be oxidized; and due to the poor sealing of the continuous rotary kiln, the air pressure in the kiln is lower than the outside world, which easily makes the outside air enter the kiln to oxidize the materials; The material is continuously fed in and out, and the furnace body is in a spiral pattern, and the material is easy to accumulate, resulting in a sintering dead angle. In the actual application process, the residence time of the material in the furnace body is inconsistent, thereby reducing the uniformity of the material.

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