Method for preparing nanometer lithium iron phosphate/carbon compound with stable low temperature performance

A technology of lithium iron phosphate and low-temperature performance, which is applied in the direction of nanotechnology, nanotechnology, nanotechnology, etc. for materials and surface science, can solve the problems of difficulty in forming uniform carbon coating, and achieve easy control of preparation conditions, The equipment and process are simple, and the effect of improving low-temperature electrochemical performance

Active Publication Date: 2012-10-31
长春劲能科技集团有限公司
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Problems solved by technology

In addition, the synthesis of LiFePO4 by the solid-state method is simple and inexpensive, and is the most ideal method for the industrialization of LiFePO4. However, the solid-phase synthesis method is used to prepare small-sized It is still difficult to obtain LiFePO4 particles, especially those below 200 nm, and it is even more difficult to form a uniform carbon coating on the surface.

Method used

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  • Method for preparing nanometer lithium iron phosphate/carbon compound with stable low temperature performance
  • Method for preparing nanometer lithium iron phosphate/carbon compound with stable low temperature performance
  • Method for preparing nanometer lithium iron phosphate/carbon compound with stable low temperature performance

Examples

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Effect test

Embodiment 1

[0025] Ferrous oxalate and lithium dihydrogen phosphate are directly mixed in the ball mill tank according to the Fe:Li:P molar ratio of 1:1:l, and 0.05 g of citric acid and 60% PVP (equivalent to the mass percentage of lithium iron phosphate) are added ), ball milled in an appropriate amount of absolute ethanol at 450 rpm / min for 20 hours, heated up in a nitrogen atmosphere after drying at a rate of 3°C / min, stayed at 350°C for 3 hours, stayed at 700°C for 8 hours, and then naturally cooling, and finally obtained nano-sized LiFePO with uniform carbon coating 4 / C complex. The particle size is 80 nm, and the discharge capacity at room temperature at 0.1 C rate can reach 160 mAh / g, at -20°C at 0.1 C rate, the discharge capacity can reach 126 mAh / g, at -20°C at 0.6C rate After 500 cycles, the discharge capacity remains above 97% of the initial capacity.

[0026] In order to reflect the role of composite carbon sources, LiFePO with a single carbon source was prepared at the same...

Embodiment 2

[0028] Ferrous oxalate, lithium carbonate, and ammonium dihydrogen phosphate are directly mixed in the ball mill tank according to the Fe:Li:P molar ratio of 1:1:l, and 0.5 g of citric acid and 10% PVP (equivalent to lithium iron phosphate mass percent), ball milled in an appropriate amount of absolute ethanol at 400 rpm / min for 15 hours, and after drying, heated up in a nitrogen atmosphere at a heating rate of 3°C / min, staying at 350°C for 3 hours, and staying at 700°C for 8 hours , followed by natural cooling, and finally obtained nano-sized LiFePO with uniform carbon coating 4 / C complex. The particle size is 140 nm, and the discharge capacity at 0.1 C rate at room temperature can reach 144 mAh / g, and the discharge capacity at 0.1 C rate at -20 °C can reach 130 mAh / g.

Embodiment 3

[0030] Ferrous oxalate, lithium carbonate, and ammonium dihydrogen phosphate are directly mixed in the ball mill tank according to the Fe:Li:P molar ratio of 1:1:l, and 0.5 g of citric acid and 30% of PVP (equivalent to lithium iron phosphate mass percent), ball milled in an appropriate amount of absolute ethanol at 400 rpm / min for 10 hours, and after drying, heated up in a nitrogen atmosphere at a heating rate of 3°C / min, stayed at 350°C for 3 hours, and stayed at 700°C for 8 hours , followed by natural cooling, and finally obtained nano-sized LiFePO with uniform carbon coating 4 / C complex. The size of the particles is 120 nm, and the discharge capacity at 0.1 C rate at room temperature can reach 131 mAh / g, and the discharge capacity at 0.1 C rate at -20 °C can reach 115 mAh / g.

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Abstract

The invention belongs to a novel energy material, and particularly relates to a method for preparing a nanometer lithium iron phosphate / carbon compound with stable low temperature performance. The method comprises the following steps of: mixing an iron source, a lithium source, a phosphorous source and a compound carbon source according to a certain proportion; performing ball milling; drying; and calcining in an inertial atmosphere to obtain a lithium iron phosphate / carbon compound, wherein the particle size is smaller than 150 nanometers; carbon is uniformly coated on the surfaces of particles; the thickness of a carbon layer is about 2 nanometers; and the compound carbon source plays an important role in controlling a material structure. After the material is assembled into a button cell, the discharging capacity is 160mAh / g at the rate of 0.1C at the room temperature, the discharging capacity is 126mAh / g at the rate of 0.1C at the temperature of 20 DEG C below zero, and the capacity conservation rate is still over 97 percent after 500 cycles at the rate of 0.6C at the temperature of 20 DEG C below zero, so that the problem of unstable low temperature performance of a lithium ion battery is solved. The method has the advantages of low cost, simple production process and high safety, and the prepared compound can be applied to the field of portable equipment, power electric vehicles and the like.

Description

technical field [0001] The invention belongs to the technical field of new energy materials, and particularly relates to a nano-sized lithium iron phosphate / carbon composite with excellent long-term cycle performance at low temperature (the capacity is almost no attenuation after charging and discharging for more than 500 times), and the surface is coated with uniform carbon. method of preparation. Background technique [0002] As the global energy and environmental problems are becoming more and more severe, lithium-ion batteries are considered to be one of the most ideal energy sources, and can be widely used in civilian small electrical appliances, electric vehicles and other fields. Lithium-ion battery is a new type of battery developed on the basis of lithium battery, and its research began in the 1980s. In 1980, the Goodenough group first proposed layered LiCoO 2 As a cathode material, it marks the birth of lithium-ion batteries. In 1982, Agarwal and Selman of the I...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01M4/58H01M4/62B82Y30/00
CPCY02E60/12Y02E60/10
Inventor 张景萍孙海珠黄国龙李微
Owner 长春劲能科技集团有限公司
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