Doped modified lithium iron phosphate and preparation method thereof

Abstract

The invention discloses a raw material formula of doped modified lithium iron phosphate. Components include a ferric iron source, a phosphorus source, a lithium source, a doped element compound and excess carbon sources, wherein the mole ratio of to ferric iron source to the phosphorus source to the lithium source to the doped element compound to the carbon sources is 1:1-1.05:1-1.1:0.01-0.05:0.1-0.2. A preparation method directly adopts the ferric iron source, so that a cockamamie step of synthesizing ferrous salt by means of other synthesizing technologies is avoided, and the problem that usual products produced by means of conventional preparation methods using a ferrous salt raw material oxidizable in the air are impure is solved. A synthesized doped modified lithium iron phosphate material is small in particle diameter, narrow in distribution, high in purity, large in compaction and excellent in electrochemistry performance. A synthesized positive pole material and a carbon negative pole are assembled to form a test battery, the specific capacity is more than 130mAh / g when discharging is performed in 1C multiplying power, and excellent circulating stability performance is displayed.

Description

technical field [0001] The invention relates to a raw material formula for preparing lithium ferrous phosphate and a preparation method thereof, belonging to the field of lithium battery electrode materials. Background technique [0002] As we all know, compared with other mainstream cathode materials, Lithium Ferrous Phosphate has the disadvantage of weak conductivity, which will directly lead to the hindering of lithium ion intercalation and movement in the system under charge and discharge of the battery based on this material, and the active material The utilization rate is low, and for the industry to devote itself to the research of lithium iron phosphate for power batteries, it is a very important and difficult lesson to improve its high-current discharge. Therefore, the improvement method in the industry is mainly in the material synthesis process. Add a conductive agent to the battery, or use the method of particle coating to coat the conductive substance on the sur...

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Problems solved by technology

[0002] As we all know, compared with other mainstream cathode materials, Lithium Ferrous Phosphate has the disadvantage of weak electrical conductivity, which will directly lead to the poor performance of batteries based on this material under charge and discharge. The deintercalation and movement of lithium ions in the system are hindered, and the utilization rate of active materials is low. For the research of lithium iron phosphate lithium iron phosphate in power batteries, it is very important and difficult to improve its high-current discharge. Therefore, the improvement methods in the industry are mainly to add conductive agents during the material synthesis process, or to use particle coating methods to coat conductive substances on the surface of lithium iron phosphate particles in the later stage, so that the materials have relatively good Conductivity, when the battery is made, a certain amount of conductive agent is also added according to the ratio

The current technology suffers from the following disadvantages, which hinder its practical application:

[0003] (1) Fe2+ in the synthesis is easily oxidized to Fe3+, and it is not easy to obtain single-phase LiFePO4;

[0004] (2) Diffusion of lithium ions in LiFePO4 is difficult, resulting in low utilization of active materials;

[0005] (3) The conductivity of LiFePO4 itself is also very low, resulting in poor high-current discharge performance;

[0006] (4) In the process of material application, due to the error caused by multiple conductive agent additions, the final battery performance is uneven, which reduces the consistency of the product

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