CN101696001B - Method for synthesizing lithium ferrous phosphate in solution - Google Patents

Abstract

The invention discloses a method for synthesizing lithium ferrous phosphate in a solution, which relates to an anode material of a lithium ion battery, and the method belongs to the technical field of chemical material preparation. The method comprises the following steps: reacting phosphoric acid, iron trioxide with reduced iron powder at a certain temperature, adding a lithium source and a carbon source, continuing the reaction to obtain a mixing solution, and filtering, drying and calcining the mixing solution to obtain the lithium ferrous phosphate. Compared with a synthetic method of using the reduced iron powder as an iron source, the method adopts the iron trioxide as most of iron sources so as to reduce the cost of raw materials greatly; the obtained product is uniform in component and good in batch stability, and the synthesized lithium ferrous phosphate material serving as the anode material of the lithium ion battery has the excellent electrochemistry performance; 3C multiplying power discharging specific capacity is more than 130mAh/g at room temperature; the synthesized lithium ferrous phosphate material is suitable for being used as power lithium ion batteries; and the method has short sintering period, simple production process, less energy consumption and no pollution, such as tail gas and waste liquor, and is suitable for mass industrial production.

Description

The method of synthesizing lithium ferrous phosphate in a kind of solution

Technical field

The invention belongs to technical field of chemical material preparation, particularly the method for synthesizing lithium ferrous phosphate in a kind of solution of lithium ferrous phosphate as anode material of lithium ion battery (LFP).

Background technology

LiFePO 4 is a kind of emerging anode material for lithium-ion batteries, has Stability Analysis of Structures, safety performance is good; Aboundresources, with low cost; Good cycle; The overcharging resisting performance is good, helps the advantage that battery combination is used.The ferrous phosphate lithium dynamical battery has following characteristics.High-level efficiency output: the standard discharge is 2～5C, and continuous high current discharge can reach 10C, and momentary pulse discharge (10S) can reach 20C; High-temperature behavior is good: internal temperature is then up to 95 ℃ during 65 ℃ of outside temperatures, and temperature can reach 160 ℃, the structural safety of battery, intact when battery discharge finished; Even inside battery or outside come to harm, battery does not burn, does not explode, security is good; Good cycle life, through 500 circulations, its loading capacity is still greater than 95%; Overdischarge does not have damage to zero volt yet.

Ferrous phosphate lithium battery has vast market prospect.Can be applied to: the energy storage device of sun power, wind generator system; Uninterrupted electric system UPS; Superpower power tool (wireless); Electric drill, weeder etc.; Light-weight electric vehicle: electriclocomotive, electric bicycle, recreation vehicle, golf cart, electric lift truck, cleaning cart; Hybrid vehicle (HEV).

Produce LiFePO 4 at present and mainly contain high temperature solid-state method, carbothermic method, hydrothermal synthesis method and liquid-phase precipitation method, main relative merits are following:

High temperature solid-state method: simple, the easy realization industrialization of technology; But the particle diameter pattern is not good, consumes energy.

Carbothermic method: production process is the simplest, only needs a step sintering; But capacity, the high rate performance aspect is on the low side.

Hydrothermal synthesis method: synthesis temperature is low, the time is short, and the crystal grain thing is excellent mutually; But need high temperature high voltage resistant equipment, be difficult to industriallization.

Liquid-phase precipitation method low temperature synthesizes, is uniformly dispersed, good cycling stability.But liquid phase control condition is harsh.

Present method is to utilize water, by chemical reaction the iron in the raw material, lithium extracted, grappling phosphate radical, surperficial coated with conductive material, the wet method of nanometer, micron compound mixture prepares process.Compare with other method, iron, lithium reclaim the degree height, and good conductivity helps environment protection, and production process is prone to realize serialization and robotization.

Summary of the invention

The method that the purpose of this invention is to provide synthesizing lithium ferrous phosphate in a kind of solution; It is characterized in that; Adopt phosphoric acid as phosphorus source, red oxide of iron as main source of iron, reduced iron powder as the basic cpd of reductive agent and part source of iron, lithium as the lithium source, water soluble organic substance is settled out LiFePO 4 as carbon source; Through dry, roasting and nano level ferrous phosphate powder for lithium, concrete steps are following:

1) N ₂Protection down (1～10L/mim), phosphoric acid, the red oxide of iron of concentration 0.1mol mixed in 20～70 ℃ stir 1～4h, reduced iron powder continues reaction 1～8h;

2) basic cpd of adding lithium and water soluble organic substance are in 20～90 ℃ of precipitin reaction 1～8h;

3) reaction soln is cooled to room temperature, at room temperature goes out the LiFePO 4 wet feed, capable again vacuum-drying or spraying drying with vacuum filtration, belt filtration or centrifuging.

4) (1～10L/mim), 110～200 ℃ are heated 1～3h in the tube furnace, and 500～800 ℃ of sintering 1～8h obtain the ferrous phosphate crystalline lithium down in the N2 protection.

Phosphoric acid in the said step 1): red oxide of iron: the mol ratio of reduced iron powder=(3～3.1): 1: (1～1.05).

Said water soluble organic substance is one or more in sugar, glucose, starch, vitamins C, polyoxyethylene glycol, epoxy resin, unsaturated polyester, resol and the vinyl resin.

Said step 2) add-on of water soluble organic substance in, should make the carbon content in the LiFePO 4 powder body material is 2～10wt%.

Said vacuum-drying is in 110～150 ℃ of drying 2～12h in the vacuum drying oven.

Said spraying drying is: after the LiFePO 4 mixing solutions is added to the spraying gun with working at high speed runner; Mixing solutions becomes LiFePO 4 nano-micrometre compound solid-liquid mixture; Atomizing LiFePO 4 particle is directed to kiln (in 50 ~ 150C); Warm air evaporates the liquid in the particulate, and LiFePO 4 is collected in the container through separator.

The invention has the beneficial effects as follows and compare existing Wet technique, the present invention has following advantage:

(1) makes main raw material with the iron oxide red of cheapness, make expensive reduced iron powder reduce 2/3rds, not only reduced production cost, and avoided the easy oxidation of ferrous iron to generate the impurity that is difficult to remove and cause product impure;

(2) in the LiFePO 4 that makes, the distributing very evenly of iron, phosphorus, lithium atom;

(3) sintering period short, production technique is simple, power consumption is few, pollutions such as emission-free, waste liquid are fit to large batch of suitability for industrialized production;

(4) spray-drying process can be avoided segregation in the composition drying process at the wink-dry slurry, and the products obtained therefrom composition is even, in batches good stability;

(5) the even carbon dope in granule interior crystallite surface, the ion of material and electron conduction are all high; And be prone to realize metal ion mixing.

(6) the synthetic ferrousphosphate lithium material has good electrochemical as anode material for lithium-ion batteries, and at room temperature 3C multiplying power discharging specific storage is suitable as power property anode material for lithium-ion batteries greater than 130mAh/g.

Description of drawings

Fig. 1 is the XRD curve of the prepared LiFePO 4 of embodiment one.

Embodiment

Below in conjunction with embodiment technical scheme of the present invention is further specified, following examples do not produce restriction to the present invention.

Embodiment

1) under the N2 of 1～10L/mim protection, 0.1mol phosphoric acid, red oxide of iron are mixed stirring 1h in 70 ℃; Add reduced iron powder reaction 4h again; Phosphoric acid wherein: red oxide of iron: the mol ratio of reduced iron powder=3.05: 1: 1.03.

2) N2 protection adds in concentration is the lithium hydroxide solution of 0.1mol that to make the carbon content in the LiFePO 4 powder body material be the resol of 5wt% down; In 90 ℃ of reaction 4h;

3) reaction soln is cooled to room temperature, vacuum filtration obtains the LiFePO 4 wet feed, again 120 ℃ of dry 12h in vacuum drying oven;

4) under the N2 of 1～10L/mim protection, 200 ℃ of heating 3h in the tube furnace, 700 ℃ of sintering 4h obtain the ferrous phosphate powder for lithium.

Claims (1)

1. the method for synthesizing lithium ferrous phosphate in the solution is characterized in that concrete steps are following:

1) at the N of 1～10L/mim ₂Protection mixes stirring 1h with 0.1mol phosphoric acid, red oxide of iron in 70 ℃ down; Add reduced iron powder reaction 4h again; Phosphoric acid wherein: red oxide of iron: the mol ratio of reduced iron powder=3.05: 1: 1.03;

2) N ₂Protection down adds in concentration is the lithium hydroxide solution of 0.1mol that to make the carbon content in the LiFePO 4 powder body material be the resol of 5wt%; In 90 ℃ of reaction 4h;

3) reaction soln is cooled to room temperature, vacuum filtration obtains the LiFePO 4 wet feed, again 120 ℃ of dry 12h in vacuum drying oven;

4) at the N of 1～10L/mim ₂Under the protection, 200 ℃ of heating 3h in the tube furnace, 700 ℃ of sintering 4h obtain the ferrous phosphate powder for lithium.

Images