CN103086343A

CN103086343A - Method for synthesizing lithium iron phosphate by liquid solid reduction

Info

Publication number: CN103086343A
Application number: CN2011103495074A
Authority: CN
Inventors: 赵显坤
Original assignee: HUBEI MINGSHEN LITHIUM TECHNOLOGY Co Ltd
Current assignee: HUBEI MINGSHEN LITHIUM TECHNOLOGY Co Ltd
Priority date: 2011-11-07
Filing date: 2011-11-07
Publication date: 2013-05-08
Anticipated expiration: 2031-11-07
Also published as: CN103086343B

Abstract

The invention provides a method for synthesizing lithium iron phosphate by liquid solid reduction; a lithium iron phosphate mixture is directly synthesized at a liquid solid phase; the lithium iron phosphate mixture is fully mixed with carbon black and metal powder, and is put into a calciner for drying, dehydration, ball milling and calcination under the protection of nitrogen and argon; the obtained lithium iron phosphate has good electrochemical properties and uniform particle size distribution, has a specific surface area of 16-28 m2/g, an average particle size of 2-6 microns, and product purity of up to more than 99%, and effectively improves the electronic conductivity and quality stability of a lithium iron phosphate anode material. Safety hidden trouble in the anode material synthesis is prevented; the invention has the effect of combination of the solid phase method with the liquid phase method, which enhances advantages and avoids disadvantages. Technical problems of instable quality, environment pollution, and high production cost for routine lithium iron phosphate preparation are solved fully and effectively. The method of the invention has the advantages of easily selected raw materials, low cost, short synthesis time, easy operation, stable control, no pollution, no public nuisance, and the like.

Description

The method of liquid-solid reduction synthesizing lithium ferrous phosphate

Technical field

The present invention relates to a kind of synthetic method of LiFePO 4, is a kind of method of liquid-solid reduction synthesis of anode material of lithium-ion battery LiFePO 4 specifically.

Background technology

Under the drive of information industry and electronic industry fast development, China has become second-biggest-in-the-world lithium ion battery production base.LiFePO 4 is as the positive electrode material of novel energy lithium ion battery, due to its special performance, is the environmental protection positive electrode material by universally acknowledged, and industry development is rapid abroad.Domestic developed in the last few years.Yet LiFePO 4 is in routine is produced, and because quality is unstable, production environment is poor, pollutes, and production cost is high, has become the production bottleneck of this industry, has limited the development of this industry.

The synthetic method of LiFePO 4 mainly is divided at present: solid phase method, hydrothermal method, liquid phase method, carbothermic method etc.Its solid phase synthesis process, the most ripe due to the easy easy operation of method.But because the method is too easy, starting material are limited by acquisition price and quality, and the impact of type selecting and technique, and cause the LiFePO 4 cost that synthesizes high, the unstable and environmental pollution of quality.

Summary of the invention

The object of the invention is to overcome the above-mentioned deficiency of prior art, provide a kind of raw material easily to select, cost is low, generated time is short, control is stable, the method for free of contamination liquid-solid reduction synthesizing lithium ferrous phosphate.

The technical solution used in the present invention is to comprise the following steps: 1. lime is formulated as 2-4mo1/l milk of lime; Get 20-60%H ₃PO ₄Solution stirs at normal temperatures and pressures, adds the Ca (OH) by formula weight ₂: H ₃PO ₄=1: the described lime slurry neutralization of 1.5-2.5mol is to pH:2.5-4.5, after reaction, separates, dry that purity be the Ca (H of 99.8-99.95% ₂PO ₄) ₂H ₂O。

Step of the present invention 1. in after reaction, isolated wet basis material is dry under 50-60 ℃, after drying 99.8-99.95%Ca (H ₂PO ₄) ₂H ₂O。

2. get the Ca (H that 1. step obtains ₂PO ₄) ₂H ₂O is formulated as 0.05-0.2moL/L solution, stirs under normal pressure, heats to 40-70 ℃, and adding content is 85%H ₃PO ₄To acidolysis.Add the 0.1-0.4% reductive agent of acidolysis solution weight in solution after acidolysis and by formula weight than Fe: Ca=1.0-1.3: 1moL adds ferrous salt solution, ferrous salt solution concentration is 0.2-0.7moL/L, reacts 2-4 hour, through cooling, isolate precipitation, get ferrophosphorus solution.

3. with ferrophosphorus solution under agitation, add carbon black and brown iron oxide, carbon black: be the 0.09-0.16% of ferrophosphorus solution weight, the feed ratio of brown iron oxide is Fe: P=1.0-1.1: 1moL, and be warming up to 40-70 ℃, and add the lithium hydroxide solution of 1.5-3.5moL/L, control Fe: Li=1.0-1.1: 1moL to PH:6-8, reaction 1-3h is through separating, make the LiFePO 4 mixture.

4. getting the LiFePO 4 mixture, is under 300-800 ℃ in temperature, and then drying, dehydration, ball milling are calcined under nitrogen or argon shield, 4-12 hour, obtains purity and reaches LiFePO 4 more than 99%.

Reductive agent of the present invention is SnCL ₂, vitamins C, glucose or sucrose.

The present invention adopts liquid-solid reduction method synthesizing lithium ferrous phosphate, has solid phase method and liquid phase method unites two into one, and poplar is long keeps away short effect.The quality that has fully effectively solved in conventional preparation LiFePO 4 is unstable, contaminate environment, the technical problem that production cost is too high.Have the advantages such as raw material is easily selected, popular, cost is low, generated time is short, easy to operate, it is stable, pollution-free, nuisanceless to control, loopful guarantor.

The battery anode material lithium iron phosphate chemical property of the present invention preparation is good, steady quality, size distribution are even, median size: 2-6um, specific surface area: 16-28m ²/ g.Effectively improve electron conduction and the quality stability of ferrous phosphate doping lithium anode material, avoided the potential safety hazard of prior art in LiFePO 4 is synthetic.

Battery anode material lithium iron phosphate performance, the cost compare data of the battery anode material lithium iron phosphate of the present invention's preparation and prior art preparation see Table 1.The battery anode material lithium iron phosphate technical indicator of the present invention's preparation detects data and sees Table 2.

Table 1

Table 2

Embodiment

Embodiment 1

1. get 40%H ₃PO ₄Solution, 970g stirs at normal temperatures and pressures, adds 2moL/L milk of lime, is neutralized to PH:2.5-4.5, and reaction 45min isolates the wet basis material dry under 50-60 ℃, gets 99.84%Ca (H ₂PO ₄) ₂H ₂O；

2. prepare Ca (H ₂PO ₄) ₂H ₂O is 0.05moL/L, gets 2000g, under normal pressure intensification 40-70 ℃, adds 85%H ₃PO ₄, 24g, acidolysis 45min adds 4gSnCL ₂With control Fe/Ca=1.0-1.3moL, quantitatively add the copperas solution 570g of 0.2moL/L, insulation reaction 2h is cooled to 25 ± 5 ℃, isolates precipitation, gets ferrophosphorus solution;

3. get ferrophosphorus solution under agitation, add brown iron oxide 20g and 2g carbon black, be warming up to 40-70 ℃, control Fe/Li=1.0-1.1moL, add the lithium hydroxide solution of 1.5moL/L, be neutralized to PH:6-8, insulation reaction 2h separates making the LiFePO 4 mixture;

4. get the LiFePO 4 mixture, dry under 300-400 ℃, dehydration 4h, LiFePO 4 material after ball milling, under nitrogen or argon shield, temperature 700-800 ℃, calcining 12h obtains purity and reaches 99.92% LiFePO 4.

Embodiment 2

1. get 40%H ₃PO ₄Solution, 970g stirs at normal temperatures and pressures, adds 3moL/L milk of lime, controls Ca (OH) ₂: H ₃PO ₄=1: 1.5-2.5moL, be neutralized to PH:2.5-4.5, reaction 45min isolates the wet basis material dry under 50-60 ℃, gets 99.90%Ca (H ₂PO ₄) ₂H ₂O；

2. prepare Ca (H ₂PO ₄) ₂H ₂O is 0.125moL/L solution, gets 2000g, stirs 40-70 ℃ of intensification under normal pressure, adds 85%H ₃PO ₄, 24g, acidolysis 45min adds vitamins C, 5g, controls Fe: Ca=1.0-1.3moL, quantitatively adds the copperas solution of 0.45moL/L: 640g, insulation reaction 2h is cooled to 25 ± 5 ℃, isolates precipitation, gets ferrophosphorus solution;

3. get ferrophosphorus solution under agitation, add brown iron oxide 21g and 3g carbon black, intensification 40-70 ℃, add the lithium hydroxide solution of 2.5moL/L and control Fe/Li=1.0-1.1moL, be neutralized to PH:6-8, separate after reaction 3h, make the LiFePO 4 mixture;

4. get the LiFePO 4 mixture, dry under 300-400 ℃, dehydration 4h, after ball milling the LiFePO 4 material, under nitrogen or argon shield, temperature 700-800 ℃, calcining 12h obtains purity and reaches 99.92% LiFePO 4.

Embodiment 3

1. get 40%H ₃PO ₄Solution, 970g stirs at normal temperatures and pressures, adds 4moL/L milk of lime, controls Ca (OH) ₂: H ₃PO ₄=1: 1.5-2.5moL, be neutralized to PH:2.5-4.5, reaction 45min isolates the wet basis material dry under 50-60 ℃, gets 99.95%Ca (H ₂PO ₄) ₂H ₂O；

2. prepare Ca (H ₂PO ₄) ₂H ₂O is 0.2moL/L solution, gets 2000g, stirs 40-70 ℃ of intensification under normal pressure, adds 85%H ₃PO ₄, 24g, acidolysis 45min adds sucrose, 5g, controls Fe: Ca=1.0-1.3moL, quantitatively adds the copperas solution of 0.7moL/L: 670g, insulation reaction 2h is cooled to 25 ± 5 ℃, isolates precipitation, gets ferrophosphorus solution;

3. get ferrophosphorus solution under agitation, add brown iron oxide 21g and 4g carbon black, intensification 40-70 ℃, add the lithium hydroxide solution of 3.5moL/L and control Fe/Li=1.0-1.1moL, be neutralized to PH:6-8, separate after reaction 3h, make the LiFePO 4 mixture;

4. get the LiFePO 4 mixture, dry under 300-400 ℃, dehydration 4h, after ball milling the LiFePO 4 material, under nitrogen or argon shield, temperature 700-800 ℃, calcining 12h obtains purity and reaches 99.80% LiFePO 4.

Claims

1. the method for a liquid-solid reduction synthesizing lithium ferrous phosphate is characterized in that comprising the following steps: Lime is formulated as 2-4mol/l milk of lime; Get 20-60%H ₃PO ₄Solution stirs at normal temperatures and pressures, adds the Ca(OH by formula weight) ₂: H ₃PO ₄The described lime slurry neutralization of=1:1.5-2.5mol is to pH 2.5-4.5, after reaction, separates, dry that purity be the Ca (H of 99.8-99.95% ₂PO ₄) ₂H ₂O；

Get step

Ca (the H that obtains ₂PO ₄) ₂H ₂O is formulated as 0.05-0.2moL/L solution, stirs under normal pressure, heats to 40-70 ℃, and adding content is 85%H ₃PO ₄To acidolysis; Add the 0.1-0.4% reductive agent of acidolysis solution weight in solution and add ferrous salt solution by formula weight than Fe:Ca=1.0-1.3:1moL after acidolysis, ferrous salt solution concentration is 0.2-0.7moL/L, reacted 2-4 hour, and isolated precipitation, get ferrophosphorus solution;

3. with ferrophosphorus solution under agitation, add carbon black and brown iron oxide, amounts of carbon black is the 0.09-0.16% of ferrophosphorus solution weight, the feed ratio of brown iron oxide is Fe:P=1.0-1.1:1 moL, and be warming up to 40-70 ℃, and add the lithium hydroxide solution of 1.5-3.5moL/L, control Fe:Li=1.0-1.1:1moL and be neutralized to PH:6-8, reaction 1-3h is through separating, make the LiFePO 4 mixture;

4. getting the LiFePO 4 mixture, is under 300-800 ℃ in temperature, drying, dehydration, and then ball milling is calcined under nitrogen or argon shield, 4-12 hour, obtains purity and reaches LiFePO 4 more than 99%.

2. the method for liquid-solid reduction synthesizing lithium ferrous phosphate according to claim 1, it is characterized in that: described reductive agent is SnCL ₂, vitamins C, glucose or sucrose.

3. the method for liquid-solid reduction synthesizing lithium ferrous phosphate according to claim 1, is characterized in that: step

After middle reaction, isolate the wet basis material dry under 50-60 ℃, get 99.8-99.95%Ca (H after drying ₂PO ₄) ₂H ₂O。