CN100435390C

CN100435390C - Synthesizing lithium ion cell positive material fluorophosphoric vanadium-lithium by sol-gel method

Info

Publication number: CN100435390C
Application number: CNB2007100342511A
Authority: CN
Inventors: 张宝; 钟胜奎; 尹周澜
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2007-01-12
Filing date: 2007-01-12
Publication date: 2008-11-19
Anticipated expiration: 2027-01-12
Also published as: CN101005134A

Abstract

The disclosed sol gel method includes steps: stirring, and mixing objects: water solutions of lithium salt, villiaumite, vandic salt in pentavalence, phosphate, and chelating agent according to mol ratio 2:2:1-2:2:4; controlling pH at 7-11, carrying out reaction in stirred reactor under 40-80 deg.C for 1-5 hours to form gel; drying the gel in vacuum drying oven for 5-15h under 80-150 deg.C, and cracking the dried gel for 1-4h; after being ground evenly, the dried gel is roasted at 400-800 deg.C under atmosphere of inert gases for 5-20h so as to obtain finished product. Using vandic salt in pentavalence as raw material, the invention solves issue that vanadium ion is to be oxidized. The invention reduces burning temperature; producing fine and grain size even distributed material so as to raise conductivity. Adjustable synthesis temperature can obtain material with different granularities. Advantages are: simple and convenient method, and shortened synthetic cycle.

Description

Sol-gal process synthesis of anode material of lithium-ion battery fluorophosphoric acid vanadium lithium

Technical field

The present invention relates to a kind of method of sol-gal process synthesis of anode material of lithium-ion battery fluorophosphoric acid vanadium lithium.

Background technology

Lithium-ions battery has a lot of good characteristics, has been widely used on portable type electronic product, communication tool, electric automobile, the energy storage device.The performance of lithium ion battery depends on positive electrode to a great extent.Wherein vanadium is the fluorophosphoric acid vanadium lithium (LiVPO in the positive electrode ₄F) because to have a reversibility good, the raw material source is abundant, specific capacity higher (theoretical capacity is 156mAh/g), platform be than higher (4.2V vs Li ⁺/ Li) etc. advantage has caused the attention of height.But following shortcoming has hindered its practical application: V during (1) is synthetic ³⁺Easily be oxidized to V ⁵⁺, be difficult to obtain single-phase LiVPO ₄F; 2) lithium ion is at LiVPO ₄The diffusion difficulty causes the utilance of active material low among the F; (3) LiVPO ₄The conductivity of F itself is also very low, causes its heavy-current discharge performance poor.Existing research improves LiVPO by following several respects ₄The performance of F: (1) adopts inert atmosphere to protect V ³⁺(2) LiVPO of synthetic small particle diameter ₄F is to improve the diffusivity of lithium ion; (3) add conductive agent and improve conductivity.Reported as J Barker etc. and to have adopted synthetic method of two step of carbothermic method, this procedure is loaded down with trivial details, complicated, is unfavorable for suitability for industrialized production, and skewness, the electric conductivity of institute's synthetic material particle diameter are low, the cycle is long, energy consumption is big.

Summary of the invention

The object of the present invention is to provide a kind of method with sol-gal process synthesis of anode material of lithium-ion battery LiVPO4F.To solve the easy oxidation of vanadium ion, to make that institute's synthetic material particle size distribution is even, tiny, conductivity improves, reduce calcining heat, reduce cost, simplify the purpose of technology.

Technical scheme of the present invention may further comprise the steps:

(1) be 2: 2 in molar ratio with Aqueous Lithium Salts, fluorine salt aqueous solution, the pentavalent vanadic salts aqueous solution, aqueous phosphatic and intercalating agent: 1-2: 2: 4, mix;

(2) pH=7-11 of control reaction solution, reaction formed gel in 1-5 hour in 40-80 ℃ stirred reactor, and dry 5-15h obtains xerogel in 80-150 ℃ vacuum drying chamber;

(3) with xerogel 200 ℃-400 ℃ heating and decomposition 1-4 hour, organic substance is decomposed;

(4) in 400 ℃ of-800 ℃ of roasting 5-20h, cool off, be finished product LiVPO after grinding evenly, in inert gas atmosphere ₄F.

Described intercalating agent is a kind of in oxalic acid, adipic acid, ascorbic acid, the citric acid.

Described Aqueous Lithium Salts is a kind of in lithium acetate, lithium chloride, lithium sulfate, lithium nitrate, lithium carbonate or the lithium fluoride.

Described fluorine salt aqueous solution is a kind of in ammonium fluoride, sodium fluoride, hydrogen fluoride or the lithium fluoride.

The described pentavalent vanadic salts aqueous solution is a kind of in vanadic oxide, the ammonium metavanadate.

Described aqueous phosphatic can be wherein a kind of of triammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, sodium phosphate, sodium dihydrogen phosphate, sodium hydrogen phosphate.

The present invention directly uses the pentavalent vanadium to make raw material, has solved the easy problem of oxidation of vanadium ion; Reduced calcining heat, organic substance is evenly dispersed in the former material precursor at the carbon that pretreatment stage decompose to generate, and can suppress too growing up of sample crystal grain effectively, makes that institute's synthetic material particle size distribution is even, tiny, conductivity improves; Adjustable between synthesis temperature 400-800 ℃, can obtain varigrained material; Method is simple and convenient, be easy to control, shortened synthesis cycle greatly, reduced cost.

Description of drawings

Fig. 1 is No. 3 sample LiVPO of embodiment 1 ₁The XRD figure spectrum of F;

Fig. 2 is No. 3 sample LiVPO of embodiment 1 ₄The SEM collection of illustrative plates of F;

Fig. 3 is the charging and discharging curve of No. 3 samples of embodiment 1;

Fig. 4 is the cycle performance curve of No. 3 samples of embodiment 1.

Embodiment

Embodiment 1:

0.1mol vanadic oxide, 0.2mol ammonium dihydrogen phosphate, 0.2mol lithium hydroxide, 0.2mol ammonium fluoride, 0.4mol oxalic acid are fully dissolved, after mixing then, adding 0.05-0.2mol NaOH control pH value is 8, and reaction 4h forms gel in 40 ℃ stirred reactor.Gel sample is sent into vacuum drying chamber obtain xerogel, after finishing mixture is sent in the tube furnace of temperature programmed control,, organic substance is decomposed,, take out sample and carefully grind with the stove natural cooling with 200 ℃ of heating 3h in 100 ℃ of further dry 10h.Then sample is sent into tube furnace, the protection of inert gas following respectively with 1,2,3, No. 4 sample respectively at 450 ℃, 550 ℃, 650 ℃, 750 ℃ calcining 10h.No. 3 sample products of gained show to be LiVPO through X-ray diffraction analysis ₄F does not have any dephasign, can obtain the particle diameter of product about 100nm by SEM.Resulting product is assembled into the experiment button cell, surveys its impulse electricity specific capacity and cycle performance, under the multiplying power of 1C, discharge and recharge, its first discharge capacity and the circulation 50 times after discharge capacity see Table 1.

The experiment condition of table 1 embodiment 1 and result

Embodiment 2:

After 0.2mol ammonium metavanadate, 0.2mol triammonium phosphate, 0.2mol lithium hydroxide, 0.2mol ammonium fluoride, 0.4mol citric acid fully mixed, adding 0.05-0.2mol NaOH control pH value is 8, and reaction 3h forms gel in 50 ℃ stirred reactor.Gel sample is sent into vacuum drying chamber obtain xerogel, after finishing mixture is sent in the tube furnace of temperature programmed control,, organic substance is decomposed,, take out sample and carefully grind with the stove natural cooling with 300 ℃ of preliminary treatment 2h in 120 ℃ of further dry 8h.Respectively 1,2,3, No. 4 sample is sent into tube furnace then, under the protection of inert gas, be heated to 650 ℃, calcined respectively 5,10,15,20 hours.The product of gained shows to be LiVPO through X-ray diffraction analysis ₄F does not have any dephasign, can obtain the particle diameter of product about 100nm by SEM.With resulting product be assembled into the experiment button cell survey its impulse electricity specific capacity and cycle performance, under the multiplying power of 1C, discharge and recharge, its first discharge capacity and the circulation 50 times after capacity see Table 2.

The experiment condition of table 2 embodiment 2 and result

Embodiment 3 is the 0.2mol lithium fluoride, the 0.2mol ammonium metavanadate, and the 0.2mol ammonium dihydrogen phosphate, the 0.4mol citric acid mixes, and after stirring, regulating pH value is 8, reaction 2h formation gel in 60 ℃ stirred reactor.Gel sample is sent into vacuum drying chamber obtain xerogel, after finishing mixture is sent in the tube furnace of temperature programmed control,, organic substance is decomposed,, take out sample and carefully grind with the stove natural cooling with 400 ℃ of preliminary treatment 1h in 150 ℃ of further dry 6h.Respectively 1,2,3, No. 4 sample is sent in the tube furnace then, under the protection of inert gas, be heated to 400 ℃ and calcined respectively 5,10,15,20 hours.The product of gained shows to be LiVPO through X-ray diffraction analysis ₄F does not have any dephasign, can obtain the particle diameter of product about 100nm by SEM.With resulting product be assembled into the experiment button cell survey its charging and discharging capacity and cycle performance, under the multiplying power of 1C, discharge and recharge, its first discharge capacity and the circulation 50 times after capacity see Table 3.

The experiment condition of table 3 embodiment 3 and result

Embodiment 4:

0.1mol vanadic oxide, 0.2mol ammonium dihydrogen phosphate, 0.2mol lithium hydroxide, 0.2mol ammonium fluoride, 0.4mol oxalic acid are fully dissolved, after mixing then, adding 0.05-0.2mol NaOH control pH value is 8, and reaction 1h forms gel in 80 ℃ stirred reactor.Gel sample is sent into vacuum drying chamber obtain xerogel, after finishing mixture is sent in the tube furnace of temperature programmed control,, organic substance is decomposed,, take out sample and carefully grind with the stove natural cooling with 100 ℃ of preliminary treatment 4h in 100 ℃ of further dry 10h.Then sample is sent into tube furnace and under the protection of inert gas, be heated to 800 ℃ and be incubated certain hour.The product of gained shows to be LiVPO through X-ray diffraction analysis ₄F does not have any dephasign, can obtain the particle diameter of product about 100nm by SEM.With resulting product be assembled into the experiment button cell survey its charging and discharging capacity and cycle performance, under the multiplying power of 1C, discharge and recharge, its first discharge capacity and the circulation 50 times after capacity see Table 4.

The experiment condition of table 4 embodiment 4 and result

Claims

1. the method for a sol-gal process synthesis of anode material of lithium-ion battery fluorophosphoric acid vanadium lithium is characterized in that, may further comprise the steps:

(1) be 2: 2 in molar ratio with lithium salts, villiaumite, pentavalent vanadic salts vanadic oxide or ammonium metavanadate, phosphate, intercalating agent oxalic acid or adipic acid or ascorbic acid or citric acid: 1-2: be made into the aqueous solution, mix at 2: 4;

(2) control pH=7-11, reaction formed gel in 1-5 hour in 40-80 ℃ stirred reactor, and dry 5-15h obtains xerogel in 80-150 ℃ vacuum drying chamber;

(3) xerogel was heated decomposing organic matter 1-4 hour at 200 ℃-400 ℃;

(4) after grinding evenly, in inert gas atmosphere,, be finished product LiVPO after the cooling in 400 ℃ of-800 ℃ of roasting 5-20h ₄F.

2. the method for sol-gal process synthesis of anode material of lithium-ion battery fluorophosphoric acid vanadium lithium according to claim 1 is characterized in that described lithium salts is a kind of in lithium acetate, lithium chloride, lithium sulfate, lithium nitrate, lithium carbonate or the lithium fluoride.

3. the method for sol-gal process synthesis of anode material of lithium-ion battery fluorophosphoric acid vanadium lithium according to claim 1 is characterized in that described villiaumite is a kind of in ammonium fluoride, sodium fluoride, hydrogen fluoride or the lithium fluoride.

4. the method for sol-gal process synthesis of anode material of lithium-ion battery fluorophosphoric acid vanadium lithium according to claim 1 is characterized in that described phosphate is a kind of in triammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, sodium phosphate, sodium dihydrogen phosphate, the sodium hydrogen phosphate.