CN100364153C

CN100364153C - Li4Ti5O12 cathode material cladden on surface of spinel LiMn2O4 and preparation method thereof

Info

Publication number: CN100364153C
Application number: CNB2005100209408A
Authority: CN
Inventors: 刘兴泉; 刘东强; 夏雨
Original assignee: Chengdu Organic Chemicals Co Ltd of CAS
Current assignee: Chengdu Organic Chemicals Co Ltd of CAS
Priority date: 2005-05-24
Filing date: 2005-05-24
Publication date: 2008-01-23
Anticipated expiration: 2025-05-24
Also published as: CN1694285A

Abstract

The present invention relates to Li4Ti5O12 coated on the surface of LiMn2O4, and a preparation method thereof. The method comprises the following steps that compounds with lithium and titanium are mixed and stirred for a certain time under the action of gelling agents, LiMn2O4 is added, and the mixture is stirred for a certain time to form dried gel which is baked for 1 to 24 hours at a temperature of 10 to 250 DEG C to form precursors; the precursors are sintered for 5 to 24 hours in air at a temperature of 300 to 900DEGC to obtain different LiMn2O4 electrode materials with a different amount of coating content. Because the present invention considers Li4Ti5O12 zero straining structure, and utilizes the high Li<+> diffusion coefficient of Li4Ti5O12, the present invention effectively reduces the capacity loss resulting from LiMn2O4 solution, and not only enhances the cycle performance of LiMn2O4, but also has a little influence on the cycle performance in the process of 10C heavy current charge and discharge; the present invention has the advantages of simple synthesis technology, low cost, and easy implementation in industry.

Description

A kind of spinelle LiMn 2O 4The surface coats Li 4Ti 5O 12Electrode material and preparation method thereof

Technical field

The invention belongs to a kind of anode active material of lithium ion battery, particularly coat Li on the surface through modification ₄Ti ₅O ₁₂LiMn ₂O ₄And preparation method thereof.

Background technology

Since lithium ion battery in 1991 came out, its positive electrode was the focus of research always.The positive electrode of commercial applications is stratiform LiCoO at present ₂Though, it have open circuit voltage height, specific energy big, have extended cycle life, can repid discharge etc. advantage, exist cost an arm and a leg, problem such as environmental pollution, substitute LiCoO so need to seek a kind of energy ₂Positive electrode.Wherein, the LiMn of spinel structure ₂O ₄Has higher operating voltage (about 3.9V vs.Li ⁺/ Li), characteristics such as cheap, environmentally friendly, so be considered to be hopeful most substitute LiCoO ₂One of first-selected positive electrode.But in commercialization process, also have following problems to wait to solve: (1) Reversible Cycle capacity on the low side (110～130mAh/g); (2) capacitance loss is serious under the high temperature.Wherein, LiMn ₂O ₄The high temperature capacitance loss be to hinder one of its business-like key factor.And cause LiMn ₂O ₄The reason of high temperature capacity attenuation is still very not clear and definite, mainly contains following several explanation: (1) Mn melts; (2) electrolyte decomposition; (3) Jahn-Teller distortion.In order to solve fast this international difficult problem of capacity attenuation, the scientific research group of various countries is to LiMn ₂O ₄Thermal stability further investigate, and material is carried out modification.In recent years, for LiMn ₂O ₄Study on the modification mainly concentrate on and mix and the surface coats, the more and surface coated research of the research of wherein mixing is inchoate in recent years.At present, the LiMn that has reported both at home and abroad ₂O ₄The surface comprises:

1. utilize lithium boron oxide compound (LBO) and acetylacetone,2,4-pentanedione (acetylacetone) to LiMn ₂O ₄Carry out surface treatment (Amatucci G.G, Blyr A. .[J such as Sigala C.] Solid State Ionics, 1997,104:13-25);

2. at LiMn ₂O ₄Surface coating layer shape LiCoO ₂(Park S.C., Kim Y.M., [J] .Journal ofPower Sources such as Kang Y.M., 2001,103:86-92; Shu D, Kumar G, [J] Solid StateIonics such as Kim K B., 2003,160:227-233);

3. Al ₂O ₃The surface coating (Lee S-W, Kim K-S, Moon H-S etc., [J] Journal of Power Sources, 2004,126:150-155);

4. MgO surface coating (Gedanken A waits [J] Electrochemistrycommunications for Gnanaraj J.S, Pol V G, and 2003,5:940-945);

5. SiO ₂The surface coating (Zheng Z.S, Tang Z.L .[J such as Zhang Z.T] Solid State Ionics, 2002,148:317-321);

More than coat, except LiCoO ₂Have higher chemical diffusion coefficient, outside the electronic conductivity, other clad materials all have weak point, and then have influence on LiMn ₂O ₄Chemical property.

Summary of the invention

At above weak point, consider Li ₄Ti ₅O ₁₂Itself can be used as electrode material, and has the LiMn of ratio ₂O ₄Higher chemical diffusion coefficient and electronic conductivity, and Li ₄Ti ₅O ₁₂Also have and LiMn ₂O ₄The same spinel structure, simultaneously, Li ₄Ti ₅O ₁₂Structure does not change in the charge/discharge process, is a kind of " zero strain " material, does not influence the stability of material.Thereby the present invention adopts Li ₄Ti ₅O ₁₂As clad material, to LiMn ₂O ₄Carry out surface modification treatment.

The present invention has following characteristics: (1) coats the structure not influence of back to former product; (2) amount of Bao Fuing can be controlled flexibly by changing technological parameter; (3) raw material of Shi Yonging all is common industrial chemicals, and is cheap, pollution-free, security performance is good; (4) coating process is simple, and flow process is short, and is easy to control; (5) material after the coating is assembled into test cell, and cyclical stability is significantly improved.

The invention process step:

(1) lithium acetate under agitation is dissolved in the mixed liquid that contains absolute ethyl alcohol, deionized water, complexing agent, wherein absolute ethyl alcohol: deionized water: the complexing agent volume ratio is (1-50): (1-5): (1-5);

(2) the above-mentioned mixed liquid of lithium that contains is dropwise joined in the titaniferous solution of stirring, become the vitreosol that contains lithium, titanium, wherein Li: the Ti mol ratio is 4: 5;

(3) contain lithium, the stirring of titanium colloidal sol after 30 minutes with above-mentioned, press different proportion and add spinelle LiMn ₂O ₄, continue stirring and became Gel Precursor in 1-24 hour;

(4) presoma is changed in the baking oven in 25-200 ℃ dry 1-24 hour down, become dry gel powder;

(5) dry gel powder is put into Muffle furnace and carried out high-temperature heat treatment, temperature maintenance is at 500-1000 ℃, and heat treatment time is 10-48 hour, reduces to room temperature then, obtains the final sample of different coating ratios.

Description of drawings

Fig. 1 is according to the Li that the present invention relates to the method preparation ₄Ti ₅O ₁₂The XRD figure spectrum of sample.

LiMn before Fig. 2 (a) coats ₂O ₄And (b) compare Li by embodiment 1 prepared 1%mol ₄Ti ₅O ₁₂The LiMn that coats ₂O ₄Powder X-ray RD collection of illustrative plates.

LiMn before Fig. 3 (a) coats ₂O ₄With press embodiment 1-example 3 prepared (b) 1%, (c) 2%, (d) 3% mol ratio Li ₄Ti ₅O ₁₂LiMn after the coating ₂O ₄The first charge-discharge curve.

Fig. 4 coats preceding LiMn ₂O ₄With according to embodiment 1-example 3 preparation 1%, 2%, 3% mol ratio Li ₄Ti ₅O ₁₂LiMn after the coating ₂O ₄Preceding 20 charge and discharge cycles test results.

Embodiment

Embodiment 1:

Lithium acetate 0.2303g under agitation joins in the 2ml absolute ethyl alcohol, in the mixed solution of 0.25ml deionized water, 0.2ml glacial acetic acid, after lithium acetate dissolves fully, stir down and slowly transfer in the 0.9701g metatitanic acid fourth lipoprotein solution, form faint yellow vitreosol, stir after 30 minutes, add 10gLiMn ₂O ₄Powder continue to stir 4 hours, and colloidal sol becomes gel gradually, gel is put into 150 ℃ of baking ovens oven dry spend the night, and became dry gel powder, with the direct 800 ℃ of sintering 24 hours in Muffle furnace of this dry gel powder, reduced to room temperature naturally, must 1%molLi ₄Ti ₅O ₁₂The LiMn that coats ₂O ₄Powder.

Embodiment 2:

Lithium acetate 0.2326g under agitation joins in the 3ml absolute ethyl alcohol, in the mixed solution of 0.28ml deionized water, 0.25ml glacial acetic acid, after lithium acetate dissolves fully, stir down and slowly transfer in the 0.9800g metatitanic acid fourth lipoprotein solution, form faint yellow vitreosol, stir after 30 minutes, add 5gLiMn ₂O ₄Powder continue to stir 4 hours, and colloidal sol becomes gel gradually, gel is put into 150 ℃ of baking ovens oven dry spend the night, and became dry gel powder, with the direct 800 ℃ of sintering 24 hours in Muffle furnace of this dry gel powder, reduced to room temperature naturally, must 2%molLi ₄Ti ₅O ₁₂The LiMn that coats ₂O ₄Powder.

Embodiment 3:

Lithium acetate 0.2115g under agitation joins in the 3.1ml absolute ethyl alcohol, in the mixed solution of 0.23ml deionized water, 0.2ml glacial acetic acid, after lithium acetate dissolves fully, stir down and slowly transfer in the 0.8911g metatitanic acid fourth lipoprotein solution, form faint yellow vitreosol, stir after 30 minutes, add 3gLiMn ₂O ₄Powder continue to stir 4 hours, and colloidal sol becomes gel gradually, gel is put into 150 ℃ of baking ovens oven dry spend the night, and became dry gel powder, with the direct 800 ℃ of sintering 24 hours in Muffle furnace of this dry gel powder, reduced to room temperature naturally, must 3%molLi ₄Ti ₅O ₁₂The LiMn that coats ₂O ₄Powder.

Claims

1. spinelle LiMn ₂O ₄The surface coats Li ₄Ti ₅O ₁₂The electrode material preparation method is characterized in that:

(1) lithium acetate under agitation is dissolved in the mixed liquid that contains absolute ethyl alcohol, deionized water, glacial acetic acid, wherein absolute ethyl alcohol: deionized water: the glacial acetic acid volume ratio is (1-50): (1-5): (1-5);

(2) the above-mentioned mixed liquid of lithium that contains is dropwise joined in the metatitanic acid fourth fat of stirring, become the vitreosol that contains lithium, titanium, wherein Li: the Ti mol ratio is 4: 5;

(4) presoma is changed in the baking oven 25-200 ℃ dry 1-24 hour down, become dry gel powder;

(5) dry gel powder is put into Muffle furnace and carried out high-temperature heat treatment, temperature maintenance is at 500-1000 ℃, and heat treatment time is 10-48 hour, reduces to room temperature then.

2. method prepares spinelle LiMn according to claim 1 ₂O ₄The lithium ion battery of electrode material comprises positive electrode, negative material, electrolyte, barrier film, it is characterized in that described positive electrode comprises: the surface coats different molar content Li ₄Ti ₅O ₁₂Spinelle LiMn ₂O ₄Positive active material, conductive agent and binding agent; Three's quality percentage composition is respectively: 93-70%, 4-20%, 3-10%.

3. as lithium ion battery as described in the claim 2, it is characterized in that described negative pole is a lithium metal.

4. as lithium ion battery as described in the claim 2, it is characterized in that described electrolyte is to contain the lithium salts of 1mol/L and the mixed liquid of organic solvent, wherein lithium salts is selected lithium hexafluoro phosphate for use; Organic solvent is selected the mixed liquid of ethylene carbonate and diethyl carbonate for use, and the two volume ratio is 1: 1; Or the mixed liquid of ethylene carbonate and diethyl carbonate and dimethyl carbonate, three's volume ratio is 1: 1: 1.

5. the described lithium ion battery of claim 2 is characterized in that described barrier film is porous polyethylene film or porousness polypropylene screen.

6. as lithium ion battery as described in the claim 2, it is characterized in that described conductive agent selects acetylene black for use; Binding agent is selected polytetrafluoroethylene for use, or Kynoar.