CN101252188A

CN101252188A - Method for low temperature preparing lithium ion battery positive pole material fluorophosphoric acid vanadium lithium

Info

Publication number: CN101252188A
Application number: CNA2008100913550A
Authority: CN
Inventors: 钟胜奎; 刘长久; 王健
Original assignee: Guilin University of Technology
Current assignee: Guilin University of Technology
Priority date: 2008-04-07
Filing date: 2008-04-07
Publication date: 2008-08-27

Abstract

The invention discloses a method for preparing anode material vanadium lithium fluoroalkylphosphate of a lithium -ion cell at low temperature, comprising the steps of: (1) heating vanadic oxide powder to six hundred to nine hundred DEG C; allowing to melt at a constant temperature for one to four hours and pouring into a container with water rapidly to form a brown-red solution; letting the solution stand for four to sixteen hours to form wet gel V2O5.nH2O; washing the wet gel, removing most of moisture, keeping drying for four to sixteen hours in a vacuum ambient of seventy to one hundred DEG C and grinding to obtain vanadic oxide powder. (2) Mixing the vanadic oxide powder obtained through the preparation method with Lithium, villiaumite, phosphates and acetylene black evenly at mol ratio of one to two to two to two to two point four, sintering for five to twenty hours at temperature between four hundred and seven hundred DEG C under the protection of an inert gas and cooling to obtain a finished product of LiVPO4F. The preparation method is easy and simple, easy to control and low in cost, reduces sintering temperature and improves the charging and discharging performance and cycle performance of samples.

Description

The method of low temperature preparing lithium ion battery positive pole material fluorophosphoric acid vanadium lithium

Technical field

The present invention relates to a kind of method of low temperature preparing lithium ion battery positive pole material fluorophosphoric acid vanadium lithium.

Background technology

Lithium rechargeable 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 (4.2Vvs 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.Bibliographical information synthesizes LiVPO at present ₄The F material mainly adopts hydrogen reduction method and pyrocarbon thermal reduction.Hydrogen reduction method is owing to adopt pure H ₂As reducing agent, when experimental implementation because H ₂Inflammable and explosive character and very dangerous, be unfavorable for suitability for industrialized production.And shortcoming such as the skewness of institute's synthetic material particle diameter and electric conductivity be low.The pyrocarbon thermal reduction since the reaction temperature that needs than higher, thereby the material particle size skewness, electric conductivity and the cycle performance that are synthesized are bad.

Summary of the invention

The object of the present invention is to provide a kind of employing low temperature preparing lithium ion battery positive pole material LiVPO ₄The method of F.To solve the easy oxidation of vanadium ion, to make that institute's synthetic material particle size distribution is even, tiny, conductivity improves, reduce sintering temperature, reduce cost, improved the chemical property of sample, simplify the purpose of technology.

Concrete steps of the present invention are:

(1) vanadium pentoxide powder is heated to 600～900 ℃, and constant temperature 1～4h makes to pour into rapidly in the container that water is housed after its fusion and form brown-red solution, this solution left standstill 4～16h can form V ₂O ₅NH ₂The O wet gel; With removing most of moisture after the wet gel washing,, grind and obtain the pentoxide gel powder then at 70～100 ℃ of following vacuumize 4～16h;

(2) be 1: 2: 2 in molar ratio with the above-mentioned pentoxide gel powder for preparing and lithium salts, villiaumite, phosphate, acetylene black: after mixing at 2: 2.4; under the protection of inert gas,, be finished product LiVPO after the cooling in 400 ℃～700 ℃ sintering 5-20h ₄F;

Described lithium salts is a kind of in lithium acetate, lithium chloride, lithium nitrate and the lithium fluoride;

Described villiaumite is a kind of in ammonium fluoride, sodium fluoride, potassium fluoride and the lithium fluoride;

Described phosphate is a kind of in ammonium dihydrogen phosphate, diammonium hydrogen phosphate, potassium phosphate and the sodium phosphate;

Described inert gas is a kind of in nitrogen and the argon gas.

The present invention directly uses the pentavalent vanadium to make raw material, has solved the easy problem of oxidation of vanadium ion; Reduced sintering temperature, can suppress too growing up of sample crystal grain effectively, made that institute's synthetic material particle size distribution is even, tiny, conductivity improves; Adjustable between 400～700 ℃ of the synthesis temperatures, can obtain varigrained material; Method is simple and convenient, be easy to control; The charge-discharge performance of sample and cycle performance improve, and have reduced cost.

Description of drawings

Fig. 1 is No. 3 sample LiVPO of the embodiment of the invention 1 ₄The XRD figure of F.

Fig. 2 is No. 3 sample LiVPO of the embodiment of the invention 1 ₄The SEM figure of F.

Fig. 3 is No. 3 sample LiVPO of the embodiment of the invention 1 ₄The first charge-discharge curve of F.

Fig. 4 is No. 3 sample LiVPO of the embodiment of the invention 1 ₄The cycle performance curve of F.

Embodiment

Embodiment 1:

The 0.1mol vanadium pentoxide powder is heated to 600 ℃, and constant temperature 4h makes to pour into rapidly in the container that water is housed after its fusion and form brown-red solution, this solution left standstill 16h can form V ₂O ₅NH ₂The O wet gel.With removing most of moisture after the wet gel washing, at 70 ℃ of following vacuumize 16h, obtain the pentoxide gel powder after the grinding then.With the pentoxide gel powder of preparation with after 0.2mol lithium acetate, 0.2mol ammonium fluoride, 0.2mol diammonium hydrogen phosphate and 0.24mol acetylene black mixes; under protection of nitrogen gas,, be finished product LiVPO after the cooling respectively at 400 ℃, 500 ℃, 600 ℃, 700 ℃ sintering 5h ₄F.Resulting product shows to be LiVPO through X-ray diffraction analysis ₄F does not have any dephasign, and the particle diameter that can obtain product by SEM is about 1 μ m.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 discharge capacity see Table 1.

The experiment condition of table 1 embodiment 1 and result

Numbering	Sintering temperature/℃	Sintering time/h	Initial charge capacity/mAhg ^-1	Discharge capacity/mAhg first ^-1	The 50th discharge capacity/mAhg ^-1
Numbering	Sintering temperature/℃	Sintering time/h	Initial charge capacity/mAhg ^-1	Discharge capacity/mAhg first ^-1	The 50th discharge capacity/mAhg ^-1	1	400	5	120	101	65
2	500	5	141	126	101	1	400	5	120	101	65
2	500	5	141	126	101	3	600	5	144	130	121
4	700	5	138	125	103	3	600	5	144	130	121

Embodiment 2:

The 0.1mol vanadium pentoxide powder is heated to 900 ℃, and constant temperature 1h makes to pour into rapidly in the container that water is housed after the vanadic oxide fusion and form brown-red solution, this solution left standstill 12h can form V ₂O ₅NH ₂The O wet gel.With removing most of moisture after the wet gel washing, at 90 ℃ of following vacuumize 12h, obtain the pentoxide gel powder after the grinding then.With the pentoxide gel powder of preparation with after 0.2mol lithium fluoride, 0.2mol sodium fluoride, 0.2mol ammonium dihydrogen phosphate and 0.24mol acetylene black mixes; under the protection of argon gas,, be finished product LiVPO after the cooling in 600 ℃ of difference sintering 5,10,15 and 20h ₄F.Resulting product shows to be LiVPO through X-ray diffraction analysis ₄F does not have any dephasign, and the particle diameter that can obtain product by SEM is about 1 μ m.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 discharge capacity see Table 2.

The experiment condition of table 2 embodiment 2 and result

Numbering	Sintering temperature/℃	Sintering time/h	Initial charge capacity/mAhg ^-1	Discharge capacity/mAhg first ^-1	The 50th discharge capacity/mAhg ^-1
Numbering	Sintering temperature/℃	Sintering time/h	Initial charge capacity/mAhg ^-1	Discharge capacity/mAhg first ^-1	The 50th discharge capacity/mAhg ^-1	1	600	5	143	130	18
2	600	10	142	127	100	1	600	5	143	130	18
2	600	10	142	127	100	3	600	15	140	124	96
4	600	20	135	120	90	3	600	15	140	124	96

Embodiment 3:

The 0.1mol vanadium pentoxide powder is heated to 800 ℃, and constant temperature 2h makes to pour into rapidly in the container that water is housed after its fusion and form brown-red solution, this solution left standstill 4h can form V ₂O ₅NH ₂The O wet gel.With removing most of moisture after the wet gel washing,, grind and obtain the pentoxide gel powder then at 100 ℃ of following vacuumize 8h.With the pentoxide gel powder of preparation with after 0.2mol lithium chloride, 0.2mol potassium fluoride, 0.2mol potassium phosphate and 0.24mol acetylene black mixes; under the protection of argon gas,, be finished product LiVPO after the cooling in respectively at 450 ℃, 550 ℃, 650 ℃, 700 ℃ sintering 20h ₄F.Resulting product shows to be LiVPO through X-ray diffraction analysis ₄F does not have any dephasign, and the particle diameter that can obtain product by SEM is about 1 μ m.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 discharge capacity see Table 3.

The experiment condition of table 3 embodiment 3 and result

Numbering	Sintering temperature/℃	Sintering time/h	Initial charge capacity/mAhg ^-1	Discharge capacity/mAhg first ^-1	The 50th discharge capacity/mAhg ^-1
Numbering	Sintering temperature/℃	Sintering time/h	Initial charge capacity/mAhg ^-1	Discharge capacity/mAhg first ^-1	The 50th discharge capacity/mAhg ^-1	1	450	20	133	110	68
2	550	20	138	125	97	1	450	20	133	110	68
2	550	20	138	125	97	3	650	20	140	130	106
4	700	20	136	119	80	3	650	20	140	130	106

Embodiment 4:

The 0.1mol vanadium pentoxide powder is heated to 700 ℃, and constant temperature 3h makes to pour into rapidly in the container that water is housed after its fusion and form brown-red solution, this solution left standstill 8h can form V ₂O ₅NH ₂The O wet gel.With removing most of moisture after the wet gel washing,, grind and obtain the pentoxide gel powder then at 80 ℃ of following vacuumize 4h.After prepared pentoxide gel powder and 0.2mol lithium nitrate, 0.2mol lithium fluoride, 0.2mol sodium phosphate and 0.24mol acetylene black mixed; under protection of nitrogen gas,, be finished product LiVPO after the cooling in 550 ℃ of difference sintering 8,11,14,17h ₄F.Resulting product shows to be LiVPO through X-ray diffraction analysis ₄F does not have any dephasign, and the particle diameter that can obtain product by SEM is about 1 μ m.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 discharge capacity see Table 4.

The experiment condition of table 4 embodiment 4 and result

Numbering	Sintering temperature/℃	Sintering time/h	Initial charge capacity/mAhg ^-1	Discharge capacity/mAhg first ^-1	The 50th specific discharge capacity/mAhg ^-1
Numbering	Sintering temperature/℃	Sintering time/h	Initial charge capacity/mAhg ^-1	Discharge capacity/mAhg first ^-1	The 50th specific discharge capacity/mAhg ^-1	1	550	8	120	89	55
2	550	11	130	116	94	1	550	8	120	89	55
2	550	11	130	116	94	3	550	14	133	120	100
4	550	17	126	112	88	3	550	14	133	120	100

Claims

1. the method for a low temperature preparing lithium ion battery positive pole material fluorophosphoric acid vanadium lithium is characterized in that concrete steps are:

(2) be 1: 2: 2 in molar ratio with the above-mentioned pentoxide gel powder for preparing and lithium salts, villiaumite, phosphate, acetylene black: after mixing at 2: 2.4; under the protection of inert gas,, be finished product LiVPO after the cooling in 400 ℃～700 ℃ sintering 5～20h ₄F;

Described lithium salts is a kind of in lithium acetate, lithium chloride, lithium nitrate and the lithium fluoride; Described villiaumite is a kind of in ammonium fluoride, sodium fluoride, potassium fluoride and the lithium fluoride; Described phosphate is a kind of in ammonium dihydrogen phosphate, diammonium hydrogen phosphate, potassium phosphate and the sodium phosphate; Described inert gas is a kind of in nitrogen and the argon gas.