Nano zine oxide-graphite-graphene composite material and its preparation method and application
Technical field
The present invention relates to nano zine oxide-graphite-graphene composite material and its preparation method and application.
Background technology
Lithium ion battery is successfully applied to various portable electric appts, as mobile phone, portable computer etc. due to its higher energy density and longer useful life.Current industrialization lithium ion battery mainly adopts graphite as negative material, and the theoretical capacity of graphite is only 370mAh/g, this impel scientific research personnel go to find the material with higher theoretical capacity substitute or doped graphite as negative material, to expect to obtain the lithium ion battery with higher storage capacity.
Zinc oxide (ZnO) is 978mAh/g as theoretical capacity during lithium ion battery negative material.When block ZnO is used as lithium ion battery negative material, electron conductivity is low, and in charge and discharge process, change in volume is large, and electrical contact loss is large, and chemical property is poor, does not reach desirable charge/discharge capacity.
Graphene has good electricity, mechanics, optics and thermal property.Desirable single-layer graphene has specific area (2630 m of super large
2/ g), be the energy storage material of great potential.Graphene has good conductivity, and the movement velocity of its electronics reaches 1/300 of the light velocity, considerably beyond the movement velocity of electronics in general conductor.Graphene has good light transmission, is the potential substitute products of conventional I TO film.Graphene has good thermal property, utilizes the thermal conductivity obtaining Graphene based on micro-Raman spectroscopy measurement to be 3080 ~ 5150 W/mK.
Existing oxidation Zinc-graphite com-posite is when using as lithium ion battery negative, in charge and discharge cycles process, volume there occurs and expands and shrink, cause die break, structural breakdown, cause the destruction of electrode, decrease the cycle life of electrode, and it inserts easy " reunion " when lithium reacts de-, causes initial irreversible capacity to increase, finally causes capacity to reduce.
Summary of the invention
Object of the present invention will overcome that existing graphite cathode material charge/discharge capacity is low, volume easily expands and shrinks exactly, cause die break, structural breakdown, cause the destruction of electrode, decrease the cycle life of electrode, and insert de-the defect that when lithium reacts, easy " reunion " causes capacity to reduce, provide a kind of nano zine oxide-graphite-graphene composite material and its preparation method and application.Nano zine oxide-graphite-graphene composite material preparation technology of the present invention is simple, change in volume caused when effectively can alleviate discharge and recharge, suppress in de-" reunion " phenomenon of inserting when lithium reacts, material electrodes capacity attenuation can be avoided too fast, reduce initial irreversible capacity, make the theoretical capacity of capacity much larger than common material with carbon element of nano zine oxide-graphite-graphene composite material, and cycle performance is better.
The present invention solves the problems of the technologies described above by the following technical solutions:
The invention provides a kind of nano zine oxide-graphite-graphene composite material, described composite material comprises core and coating layer, and described core is made up of graphite and Graphene, and described coating layer is the even complex of nano zine oxide and amorphous carbon.
Wherein, the particle diameter of described graphite is preferably 0.1 ~ 5 μm, is more preferably 0.5 ~ 1 μm.Described graphite be preferably selected from natural spherical plumbago, natural flake graphite and aquadag one or more.The mass percentage that described graphite accounts for described composite material is preferably 65 ~ 85%.
Wherein, the mass percentage that described Graphene accounts for described composite material is preferably 1 ~ 5%.
Wherein, the mass percentage that described nano zine oxide accounts for described composite material is preferably 5% ~ 25%.
Wherein, the mass percentage that described amorphous carbon accounts for described composite material is preferably 5% ~ 10%.
Present invention also offers the preparation method of above-mentioned nano zine oxide-graphite-graphene composite material, it comprises the steps:
(1) soluble zinc salt and organic high molecular polymer are dissolved in alcohol organic solvent, mix and obtain solution A;
(2) join in Aqueous Solutions of Polyethylene Glycol by the mixture of graphite and graphene oxide, ultrasonic disperse evenly obtains suspension B;
(3) solution A is mixed with suspension B, add polyvinylpyrrolidone, after stirring, then drip the mixture of ammoniacal liquor and ethanol, obtain sol-gel system C;
(4) described sol-gel system C is dry, obtain presoma D;
(5) by described presoma D roasting heat process in protective gas.
Wherein, in step (1), described alcohol organic solvent is preferably one or more in methyl alcohol, ethanol and isopropyl alcohol.
Wherein, described soluble zinc salt is generally water-soluble zinc salt that this area routine uses, and the present invention is four ammino zinc complexes preferably, further preferably sulfuric acid four ammino zinc (Zn (NH
3)
4sO
4), carbonic acid four ammino zinc (Zn (NH
3)
4cO
3) and dichloride four ammino zinc (Zn (NH
3)
4cl
2) in one or more.
Wherein, described organic high molecular polymer is as presoma, is preferably one or more in phenolic resins, furane resins, coal tar pitch and petroleum asphalt.
Wherein, the mass ratio of described soluble zinc salt and described organic high molecular polymer is preferably 1:(0.5 ~ 2).
Wherein, described graphite can be the various graphite that this area routine uses, and is preferably one or more in natural spherical plumbago, aquadag and natural flake graphite.The particle diameter of described graphite is preferably 0.1 ~ 5 μm, is more preferably 0.5 ~ 1 μm.
Wherein, described graphene oxide can be the graphene oxide that this area routine uses, and generally refers to the graphite oxide that graphite (Graphite) obtains after the oxidation of HUMMMERS method, then with ultrasonic wave dispersion, oxidized graphite flake layer is peeled off and get final product.
Wherein, described graphite and the mass ratio of graphene oxide are preferably (20 ~ 100): 1.
Wherein, the mass ratio of described graphite and described soluble zinc salt is preferably (3 ~ 15): 1.
Wherein, one or more in described polyethylene glycol preferred PEG-4000, PEG-6000 and PEG-8000; The mass percent concentration of described Aqueous Solutions of Polyethylene Glycol is preferably 5 ~ 20%.
Wherein, the weight average molecular weight of described polyvinylpyrrolidone is preferably 8000 ~ 10000.
Wherein, the mass ratio of described polyvinylpyrrolidone and described soluble zinc salt is preferably (1 ~ 20): 1.
Wherein, described ammoniacal liquor and the volume ratio of ethanol are preferably 1:(10 ~ 100).
Wherein, it is dry and dry for the second time that described drying preferably comprises first time; The temperature of described first time drying is preferably 80 ~ 90 DEG C, and the time of described first time drying is preferably 2 ~ 3 hours; The temperature of described second time drying is preferably 180 ~ 200 DEG C, and the time of described second time drying is preferably 4 ~ 6 hours.
Wherein, described protective gas is preferably nitrogen or inert gas, and described inert gas is one or more in helium, neon, argon gas, Krypton and xenon.
Wherein, the heat treated temperature of described roasting is preferably 1200 ~ 2000 DEG C, and the described roasting heat treated time is preferably 5 ~ 10 hours.
Present invention also offers the above-mentioned nano zine oxide-application of graphite-graphene composite material in lithium ion battery negative.
On the basis meeting this area general knowledge, above-mentioned each optimum condition, can combination in any, obtains the preferred embodiments of the invention.
Agents useful for same of the present invention and raw material are all commercially.
Positive progressive effect of the present invention is:
(1) the present invention adopts organic solvent system, but not general water solution system, graphite, Graphene, zinc salt and organic high molecular polymer is made to form a kind of uniform collosol-gelatum system, do not precipitate from start to finish in material preparation process, thus finally obtain the composite material with coating layer structure, the composite material of similar a kind of nucleocapsid structure.
(2) in this composite material, zinc oxide is high uniformity dispersion in amorphous carbon material, and oxide particle is not easily reunited, and material structure is stablized.
(3) change in volume that nano zine oxide-graphite-graphene composite material preparation technology of the present invention is simple, caused when effectively can alleviate discharge and recharge, suppress in de-" reunion " phenomenon of inserting when lithium reacts, material electrodes capacity attenuation can be avoided too fast, reduce initial irreversible capacity, make the theoretical capacity of capacity much larger than common material with carbon element of nano zine oxide-graphite-graphene composite material, and cycle performance is better.
Accompanying drawing explanation
Fig. 1 is the SEM photo of nano zine oxide-graphite-graphene composite material that the present invention obtains.
Fig. 2 is the cycle performance curve of the obtained nano zine oxide-graphite-graphene composite material of embodiment 1 as lithium ion battery negative material.
Embodiment
By reference to the accompanying drawings the present invention is described in further detail below by embodiment, but does not therefore limit the present invention within described scope of embodiments.The experimental technique of unreceipted actual conditions in the following example, conventionally and condition, or selects according to catalogue.
Graphene oxide in following embodiment is obtained by HUMMMERS oxidizing process, concrete list of references Fast and Facile Preparation of Graphene Oxide and Reduced Graphene Oxide Nanoplatelets, Chem. Mater., 21st volume, 3514th ~ 3520 pages and " technique study of Graphene is prepared in graphene oxide reduction ", Chinese material science and technology and equipment, the 4th phase in 2012,36 ~ 39 pages.
embodiment 1
Take 10g sulfuric acid four ammino zinc (Zn (NH
3)
4sO
4) and 10g petroleum asphalt be dissolved in 300ml ethanol to stir and obtain solution A.It is that in polyethylene glycol (PEG-4000) aqueous solution of 10%, ultrasonic disperse 30min, obtains suspension B that 100g natural spherical plumbago (particle diameter is 0.5 ~ 1 μm) and 2g graphene oxide are joined mass percent concentration.After solution A being mixed with suspension B, add 50g polyvinylpyrrolidone (weight average molecular weight is 8000 ~ 10000), after stirring, then drip the mixture 300mL of ammoniacal liquor and ethanol (volume ratio of ammoniacal liquor and ethanol is 1:50), obtain sol-gel system C.By above-mentioned sol-gel system C 80 DEG C of dryings 3 hours, and then be warmed up to 200 DEG C of dryings and obtain presoma D in 4 hours; By this presoma D roasting heat process 9 hours under 1500 DEG C of conditions in nitrogen, nano zine oxide-graphite-graphene composite material can be obtained.
In this composite sample, content of graphite is 70wt%, and Graphene content is 2wt%, and nano oxidized Zn content is 18wt%, and agraphitic carbon content is 10wt%.
Get wherein sample segment and carry out scanning electron microscopy photograph, Fig. 1 is shown in by gained SEM photo.As can be seen from Figure 1, nano zine oxide-graphite-graphene composite material particle maintains spherical appearance characteristics, composite material surface ratio raw graphite ball smooth, coated one deck shell on raw graphite ball is described, tiny particles coat is on the surface of graphite matrix, constitute relatively uniform shell, and core-shell structure copolymer combines, and does not depart from good.
embodiment 2
Take 10g carbonic acid four ammino zinc (Zn (NH
3)
4cO
3) and 20g coal tar pitch be dissolved in 400ml methyl alcohol to stir and obtain solution A.It is that in polyethylene glycol (PEG-8000) aqueous solution of 5%, ultrasonic disperse 50min, obtains suspension B that 80g aquadag (particle diameter is 0.5 ~ 1 μm) and 1g graphene oxide are joined mass percent concentration.After solution A being mixed with suspension B, add 60g polyvinylpyrrolidone (weight average molecular weight is 8000 ~ 10000), after stirring, then drip the mixture 500mL of ammoniacal liquor and ethanol (volume ratio of ammoniacal liquor and ethanol is 1:20), obtain sol-gel system C.By above-mentioned sol-gel system C 90 DEG C of dryings 3 hours, and then be warmed up to 180 DEG C of dryings and obtain presoma D in 6 hours; By this presoma D roasting heat process 6 hours under 2000 DEG C of conditions in nitrogen, nano zine oxide-graphite-graphene composite material can be obtained.
In this composite sample, content of graphite is 64wt%, and Graphene content is 3wt%, and nano oxidized Zn content is 23wt%, and agraphitic carbon content is 10wt%.
The SEM photo of nano zine oxide-graphite-graphene composite material that the present embodiment obtains is with embodiment 1.
embodiment 3
Take 10g dichloride four ammino zinc (Zn (NH
3)
4cl
2) and 5g phenol formaldehyde resin dissolves stir in 200ml isopropyl alcohol and obtain solution A.It is that in polyethylene glycol (PEG-6000) aqueous solution of 20%, ultrasonic disperse 40min, obtains suspension B that 50g natural spherical plumbago (particle diameter is 0.5 ~ 1 μm) and 2g graphene oxide are joined mass percent concentration.After solution A being mixed with suspension B, add 50g polyvinylpyrrolidone (weight average molecular weight is 8000 ~ 10000), after stirring, then drip the mixture 200mL of ammoniacal liquor and ethanol (volume ratio of ammoniacal liquor and ethanol is 1:10), obtain sol-gel system C.By above-mentioned sol-gel system C 90 DEG C of dryings 3 hours, and then be warmed up to 190 DEG C of dryings and obtain presoma D in 5 hours; By this presoma D roasting heat process 10 hours under 1200 DEG C of conditions in helium, nano zine oxide-graphite-graphene composite material can be obtained.
In this composite sample, content of graphite is 67wt%, and Graphene content is 5wt%, and nano oxidized Zn content is 20wt%, and agraphitic carbon content is 8wt%.
The SEM photo of nano zine oxide-graphite-graphene composite material that the present embodiment obtains is with embodiment 1.
the composite material that effect example 1 the present invention obtains is as the electric performance test (half-cell method of testing) of lithium ion battery negative material
The present invention's half-cell method of testing used is: make 2430 type batteries, composite sample, 1-METHYLPYRROLIDONE containing 6 ~ 7% Kynoar and 2% conductive black mix, be applied on Copper Foil, the pole piece coated being put into temperature is that 110 DEG C of vacuum drying chamber vacuumizes 4 hours are for subsequent use.Simulated battery is assemblied in the German Braun glove box of applying argon gas and carries out, electrolyte is 1M LiPF6+EC: EMC: DMC=1: 1: 1 (volume ratio), metal lithium sheet is to electrode, electrochemical property test carries out on U.S. ArbinBT2000 type cell tester, discharge and recharge system: current potential is restricted to 0-1.5V and carries out charge/discharge test, that is, charging current 0.5mA/cm is used
2keep voltage to be that 0.01V charges to battery simultaneously, then use charging current 0.02mA/cm
2keep voltage to be that 0.01V continues charging simultaneously.Use discharging current 0.5mA/cm
2discharge battery to voltage is 1.5V.Test result is in table 1.
Table 1
Embodiment |
Discharge capacity (mAh/g) first |
First charge-discharge efficiency (%) |
Circulate 500 weeks capability retentions (%) |
Circulate 500 weeks electrode expansion rates (%) |
1 |
535.6 |
92.8 |
90.0 |
129.2 |
2 |
538.0 |
92.7 |
91.9 |
128.6 |
3 |
540.2 |
92.1 |
90.6 |
127.7 |
As can be seen from data above, discharge capacity is up to 535 more than mAh/g first for the composite material that the present invention obtains, and first charge-discharge efficiency is higher, and after circulating 500 weeks, capability retention is all more than 90%.And change in volume caused when composite material of the present invention can alleviate discharge and recharge effectively, suppress in de-" reunion " phenomenon of inserting when lithium reacts, all 130% is less than in circulation 500 weeks rear electrode expansion rates, be conducive to suppressing lithium-ion battery system to produce ballooning, the security performance of battery is good, is greatly better than graphite negative material of lithium ion battery of the prior art.
the electric performance test (full battery testing method) of the graphite negative material of lithium ion battery that effect example 2 the present invention obtains
The present invention's full battery testing method used is: make negative pole with the composite material that the embodiment of the present invention 1 is obtained, cobalt acid lithium makes positive pole, 1M-LiPF6EC: EMC: DMC=1: 1: 1 (volume ratio) solution is done electrolyte assembling and is helped battery, test 1C charge and discharge 500 weeks capability retentions more than 90.0%, as shown in Figure 2.