CN102225756A

CN102225756A - Method for preparing asphalt mesocarbon microbeads and application in lithium battery cathode material thereof

Info

Publication number: CN102225756A
Application number: CN2011101187647A
Authority: CN
Inventors: 宋怀河; 徐斌; 陈晓红
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2011-05-09
Filing date: 2011-05-09
Publication date: 2011-10-26

Abstract

Based on the emulsification method and the suspension method, mesocarbon microbeads, which are successfully prepared by improving technologies with the particle size being 1-5 microns, have good dispersibility. When the asphalt mesocarbon microbeads are used as the lithium battery cathode material, battery storage capacity and rate capacity have prominent performance: with the increase of charge-discharge current, the capacity fading rate is low and the rate capacity is good at 50 mA/G-400mA/g with the specific discharge capacity being 271 mAh/g-114.7 mAh/g.

Description

A kind of preparation method of mesophase pitch carbon microspheres and the application in lithium cell cathode material thereof

Technical field

The present invention relates to the lithium ion battery negative material field, particularly a kind of preparation method of MCMB.

Background technology

Mesophase pitch carbon microspheres (MCMB) is a kind of novel raw material of wood-charcoal material, aspect ion secondary battery cathode material lithium, also demonstrate very excellent performance [Song Huaihe, Chen Xiaohong, Zhang Songyun, high swallow. mesophase pitch carbon microspheres and the application aspect lithium-ion secondary cell [J] thereof. carbon material, 2002 (1): 28].The electrochemistry of lithium ion embeds and takes off the control that the embedding process is subjected to charge transfer and mass transport, therefore when using mesophase pitch carbon microspheres (MCMB) as lithium cell cathode material, the MCMB particle diameter is more little, and piling up between the particle can be tight more, and the lithium ion the evolving path is just short.This not only improves cycle performance of battery, simultaneously also can make charge and discharge process easier, be better [the Chang Y C of high rate performance of battery, Sohn H J, Ku C H, etal.Anodic performance of mesocarbon microbeads (MCMB) prepared from sytheticnaphthlene istropic pitch[J] .Carbon, 1999,37:1285-1297.].

The preparation method of mesophase pitch carbon microspheres (MCMB) mainly contains two kinds at present: polycondensation method and emulsion process.The polycondensation method is to make the polycondensation of condensed-nuclei aromatics raw material become mesophase ball by thermal treatment, take suitable means that bead is proposed then, but higher, the separation difficulty of polymerisate viscosity that this method obtains, and yield is low, sphere diameter wider distribution [Wang Hongqiang, Li Xinjun, Guo Huajun etc. the MCMB structure is to the influence [J] of its chemical property. Zhongnan Polytechnic Univ's journal, 2003,34 (2): 140-143].Emulsion process directly is that raw material passes through high temperature dispersion medium emulsification balling-up with the mesophase pitch, and comparing its advantage of polycondensation method is that the product size is controlled, narrowly distributing, productive rate height; Shortcoming is that the mesophase pitch raw material is not easy to be uniformly dispersed in dispersion medium, and existing emulsion process can only obtain the bead about diameter 20 μ m, be difficult to obtain the littler product [Li Fuhu of diameter, Shen Cengmin, Xue Ruisheng, Deng. emulsion method prepares the research [J] of MCMB. novel charcoal material, 2004,19 (1): 21-27.].Therefore, further improve technology, it is significant to explore the method for preparing the small particle size mesophase pitch carbon microspheres with excellent electrical properties.

Summary of the invention

At the problems referred to above, the purpose of this invention is to provide a kind of preparation method of new mesophase pitch carbon microspheres, make by following method:

Step 1: the powder that the mesophase pitch raw material powder is broken into 1～30 μ m, join ultra-sonic dispersion in the dehydrated alcohol, under the 1000-2000r/min rotating speed centrifugal five minutes, get upper strata liquid, isolate the mesophase pitch particle of 1～5 μ m, the 1g that gets wherein joins in the 20ml sherwood oil and ultra-sonic dispersion, mix with the high temperature resistant silicone oil of 100ml then, under 100～500r/min speed stirs with system heat temperature raising to 260 ℃～270 ℃, stop heating and be cooled to room temperature, centrifugation goes out product, cleans repeatedly to the filtrate clarification with organic solvent, and promptly getting diameter is the mesophase pitch microballoon of 1～5 μ m;

Step 2: will go up the step makes the mesophase pitch microballoon and puts into convection oven, pre-oxidation treatment 4～6h under 150 ℃～200 ℃ and 200 ℃～300 ℃ conditions respectively, handle 1h through 1000 ℃ of charings again, 2800 ℃ of greying 1h, both getting diameter is the MCMB of 1～5 μ m.

The further preferred version of the present invention is: described organic solvent is selected from a kind of in dehydrated alcohol, acetone, the sherwood oil.

The further preferred version of the present invention is: the lithium cell cathode material that is prepared by described method gained mesophase pitch carbon microspheres.

Method of the present invention adds sherwood oil in original emulsification system, the mesophase pitch carbon microspheres particle diameter littler (1～5 μ m) that makes preparation, and pattern homogeneous, the difficult reunion.This procedure is simple, productive rate is very high, use the negative material of the mesophase pitch carbon microspheres of this method preparation as lithium cell, outstanding behaviours is being arranged: on cell container and the high rate performance when 50mA/g～400mA/g, specific discharge capacity is 271mAh/g～114.7mAh/g, along with the increase of charging and discharging currents, the capacity attenuation rate is lower, good rate capability.

Description of drawings:

Accompanying drawing 1 is a mesophase pitch carbon microspheres sem photograph.

Accompanying drawing 2 is mesophase pitch carbon microspheres X-ray diffraction (XRD) figure.

Accompanying drawing 3 is different-grain diameter MCMB specific discharge capacity figure.

Accompanying drawing 4 is a different-grain diameter MCMB charge-discharge magnification performance map.

Embodiment

The present invention is described in detail below in conjunction with drawings and Examples:

Embodiment 1

With the asphalt stock particle of the particle diameter after pulverizing at 1-30 μ m, speed by 2000r/min, centrifugal 5min isolates the feed particles of particle diameter 1-2 μ m, get wherein 1g feed particles, it is distributed in the 20ml sherwood oil uniformly, then this pitch sherwood oil mixed solution is joined in the high temperature resistant silicone oil of 100ml, keep 300r/min speed to stir 5min; When continuing to stir, stop heating when being rapidly heated system to 270 ℃, naturally cool to room temperature; Use that supercentrifuge is centrifugal to go out the product bead, clean with sherwood oil and obtain purified small particle size mesophase pitch microballoon.

In convection oven, respectively at 150 ℃ of pre-oxidation treatment 6h, 250 ℃ of pre-oxidation treatment 6h, again through 1000 ℃ of charing 1h, 2800 ℃ of greying 1h obtain MCMB, and particle diameter is at 1-2 μ m.

Shown in accompanying drawing 1 sem photograph, MCMB spherolite footpath is uniformly dispersed about 1.5 μ m; X-ray diffraction map analysis as shown in Figure 2, the MCMB degree of graphitization is about 81.4%, and the graphite flake layer spacing is 0.337nm; 3 electrochemical property test results show as accompanying drawing, are stabilized in 250mAh/g after the 50mA/g circulation 50 times; Shown in accompanying drawing 4 charge-discharge magnification performance map, 50mA/g specific discharge capacity average is 271.4mAh/g, 100mA/g specific discharge capacity average 245.1mAh/g, 200mA/g, specific discharge capacity average 170.1mAh/g, 400mA/g, specific discharge capacity average 114.7mAh/g, charging and discharging capacity height under high current density.

Embodiment 2

The preparation method is as embodiment 1, different is with the feed particles of particle diameter 3-30 μ m (among the embodiment 1, removed the feed particles of particle diameter) at 1-2 μ m, at the centrifugal 5min of 1500r/min, isolate particle diameter 3-5 μ m left and right sides mesophase pitch particle, when being rapidly heated to 260 ℃, system stops heating

In convection oven, respectively at 200 ℃ of pre-oxidation treatment 4h, 300 ℃ of pre-oxidation treatment 4h, again through 1000 ℃ of charing 1h, 2800 ℃ of greying 1h obtain MCMB, and particle diameter is at 3～5 μ m.

3 electrochemical property test results show as accompanying drawing, are stabilized in about 300mAh/g after the battery circulation 50 times; Shown in accompanying drawing 4 charge-discharge magnification performance map, 50mA/g specific discharge capacity average is 305.3mAh/g, 100mA/g specific discharge capacity average 218.3mAh/g, 200mA/g, specific discharge capacity average 118.2mAh/g, 400mA/g, specific discharge capacity average 49.7mAh/g, charging and discharging capacity is lower under high current density, and high rate performance is poorer than the intermediate phase charcoal ball effect of particle diameter 1～2 μ m.

Embodiment 3

The preparation method is as embodiment 1, and different is with the asphalt stock particle of the particle diameter after pulverizing at 1-30 μ m, by the centrifugal 5min of 1000r/min, isolates the feed particles of particle diameter 1-5 μ m, finally obtains particle diameter 1-5 μ m MCMB.

3 electrochemical property test results show as accompanying drawing, are stabilized in about 300mAh/g after the battery circulation 50 times; Shown in accompanying drawing 4 charge-discharge magnification performance map, 50mA/g specific discharge capacity average is 379.3mAh/g, 100mA/g specific discharge capacity average 341.8mAh/g, 200mA/g, specific discharge capacity average 248.3mAh/g, 400mA/g, specific discharge capacity average 122.4mAh/g, because 1-2 μ m particulate exists, charging and discharging capacity is higher under high current density, good rate capability, and still keep higher charging and discharging capacity.

Below concrete comparative descriptions has been carried out in preferred embodiment of the present invention, thus the advantage of small particle size MCMB on lithium-ion-power cell is used of checking the present invention preparation.But the present invention is not limited to described embodiment, those of ordinary skill in the art also can make all modification that is equal to or replacement under the prerequisite of spirit of the present invention, modification that these are equal to or replacement all are included in the application's claim institute restricted portion.

Claims

1. the preparation method of a mesophase pitch carbon microspheres is characterized in that making by following method:

Step 1: the powder that the mesophase pitch raw material powder is broken into 1～30 μ m, join ultra-sonic dispersion in the dehydrated alcohol, under 1000～2000r/min rotating speed centrifugal five minutes, get upper strata liquid, isolate the mesophase pitch particle of 1～5 μ m, the 1g that gets wherein joins in the 20ml sherwood oil and ultra-sonic dispersion, mix with the high temperature resistant silicone oil of 100ml then, under 100～500r/min speed stirs with system heat temperature raising to 260 ℃～270 ℃, stop heating and be cooled to room temperature, centrifugation goes out product, cleans repeatedly to the filtrate clarification with organic solvent, and promptly getting diameter is the mesophase pitch microballoon of 1～5 μ m;

2. according to the preparation method of claims 1 described mesophase pitch carbon microspheres, it is characterized in that: described organic solvent is selected from a kind of in dehydrated alcohol, acetone, the sherwood oil.

3. lithium cell cathode material for preparing by the described method gained of claim 1 to 2 mesophase pitch carbon microspheres.