CN107799770A - A kind of micro crystal graphite for lithium cell cathode material and preparation method thereof - Google Patents
A kind of micro crystal graphite for lithium cell cathode material and preparation method thereof Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
Abstract
The present invention relates to lithium cell cathode material technical field, discloses a kind of micro crystal graphite for lithium cell cathode material and preparation method thereof.Microcrystalline graphite material of the present invention is under 100 mA/g current density, and it, which circulates specific capacity, can reach 224 mAh/g, and head effects are higher, and more than 90%, and stability is good.Under the conditions of big multiplying power, the circulation specific capacity of the material is smaller, and reversible specific capacity is about 50 mAh/g；But its big circulation superior performance, particularly under conditions of the conversion of different charge-discharge magnifications, higher cyclical stability can still be kept, can by micro crystal graphite negative material of the present invention be applied to it is less demanding to circulation volume, to big circulation stability will just high ultracapacitor field.
Description
Technical field
The present invention relates to lithium cell cathode material technical field, is used for lithium cell cathode material more particularly, to one kind
Micro crystal graphite and preparation method thereof.
Background technology
Graphite is one kind of most study in carbon negative electrode material of lithium ion cell, and graphite material good conductivity, crystallinity is high,
With good layer structure, similar phenyl ring that its aspect is made up of the carbon atom of the states of sp 2 it is hexagonal huge flat
Face.Carbon atom in aspect is connected with δ covalent bonds, and bond distance 0.1421nm, three δ keys are mutually hexagonal angle, in addition in face also
There is a big pi bond for being coupled whole carbon atoms.Then it is connected between layers by weaker Van der Waals force, the interlamellar spacing of ideal graphite
For 0.3354nm.In low potential, lithium ion can reversibly be embedded in and deviate from graphite layers, form graphite layers chemical combination
Thing.
The natural micro crystal graphite in China is rich in minerals, and grade is high, and fixed carbon content is generally up to 60%~80%, wherein Chenzhou
Aphanitic graphite accounts for 74.7% or so of national gross reserves, and the aphanitic graphite quality is preferable, and fixed carbon content is high.Naturally
Micro crystal graphite may be used as lithium ion battery negative material after crushing, purifying.Natural micro crystal graphite is born as lithium ion battery
Pole material has higher reversible specific capacity, relatively low charging/discharging voltage platform, but has that first charge-discharge efficiency is low, high current
The shortcomings of charge-discharge performance difference, it is necessary to certain modification is carried out to micro crystal graphite, its charge-discharge performance could be improved.
The content of the invention
The present invention technical problems to be solved be for the natural micro crystal graphite electrical property of prior art it is poor, using change
Learn purification to be handled, improve its charge-discharge performance, there is provided a kind of micro crystal graphite for lithium cell cathode material.
The present invention also provides a kind of micro crystal graphite for lithium cell cathode material being prepared using the above method.
The purpose of the present invention is achieved by the following technical programs：
A kind of micro crystal graphite chemical purification methods are provided, comprised the following steps：
S1. raw ore is handled：It is 75~80% micro crystal graphite crushing raw ores by fixed carbon content, then to micro crystal graphite raw ore
Depth ore grinding is carried out, it is -0.074mm level materials to obtain fineness by ore grinding, is -0.074mm level material contents to mog
The primary sample for accounting for 90% carries out flotation, afterwards drying, magnetic separation, and it is 85~90% micro crystal graphites to be fixed carbon content；
S2. acidleach purifies：Micro crystal graphite obtained by step S1 and mixed acid are mixed, the mixed acid is the mixed of HF and HCL
Acid is closed, mixed acid is 2~3.5 with graphite liquid-solid ratio:1ml/g, HF volume content 30~60%, HCL volume content for 10~
20%, then under conditions of 50~80 DEG C of temperature, 1~4h of reaction time carry out normal pressure acidleach, leached mud distilled water or
Deionized water clean graphite to rinsing solution for it is neutral when precipitate, then filter, dry, obtain micro crystal graphite after purification, Gu
Carbon content is determined for more than 99%；
S3. it is ultrasonically treated：The obtained micro crystal graphites of step S2 are ultrasonically treated, 5~20min of ultrasonic time, frequency
20~50KHz, finally give the micro crystal graphite for lithium cell cathode material.
The present invention does not change micro crystal graphite crystal structure to ensure the storage lithium performance of the micro crystal graphite after chemical purification,
Purification processes are carried out to micro crystal graphite from the mixed acid of hydrochloric acid and hydrofluoric acid composition, while added to the micro crystal graphite after purification
Be ultrasonically treated, on the one hand micro crystal graphite can be made to be additionally separated with impurity, be mainly partly difficult to washing remove it is miscellaneous
Matter, on the other hand, the scrubbing action of ultrasonic wave make particle surface become more smooth, contribute to micro crystal graphite ratio after reduction purification
Surface area.
Preferably, micro crystal graphite raw ore described in step S1 is Shandong pool aphanitic graphite, wherein moisture 2.4%, volatile matter
2.99%, the carbon content 78.64% of ash content 18.37%.
Preferably, flotation described in step S1 uses four selected once purging selection flows of one roughing.
Preferably, reaction time 3h described in step S2, HF volume fractions 30%, liquid-solid ratio 3.5ml/g, reaction temperature 50
℃。
Preferably, the volume fraction of HCL described in step S2 is 15~20%.
Preferably, the volume fraction of HCL described in step S2 is 20%.
Preferably, dried described in step S2 and dry 2~3h in the case where temperature is 80~150 DEG C.
The present invention also provides a kind of high-purity micro crystal graphite being prepared using the above method, and fixed carbon content is 99%
More than, specific surface area is 15.4~17.4 ㎡/g.
Compared with prior art, the beneficial effects of the invention are as follows：
The present invention carries out crystallite stone mill raw ore and is crushed and ground first, coordinates the one roughing four times selected one of flotation
It is secondary to scan flow, the purity of raw ore is at utmost improved (if fixed carbon content is gone back for 90% micro crystal graphite by physical method
Its grade is set to be further enhanced, floatation is all than relatively difficult to achieve in technology or economically) while reduce
Micro crystal graphite particle diameter, increase the specific surface area of micro crystal graphite.
The present invention does not change micro crystal graphite crystal structure to ensure the storage lithium performance of the micro crystal graphite after chemical purification,
Purification processes are carried out to micro crystal graphite from the mixed acid of hydrochloric acid and hydrofluoric acid composition, reduce the usage amount of hydrofluoric acid, and lead to
Cross orthogonal test and draw optimised process.The present invention is ultrasonically treated to the micro crystal graphite after purification, on the one hand can make crystallite
Graphite is additionally separated with impurity, is mainly partly difficult to the impurity that washing is removed, on the other hand, the scrubbing action of ultrasonic wave
Particle surface is become more smooth, contribute to micro crystal graphite specific surface area after reduction purification.
For microcrystalline graphite material of the present invention under 100mA/g current density, it, which circulates specific capacity, can reach 224mAh/
G, head effect are higher, and more than 90%, and stability is good.Under the conditions of big multiplying power, the circulation specific capacity of the material is smaller, reversible specific volume
Amount is about 50mAh/g；But its big circulation superior performance, particularly under conditions of the conversion of different charge-discharge magnifications, according to
It is old to keep higher cyclical stability, micro crystal graphite negative material of the present invention can be applied to circulation volume requirement not
It is high, will just high ultracapacitor field to big circulation stability.
Brief description of the drawings
Fig. 1 flotation flowsheet figures
Charging and discharging curve figure of Fig. 2 micro crystal graphites negative material under 100mA/g current densities.
Discharge and recharge cycle and efficiency chart of Fig. 3 micro crystal graphites negative material under 100mA/g current densities.
The high rate performance of Fig. 4 micro crystal graphite negative materials.
Fig. 5 micro crystal graphite cycle volt-ampere (CV) characteristic.
Fig. 6 micro crystal graphites negative material exchanges anti-group of test.
Embodiment
The present invention is further illustrated with reference to specific embodiment.Following examples are only illustrative examples, not structure
Into inappropriate limitation of the present invention, the multitude of different ways that the present invention can be limited and covered by the content of the invention is implemented.It is unless special
Do not mentionlet alone bright, the present invention reagent, compound and the equipment that use is the art conventional reagent, compound and equipment.
Natural micro crystal graphite, which is used as lithium ion battery negative material, has higher reversible specific capacity, relatively low discharge and recharge electricity
Flattening bench, but the shortcomings of first charge-discharge efficiency is low, high rate during charging-discharging is poor be present, it is necessary to micro crystal graphite is carried out certain
Modification, its charge-discharge performance could be improved.
Natural micro crystal graphite may be used as lithium ion battery negative material after crushing, purifying, and the present invention surrounds microlite
Ink purification, in the case where not changing micro crystal graphite crystal structure, while micro crystal graphite specific surface area is reduced as far as possible.
The present invention use chemical purification methods, it is contemplated that as far as possible reduction hydrofluoric acid dosage, can from hydrochloric acid, sulfuric acid,
To be chosen in four kinds of most widely used acid of nitric acid and phosphoric acid, phosphoric acid easily generates insoluble precipitation with various metals ions binding,
Thus it is not suitable for purifying, nitric acid is a kind of volatile acid, sees that light easily decomposes, and catabolite corrosivity is strong, and toxicity is big, thus
It is not suitable for purifying, in addition the acid of cerous nitrate strong oxidizing property, the property of the change of graphite surface structure, sulfuric acid and hydrochloric acid can be caused yet
Matter is more suitable as, and the solubility of sulfate is generally less than halogen, so the present invention is in order to ensure the microlite after chemical purification
The storage lithium performance of ink, purification processes are carried out to micro crystal graphite from the mixed acid of hydrochloric acid and hydrofluoric acid composition.
When the present invention determines hydrofluoric acid and graphite liquid-solid ratio, HF volume contents, reaction temperature and reaction using orthogonal experiment
Between optimised process, add HCL on this basis and further improve graphite purity, it is specific as follows：
S1. the raw material that the present invention uses is Shandong pool aphanitic graphite, wherein moisture 2.4%, volatile matter 2.99%, ash content
18.37% carbon content 78.64%, first by micro crystal graphite crushing raw ore, depth ore grinding then is carried out to micro crystal graphite raw ore, passed through
It is -0.074mm level materials that ore grinding, which obtains fineness, is the primary sample progress that -0.074mm level material contents account for 90% to mog
Flotation, specific as shown in figure 1, using four selected once purging selection flows of one roughing, drying, magnetic separation, are fixed carbon afterwards
Content is 90%.
The aphanitic graphite is purified for HF-HCL mixed acid one-step method, on the basis of experiment of single factor, used
Orthogonal experiment determines the optimised process of purification, has investigated hydrofluoric acid and graphite liquid-solid ratio, HF volume contents, reaction temperature and reaction
Time fixes the influence of carbon content and the primary and secondary order of each influence factor to aphanitic graphite, as shown in table 1.
The orthogonal experiment factor level table of table 1
Experimentation：Tested successively according to orthogonal design table, it is 90% to weigh the fixation carbon content that step S1 is obtained every time
Micro crystal graphite 20.00g, add the HF of designated volume, be placed in oil bath after well mixed and taken out after isothermal reaction certain time,
Neutrality is washed to, filtering, 2~3h is dried at being 80~150 DEG C in temperature, obtains final sample.Wherein, orthogonal experiments are shown in
Table 2, range analysis are shown in Table 3, and variance analysis is shown in Table 4.
Micro crystal graphite fixes carbon content after table 2 purifies
The orthogonal experiment range analysis table of table 3
The orthogonal experiment analysis of variance table of table 4
As shown in Table 3, RD ＞ RB ＞ RA ＞ RC, the primary and secondary order that each factor influences on fixed carbon content is the reaction time,
HF volume contents, liquid-solid ratio, reaction temperature.
As shown in Table 4, reaction time, HF volume contents, the F values of 3 factors of liquid-solid ratio are all higher than corresponding F0.01 values,
Illustrate that they have significant influence to fixed carbon content, factor reaction temperature F values are merely greater than F0.10 values, illustrate it to solid
Body carbon content influences typically, minimum to be influenceed in 4 factors, consistent with range analysis structure.
It can learn that optimised process is D2B1A2C4, i.e. reaction time 3h by above-mentioned orthogonal experiment, HF volume fractions
30%, liquid-solid ratio 3.5ml/g, 50 DEG C of reaction temperature.
The present invention further determines HCL addition on this basis, specific as shown in table 5.
Table 5
As shown in Table 5, HCL volume fraction is the most obvious in 15~20% effects, and more than more than 20%, graphite is pure
Degree has reached the upper limit, and now hydrochloric acid is excessive, does not substantially help reducing content of ashes.
The present invention carries out purification process, micro crystal graphite crystal after purification using HCL and HF mixed acid to micro crystal graphite
Structure does not change, and can further apply in negative material and field of lithium.
Embodiment 1
The present embodiment provides a kind of micro crystal graphite preparation method for lithium cell cathode material, comprises the following steps：
S1. raw ore is handled：Shandong pool aphanitic graphite is crushed, depth ore grinding then is carried out to micro crystal graphite raw ore, passed through
It is -0.074mm level materials that ore grinding, which obtains fineness, is the primary sample progress that -0.074mm level material contents account for 90% to mog
Flotation, specific as shown in figure 1, using four selected once purging selection flows of one roughing, drying, magnetic separation, are fixed carbon afterwards
Content is 90% micro crystal graphite；
Wherein, the performance of Shandong pool aphanitic graphite is as follows described in step S1：Moisture 2.4%, volatile matter 2.99%, ash content
18.37% carbon content 78.64%, 12.8 ㎡ of specific surface area/g.
S2. acidleach purifies：Micro crystal graphite obtained by step S1 and mixed acid are mixed, the mixed acid is the mixed of HF and HCL
Acid is closed, mixed acid is 3.5ml/g with graphite liquid-solid ratio, and HF volume contents 30%, HCL volume content is 20%, then in temperature
Normal pressure acidleach is carried out under conditions of 50 DEG C of degree, reaction time 3h, leached mud cleans graphite to water with distilled water or deionized water
Dilution precipitates when being neutral, and then filtering, dry 2~3h in the case where temperature is 80~150 DEG C, obtain microlite after purification
Ink, fixed carbon content are 99.56%；
S3. it is ultrasonically treated：The obtained micro crystal graphites of step S2 are ultrasonically treated, ultrasonic time 15min, frequency
40KHz, the micro crystal graphite for lithium cell cathode material is finally given, wherein specific surface area is 15.4 ㎡/g.
The micro crystal graphite after purification is ultrasonically treated in the present embodiment, micro crystal graphite on the one hand can be made to enter one with impurity
The separation of step ground, mainly partly it is difficult to the impurity that washing is removed, on the other hand, the scrubbing action of ultrasonic wave becomes particle surface
It is more smooth, contribute to the specific surface area of micro crystal graphite after reduction purification.
Embodiment 2
This implementation is substantially the same manner as Example 1, and difference is, process conditions are different in step S2, specific as follows：
S2. acidleach purifies：Micro crystal graphite obtained by step S1 and mixed acid are mixed, the mixed acid is the mixed of HF and HCL
Acid is closed, mixed acid is 2ml/g with graphite liquid-solid ratio, and HF volume contents 30%, HCL volume content is 10%, then in temperature
60 DEG C, normal pressure acidleach is carried out under conditions of reaction time 1h, leached mud clean graphite to washing with distilled water or deionized water
Solution precipitates when being neutral, and then filtering, dry 2~3h in the case where temperature is 80~150 DEG C, obtain micro crystal graphite after purification,
Fixed carbon content is 99.12%.
Embodiment 3
This implementation is substantially the same manner as Example 1, and difference is, process conditions are different in step S2, specific as follows：
S2. acidleach purifies：Micro crystal graphite obtained by step S1 and mixed acid are mixed, the mixed acid is the mixed of HF and HCL
Acid is closed, mixed acid is 3.5ml/g with graphite liquid-solid ratio, and HF volume contents 60%, HCL volume content is 20%, then in temperature
Normal pressure acidleach is carried out under conditions of 80 DEG C of degree, reaction time 4h, leached mud cleans graphite to water with distilled water or deionized water
Dilution precipitates when being neutral, and then filtering, dry 2~3h in the case where temperature is 80~150 DEG C, obtain microlite after purification
Ink, fixed carbon content are 99.56%.
Embodiment 4
The present embodiment is substantially the same manner as Example 1, and difference is, process conditions are different in step S3, specific as follows：
S3. it is ultrasonically treated：The obtained micro crystal graphites of step S2 are ultrasonically treated, 5~20min of ultrasonic time, frequency
20KHz, finally give the micro crystal graphite for lithium cell cathode material.
The micro crystal graphite specific surface area for lithium cell cathode material that the present embodiment is prepared is 17.4 ㎡/g, phase
Than embodiment 1, main reason is that supersonic frequency is too low, DeGrain.
Embodiment 5
The present embodiment is substantially the same manner as Example 1, and difference is, process conditions are different in step S3, specific as follows：
S3. it is ultrasonically treated：The obtained micro crystal graphites of step S2 are ultrasonically treated, 5~20min of ultrasonic time, frequency
50KHz, finally give the micro crystal graphite for lithium cell cathode material.
The micro crystal graphite specific surface area for lithium cell cathode material that the present embodiment is prepared is 15.4 ㎡/g, phase
Than embodiment 1, then to improve supersonic frequency effect little.
Comparative example 1
This comparative example is substantially the same manner as Example 1, and difference is, without step S3 supersound process, this contrast
The micro crystal graphite specific surface area that example obtains is 18.4 ㎡/g.
Embodiment 6
The present embodiment provides a kind of preparation method of micro crystal graphite negative electricity pole piece, comprises the following steps：
S1. the prepared micro crystal graphite for lithium cell cathode material of embodiment 1 is dried using vacuum drying chamber
Processing, drying temperature are 60 DEG C, drying time 24h, obtain micro crystal graphite negative active core-shell material；
S2. micro crystal graphite negative active core-shell material step S1 obtained is with adhesive using mass ratio as 95:50 are ground,
Adhesive uses PVDF Kynoar in the present embodiment, and milling time is 30~50s, is fully ground with reaching；
S3. 70Wt% NMP+super-P mixed solutions are added after being fully ground, continue to be ground to uniformly thick, are obtained
To slurry；
S4. step S3 is obtained into slurry to be evenly coated in copper foil, using vacuum drying, concrete operations are put into vacuum drying chamber
Interior 60 DEG C of more than constant temperature 12h, the solvent NMP removed in electrode slice obtain electrode slice；
S5. the former piece that the electrode obtained piece in step S4 is washed into a diameter of 16mm is taken out；Finally give micro crystal graphite negative electricity
Pole piece.
Embodiment 7
The present embodiment provides a kind of preparation method of micro crystal graphite fastening lithium ionic cell, comprises the following steps：
S1. the micro crystal graphite negative electricity pole piece being prepared using embodiment 6 carries out battery assembling；
S2. cell assembling processes are carried out in Brian participants in a bridge game's casing of closed argon atmosphere, during operation in glove box
Oxygen content and water content are controlled in below 5ppm.
S3. 2025 anode covers → micro crystal graphite negative electricity pole piece → polypropylene (PP) barrier film → lithium piece → stainless steel gasket is pressed
The order of the negative electrode casing of → spring leaf → 2025 from bottom to top is put well successively, and electrolyte lithium hexafluoro phosphate is added dropwise, seals, be assembled into
2025 type button cells, activate 24h.
Electro-chemical test is carried out to embodiment 7, it is specific as follows：
1. charge-discharge test
Charge-discharge test is the conventional means of research material electrochemical characteristic.The present invention uses Shenzhen NEWARE and LAND
Battery detection equipment, existed respectively with different charging or discharging currents (100mA/g, 500mA/g, 1A/g, 2A/g, 5A/g) at room temperature
0.01~2.00V and the interior charge-discharge performance to micro crystal graphite negative material of voltage range are tested.
To find out under different circulating ring said conditions from Fig. 2, in the charging and discharging curve of micro crystal graphite negative material of the present invention
There are a pair of charge and discharge platforms, there is reversible redox reaction.Wherein, in the discharge curve of first lap, without more apparent
Platform, and the second circle discharge curve are roughly the same.By consulting pertinent literature, negative material consumes lithium in discharge process first
Ion produces platform when forming SEI films (solid electrolyte film), and micro crystal graphite is because specific surface area is smaller, when forming SEI films
The lithium ion of consumption is less, and therefore, first charge-discharge efficiency is more than 90%.Micro crystal graphite negative material the 2nd of the present invention circle, the 10th
The charging and discharging curve of circle and the 50th circle, it can be seen that with the increase of charge and discharge cycles number, the charge/discharge capacity of sample by
It is cumulative big, and efficiency for charge-discharge is also constantly increasing.This is due to that micro crystal graphite surface is during electric discharge (embedding lithium) first
One layer of intact SEI film has been basically formed, and graphite has been played a protective role, Li+ free deintercalation has been ensure that, prevents electrolyte
In organic solvent molecule and Li+ it is embedding altogether in graphite.With the increase of charge and discharge cycles number, the SEI films of graphite surface are held
Continuous growth, until having enough thickness and compactness, can prevent the common insertion of solvent molecule, ensure that the steady of the electrode cycle
It is qualitative, so efficiency for charge-discharge is also constantly to increase；In addition, with the increase of charge and discharge cycles number, the lamella heap of graphite
Product structure gradually tends towards stability, and takes off, embedding lithium passage constantly improve, so increasing of the charge/discharge capacity of the material with cycle-index
Add, constantly increase.
As can be seen from Figure 3 micro crystal graphite negative material first charge-discharge efficiency of the present invention under 100mA/g current densities
It is higher, more than 90%.With the increase of charge and discharge cycles number, its coulombic efficiency is also gradually increased to 100%, even more than
100%.This is probably because a small amount of Li+ deintercalations on SEI films come out.
Fig. 4 is micro crystal graphite negative material of the present invention in 5 electricity such as 100mA/g, 500mA/g, 1A/g, 2A/g and 5A/g
The charge-discharge performance tested under current density, their high rate performance is investigated with this.As can be seen from the figure with charge and discharge
The increase of electric current density, charge and discharge cycles specific capacity are gradually reduced；And when current density is more than 1A/g, charging and discharging capacity
Drastically decline；Under 5A/g current density, the circulation specific capacity of micro crystal graphite negative material of the present invention is respectively less than 50mAh/g.
But by 5A/g (current density) discharge and recharge of big multiplying power and then return to 100mA/g, the circulation specific capacity of material remains unchanged
The circulation specific capacity under initial current density can also be reached, and have the trend of increase.Crystallite indicated above, prepared by the present invention
For graphite under the conditions of big multiplying power, circulation specific capacity is smaller；But its big circulation superior performance, particularly in different discharge and recharges
Under conditions of multiplying power conversion, higher cyclical stability can be still kept.
2. cyclic voltammetry (CV)
Cyclic voltammetry is one of most basic experimental technique of electrochemical field, with this method can carry out reversibility of electrode and
The judgement of electrochemical reaction mechanism, its current -voltage curve are referred to as cyclic voltammogram.The present invention uses Shanghai Chen Hua CHI660e
Type electrochemical workstation carries out cyclic voltammetric analysis to material.The test voltage section of negative material is 0.01~2.00V, scanning
Speed is 0.1mVs-1.
Fig. 5 be micro crystal graphite negative material of the present invention in 0.01V~2.00V voltage ranges, 0.1mV/s sweeps fast condition
Under the cyclic voltammetry curve collection of illustrative plates that measures.It can be seen that in first lap, occurs one also in 0.5V opening positions
Parent peak, this is the process that Li+ forms SEI in micro crystal graphite surface reduction, meanwhile, the peak is gentle, illustrates to put embedding in discharge process
Lithium capacity is less；In the second circle CV curves, the reduction peak that 0.5V positions go out disappears, and shows micro crystal graphite surface fundamental form
The SEI film solid, fine and close into one layer.After the second circle, there are a pair of obvious reduction in 0.1V and 0.2V opening positions
Peak and oxidation peak, and be gradually reduced with the increase reduction peak potential difference of cycle-index, it is preferably reversible to show that the material has
Property.With the increase of the circulation number of turns, the area of the oxidation peak of the reduction peak of 0.1V opening positions and 0.2V opening positions in CV curves
Gradually increase, show that Li+ is de-, embedding passage is gradually perfect, and circulation (can with the increase of cycle-index (Li+ takes off, embedding number)
It is inverse) capacity is continuously increased.In addition, with the increase of cycle-index, the peak shape of oxidation peak and reduction peak becomes more sharp, shows
With the increase of charge and discharge cycles number, the degree of polarization of material is gradually reduced, cyclic reversibility enhancing.
3. electrochemical impedance tests (EIS)
AC impedence method mainly obtains battery pole piece interfacial reaction by studying complex impedance plane figure and Bode figures
Relevant information.EIS tests are carried out to negative material button cell using Shanghai Chen Hua CHI660e types electrochemical workstation herein.
Potential amplitude is 5mV, and frequency range is 0.01Hz~100KHz.
Fig. 6 is micro crystal graphite negative material ac impedance measurement figure of the present invention, in order to further probe into chemical property with
Relation between electrode reaction mechanism, we have carried out electrochemical impedance (EIS) test to micro crystal graphite negative material of the present invention,
As shown in fig. 6, material shows the ion cathode material lithium Nyquist figure features of standard, the important part of two of which
Respectively in the semicircle of high-frequency region and the oblique line of low frequency region, Charge-transfer resistance (Rct) and Li+ are represent in negative material
In diffusion (weber impedance, Zw).From fig. 6, it can be seen that the charge transfer resistance R of micro crystal graphite negative material of the present invention
Ct is 397.9 Ω.
Interpretation of result
It is used as the fastening lithium ionic cell of negative pole by assembling micro crystal graphite negative electricity pole piece of the present invention, and uses discharge and recharge
Loop test, high rate performance test and ac impedance measurement, the system research storage lithium of the micro crystal graphite of the invention prepared
Can, and obtain to draw a conclusion：
For microcrystalline graphite material of the present invention under 100mA/g current density, it, which circulates specific capacity, can reach 224 mAh/
G, head effect are higher, and more than 90%, and stability is good.Under the conditions of big multiplying power, the circulation specific capacity of the material is smaller, reversible specific volume
Amount is about 50mAh/g；But its big circulation superior performance, particularly under conditions of the conversion of different charge-discharge magnifications, according to
It is old to keep higher cyclical stability, micro crystal graphite negative material of the present invention can be applied to circulation volume requirement not
It is high, will just high ultracapacitor field to big circulation stability.
Claims (10)
1. a kind of micro crystal graphite preparation method for lithium cell cathode material, it is characterised in that comprise the following steps：
S1. raw ore is handled：It is 75~80% micro crystal graphite crushing raw ores by fixed carbon content, then micro crystal graphite raw ore is carried out
Depth ore grinding, it is -0.074mm level materials to obtain fineness by ore grinding, is that -0.074mm level material contents account for 90% to mog
Primary sample carry out flotation, afterwards drying, magnetic separation, it is 85~90% micro crystal graphites to be fixed carbon content；
S2. acidleach purifies：Micro crystal graphite obtained by step S1 and mixed acid are mixed, the mixed acid is HF and HCL mixed acid,
Mixed acid is 2~3.5 with graphite liquid-solid ratio:1ml/g, HF volume content 30~60%, HCL volume content is 10~20%, so
Normal pressure acidleach, leached mud distilled water or deionized water are carried out under conditions of 50~80 DEG C of temperature, 1~4h of reaction time afterwards
Cleaning graphite to rinsing solution for it is neutral when precipitate, then filter, dry, obtain micro crystal graphite after purification, fixed carbon content
For more than 99%；
S3. it is ultrasonically treated：The obtained micro crystal graphites of step S2 are ultrasonically treated, 5~20min of ultrasonic time, frequency 20~
50KHz, finally give the micro crystal graphite for lithium cell cathode material.
2. it is used for the micro crystal graphite preparation method of lithium cell cathode material according to claim 1, it is characterised in that step S1
The micro crystal graphite raw ore is Shandong pool aphanitic graphite, wherein moisture 2.4%, volatile matter 2.99%, the carbon content of ash content 18.37%
78.64%。
3. it is used for the micro crystal graphite preparation method of lithium cell cathode material according to claim 1, it is characterised in that step S1
Described in flotation use four selected once purging selection flows of one roughing.
4. it is used for the micro crystal graphite preparation method of lithium cell cathode material according to claim 1, it is characterised in that step S2
Described in reaction time 3h, HF volume fractions 30%, liquid-solid ratio 3.5ml/g, 50 DEG C of reaction temperature.
5. it is used for the micro crystal graphite preparation method of lithium cell cathode material according to claim 4, it is characterised in that step S2
Described in HCL volume fraction be 15~20%.
6. it is used for the micro crystal graphite preparation method of lithium cell cathode material according to claim 5, it is characterised in that step S2
Described in HCL volume fraction be 20%.
7. it is used for the micro crystal graphite preparation method of lithium cell cathode material according to claim 1, it is characterised in that step S2
Described in dry temperature be 80 ~ 150 DEG C at dry 2 ~ 3h.
8. it is used for the micro crystal graphite preparation method of lithium cell cathode material according to claim 1, it is characterised in that step S3
Described in frequency be 40KHz.
9. it is used for the micro crystal graphite preparation method of lithium cell cathode material according to claim 1, it is characterised in that step S3
Described in ultrasonic time be 15min.
10. a kind of micro crystal graphite for lithium cell cathode material, it is characterised in that as described in claim 1~7 any one
Micro crystal graphite preparation method for lithium cell cathode material is prepared.
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| CN116273445A (en) * | 2023-02-20 | 2023-06-23 | 湖南五创循环科技股份有限公司 | Method for improving separation efficiency of mixed materials of waste lithium manganate batteries |
| CN116273445B (en) * | 2023-02-20 | 2024-02-02 | 湖南五创循环科技股份有限公司 | Method for improving separation efficiency of mixed materials of waste lithium manganate batteries |
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Application publication date: 20180313 |