CN108448100A - A kind of LiFePO4 of surface chemical modification and its application - Google Patents
A kind of LiFePO4 of surface chemical modification and its application Download PDFInfo
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- CN108448100A CN108448100A CN201810334092.5A CN201810334092A CN108448100A CN 108448100 A CN108448100 A CN 108448100A CN 201810334092 A CN201810334092 A CN 201810334092A CN 108448100 A CN108448100 A CN 108448100A
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- H01M4/02—Electrodes composed of, or comprising, active material
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- 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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- 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
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Abstract
The present invention relates to the surface chemical modifications of anode material of lithium battery, provide a kind of LiFePO4 of surface chemical modification, and the present invention also provides the purposes of the LiFePO4 of surface chemical modification, are used as anode material of lithium battery.A kind of LiFePO4 of surface chemical modification, which is characterized in that lithium iron phosphate particles surface covers layer of surface decorative layer.The LiFePO4 of the surface chemical modification, the specific discharge capacity that 100 circles are recycled at 1 C are 125 ~ 140 mA h g‒1, capacity retention ratio is 85 ~ 92%.The LiFePO4 of the surface chemical modification of the present invention, its particle surface have normal pressure, under the conditions of room temperature environment, the polymer-modified layer that is formed in situ, this is conducive to inhibit being in direct contact for surrounding air, electrolyte and active material, improves the high rate performance and cyclical stability of LiFePO4.
Description
Technical field
The present invention relates to lithium ion batteries（Abbreviation lithium battery）The surface chemical modification more particularly to lithium battery of positive electrode
The surface chemical modification of LiFePO 4 of anode material belongs to electrode material of lithium battery process for modifying surface field.
Background technology
Positive electrode（Also known as cathode material）It is the important component of lithium battery, it decides that the energy of lithium battery is close
Degree, cyclical stability, safety and cost（Electrochimica Acta, 2016, 222, 685-692）.Common lithium
Cell positive material has：Cobalt acid lithium (LiCoO2, be abbreviated as LCO), LiMn2O4 (LiMn2O4, be abbreviated as LMO), LiFePO4
(LiFePO4, it is abbreviated as LFP) and manganese, nickel doping cobalt acid lithium ternary electrode material (LiNi x Mn y Co z O2, x + y + z = 1)。
Above-mentioned positive electrode there is a problem that in actual application two kinds it is important：First, positive electrode electronic conductivity and ion
The low problem of conductivity；Second is that positive electrode is exposed to the problem of performance degradation in surrounding air, i.e. problem of aging.
Just there are researcher discovery, positive electrode early in 2008（Such as LFP, carbon coating LFP (LFP/C)）It is exposed to
It contacts in air or with water, since the hydrophily of Li can cause positive electrode to take off lithium, decays so as to cause its chemical property
（Electrochemical and Solid-State Letters, 2008, 11, A4-A8; Journal of Power
Sources, 2008, 185, 698-710; Electrochemical and Solid-State Letters, 2008,
11, A12-A16.）.Positive electrode in weighing, dispense, take and can be contacted with surrounding air during electrode fabrication, with air
Positive electrode after contact undergoes long-time storage（January or several months）Afterwards, chemical property can be substantially reduced.
CN1617371A discloses a kind of surface decorated lithium ion cell positive electrode material and preparation method thereof, and this method is first
It is by lithium ion anode powder body material Li-M1M2- O (M1, M2=Co, Mn, Ni, Cr) is put into a concentration of 0.05~2.00
This mixture is placed in the hydrothermal reactor with stirring by the aqueous solution containing organic substance of mol/L, in 150~200 DEG C, warp
It reacts within 0.1~4.0 hour, solution after reaction is spray-dried, then can obtain the positive electrode for being coated with uniform carbosphere.
CN102544514A discloses a kind of surface-carbon-modified cathode anode material for lithium-ion batteries and preparation method thereof, the preparation
Method is that anode material for lithium-ion batteries LiMn is made first0.5Ni1.5O4, then with LiMn obtained0.5Ni1.5O4It is molten with organic matter
The concurrent biochemical reaction of liquid uniform stirring under 80~100 °C of heating condition 15~60 minutes, obtains to surface and is coated with high score
Then the anode material for lithium-ion batteries of son is carbonized in 550 ~ 750 °C in an inert atmosphere by being filtered, washed and drying,
To obtain the anode material for lithium-ion batteries of surface-carbon-modified cathode.
Positive electrode and carbon or inorganic matter is compound, be conducive to the electronics and/or ionic conductivity that improve positive electrode.Together
When, such carbon or inorganic matter clad can prevent the hydrone in air and active material to a certain extent（I.e. above
The LiMn0.5Ni1.5O4, cobalt acid lithium, lithium nickelate etc.）It is in direct contact, this is conducive to improve positive electrode in surrounding air
Ageing resistance.But as described in CN1617371A anode material for lithium-ion batteries way, due to organic matter be coated with process
Middle positive electrode is contacted with water, thus can inevitably result in the dissolution of Li, M1, M2 metal ion, damages positive electrode
Chemical property.The way of positive electrode surface modification or cladding described in CN102544514A and CN104600282A, due to
During surface modification or cladding, positive electrode experienced high-temperature burning process, this can cause finishing coat to shrink, divide
It splits, be unevenly distributed, coating incomplete phenomenon.In other words, disposable surface modification or cladding are carried out to positive electrode, it is difficult to
It obtains and is evenly distributed on positive electrode surface, coats complete decorative layer（Journal of Materials Chemistry,
2011, 21, 14680;Journal of The Electrochemical Society, 2015, 162, A2201-
A2207;Journal of Alloys and Compounds, 2017, 706, 24-40.）, this can undoubtedly cause positive material
The phenomenon that expecting partial denudation.Hydrone in surrounding air can be contacted by diffusion with exposed position, cause positive electrode take off lithium,
Aging reduces its chemical property.
CN1652376A discloses a kind of anode material for lithium-ion batteries, preparation method and its lithium ion battery.It is described
Lithium ion anode material refer to functional polymer moditied processing LiMn2O4, the functional polymer be by contain CN,
The vinyl monomer of CON, CO or COO functional group is in the solution through a kind of polymer obtained from Raolical polymerizable.
The LiMn for the functional polymer modification that CN1652376A is provided2O4It has as a drawback that, is as coating material first
Functional polymer is not easy to obtain and non-conductive, is grafted to active material（That is LiMn2O4）Electrode material can be reduced behind surface
Electronic conductivity；Secondly, either by LiMn2O4It is mixed LiMn with functional polymer solution still2O4It polymerize with functionality
Object monomer, initiator mix in the solution, in-situ polymerization, obtains functional polymer and is grafted LiMn2O4Process be necessarily accompanied with
The volatilization of the organic matters such as solvent, unreacted monomer, environment are unfriendly.
CN106299299A discloses a kind of anode material for lithium-ion batteries and preparation method thereof with surface hydrophobic,
The surface of anode material for lithium-ion batteries with surface hydrophobic has the one layer of organic matter hydrophobic layer, the thickness of the hydrophobic layer to be
The mass content of 0.5~20 nm, hydrophobic layer are 0.1~10%；The system of anode material for lithium-ion batteries with surface hydrophobic
Preparation Method is to be uniformly mixed the organic matter with hydrophobic performance and organic solvent to stir at 30~80 DEG C with positive electrode again
And mixture is obtained by the reaction, solid filter cake is obtained by filtration in mixture, then solid filter cake is carried out to the place of two temperature gradients
Reason obtains the positive electrode of the present invention.The way of above-mentioned surface modification anode material of lithium battery is related to the use of organic solvent with after
Continuous heat treatment, complex steps, environment are unfriendly.
CN107437617A discloses a kind of improvement richness lithium material electrification driven based on metal-organic framework material
The surface modification method of performance is learned, includes mainly following steps：（1）By suitable rich lithium material and suitable organic ligand
Mixing；（2）Said mixture is positioned over heated under vacuum reaction；（3）By product obtained in the previous step in inert atmosphere
Under be thermally treated resulting in carbon ＆ nickel cobalt (alloy) quantum dot heterostructures structures cladding rich lithium material.The carbon ＆ nickel that CN107437617A is provided
The rich lithium material of cobalt alloy quantum dot heterostructures structure cladding, the advantage is that, what organic ligand was formed under vacuum, heating condition
Organic ligand steam can be combined in a manner of vapor deposition with richness lithium material particle surface, this is conducive in rich lithium material
Grain surface forms uniform decorative layer；The disadvantage is that, selected organic ligand（Methylimidazole or 2-methylimidazole）Boiling point is high,
Vapor deposition processes needs carry out under vacuum, heating condition, and technological requirement is high；It is deposited on active material（Rich lithium material）Particle
The organic ligand on surface is non-conductive, needs further high-temperature heat treatment（450~480 °C）It is converted into carbon, complex steps, energy consumption
It is high；Moreover, the carbon-coating complete cladding difficult to realize to rich lithium material particle surface obtained through high-temperature heat treatment.
Aging after being contacted with surrounding air in view of positive electrode is attributed to exposed position and environment not by surface modification
Lithium is taken off caused by after hydrone contact in air, it is clear that it is to improve it to surrounding air to carry out secondary cladding to positive electrode
The effective way of ageing resistance.Secondary surface modification/cladding is carried out to positive electrode, to meet following requirement as far as possible：（1）
It is complete to the cladding of positive electrode particle, to cut off contact path of the hydrone with active material；（2）Cladding layer component will use up
May be conductive, the high rate performance of material cannot be reduced；（3）The thickness of clad wants moderate, coats layer component institute in the composite
Accounting for mass percent cannot be excessive, i.e., cannot be to sacrifice the specific energy of positive electrode as cost；（4）Technique is simple, nothing
Waste, it is environmental-friendly.Secondary surface modification is carried out to carbon coating positive electrode, existing literature there are a large amount of records, such as uses machine
Tool mixing method（Such as ball-milling method）, mixing method, the in-situ modification method completed in the solution in solvent（Advanced Materials,
2007, 19, 848-851; J. Mater. Chem. A, 2014, 2, 19315-19323; Journal of Power
Sources, 2010, 195, 5351-5359; Angewandte Chemie, 2011, 50, 6884-6887.）.Machinery
Mixing method is unfavorable for realizing active material particle cladding, and the modification method process route based on solvent/solution is long, can generate waste liquid,
It easily leads to active material in modification and takes off lithium.In short, the above method cannot meet carries out secondary surface to positive electrode
The requirement of modification/cladding.
Invention content
In view of the deficiencies of the prior art, the present invention provides a kind of positive electrodes of surface chemical modification, are improving lithium battery just
The ageing resistance and chemical property of pole material.
Term is explained：
LCO：Cobalt acid lithium (LiCoO2)。
LCO/C：Carbon coating cobalt acid lithium (LiCoO2/C)。
LMO:LiMn2O4 (LiMn2O4)。
LMO/C:Carbon coating LiMn2O4 (LiMn2O4/C)。
LFP：LiFePO4 (LiFePO4)。
LFP/C：Carbon-coated LiFePO 4 for lithium ion batteries (LiFePO4/C)。
LNMCO:Manganese, nickel doping cobalt acid lithium ternary electrode material (LiNi x Mn y Co z O2, x + y + z = 1)。
LNMCO/C：Carbon coating manganese, nickel adulterate cobalt acid lithium ternary electrode material.
Carbon coating cobalt acid lithium (LiCoO2/ C), carbon coating LiMn2O4 (LiMn2O4/ C), carbon-coated LiFePO 4 for lithium ion batteries (LiFePO4/
C), carbon coating manganese, nickel doping cobalt acid lithium ternary electrode material are referred to as carbon coating positive electrode.
" carbon " described in above-mentioned " carbon coating " is synthesis carbon, i.e., with organic compound, organic polymer, organic polymer
For precursor, the part graphitized carbon obtained by high-temperature heat treatment.
Aging：Positive electrode is exposed to certain time in surrounding air, compared with the starting positive electrode, electrochemistry
The phenomenon that performance degradation.
Ageing resistance：The positive electrode of surface chemical modification is exposed to certain time in surrounding air, and without table
The starting positive electrode of face modification is compared, the unattenuated phenomenon of chemical property；Alternatively, with it is in identical environment,
The phenomenon that positive electrode of non-surface modification is compared, and chemical property attenuation degree is substantially reduced.
Curing：After coating material is mixed with positive electrode powder to be finished in closed container, coating material
Molecule evaporation is deposited on positive electrode powder surface, then nucleation in situ, growth, the process for forming polymer.
Specific discharge capacity：The electricity that unit mass active material or battery can release, unit：MAh/g（mA
h/g）.
Capacity retention ratio：The electricity that active material is released under certain current density and the electric discharge under a certain current density
The ratio between amount, alternatively, active material recycles the electricity and discharge capacity for the first time that can be released after a fixing turn under certain current density
The ratio between.
In order to solve the problems, such as positive electrode performance degradation after contacting with the air during transport, storage and use, carry
It is high its to tolerance in surrounding air, the present invention provides a kind of positive electrode of surface chemical modification, and the surface of positive electrode is covered
Lid layer of surface decorative layer.Reach the purpose of the present invention by the way that positive electrode is surface modified/is coated.The surface
Modification/method for coating uses aumospheric pressure cvd technology, makes coating material molecular vapor deposition in positive electrode particle
Surface, and in particle surface growth in situ, form isolated environment air water molecule and active substances in cathode materials contact channel
Polymer film.The positive electrode modified using the technology of the present invention is had good tolerance to surrounding air, and can be obviously improved
Originate the chemical property of positive electrode.Present invention process flow is short, without waste, environmental-friendly, at low cost, is suitble to scale
Commercial Application.
The present invention provides a kind of LiFePO4 of surface chemical modification, which is characterized in that covers on the surface of LiFePO 4 powder
Lid layer of surface decorative layer.The LiFePO4 of the surface chemical modification, the specific discharge capacity that 100 circles are recycled at 1 C are 125
~140 mA h g‒1, capacity retention ratio is 85 ~ 92%.
The LiFePO4 is LFP or LFT/C.Wherein, the mass percentage of carbon is less than 5% in LFT/C.
Preferably, finishing coat is conducting polymer oligomer.The conducting polymer oligomer, to contain 8 ~ 14
The oligomer of monomer, weight average molecular weight distribution are 522 ~ 912；Molecular weight distribution index is 1.1 ~ 1.3.Preferably, described
Monomer is pyrroles, 3,4- ethylene dioxies pyrroles, 1- benzyl -3,4- ethylene dioxies pyrroles, 3- methylpyrroles, 3- N-ethyl pyrrole Ns or 3-
Vinyl pyrrole.
Preferably, the conducting polymer oligomer, it is characterised in that：Monomer is pyrroles, N 1s high-resolution XPS spectrum figures
Display is positioned at the peak of 400,400.7,402 eV.
Preferably, the quality of finishing coat accounts for about the 0.05 ~ 3% of powder quality.
The preparation method of the LiFePO4 of the surface chemical modification, it is characterised in that：
A. under room temperature environment air conditions, LiFePO 4 powder is transferred in container；
B. it by coating material, is added in the container described in step a, container is sealed；
C. by mixing in coating material and container of the LiFePO 4 powder described in step b, curing obtains surface chemical modification
LiFePO4.
Room temperature environment air conditions described in step a, range of temperature therein are 0 40 °C, surrounding air
Relative humidity is 20 80%.
LiFePO4 described in step a is LFP or LFT/C.Wherein, the mass percentage of carbon is less than in LFT/C
5%.LiFePO 4 powder described in step a, the mesh of particle size >=2500.Preferably, the LiFePO4 described in step a
Powder, particle size are 0.1 ~ 5 μm.
Container described in step a is salable, with stirring, the container with charge door.
Container described in step a, material are stainless steel, enamel, enamel, ceramics, glass or plastics.
Material powder described in step a and container, wherein the volume of powder is no more than the 60% of vessel volume.
Coating material described in step b refers to that the volume mass ratio of coating material and LiFePO 4 powder is
0.5‒30 mL/kg。
Coating material described in step b is pyrroles, 3,4- ethylene dioxies pyrroles, 1- benzyl -3,4- ethylene dioxy pyrroles
It coughs up, 3- methylpyrroles, 3- N-ethyl pyrrole Ns or 3- vinyl pyrroles.
Mixing described in step c, mode are stirring, shake or vibrate.
Curing described in step c, curing time are 7 30 days, stir material during curing daily 24 times, stir every time
It is 1 15 min to mix the time.
The present invention also provides the purposes of the LiFePO4 of the surface chemical modification, are used for anode material of lithium battery.
A kind of anode material of lithium battery, which is characterized in that used the ferric phosphate of surface chemical modification of the present invention
Lithium.
Advantageous effect
The LiFePO4 of the surface chemical modification of the present invention can solve anode material of lithium battery in transport, storage and use process
In after contacting with the air performance degradation the problem of, i.e. problem of aging.The LiFePO4 of the surface chemical modification of the present invention, particle table
Face has the conducting polymer oligomer that is formed in situ, this is conducive to mitigate being in direct contact for electrolyte and active material, improves
The high rate performance and cyclical stability of LiFePO4.
The present invention utilizes chemical vapour deposition technique, makes coating material molecular vapor deposition in lithium iron phosphate particles table
Face, growth in situ, the polymer film for forming isolation hydrone and active contacts channel.Relative to LiFePO4, only need micro-
The coating material of amount can significantly improve ageing resistance of the LiFePO4 in surrounding air.Surface provided by the invention
The LiFePO4 of chemical modification, technical method is simple, technological process is short, without waste, environmental-friendly, at low cost, suitable scale
Chemical industry application.
Description of the drawings
Fig. 1 is the XRD diagram of sample：(a) LFP/C; (b) cLFP-2; (c) cLFPM-2; (d) cLFP-4; (e)
cLFPM-4。
Fig. 2 is the graph of molecular weight distribution of the surfaces sample cLFPM-2 pyrroles's oligomer.
Fig. 3 is the N 1s spectrograms of sample：(a) LFP/C; (b) cLFP-2; (c) cLFPM-2.
The SEM that Fig. 4 is sample LFP/C schemes.
The SEM that Fig. 5 is sample cLFPM-4 schemes.
The high rate performance figure of Fig. 6 samples cLFPM-2, LFP/C and cLFP-2.
Fig. 7 is the stable circulation linearity curve that sample cLFPM-2, LFP/C and cLFP-2 recycle 100 circles at 1 C.
Fig. 8 is the high rate performance figure of sample cLFPM-4, LFP/C and cLFP-4.
Fig. 9 is the stable circulation linearity curve that sample cLFPM-4, LFP/C and cLFP-4 recycle 100 circles at 1 C.
Table 1 is the unit cell volume and pore volume tables of data of sample.
Table 2 is the composition and electrochemical performance data table of sample.
Specific implementation mode
It is further elaborated below by specific embodiment and in conjunction with attached drawing to technical scheme of the present invention, these embodiments are
In order to illustrate technical scheme of the present invention, and the limitation to the claims in the present invention content cannot be considered as.
In embodiment
LFP, LFP/C win electrochemical material net purchased from match；
Pyrroles, 3,4- ethylene dioxies pyrroles, 3- methylpyrroles, 3- N-ethyl pyrrole Ns, 3- vinyl pyrroles are purchased from Mike's woods biochemistry section
Skill Co., Ltd.
X-ray powder diffraction (XRD) figure of sample is through German Bruker companies Advance D8 in description of the invention
The detection of X-ray powder diffraction instrument obtains；The molecular weight distribution of sample surfaces oligomer is through U.S.'s Waters E2695 gel infiltrations
Chromatograph (GPC) detection obtains；Level four bars flight time liquid phase-mass spectrogram (TOF LC-MS) is through 6520 level four bars of Agilent
Flight time liquid phase-mass spectrometer detection obtains；Scanning electron microscope (SEM) figure, X-ray energy dispersive spectrum (EDS) and element point
Butut is detected through Hitachi S-4800 field emission scanning electron microscopes and is obtained；The transmission electron microscope photo (TEM) of sample is through Japanese JEOL
Company's JEM-2100 transmission electron microscopes detection obtains；X-ray photoelectron spectroscopy (XPS) is through Thermo Fisher
The detection of 250 x-ray photoelectron spectroscopies of Scientific Escalab obtains；The chemical property of sample is through CHI 660E
Electrochemical analyser and the detection of LANHE CT2001A cell testers obtain.
Unless otherwise instructed, the size of LiFePO 4 powder of the present invention is 0.1 ~ 5 μm.In above-mentioned size range
The purpose of the present invention is inside can reach, those skilled in the art can select the size range of powder as needed.
Embodiment 1
(1) preparation of the LFP/C of surface modification
5 μ L pyrroles are added to and fill 10 g LFP/C powders（The size of powder granule is 0.1 ~ 1.5 μm）50 mL containers
In, container is sealed, shaking container makes LFP/C powders be uniformly mixed with pyrroles, cures 7 days at room temperature.During curing, shake daily
Visibly moved device 2 times, each shake time are no less than 1 min, the LFP/C samples of surface modification are obtained after the maturation period, by the sample
Referred to as cLFPM.
(2) senile experiment
The container stopper for filling cLFPM samples is opened, so that cLFPM samples is exposed in surrounding air, to make sample and surrounding air
It comes into full contact with, daily shakes container occlusion 3 times, each shake time is no less than 1 min, opens plug after shaking every time, makes sample
Again it exposes in surrounding air.Ageing time is continuously 2 months, ranging from 15 38 °C of variation of ambient temperature, and humidity changes model
Enclose is 20 75%.Sample after senile experiment is known as cLFPM-2, wherein 2 be ageing time（Month）.
Compare senile experiment
CLFPM samples described in above-mentioned senile experiment are replaced with starting LFP/C samples, remaining experimental implementation and condition are constant.
Sample after senile experiment is known as cLFP-2, wherein 2 be ageing time（Month）.
(3) electrochemical property test of sample
Using sample obtained by embodiment, as positive active material, lithium piece is cathode, the LiPF of 1 mol/L6It is dissolved in ethylene carbonate：
Dimethyl carbonate：Diethyl carbonate（Volume ratio is 1:1:1）For electrolyte, microporous polypropylene membrane is diaphragm, assembles CR2032 knobs
Detain battery（Int. J. Electrochem. Sci., 2018, 13,1376-1389.）.
Using CHI 660E electrochemical analysers and LANHE CT2001A cell testers to the button cell that is assembled into
Row test, the chemical property of evaluation starting LFP/C, cLFPM-2 and cLFP-2 sample.
Embodiment 2
(1) preparation of the LFP/C powders of surface modification
20 μ L pyrroles are added to and fill 10 g LFP/C powders（（The size of powder granule is 0.1 ~ 1.5 μm）50 mL hold
In device, container is sealed, shaking container makes LFP/C powders be uniformly mixed with pyrroles, cures 30 days at room temperature.During curing, often
Its shake container 2 times, each shake time are no less than 1 min, the LFP/C samples of surface modification are obtained after the maturation period, by this
Sample is referred to as cLFPM.
(2) senile experiment
The container stopper for filling cLFPM samples is opened, so that cLFPM samples is exposed in surrounding air, to make sample and surrounding air
It comes into full contact with, daily shakes container occlusion 3 times, each shake time is no less than 1 min, opens plug after shaking every time, makes sample
Again it exposes in surrounding air.Ageing time is continuously 4 months, ranging from 15 40 °C of variation of ambient temperature, and humidity changes model
Enclose is 20 80%.Sample after senile experiment is known as cLFPM-4, wherein 4 be ageing time（Month）.
Compare senile experiment
CLFPM samples described in above-mentioned senile experiment are replaced with starting LFP/C samples, remaining experimental implementation and condition are constant.
Sample after senile experiment is known as cLFP-4, wherein 4 be ageing time（Month）.
(3) electrochemical property test of sample
Electrochemical property test is carried out to sample according to method described in embodiment 1 (3).
Interpretation of result
Fig. 1 is the XRD diagram of sample cLFPM-2, LFP/C and cLFP-2.It will be seen from figure 1 that each diffraction maximum in Fig. 1 a, b, c
LFP in position and document（JCPDS 83-2092）The position of each diffraction maximum is very identical, this explanation is old by surface modification, air
After change, the object of LFP components is mutually without substantially changeing in cLFPM-2 with cLFP-2 samples.But from the change of sample unit cell volume
Change is seen（Table 1）, compared with LFP/C, the unit cell volume of cLFP-2 slightly reduces, and the unit cell volume of cLFPM-2 is almost unchanged；
The reduction of cLFP-2 unit cell volumes is caused by taking off lithium due to LFP.The result shows the sample of non-surface modification can be by ring
Border air aging, and the sample Jing Guo surface modification will not be by surrounding air aging.
The pyrroles added in experimentation can be in LFP/C after being adsorbed by LFP/C particle surfaces by vapor deposition
The synergistic effect of micro-air is lower in the metal ion and system of surface exposure aoxidizes, polymerize, in exposed particle surface shape
At one layer of pyrroles's oligomer protective film.Pyrroles's oligomer weight average molecular weight (M w) it is 780, molecular weight distribution index is
1.27, the oligomer that corresponding pyrrole ring average number is 12（Fig. 2）.
Fig. 3 is the N 1s high-resolution XPS spectrum figures of sample.From figure 3, it can be seen that with sample LFP/C（Fig. 3 a）And cLFP-2
（Fig. 3 b）It compares, the cLFPM-2 samples modified by pyrroles's oligomer（Fig. 3 c）Middle N 1s peak-to-peak signals are remarkably reinforced.Position in Fig. 3 c
N H, C N are corresponded to respectively in the peak of 400,400.7,402 eV+With C=N+Component, N 1s of these three components in traditional polypyrrole
It is frequently seen in spectrogram（Synthetic Metals, 2004, 145, 15-22; Polymer Degradation and Stability, 2015, 120, 392-401.）.XPS the result shows that, can be at LFP/C using patented technology of the present invention
Grain surface forms pyrroles's oligomer.
Fig. 4 and Fig. 5 is sample LFP/C（Fig. 4）、cLFPM-4（Fig. 5）SEM figure.Compared with originating LFP/C samples, pass through
Variation of the sample in particle size and pattern after surface modification is difficult to differentiate between, this is because formed in LFP/C particle surfaces
Azole polymer is the result of atomic size thickness.
Molecular dynamics simulation result of calculation shows pyrroles's vapour molecule preferentially at LFP/C carbon layer on surface hole position（I.e.
LFP exposed positions combine）, then nucleation in situ, growth, form the atomic layer level thickness for inhibiting surrounding air to be in direct contact with LFP
Azole polymer protective film.The nitrogen adsorption desorption test result of sample shows with pyrroles and LFP/C volume mass ratios（μL/
g）Increase, the pore volume of sample is gradually reduced（Table 1）.This explanation, the calculated results and experimental result are identical.
Table 1
Fig. 6 is the high rate performance figure of sample cLFPM-2, LFP/C and cLFP-2.Although compared with low range（< 0.5 C）Under,
The specific discharge capacity of cLFPM-2 and LFP/C is closer to, but compared with high magnification（≥ 0.5 C）Under, the electric discharge specific volume of cLFPM-2
Amount is apparently higher than the specific discharge capacity of LFP/C.And compared to LFP/C, in the case where multiplying power is higher than 0.2 C, cLFP-2's puts
Electric specific capacity is substantially reduced.
Fig. 7 is the stable circulation linearity curve that sample cLFPM-2, LFP/C and cLFP-2 recycle 100 circles at 1 C.From figure
As can be seen that the initial discharge specific capacity of cLFPM-2, LFP/C and cLFP-2 are respectively 147,137 and 132 mA h g‒1, cycle
After 100 circles, the specific discharge capacity of cLFPM-2, LFP/C and cLFP-2 are respectively 137,116 and 97 mA h g‒1, capacity retention ratio
Respectively 88.4%, 84.7% and 73.5%（Table 2）.
Fig. 8 is the high rate performance figure of sample cLFPM-4, LFP/C and cLFP-4.In multiplying power≤2 C, cLFPM-4 with
The specific discharge capacity of LFP/C is closer to, but when multiplying power increases to 5 C, specific discharge capacity the putting higher than LFP/C of cLFPM-4
Electric specific capacity.And compared to LFP/C, it is within the scope of 0.1 5 C in multiplying power, the specific discharge capacity of cLFP-4 is substantially reduced.
Fig. 9 is the stable circulation linearity curve that sample cLFPM-4, LFP/C and cLFP-4 recycle 100 circles at 1 C.cLFPM-
4, the initial discharge specific capacity of LFP/C and cLFP-4 is respectively 140,137 and 121 mA h g‒1, after cycle 100 is enclosed, discharge ratio
Capacity remains 127,116 and 94 mA h g respectively‒1, capacity retention ratio is respectively 90.7%, 84.7% and 77.7%（Table 2）.
The above results show that even if mass percentage of pyrroles's oligomer in cLFPM compounds be about 5/10000ths
In the case of, the sample of surface modification after aging 2 months, recycles the specific discharge capacity ratios of 100 circles in surrounding air under 1 C
The specific discharge capacity of starting LFP/C samples improves 18.1%；And the sample of non-surface modification, aging 2 in surrounding air
The specific discharge capacity of 100 circles is recycled after month, under 1 C reduces 16.4% compared with the specific discharge capacity of beginning LFP/C sample.
Table 2
When mass percentage of pyrroles's oligomer in cLFPM compounds is about 2/1000ths, the sample of surface modification exists
Specific discharge capacity of the specific discharge capacity compared with beginning LFP/C sample of 100 circles is recycled in surrounding air after aging 4 months, under 1 C
Improve 9.5%；And the sample of non-surface modification, putting for 100 circles is recycled in surrounding air after aging 4 months, under 1 C
Electric specific capacity reduces 20.0% compared with the specific discharge capacity of beginning LFP/C sample.
To sum up, patented technology of the present invention can improve LFP/C in ring in the case where conducting polymer monomer dosage is few
Ageing resistance in the air of border, and its chemical property can be improved.
Embodiment 3
Other with embodiment 1, the difference is that, by 300 μ L 3,4- ethylene dioxy pyrroles, which is added to, fills 10 g LFP powder
Body（The size of powder granule is 0.5 ~ 5 μm）50 mL containers in, container is sealed, shake container make LFP powders and 3,4-
Ethylene dioxy pyrroles is uniformly mixed, and cures 10 days at room temperature.During curing, it is shaken every day container 4 times, it is many to shake the time every time
In 10 min, the LFP samples of surface modification are obtained after the maturation period.
Compared to starting LFP samples, the LFP of surface modification is after surrounding air aging 2 months, sample putting at 1 C
Electric specific capacity can be improved 25.6%.
Embodiment 4
Other with embodiment 3, the difference is that, 200 μ L 3- methylpyrroles are added to and fill 10 g LFP powders（（Powder
The size of body particle is 0.5 ~ 5 μm）50 mL containers in, container is sealed, shake container make LFP powders and 3- methylpyrroles
It is uniformly mixed, cures 14 days at room temperature.During curing, it is shaken every day container 3 times, each shake time is no less than 5 min, cures
The LFP samples of surface modification are obtained after phase.
Compared to starting LFP samples, the LFP of surface modification is after surrounding air aging 2 months, sample putting at 1 C
Electric specific capacity can be improved 27.5%.
Embodiment 5
Other with embodiment 1, the difference is that, 100 μ L 3- vinyl pyrroles are added to and fill 10 g LFP/C powders
（The size of powder granule is 0.1 ~ 1.5 μm）50 mL containers in, container is sealed, shake container make LFP/C powders and 3-
Vinyl pyrrole is uniformly mixed, and is cured 14 days at room temperature.During curing, it is shaken every day container 4 times, each shake time is no less than
5 min obtain the LFP/C samples of surface modification after the maturation period.
Compared to starting LFP/C samples, the LFP/C of surface modification is after surrounding air aging 2 months, and sample is at 1 C
Specific discharge capacity can be improved 18.7%.
Embodiment 6
Other with embodiment 3, the difference is that, 300 μ L 3- N-ethyl pyrrole Ns are added to and fill 10 g LFP/C powders（Powder
The size of body particle is 0.5 ~ 5 μm）50 mL containers in, container is sealed, shake container make LFP/C powders and 3- ethyl pyrroles
Cough up it is uniformly mixed, at room temperature cure 10 days.During curing, it being shaken every day container 4 times, each shake time is no less than 10 min,
The LFP/C samples of surface modification are obtained after maturation period.
Compared to starting LFP/C samples, the LFP/C of surface modification is after surrounding air aging 2 months, and sample is at 1 C
Specific discharge capacity can be improved 19.2%.
Claims (10)
1. a kind of LiFePO4 of surface chemical modification, it is characterised in that：It is characterized in that, the surface covering of LiFePO 4 powder
Layer of surface decorative layer；
The LiFePO4 of the surface chemical modification, the specific discharge capacity that 100 circles are recycled at 1 C reach 125 ~ 140 mA h g‒1, capacity retention ratio is 85 ~ 92%.
2. the LiFePO4 of surface chemical modification as described in claim 1, which is characterized in that the LiFePO4 is
LiFePO4(LFP) or LiFePO4/C(LFT/C)；Wherein, the mass percentage of carbon is less than 5% in LFT/C；
Finishing coat is conducting polymer oligomer；The conducting polymer oligomer, to contain the oligomeric of 8 ~ 14 monomers
Body, weight average molecular weight distribution are 522 ~ 912；Molecular weight distribution index is 1.1 ~ 1.3；
The monomer is pyrroles, 3,4- ethylene dioxies pyrroles, 1- benzyl -3,4- ethylene dioxies pyrroles, 3- methylpyrroles, 3- ethyls
Pyrroles or 3- vinyl pyrroles.
3. the LiFePO4 of surface chemical modification as claimed in claim 2, which is characterized in that finishing coat conducting polymer
Oligomer, monomer are pyrroles, and N 1s high-resolution XPS spectrum figures are shown positioned at the peak of 400,400.7,402 eV.
4. the LiFePO4 of surface chemical modification as described in any one of claims 1-3, which is characterized in that finishing coat
Quality accounts for about the 0.05 ~ 3% of powder quality.
5. the preparation method of the LiFePO4 of surface chemical modification according to any one of claims 1-4, it is characterised in that：
A. under room temperature environment air conditions, LiFePO 4 powder is transferred in container；
B. it by coating material, is added in the container described in step a, container is sealed；
C. by mixing in coating material and container of the LiFePO 4 powder described in step b, curing obtains surface chemical modification
LiFePO4.
6. the preparation method of the LiFePO4 of surface chemical modification as claimed in claim 5, it is characterised in that：Institute in step a
The room temperature environment air conditions stated, range of temperature therein are 0 40 °C, and the relative humidity of surrounding air is 20 80%；
LiFePO4 described in step a is LFP or LFT/C；Wherein, the mass percentage of carbon is less than 5% in LFT/C；
LiFePO 4 powder described in step a, the mesh of particle size >=2500；Preferably, the LiFePO4 described in step a
Powder, particle size are 0.1 ~ 5 μm；
LiFePO 4 powder described in step a and container, wherein the volume of powder is no more than the 60% of vessel volume.
7. the preparation method of the LiFePO4 such as surface chemical modification described in claim 5 or 6, it is characterised in that：In step b
The volume mass ratio of the coating material, coating material and LiFePO 4 powder is 0.5 30 mL/kg；
Coating material described in step b, be pyrroles, 3,4- ethylene dioxies pyrroles, 1- benzyl -3,4- ethylene dioxies pyrroles,
3- methylpyrroles, 3- N-ethyl pyrrole Ns or 3- vinyl pyrroles.
8. the preparation method of the LiFePO4 such as claim 5-7 any one of them surface chemical modifications, it is characterised in that：Step
Mixing described in rapid c, mode are stirring, shake or vibrate；
Curing described in step c, curing time are 7 30 days, stir material during curing daily 24 times, every time when stirring
Between be 1 15 min.
9. the purposes or claim 5-8 of the LiFePO4 of claim 1-4 any one of them surface chemical modifications are any
The purposes of the LiFePO4 of surface chemical modification prepared by the method described in, is used for anode material of lithium battery.
10. a kind of anode material of lithium battery, which is characterized in that claim 1-4 any one of them surface chemistries has been used to repair
The LiFePO4 of decorations, or used the ferric phosphate of the surface chemical modification of claim 5-8 any one of them methods preparation
Lithium.
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| CN115911254A (en) * | 2021-09-30 | 2023-04-04 | 湖州卫蓝科技有限公司 | High-safety electrode slice and preparation method and application thereof |
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| CN101478039A (en) * | 2009-02-05 | 2009-07-08 | 上海交通大学 | Preparation for polypyrole coated lithium iron phosphate |
| CN102544505A (en) * | 2011-12-15 | 2012-07-04 | 湖北万润新能源科技发展有限公司 | Surface modification method of lithium iron phosphate cathode material |
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|---|---|---|---|---|
| CN101478039A (en) * | 2009-02-05 | 2009-07-08 | 上海交通大学 | Preparation for polypyrole coated lithium iron phosphate |
| CN102544505A (en) * | 2011-12-15 | 2012-07-04 | 湖北万润新能源科技发展有限公司 | Surface modification method of lithium iron phosphate cathode material |
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| CN115911254A (en) * | 2021-09-30 | 2023-04-04 | 湖州卫蓝科技有限公司 | High-safety electrode slice and preparation method and application thereof |
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