CN113675374B - Negative electrode, preparation method thereof and lithium ion battery - Google Patents
Negative electrode, preparation method thereof and lithium ion battery Download PDFInfo
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- CN113675374B CN113675374B CN202010414686.4A CN202010414686A CN113675374B CN 113675374 B CN113675374 B CN 113675374B CN 202010414686 A CN202010414686 A CN 202010414686A CN 113675374 B CN113675374 B CN 113675374B
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- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/134—Electrodes based on metals, Si or alloys
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- 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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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1395—Processes of manufacture of electrodes based on metals, Si or alloys
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- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/40—Alloys based on alkali metals
- H01M4/405—Alloys based on lithium
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- H01—ELECTRIC ELEMENTS
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/621—Binders
- H01M4/622—Binders being polymers
- H01M4/623—Binders being polymers fluorinated polymers
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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract
The invention relates to the technical field of lithium ion batteries, and discloses a negative electrode, a preparation method thereof and a lithium ion battery. The negative electrode comprises a porous metal mesh current collector and a lithium alloy attached to the porous metal mesh current collector, hot melt polymers are filled in holes of the porous metal mesh current collector, and the hot melt polymers are connected with the lithium alloy and the porous metal mesh current collector. The use of the negative electrode can increase the cycle life of the lithium battery; and the expansion rate of the lithium battery is low, and meanwhile, the safety of the lithium ion battery can be ensured.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a negative electrode, a preparation method thereof and a lithium ion battery.
Background
Currently, commercial lithium ion batteries mostly use graphite, silicon or silicon-carbon composite as the negative electrode material. When graphite is used as the negative electrode material, the theoretical specific capacity of the graphite is only 372mAh/g, so that the further improvement of the capacity of the lithium ion battery is limited.
In order to provide battery capacity, lithium metal is selected, and in the prior art, lithium metal is one of candidates for next-generation high-specific-energy secondary batteries. However, lithium metal is unsafe, and when used in a negative electrode of a lithium secondary battery, uneven dissolution-deposition of lithium metal during charge and discharge may cause growth of lithium dendrites, thereby causing consumption of lithium metal and serious volume change.
In addition, the negative electrode of the secondary lithium battery is positioned in a thermodynamically unstable area of the carbonate non-aqueous solvent in the electrolyte during normal operation. The solvent molecules are decomposed by electrons on the surface of the negative electrode, and the decomposition products are deposited on the surface of the electrode to form a solid electrolyte membrane. However, this solid electrolyte membrane is rigid, and if the anode material undergoes a large volume change during charge and discharge, this membrane may break and fall off, thereby allowing the electrolyte to continue to decompose and form a solid electrolyte membrane, which necessarily causes capacity fade of the lithium ion battery during cycling. In addition, as the common knowledge of the person skilled in the art, the solid electrolyte membrane formed on the surface of the anode material during charge and discharge is electronically insulating; as the cycle proceeds, the particles of the negative electrode material are continually broken into smaller particles, and the solid electrolyte film that is continually formed and thickened on the surface thereof blocks the electronic conductance between the materials and the negative electrode current collector, resulting in loss of electrical contact between the materials and the negative electrode current collector, becoming a "dead capacity", and further causing capacity fade during the cycle of the lithium ion battery.
Based on this, in the prior art, a method for improving the capacity of a lithium ion battery by adding some lithium-containing alloy to the negative electrode material, the lithium alloy is far superior to lithium metal in terms of volume change.
However, lithium alloy type negative electrode materials such as lithium aluminum alloy (aluminum content less than 60%), lithium magnesium alloy (magnesium content less than 25%), lithium boron alloy (boron content less than 45%) and the like can be formed separately into strips, but such alloy strips are harder than lithium metal and have poor adhesion, and cannot be well adhered to a negative electrode current collector. And even cannot be combined with porous current collectors. I.e., poor contact with the current collector, thereby affecting the battery cycle performance.
Disclosure of Invention
The invention aims to solve the problem that a lithium alloy cannot be combined with a current collector in the prior art, and provides a negative electrode, a preparation method thereof and a lithium ion battery, wherein the cycle life of the lithium battery containing the negative electrode is prolonged; and has a low expansion rate of the lithium battery.
In order to achieve the above object, a first aspect of the present invention provides a negative electrode, wherein the negative electrode comprises a porous metal mesh current collector and a lithium alloy attached to the porous metal mesh current collector, wherein pores of the porous metal mesh current collector are filled with a hot-melt polymer, and the hot-melt polymer connects the lithium alloy and the porous metal mesh current collector.
The second aspect of the present invention provides a method for producing a negative electrode as described above, comprising: sequentially stacking the first lithium alloy foil layer, the hot melt polymer film, the porous copper mesh current collector and the second lithium alloy foil layer, and then performing pressing treatment to obtain a negative electrode; wherein the hot melt polymer film is made of a hot melt polymer.
The third aspect of the present invention provides another method for producing a negative electrode as described by the foregoing, wherein the method comprises:
(1) Injecting the hot melt polymer into the pores of the porous metal mesh current collector by nano injection molding to obtain a filled current collector;
(2) And sequentially stacking the first lithium alloy foil layer, the filling type current collector and the second lithium alloy foil layer, and then performing pressing treatment to obtain the negative electrode.
A fourth aspect of the present invention provides a lithium battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode described above.
Through the technical scheme, the invention has the following advantages:
(1) The forming and mechanical properties in the prior art are good, and the lithium alloy negative electrode is difficult to directly attach to a current collector. The invention adopts the hot-melt polymer to bond the lithium alloy strip which has good forming and mechanical properties but is difficult to be directly bonded with the current collector with the porous metal net current collector together to ensure good electronic conduction, and the electrode lugs can be led out through the porous current collector, thereby ensuring the application of the negative electrode with high capacity and high lithium content.
(2) The lithium alloy (foil) adopted in the invention has excessive active lithium which can participate in the electrochemical circulation of the lithium battery, and the capacity loss caused by the consumption of the active lithium is supplemented. Meanwhile, the lithium alloy foil has more pores relative to metal lithium, is beneficial to the deposition and dissolution of active lithium, and avoids the generation of lithium with a dendritic or mossy fluffy structure.
(3) The technical scheme of the invention can effectively exert the high capacity characteristic of the lithium alloy negative electrode and lithium metal, avoid the problems of lithium dendrite and severe volume change caused by independently using the lithium metal, and can reduce the expansion rate of the lithium battery while prolonging the cycle life of the lithium battery.
(4) The problems of sheet making of the lithium alloy foil and current collector leading-out are solved through the scheme, and the negative electrode can be prepared by the lithium alloy foil in a continuous production mode.
Detailed Description
The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.
The first aspect of the invention provides a negative electrode, wherein the negative electrode comprises a porous metal mesh current collector and a lithium alloy attached to the porous metal mesh current collector, hot melt polymers are filled in holes of the porous metal mesh current collector, and the hot melt polymers are connected with the lithium alloy and the porous metal mesh current collector.
According to the present invention, the inventors of the present invention found that: in the prior art, an adhesive conductive layer (adhesive+conductive agent) is often provided to increase interlayer adhesion, that is, the conductive coating in the prior art is to coat the adhesive+conductive agent between the electrode layer and the current collector. However, it is not suitable for the alloy foil having no adhesion property to the current collector, and the direct coating of the polymer binder between the alloy foil and the current collector may affect the electron conduction between the current collector and the alloy foil, and may also result in an increase in the thickness of the electrode.
And the inventors of the present invention consider: the alloy foil materials with the characteristic of no adhesion with the current collector have the advantages of good stability, easy molding, easy processing and the like. The lithium alloy foil also has higher volume specific capacity and mass specific capacity, has good affinity with lithium metal, and can accept additional lithium metal deposition beyond the upper limit of the alloy proportion. Particularly in a battery system with high energy density, the lithium alloy anode can replace a graphite anode material with low energy density, and the volume expansion and the safety problems caused by a lithium metal simple substance are reduced.
Accordingly, the inventors of the present invention found through experiments that: and filling the hot-melt polymer into holes of the porous metal net current collector to prepare an ultrathin lithium alloy negative electrode, wherein the porous metal net current collector can provide electron conduction and tab extraction, and the 'net-shaped' porous metal current collector can fill the hot-melt polymer into the meshes without affecting the electron contact between the porous metal net current collector framework and the alloy negative electrode material.
In conclusion, the adoption of the technical scheme of the invention can reduce the volume ratio of the negative electrode in the whole battery; on the other hand, the lithium alloy foil is bonded with the porous metal mesh current collector through the hot melt polymer, so that good electron conduction between the alloy foil negative electrode material and the current collector is ensured, and the electrode lug is led out through the porous metal mesh current collector; in addition, the lithium alloy negative electrode high-capacity characteristic can be effectively exerted, the problems of lithium dendrite and severe volume change caused by single use of lithium metal are avoided, and the safety and the cycle life of the battery are ensured.
According to the invention, the degree of filling of the hot-melt polymer is less than the porosity of the porous metal mesh current collector, and the degree of filling is preferably 40-98%. In the invention, the hot-melt polymer and the lithium alloy foil are in dispersed point contact, and the porous metal mesh current collector and the lithium alloy foil are continuous conductive networks, so that the electron conduction between the anode active material and the current collector can be satisfied as long as good contact exists between the porous metal mesh current collector and the lithium alloy foil. The lithium alloy foil has good electron conductivity, and under the condition that the filling degree of the hot melt polymer defined by the invention is smaller than the porosity of the porous metal mesh current collector, the contact between the lithium alloy foil and the porous metal mesh current collector can ensure the electron conduction between the electrode and the current collector. In the present invention, if the filling degree of the hot-melt polymer is greater than the porosity of the porous metal mesh current collector, it may cause the hot-melt polymer to overflow the pores in the current collector to completely wrap the current collector, and preferably, in case the hot-melt polymer is an insulating material, it may block the electron conduction between the lithium alloy electrode material and the current collector.
In the present invention, "dispersed point contact" means contact between a filler and a lithium alloy-based foil in a mesh in which a porous current collector is independently dispersed.
According to the invention, the hot melt polymer may be a conductive polymer and/or an insulating material, preferably an insulating material.
According to the present invention, in particular, the hot-melt polymer is selected from one or more of PET (polyethylene terephthalate), PI (polyimide), PP (polypropylene), PE (polyethylene), PVA (polyvinyl alcohol), PVB (polyvinyl butyral), PAA (polyacrylic acid), PVDF (polyvinylidene fluoride), PEO (polyethylene oxide), PPC (polypropylene carbonate), CMC (carboxymethyl cellulose), EVA (ethylene/vinyl acetate copolymer), PAN (polyacrylonitrile), SBR (styrene butadiene rubber), PMMA (polymethyl methacrylate), polyurethane resin, ureido-pyrimidinone, dopamine methacrylamide, polydopamine homopolymer and copolymers thereof.
Preferably, the hot-melt polymer is selected from one or more of PVB (polyvinylbutyral), PAA (polyacrylic acid), PVDF (polyvinylidene fluoride), PEO (polyethylene oxide), PMMA (polymethyl methacrylate), polyurethane resin, and PET (polyethylene terephthalate).
According to the invention, the melting point of the hot-melt polymer is 80-350 ℃, preferably 90-220 ℃. In the invention, the melting point of the hot-melt polymer is limited within the range, so that the hot-melt polymer is in a molten softening state in the process of preparing the negative electrode, thereby naturally leveling and filling the pores of the porous metal mesh, and the bonding effect of the hot-melt polymer is exerted after the hot-melt polymer is cooled, so that the sufficient bonding of the porous current collector and the lithium alloy foil is ensured.
According to the invention, the lithium alloy is made of a lithium alloy foil, and the content of lithium element in the lithium alloy foil is more than 20wt%, preferably 40-95wt%; in the invention, the content of lithium element in the lithium alloy foil is limited to be within the range, and the lithium alloy foil has the advantage that excessive active lithium can participate in electrochemical circulation of the lithium battery to supplement capacity loss caused by active lithium consumption.
According to the invention, the lithium alloys have the same or different thicknesses, each of 2 to 50 μm, preferably 8 to 40 μm.
According to the invention, the melting point of the main phase of the lithium alloy foil is greater than 300 ℃, more preferably 400-1100 ℃.
According to the invention, the lithium alloy foil is selected from one or more of lithium boron alloy, lithium magnesium alloy, lithium aluminum alloy, lithium tin alloy, lithium germanium alloy, lithium gallium alloy, lithium indium alloy, lithium antimony alloy, lithium indium alloy, lithium zinc alloy, lithium lead alloy and lithium bismuth alloy; preferably, the lithium alloy foil is selected from one or more of lithium boron alloy, lithium magnesium alloy, lithium aluminum alloy and lithium indium alloy. Most preferred is a lithium boron alloy.
According to the invention, the thickness of the porous metal net current collector is 5-50 μm; preferably, the porous metal mesh current collector has a porosity of 5 to 90%. In the present invention, the porous metal mesh current collector may be a porous copper mesh current collector. In addition, in the present invention, the thickness and the void ratio of the porous metal net current collector are limited to be within the aforementioned ranges, which is advantageous for the filling of the hot-melt polymer.
According to the invention, the thickness of the negative electrode is 21-130 μm, preferably 25-100 μm.
The second aspect of the present invention provides a method for preparing the negative electrode described above, wherein the method comprises: and sequentially stacking the first lithium alloy foil layer, the hot-melt polymer film, the porous copper mesh current collector and the second lithium alloy foil layer, and then performing pressing treatment to obtain the negative electrode.
According to the present invention, the hot-melt polymer film is prepared from the hot-melt polymer, and for example, can be obtained by electrospinning, phase separation, stretch forming, slit coating, melt-casting, or the like.
According to the present invention, the thickness of the hot-melt polymer film is preferably 1 to 20. Mu.m, more preferably 2 to 5. Mu.m.
According to the invention, the pressing conditions include: the temperature is 60-500 ℃, the pressure is 0.1-50MPa, and the time is 3-1200min; preferably, the temperature is 80-300 ℃, the pressure is 0.5-10MPa, and the time is 5-60min. In the invention, the negative electrode with good contact can be obtained by adjusting the hot pressing temperature and pressure, and the lithium boron alloy is different from lithium metal with the melting point of 180 ℃ only and can resist the temperature of more than 300 ℃. Therefore, under the pressing condition defined by the invention, the hot-melt polymer can be ensured to be in a molten softening state, and the leveling effect of the hot-melt polymer can ensure that the hot-melt polymer is well filled in the holes of the porous current collector after the pressure is applied, but not between the porous metal mesh current collector and the lithium alloy foil layer.
According to the invention, the main purpose of the method is to realize a sheet structure, and the method is easy to process and shape, and can be used for lithium alloy foil materials with small expansion in the circulation process.
The third aspect of the present invention provides another method for producing the negative electrode described above, wherein the method comprises:
(1) Injecting the hot melt polymer into the pores of the porous metal mesh current collector by nano injection molding to obtain a filled current collector;
(2) And sequentially stacking the first lithium alloy foil layer, the filling type current collector and the second lithium alloy foil layer, and then performing pressing treatment to obtain the negative electrode.
According to the invention, the pressing conditions include: the temperature is 60-500 ℃, the pressure is 0.1-50MPa, and the time is 3-1200min; preferably, the temperature is 80-300 ℃, the pressure is 0.5-10MPa, and the time is 5-60min.
In a fourth aspect, the present invention provides a lithium battery, which includes a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode.
According to the invention, the electrolyte contains a lithium salt selected from the group consisting of LiN (SO) 2 F) 2 (lithium bis-fluorosulfonyl imide), liN (CF) 3 SO 2 ) 2 、LiCF 3 SO 3 、LiC(CF 3 SO 2 ) 3 、LiB(C 2 O 4 ) 2 、Li 2 Al(CSO 3 Cl 4 )、LiP(C 6 H 4 O 2 ) 3 、LiPF 3 (C 2 F 5 ) 3 、LiN(CF 3 SO 2 ) 2 And LiN (SiC) 3 H 9 ) 2 One or more of the following; preferably, the lithium salt is selected from fluorine-containing lithium salts, from LiN (SO 2 F) 2 、LiN(CF 3 SO 2 ) 2 、LiCF 3 SO 3 、LiC(CF 3 SO 2 ) 3 、LiPF 3 (C 2 F 5 ) 3 And LiN (CF) 3 SO 2 ) 2 One or more of the following.
According to the present invention, the solvent is selected from one or more of an ether solvent, a fluorocarboxylate solvent, and a fluoroether solvent; preferably, the solvent is a mixed solvent of an ether solvent, a fluorocarboxylate solvent and a fluoroether solvent; more preferably, the solvent is a mixed solvent of a fluorocarboxylic acid ester solvent and a fluoroether solvent.
In the invention, the ether solvent, the fluorocarboxylate solvent and the fluoroether solvent, and the ether solvent, the fluorocarboxylate solvent and the fluoroether solvent with specific proportions are adopted, so that the ether solvent, the fluorocarboxylate solvent and the fluoroether solvent are more stable with metal lithium or lithium alloy, and the side reaction is far less than that of the carbonate solvent.
According to the invention, the concentration of the lithium salt is 12-70 wt.%, preferably 20-66 wt.%.
According to the invention, the ether solvent is selected from one or more of ethylene glycol dimethyl ether (DME), dipropylene glycol dimethyl ether (DMM), tripropylene glycol monomethyl ether (TPM) and tetraethylene glycol dimethyl ether.
According to the invention, the fluorinated carboxylic ester solvent is selected from one or more of ethyl Difluoroacetate (DFEA), ethyl Fluoroacetate (FEA), ethyl 2,2 difluoropropionate and ethyl trifluoropropionate;
in accordance with the present invention, the fluoroether solvent is selected from 1, 2-tetrafluoroethyl ether (ETFE), 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether (TTE), hexafluoroisopropyl ether (HFPE) tetrafluoroethyl-tetrafluoropropyl ether (HFE), 2-trifluoroethyl ether (BTFE), 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether tetrafluoroethyl-tetrafluoropropyl ether (HFE), 2-trifluoroethyl ether (BTFE) 1, 2-tetrafluoroethyl-2, 2-trifluoroethyl ether.
According to the invention, the positive electrode comprises lithium cobaltate.
The present invention will be described in detail by examples.
In the following examples and comparative examples:
(1) Measurement of cycle life of battery:
the battery was subjected to a charge-discharge cycle test at 0.2C on a LAND CT 2001C secondary battery performance test device purchased from marvelian blue electricity at 25±1 ℃.
The method comprises the following steps: standing for 10min; constant voltage charging to 4.2V/0.05C cut-off; standing for 10min; constant current discharge to 3.0V is 1 cycle. And repeating the steps, wherein the cycle is ended when the battery capacity is lower than 80% of the first discharge capacity in the cycle process, and the cycle times are the cycle life of the battery, and each group is averaged.
(2) Cell expansion ratio:
and after the cycle life is finished, the size of the battery is tested, and the expansion rate of the battery is calculated by comparing the size with the size before the cycle.
(3) The raw material sources are as follows:
in the present invention, the raw materials used are all commercially available, for example, from the company Ama Ding Jia, angstrom chemical Co., ltd.
Example 1
This example is intended to illustrate the preparation of a lithium ion battery using the negative electrode of the present invention.
(1) Fabrication of negative electrode
Sequentially placing a first 35 mu m-thick lithium-boron alloy foil with the lithium content of 60%, a PET non-woven fabric film with the porosity of 86% and the thickness of 8 mu m, a porous copper foil with the porosity of 40% and the thickness of 25 mu m, and a second 35 mu m-thick lithium-boron alloy belt with the lithium content of 60% under a flat plate hot press for pressing for 10min at 300 ℃ and 2 MPa; a negative electrode was obtained.
And cutting the negative electrode into a pole piece with the thickness of 49mm and 57mm to obtain the negative electrode pole piece prepared in the embodiment 1.
(2) Preparation of electrolyte
In a glove box filled with argon (H 2 O≤5PPM，O 2 Less than or equal to 5 PPM), ethylene glycol dimethyl ether (DME), ethyl Difluoroacetate (DFEA), 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether (TTE). According to the mass ratio, according to DME: DFEA: tte=20:70:10, and then 60wt% lithium bis (fluorosulfonyl) imide LiN (SO 2 F) 2 。
(3) Fabrication of positive electrode
The lithium cobalt oxide positive plate with the thickness of 110 mu m on both sides is obtained through size mixing, coating, drying and rolling, and is cut into rectangular pole pieces with the size of 48mm and 56mm, and the pole lugs are spot-welded at the positions in the width direction.
(4) Battery fabrication
And (3) alternately stacking the positive plate obtained in the step (1) and the negative plate obtained in the step (3) together with the diaphragm, and preparing the battery in a lamination mode, wherein the positive plate and the negative plate are alternately isolated by the diaphragm, so as to obtain the dry battery core. Placing the dry battery cell in an aluminum plastic film outer package, injecting the electrolyte obtained in the step (2), vacuumizing and sealing, placing at 60 ℃ for 48 hours, pressurizing the layer at 60 ℃, packaging for the second time, exhausting and separating the volume to obtain the lithium battery mark S1 prepared in the embodiment 1.
Example 2
This example is intended to illustrate the preparation of a lithium ion battery using the negative electrode of the present invention.
A lithium ion battery was fabricated in the same manner as in example 1, except that: in step (1), the "first and second 35 μm thick lithium-boron alloy foils having a lithium content of 60% are replaced with" first and second 40 μm thick lithium-magnesium alloy foils having a lithium content of 75%.
As a result, the lithium battery prepared in this example 2 was labeled S2.
Example 3
This example is intended to illustrate the preparation of a lithium ion battery using the negative electrode of the present invention.
A lithium ion battery was fabricated in the same manner as in example 1, except that: in step (1), the "first and second 35 μm thick lithium-boron alloy foils having a lithium content of 60% are replaced with the" first and second 45 μm thick lithium-indium alloy foils having a lithium content of 35%.
As a result, the lithium battery prepared in this example 3 was labeled S3.
Example 4
This example is intended to illustrate the preparation of a lithium ion battery using the negative electrode of the present invention.
A lithium ion battery was fabricated in the same manner as in example 1, except that: in the step (1), the "8 μm thick 86% porosity PET nonwoven film" was replaced with the "5 μm thick dense PVDF film", and the "25 μm thick 40% porosity porous copper foil" was replaced with the "20 μm thick 60% porosity porous copper foil".
As a result, the lithium battery prepared in this example 4 was labeled S4.
Example 5
This example is intended to illustrate the preparation of a lithium ion battery using the negative electrode of the present invention.
A lithium ion battery was fabricated in the same manner as in example 1, except that: in step (1), the "first and second 35 μm thick lithium-boron alloy foils having a lithium content of 60% are replaced with" first and second 30 μm thick lithium-aluminum alloy foils having a lithium content of 75%.
As a result, the lithium battery prepared in this example 2 was labeled S5.
Example 6
This example is intended to illustrate the preparation of a lithium ion battery using the negative electrode of the present invention.
A lithium ion battery was fabricated in the same manner as in example 1, except that: in step (1), the "first and second 35 μm thick lithium-boron alloy foils having a lithium content of 60% are replaced with the" first and second 50 μm thick lithium-indium alloy foils having a lithium content of 45%.
As a result, the lithium battery prepared in this example 2 was labeled S6.
Comparative example 1
(1) Fabrication of negative electrode
And cutting the commercial lithium foil based on copper into pole pieces with the size of 49mm and 57mm to obtain the negative pole piece, wherein the thickness of the lithium foil is 40 mu m.
(2) Preparation of electrolyte
In a glove box filled with argon (H 2 O≤5PPM，O 2 Less than or equal to 5 PPM), ethylene glycol dimethyl ether (DME), ethyl Difluoroacetate (DFEA), 1, 2-tetrafluoroethyl-2, 3-tetrafluoropropyl ether (TTE). According to the mass ratio, according to DME: DFEA: tte=20:70:10, and then 60wt% lithium bis (fluorosulfonyl) imide LiN (SO 2 F) 2 。
(3) Fabrication of positive electrode
The lithium cobalt oxide positive plate with the thickness of 110 mu m on both sides is obtained through size mixing, coating, drying and rolling, and is cut into rectangular pole pieces with the size of 48mm and 56mm, and the pole lugs are spot-welded at the positions in the width direction.
(4) Battery fabrication
And (3) alternately stacking the negative electrode plate obtained in the step (1) and the positive electrode plate obtained in the step (3) together with the diaphragm, and preparing the battery in a lamination mode, wherein the positive electrode plate and the negative electrode plate are alternately isolated by the diaphragm, so as to obtain the dry battery core. Placing the dry cell in an aluminum plastic film outer package, injecting the electrolyte obtained in the step (2), vacuumizing and sealing, placing at 60 ℃ for 48 hours, pressurizing the layer at 60 ℃, packaging for the second time, exhausting and separating the volume to obtain the lithium battery mark DS1 prepared in the comparative example 1.
Comparative example 2
A lithium ion battery was fabricated in the same manner as in example 1, except that: in the step (2), the electrolyte is replaced by a traditional carbonate electrolyte, and the preparation process is EC: DEC is 4 in volume ratio: 6-proportion of LiPF6 was added as solvent after which 12.5wt% of LiPF6 was added.
As a result, the lithium battery prepared in this comparative example 2 was labeled DS2.
Comparative example 3
A lithium ion battery was fabricated in the same manner as in example 1, except that: the first lithium boron alloy foil, the porous copper foil, and the second lithium boron alloy foil were sequentially pressed for 10min at 300 ℃ under 2MPa in a flat-plate hot press for Ji Diefang to obtain the electrode of the comparative example.
As a result, the lithium battery prepared in this comparative example 3 was labeled DS3.
Comparative example 4
A lithium ion battery was fabricated in the same manner as in example 1, except that: in step (1), the "first lithium-boron alloy foil and the second lithium-boron alloy foil having a lithium content of 60% are replaced with the" first lithium-indium alloy foil and the second lithium-indium alloy foil having a lithium content of 20%.
As a result, the lithium battery prepared in this comparative example 4 was labeled DS4.
Test case
The lithium batteries prepared in examples 1 to 6 and comparative examples 1 to 4 were subjected to a cycle life and a battery expansion ratio test of lithium batteries.
The results are shown in Table 1.
TABLE 1
As can be seen from the results of table 1, the lithium batteries of examples 1 to 6 using the negative electrode of the present invention have good cycle performance of the lithium battery, and can increase the cycle life of the lithium battery; and has lower expansion rate of the lithium battery and obviously better effect.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.
Claims (15)
1. The negative electrode is characterized by comprising a porous metal mesh current collector and a lithium alloy attached to the porous metal mesh current collector, wherein the lithium alloy is prepared from a lithium alloy foil, the content of lithium element in the lithium alloy foil is more than 20wt%, holes of the porous metal mesh current collector are filled with hot melt polymers, the hot melt polymers are connected with the lithium alloy and the porous metal mesh current collector, the hot melt polymers are in dispersed point contact with the lithium alloy foil, the filling degree of the hot melt polymers is less than the porosity of the porous metal mesh current collector, and the filling degree is 40-98%.
2. The negative electrode of claim 1, wherein the hot melt polymer has a melting point of 80-350 ℃.
3. The negative electrode of claim 2, wherein the hot melt polymer has a melting point of 90-220 ℃.
4. The negative electrode according to any one of claims 1-3, wherein the hot-melt polymer is selected from one or more of polyethylene terephthalate, polyimide, polypropylene, polyethylene, polyvinyl alcohol, polyvinyl butyral, polyacrylic acid, polyvinylidene fluoride, polyethylene oxide, polypropylene carbonate, carboxymethyl cellulose, ethylene/vinyl acetate copolymer, polyacrylonitrile, styrene-butadiene rubber, polymethyl methacrylate, polyurethane resin, ureido-pyrimidinone, dopamine methacrylamide, polydopamine homopolymer, and copolymers thereof.
5. The negative electrode according to claim 1, wherein the content of lithium element in the lithium alloy foil is 40-95wt%.
6. The negative electrode of claim 1, wherein the lithium alloy has a thickness of 2-50 μιη.
7. The negative electrode of claim 1 or 5, wherein the melting point of the primary phase in the lithium alloy foil is greater than 300 ℃.
8. The negative electrode of claim 7, wherein the melting point of the primary phase in the lithium alloy foil is 400-1100 ℃.
9. The negative electrode of claim 1, wherein the lithium alloy foil is selected from one or more of a lithium boron alloy, a lithium magnesium alloy, a lithium aluminum alloy, a lithium tin alloy, a lithium germanium alloy, a lithium gallium alloy, a lithium indium alloy, a lithium antimony alloy, a lithium zinc alloy, a lithium lead alloy, and a lithium bismuth alloy.
10. The negative electrode of claim 9, wherein the lithium alloy foil is selected from one or more of a lithium boron alloy, a lithium magnesium alloy, a lithium aluminum alloy, and a lithium indium alloy.
11. The negative electrode of claim 1, wherein the porous metal mesh current collector has a thickness of 5-50 μm.
12. The negative electrode according to claim 1 or 11, wherein the porous metal mesh current collector has a porosity of 5-90%.
13. A method of producing the negative electrode according to any one of claims 1 to 12, comprising: sequentially stacking a first lithium alloy foil, a hot melt polymer film, a porous copper mesh current collector and a second lithium alloy foil, and then performing pressing treatment to obtain a negative electrode; wherein the hot melt polymer film is made of a hot melt polymer.
14. A method of making the negative electrode of any one of claims 1-12, comprising:
(1) Injecting the hot melt polymer into the pores of the porous metal mesh current collector by nano injection molding to obtain a filled current collector;
(2) And sequentially stacking the first lithium alloy foil, the filling type current collector and the second lithium alloy foil, and then performing pressing treatment to obtain the negative electrode.
15. A lithium battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode is the negative electrode of any one of claims 1-12.
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| CN101714669A (en) * | 2009-05-26 | 2010-05-26 | 张新 | Gel polymer lithium ion battery and preparation method thereof |
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| CN110875478A (en) * | 2018-08-29 | 2020-03-10 | 中南大学 | Current collector and negative electrode for metal lithium battery, and preparation and application of current collector and negative electrode |
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| US11152639B2 (en) * | 2016-01-15 | 2021-10-19 | Global Graphene Group, Inc. | Alkali metal-sulfur batteries having high volumetric and gravimetric energy densities |
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| CN101447561A (en) * | 2007-11-28 | 2009-06-03 | 三星Sdi株式会社 | Negative electrode for rechargeable lithium battery, and rechargeable lithium battery including the same |
| CN101714669A (en) * | 2009-05-26 | 2010-05-26 | 张新 | Gel polymer lithium ion battery and preparation method thereof |
| KR20150016897A (en) * | 2013-08-05 | 2015-02-13 | 주식회사 아모그린텍 | Flexible current collector, manufacturing method thereof and secondary battery using the same |
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