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CN115275336A - Lithium metal battery and application thereof - Google Patents

Lithium metal battery and application thereof Download PDF

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Publication number
CN115275336A
CN115275336A CN202210920466.8A CN202210920466A CN115275336A CN 115275336 A CN115275336 A CN 115275336A CN 202210920466 A CN202210920466 A CN 202210920466A CN 115275336 A CN115275336 A CN 115275336A
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China
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gel electrolyte
lithium metal
metal battery
network
dimensional organic
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Chinese (zh)
Inventor
王晨
何华锦
陈茂华
谢远森
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
    • 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
    • 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
    • H01M10/058—Construction or manufacture
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0085—Immobilising or gelification of electrolyte
    • 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
    • Y02E60/10—Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Dispersion Chemistry (AREA)
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  • Inorganic Chemistry (AREA)
  • Secondary Cells (AREA)

Abstract

The application discloses a lithium metal battery, which relates to the technical field of lithium batteries and comprises a gel electrolyte; the gel electrolyte comprises an uncrosslinked polymer and a three-dimensional organic crosslinked network, wherein the uncrosslinked polymer and the three-dimensional organic crosslinked network are mutually interpenetrated to form a semi-interpenetrating network structure. The gel electrolyte with the semi-interpenetrating network structure has good bonding strength with the pole piece, is beneficial to inhibiting uneven contact between the pole piece and the gel electrolyte caused by volume expansion of the pole piece in the charging and discharging processes, has good mechanical property, and is beneficial to maintaining the structural stability of the pole piece in the circulating process, thereby improving the circulating performance and the safety performance of the lithium metal battery.

Description

Lithium metal battery and application thereof
Technical Field
The application relates to the technical field of lithium batteries, in particular to a lithium metal battery and application thereof.
Background
In recent years, there has been an increasing demand for high energy density lithium ion batteries. At present, the graphite negative electrode of the commercial lithium battery cannot meet the requirement of the lithium battery with high energy density. The lithium metal has a lower standard electrode potential (-3.045V) and a larger theoretical gram capacity (3860 mAh/g), and can realize a higher working voltage and energy density when matched with a positive electrode material with high energy density; however, lithium metal is susceptible to side reactions with the electrolyte due to its extremely reactive metallic nature, thereby consuming the lithium metal itself as well as the electrolyte, resulting in lower coulombic efficiency.
In the charging process of the lithium metal battery, the local deposition of lithium ions on the surface of the lithium metal is easy to cause due to the uneven distribution of current density and lithium ions in the electrolyte, so that a dendritic crystal structure is formed, and the dendritic crystal structure can reduce the deposition density of the lithium ions; in severe cases, lithium dendrites can puncture the separator, causing serious safety problems. In the process of charging and discharging, the lithium metal negative electrode can generate serious volume expansion and shrinkage, and the surface protective layer is easy to break and peel off due to violent volume change, so that the protective effect is lost.
The solid electrolyte can effectively inhibit side reactions of a lithium metal interface and safety problems caused by lithium dendrites, but most of the solid electrolytes are difficult to form excellent interface contact with a pole piece, the ionic conductivity of the polymer solid electrolyte is low, and the application of the inorganic solid electrolyte in actual products is severely limited due to the problems of poor processability and poor mechanical property of the inorganic solid electrolyte; the gel electrolyte has the advantages of both liquid electrolyte and solid electrolyte, but the gel electrolyte can sacrifice part of mechanical properties to realize excellent contact effect with the pole piece, and the mechanical properties are key factors for maintaining the structural stability of the gel electrolyte in the charge/discharge cycle process.
Disclosure of Invention
The embodiment of the application provides a lithium metal battery and application thereof, and can solve the problem that in the prior art, gel electrolyte sacrifices partial mechanical properties in order to realize excellent contact effect with a pole piece, so that the structural stability of the gel electrolyte in a circulating process is difficult to maintain.
In a first aspect, an embodiment of the present application provides a lithium metal battery, including: a gel electrolyte; the gel electrolyte comprises an uncrosslinked polymer and a three-dimensional organic crosslinked network, wherein the uncrosslinked polymer and the three-dimensional organic crosslinked network are mutually interpenetrated to form a semi-interpenetrating network structure. The three-dimensional organic crosslinking network is a gel-state elastic network and has the characteristic that the storage modulus is larger than the loss modulus, and the gel-state elastic network is used for improving the mechanical property of the gel electrolyte; the non-crosslinked polymer is not bound by chemical crosslinking points, has high degree of freedom of interface polymer chains, and is used for improving the interface contact capacity of the gel electrolyte; the uncrosslinked polymer and the three-dimensional organic crosslinked network form physical crosslinking points in a non-covalent crosslinking mode, so that a semi-interpenetrating network structure is formed, the mechanical property of the gel electrolyte and the freedom degree of movement of a surface polymer chain are improved, the gel electrolyte is in excellent contact with a pole piece, the structural integrity of the gel electrolyte in the battery circulation process can be ensured, and the circulation performance and the safety performance of the lithium metal battery are improved; the gel electrolyte has obvious loss angle in rheological property test.
In some embodiments, the three-dimensional organic crosslinked network comprises a monomer comprising a polymerizable group; wherein the polymerizable group comprises any one of double bonds, amino groups, carboxyl groups or hydroxyl groups, and the monomer comprises at least one of methacrylate, sodium acrylate, acrylamide, vinylene carbonate, adipic acid and polyethylene glycol.
In some embodiments, the polymerizable group-containing monomer is in a molar amount n', the crosslinker is in a molar amount n ″, such that: 10, 1 is less than or equal to n '/n' is less than or equal to 1000.
In some embodiments, the uncrosslinked polymer satisfies at least one of the following conditions: condition a: the degree of polymerization DP of the uncrosslinked polymer satisfies the following conditions: DP is more than or equal to 1000 and less than or equal to 100000; condition b: the length of a Kuhn chain segment in the uncrosslinked polymer is less than 5nm.
In some embodiments, the uncrosslinked macromolecule comprises at least one of polyoxyethylene, end-group-modified polyoxyethylene, polyurethane, polycarbonate, or polyphosphate;
in some embodiments, the uncrosslinked macromolecule comprises a terminal amino-modified polyoxyethylene.
In some embodiments, the mass ratio of the uncrosslinked polymer to the three-dimensional organic crosslinked network is 10 to 0.5:1.
in some embodiments, the sum of the mass content of the uncrosslinked macromolecule and the mass content of the three-dimensional organic crosslinked network is from 1wt% to 10wt%, based on the mass of the gel electrolyte.
In some embodiments, the gel electrolyte has a loss angle tan δ > 1.
In some embodiments, at least one of the following conditions is met:
(1) The degree of polymerization DP of the uncrosslinked polymer satisfies the following conditions: DP more than or equal to 5000 and less than or equal to 7000;
(2) The three-dimensional organic crosslinking network is obtained by polymerizing a monomer and a crosslinking agent, wherein the molar weight of the monomer is n', the molar weight of the crosslinking agent is n ″, and the following conditions are met: 50, 1 is more than or equal to n '/n' is more than or equal to 200;
(3) Based on the mass of the gel electrolyte, the sum of the mass content of the uncrosslinked macromolecules and the mass content of the three-dimensional organic crosslinked network is 3-5%;
(4) Based on the mass of the gel electrolyte, the mass ratio of the uncrosslinked polymer to the three-dimensional organic crosslinked network is 2:1-0.8.
In a second aspect, embodiments of the present application provide a method for manufacturing a lithium metal battery, including the following steps:
(1) Preparing a gel electrolyte precursor solution: adding a cross-linking agent into an electrolyte containing a polymerizable group-containing monomer and an uncrosslinked polymer to obtain a precursor solution;
(2) Injecting the precursor solution obtained in the step (1) into a battery cell, and reacting at 65-75 ℃.
In a third aspect, embodiments of the present application provide an electrical device, where the electrical device includes any one of the lithium metal batteries described above.
The beneficial effects brought by the technical scheme provided by some embodiments of the application at least comprise:
the gel electrolyte with the semi-interpenetrating network structure in the embodiment of the application has good bonding strength with the pole piece, is beneficial to inhibiting uneven contact between the pole piece and the gel electrolyte caused by volume expansion of the pole piece in the charging and discharging process, has good mechanical property, and is beneficial to maintaining structural stability in the circulating process, so that the circulating performance and the safety performance of the lithium metal battery are improved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic structural diagram of a gel electrolyte in an embodiment of the present application (black lines are three-dimensional organic crosslinked networks, and gray lines are uncrosslinked polymers).
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
For the sake of brevity, only a few numerical ranges are explicitly disclosed herein. However, any lower limit may be combined with any upper limit to form ranges not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and any upper limit may be combined with any other upper limit to form a range not explicitly recited. Also, although not explicitly recited, each point or individual value between endpoints of a range is encompassed within the range. Thus, each point or individual value can form a range not explicitly recited as its own lower or upper limit in combination with any other point or individual value or in combination with other lower or upper limits.
In the detailed description and claims, a list of items linked by the term "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means a only; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" means a only; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and all of C.
The high molecular polymer solid electrolyte has good flexibility and safety, can be obtained by dissolving lithium salt in high molecules and then drying a coating film, lithium ions can move through the movement of chains, the number of free lithium ions and the mobility of the chains significantly influence the transmission efficiency of the lithium ions, but the high molecular polymer electrolyte generally has low room-temperature ionic conductivity (10) -6 ～10 -5 S/cm), poor compatibility with metallic lithium negative electrodes, and structural instability during cycling; inorganic solid electrolyte with room temperature ionic conductivity up to 10 -4 ～10 -2 S/cm, however, after the organic electrolyte is replaced by the inorganic solid electrolyte, the solid-liquid interface of the electrode material/electrolyte in the lithium battery system is replaced by the solid-solid interface of the electrode material/solid electrolyte, and the interface contact between the solid-solid interfaces of the inorganic solid electrolyte is very poor, which results in very high interface impedance, and the inorganic solid electrolyte has very high mechanical strength but poor flexibility.
The network structure in the gel electrolyte has a great influence on the performance of the gel electrolyte, for example, the gel network with high crosslinking degree has excellent mechanical properties, is beneficial to maintaining the structural stability of the gel electrolyte in the battery cycle process, and has a certain inhibiting effect on the formation of lithium dendrites, but for the gel network with high crosslinking degree, the high molecular chains at the interface of the gel network are restrained by the high-density crosslinking structure in the gel network, and the gel network does not have excellent movement capability. Therefore, the gel network with high crosslinking degree cannot be in full contact with the pole piece, so that uneven current is easily formed on the surface of the pole piece in the battery circulation process, uneven lithium deposition is caused, and the cycle life and safety performance of the battery are influenced; the gel network with low crosslinking degree has excellent interface contact capacity but no excellent mechanical property, and the structural stability of the gel network in the circulating process is difficult to maintain.
Therefore, there is no gel electrolyte capable of combining excellent mechanical properties and good interface contact in the prior art.
Lithium metal battery
In order to solve the technical problem, the application provides a lithium metal battery, which comprises a positive pole piece, a diaphragm, a negative pole piece and a gel electrolyte.
Gel electrolyte
The gel electrolyte comprises an uncrosslinked polymer and a three-dimensional organic crosslinked network, wherein the uncrosslinked polymer and the three-dimensional organic crosslinked network are mutually interpenetrated to form a semi-interpenetrating network structure; the gel electrolyte has obvious loss angle in rheological property test.
The three-dimensional organic crosslinking network is a gel-state elastic network and has the characteristic that the storage modulus is larger than the loss modulus, and the high crosslinking density and the high elastic modulus of the three-dimensional organic crosslinking network ensure that the three-dimensional organic crosslinking network has excellent mechanical properties, thereby being beneficial to maintaining the structural stability of the three-dimensional organic crosslinking network in the battery cycle process and having a certain inhibiting effect on the formation of lithium dendrites;
the non-crosslinked polymer is not bound by chemical crosslinking points, has higher degree of freedom of interface polymer chains and is used for realizing excellent interface contact capacity with the pole piece;
the non-crosslinked polymer and the three-dimensional organic crosslinked network form temporary physical crosslinking points in a non-covalent crosslinking mode, so that the mechanical property of the gel electrolyte and the freedom degree of movement of a surface polymer chain are improved simultaneously, the negative coupling relation between the gel electrolyte body mechanics and the surface polymer chain freedom degree in the prior art can be broken, the dual promotion of the gel electrolyte and the surface polymer chain freedom degree is realized, the excellent contact between the gel electrolyte and a pole piece is ensured, the structural integrity of the gel electrolyte in the battery circulation process can be ensured, and the circulation performance and the safety performance of the lithium metal battery are improved; the gel electrolyte is obtained by in-situ polymerization under high temperature conditions by using an electrolyte solution containing a polymerizable group monomer and an uncrosslinked polymer as a precursor solution.
In some embodiments, the three-dimensional organic crosslinked network comprises monomers comprising polymerizable groups; the polymerizable group includes any one of a double bond, an amino group, a carboxyl group, or a hydroxyl group; the polymerization includes but is not limited to any one of free radical polymerization and condensation polymerization. Wherein the double bonds are primarily suitable for free radical polymerization and the amino, carboxyl and hydroxyl groups are primarily suitable for condensation polymerization.
In some embodiments, the monomer comprises at least one of methacrylate, sodium acrylate, acrylamide, vinylene carbonate, adipic acid, polyethylene glycol.
In some embodiments, the polymerizable group-containing monomer is in a molar amount n', the crosslinker is in a molar amount n ″, such that: 10, 1 is not less than n '/n' is not less than 1000; the crosslinking density of the three-dimensional organic crosslinking network is determined by the molar ratio of the monomer to the crosslinking agent, and the larger the crosslinking density of the three-dimensional organic crosslinking network is, the better the mechanical property is, and the structural stability of the gel electrolyte can be maintained. In some embodiments, n'/n "is 100.
Illustratively, the ratio of the molar amount n' of monomers containing polymerizable groups to the molar amount n "of the crosslinking agent is 10.
In some embodiments, the crosslinking agent is a compound containing multiple unsaturated double bonds within the molecule, including but not limited to one or more of divinylbenzene, diisocyanate, N-methylenebisacrylamide, terminal double bond modified polyethylene oxide (PEO).
In some embodiments, the uncrosslinked polymer satisfies at least one of the following conditions: condition a: the degree of polymerization DP of the uncrosslinked polymer satisfies the following conditions: DP is more than or equal to 1000 and less than or equal to 100000; condition b: the length of a Kuhn chain segment in the uncrosslinked polymer is less than 5nm. In some embodiments, the degree of polymerization DP of the uncrosslinked polymer is 6000.
Under the condition a, if the molecular weight of the non-crosslinked polymer is too low (for example, DP is less than 1000), an entanglement interaction force with the three-dimensional organic crosslinked network cannot be formed, which is not beneficial to improving the mechanical property of the gel electrolyte, and the entanglement between the non-crosslinked polymer and the three-dimensional organic crosslinked network can improve the mechanical property of the gel electrolyte; if the molecular weight of the non-crosslinked polymer is too high (for example, DP > 100000), the entanglement between the non-crosslinked polymer and the three-dimensional organic crosslinked network is more obvious, so that the movement of the non-crosslinked polymer at the interface of the pole piece is limited, and the improvement of the interface bonding force of the gel electrolyte is not facilitated. For the condition b, the Kuhn chain segment is used for representing the flexibility of the polymer chain, and in order to ensure that the movement of the non-crosslinked polymer at the pole piece interface is not limited and has higher freedom of movement, the length of the Kuhn chain segment in the non-crosslinked polymer is required to be less than 5nm.
Illustratively, the degree of polymerization DP of the uncrosslinked polymer is 1000, 3000, 5000, 7000, 10000, 50000, 100000, or a range consisting of any two of the above values.
Illustratively, the length of the Kuhn segment in the uncrosslinked polymer is 0.01nm, 2nm, 4nm, or a range consisting of any two of the foregoing values.
In some embodiments, the uncrosslinked macromolecule comprises at least one of polyethylene oxide, end-group modified polyethylene oxide, polyurethane, polycarbonate, or polyphosphate; preferably, the terminal modified polyoxyethylene comprises a terminal amino modified polyoxyethylene (N-PEO).
In some embodiments, the mass ratio of the uncrosslinked polymer to the three-dimensional organic crosslinked network is 10 to 0.5:1. in some embodiments, the mass ratio of the uncrosslinked macromolecule to the three-dimensional organic crosslinked network is 1:1.
the addition of the non-crosslinked polymer can simultaneously improve the mechanical property and the interface bonding force of the gel electrolyte, but the improvement degrees of the two properties are different due to the addition of different proportions. The physical entanglement of the three-dimensional organic crosslinked network is derived from uncrosslinked macromolecules, and under the condition of the same content of the three-dimensional organic crosslinked network, the more the content of the uncrosslinked macromolecules is, the more the physical interaction between the uncrosslinked macromolecules is, and the larger the inhibition degree of the surface movement of the gel electrolyte is; it can be seen that, too high mass content of the non-crosslinked polymer (for example, mass ratio is greater than 10: 1) has little effect on improvement of mechanical properties, and the improvement of mechanical properties of the gel electrolyte mainly comes from the three-dimensional organic crosslinked network and high crosslinking density thereof, and too high content of the non-crosslinked polymer affects the content of the three-dimensional organic crosslinked network; and excessively low mass content of the uncrosslinked polymer (for example, mass ratio of less than 0.5).
Illustratively, the mass ratio of the uncrosslinked polymer to the three-dimensional organic crosslinked network is 10.
In some embodiments, the sum of the mass content of the uncrosslinked macromolecules and the mass content of the three-dimensional organic crosslinked network is 1wt% to 10wt%, based on the mass of the gel electrolyte. In some embodiments, the sum of the mass content of the uncrosslinked macromolecules and the mass content of the three-dimensional organic crosslinked network is 4wt%.
The mass content of the uncrosslinked macromolecules and the mass content of the three-dimensional organic crosslinked network are collectively called as solid content; if the solid content is too low (e.g., less than 1 wt%), the mechanical properties of the gel electrolyte are too weak; if the solid content is too high (for example, the solid content is higher than 10 wt%), the interface bonding between the electrode plate and the solid is not good, and a gap is easily formed between the electrode plate and the solid.
Illustratively, the sum of the mass content of the uncrosslinked polymer and the mass content of the three-dimensional organic crosslinked network is 1wt%, 3wt%, 5wt%, 8wt%, 10wt%, or a range consisting of any two of the foregoing values.
In some embodiments, the gel electrolyte has a loss angle tan δ > 1.
The uncrosslinked polymer does not react with the three-dimensional organic crosslinked network, but has strong physical interaction, such as hydrogen bond interaction, electrostatic interaction or entanglement among polymer chains, and the three-dimensional organic crosslinked network interspersed and entangled with the uncrosslinked polymer can be destroyed and reconstructed in a dynamic shearing process in a rheological test, so that energy is absorbed, and the three-dimensional organic crosslinked network has a remarkable loss angle (tan & gt 1).
In some embodiments, the degree of polymerization DP of the uncrosslinked macromolecule satisfies: DP more than or equal to 5000 and less than or equal to 7000.
Illustratively, the degree of polymerization DP of the uncrosslinked polymer is 5000, 5500, 6000, 6500, 7000 or a range consisting of any two of the above values.
In some embodiments, the three-dimensional organic crosslinked network is polymerized from monomers and a crosslinking agent, the monomers being in a molar amount n', the crosslinking agent being in a molar amount n ″, such that: 50 is more than or equal to 1 and less than or equal to n '/n' and less than or equal to 200.
Illustratively, the ratio of the molar amount n' of polymerizable group-containing monomer to the molar amount n "of crosslinking agent is 50.
In some embodiments, the sum of the mass content of the uncrosslinked macromolecules and the mass content of the three-dimensional organic crosslinked network is from 3% to 5% based on the mass of the gel electrolyte.
Illustratively, the sum of the mass content of the uncrosslinked polymer and the mass content of the three-dimensional organic crosslinked network is 3%, 3.5%, 4%, 4.5%, 5%, or a range consisting of any two of the foregoing values.
In some embodiments, the mass ratio of the uncrosslinked polymer to the three-dimensional organic crosslinked network is 2:1 to 0.8.
Illustratively, the mass ratio of the uncrosslinked polymer to the three-dimensional organic crosslinked network is 2:1, 1:1, 0.8:1, or any two of the above values.
Others
The electrolyte is common commercial lithium ion electrolyte comprising an organic solvent and lithium salt;
the organic solvent comprises a carbonate solvent, an ether solvent, a sulfone solvent, other aprotic solvents or a combination thereof;
wherein the carbonate solvent comprises one or more of diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene Carbonate (EC), propylene Carbonate (PC), butylene Carbonate (BC), vinyl Ethylene Carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate in combination.
The ether solvent includes one or more of tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl 1,3-dioxolane, 4-methyl 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, dimethoxypropane, dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxyethane, or 1,2-ethoxymethoxyethane in combination.
The sulfone solvent includes sulfolane, dimethyl sulfoxide, methyl sulfolane, etc. Other organic solvents include 1,3-dimethyl-2-imidazolidinone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, or phosphate esters.
The lithium salt includes lithium hexafluorophosphate (LiPF) 6 ) Lithium bis (oxalato) borate (LiB (C) 2 O 4 ) 2 LiBOB), lithium difluorooxalato borate (LiBF) 2 (C 2 O 4 ) LiDFOB), lithium tetrafluoroborate (LiBF) 4 ) Lithium hexafluoroantimonate (LiSbF) 6 ) Lithium hexafluoroarsenate (LiAsF) 6 ) Lithium perfluorobutylsulfonate (LiC) 4 F 9 SO 3 ) Lithium perchlorate (LiClO) 4 ) Lithium aluminate (LiAlO) 2 ) Lithium aluminum tetrachloride (LiAlCl) 4 ) Lithium bis (sulfonimide) (LiN (C) x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ) Where x and y are natural numbers), lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethylsulfonic acid) imide (LiTFSI), lithium chloride (LiCl), or lithium fluoride (LiF).
The electrolyte may further include an electrolyte additive, which may be, but not limited to, one or more of fluoroethylene carbonate (FEC) and dimethyl Fluorocarbonate (FDMC).
Preparation of gel electrolyte
The method mainly comprises the following steps:
(1) Preparing a precursor solution of the gel electrolyte: preparing electrolyte, adding a cross-linking agent into the electrolyte containing a polymerizable group-containing monomer and an uncrosslinked polymer to obtain a precursor solution;
wherein, electrolyte: polymerizable monomer: the mass ratio of the non-crosslinked long-chain polymer is 90-99: 0.67 to 6.67:0.37 to 9.1.
(2) Injecting the precursor solution obtained in the step (1) into a battery cell, and reacting at 65-75 ℃; preferably, the precursor solution is injected into the cell and reacted at a temperature of 70 ℃ for 12 hours.
In the preparation process of the gel electrolyte, uncrosslinked macromolecules are mixed into electrolyte containing polymerizable monomers (monomers containing polymerizable groups) in advance, and under the action of an initiator, in-situ polymerization is carried out to form a composite structure with a three-dimensional organic crosslinked network (elastic network) and the uncrosslinked macromolecules interpenetrating in space; and the tensile elastic modulus of the gel electrolyte is more than 50kPa, and the pole piece adhesive strength is more than 50kPa when the breaking strain is more than 100%. Wherein, the in-situ polymerization mode includes but is not limited to one of thermal initiation, ultraviolet initiation or radiation initiation.
In some embodiments, the initiator comprises one or more of benzoyl peroxide, potassium persulfate, ammonium persulfate, azobisisobutyronitrile, or azobisisoheptonitrile.
The mechanical property of the gel electrolyte is mainly influenced by a three-dimensional organic crosslinking network, and if the gel electrolyte contains high crosslinking density, the mechanical property is excellent, so that the structural integrity of a gel electrolyte body is maintained, and the formation of lithium dendritic crystals is better inhibited; however, an excessively high crosslinking density can generate a large inhibiting effect on the freedom of motion of a polymer chain (namely, non-crosslinked polymer) on the surface of the gel electrolyte, the freedom of motion of the polymer chain on the surface can be inhibited due to the control of an internal crosslinking structure, and when the polymer chain is contacted with a pole piece, the polymer (namely, non-crosslinked polymer) on the surface of the gel electrolyte cannot fully infiltrate the pole piece to form uneven contact, so that uneven current is easily formed on the surface of the pole piece in the battery circulation process, and the problem of uneven lithium deposition is generated, and the circulation and safety performance of the lithium metal battery are influenced finally.
By introducing the non-crosslinked long-chain polymer into the gel-state three-dimensional organic crosslinked network, the relationship between the mechanics of the gel electrolyte body and the negative coupling of the degree of freedom of the surface polymer chain in the prior art can be broken, and the dual promotion of the two is realized; meanwhile, through a preparation method of in-situ introduction, non-crosslinked macromolecules are limited in a gel-state elastic network (namely a three-dimensional organic crosslinked network) to form a gel electrolyte of a semi-interpenetrating network; physical interaction exists between the non-crosslinked polymer and the elastic network, including physical entanglement of long-chain polymers (namely the non-crosslinked polymer), hydrogen bond interaction with the elastic network, electrostatic interaction and the like, and the physical interaction formed by the non-crosslinked polymer and the elastic network is equivalent to the formation of temporary physical crosslinking points in the elastic network, so that the bulk mechanical property of the semi-interpenetrating gel electrolyte can be effectively improved;
moreover, the long-chain polymer shuttles in the elastic network, the freedom of motion of the long-chain polymer shuttles on the surface is only influenced by the physical interaction between the long-chain polymer shuttles and the elastic network and the crosslinking density of the elastic network, and compared with the constraint of chemical bonding, the physical interaction between the non-crosslinked polymer and the elastic network can be changed spatially and dynamically, and the freedom of motion of the non-crosslinked polymer chain on the surface of the gel electrolyte is not influenced;
in addition, the crosslinking density of the elastic network can be regulated and controlled by changing the ratio of the crosslinking agent to the monomer, and the gel electrolyte with the internal interaction semi-interpenetrating network structure can have excellent body mechanical property and interface contact capability of uniform contact with the surface of a pole piece, so that the cycle and safety capability of the lithium metal battery are improved.
The lithium metal battery may be prepared according to a conventional method in the art.
Exemplarily, the positive electrode plate, the diaphragm and the negative electrode plate are stacked in sequence, and the diaphragm is positioned between the positive electrode plate and the negative electrode plate to play a role of isolation, so as to obtain an electrode assembly, or the electrode assembly can be obtained by winding; and (3) placing the electrode assembly in a packaging shell, injecting liquid, packaging, heating and curing to obtain the lithium metal battery.
Electrical equipment
The electrical equipment of the present application includes any one of the lithium metal batteries described above in the present application. The electrical appliance of the present application can be used for, but is not limited to, notebook computers, pen input computers, mobile computers, electronic book players, cellular phones, portable facsimile machines, portable copiers, portable printers, headsets, video recorders, lcd tvs, portable cleaners, portable CDs, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, mopeds, bicycles, lighting fixtures, toys, game machines, clocks, electric tools, flashlights, cameras, household large-sized batteries, lithium ion capacitors, and the like.
Examples
The present disclosure is more particularly described in the following examples that are intended as illustrative only, since various modifications and changes within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are on a weight basis, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the equipment used in the examples is commercially available.
Example 1
Negative pole piece preparation of
The 30 μm thick lithium copper composite tape was cut into a size of (40 mm. Times.60 mm) for use.
Preparation of positive pole piece
The anode is made of ternary active material Ni 0.8 Mn 0.1 Co 0.1 Mixing conductive carbon black (Super P) and polyvinylidene fluoride (PVDF) according to a weight ratio of 96. And uniformly coating the slurry on an aluminum foil of the positive current collector, and drying at 90 ℃ to obtain the positive pole piece. After coating, the positive electrode sheet was cut into a size of (38 mm × 58 mm) for use.
Preparation of gel electrolyte
In a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed at a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC) (i.e., monomer), terminal double bond-modified polyethylene oxide (PEO) (i.e., crosslinking agent), terminal amino-modified polyethylene oxide (N-PEO, degree of polymerization 6000) (i.e., uncrosslinked polymer), azobisisobutyronitrile (i.e., initiator), fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC), and lithium hexafluorophosphate (LiPF), which is a lithium salt, were added to the mixed solution 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 The in20% of the FDMC +30% of the EC +26% of the EC +3.63% (VC + PEO) +0.37% (N-PEO), where the molar ratio of VC to PEO is 100.
In the following examples, the same substances have the same effects and are not described in detail.
Preparation of lithium metal battery
Polyethylene (PE) with the thickness of 15 mu m is selected as an isolating film, a Z-shaped lamination mode is adopted, a positive pole piece and a negative pole piece are respectively arranged on two sides of the isolating film, and the isolating film is arranged between the pole pieces. And after the lamination is finished, welding the lug. And then placing the lithium metal laminated battery into an aluminum-plastic film, and finally obtaining the lithium metal laminated battery through top side sealing, liquid injection, packaging, heating and curing.
Example 2
Different from example 1, regarding the preparation of the gel electrolyte, the following was specified:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed at a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified polyethylene oxide (PEO), terminal amino-modified polyethylene oxide (N-PEO, degree of polymerization 6000), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC), and lithium hexafluorophosphate (LiPF) were added to the mixed solution 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 The in20% of the total% FDMC +30% of the total% EC +26% of the total% TTE +2% (VC + PEO) +2% (N-PEO), where the molar ratio of VC to PEO is 100.
Example 3
In contrast to example 1, the preparation of the gel electrolyte was as follows:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed at a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified polyethylene oxide (PEO), terminal amino-modified polyethylene oxide (N-PEO, degree of polymerization 6000), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC), and lithium hexafluorophosphate (LiPF) were added to the mixed solution 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 in20% FDMC +30% EC +26% TTE +1.33% (VC + PEO) +2.67% (N-PEO) with a molar ratio of VC to PEO of 100.
Example 4
In contrast to example 1, the preparation of the gel electrolyte was as follows:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) are first mixed in a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified polyethylene oxide (PEO), terminal amino-modified polyethylene oxide (PEO) are added to the mixed solution(N-PEO, DP 6000), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC) and lithium hexafluorophosphate (LiPF) 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 The in20% of the FDMC +30% of the EC +29% of the TTE +0.5% (VC + PEO) +0.5% (N-PEO), where the molar ratio of VC to PEO is 100.
Example 5
Different from example 1, regarding the preparation of the gel electrolyte, the following was specified:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed at a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified polyethylene oxide (PEO), terminal amino-modified polyethylene oxide (N-PEO, degree of polymerization 6000), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC), and lithium hexafluorophosphate (LiPF) were added to the mixed solution 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 <xnotran> in 20%FEC+30%FDMC+20%EC+20%TTE+5% (VC + PEO) +5% (N-PEO), VC PEO 100:1. </xnotran>
Example 6
In contrast to example 1, the preparation of the gel electrolyte was as follows:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed at a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified polyethylene oxide (PEO), terminal amino-modified polyethylene oxide (N-PEO, degree of polymerization 6000), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC), and lithium hexafluorophosphate (LiPF) were added to the mixed solution 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 The in20% of the total% FDMC +30% of the total% EC +26% of the total% TTE +2% (VC + PEO) +2% (N-PEO), where the molar ratio of VC to PEO is 100.
Example 7
In contrast to example 1, the preparation of the gel electrolyte was as follows:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed at a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified polyethylene oxide (PEO), terminal amino-modified polyethylene oxide (N-PEO, degree of polymerization 6000), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC), and lithium hexafluorophosphate (LiPF) were added to the mixed solution 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 The in20% of the total% FDMC +30% of the total% EC +26% of the total% TTE +2% (VC + PEO) +2% (N-PEO), where the molar ratio of VC to PEO is 100.
Example 8
In contrast to example 1, the preparation of the gel electrolyte was as follows:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed at a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified Polyoxyethylene (PEO), polyurethane (PU, polymerization degree 7000) (i.e., an uncrosslinked polymer), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC), and lithium hexafluorophosphate (LiPF) were added to the mixed solution 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 The in20% of the% FDMC +20% of the% EC +26% of the% TTE +2% (VC + PEO) +2% (PU), wherein the molar ratio of VC to PEO is 100.
Example 9
In contrast to example 1, the preparation of the gel electrolyte was as follows:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed at a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified polyethylene oxide (PEO), terminal amino-modified polyethylene oxide (N-PEO, polymerization) was added to the mixed solutionDegree 6000), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC) and lithium hexafluorophosphate (LiPF) 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 The in20% of the total% FDMC +30% of the total% EC +26% of the total% TTE +2% (VC + PEO) +2% (N-PEO), where the molar ratio of VC to PEO is 10.
Example 10
Different from example 1, regarding the preparation of the gel electrolyte, the following was specified:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed at a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified polyethylene oxide (PEO), terminal amino-modified polyethylene oxide (N-PEO, degree of polymerization 6000), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC), and lithium hexafluorophosphate (LiPF) were added to the mixed solution 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 in20% FDMC +30% EC +26% C +2% (VC + PEO) +2% (N-PEO) where the molar ratio of VC to PEO is 1000.
Example 11
In contrast to example 1, the preparation of the gel electrolyte was as follows:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed in a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified polyethylene oxide (PEO), terminal amino-modified polyethylene oxide (N-PEO, degree of polymerization 1000), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC), and lithium hexafluorophosphate (LiPF) were added to the mixed solution 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 The in20% of the total% FDMC +30% of the total% EC +26% of the total% TTE +2% (VC + PEO) +2% (N-PEO), where the molar ratio of VC to PEO is 100.
Example 12
In contrast to example 1, the preparation of the gel electrolyte was as follows:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed at a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified Polyoxyethylene (PEO), terminal amino-modified polyoxyethylene (N-PEO, polymerization degree 100000), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC), and lithium hexafluorophosphate (LiPF) were added to the mixed solution 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 The in20% of the total% FDMC +30% of the total% EC +26% of the total% TTE +2% (VC + PEO) +2% (N-PEO), where the molar ratio of VC to PEO is 100.
Example 13
In contrast to example 1, the preparation of the gel electrolyte was as follows:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed at a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified Polyoxyethylene (PEO), polyurethane (PU, polymerization degree 7000), terminal amino group-modified polyoxyethylene (N-PEO, polymerization degree 6000), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC), and lithium hexafluorophosphate (LiPF) were added to the mixed solution 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 The in20% of the FDMC +30% of the EC +26% of the EC +2% (VC + PEO) +1% (PU) +1% (N-PEO), where the molar ratio of VC to PEO is 100.
Comparative example 1
Different from example 1, regarding the preparation of the gel electrolyte, the following was specified:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) are firstly mixed in a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond modified Polyoxyethylene (PEO), azobisisobutyric Acid (AIB) are added to the mixed solutionNitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC) and lithium salt lithium hexafluorophosphate (LiPF) 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 in20% FEC +30% EC +26% TTE +4% (VC + PEO) with a molar ratio of VC to PEO of 100.
Comparative example 2
In contrast to example 1, the preparation of the gel electrolyte was as follows:
in a dry argon atmosphere, an organic solvent of Ethylene Carbonate (EC) and 1,1,2,2-tetrafluoro-3- (1,1,2,2-tetrafluoroethoxy) propane (TTE) was first mixed at a mass ratio of EC: TTE =2:3, and then Vinylene Carbonate (VC), terminal double bond-modified polyethylene oxide (PEO), azobisisobutyronitrile, fluoroethylene carbonate (FEC), dimethyl Fluorocarbonate (FDMC), and lithium salt lithium hexafluorophosphate (LiPF) were added to the mixed solution 6 ) Dissolving and mixing uniformly to obtain 1M LiPF of gel electrolyte with lithium salt concentration of 1.0M 6 In20% FEC +30% EC +26% The EC +4% (VC + PEO) where the molar ratio of VC to PEO is 100.
Test method
(1) Adhesion Strength test
Take 2 x 2cm 2 The pole piece is attached to the surface of an aluminum flat plate test mould, and 2 x 2cm is taken 2 The gel electrolyte sheet is attached to the surface of the pole piece (the thickness of the gel electrolyte sheet is 2 mm), the gel electrolyte is fully attached to the pole piece, and the bonding area S =2 x 2cm 2 And (3) stretching the test mould at a constant speed of 1mm/min by using a universal mechanical testing machine, and measuring the maximum force value F in the separation process of the gel electrolyte and the pole piece, wherein the adhesive strength of the gel electrolyte and the pole piece is = F/S.
(2) Mechanical testing
Taking a gel electrolyte sheet with the length a of 5cm, the width b of 2cm and the thickness c of 3mm, fixing the gel electrolyte sheet on a universal mechanical testing machine by a clamp in the width direction, wherein the center of the gel electrolyte sheet is coincided with the centers of an upper clamp and a lower clamp, the distance between the upper clamp and the lower clamp is 3cm, and stretching the gel electrolyte sheet by the universal mechanical testing machine at the speed of 1.5cm/min to obtain the real-time tensile force F (N) and the displacement L (cm) in the stretching process. A stress-strain curve is plotted, where stress = F/(b × c), strain = L × 100%/3, and the breaking strain becomes the strain at which the gel electrolyte breaks. The elastic modulus is calculated by taking Hu Ke elastic zone with 10% strain in front of the gel electrolyte, and the elastic modulus is the ratio of the stress variation to the strain variation of Hu Ke elastic zone. (both modulus and strain belong to the mechanical test, both parameters being combined in one test procedure)
(3) And (3) testing the cycle performance:
comparative and example the cycling performance of the cells was intended to characterize the effectiveness of this protocol. The specific test method comprises the following steps:
at 25 ℃, charging the soft-package battery cell to 4.3V at a constant current of 0.3C, then charging at a constant voltage until the current is 0.025C, wherein the soft-package battery cell is in a full-charge state at the moment, and recording the charge capacity at the moment, namely the 1 st circle of charge capacity; and (3) standing the soft-package battery cell for 5min, discharging to 2.8V at a constant current of 0.5C, standing for 5min, wherein the process is a cyclic charge-discharge process, and recording the discharge capacity at the moment, namely the discharge capacity of the 1 st circle. And repeating the charge-discharge cycle until the current-circle discharge capacity is attenuated to 80% of the first-circle discharge capacity or the battery core is failed. Wherein, the capacity retention ratio = discharge capacity at one cycle/discharge capacity at 1 st cycle.
The degree of freedom of motion of the semi-interpenetrating gel electrolyte interface polymer chain is directly related to the infiltration condition and the adhesive force of the pole piece, and because the degree of freedom of motion of the interface polymer chain is difficult to directly test, the degree of freedom of the surface polymer chain is indirectly represented by the adhesive strength of the semi-interpenetrating gel electrolyte and the pole piece.
The data of comparative example and example are intended to characterize the effectiveness of the protocol by the adhesive strength of the gel electrolyte on the copper foil surface, the mechanical properties of itself, and the cycle performance of the cell. The tensile speed of a mechanical test is 5cm/min, the cut-off voltage of a battery test is 2.8-4.3V, and the cycle rate is 03/05C. Specific data are shown in table 1 below.
TABLE 1
Figure BDA0003777231610000201
Figure BDA0003777231610000211
Analysis is carried out by combining table 1 and fig. 1, and comparison of examples 1 to 3 shows that the ratio of the three-dimensional organic crosslinked network (elastic network) and the uncrosslinked polymer (uncrosslinked polymer chain) in the gel electrolyte with the semi-interpenetrating network structure significantly affects the interfacial adhesion with the pole piece, and further affects the cycle performance of the lithium metal battery; for example, an excessively high elastic network occupancy ratio (for example, example 1) may affect the degree of freedom of the interface polymer chain, and further affect the adhesion between the gel electrolyte and the electrode sheet, and affect the cycle performance of the lithium metal battery; while too low an elastic network occupancy ratio (e.g., example 3) cannot ensure the structural integrity of the gel electrolyte during cycling, thereby affecting the cycling performance of the lithium metal battery; therefore, the three-dimensional organic crosslinked network and the uncrosslinked polymer are in a proper mass ratio range, and the cycle performance of the lithium metal battery is favorably improved.
A comparison of examples 2, 4, 5 illustrates that the range of solid content in the gel electrolyte of the semi-interpenetrating network structure significantly affects the cycling performance of the lithium metal battery; for example, too low a solids content (e.g., example 4) does not provide sufficient interfacial adhesion and has a low elastic modulus, thus affecting lithium metal battery cycling performance; with too high solid content (for example, example 5), the polymer chains at the gel electrolyte interface are easily constrained by a denser elastic network to reduce the degree of freedom, resulting in low interface adhesion and low tensile strength, which further affects the cycle performance of the lithium metal battery; therefore, the appropriate solid content is beneficial to improving the cycle performance of the lithium metal battery.
Comparison of examples 2, 6, 7, 9, 10 illustrates that the crosslink density of the elastomeric network in the gel electrolyte of the semi-interpenetrating network structure significantly affects the cycling performance of the lithium metal battery; for example, too high amount of cross-linking agent (e.g. example 9) can limit the freedom of the non-cross-linked polymer shuttled inside the elastic network at the interface, resulting in low adhesion strength with the electrode plate, and further affecting the cycle performance of the lithium metal battery; too low a crosslinker dosage (e.g., example 10) may not provide sufficient mechanical strength, and thus may not ensure structural integrity of the gel electrolyte during cycling, which may also affect cycling performance of the lithium metal battery; therefore, the elastic network has proper crosslinking density, which is beneficial to improving the cycle performance of the lithium metal battery.
The comparison of examples 2, 11 and 12 shows that the polymerization degree of the non-crosslinked macromolecules in the gel electrolyte with the semi-interpenetrating network structure has certain influence on the cycle performance of the lithium metal battery; for example, too low a degree of polymerization (e.g., example 11) lacks sufficient self-entanglement mechanism, which is not favorable for improving the mechanical properties of the gel electrolyte, and further influences the cycle performance of the lithium metal battery; too high polymerization degree (for example, example 12) has too many self-entanglement mechanisms, which affects the degree of freedom of interfacial polymers, is not beneficial to improving the adhesion strength with the pole piece, and also affects the cycle performance of the lithium metal battery; therefore, the polymerization degree of the uncrosslinked polymer is in a proper range, so that the cycle performance of the lithium metal battery is improved.
As can be seen from the comparison of examples 2, 8 and 13, the uncrosslinked polymer in the gel electrolyte with semi-interpenetrating network structure may be non-ether polymer, or one or more of the uncrosslinked polymers may be used, for example, the uncrosslinked polymer in example 2 is terminal amino modified polyoxyethylene (N-PEO), the uncrosslinked polymer in example 8 is polyurethane, and the uncrosslinked polymer in example 13 is a mixture of an appropriate amount of N-PEO and polyurethane, and as can be seen from the data in table 1, the lithium metal battery prepared by using terminal amino modified polyoxyethylene (N-PEO, degree of polymerization 6000) as the uncrosslinked polymer and having a mass ratio to the elastic network of 1:1 has the best cycle performance, and the gel electrolyte of the prepared lithium metal battery has a total mass content of the terminal amino modified polyoxyethylene (N-PEO, degree of polymerization 6000) and the three-dimensional organic crosslinked network of which is 100 mol ratio of the monomer to the crosslinking agent.
The comparative examples 1 and 2 are conventional single-network cross-linked systems, which have a negative coupling relationship between mechanics and adhesion, and it can be seen from the data in table 1 that the increase in cross-linking density can effectively improve the bulk mechanical properties of the gel electrolyte, but the freedom of movement of the interfacial polymer is significantly reduced, thereby resulting in poorer cycle performance, and thus, the single-network cross-linked systems cannot simultaneously improve the bulk mechanical properties and the interfacial adhesion of the gel electrolyte.
The gel electrolyte containing the semi-interpenetrating network structure comprising the uncrosslinked polymer and the three-dimensional organic crosslinked network in the embodiment of the application has better bonding strength with the pole piece, is beneficial to inhibiting uneven contact between the pole piece and the gel electrolyte caused by volume expansion of the pole piece in the charging and discharging process, has better mechanical property, and is beneficial to maintaining the structural stability in the circulating process, thereby realizing better battery circulating performance.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims (10)

1. A lithium metal battery, comprising: a gel electrolyte;
the gel electrolyte comprises an uncrosslinked polymer and a three-dimensional organic crosslinked network, wherein the uncrosslinked polymer and the three-dimensional organic crosslinked network are mutually interpenetrated to form a semi-interpenetrating network structure.
2. The lithium metal battery of claim 1, wherein the three-dimensional organic crosslinked network comprises monomers comprising polymerizable groups;
the polymerizable group includes any one of a double bond, an amino group, a carboxyl group, or a hydroxyl group;
preferably, the monomer comprises at least one of methacrylate, sodium acrylate, acrylamide, vinylene carbonate, adipic acid and polyethylene glycol.
3. The lithium metal battery of claim 2, wherein the polymerizable group-containing monomer is in a molar amount of n', and the crosslinking agent is in a molar amount of n ″, such that: 10, 1 is less than or equal to n '/n' is less than or equal to 1000.
4. The lithium metal battery of claim 1, wherein the uncrosslinked polymer satisfies at least one of the following conditions:
condition a: the degree of polymerization DP of the uncrosslinked polymer satisfies the following conditions: DP is more than or equal to 1000 and less than or equal to 100000;
condition b: the length of a Kuhn chain segment in the uncrosslinked polymer is less than 5nm.
5. The lithium metal battery of claim 1, wherein the non-crosslinked polymer comprises at least one of polyethylene oxide, end-modified polyethylene oxide, polyurethane, polycarbonate, or polyphosphate;
preferably, the terminal modified polyoxyethylene comprises a terminal amino modified polyoxyethylene.
6. The lithium metal battery of claim 1, wherein the mass ratio of the uncrosslinked polymer to the three-dimensional organic crosslinked network is 10 to 0.5:1.
7. the lithium metal battery according to claim 1, wherein the sum of the mass content of the non-crosslinked polymer and the mass content of the three-dimensional organic crosslinked network is 1 to 10wt% based on the mass of the gel electrolyte.
8. The lithium metal battery of claim 1, wherein the gel electrolyte has a loss angle tan δ > 1.
9. The lithium metal battery of any of claims 1-8, wherein at least one of the following conditions is met:
(1) The degree of polymerization DP of the uncrosslinked polymer satisfies the following conditions: DP is more than or equal to 5000 and less than or equal to 7000;
(2) The three-dimensional organic crosslinking network is obtained by polymerizing a monomer and a crosslinking agent, wherein the molar quantity of the monomer is n', and the molar quantity of the crosslinking agent is n ″, and the three-dimensional organic crosslinking network satisfies the following conditions: 50, 1 is more than or equal to n '/n' is more than or equal to 200;
(3) Based on the mass of the gel electrolyte, the sum of the mass content of the uncrosslinked macromolecules and the mass content of the three-dimensional organic crosslinked network is 3-5%;
(4) Based on the mass of the gel electrolyte, the mass ratio of the uncrosslinked polymer to the three-dimensional organic crosslinked network is 2:1-0.8.
10. An electrical device comprising the lithium metal battery according to any one of claims 1 to 9.
CN202210920466.8A 2022-08-02 2022-08-02 Lithium metal battery and application thereof Pending CN115275336A (en)

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