CN113140788A - Quasi-solid electrolyte and quasi-solid lithium ion battery - Google Patents
Quasi-solid electrolyte and quasi-solid lithium ion battery Download PDFInfo
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Abstract
The invention relates to a quasi-solid electrolyte and a quasi-solid lithium ion battery. The raw materials for preparing the quasi-solid electrolyte comprise the following components in percentage by mass: 5% -8% of polymer electrolyte; 10-25% of a first lithium salt; and 70-85% of linear carbonate solvent. The invention selects specific raw materials to reasonably combine according to a specific proportion, and the prepared quasi-solid electrolyte can play a role in buffering, is beneficial to improving the affinity between interfaces, reducing the interface impedance and eliminating the space charge effect bothering solid batteries. When the quasi-solid electrolyte is used for a quasi-solid lithium ion battery, the formation of lithium dendrites can be inhibited, the cycle and safety performance of the battery are improved, and the application is facilitated.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a quasi-solid electrolyte and a quasi-solid lithium ion battery.
Background
The electrolyte of the secondary lithium ion battery uses more inflammable organic solvents and corrosive electrolyte salt, the electrolyte is easy to react on the surface of a high-oxidation-state positive electrode material to generate combustible gas when overcharged, the internal pressure is increased, the battery generates phenomena of gas expansion, liquid leakage and the like, and the corrosion and the damage of an electric appliance are caused; lithium dendrite is easily formed on the surface of the negative electrode to pierce the diaphragm to cause internal short circuit of the battery, so that the internal temperature of the battery is sharply increased to cause explosion. Safety issues have greatly limited the application area of lithium ion batteries. The safety problem of the lithium ion battery can be solved from the source by replacing the organic liquid electrolyte with the nonflammable or nonflammable solid electrolyte. Batteries using solid electrolytes can be used at higher and lower temperatures while avoiding capacity loss and cycle life decay due to the generation of Solid Electrolyte Interphase (SEI) at the electrode surface. Therefore, the solid state of the lithium ion battery is a necessary trend.
The mainstream research and development trend of the industry at present is to develop a composite electrolyte solid-liquid mixed battery, and then the solid-liquid mixing gradually transits to an all-solid battery. The solid-liquid hybrid battery improves the safety of the battery by reducing the content of combustible liquid in the battery under the condition of not reducing the energy density, however, the interface impedance of a composite electrode and a composite solid electrolyte membrane in the solid-liquid hybrid battery is too large, the charging and discharging performance of the battery is seriously influenced, and the solid-liquid hybrid battery is not beneficial to wide application.
Disclosure of Invention
In view of the above, it is necessary to provide a quasi-solid electrolyte and a quasi-solid lithium ion battery capable of reducing the interface impedance, aiming at the problem of reducing the interface impedance.
The quasi-solid electrolyte is prepared from the following raw materials in percentage by mass:
5% -8% of polymer electrolyte;
10% -25% of a first lithium salt; and
70 to 85 percent of linear carbonate solvent.
The invention selects specific raw materials to reasonably combine according to a specific proportion, and the prepared quasi-solid electrolyte can play a role in buffering, is beneficial to improving the affinity between interfaces, reducing the interface impedance and eliminating the space charge effect bothering solid batteries. When the quasi-solid electrolyte is used for a quasi-solid lithium ion battery, the formation of lithium dendrites can be inhibited, the cycle and safety performance of the battery are improved, and the application is facilitated.
In one embodiment, the raw materials for preparing the quasi-solid electrolyte comprise the following components in percentage by mass:
6% -8% of polymer electrolyte;
10% -12% of a first lithium salt; and
80 to 83 percent of linear carbonate solvent.
In one embodiment, the polymer electrolyte is selected from at least one of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, and polyvinyl chloride; and/or
The first lithium salt is selected from at least one of lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide and lithium tetrafluoroborate; and/or
The linear carbonate solvent is at least one selected from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate.
The invention also provides a quasi-solid lithium ion battery which comprises a positive electrode, a negative electrode and an electrolyte membrane positioned between the positive electrode and the negative electrode, wherein any quasi-solid electrolyte is arranged between the positive electrode and the electrolyte membrane and between the negative electrode and the electrolyte membrane.
The quasi-solid-state lithium ion battery provided by the technical scheme of the invention has high safety and excellent electrochemical performance.
In one embodiment, the raw materials for preparing the electrolyte membrane comprise the following components in percentage by mass:
80% -93% of a first inorganic ceramic electrolyte;
5% -8% of a first binder; and
2 to 12 percent of second lithium salt.
In one embodiment, the first inorganic ceramic electrolyte is selected from at least one of LATP, LAGP, LLZO, LLZTO, and LLAZO; and/or
The first binder is selected from at least one of PVDF 5130, PVDF-HFP, HSV900, kynar761A, PVDF5140, PTFE and PEO; and/or
The second lithium salt is at least one selected from lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide and lithium tetrafluoroborate.
In one embodiment, the raw materials for preparing the positive electrode comprise the following components in percentage by mass:
in one embodiment, the positive electrode material is selected from at least one of lithium cobaltate, lithium manganate and nickel cobalt manganese; and/or
The first conductive agent is at least one selected from Surpe-P (C65T), acetylene black, KS-6, CNT and graphene; and/or
The second inorganic ceramic electrolyte is selected from at least one of LATP, LAGP, LLZO, LLTO, LLZTO, and LLAZO; and/or
The second binder is selected from at least one of PVDF 5130, PVDF5140, HSV900, kynar761A, PVDF-HFP, PTFE and PEO; and/or
The third lithium salt is at least one selected from lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide and lithium tetrafluoroborate.
In one embodiment, the raw materials for preparing the negative electrode comprise the following components in percentage by mass:
in one embodiment, the negative electrode material is selected from at least one of artificial graphite, natural graphite, and mesocarbon microbeads; and/or
The second conductive agent is at least one selected from Surpe-P, acetylene black, KS-6, CNT and graphene; and/or
The third inorganic ceramic electrolyte is selected from at least one of LATP, LAGP, LLZO, LLZTO and LLAZO; and/or
The third binder is selected from at least one of PVDF 5130, PVDF5140, HSV900, kynar761A, PVDF-HFP, PTFE and PEO; and/or
The fourth lithium salt is at least one selected from lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide and lithium tetrafluoroborate.
Drawings
FIG. 1 shows capacity retention and recovery after 300-fold cycles of quasi-solid lithium ion batteries of examples 15 to 33 and comparative examples 4 to 9.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The quasi-solid electrolyte of one embodiment of the present invention is prepared from the following raw materials in percentage by mass:
5% -8% of polymer electrolyte;
10% -25% of a first lithium salt; and
70 to 85 percent of linear carbonate solvent.
The polymer electrolyte has the advantages of good safety performance, flexibility, easy processing into a film, excellent interface contact and the like, and can well inhibit the problem of lithium dendrite.
The first lithium salt is used for providing lithium ions, and the lithium ions move between the anode and the cathode of the lithium ion battery to realize charging and discharging of the lithium ion battery.
Wherein a linear carbonate-based solvent is used to dissolve the polymer electrolyte and the first lithium salt.
When the quasi-solid electrolyte prepared by the raw materials is used for a lithium ion battery, the linear carbonate solvent can perform a crosslinking reaction with the anode, the cathode and the binder in the composite electrolyte membrane, so that the binding force among the anode, the cathode and the electrolyte membrane is stronger, the phenomenon of mutual layering during bending is avoided, a space charge layer is eliminated, and the impedance is reduced.
In one embodiment, the raw materials for preparing the quasi-solid electrolyte comprise the following components in percentage by mass:
6% -8% of polymer electrolyte;
10% -12% of a first lithium salt; and
80 to 83 percent of linear carbonate solvent.
The quasi-solid electrolyte prepared by adopting the proportion has better effects on improving the affinity between interfaces, reducing the interface impedance and eliminating the space charge effect disturbing the solid battery.
In one embodiment, the polymer electrolyte is selected from at least one of PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer), polyethylene oxide (PEO), Polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), and polyvinyl chloride (PVC).
In one embodiment, the first lithium salt is selected from lithium hexafluorophosphate (LiPF)6) Lithium trifluoromethanesulfonate (LiOTF), lithium bis (oxalato) borate (LiBOB), lithium difluoro (oxalato) borate (LiDFOB), lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethylsulfonyl) imide (LiTFSi) and lithium tetrafluoroborate (LiBF)4) At least one of (1).
In one embodiment, the linear carbonate-based solvent is selected from at least one of Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC), diethyl carbonate (DEC), and Propylene Carbonate (PC). These types of linear carbonate solvents have a higher electrochemical window, and can make the prepared quasi-solid electrolyte more stable.
The invention selects specific raw materials to reasonably combine according to a specific proportion, and the prepared quasi-solid electrolyte can play a role in buffering, is beneficial to improving the affinity between interfaces, reducing the interface impedance and eliminating the space charge effect bothering solid batteries. When the quasi-solid electrolyte is used for a quasi-solid lithium ion battery, the formation of lithium dendrites can be inhibited, the cycle and safety performance of the battery are improved, and the application is facilitated.
Compared with commercial lithium ion batteries, the quasi-solid electrolyte of the embodiment of the invention simultaneously plays the roles of lithium salt, organic solvent and isolating membrane, completely inhibits thermal runaway caused by short circuit in the battery due to penetration of lithium dendrite on the membrane, and eliminates the risks of corrosion of a packaging membrane and leakage of liquid electrolyte. Due to the solid characteristic of the quasi-solid electrolyte, the quasi-solid electrolyte has excellent machining performance, and can be made into different shapes to meet the requirements of various consumer electronic products.
The preparation method of the quasi-solid electrolyte comprises the following steps:
according to the mass percentage, the polymer electrolyte, the first lithium salt and the linear carbonate solvent are uniformly mixed to obtain the quasi-solid electrolyte.
Wherein, the condition of uniform mixing is as follows: the drying environment is that the moisture content is less than 20ppm, the oxygen content is less than 5ppm, and the dispersion is carried out for 5 to 8 hours at the normal temperature. After the quasi-solid electrolyte is obtained, the quasi-solid electrolyte is sealed and placed in an environment with the temperature of 5 +/-3 ℃ for refrigeration and standby.
The quasi-solid lithium ion battery provided by one embodiment of the invention comprises a positive electrode, a negative electrode and an electrolyte membrane positioned between the positive electrode and the negative electrode, wherein any quasi-solid electrolyte is arranged between the positive electrode and the electrolyte membrane and between the negative electrode and the electrolyte membrane.
In one embodiment, the raw materials for preparing the electrolyte membrane comprise the following components in percentage by mass:
80% -93% of a first inorganic ceramic electrolyte;
5% -8% of a first binder; and
2 to 12 percent of second lithium salt.
Compared with the traditional electrolyte membrane, the raw materials for preparing the electrolyte membrane in the embodiment of the invention have more lithium salt content, can play the role of a plasticizer, improves the toughness of the electrolyte membrane and ensures that the electrolyte membrane is not easy to break.
In one embodiment, the first inorganic ceramic electrolyte is selected from at least one of LATP, LAGP, LLZO, LLZTO, and LLAZO.
In one embodiment, the first binder is selected from at least one of PVDF 5130, PVDF-HFP, HSV900, kynar761A, PVDF5140, PTFE, and PEO. The first binder is preferably PVDF-HFP (polyvinylidene fluoride-hexafluoropropylene copolymer), and the propylene carbonate can be crosslinked with H-F bonds in the PVDF-HFP, so that the binding force between the positive electrode, the negative electrode and the electrolyte membrane is stronger, the mutual layering after bending is avoided, the space charge layer is eliminated, and the impedance is reduced.
In one embodiment, the second lithium salt is selected from at least one of lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethylsulfonyl) imide, and lithium tetrafluoroborate.
The method for producing the electrolyte membrane of the above embodiment includes the steps of:
according to the mass percentage, dissolving a first inorganic ceramic electrolyte, a first binder and a second lithium salt in an N-methyl pyrrolidone solution, wherein the mass of the N-methyl pyrrolidone solution is 1.2-2.5 times of the total mass of the first inorganic ceramic electrolyte, the first binder and the second lithium salt. And then mixing the materials for 3 to 5 hours in vacuum, and obtaining the composite electrolyte slurry at a high-speed dispersion speed of 3500rpm to 5500 rpm.
And then, casting the electrolyte slurry onto a glass plate by adopting a laboratory casting technology, regulating and controlling the thickness of the electrolyte membrane by adjusting the gap between a casting knife and the glass plate, the viscosity and the solid content of the slurry, flatly placing the slurry in a blast drying box for drying after casting, separating the electrolyte membrane from the glass plate after the solvent is completely volatilized to obtain a uniform composite solid electrolyte membrane, and controlling the drying thickness to be between 20 and 40 mu m for later use.
In one embodiment, the raw materials for preparing the positive electrode comprise the following components in percentage by mass:
the positive electrode material in the present invention refers to a host material for preparing a positive electrode. Further, the positive electrode material is selected from at least one of lithium cobaltate, lithium manganate and nickel cobalt manganese.
In one embodiment, the first conductive agent is selected from at least one of Surpe-P (C65T), acetylene black, KS-6, CNT, and graphene.
In one embodiment, the second inorganic ceramic electrolyte is selected from at least one of LATP, LAGP, LLZO, LLTO, LLZTO, and LLAZO.
In one embodiment, the second binder is selected from at least one of PVDF 5130, PVDF5140, HSV900, kynar761A, PVDF-HFP, PTFE, and PEO.
In one embodiment, the third lithium salt is selected from at least one of lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethylsulfonyl) imide, and lithium tetrafluoroborate.
The preparation method of the positive electrode of the embodiment comprises the following steps:
according to the mass percentage, the anode material, the first conductive agent, the second inorganic ceramic electrolyte, the second binder, the second lithium salt and the N-methylpyrrolidone solution are sequentially added into a lithium mixer, and the high-speed dispersion speed is 3500 rpm-6500 rpm, so that the composite anode slurry is obtained. The mass of the N-methyl pyrrolidone solution is 1-1.5 times of the total mass of the positive electrode material, the first conductive agent, the second inorganic ceramic electrolyte, the second binder and the second lithium salt.
Coating the composite anode slurry on a carbon-coated aluminum foil with the thickness of 12-16 mu m by a coating machine, wherein the coating thickness is 130-200 mu m, the drying temperature of the coating machine is 95-135 ℃, drying the wound electrode piece in a vacuum oven at the temperature of 115-135 ℃, the drying time is 24-36 h, rolling the dried electrode piece, and compacting to 2.5g/cm3～3.5g/cm3And slitting to obtain the composite positive pole piece.
In one embodiment, the raw materials for preparing the negative electrode comprise the following components in percentage by mass:
the negative electrode material in the present invention refers to a host material for preparing a negative electrode. Further, the negative electrode material is selected from at least one of Artificial graphite (Artificial graphite), natural graphite (natural graphite), and mesocarbon microbeads (MCMB).
In one embodiment, the second conductive agent is selected from at least one of Surpe-P, acetylene black, KS-6, CNT, and graphene.
In one embodiment, the third inorganic ceramic electrolyte is selected from at least one of LATP, LAGP, LLZO, LLZTO, and LLAZO.
In one embodiment, the third binder is selected from at least one of PVDF 5130, PVDF5140, HSV900, kynar761A, PVDF-HFP, PTFE, and PEO.
In one embodiment, the fourth lithium salt is selected from at least one of lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethylsulfonyl) imide, and lithium tetrafluoroborate.
The preparation method of the positive electrode of the embodiment comprises the following steps:
according to the mass percentage, the negative electrode material, the second conductive agent, the third inorganic ceramic electrolyte, the third binder, the fourth lithium salt and the N-methylpyrrolidone solution are sequentially added into a lithium electric mixer, the materials are mixed for 3h to 5h in vacuum, and the high-speed dispersion speed is 3500rpm to 5500rpm, so that the composite negative electrode slurry is obtained. The mass of the N-methylpyrrolidone solution is 0.4-0.5 times of the total mass of the negative electrode material, the second conductive agent, the third inorganic ceramic electrolyte, the third binder and the fourth lithium salt.
Coating the composite negative electrode slurry on a carbon-coated copper foil with the thickness of 6-8 mu m by a coating machine, wherein the coating thickness is 80-150 mu m, the drying temperature of the coating machine is 95-135 ℃, drying the wound pole piece in a vacuum oven with the temperature of 95-115 ℃, the drying time is 12-24 h, rolling the dried pole piece, and compacting to 1.45g/cm3～1.55g/cm3And slitting to obtain the composite negative pole piece.
The quasi-solid-state lithium ion battery provided by the technical scheme of the invention has high safety and excellent electrochemical performance.
A method of manufacturing a lithium ion battery according to an embodiment includes the steps of:
and assembling and hot-pressing the structure of the positive electrode/quasi-solid electrolyte/electrolyte membrane/quasi-solid electrolyte/negative electrode by adopting a lamination or unequal-distance multi-tab winding process to obtain the flexible quasi-solid lithium ion battery. Wherein the quasi-solid electrolyte can be uniformly sprayed on the surface of the anode, the surface of the cathode and two sides of the electrolyte membrane by spraying and other processes.
With reference to the above implementation contents, in order to make the technical solutions of the present application more specific and clear and easier to understand, the technical solutions of the present application are exemplified, but it should be noted that the contents to be protected by the present application are not limited to the following embodiments 1 to 33.
Examples 1 to 14
The quasi-solid electrolytes of examples 1 to 14 were prepared as follows:
weighing the raw materials according to the mass percentage in the table 1; mixing the polymer electrolyte, the first lithium salt and the linear carbonate solvent, dispersing for 6 hours at normal temperature under the dry environment that the moisture is less than 20ppm and the oxygen content is less than 5ppm to obtain the quasi-solid electrolyte, and then sealing and refrigerating the quasi-solid electrolyte in the environment of 5 +/-3 ℃ for later use.
TABLE 1 raw material tables for preparing quasi-solid electrolytes of examples 1 to 14 and comparative examples 1 to 3
In table 1, "/" indicates that the substance is not present or the content of the substance is 0.
Comparative example 1
This comparative example is a comparative example to example 1, the starting materials are as in table 1, and the comparative example differs from example 1 only in that: the quasi-solid electrolyte does not contain the first lithium salt.
Comparative example 2
This comparative example is a comparative example to example 1, the starting materials are as in table 1, and the comparative example differs from example 1 only in that: the quasi-solid electrolyte does not contain a polymer electrolyte.
Comparative example 3
This comparative example is a comparative example to example 1, the starting materials are as in table 1, and the comparative example differs from example 1 only in that: the quasi-solid electrolyte does not contain a linear carbonate solvent.
Examples 15 to 33
The preparation process of the quasi-solid lithium ion battery of the embodiment 15 to 33 is as follows:
(1) an electrolyte membrane was prepared by the following procedure:
weighing the raw materials according to the mass percentage in the table 2; dissolving a first inorganic ceramic electrolyte, a first binder and a second lithium salt in an N-methyl pyrrolidone solution, wherein the mass of the N-methyl pyrrolidone solution is 1.2 times of the total mass of the first inorganic ceramic electrolyte, the first binder and the second lithium salt. And then mixing materials for 3 hours in vacuum, and obtaining the composite electrolyte slurry at a high-speed dispersion speed of 5500 rpm. And then, casting the electrolyte slurry onto a glass plate by adopting a laboratory casting technology, regulating and controlling the thickness of the electrolyte membrane by adjusting the gap between a casting knife and the glass plate, the viscosity and the solid content of the slurry, flatly placing the slurry in a blast drying box for drying after casting, separating the electrolyte membrane from the glass plate after the solvent is completely volatilized to obtain a uniform composite solid electrolyte membrane, and controlling the drying thickness to be about 20 mu m for later use.
(2) The positive electrode was prepared by the following procedure:
weighing the raw materials according to the mass percentage in the table 3; and successively adding the positive electrode material, the first conductive agent, the second inorganic ceramic electrolyte, the second binder, the second lithium salt and the N-methylpyrrolidone solution into a lithium electric mixer, and dispersing at a high speed of 4000rpm to obtain the composite positive electrode slurry. Wherein the mass of the N-methyl pyrrolidone solution is 1.2 times of the total mass of the cathode material, the first conductive agent, the second inorganic ceramic electrolyte, the second binder and the second lithium salt.
Coating the composite anode slurry on a carbon-coated aluminum foil with the thickness of 12 mu m by a coating machine, wherein the coating thickness is 130 mu m, the drying temperature of the coating machine is 95 ℃, drying the wound pole piece in a vacuum oven at 115 ℃ for 36h, rolling the dried pole piece, and compacting to 3.5g/cm3And slitting to obtain the composite positive pole piece.
(3) The negative electrode was prepared by the following procedure:
weighing the raw materials according to the mass percentage in the table 3; and successively adding the negative electrode material, a second conductive agent, a third inorganic ceramic electrolyte, a third binder, a fourth lithium salt and an N-methylpyrrolidone solution into a lithium electric mixer, mixing materials for 5 hours in vacuum, and obtaining the composite negative electrode slurry at a high-speed dispersion speed of 5500 rpm. Wherein the mass of the N-methylpyrrolidone solution is 0.5 times of the total mass of the negative electrode material, the second conductive agent, the third inorganic ceramic electrolyte, the third binder and the fourth lithium salt.
Coating the composite negative electrode slurry on a carbon-coated copper foil with the thickness of 8 mu m by adopting a coating machine, wherein the coating thickness is 150 mu m, the drying temperature of the coating machine is 135 ℃, drying the wound pole piece in a vacuum oven at 115 ℃ for 12h, rolling the dried pole piece, and compacting to 1.55g/cm3And slitting to obtain the composite negative pole piece.
(4) The quasi-solid lithium ion battery is prepared by the following steps:
and assembling and hot-pressing the structure of the positive electrode/quasi-solid electrolyte/electrolyte membrane/quasi-solid electrolyte/negative electrode by adopting a lamination or unequal-distance multi-tab winding process to obtain the flexible quasi-solid lithium ion battery. Wherein, the quasi-solid electrolyte is evenly sprayed on the surface of the anode, the surface of the cathode and two sides of the electrolyte membrane by a spraying process. The quasi-solid lithium ion batteries of embodiments 15 to 28 sequentially include the quasi-solid electrolytes of embodiments 1 to 14, the quasi-solid lithium ion batteries of embodiments 29 to 33 include the quasi-solid electrolyte of embodiment 1, and the quasi-solid lithium ion batteries of comparative examples 4 to 6 sequentially include the quasi-solid electrolytes of comparative examples 1 to 3.
TABLE 2 raw material tables for preparing electrolyte membranes of quasi-solid lithium ion batteries of examples 15 to 33 and comparative examples 4 to 9
In table 2, "/" indicates that the substance is not present or the content of the substance is 0.
TABLE 3 raw material tables for preparing positive and negative electrodes of quasi-solid lithium ion batteries of examples 15 to 33 and comparative examples 4 to 9
Comparative example 4
This comparative example is a comparative example to example 15, the starting materials are as in table 2, and the comparative example differs from example 15 only in that: the quasi-solid electrolyte of the quasi-solid lithium ion battery does not contain the first lithium salt.
Comparative example 5
This comparative example is a comparative example to example 15, the starting materials are as in table 2, and the comparative example differs from example 15 only in that: the quasi-solid electrolyte of the quasi-solid lithium ion battery does not contain polymer electrolyte.
Comparative example 6
This comparative example is a comparative example to example 15, the starting materials are as in table 2, and the comparative example differs from example 15 only in that: the quasi-solid electrolyte of the quasi-solid lithium ion battery does not contain a linear carbonate solvent.
Comparative example 7
This comparative example is a comparative example to example 15, the starting materials are as in table 2, and the comparative example differs from example 15 only in that: the electrolyte membrane of the quasi-solid lithium ion battery does not contain the second lithium salt.
Comparative example 8
This comparative example is a comparative example to example 15, the starting materials are as in table 2, and the comparative example differs from example 15 only in that: the electrolyte membrane of the quasi-solid lithium ion battery does not contain the first inorganic ceramic electrolyte.
Comparative example 9
This comparative example is a comparative example to example 15, the starting materials are as in table 2, and the comparative example differs from example 15 only in that: the electrolyte membrane of the quasi-solid lithium ion battery does not contain the first binder.
And (3) testing the charge and discharge performance:
the quasi-solid lithium ion batteries of examples 15 to 33 and comparative examples 4 to 9 were charged at a constant current of 0.5C at 25 ± 3 ℃ until the battery voltage reached 4.2V, and then charged at a constant voltage until the charging current decreased to 0.05C. After charging, the cell was left to stand for 5min, and discharged to 3.0V at 25. + -. 3 ℃ with a current of 0.5C, and the above-mentioned charging and discharging was repeated 3 times, and the average discharge capacity C0 was recorded 3 times.
The quasi-solid lithium ion batteries of examples 15 to 33 and comparative examples 4 to 9 were charged at a constant current of 0.5C at 25 ± 3 ℃, charged until the battery voltage reached 4.2V, charged at a constant voltage until the charging current decreased to 0.05C, and bent back and forth at a curvature of 50mm in diameter, and the capacity calibration was performed after 50, 100, 200, and 300 times of bending.
Capacity calibration: discharging the soft-packaged flexible quasi-solid lithium ion battery to 3.0V at 25 +/-3 ℃ by using a 0.5C current, standing for 5min, charging by using a 0.5C constant current, stopping charging when the battery voltage reaches 4.2V by converting constant voltage charging until the charging current is reduced to 0.05C, repeating the charging and discharging for 4 times, recording the first-time discharge capacity of the step as C1 and the average discharge capacity of the last 3 times as C2, calculating the capacity retention rate and the recovery rate according to the following formulas, and obtaining results shown in the table 4 and the figure 1:
capacity retention (%) — retention capacity C1/initial capacity C0 × 100%;
the capacity recovery ratio (%) — recovery capacity C2/initial capacity C0 × 100%.
TABLE 4 Performance test results of quasi-solid lithium ion batteries of examples 15 to 33 and comparative examples 4 to 9
The following conclusions can be drawn in conjunction with table 4 and fig. 1:
(1) the quasi-solid-state lithium ion batteries of embodiments 15-33 of the present invention can continue to perform charge and discharge operations after being bent, and after being bent for 300 times, the capacity retention rate is above 86%, and the capacity recovery rate can be above 95%. After the quasi-solid lithium ion batteries of comparative examples 4 to 9 are bent 300 times, the capacity retention rate is below 61%, and the capacity recovery rate can be below 63%. The invention can improve the affinity between interfaces, reduce the interface impedance, eliminate the space charge effect disturbing the solid-state battery, and ensure that the positive and negative electrodes and the electrolyte membrane are not delaminated in the bending process and keep a normal and close fit state.
(2) Example 15 was compared with comparative examples 4 to 6, respectively, except that the components of the semi-solid electrolyte were different. The result shows that the quasi-solid-state lithium ion battery in the embodiment 15 can continue to perform charge and discharge work after being bent, and after being bent for 300 times, the capacity retention rate can reach 86.43%, and the capacity recovery rate can reach 90.14%. The quasi-solid lithium ion batteries of comparative examples 4 and 5, after being bent 200 times, have the anode and cathode and electrolyte membranes delaminated and cannot be charged and discharged normally, while the quasi-solid lithium ion battery of comparative example 6, after being bent 300 times, has the capacity retention rate of only 57.20% and the capacity recovery rate of only 61.50%, which are far lower than the quasi-solid lithium ion battery of example 15. The results show that the polymer electrolyte, the first lithium salt and the linear carbonate solvent in the quasi-solid electrolyte can improve the affinity among interfaces, reduce the interface impedance, eliminate the space charge effect which troubles the solid-state battery, and ensure that the positive and negative electrodes and the electrolyte membrane are not delaminated in the bending process and keep a normal and close fit state.
(3) Example 15 was compared with comparative examples 7 to 9, respectively, except that the composition of the electrolyte membrane was different. The result shows that the quasi-solid-state lithium ion battery in the embodiment 15 can continue to perform charge and discharge work after being bent, and after being bent for 300 times, the capacity retention rate can reach 86.43%, and the capacity recovery rate can reach 90.14%. The quasi-solid lithium ion batteries of comparative examples 7 to 9 can be charged and discharged normally after being bent, but after being bent for 300 times, the capacity retention rates are only 57.10%, 59.63% and 60.18%, and the capacity recovery rates are only 60.23%, 61.28% and 62.22%, which are much lower than those of the quasi-solid lithium ion battery of example 15. The first inorganic ceramic electrolyte, the first binder and the second lithium salt in the electrolyte membrane of the quasi-solid lithium ion battery are matched for use, so that the toughness of the electrolyte membrane can be improved, the electrolyte membrane is not easy to break, the binding force between the anode and the cathode and the electrolyte membrane can be enhanced, the phenomenon that the electrolyte membrane is mutually layered after being bent is avoided, a space charge layer is eliminated, and the impedance is reduced.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. The quasi-solid electrolyte is characterized in that raw materials for preparing the quasi-solid electrolyte comprise the following components in percentage by mass:
5% -8% of polymer electrolyte;
10% -25% of a first lithium salt; and
70 to 85 percent of linear carbonate solvent.
2. The quasi-solid electrolyte according to claim 1, wherein the raw materials for preparing the quasi-solid electrolyte comprise the following components in percentage by mass:
6% -8% of polymer electrolyte;
10% -12% of a first lithium salt; and
80 to 83 percent of linear carbonate solvent.
3. The quasi-solid electrolyte of claim 1 or 2, wherein the polymer electrolyte is selected from at least one of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, and polyvinyl chloride; and/or
The first lithium salt is selected from at least one of lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide and lithium tetrafluoroborate; and/or
The linear carbonate solvent is at least one selected from ethylene carbonate, ethyl methyl carbonate, diethyl carbonate and propylene carbonate.
4. A quasi-solid lithium ion battery, comprising a positive electrode, a negative electrode and an electrolyte membrane located between the positive electrode and the negative electrode, wherein the quasi-solid electrolyte of any one of claims 1 to 3 is arranged between the positive electrode and the electrolyte membrane and between the negative electrode and the electrolyte membrane.
5. The quasi-solid state lithium ion battery of claim 4, wherein the raw materials for preparing the electrolyte membrane comprise the following components in percentage by mass:
80% -93% of a first inorganic ceramic electrolyte;
5% -8% of a first binder; and
2 to 12 percent of second lithium salt.
6. The quasi-solid lithium ion battery of claim 5, wherein the first inorganic ceramic electrolyte is selected from at least one of LATP, LAGP, LLZO, LLZTO, and LLAZO; and/or
The first binder is selected from at least one of PVDF 5130, PVDF-HFP, HSV900, kynar761A, PVDF5140, PTFE and PEO; and/or
The second lithium salt is at least one selected from lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide and lithium tetrafluoroborate.
7. The quasi-solid state lithium ion battery of claim 4, wherein the raw materials for preparing the positive electrode comprise the following components in percentage by mass:
8. the quasi-solid state lithium ion battery of claim 7, wherein the positive electrode material is selected from at least one of lithium cobaltate, lithium manganate, and nickel cobalt manganese; and/or
The first conductive agent is at least one selected from Surpe-P (C65T), acetylene black, KS-6, CNT and graphene; and/or
The second inorganic ceramic electrolyte is selected from at least one of LATP, LAGP, LLZO, LLTO, LLZTO, and LLAZO; and/or
The second binder is selected from at least one of PVDF 5130, PVDF5140, HSV900, kynar761A, PVDF-HFP, PTFE and PEO; and/or
The third lithium salt is at least one selected from lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide and lithium tetrafluoroborate.
9. The quasi-solid state lithium ion battery of claim 4, wherein the raw materials for preparing the negative electrode comprise, in mass percent:
10. the quasi-solid state lithium ion battery of claim 9, wherein the negative electrode material is selected from at least one of artificial graphite, natural graphite, and mesocarbon microbeads; and/or
The second conductive agent is at least one selected from Surpe-P, acetylene black, KS-6, CNT and graphene; and/or
The third inorganic ceramic electrolyte is selected from at least one of LATP, LAGP, LLZO, LLZTO and LLAZO; and/or
The third binder is selected from at least one of PVDF 5130, PVDF5140, HSV900, kynar761A, PVDF-HFP, PTFE and PEO; and/or
The fourth lithium salt is at least one selected from lithium hexafluorophosphate, lithium trifluoromethanesulfonate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide and lithium tetrafluoroborate.
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