CN107731542B - A kind of solid state battery capacitor - Google Patents

Abstract

The invention discloses a solid-state battery capacitor. The solid-state battery capacitor includes a positive electrode, a negative electrode, and a solid electrolyte. Graphite material, wherein the negative electrode graphite material should be pre-lithiated. In the solid battery capacitor of the present invention, the solid electrolyte can form a good solid solution with the positive and negative electrodes during the charging and discharging cycle, and can produce a stable interface effect, greatly improving the first charge and discharge efficiency, Coulombic efficiency during the cycle, and reducing impedance. And the negative electrode adopts pre-lithiated graphite electrode, which can significantly reduce the loss of lithium salt during charging and discharging, greatly improve the cycle life, and reduce the leakage current. The working voltage of the solid-state battery capacitor can reach 5.35V, which greatly improves the energy density. In addition, solid electrolyte is used to ensure safety performance.

Description

A solid battery capacitor

technical field

The invention belongs to the field of power/energy storage batteries, in particular to a solid-state battery capacitor.

Background technique

The increasing energy crisis and environmental problems have accelerated the rapid development of the new energy industry. Under the current situation, the environment-friendly electrochemical energy storage technology that maximizes green energy supply and low-carbon energy conservation and emission reduction has attracted more and more attention. Recently, the state has proposed to establish a near-zero carbon emission project based on the Energy Internet, the core content of which includes renewable energy power generation, distributed energy storage technology, etc., which puts forward higher requirements for new and efficient energy storage technologies. In addition, new energy Electrochemical energy storage devices with high energy density and high power density are also required in fields such as electric vehicles, low-temperature starting power supplies, high-speed rail/urban rail transit braking energy recovery, marine ship platforms, underwater submersible power supplies, and UPS uninterruptible power supplies. .

At present, there are two most mature commercialized electrochemical energy storage technologies, one is lithium-ion battery, the positive electrode uses lithium-containing metal oxide as the active material, and the negative electrode uses graphite as the activated carbon material, through which the positive and negative electrodes electrochemically intercalate lithium to store energy , the energy density of a single cell can reach more than 150 Wh/kg, but its power density is only 100~500 W/kg, the power performance is poor, the cycle life is only ~500 times, and the low temperature performance is poor; the other is the electric double layer supercapacitor , the device uses activated carbon with high specific surface area as the positive and negative active materials, and stores energy through physical adsorption of charges, so its power density can reach more than 5000 W/kg, cycle life can reach more than 10000 times, 2~5Wh/kg, battery life is limited Limit, can not supply power for a long time. Lithium-ion capacitors, that is, battery capacitors, which have the advantages of both of the above, have become a research hotspot.

In principle, conventional battery capacitors use the negative electrode to electrochemically intercalate Li ⁺ , and the positive electrode uses physical adsorption of PF ₆ ^- and other anions to store energy. The electrolyte is a liquid organic system with a working voltage of 3.8V and an energy density of 10~20Wh/kg. , the power density is 3000~5000W/kg, another battery capacitor relies on the physical adsorption of Li ⁺ cations on the negative electrode, and the electrochemical embedding of PF ₆ ^- on the positive electrode to store energy. The electrolytes of the above two battery capacitors are liquid organic electrolytes. The embedded active material is graphite material, and the adsorption material is porous carbon. The disadvantage of using organic electrolyte is that the safety performance is poor, and it is easy to catch fire and explode under abuse conditions; one pole uses physical adsorption to store energy, which makes the leakage current large; in addition, For the latter type of battery capacitor, under the liquid electrolyte system, during the repeated intercalation/extraction process of PF ₆ ^- , the surface of the active material will continue to peel off, the interface will be destroyed, and irreversible reactions will occur repeatedly, so that the irreversible capacity will continue to be generated. Discharge efficiency and Coulombic efficiency during long-term cycling are low.

Contents of the invention

In order to solve the above existing problems, the present invention provides a solid battery capacitor.

In order to achieve the above object, technical scheme of the present invention is:

A solid-state battery capacitor, the solid-state battery capacitor includes a positive electrode, a negative electrode, and a solid electrolyte, the solid electrolyte is lithium salt, polyvinylidene fluoride and polyvinyl acetate composite film, the positive and negative electrode active materials are graphite materials, and the negative electrode graphite The base material should be pre-lithiated.

The mass ratio of polyvinylidene fluoride to polyvinyl acetate is adjustable between 0.5:9.5-9.5:0.5.

The lithium salt is lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium bisoxalate borate (LiBOB), difluorooxalic acid Lithium borate (LiDFOB), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bisfluorosulfonylimide (LiFSI), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), hexafluoroantimonic acid One or more of lithium (LiSbF ₆ ) and lithium tris(pentafluoroethyl)trifluorophosphate (LiFAP).

The lithium content of the negative electrode graphite material is 100-150 mAh/g.

The positive and negative active materials are graphite materials, and the graphite materials are one or more of natural graphite, artificial graphite, graphitized mesocarbon microspheres, graphitized carbon fibers, and soft carbon.

The method for forming the composite film is as follows: dissolving lithium salt, polyvinylidene fluoride and polyvinyl acetate in a solvent according to the mass ratio to form a solution, and applying the solution to the polytetrafluoroethylene plate substrate by scraping Above, the solvent is evaporated at room temperature to form a film with a thickness of 5-100 μm, which is cut into a fixed shape after drying to obtain a composite film containing lithium salt.

The preparation method of the positive and negative pole pieces is as follows: the active material, the conductive agent, and the binder are mixed into a slurry according to a mass ratio of 90:1~5:1~5, the positive electrode is coated on the aluminum foil, and the negative electrode is coated with Put it on copper foil, keep it in a vacuum oven at 120°C for 24 hours, and cut it into a fixed shape.

The binder is one or more of acrylonitrile multi-polymer, polytetrafluoroethylene, polyvinylidene fluoride, hydroxypropylmethylcellulose, sodium carboxymethylcellulose and styrene-butadiene rubber.

The conductive agent is one or more of carbon black, graphite, graphitized carbon fiber, and carbon nanotube.

The present invention adopts the solid electrolyte solid battery capacitor, and the solid electrolyte can form a good solid solution with the positive and negative electrodes during the charging and discharging cycle, and can produce a stable interface effect, effectively avoiding the anion co-embedded into the positive electrode during repeated charging and discharging. The destruction of the solid material interface greatly improves the first charge and discharge efficiency and the Coulomb effect during the cycle, suppresses the increase in impedance caused by the destruction of the electrode interface during the charge and discharge process, and ensures the power performance, and the negative electrode uses pre-lithiated graphite The high-quality electrode can significantly reduce the loss of lithium salt in the solid electrolyte during charging and discharging, greatly improve the cycle life, and reduce the leakage current. In addition, the working voltage of the solid-state battery capacitor can reach 5.35V, which greatly improves the battery life. Energy density, and the use of solid electrolytes, the safety performance is guaranteed.

Detailed ways

Below by embodiment, the present invention will be further described.

Example 1

Dissolve 0.6 polyvinylidene fluoride, 0.4 g polyvinyl acetate powder and a certain mass of lithium salt LiPF ₆ in 25 ml acetone to form a solution, and apply this solution on a polytetrafluoro flat substrate by scraping method, and place it at room temperature The solvent acetone volatilizes to form a film with a thickness of 30 μm, and it is dried in vacuum at 60° C. for 12 hours to completely remove the remaining acetone. Punch into a circular diaphragm with a diameter of 18mm, and set aside.

The active material graphitized mesophase carbon microspheres, the binder acrylonitrile multi-polymer, and the conductive carbon black are fully stirred and mixed into a slurry according to the mass ratio of 90:5:5, and coated on the aluminum foil and copper foil current collectors respectively. After vacuum baking at 120°C for 24 hours, it was punched into circular electrodes with a diameter of 14 mm. Assemble the negative electrode sheet and the solid electrolyte obtained above into a button battery, and use a 0.02C rate current to perform pre-lithiation in a charge-discharge instrument. Assembled into a button-type solid-state battery capacitor, the initial efficiency reached 95.2% at 0.5 C. After 5000 cycles at 2C, the capacity retention rate reached 97%. The Coulombic efficiency during the cycle was ~99.97%. The energy density based on the active material was 120Wh/kg. The power density can reach 3500W/kg, and when ordinary glass fiber separators and 1M LiPF ₆ /EMC+SL (solvent volume ratio 1:4) electrolyte are used, the first reversible capacity of 0.5 C for the first charge and discharge is 95 mAh/g, and the first efficiency After 5000 2C cycles, the capacity retention rate is 63%, and the Coulombic efficiency during the cycle is ~92%.

Example 2

In Example 1, the weights of polyvinylidene fluoride and polyvinyl acetate were changed to 0.4g and 0.6g respectively, and the assembled button battery capacitor was used at 0.5 C. The efficiency reached 92.5% for the first time, and after 5000 cycles at 2C, The capacity retention rate reaches 96.7%, the coulombic efficiency in the cycle process is 99.96%, the energy density based on the active material is 119.6Wh/kg, and the power density can reach 3450W/kg.

Example 3

In Example 1, the weights of polyvinylidene fluoride and polyvinyl acetate were changed to 0.8g and 0.2g respectively, and the assembled button battery capacitor was used at 0.5 C for the first time. The efficiency reached 90.3%, and after 5000 cycles at 2C, The capacity retention rate reaches 93.7%, the coulombic efficiency in the cycle process is 99.93%, the energy density based on the active material is 119.4Wh/kg, and the power density can reach 3425W/kg.

Example 4

In Example 1, the lithium salt was replaced by LiBF ₄ , and the assembled button battery capacitor was used at 0.5 C. The efficiency reached 91.2% for the first time. After 5000 cycles at 2C, the capacity retention rate reached 94.8%, and the Coulombic efficiency during the cycle was 99.91%. Based on the energy density of the active material is 119.5Wh/kg, the power density can reach 3455W/kg.

Example 5

In Example 1, the thickness of the solid electrolyte composite film was changed to 60 μm, and the assembled button battery capacitor was used at 0.5 C. The efficiency reached 89.2% for the first time. After 5000 cycles at 2C, the capacity retention rate reached 87.9%, and the Coulombic efficiency during the cycle 99.6%, the energy density based on the active material is 118.2Wh/kg, and the power density can reach 3058W/kg.

Example 6

In Example 1, the active material is changed into spherical natural graphite, and the assembled button battery capacitor adopts 0.5C for the first time with an efficiency of 88.2%, after 5000 cycles at 2C, the capacity retention rate reaches 85.9%, and the Coulombic efficiency during the cycle is 99.1% %, the energy density based on the active material is 119.2Wh/kg, and the power density can reach 3460W/kg.

Example 7

In Example 1, the binder was changed to N-methylpyrrolidone solution of polyvinylidene fluoride, and the assembled button battery capacitor was used at 0.5 C. The first efficiency reached 92.5%. After 5000 cycles at 2C, the capacity retention rate reached 90.6%, the coulombic efficiency in the cycle process is 99.4%, the energy density based on the active material is 119.7Wh/kg, and the power density can reach 3470W/kg.

Example 8

In Example 1, the lithium salt was replaced with LiTFSI, and the assembled button battery capacitor was used at 0.5 C. The efficiency reached 93.5% for the first time. After 5000 cycles at 2C, the capacity retention rate reached 94.6%, and the coulombic efficiency during the cycle was 99.5%. Based on the energy density of the active material is 119.9Wh/kg, the power density can reach 3480W/kg.

Example 9

In Example 1, the conductive agent was changed to carbon nanotubes, and the assembled button battery capacitor was used at 0.5 C. The efficiency reached 94.7% for the first time. After 5000 cycles at 2C, the capacity retention rate reached 96.8%, and the Coulombic efficiency during the cycle was 99.7%. %, the energy density based on the active material is 120.1Wh/kg, and the power density can reach 3600W/kg.

The above-mentioned embodiments only represent several implementation modes in the present invention, and the description thereof is relatively specific and detailed, but should not be construed as limiting the patent scope of the present invention. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (8)

1. A solid-state battery capacitor, which comprises a positive pole, a negative pole, and a solid electrolyte, is characterized in that the solid electrolyte is a composite film of lithium salt, polyvinylidene fluoride and polyvinyl acetate, and the positive and negative active materials are graphite Among them, the negative electrode graphite material should be pre-lithiated, and the pre-lithium content of the negative electrode graphite material is 100~150 mAh/g. 2. A solid-state battery capacitor according to claim 1, wherein the ratio of polyvinylidene fluoride to polyvinyl acetate is adjustable between 0.5:9.5~9.5:0.5. 3. A solid-state battery capacitor according to claim 1, wherein the lithium salt is lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), tetrafluoroboric acid Lithium (LiBF ₄ ), lithium bisoxalate borate (LiBOB), lithium difluorooxalate borate (LiDFOB), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bisfluorosulfonylimide (LiFSI), One or more of lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium hexafluoroantimonate (LiSbF ₆ ), and lithium tris(pentafluoroethyl)trifluorophosphate (LiFAP). 4. A solid-state battery capacitor according to claim 1, characterized in that: the positive and negative active materials are graphite materials, and the graphite materials are natural graphite, artificial graphite, graphitized mesophase carbon microspheres, graphitized carbon fibers , one or more of soft carbon. 5. A solid-state battery capacitor according to claim 1, characterized in that: the method for forming a composite film is: dissolving lithium salt, polyvinylidene fluoride and polyvinyl acetate in a solvent by mass ratio to form a solution, The solution is coated on the polytetrafluoroethylene flat substrate by the scraping method, and the solvent is evaporated at room temperature to form a film with a thickness of 5-100 μm. After drying, it is cut into a fixed shape to obtain a composite film containing lithium salt. 6. A solid-state battery capacitor according to claim 1, characterized in that: the positive and negative electrodes are made by mixing active materials, conductive agents, and binders in a mass ratio of 90:1~5:1~5 The ratio of the slurry was mixed into a slurry, the positive electrode was coated on the aluminum foil, and the negative electrode was coated on the copper foil, kept in a vacuum oven at 120 °C for 24 h, and cut into a fixed shape. 7. A solid battery capacitor according to claim 6, characterized in that: the binder is polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), hydroxypropyl methylcellulose (HPMC ), sodium carboxymethylcellulose (CMC) and styrene-butadiene rubber (SBR). 8 . A solid battery capacitor according to claim 6 , wherein the conductive agent is one or more of carbon black, graphite, graphitized carbon fiber, and carbon nanotube.