Cyclic ether electrolyte of potassium ion battery as well as preparation method and application of cyclic ether electrolyte
By using a cyclic ether electrolyte composed of bisfluorosulfonimide potassium and tetrahydropyran in potassium ion batteries, the problem of easy damage to the graphite electrode material in potassium ion batteries is solved, and the stable circulation of graphite and the extension of battery life are achieved.
Patent Information
- Application Number
- CN202411671118.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-21
- Publication Date
- 2025-02-28
AI Technical Summary
During the circulation process, the graphite electrode material in potassium ion batteries easily produces volume effects due to the large ion radius of potassium ions, resulting in damage to the graphite electrode structure, powdering, capacity loss and cycle life attenuation.
A potassium ion battery cyclic ether electrolyte solution is provided, including potassium bisfluorosulfonimide (KFSI) and tetrahydropyran (THP) solvents. The concentration of potassium bisfluorosulfonimide is 1-2 mol/L. It is used in potassium ion batteries with graphite as the negative electrode active material. Through its solvation structure, the interface reaction activation energy is reduced and the desolvation process of potassium ions is promoted.
This electrolyte effectively prevents or reduces damage to graphite materials, realizes stable circulation of graphite in potassium ion batteries, extends the cycle life of the battery, and has important application prospects.
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of electrolytes, and in particular relates to a potassium ion battery cyclic ether electrolyte and a preparation method and application thereof. Background Art
[0002] With the continuous development of society and economy, human demand for energy is increasing day by day, but due to human over-reliance on fossil fuels, it has now caused serious environmental crises and excessive resource consumption. Currently, most of the widely used energy systems are traditional non-renewable energy sources. Therefore, in order to reduce a series of environmental problems caused by the use of fossil fuels, today's global energy structure is rapidly turning to a more environmentally friendly clean energy system. Among the many energy storage technologies, electrochemical energy storage technology is the most promising energy storage technology.
[0003] Although lithium-ion batteries are already a relatively mature energy storage system, the uneven distribution of lithium resources and insufficient reserves make the current cost of lithium-ion batteries high and unable to meet the growing demand for large-scale energy storage. As a result, the need to develop alternative energy systems with high energy density, high power density and low cost has become increasingly urgent. Since potassium is low in cost and abundant in reserves, and potassium ions have smaller solvation energy, the Stokes radius formed in the electrolyte is smaller than that of lithium ions, and it has better diffusion kinetics and good development prospects. Graphite is the most promising negative electrode material for potassium ion batteries due to its low cost and low pollution. However, the electrode materials of potassium ion batteries are prone to volume effects during the cycle due to the large ionic radius of potassium ions, which will lead to damage and pulverization of the graphite electrode structure, capacity loss and cycle life decay. Therefore, the main challenge in the current development of potassium ion batteries is the lack of electrolytes with good compatibility with graphite electrode materials to maintain the stable cycle of graphite materials. Summary of the invention
[0004] In view of this, the object of the present invention is to provide a potassium ion battery cyclic ether electrolyte and a preparation method and application thereof. When the electrolyte is used in a potassium ion battery using graphite as a negative electrode active material, it can effectively prevent or reduce damage to the graphite material, achieve stable circulation of graphite in the potassium ion battery, and extend the cycle life of the battery.
[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:
[0006] Provided is a potassium ion battery cyclic ether electrolyte, comprising potassium bisfluorosulfonyl imide (KFSI) and tetrahydropyran (THP) solvent; wherein the concentration of the potassium bisfluorosulfonyl imide is 1-2 mol / L.
[0007] According to the above scheme, the concentration of potassium bis(fluorosulfonyl)imide is 1.5-2 mol / L.
[0008] According to the above scheme, the potassium ion battery uses graphite as the negative electrode active material.
[0009] A method for preparing the above-mentioned potassium ion battery cyclic ether electrolyte is provided, comprising the following steps:
[0010] Potassium bis(fluorosulfonyl)imide is mixed with tetrahydropyran, and the potassium bis(fluorosulfonyl)imide is completely dissolved to obtain a cyclic ether electrolyte for a potassium ion battery.
[0011] Provided is an application of the potassium ion battery cyclic ether electrolyte in a potassium ion battery, wherein the potassium ion battery uses graphite as a negative electrode active material.
[0012] Provided is a potassium ion battery, comprising a positive electrode, a negative electrode, an electrolyte and a diaphragm, wherein the negative electrode uses graphite as an active material; and the electrolyte is the above-mentioned potassium ion battery cyclic ether electrolyte.
[0013] According to the above scheme, the negative electrode is prepared by coating a mixture of graphite, a conductive agent and a binder on a negative electrode current collector.
[0014] Preferably, the mass ratio of graphite, conductive agent and binder is 7-9.5:0.25-1.1:0.5-1.1.
[0015] Preferably, the conductive agent is one or more of conductive carbon black, carbon nanotubes, graphene oxide, acetylene black, and graphite.
[0016] Preferably, the negative electrode current collector is copper foil.
[0017] Preferably, the binder is one or more of polyvinylidene fluoride, polyvinyl alcohol and polytetrafluoroethylene.
[0018] The beneficial effects of the present invention are as follows:
[0019] 1. The present invention provides a potassium ion battery cyclic ether electrolyte, which uses potassium bis(fluorosulfonyl)imide as potassium salt and tetrahydropyran as solvent, and has a wider electrochemical window; when used in a potassium ion battery using graphite as a negative electrode active material, the solvation structure enables it to have a lower interfacial reaction activation energy, which promotes the desolvation process of potassium ions, and the generated solid electrolyte interface film (SEI) in which most of the S exists in an inorganic state makes the SEI thinner and stronger, more conducive to ion transmission, and can effectively prevent or reduce the damage of the graphite material, so that the battery exhibits a longer cycle life, and has important application prospects.
[0020] 2. The present invention realizes the stable circulation of graphite in potassium ion batteries using graphite as negative electrode active material through an electrolyte with simple components, promotes the development of potassium ion batteries, and has important industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is the infrared spectrum of 2M KFSI in THP described in Example 1 of the present invention.
[0022] Figure 2 The potassium ion battery assembled with 2M KFSI in THP and graphite at 0.2C (55.8mA g -1 ) Cycling performance diagram under different current densities.
[0023] Figure 3 The potassium ion battery assembled with 2M KFSI in THP and graphite at 0.2C (55.8mA g -1 )Charge and discharge curves under current density.
[0024] Figure 4 The potassium ion battery assembled with 2M KFSI in THP and graphite at 0.2C (55.8mA g -1 ) SEM image of the graphite electrode surface after cycling at different current densities.
[0025] Figure 5 The potassium ion battery assembled with 2M KFSI in THP and graphite at 0.2C (55.8 mA g -1 ) HRTEM image of the graphite electrode after cycling at 2 current density.
[0026] Figure 6 The potassium ion battery assembled with 2M KFSI in THP and graphite at 0.2C (55.8 mA g -1 ) XPS S2p etching spectra of the graphite electrode after cycling at different current densities (ac); (d) activation energy of potassium ion desolvation; (e) activation energy of charge transfer. DETAILED DESCRIPTION
[0027] In order to better understand the present invention, the content of the present invention is further explained below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.
[0028] Embodiment 1:
[0029] This embodiment provides a method for preparing a 2M KFSI in THP electrolyte, comprising the following steps:
[0030] In a glove box with an argon atmosphere, 21.923 g of potassium bis(fluorosulfonyl)imide (KFSI) was added to a 50 mL volumetric flask and then 49 mL of tetrahydropyran (THP) was added. After complete dissolution, THP was added to 50 mL to prepare a 2M KFSI in THP electrolyte.
[0031] The obtained electrolyte was characterized by spectroscopy. Figure 1 , 2 Spectrum shown.
[0032] Figure 1 This is the infrared spectrum (IR) of the 2M KFSI in THP electrolyte described in Example 1; the figure shows that after being prepared as an electrolyte, the spectrum has only a small offset change, indicating that the solvation ability of THP is very weak, and the solvation coordination of potassium ions involved in the solvation is relatively small.
[0033] The 2M KFSI in THP in Example 1 was used as the electrolyte, the graphite pole piece (graphite: conductive carbon black: binder polyvinylidene fluoride PVDF = 8:1:1 was mixed and coated on copper foil and cut into a circular pole piece with a diameter of 10 mm) was used as the working electrode, potassium metal was used as the counter electrode, and GF / D glass fiber was used as the separator. A CR2016 stainless steel battery housing was used to assemble a potassium ion button half-cell in an argon atmosphere glove box. The half-cell was tested and the following results were obtained: Figure 2 , 3 The result graph is shown.
[0034] Figure 2 The 2M KFSI in THP electrolyte described in Example 1 was used to assemble the graphite material into a battery at 0.2C (55.8 mAg -1 ) Cyclic performance diagram at current density. It can be seen that the Coulomb efficiency quickly rises to 100%, and the specific capacity remains at 174.1 mAh g after 800 cycles. -1 Compared with the cycle stable specific capacity, its capacity retention rate is 76.99%, which has good cycle stability and capacity retention rate.
[0035] Figure 3 The 2M KFSI in THP electrolyte described in Example 1 was used to assemble the graphite material into a battery at 0.2C (55.8 mAg -1 ) The charge-discharge curves at different current densities. It can be seen that the discharge curve has three distinct stages corresponding to different degrees of potassiumization of graphite, and there is no solvent co-embedding platform near 0.9V, which reduces the damage to the graphite structure caused by the insertion and extraction of solvated potassium ions, and is conducive to reducing the damage to the graphite structure.
[0036] The 2M KFSI in THP in Example 1 was used as the electrolyte, the graphite pole piece (graphite: conductive carbon black: binder = 8:1:1 mixed and coated on copper foil to form a circular pole piece with a diameter of 10 mm) was used as the working electrode, potassium metal was used as the counter electrode, and GF / D glass fiber was used as the diaphragm. The potassium ion button half-cell was assembled in an argon atmosphere glove box using a CR2016 stainless steel battery housing. After the battery cycle was completed, it was disassembled to obtain the graphite pole piece and the residual electrolyte salt on the surface was cleaned and photographed. Figure 4-6 The result graph is shown.
[0037] Figure 4 The 2M KFSI in THP electrolyte described in Example 1 was used to assemble the graphite material into a battery at 0.2C (55.8 mAg -1 ) scanning electron microscope (SEM) image after cycling at 100 % current density. It can be seen that the graphite still maintains its good layered structure after cycling and there is no trace of corrosion on the graphite surface, indicating that the electrolyte is highly compatible with the graphite material and can effectively reduce the damage to the graphite structure.
[0038] Figure 5 The 2M KFSI in THP electrolyte described in Example 1 was used to assemble the graphite material into a battery at 0.2C (55.8 mAg -1 ) after cycling at a current density of 1.3 GHz. It can be seen that the surface of the graphite after cycling is covered with a uniform SEI film, which is conducive to the stable insertion and extraction of potassium ions by graphite, thereby improving the cycling stability of graphite.
[0039] Figure 6 The 2M KFSI in THP electrolyte described in Example 1 was used to assemble the graphite material into a battery at 0.2C (55.8 mAg -1 ) XPS S2p etching spectrum of the graphite electrode after cycling at 2 current density, as well as the desolvation energy and charge transfer activation energy.
[0040] like Figure 6 As shown, the source of S in the electrolyte is KFSI, where the O=S=O group comes from FSI -Decomposition, it can be seen in the figure that the SEI film induced by 2M KFSI in THP electrolyte has a low proportion of O=S=O groups after etching for 30s, indicating that most of S exists in an inorganic state. In contrast, the proportion of O=S=O in 2M KFSI in THF and 2M KFSI in DME is still high after etching for 30s, indicating that most of S exists in an organic state in the two comparative electrolytes. The solvents of the two comparative electrolytes, THF, are cyclic ethers and DME, are chain ethers, indicating that making most of the S in the SEI in an inorganic state promotes the density and firmness of the SEI, which is not an effect that all electrolytes can achieve. The activation energy data E obtained by fitting the variable temperature EIS test a,THP (167.87 kJmol-1) <E a,THF (176.69 kJ mol-1) <E a,DME (286.78 kJ mol-1) indicates that 2M KFSI in THP electrolyte can provide the lowest interfacial reaction activation energy in the entire interfacial reaction, thus ensuring its cycle life. a,SEI,DME (89.21 kJ mol-1)>E a,SEI,THF (45.75 kJ mol-1)>E a,SEI,THP (29.86 kJ mol-1) is the lowest, which is also the reason why 2M KFSI in THP can not be co-intercalated into graphite.
[0041] The above test results show that the 2M KFSI in THP electrolyte described in this embodiment can significantly reduce the damage to the graphite structure and is a potential electrolyte particularly suitable for graphite materials.
[0042] Comparative Example 1:
[0043] A method for preparing a 2M KFSI in THF electrolyte is provided, comprising the following steps:
[0044] In a glove box with an argon atmosphere, 21.923 g of potassium bis(fluorosulfonyl)imide (KFSI) was added to a 50 mL volumetric flask and then 49 mL of tetrahydrofuran (THF) was added. After complete dissolution, THP was added to 50 mL to prepare a 2 M KFSI in THF electrolyte.
[0045] The 2M KFSI in THF obtained in Comparative Example 1 was used as the electrolyte, and the button-type half-cell was assembled according to the method in Example 1 for electrochemical performance testing. The results are as follows: -1 ) current density, the battery failed after 175 cycles due to overcharge, and the remaining specific capacity was 193.4 mAh g -1(The remaining specific capacity of the 2M KFSI in THP electrolyte of Example 1 with the corresponding number of cycles is 210 mAh g -1 ).
[0046] Comparative Example 2:
[0047] A method for preparing a 2M KFSI in DME electrolyte is provided, comprising the following steps:
[0048] In a glove box with an argon atmosphere, 21.923 g of potassium bis(fluorosulfonyl)imide (KFSI) was added to a 50 mL volumetric flask and then 49 mL of ethylene glycol dimethyl ether (DME) was added. After complete dissolution, DME was added to 50 mL to prepare a 2M KFSI in DME electrolyte.
[0049] The 2M KFSI in DME obtained in Comparative Example 2 was used as the electrolyte, and the button-type half-cell was assembled according to the method in Example 1 for electrochemical performance testing. The results are as follows: -1 ) current density, the battery failed after 30 cycles and the specific capacity was only 97.6 mAh g -1 .
[0050] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.
Claims
1. A potassium ion battery cyclic ether electrolyte, characterized in that The method comprises potassium bis(fluorosulfonyl)imide and solvent tetrahydropyran, wherein the concentration of the potassium bis(fluorosulfonyl)imide is 1-2 mol / L.
2. The potassium ion battery cyclic ether electrolyte according to claim 1, characterized in that The concentration of potassium bis(fluorosulfonyl)imide is 1.5-2 mol / L.
3. A method for preparing a potassium ion battery cyclic ether electrolyte according to any one of claims 1 to 2, characterized in that: The following steps are involved: Potassium bis(fluorosulfonyl)imide is mixed with tetrahydropyran, and the potassium bis(fluorosulfonyl)imide is completely dissolved to obtain a cyclic ether electrolyte for a potassium ion battery.
4. Use of the potassium ion battery cyclic ether electrolyte according to any one of claims 1 to 2 in a potassium ion battery, characterized in that: The potassium ion battery uses graphite as the negative electrode active material.
5. A potassium ion battery comprising a positive electrode, a negative electrode, an electrolyte and a separator, characterized in that: The negative electrode uses graphite as an active material; the electrolyte is the potassium ion battery cyclic ether electrolyte according to any one of claims 1-2.
6. The potassium ion battery according to claim 5, characterized in that The negative electrode is prepared by coating a mixture of graphite, a conductive agent and a binder on a negative electrode current collector.
7. The potassium ion battery according to claim 6, characterized in that The mass ratio of graphite, conductive agent and binder is 7-9.5:0.25-1.1:0.5-1.
1.
8. The potassium ion battery according to claim 6, wherein the conductive agent is one or more of conductive carbon black, carbon nanotubes, graphene oxide, acetylene black, and graphite.
9. The potassium ion battery according to claim 6, wherein the negative electrode current collector is copper foil.
10. The potassium ion battery according to claim 6, wherein the binder is one or more of polyvinylidene fluoride, polyvinyl alcohol, and polytetrafluoroethylene.