Symmetrical potassium ion battery and preparation method thereof

Abstract

The invention relates to the technical field of new energy storage devices, and provides a symmetric potassium ion battery and a preparation method thereof. The symmetric potassium ion battery provided by the invention comprises a positive pole piece, a negative pole piece, a diaphragm and an electrolyte, the positive pole piece and the negative pole piece both take the same potassium-based Prussian blue compound as an active material, and the potassium-based Prussian blue compound has two or more potassium-intercalation and de-intercalation voltage platforms. The voltage difference value between the highest voltage platform and the lowest voltage platform is greater than 0.5 V; the general formula of the potassium-based Prussian blue compound is KxM1 [M2 (CN) 6], M1 and M2 are respectively and independently one of Fe, Co, Mn, Cu, Zn, Zr and V, and x is more than or equal to 0.5 and less than or equal to 1.5. The electrode pole piece prepared from the potassium-based Prussian blue compound adopting the multi-deintercalation potassium platform can be used as a positive electrode and a negative electrode at the same time, and the prepared symmetrical potassium ion battery can improve the battery cell manufacturing efficiency and has power charge and discharge performance at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy storage devices, and more specifically, to a symmetrical potassium ion battery and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are widely used in portable electronic devices and electric vehicles due to their long service life and high energy density. However, due to the scarcity of lithium resources and uneven geographical distribution, the price of lithium has steadily increased, limiting its sustainable application in the future. Potassium-ion batteries have a similar working principle to lithium-ion batteries and are called "rocking chair batteries." Potassium-ion batteries are considered to be the next generation of battery technology that can replace lithium-ion batteries because potassium has the advantages of abundant earth resources, low cost, eco-friendliness and high energy density.

[0003] At present, potassium ion batteries usually use different positive and negative electrode materials, and use the potential difference between the positive and negative electrodes to form voltage. Potassium-based Prussian blue materials have a perovskite structure, a three-dimensional network skeleton, and large interstitial sites that are conducive to the rapid deintercalation of potassium ions. They have the advantages of large ion channels, high theoretical capacity, simple preparation, and low cost. They are regarded as ideal positive electrode materials for potassium ion batteries. Conventional potassium ion battery negative electrodes are carbon materials such as graphite, carbon nanotubes, activated carbon, and graphene. On the one hand, due to the low potential of the negative electrode, potassium precipitation problems will be encountered during high-rate charging, resulting in limited power performance; on the other hand, the positive and negative electrode sheets need to be prepared separately during the battery manufacturing process, and different coating surface densities are designed. During the assembly process, they also need to be assembled in the order of "negative electrode-diaphragm-positive electrode-diaphragm", which affects the manufacturing efficiency.

[0004] Symmetrical batteries are constructed with the same positive and negative electrode materials, which reduces manufacturing costs and simplifies the manufacturing process, and has become a hot topic of research in recent years. Symmetrical batteries can not only significantly simplify the manufacturing process and reduce production costs, but also help reduce the complexity of materials. This consistency helps improve production efficiency and has a positive impact on the recycling and reuse of battery components, thereby reducing the environmental impact of the overall energy storage system. Fully symmetrical batteries can better compensate for each other's volume changes during charging and discharging, so they have better stability and cycle life. Because the cathode and anode have the same chemical properties and reaction kinetics, fully symmetrical batteries can achieve higher power density, thereby improving battery performance.

[0005] The existing technology has designed and developed a potassium-based layered material with "cathode (positive) and anodic (negative) bipolar" properties, and used this material as both the positive and negative electrodes to construct a "symmetric potassium-ion battery". This unique battery assembly method simplifies the preparation process of positive and negative electrode materials while solving problems such as capacity attenuation caused by the mismatch of the physical properties of positive and negative electrode materials, thereby achieving a synergistic improvement in cycle stability and rate performance.

[0006] The existing technology has also developed a new type of NASICON material, and used this material to prepare electrodes to construct a potassium ion symmetric battery. This material has a high degree of lattice reversibility in the process of K+ insertion and extraction, and can produce reversible conversions in the process of depotassium and potassiumization at around 4.0V and below 1.0V. This potassium ion symmetric battery has good cycle stability and initial coulombic efficiency, which provides a good advantage for the development of new energy storage systems in the future.

[0007] However, the research and development of symmetrical batteries is still in its infancy. Developing and designing more potassium-ion symmetrical batteries to improve the production efficiency of potassium-ion batteries, reduce production costs, and improve power performance is still one of the technical difficulties in this field. Summary of the invention

[0008] The primary purpose of the present invention is to overcome the defects and shortcomings of the prior art and provide a symmetrical potassium ion battery.

[0009] Another object of the present invention is to provide a method for preparing the above-mentioned symmetrical potassium ion battery.

[0010] The above-mentioned object of the present invention is achieved by the following technical solutions:

[0011] The present invention protects a symmetrical potassium ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet and the negative electrode sheet both use the same potassium-based Prussian blue compound as an active material, and the potassium-based Prussian blue compound has at least two potassium deintercalation voltage platforms, and the voltage difference between the highest voltage platform and the lowest voltage platform is greater than 0.5V;

[0012] The general formula of the potassium-based Prussian blue compound is K x M1[M2(CN)6], wherein M1 and M2 are each independently at least one of Fe, Co, Mn, Cu, Zn, Zr, V, and 0.5≤x≤1.5.

[0013] The positive and negative electrodes of the symmetrical potassium ion battery of the present invention are made of the same material, so there is no need to distinguish between the positive and negative electrodes, and the battery cell is manufactured in the order of "pole piece-diaphragm-pole piece-diaphragm", which is beneficial to improving the efficiency of battery cell manufacturing. Since the positive and negative electrode materials are the same, the battery cell has the characteristics of short circuit resistance and reverse charging resistance.

[0014] The present invention has found through research that potassium-based Prussian blue compounds capable of preparing symmetrical potassium ion batteries need to have at least two potassium deintercalation voltage platforms, and the voltage difference between the highest voltage platform and the lowest voltage platform is greater than 0.5V. The potassium-based Prussian blue compound K used in the present invention x M1[M2(CN)6] has two or more potassium embedding and de-embedding platforms, and can be used as both the positive and negative electrodes of potassium ion batteries. The electrode running in the high voltage platform segment is the positive electrode, and the electrode running in the low voltage platform segment is the negative electrode. The charging and discharging process is as follows:

[0015] Positive electrode: K x M1[M2(CN)6]-ne - -nK + =K x-n M1[M2(CN)6],

[0016] Negative electrode: K x M1[M2(CN)6]+ne - +nK + =K x+n M1[M2(CN)6], where 0<xn≤x+n≤2.

[0017] Preferably, the potassium-based Prussian blue compound is K 0.8 Mn[Mn(CN)6] or K 1.0 At least one of Fe[Fe(CN)6].

[0018] Preferably, the active material surface loading of the positive electrode sheet or the negative electrode sheet is 15 mg / cm 2 ~500mg / cm 2 .

[0019] Preferably, the positive electrode sheet or the negative electrode sheet further includes a conductive agent and / or an adhesive.

[0020] More preferably, the mass ratio of the potassium-based Prussian blue compound, the conductive agent, and the adhesive is 80-98:1-10:1-10.

[0021] Preferably, the positive electrode sheet or the negative electrode sheet uses at least one of aluminum foil, aluminum mesh or foamed aluminum as a current collector.

[0022] Preferably, the length and width of the positive electrode sheet or the negative electrode sheet are the same size.

[0023] Preferably, the electrolyte is selected from an aqueous solvent system or an organic solvent system; when the battery voltage is less than 1.5 V, the electrolyte is an aqueous solvent system; when the battery voltage is greater than 1.5 V, the electrolyte is an organic solvent system.

[0024] Specifically, the aqueous solvent system includes water and a potassium salt; the organic solvent system includes an organic solvent and a potassium salt, the organic solvent is selected from at least one of esters, ethers, and nitriles; the potassium salt is selected from at least one of potassium hexafluorophosphate, potassium pyrophosphate, potassium phosphate, potassium bis(fluorosulfonyl)imide (KFSI), potassium trifluoromethanesulfonate, potassium perchlorate, potassium bis(trifluoromethanesulfonyl)imide, and potassium tetrafluoroborate.

[0025] Specifically, the esters are selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate; the ethers are selected from at least one of dimethoxyethane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; and the nitriles are selected from at least one of acetonitrile and succinonitrile.

[0026] Preferably, the separator is selected from at least one of PE, PP, cellulose, PI or glass fiber.

[0027] The present invention also protects a method for preparing the above-mentioned symmetrical potassium ion battery, comprising the following steps:

[0028] The potassium-based Prussian blue compound is mixed with a conductive agent and a binder, and then coated on a current collector to obtain an electrode plate;

[0029] The electrode plates are stacked layer by layer, the adjacent electrode tabs are staggered, and an isolation film or isolation plate is used in the middle of each layer for electronic insulation. Then, the battery cells are assembled and packaged by liquid injection to obtain the symmetrical potassium ion battery.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention adopts a potassium-based Prussian blue compound with a multi-potassium intercalation and deintercalation platform as an active material to prepare the positive electrode sheet and the negative electrode sheet of the potassium ion battery. The prepared positive electrode sheet and the negative electrode sheet have the same parameters such as material, formula, surface density, and size. There is no need to distinguish between the positive and negative electrodes, which is beneficial to improving the efficiency of battery cell production. Since the positive and negative electrode materials are the same, the battery cell is resistant to short circuits and reverse charging.

[0032] 2. The potassium ion battery prepared by the present invention has a 10C-20C rate charge and discharge performance, a cell energy density of 10-20Wh / kg, and a power density>1000W / kg. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 K 0.8 Diagram of potassium deintercalation platform of Mn[Mn(CN)6.

[0034] Figure 2This is a charge and discharge curve diagram of the Prussian blue-based symmetrical potassium ion battery prepared in Example 1 of the present invention.

[0035] Figure 3 This is a cycle test diagram of the Prussian blue-based symmetrical potassium ion battery prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] In the present invention, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers in the numerical interval, including the two endpoint integers of the numerical range, and each integer between the two endpoints, is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical range disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0037] In order to more clearly and completely describe the technical solution of the present invention, the present invention is further described in detail through specific embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention. Various changes can be made within the scope of the rights of the present invention.

[0038] Example 1

[0039] A symmetrical potassium ion battery:

[0040] K 0.8 Mn[Mn(CN)6], conductive agent acetylene black and adhesive PVDF were mixed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 90:5:5 and evenly coated on aluminum foil with a coating surface density of 20 mg / cm 2 After drying, the pole piece is obtained by roller pressing and cutting, and the pole piece is vacuum baked at 120℃ for 6h; the battery cell is assembled in a low humidity room in the order of "pole piece-diaphragm-pole piece-diaphragm"; after liquid injection and packaging, a Prussian blue-based symmetrical potassium ion battery is obtained. The diaphragm is a PP-based diaphragm, the electrolyte is a 1 mol / L potassium hexafluorophosphate solution, and the solvent is succinonitrile.

[0041] Potassium-based Prussian blue compound materials were prepared by coprecipitation method. According to the ICP test results, the molecular formula of the synthesized compound was K 0.8 Mn[Mn(CN)6].

[0042] Example 2

[0043] A symmetrical potassium ion battery:

[0044] K 1.0 Fe[Fe(CN)6], conductive agent acetylene black and adhesive PVDF were mixed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 90:5:5 and evenly coated on aluminum foil with a coating surface density of 20 mg / cm 2 After drying, the pole piece is obtained by roller pressing and cutting, and the pole piece is vacuum baked at 120℃ for 6h; the battery cell is assembled in a low humidity room in the order of "pole piece-diaphragm-pole piece-diaphragm"; after liquid injection and packaging, a Prussian blue-based symmetrical potassium ion battery is obtained. The diaphragm is a PP-based diaphragm, the electrolyte is a 1 mol / L potassium hexafluorophosphate solution, and the solvent is succinonitrile.

[0045] Potassium-based Prussian blue compound materials were prepared by coprecipitation method. According to the ICP test results, the molecular formula of the synthesized compound was K 1.0 Fe[Fe(CN)6].

[0046] Example 3

[0047] A symmetrical potassium ion battery:

[0048] K 1.0 Fe[Fe(CN)6], conductive agent acetylene black and adhesive PVDF were mixed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 90:5:5 and uniformly cast on the aluminum mesh with a coating surface density of 500 mg / cm 2 After drying, the pole piece is obtained by roller pressing and cutting, and the pole piece is vacuum baked at 120°C for 6 hours; the battery cell is assembled in a low humidity room in the order of "pole piece-diaphragm-pole piece-diaphragm"; after liquid injection and packaging, a Prussian blue-based symmetrical potassium ion battery is obtained. The diaphragm is a glass fiber-based diaphragm, the electrolyte is a 1 mol / L potassium hexafluorophosphate solution, and the solvent is succinonitrile.

[0049] Potassium-based Prussian blue compound materials were prepared by coprecipitation method. According to the ICP test results, the molecular formula of the synthesized compound was K 1.0 Fe[Fe(CN)6].

[0050] Comparative Example 1

[0051] A symmetrical potassium ion battery:

[0052] K 0.2Mn[Mn(CN)6], conductive agent acetylene black and adhesive PVDF were mixed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 90:5:5 and evenly coated on aluminum foil with a coating surface density of 20 mg / cm 2 After drying, the pole piece is obtained by roller pressing and cutting, and the pole piece is vacuum baked at 120°C for 6 hours; the battery cell is assembled in a low humidity room in the order of "pole piece-diaphragm-pole piece-diaphragm"; after liquid injection and packaging, a Prussian blue-based symmetrical potassium ion battery is obtained. The diaphragm is a PP-based diaphragm, and the electrolyte is a potassium hexafluorophosphate-succinonitrile mixed solution.

[0053] Potassium-based Prussian blue compound materials were prepared by coprecipitation method. According to the ICP test results, the molecular formula of the synthesized compound was K 0.2 Mn[Mn(CN)6].

[0054] Comparative Example 2

[0055] A symmetrical potassium ion battery:

[0056] K 1.8 Mn[Mn(CN)6], conductive agent acetylene black and adhesive PVDF were mixed in N-methylpyrrolidone (NMP) solvent at a mass ratio of 90:5:5 and evenly coated on aluminum foil with a coating surface density of 20 mg / cm 2 After drying, the pole piece is obtained by roller pressing and cutting, and the pole piece is vacuum baked at 120°C for 6 hours; the battery cell is assembled in a low humidity room in the order of "pole piece-diaphragm-pole piece-diaphragm"; after liquid injection and packaging, a Prussian blue-based symmetrical potassium ion battery is obtained. The diaphragm is a PP-based diaphragm, and the electrolyte is a potassium hexafluorophosphate-succinonitrile mixed solution.

[0057] Potassium-based Prussian blue compound materials were prepared by coprecipitation method. According to the ICP test results, the molecular formula of the synthesized compound was K 1.8 Mn[Mn(CN)6].

[0058] Performance Testing

[0059] 1. Experimental setup for electrochemical performance testing:

[0060] (1) Potassium deintercalation platform test:

[0061] The electrode, separator and potassium metal sheet are stacked in sequence, and the electrolyte is dripped in the middle to assemble a half-cell. Before the electrochemical test, it is kept at a constant temperature of 25°C in a dry environment for 12 hours, and then charged and discharged at a current density of 10mA / g. The voltage range is 0~5V.

[0062] like Figure 1The figure shows the potassium deintercalation platform diagram of the Prussian blue-based symmetric potassium ion battery prepared in Example 1. As can be seen from the figure, there are three potassium deintercalation platforms from 0V to 4.8V, and the difference between the highest voltage platform and the lowest voltage platform is 1.2V.

[0063] (2) Cycle test:

[0064] The potassium ion battery prepared in each embodiment and comparative example was charged to the upper limit cut-off voltage at a 1C rate of the designed capacity, and then discharged to the lower limit cut-off voltage at a 5C rate for 100 cycles. Then, it was charged to the upper limit cut-off voltage at a 10C rate, and then discharged to the upper limit cut-off voltage at a 10C rate until the discharge capacity decayed to 80% of the initial capacity.

[0065] (3) Power density test:

[0066] The power density is the maximum discharge power of the battery cell divided by the battery cell mass.

[0067] (4) Battery cell energy density test:

[0068] The energy that can be released when the battery is fully charged divided by the battery mass is the battery energy density.

[0069] 2. Electrochemical performance test results:

[0070] The electrochemical performance parameters of the potassium ion batteries prepared in each embodiment are shown in Table 1. The symmetrical potassium ion batteries prepared in each embodiment have good cell energy density, power density and cycle test performance.

[0071] For comparative example 1, since both the positive and negative electrodes are in a potassium-deficient state, the charge and discharge voltage of the system is 0V, and it cannot be used as a battery; for comparative example 2, since the negative electrode contains too much potassium, both the positive and negative electrodes are in a potassium-rich state, and the charge and discharge voltage of the system is close to 0V, and it cannot be used as a battery.

[0072] Table 1 Performance parameters of potassium ion batteries in various embodiments

[0073] Cell energy density Power Density Cycle test performance Example 1 20Wh / kg 1200W / kg 2000 times>95% Example 2 10Wh / kg 1000W / kg 4000 times>95% Example 3 15Wh / kg 800W / kg 4000 times>95%

[0074] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A symmetrical potassium ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, characterized in that: The positive electrode plate and the negative electrode plate both use the same potassium-based Prussian blue compound as an active material, and the potassium-based Prussian blue compound has two or more potassium deintercalation voltage platforms, and the voltage difference between the highest voltage platform and the lowest voltage platform is greater than 0.5V; The general formula of the potassium-based Prussian blue compound is K x M1[M2(CN)6], wherein M1 and M2 are each independently one of Fe, Co, Mn, Cu, Zn, Zr, V, 0.5≤x≤1.

5.

2. The symmetrical potassium ion battery according to claim 1, characterized in that: The potassium-based Prussian blue compound is K 0.8 Mn[Mn(CN)6] or K 1.0 One of Fe[Fe(CN)6].

3. The symmetrical potassium ion battery according to claim 1, characterized in that: The active material surface loading of the positive electrode sheet or the negative electrode sheet is 15 mg / cm 2 ~500mg / cm 2 .

4. The symmetrical potassium ion battery according to claim 1, characterized in that: The positive electrode sheet or the negative electrode sheet further includes a conductive agent and / or an adhesive.

5. The symmetrical potassium ion battery according to claim 4, characterized in that: The mass ratio of the potassium-based Prussian blue compound, the conductive agent and the adhesive is 80-98:1-10:1-10.

6. The symmetrical potassium ion battery according to claim 1, characterized in that: The positive electrode sheet or the negative electrode sheet uses at least one of aluminum foil, aluminum mesh or foamed aluminum as a current collector.

7. The symmetrical potassium ion battery according to claim 1, characterized in that: The electrolyte is selected from an aqueous solvent system or an organic solvent system.

8. The symmetrical potassium ion battery according to claim 1, characterized in that: The aqueous solvent system comprises water and a potassium salt; and / or, the organic solvent system comprises an organic solvent and a potassium salt.

9. The symmetrical potassium ion battery according to claim 1, characterized in that: The separator is selected from at least one of PE, PP, cellulose, PI or glass fiber.

10. The method for preparing a symmetrical potassium ion battery according to any one of claims 1 to 9, characterized in that: The following steps are involved: The potassium-based Prussian blue compound is mixed with a conductive agent and a binder, and then coated on a current collector to obtain an electrode plate; The electrode plates are stacked layer by layer, the adjacent electrode tabs are staggered, and an isolation film or isolation plate is used in the middle of each layer for electronic insulation. Then, the battery cells are assembled and packaged by liquid injection to obtain the symmetrical potassium ion battery.

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