A method for preparing a magnesium-based battery
By using conventional raw materials and an improved electrolyte formulation, combined with an octahedral cathode material, the problems of complex and costly magnesium-ion battery electrolyte manufacturing have been solved, achieving high-capacity and stable magnesium-based battery performance, suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHONGQING INST OF NEW ENE STOR MATER & EQUIP
- Filing Date
- 2023-12-22
- Publication Date
- 2026-06-12
Smart Images
Figure CN117936915B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of secondary batteries, and particularly to a preparation method of a magnesium-based battery. Background Art
[0002] With the continuous increase in energy demand, people have begun to seek energy storage technologies with higher specific capacities and greater safety and reliability. Among them, magnesium-ion batteries are one of them. However, there are still many problems with magnesium-ion batteries that hinder their practical applications. For example, the ion migration in magnesium-ion batteries is relatively slow, there is no suitable commercial magnesium-ion electrolyte, and the use of cathode materials is limited.
[0003] Currently, the more common cathode materials for magnesium-ion batteries include Chevrel phase Mo6S8 and Prussian blue analogs. Chevrel phase Mo6S8 can form a battery with APC electrolyte and magnesium metal. The discharge specific capacity of this battery can reach up to 120 mAhg -1 or so, and it has good cycling performance. However, it has problems such as low working voltage and low energy density, and the synthesis difficulty is high and the yield is low. Therefore, it cannot be commercially applied at present. Prussian blue analogs have a rigid open structure, and have advantages such as a high voltage platform, simple and convenient synthesis, and low cost. Therefore, they have received extensive attention in practical applications.
[0004] Generally, the chemical formula of Prussian blue analogs is A x M y [Fe(CN)6] z , where A is any one of Na, K, Mg, and Ca, M is selected from any one of transition metals, 0 ≤ x ≤ 2, 0 < y < 2, 0 < z < 1. However, compared with lithium and sodium ions, the diffusion energy barrier of magnesium ions is higher. Directly using existing Prussian blue analogs as cathode materials has the problem of low battery capacity, and the solvation of magnesium ions is serious, and it is also difficult to find a suitable electrolyte to match it.
[0005] For example, a magnesium-based battery cathode material and a high-voltage magnesium-based battery disclosed in the prior art with the publication number CN115133019A. The chemical formula of the magnesium-based battery cathode material is A x Mn y M 1-y [Fe(CN)6]z·nH2O; where A is any one of Na, K, Mg, and Ca, M is selected from any one of transition metals, 0 ≤ x ≤ 2, 0 < y < 1, 0 < z < 1, 0 ≤ n < 4. Its electrolyte uses an organic borate complex salt or an inorganic borate salt, and the working voltage can reach 3V, and the discharge specific capacity is large, reaching 117 mAhg -1 ; and it has good cycling performance, at 100 mAg -1At the specified current density, the specific capacity can still be maintained at over 50% after 100 cycles. However, the electrolytes in the aforementioned existing technologies are expensive and difficult to obtain, and the manufacturing process is quite complicated, requiring at least 15 hours. It also has extremely high requirements for the purity of the organic salts and the preparation environment, making it difficult to produce. Summary of the Invention
[0006] The present invention aims to provide a method for preparing magnesium-based batteries, so as to solve the technical problem of complex electrolyte manufacturing processes in existing magnesium-based batteries.
[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a magnesium-based battery, comprising the following steps:
[0008] Step 1: Preparation of the positive electrode sheet: The positive electrode material is ground and mixed with a binder and conductive agent, then added to a solvent and stirred to form a positive electrode material slurry. The positive electrode slurry is then coated onto the positive electrode current collector, dried, and cut to form the positive electrode sheet for later use.
[0009] Step 2: Prepare the electrolyte: Add magnesium chloride, aluminum chloride, magnesium bis(trifluoromethanesulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide to an organic solvent and stir for 2-3 hours until homogeneous before use.
[0010] Step 3: Prepare the negative electrode sheet: polish the negative electrode material until smooth, clean it, and dry it for later use;
[0011] Step 4: Assembly: Assemble the positive electrode, electrolyte and negative electrode obtained in the above steps with the battery case and separator to obtain a magnesium-based battery.
[0012] The principles and advantages of this scheme are:
[0013] The electrolyte preparation process in this invention is simple and has low environmental requirements. Different amounts of sodium salt are added to the magnesium ion-containing chlorine electrolyte, and the two salt electrolytes of different concentrations can be obtained by direct mixing. It can also be easily prepared in general experimental environments.
[0014] Existing technologies using organoboronate complex salts require high purity raw materials and necessitate secondary preparation. This secondary preparation demands stringent environmental conditions, with moisture and oxygen levels strictly controlled below 0.01 ppm, and requires highly skilled operators, making successful preparation difficult. Furthermore, the raw materials for preparing organoboronate complex salts are scarce and expensive, limiting their industrial-scale production prospects. In contrast, this invention uses lower-cost metal salts and conventional solvents as the electrolyte, with widely available and readily accessible raw materials, thus demonstrating greater potential for industrial production and commercial application.
[0015] Meanwhile, the present invention creatively adds sodium bis(trifluoromethanesulfonyl)imide to the electrolyte, which broadens the electrochemical stability window and improves the cycle stability of the battery.
[0016] Preferably, as an improvement, the structural formula of the positive electrode material in Step 1 is A X My[Fe(CN)5NO)]; wherein, A is any one of Na, K, Mg, and Ca, M is one or more transition metal elements, 0 < x < 2, 0 < y < 2; the transition metal salt is one or more of manganese salt, zinc salt, cobalt salt, and nickel salt; the positive electrode material has an octahedral morphology, and the particle size of the positive electrode material is 2 - 3 μm.
[0017] In this application, the positive electrode material is doped with multiple transition metals, and part of C≡N in the N=O substitution structure synthesized by sodium nitroprusside is replaced, so as to achieve the purpose of reducing the diffusion energy barrier of magnesium ions in the structure and improving the battery capacity. Among them, replacing part of C≡N in the structure with N=O can reduce the impedance of magnesium ion transfer, promote the diffusion of magnesium ions, and has a smaller structural water after substitution, thereby improving the cycle stability. The octahedral morphology and larger particle size can bring a more stable structure to the positive electrode material and improve the stability of the material.
[0018] Preferably, as an improvement, the conductive agent in Step 1 is any one of acetylene black and Ketjen black; the binder is PVDF (polyvinylidene fluoride) or PTEF (polytetrafluoroethylene); the solvent is N-methylpyrrolidone.
[0019] In this application, the binder and conductive agent used are both materials commonly used, and the raw materials are widely available, which is suitable for laboratory and industrial large-scale production.
[0020] Preferably, as an improvement, the mass ratio of the positive electrode material: binder: conductive agent in Step 1 is 6 - 8:1 - 3:1 - 3.
[0021] In this application, controlling the mass ratio of the positive electrode material, binder, and conductive agent can obtain a positive electrode sheet with stable quality. If the content of the conductive agent is too high, it is easy to cause excessive discharge performance of the positive electrode sheet, mismatch with the negative electrode material, and reduce the battery performance. If the content of the binder is too high, the positive electrode sheet cannot be used normally.
[0022] Preferably, as an improvement, the molar ratio of the addition amounts of magnesium chloride, aluminum chloride, magnesium bis(trifluoromethanesulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide is 2:1:1:1 - 3.
[0023] In this application, magnesium chloride, aluminum chloride, and magnesium bis(trifluoromethanesulfonyl)imide are used as conventional electrolytes, and their ratio is relatively stable. However, after adding sodium bis(trifluoromethanesulfonyl)imide, the amount of sodium bis(trifluoromethanesulfonyl)imide added needs to be limited to ensure that the electrolyte can function properly. If the amount of sodium bis(trifluoromethanesulfonyl)imide added is too high, it cannot dissolve, and the electrolyte cannot function properly; if the content is too low, the specific capacity of the prepared magnesium-based battery will be low.
[0024] Preferably, as an improvement, the organic solvent in step two includes any one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, or triethylene glycol dimethyl ether.
[0025] In this application, magnesium chloride, aluminum chloride, and other materials have low solubility, and the addition of organic solvents can ensure that the raw materials are fully dissolved and mixed. Furthermore, the aforementioned solvents are all conventional solvents, resulting in low production costs.
[0026] Preferably, as an improvement, the negative electrode material in step three includes magnesium foil; the thickness of the magnesium foil is greater than or equal to 0.1 mm.
[0027] In this application, since the obtained electrolyte is corrosive, it will have a certain corrosive effect on the negative electrode under high voltage, which will easily cause soft short circuit during cycling, thus causing negative electrode perforation. Therefore, it is necessary to select magnesium foil with a thickness of 0.1 mm or more to avoid the occurrence of perforation. Attached Figure Description
[0028] Figure 1 This is a charge-discharge curve diagram of Embodiment 1 of the present invention;
[0029] Figure 2 This is a cyclic voltammetry curve of Embodiment 1 of the present invention;
[0030] Figure 3 This is a cyclic curve diagram of Embodiment 1 of the present invention. Detailed Implementation
[0031] The following detailed description illustrates the specific implementation method:
[0032] Example 1
[0033] A method for preparing a magnesium-based battery includes the following steps:
[0034] Step 1: Preparation of the positive electrode sheet: The above-mentioned positive electrode material, binder, and conductive agent are mixed in a mass ratio of 7:2:1 and added to NMP (N-methylpyrrolidone). The mixture is stirred for 12 hours to obtain a positive electrode material slurry. The obtained positive electrode material slurry is coated onto molybdenum foil and placed in a vacuum oven to dry at 80°C for 12 hours. Finally, it is cut into 10mm diameter circular pieces as positive electrode sheets and stored in a glove box for later use. The conductive agent can be acetylene black or Ketjen black; the binder can be PVDF (polyvinylidene fluoride) or PTEF (polytetrafluoroethylene). N-methylpyrrolidone is used as the organic solvent, and 1mg of binder is added to 20µL of N-methylpyrrolidone.
[0035] In this embodiment, the structural formula of the positive electrode material is Na. 1.7 Zn 0.36 Mn 0.15 Fe 0.724 [Fe 0.276 [CN)5NO], its microstructure is octahedral; its specific preparation method includes the following steps:
[0036] S1: Add the transition metal salt and chelating agent to deionized water one after another, and stir until homogeneous to obtain solution A;
[0037] Specifically, weigh 2 mmol (0.272 g) of zinc chloride and 2 mmol (0.252 g) of manganese chloride, pour them into 80 ml and 20 ml of deionized water respectively and stir. Then add 3.2 g and 0.8 g of sodium citrate respectively and stir for 3 hours to obtain solution A1 and solution A2.
[0038] S2: Add sodium nitroprusside, PVP and ascorbic acid to deionized water and stir until homogeneous to obtain solution B;
[0039] Specifically, 3 mmol (0.789 g) of sodium nitroprusside, 2 g of PVP (polyvinylpyrrolidone), and 2.48 g of ascorbic acid were weighed and added to 100 ml of deionized water and stirred for 3 hours to obtain solution B.
[0040] S3: Slowly add solution A dropwise to solution B and stir until homogeneous to obtain solution C;
[0041] Specifically, solutions A1 and A2 are added dropwise to solution B at a rate of 5 ml / min while stirring. After the addition is complete, stirring is continued for 5 hours to obtain solution C.
[0042] S4: Heat solution C to a constant temperature, react at a constant temperature, and then cool to obtain a precipitate;
[0043] Specifically, solution C is transferred to a reaction vessel, heated to 110°C, kept at that temperature for 3 hours, and then cooled to obtain a precipitate.
[0044] S5: Wash and dry the precipitate obtained in S4 to obtain the cathode material.
[0045] Specifically, the obtained precipitate is repeatedly washed with deionized water and ethanol, and then placed in a vacuum oven and dried at 60°C for 12 hours to obtain the positive electrode material.
[0046] Step 2: Preparation of electrolyte: Add 0.8 mmol magnesium chloride, 0.4 mmol aluminum chloride, 0.4 mmol magnesium bis(trifluoromethanesulfonyl)imide and 0.8 mmol sodium bis(trifluoromethanesulfonyl)imide to 2 ml of DME (ethylene glycol dimethyl ether) and stir for 2-3 hours to prepare the electrolyte.
[0047] Step 3: Preparation of the negative electrode sheet. A 0.1mm thick, 11mm diameter magnesium foil disc is polished using 1200 grit molybdenum sandpaper until it is smooth and free of scratches. It is then ultrasonically cleaned in anhydrous ethanol. Next, it is dried in a vacuum oven at 60℃ for 12 hours. Finally, it is transferred to a glove box for later use.
[0048] Step 4: Preparation of the magnesium-based battery: Using a molded battery casing, the separator, the positive electrode, the negative electrode prepared by the above method, and the electrolyte are assembled in a conventional manner to obtain the magnesium-based battery, which is then subjected to performance testing. The performance test results are as follows: Figure 2-3 As shown, the operating voltage can reach 3.25V, at 50mAg -1 The actual discharge specific capacity can reach 126mAhg. -1 It also exhibits good cycle stability at 100 mAg. -1 After 60 cycles, the specific capacity can still be maintained above 85%.
[0049] Example 2
[0050] The difference between this embodiment and Example 1 lies in the content of the electrolyte components. Specifically, the amount of sodium bis(trifluoromethanesulfonyl)imide added is 0.4 mmol.
[0051] Example 3
[0052] The difference between this embodiment and Example 1 lies in the content of the electrolyte components. Specifically, the amount of sodium bis(trifluoromethanesulfonyl)imide added is 1.2 mmol.
[0053] Comparative Example 1
[0054] The difference between this comparative example and Example 1 is the composition of the electrolyte. Specifically, the electrolyte does not contain aluminum chloride.
[0055] Comparative Example 2
[0056] The difference between this comparative example and Example 1 lies in the composition of the electrolyte. Specifically, sodium bis(trifluoromethanesulfonyl)imide was not added to the electrolyte.
[0057] Comparative Example 3
[0058] The difference between this comparative example and Example 1 lies in the composition of the electrolyte. Specifically, magnesium bis(trifluoromethanesulfonyl)imide was not added to the electrolyte.
[0059] The experimental data for the examples and comparative examples are recorded in Table 1 below. The specific capacity test used a current density of 50 mAg. -1 .
[0060]
[0061] Analysis of experimental results:
[0062] The highest specific capacity of the magnesium-based battery in the embodiments of this invention is 50 mAg. -1 It can reach 120mAh g at the current density. -1 Furthermore, even after more than 60 cycles, the specific capacity can still be maintained at over 84%, indicating relatively high battery stability and specific capacity.
[0063] In Comparative Example 1, since aluminum chloride was not added to the electrolyte, a multi-ion electrolyte could not be formed, and the prepared magnesium-based battery could not achieve a performance of 50 mAg. -1 The maximum specific capacity at the current density is only 20 mAh g. -1 Furthermore, after 10 cycles, the specific capacitance had decreased to 50%.
[0064] In Comparative Example 2, sodium bis(trifluoromethanesulfonyl)imide was not added to the electrolyte, and like in Comparative Example 1, a multi-ion electrolyte could not be formed. The prepared magnesium-based battery achieved a performance of 50 mAg. -1 The maximum specific capacity at the current density is only 79 mAh g. -1 Furthermore, after 15 cycles, the specific capacitance had decreased to 65%.
[0065] In Comparative Example 3, the electrolyte did not contain magnesium bis(trifluoromethanesulfonyl)imide. Although a multi-ion electrolyte could be formed, its performance was significantly reduced, and the prepared magnesium-based battery achieved a performance of 50 mAg. -1 The maximum specific capacity at the current density is only 100 mAh g. -1 Furthermore, after 40 cycles, the specific capacitance had decreased to 70%.
[0066] As can be seen from the above embodiments and comparative examples, the four components in the electrolyte configuration of this application have a synergistic effect, and none of them can be omitted in magnesium-ion batteries. Any change in any component will lead to a decrease in battery performance.
[0067] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.
Claims
1. A method for preparing a magnesium-based battery, characterized in that: Includes the following steps: Step 1: Preparation of positive electrode sheet: Grind the positive electrode material and mix it with binder and conductive agent. Add the mixture to a solvent and stir to make a positive electrode material slurry. Then, apply the positive electrode slurry to the positive electrode current collector, dry and cut it to make a positive electrode sheet for later use. The positive electrode material has a structure formula A X M y [Fe(CN)5NO]; wherein A is any one of Na, K, Mg, and Ca, M is one or more transition metal elements, 0 < x < 2, 0 < y < 2; the transition metal element is one or more of manganese, zinc, cobalt, and nickel; the positive electrode material has a cubic octahedral morphology, and the particle size of the positive electrode material is 2-3 microns. Step 2: Prepare the electrolyte: Add magnesium chloride, aluminum chloride, magnesium bis(trifluoromethanesulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide to an organic solvent and stir for 2-3 hours until homogeneous. The molar ratio of magnesium chloride to aluminum chloride, magnesium bis(trifluoromethanesulfonyl)imide, and sodium bis(trifluoromethanesulfonyl)imide is 2:1:1:1-3. Step 3: Prepare the negative electrode sheet: polish the negative electrode material until smooth, clean it, and dry it for later use; Step 4: Assembly: Assemble the positive electrode, electrolyte and negative electrode obtained in the above steps with the battery case and separator to obtain a magnesium-based battery.
2. The method for preparing a magnesium-based battery according to claim 1, characterized in that: In step one, the conductive agent is either acetylene black or Ketjen black; the binder is polyvinylidene fluoride or polytetrafluoroethylene; and the solvent is N-methylpyrrolidone.
3. The method for preparing a magnesium-based battery according to claim 2, characterized in that: In step one, the mass ratio of positive electrode material: binder: conductive agent is 6-8:1-3:1-3.
4. The method for preparing a magnesium-based battery according to claim 3, characterized in that: The organic solvent in step two includes any one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, or triethylene glycol dimethyl ether.
5. The method for preparing a magnesium-based battery according to claim 4, characterized in that: The negative electrode material in step three includes magnesium foil; the thickness of the magnesium foil is greater than or equal to 0.1 mm.