A nitrogen-containing boron-based double salt electrolyte, a preparation process and application thereof
By introducing a nitrogen-boron-based dual-salt electrolyte into the magnesium battery and utilizing the mixture of Mg(hftab)2 and Mg(B(hfip)2)4, the problem of uneven magnesium ion deposition was solved, achieving high cycle stability and an expanded electrochemical window for the magnesium battery, thus breaking through the performance limitations of traditional magnesium batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHONGQING INST OF NEW ENE STOR MATER & EQUIP
- Filing Date
- 2025-09-15
- Publication Date
- 2026-05-15
AI Technical Summary
In existing magnesium batteries, uneven deposition of magnesium ions leads to instability of the interfacial film, affecting cycle life and electrochemical window. Traditional electrolytes are unable to meet the market demand for high energy density and low cost.
A nitrogen-boron-based double salt electrolyte is used. By mixing Mg(hftab)2 and Mg(B(hfip)2)4 synthesized in-house, a unique N-Mg Lewis acid-base interaction is formed, which regulates the composition of the negative electrode interface film, reduces the magnesium ion desolvation energy barrier, and increases the magnesium ion concentration to 0.6M.
It achieves high cycle stability and capacity retention of magnesium batteries, with a discharge capacity of 90.6% after 1000 cycles. The electrochemical window is expanded, which solves the traditional technical bottleneck of magnesium batteries and promotes their rapid development.
Smart Images
Figure CN121097216B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of new energy magnesium-ion battery technology, specifically to a nitrogen-boron-based dual-salt electrolyte, its preparation process, and its application. Background Technology
[0002] Lithium metal batteries are considered the "holy grail" of future high-energy-density electrochemical systems due to their high energy density and low redox potential. However, the scarcity of lithium resources and the ubiquitous dendrite growth problem limit their development and application. Among many alternative metal anode candidates, deposited magnesium atoms exhibit the lowest diffusion barrier, tending to produce uniform three-dimensional deposition morphologies rather than one-dimensional dendritic metal dendrites. Simultaneously, the chemical process of two-electron transfer offers the possibility of developing energy storage systems with high energy density. Therefore, rechargeable magnesium metal batteries are widely considered one of the safest and most promising next-generation new energy storage systems.
[0003] In magnesium metal batteries, the interfacial passivation of the magnesium metal anode surface leads to poor ion conduction capacity, hindering stable and reversible deposition and stripping processes. Simultaneously, the solvation effect caused by the divalent state of magnesium ions severely impacts the insertion and extraction energy barriers. Researchers typically add Cl--containing components to the electrolyte, such as MgCl2 and AlCl3 in APC electrolytes, utilizing the Cl-'s disruptive effect on the interface to eliminate passivation film formation and improve the solvation structure of magnesium ions, forming MgCl2. l+ Monovalent ions participate in insertion and extraction. Although this type of halogen system improves the long cycle life of magnesium metal batteries, it inevitably leads to a lower electrochemical window (0-2.0V) for Cl- containing electrolyte systems and causes problems such as corrosion of conventional current collectors. This contradicts the low-cost advantage of magnesium batteries and the expectation of high energy density.
[0004] In contrast, a series of novel boron-based magnesium salts with large-sized boron-centered anions exhibit high oxidation stability and good compatibility with magnesium metal anodes. The boron-based magnesium salt system, represented by Mg(B(hfip)4)2, possesses excellent charge distribution characteristics from a molecular structure perspective, significantly reducing solvation with magnesium ions. Furthermore, the fluorine-containing boron-based system has a wider electrochemical window, demonstrating good high-voltage performance in many battery tests. However, recent literature reports that Mg(B(hfip)4)2 electrolytes still exhibit anode passivation. Inhomogeneous SEI film composition leads to uneven deposition of magnesium ions, making further performance improvements difficult, especially in long-cycle testing. This poses a significant challenge to the industrialization of magnesium metal batteries.
[0005] In current magnesium battery electrolyte systems, boron-based electrolytes can only cycle 400 times at 1C before experiencing rapid capacity decay. Chlorine-containing systems, on the other hand, have a charge / discharge voltage of only 0.1-2.0V. Compared to the widely used lithium-ion batteries, these two mainstream magnesium electrolyte battery types cannot meet the high standards of the market, even though their production costs are lower. Summary of the Invention
[0006] The first objective of this invention is to provide a nitrogen-boron-based dual-salt electrolyte to stabilize magnesium ion deposition and improve the electrode interface film, thereby breaking through the technical bottleneck of magnesium ion concentration in traditional electrolytes and significantly improving the cycle life of magnesium batteries.
[0007] To achieve the above objectives, the present invention adopts the following technical solution: a nitrogen-boron-based dual-salt electrolyte, comprising a chlorine-free boron-based magnesium salt, Mg(hftab)2, and small molecule ethers, wherein the molar ratio of the chlorine-free boron-based magnesium salt to Mg(hftab)2 is 1:(4-20).
[0008] Preferably, as an improvement, the magnesium ion concentration of the nitrogen-boron-based dual-salt electrolyte is 0.4M-0.6M.
[0009] Preferably, as an improvement, the molar ratio of the chlorine-free boron-based magnesium salt to Mg(hftab)2 is 10:1.
[0010] Preferably, as an improvement, the chlorine-free boron-based magnesium salt is Mg(B(hfip)4)2, Mg(B(tfe)4)2, MgB2O4, Mg3B2O6, or Mg(BF4)2, with Mg(B(hfip)4)2 being the most preferred.
[0011] The second objective of this invention is to provide a method for preparing a nitrogen-boron-based dual-salt electrolyte to obtain a Mg(hftab)2 with unique N-Mg Lewis acid-base properties, and to effectively control the SEI composition at the negative electrode interface by rationally preparing Mg(hftab)2 and Mg(B(hfip)4)2.
[0012] A process for preparing a nitrogen-boron-based dual-salt electrolyte involves uniformly mixing a chlorine-free boron-based magnesium salt with Mg(hftab)2 at a molar ratio of (4-20):1, and then adding a small molecule ether and stirring until completely dissolved.
[0013] Preferably, as an improvement, the method for preparing Mg(hftab)2 includes the following steps:
[0014] SO1. Prepare TEAB, ethers, and n-hexane;
[0015] SO2, TEAB and ether are added to the bottle one after another, and stirred at room temperature for 65-80 hours until TEAB is completely dissolved to obtain a yellow liquid;
[0016] SO3 was added to a yellow solution with 50 ml of n-hexane. The product was precipitated under ice bath conditions. After removing the supernatant, the product was washed repeatedly with n-hexane 3-5 times. Finally, it was dried under vacuum at room temperature for 65-80 h to obtain the nitrogen-boron-based magnesium salt Mg(hftab)2.
[0017] Preferably, as an improvement, the addition ratio of TEAB to ether is 1.6g:5-20ml.
[0018] Preferably, as an improvement, the chlorine-free boron-based magnesium salt is Mg(B(hfip)4)2. The preparation method of Mg(B(hfip)4)2 is as follows: add dibutylmagnesium to a bottle, then slowly add hexafluoroisopropanol to the solution under ice bath conditions, slowly stir until a colorless and transparent solid is formed, and stir the reaction for 1 hour to generate Mg(B(hfip)4)2.
[0019] Preferably, as an improvement, the molar ratio of dibutylmagnesium to hexafluoroisopropanol is 1:1-2.
[0020] A third objective of this invention is to provide an application of a nitrogen-boron-based dual-salt electrolyte, specifically applying the nitrogen-boron-based dual-salt electrolyte according to any one of claims 1-4 to the field of magnesium-ion batteries. This results in magnesium-ion batteries exhibiting extremely high cycle stability and capacity retention.
[0021] The principle and advantages of this scheme are:
[0022] To address the severe problem of uneven magnesium ion deposition in current magnesium batteries, this innovative approach involves adding nitrogen salts to the electrolyte. Experimental results show that this has a significant effect on stabilizing magnesium ion deposition and the interfacial film. Specific analysis follows:
[0023] Magnesium ions have two positive charges and a small ionic radius, resulting in an extremely high charge density. This makes them very strong at coordinating with strongly negatively charged groups (such as anions, oxygen, and nitrogen). This strong binding ability makes the solvation shell too stable, leading to problems such as slow magnesium ion migration, low electrolyte ionic conductivity, and unstable interfacial film, resulting in poor cycle performance. Therefore, this is the main reason why there has been no breakthrough in magnesium battery electrolytes.
[0024] To address this issue, a traditional approach is to reduce the binding strength between magnesium ions and anions. For example, boron-based magnesium salt systems, such as Mg(B(hfip)4)2, are added to the electrolyte. These anions have a particularly uniform charge distribution and weak electronegativity, thus reducing the binding affinity between magnesium ions and anions. However, this approach suffers from insufficient interfacial film growth, leading to difficulties in ion conduction and preventing high-rate charge / discharge of the battery. Furthermore, the poor ion conduction also results in uneven deposition.
[0025] To address the issues of uneven deposition or interfacial films, the applicant, after extensive analysis and experimentation, ultimately introduced a self-synthesized nitrogen-boron-based magnesium salt, Mg(hftab)2. A key contradiction with traditional methods is that the addition of nitrogen salts can actually enhance electrolyte solvation, a result undesirable for magnesium battery designers. Therefore, currently, no one considers adding nitrogen salts to the electrolyte. However, this approach synthesizes a novel nitrogen-boron-based magnesium salt, Mg(hftab)2, which effectively reduces the desolvation barrier of magnesium ions through steric hindrance. By mixing it with Mg(B(hfip)4)2 and precisely configuring their ratio, a suitable interfacial film is formed to stabilize magnesium ion deposition while having minimal impact on volumetric properties and not affecting the overall battery polarization voltage.
[0026] The following technical effects can be achieved by implementing this solution:
[0027] 1. Unique N-Mg Lewis Acid-Base Relationship: This scheme utilizes a novel stereochemically synthesized nitrogen-boron-based magnesium salt, Mg(hftab)2, whose unique N-Mg Lewis acid-base relationship effectively modulates the SEI composition at the negative electrode interface. In high-concentration electrolytes, the total LUMO energy shifts from solvent-dominated to salt-dominated, resulting in salt reduction prior to solvent reduction at the electrode surface. The lower LUMO energy level of TEABhfip promotes the formation of a nitrogen-containing solid interface film with excellent reversible magnesium ion insertion / extraction properties. Therefore, compared to traditional solvated magnesium ions, coordinated magnesium ions tend to undergo stable and uniform deposition, effectively extending the cycle life of the battery system.
[0028] 2. A breakthrough has been made in overcoming the technical bottleneck of magnesium ion concentration in traditional magnesium batteries, increasing it from the traditional maximum of 0.3M to 0.7M. Traditional boron-based magnesium battery electrolytes can only achieve a maximum magnesium salt concentration of 0.3M; otherwise, electrolyte solvation becomes more severe, leading to a significant performance degradation. Therefore, compared to the 1.0M concentration of lithium batteries, magnesium batteries lag far behind in power density, fast charging capability, cycle life, and reversibility, which is one of the key factors restricting the development of magnesium batteries.
[0029] The working mechanism of this solution is completely different from that of traditional magnesium salt electrolytes. Therefore, there is no need to worry about solvation. It is only necessary to stabilize the deposition of magnesium ions and improve its interfacial film. Although the magnesium ion concentration is increased, its performance will not be significantly reduced due to solvation. Therefore, the ion concentration of this solution can reach 0.6M, which is 50% higher than that of traditional ion concentrations. This breakthrough will directly promote the rapid development of magnesium ion batteries.
[0030] 3. Extremely high cycle stability and capacity retention: The traditional boron-based magnesium battery electrolyte Mg(B(hfip)4)2 is considered the best performing magnesium secondary battery electrolyte, but its performance is limited by the uneven deposition of magnesium ions, and it can only cycle 400 times at 1C rate. However, this solution shows excellent cycle stability and capacity retention, and after 1000 cycles at 1C rate, the battery discharge capacity is still 90.6%.
[0031] 4. Achieving high efficiency at low cost: This solution effectively reduces the desolvation energy barrier of magnesium ions and stabilizes the deposition mode of magnesium ions by adding only a small amount of self-developed nitrogen-boron-magnesium salt to the traditional boron-based magnesium salt system, thereby greatly extending the cycle life of magnesium metal batteries and achieving a breakthrough in the performance of boron-based magnesium electrolyte. Attached Figure Description
[0032] Figure 1 The chemical equation for Mg(hftab)2 is given.
[0033] Figure 2 The NMR spectrum of (hftab)2 is shown in the figure.
[0034] Figure 3 This is a mass spectrometry characterization of the electrolyte containing (hftab)2.
[0035] Figure 4 The NMR carbon spectra of Mg(hftab)2 and TEAB are shown.
[0036] Figure 5 This is a SEM image of magnesium deposition after testing with a nitrogen-boron-based dual-salt electrolyte.
[0037] Figure 6 The graph shows the cyclic test results of Examples 2 and 3 at a 1C rate.
[0038] Figure 7 The graph shows the cyclic test results of Example 1 and Comparative Example 1 at a 1C rate.
[0039] Figure 8 This is a test diagram of the electrochemical window for different electrolytes.
[0040] Figure 9This is a graph showing the deposition potential at different magnesium salt concentrations.
[0041] Figure 10 The graph shows a full-cell test at a 1C rate.
[0042] Figure 11 This is a long-term constant current polarization test diagram.
[0043] Figure 12 This is a TOF-SIMS test image of the magnesium anode surface after cycling according to the present invention. Detailed Implementation
[0044] The following detailed description illustrates the specific implementation method:
[0045] A nitrogen-boron-based dual-salt electrolyte comprises a chlorine-free boron-based magnesium salt, Mg(hftab)2, and small molecule ethers, wherein the molar ratio of Mg(hftab)2 to the chlorine-free boron-based magnesium salt is (4-20):1, and the magnesium ion concentration of the nitrogen-boron-based dual-salt electrolyte is 0.4M-0.6M.
[0046] The boron-based magnesium salts that do not contain chlorine include any one of Mg(B(hfip)4)2, Mg(B(tfe)4)2, MgB2O4, Mg3B2O6, and Mg(BF4)2, with Mg(B(hfip)4)2 being the preferred option in this scheme.
[0047] Small molecule ethers include DME, THF, MTBE, etc., and DME is preferred in this scheme.
[0048] The preparation process of nitrogen-boron-based dual-salt electrolyte includes the following steps:
[0049] Methods for preparing Mg(hftab)2 include:
[0050] SO1, prepare TEAB, ethers, and n-hexane; in this embodiment, ultra-dry DME is preferred as the ether.
[0051] SO2, add 1.6g (10.2mmol) TEAB to a Shrek bottle in a glove box, then add 10ml of ultra-dry DME, stir at room temperature for 72h until the TEAB is completely dissolved, and a yellow liquid is obtained;
[0052] SO3 was used to transfer the yellow liquid to a 100 ml Shrek bottle in a glove box. 50 ml of ultra-dry hexane was added, and the product was precipitated under ice bath conditions. After removing the supernatant, the mixture was washed four times repeatedly with 20 ml of hexane. Finally, it was dried under vacuum at room temperature for 72 hours to obtain the nitrogen-boron-based magnesium salt Mg(hftab)2. The chemical equation is as follows: Figure 1 As shown.
[0053] Methods for preparing Mg(B(hfip)4)2 include:
[0054] Add 5 ml (5 mmol) of dibutylmagnesium to a 50 ml Shrek flask, then slowly add 1.06 ml (10.2 mmol) of hexafluoroisopropanol to the solution under ice bath conditions, and slowly stir until a colorless and transparent solid is formed. Stir the reaction for 1 h to generate Mg(B(hfip)4)2.
[0055] Mix Mg(hftab)2 and Mg(B(hfip)4)2 at a molar ratio of (4-20):1 until homogeneous, then dissolve them in ultra-dry DME and stir for 12 h to obtain a nitrogen-boron-based double salt electrolyte.
[0056] I. The features and performance of the present invention will be further described in detail below with reference to embodiments and comparative examples.
[0057] Example 1: A nitrogen-boron-based dual-salt electrolyte comprising Mg(hftab)2, Mg(B(hfip)4)2, and DME, wherein the molar ratio of Mg(B(hfip)4)2 to Mg(hftab)2 is 4:1, and the magnesium ion concentration of the nitrogen-boron-based dual-salt electrolyte is 0.5M;
[0058] Example 2: Unlike Example 1, the molar ratio of Mg(B(hfip)4)2 to Mg(hftab)2 is 10:1;
[0059] Example 3: Unlike Example 1, the molar ratio of Mg(B(hfip)4)2 to Mg(hftab)2 is 20:1;
[0060] Example 4: Unlike Example 1, the magnesium ion concentration in the nitrogen-boron-based dual-salt electrolyte is 0.4 M;
[0061] Example 5: Unlike Example 1, the magnesium ion concentration in the nitrogen-boron-based dual-salt electrolyte is 0.6 M;
[0062] Comparative Example 1: Unlike Example 1, the molar ratio of Mg(B(hfip)4)2 to Mg(hftab)2 is 2:1;
[0063] Comparative Example 2: Unlike Example 1, the magnesium ion concentration in the nitrogen-boron-based dual-salt electrolyte was 0.7 M;
[0064] Comparative Example 3: The electrolyte does not contain Mg(hftab)2.
[0065] II. Experiment
[0066] 1. Characterization of Mg(hftab)₂ using 1H NMR and mass spectrometry
[0067] To demonstrate the successful synthesis of the nitrogen-containing magnesium salt Mg(hftab)2, the synthesized product was subjected to 1H NMR spectroscopy, and the electrolyte system was also characterized by mass spectrometry.
[0068] Figure 2 The 1H NMR spectrum of (hftab)2 shows that, through the Lewis acid-base interaction of N-Mg, the electron vacancies of boron combine with hexafluoroisopropanol groups to generate the nitrogen-containing boron-based magnesium salt Mg(hftab)2.
[0069] Figure 3 This is a mass spectrometry characterization of an electrolyte containing (hftab)2. In the mass spectrometry characterization of the electrolyte, individually coordinated Mghftab can be clearly observed. 1+ And (Mghftab / DME) bound to small DME molecules. 1+ This indicates that this novel nitrogen-boron salt tends to bind with an hftab anion in the electrolyte, existing in the electrolyte system in a monovalent form, which facilitates the migration of magnesium ions.
[0070] Figure 4 The carbon NMR spectra of Mg(hftab)₂ and TEAB are shown. To visually demonstrate the Lewis acid-base interaction of N-Mg, the NMR shifts in the C-particles near the N atom can be used for characterization. In the hftab anion, the lone pair electrons of N are absorbed by Mg. 2+ Attraction, Mg 2+ As a strong Lewis acid, it pulls lone pairs of electrons from nitrogen (N) through coordination interactions, leading to a decrease in the electron cloud density around N and polarization of the electron cloud of neighboring carbon (C). This results in electrons from N being pulled towards Mg. 2+ The electron clouds of C atoms directly bonded to N (and neighboring C atoms) may be partially "extracted," leading to a decrease in the electron density of these C atoms and enhancing the deshielding effect. This decrease in electron density reduces the shielding effect on NMR (i.e., deshielding), thus shifting the chemical shifts of C1 and C2 in the carbon NMR spectrum of Mg(hftab)2 towards the low-field, high-chemical-shift direction.
[0071] Magnesium ion deposition test
[0072] To demonstrate the alteration of magnesium ion deposition behavior induced by N-Mg Lewis acid-base interactions in nitrogen-containing dual-salt systems, this experiment designed a magnesium / / stainless steel asymmetric cell with a current of 1 mA / cm². 2 Magnesium plating was deposited on stainless steel foil at current densities of 0.5 h, 1 h, and 2 h. After the deposition experiments, the disassembled stainless steel foil was characterized by SEM, as shown in the attached figure. Figure 5The results show that in the Mg(hftab)2 system, the deposition morphology of magnesium is more uniform and dense, and there is no growth process of blocky magnesium caused by uneven distribution of current density.
[0073] 3. Test on the effect of different proportions of two magnesium salts on battery performance
[0074] To test the effect of electrolytes prepared by mixing two magnesium salts, Mg(B(hfip)4)2 and Mg(hftab)2, in different proportions on battery performance, dual-salt electrolytes were prepared in various examples and comparative examples, and then combined with Mo6S8 cathode material and magnesium metal anode to assemble coin cells for full-cell cycle testing, as shown in the attached figures.
[0075] Figures 6-7 Cycling tests at 1C rate were conducted on electrolytes prepared with different molar ratios of Mg(B(hfip)4)2 and Mg(hftab)2. The results show that the dual-salt electrolyte exhibits good long-cycle performance within a molar ratio range of (4-20:1). The optimal long-cycle performance is observed at a ratio of 10:1, where the nitrogen-containing magnesium salt Mg(hftab)2 effectively participates in the SEI formation process and minimizes battery polarization and desolvation caused by N-Mg Lewis acid-base interactions. However, when the molar ratio is 2:1 (i.e., excessive Mg(hftab)2 is added), the electrolyte becomes excessively volumetric, leading to continuously increasing polarization and ultimately poor cycle performance.
[0076] 4. Electrochemical window test
[0077] To demonstrate that this dual-salt electrolyte has a wide electrochemical window, LSV tests were performed on two concentrations of the traditional boron-based magnesium salt Mg(B(hfip)4)2 at 0.3M and 0.7M, as well as on the 0.5M Mg(B(hfip)4)2 + 0.05M Mg(hftab)2 solution in this formulation. Figure 8 The test results show that the voltage window of the boron-based system increases with increasing salt concentration. Compared with traditional pure boron-based electrolytes, the nitrogen-containing dual-salt system in this scheme exhibits superior electrochemical stability and has the potential to be matched with high-voltage cathodes.
[0078] 5. The effect of different magnesium ion concentrations on battery performance
[0079] Deposition potential tests were conducted on assembled magnesium / / stainless steel batteries using different concentrations of magnesium salt at the same nitrogen salt ratio. (See attached image.) Figure 9The test results show that as the magnesium salt concentration increases, the deposition potential of magnesium ions increases from 0.7V to 1.3V, indicating that excessively high salt concentrations can also lead to uneven distribution of magnesium ion nuclei. When the magnesium ion concentration is in the range of 0.4M-0.6M, the nucleation potential remains at a low level, representing a uniform nucleation process for the initial deposition of magnesium ions. The best effect is observed at a concentration of 0.5M, as shown in the figure, where the growth and peeling potential is lowest, demonstrating the best reversible deposition and peeling process. During the discharge process, the 0.5M system significantly precedes other concentration systems, with magnesium ions preferentially depositing on the stainless steel foil, which is consistent with the SEM test results.
[0080] However, when the magnesium ion concentration is 0.7 (greater than 0.6 M), the nucleation overpotential changes significantly. This is because the solvent is reduced, and the solvation degree of Mg(hftab)₂ is further intensified. In subsequent deposition-deposition cycles, the severe solvation structure also generates a large polarization voltage, which is also detrimental to the long-term cycling of the battery.
[0081] 6. Cyclic performance test
[0082] Cycle performance tests were conducted on full cells assembled with traditional boron-based magnesium salt Mg(B(hfip)4)2 and the nitrogen-containing dual-salt electrolyte of 0.5M Mg(B(hfip)4)2+0.05M Mg(hftab)2 in this scheme, matched with traditional Mo6S8 cathode material. See attached figures. Figure 10 The test results show that the nitrogen-containing dual-salt electrolyte exhibits extremely high cycle stability and capacity retention at 1C rate; after 1000 cycles, the battery discharge capacity still reaches 90.6%. For example... Figure 11 The long-term constant current polarization test results show that, during the test of up to 1100 hours, the voltage of the electrolyte using this scheme was maintained at almost 0V, demonstrating its excellent long-term stability; while the traditional boron-based magnesium salt Mg(B(hfip)4)2 without the addition of Mg(hftab)2 deviated significantly from the 0V range after 200 hours, indicating its poor stability.
[0083] The above performance reflects the poor performance of this nitrogen-boron-based dual-salt electrolyte compared to traditional boron-based electrolytes at high concentrations due to solvation. The N-Mg Lewis acid-base action plays an important role in desolvation in the nitrogen-containing dual-salt system.
[0084] 7. TOF-SIMS test on magnesium anode surface
[0085] from Figure 12The test results show that this dual-salt electrolyte successfully constructed an organic nitrogen-containing SEI film with C=NF as the component on the surface of the magnesium metal anode. Notably, the TOF-SIMS results clearly show the competition between N and O and F. A portion of the non-magnesium-conducting MgO and MgF2 components in the traditional SEI film are converted into organic groups with higher ionic conductivity, namely MgNO3 and C=NF, thus avoiding the negative impacts of the passivation layer in the traditional boron-based magnesium electrolyte system.
[0086] 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 nitrogen-boron-based dual-salt electrolyte, characterized in that: Including Mg(B(hfip)4)2, Mg(hftab)2, and small molecule ethers, wherein the molar ratio of Mg(B(hfip)4)2 to Mg(hftab)2 is (4-20):1; The chemical equation for Mg(hftab)2 is as follows: 。 2. The nitrogen-boron-based dual-salt electrolyte according to claim 1, characterized in that: The magnesium ion concentration in the nitrogen-boron-based double salt electrolyte is 0.4M-0.6M.
3. The nitrogen-boron-based dual-salt electrolyte according to claim 2, characterized in that: The molar ratio of Mg(B(hfip)4)2 to Mg(hftab)2 is 10:
1.
4. A preparation process for a nitrogen-boron-based dual-salt electrolyte, characterized in that: Mix Mg(B(hfip)4)2 and Mg(hftab)2 uniformly at a molar ratio of (4-20):1, add small molecule ethers and stir until completely dissolved; The preparation method of Mg(hftab)2 includes the following steps: SO1. Prepare TEAB, ethers, n-hexane, hexafluoroisopropanol, and dibutylmagnesium; SO2, add hexafluoroisopropanol and dibutylmagnesium to the bottle one after another, stir in an ice bath for 3 hours, then add TEAB and ether, stir at 60 degrees Celsius for 65-80 hours until TEAB is completely dissolved, and a yellow liquid is obtained. SO3 was added to a yellow solution with 50 ml of n-hexane. The product was precipitated under ice bath conditions. After removing the supernatant, the product was washed repeatedly with n-hexane 3-5 times. Finally, it was dried under vacuum at room temperature for 65-80 h to obtain the nitrogen-boron-based magnesium salt Mg(hftab)2.
5. The preparation process of a nitrogen-boron-based dual-salt electrolyte according to claim 4, characterized in that: The addition ratio of TEAB to ether is 1.6g:(5-20ml).
6. The preparation process of a nitrogen-boron-based dual-salt electrolyte according to claim 5, characterized in that: The preparation method of Mg(B(hfip)4)2 is as follows: add dibutylmagnesium to a bottle, then slowly add hexafluoroisopropanol to the solution under ice bath conditions, stir slowly until a colorless and transparent solid is formed, stir for 1 hour, then add boranetetrahydrofuran solution and add excess hexafluoroisopropanol, stir for 24 hours, and then wash the precipitate with n-hexane 3-5 times to generate Mg(B(hfip)4)2.
7. The preparation process of a nitrogen-boron-based dual-salt electrolyte according to claim 6, characterized in that: The molar ratio of dibutylmagnesium to hexafluoroisopropanol is 1:(1-2).
8. An application of a nitrogen-boron-based dual-salt electrolyte, characterized in that: The nitrogen-boron-based dual-salt electrolyte according to any one of claims 1-3 is applied to the field of magnesium-ion batteries.