Additive for inhibiting co-intercalation of solvents in dual-carbon battery and application
By adding competitive coordination divalent metal salt additives to the dual-carbon battery, a stable complex is formed, which solves the problem of solvent molecules and anions co-intercalating into the graphite cathode, improves the cycle life and high voltage stability of the battery, and achieves efficient structural stability and conductivity maintenance.
Patent Information
- Application Number
- CN202510980315.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-16
- Publication Date
- 2025-11-07
AI Technical Summary
In existing technologies, under high voltage, solvent molecules in dual-carbon batteries tend to co-intercalate with fluorine-containing anions between the graphite cathode layers, leading to structural oxidation and decomposition, particle breakage, and interfacial contact failure, which severely limits their cycle stability and service life.
By employing salt additives of competitive coordination divalent metal salts such as Mg2+ or Ca2+, stable complexes are formed with carbonate solvents, blocking the path of solvent molecules and anions co-intercalating into the graphite cathode, thereby improving the ionic conductivity of the electrolyte and stabilizing the graphite cathode structure.
It significantly improves the cycle life and high-voltage cycle stability of dual-carbon batteries, maintains the integrity of the graphite cathode structure, retains ≥90% capacity, and forms stable metal ion-solvent complexes in the electrolyte, reducing the content of free solvent molecules.
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Figure CN120914342A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of electrochemical energy storage, and particularly relates to an additive for inhibiting solvent co-intercalation in a dual-graphite battery (DGB) and application, in particular, an additive capable of effectively inhibiting the co-intercalation of solvent molecules and fluorine-containing anions in a graphite positive electrode of a dual-graphite battery, thereby improving the cycle stability and service life of the dual-graphite battery. BACKGROUND
[0002] A dual-graphite battery (DGB) is a typical dual-ion battery, in which both the positive and negative electrodes are made of graphite-based carbon materials. During charging, lithium ions are intercalated into the graphite negative electrode from the electrolyte, while fluorine-containing anions (such as PF6 - , TFSI - , etc.) are intercalated into the graphite positive electrode. Due to the use of inexpensive and environmentally friendly carbon materials as active materials, the dual-graphite battery has shown good application prospects in large-scale energy storage systems. However, under high voltage conditions (> 4.5 V vs. Li + / Li), carbonic acid solvent molecules in the electrolyte are easily co-intercalated into the graphite positive electrode interlayer along with fluorine-containing anions, and are oxidized and decomposed at high potentials, releasing CO2 and other gases. This process leads to irreversible peeling of the graphite interlayer, particle breakage, and failure of the positive electrode-current collector interface contact, thereby causing rapid capacity decay and severely limiting the practical application performance of the dual-graphite battery.
[0003] In the prior art, the method for inhibiting solvent co-intercalation is mainly to develop electrolyte systems that do not contain solvent molecules or have a low proportion of solvent molecules, such as ionic liquid electrolytes, polymer electrolytes, or gel electrolytes (Energy Environ. Sci. 2014, 7, 3412-3423; Adv. Mater. 2022, 34, 2108665; J Mater Chem A. 2018, 6, 4313-4323). However, these methods not only have the disadvantage of high electrolyte cost, but also cause problems such as low ionic conductivity of the electrolyte and poor interface compatibility with the electrode, which seriously sacrifices the rate performance of the dual-graphite battery. Therefore, it is urgent to develop a low-cost, efficient, and highly process-compatible electrolyte additive to fundamentally inhibit solvent co-intercalation and improve the high-voltage cycle stability of the dual-graphite battery. SUMMARY
[0004] The present application aims to provide an additive for inhibiting solvent co-intercalation in a dual-graphite battery.
[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:
[0006] An additive for inhibiting solvent co-intercalation in a dual-carbon battery, the additive being a competitive coordination type divalent metal salt (the additive has high solubility in carbonate solvents and high self-oxidation stability), and the additive being added in an amount of 2wt%-10wt% in the electrolyte, preferably 4-6wt%.
[0007] The additive is a competitive coordination type divalent metal salt containing magnesium ions (Mg 2+ ) or calcium ions (Ca 2+ ).
[0008] The additive has a general formula of M(X)2, wherein M is Mg or Ca, and X is TFSI - , ClO4 - or FSI - with high oxidation stability.
[0009] The additive for inhibiting solvent co-intercalation in a dual-carbon battery, and the use of the additive as an additive in an electrolyte of a dual-carbon battery.
[0010] A dual-carbon battery, a positive electrode and a negative electrode and an electrolyte, the electrolyte containing the additive.
[0011] Both the positive electrode and the negative electrode are graphite materials, the electrolyte containing a lithium salt, a fluorine-containing anion and the additive.
[0012] The charging cutoff voltage range of the battery is 4.8-5.2V.
[0013] The dual-carbon battery has a capacity retention rate of ≥90% after 1000 cycles under a 2C charging and discharging condition, and the XRD half-peak width of the (002) crystal plane of the positive electrode graphite after the cycles is <0.3°.
[0014] The additive inhibits solvent co-intercalation into the graphite positive electrode, and the mechanism is as follows: the Lewis acidity of the divalent metal (Mg 2+ and Ca 2+ ) in the additive is stronger than that of Li + , and the divalent metal (Mg 2+ and Ca 2+ ) in the additive preferentially forms stable complexes (such as [Mg(EMC) n ] 2+ with solvent molecules (such as EMC), reduces the co-intercalation of free solvent molecules and anions, does not affect the ionic conductivity of the electrolyte, and thus solves the high-voltage failure problem of the graphite positive electrode, thereby stabilizing the structure of the graphite positive electrode and improving the cycle life of the dual-carbon battery.
[0015] The present application has the following advantages:
[0016] The additive of the application introduces the Lewis acid regulation mechanism of divalent metal salt into the double-carbon battery system, which preferentially binds with carbonate solvent molecules in the electrolyte through competitive coordination to form a stable complex, effectively blocking the solvent co-intercalation path, significantly reducing the possibility of solvent molecules and fluorine-containing anions co-intercalating into the graphite positive electrode, thereby inhibiting the degradation of the positive electrode structure, stabilizing the graphite positive electrode structure, and improving the cycle life of the double-carbon battery; specifically:
[0017] 1. The double-carbon battery assembled using the additive of the application maintains the integrity of the graphite positive electrode structure after 1000 cycles without peeling.
[0018] 2. The double-carbon battery assembled using the additive of the application has a capacity retention rate of ≥90% after 1000 cycles at a cutoff voltage of 4.8-5.2V.
[0019] 3. The electrolyte Raman spectrum of the double-carbon battery assembled using the additive of the application after cycling is in the range of 945-955cm -1 [M(EMC)4] appears 2+ characteristic peak (M = Mg / Ca), indicating strong Lewis acidity of M 2+ preferentially coordinates with solvent molecules, reducing the co-intercalation tendency of solvent molecules and anions. BRIEF DESCRIPTION OF DRAWINGS
[0020] Figure 1 is the cycle performance effect diagram of the double-carbon battery in Example 1 and Comparative Example 1 of the application.
[0021] Figure 2 is the XRD of the graphite positive electrode of the double-carbon battery after cycling in Example 1 and Comparative Example 1 of the application.
[0022] Figure 3 is the SEM of the graphite positive electrode of the double-carbon battery after cycling in Example 1 and Comparative Example 1 of the application.
[0023] Figure 4 is the Raman spectrum of the electrolyte of the double-carbon battery after cycling in Example 1 and Comparative Example 1 of the application. DETAILED DESCRIPTION
[0024] The application is further described below through specific examples, which are helpful for those skilled in the art to more fully understand the application, but do not limit the application in any way.
[0025] The application utilizes the addition of an additive to the electrolyte, and then assembles a double-carbon battery, which works under high-voltage conditions (>4.5V vs. Li +The additive Mg(TFSI)2 can inhibit the co-intercalation of solvent molecules and fluorine-containing anions into the graphite positive electrode layer in the electrolyte, thereby preventing the structural oxidation and decomposition, particle breakage and interface contact failure, and thus preventing the rapid capacity decay; the capacity retention rate of the additive added to the electrolyte is ≥90% after 1000 cycles at a cutoff voltage of 4.8-5.2V, which is much higher than 65% of the group without the additive. The additive has the advantages of low cost, strong process compatibility and significant improvement of the high-voltage cycle stability of the battery, and is suitable for the double-carbon battery system in the large-scale energy storage field.
[0026] Example 1: Application of Mg(TFSI)2 additive in double-carbon battery
[0027] 1. Preparation of electrolyte: In an argon-protected glove box, 1.5M LiPF6 was dissolved in ethyl methyl carbonate (EMC) solvent, and then 5wt% of bis-trifluoromethanesulfonylimide magnesium (Mg(TFSI)2) was added to the total mass of the electrolyte. A magnetic stirrer was used to continuously stir at 500rpm at 25℃ for 2 hours to obtain a homogeneous transparent electrolyte.
[0028] 2. Assembly of double-carbon battery: graphite was used as the positive and negative electrodes, copper foil and aluminum foil were used as the current collectors of the negative and positive electrodes respectively, glass fiber separator was used, and the above obtained electrolyte was injected and packaged to obtain a double-carbon battery.
[0029] 3. Electrochemical performance test and characterization:
[0030] (1) Charge-discharge test procedure: a blue electric test system was used to perform cycle test at 2C rate (based on the total capacity of the positive electrode) in the voltage range of 3.0-5.0V at 25℃;
[0031] (2) Cycle performance: the capacity retention rate was 92.5% after 1000 cycles, as shown in Figure 1 ;
[0032] (3) Structural characterization: the graphite positive electrode was disassembled after cycling and subjected to XRD analysis, the (002) crystal plane diffraction peak half-width (FWHM) was 0.14°, as shown in Figure 2 , indicating that the layered structure was well maintained. SEM observation showed that there was no obvious crack on the surface of the graphite particles and no peeling phenomenon between the layers, as shown in Figure 3 a Figure 3 b
[0033] (4) Electrolyte characterization: after 1000 cycles, the electrolyte was subjected to Raman spectrum characterization (excitation wavelength 532nm), and [Mg(EMC)4] -1 characteristic peaks appeared in the range of 945-955cm 2+ , as shown in Figure 4The results show that the additive can regulate the solvation structure through Lewis acidity, form stable metal ion-solvent complex, reduce the content of free solvent molecules, and thus inhibit the co-intercalation of solvents.
[0034] Example 2: Application of Mg(ClO4)2additive in double-carbon batteries
[0035] 1. Electrolyte preparation: same as Example 1, only replace Mg(TFSI)2with magnesium perchlorate (Mg(ClO4)2) with a concentration of 5wt%.
[0036] 2. Double-carbon battery assembly: same as Example 1.
[0037] 3. Electrochemical performance testing and characterization:
[0038] (1) Charge-discharge test procedure: same as Example 1.
[0039] (2) Cycle performance: the capacity retention rate reaches 91.1% after 1000 cycles;
[0040] (3) Structural characterization: after cycling, the positive electrode was disassembled for XRD analysis, and the (002) crystal plane diffraction peak half-width (FWHM) was 0.22°. SEM observation showed that there were no obvious cracks on the surface of graphite particles and no peeling phenomenon between layers.
[0041] (4) Electrolyte characterization: after 1000 cycles, the electrolyte was characterized by Raman spectroscopy (excitation wavelength 532nm), and the characteristic peaks of [Mg(EMC)4] appeared in the same range as Example 1, 945-955cm -1 , which proves that the additive can regulate the solvation structure through Lewis acidity, form stable metal ion-solvent complex, reduce the content of free solvent molecules, and thus inhibit the co-intercalation of solvents. 2+
[0042] Example 3: Application of Mg(FSI)2additive in double-carbon batteries
[0043] 1. Electrolyte preparation: same as Example 1, but replace Mg(TFSI)2with Mg(FSI)2with a concentration of 5wt%.
[0044] 2. Double-carbon battery assembly: same as Example 1.
[0045] 3. Electrochemical performance testing and characterization:
[0046] (1) Charge-discharge test procedure: same as Example 1.
[0047] (2) Cycle performance: the capacity retention rate reaches 92.6% after 1000 cycles;
[0048] (3) Structure characterization: After cycling, the positive electrode was disassembled for XRD analysis, and the half-peak width (FWHM) of the (002) crystal plane diffraction peak was 0.22°. SEM observation showed that there were no obvious cracks on the surface of the graphite particles, and there was no peeling phenomenon between the layers.
[0049] (4) Electrolyte characterization: After 1000 cycles, the electrolyte was characterized by Raman spectroscopy (excitation wavelength 532 nm). In the range of 945-955 cm -1 , the same as in Example 1, [Mg(EMC)4] 2+ characteristic peaks appeared, proving that the additive regulates the solvation structure through Lewis acidity, forms a stable metal ion-solvent complex, reduces the content of free solvent molecules, and thus inhibits solvent co-intercalation.
[0050] Example 4: Application of Mg(TFSI)2 additive in 5.2V high-voltage dual-carbon battery
[0051] 1. Electrolyte preparation: The same as in Example 1, but the concentration of Mg(TFSI)2 was increased to 10wt%.
[0052] 2. Dual-carbon battery assembly: The same as in Example 1.
[0053] 3. Electrochemical performance testing and characterization:
[0054] (1) Charge-discharge test procedure: At 25°C, using a blue electric test system, cycle test at 2C rate (based on the total capacity of the positive electrode) in the range of 3.0-5.2V (higher cut-off voltage);
[0055] (2) Cycle performance: After 1000 cycles, the capacity retention rate reached 90.2%;
[0056] (3) Structure characterization: After cycling, the positive electrode was disassembled for XRD analysis, and the half-peak width (FWHM) of the (002) crystal plane diffraction peak was 0.27°. SEM observation showed that there were no obvious cracks on the surface of the graphite particles, and there was no peeling phenomenon between the layers.
[0057] (4) Electrolyte characterization: After 1000 cycles, the electrolyte was characterized by Raman spectroscopy (excitation wavelength 532 nm). In the range of 945-955 cm -1 , the same as in Example 1, [Mg(EMC)4] 2+ characteristic peaks appeared, proving that the additive regulates the solvation structure through Lewis acidity, forms a stable metal ion-solvent complex, reduces the content of free solvent molecules, and thus inhibits solvent co-intercalation.
[0058] Example 5: Application of Ca(TFSI)2 additive in dual-carbon battery
[0059] 1. Electrolyte preparation: same as Example 1, but replace Mg(TFSI)2 with Ca(TFSI)2, concentration is 5wt%.
[0060] 2. Assembling of dual-carbon battery: same as Example 1.
[0061] 3. Electrochemical performance test and characterization:
[0062] (1) Charge-discharge test procedure: same as Example 1;
[0063] (2) Cycle performance: the capacity retention rate reaches 91.7% after 1000 cycles;
[0064] (3) Structure characterization: after cycling, the positive electrode was disassembled for XRD analysis, the half-peak width (FWHM) of the (002) crystal plane diffraction peak was 0.21°. SEM observation showed that there were no obvious cracks on the surface of graphite particles and no peeling phenomenon between layers.
[0065] (4) Electrolyte characterization: after 1000 cycles, the electrolyte was characterized by Raman spectroscopy (excitation wavelength 532 nm), and the characteristic peaks of [Ca(EMC)4] appeared in the same range as Example 1, 945-955 cm -1 , which proved that the additive could regulate the solvation structure through Lewis acidity, form stable metal ion-solvent complex, reduce the content of free solvent molecules, and thus inhibit the co-intercalation of solvents. 2+
[0066] Comparative Example 1: no additive in the electrolyte of the dual-carbon battery
[0067] 1. Electrolyte preparation: same as Example 1, but no Mg(TFSI)2 additive was added.
[0068] 2. Assembling of dual-carbon battery: same as Example 1.
[0069] 3. Electrochemical performance test and characterization:
[0070] (1) Charge-discharge test procedure: same as Example 1;
[0071] (2) Cycle performance: the capacity retention rate reaches 44.5% after 1000 cycles, as shown in Figure 1 ;
[0072] (3) Structure characterization: after cycling, the positive electrode was disassembled for XRD analysis, the half-peak width (FWHM) of the (002) crystal plane diffraction peak was 0.46° (as shown in Figure 2 ), indicating that the graphite interlayer structure was severely degraded. SEM observation showed that there were obvious cracks on the surface of graphite particles, and some flaky graphite became multi-layer stacked sheets (as shown in Figure 3 ), indicating that serious peeling occurred.
[0073] (4) Electrolyte characterization: Raman spectrum characterization (excitation wavelength 532 nm) of electrolyte after 1000 cycles, only the characteristic peak of non-complex EMC (as shown in -1 ) appeared in the range of 928-937 cm Figure 4 , and no [Mg(EMC)4] -1 characteristic peak appeared in the range of 945-955 cm 2+ .
[0074] Comparative Example 2: Double-car battery electrolyte containing other additives
[0075] 1. Electrolyte preparation: the same as Example 1, but replace Mg(TFSI)2 with MgSO4, the concentration is 5wt%.
[0076] 2. Double-car battery assembly: the same as Example 1.
[0077] 3. Electrochemical performance test and characterization:
[0078] (1) Charge-discharge test procedure: the same as Example 1;
[0079] (2) Cycle performance: the capacity retention rate reached 48.8% after 1000 cycles;
[0080] (3) Structural characterization: XRD analysis of the disassembled positive electrode after cycling, the (002) crystal plane diffraction peak half-peak width (FWHM) is 0.45°, indicating that the graphite interlayer structure is severely degraded. SEM observation shows that obvious cracks appear on the surface of graphite particles, and part of the flaky graphite becomes a multi-layer stacked sheet, indicating that serious peeling phenomenon occurs.
[0081] (4) Electrolyte characterization: Raman spectrum characterization (excitation wavelength 532 nm) of electrolyte after 1000 cycles, only the characteristic peak of non-complex EMC (as shown in -1 ) appeared in the range of 928-937 cm -1 , and no [Mg(EMC)4] 2+ characteristic peak appeared in the range of 945-955 cm
Claims
1. An additive to suppress co-intercalation of solvents in a dual carbon battery, characterized by, The additive is a competitive coordination type divalent metal salt additive, and the adding amount is 2wt%-10wt% in the electrolyte.
2. The additive for suppressing co-intercalation of a solvent in a dual-carbon battery according to claim 1, characterized by, The additive is a competitive coordination type divalent metal salt containing magnesium ions (Mg 2+ ) or calcium ions (Ca 2+ ).
3. The additive for suppressing co-intercalation of a solvent in a dual-carbon battery according to claim 1 or 2, characterized by, The additive has a general formula of M(X)2, wherein M is Mg or Ca, and X is TFSI-, ClO4- or FSI-.
4. The additive of claim 1 for suppressing co-intercalation of solvents in dual carbon batteries, characterized in that, The additive is used in the application of a double-carbon battery electrolyte additive.
5. A dual carbon battery, positive and negative electrodes and electrolyte, characterized in that: The electrolyte of the double-carbon battery contains the additive of claim 1.
6. The dual-carbon battery of claim 5, wherein: The positive and negative electrodes are both graphite materials, the electrolyte contains lithium salt, fluorine-containing anion and the additive of claim 1.