Electrolyte for lithium iron manganese phosphate system battery and lithium ion battery
By using electrolyte containing sulfonylaminophenylborate compound in lithium manganese ferric phosphate batteries, the shortcomings of the battery in high-temperature circulation and low-temperature discharge performance are solved, and a longer cycle life and lower interface impedance are achieved.
Patent Information
- Application Number
- CN202411893309.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-20
- Publication Date
- 2025-03-28
AI Technical Summary
The existing lithium manganese iron phosphate batteries have shortcomings in high-temperature circulation and low-temperature discharge performance, especially the problems of manganese dissolution and negative electrode film formation impedance, which affects its cycle life and low-temperature performance.
An electrolyte containing a sulfonaminophenylborate esters compound is used to combine a specific lithium salt and a non-aqueous organic solvent to form an SEI film with excellent conductivity and lithium conductivity. By synergistically acting with other additives in the electrolyte, the positive electrode material is stabilized and the dissolution of manganese is inhibited.
It significantly improves the high-temperature circulation and low-temperature discharge performance of LiMnPO4 batteries, extends the cycle life of the battery, and reduces the interface impedance and manganese dissolution rate.
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Figure CN119725741A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of electrode material preparation, and specifically relates to an electrolyte for lithium manganese iron phosphate system batteries and a lithium ion battery. Background Art
[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.
[0003] Since the beginning of the 21st century, lithium-ion batteries have developed in the energy field due to their high energy density, low self-discharge rate, and no memory effect. In particular, driven by the demand for lithium-ion batteries (LIBs) in electric vehicles (EVs), lithium iron phosphate (LiFePO 4 ) is widely used in power batteries and is one of the safest commercial positive electrodes.
[0004] Olivine structure LiFePO 4 With 170mAh g -1 However, its energy density cannot meet the growing demand for electric vehicles. LiMnPO with the same structure and theoretical capacity 4 Due to its high energy density of 700 (Wh kg -1 ) and a high operating voltage platform (4.1V), while LiMnPO 4 Has excellent low temperature performance, but LiMnPO 4 The difficulty of large-scale industrial production lies in the fact that the Jahn-Teller effect promotes the dissolution of manganese in the material, resulting in the reduction of battery cycle life, especially high-temperature cycle performance. In addition, trace amounts of water in the electrolyte will produce corrosive hydrofluoric acid (HF), which will further corrode the manganese ions in the positive electrode material and accelerate the degradation of Mn. 3+ The disproportionation reaction process promotes Mn 2+ and Mn 4+ It dissolves in the electrolyte and migrates to the negative electrode through the diaphragm, thereby destroying the SEI film of the negative electrode, resulting in increased impedance, which in turn affects its cycle performance and low-temperature performance. Therefore, inhibiting the dissolution of Mn in lithium manganese iron phosphate material and reducing the film formation impedance of the negative electrode are the key to improving LiMnPO 4 The key to the high temperature cycle and low temperature discharge performance of the battery, the optimization of the electrolyte components has a good effect on improving the performance of lithium manganese iron phosphate batteries, and the development of a matching electrolyte is an important means to promote the application of lithium manganese iron phosphate batteries. 3+ Disproportionation causes manganese to dissolve easily at the cathode / electrolyte interface, resulting in severe capacity fade. Summary of the invention
[0005] In view of the shortcomings of the prior art, the present invention aims to provide an electrolyte for lithium manganese iron phosphate battery and a lithium ion battery, aiming to solve the problem of increasing the 4 High temperature cycling and low temperature discharge performance of the battery.
[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:
[0007] In a first aspect, the present invention provides an electrolyte for a lithium manganese iron phosphate system battery, which includes a lithium salt, a non-aqueous organic solvent and a sulfonylaminophenylboronic acid pinacol ester compound additive, wherein the sulfonylaminophenylboronic acid pinacol ester compound is a compound represented by formula (I):
[0008]
[0009] Among them, R 1 ~R 5 Each is independently selected from the structure of formula (II), H, a halogen atom, an unsaturated hydrocarbon group, an amino group, a phenyl group, and a silane group, and R 1 ~R 5 At least one of them is of formula (II);
[0010] Among them, in formula (II), R 6 One selected from H, a halogen atom, an unsaturated hydrocarbon group, an amino group, a phenyl group or a silane group.
[0011] In some embodiments, R 1 ~R 5 wherein the halogen atom is fluorine; R 6 In the above, the halogen atom is fluorine.
[0012] In some embodiments, the sulfonylaminophenylboronic acid pinacol ester compound is selected from at least one of the following compounds:
[0013]
[0014]
[0015] In some embodiments, the mass percentage of the sulfonylaminophenylboronic acid pinacol ester compound additive in the electrolyte is 0.1 to 5 wt %;
[0016] Preferably, the mass percentage of the sulfonylaminophenylboronic acid pinacol ester compound additive in the electrolyte is 0.2-3wt%, and the addition amount thereof is 0.2%-2wt%.
[0017] In some embodiments, the electrolyte further includes at least one of the following additives: vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, vinyl bissulfate, propylene sulfate, 1,3-propane sultone, 1,3-propylene sultone, 1,4-butane sultone, methylene disulfonate, triallyl phosphate, tris(trimethylsilane) phosphate, trimethyl phosphite, triphenyl phosphite, tetramethylmethylene diphosphate, propargyl phosphate, (2-allylphenoxy)trimethylsilane, tris(trimethylsilane) borate, tripropyl borate, 1,3,6-hexanetrinitrile, 1,2-bis(cyanoethoxy)ethane, lithium difluorophosphate or lithium bis(oxalatoborate).
[0018] Negative electrode film-forming additives such as VC, FEC, DTD, and PS are superior to solvent systems in forming SEI films on the negative electrode side, and work synergistically with sulfonylaminophenylboronic acid pinacol ester compounds to construct a thin SEI film with strong lithium ion conductivity.
[0019] Preferably, the mass percentage of the additive in the electrolyte is 0.1-5%.
[0020] In some embodiments, the lithium salt is selected from lithium hexafluorophosphate (LiPF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium tetrafluoroborate (LiBF 4 ), preferably LiPF 6 One or both of and LiFSI.
[0021] Preferably, the mass percentage of the lithium salt in the electrolyte is 10% to 25%, preferably 11% to 16%.
[0022] In some embodiments, the non-aqueous organic solvent is selected from one or a combination of organic ester, ether, sulfone or nitrile solvents.
[0023] Preferably, the non-aqueous organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, 1,4-butyrolactone, methyl formate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, ethyl butyrate, methyl difluoroacetate, ethyl difluoroacetate, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dimethyl sulfoxide, cyclopentane sulfone or dimethyl sulfone.
[0024] Preferably, the mass percentage of the wastewater organic solvent in the electrolyte is 70% to 88%, preferably 72% to 85%.
[0025] In a second aspect, the present invention provides a lithium-ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode material on the positive electrode sheet is lithium iron manganese phosphate, and the electrolyte is the electrolyte for the lithium iron manganese phosphate system battery.
[0026] The beneficial effects achieved by one or more embodiments of the present invention are as follows:
[0027] The electrolyte for lithium ion batteries provided by the present invention selects sulfonylaminophenylboronic acid pinacol ester as an electrolyte additive, which has a higher HOMO energy level and a lower LUMO energy level; in the high-temperature and high-pressure charging and discharging process, the heterocyclic part and the boric acid pinacol ester in the boric acid pinacol ester additive preferentially undergo oxidative polymerization reaction and decomposition reaction with the solvent, forming a relatively thin B derivative-containing CEI film on the positive electrode surface, which has excellent electrical conductivity and lithium conductivity, thereby improving Li + Migration ability, reducing interface impedance and improving low-temperature discharge performance of the battery;
[0028] The compound contains an amino group that can react with H 2 O and HF form hydrogen bonds, effectively preventing LiPF 6 The hydrolysis and stabilization of acidic substances, at the same time, the B atom has electron deficiency and PF 6 - , have strong interaction and stabilize PF 6 - The HF generated by decomposition can effectively curb the corrosion of HF on the positive electrode material and CEI membrane, and can inhibit the Mn 2+ Dissolution, improving the high temperature cycle performance and high temperature storage performance of the battery;
[0029] By selecting boric acid pinacol ester containing a specific heterocycle and adding it to the electrolyte, an SEI film with ion conductivity can be formed at the negative electrode, which is reduced on the surface of the negative electrode to form an SEI film containing S derivatives. The SEI is thin and has strong lithium ion conductivity, while reducing the content of the non-conductive substance LiF, which is beneficial to the low-temperature discharge performance of the battery. DETAILED DESCRIPTION
[0030] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.
[0031] In order to better illustrate the purpose, technical scheme and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the following implementation method is a further explanation of the present invention and should not be used as a limitation of the present invention.
[0032] Example 1
[0033] Preparation of electrolyte:
[0034] In a glove box filled with argon (water <10 ppm, oxygen <10 ppm), ethylene carbonate (EC) and dimethyl carbonate (EMC) were mixed at a mass ratio of 3:7, and then 12% lithium hexafluorophosphate (LiPF 6 ) and 2.5% of lithium bis(fluorosulfonyl)imide (LiFSI), stirred to completely dissolve, added 1% of vinylene carbonate (VC), 0.5% of fluoroethylene carbonate (FEC) and 0.8% of compound formula (2) 3-methanesulfonylaminophenylboronic acid pinacol ester (CAS No. 305448-92-4) to obtain an electrolyte.
[0035] Example 2
[0036] This embodiment provides a lithium ion battery electrolyte, and the same points as those in Example 1 are not repeated here. The difference from Example 1 is that 0.8% of the compound formula (2) 3-methanesulfonylaminophenylboronic acid pinacol ester is replaced with 0.8% of the compound formula (4) 4-benzenesulfonylaminophenylboronic acid pinacol ester (CAS No. 914606-88-5) to obtain an electrolyte.
[0037] Example 3
[0038] This embodiment provides a lithium ion battery electrolyte, and the same points as those in Example 1 are not repeated here. The difference from Example 1 is that 0.8% of the compound formula (2) 3-methanesulfonylaminophenylboronic acid pinacol ester in Example 1 is replaced with 0.8% of the compound formula (12) 3-fluoro-4-(2-fluorophenylsulfonylamino)phenylboronic acid pinacol ester (CAS No. 1314069-48-1) to obtain an electrolyte.
[0039] Example 4
[0040] This embodiment provides a lithium ion battery electrolyte, and the same points as those in Example 1 are not repeated here. The difference from Example 1 is that 0.8% of the compound formula (2) 3-methanesulfonylaminophenylboronic acid pinacol ester in Example 1 is replaced by 0.8% of the compound formula (13) 4-(2-fluorobenzenesulfonylamino)phenylboronic acid pinacol ester (CAS No. 1637249-14-9) to obtain an electrolyte.
[0041] Comparative Example 1
[0042] The difference from Example 1 is that the "0.8% compound formula (2) 3-methanesulfonylaminophenylboronic acid pinacol ester" in Example 1 is omitted, and the rest is the same as Example 1. The details are as follows:
[0043] In a glove box filled with argon (water <10ppm, oxygen <10ppm), ethylene carbonate (EC) and dimethyl carbonate (EMC) were mixed in a mass ratio of 3:7, and then 12% by mass of lithium hexafluorophosphate (LiPF6) and 2.5% of bis(fluorosulfonyl)imide (LiFSI) were slowly added to the mixed solvent and stirred to completely dissolve, and 1% vinylene carbonate (VC) and 0.5% fluoroethylene carbonate (FEC) were added to obtain an electrolyte.
[0044] Comparative Example 2
[0045] The difference from Example 4 is that the "0.8% compound formula (13) 4-(2-fluorobenzenesulfonylamino)phenylboronic acid pinacol ester" in Example 4 is replaced by "0.05% compound formula (13) 4-(2-fluorobenzenesulfonylamino)phenylboronic acid pinacol ester". The rest is the same as Example 4.
[0046] In a glove box filled with argon (water <10 ppm, oxygen <10 ppm), ethylene carbonate (EC) and dimethyl carbonate (EMC) were mixed at a mass ratio of 3:7, and then 12% lithium hexafluorophosphate (LiPF 6 ) and 2.5% of bis(fluorosulfonyl)imide (LiFSI), stirring to completely dissolve them, adding 1% of vinylene carbonate (VC), 0.5% of fluoroethylene carbonate (FEC) and 0.05% of compound formula (13) 4-(2-fluorobenzenesulfonylamino)phenylboronic acid pinacol ester (CAS No. 1637249-14-9) to obtain an electrolyte.
[0047] Comparative Example 3
[0048] The difference from Example 4 is that the "0.8% compound formula (13) 4-(2-fluorobenzenesulfonylamino)phenylboronic acid pinacol ester" in Example 4 is replaced by "2.5% compound formula (13) 4-(2-fluorobenzenesulfonylamino)phenylboronic acid pinacol ester". The rest is the same as Example 4.
[0049] In a glove box filled with argon (water <10 ppm, oxygen <10 ppm), ethylene carbonate (EC) and dimethyl carbonate (EMC) were mixed at a mass ratio of 3:7, and then 12% lithium hexafluorophosphate (LiPF 6) and 2.5% of bis(fluorosulfonyl)imide (LiFSI), stirring to completely dissolve them, adding 1% of vinylene carbonate (VC), 0.5% of fluoroethylene carbonate (FEC) and 2.5% of compound formula (13) 4-(2-fluorobenzenesulfonylamino)phenylboronic acid pinacol ester (CAS No. 1637249-14-9) to obtain an electrolyte.
[0050] The lithium ion battery is prepared by using the electrolyte of the embodiment and the comparative example, which specifically comprises the following steps:
[0051] Preparation of positive electrode sheets: The positive electrode material lithium manganese iron phosphate, conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF) are mixed evenly in a mass ratio of 96.8:2:1.2, and then dispersed in N-methyl-2-pyrrolidone (NMP) to obtain positive electrode slurry, and then the slurry is evenly coated on both sides of the aluminum foil, and the positive electrode sheet is obtained after drying and rolling.
[0052] Preparation of negative electrode sheet: Graphite, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) are mixed evenly in a mass ratio of 95:2:2:1, and then dispersed in deionized water to obtain negative electrode slurry. The slurry is then evenly coated on both sides of the aluminum foil, and the negative electrode sheet is obtained after drying and rolling.
[0053] Preparation of lithium manganese iron phosphate battery: stack the positive electrode sheet, separator, and negative electrode sheet in order, ensure that the separator separates the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet completely covers the positive electrode sheet, and then put the stacked battery cell into an aluminum-plastic film packaging bag, and then inject the above-prepared electrolyte into the battery cell for formation, sealing, aging, secondary sealing, capacity division and other processes to make a lithium manganese iron phosphate battery with a capacity of 10000mAh.
[0054] The specific test conditions are as follows:
[0055] (1) Test of acidity and color of high-temperature electrolyte: Prepare the electrolyte in a glove box filled with argon gas, put it into an aluminum-plastic bottle, place it in a 55°C oven for 48 hours, and then measure the changes in the electrolyte color and acidity;
[0056] (2) High temperature cycle test: At high temperature (45°C), the lithium-ion battery is charged and discharged at 1C / 1C (the battery discharge capacity is C 0 ), the upper voltage is 4.4V, and then 1C / 1C charging and discharging is performed at room temperature for 800 cycles (the battery discharge capacity is C 1 );
[0057] Capacity retention rate = (C 1 / C 0 )*100%;
[0058] (3) Negative electrode sheet metal ion test after cycling: The battery after 800 cycles at high temperature (45°C) was disassembled in a drying room, the negative electrode sheets were collected, the negative electrode sheets were rinsed with DMC several times and then dried, and the negative electrode powder was scraped for ICP testing;
[0059] (4) Low temperature discharge test: At room temperature (25°C), the lithium-ion battery is charged and discharged at 0.3C / 0.3C (the battery discharge capacity is recorded as C 0 ), the upper limit voltage is 4.4V; the battery is placed in a -20℃ oven for 4h, and the battery is discharged at 0.3C, and the discharge capacity is recorded as C 1 , the cut-off voltage is 2.8V, and the capacity retention rate is (C 1 / C 0 )*100%.
[0060] The test data of the embodiments and comparative examples are shown in Table 1.
[0061] Table 1
[0062]
[0063]
[0064] The results show that:
[0065] Comparative Example 1 is the basic formula group. From the analysis of the physical properties of the electrolyte after high-temperature storage: Examples 1-4 and Comparative Example 3 add sulfonylaminophenylboronic acid pinacol ester compounds. Because the central B atom of the compound has electron deficiency and PF 6 - , have strong interaction and stabilize PF 6 - HF produced by decomposition, and the compound contains amino groups, can react with H 2 O and HF form hydrogen bonds, effectively preventing LiPF 6 This also explains why the acidity and chromaticity in the examples are less changed than those in the control group.
[0066] High temperature cycle performance analysis: The high temperature cycle performance of Examples 1-4 and Comparative Example 3 is significantly better than that of Comparative Example 1 and Comparative Example 2. This is because the addition of sulfonylaminophenylboronic acid pinacol ester compounds inhibits the increase in electrolyte acidity. At the same time, the boric acid pinacol ester of the electrolyte additive undergoes oxidative polymerization and decomposition reactions before the solvent, forming a thinner CEI film containing B derivatives on the positive electrode surface. The formed CEI film has excellent electrical conductivity and lithium conductivity, which improves Li +It can enhance the migration ability, reduce the interface impedance, and effectively inhibit the dissolution of metal ions. At the same time, ICP test is carried out on the negative electrode after cycling, and the reduction of Mn ions is obviously analyzed.
[0067] Analysis of low-temperature discharge performance: The low-temperature discharge performance of Examples 1-4 is significantly better than that of the control group. This is because sulfonylaminophenylboronic acid pinacol ester contains sulfonyl functional groups with a low LUMO energy level, which is reduced on the negative electrode surface before the solvent in the electrolyte to form an SEI film containing S derivatives. The SEI is thin and has strong lithium ion conductivity, while reducing the content of the non-conductive substance LiF, which is beneficial to the low-temperature discharge performance of the battery.
[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. An electrolyte for lithium manganese iron phosphate battery, characterized in that: The invention comprises a lithium salt, a non-aqueous organic solvent and a sulfonylaminophenylboronic acid pinacol ester compound additive, wherein the sulfonylaminophenylboronic acid pinacol ester compound is a compound represented by formula (I): Wherein, R1 to R5 are each independently selected from one of the structures of formula (II), H, halogen atoms, unsaturated hydrocarbon groups, amino groups, phenyl groups, and silane groups, and at least one of R1 to R5 is the structure of formula (II); Wherein, in formula (II), R6 is selected from one of H, halogen atom, unsaturated hydrocarbon group, amino group, phenyl group or silane group.
2. The electrolyte for lithium manganese iron phosphate battery according to claim 1, characterized in that: In R1 to R5, the halogen atom is fluorine; in R6, the halogen atom is fluorine.
3. The electrolyte for lithium manganese iron phosphate battery according to claim 1, characterized in that: The sulfonylaminophenylboronic acid pinacol ester compound is selected from at least one of the following compounds:
4. The electrolyte for lithium manganese iron phosphate battery according to claim 1, characterized in that: The mass percentage of the sulfonylaminophenylboronic acid pinacol ester compound additive in the electrolyte is 0.1 to 5 wt %; Preferably, the mass percentage of the sulfonylaminophenylboronic acid pinacol ester compound additive in the electrolyte is 0.2-3wt%, and the addition amount thereof is 0.2%-2wt%.
5. The electrolyte for lithium manganese iron phosphate battery according to claim 1, characterized in that: The electrolyte further includes at least one of the following additives: vinylene carbonate, fluoroethylene carbonate, vinyl sulfate, vinyl bissulfate, propylene sulfate, 1,3-propane sultone, 1,3-propylene sultone, 1,4-butane sultone, methylene disulfonate, triallyl phosphate, tris(trimethylsilyl) phosphate, trimethyl phosphite, triphenyl phosphite, tetramethyl methylene diphosphate, propargyl phosphate, (2-allylphenoxy) trimethylsilane, tris(trimethylsilyl) borate, tripropyl borate, 1,3,6-hexane trinitrile, 1,2-bis(cyanoethoxy)ethane, lithium difluorophosphate or lithium bis(oxalatoborate); Preferably, the mass percentage of the additive in the electrolyte is 0.1-5%.
6. The electrolyte for lithium manganese iron phosphate battery according to claim 1, characterized in that: The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium tetrafluoroborate, preferably one or two of LiPF6 and LiFSI; Preferably, the mass percentage of the lithium salt in the electrolyte is 10% to 25%, preferably 11% to 16%.
7. The electrolyte for lithium manganese iron phosphate battery according to claim 1, characterized in that: The non-aqueous organic solvent is selected from one or a combination of organic ester, ether, sulfone or nitrile solvents.
8. The electrolyte for lithium manganese iron phosphate battery according to claim 1, characterized in that: The non-aqueous organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, 1,4-butyrolactone, methyl formate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, ethyl butyrate, methyl difluoroacetate, ethyl difluoroacetate, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dimethyl sulfoxide, cyclopentane or dimethyl sulfone.
9. The electrolyte for lithium manganese iron phosphate battery according to claim 1, characterized in that: The mass percentage of the wastewater organic solvent in the electrolyte is 70% to 88%, preferably 72% to 85%.
10. A lithium ion battery, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. The positive electrode material on the positive electrode sheet is lithium iron manganese phosphate, and the electrolyte is the electrolyte for a lithium iron manganese phosphate system battery as claimed in any one of claim 9.