A local high-concentration electrolyte capable of realizing high energy density and long cycle life of lithium metal batteries, and a preparation method and application thereof
By forming a stable SEI film using a diluent in a locally high-concentration electrolyte, the problems of lithium dendrite growth and electrolyte consumption in lithium metal batteries are solved, thus achieving improved performance of lithium metal batteries with high energy density and long cycle life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-27
- Publication Date
- 2026-03-24
AI Technical Summary
Lithium metal batteries suffer from problems such as increased battery impedance, rapid capacity decay, and short cycle life due to disordered growth of lithium dendrites in the negative electrode and rapid electrolyte consumption. Existing electrolytes cannot effectively form a stable solid electrolyte interphase (SEI) film, which affects the high energy density and long cycle life of the battery.
By employing a locally high-concentration electrolyte and adding the diluent 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether, a solvation structure dominated by contact ion pairs/aggregated ion pairs is formed, which promotes the formation of a stable and robust SEI film and achieves dense and uniform deposition of lithium metal.
Significantly improves the cycle performance of lithium metal batteries, achieving 500 stable cycles with an average coulombic efficiency of over 99.9%. The energy density of the lithium metal pouch battery is as high as 500 Wh/kg, with a capacity retention rate of 99.02% after 50 cycles and 79.08% after 90 cycles.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium metal battery technology, specifically to a locally high-concentration electrolyte for lithium metal batteries that can achieve high energy density and long cycle life, its preparation method, and its application. Background Technology
[0002] Against the backdrop of global advocacy for sustainable development, the development and application of green and environmentally friendly energy storage technologies have become an inevitable trend. Lithium-ion batteries have advantages such as no memory effect, no toxic / harmful substances, and recyclability, making them more environmentally friendly than traditional batteries and in line with the requirements of sustainable development. However, the energy density of lithium-ion battery systems based on graphite anodes has reached its theoretical limit (<300 Wh / kg), thus there is an urgent need to improve the energy density of next-generation battery systems and develop new high-energy-density batteries. Lithium metal batteries (LMBs) are considered a promising alternative, combining an ultra-thin lithium metal anode (<50 μm) with a high-voltage cathode (such as LiNi). 0.8 Mn 0.1 Co 0.1 Coupling with O2 (abbreviated as NMC811) can increase the energy density of lithium metal batteries to over 400 Wh / kg. However, in practical applications, lithium metal batteries still face key challenges such as increased battery impedance, rapid capacity decay, and short cycle life due to disordered lithium dendrite growth at the negative electrode and rapid electrolyte consumption. First, compared to traditional graphite negative electrodes, lithium metal negative electrodes exhibit more and uncontrollable side reactions with traditional electrolytes, resulting in low coulombic efficiency. Second, the significant volume change of lithium metal negative electrodes during cycling makes the solid electrolyte interphase (SEI) film prone to rupture and repeated formation, leading to substantial electrolyte consumption and shortened battery life. Furthermore, the uneven deposition / stripping behavior at the lithium metal negative electrode interface causes continuous dendrite growth and the formation of "dead lithium," resulting in short circuits and safety hazards.
[0003] High-performance electrolytes are crucial for achieving stable cycling of lithium metal anodes, and finding electrolytes compatible with both the positive and negative electrodes is essential for developing high-energy-density, long-cycle-life lithium metal batteries. Thermodynamically, due to the very low electronegativity of lithium metal, no single liquid electrolyte is stable. However, forming a passivation layer at the interface between the lithium anode and the electrolyte can broaden the electrochemical window and dynamically stabilize the lithium metal anode. Since the ultra-high reducing power of the lithium metal anode inevitably reacts with the electrolyte to form an electrolyte-encapsulated electrolyte interphase (SEI), forming a suitable and highly stable SEI layer on the lithium metal anode is crucial, as it can prevent further side reactions between the electrolyte and the lithium anode.
[0004] Researchers have proposed several new strategies, including increasing the salt concentration of the electrolyte, designing novel fluorinated solvent molecules, and introducing functional additives, to broaden the electrochemical window and improve the electrochemical stability of the electrolyte. These novel electrolytes enable a more stable and uniform SEI film, resulting in larger and denser deposited lithium particles, effectively suppressing the formation of "dead lithium" and significantly improving the coulombic efficiency of the anode. However, based on currently reported electrolytes and using a high-load cathode and a thin lithium anode, the stable cycle count of the resulting lithium metal battery is still below 300 cycles, which is still far from meeting the requirements for practical applications. Summary of the Invention
[0005] To address the aforementioned issues, this invention provides a locally high-concentration electrolyte for lithium metal batteries with high energy density and long cycle life, along with its preparation method and applications. By adding the diluent 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether, the electrolyte participates in the solvation structure of lithium ions, forming a solvation structure dominated by contact ion pairs / aggregated ion pairs. This promotes the formation of a stable and robust SEI film, while simultaneously achieving dense and uniform deposition of lithium metal, significantly improving the cycle performance of lithium metal batteries.
[0006] The object of the present invention is achieved in the following manner: a locally high-concentration electrolyte for lithium metal batteries that can achieve high energy density and long cycle life, comprising lithium salt, ether solvent, and diluent, wherein the diluent is 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether (abbreviated as HTE).
[0007] The lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI), and the ether solvent is dimethyl ethylene glycol ether (DME).
[0008] The molar concentration of lithium salt ranges from 1.4 to 1.7 mol / L; the molar ratio of ether solvent to diluent is (1 to 2):3.
[0009] A method for preparing a locally high-concentration electrolyte for lithium metal batteries with high energy density and long cycle life includes the following steps:
[0010] Under a protective atmosphere, lithium salt is dissolved in an ether solvent, then a diluent is added, and the mixture is magnetically stirred until homogeneous to obtain a locally high-concentration electrolyte.
[0011] Application of a locally high-concentration electrolyte in lithium metal batteries that enables high energy density and long cycle life.
[0012] A lithium metal battery includes a positive electrode, a negative electrode, and a locally high-concentration electrolyte, wherein the positive electrode is a nickel-cobalt-manganese layered oxide and the negative electrode is lithium metal.
[0013] Nickel-cobalt-manganese layered oxide is LiNi 0.8Mn 0.1 Co 0.1 O2.
[0014] A lithium metal pouch battery includes a positive electrode, a negative electrode, and a locally high-concentration electrolyte for the lithium metal battery. The positive electrode is a nickel-cobalt-manganese layered oxide, and the negative electrode is lithium metal. The nickel-cobalt-manganese layered oxide is LiNi. 0.83 Mn 0.05 Co 0.12 O2 (abbreviated as Ni83).
[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0016] (1) The addition of 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether diluent effectively reduced the viscosity of the electrolyte, improved the wettability and ion transport capacity of the electrolyte, and broadened the electrochemical window.
[0017] (2) Uniform and dense lithium deposition can be achieved. At the same time, the salt anions decompose first to form an SEI film rich in inorganic products. This robust and stable negative electrode / electrolyte interface can reduce the occurrence of side reactions and electrolyte consumption, and improve the cycle performance of the battery.
[0018] (3) At ultra-high load cathode (~20 mg / cm) 2 Under the coupling condition of a thin lithium anode (50 μm), the assembled lithium metal battery can achieve 500 stable cycles at 25°C, with an average coulombic efficiency of over 99.9%.
[0019] (4) At ultra-high load cathode (~25 mg / cm) 2 Under the coupling conditions of a thin lithium anode (20 μm), the energy density of the assembled lithium metal pouch battery can reach up to 500 Wh / kg, and the capacity retention rate is 99.02% after 50 cycles at 25℃ and 79.08% after 90 cycles.
[0020] The high-concentration electrolyte provided in this application, which enables high-energy-density and long-cycle-life lithium metal batteries, involves the addition of a diluent, 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether, to participate in the solvation structure of lithium ions, forming a solvation structure dominated by contact ion pairs / aggregated ion pairs. This promotes the formation of a stable and robust SEI film, while simultaneously achieving dense and uniform deposition of lithium metal, significantly improving the cycle performance of lithium metal batteries. Attached Figure Description
[0021] Figure 1The cycling performance of the NMC811 || Li batteries prepared in Example 1 and Comparative Example 1 at 25°C and 2.7~4.4 V is shown. Wherein A is the coulombic efficiency curve of Example 1, B is the specific capacity curve of Example 1, C is the coulombic efficiency curve of Comparative Example 1, and D is the specific capacity curve of Comparative Example 1.
[0022] Figure 2 The cycling performance of NMC811 || Li batteries prepared for Example 1 and Comparative Example 2 at 25°C and 2.7~4.4 V is shown in Figure 2. Wherein A is the coulombic efficiency curve of Example 1, B is the specific capacity curve of Example 1, C is the coulombic efficiency curve of Comparative Example 2, and D is the specific capacity curve of Comparative Example 2.
[0023] Figure 3 From top to bottom, Figures A, B, and C show the charge-discharge curves of NMC811 || Li batteries prepared in Comparative Example 1, Comparative Example 2, and Example 1, respectively, under conditions of 25°C and 2.7~4.4 V.
[0024] Figure 4 From top to bottom, Figures A, B, and C are scanning electron microscope cross-sectional views of lithium deposition in Comparative Example 1, Comparative Example 2, and Example 1, respectively.
[0025] Figure 5 The cycling performance of the lithium metal pouch cell prepared in Example 1 at 25°C and 2.7~4.4 V is shown in Figure A, where A is the coulombic efficiency curve of Example 1 and B is the discharge capacity curve of Example 1. Detailed Implementation
[0026] A locally high-concentration electrolyte for lithium metal batteries that can achieve high energy density and long cycle life includes lithium salt, ether solvent, and diluent, wherein the diluent is 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether.
[0027] The lithium salt is one or a mixture of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, lithium bis(oxalate)difluorophosphate, lithium bis(trifluoromethyl)difluoroborate, and lithium bis(malonate)borate. The ether solvent is at least one of ethylene glycol dimethyl ether, ethylene glycol monobutyl ether, methyl tert-butyl ether, diphenyl ether, and diethylene glycol monomethyl ether.
[0028] Preferably, the lithium salt is lithium bis(fluorosulfonyl)imide, and the ether solvent is ethylene glycol dimethyl ether.
[0029] The molar concentration of lithium salt ranges from 1.4 to 1.7 mol / L; the molar ratio of ether solvent to diluent is (1 to 2):3.
[0030] A method for preparing a locally high-concentration electrolyte for lithium metal batteries with high energy density and long cycle life includes the following steps: under a protective atmosphere, dissolving lithium salt in an ether solvent, then adding a diluent, and magnetically stirring until uniformly mixed to obtain a locally high-concentration electrolyte.
[0031] If the ether solvent and diluent contain moisture, molecular sieves can be added for adsorption and purification to reduce the moisture content of the ether solvent and diluent to below 20 ppm.
[0032] The application of a locally high-concentration electrolyte in lithium metal batteries, enabling high energy density and long cycle life, is disclosed. The lithium metal battery is a Cu||Li battery, an NMC811||Li battery, or a Ni83||Li battery.
[0033] A lithium metal battery includes a positive electrode, a negative electrode, and a locally high-concentration electrolyte, wherein the positive electrode is a nickel-cobalt-manganese layered oxide, and the negative electrode is lithium metal. The nickel-cobalt-manganese layered oxide can be LiNi. 0.8 Mn 0.1 Co 0.1 O2.
[0034] A lithium metal pouch battery includes a positive electrode, a negative electrode, and a locally high-concentration electrolyte for achieving high energy density and long cycle life. The positive electrode is a nickel-cobalt-manganese layered oxide, and the negative electrode is lithium metal. The nickel-cobalt-manganese layered oxide can be LiNi. 0.83 Mn 0.05 Co 0.12 O2.
[0035] The present invention will now be described in detail with reference to specific embodiments. It should be noted that these embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above description of the present invention.
[0036] The sources of raw materials in the embodiments and comparative examples of this application are as follows:
[0037] Comparative Example 1 is a commercially available finished electrolyte, purchased from Suzhou Duoduo Chemical Technology Co., Ltd.; in Comparative Example 2 and the examples, lithium bisfluorosulfonylimide (LiFSI) was purchased from Tokyo Chemical Industry Co., Ltd. (TCI), diethylene glycol dimethyl ether (DME) was purchased from Sinopharm Holdings Co., Ltd., 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) was purchased from Suzhou Duoduo Chemical Technology Co., Ltd., and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether (HTE) was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.
[0038] The glove box was purchased from Wigtech Technology (Suzhou) Co., Ltd., the magnetic stirrer from Shanghai Heyue Instrument Co., Ltd., the battery casing and separator from Kelude Experimental Equipment Technology Co., Ltd., the cathode material from Fulim Precision Co., Ltd., and the lithium copper composite strip from Tianjin Zhongneng Lithium Industry Co., Ltd. All batteries were tested using the Blue Battery Testing System.
[0039] Example 1
[0040] A locally high-concentration electrolyte for achieving high energy density and long cycle life lithium metal batteries comprises lithium bisfluorosulfonylimide (LiFSI), dimethyl ethylene glycol (DME), and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether; the molar ratio of lithium bisfluorosulfonylimide (LiFSI), dimethyl ethylene glycol (DME), and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether is 1:1.2:3.
[0041] The method for preparing a locally high-concentration electrolyte for a lithium metal battery with high energy density and long cycle life includes the following steps:
[0042] In a glove box filled with argon atmosphere, lithium salt was dissolved in the solvent ethylene glycol dimethyl ether and magnetically stirred until the lithium salt was completely dissolved at a stirring speed of 400 rpm. Then, the diluent 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether was added, and magnetic stirring was continued until the mixture was homogeneous to obtain a locally high-concentration electrolyte. The total stirring time was 4 hours.
[0043] Comparative Example 1
[0044] Common commercial lithium metal battery electrolytes were purchased from Suzhou Duoduo Chemical Technology Co., Ltd., and the raw materials are lithium salts, solvents, and additives; among which:
[0045] The lithium salt is lithium hexafluorophosphate (LiPF6) with a molar concentration of 1.0 mol / L.
[0046] The solvents are ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.
[0047] The additive is vinylene carbonate (VC), and the addition amount is 2%.
[0048] Comparative Example 2
[0049] Commonly used high-concentration electrolytes for lithium metal batteries consist of lithium salts, solvents, and diluents; among which:
[0050] The lithium salt is lithium bis(fluorosulfonyl)imide (LiFSI) with a molar concentration of 1.74 mol / L.
[0051] The solvent is dimethyl ethylene glycol (DME).
[0052] The diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE).
[0053] The molar ratio of LiFSI, DME, and TTE is 1:1.2:3.
[0054] In a glove box filled with argon atmosphere, lithium salt is first dissolved in DME, then diluent TTE is added, and the mixture is stirred magnetically to obtain a locally high-concentration electrolyte.
[0055] Examples 1, 1 (Comparative Example), and 2 (Comparative Example) were all used to assemble 2016-type button cells and conduct performance tests.
[0056] (1) NMC811 || Li battery: A lithium copper composite strip with a thickness of 50 μm is selected as the negative electrode in lithium metal batteries, with a loading of 20 mg / cm. 2 LiNi 0.8 Mn 0.1 Co 0.1 O2 (NMC811) is used as the positive electrode, and a 20 μm thick PP / PE / PP separator is used. The electrolyte volume of each battery is 100 μL.
[0057] The electrolytes from Example 1, Comparative Example 1, and Comparative Example 2 were used to perform cycle performance tests on NMC811 || Li batteries. The test conditions were as follows: at 25°C, the batteries were charged at a constant current rate of 0.1C (1C=200 mAh / g) to 4.4 V, then discharged at a constant current rate of 0.1C to 2.7 V. After two cycles, the batteries were charged again at a constant current rate of 0.1C to 4.4 V, and then discharged at 0.33C to 2.7 V.
[0058] (2) Cu || Li battery: A lithium copper composite strip with a thickness of 50 μm is used as the negative electrode, and an 8 μm thick Cu foil is used as the positive electrode. A 20 μm thick PP / PE / PP separator is used. The electrolyte amount for each battery is 100 μL.
[0059] The electrolytes from Example 1, Comparative Example 1, and Comparative Example 2 were used in Cu||Li batteries for testing. The test conditions were: 25°C at 0.5 mA / cm². 2 Constant current charging at current density for 8 hours.
[0060] (3) Lithium metal pouch cell Ni83 || Li battery: In the lithium metal battery, a lithium copper composite strip with a thickness of 20 μm is selected as the negative electrode, with a loading of 25 mg / cm. 2The positive electrode is Ni83, the separator is a 20 μm thick PP / PE / PP separator, the battery capacity is 6 Ah, the E / C ratio is 1.2 g / Ah, and the energy density is 500 Wh / kg.
[0061] The electrolyte from Example 1 was used to test a Ni83||Li lithium metal pouch battery. The test conditions were as follows: at 25°C, it was charged at a constant current rate of 0.1C (1C=200 mAh / g) to 4.4 V, then discharged at a constant current rate of 0.1C to 2.7 V. After two cycles, it was charged again at a constant current rate of 0.1C to 4.4 V, and then discharged at 0.33C to 2.7 V.
[0062] Test results:
[0063] (1) The electrolyte prepared in Example 1 was used for cycle performance testing of NMC811 || Li batteries. The test results are as follows: Figure 1 and Figure 2 As shown, it can be stably cycled 500 times with a capacity retention rate of 66.03%.
[0064] The electrolyte of Comparative Example 1 was used in the NMC811 || Li battery for cycle performance testing. The test results are as follows: Figure 1 As shown, Comparative Example 1 only achieved stable cycling for 200 cycles before experiencing a sharp capacity decay. Example 1 of this application, used in an NMC811 || Li battery, demonstrated stable cycling performance for 500 cycles with a capacity retention of 66.03%, and its capacity remained superior to that of Comparative Example 1 throughout the cycling process.
[0065] The electrolyte of Comparative Example 2 was used in the NMC811 || Li battery for cycle performance testing. The test results are as follows: Figure 2 As shown, Comparative Example 2 can cycle stably for 350 cycles before experiencing capacity fluctuations, subsequently leading to battery failure. Example 1 of this application, used in an NMC811 || Li battery, underwent cycle performance testing and achieved stable cycling for 500 cycles with a capacity retention rate of 66.03%, consistently outperforming Comparative Example 2 throughout the cycling process.
[0066] The electrolytes prepared in Comparative Examples 1, 2, and 1 were used for charging and discharging NMC811 || Li batteries, such as... Figure 3 As shown, in Comparative Example 1, the capacity decayed slowly in the first 150 cycles, and the polarization increased rapidly after 150 cycles, accompanied by a sharp drop in capacity. In Comparative Example 2, the capacity was not much different from that in Example 1 in the first 300 cycles, but after 300 cycles, the polarization of Comparative Example 2 increased significantly, accompanied by a rapid decrease in capacity, which led to battery failure. In contrast, the capacity of Example 1 decayed slowly and could be guaranteed to be stable for 500 cycles.
[0067] (2) After deposition of 4 mAh / cm in Cu || Li battery 2 Post-scanning electron microscopy image results are as follows Figure 4 As shown, the lithium deposits in Comparative Example 1, Comparative Example 2, and Example 1 were approximately 108 μm, 32 μm, and 30 μm thick, respectively. Comparative Example 1 had the thickest lithium deposition and contained many voids, indicating poor lithium deposition / stripping ability. Example 1, on the other hand, yielded the thinnest and densest lithium metal deposition, demonstrating excellent lithium deposition / stripping ability.
[0068] (3) The electrolyte prepared in Example 1 was used for cycle performance testing of a lithium metal pouch cell Ni83 || Li battery. The test results are as follows: Figure 5 As shown, the capacity retention rate after 50 cycles at 25°C is 99.02%, and the capacity retention rate after 90 cycles is 79.08%.
[0069] The embodiments of this application may also be the following embodiments:
[0070] Example 2
[0071] A locally high-concentration electrolyte for achieving high energy density and long cycle life lithium metal batteries comprises lithium bisfluorosulfonylimide (LiFSI), dimethyl ethylene glycol (DME), and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether; the molar ratio of lithium bisfluorosulfonylimide (LiFSI), dimethyl ethylene glycol (DME), and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether is 1:1:3.
[0072] The method for preparing a locally high-concentration electrolyte for a lithium metal battery with high energy density and long cycle life includes the following steps:
[0073] In a glove box filled with argon atmosphere, lithium salt is dissolved in the solvent ethylene glycol dimethyl ether and magnetically stirred until the lithium salt is completely dissolved. The stirring speed is usually 380 rpm. Then, the diluent 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether is added, and magnetic stirring is continued until the mixture is homogeneous to obtain a locally high-concentration electrolyte.
[0074] Example 3
[0075] A locally high-concentration electrolyte for achieving high energy density and long cycle life lithium metal batteries comprises lithium bisfluorosulfonylimide (LiFSI), dimethyl ethylene glycol (DME), and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether; the molar ratio of lithium bisfluorosulfonylimide (LiFSI), dimethyl ethylene glycol (DME), and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether is 1:1.4:3.
[0076] The method for preparing a locally high-concentration electrolyte for a lithium metal battery with high energy density and long cycle life includes the following steps:
[0077] In a glove box filled with argon atmosphere, lithium salt is dissolved in the solvent ethylene glycol dimethyl ether and magnetically stirred until the lithium salt is completely dissolved. The stirring speed is usually 420 rpm. Then, the diluent 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether is added, and magnetic stirring is continued until the mixture is homogeneous to obtain a locally high-concentration electrolyte.
[0078] Example 4
[0079] A locally high-concentration electrolyte for achieving high energy density and long cycle life lithium metal batteries comprises lithium bisfluorosulfonylimide (LiFSI), dimethyl ethylene glycol (DME), and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether; the molar ratio of lithium bisfluorosulfonylimide (LiFSI), dimethyl ethylene glycol (DME), and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether is 1:1.6:3.
[0080] The method for preparing a locally high-concentration electrolyte for a lithium metal battery with high energy density and long cycle life includes the following steps:
[0081] In a glove box filled with argon atmosphere, lithium salt is dissolved in the solvent ethylene glycol dimethyl ether and magnetically stirred until the lithium salt is completely dissolved. The stirring speed is usually 400 rpm. Then, the diluent 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether is added, and magnetic stirring is continued until the mixture is homogeneous to obtain a locally high-concentration electrolyte.
[0082] Example 5
[0083] A locally high-concentration electrolyte for achieving high energy density and long cycle life lithium metal batteries comprises lithium bisfluorosulfonylimide (LiFSI), dimethyl ethylene glycol (DME), and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether; the molar ratio of lithium bisfluorosulfonylimide (LiFSI), dimethyl ethylene glycol (DME), and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether is 1:1.8:3.
[0084] The method for preparing a locally high-concentration electrolyte for a lithium metal battery with high energy density and long cycle life includes the following steps:
[0085] In a glove box filled with argon atmosphere, lithium salt is dissolved in the solvent ethylene glycol dimethyl ether and magnetically stirred until the lithium salt is completely dissolved. The stirring speed is usually 380 rpm. Then, the diluent 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether is added, and magnetic stirring is continued until the mixture is homogeneous to obtain a locally high-concentration electrolyte.
[0086] Example 6
[0087] A locally high-concentration electrolyte for achieving high energy density and long cycle life lithium metal batteries comprises lithium bisfluorosulfonylimide (LiFSI), dimethyl ethylene glycol (DME), and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether; the molar ratio of lithium bisfluorosulfonylimide (LiFSI), dimethyl ethylene glycol (DME), and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether is 1:2:3.
[0088] The method for preparing a locally high-concentration electrolyte for a lithium metal battery with high energy density and long cycle life includes the following steps:
[0089] In a glove box filled with argon atmosphere, lithium salt is dissolved in the solvent ethylene glycol dimethyl ether and magnetically stirred until the lithium salt is completely dissolved. The stirring speed is usually 400 rpm. Then, the diluent 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether is added and magnetically stirred until the mixture is homogeneous to obtain a locally high-concentration electrolyte.
[0090] This invention provides a locally high-concentration electrolyte for lithium metal batteries that achieves high energy density and long cycle life. The electrolyte viscosity is reduced and wetting properties are improved using 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether diluent. Simultaneously, the 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether diluent enters the Li... + The solvation shell inhibits the oxidative decomposition of solvent molecules. Furthermore, it promotes uniform lithium metal deposition, forming a robust and stable SEI film, suppressing side reactions between the electrode and electrolyte; and enhancing the stable long-cycle capability of lithium metal batteries, even at ultra-high cathode loads (~20 mg / cm³). 2 Under the coupling condition of a thin lithium anode (50 μm), a lithium metal battery can achieve 500 stable long-term cycles at 25°C with an average coulombic efficiency exceeding 99.9%. This locally high-concentration electrolyte enables a 500 Wh / kg lithium metal pouch battery to cycle stably for 90 cycles at 25°C.
[0091] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. It should be noted that for those skilled in the art and any person skilled in the art, any equivalent substitutions or changes made to the technical solution and inventive concept of the present invention without departing from the overall concept of the present invention, as well as any changes and improvements made, should also be considered within the scope of protection of the present invention.
Claims
1. A locally high-concentration electrolyte for achieving high energy density and long cycle life lithium metal batteries, characterized in that: The mixture includes lithium salt, ether solvent, and diluent. The lithium salt is lithium difluorosulfonylimide, the ether solvent is ethylene glycol dimethyl ether, and the diluent is 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether. The molar concentration of lithium difluorosulfonylimide is 1.4~1.7 mol / L. The molar ratio of lithium difluorosulfonylimide, ethylene glycol dimethyl ether, and 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether is 1:(1~2):
3. The diluent 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether enters the Li... + The solvation shell participates in the solvation structure of lithium ions, forming a solvation structure dominated by contact ion pairs / aggregated ion pairs.
2. The method for preparing a locally high-concentration electrolyte for a lithium metal battery with high energy density and long cycle life according to claim 1, characterized in that: Includes the following steps: Under a protective atmosphere, lithium salt is completely dissolved in an ether solvent, then a diluent is added, and the mixture is magnetically stirred until homogeneous to obtain a locally high-concentration electrolyte.
3. The application of a locally high-concentration electrolyte as described in claim 1 or 2, which enables high energy density and long cycle life in lithium metal batteries.
4. A lithium metal battery, characterized in that: It includes a positive electrode, a negative electrode, and a locally high-concentration electrolyte as described in claim 1 or 2, wherein the positive electrode is a nickel-cobalt-manganese layered oxide and the negative electrode is lithium metal.
5. The lithium metal battery according to claim 4, characterized in that: Nickel-cobalt-manganese layered oxide is LiNi 0.8 Mn 0.1 Co 0.1 O2.
6. A lithium metal pouch battery, comprising a positive electrode, a negative electrode, and a locally high-concentration electrolyte as described in claim 1 or 2 for achieving a high energy density and long cycle life lithium metal battery, wherein, The positive electrode is a nickel-cobalt-manganese layered oxide, and the negative electrode is lithium metal; the nickel-cobalt-manganese layered oxide is LiNi. 0.83 Mn 0.05 Co 0.12 O2.
Citation Information
Patent Citations
Electrolyte and lithium ion battery
CN118073654A