High-voltage fast-charging electrolyte and dual-ion battery

Abstract

The application relates to a high-voltage fast-charging type electrolyte and a dual-ion battery, and belongs to the technical field of batteries. The technical problems of poor high-voltage resistance of a commercial electrolyte to a dual-ion battery, fast capacity attenuation in application to a battery, low coulomb efficiency and poor compatibility with positive and negative electrodes in the prior art are solved. The application improves the oxidation resistance of the electrolyte by fluorination adjustment of a main solvent ethylene carbonate (EC), so that the electrolyte can operate in a high-voltage environment, and the synergistic solvation of anions is realized by matching the main solvent propylene carbonate (PC), so that the anions can realize efficient intercalation and deintercalation of a graphite positive electrode in a solvent co-intercalation mode, and meanwhile, due to the absence of a desolvation process, the battery can operate well under high rate and low temperature conditions. The high-voltage fast-charging type electrolyte has a wide electrochemical window, good compatibility with positive and negative electrodes, and greatly improves the cycle life of the high-voltage fast-charging type dual-ion battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and specifically to a high-voltage fast-charging electrolyte and a dual-ion battery that are particularly suitable for dual-ion batteries. Background Technology

[0002] Dual-ion batteries (DIBs) have gained greater interest than lithium-ion batteries (LIBs) in high-efficiency energy storage due to their advantages such as high operating voltage (3.8-4.6V), high charging cut-off voltage (≥5V), high material availability, low cost, good safety, and fast charging performance. The working mechanism of DIBs is based on storing cations and anions at the negative and positive electrodes respectively during charging and discharging. Despite progress, their practical application is still hindered by negative issues such as limited capacity and cycle stability. These problems have spurred research into suitable electrode materials with highly reversible capacity and electrolytes with high oxidation stability and sufficient reaction kinetics for active ions. In DIBs, the electrolyte is the sole source of both cations and anions, making its selection crucial and directly impacting the electrochemical performance of the battery. Currently available commercial electrolytes suffer from poor high-voltage performance in DIBs, rapid capacity decay, low coulombic efficiency, poor fast charging performance, and poor compatibility with the positive and negative electrodes. Therefore, developing novel electrolytes is urgently needed to improve battery life. Especially when batteries operate at high cutoff voltages, the electrolyte undergoes severe oxidative decomposition. Therefore, designing novel high-voltage, fast-charging electrolytes for use in dual-ion batteries is imperative.

[0003] Ethylene carbonate (EC) is a key component of commercially available electrolytes, capable of forming excellent solid electrolyte films (CEI and SEI) at the interfaces between the positive and negative electrodes and the electrolyte. However, its high melting point of 36.4°C leads to increased electrolyte viscosity and decreased ionic conductivity at low temperatures, severely hindering its application at lower temperatures. EC also exhibits poor oxidation resistance when used as the primary solvent in electrolytes, failing to meet the high-voltage operation requirements of dual-ion batteries. Furthermore, EC inhibits the anion insertion into the graphite positive electrode during charging, significantly limiting the performance of dual-ion batteries. Introducing the advantages of EC into dual-ion batteries while mitigating its disadvantages represents a promising electrolyte design strategy for dual-ion batteries. Summary of the Invention

[0004] To address the technical problems of existing commercial electrolytes in dual-ion batteries, such as poor high-voltage performance, rapid capacity decay, low coulombic efficiency, and poor compatibility with positive and negative electrodes, this invention provides a high-voltage fast-charging electrolyte and a dual-ion battery using this electrolyte, particularly suitable for dual-ion batteries. The electrolyte of this invention involves varying degrees of fluorine substitution treatment of EC molecules, combined with propylene carbonate (PC) as the main solvent. PC stabilizes fluorinated ethylene carbonate and also participates in the solvation sheath of anions, thereby achieving synergistic solvation of anions. With the addition of a low-viscosity diluent, this invention achieves a high-voltage fast-charging electrolyte, which is then applied to dual-ion batteries. This high-voltage fast-charging electrolyte has a wide electrochemical window, good compatibility with both positive and negative electrodes, and the ability to operate over a wide temperature range, significantly improving the cycle life of dual-ion batteries and broadening their application areas.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0006] This invention provides a high-voltage fast-charging electrolyte, composed of a lithium salt, a main solvent, and a low-viscosity co-solvent; the main solvent accounts for 20% to 100% of the volume in the solvent, and the low-viscosity co-solvent accounts for 0% to 80% of the volume in the solvent.

[0007] The main solvent is a mixture of fluorinated ethylene carbonate or its derivatives and propylene carbonate (PC);

[0008] The fluorinated ethylene carbonate has the following structural formula:

[0009] or

[0010] Where R1 and R2 are both F or CH x F 3-x x = 0, 1 or 2, and the number of R1 and R2 is one or more.

[0011] In the above technical solution, preferably, the fluorinated ethylene carbonate or its derivatives include, but are not limited to, at least one of the following compounds:

[0012] (1) Monofluoroethylene carbonate (FEC) ;

[0013] (2) 4,5-cis-difluoroethylene carbonate ;

[0014] (3) 4,5-trans-difluoroethylene carbonate ;

[0015] (4) 4,4-Difluoroethylene carbonate ;

[0016] (5) Ethylene trifluorocarbonate ;

[0017] (6) Tetrafluoroethylene carbonate .

[0018] In the above technical solution, preferably, the volume percentage of fluorinated ethylene carbonate or its derivatives in the main solvent is 30% to 95%, and the volume percentage of propylene carbonate (PC) in the main solvent is 5% to 70%.

[0019] In the above technical solution, it is further preferred that the volume percentage of fluorinated ethylene carbonate or its derivatives in the main solvent is 55%–95%, and the volume percentage of propylene carbonate (PC) in the main solvent is 5%–45%. Even more preferably, the volume percentage of fluorinated ethylene carbonate or its derivatives in the main solvent is 65%–85%, and the volume percentage of propylene carbonate (PC) in the main solvent is 15%–35%.

[0020] In the above technical solution, preferably, the low-viscosity co-solvent is methyl difluoroacetate (Methyl difluoroacetate). ), methyl trifluoroacetate ( ), Ethyl fluoroacetate ( ), ethyl difluoroacetate ( ), ethyl trifluoroacetate ( ), hexafluoroisopropyl methyl ether ( ), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether ( ), 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether ( ), 2,2,2-trifluoroethyl ether ( ) and tri(trifluoroethoxy)methane ( At least one of the following.

[0021] In the above technical solution, preferably, the lithium salt is an inorganic anionic lithium salt and / or an organic anionic lithium salt.

[0022] In the above technical solution, it is further preferred that the lithium salt is at least one selected from lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate borate) (LiBOB), lithium trifluoromethanesulfonate (LiCF3SO3), lithium difluorodioxalate phosphate (LiDODFP), lithium tetrafluorooxalate phosphate (LiOTFP), and lithium difluorophosphate (LiPO2F2). More preferably, the lithium salt is at least one selected from lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium difluorooxalate borate (LiDFOB), and lithium bis(fluorosulfonyl)imide (LiFSI).

[0023] In the above technical solution, preferably, the molar concentration of the lithium salt in the electrolyte is 0.2 mol / L to the saturation concentration. More preferably, the molar concentration of the lithium salt in the electrolyte is 0.75 mol / L to 4 mol / L.

[0024] The present invention also provides a dual-ion battery comprising the above-mentioned high-voltage fast-charging electrolyte.

[0025] In the above technical solution, preferably, the dual-ion battery includes a casing and a cell sealed inside the casing. The cell includes a positive electrode, a negative electrode, a separator between the positive and negative electrodes, and an electrolyte. The electrolyte is the high-voltage fast-charging electrolyte of the present invention.

[0026] This invention does not impose any special restrictions on the positive electrode material used. The active material of the positive electrode is a material that can reversibly insert / extract anions from the electrolyte. Those skilled in the art can select and adjust the material according to the actual situation, product performance, and quality requirements.

[0027] There are no special restrictions on the negative electrode material used. The active material of the negative electrode is a material that can undergo a reversible electrochemical reaction with alkali metal ions. Those skilled in the art can select and adjust it according to the actual situation, product performance and quality requirements.

[0028] There are no special restrictions on the material of the diaphragm. The diaphragm is a material that can separate the positive and negative electrodes and allow ions of the electrolyte to pass through. Those skilled in the art can select and adjust it according to the actual situation, product performance and quality requirements.

[0029] The beneficial effects of this invention are:

[0030] This invention improves the electrolyte's antioxidant properties by fluorinating the main solvent ethylene carbonate (EC), enabling it to operate under high voltage conditions. Furthermore, by combining it with the main solvent propylene carbonate (PC), it achieves synergistic solvation of anions, allowing for efficient insertion and extraction of graphite cathodes via solvent co-intercalation. Simultaneously, due to the absence of a desolvation process, the battery can operate well at high rates and low temperatures. The high-voltage fast-charging electrolyte of this invention has a wide electrochemical window and good compatibility with both positive and negative electrodes, enabling dual-ion batteries using this electrolyte to operate at high cutoff voltages, thus achieving higher energy density, significantly improving cycle life, and broadening the application range of dual-ion batteries. In addition, the high concentration of the electrolyte reduces the amount of solvent used, allowing the battery to operate with a sufficient source of active carriers, thereby increasing the overall energy density of the battery. Moreover, the wide liquid window of the solvent components ensures that dual-ion batteries using this electrolyte can operate over a wide temperature range.

[0031] The capacity and cycle performance of the dual-ion battery containing a high-voltage, low-temperature electrolyte provided by this invention were characterized by charge-discharge tests at room temperature and low temperature. Experimental results show that the dual-ion battery using the high-voltage fast-charging electrolyte provided by this invention can achieve a discharge capacity density of ~100 mAh g⁻¹ at 25°C using the graphite cathode. -1 After 1000 cycles, the capacity shows almost no decay; at 0℃, the graphite cathode can stably output ~95mAh g. -1 It achieves a high discharge capacity density and can cycle over 100 times; it can operate stably and output ~100mAh g at an ultra-high cutoff voltage of 5.4V. -1 The high capacity density of the electrolyte of this invention results in dual-ion batteries exhibiting excellent capacity retention and cycle stability, thus expanding the temperature application range of dual-ion batteries. Attached Figure Description

[0032] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0033] Figure 1 This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles for the batteries prepared in Comparative Examples 1 and 2 of this invention.

[0034] Figure 2 This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles of the battery prepared in Example 1 of the present invention.

[0035] Figure 3 This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles of the battery prepared in Example 2 of the present invention.

[0036] Figure 4 This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles of the battery prepared in Example 3 of the present invention.

[0037] Figure 5 This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles of the battery prepared in Example 4 of the present invention.

[0038] Figure 6 This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles of the battery prepared in Example 5 of the present invention.

[0039] Figure 7 This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles of the battery prepared in Example 6 of the present invention.

[0040] Figure 8 This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles of the battery prepared in Example 7 of the present invention.

[0041] Figure 9 This is a graph showing the relationship between the positive electrode discharge capacity density and the cutoff voltage of the battery prepared in Example 8 of the present invention.

[0042] Figure 10 This is a graph showing the relationship between the positive electrode discharge capacity density and the cutoff voltage of the full cell prepared in Example 9 of the present invention.

[0043] Figure 11 This is a graph showing the relationship between the positive electrode discharge capacity density and the cutoff voltage of the battery prepared in Example 10 of the present invention. Detailed Implementation

[0044] The technical solution of the present invention will be further illustrated below through embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] All raw materials used in this invention are not particularly restricted in their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0046] There are no particular restrictions on the purity of any raw materials used in this invention, but analytical grade is preferred.

[0047] This invention provides a high-voltage fast-charging electrolyte, which is composed of a lithium salt, a main solvent, and a low-viscosity co-solvent. This invention does not impose any particular limitation on the application of the high-voltage fast-charging electrolyte; any application familiar to those skilled in the art is acceptable. Preferably, this invention relates to an electrolyte for dual-ion batteries.

[0048] Comparative Example 1

[0049] A 1 mol / L lithium hexafluorophosphate (LiPF6) solution was prepared in a glove box, wherein the solvent of the solution was ethylene monofluorocarbonate (FEC), and the prepared solution was allowed to stand for 12 hours. Using the above solution as the electrolyte, coin cells were assembled in the glove box using a CR2032 casing made of 304 stainless steel, wherein the negative electrode active material was lithium foil, the positive electrode active material was flake graphite blank, and the separator was glass fiber; the battery was placed in a 25°C environment for constant current charge-discharge testing, with a charge-discharge voltage range of 3–5.2V.

[0050] Comparative Example 2

[0051] A 1 mol / L lithium hexafluorophosphate (LiPF6) solution was prepared in a glove box, wherein the solvent of the solution was propylene carbonate (PC), and the prepared solution was allowed to stand for 12 hours. Using the above solution as the electrolyte, coin cells were assembled in the glove box using a CR2032 casing made of 304 stainless steel. The negative electrode active material was lithium foil, the positive electrode active material was flake graphite blank, and the separator was glass fiber. The batteries were subjected to constant current charge-discharge cycle testing at 25°C, with a charge-discharge voltage range of 3–5.2V and a charge-discharge rate of 1C (1C = 100 mAh g⁻¹). -1 ).

[0052] Figure 1 This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles for the batteries prepared in Comparative Examples 1 and 2 of this invention; Figure 1 It is known that the dual-ion battery using an electrolyte of 1 mol / L lithium hexafluorophosphate (LiPF6) dissolved in fluoroethylene carbonate (FEC) experiences extremely rapid capacity decay, becoming almost unusable after 30 cycles, indicating poor compatibility between this electrolyte and the graphite cathode. A dual-ion battery using an electrolyte of 1 mol / L lithium hexafluorophosphate (LiPF6) dissolved in propylene carbonate (PC) achieves a capacity of 60 mAh / g. -1 The discharge capacity density is around 100%, and there is no significant decay after 100 cycles. It is compatible with graphite cathodes, but its performance is poor.

[0053] Example 1

[0054] A 1 mol / L lithium hexafluorophosphate (LiPF6) solution was prepared in a glove box. The main solvent of the solution was a mixture of ethylene monofluorocarbonate (FEC) and propylene carbonate (PC), with a PC volume content of 25% and a FEC volume content of 75%. The prepared solution was allowed to stand for 12 hours. Using the above solution as the electrolyte, coin cells were assembled in a glove box using a CR2032 casing made of 304 stainless steel. The negative electrode active material was lithium foil, the positive electrode active material was flake graphite blank, and the separator was glass fiber. The battery was placed in a 25°C environment for constant current charge-discharge rate testing, with a charge-discharge voltage of 3–5.2V.

[0055] Figure 2 This is a graph showing the relationship between the positive electrode discharge capacity density and the constant current charge / discharge rate of the battery prepared in Example 1 of this invention; Figure 2 It is known that in a battery where 1 mol / L lithium hexafluorophosphate (LiPF6) is dissolved in a mixed organic solvent of 25% (volume content) propylene carbonate (PC) as the electrolyte, the battery can achieve a charge / discharge rate range of 1C to 10C (1C = 100 mAh g⁻¹). -1 During constant current charging and discharging, the graphite positive electrode can output ~100 mAh g. -1 With a discharge capacity density of ~85 mAh g⁻¹, under constant current charge-discharge at a rate of 10C, the graphite cathode can output ~85 mAh g⁻¹. -1 With a discharge capacity density of ~45 mAh g⁻¹, under constant current charge-discharge at a rate of 20C, the graphite cathode can output ~45 mAh g⁻¹. -1 The discharge capacity density. This test reflects that the dual-ion battery using the electrolyte of this invention has excellent high-power discharge performance, that is, it has very good fast-charging performance.

[0056] Example 2

[0057] A 1 mol / L lithium hexafluorophosphate (LiPF6) solution was prepared in a glove box. The main solvent of this solution was a mixture of ethylene monofluorocarbonate (FEC) and propylene carbonate (PC), with a PC volume content of 35% and a FEC volume content of 65%. The prepared solution was allowed to stand for 12 hours. Using this solution as the electrolyte, coin cells were assembled in a glove box using a CR2032 casing made of 304 stainless steel. The negative electrode active material was lithium foil, the positive electrode active material was flake graphite blank, and the separator was glass fiber. The batteries were subjected to constant current charge-discharge cycle testing at 25°C, with a charge-discharge voltage of 3–5.2 V and a charge-discharge rate of 1C (1C = 100 mAh g⁻¹). -1 ).

[0058] Figure 3This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles for the battery prepared in Example 2 of this invention. This test demonstrates that the dual-ion battery using the electrolyte of this invention has the ability to operate stably at a high cutoff voltage of 5.2V.

[0059] Example 3

[0060] A 1 mol / L lithium hexafluorophosphate (LiPF6) solution was prepared in a glove box. The main solvent of this solution was a mixture of ethylene monofluorocarbonate (FEC) and propylene carbonate (PC), with PC comprising 30% by volume and FEC comprising 70% by volume. The prepared solution was allowed to stand for 12 hours. Using this solution as the electrolyte, coin cells were assembled in a glove box using a CR2032 casing made of 304 stainless steel. The negative electrode active material was lithium foil, the positive electrode active material was flake graphite blank, and the separator was glass fiber. The batteries were subjected to constant current charge-discharge cycle testing at 25°C, with a charge-discharge voltage of 3–5.3 V and a charge-discharge rate of 1C (1C = 100 mAh g⁻¹). -1 ).

[0061] Figure 4 This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles for the battery prepared in Example 3 of this invention. This test demonstrates that the dual-ion battery using the electrolyte of this invention has the ability to operate stably at a high cutoff voltage of 5.3V.

[0062] Example 4

[0063] A 1 mol / L lithium hexafluorophosphate (LiPF6) solution was prepared in a glove box. The main solvent of this solution was a mixture of ethylene monofluorocarbonate (FEC) and propylene carbonate (PC), with a PC volume content of 15% and a FEC volume content of 85%. The prepared solution was allowed to stand for 12 hours. Using this solution as the electrolyte, coin cells were assembled in a glove box using a CR2032 casing made of 304 stainless steel. The negative electrode active material was lithium foil, the positive electrode active material was flake graphite blank, and the separator was glass fiber. The batteries were subjected to constant current charge-discharge cycle testing at 25°C, with a charge-discharge voltage of 3–5.4 V and a charge-discharge rate of 1C (1C = 100 mAh g⁻¹). -1 ).

[0064] Figure 5 This is a graph showing the relationship between the discharge capacity density and the number of cycles of the positive electrode battery prepared in Example 4 of this invention. This test demonstrates that the dual-ion battery using the electrolyte of this invention has the ability to operate stably at a high cutoff voltage of 5.4V.

[0065] Example 5

[0066] A 1 mol / L lithium hexafluorophosphate (LiPF6) solution was prepared in a glove box. The main solvent of this solution was a mixture of ethylene monofluorocarbonate (FEC) and propylene carbonate (PC), with PC comprising 30% by volume and FEC comprising 70% by volume. The prepared solution was allowed to stand for 12 hours. Using this solution as the electrolyte, coin cells were assembled in a glove box using a CR2032 casing made of 304 stainless steel. The negative electrode active material was pre-lithiated spherical natural graphite, and the positive electrode active material was also spherical natural graphite, with a mass ratio of 1:1. The separator was made of glass fiber. The battery was subjected to constant current charge-discharge cycle testing at 25°C, with a charge-discharge voltage of 2.75–5.2V and a charge-discharge rate of 4C (1C = 100 mAh g⁻¹). -1 ).

[0067] Figure 6 This is a graph showing the relationship between the discharge capacity density and the number of cycles of the positive electrode battery prepared in Example 5 of the present invention. This test demonstrates that the dual-ion battery using the electrolyte of the present invention has the ability to operate stably at high charge-discharge rates under a high cutoff voltage of 5.2V.

[0068] Example 6

[0069] A 1 mol / L lithium hexafluorophosphate (LiPF6) solution was prepared in a glove box. The main solvent of this solution was a mixture of ethylene monofluorocarbonate (FEC) and propylene carbonate (PC), with PC comprising 30% by volume and FEC comprising 70% by volume. The prepared solution was allowed to stand for 12 hours. Using this solution as the electrolyte, coin cells were assembled in a glove box using a CR2032 casing made of 304 stainless steel. The negative electrode active material was lithium foil, the positive electrode active material was flake graphite, and the separator was glass fiber. After 10 pre-activation cycles at 5C at room temperature, the cells were placed at 0°C for constant current charge-discharge cycle testing. The charge-discharge voltage was 2–5.2V, and the charge-discharge rate was 1C (1C = 100 mAh g⁻¹). -1 ).

[0070] Figure 7 This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles for the battery prepared in Example 6 of this invention. This test reflects the ability of the dual-ion battery using the electrolyte of this invention to operate stably at a high rate of charge and discharge at a low temperature and a high cutoff voltage of 5.2V.

[0071] Example 7

[0072] A 1 mol / L lithium hexafluorophosphate (LiPF6) solution was prepared in a glove box. The main solvent of the solution was a mixture of ethylene monofluorocarbonate (FEC) and propylene carbonate (PC), with a volume content of 30% for PC and 70% for FEC. The prepared solution was allowed to stand for 12 hours. Using the above solution as the electrolyte, coin cells were assembled in a glove box using a CR2032 casing made of 304 stainless steel. The negative electrode active material was pre-lithiated spherical natural graphite, and the positive electrode active material was also spherical natural graphite, with a mass ratio of 1:1. The separator was made of glass fiber. After 10 pre-activation cycles at 5C at room temperature, the batteries were placed in a 0°C environment for constant current charge-discharge cycle testing. The charge-discharge voltage was 2–5.2V, and the charge rate was 1C (1C = 100 mAh g⁻¹). -1 The discharge rate is 2C (1C = 100 mAh g). -1 ).

[0073] Figure 8 This is a graph showing the relationship between the positive electrode discharge capacity density and the number of cycles for the battery prepared in Example 7 of this invention. This test reflects the ability of the dual-ion full battery using the electrolyte of this invention to operate stably at a high rate of charge and discharge at a low temperature and a high cutoff voltage of 5.2V.

[0074] Example 8

[0075] A 2 mol / L lithium hexafluorophosphate (LiPF6) solution was prepared in a glove box. The solvent in this solution was a mixture of ethylene monofluorocarbonate (FEC) and propylene carbonate (PC), with PC comprising 30% by volume and FEC comprising 70% by volume. The prepared solution was allowed to stand for 12 hours. Using this solution as the electrolyte, coin cells were assembled in a glove box using a CR2032 casing made of 304 stainless steel. The negative electrode active material was lithium foil, and the positive electrode active material was D... 50 The battery is constructed from 127μm natural flake graphite, with a glass fiber separator; the battery is operated at room temperature at 1C (1C = 100 mAh g⁻¹). -1 The battery was subjected to a cutoff voltage step test at a charge / discharge voltage range of 3 to a specified cutoff voltage. The cutoff voltages were 4.8V, 4.85V, 4.9V, 4.95V, 5V, 5.05V, 5.1V, 5.15V, 5.2V, 5.25V, 5.3V, 5.35V, and 5.4V. The battery was run for 5 cycles at each cutoff voltage.

[0076] Figure 9This is a graph showing the relationship between the positive electrode discharge capacity density and the cutoff voltage of the battery prepared in Example 8 of this invention. This test demonstrates the discharge capacity density of the dual-ion battery using the electrolyte of this invention under different cutoff voltages, reflecting the excellent adaptability of the dual-ion battery using the electrolyte of this invention to different voltages.

[0077] Example 9

[0078] A solution of 3 mol / L lithium difluorosulfonyl imide (LiFSI) + 1 mol / L lithium hexafluorophosphate (LiPF6) (i.e., a salt concentration of 4 mol / L) was prepared in a glove box. The main solvent of this solution was a mixture of ethylene monofluorocarbonate (FEC) and propylene carbonate (PC), with propylene carbonate (PC) comprising 30% by volume and ethylene monofluorocarbonate (FEC) comprising 70% by volume. The low-viscosity co-solvent was methyl trifluoroacetate, and the volume ratio of the main solvent to the low-viscosity co-solvent was 1:1. The prepared solution was allowed to stand for 12 hours. Using this solution as the electrolyte, coin cells were assembled in a glove box using a CR2032 casing made of 304 stainless steel. The negative electrode active material was lithium foil, and the positive electrode active material was D... 50 The battery is constructed from 127μm natural flake graphite, with a glass fiber separator; the battery is operated at room temperature at 1C (1C = 100 mAh g⁻¹). -1 The battery was subjected to a cutoff voltage step test at a charge / discharge voltage range of 3 to a specified cutoff voltage. The cutoff voltages were 4.8V, 4.85V, 4.9V, 4.95V, 5V, 5.05V, 5.1V, 5.15V, 5.2V, 5.25V, 5.3V, and 5.35V. The battery was run for 5 cycles at each cutoff voltage.

[0079] Figure 10 This is a graph showing the relationship between the positive electrode discharge capacity density and the cutoff voltage of the full cell prepared in Example 9 of this invention. This test demonstrates the discharge capacity density of the dual-ion battery using the electrolyte of this invention under different cutoff voltages, reflecting the excellent adaptability of the dual-ion battery using the electrolyte of this invention to different voltages.

[0080] Example 10

[0081] A 1 mol / L lithium hexafluorophosphate (LiPF6) solution was prepared in a glove box. The main solvent of this solution was a mixture of 4,5-trans-difluoroethylene carbonate and propylene carbonate (PC), with a PC volume content of 5% and a 4,5-trans-difluoroethylene carbonate volume content of 95%. The prepared solution was allowed to stand for 12 hours. Using this solution as the electrolyte, coin cells were assembled in a glove box using a CR2032 casing made of 304 stainless steel. The negative electrode active material was lithium foil, the positive electrode active material was flake graphite blank, and the separator was glass fiber. The batteries were subjected to constant current charge-discharge cycle testing at 25°C, with a charge-discharge voltage of 3–5.2 V and a charge-discharge rate of 1C (1C = 100 mAh g⁻¹). -1 ).

[0082] Figure 11 This is a graph showing the relationship between the discharge capacity density and the number of cycles for the battery prepared in Example 10 of this invention. This test reflects the ability of the dual-ion battery using the electrolyte of this invention to operate stably at a high cutoff voltage of 5.2V.

[0083] As demonstrated by the examples and comparative examples, the electrolyte prepared in this invention successfully combines the excellent properties of different cyclic ester solvents through solvation structure regulation. This allows the new electrolyte system to maintain good battery performance at high rates and good cycle life at high voltages. Batteries using this electrolyte system can still cycle at a good rate for a long time at 0°C, and the output capacity density can reach more than 80% of that at 25°C.

[0084] The volume percentages of lithium salt, main solvent, and low-viscosity co-solvent used in the above embodiments can be any substance or any volume percentage within the above-defined range, and the types can also be other substances within the above-defined range, which will not be listed here.

[0085] 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. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A dual-ion battery, comprising a casing and a cell sealed within the casing, the cell comprising a positive electrode, a negative electrode, a separator between the positive and negative electrodes, and an electrolyte; characterized in that, The active material of the positive electrode is a material capable of reversibly inserting / extracting anions from the electrolyte, and the active material of the negative electrode is a material capable of undergoing a reversible electrochemical reaction with alkali metal ions. The electrolyte is a high-voltage fast-charging electrolyte, composed of lithium salt, main solvent, and low-viscosity co-solvent; the main solvent accounts for 20% to 100% of the volume in the solvent, and the low-viscosity co-solvent accounts for 0% to 20% of the volume in the solvent; The main solvent is a mixture of fluorinated ethylene carbonate and propylene carbonate (PC); The fluorinated ethylene carbonate is at least one of the following compounds: (1) Monofluoroethylene carbonate (FEC) ; (2) 4,5-cis-difluoroethylene carbonate ; (3) 4,5-trans-difluoroethylene carbonate ; (4) 4,4-Difluoroethylene carbonate ; (5) Ethylene trifluorocarbonate ; (6) Tetrafluoroethylene carbonate ; The main solvent contains fluorinated ethylene carbonate at a volume percentage of 65%–85% and propylene carbonate (PC) at a volume percentage of 15%–35%.

2. The dual-ion battery according to claim 1, characterized in that, The low-viscosity co-solvent is methyl difluoroacetate. Methyl trifluoroacetate Ethyl fluoroacetate Ethyl difluoroacetate Ethyl trifluoroacetate Hexafluoroisopropyl methyl ether 1,1,2,2-Tetrafluoroethyl-2,2,3,3-Tetrafluoropropyl ether 1,1,2,2-Tetrafluoroethyl-2,2,2-trifluoroethyl ether 2,2,2-trifluoroethyl ether and tri(trifluoroethoxy)methane At least one of them.

3. The dual-ion battery according to claim 1, characterized in that, The lithium salt is at least one of the inorganic and organic anionic lithium salts of lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluorooxalate borate (LiDFOB), lithium bis(oxalate borate) borate (LiBOB), lithium tetrafluoroborate (LiBF4), and lithium difluorophosphate (LiPO2F2).

4. The dual-ion battery according to claim 1, characterized in that, The molar concentration of the lithium salt in the electrolyte is 0.2 mol / L to the saturation concentration.

Images