CN116914264A

CN116914264A - Electrolyte, preparation method thereof, battery, electrochemical device and assembly

Info

Publication number: CN116914264A
Application number: CN202311182346.3A
Authority: CN
Inventors: 林楷睿
Original assignee: Botai Semiconductor Technologies Co ltd
Current assignee: Botai Semiconductor Technologies Co ltd
Priority date: 2023-09-14
Filing date: 2023-09-14
Publication date: 2023-10-20
Anticipated expiration: 2043-09-14
Also published as: CN116914264B

Abstract

The invention belongs to the technical field of electrolyte, and in particular relates to electrolyte, a preparation method thereof, a battery, an electrochemical device and a component, wherein the electrolyte comprises electrolyte salt and a solvent, the solvent comprises a first solvent and a second solvent, and the volume ratio of the first solvent to the second solvent is 2-5:1, and the dielectric constant epsilon of the electrolyte is 5-7, and the donor number DN of the electrolyte is 10-13. The first solvent comprises a compound shown in a formula I, and the second solvent comprises a compound shown in a formula II. The invention can balance various performances of the electrolyte, not only remarkably enhances solvation capability of the solvent and the electrolyte salt, has no layering problem of the electrolyte, has strong universality, but also has fire extinguishing effect, high heat conductivity and excellent electrochemical performance, and is clean electrolyte.

Description

Electrolyte, preparation method thereof, battery, electrochemical device and assembly

Technical Field

The invention belongs to the technical field of electrolyte, and particularly relates to electrolyte, a preparation method thereof, a battery, an electrochemical device and a component.

Background

In recent years, secure and robust electrical Energy Storage Systems (ESS) have become increasingly important worldwide. Battery storage has been widely used for Electric Vehicles (EVs) and large power grids. However, in essence, the temperature of the battery varies during charge and discharge due to the internal resistance of the battery itself, which is unavoidable. Thermal Runaway (TR) caused by uneven or local excessive temperature of the battery has become a serious threat to further development of the battery, especially when the battery reaches a dense energy storage level. Its danger severely affects its performance in dense energy storage applications.

In the current electric vehicle industry, real Battery Thermal Management (BTM) technology will have an immediate impact. Air cooling/liquid cooling is commonly used to improve BTM response speed. These BTM technologies typically account for 6% -10% of the battery energy, with relatively low weight and volume ratios, particularly volume ratios, most only exceeding 30%. This consumption of energy may be interpreted as a lower efficiency of heat transfer in the battery. The large volume cooling technology reduces the volume ratio, so that the weight of the cooling technology is greatly increased, and the weight ratio is reduced. The search and development of a more efficient, low energy, low weight BTM technology is of great practical importance. Increasing the thermal response speed at the monomer level is critical to the mitigation of BTM burden and electrode engineering is currently considered a promising approach. By adjusting the composition of the electrodes, the physical solid state heat conduction can be adjusted to improve the response speed. However, the improvement provided by this method is difficult to compare with the effect of liquid phase heat conduction.

Electrolyte engineering is considered as an economical and practical way to solve the underlying problem, namely to accelerate heat transfer and avoid localized high temperatures. To achieve this goal, it is necessary to develop and adapt the available electrolyte with efficient heat transfer characteristics. In the context of the rapid increase in energy demand, new solvents for the composition of electrolyte salts must be economical and capable of mass production to avoid increasing electrolyte salt costs. The selection of an appropriate commercially available solvent is a good choice.

However, on the electrochemical level, on the one hand, a practical problem is that the parasitic reaction between the metal negative electrode and the electrolyte leads to irreversibility of the negative electrode cycle, thus leading to cracking of the solid electrolyte salt interface (SEI), porous coating morphology and formation of metal dendrites, affecting the cycle performance of the battery, limiting the progress of efficient electrolytes. By adjusting the electrolyte components, SEI chemistry and metal anode morphology can be tailored to improve cycle performance. Inorganic-based SEI is considered as a promising approach to optimize electrochemical performance, and efforts to introduce inorganic elements F into electrolytes are continually underway. However, most F, C and H containing compounds have high Global Warming Potential (GWP) and Ozone Depletion Potential (ODP), which are not compatible with the sustainable development goals of the battery industry. Therefore, there is a need to develop a clean F source for the electrolyte.

On the other hand, in order to meet the requirement of incombustibility, some solvents such as trimethyl phosphate and triethyl phosphate have been developed. However, these solvents do not form stable SEI on the surface of graphite or metal cathodes and their stable operation must depend on the salt concentration in the trimethyl phosphate electrolyte. However, high salt concentrations inevitably affect cost, viscosity and electrode wettability. From an industrial production point of view, the salt concentration cannot be too high, but the durability of the battery should be sufficient, as this directly affects the price and profits of the battery. It is important to explore electrodes in the laboratory that have thousands of stable cycles and that can recover electrolyte. In view of all these factors, it is a great challenge to develop electrolytes with high heat transfer characteristics, intrinsically safe physical properties, beneficial SEI chemistry, and viable environmental and economic sustainable application routes.

Disclosure of Invention

The invention aims to overcome the defect that the electrolyte in the prior art cannot balance the incombustibility, the high heat conduction characteristic, the battery cycle performance and the clean energy, and provides an electrolyte, a preparation method thereof, a battery, an electrochemical device and a component.

In order to achieve the above object, in a first aspect, the present invention provides an electrolyte comprising an electrolyte salt and a solvent, the solvent comprising a first solvent and a second solvent, the first solvent and the second solvent having a volume ratio of 2 to 5:1. preferably 3.5-5:1, and the dielectric constant epsilon of the electrolyte is 5-7, preferably 6-7, and the donor number DN of the electrolyte is 10-13, preferably 12-13.

Wherein the first solvent comprises a compound of formula one:

formula I;

the second solvent comprises a compound of formula II:

and formula II.

In some preferred embodiments of the present invention, the solvent further comprises a non-aqueous organic solvent, the first solvent comprises 40% -50% of the total volume of the solvent, the sum of the volumes of the non-aqueous organic solvent and the first solvent comprises 80% -95% of the total volume of the solvent, and the volume of the second solvent comprises 5% -20% of the total volume of the solvent.

More preferably, the volume of the second solvent is 5% -15% of the total volume of the solvent.

Further preferably, the nonaqueous organic solvent is selected from alcohol ether solvents including at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, diglyme, triglyme, and tetraglyme, and ester solvents including at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ -butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, butyl propionate.

Further preferably, the nonaqueous organic solvent is selected from at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether and diethylene glycol diethyl ether.

In some preferred embodiments of the invention, the electrolyte salt has a solubility in the solvent above 1M at room temperature.

In some preferred embodiments of the present invention, the electrolyte salt is an organic lithium salt or an organic potassium salt, the organic lithium salt is selected from at least one of lithium bis (difluorosulfonimide), lithium bis (oxalato) borate, lithium difluoro (oxalato) borate, and lithium bis (trifluoromethylsulfonyl) imide, and the organic potassium salt is selected from at least one of potassium bis (difluorosulfonimide), potassium bis (oxalato) borate, potassium difluoro (oxalato) borate, and potassium bis (trifluoromethylsulfonyl) imide.

In a second aspect, the present invention provides a method for preparing an electrolyte, where the electrolyte is the electrolyte in the first aspect, and the method includes: the first solvent and the second solvent are subjected to first mixing to obtain a solvent, and then the electrolyte salt is introduced into the solvent for second stirring and mixing.

In some preferred embodiments of the invention, the method of making further comprises: firstly, mixing a first solvent and a non-aqueous organic solvent to obtain a mixed solvent, and then introducing the mixed solvent into a second solvent to perform the first mixing.

In a third aspect, the present invention provides a metal ion battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the electrolyte is the electrolyte in the first aspect.

In the third aspect, preferably, the metal in the metal ion battery is selected from one or more of potassium, lithium and sodium.

In a fourth aspect, the present invention provides a metal battery, which comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the electrolyte is the electrolyte in the first aspect.

In the fourth aspect, preferably, the metal in the metal battery is selected from one or more of potassium, lithium and sodium.

In a fifth aspect, the present invention provides an electrochemical device comprising the electrolyte according to the first aspect, and the electrolyte is directly injected into the electrochemical device.

In a sixth aspect, the present invention provides an assembly comprising the battery of the third or fourth aspect or the electrochemical device of the fifth aspect.

The beneficial effects are that:

1,2,3,4, 5-decafluoro-3-methoxy-2- (trifluoromethyl) pentane (a compound of formula one) is now used as the main component of electrical coolant formulations, has excellent heat transfer properties and incombustibility, and has a low Global Warming Potential (GWP) value, ozone Depletion Potential (ODP) of 0, relative to other hydrofluorocarbons. The inventors of the present invention innovatively used the compound for an electrolyte in hopes of obtaining a liquid electrolyte capable of realizing direct injection into an electrode, i.e., obtaining an electrolyte formulation excellent in thermal conductivity and self-extinguishing property. The formulation needs to meet both electrochemical and thermal conductivity requirements.

The inventors have found that the first solvent has a low solvating power with an electrolyte salt (e.g., K salt) due to the strong bond energy and low polarity of the C-F bond of the compound of formula one in the first solvent and acts mainly as an inert agent, which makes it difficult to satisfy all criteria of the electrolyte when the first solvent is used as a single electrolyte salt solvent. Whereas the ether solvents commonly used in the prior art (e.g.DME) have a relatively high dielectric constant ε (e.g.ε _DME =7.5) with a compound of formula (ε) _{A compound of formula (I)} =6.1) may not meet certain electrochemical performance requirements, as high epsilon solvents always lead to defective SEI. It has been found experimentally that equal volumes of the compound of formula one and DME solvent are successfully mixed, but with the addition of an electrolyte salt (e.g., an acyl imideAmine salts) due to the difference in ionic solubility between the compound of formula one and DME, expressed as their Donor Number (DN) _{A compound of formula (I)} = 7.8，DN _DME =20). Based on this, the present invention has been further studied.

According to the technical scheme, the first solvent and the second solvent (with ultralow epsilon and DN) with proper proportions are particularly added for coupling, the F atomic ratio is higher, the F atomic ratio is coordinated with cations of electrolyte salt, a beneficial interface mainly containing inorganic matters is formed, various properties of the electrolyte can be balanced, the solvation capacity of the solvent and the electrolyte salt is obviously enhanced, the layering problem of the electrolyte is avoided, the universality is strong, and the fire extinguishing effect and the high thermal conductivity are realized; and the first solvent has a low Global Warming Potential (GWP) and low Ozone Depletion Potential (ODP), is a clean solvent; and the dielectric constant epsilon of the electrolyte is reduced to 5-7, the donor number DN is reduced to 10-13, and SEI dissolution is not caused by the composition, so that the electrolyte can have excellent electrochemical properties (such as excellent cycle performance, high battery capacity, long-time operation and the like) when applied. The electrolyte provided by the invention has low/incombustibility, low viscosity and high enough heat conductivity, so that the electrolyte has excellent fire extinguishing effect and high heat conductivity, is a recyclable electrolyte capable of realizing real-time thermal response, can be used as a liquid coolant of a built-in battery, can be combined with a direct electrode cooling technology, can monitor the temperature of a battery pack more easily, thereby relieving the load of BTM, and improves the GCTP/VCTP ratio and available energy of the battery pack, and has high safety due to fire extinguishing performance. Under the same conditions, if the ratio of the first solvent to the second solvent is not proper, if the first solvent is excessive, the electrolyte is layered due to the excessive difference of the solubility of the first solvent and other solvents (especially, the non-aqueous organic solvent which is preferably added) on the salt, and if the second solvent is excessive, the SEI is unstable due to the reduced content of the electrolyte F; if the dielectric constant epsilon of the electrolyte is too high, SEI is easily dissolved, and if the donor number DN of the electrolyte is too high, high voltage stability is reduced.

The electrolyte of the invention can realize the direct cooling configuration of the electrode, has wide application range,for example, is particularly suitable for lithium ion/potassium ion batteries. In some embodiments, the electrolyte of the present invention achieves long-life cycling (cycle life exceeding 11 months, exceeding 8400 h) of K I K batteries, stable operation of graphite batteries (e.g., li I graphite batteries: 80% capacity retention after 1200 cycles; K I graphite batteries: 93% capacity retention after 2000 cycles), and high coulombic efficiency (e.g., 99.6%) operation of K I Cu batteries. In addition, the electrolyte can expand the electrochemical window and improve the stability of the high voltage side, and the cycle performance of the cathode is also improved along with the expansion of the electrochemical window, such as Prussian blue (PB, K) _0.220 Fe[Fe(CN) ₆ ] _0.805 •4.01H ₂ O) the cycle times of the potassium ion battery serving as the positive electrode exceeds 700 times, the capacity is not attenuated, the cycle life of the lithium ion battery serving as the positive electrode exceeds 5400 times, and the capacity retention rate is 80%; for another example, a 18650 cell of 1.2 Ah with an N/P ratio below commercial level and 1.08 achieved a lifetime of over 1000 cycles and a capacity retention of 91.7%.

The electrolyte can be recovered after the battery is applied, and the recovered electrolyte still has the same effect as the original electrolyte in terms of maintaining the structure and the cycle stability of the positive electrode material (such as LFP).

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a graph showing the change of temperature with time in the electrolyte thermal conductivity test of example 1 and comparative example 1.

Fig. 2 is a graph showing the cycle performance of the electrolytes of example 1 and comparative examples 1 and 2, respectively, in a k|k battery.

Fig. 3 is a graph of the run time comparisons of the electrolyte of example 1 and the electrolyte of comparative example 1, and their low and high concentration electrolytes, as well as other conventional electrolytes, respectively, used in K battery.

Fig. 4 is a graph of coulombic efficiency versus cycle number for both electrolytes of example 1 and comparative example 1 used in a k|cu cell (i.e., top graph), and a typical charge-discharge curve (i.e., bottom voltage versus capacity graph) for cycling in a k|cu cell using the electrolyte of example 1.

Fig. 5 is a graph showing the final effects of the fire extinguishing experiments of the electrolytes of example 1 and comparative example 1 and air and water.

Detailed Description

In the present disclosure, the terms "first," "second," and "second" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implying a number of technical features being indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein. Wherein the terms "optional" and "optionally" mean either comprising or not comprising (or may not be present).

In a first aspect, the present invention provides an electrolyte comprising an electrolyte salt and a solvent, the solvent comprising a first solvent and a second solvent, the first solvent and the second solvent being in a volume ratio of from 2 to 5:1, and the dielectric constant epsilon of the electrolyte is 5-7, and the donor number DN of the electrolyte is 10-13.

Wherein the first solvent comprises a compound of formula one:

formula I;

the second solvent comprises a compound of formula II:

and formula II.

The boiling point and viscosity of the electrolyte can meet the requirements of battery electrolyte, and the electrolyte can normally work in a temperature range which can be born by a metal negative electrode. Wherein the viscosity of the compound of formula II is higher than that of the compound of formula I (or other added solvents such as non-aqueous organic solvents) but still lower than commercial Ethylene Carbonate (EC) so that the ionic conductivity of the electrolyte of the present invention is reduced compared to conventional ether electrolytes, but still very close to that of carbonate electrolytes so as not to interfere with ion transport.

Preferably, the volume ratio of the first solvent to the second solvent is 3.5-5:1. The preferred scheme is more beneficial to improving the coulombic efficiency and the cycle life of the battery in application.

Preferably, the dielectric constant epsilon of the electrolyte is 6-7, and the donor number DN of the electrolyte is 12-13. The preferable scheme is more favorable for the full fusion of the solvent and avoids the possible occurrence of solvent layering.

Preferably, the solvent further comprises a non-aqueous organic solvent. According to the invention, the nonaqueous organic solvent is added, so that the solubility of the solvent to the electrolyte salt can be improved, and the first solvent and the second solvent are matched, so that the control of the anion-cation dissociation and solvation structure of the salt is facilitated.

In some preferred embodiments of the present invention, the first solvent comprises 40% -50% of the total volume of the solvent, the sum of the volumes of the non-aqueous organic solvent and the first solvent comprises 80% -95% of the total volume of the solvent, and the volume of the second solvent comprises 5% -20% of the total volume of the solvent. According to the preferred scheme, the non-aqueous organic solvent has a proper ratio, so that the solubility of the solvent to the electrolyte salt can be controlled, and the solubility of various electrolyte salts can be improved more easily; and the first solvent has proper proportion, can promote the boiling point of electrolyte, strengthen fire extinguishing performance, promote heat conductivity, increase electrolyte F content, do benefit to the safe operation of battery. While if the volume ratio of the first solvent is too large, the electrolyte is layered, and if the volume ratio of the first solvent is too small, the safety performance of the electrolyte is reduced.

More preferably, the volume of the second solvent is 5% -15% of the total volume of the solvent. By adopting the preferable scheme of the invention, the second solvent has relatively proper duty ratio, can serve as a stabilizer while avoiding electrolyte layering, promotes the fusion of other two solvents, and is more beneficial to improving the cycle performance of the electrolyte.

In the present invention, preferably, the ratio of the sum of the volumes of the nonaqueous organic solvent and the first solvent to the volume of the second solvent is 7-9:1, and the volume ratio of the nonaqueous organic solvent to the first solvent is 0.8-1.2:1. According to the preferred scheme, the proportion of each component of the solvent is proper, so that the battery performance is facilitated.

Preferably, the nonaqueous organic solvent is selected from alcohol ether solvents and ester solvents.

Further preferably, the alcohol ether solvent includes at least one of ethylene glycol dimethyl ether (DME), ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether.

Further preferably, the ester solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, γ -butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, butyl propionate.

Further preferably, the nonaqueous organic solvent is selected from at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether and diethylene glycol diethyl ether. According to the preferred scheme, the nonaqueous organic solvent is properly selected, so that stable SEI can be formed, and the improvement of the coulombic efficiency of the battery is facilitated.

In addition to the first solvent, the second solvent and the nonaqueous organic solvent, other conventional auxiliary agents or additives can be added to promote the fusion of the compound of formula one and the nonaqueous organic solvent, so that the possible occurrence of solvent delamination is further avoided, and fluoroethylene carbonate (FEC), fluoroethylene carbonate (DFEC), 2-trifluoroethyl ether (BTFE) and the like can be added (or selected).

In some preferred embodiments of the invention, the electrolyte salt has a solubility in the solvent above 1M at room temperature, thereby facilitating dissolution of more electrolyte salt. It is understood that "M" represents the molar concentration in this work, i.e. 1M refers to one mole of electrolyte salt dissolved in one liter of solvent.

The type of the electrolyte salt may be selected by those skilled in the art according to actual needs as long as the electrolyte salt is dissolved in a solvent and satisfies a desired function. Preferably, the electrolyte salt is an organolithium salt or an organopotassium salt.

In some preferred embodiments of the present invention, the organolithium salt is selected from lithium bis-difluorosulfonimide (LiFSI), lithium hexafluorophosphate (LiPF) ₆ ) At least one of lithium bis (oxalato) borate (LiBOB), lithium difluoro (LiDFOB) oxalato borate (LiTFSI), and lithium bis (trifluoromethylsulfonyl) imide.

Preferably, the organic potassium salt is selected from at least one of potassium bis (difluorosulfimide), potassium bis (oxalato) borate, potassium difluoro (oxalato) borate, and potassium bis (trifluoromethylsulfonyl) imide.

In the preferred types of the organic lithium salt and the organic potassium salt, the solubility of the solvent and the electrolyte salt and the voltage window can be further enhanced, and the configuration of the anode and the cathode of the battery with wide voltage is facilitated.

In the prior art, not all electrolyte formulations can realize high-performance operation of different batteries through simple electrolyte salt replacement, because the salt replacement process can suffer from problems of incomplete salt dissolution, partial electrolyte salt layering, mismatching of solvent electrodes and the like. The electrolyte provided by the invention has universality to electrolyte salts such as lithium salt, potassium salt and the like in the prior art, and can completely dissolve the electrolyte salts, so that the solvent electrodes are matched.

In some preferred embodiments of the invention, the method of making further comprises: firstly, mixing a first solvent and a non-aqueous organic solvent to obtain a mixed solvent, and then introducing the mixed solvent into a second solvent to perform the first mixing. According to the preferred scheme, a specific mixing sequence is adopted, so that salt can be quickly dissolved, and industrial preparation of electrolyte is facilitated.

The electrolyte provided by the invention has wide universality and is especially suitable for lithium batteries and potassium batteries.

In the third aspect, preferably, the metal in the metal ion battery is selected from one or more of potassium, lithium and sodium. For the ion battery of the corresponding metal, those skilled in the art can select the positive electrode, the negative electrode and the separator thereof in the prior art, and the present invention is not limited thereto.

When the metal in the metal ion battery is lithium, the negative electrode may be selected from, for example, graphite. The positive electrode may be selected from, for example, lithium iron phosphate, layered oxides, and the like.

When the metal in the metal ion battery is potassium, the negative electrode may be selected from copper, graphite, and the like, and the positive electrode may be selected from organic dye perylene brilliant violet red 29 (PTCDI), prussian blue, polyanion compounds, and the like, for example.

When the metal in the metal ion battery is sodium, the negative electrode may be selected from, for example, hard carbon, alloy metal, and the like. The positive electrode may be selected from, for example, prussian blue, polyanion compounds, and the like.

In the fourth aspect, preferably, the metal in the metal battery is selected from one or more of potassium, lithium and sodium. For the metal battery of the corresponding metal, the positive electrode and the negative electrode, and the separator thereof can be selected by those skilled in the art, and the present invention is not limited thereto.

When the metal in the metal battery is lithium, the negative electrode includes any one of lithium metal, lithium carbon composite material and lithium silicon composite material, and the positive electrode may be selected from lithium iron phosphate, layered oxide and the like, for example.

When the metal in the metal battery is potassium, the negative electrode may be selected from, for example, potassium metal, copper, graphite, and the like. The positive electrode may be selected from, for example, organic dyes perylene brilliant violet 29 (PTCDI), prussian blue, polyanion compounds, and the like.

When the metal in the metal battery is sodium, the negative electrode may be selected from sodium metal, hard carbon, alloy metal, and the like, for example. The positive electrode may be selected from, for example, prussian blue, polyanion compounds, and the like.

The following detailed description of the embodiments of the invention is exemplary and is merely illustrative of the invention and not to be construed as limiting the invention.

Example 1

The preparation method of the electrolyte comprises the following steps: DME and a compound of formula I (marked as A) are uniformly mixed in a volume ratio of 1:1 to form a mixed solvent, and then the mixed solvent is added into a compound of formula II (marked as B), wherein the volume ratio of the compound of formula II to the mixed solvent is 1:9. after the three solvents are uniformly mixed, KFSI with the solubility of 1M in the solvents is added, and stirring is continuously carried out, so that the final electrolyte 1M KFSI DME/A-B is obtained. The dielectric constant epsilon of the electrolyte was 6.3 and the donor number DN of the electrolyte was 12.7.

The resulting electrolyte was tested for heat transfer characteristics by an infrared camera and a heated L-shaped metal wrench, with the heated L-shaped metal wrench specifically placed in the electrolyte. The thermal conductivity of the electrolyte was observed by an infrared camera as shown in fig. 1, and it can be seen that the time for the metal wrench to cool from 73 ℃ to 28 ℃ in the 1M KFSI DME/a-B electrolyte was 1.5 seconds, and the temperature difference inside the electrolyte was not significant, indicating uniform and rapid heat transfer.

In the spray fire extinguishing test, the candle flame is sprayed by adopting 1M KFSI DME/A-B electrolyte, and the candle flame is extinguished quickly as shown in FIG. 5. The electrolyte is a nonflammable substance, and does not cause fire. The electrolyte can play a good role in extinguishing fire even if the equipment catches fire due to other reasons. In the spray fire extinguishing test under the same conditions, both air and water cannot play a role in extinguishing a fire, as shown in fig. 5.

Example 2

The procedure of example 1 was followed except that KFSI was replaced with LiFSI. The final electrolyte salt 1M LiFSI DME/A-B was obtained. The dielectric constant epsilon of the electrolyte was 6.3 and the donor number DN of the electrolyte was 12.7.

In the same heat conduction characteristic test, substantially the same effect as in example 1 was obtained, and the temperature difference inside the electrolyte was not significant, indicating uniform and rapid heat transfer. In the same spray fire extinguishing test, the electrolyte of the embodiment can play a good role in extinguishing fire.

Example 3

The procedure of example 1 was followed, except that the amount of the compound of formula II was changed so that the volume ratio of the compound of formula II to the mixed solvent was 2:8. the dielectric constant epsilon of the electrolyte was 5.88 and the donor number DN of the electrolyte was 11.5.

In the same heat conduction characteristic test, the time for the metal wrench to cool from 80 ℃ to 28 ℃ in the electrolyte was 2 seconds, and the temperature difference inside the electrolyte was not significant, indicating uniform and rapid heat transfer.

In the same spray fire extinguishing test, the electrolyte of the embodiment can play a good role in extinguishing fire.

Example 4

With reference to the method of example 1, except that fluoroethylene carbonate (FEC) was further included in the electrolyte as a co-solvent of the formula II, the volume of the component was 5% of the volume of the formula II, and the mixture obtained by mixing it with the formula II was compressed to be equal to the original volume of the formula II; the component is introduced before the step of mixing the compound of formula II with the mixed solvent, i.e. by mixing with the compound of formula II, compressing the resulting mixture and then mixing with the mixed solvent.

In the same heat transfer characteristic test, the temperature difference inside the electrolyte was not significant, indicating uniform and rapid heat transfer. In the same spray fire extinguishing test, the electrolyte of the embodiment can play a good role in extinguishing fire.

Comparative example 1

The procedure of example 1 was followed except that the compound of formula one and the compound of formula two were not introduced to give a 1M KFSI DME electrolyte. The dielectric constant epsilon of the electrolyte was 7.5 and the donor number DN of the electrolyte was 20.

In the corresponding heat conduction test, as shown in fig. 1, the metal wrench took 4.0 seconds to cool from 76 ℃ to 30 ℃, which severely impeded heat transfer inside the battery equipped with the electrolyte, and it was difficult to achieve real-time Battery Thermal Management (BTM). Moreover, it is easily observed that uneven heat transfer and significant differences in the internal temperature of the electrolyte are easily observed at 2.0 seconds and 3.0 seconds therein, which are manifested as color abrupt changes and significant color delamination. The battery provided with the electrolyte has a risk of causing Thermal Runaway (TR) due to local high temperature caused by uneven heat transfer.

Ignition tests indicate that the 1M KFSI DME electrolyte is flammable and may be the ignition source. The spray test shown in fig. 5 further shows that the electrolyte has a combustion supporting effect, which can increase the flame of the candle, and becomes a great fire hazard.

Comparative example 2

The procedure of example 1 was followed except that no compound of formula one was introduced to give 1M KFSI DME-B. The dielectric constant epsilon of the electrolyte was 7 and the donor number DN of the electrolyte was 18.

In the same heat conduction characteristic test, the time for the metal wrench to cool from 75 ℃ to 28 ℃ in the electrolyte is 4 seconds, and the temperature difference inside the electrolyte is remarkable, which indicates that the heat transfer is uneven and local high temperature is caused.

In the same spray fire extinguishing test, the electrolyte of this comparative example can extinguish fire but requires multiple continuous sprays to extinguish fire, the spraying time and the amount of spray liquid are significantly higher than those of example 1, and the effect is inferior to that of example 1.

Comparative example 3

The procedure of example 1 was followed except that no compound of formula II was introduced to give 1M KFSI DME/A. The electrolyte is obviously layered and cannot be used.

Comparative example 4

The procedure of example 1 is followed except that the methyl ether group of the compound of formula one is modified to be a propyl ether group. The dielectric constant epsilon of the electrolyte was 8.1 and the donor number DN of the electrolyte was 15.

In the same heat conduction characteristic test, the time for the metal wrench to cool from 80 ℃ to 30 ℃ in the electrolyte is 2 seconds, and the temperature difference inside the electrolyte is not significant, which indicates that the heat transfer is uniform and rapid.

Electrochemical Performance test examples

The electrolytes obtained in the above examples and comparative examples were used for testing the electrochemical properties in k||k battery, k||cu battery, 18650 lithium battery, and the results are shown in table 1.

Also, the cycle performance of the electrolytes of example 1 and comparative example 1, comparative example 2 in the k|k battery is shown in fig. 2, the running time of the electrolytes of example 1 and comparative example 1 and other conventional electrolytes (in which the volume ratio of the mixed solvents is equal unless otherwise stated) in the k|k battery is shown in fig. 3, fig. 4 is a graph of change in coulombic efficiency versus cycle number (i.e., top graph) of the two electrolytes using example 1 and comparative example 1 in the k|cu battery, and a typical charge-discharge curve (i.e., bottom voltage versus capacity graph) of the electrolyte of example 1 in the k|cu battery.

TABLE 1

Note that: N/A indicates inapplicability.

From the above examples and comparative examples and tables 1 and 1 to 4, it can be seen that, compared with the comparative examples, the solution of the electrolyte according to the embodiment of the present invention can balance various properties of the electrolyte, not only significantly enhance solvation ability of the solvent and the electrolyte salt, but also has fire extinguishing effect and high thermal conductivity as well as excellent electrochemical properties. Comparative examples 1 to 3 and comparative example 4, which are not within the scope of the present invention, either do not satisfy both the fire extinguishing effect and the thermal conductivity as well as the electrochemical properties, or the electrolyte may be layered.

Further, according to the embodiment 1 and the embodiment 3, the solvent with the preferable proportion is adopted, so that the improvement of coulombic efficiency and cycle life is facilitated.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. An electrolyte comprising an electrolyte salt and a solvent, wherein the solvent comprises a first solvent and a second solvent, and the volume ratio of the first solvent to the second solvent is 2-5:1, wherein the dielectric constant epsilon of the electrolyte is 5-7, and the donor number DN of the electrolyte is 10-13;

wherein the first solvent comprises a compound of formula one:

formula I;

the second solvent comprises a compound of formula II:

and formula II.

2. The electrolyte of claim 1 wherein the solvent further comprises a non-aqueous organic solvent, the first solvent comprising 40% -50% of the total volume of the solvent, the sum of the volumes of the non-aqueous organic solvent and the first solvent comprising 80% -95% of the total volume of the solvent, the volume of the second solvent comprising 5% -20% of the total volume of the solvent.

3. The electrolyte of claim 2, wherein the volume of the second solvent is 5% -15% of the total volume of the solvent.

4. The electrolyte according to claim 2, wherein the nonaqueous organic solvent is selected from alcohol ether solvents including at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether, and ester solvents including at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ -butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, butyl propionate.

5. The electrolyte according to claim 2, wherein the nonaqueous organic solvent is selected from at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether.

6. The electrolyte of claim 1, wherein the electrolyte salt has a solubility in a solvent of 1M or more at room temperature;

and/or the number of the groups of groups,

the electrolyte salt is organic lithium salt or organic potassium salt, the organic lithium salt is at least one selected from lithium bis (difluorosulfimide), lithium bis (oxalato) borate, lithium difluoro (oxalato) borate and lithium bis (trifluoromethylsulfonyl) imide, and the organic potassium salt is at least one selected from potassium bis (difluorosulfimide), potassium bis (oxalato) borate, potassium difluoro (oxalato) borate and potassium bis (trifluoromethylsulfonyl) imide.

7. A method for producing an electrolyte, characterized in that the electrolyte is the electrolyte according to any one of claims 1 to 6, and the method comprises: the first solvent and the second solvent are subjected to first mixing to obtain a solvent, and then the electrolyte salt is introduced into the solvent for second stirring and mixing.

8. The method of manufacturing according to claim 7, further comprising: firstly, mixing a first solvent and a non-aqueous organic solvent to obtain a mixed solvent, and then introducing the mixed solvent into a second solvent to perform the first mixing.

9. A metal ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is the electrolyte of any one of claims 1-6.

10. The metal-ion battery of claim 9, wherein the metal in the metal-ion battery is selected from one or more of potassium, lithium, sodium.

11. A metal battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is the electrolyte according to any one of claims 1 to 6.

12. The metal battery of claim 11, wherein the metal in the metal battery is selected from one or more of potassium, lithium, sodium.

13. An electrochemical device comprising the electrolyte according to any one of claims 1 to 6, and the electrolyte is directly injected into the interior of the electrochemical device.

14. An assembly comprising a battery according to any one of claims 9-12 or an electrochemical device according to claim 13.