Electrolyte additive, electrolyte, lithium ion battery, battery pack and electric equipment

Abstract

The invention discloses an electrolyte additive, an electrolyte, a lithium ion battery, a battery pack and electric equipment. The electrolyte additive comprises a compound containing an oxalate group and an alkynyl group. According to the electrolyte additive disclosed by the invention, the oxalate group and the electrolyte salt in the electrolyte additive form a low-impedance and compact protective film on the surfaces of a positive electrode and a negative electrode of a battery, so that the side reaction of the positive electrode and the electrolyte is inhibited, meanwhile, the stability of an SEI film of the negative electrode is improved, and the high-temperature performance and the cycle performance are improved. In addition, alkynyl is easily subjected to reduction reaction on the surface of the negative electrode and oxidation reaction on the surface of the positive electrode, so that electrochemical polymerization is carried out to generate a polymer passive film. The two functional groups (oxalate group and alkynyl) have a synergistic effect, so that the advantages of the two functional groups can be fully exerted, the quality of a positive electrode-electrolyte interface (CEI) and a negative electrode-electrolyte interface (SEI) is improved, the cycle life of the battery can be effectively prolonged, and meanwhile, the battery can have both high-temperature performance and gas production performance.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytes, and in particular, to an electrolyte additive, an electrolyte, a lithium-ion battery, a battery pack, and an electrical device using the same. Background Art

[0002] Lithium-ion batteries are a crucial part of the power battery field in the current new energy vehicle industry. With the rapid development of the new energy vehicle industry, consumers have put forward higher requirements for the cruising range and application scenarios, that is, the battery needs to have a higher energy density and be able to balance the high and low temperature performance. In related technologies, high-voltage cathode active materials are often used to increase the energy density of the battery. However, at high voltages, the cathode active materials have high oxidizing properties, which easily exacerbate the side reactions at the cathode / electrolyte interface, resulting in battery swelling, and this situation is particularly serious under high-temperature conditions. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the first object of the present invention is to provide an electrolyte that can improve the quality of the cathode-electrolyte interface (CEI) and the anode-electrolyte interface (SEI), effectively improve the cycle life of the battery, and enable the battery to balance the high-temperature performance and the gas generation performance.

[0004] The second object of the present invention is to provide an electrolyte additive.

[0005] The third object of the present invention is to provide a lithium-ion battery.

[0006] The fourth object of the present invention is to provide a battery pack.

[0007] The fifth object of the present invention is to provide an electrical device using the same.

[0008] The electrolyte additive according to the first aspect embodiment of the present invention includes a compound containing an oxalate group and an alkyne group.

[0009] The electrolyte additive according to an embodiment of the present invention, by adding the electrolyte additive to the electrolyte, the oxalate group and the electrolyte salt in the electrolyte additive form a low-impedance and dense protective film on the surfaces of the positive and negative electrodes of the battery, inhibiting the side reaction between the positive electrode and the electrolyte, while increasing the stability of the SEI film on the negative electrode, improving the high-temperature performance and cycling performance, so that the battery has a high high-temperature storage capacity retention rate, a low high-temperature storage gas production expansion rate, and good cycling performance. In addition, the alkynyl group in the molecular structure of the above electrolyte additive is prone to undergo a reduction reaction on the surface of the negative electrode and an oxidation reaction on the surface of the positive electrode, thereby undergoing electrochemical polymerization to generate a polymer passivation film. The synergistic effect of the above two functional groups (oxalate group and alkynyl group) can give full play to the advantages of both, improve the quality of the cathode-electrolyte interface (CEI) and the anode-electrolyte interface (SEI), effectively improve the cycle life of the battery, and at the same time enable the battery to take into account the high-temperature performance and gas production performance.

[0010] According to some embodiments of the present invention, the electrolyte additive includes at least one of the compounds represented by the following formula; , In the formula, x and y are independent positive integers; 1 ≤ x ≤ 5; 1 ≤ y ≤ 5; R1 to R6 are each independently selected from a hydrogen atom, a trimethylsilyl group, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an unsaturated hydrocarbon group having 2 to 5 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an alkaryl group having 7 to 10 carbon atoms; wherein, the hydrogen atoms in the alkyl group having 1 to 5 carbon atoms, the unsaturated hydrocarbon group having 2 to 5 carbon atoms, the aryl group having 6 to 10 carbon atoms, and the alkaryl group having 7 to 10 carbon atoms may be partially or completely substituted by substituents; preferably, R5 and R6 are each independently selected from a hydrogen atom and a trimethylsilyl group.

[0011] According to some embodiments of the present invention, the electrolyte additive includes at least one of the compounds represented by formula (I-1) - formula (I-6), wherein the compounds of formula (I-1) - formula (I-6) are: I-1 I-2 I-3 I-4 I-5 I-6.

[0012] The electrolyte according to an embodiment of the second aspect of the present invention includes an electrolyte additive, and the electrolyte additive is the electrolyte additive according to the embodiment of the first aspect of the present invention above; the content of the electrolyte additive in the electrolyte is 0.05% to 11% by mass percentage; preferably, the content of the first additive in the electrolyte is 0.5% to 3% by mass percentage.

[0013] According to some embodiments of the present invention, the electrolyte further includes a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium difluoro bis(oxalato) phosphate, lithium tetrafluorooxalate phosphate, lithium bis(trifluoromethylsulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0014] According to some embodiments of the present invention, the concentration of the lithium salt is 0.1 mol / L to 2 mol / L, and preferably, the concentration of the lithium salt is 0.9 mol / L to 1.3 mol / L.

[0015] According to some embodiments of the present invention, when the lithium salt includes lithium bis(fluorosulfonyl)imide, the concentration of the lithium bis(fluorosulfonyl)imide is 0.1 mol / L to 0.4 mol / L.

[0016] According to some embodiments of the present invention, the electrolyte further includes a solvent, and the solvent includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.

[0017] The lithium ion battery according to an embodiment of the third aspect of the present invention includes the electrolyte additive according to the embodiment of the first aspect of the present invention above; or at least one electrolyte according to the embodiment of the second aspect of the present invention above.

[0018] The battery pack according to an embodiment of the fourth aspect of the present invention includes the lithium ion battery according to the embodiment of the third aspect of the present invention above.

[0019] The electrical equipment according to an embodiment of the fifth aspect of the present invention includes the lithium ion battery according to the embodiment of the third aspect of the present invention above; or the battery pack according to the embodiment of the fourth aspect of the present invention above.

[0020] The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. Detailed Embodiments

[0021] Reference will be made below to describe the electrolyte additive according to an embodiment of the first aspect of the present invention.

[0022] The electrolyte additive according to the embodiment of the first aspect of the present invention includes a compound containing an oxalate group and an alkynyl group.

[0023] Adding the above electrolyte additive (an oxalate compound containing an unsaturated bond) and an electrolyte salt (such as a lithium salt containing fluorine and phosphorus elements (LiPF6)) to the electrolyte, the above electrolyte additive and the electrolyte salt can undergo an in-situ reaction before formation to generate an oxalate phosphate compound. Moreover, the above electrolyte additive and the electrolyte salt are prone to generate a lithium salt-type additive through an in-situ reaction, which can provide better electrochemical performance for the battery, such as improving the energy density, extending the cycle life, enhancing the charge and discharge efficiency, etc., and contributing to reducing the capacity attenuation and performance degradation of the battery, and improving the reliability and service life of the battery. Among them, the oxalate group in the electrolyte additive and the P-F group in the electrolyte salt can form a low-impedance and dense protective film on the surfaces of the positive and negative electrodes of the battery, inhibiting the side reaction between the positive electrode and the electrolyte, while increasing the stability of the SEI film on the negative electrode, improving the high-temperature performance and cycle performance. The lithium-ion battery has a high high-temperature storage capacity retention rate, a low high-temperature storage gas generation expansion rate, and good cycle performance. In addition, the molecular structure of the above electrolyte additive contains an unsaturated bond (alkynyl group), which is prone to undergo a reduction reaction on the surface of the negative electrode and an oxidation reaction on the surface of the positive electrode, thereby undergoing electrochemical polymerization to generate a polymer passivation film. The synergistic effect of the above two functional groups (oxalate group and alkynyl group) can give full play to the advantages of both, improve the quality of the positive electrode-electrolyte interface (CEI) and the negative electrode-electrolyte interface (SEI), effectively improve the cycle life of the battery, and at the same time enable the battery to take into account the high-temperature performance and gas generation performance.

[0024] In addition, compared with solvent molecules, the above electrolyte additive has a higher HOMO energy level and a lower oxidation potential, and can be preferentially oxidized and decomposed on the surface of the positive electrode to form a complete, dense and uniform protective film (CEI), thereby improving the stability of the positive electrode / electrolyte interface. The stable interfacial protective film effectively reduces the contact between the electrolyte and the active material, inhibits the dissolution of transition metal ions, reduces the gas generation of the battery, and improves the cycle life and storage performance of the battery. At the same time, compared with directly adding a lithium salt-type additive, the raw material cost of the oxalate compound containing an unsaturated bond used in the electrolyte additive of the present invention is low, which not only ensures good performance but also greatly reduces the cost of the electrolyte.

[0025] At the same time, the electrolyte additive can also participate in film formation (SEI) on the negative electrode. The above compound decomposes during the first cycle, adjusts and modifies the components and morphology of the SEI film on the negative electrode, can increase the content of inorganic components in the SEI film, and effectively reduce the interfacial impedance of the negative electrode. Therefore, the battery prepared with this electrolyte can maintain excellent long-term cycle performance and storage performance at high voltages.

[0026] The electrolyte additive according to an embodiment of the present invention, by adding the electrolyte additive to the electrolyte, the oxalate group and the electrolyte salt in the electrolyte additive form a low-impedance and dense protective film on the surfaces of the positive and negative electrodes of the battery, inhibiting the side reaction between the positive electrode and the electrolyte. At the same time, the stability of the negative electrode SEI film is increased, the high-temperature performance and the cycle performance are improved, so that the battery has a high high-temperature storage capacity retention rate, a low high-temperature storage gas generation expansion rate, and good cycle performance. In addition, the alkynyl group in the molecular structure of the above electrolyte additive is prone to undergo a reduction reaction on the surface of the negative electrode and an oxidation reaction on the surface of the positive electrode, thereby undergoing electrochemical polymerization to generate a polymer passivation film. The synergistic effect of the above two functional groups (oxalate group and alkynyl group) can give full play to the advantages of both, improve the quality of the cathode-electrolyte interface (CEI) and the anode-electrolyte interface (SEI), effectively improve the cycle life of the battery, and at the same time enable the battery to take into account the high-temperature performance and the gas generation performance.

[0027] According to some embodiments of the present invention, the electrolyte additive includes at least one of the compounds represented by the following formula; , In the formula, x and y are independent positive integers; 1≤x≤5; 1≤y≤5; R1 to R6 are each independently selected from a hydrogen atom, a trimethylsilyl group, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an unsaturated hydrocarbon group having 2 to 5 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an alkaryl group having 7 to 10 carbon atoms; wherein, the hydrogen atoms in the alkyl group having 1 to 5 carbon atoms, the unsaturated hydrocarbon group having 2 to 5 carbon atoms, the aryl group having 6 to 10 carbon atoms, and the alkaryl group having 7 to 10 carbon atoms may be partially or completely substituted by substituents; preferably, R5 and R6 are each independently selected from a hydrogen atom and a trimethylsilyl group.

[0028] By adjusting the groups of R1 to R6 and the number of branches, it is beneficial to adjust the physical and chemical properties of the electrolyte additive, so as to facilitate adjusting the type of the electrolyte additive according to different electrolyte requirements, thereby improving the applicability of the electrolyte additive. In addition, by controlling the lengths of the main chain and the branches to be small, it is beneficial to control the length of the solvent molecules, avoid an increase in the viscosity of the electrolyte caused by the too long length of the molecules of the electrolyte additive, and avoid the excessive concentration and aggregation of the molecules of the electrolyte additive in the electrolyte, which is beneficial to improving the uniformity of the electrolyte, and further improving the conductive stability and cycle stability of the battery.

[0029] According to some embodiments of the present invention, the electrolyte additive includes at least one of the compounds represented by formula (I-1) - formula (I-6), wherein the compounds of formula (I-1) - formula (I-6) are: I-1 I-2 I-3 I-4 I-5 I-6.

[0030] The oxalate compounds of formula (I-1) - formula (I-6) all have two unsaturated bonds (alkynyl groups), so they can form stable interfacial protective films on the negative electrode and the positive electrode respectively at the same time. The battery prepared with this electrolyte can maintain excellent long-term cycling performance and storage performance at high voltages. For example, the oxalate group in the above electrolyte additive and the P-F group in the electrolyte salt can form a low-impedance and dense protective film on the surfaces of the positive electrode and the negative electrode of the battery, inhibit the side reaction between the positive electrode and the electrolyte, and at the same time increase the stability of the SEI film on the negative electrode, improve the high-temperature performance and cycling performance, so that the high-temperature storage capacity retention rate of the lithium-ion battery is high, the gas generation expansion rate during high-temperature storage is low, and the cycling performance is good. Thus, using the electrolyte additive of formula (I-1) - formula (I-6) helps to improve the high-temperature performance and cycling performance of the battery and enhance the use safety of the battery.

[0031] According to the electrolyte of the second aspect embodiment of the present invention, it includes an electrolyte additive, and the electrolyte additive is the electrolyte additive of the first aspect embodiment of the present invention above; the content of the electrolyte additive in the electrolyte is 0.05% - 11% by mass percentage. Thus, the content of the electrolyte additive in the electrolyte is relatively reasonable, which is conducive to giving full play to the role of the electrolyte additive, enabling the electrolyte additive to quickly form a complete, dense and well-uniform protective film (CEI) on the electrode surface, improving the cycling performance and safety of the battery, and also avoiding the decrease in the conductivity of the electrolyte caused by a large amount of the electrolyte additive, ensuring the charge and discharge efficiency of the battery using the above electrolyte. In addition, an appropriate amount of the electrolyte additive helps to control the cost of the electrolyte and the battery.

[0032] Preferably, the content of the electrolyte additive in the electrolyte is 0.5% - 3% by mass percentage.

[0033] According to some other embodiments of the present invention, the electrolyte further includes a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium difluoro bis(oxalato) phosphate, lithium tetrafluorooxalate phosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide. During the charge and discharge process of the battery, the lithium salt ionizes lithium ions in the electrolyte, and the lithium ions are intercalated and deintercalated back and forth between the positive electrode and the negative electrode to realize the charge and discharge function of the battery, which is the key for the battery to store and release electrical energy.

[0034] Among them, lithium hexafluorophosphate has high ionic conductivity and good electrochemical stability, can effectively conduct lithium ions between the positive and negative electrodes of the battery, and enables the battery to have good charge and discharge performance. Lithium perchlorate has high ionic conductivity. In high-temperature lithium batteries or battery systems that require high energy density, lithium perchlorate helps to improve the performance of the battery. Lithium tetrafluoroborate has good solubility and chemical stability, and as a lithium salt, it helps to improve the high-temperature performance and cycle stability of the battery. Lithium difluoro(oxalato)borate can enhance the transport ability of lithium ions at low temperatures, enabling the battery to still maintain good charge and discharge performance in a low-temperature environment and reducing the polarization phenomenon of the battery. Lithium bis(oxalato)difluorophosphate has high oxidation stability, can adapt to a relatively high battery operating voltage, can effectively inhibit the oxidation and decomposition of the electrolyte in a high-voltage battery system, and improve the energy density of the battery; it can also increase the ionic conductivity of the electrolyte, which helps the rapid transport of lithium ions inside the battery, thereby improving the charge and discharge efficiency of the battery. Lithium tetrafluoro(oxalato)phosphate can maintain good stability at relatively high temperatures, can reduce the risk of thermal runaway of the battery in a high-temperature environment, improve the safety of the battery, and at the same time help to reduce the capacity attenuation of the battery at high temperatures, and improve the cycle performance and storage performance of the battery in a high-temperature environment. Lithium bis(trifluoromethanesulfonyl)imide has excellent ionic conductivity, can enable the battery to maintain good charge and discharge performance in a relatively wide temperature range, and improve the power density of the battery. Lithium bis(fluorosulfonyl)imide has high ionic conductivity, good thermal stability and electrochemical stability, and is suitable for use in batteries with high voltage and wide temperature range.

[0035] Therefore, adopting at least one of the above-mentioned lithium salts helps to improve the ionic conductivity, electrochemical stability, operating voltage, energy density, cycle life and safety of the battery, etc., and also helps to improve the applicability of the battery using the above-mentioned lithium salts.

[0036] Preferably, a combination of lithium salts of lithium hexafluorophosphate with a specific concentration and lithium bis(fluorosulfonyl)imide with a specific concentration can be adopted, which can not only increase the conductivity and thermal decomposition temperature of the non-aqueous electrolyte, but also reduce the decomposition of lithium hexafluorophosphate, thereby further improving the service life of the battery.

[0037] Furthermore, the concentration of the lithium salt is 0.1 mol / L to 2 mol / L. Thus, the concentration of the lithium salt is relatively reasonable, and a good balance can be achieved between the ionic conductivity and the comprehensive performance of the battery, which not only ensures the rapid transport of lithium ions, but also enables the battery to maintain good stability and charge and discharge efficiency during the cycle. At the same time, it helps to form a more stable solid electrolyte interface (SEI) film on the surface of the lithium metal, reduce the generation of lithium dendrites, improve the safety and cycle performance of the battery, and extend the cycle life of the battery.

[0038] Preferably, the concentration of the lithium salt is 0.9 mol / L to 1.3 mol / L.

[0039] According to some embodiments of the present invention, when the lithium salt includes lithium bis(fluorosulfonyl)imide, the concentration of lithium bis(fluorosulfonyl)imide is 0.1 mol / L to 0.4 mol / L. Lithium bis(fluorosulfonyl)imide (LiFSI) has high ionic conductivity and good chemical stability. The fluorine atoms in its anion structure endow it with high electronegativity, enabling LiFSI to dissociate well in organic solvents to provide a high concentration of lithium ions, which is beneficial to the charge and discharge of the battery. In the electrolyte, lithium bis(fluorosulfonyl)imide has high ionic conductivity, which can effectively reduce the internal resistance of the battery, improve the charge and discharge efficiency and power performance of the battery. At the same time, lithium bis(fluorosulfonyl)imide has a wide chemical window and can remain stable within a wide voltage range, meeting the requirements of different types of batteries for high voltage, which is conducive to the development of high-energy-density battery systems. Lithium bis(fluorosulfonyl)imide can form a stable and well-performing solid electrolyte interface (SEI) film on the electrode surface, which can effectively prevent side reactions between the electrolyte and the electrode material, improve the cycle life and Coulomb efficiency of the battery. In addition, lithium bis(fluorosulfonyl)imide has good thermal stability and is not easily decomposed at high temperatures, which helps to improve the safety and stability of the battery in high-temperature environments and reduce the probability of safety problems such as thermal runaway.

[0040] The above concentration of lithium bis(fluorosulfonyl)imide is relatively reasonable, which is conducive to giving full play to the synergistic effect of LiFSI and other components, helping to reduce the internal resistance of the battery, improve the performance of the battery under high-current charge and discharge conditions, and enhance the energy density and cruising range of the battery.

[0041] According to some embodiments of the present invention, lithium hexafluorophosphate LiPF6 can be selected as the main lithium salt and combined with the remaining lithium salts. For example, a LiPF6 / LiFSI mixed double-lithium salt can be selected. No specific limitation is made here. The electrolyte additive can react with the lithium salt containing fluorine and phosphorus elements during the formation stage to generate oxalate phosphate compounds.

[0042] According to some embodiments of the present invention, the electrolyte further includes a solvent, and the solvent includes at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate. As an organic solvent, the above solvent has good solubility for both the lithium salt and the electrolyte additive, which is beneficial to optimizing the physical and chemical properties of the electrolyte and improving the overall performance of the battery. For example, it can increase the fluidity of the electrolyte, reduce the viscosity of the electrolyte, enable the smooth transmission of lithium ions, and thus improve the charge and discharge efficiency of the battery.

[0043] The lithium-ion battery according to an embodiment of the third aspect of the present invention includes an electrolyte additive according to the embodiment of the first aspect of the present invention above; or at least one electrolyte according to the embodiment of the second aspect of the present invention above.

[0044] For the lithium-ion battery according to an embodiment of the present invention, by adopting the above electrolyte, it is beneficial to increase the use safety of the lithium-ion battery, extend the cycle life of the battery, and enhance the market competitiveness of the lithium-ion battery.

[0045] The battery pack according to an embodiment of the fourth aspect of the present invention includes the lithium-ion battery according to the embodiment of the third aspect of the present invention above.

[0046] For the battery pack according to an embodiment of the present invention, it helps to enhance the safety of the battery pack and the electrochemical performance of the battery pack, thereby facilitating the enhancement of the market competitiveness of the battery pack.

[0047] The electrical equipment according to an embodiment of the fifth aspect of the present invention includes the lithium-ion battery according to the embodiment of the third aspect of the present invention above; or the battery pack according to the embodiment of the fourth aspect of the present invention above.

[0048] For the electrical equipment according to an embodiment of the present invention, it helps to enhance the power supply stability and reliability of the electrical equipment, improve the use experience of the electrical equipment, and enhance the market competitiveness of the electrical equipment.

[0049] The embodiments of the present invention will be described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as a limitation of the present invention. Additionally, if not explicitly stated, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For the reaction conditions not listed, they are also easily obtained by those skilled in the art.

[0050] Among them, the preparation methods of the compounds represented by formula (I-1) - formula (I-6) are as follows:

[0051] In the above preparation process, oxalic acid (CAS No. 144-62-7) and 3-methyl-1-butyn-3-ol (CAS No. 115-19-5) can react under the action of a catalyst to obtain the compound represented by formula (I-1). Among them, the catalyst includes nano Pd / α-Al2O3. In the above preparation process, oxalic acid and 3-methyl-1-butyn-3-ol are mixed, using toluene as a solvent, reacting at 80 °C to 100 °C for 4 h to 6 h to obtain the compound represented by formula (I-1).

[0052]

[0053] In the above preparation process, oxalic acid (CAS No. 144-62-7) and 3-trimethylsilyl-2-propyn-1-ol (CAS No. 5272-36-6) can react under the action of a catalyst to obtain the compound shown in formula (I-2). Among them, the catalyst includes nano Pd / α-Al2O3. In the above preparation process, oxalic acid and 3-trimethylsilyl-2-propyn-1-ol are mixed, using toluene as a solvent, reacting at 80 °C to 100 °C for 4 h to 6 h to obtain the compound shown in formula (I-2).

[0054]

[0055] In the above preparation process, oxalic acid (CAS No. 144-62-7) and 4-trimethylsilyl-3-butyn-2-ol (CAS No. 6999-19-5) can react under the action of a catalyst to obtain the compound shown in formula (I-3). Among them, the catalyst includes nano Pd / α-Al2O3. In the above preparation process, oxalic acid and 4-trimethylsilyl-3-butyn-2-ol are mixed, using toluene as a solvent, reacting at 80 °C to 100 °C for 4 h to 6 h to obtain the compound shown in formula (I-3).

[0056]

[0057] In the above preparation process, oxalic acid (CAS No. 144-62-7) and 3-butyn-1-ol (CAS No. 927-74-2) can react under the action of a catalyst to obtain the compound shown in formula (I-4). Among them, the catalyst includes nano Pd / α-Al2O3. In the above preparation process, oxalic acid and 3-butyn-1-ol are mixed, using toluene as a solvent, reacting at 80 °C to 100 °C for 4 h to 6 h to obtain the compound shown in formula (I-4).

[0058]

[0059] In the above preparation process, oxalic acid (CAS No. 144-62-7) and 4-trimethylsilyl-3-butyn-1-ol (CAS No. 2117-12-6) can react under the action of a catalyst to obtain the compound shown in formula (I-5). Among them, the catalyst includes nano Pd / α-Al2O3. In the above preparation process, oxalic acid and 4-trimethylsilyl-3-butyn-1-ol are mixed, using toluene as a solvent, reacting at 80 °C to 100 °C for 4 h to 6 h to obtain the compound shown in formula (I-5).

[0060]

[0061] In the above preparation process, oxalic acid (CAS No. 144-62-7) and propargyl alcohol (CAS No. 107-19-7) can react under the action of a catalyst to obtain the compound shown in formula (I-6). Among them, the catalyst includes nano Pd / α-Al2O3. In the above preparation process, oxalic acid and propargyl alcohol are mixed, using toluene as a solvent, reacting at 80 °C to 100 °C for 4 h to 6 h to obtain the compound shown in formula (I-6).

[0062] Example 1 The preparation method of the electrolyte in Example 1 includes the following steps: Prepare the electrolyte in a glove box. The glove box is filled with argon with a purity of 99.999%, the moisture in the glove box is controlled at ≤0.1 ppm, and the temperature is controlled at room temperature. Mix ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) according to a mass ratio of EC:DMC:DEC = 3:2:5, then add lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI) to dissolve the above lithium salts in the above mixed solvent respectively, and configure the concentrations to be 1.0 mol / L and 0.2 mol / L respectively. Then add the compound shown in formula I-1 as an additive, and after mixing evenly, obtain the electrolyte; Among them, the mass proportion of the compound shown in formula I-1 in the electrolyte is 0.3%.

[0063] Example 2 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass proportion of the compound shown in formula I-1 in the electrolyte is 0.5%.

[0064] Example 3 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass proportion of the compound shown in formula I-1 in the electrolyte is 1.0%.

[0065] Example 4 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass proportion of the compound shown in formula I-1 in the electrolyte is 1.5%.

[0066] Example 5 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass proportion of the compound shown in formula I-1 in the electrolyte is 2%.

[0067] Example 6 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass proportion of the compound shown in formula I-1 in the electrolyte is 2.5%.

[0068] Example 7 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass percentage of the compound shown in Formula I-1 in the electrolyte is 3%.

[0069] Example 8 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass percentage of the compound shown in Formula I-1 in the electrolyte is 0.1%.

[0070] Example 9 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass percentage of the compound shown in Formula I-1 in the electrolyte is 10%.

[0071] Example 10 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass percentage of the compound shown in Formula I-1 in the electrolyte is 0.05%.

[0072] Example 11 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that the mass percentage of the compound shown in Formula I-1 in the electrolyte is 11%.

[0073] Example 12 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that an electrolyte additive is added: the compound shown in Formula I-2, and the mass percentage of the compound shown in Formula I-2 in the electrolyte is 2%.

[0074] Example 13 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that an electrolyte additive is added: the compound shown in Formula I-3, and the mass percentage of the compound shown in Formula I-3 in the electrolyte is 2%.

[0075] Example 14 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that an electrolyte additive is added: the compound shown in Formula I-4, and the mass percentage of the compound shown in Formula I-4 in the electrolyte is 2%.

[0076] Example 15 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that an electrolyte additive is added: the compound shown in Formula I-5, and the mass percentage of the compound shown in Formula I-5 in the electrolyte is 2%.

[0077] Example 16 The preparation method of the electrolyte in this example is substantially the same as that in Example 1, except that an electrolyte additive, the compound shown in Formula I-6, is added, and the mass ratio of the compound shown in Formula I-6 in the electrolyte is 2%.

[0078] Comparative Example 1 The preparation method of the electrolyte in Comparative Example 1 is substantially the same as that in Example 1, except that an additive, tripropargyl phosphate (TPP), is added, and the mass ratio of TPP in the electrolyte is 1.0%.

[0079] Comparative Example 2 The preparation method of the electrolyte in Comparative Example 2 is substantially the same as that in Example 1, except that additives, lithium difluorobis(oxalato)phosphate (LiDFOP) and tripropargyl phosphate (TPP), are added, the mass ratio of LiDFOP in the electrolyte is 1.0%, and the mass ratio of tripropargyl phosphate in the electrolyte is 1.0%.

[0080] Comparative Example 3 The preparation method of the electrolyte in Comparative Example 3 is substantially the same as that in Example 1, except that additives, lithium difluorobis(oxalato)phosphate (LiDFOP), tripropargyl phosphate (TPP) and tris(trimethylsilyl) phosphate (TMSP), are added, the mass ratio of LiDFOP in the electrolyte is 1.0%, the mass ratio of TPP in the electrolyte is 1.0%, and the mass ratio of TMSP in the electrolyte is 1.0%.

[0081] Comparative Example 4 The preparation method of the electrolyte in Comparative Example 4 is substantially the same as that in Example 1, except that no additive is added to the electrolyte.

[0082] Table 1 Specific parameters of the electrolyte formulations provided in Examples 1-16 and Comparative Examples 1-4

[0083] Fabrication of Lithium-Ion Batteries The electrode core is prepared by laminating the positive electrode sheet, negative electrode sheet and separator. After the electrode core is placed in an aluminum-plastic film packaging shell, the electrolyte in Table 1 above is injected, and then sealed in sequence. After standing, hot and cold pressing, formation and grading processes, a lithium-ion battery is fabricated. The positive electrode active material is LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), the negative electrode active material is artificial graphite, and the separator is a PE film.

[0084] Performance Testing (1) Room Temperature Cycling Test In an incubator at 25°C, the battery is charged at a constant current of 1C to 4.5V, then switched to constant voltage charging until the cut-off current is 0.05C, left standing for 0.5h, and then discharged at a constant current of 1C to 2.8V, which is recorded as one charge-discharge cycle. Then, 500 cycles are carried out according to the above conditions; the discharge capacity in the first week is denoted as C0, and the discharge capacity in the 500th cycle is denoted as C1; Normal temperature cycle capacity retention rate (%) = (C1 / C0) × 100%; (2) High temperature cycle test In an incubator at 45°C, the battery is charged at a constant current of 1C to 4.5V, then switched to constant voltage charging until the cut-off current is 0.05C, left standing for 0.5h, and then discharged at a constant current of 1C to 2.8V, which is recorded as one charge-discharge cycle. Then, 500 cycles are carried out according to the above conditions; the discharge capacity in the first week is denoted as C0, and the discharge capacity in the 300th cycle is denoted as C1; High temperature cycle capacity retention rate (%) = (C1 / C0) × 100%; (3) High temperature storage test The lithium-ion battery is charged at a constant current of 1C and switched to constant voltage charging to 4.5V at 25°C, with a cut-off of 0.05C, left standing for 0.5h, and then discharged at a constant current of 1C to 2.8V. This discharge capacity is denoted as the initial capacity C0. The thickness of the battery before storage, H0, is measured. The battery is transferred to a high temperature test cabinet and stored at 60°C for 14 days; after storage, the test battery is taken out, left at room temperature for 10h, the thickness of the battery after storage, H1, is measured, and then it is discharged at a constant current of 1C to 2.8V, and the discharge capacity C1 is recorded. After leaving it standing for 2h, it is charged at a constant current of 1C and switched to constant voltage charging to 4.5V, with a cut-off of 0.05C, and after leaving it standing for 0.5h, it is discharged at a constant current of 1C to 2.8V, and the discharge capacity C2 is recorded; High temperature storage capacity remaining rate (%) = (C1 / C0) × 100%; High temperature storage capacity recovery rate (%) = (C2 / C0) × 100%.

[0085] Battery thickness growth rate (%) = [(H1 - H0) / H0] × 100%.

[0086] Test result analysis Table 2 Performance test data of Examples 1-16 and Comparative Examples 1-4

[0087] Combined with Table 1 and Table 2, compared with the lithium-ion batteries of Comparative Examples 1-4, the lithium-ion batteries of the above Examples 1-16 have better improvement effects on normal temperature / high temperature cycle performance and high temperature storage performance.

[0088] Comparing the data of Examples 1-11, it can be seen that there is an optimal range for the dosage of Additive I provided in this application. When the addition amount in the electrolyte is too much (such as in Example 11), it will greatly increase the viscosity of the electrolyte and deteriorate the cycling and storage performance to a certain extent.

[0089] Comparing Example 14 and Example 15, when the hydrogen atom on the alkynyl group is replaced by a trimethylsilyl group, the cycling and storage performance are further improved.

[0090] In addition, the following experiment can be used to determine whether the electrolyte additive contains an ester group: First, through the hydroxamic acid iron color reaction, the ester group reacts with hydroxylamine hydrochloride under alkaline conditions to form hydroxamic acid, and then hydroxamic acid reacts with ferric chloride to form a purple-red complex. The specific operation steps are as follows: Take about 0.1 g of the sample, add 1 mL of the ethanol solution of hydroxylamine hydrochloride, then add 3 drops of 10% NaOH solution, and boil for 1 min - 2 min. After cooling, add dilute hydrochloric acid dropwise until the solution becomes acidic (pH≈2 - 3). Add 1 drop - 2 drops of 5% FeCl3 solution. If the solution turns purple-red or dark red, it indicates the presence of an ester group.

[0091] The above reaction process is a step-by-step reaction: Ester + hydroxylamine hydrochloride (under NaOH condition) → hydroxamic acid + alcohol Hydroxamic acid + FeCl3 → purple-red complex (Fe(ROCONHO)3) At the same time, it can also be determined through hydrolysis reaction: After alkaline hydrolysis and acidification, first distinguish with NaHCO3 (carboxylic acid directly generates gas, and the ester group needs to be hydrolyzed to generate gas), exclude the presence of carboxyl groups in the compound, and indirectly prove the presence of the ester group.

[0092] In addition, it can also be observed through infrared spectroscopy at 1735 cm -1 (C=O) and 1050 cm -1 ~1300 cm -1 (C-O) peaks.

[0093] The following experiment can be used to determine whether the electrolyte additive contains an alkynyl group: By adding silver ammonia solution to Compound I-1, Compound I-4, and Compound I-6, if a white precipitate is formed, it indicates the presence of a terminal alkynyl group, excluding the interference of alkenes. The active hydrogen of terminal alkynes (R-C≡C-H) can react with silver ammonia solution to form a white silver acetylide precipitate, while alkenes (R-CH=CH2) do not have this reaction.

[0094] For the remaining compounds, it can be determined by nuclear magnetic resonance carbon spectrum that there is a chemical shift at 60 ppm - 100 ppm in the compound (sp hybridized carbon, lower field than alkene carbon).

[0095] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example.

[0096] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the claims and their equivalents.

Claims

1. An electrolyte additive, characterized in that, Comprising: Compounds containing oxalate groups and alkynyl groups.

2. The electrolyte additive according to claim 1, wherein, At least one of the compounds represented by the following formula; ， In the formula, x and y are each independently a positive integer; 1 ≤ x ≤ 5; 1 ≤ y ≤ 5; R1 to R6 are each independently selected from a hydrogen atom, a trimethylsilyl group, a halogen atom, an alkyl group having 1 to 5 carbon atoms, an unsaturated hydrocarbon group having 2 to 5 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an alkaryl group having 7 to 10 carbon atoms; Among them, the hydrogen atoms in the alkyl group having 1 to 5 carbon atoms, the unsaturated hydrocarbon group having 2 to 5 carbon atoms, the aryl group having 6 to 10 carbon atoms, and the alkaryl group having 7 to 10 carbon atoms may be partially or completely substituted by substituents; Preferably, R5 and R6 are each independently selected from a hydrogen atom and a trimethylsilyl group.

3. The electrolyte additive according to claim 1 or 2, wherein Comprising at least one of the compounds represented by formula (I-1) - formula (I-6), wherein the compounds of formula (I-1) - formula (I-6) are: I-1 I-2 I-3 I-4 I-5 I-6。 4. An electrolyte, characterized in that, Comprising an electrolyte additive, the electrolyte additive being the electrolyte additive according to any one of claims 1-3; the content of the electrolyte additive in the electrolyte is 0.05% to 11% by mass; preferably, the content of the electrolyte additive in the electrolyte is 0.5% to 3% by mass.

5. The electrolyte according to claim 4, characterized in that, Further comprising a lithium salt, the lithium salt including at least one of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium difluoro bis(oxalato) phosphate, lithium tetrafluorooxalate phosphate, lithium bis(trifluoromethylsulfonyl)imide, and lithium difluorosulfonylimide.

6. The electrolyte according to claim 5, wherein The concentration of the lithium salt is 0.1 mol / L to 2 mol / L, preferably, the concentration of the lithium salt is 0.9 mol / L to 1.3 mol / L.

7. The electrolyte according to claim 6, characterized in that, When the lithium salt includes lithium difluorosulfonylimide, the concentration of the lithium difluorosulfonylimide is 0.1 mol / L to 0.4 mol / L.

8. The electrolyte according to any one of claims 4-7, characterized in that, Further comprising a solvent, the solvent including at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, γ-butyrolactone, methyl formate, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate.

9. A lithium-ion battery, characterized in that, Comprising the electrolyte additive according to any one of claims 1-3; or at least one electrolyte according to any one of claims 4-8.

10. A battery pack, characterized in that, Comprising the lithium ion battery according to claim 9.

11. An electrical device, characterized in that, Comprising the lithium ion battery according to claim 9; or the battery pack according to claim 10.

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