Electrochemical and electronic devices

Abstract

The present invention provides an electrochemical device and an electronic device, comprising a positive electrode, a negative electrode, a separator and an electrolyte, the electrolyte comprising fluoroethylene carbonate and a trinitrile compound, where, when the mass content of fluoroethylene carbonate is A%, relative to the mass of the electrolyte, A satisfies 4≦A≦10, and when the mass content of the trinitrile compound is B%, B satisfies 1≦B≦3, the positive electrode active material of the positive electrode comprises a metal element M, the metal element M comprising at least one of Ti, Mg and Al, and when the content of the metal element M in the positive electrode active material is C ppm, C and B satisfy 7≦C×B / 1000≦27. The present invention improves the float charge characteristics and cycle characteristics of the electrochemical device.

Description

[Technical Field]

[0001] The present invention relates to the field of electrochemical technology, and more particularly to electrochemical and electronic devices. [Background technology]

[0002] Lithium-ion batteries have advantages such as high specific energy, high operating voltage, low self-discharge rate, small volume, and light weight, and are widely used in various fields such as power storage, portable electronic devices, and electric vehicles. As the range of use of lithium-ion batteries expands, higher requirements are placed on lithium-ion batteries, such as faster charging speeds and longer service lives.

[0003] However, as the charging speed of lithium ion batteries increases, the temperature also increases. At high temperatures, side reactions in lithium ion batteries increase, which affects the cycle performance of lithium ion batteries. Summary of the Invention

[0004] The present invention aims to provide an electrochemical device and an electronic device that can improve the cycle characteristics of the electrochemical device.

[0005] In a first aspect of the present invention, an electrochemical device is provided. The electrochemical device includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte contains fluoroethylene carbonate and a trinitrile compound. When the mass content of fluoroethylene carbonate is A% relative to the mass of the electrolyte, A satisfies 4≦A≦10, and for example, A may be 4, 5, 6, 7, 8, 9, 10, or any range therebetween. When the mass content of the trinitrile compound is B%, B satisfies 1≦B≦3, and for example, B may be 1, 1.5, 2, 2.5, 3, or any range therebetween. The positive electrode includes a positive electrode active material, the positive electrode active material including a metal element M, the metal element M including at least one of Ti, Mg, and Al, and when the content of the metal element M in the positive electrode active material is C ppm, C and B satisfy 7≦C×B / 1000≦27, and for example, C×B / 1000 may be 7, 10, 13, 15, 18, 20, 22, 25, 27, or any range therebetween. In the present invention, the positive electrode may be a positive electrode piece, and the negative electrode may be a negative electrode piece.

[0006] The inventors of the present invention have found that adjusting A, B, and C×B / 1000 within the above ranges can improve the high-temperature cycle performance and float charge performance of a lithium-ion battery. Without being bound by any theory, it is believed that the inclusion of a metal element M in the positive electrode active material can improve the structural stability of the positive electrode. However, in order to improve the overall dynamic performance of a lithium-ion battery, it is also necessary to improve the structural stability of the negative electrode. Based on this, the present invention improves the film formation stability of the negative electrode by adjusting the content of fluoroethylene carbonate in the electrolyte, and improves the high-temperature cycle performance of a lithium-ion battery by adjusting the content of a trinitrile compound in the electrolyte, thereby resulting in a lithium-ion battery with good high-temperature cycle performance and float charge performance.

[0007] In one embodiment of the present invention, A and B satisfy 6 ≦ A×B ≦ 22. For example, A×B may be 6, 8, 10, 12, 15, 17, 20, 22, or any range therebetween. By adjusting A×B within the above range, fluoroethylene carbonate and trinitrile compound act synergistically in the electrolyte, and the lithium-ion battery has good high-temperature cycle characteristics and float charging characteristics.

[0008] In one embodiment of the present invention, when the degree of the negative electrode defect is defined as Id / Ig, Id / Ig satisfies 0.13 < Id / Ig ≦ 0.3. Id / Ig and A satisfy 6 ≦ A×(10×Id / Ig) ≦ 24. For example, Id / Ig may be 0.13, 0.15, 0.2, 0.25, 0.3, or any range therebetween, and A×(10×Id / Ig) may be 6, 8, 9, 10, 12, 15, 17, 29, 20, 22, 24, or any range therebetween. Without being limited to any theory, if A×(10×Id / Ig) is too small (e.g., less than 6), the kinetic characteristics on the negative electrode side are not sufficient, side reactions increase, and the cycle stability of the lithium-ion battery deteriorates. If A×(10×Id / Ig) is too large (e.g., greater than 24), it affects the high-temperature stability of the lithium-ion battery. By adjusting A×(10×Id / Ig) within the above range, a lithium-ion battery having good high-temperature cycle characteristics and float charging characteristics can be obtained.

[0009] In the present invention, regarding the degree of the negative electrode defect Id / Ig, Id is the intensity of the D peak in the Raman spectrum of the negative electrode active material, Ig is the intensity of the G peak in the Raman spectrum of the negative electrode active material, Id / Ig indicates the defect concentration of the negative electrode active material, and the larger the value of Id / Ig, the greater the degree of the defect.

[0010] In one embodiment of the present invention, the content C of the metal element M in the positive electrode active material satisfies the relationship 5000 ppm≦C≦9000 ppm. For example, C may be 5000 ppm, 5500 ppm, 6000 ppm, 6500 ppm, 7000 ppm, 7500 ppm, 8000 ppm, 8500 ppm, 9000 ppm, or any range therebetween. Without being limited by any theory, adjusting C within the above range can provide a lithium-ion battery with good high-temperature cycle characteristics and energy density.

[0011] In one embodiment of the present invention, C and Id / Ig satisfy the relationship 6≦C / (3000×Id / Ig)≦20. For example, C / (3000×Id / Ig) may be 6, 7, 10, 12, 15, 18, 20, or any range therebetween. Without being limited to any theory, by adjusting C / (3000×Id / Ig) within the above range, a lithium ion battery with good high-temperature cycle characteristics and float charge characteristics can be obtained.

[0012] In one embodiment of the present invention, the electrolyte further contains ethylene carbonate and propylene carbonate, where D% is the mass content of ethylene carbonate and E% is the mass content of propylene carbonate relative to the mass of the electrolyte, and D and E satisfy the relationships 20≦D+E≦50 and 1≦E / D≦3. For example, D+E may be 20, 25, 30, 35, 40, 45, 50, or any range therebetween, and E / D may be 1, 1.5, 2, 2.5, 3, or any range therebetween. Without being limited by theory, adjusting D+E and E / D simultaneously within the above ranges can further improve the high-temperature cycle characteristics and float charge characteristics of a lithium-ion battery.

[0013] In one embodiment of the present invention, the electrolyte further comprises a dinitrile compound, where F% is the mass content of the dinitrile compound relative to the mass of the electrolyte, and F satisfies the relationship 1≦F≦3. For example, F may be 1, 1.5, 2, 2.5, 3, or any range therebetween. Without being limited to any theory, if the content of the dinitrile compound is too low (e.g., less than 1%), the protective effect on the positive electrode is insignificant. If the content of the dinitrile compound is too high (e.g., greater than 3%), it affects the viscosity of the electrolyte and increases the internal resistance of the lithium-ion battery. By adjusting the content of the dinitrile compound within the above range, the high-temperature cycle characteristics and float charge characteristics of the lithium-ion battery can be further improved.

[0014] In one embodiment of the present invention, F and B satisfy the relationship 2≦F+B≦6. For example, F+B may be 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, or any range therebetween. Without being limited to any theory, adjusting F+B within the above range can further improve the high-temperature cycle characteristics and float charge characteristics of the lithium-ion battery.

[0015] In one embodiment of the present invention, the electrolyte further comprises at least one of 1,3-propane sultone, ethylene sulfate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and γ-butyrolactone. The electrochemical device satisfies at least one of the following characteristics (a) to (g): a) a mass content of the 1,3-propane sultone is 0.5% to 5% with respect to the mass of the electrolytic solution; b) a mass content of the ethylene sulfate is 0.1% to 1% with respect to the mass of the electrolytic solution; c) a mass content of the vinylene carbonate is 0.1% to 1% with respect to the mass of the electrolytic solution; d) a mass content of the dimethyl carbonate is 0.1% to 30% with respect to the mass of the electrolytic solution; e) a mass content of the diethyl carbonate is 0.1% to 30% with respect to the mass of the electrolytic solution; f) a mass content of the ethyl methyl carbonate is 0.1% to 30% with respect to the mass of the electrolytic solution; and g) a mass content of the γ-butyrolactone is 0.01% to 5% with respect to the mass of the electrolytic solution. Without being limited to any theory, it is believed that by adjusting the additives of the electrolyte to fall within the range of the present invention, the high temperature cycle characteristics and float charge characteristics of the lithium ion battery can be further improved.

[0016] The present invention is not particularly limited to the trinitrile compound, as long as the object of the present invention can be achieved. For example, the trinitrile compound includes at least one of 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, and 1,2,5-tris(cyanoethoxy)pentane.

[0017] The electrolyte solution of the present invention contains a lithium salt, and the lithium salt is not particularly limited as long as it can achieve the object of the present invention. For example, the lithium salt may include at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, and lithium difluorophosphate.

[0018] The dinitrile compound of the present invention is not particularly limited as long as it can achieve the object of the present invention. For example, the dinitrile compound includes at least one of succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanooctane, 1,9-dicyanononane, 1,10-dicyanodecane, 1,12-dicyanododecane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, and 2,2,4,4-tetramethylglutaronitrile.

[0019] In a second aspect of the present invention, there is provided an electronic device, which comprises the electrochemical device according to any of the above embodiments of the present invention.

[0020] The present invention provides an electrochemical device and an electronic device, in which the electrolyte in the electrochemical device comprises fluoroethylene carbonate and a trinitrile compound, wherein, when the mass content of the fluoroethylene carbonate is A%, A satisfies 4≦A≦10, and when the mass content of the trinitrile compound is B%, B satisfies 1≦B≦3, and the mass content C% of the metal element M in the positive electrode active material and the mass content B% of the trinitrile compound are adjusted to satisfy 7≦C×B / 1000≦27, thereby improving the float charge characteristics and cycle characteristics of the electrochemical device. DETAILED DESCRIPTION OF THE INVENTION

[0021] In order to clarify the objectives, technical solutions and advantages of the present invention, the present invention will be further described in detail below with reference to examples. Obviously, the described examples are only some examples of the present invention, but not all examples. Based on the examples in the present invention, all other technical solutions that those skilled in the art can obtain fall within the scope of protection of the present invention.

[0022] In the embodiments of the present invention, the present invention will be described using a lithium ion battery as an example of an electrochemical device, but the electrochemical device of the present invention is not limited to a lithium ion battery.

[0023] The present invention does not impose any particular limitations on the preparation method of a cathode active material containing metal element M (hereinafter simply referred to as a modified cathode active material), and any preparation method known to those skilled in the art may be used. For example, the modified cathode active material can be obtained by adding an aluminum-containing compound (e.g., Al2O3, Al(OH)3, AlF3), a magnesium-containing compound (e.g., MgO), or a Ti-containing compound (e.g., TiO2) to the cathode active material LiCoO2. The present invention also allows for the modification of the metal element M in the cathode active material layer by adjusting the content of the metal element M in the modified cathode active material, for example, by adjusting the amount of the compound containing metal element M added. The present invention does not impose any specific limitations on the preparation process, as long as the object of the present invention can be achieved.

[0024] The positive electrode current collector in the present invention is not particularly limited and may be any positive electrode current collector in the relevant field, for example, aluminum foil, aluminum alloy foil, or composite current collector.

[0025] The negative electrode current collector in the present invention is not particularly limited and may be a metal foil material or a porous metal plate, for example, a foil material or a porous plate of a metal such as copper, nickel, titanium, or iron, or an alloy thereof, such as copper foil. The negative electrode active material layer contains a negative electrode active material, a conductive agent, a binder, and a thickener. The binder may be at least one of styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), water-based acrylic resin, and carboxymethyl cellulose (CMC), and the thickener may be carboxymethyl cellulose (CMC).

[0026] The substrate of the separator of the present invention includes, but is not limited to, at least one selected from polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyimide (PI), and aramid. For example, the polyethylene includes at least one component selected from high-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene. In particular, polyethylene and polypropylene have excellent short-circuit prevention properties and can improve the stability of electrochemical devices through their shutdown effect. The substrate may have a single-layer structure or a multi-layer composite structure in which multiple types are mixed, and has a thickness of 3 μm to 20 μm.

[0027] The electronic device of the present invention is not particularly limited and may be any electronic device used in the prior art. In some embodiments, the electronic device may include, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an e-book player, a mobile phone, a mobile fax machine, a portable copier, a portable printer, a head-mounted stereo headphone, a video recorder, an LCD television, a portable vacuum cleaner, a portable CD player, a minidisc, a transceiver, an electronic organizer, a calculator, a memory card, a portable recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an electric bicycle, a bicycle, a lighting fixture, a toy, a game console, a watch, a power tool, a flashlight, a camera, a large-scale household battery, a lithium-ion capacitor, etc.

[0028] The manufacturing process of an electrochemical device is well known to those skilled in the art, and is not particularly limited in the present invention. For example, a lithium-ion battery is manufactured by stacking a positive electrode and a negative electrode with a separator interposed therebetween, and then winding or folding the stack as necessary, placing the stack in a case, injecting an electrolyte into the case, and sealing the case. If necessary, an overcurrent protection element, lead plates, etc. may be placed in the case to prevent pressure buildup within the lithium-ion battery and overcharging and discharging.

[0029] Hereinafter, the embodiments of the present invention will be described in more detail with reference to examples and comparative examples. Various tests and evaluations were carried out according to the following methods. Unless otherwise specified, "parts" and "%" are by mass.

[0030] Measurement methods and equipment Measurement of the content of metal element M in the positive electrode active material The active material of the positive electrode piece washed with DMC (dimethyl carbonate) was taken with a doctor blade and dissolved in a mixed solvent (for example, a mixed solvent of 10 ml of aqua regia (a 1:1 mixture of nitric acid and hydrochloric acid) and 2 ml of HF was used for 0.4 g of the positive electrode active material), and the volume was adjusted to 100 mL. The content of metal elements M such as Ti, Mg, and Al in the solution was measured using an ICP analyzer, and the unit was ppm.

[0031] Measuring the degree of defects in the negative electrode The dried negative electrode piece was placed on the sample stage of a Raman measurement device (JobinYvonLabRAM HR) to maintain a flat surface, and a Raman spectrum was obtained. The D peak intensity and G peak intensity were measured in the Raman spectrum, and Id / Ig was calculated to indicate the degree of defects in the negative electrode.

[0032] Measurement of cycle characteristics of lithium-ion batteries At 45°C, a lithium-ion battery was charged at a constant current of 0.7C (rate) to 4.5V, then charged at a constant voltage until the current reached 0.05C, and then discharged at a constant current of 1C to 3.0V. This constituted one charge-discharge cycle, which was the first cycle, and the discharge capacity of the lithium-ion battery was recorded. The lithium-ion battery was subjected to charge-discharge cycles according to the above method, and the discharge capacity of each cycle was recorded. The cycle ended when the discharge capacity of the lithium-ion battery had decayed to 80% of the discharge capacity of the first cycle, and the number of charge-discharge cycles was recorded.

[0033] Measurement of charging characteristics of a lithium-ion battery float At 45°C, the lithium-ion batteries were charged at a constant current of 0.7C to 4.5V, and then at a constant voltage for 90 days. The thickness of the lithium-ion batteries was measured and recorded using a micrometer, and the thickness was measured and recorded every three days during this period. The thickness expansion rate of the lithium-ion batteries during float charging was calculated using the following formula, and the time it took for the thickness expansion rate to reach 10% was used as an index to evaluate the float charging characteristics of the lithium-ion batteries. The longer the time it took for the thickness expansion rate to reach 10%, the better the float charging characteristics of the lithium-ion battery.

[0034] Lithium-ion battery thickness expansion rate = (Lithium-ion battery thickness during float charging process - Lithium-ion battery initial thickness) / Lithium-ion battery initial thickness × 100%.

[0035] Example 1 <Preparation of modified positive electrode active material> Commercially available lithium cobalt oxide (LiCoO) was mixed with an oxide containing metal element M (a mixture of magnesium oxide (MgO), titanium dioxide (TiO), and aluminum oxide (AlO)) and mixed in a high-speed mixer at 300 r / min for 20 minutes. The mixture was then placed in an air furnace, heated to 820°C at 5°C / min, held at this temperature for 24 hours, and naturally cooled. After removal and sieving through a 300-mesh sieve, a modified cathode active material (i.e., modified LiCoO) was obtained. In this modified cathode active material, the total content of metal element M (Mg, Ti, and Al) in the cathode active material was 7000 ppm, and the molar ratio of Mg, Ti, and Al was 1:1:1.

[0036] <Production of positive electrode sheets> The prepared modified LiCoO2, carbon nanotubes (CNTs) as a conductive agent, and polyvinylidene fluoride as a binder were mixed in a mass ratio of 95:2:3, and N-methylpyrrolidone (NMP) was added as a solvent. The mixture was stirred with a vacuum mixer until a uniform cathode slurry with a solids content of 75 wt% was obtained. The cathode slurry was uniformly applied to a 12 μm-thick aluminum foil cathode current collector, dried at 85°C, and cold-pressed to obtain a cathode piece with a cathode active material layer thickness of 100 μm. The above process was then repeated on the other surface of the same cathode piece, yielding a cathode piece with a cathode active material layer coated on both sides. The cathode piece was cut to a size of 74 mm x 867 mm, tabs were welded, and the piece was left to stand.

[0037] <Preparation of negative electrode pieces> Negative electrode active materials, artificial graphite, styrene butadiene rubber (SBR), and carboxymethyl cellulose (CMC), were mixed in a mass ratio of 95:2:3 and deionized water was added as a solvent to prepare a slurry with a solids content of 70 wt%. The slurry was then uniformly mixed. The slurry was uniformly coated on one surface of an 8 μm-thick copper foil, dried at 110°C, and cold-pressed to obtain a negative electrode piece coated with a negative electrode active material layer on one side, with a thickness of 150 μm. The same procedure was then repeated on the other surface of the negative electrode piece to obtain a negative electrode piece coated with a negative electrode active material layer on both sides. The negative electrode piece was cut into a size of 74 mm x 867 mm, tabs were welded, and the negative electrode piece was left to stand. The defect level (Id / Ig) of the negative electrode piece was 0.17.

[0038] <Preparation of electrolyte> In a glove box with an argon gas atmosphere containing less than 10 ppm of water, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed uniformly in a weight ratio of 1:1:1 to form a base solvent. LiPF6, the trinitrile compound 1,3,6-hexanetricarbonitrile, and fluoroethylene carbonate were added and stirred uniformly to form an electrolyte solution. The LiPF6 concentration was 12.5 wt%, and the mass contents of the trinitrile compound 1,3,6-hexanetricarbonitrile and fluoroethylene carbonate are shown in Table 1.

[0039] <Preparation of separator> A 15 μm thick porous polyethylene (PE) polymer film was used as the separator.

[0040] <Lithium-ion battery manufacturing> The positive electrode, separator, and negative electrode were stacked in this order, with the separator positioned between the positive and negative electrodes to act as an insulator, and then wound to form an electrode assembly. The electrode assembly was then placed in an aluminum plastic film packaging bag, the moisture was removed at 80°C, the prepared electrolyte was injected, and the assembly was vacuum packaged, left to stand, formed, and shaped to form a lithium-ion battery.

[0041] Examples 2 to 12 The content of fluoroethylene carbonate, the type and content of trinitrile compound, and the total content of metal element M in the electrolyte were adjusted, and the correlation preparation parameters and property changes were as shown in Table 1, and the rest were the same as in Example 1.

[0042] Example 13 In <Preparation of modified positive electrode active material>, the oxide containing metal element M was a mixture of MgO and Al2O3, and the molar ratio of Mg element to Al element was 1:1. The correlation preparation parameters and property changes were as shown in Table 1, and the rest was the same as in Example 10.

[0043] Example 14 In <Preparation of modified positive electrode active material>, the oxide containing the metal element M was Al2O3, and the correlated preparation parameters and changes in properties were as shown in Table 1; otherwise, it was the same as in Example 10.

[0044] Examples 15 to 17 As shown in Table 2, the content of fluoroethylene carbonate in the electrolyte and the degree of defects Id / Ig in the negative electrode pieces were adjusted, but the other conditions were the same as in Example 1.

[0045] Example 18 <Preparation of the electrolyte solution> was different from that in Example 1, but the rest was the same as in Example 1. In a glove box with an argon gas atmosphere containing less than 10 ppm of water, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed uniformly in a weight ratio of 10:15:54.5 to form a base solvent. LiPF6, the trinitrile compound 1,3,6-hexanetricarbonitrile, and fluoroethylene carbonate were added and stirred uniformly to form an electrolyte solution. The LiPF6 concentration was 12.5 wt%, and the mass contents of the trinitrile compound 1,3,6-hexanetricarbonitrile and fluoroethylene carbonate, as well as the corresponding preparation parameters and property changes, are shown in Table 3.

[0046] Example 19 <Preparation of the electrolyte solution> was different from that in Example 1, but the rest was the same as in Example 1. In a glove box with an argon gas atmosphere containing less than 10 ppm of water, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed uniformly in a weight ratio of 10:15:39.5 to form a base solvent. LiPF6, the trinitrile compound 1,3,6-hexanetricarbonitrile, and fluoroethylene carbonate were added and stirred uniformly to form an electrolyte solution. The LiPF6 concentration was 12.5 wt%, and the mass contents of the trinitrile compound 1,3,6-hexanetricarbonitrile and fluoroethylene carbonate, as well as the corresponding preparation parameters and property changes, are shown in Table 3.

[0047] Example 20 <Preparation of the electrolyte solution> was different from that in Example 1, but the rest was the same as in Example 1. In a glove box with an argon gas atmosphere containing less than 10 ppm of water, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed uniformly in a weight ratio of 10:15:34.5 to form a base solvent. LiPF6, the trinitrile compound 1,3,6-hexanetricarbonitrile, and fluoroethylene carbonate were added and stirred uniformly to form an electrolyte solution. The LiPF6 concentration was 12.5 wt%, and the mass contents of the trinitrile compound 1,3,6-hexanetricarbonitrile and fluoroethylene carbonate, as well as the corresponding preparation parameters and property changes, are shown in Table 3.

[0048] Example 21 <Preparation of the electrolyte solution> was different from that in Example 2, but the rest was the same as in Example 2. <Preparation of electrolyte> In an argon gas glove box with a water content of less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed uniformly in a 1:1:1 weight ratio to form the base solvent. LiPF6, the trinitrile compound 1,3,6-hexanetricarbonitrile, fluoroethylene carbonate, and the dinitrile compound succinonitrile were added and stirred uniformly to form the electrolyte. The LiPF6 concentration was 12.5 wt%, and the mass contents of the trinitrile compound 1,3,6-hexanetricarbonitrile, fluoroethylene carbonate, and dinitrile compound succinonitrile, as well as the corresponding preparation parameters and property changes, are shown in Table 4.

[0049] Examples 22 to 27 In <Preparation of Electrolyte Solution>, the type and content of the dinitrile compound were adjusted as shown in Table 4, and the other conditions were the same as in Example 21.

[0050] Example 28 <Preparation of the electrolyte solution> was different from that in Example 2, but the rest was the same as in Example 2. <Preparation of electrolyte> In an argon gas glove box with a water content of less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) were mixed uniformly in a 1:1:1 weight ratio to form the base solvent. LiPF6, the trinitrile compound 1,3,6-hexanetricarbonitrile, fluoroethylene carbonate, and the additive 1,3-propane sultone were added and stirred to form the electrolyte. The LiPF6 concentration was 12.5 wt%, and the mass contents of the trinitrile compound 1,3,6-hexanetricarbonitrile, fluoroethylene carbonate, and the additive 1,3-propane sultone, as well as the corresponding preparation parameters and property changes, are shown in Table 5.

[0051] Examples 29 to 30 In <Preparation of Electrolyte Solution>, the types and contents of additives were adjusted as shown in Table 5, and the rest was the same as in Example 28.

[0052] Comparative Examples 1 to 6 The type of trinitrile compound, the content of fluoroethylene carbonate, the content of trinitrile compound, and the total content of metal element M in the electrolyte were adjusted, and the correlation preparation parameters and property changes were as shown in Table 1, and the rest were the same as in Example 1.

[0053] Comparative Example 7 As shown in Table 2, the content of fluoroethylene carbonate in the electrolyte and the degree of defects Id / Ig in the negative electrode pieces were adjusted, but the other conditions were the same as in Example 1.

[0054] [Table 1]

[0055] [Table 2]

[0056] [Table 3]

[0057] [Table 4] In Table 4, " / " indicates not included or not measurable.

[0058] [Table 5] In Table 5, " / " indicates not included or not measurable.

[0059] As can be seen from Examples 1 to 7 and Comparative Examples 1 to 4 in Table 1, by adjusting A, B, and C×B / 1000 to fall within the ranges of the present invention, the capacity retention rate at 45° C. and float charge characteristics of the lithium ion battery are clearly improved. This indicates that the lithium ion battery of the present invention has good high-temperature cycle characteristics and float charge characteristics.

[0060] As can be further seen from Examples 1 to 14 in Table 1, by adjusting A×B while keeping A, B, and C×B / 1000 within the ranges of the present invention, the fluoroethylene carbonate and trinitrile compound in the electrolyte act synergistically, and a lithium ion battery having good high-temperature cycle characteristics and float charge characteristics can be obtained.

[0061] As can be seen from Example 8, Example 9, and Comparative Example 6 in Table 1, when the content of metal element M is too low (for example, Comparative Example 6), the capacity retention rate at 45°C and float charge characteristics of the lithium ion battery are clearly reduced. As can be seen from Example 9 and Comparative Example 5 in Table 1, when the content of metal element M is too high (for example, Comparative Example 5), the improvement in the float charge characteristics of the lithium ion battery is not clear, but the capacity retention rate at 45°C is conversely significantly reduced. As can be seen from this, by setting A, B, and C×B / 1000 within the ranges of the present invention and adjusting the content of metal element M within the ranges of the present invention, a lithium ion battery with good high-temperature cycle characteristics and float charge characteristics can be obtained.

[0062] As can be seen from Examples 9 and 10 in Table 1, by increasing the content of the trinitrile compound while keeping A, B, and C×B / 1000 within the ranges of the present invention, the float charge characteristics of the lithium ion battery can be further improved.

[0063] As can be seen from Examples 2, 11, and 12 in Table 1, as long as A, B, and C×B / 1000 are within the ranges of the present invention and the type of trinitrile compound is within the ranges of the present invention, a lithium ion battery having good high-temperature cycle characteristics and float charge characteristics can be obtained.

[0064] As can be seen from Examples 10, 13, and 14 in Table 1, as long as A, B, and C×B / 1000 are within the ranges of the present invention and the type of metal element M is within the range of the present invention, a lithium ion battery having good high-temperature cycle characteristics and float charge characteristics can be obtained.

[0065] As can be seen from Examples 15 to 17 and Comparative Example 7 in Table 2, by adjusting A×(10×Id / Ig) within the range of the present invention after setting A, B, and C×B / 1000 within the range of the present invention, a lithium ion battery with good high-temperature cycle characteristics and float charge characteristics can be obtained.

[0066] As can be seen from Examples 1 to 17 in Table 3, by setting A, B, and C×B / 1000 within the ranges of the present invention and then adjusting C / (3000×Id / Ig) within the ranges of the present invention, a lithium ion battery with good high-temperature cycle characteristics and float charge characteristics can be obtained.

[0067] As can be seen from Example 8 and Examples 18 to 20 in Table 3, by adjusting the contents of ethylene carbonate and propylene carbonate in the electrolyte solution while keeping A, B, and C×B / 1000 within the ranges of the present invention, the high-temperature cycle characteristics and float charge characteristics of the lithium-ion battery can be further improved.

[0068] As can be seen from Example 2 and Examples 21 to 26 in Table 4, when A, B, and C×B / 1000 are within the ranges of the present invention, and the electrolyte solution further contains a dinitrile compound, and the total content of the dinitrile compound and the trinitrile compound is within the ranges of the present invention, the high-temperature cycle characteristics and float charge characteristics of the lithium-ion battery can be further improved.

[0069] As can be seen from Examples 2 and 28 to 30 in Table 5, when A, B, and C×B / 1000 are within the ranges of the present invention and the electrolyte solution contains at least one additive selected from 1,3-propane sultone, ethylene sulfate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and γ-butyrolactone, the high-temperature cycle characteristics and float charge characteristics of the lithium ion battery can be further improved.

[0070] The above description is only a preferred embodiment of the present invention, and does not limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. 1. An electrochemical device comprising: a positive electrode, a negative electrode, a separator, and an electrolyte; the electrolyte solution comprises fluoroethylene carbonate and a trinitrile compound; When the mass content of the fluoroethylene carbonate is A% with respect to the mass of the electrolytic solution, A satisfies 4≦A≦10, When the mass content of the trinitrile compound is B% with respect to the mass of the electrolytic solution, B satisfies 1≦B≦3; the positive electrode includes a positive electrode active material, The positive electrode active material contains a metal element M, the metal element M includes at least one of Ti, Mg, and Al; When the content of the metal element M in the positive electrode active material is C ppm, C and B satisfy 7≦C×B / 1000≦27, A and B satisfy 6≦A×B≦20, C satisfies 5000 ppm < C ≦ 9000 ppm; Electrochemical equipment.

2. 2. The electrochemical device according to claim 1, wherein when the degree of defects in the negative electrode is Id / Ig, A and Id / Ig satisfy 0.13<Id / Ig≦0.3 and 6≦A×(10×Id / Ig)≦24.

3. 3. The electrochemical device according to claim 2, wherein C and Id / Ig satisfy 6≦C / (3000×Id / Ig)≦20.

4. the electrolyte further comprises ethylene carbonate and propylene carbonate; 2. The electrochemical device according to claim 1, wherein, when a mass content of the ethylene carbonate is D % and a mass content of the propylene carbonate is E % relative to the mass of the electrolytic solution, D and E satisfy 20≦D+E≦50 and 1≦E / D≦3.

5. the electrolyte solution further comprises a dinitrile compound; 2. The electrochemical device according to claim 1, wherein when a mass content of the dinitrile compound is F % with respect to a mass of the electrolytic solution, F satisfies 1≦F≦3.

6. The electrochemical device according to claim 5 , wherein F and B satisfy the relationship 2≦F+B≦6.

7. 10. The electrochemical device of claim 1, wherein the electrolyte further comprises at least one of 1,3-propane sultone, ethylene sulfate, vinylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and γ-butyrolactone.

8. The electrochemical device satisfies at least one of the following characteristics (a) to (g): a) the mass content of the 1,3-propane sultone is 0.5% to 5% relative to the mass of the electrolyte; b) the mass content of the ethylene sulfate is 0.1% to 1% relative to the mass of the electrolyte; c) the mass content of the vinylene carbonate is 0.1% to 1% relative to the mass of the electrolyte; d) the mass content of the dimethyl carbonate is 0.1% to 30% relative to the mass of the electrolyte; e) the mass content of the diethyl carbonate is 0.1% to 30% relative to the mass of the electrolyte; f) the mass content of the ethyl methyl carbonate is 0.1% to 30% relative to the mass of the electrolyte; g) the mass content of the gamma-butyrolactone is 0.01% to 5% relative to the mass of the electrolyte; 8. The electrochemical device of claim 7.

9. 2. The electrochemical device of claim 1, wherein the trinitrile compound comprises at least one of 1,3,5-pentanetricarbonitrile, 1,2,3-propanetricarbonitrile, 1,3,6-hexanetricarbonitrile, 1,2,6-hexanetricarbonitrile, 1,2,3-tris(2-cyanoethoxy)propane, 1,2,4-tris(2-cyanoethoxy)butane, and 1,2,5-tris(cyanoethoxy)pentane.

10. the electrolyte solution contains a lithium salt; 2. The electrochemical device of claim 1, wherein the lithium salt comprises at least one of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, and lithium difluorophosphate.

11. The electrochemical device according to claim 5, wherein the dinitrile compound includes at least one of succinonitrile, glutaronitrile, adiponitrile, 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanoctane, 1,9-dicyanononane, 1,10-dicyanodecane, 1,12-dicyanododecane, tetramethylsuccinonitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, and 2,2,4,4-tetramethylglutaronitrile.

12. An electronic device comprising an electrochemical device according to any one of claims 1 to 11.

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