Electrochemical device and electronic device

Abstract

The present invention belongs to the technical field of lithium-ion batteries and provides an electrolyte, as well as an electrochemical device and an electronic device containing the electrolyte. The electrolyte of the present invention comprises an organic solvent, a lithium salt, and an additive, the additive comprising fluoroethylene carbonate and a PN bond-containing compound, the PN bond-containing compound having a structure represented by Formula I. Based on the mass of the electrolyte, the mass percentage of the fluoroethylene carbonate in the electrolyte is a %, and the mass percentage of the PN bond-containing compound in the electrolyte is b %, where a and b satisfy the relationship 0.1≦a / b≦200. The electrolyte of the present invention effectively improves the high-temperature cycle and high-temperature storage characteristics of electrochemical devices.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical technology, and specifically to electrolytes, electrochemical devices, and electronic devices using such electrolytes.

Background Art

[0002] Lithium cobalt oxide (LCO) is superior to other ternary cathode materials such as lithium manganese oxide and lithium iron phosphate in terms of characteristics such as compression density, high voltage, high capacity, and high temperature resistance. Therefore, conventionally, it has been the optimal cathode material for batteries in consumer electronics products (abbreviated as 3C electronics) such as mobile phones, notebook computers, and digital cameras. With the development of 3C electronics products and the advent of the 5G era, a high energy density has become an inevitable trend. Researchers are improving the specific capacity of lithium cobalt oxide by increasing the charge cut-off voltage of LCO to allow more ions to participate in charge and discharge.

[0003] It is known that in the layered structure of LCO, Li ions and cobalt (Co) ions are alternately arranged in the skeleton composed of oxygen anions. When lithium release does not occur, the positive and negative ions are alternately arranged inside the crystal structure, so the structure of the material is stable. However, when charging starts, the following reaction process occurs. First, the cathode material begins to release lithium. After releasing lithium ions, the negative ion barrier is lost between the oxygen atoms in the Li layer, resulting in repulsion and an unstable surface structure. As lithium ions continue to be released, the lattice oxygen activity on the surface rises to a certain extent, and gas overflows, which deteriorates the stability of the Co atoms on the surface, causing them to dissolve, oxidizing the electrolyte, and deteriorating the high-temperature storage characteristics of the lithium-ion battery. As a result, the battery expands, its thickness increases, and safety problems in use occur. In particular, as the charge cut-off voltage increases and the lithium release amount increases, the activities of oxygen atoms and Co elements become higher, so the high-temperature characteristics further deteriorate. Therefore, the development of a lithium-ion battery with good high-temperature characteristics is required.

Summary of the Invention

[0004] To solve the problems existing in the prior art, the present invention provides an electrolyte solution. In one aspect of the present invention, there is provided an electrolyte solution comprising fluoroethylene carbonate and a P-N bond-containing compound, wherein the P-N bond-containing compound comprises a compound represented by Formula I.

Chemical formula

Chemical formula

Chemical formula

[0005] In some embodiments of the present invention, the P-N bond-containing compound comprises at least one of the following compounds.

Chemical formula

[0006] In some embodiments of the present invention, based on the mass of the electrolyte, the mass percentage of the P-N bond-containing compound in the electrolyte is 0.1% to 5%.

[0007] In some embodiments of the present invention, the electrolyte further contains a sulfur-containing compound represented by Formula II.

Chemical formula

[0008] R 21 and R 22 are each independently a linear or branched, substituted or unsubstituted C1-C6 alkyl group, a substituted or unsubstituted C3-C6 cycloalkyl group, a substituted or unsubstituted C1-C6 alkoxy group, a substituted or unsubstituted C2-C6 alkenyl group, a substituted or unsubstituted C2-C6 alkynyl group, a sulfone group, a silane group, a cyano group, R 23 O-, and the substituent is a halogen atom, and R 23 is selected from a C1-C6 alkyl group, a substituted or unsubstituted C3-C6 cycloalkyl group, or a substituted or unsubstituted C3-C6 heterocyclyl group. Alternatively, R 21 and R 22 are bonded to each other to form a substituted or unsubstituted cyclic group having 3 to 4 carbon atoms together with the sulfone group.

[0009] In some embodiments of the present invention, the sulfur-containing compound includes one or more of the following compounds.

Chemical formula

[0010] In some embodiments of the present invention, the mass percentage of the sulfur-containing compound of Structural Formula II in the electrolyte is 1% to 6%.

[0011] In some embodiments of the present invention, the electrolyte further contains a cyclic phosphoric anhydride compound, and the cyclic phosphoric anhydride compound has a compound represented by Formula III. [Chemical formula] R 31 and R 32 and R 33 are each independently selected from H, a substituted or unsubstituted C1-C5 saturated alkyl group, a substituted or unsubstituted C2-C 10 unsaturated alkyl group, and a C6-C 18 aromatic ring. For example, the substituted or unsubstituted C1-C5 saturated alkyl group includes, but is not limited to, a methyl group, a methylene group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, etc. The substituted or unsubstituted C2-C 10 unsaturated alkyl group includes, but is not limited to, a vinyl group, a propenyl group, a cyclopropenyl group, a 1-butenyl group, a 3-pentenyl group, a propynyl group, etc.

[0012] In some embodiments of the present invention, the cyclic phosphate anhydride compound includes one or more of the following compounds. [Chemical formula]

[0013] In some embodiments of the present invention, based on the mass of the electrolyte, the mass percentage of the cyclic phosphate anhydride compound in the electrolyte is 0.01% to 3%. For example, the content of the cyclic phosphate anhydride compound may be 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.3%, 1.5%, 2.0%, 3.0%, or a range between any two of the above values.

[0014] Next, a lithium-ion battery according to the second aspect of the present invention will be described.

[0015] In another aspect of the present invention, there is provided an electrochemical device including a positive electrode sheet, a negative electrode sheet, a separator provided between the positive electrode sheet and the negative electrode sheet, an electrolytic solution, and an exterior foil. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector. The positive electrode active material layer contains a positive electrode active material. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on the negative electrode current collector. The negative electrode active material layer contains a negative electrode active material. The electrolytic solution is the electrolytic solution according to the present invention.

[0016] In some embodiments of the present invention, in g / Ah, the ratio W:K of the content value W of the compound of Formula I required per Ah capacity to K is 0.12 to 1.15. K represents the value of the specific surface area per unit mass of the negative electrode active material in m 2 / g, and 1.0 ≤ K ≤ 2.0. The present invention further provides an electronic device including the electrochemical device as described above.

[0017] According to the technical solution of the present invention, the following technical effects can be obtained. Since the electrolytic solution of the present invention contains a P-N bond-containing compound of Formula I, the stability on the surface of the positive electrode active material of the electrolytic solution can be improved. At the same time, this compound can absorb the oxygen released to the positive electrode, suppress the decomposition of the electrolytic solution, reduce the generation of gas, and effectively improve the high-temperature cycle and high-temperature storage characteristics of the lithium-ion battery.

Brief Description of the Drawings

[0018]

Figure 1

Embodiments for Carrying Out the Invention

[0019] In the following, in order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described with reference to the embodiments. It is obvious that the embodiments described below are only a part of the embodiments of the present invention, and not all of the embodiments. The embodiments described here are exemplary and are used for generally understanding the present invention. The embodiments of the present invention should not be construed as limiting the present invention. Based on the technical solutions and embodiments described in the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.

[0020] In the specific embodiments and claims, a list of items connected by terms such as "one of", "a", "a kind of", or other similar terms means any one of the listed items. For example, if items A and B are listed, the phrase "one of A and B" means only A or only B. In other examples, if items A, B, and C are listed, the phrase "one of A, B, and C" means only A, only B, only C, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B, and C. Item A may include one element or a plurality of elements. Item B may include one element or a plurality of elements. Item C may include one element or a plurality of elements.

[0021] In the specific embodiments and claims, a list of items connected by terms such as "at least one of", "at least a", "at least a kind of", or other similar terms means any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A, only B, or A and B. In other examples, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A, only B, only C, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B, and C. Item A may include one element or a plurality of elements. Item B may include one element or a plurality of elements. Item C may include one element or a plurality of elements.

[0022] In the present invention, the following definitions are used (unless otherwise specified). For convenience, the group "C n ~C m " group means a group having "n" to "m" carbon atoms, and "n" and "m" are integers. For example, the "C1~C10" alkyl group is an alkyl group having 1 to 10 carbon atoms.

[0023] As used herein, the term "halogen" may be F, Cl, Br, or I. As used herein, the term "cyano group" includes an organic substance containing the organic group -CN. In order to solve the problems existing in the prior art, the present invention provides an electrolytic solution.

[0024] I. Electrolytic solution One aspect of the present invention provides an electrolytic solution containing fluoroethylene carbonate (FEC) and a P-N bond-containing compound having a compound represented by Formula I.

Chemical formula

[0025] In one embodiment of the present invention, a and b satisfy 0.1 ≦ a / b ≦ 150. When a and b satisfy 0.1 ≦ a / b ≦ 150, better high-temperature characteristics can be obtained.

[0026] In one embodiment of the present invention, the compound having the structure represented by the formula I includes at least one of the compound represented by the formula I-A and the compound represented by the formula I-B.

Chemical formula

Chemical formula

[0027] In some embodiments of the present invention, the P-N bond-containing compound includes at least one of the following compounds.

Chemical formula

Chemical formula

[0028] In some embodiments of the present invention, based on the mass of the electrolyte, the mass percentage of the P-N bond-containing compound in the electrolyte is 0.1% to 5%. When the content of the phosphorus-containing additive is less than 0.1%, the formed protective film becomes insufficient, and the influence on the battery characteristics is not significant. However, when the content exceeds 5%, the impedance of the formed film increases, affecting the battery characteristics.

[0029] In some embodiments of the present invention, based on the mass of the electrolyte, the mass percentage of the P-N bond-containing compound in the electrolyte is 0.1% to 3%. For example, the content of the P-N bond-containing compound may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, or within a range between any two of the above values.

[0030] In some embodiments of the present invention, the electrolyte further contains a sulfur-containing compound represented by Formula II.

Chemical formula

[0031] In some embodiments of the present invention, the sulfur-containing compound includes one or more of the following compounds.

Chemical formula

Chemical formula

[0032] In some embodiments of the present invention, the mass percentage of the sulfur-containing compound of Structural Formula II in the electrolyte is 1% to 6%. For example, the content of the sulfur-containing compound of Structural Formula II may be 1%, 1.5%, 1.8%, 2.0%, 2.2%, 2.4%, 2.5%, 3%, 3.2%, 3.5%, 3.7%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, or within the range between any two of the above values.

[0033] The sulfur-containing compound has high positive and negative electrode film-forming potentials, excellent thermal stability in the formed interfacial film, is rich in lithium ion transmission groups, and due to the synergistic effect with the phosphorus-containing compound of Formula I, it can greatly improve the stability of the interface on the surface of the positive electrode, protect the interface of the positive electrode, and suppress the consumption of the electrolyte. Therefore, the high-temperature cycle and high-temperature storage characteristics of the battery can be improved.

[0034] In some embodiments of the present invention, the electrolyte further contains a cyclic phosphoric anhydride compound, and the cyclic phosphoric anhydride compound includes a compound represented by Formula III.

Chemical formula

[0035] In some embodiments of the present invention, the cyclic phosphoric anhydride compound includes one or more of the following compounds.

Chem.

[0036] In some embodiments of the present invention, based on the mass of the electrolyte, the mass percentage of the cyclic phosphoric anhydride compound in the electrolyte is 0.01% to 3%. For example, the content of the cyclic phosphoric anhydride compound may be 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.3%, 1.5%, 2.0%, 3.0%, or in the range between any two of the above values.

[0037] Since the cyclic phosphoric anhydride compound can undergo complex reactions with the components in the SEI film formed at the negative electrode interface, it contributes to the formation of a more stable SEI film for the interface film and can significantly reduce the impedance of the negative electrode interface film. However, due to the synergistic effect with the above additives, the lithium-ion battery has good high-temperature cycle, high-temperature storage characteristics and low resistance.

[0038] In some embodiments of the present invention, the lithium salt is selected from inorganic lithium salts and / or organic lithium salts. Preferably, the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(oxalato)borate (LiBOB), and lithium difluoro(oxalato)borate (LiDFOB).

[0039] In some embodiments of the present invention, the concentration of the lithium salt in the electrolyte is 0.6 mol / L to 2 mol / L.

[0040] II. Electrochemical device The present invention further provides an electrochemical device comprising the electrolyte according to the present invention. Next, a lithium-ion battery according to the second aspect of the present invention will be described.

[0041] Another aspect of the present invention provides an electrochemical device including a positive electrode sheet, a negative electrode sheet, a separator provided between the positive electrode sheet and the negative electrode sheet, an electrolytic solution, and an exterior foil. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material. The electrolytic solution is the electrolytic solution according to the present invention.

[0042] In some embodiments of the present invention, in terms of g / Ah, the ratio W:K of the value W of the content of the compound represented by the formula I required per Ah capacity is 0.12 to 1.15. K is m 2 It represents the value of the specific surface area per unit mass of the negative electrode active material expressed in / g, and 1.0 ≤ K ≤ 2.0. The specific surface area of the negative electrode active material can be achieved by controlling the selection of the negative electrode active material.

[0043] The present invention further provides an electronic device including the electrochemical device. The technical solution provided by the present invention can achieve the following beneficial effects. Since the electrolytic solution of the present invention contains a P-N bond-containing compound of formula I, the stability on the surface of the positive electrode active material of the electrolytic solution can be improved. At the same time, this compound absorbs the oxygen released to the positive electrode and suppresses the decomposition of the electrolytic solution, thereby reducing the generation of gas, and effectively improving the high-temperature cycle and high-temperature storage characteristics of the lithium-ion battery.

[0044] Examples Hereinafter, the present invention will be further described with reference to examples. It should be understood that these examples are merely for explaining the present invention and do not limit the scope of the present invention.

[0045] Preparation of electrolyte: In a glove box with an argon gas atmosphere having a water content of < 10 ppm, ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at a mass ratio of EC:EMC:DEC = 30:50:20. Further, a sufficiently dried lithium salt LiPF6 was dissolved in the above non-aqueous solvent to make the content of LiPF6 1 mol / L. Finally, an additive of a certain mass was added to prepare the electrolyte in the examples. As shown in Table 1, a compound containing the formula I or other blended additives were added to the base electrolyte.

[0046] Preparation of electrolyte: In a glove box with an argon gas atmosphere having a water content of < 10 ppm, ethylene carbonate (abbreviated as EC), diethyl carbonate (abbreviated as DEC), and propylene carbonate (abbreviated as PC) were uniformly mixed at a mass ratio of 3:4:3. Further, a sufficiently dried lithium salt LiPF6 was dissolved in the above non-aqueous solvent, and finally, an additive of a certain mass was added to prepare the electrolyte in the examples. As shown in Table 1, a phosphorus-containing additive, a linear or cyclic sulfur-containing compound, and a cyclic phosphate ester additive were added to the base electrolyte.

[0047] 1. Preparation of battery (1) Preparation of positive electrode sheet Lithium cobaltate, conductive agent Super P, and polyvinylidene fluoride were mixed at a mass ratio of 96:2:2, N-methylpyrrolidone was added, and the mixture was stirred by a vacuum stirrer until the system became uniform to obtain a positive electrode slurry with a solid content of 75 wt%. The positive electrode slurry was uniformly coated on an aluminum foil which is a positive electrode current collector. After drying the aluminum foil at 85 °C, it was cold-rolled, cut, and slit, and then dried under vacuum conditions at 85 °C for 4 h to obtain a positive electrode sheet.

[0048] (2) Preparation of negative electrode sheet Artificial graphite, sodium carboxymethyl cellulose (abbreviated as CMC), and styrene-butadiene rubber (abbreviated as SBR) were mixed at a mass ratio of 97:1:2, deionized water was added, and a negative electrode slurry with a solid content of 54 wt% was obtained using a vacuum stirrer. The negative electrode slurry was uniformly coated on a copper foil, which is the negative electrode current collector. After drying the copper foil at 85 °C, it was subjected to cold pressing, cutting, and slitting, and then dried under vacuum conditions at 120 °C for 12 h to obtain a negative electrode sheet.

[0049] (3) Preparation of the electrolyte In a glove box under a dry argon gas atmosphere, ethylene carbonate (abbreviated as EC), diethyl carbonate (abbreviated as DEC), and propylene carbonate (abbreviated as PC) were mixed at a mass ratio of 3:4:3. Next, additives were added and dissolved, and after sufficient stirring, lithium salt LiPF6 was added and uniformly mixed to obtain an electrolyte with a LiPF6 concentration of 1.15 mol / L. The specific types and contents of the additives used in the electrolyte are as shown in Tables 1, 2, and 3. The content of the additive is the mass percentage calculated based on the mass of the electrolyte.

[0050] (4) Preparation of the separator As the separator, polyethylene (PE) with a thickness of 7 μm was used.

[0051] (5) Preparation of the lithium-ion battery The positive electrode sheet, separator, and negative electrode sheet were stacked in sequence, with the separator interposed between the positive electrode sheet and the negative electrode sheet to play a role in isolation, and then wound to obtain a bare cell. After welding the tabs, the bare cell was placed in an aluminum plastic film, which is the outer packaging foil, and the electrolyte prepared above was injected into the dried bare cell. Through processes such as vacuum sealing, standing, formation (charging to 3.3 V at a constant current of 0.02C and then charging to 3.6 V at a constant current of 0.1C), shaping, and capacity measurement, a soft package lithium-ion battery (thickness 3.3 mm, width 39 mm, length 96 mm) was obtained.

[0052] 2. Measurement method Measurement 1: Measurement of the high-temperature storage characteristics of the lithium-ion battery The battery was discharged to 3.0 V at 25 °C and 0.5 C, then charged at a constant current of 0.7 C to 4.45 V, and charged at a constant voltage until the current reached 0.05 C at 4.45 V. The thickness of the battery was measured with a micrometer and recorded as H 11 It was fully charged at 85 °C and stored for 24 hours. After 24 hours, the thickness of the battery was measured with a micrometer and recorded as H 12 and recorded as such. Thickness expansion rate = (H 12 - H 11 ) / H 11 × 100%

[0053] Measurement Two: Measurement of the high-temperature cycle of the lithium-ion battery The lithium-ion battery was placed in a constant-temperature box at 45 °C and left to stand for 30 minutes to bring the lithium-ion battery to a constant temperature. The lithium-ion battery at a constant temperature was discharged at a constant current of 0.2 C to 3.0 V at 45 °C and left to stand for 3 minutes. After charging at a constant current of 0.7 C to 4.45 V, it was charged at a constant voltage of 4.45 V until the current reached 0.025 C and left to stand for 5 minutes. Next, it was discharged at a constant current of 0.2 C until the voltage reached 3.0 V and left to stand for 3 minutes. This was regarded as one charge-discharge cycle. In this way, it was charged / discharged, and the capacity retention rate after the battery had undergone 500 cycles was calculated. Capacity retention rate (%) of the lithium-ion battery after 500 cycles = Discharge capacity of the 500th cycle / Discharge capacity of the first cycle × 100%

[0054] Measurement Three: Measurement of the direct current resistance DCR (0 °C) of the lithium-ion battery The lithium-ion battery was left standing in a high and low temperature test chamber at 0°C for 4 hours to equilibrate the temperature of the lithium-ion battery. It was charged at a constant current of 0.1C up to 4.45V, then charged at a constant voltage until the current reached 0.05C, and left standing for 10 minutes. Further, it was discharged at a constant current of 0.1C down to 3.4V, left standing for 5 minutes, and the capacity in this step was used as a reference. Under the condition of 0°C, the battery was charged at a constant current of 0.1C up to 4.45V, then charged at a constant voltage until the current reached 0.05C, and left standing for 10 minutes. It was discharged at a constant current of 0.1C for 8h (calculated using the actual capacity obtained in the previous step), and the voltage at this time was recorded as V1. Next, it was discharged at a constant current of 1C for 1s (the capacity was calculated based on the nominal capacity of the battery), and the voltage at this time was recorded as V2. The DC resistance corresponding to the 20% SOC state of the battery was calculated. 20% SOC DC resistance = (V2 - V1) / (1C - 0.1C)

[0055] 3. Measurement Results (1) Influence of P-N type-containing additives and fluoroethylene carbonate additives on the battery characteristics.

[0056] [Table 1]

[0057] By comparing Comparative Example 1 and Comparative Example 2, it was found that the addition of the P-N bond-containing compound has a good effect on improving the high-temperature cycle and high-temperature storage. This is because the P-N bond-containing compound can improve the stability of the active material on the surface of the electrolyte, absorb the oxygen released from the positive electrode, and suppress the decomposition of the electrolyte, thereby reducing the generation of gas and effectively improving the high-temperature cycle characteristics and high-temperature storage characteristics of the lithium-ion battery. By comparing Examples 1 to 9, it was found that when the P-N bond-containing compound (content b%) and FEC (content a%) are used in combination and 0.1 ≦ a / b ≦ 200 is satisfied, the high-temperature storage characteristics and cycle characteristics can be further improved.

[0058] By comparing Examples 1 to 16 with Comparative Examples 3 to 4, when a / b < 0.1, the improvement of the high-temperature cycle is not significant. This is because the low LiF content in the negative electrode results in poor mechanical stability of the formed SEI film, which is disadvantageous for cycle improvement. When a / b > 200, the improvement of the high-temperature cycle is significant, but the deterioration of high-temperature storage is relatively obvious. This is because when the FEC content is too high, it is easily oxidized and decomposed to generate gas, deteriorating the high-temperature storage characteristics. (2) Influence of P-N-containing additives and S-containing additives on battery characteristics.

[0059]

Table 2

[0060] By comparing Examples 17 to 22 with Example 6 and Comparative Example 5, the addition of the compound of Formula II has a good effect on improving the high-temperature cycle and high-temperature storage. This is because the addition of the compound of Formula II can further improve the stability of the SEI interfacial film, and further improve the stability of the electrolyte on the surface of the active material, suppress the decomposition of the electrolyte, reduce the generation of gas, and effectively improve the high-temperature cycle and high-temperature storage characteristics of the lithium-ion battery.

[0061] By comparing Examples 23 to 26, similar effects can be achieved by the synergistic effect of different compounds of Formula I and Formula II. However, it was found that when the addition amount of the compound of Formula II is too high, the high-temperature storage characteristics are affected. This is because the protective films formed on the positive and negative electrodes are too thick, increasing the resistance and affecting the electrical characteristics.

[0062] By comparing Examples 27 to 29, similar improvement effects can be achieved by using different combinations of compounds of Formula II. (3) Influence of the synergistic effect of P-N-containing additives, S-containing additives, and cyclic phosphoric anhydride on battery characteristics

[0063] Table 3 shows the electrolyte parameters and electrical property data of Example 4, Example 23, Examples 24 to 29, and Comparative Example 6. Examples 30 to 40 are obtained by adding the substances shown in Table 3 based on Example 4.

[0064]

Table 3

[0065] By comparing the measurement results of Comparative Example 6 with those of Examples 30 to 41, it was found that when only the additive of Formula III is added to the electrolyte, the high-temperature cycle capacity retention rate and the high-temperature storage volume expansion rate characteristics of the lithium-ion battery deteriorate. This is because there is no cathode film-forming additive to protect the cathode, so the electrolyte and the cathode react easily, resulting in deterioration of the characteristics of the lithium-ion battery.

[0066] (3) Table 4 shows the influence of the content of the Formula I compound in the electrolyte on the high-temperature storage volume expansion rate and the capacity retention rate of the lithium-ion battery. Each example shown in Table 4 is improved based on Example 4.

[0067]

Table 4

[0068] By comparing the measurement results of Example 4 with those of Examples 42 to 45, when W / K is constant, due to the synergistic effect between Formula I and Formula II, and Formula III, the lithium-ion battery simultaneously has a high high-temperature cycle capacity retention rate, a low high-temperature storage volume expansion rate, and the lithium-ion battery also has a low room-temperature DC resistance.

[0069] As shown in Example 51, when W:K exceeds 1.15, the capacity retention rate of the lithium-ion battery is low. As shown in Example 52, when W:K is less than 0.12, the high-temperature storage volume expansion rate of the lithium-ion battery is large.

[0070] As shown in Examples 46 to 50, as W:K gradually increases within the range of 0.12 to 1.14, the high-temperature storage volume expansion rate of the lithium-ion battery gradually decreases, but the capacity retention rate first increases and then decreases. This is because as the content of the compound of Formula I increases, the positive electrode interface is improved, the stability of the electrolyte is improved, and the P-N bond of the compound of Formula I undergoes a complex reaction with the lithium salt to stabilize the lithium salt and improve the decomposition reaction of the lithium salt at high temperatures, thereby reducing the volume expansion rate during high-temperature storage. However, since the positive electrode film-forming potential of the compound of Formula I is low, it is easy to form a film on the surface of the positive electrode. However, as the content increases, the film-forming resistance increases, resulting in a decrease in the capacity retention rate.

[0071] What is described above are only some embodiments of the present invention and do not limit the present invention to any form. The preferred embodiments of the present invention are disclosed as above, but do not limit the present invention. Those skilled in the art can make changes or modifications to the technical content disclosed above without departing from the technical solution of the present invention, and all of them are the same as equivalent embodiments and all belong to the scope of the technical solution of the present invention.

Claims

1. An electrochemical device comprising: a positive electrode; a negative electrode; a separator provided between the positive electrode and the negative electrode; and an electrolytic solution, wherein the electrolytic solution contains fluoroethylene carbonate and a P-N bond-containing compound, and the P-N bond-containing compound contains a compound having a structure represented by Formula I; 【Chemical 1】 R ０ represents an oxygen atom or is absent, R １ 、 R ２ 、 R ３ 、 R ４ 、 R ５ 、 R ６ are each independently selected from C １ to C ６ alkyl groups, C ２ to C ６ alkenyl groups, C ２ to C ６ alkynyl groups, C １ to C ６ alkoxy groups, and Or, R １ and R ２ R ３ and R ４ or R ５ and R ６ are each bonded to each other to form a cyclic group having 2 to 5 carbon atoms together with the N atom, when the mass percentage of fluoroethylene carbonate in the electrolytic solution is a% and the mass percentage of the P-N bond-containing compound in the electrolytic solution is b% based on the mass of the electrolytic solution, 0.1 ≦ a / b ≦ 200 is satisfied; the electrolytic solution further contains a sulfur-containing compound represented by Formula II; [Chemical Formula 2] R ２１ and R ２２ are each independently a straight-chain or branched-chain, substituted or unsubstituted C １ -C ６ alkyl group, substituted or unsubstituted C ３ -C ６ cycloalkyl group, substituted or unsubstituted C １ -C ６ alkoxy group, substituted or unsubstituted C ２ -C ６ alkenyl group, substituted or unsubstituted C ２ -C ６ alkynyl group, sulfone group, silane group, cyano group, R ２３ O-, selected from, the substituent is a halogen atom, R ２３ is a C １ -C ６ alkyl group, substituted or unsubstituted C ３ -C ６ cycloalkyl group, or substituted or unsubstituted C ３ -C ６ heterocyclyl group, Alternatively, R ２１ and R ２２ are combined with each other to form a substituted or unsubstituted cyclic group having 3 to 4 carbon atoms together with a sulfone group, based on the mass of the electrolytic solution, the mass percentage of the sulfur-containing compound in the electrolytic solution is 1% to 6%; the electrolytic solution further contains a cyclic phosphoric anhydride compound, and the cyclic phosphoric anhydride compound contains a compound represented by Formula III; [Chemical 3] R ３１ , R ３２ , R ３３ are each independently selected from H, a substituted or unsubstituted C １ -C ５ saturated alkyl group, a substituted or unsubstituted C ２ -C １０ unsaturated alkyl group, C ６ -C １８ aromatic ring, and based on the mass of the electrolytic solution, the mass percentage of the cyclic phosphoric anhydride compound in the electrolytic solution is 0.01% to 3%; based on g / Ah, the ratio W:K of the content value W of the compound having the structure represented by Formula I required per Ah capacity to K is 0.12 to 1.15; K represents the value of the specific surface area per unit mass of the negative electrode active material expressed in m2 / g, and 1.0 ≦ K ≦ 2.0, an electrochemical device.

2. The compound having the structure represented by Formula I contains at least one of a compound represented by Formula I-A and a compound represented by Formula I-B. [Chemical Formula 4] [Chemical Formula 5] A １ and A ２ and A ３ is the electrochemical device according to claim 1, each independently selected from a carbon atom, an oxygen atom, and a single bond.

3. The P-N bond-containing compound contains at least one of 【Chemical Formula 6】 The electrochemical device according to Claim 1.

4. Based on the mass of the electrolytic solution, the mass percentage of the P-N bond-containing compound in the electrolytic solution is 0.1% to 5%, and the mass percentage of fluoroethylene carbonate in the electrolytic solution is 0.5% to 15%. The electrochemical device according to any one of Claims 1 to 3.

5. The sulfur-containing compound contains one or more of 【Chemical Formula 7】 The electrochemical device according to any one of Claims 1 to 3.

6. The cyclic phosphoric anhydride compound contains one or more of 【Chemical Formula 8】 The electrochemical device according to any one of Claims 1 to 3.

7. Based on the mass of the electrolytic solution, the mass percentage of the cyclic phosphoric anhydride compound in the electrolytic solution is 0.1% to 3%. The electrochemical device according to Claim 1.

8. The electrolytic solution further contains a trinitrile compound. The trinitrile compound contains at least one of 1,3,5-pentane tricarbonitrile, 1,3,6-hexane tricarbonitrile, 1,2,6-hexane tricarbonitrile, and 1,2,3-tris(2-cyanoethoxy)propane, Based on the mass of the electrolytic solution, the mass percentage of the trinitrile compound in the electrolytic solution is 0.1% to 6%. The electrochemical device according to claim 1.

9. An electronic device including the electrochemical device according to any one of claims 1 to 8.

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