Electrochemical device and electronic device

Abstract

The application discloses an electrochemical device and an electronic device. The electrochemical device comprises a positive electrode and a non-aqueous electrolyte, the positive electrode comprises a positive electrode material layer arranged on at least one surface of a positive electrode current collector, the positive electrode material layer comprises a lithium-containing transition metal composite oxide, the lithium-containing transition metal composite oxide comprises Li x Na z Co 1‑y M y O2, wherein 0.6 < x < 0.95, 0 < y < 0.15, 0 < z < 0.03, M is at least one selected from the group consisting of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr and Zr; the non-aqueous electrolyte comprises a compound of formula I, the mass percentage of the compound of formula I is A%, and 1 < A / z < 200. The electrochemical device provided by the application has relatively optimal electrochemical performance, in particular, relatively optimal high-temperature storage performance and low-temperature discharge performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, and in particular to an electrochemical device and an electronic device. BACKGROUND

[0002] With the increasing demand for electronic products such as mobile phones, notebook computers, cameras and the like year by year, electrochemical devices as power sources for electronic products play an increasingly important role in our daily life, thus promoting the demand for improving the performance of electrochemical devices in various scenarios. While existing technical means improve the high-temperature performance of electrochemical devices, they often lead to the deterioration of the low-temperature discharge performance of electrochemical devices. Therefore, it is urgent to provide electrochemical devices with good high-temperature performance and low-temperature discharge performance. SUMMARY

[0003] The embodiments of the present application provide an electrochemical device and an electronic device, which achieve better high-temperature storage performance, and improve low-temperature discharge performance and cycle performance.

[0004] In a first aspect, the embodiments of the present application provide an electrochemical device, comprising a positive electrode and a non-aqueous electrolyte, the positive electrode comprising a positive electrode material layer disposed on at least one surface of a positive electrode current collector, the positive electrode material layer comprising a lithium-containing transition metal composite oxide, the lithium-containing transition metal composite oxide comprising Li x Na z Co 1-y M y O2, wherein 0.6 < x < 0.95, 0 ≤ y < 0.15, 0 < z ≤ 0.03, M is selected from at least one of the group consisting of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr and Zr; the non-aqueous electrolyte comprising a compound of Formula I:

[0005] compound;

[0006] wherein R is selected from C2 to C6 alkyl unsubstituted or substituted with Ra, C2 to C6 alkenyl unsubstituted or substituted with Ra, C2 to C6 alkynyl unsubstituted or substituted with Ra, C5 to C 12 nitrogen-containing heteroaryl unsubstituted or substituted with Ra, C6 to C 12 aryl unsubstituted or substituted with Ra, each substituent group Ra is independently selected from fluorine or C1 to C6 fluoroalkyl. Wherein the mass percentage content of the compound of Formula I is A% based on the total mass of the non-aqueous electrolyte, 1 ≤ A / z ≤ 200.

[0007] Based on the electrochemical device according to the embodiments of the present application, the inventors found that when the positive electrode material layer comprises a lithium-containing transition metal composite oxide Li x Naz Co 1-y M y O2, wherein element M is selected from at least one of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, and Zr, and compound of formula I is added to the non-aqueous electrolyte in the electrochemical device, and the mass percentage A of compound of formula I in the non-aqueous electrolyte is controlled to be the same as that of lithium-containing transition metal composite oxide Li. x Na z Co 1-y M y The z-value of the Na atom ratio in O2 satisfies the above range, enabling the lone pair electrons in the sulfone functional group of compound I to specifically bind to the lithium-containing transition metal composite oxide Li. x Na z Co 1-y M y During battery formation, the cobalt and M atoms on O2 form a highly stable inorganic protective thin layer containing fluorides and sulfonic acid / sulfate. This reduces the interfacial impedance without affecting high-temperature storage performance, promotes lithium-ion interfacial transport at low temperatures, improves the low-temperature discharge performance of the electrochemical device, and also helps to improve the stability of the cathode material layer at high temperatures, giving the electrochemical device excellent high-temperature storage performance.

[0008] In some embodiments, the mass percentage A% of the Formula I compound in the electrochemical device and the lithium-containing transition metal complex oxide Li x Na z Co 1-y M y The Na content z in O2 satisfies at least one of the following conditions: (1) 5 ≤ A / z ≤ 100; (2) 0.1 ≤ A ≤ 5; (3) 0.005 ≤ z ≤ 0.02. Based on the above embodiments, by adjusting the mass percentage A% of compound I and the Na content z in the lithium transition metal composite oxide to satisfy any of the above conditions, the lithium transition metal composite oxide can better cooperate with compound I in the electrolyte, so that the sulfone functional group in compound I can more completely react with the lithium transition metal composite oxide Li. x Na z Co 1-y M y The cobalt atoms on O2 combine with M atoms, which can further improve the high-temperature storage performance and low-temperature discharge performance of electrochemical devices.

[0009] In some embodiments, the compound of formula I above includes at least one of the following compounds:

[0010]

[0011] Based on the above embodiments, by selecting the above-mentioned type of compound of formula I, the structural R group can better promote the combination of the sulfone functional group and the lithium transition metal composite oxide Li x Na z Co 1-y M y The combination of the cobalt atom and the M atom on O2 takes into account the improvement of the high-temperature storage performance and the low-temperature discharge performance of the electrochemical device.

[0012] In some embodiments, the above-mentioned non-aqueous electrolyte further includes a dinitrile compound as shown in formula II and a trinitrile compound as shown in formula III:

[0013] Compound,

[0014] wherein R0 is selected from a chain alkylene group of C2 to C 10 , an alkenylene group of C2 to C 10 , or -R a -(O-R b ) n -R c -, R a , R b and R c are each independently selected from an alkylene group of C1 to C3 or an alkenylene group of C2 to C3, and n is an integer of 1 to 3;

[0015] Compound,

[0016] wherein R 11 , R 12 and R 13 are each independently selected from an alkylene group of C1 to C3 or -R A -(O-R B ) n -R C -, R A , R B and R C are each independently selected from a single bond, an alkylene group of C1 to C2, and n is an integer of 1 to 3, and R 21 is selected from a hydrogen atom, an alkylene group of C1 to C3; the mass percentage content of the compound of formula II is B%, and the mass percentage content of the compound of formula III is C% based on the total mass of the non-aqueous electrolyte, and 0.05≤A / (B+C)≤50. Based on the above embodiments, the electrochemical device of the present application further adds a certain amount of dinitrile compound and trinitrile compound in the electrolyte. Among them, when 0.05≤A / (B+C)≤50 is controlled, the nitrile molecules in the dinitrile compound and the trinitrile compound can better promote the combination of the sulfone functional group and the lithium transition metal composite oxide Li x Na z Co1-y The cobalt atoms of MyO2 form an oxidation-resistant coating layer rich in cyan groups, and the use of dinitrile compounds and trinitrile compounds in combination can also improve the surface coverage of the oxidation-resistant coating layer, sufficiently passivate the material interface, effectively block the electrolyte molecules from reaching the interface to undergo continuous oxidation reaction, thereby further improving the high-temperature storage performance and low-temperature discharge performance of the electrochemical device.

[0017] In some embodiments, for the mass percentage content A% of the compound of formula I, the mass percentage content B% of the compound of formula II, and the mass percentage content C% of the compound of formula III in the electrochemical device, at least one of the following conditions is satisfied: (1) 0.5≤B+C≤8; (2) 0.1≤A / (B+C)≤2; (3) 0.1≤B≤6; (4) 0.1≤C≤6. Based on the above embodiments, the electrochemical device of the present application regulates the content parameters of the mass percentage content A% of the compound of formula I, the mass percentage content B% of the compound of formula II, and the mass percentage content C% of the compound of formula III within the above ranges, so that the content of each compound, especially the content ratio of dinitrile compounds and trinitrile compounds, is within a suitable range, which is more conducive to the synergistic effect of dinitrile compounds and trinitrile compounds, further improving the surface coverage, more fully passivating the material interface, thereby further improving the high-temperature storage performance and low-temperature discharge performance of the electrochemical device.

[0018] In some embodiments, the compound of formula II described above is selected from at least one of butanedinitrile, pentanedinitrile, methylpentanedinitrile, hexanedinitrile, heptanedinitrile, octanedinitrile, trans-butenedinitrile, or 1,2-bis(cyanoethoxy)ethane.

[0019] In some embodiments, the compound of formula III described above is selected from at least one of 1,3,5-pentanetristrile, 1,3,6-hexanetristrile, or 1,2,3-tris(2-cyanoethoxy)propane. The use of the above-mentioned compounds of formula II and / or formula III can improve the combination efficiency of the cobalt atoms of MyO2, improve the surface coverage of the oxidation-resistant coating layer rich in cyan groups, and more fully passivate the material interface, thereby further improving the high-temperature storage performance and low-temperature discharge performance of the electrochemical device. x Na z Co 1-y M y O2, improve the surface coverage of the oxidation-resistant coating layer rich in cyan groups, and more fully passivate the material interface, thereby further improving the high-temperature storage performance and low-temperature discharge performance of the electrochemical device.

[0020] In some embodiments, the non-aqueous electrolyte further comprises a cyclic carbonate selected from at least two of ethylene carbonate, propylene carbonate, or fluoroethylene carbonate; and the cyclic carbonate has a mass percentage of 1% to 30% based on the total mass of the non-aqueous electrolyte. Preferably, the cyclic carbonate has a mass percentage of 2% to 15%. Based on the above embodiments, the cyclic carbonate is selected and the content of the cyclic carbonate is controlled within the above range, which can further improve the high-temperature storage performance, and further improve the low-temperature discharge performance of the electrochemical device.

[0021] In some embodiments, the non-aqueous electrolyte further comprises a linear ester, which includes a fluorinated linear ester and a non-fluorinated linear ester. The linear ester satisfies at least one of the following conditions: (1) the fluorinated linear ester is selected from at least one of methyl difluoroethyl carbonate, methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate, methyl hexafluoroisopropyl carbonate, di(2,2,2-trifluoroethyl) carbonate, 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, hexafluoroisopropyl acetate, 2,2-difluoroethyl propionate, 2,2,2-trifluoroethyl propionate, or hexafluoroisopropyl propionate. (2) the non-fluorinated linear ester is selected from at least one of dimethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate. (3) the linear ester has a mass percentage of X0% based on the total mass of the non-aqueous electrolyte, and 10≤X0≤70, preferably 15≤X0≤50. Based on the above embodiments, the linear ester including the fluorinated linear ester and the non-fluorinated linear ester is selected and the content of the linear ester is controlled within the above range, which can further improve the high-temperature storage performance, and further improve the low-temperature discharge performance of the electrochemical device.

[0022] In some embodiments, the mass percentage of the linear ester X0%, the mass percentage of the fluorinated linear ester X1%, and the mass percentage of the non-fluorinated linear ester X2% in the non-aqueous electrolyte satisfy at least one of the following conditions: (1) 10≤X1≤50; (2) 5≤X2≤50. Based on the above embodiments, the content parameters of the fluorinated linear ester X1% and the non-fluorinated linear ester X2% in the non-aqueous electrolyte are controlled within the above range, so that the content of each compound, especially the content of the fluorinated linear ester, is within a suitable range, which is more conducive to further improving the high-temperature storage performance, and further improving the low-temperature discharge performance of the electrochemical device.

[0023] In some embodiments, the non-aqueous electrolyte further comprises an inner salt, specifically including a compound of formula IV and / or a compound of formula V:

[0024] Compound, Compound.

[0025] wherein R1 to R5 are each independently selected from a hydrogen atom, a fluorine atom, a vinyl group, an ethynyl group or an anhydride group; the total mass percentage of the compound of formula IV and the compound of formula V is 0.1% to 1% based on the total mass of the non-aqueous electrolyte; any two adjacent groups among R1 to R5 are independently present or connected by a covalent bond and connected to the parent ring to form a ring. Based on the above-mentioned embodiments, the electrochemical device of the present application further adds a certain amount of internal salt substances in the electrolyte, which can complex the lithium-containing transition metal composite oxide Li x Na z Co 1-y M y O2dissolved and free in the electrolyte, greatly reduces the deposition of transition metal ions on the negative electrode, improves the stability of SEI, and further improves the cycle performance, high-temperature storage performance and low-temperature discharge performance of the electrochemical device.

[0026] In some embodiments, the compound of formula IV includes at least one of the following compounds:

[0027]

[0028] The compound of formula V includes at least one of the following compounds:

[0029]

[0030] Based on the above-mentioned embodiments, the above-mentioned internal salt substances can be selected to more efficiently complex the lithium-containing transition metal composite oxide Li x Na z Co 1-y M y O2dissolved and free in the electrolyte, reduces the deposition of transition metal ions on the negative electrode, improves the stability of SEI, and further improves the cycle performance, high-temperature storage performance and low-temperature discharge performance of the electrochemical device.

[0031] In a second aspect, the embodiments of the present application provide an electronic device comprising the above-mentioned electrochemical device. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0033] The embodiments of the present application provide an electrochemical device, which comprises a positive electrode, a non-aqueous electrolyte, a negative electrode and a separator.

[0034] positive electrode

[0035] The positive electrode includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector. The positive electrode material layer includes a lithium-containing transition metal complex oxide including Li x Na z Co 1-y M y O2, where 0.6 < x < 0.95, 0 ≤ y < 0.15, 0 < z ≤ 0.03, and M is selected from at least one of the group consisting of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, and Zr. For example, the above indices can be 0.6 < x < 0.7, 0 ≤ y < 0.10, and 0 < z < 0.01; 0.7 < x < 0.8, 0.05 < y < 0.10, and 0 < z < 0.02; 0.8 < x < 0.9, 0.06 < y < 0.09, and 0 < z ≤ 0.03; 0.9 < x < 0.95, 0.07 < y < 0.08, and 0.01 < z < 0.02; 0.6 < x < 0.9, 0.08 < y < 0.15, and 0.01 < z ≤ 0.03. The addition of the above-described lithium-containing transition metal complex oxide to the positive electrode material layer in the electrochemical device, and the control of the content ratio of each metal atom, particularly the content ratio of sodium atoms, in the lithium-containing transition metal complex oxide to satisfy the above ranges, can improve both the high-temperature storage performance and the low-temperature discharge performance of the electrochemical device.

[0036] In some embodiments, the positive electrode material layer includes a positive electrode conductive material; the type of the positive electrode conductive material is not limited, and any known conductive material can be used. Examples of the positive electrode conductive material can include, but are not limited to, carbon black such as acetylene black, Super-P, and the like; amorphous carbon such as needle coke and the like; carbon nanotubes; graphene and the like. The above-described positive electrode conductive materials can be used alone or in any combination.

[0037] In some embodiments, the positive electrode material layer includes a positive electrode binder; the kind of the positive electrode binder is not particularly limited, and in the case of a coating method, it is only required to be a material that is soluble or dispersible in a liquid medium used at the time of electrode production. Examples of the positive electrode binder can include, but are not limited to, one or more of the following: resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, nitrocellulose, and the like; rubber-like polymers such as styrene butadiene rubber, nitrile rubber, fluororubber, isoprene rubber, polybutadiene rubber, ethylene-propylene rubber, and the like; thermoplastic elastomer-like polymers such as styrene-diene-styrene block copolymer or hydrogenated product thereof, ethylene-propylene-diene terpolymer, styrene-ethylene-butadiene-ethylene copolymer, styrene-isoprene-styrene block copolymer or hydrogenated product thereof, and the like; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, propylene-a-olefin copolymer, and the like; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene-ethylene copolymer, and the like; and ion-conducting polymer compositions having alkali metal ions, and the like. The above positive electrode binders can be used alone or in any combination.

[0038] The kind of the solvent used to form the positive electrode slurry is not limited, and it is only required to be a solvent capable of dissolving or dispersing the positive electrode active material, the conductive material, the positive electrode binder, and a thickening agent used as necessary. Examples of the solvent used to form the positive electrode slurry can include any one of an aqueous solvent and an organic solvent. Examples of the aqueous medium can include, but are not limited to, a mixed medium of alcohol and water or water, and the like. Examples of the organic medium can include, but are not limited to, aliphatic hydrocarbons such as hexane, and the like; aromatic hydrocarbons such as benzene, toluene, xylene, methylnaphthalene, and the like; heterocyclic compounds such as quinoline, pyridine, and the like; ketones such as acetone, methyl ethyl ketone, cyclohexanone, and the like; esters such as methyl acetate, methyl acrylate, and the like; amines such as diethylenetriamine, N,N-dimethylaminopropylamine, and the like; ethers such as diethyl ether, propylene oxide, tetrahydrofuran, and the like; amides such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, and the like; aprotic polar solvents such as hexamethylphosphoramide, dimethyl sulfoxide, and the like.

[0039] The thickening agent is generally used to adjust the viscosity of the slurry. In the case of using an aqueous medium, the slurry can be formed using a thickening agent and a styrene butadiene rubber emulsion. The kind of the thickening agent is not particularly limited, and examples thereof can include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphated starch, casein, and salts thereof, and the like. The above thickening agents can be used alone or in any combination.

[0040] The kind of the positive electrode current collector is not particularly limited, and it can be any material known to be suitable for use as a positive electrode current collector. Examples of the positive electrode current collector can include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, and the like; and materials such as carbon cloth, carbon paper, and the like. In some embodiments, the positive electrode current collector is a metal material. In some embodiments, the positive electrode current collector is aluminum.

[0041] In order to reduce the electronic contact resistance of the positive electrode current collector and the positive electrode material layer, the surface of the positive electrode current collector can include a conductive aid or a conductive coating. Examples of the conductive aid can include, but are not limited to, carbon and noble metals such as gold, platinum, silver, and the like. Examples of the conductive coating can include a mixture layer containing an inorganic oxide, a conductive agent, and a binder.

[0042] Non-aqueous electrolyte

[0043] The non-aqueous electrolyte used in the electrochemical device of the embodiments of the present application includes an electrolyte and a solvent that dissolves the electrolyte. In some embodiments, the non-aqueous electrolyte of the present application includes a compound of Formula I:

[0044] Compound;

[0045] wherein R is selected from the group consisting of C2 to C6 alkyl unsubstituted or substituted with Ra, C2 to C6 alkenyl unsubstituted or substituted with Ra, C2 to C6 alkynyl unsubstituted or substituted with Ra, C5 to C 12 nitrogen-containing heteroaryl unsubstituted or substituted with Ra, C6 to C 12 aryl unsubstituted or substituted with Ra, each substituent group Ra is independently selected from the group consisting of fluorine or C1 to C6 fluoroalkyl. For example, R is selected from the group consisting of C2 alkyl, C4 alkyl, C6 alkyl, fluorine-substituted C5 alkenyl, fluorine-substituted C7 alkynyl, fluorine-substituted C 10 nitrogen-containing heteroaryl, C2 fluoroalkyl-substituted C6 alkyl, C2 fluoroalkyl-substituted C 12 aryl.

[0046] In some embodiments, the mass percentage content of the compound of Formula I is A% based on the total mass of the non-aqueous electrolyte, and the lithium-containing transition metal composite oxide Li x Na z Co 1-y M yO2, 1≤A / z≤200. In some embodiments, 5≤A / z≤100. In some embodiments, 10≤A / z≤20. In some embodiments, 50≤A / z≤80. In some embodiments, 25≤A / z≤70. In some embodiments, 35≤A / z≤55. In some embodiments, 0.1≤A≤5, for example, A is 0.1, 0.2, 0.5, 1.0, 2.0, 2.5, 3.0, 4.0, 5.0, or a value within a range defined by any two of these values. In some embodiments, 0.005≤z≤0.03. For example, z is 0.005, 0.01, 0.015, 0.02, 0.023, 0.028, 0.03, or a value within a range defined by any two of these values. By adding the compound of formula I to the nonaqueous electrolyte in the electrochemical device and controlling the value of A in the mass percentage of the compound of formula I in the nonaqueous electrolyte and the value of z in the lithium-containing transition metal composite oxide and the ratio thereof to satisfy the above ranges, the high-temperature storage performance of the electrochemical device can be improved, and the low-temperature discharge performance of the electrochemical device can also be improved.

[0047] In some embodiments, the compound of formula I described above includes at least one of the following compounds:

[0048]

[0049] For example, the compound of formula I is a mixture of a compound of formula I-1, a compound of formula I-8, a compound of formula I-13, a compound of formula I-2, and a compound of formula I-7, a mixture of a compound of formula I-4 and a compound of formula I-11, a mixture of a compound of formula I-2 and a compound of formula I-14. By selecting the compound of formula I of the above type, the high-temperature storage performance and the low-temperature discharge performance of the electrochemical device can be improved.

[0050] In some embodiments, the nonaqueous electrolyte described above further includes a dinitrile compound as shown in formula II and a trinitrile compound as shown in formula III:

[0051] Compound.

[0052] wherein R0is selected from C2to C 10 chained alkylene, C2to C 10 alkenylene, or -R a -(O-R b ) n -R c -, R a , R b , and R c are each independently selected from C1to C3alkylene or C2to C3alkenylene, and n is an integer from 1 to 3.

[0053] Compound.

[0054] wherein R 11 , R 12 and R 13 are each independently selected from a C1 to C3 alkylene group or -R A -(O-R B ) n -R C -, R A , R B and R C are each independently selected from a single bond, a C1 to C2 alkylene group, n is an integer of 1 to 3, and R 21 is selected from a hydrogen atom, a C1 to C3 alkylene group. In some embodiments, the mass percentage content of the compound of formula II is B%, the mass percentage content of the compound of formula III is C%, and 0.05≤A / (B+C)≤50. In some embodiments, 1≤A / (B+C)≤30. In some embodiments, 10≤A / (B+C)≤20. In some embodiments, 5≤A / (B+C)≤25. In some embodiments, 0.1≤A / (B+C)≤2. By adding the compound of formula II and the compound of formula III in a nonaqueous electrolyte in an electrochemical device, and controlling the ratio of the sum of the mass percentage content of the compound of formula II and the compound of formula III to the A value in the mass percentage content of the compound of formula I in the nonaqueous electrolyte to satisfy the above range, both the high-temperature storage performance and the low-temperature discharge performance of the electrochemical device can be improved.

[0055] In some embodiments, the mass percentage content B% of the compound of formula II and the mass percentage content C% of the compound of formula III satisfy 0.5≤B+C≤8. In some embodiments, 2≤B+C≤8. In some embodiments, 5≤B+C≤7. In some embodiments, 4≤B+C≤6. In some embodiments, 0.5≤B+C≤3. In some embodiments, 0.1≤B≤6, for example, B is 0.1, 0.5, 1, 2, 3.5, 4, 6, or a value within a range consisting of any two of these values. In some embodiments, 0.1≤C≤6. For example, C is 0.1, 0.3, 1, 2, 4, 5, 6, or a value within a range consisting of any two of these values. By controlling the mass percentage content B% of the compound of formula II, the mass percentage content C% of the compound of formula III, and the sum of their mass percentage contents to satisfy the above range in a nonaqueous electrolyte, both the high-temperature storage performance and the low-temperature discharge performance of the electrochemical device can be improved.

[0056] In some embodiments, the compound of Formula II is selected from at least one of succinonitrile, glutaronitrile, methylglutaronitrile, adiponitrile, pimelonitrile, suberonitrile, fumaronitrile, or 1,2-bis(cyanoethoxy)ethane. In some embodiments, the compound of Formula III is selected from at least one of 1,3,5-pentanetricarbonitrile, 1,3,6-hexanetricarbonitrile, or 1,2,3-tris(2-cyanoethoxy)propane. By selecting the compound of Formula II and the compound of Formula III of the above-mentioned kinds, both the high-temperature storage performance and the low-temperature discharge performance of the electrochemical device can be improved.

[0057] In some embodiments, the above-mentioned nonaqueous electrolyte further includes a cyclic carbonate selected from at least two of ethylene carbonate, propylene carbonate, or fluoroethylene carbonate. In some embodiments, the mass percentage of the cyclic carbonate is 1% to 30% based on the total mass of the nonaqueous electrolyte. In some embodiments, for example, the mass percentage of the cyclic carbonate is 2%, 5%, 10%, 17%, 22%, 29%, or a value within a range consisting of any two of these values. In some embodiments, preferably, the mass percentage of the cyclic carbonate is 2% to 15%. By adding the cyclic carbonate to the nonaqueous electrolyte in the electrochemical device and controlling the mass percentage of the cyclic carbonate in the nonaqueous electrolyte to satisfy the above-mentioned range, both the high-temperature storage performance and the low-temperature discharge performance of the electrochemical device can be improved.

[0058] In some embodiments, the above-mentioned nonaqueous electrolyte further includes a linear ester, which includes a fluorinated linear ester and a non-fluorinated linear ester. The above-mentioned fluorinated linear ester is selected from at least one of methyl difluoroethyl carbonate, methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate, methyl hexafluoroisopropyl carbonate, di(2,2,2-trifluoroethyl) carbonate, 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, hexafluoroisopropyl acetate, 2,2-difluoroethyl propionate, 2,2,2-trifluoroethyl propionate, or hexafluoroisopropyl propionate. The above-mentioned non-fluorinated linear ester is selected from at least one of dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate. In some of these embodiments, the mass percentage of the linear ester is X0% based on the total mass of the nonaqueous electrolyte, 10 ≤ X0 ≤ 70, preferably 15 ≤ X0 ≤ 50. For example, X0 is 10, 15, 25, 22, 31, 45, 50, 70, or a value within a range consisting of any two of these values. By selecting the linear ester of the above-mentioned kinds and controlling the mass percentage of the linear ester in the nonaqueous electrolyte to satisfy the above-mentioned range, both the high-temperature storage performance and the low-temperature discharge performance of the electrochemical device can be improved.

[0059] In some embodiments, the above non-aqueous electrolyte includes the fluorinated linear ester in a mass percentage X1%, 10≤X1≤50. For example, X1 is 10, 12, 26, 35, 41, 47, 50, or a value within a range defined by any two of these values. In some embodiments, the non-fluorinated linear ester is included in a mass percentage X2%, 5≤X2≤50. For example, X2 is 5, 9, 18, 24, 33, 40, 50, or a value within a range defined by any two of these values. By controlling the mass percentages of the fluorinated linear ester and the non-fluorinated linear ester in the non-aqueous electrolyte to satisfy the above ranges, both the high-temperature storage performance and the low-temperature discharge performance of the electrochemical device can be improved.

[0060] In some embodiments, the above non-aqueous electrolyte further includes an inner salt-type substance, specifically including a compound of Formula IV and / or a compound of Formula V:

[0061] a compound, a compound.

[0062] wherein R1 to R5 are each independently selected from a hydrogen atom, a fluorine atom, a vinyl group, an ethynyl group, or an anhydride group; the sum of the mass percentages of the compound of Formula IV and the compound of Formula V is 0.1% to 1% based on the total mass of the non-aqueous electrolyte. For example, the sum of the mass percentages of the compound of Formula IV and the compound of Formula V is 0.1%, 0.3%, 0.5%, 0.6%, 0.9%, 1%, or a value within a range defined by any two of these values. In some embodiments, any two adjacent groups among R1 to R5 are independently present or connected by a covalent bond to form a ring with the parent ring. By selecting the above types of compound of Formula IV and compound of Formula V, and controlling the sum of the mass percentages of the compound of Formula IV and the compound of Formula V in the non-aqueous electrolyte to satisfy the above ranges, both the high-temperature storage performance, the low-temperature discharge performance, and the cycle performance of the electrochemical device can be improved.

[0063] In some embodiments, the above compound of Formula IV includes at least one of the following compounds:

[0064]

[0065] The above compound of Formula V includes at least one of the following compounds:

[0066]

[0067] By selecting the above types of compound of Formula IV and compound of Formula V, both the high-temperature storage performance, the low-temperature discharge performance, and the cycle performance of the electrochemical device can be improved.

[0068] The non-aqueous electrolyte can further include a lithium salt and a non-aqueous solvent. The type of lithium salt is not particularly limited in the present application as long as the object of the present application is achieved, for example, the lithium salt can include, but is not limited to, at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bis-trifluoromethanesulfonimide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, or lithium difluoro(oxalato)borate. The mass percentage content of the lithium salt can be 8% to 15% based on the mass of the non-aqueous electrolyte, for example, the mass percentage content of the lithium salt can be 8%, 9%, 10%, 11%, 12.5%, 13%, 15%, or a range between any two of the above values. The type of the above-mentioned non-aqueous solvent is not particularly limited in the present application as long as the object of the present application is achieved, for example, can include, but is not limited to, at least one of an ether compound or other organic solvents. The above-mentioned ether compound can include, but is not limited to, at least one of ethylene glycol dimethyl ether, dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The above-mentioned other organic solvents can include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate.

[0069] Negative electrode

[0070] The negative electrode includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, the negative electrode material layer including a negative electrode active material. In some embodiments, the chargeable capacity of the negative electrode active material is greater than the discharge capacity of the positive electrode active material to prevent unintentional deposition of lithium metal on the negative electrode during charging.

[0071] The negative electrode active material can include at least one of natural graphite, artificial graphite, meso-carbon microbead (MCMB), silicon, silicon-carbon composite, SiO x (0.5 < x < 1.6), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithium titanate Li4Ti5O 12 12, Li-Al alloy, or metallic lithium, etc. Optionally, the negative electrode active material can further include an amorphous carbon material, which can be soft carbon (low-temperature calcined carbon), hard carbon, mesophase pitch carbonizate, or calcined coke, etc.

[0072] The negative electrode material layer of the present application further includes a negative electrode binder. The negative electrode binder can improve the binding of the negative electrode active material particles to each other and the binding of the negative electrode active material to the current collector. The type of the negative electrode binder is not particularly limited as long as it is a material stable to an electrolyte or a solvent used in the electrode manufacturing. In some embodiments, the negative electrode binder includes a resin binder. Examples of the resin binder include, but are not limited to, a fluorine resin, a polyacrylonitrile (PAN), a polyimide resin, an acrylic resin, a polyolefin resin, and the like. When a water-based solvent is used to prepare a negative electrode mixture slurry, the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or a salt thereof, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, and the like.

[0073] The negative electrode material layer of the present application further includes a conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent as long as it can achieve the object of the present application. For example, the negative electrode conductive agent can be at least one of acetylene black, ketjen black, a carbon nanotube, a carbon fiber, a carbon dot, or graphene, and the like, and the carbon nanotube can include, but is not limited to, at least one of a single-walled carbon nanotube or a multi-walled carbon nanotube.

[0074] The present application does not particularly limit the negative electrode current collector as long as it can achieve the object of the present application. For example, the negative electrode current collector can include a copper foil, an aluminum foil, a nickel foil, a stainless steel foil, a titanium foil, a nickel foam, a copper foam, or a polymer substrate coated with a conductive metal, and the like. Among them, the conductive metal includes, but is not limited to, copper, nickel, or titanium, and the material of the polymer substrate includes, but is not limited to, at least one of polyethylene, polypropylene, an ethylene-propylene copolymer, polyethylene terephthalate, polyethylene naphthalate, or poly-p-phenylene terephthalamide. In the present application, the thickness of the negative electrode current collector and the negative electrode material layer is not particularly limited as long as it can achieve the object of the present application. For example, the thickness of the negative electrode current collector is 4 μm to 12 μm, and the thickness of the single-sided negative electrode material layer is 30 μm to 160 μm. In the present application, the negative electrode mixture layer can be disposed on one surface in the thickness direction of the negative electrode current collector, or on both surfaces in the thickness direction of the negative electrode current collector. It should be noted that the "surface" here can be the entire area of the negative electrode current collector, or a partial area of the negative electrode current collector, and the present application does not particularly limit it as long as it can achieve the object of the present application.

[0075] The present application does not particularly limit the compaction density of the negative electrode tab as long as it can achieve the object of the present application. For example, the compaction density of the negative electrode tab can be 1.0 g / cm 3 to 1.85 g / cm 3 The present application does not particularly limit the cold-pressing pressure of the negative electrode tab as long as it can achieve the object of the present application. For example, the cold-pressing pressure of the negative electrode tab can be 3 tons to 30 tons.

[0076] Optionally, the negative electrode sheet can further include a conductive layer between the negative current collector and the negative material layer. The composition of the conductive layer is not particularly limited in the present application and can be a conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. The conductive agent and the binder in the conductive layer are not particularly limited in the present application and can be at least one of the conductive agent and the binder described above. The mass ratio of the conductive agent and the binder in the conductive layer is not particularly limited in the present application and can be selected by a person skilled in the art according to actual needs, as long as the purpose of the present application can be achieved. The thickness of the conductive layer is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the thickness of the conductive layer is 1 μm to 10 μm.

[0077] Separator

[0078] The present application usually provides a separator between the positive electrode and the negative electrode. The separator is used to separate the positive electrode sheet and the negative electrode sheet, prevent internal short circuit of the secondary battery, allow electrolyte ions to pass freely, and does not affect the electrochemical charging and discharging process.

[0079] The separator is not particularly limited in the present application, as long as the purpose of the present application can be achieved. For example, the material of the separator can include, but is not limited to, at least one of polyethylene (PE), polyolefin (PO) based on polypropylene (PP), polyester (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid; and the type of the separator can include at least one of woven film, non-woven film, microporous film, composite film, calendered film or spunlaced film.

[0080] In the present application, the separator can include a base material and a surface treatment layer. The base material can be a nonwoven fabric or a composite film having a porous structure, and the material of the base material can include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used. Optionally, a surface treatment layer is provided on at least one surface of the base material, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. For example, the inorganic layer includes inorganic particles and a binder, and the inorganic particles are not particularly limited in the present application, and for example, can include at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder is not particularly limited in the present application, and for example, can be at least one of the aforementioned binders. The polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0081] In the present application, the separator has a pore diameter of 0.01 μm to 1 μm and a thickness of 5 μm to 50 μm. In some embodiments, the thickness of the separator is greater than 1 μm, greater than 5 μm, or greater than 8 μm. In some embodiments, the thickness of the separator is less than 50 μm, less than 40 μm, or less than 30 μm. When the thickness of the separator is within the above range, insulation and mechanical strength can be ensured, and the rate characteristics and energy density of the secondary battery can be ensured.

[0082] The electrochemical device of the present application further includes a packaging bag for containing the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte, and other components known in the art in the electrochemical device, which are not limited in the present application. The packaging bag is not particularly limited in the present application, and can be a packaging bag known in the art, as long as the purpose of the present application can be achieved.

[0083] The present application further provides an electronic device including the electrochemical device of the present application. The electronic device includes, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile, a portable copier, a portable printer, a headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio player, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, a lighting appliance, a toy, a game machine, a clock, an electric tool, a flashlight, a camera, a household large storage battery, and a lithium ion capacitor, etc.

[0084] Examples

[0085] Hereinafter, examples and comparative examples are given to more specifically describe the embodiments of the secondary battery of the present application, taking lithium ion batteries as examples. The preparation methods described in the present application are only examples, and any other suitable preparation method is within the scope of the present application. In addition, unless otherwise specified, "parts" and "%" are mass-based.

[0086] Example 1-1

[0087] <Preparation of lithium ion batteries>

[0088] (1) Preparation of the positive electrode:

[0089] <Preparation of the positive electrode active material>

[0090] a. Dissolve cobalt nitrate and aluminum nitrate in deionized water according to the molar ratio Co:Al = 0.985:0.015, add a precipitating agent sodium carbonate and a complexing agent ammonia water until complete precipitation; then sinter the precipitate at 900-1100°C, grind to obtain (Co 0.985 Al 0.015 )3O4 powder; finally, react (Co 0.985 Al 0.015 )3O4 powder with Na2CO3 according to the molar ratio Al:Na = 0.015:0.7 in an air atmosphere at 700-900°C to obtain Na 0.7 Co 0.985 Al 0.015 O2;

[0091] b. Use the Na 0.7 Co 0.985 Al 0.015 O2 obtained in step a as a precursor, mix it uniformly with lithium nitrate according to the molar ratio Na:Li = 0.01:0.01, react in an air atmosphere at 200-400°C, and after the reaction is complete, wash the obtained reaction product, molten salt powder, with deionized water several times, dry it after cleaning, and obtain the positive electrode active material Li 0.73 Na 0.01 Co 0.985 Al 0.015 O2.

[0092] <Preparation of the positive electrode sheet>

[0093] The positive electrode active material prepared in the above step, conductive agent conductive carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 95:2:3, N-methyl pyrrolidone (NMP) was added, and the mixture was stirred uniformly under the action of a vacuum stirrer to obtain a positive electrode slurry with a solid content of 70 wt%. The positive electrode slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 9 μm, and was dried to obtain a positive electrode tab with a single-sided coated positive electrode mixture layer. The above step was repeated on the other surface of the positive electrode current collector aluminum foil to obtain a positive electrode tab with a double-sided coated positive electrode mixture layer. After cold pressing, cutting, and drying, a positive electrode tab with a size of 74 mm x 867 mm was obtained.

[0094] (2) Preparation of non-aqueous electrolyte: In a dry argon glove box, diethyl carbonate was used as a base solvent, then the compound of formula I and lithium hexafluorophosphate (LiPF6) were dissolved in the base solvent, and vinylene carbonate was added as an additive to obtain an electrolyte. The mass percentage of LiPF6 was 12.5%, the mass percentage of vinylene carbonate was 2%, the mass percentage of the compound of formula I was 0.1%, and the rest was diethyl carbonate, based on the total mass of the electrolyte.

[0095] (3) Preparation of negative electrode: Artificial graphite was used as a negative electrode active material, the negative electrode active material, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), carbon nanotubes (CNT), and carboxymethyl cellulose (CMC) were mixed in a mass ratio of 95.8:2.4:0.5:0.5:0.8, then deionized water was added as a solvent and stirred uniformly to prepare a negative electrode slurry with a solid content of 45 wt%. The negative electrode slurry was uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 6 μm, and was dried to obtain a negative electrode tab with a single-sided coated negative electrode mixture layer. The above step was repeated on the other surface of the negative electrode current collector copper foil to obtain a negative electrode tab with a double-sided coated negative electrode mixture layer. After cold pressing, cutting, and drying, a negative electrode tab with a size of 76.6 mm x 875 mm was obtained.

[0096] (4) Preparation of separator: A porous polyethylene film with a thickness of 15 μm was used as a separator.

[0097] (5) Preparation of lithium ion battery: The positive electrode tab, the separator, and the negative electrode tab were stacked in order, with the separator between the positive electrode tab and the negative electrode tab to serve as a separator, and were wound to obtain a bare cell. The bare cell was placed in a packaging bag, electrolyte was injected, and the bag was sealed. After processes such as formation, degassing, edge cutting, and capacity testing, a lithium ion battery was obtained.

[0098] <TEST METHODS>

[0099] (1) Test of atomic number ratio of lithium-containing transition metal composite oxide in positive electrode material layer

[0100] The lithium ion battery is disassembled to obtain a positive electrode sheet, the positive electrode sheet is cleaned with dimethyl carbonate (DMC), the positive electrode material layer of the cleaned positive electrode sheet is scraped off with a scraper, 0.4 g of the positive electrode material layer is dissolved in 10 mL of aqua regia (nitric acid and hydrochloric acid are mixed at a ratio of 1:1) and 2 mL of HF mixed solvent, the volume is made up to 100 mL, then the mass percentage contents of lithium element, sodium element, cobalt element and M element are tested by using an ICP (Inductively coupled plasma) analyzer, the rest is the percentage content of oxygen, the molar percentage contents of each element are converted according to the atomic mass, and the molar percentage content ratio of each element is normalized to calculate the corresponding x value, y value and z value. The z value is the number of sodium atoms in the lithium-containing transition metal composite oxide in the positive electrode material layer. For example, Li 0.73 Na 0.01 Co 0.985 Al 0.015 O2, 0.4 g of the positive electrode material layer is dissolved in 10 mL of aqua regia (nitric acid and hydrochloric acid are mixed at a ratio of 1:1) and 2 mL of HF mixed solvent, the volume is made up to 100 mL, then the mass percentage contents of lithium element, sodium element, cobalt element and aluminum element are tested by using an ICP analyzer to obtain 52919 ppm, 2401 ppm, 606266 ppm and 4227 ppm respectively, the remaining mass is recorded as the mass of oxygen element, and the mass percentage of oxygen element is 1000000 ppm-(52919+2401+606266+4277) ppm=334187 ppm, then the mass percentage contents of each element are divided by the atomic mass of each element to obtain the molar ratio of each element Li:Na:Co:Al:O=0.762:0.0104:1.029:0.0157:2.089. The value of oxygen element is 2, and the above ratio is normalized to obtain Li:Na:Co:Al:O=0.73:0.01:0.985:0.015:2. That is, x=0.73; y=0.015; z=0.01.

[0101] (2) High-temperature storage performance test:

[0102] The lithium ion battery is placed in a constant temperature environment of 25°C, and is allowed to stand for 30 minutes to allow the lithium ion battery to reach a constant temperature. The lithium ion battery is charged at a constant current of 0.5C to 4.5V, and then charged at a constant voltage of 4.5V to a current of 0.025C. The thickness of the battery is measured using a PPG soft pack battery thickness gauge with a pressure of 700g, and the thickness is measured at five different points on the non-tab position. The average of the five measurements is recorded as the initial thickness. The lithium ion battery is then stored in a constant temperature oven at 60°C for 30 days. After the battery is removed and allowed to cool to room temperature, the thickness of the battery is measured at five different points on the non-tab position using a PPG soft pack battery thickness gauge with a pressure of 700g. The average of the five measurements is recorded as the storage thickness. The thickness expansion rate of the lithium ion battery is calculated and used as an indicator of the high temperature storage performance of the lithium ion battery.

[0103] High temperature storage thickness expansion rate = (storage thickness - initial thickness) / initial thickness x 100%.

[0104] (3) Low temperature discharge performance test:

[0105] The lithium ion battery is placed in a high and low temperature oven, and the temperature is adjusted to 25°C. The lithium ion battery is allowed to stand for 30 minutes to reach a constant temperature. The lithium ion battery is discharged at a constant current of 0.5C to 3.0V, and then charged at a constant current of 0.5C to 4.5V. The battery is then charged at a constant voltage of 4.5V to a current of 0.05C. At the same temperature of 25°C, the battery is discharged at a constant current of 0.5C to 3.0V, and the discharge capacity is recorded as the initial discharge capacity. At a temperature of 25°C, the battery is charged at a constant current of 0.5C to 4.5V, and then charged at a constant voltage of 4.5V to a current of 0.05C. Then, the lithium ion battery is placed in a temperature of 0°C, and allowed to stand for 30 minutes to allow the temperature of the lithium ion battery to reach the same temperature as the outside. The battery is discharged at a constant current of 0.5C to 3.0V at a temperature of 0°C, and the discharge capacity is recorded as the low temperature discharge capacity.

[0106] Low temperature discharge capacity retention rate = (low temperature discharge capacity / initial discharge capacity) x 100%.

[0107] (4) Cycle performance test:

[0108] The lithium ion battery is placed in a constant temperature test box at 45°C, and is allowed to stand for 30 minutes to allow the lithium ion battery to reach a constant temperature. The lithium ion battery is charged at a constant current of 0.5C to 4.5V, and then charged at a constant voltage of 4.5V to a current of 0.025C. The battery is allowed to stand for 5 minutes, and then discharged at a constant current of 0.5C to 3.0V. The initial discharge capacity C0 is recorded. The battery is cycled 100 times using the same procedure, and the discharge capacity C1 after 100 cycles is recorded. The cycle capacity retention rate of the lithium ion battery is calculated. Cycle capacity retention rate = C1 / C0 x 100%.

[0109] The lithium ion batteries of the following examples or comparative examples differ from example 1-1 only in that the type of compound of formula I and the value of the mass percentage content A, the type of M element in the lithium-containing transition metal composite oxide, and the value of z in the nonaqueous electrolyte are adjusted according to Table 1, wherein in adjusting the value of z, lithium-containing transition metal composite oxides with different numbers of sodium atoms are used as raw materials, and x and y are controlled to satisfy 0.6 < x < 0.95 and 0 ≤ y < 0.15, respectively. The performance test results of the lithium ion batteries of each example and comparative example are shown in Table 1 below.

[0110] Table 1

[0111]

[0112] In the above table, " / " indicates that the substance is not contained. M is the type of M element, A is the value of the mass percentage content A% of the compound of formula I, and z is the value of z in the lithium-containing transition metal composite oxide, based on the mass of the electrolyte.

[0113] As can be seen from Table 1, the lithium ion batteries prepared in the examples of the present application have lithium-containing transition metal composite oxides Li x Na z Co 1-y M y O2, the value of z satisfies 0 < z ≤ 0.03, and the mass percentage content A% of the compound of formula I satisfies 1 ≤ A / z ≤ 200, which can improve the low-temperature discharge performance of the lithium ion battery and is also conducive to improving the stability of the positive electrode material layer under high-temperature conditions, so that the lithium ion battery has excellent high-temperature storage performance. Among them, when the above conditions satisfy at least one of the following cases: (1) 5 ≤ A / z ≤ 100; (2) 0.1 ≤ A ≤ 5; (3) 0.005 ≤ z ≤ 0.02, the low-temperature discharge capacity retention rate of the lithium ion battery can be further improved, and the high-temperature storage expansion rate of the lithium ion battery is also taken into account.

[0114] The lithium ion batteries of the following examples 2-1 to 2-28 differ from example 1-5 only in that specific types and contents of dinitrile compounds and trinitrile compounds are added during the preparation of the electrolyte. The lithium ion batteries of examples 2-29 to 2-34 differ from example 1-5 only in that specific types and contents of dinitrile compounds and trinitrile compounds are added during the preparation of the electrolyte, and the value of the mass percentage content A% of the compound of formula I is adjusted. The mass percentage contents of the above compound of formula I, dinitrile compounds and trinitrile compounds in the electrolyte are shown in Table 2, and the performance test results of the lithium ion batteries of each example are shown in Table 2 below.

[0115] Table 2

[0116]

[0117]

[0118] In the above table, " / " means that the substance is not contained. A is the value of the mass percentage A% of the compound of formula I, B is the value of the mass percentage B% of the compound of formula II, and C is the value of the mass percentage C% of the compound of formula III, based on the mass of the electrolyte.

[0119] As can be seen from Table 2, when the non-aqueous electrolyte of the lithium ion battery prepared in the embodiments of the present application further comprises the compound of formula II and the compound of formula III, and satisfies 0.05≤A / (B+C)≤50, the high-temperature storage expansion rate and the low-temperature discharge capacity retention rate of the lithium ion battery can be further improved. In particular, when the content relationship of the compound of formula I, the compound of formula II and the compound of formula III in the electrolyte satisfies any one of the following conditions, (1) 0.5≤B+C≤8; (2) 0.1≤A / (B+C)≤2; (3) 0.1≤B≤6; (4) 0.1≤C≤6, the effect of improving the high-temperature storage expansion rate and the low-temperature discharge capacity retention rate of the lithium ion battery is more significant.

[0120] The lithium ion batteries of Examples 3-1 to 3-40 below are adjusted based on the parameters of Example 1-5; the lithium ion battery of Example 3-41 is adjusted based on the parameters of Example 2-30. The specific adjustment is that specific types and contents of cyclic carbonates, fluorinated linear esters, non-fluorinated linear esters, compounds of formula IV and compounds of formula V are added during the preparation of the electrolyte. The mass percentage of these substances in the electrolyte is shown in Table 3, and the performance test results of the lithium ion batteries of each example are shown in Table 3.

[0121] Table 3

[0122]

[0123]

[0124] In the above table, " / " means that the substance is not contained. Each content is based on the mass of the electrolyte, and each code corresponds to the following compound:

[0125] EC: ethylene carbonate, PC: propylene carbonate, FEC: fluorinated ethylene carbonate.

[0126] As can be seen from Table 3, when the non-aqueous electrolyte of the lithium ion battery prepared by the embodiment of the present application further comprises a cyclic carbonate, a linear ester or an inner salt substance, the cycle capacity retention rate of the lithium ion battery can be further improved, while the high-temperature storage expansion rate and the low-temperature discharge capacity retention rate are also improved. In particular, when the mass percentage content of the cyclic carbonate is 2% to 15%, the cycle capacity retention rate of the lithium ion battery can be significantly improved, while the high-temperature storage expansion rate and the low-temperature discharge capacity retention rate are also improved. In particular, when the mass percentage content of the linear ester is 15% to 50%, the cycle capacity retention rate of the lithium ion battery can be significantly improved, while the high-temperature storage expansion rate and the low-temperature discharge capacity retention rate are also improved. In particular, when the sum of the mass percentage contents of the inner salt substance compound of formula IV and the compound of formula V is 0.1% to 1%, the cycle capacity retention rate of the lithium ion battery can be significantly improved, while the high-temperature storage expansion rate and the low-temperature discharge capacity retention rate are also improved.

[0127] The above description is merely preferred embodiments of the present application, but not to limit the present application. Any modification, equivalent replacement and improvement made within the principle of the present application should be included in the protection scope of the present application.

Claims

1. An electrochemical device, characterized by, A non-aqueous electrolyte including a positive electrode and a non-aqueous electrolyte, the positive electrode including a positive electrode material layer disposed on at least one surface of a positive electrode current collector, the positive electrode material layer including a lithium-containing transition metal composite oxide, the lithium-containing transition metal composite oxide including Li x Na z Co 1-y M y O2, wherein 0.6 < x < 0.95, 0 ≤ y < 0.15, 0 < z ≤ 0.03, M is selected from at least one of the group consisting of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, and Zr; the non-aqueous electrolyte including a compound of Formula I: wherein R is selected from the group consisting of C2to C6alkyl unsubstituted or substituted with Ra, C2to C6alkenyl unsubstituted or substituted with Ra, C2to C6alkynyl unsubstituted or substituted with Ra, C5to C12cycloalkyl unsubstituted or substituted with Ra, C6to C10aryl unsubstituted or substituted with Ra, and a nitrogen containing heteroaryl of 5 to 10 ring members unsubstituted or substituted with Ra, and each substituent Raof the respective group is independently selected from the group consisting of fluorine or C1to C6fluoroalkyl; and 12 C6to C10aryl unsubstituted or substituted with Ra, and a nitrogen containing heteroaryl of 5 to 10 ring members unsubstituted or substituted with Ra, and each substituent Raof the respective group is independently selected from the group consisting of fluorine or C1to C6fluoroalkyl; and 12 C6to C10aryl unsubstituted or substituted with Ra, and a nitrogen containing heteroaryl of 5 to 10 ring members unsubstituted or substituted with Ra, and each substituent Raof the respective group is independently selected from the group consisting of fluorine or C1to C6fluoroalk A % based on the total mass of the nonaqueous electrolyte solution, 1≤A / z≤200.

2. The electrochemical device of claim 1, wherein The electrochemical device satisfies at least one of the following conditions: (1) 5≤A / z≤100; (2)0.1≤A≤5； (3)0.005≤z≤0.02。 3. The electrochemical device of claim 1, wherein The compound of Formula I includes at least one of the following compounds:

4. The electrochemical device of claim 1, wherein The nonaqueous electrolyte solution further includes a compound of Formula II and a compound of Formula III: wherein R0is selected from a chain alkylene group of C2to C 10 , a chain alkenylene group of C2to C 10 , or -R a -(O-R b ) n -R c -, R a , R b and R c are each independently selected from a C1to C3alkylene group or a C2to C3alkenylene group, and n is an integer from 1 to 3; wherein R 11 , R 12 and R 13 are each independently selected from a Ci to C3 alkylene group or -R A -(O-R B ) n -R C -, R A , R B and R C are each independently selected from a single bond, a Ci to C2 alkylene group, n is an integer from 1 to 3, R 21 is selected from a hydrogen atom, a Ci to C3 alkylene group; B % based on the total mass of the nonaqueous electrolyte solution, and C % based on the total mass of the nonaqueous electrolyte solution, 0.05≤A / (B+C)≤50.

5. The electrochemical device of claim 4, wherein, The nonaqueous electrolyte solution satisfies at least one of the following conditions: (1) 0.5≤B+C≤8; (2) 0.1≤A / (B+C)≤2; (3)0.1≤B≤6； (4)0.1≤C≤6。 6. The electrochemical device of claim 4, wherein, The compound of Formula II is selected from at least one of succinonitrile, glutaronitrile, methylglutaronitrile, adiponitrile, pimelonitrile, suberonitrile, fumaronitrile, or 1,2-bis(cyanoethoxy)ethane; and / or, The compound of Formula III is selected from at least one of 1,3,5-pentanetricarbonitrile, 1,3,6-hexanetricarbonitrile, or 1,2,3-tris(2-cyanoethoxy)propane.

7. The electrochemical device according to any one of claims 1 to 6, wherein The nonaqueous electrolyte solution further includes a cyclic carbonate selected from at least two of ethylene carbonate, propylene carbonate, or fluoroethylene carbonate; the mass percentage of the cyclic carbonate is 1% to 30% based on the total mass of the nonaqueous electrolyte solution.

8. The electrochemical device of claim 7, wherein, The mass percentage of the cyclic carbonate is 2% to 15% based on the total mass of the nonaqueous electrolyte solution.

9. The electrochemical device according to any one of claims 1 to 6, wherein The nonaqueous electrolyte solution further includes a linear ester, the linear ester including a fluorinated linear ester and a non-fluorinated linear ester; the linear ester satisfies at least one of the following conditions: (1) the fluorinated linear ester is selected from at least one of methyl difluoroethyl carbonate, methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate, methyl hexafluoroisopropyl carbonate, di(2,2,2-trifluoroethyl) carbonate, 2,2-difluoroethyl acetate, 2,2,2-trifluoroethyl acetate, hexafluoroisopropyl acetate, 2,2-difluoroethyl propionate, 2,2,2-trifluoroethyl propionate, or hexafluoroisopropyl propionate; (2) the non-fluorinated linear ester is selected from at least one of dimethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, or propyl propionate; (3) the mass percentage of the linear ester is X0% based on the total mass of the nonaqueous electrolyte solution, 10≤X0≤70.

10. The electrochemical device of claim 9, wherein, The nonaqueous electrolyte solution satisfies at least one of the following conditions based on the total mass of the nonaqueous electrolyte solution: (1) the mass percentage of the fluorinated linear ester is X1%, 10≤X1≤50; (2) the mass percentage of the non-fluorinated linear ester is X2%, 5≤X2≤50; (3)15≤X0≤50。 11. The electrochemical device according to any one of claims 1 to 6, wherein The nonaqueous electrolyte solution further includes a compound of Formula IV and / or a compound of Formula V; wherein R1 to R5 are each independently selected from a hydrogen atom, a fluorine atom, a vinyl group, an ethynyl group, or an acid anhydride group; The mass percentage of the compound of Formula IV and the compound of Formula V is 0.1% to 1% based on the total mass of the nonaqueous electrolyte solution. independently present between any two adjacent groups of R1to R5, or are connected by a covalent bond and connected to the parent ring to form a ring.

12. The electrochemical device of claim 11, wherein, The compound of Formula IV includes at least one of the following compounds: and / or, the compound of Formula V includes at least one of the following compounds:

13. An electronic device comprising the electrochemical device of any one of claims 1 to 12.

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