Secondary battery and electronic device

Abstract

The invention provides a secondary battery and electronic equipment, the secondary battery comprises a positive pole piece, a negative pole piece and an electrolyte, the positive pole piece comprises a composite current collector and a positive pole material layer arranged on at least one surface of the composite current collector, the positive pole material layer comprises a nickel cobalt lithium manganate compound, and based on the total molar weight of metal elements except lithium, the total molar weight of the nickel cobalt lithium manganate compound is smaller than the total molar weight of metal elements except lithium; the molar percentage content of the nickel element in the nickel cobalt lithium manganate compound is X, and X is greater than 80%. The electrolyte comprises adiponitrile and butanedinitrile, based on the mass of the electrolyte, the mass percentage content of the adiponitrile is B1, the mass percentage content of the butanedinitrile is B 2, and X * B / B 2 is larger than or equal to 0.01 and smaller than or equal to 90. According to the invention, the capacity retention ratio and the lithium ion acceptability of the secondary battery after the high and low temperature impact test can be improved.

Description

[0001] This application is a divisional application with application number 202410876577.2, application date July 2, 2024, and invention name “Secondary battery and electronic device”. Technical Field

[0002] The present application relates to the field of electrochemical energy storage, and in particular to a secondary battery and an electronic device using the secondary battery. Background Art

[0003] Secondary batteries have been increasingly used in various fields of new energy, which has also increased the requirements for their performance in all aspects.

[0004] As usage scenarios become increasingly diversified, how to provide a secondary battery with more stable and efficient performance under high and low temperature conversion conditions has become an urgent problem that needs to be solved. Summary of the invention

[0005] The present application provides a secondary battery and an electronic device.

[0006] In a first aspect, the present application provides a secondary battery, comprising a positive electrode plate, a negative electrode plate and an electrolyte, wherein the positive electrode plate comprises a composite current collector and a positive electrode material layer disposed on at least one surface of the composite current collector, the composite current collector comprises a polymer support layer and a metal conductive layer disposed on at least one surface of the polymer support layer, the positive electrode material layer comprises a nickel cobalt manganese oxide compound, and the molar percentage of the nickel element in the nickel cobalt manganese oxide compound is X based on the total molar amount of metal elements other than lithium, and X>80%; the electrolyte comprises adiponitrile and succinonitrile, and the mass percentage of adiponitrile is B1, the mass percentage of succinonitrile is B2 based on the mass of the electrolyte, and 0.01≤X×B 1 / B 2≤90.

[0007] In the present application, the composite current collector and the high-nickel ternary positive electrode material work together, and cooperate with adiponitrile and succinonitrile present in a specific ratio in the electrolyte, which can improve the capacity retention rate and lithium ion acceptance of the secondary battery after high and low temperature impact tests.

[0008] Based on the first aspect, in some possible implementations, 0.02≤X×B 1 / B 2≤40. Meeting this condition can further improve the capacity retention rate and lithium ion acceptance of the secondary battery after the high and low temperature impact test. Based on the first aspect, in some possible implementations, 0.01%≤B 1≤3.5%. Meeting this condition can further improve the capacity retention rate and lithium ion acceptance of the secondary battery after the high and low temperature impact test.

[0009] Based on the first aspect, in some possible implementations, 0.03%≤B 2≤4%. Meeting this condition can further improve the capacity retention rate and lithium ion acceptance of the secondary battery after high and low temperature impact tests.

[0010] Based on the first aspect, in some possible implementations, the electrolyte further includes vinylene carbonate, and the mass percentage of vinylene carbonate is B 3, 0.01%≤B 3≤2% based on the mass of the electrolyte. Meeting this condition can further improve the capacity retention rate and lithium ion acceptance of the secondary battery after high and low temperature impact tests.

[0011] Based on the first aspect, in some possible embodiments, the electrolyte further includes 1,3-propane sultone, and based on the mass of the electrolyte, the mass percentage of 1,3-propane sultone is B4, 0.01%≤B4≤4.5%, and the sum of the mass percentages of adiponitrile, succinonitrile, vinylene carbonate and 1,3-propane sultone is greater than or equal to 0.1% and less than or equal to 10%. Meeting this condition can further improve the capacity retention rate and lithium ion acceptance of the secondary battery after high and low temperature impact tests.

[0012] Based on the first aspect, in some possible implementations, the polymer support layer includes polyethylene terephthalate and / or polypropylene, which can further improve the capacity retention rate and lithium ion acceptance of the secondary battery after high and low temperature impact tests.

[0013] Based on the first aspect, in some possible implementations, the metal conductive layer includes aluminum, and the thickness of the metal conductive layer is greater than or equal to 0.8 μm and less than or equal to 3 μm, which can further improve the capacity retention rate and lithium ion acceptance of the secondary battery after high and low temperature impact tests.

[0014] Based on the first aspect, in some possible implementations, the negative electrode plate includes a negative electrode material layer, the negative electrode material layer includes graphite and silicon material, and the graphite includes artificial graphite and / or natural graphite.

[0015] The second aspect of the present application provides an electronic device, including a secondary battery. The secondary battery supplies power to the electronic device, and the secondary battery has good capacity retention and lithium ion acceptance after high and low temperature impact tests, which is conducive to improving the universality of the electronic device in switching between high and low temperatures. DETAILED DESCRIPTION

[0016] The technical scheme in the embodiment of the present application is described clearly and in detail below. Obviously, the described embodiment is a part of the embodiment of the present application, rather than all the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0017] An embodiment of the present application provides a secondary battery, which includes a housing, an electrode assembly and an electrolyte. The electrode assembly and the electrolyte are both located in the housing.

[0018] The outer shell can be a packaging bag encapsulated by an encapsulation film (such as an aluminum-plastic film), such as a soft-pack battery. In other embodiments, the secondary battery can also be a steel shell battery, an aluminum shell battery, etc.

[0019] The electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is disposed between the positive electrode sheet and the negative electrode sheet. The electrode assembly may be a laminated structure, which is formed by alternating the positive electrode sheet, the separator and the negative electrode sheet. In other embodiments, the electrode assembly may also be a wound structure, which is formed by stacking the positive electrode sheet, the separator and the negative electrode sheet and then winding them.

[0020] The positive electrode plate includes a composite current collector and a positive electrode material layer arranged on at least one surface of the composite current collector, the composite current collector includes a polymer support layer and a metal conductive layer arranged on at least one surface of the polymer support layer, the positive electrode material layer includes a nickel cobalt manganese oxide compound, based on the total molar amount of metal elements other than lithium, the molar percentage of nickel element in the nickel cobalt manganese oxide compound is X, X>80%; the electrolyte includes adiponitrile (ADN) and succinonitrile (SN), based on the mass of the electrolyte, the mass percentage of adiponitrile is B1, the mass percentage of succinonitrile is B2, 0.01≤X×B1 / B2≤90.

[0021] In the secondary battery provided by the present application, the composite current collector and the high-nickel ternary positive electrode material work together, and cooperate with the adiponitrile and succinonitrile present in a specific ratio in the electrolyte, which can improve the capacity retention rate and lithium ion acceptance of the secondary battery after the high and low temperature impact test. It is speculated that the positive electrode system and the electrolyte system in the present application can improve the binding force between the composite current collector and the high-nickel ternary positive electrode material, and enhance the anti-temperature difference effect of the adiponitrile and succinonitrile in the electrolyte of the present application on the high-nickel ternary positive electrode interface film formation under the support of the composite current collector. The above synergistic effect enables the secondary battery to withstand the impact of high and low temperature conversion.

[0022] In some embodiments, X can be 82%, 85%, 87%, 90%, 92%, 95%, or any value within the range formed by any two of the above values. The value of X×B 1 / B 2 can be 0.01, 1, 2, 5, 7, 9, 12, 15, 17, 19, 22, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or any value within the range formed by any two of the above values.

[0023] The nickel cobalt manganese oxide compound includes nickel cobalt manganese oxide and nickel cobalt manganese oxide derivatives, such as coating materials or derivatives doped with other metal elements. For example, the nickel cobalt manganese oxide compound can be LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.88 C o 0.1 Mn 0.02 O2. Nickel cobalt manganese oxide derivatives can be Li 0.8 Ni 0.8982 C o 0.0589 Mn 0.0409 Zr 0.002 O2.

[0024] Preferably, 0.02≤X×B 1 / B 2≤40. Meeting this condition can further improve the capacity retention rate and lithium ion acceptance of the secondary battery after the high and low temperature impact test.

[0025] In some embodiments, 0.01% ≤ B1 ≤ 3.5%. Meeting this condition can further improve the capacity retention rate and lithium ion acceptance of the secondary battery after high and low temperature impact test. In some optional embodiments, B1 can be 0.01%, 0.02%, 0.05%, 0.07%, 0.1%, 0.15%, 0.5%, 0.7%, 0.9%, 1%, 1.2%, 1.5%, 1.7%, 2%, 2.4%, 2.5%, 3%, 3.2%, 3.5% or any value within the range formed by any two of the above values.

[0026] In some embodiments, 0.03% ≤ B 2 ≤ 4%. Meeting this condition can further improve the capacity retention rate and lithium ion acceptance of the secondary battery after high and low temperature impact tests. In some optional embodiments, B 2 can be 0.03%, 0.05%, 0.1%, 0.15%, 0.3%, 0.5%, 1%, 1.2%, 1.5%, 2%, 2.2%, 2.5%, 3%, 3.5%, 3.7%, 4% or any value within the range of any two of the above values.

[0027] In some embodiments, the electrolyte further includes vinylene carbonate (VC), and based on the mass of the electrolyte, the mass percentage of vinylene carbonate is B 3, 0.01% ≤ B 3 ≤ 2%. Meeting this condition can further enhance the synergistic effect between the positive electrode including the composite current collector and the high nickel ternary and the electrolyte including adiponitrile and succinonitrile, and further improve the capacity retention rate and lithium ion acceptance of the secondary battery after the high and low temperature impact test. In some optional embodiments, B 3 can be 0.01%, 0.03%, 0.05%, 0.07%, 0.1%, 0.5%, 1%, 1.5%, 1.7%, 2% or any value within the range of any two of the above values.

[0028] In some embodiments, the electrolyte further includes 1,3-propane sultone (PS), and the mass percentage of 1,3-propane sultone is B 4, 0.01%≤B 4≤4.5%, 0.1%≤B 1+B 2+B 3+B 4≤10% based on the mass of the electrolyte. Meeting this condition can further enhance the synergistic effect between the positive electrode including the composite current collector and the high nickel ternary and the electrolyte including adiponitrile and succinonitrile, and further improve the capacity retention rate and lithium ion acceptance of the secondary battery after the high and low temperature impact test. In some optional embodiments, B 4 can be 0.01%, 0.03%, 0.05%, 0.07%, 0.1%, 0.5%, 1%, 1.5%, 1.7%, 2%, 2.5%, 2.8%, 3%, 3.7%, 4%, 4.5% or any value within the range of any two of the above values. The sum of B1+B2+B3+B4 can be 0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 9.5%, 10% or any value within the range formed by any two of the above values.

[0029] In some embodiments, the electrolyte further includes lithium salicylate, and the mass percentage of lithium salicylate is 0.4% to 0.6% based on the mass of the electrolyte. Meeting this condition can further improve the capacity retention rate and lithium ion acceptance of the secondary battery after high and low temperature impact tests. The mass percentage of lithium salicylate can be 0.4%, 0.45%, 0.5%, 0.55%, 0.6% or any value within the range of any two of the above values.

[0030] Electrolyte

[0031] According to some embodiments of the present application, the electrolyte includes adiponitrile, succinonitrile, vinylene carbonate, 1,3-propane sultone and lithium salt as described above.

[0032] In some embodiments, the electrolyte further includes an organic solvent, including, but not limited to, propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate or ethyl propionate.

[0033] In some embodiments, the organic solvent further comprises an ether solvent, and in some optional embodiments comprises at least one of 1,3-dioxolane (DOL) and ethylene glycol dimethyl ether (DME).

[0034] In some embodiments, the lithium salt includes at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt includes, but is not limited to: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium trifluoromethanesulfonyl imide LiN(CF3 S O2)2 (LiTF SI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiF SI), lithium bis(oxalate borate) LiB(C2O4)2 (LiB OB) or lithium difluorooxalate borate LiBF2(C2O4) (LiDFOB). In some embodiments, the additive includes at least one of fluoroethylene carbonate and adiponitrile.

[0035] Positive electrode

[0036] In some embodiments, the polymer support layer can be selected from polyethylene terephthalate and / or polypropylene. The above polymer materials as the polymer support layer have good thermal stability and mechanical properties.

[0037] In some embodiments, the metal conductive layer contains aluminum elements, and the thickness T of the metal conductive layer is greater than or equal to 0.8 μm and less than or equal to 3 μm. Meeting the above conditions is conducive to further improving the capacity retention rate and lithium ion acceptance of the secondary battery after high and low temperature impact tests. In some embodiments, T can be 0.8 μm, 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.3 μm, 2.5 μm, 2.8 μm, 3 μm or any value within the range of any two of the above values.

[0038] The metal conductive layer may include at least one of aluminum or an aluminum alloy.

[0039] The metal conductive layer is obtained by vapor deposition or electroplating, and the thickness of the metal conductive layer can be adjusted by changing the deposition time or the electroplating time.

[0040] The positive electrode material layer further includes a binder for binding the positive electrode active material particles to facilitate the formation of the film layer and at the same time improve the bonding force between the positive electrode material layer and the positive electrode current collector. In some embodiments, the binder may include but is not limited to at least one of polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc.

[0041] The positive electrode material layer may further include a conductive material, and the conductive material includes but is not limited to carbon-based materials, metal-based materials, conductive polymers, or any combination thereof. In some embodiments, the carbon-based materials may include but are not limited to natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based materials may include but are not limited to metal powders or metal fibers, and in some alternative embodiments, copper, nickel, aluminum, or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative.

[0042] Negative electrode sheet

[0043] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on the negative electrode current collector. The negative electrode material layer includes graphite and a silicon material. The graphite includes artificial graphite and / or natural graphite.

[0044] The silicon material includes at least one of (a composite of silicon-based substances and carbon-based substances) or silicon oxide (SiOx, 0 < x ≤ 2). The silicon-based substances may be silicon particles, silicon alloy particles, etc.

[0045] Since graphite has a certain flexibility, its combination with the silicon-carbon composite material can alleviate the overall volume expansion of the negative electrode material layer. At the same time, graphite and the silicon-carbon composite material as the negative electrode active material can also make full use of the advantages of both the silicon-carbon composite material and graphite to achieve better electrochemical performance.

[0046] In this application, the mass ratio of graphite in the negative electrode material layer is 35 wt.% to 95 wt.%. When the mass ratio of graphite in the negative electrode material layer is within the above range, the cycle performance of the negative electrode material layer can be further improved, thereby improving the cycle performance of the secondary battery.

[0047] The negative electrode current collector may be at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or carbon-based current collector, and may also be a composite current collector disclosed in any prior art, and in some alternative embodiments, but not limited to the current collector formed by combining the aforementioned conductive foil and a polymer substrate.

[0048] The negative electrode material layer also includes a binder to bind the negative electrode active material particles to facilitate the formation of a film layer, and at the same time, it can also improve the binding force between the negative electrode material layer and the negative electrode current collector. In some embodiments, the binder may include but is not limited to polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin or nylon, etc.

[0049] The negative electrode material layer may also include a conductive material, including but not limited to a carbon-based material, a metal-based material, a conductive polymer, or any combination thereof. In some embodiments, the carbon-based material may include but is not limited to natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof. In some embodiments, the metal-based material may include but is not limited to metal powder or metal fiber, in some optional embodiments copper, nickel, aluminum or silver. In some embodiments, the conductive polymer may be a polyphenylene derivative.

[0050] The negative electrode material layer may further include a dispersant, the dispersant including at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, carboxymethyl cellulose, lithium hydroxypropyl carboxymethyl cellulose, sodium hydroxypropyl carboxymethyl cellulose, hydroxypropyl carboxymethyl cellulose, lithium hydroxyethyl carboxymethyl cellulose, sodium hydroxyethyl carboxymethyl cellulose or hydroxyethyl carboxymethyl cellulose.

[0051] Isolation film

[0052] The material and shape of the separator used in the secondary battery of the present application are not particularly limited, and can be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance formed of a material that is stable to the electrolyte of the present application.

[0053] In some optional embodiments, the isolation film may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film having a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene non-woven fabric, a polyethylene non-woven fabric or a polypropylene-polyethylene-polypropylene porous composite film can be selected.

[0054] A surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer can be a polymer layer or an inorganic layer, or a layer formed by a mixed polymer and an inorganic substance. The inorganic layer includes inorganic particles and a binder, and the inorganic particles are selected from at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide and barium sulfate. The binder is selected from at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyethylene alkoxy, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene. The polymer layer contains a polymer, and the material of the polymer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylic acid salt, polyvinylpyrrolidone, polyethylene alkoxy, polyvinylidene fluoride and poly (vinylidene fluoride-hexafluoropropylene).

[0055] The secondary battery is applied to electronic devices to power the loads in the electronic devices, which may include but are not limited to laptop computers, pen-type computers, mobile computers, electronic book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors.

[0056] The present application is described below by specific examples and comparative examples. It should be understood by those skilled in the art that the preparation methods described in the present application are only examples, and any other suitable preparation methods are within the scope of the present application.

[0057] Example 1

[0058] 1. Preparation of positive electrode

[0059] LiNi 0.88 Co 0.1 Mn 0.02 O2, Super-P and polyvinylidene fluoride are mixed with N-methylpyrrolidone (NMP) in a mass ratio of 96:2:2, and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is coated on a 12μm composite aluminum foil (commercially available, a composite current collector made of polyethylene terephthalate (PET) as a base material and deposited with a metal aluminum layer on both sides of the foil using an advanced vacuum coating process), dried, cold pressed, and then cut and welded to obtain a positive electrode.

[0060] 2. Preparation of negative electrode

[0061] Artificial graphite and SiO2 (mass ratio 90:10), styrene-butadiene rubber, sodium hydroxyethyl carboxymethyl cellulose, in a mass ratio of 96.5%:1.5%:2% are mixed with deionized water, and then triazine compound is added and stirred evenly to obtain slurry. The slurry is coated on a 9μm copper foil. Drying, cold pressing, cutting and welding of the tabs are performed to obtain the negative electrode.

[0062] 3. Preparation of Electrolyte

[0063] In a dry argon environment, propylene carbonate (PC), diethyl carbonate (DMC) and ethyl propionate (EP) (weight ratio 2:2:3) were mixed, and LiPF6 was added, wherein the concentration of LiPF6 was 12.5%, to obtain a basic electrolyte. Ethylene carbonate (EC) and fluoroethylene carbonate (FEC) and other optional substances were added to the basic electrolyte according to the contents shown in Table 1 to obtain electrolytes of different embodiments and comparative examples.

[0064] 4. Preparation of Isolation Membrane

[0065] A 7-micron polyethylene porous polymer film was used as the separator.

[0066] 5. Preparation of Secondary Batteries

[0067] The obtained positive electrode, separator and negative electrode are wound in order and placed in an outer packaging foil, leaving a liquid injection port. The electrolyte is poured from the liquid injection port, packaged, and then subjected to formation, capacity and other processes to obtain a secondary battery.

[0068] Example 2 to Example 18

[0069] The difference between Example 2 to Example 18 and Example 1 is that, except for adjusting the parameters related to the electrolyte or the composite current collector according to Table 1, the rest are the same as Example 1.

[0070] Example 19 to Example 22

[0071] The difference between Example 19 to Example 22 and Example 12 is that, except for adjusting the relevant parameters of the composite current collector according to Table 1, the rest are the same as Example 12.

[0072] Comparative Examples 1 to 5

[0073] Comparative Example 1 is the same as Example 1 except that a conventional positive electrode current collector with a thickness of 10 μm is used. Comparative Examples 2 to 5 are the same as Example 1 except that the preparation parameters of the electrolyte are adjusted according to Table 1.

[0074] Test Method

[0075] 1. Capacity retention rate after high and low temperature impact test

[0076] Take 3 secondary batteries from each group, charge and discharge the 3 lithium-ion batteries respectively through the following steps, and calculate the discharge capacity retention rate of the batteries.

[0077] First, in an environment of 25°C, the first charge and discharge were performed. First, a constant current charge was performed at 0.5C, and constant voltage charge was performed after charging to 4.3V. Then, a constant current discharge was performed at a current of 1C, and the discharge was performed to 2.8V. The discharge capacity of the first cycle was recorded. Then, the lithium-ion battery was placed in an environment of -20°C for 100 charge and discharge cycles. After the low-temperature cycle was completed, the lithium-ion battery was transferred to an environment of 45°C within one hour for 200 charge and discharge cycles, and the discharge capacity of the 200th cycle at 45°C was recorded.

[0078] Capacity retention rate=(discharge capacity at the 200th cycle / discharge capacity at the first cycle)×100%.

[0079] Evaluation was performed according to the following criteria: A higher capacity retention rate indicates that the performance of the secondary battery after the high and low temperature impact test is better.

[0080] A: Capacity retention rate is greater than 85%;

[0081] B: Capacity retention rate is greater than or equal to 80% and less than 85%;

[0082] C: Capacity retention rate is greater than or equal to 75% and less than 80%;

[0083] D: The capacity retention rate is less than 75%.

[0084] 2. Lithium ion acceptance after high and low temperature impact test

[0085] After the secondary battery is allowed to stand at 35°C for 24 hours, it is charged at a constant current of 1.0C for 1 hour at 35°C to measure the high-temperature charge capacity (C0). Then, at 35°C, the discharge is stopped at a constant current of 0.1C until it reaches 3V. Next, at -15°C, the charge is performed at a constant current of 1.0C for 1 hour to measure the low-temperature charge capacity (C1). Then, the ratio of C1 to C0 (C1 / C0) is calculated and evaluated according to the following criteria. The larger the value of C1 / C0, the better the lithium ion acceptance of the secondary battery at low temperatures.

[0086] A: C1 / C0 is 0.65 or more;

[0087] B: C1 / C0 is greater than 0.55 and less than 0.65;

[0088] C: C1 / C0 is greater than 0.5 and less than 0.55;

[0089] D: C1 / C0 is less than 0.5.

[0090] Table 1

[0091]

[0092]

[0093] It can be seen from Table 1 above that, compared with the comparative example, the positive electrode plate of the secondary battery in the embodiment includes a composite current collector and a high-nickel nickel cobalt manganese oxide compound, which cooperates with adiponitrile and succinonitrile and satisfies the appropriate content relationship range in the present application, thereby improving the capacity retention rate and lithium ion acceptance of the secondary battery after high and low temperature impact tests.

[0094] In Examples 11 to 12, vinylene carbonate is added to the electrolyte of the secondary battery, which further improves the capacity retention rate and lithium ion acceptance of the secondary battery after the high and low temperature impact test.

[0095] In Example 10 and Examples 14 to 15, 1,3-propane sultone is added to the electrolyte of the secondary battery, which further improves the capacity retention rate and lithium ion acceptance of the secondary battery after the high and low temperature impact test.

[0096] In Examples 16 to 18, lithium salicylate is added to the electrolyte of the secondary battery, which improves the capacity retention rate and lithium ion acceptance of the secondary battery after the high and low temperature impact test.

[0097] In Examples 19 to 22, the thickness T of the metal conductive layer was changed, which improved the capacity retention rate and lithium ion acceptance of the secondary battery after the high and low temperature impact test.

[0098] Although illustrative embodiments have been shown and described, those skilled in the art should understand that the above embodiments should not be construed as limitations on the present application, and that changes, substitutions and modifications may be made to the embodiments without departing from the principles and scope of the present application.

Claims

1. A secondary battery, characterized in that: Including positive electrode sheet, negative electrode sheet and electrolyte, The positive electrode plate comprises a composite current collector and a positive electrode material layer disposed on at least one surface of the composite current collector, the composite current collector comprises a polymer support layer and a metal conductive layer disposed on at least one surface of the polymer support layer, the positive electrode material layer comprises a nickel cobalt manganese oxide compound, and based on the total molar amount of metal elements other than lithium, the molar percentage of nickel element in the nickel cobalt manganese oxide compound is X, X>80%; The electrolyte includes adiponitrile and succinonitrile. Based on the mass of the electrolyte, the mass percentage of the adiponitrile is B1, the mass percentage of the succinonitrile is B2, and 0.01≤X×B 1 / B 2≤90.

2. The secondary battery according to claim 1, wherein: The secondary battery satisfies at least one of the following conditions: (1) 0.01％≤B 1≤3.5％； (2) 0.03％≤B 2≤4％； (3) 0.02≤X×B1 / B2≤40.

3. The secondary battery according to claim 1, wherein: The electrolyte further comprises vinylene carbonate. Based on the mass of the electrolyte, the mass percentage of the vinylene carbonate is B 3, 0.01%≤B 3≤2%.

4. The secondary battery according to claim 3, characterized in that: The electrolyte also includes 1,3-propane sultone. Based on the mass of the electrolyte, the mass percentage of the 1,3-propane sultone is B4, 0.01%≤B4≤4.5%, and the sum of the mass percentages of the adiponitrile, the succinonitrile, the vinylene carbonate and the 1,3-propane sultone is greater than or equal to 0.1% and less than or equal to 10%.

5. The secondary battery according to claim 1, wherein: The metal conductive layer includes aluminum element, and a thickness T of the metal conductive layer is greater than or equal to 0.8 μm and less than or equal to 3 μm.

6. The secondary battery according to claim 1, wherein: The polymer support layer includes polyethylene terephthalate and / or polypropylene.

7. The secondary battery according to any one of claims 1 to 6, characterized in that: The electrolyte also includes lithium salicylate.

8. The secondary battery according to any one of claims 1 to 6, characterized in that: The negative electrode plate includes a negative electrode material layer, the negative electrode material layer includes graphite and silicon material, and the graphite includes artificial graphite and / or natural graphite.

9. An electronic device, characterized in that: The invention comprises the secondary battery according to any one of claims 1 to 8.

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