Lithium-ion battery and electronic device

Abstract

The present application discloses a lithium-ion battery and an electronic device. The battery comprises a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. The separator is arranged between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet comprises a positive electrode current collector and a positive electrode material layer arranged on at least one surface of the positive electrode current collector. The positive electrode material layer comprises a positive electrode active material containing cobalt element and T element. The T element is selected from at least one element from Groups VB and VIB in periods 4 to 6. The content A of the T element and the content B of the cobalt element in the positive electrode active material layer satisfy: 0.002≤A / B≤0.01.

Description

A lithium-ion battery and electronic device Technical Field

[0001] This application relates to the field of battery technology, and in particular to a lithium-ion battery and electronic device. Background Technology

[0002] Lithium-ion batteries are promising energy storage devices in power tools, electric vehicles, and energy storage systems due to their high energy and power density, long cycle life, low self-discharge rate, and high safety.

[0003] As lithium-ion batteries become increasingly widely used, the demands on them are also rising. However, existing lithium-ion battery technologies often fail to adequately balance high-temperature cycle performance and safety with low-temperature discharge performance, thus limiting their application scope. Therefore, it is essential to develop a lithium-ion battery that simultaneously achieves high-temperature cycle performance, safety, and low-temperature discharge performance. Summary of the Invention

[0004] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a lithium-ion battery and an electronic device.

[0005] A first aspect of this application provides a lithium-ion battery, comprising a positive electrode, a separator, a negative electrode, and an electrolyte; wherein the separator is sandwiched between the positive electrode and the negative electrode.

[0006] The positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one side surface of the positive current collector. The positive electrode material layer includes a positive electrode active material, which contains cobalt and titanium (T). The T element is selected from at least one element in Groups VB and VIB of Periods 4 to 6 of the periodic table. The mass percentage of T element in the positive electrode active material is A, and the mass percentage of cobalt element in the positive electrode active material is B, and A and B satisfy: 0.002 ≤ A / B ≤ 0.01.

[0007] The electrolyte contains nitrile compounds; the mass percentage of the nitrile compounds in the electrolyte is C; the porosity of the positive electrode is D; the resistance of the positive electrode at 50% SOC (State of Charge) is R; and A, B, C, D, and R satisfy: 15≤R*D / A≤110, 30≤B*R / (A+C)≤100.

[0008] The lithium-ion battery according to the embodiments of this application has at least the following beneficial effects: The lithium-ion battery uses a positive electrode active material containing cobalt and T (i.e., at least one element from Group VB and Group VIB of the periodic table, periods 4 to 6) to construct the positive electrode sheet. When the contents A and B of T and cobalt in the positive electrode active material satisfy 0.002 ≤ A / B ≤ 0.01, T can maximize the conductivity of the positive electrode material. Simultaneously, after T is doped into cobalt sites, it can act as a supporting element, effectively reducing the migration resistance of lithium ions during insertion / extraction and increasing the lithium ion migration rate. Furthermore, by controlling the T content A in the positive electrode active material, the porosity D of the positive electrode sheet, and other parameters within a range of 50%, the battery achieves better performance. At SOC, the ratio of the positive electrode resistance R to the electrolyte satisfies 15 ≤ R*D / A ≤ 110, indicating that the positive electrode possesses excellent electron transport channels. Furthermore, thanks to nitrogen doping, electronic conductivity is improved. The controlled porosity of the positive electrode ensures the lithium-ion transport rate in the electrolyte, while optimizing both electronic and ionic conductivity, effectively enhancing the discharge performance of lithium-ion batteries at low temperatures. Moreover, by adding a nitrile compound with a mass percentage (C) of the electrolyte and controlling the ratio to 30 ≤ B*R / (A+C) ≤ 100, the nitrogen in the positive electrode material synergistically improves the electrode-electrolyte interface contact, thereby enhancing both low-temperature discharge performance and the high-temperature cycle performance and safety of lithium-ion batteries.

[0009] The resistance of the positive electrode at 50% SOC can be obtained by the following method: Charge the lithium-ion battery at a constant current rate of 0.5C to 50% SOC, with a cutoff current of 0.025C; then disassemble the positive electrode from the lithium-ion battery and place it in an environment with a humidity of 5% to 15% for 30 minutes. The resistance value of the positive electrode is then measured and denoted as R. Alternatively, the positive electrode can be sealed and transferred to the resistance testing location for testing. Specifically, a BER1200 film resistance meter can be used for the positive electrode resistance test. Furthermore, the above resistance test requires adjacent test points to be spaced 2mm to 3mm apart, and at least 15 different points should be tested. The average resistance of all test points is recorded as the final resistance value.

[0010] In some embodiments of this application, A, B, C, D, and R satisfy: 15 ≤ R*D / A ≤ 70, and 30 ≤ B*R / (A+C) ≤ 90.

[0011] In some embodiments of this application, the lithium-ion battery satisfies at least one of the following conditions:

[0012] 1) A satisfies: 0.5% ≤ A ≤ 0.55%;

[0013] 2) B satisfies: 55% ≤ B ≤ 65%;

[0014] 3) C satisfies: 0.1% ≤ C ≤ 1%;

[0015] 4) D satisfies: 10% ≤ D ≤ 20%;

[0016] 5) R satisfies: 0.5Ω≤R≤1Ω.

[0017] In some embodiments of this application, the chemical formula of the positive electrode active material is Li. a Co 1-x-y T x N y O b Wherein, 0.90≤a≤1.10, 0.001≤x≤0.05, 0≤y≤0.02, 1.90≤b≤2.10; T is at least one element in subgroups VB and VIB of the periodic table from period 4 to 6, specifically at least one of vanadium, chromium, niobium, molybdenum, tantalum, and tungsten; N is at least one of aluminum, magnesium, titanium, zirconium, yttrium, and lanthanum.

[0018] Nitrile compounds are specifically compounds containing a cyano group (-CN). In some embodiments of this application, the nitrile compounds are selected from one or more of dinitrile compounds, trinitrile compounds, and tetranitrile compounds.

[0019] In some embodiments of this application, the dinitrile compound has the structural formula NC-R. 21 -CN;

[0020] The structural formula of the trinitrile compound is:

[0021] The structural formula of the tetranitrile compound is:

[0022] Among them, R 21 R 22 and R 23 Each is independently selected from halogen-substituted or unsubstituted C1-C10 alkyl, halogen-substituted or unsubstituted C1-C10 alkenyl, halogen-substituted or unsubstituted C1-C10 alkynyl, halogen-substituted or unsubstituted C5-C10 heteroaryl, or halogen-substituted or unsubstituted C6-C10 aryl.

[0023] In some embodiments of this application, the dinitrile compound is selected from one or more of butadionitrile, glutaronitrile, adiponitrile, sebaconitrile, anonadionitrile, dicyanbenzene, terephthalonitrile, pyridine-3,4-dianitrile, 2,5-dicyanopyridine, 2,2,3,3-tetrafluorobutadionitrile, 3,3'-[1,2-ethylenedimethylbis(oxy)]bispropionitrile, tetrafluoroterephthalonitrile, 4-tetrahydrothiamethylenemalonium, trans-butenedionitrile, ethylene glycol bis(propionitrile) ether, and 1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarboxynitrile; and / or,

[0024] The trinitrile compound is selected from one or more of 1,3,6-hexanetrionitrile, 1,3,5-cyclohexanetrionitrile, 1,3,5-phenyltricyanide, 1,2,3-propanetrionitrile, and glyceryltrionitrile; and / or,

[0025] The tetranitrile compound is selected from one or more of 1,1,3,3-propanetetracarbonitrile, 1,2,2,3-tetracyanopropane, 1,2,4,5-tetracyanobenzene, 2,3,5,6-pyrazinetetracarbonitrile, 3-methyl-3-propyl-cyclopropane-1,1,2,2-tetracarbonitrile, and 7,7,8,8-tetracyano-p-benzodiquinone dimethylane.

[0026] In some embodiments of this application, the electrolyte further includes lithium salt and organic solvent.

[0027] In some embodiments of this application, the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate (LiAsF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium trifluoromethanesulfonate (LiCF3SO3), lithium difluorophosphate (LiPO2F2), lithium 2-trifluoromethyl-4,5-dicyanimidazolium (C6F3LiN4), lithium difluorooxalate borate (LiODFB), lithium tetrafluorooxalate phosphate (LiOTFP), lithium bis(oxalate)borate (LiBOB), lithium bis(trifluoromethanesulfonylimide) (LiN(SO2CF3)2), and lithium bis(fluorosulfonylimide) (LiN(SO2F)2).

[0028] In some embodiments of this application, the organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, γ-butyrolactone, 1,3-propanesulfonate lactone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, propyl propionate, ethyl butyrate, 1,3-dioxolane, and ethylene glycol dimethyl ether.

[0029] In some embodiments of this application, the positive electrode material layer further includes a conductive agent and a binder.

[0030] In some embodiments of this application, the conductive agent is selected from one or more of natural graphite, artificial graphite, conductive carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, carbon fiber, conductive polymer, and metal powder.

[0031] In some embodiments of this application, the adhesive is selected from one or more of polyvinylidene fluoride, copolymers of polyvinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyethylene oxide, styrene-butadiene rubber, and polyacrylate materials.

[0032] In some embodiments of this application, the positive electrode material layer comprises 93 wt% to 99 wt% of positive electrode active material, 0.5 wt% to 5 wt% of conductive agent, and 0.5 wt% to 2 wt% of binder. This allows the mass ratio of positive electrode active material, conductive agent, and binder in the positive electrode material layer to be controlled to be 93 to 99:0.5 to 5:0.5 to 2.

[0033] In some embodiments of this application, the mass ratio of the positive electrode active material, the conductive agent, and the binder is 97:1.5:1.5.

[0034] In some embodiments of this application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one side surface of the negative electrode current collector, the negative electrode material layer including a negative electrode active material, a conductive agent and a binder.

[0035] In some embodiments of this application, the lithium-ion battery further includes a packaging shell, in which the positive electrode, separator, negative electrode and electrolyte are housed.

[0036] In some embodiments of this application, the positive electrode, separator, and negative electrode are wound to form a bare battery cell, and the bare battery cell and the electrolyte are housed within the packaging shell.

[0037] The above lithium-ion batteries can be prepared by a method including the following steps:

[0038] A positive electrode slurry is prepared using raw materials including the positive electrode active material, and then coated onto at least one side surface of the positive electrode current collector to obtain a positive electrode sheet;

[0039] The positive electrode, separator, and negative electrode are stacked and wound to form a bare cell. The bare cell is then placed in a packaging shell and injected with the electrolyte to obtain a lithium-ion battery.

[0040] The positive electrode active material can be prepared by a method comprising the following steps: uniformly mixing lithium cobalt oxide and a compound containing the element T, and calcining in an air atmosphere to obtain the positive electrode active material. The compound containing the element T can be selected from one or more of carbonates containing the element T, oxides containing the element T, and hydroxides containing the element T.

[0041] During the preparation of the positive electrode active material, the calcination temperature can be controlled between 650℃ and 850℃; the calcination time can be controlled between 22h and 26h; and the heating rate can be controlled between 2℃ / min and 8℃ / min.

[0042] In the preparation of the positive electrode sheet, after coating the surface of the positive electrode current collector with a positive electrode slurry, it is further dried and rolled to obtain the positive electrode sheet. The drying temperature can be controlled between 100℃ and 150℃, for example, any value or a range of any two of 100℃, 110℃, 120℃, 125℃, 130℃, 140℃, and 150℃; the drying time can be between 6h and 10h, for example, any value or a range of any two of 6h, 7h, 8h, 8.5h, 9h, and 10h. Furthermore, the structural parameters of the positive electrode sheet can be controlled by controlling the rolling thickness during the rolling process. Further, after the rolling process, it can be slit.

[0043] In addition, during the battery assembly process, after the electrolyte is injected, the battery undergoes further vacuum sealing, settling, formation, and shaping processes to obtain a lithium-ion battery.

[0044] A second aspect of this application provides an electronic device comprising any of the aforementioned lithium-ion batteries. Detailed Implementation

[0045] The following will clearly and completely describe the concept and technical effects of this application in conjunction with embodiments, so as to fully understand the purpose, features and effects of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are all within the scope of protection of this application.

[0046] Example 1

[0047] This embodiment proposes a lithium-ion battery, including a positive electrode, a separator, a negative electrode, and an electrolyte, with the separator sandwiched between the positive and negative electrode. The positive electrode includes a positive current collector and positive electrode material layers disposed on opposite sides of the positive current collector; the positive electrode material layers include a positive active material in a mass ratio of 97:1.5:1.5, a conductive agent acetylene black, and a binder polyvinylidene fluoride (PVDF); the positive active material contains cobalt and tantalum, specifically tantalum; the mass percentages of tantalum (A) and cobalt (B) in the positive active material are 0.37% and 59.94%, respectively, thus 0.002 < A / B = 0.006 < 0.01; and the positive electrode has a porosity (D) of 15% and a thickness of 80 μm.

[0048] In addition, the resistance R of the positive electrode of the lithium-ion battery at 50% SOC is 0.76Ω. This resistance value was obtained by testing as follows: the lithium-ion battery was charged to 50% SOC at a constant current rate of 0.5C, and the cutoff current was 0.025C; then the positive electrode of the lithium-ion battery was disassembled and placed in an environment with 10% humidity for 30 minutes, and then sealed and transferred to the resistance test location. The resistance value of the positive electrode was tested using a BER1200 film resistance meter. During the test, adjacent test points were spaced 2mm to 3mm apart, and 15 different points were tested. The average resistance of all test points was calculated to obtain the final resistance value R.

[0049] The electrolyte includes lithium salt LiPF6, organic solvent, and nitrile compound; the mass percentage of LiPF6 in the electrolyte is 15%, and the nitrile compound used is adiponitrile, whose mass percentage C in the electrolyte satisfies 0.1% < C = 0.5% < 1%; thus, the lithium-ion battery satisfies: 15 < R*D / A = 30.8 < 110, 30 < B*R / (A+C) = 52.4 < 100.

[0050] The lithium-ion battery is prepared by a method including the following steps:

[0051] Preparation of positive electrode active material: Lithium cobalt oxide and tantalum carbonate containing tantalum were mixed evenly at a molar ratio of 1:0.007, and then calcined at 750°C for 24 hours in air at a rate of 5°C / min to obtain positive electrode active material.

[0052] Preparation of the positive electrode sheet: The positive electrode active material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 97:1.5:1.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until a homogeneous and fluid positive electrode slurry was formed. The positive electrode slurry was uniformly coated onto the two opposing surfaces of the positive electrode current collector aluminum foil. The coated aluminum foil was placed in an oven and baked at five different temperature gradients (100℃, 110℃, 120℃, 110℃, and 100℃) for 1 minute each, and then dried in an oven at 120℃ for 8 hours. After that, the positive electrode sheet was obtained by rolling and slitting. The core element T in this positive electrode active material is tantalum. Based on the mass of the positive electrode active material, the tantalum content in the positive electrode sheet is 0.37%. The thickness of the positive electrode sheet after rolling is 80 μm, and the porosity of the electrode sheet is 15%.

[0053] Preparation of negative electrode sheet: The negative electrode active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are thoroughly mixed in a deionized water solvent system at a mass ratio of 96:1:1.5:1.5. The mixture is then coated onto the two opposite surfaces of the negative electrode current collector Cu foil. After drying, cold pressing, and slitting, the negative electrode sheet is obtained.

[0054] Electrolyte preparation: In an argon atmosphere glove box with a water content of <10ppm, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), propyl propionate (PP), and dimethyl carbonate (DMC) were mixed evenly in a mass ratio of 20:10:10:10:50 to obtain a non-aqueous solvent. Then, 15 wt.% of LiPF6 based on the total mass of the electrolyte was slowly added to the non-aqueous solvent and stirred until it was completely dissolved. Finally, 0.5 wt.% of adiponitrile based on the total mass of the electrolyte was added to obtain the electrolyte.

[0055] Assembly and preparation of lithium-ion batteries: Using a porous polyethylene (PE) polymer film as a separator, the positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. Then, the cells are wound to obtain bare cells, which are placed in outer packaging foil. The prepared electrolyte is injected into the dried battery. After vacuum sealing, settling, formation, and shaping, the lithium-ion battery is obtained.

[0056] Example 2 group

[0057] This set of embodiments includes embodiments 2a to 2b, each of which provides a lithium-ion battery. The difference between these embodiments and embodiment 1 is that the tantalum content A in the positive electrode active material of the positive electrode material layer on the positive electrode sheet is different from that in embodiment 1, and thus the resistance value of the positive electrode sheet is different from that of the positive electrode sheet in embodiment 1. Otherwise, they are basically the same as the lithium-ion battery in embodiment 1.

[0058] The preparation of lithium-ion batteries in Examples 2a to 2b was carried out in accordance with Example 1, except that in the preparation process of the positive electrode active material in Examples 2a to 2b, the molar ratio of lithium cobalt oxide and tantalum carbonate was adjusted from 1:0.007 in Example 1 to 1:0.0036 and 1:0.01, respectively, thereby adjusting the tantalum element content A in the positive electrode active material. See Table 1 for details.

[0059] Example 3 Group

[0060] This set of embodiments includes embodiments 3a to 3c, each of which provides a lithium-ion battery. The difference between these embodiments and embodiment 1 is that the content C of adiponitrile in the electrolyte is different from that in embodiment 1, while the rest is basically the same as the lithium-ion battery in embodiment 1.

[0061] The lithium-ion battery in this embodiment was prepared in accordance with Example 1, except that the content C of adiponitrile in the electrolyte was adjusted, as detailed in Table 1.

[0062] Example 4 group

[0063] This set of embodiments includes embodiments 4a to 4c, each of which provides a lithium-ion battery. The difference between these embodiments and embodiment 1 is that the porosity and thickness of the positive electrode sheet are different from those of embodiment 1, while the rest are basically the same as those of the lithium-ion battery in embodiment 1.

[0064] The lithium-ion battery in this embodiment was prepared in accordance with Example 1, except that the porosity of the positive electrode sheet was adjusted. Specifically, this was achieved by adjusting the thickness of the positive electrode sheet after rolling. The thickness of the positive electrode sheet was adjusted from 70 μm to 90 μm, as detailed in Table 1.

[0065] Example 5 group

[0066] This set of examples includes Examples 5a to 5c, each of which provides a lithium-ion battery. The difference between Examples 5a and 5c and Example 1 is that the nitrile compound in the electrolyte is different from that in Example 1, while the rest is basically the same as the lithium-ion battery in Example 1.

[0067] The lithium-ion batteries in this embodiment were prepared in accordance with Example 1, except that the selection of nitrile compounds in the electrolyte was adjusted, as detailed in Table 1.

[0068] Example 6 group

[0069] This set of embodiments includes embodiments 6a to 6e, each of which provides a lithium-ion battery. The difference between these embodiments and embodiment 1 is that the type of T element in the positive electrode active material on the positive electrode sheet is different from that in embodiment 1, while the rest is basically the same as the lithium-ion battery in embodiment 1.

[0070] The preparation of the lithium-ion batteries in this embodiment was carried out in accordance with Example 1, except that in the preparation of the positive electrode active material in Examples 6a to 6e, the compounds containing element T were vanadium carbonate, chromium carbonate, niobium carbonate, tungsten carbonate, and molybdenum carbonate, respectively. In Example 6a, the molar ratio of lithium cobalt oxide to vanadium carbonate was 1:0.007; in Example 6b, the molar ratio of lithium cobalt oxide to chromium carbonate was 1:0.0035; in Example 6c, the molar ratio of lithium cobalt oxide to niobium carbonate was 1:0.007; in Example 6d, the molar ratio of lithium cobalt oxide to tungsten carbonate was 1:0.007; and in Example 6e, the molar ratio of lithium cobalt oxide to molybdenum carbonate was 1:0.007. This adjusted the types of element T in the positive electrode active material on the positive electrode sheet, as detailed in Table 1.

[0071] Comparative Example 1

[0072] This comparative example provides a lithium-ion battery that differs from Example 1 in that the positive electrode active material on the positive electrode sheet does not contain the element T, and the electrolyte does not contain nitrile compounds, while the internal proportions of other materials remain unchanged, as detailed in Table 1.

[0073] Comparative Example 2

[0074] This comparative example group includes comparative examples 2a to 2b, each of which provides a lithium-ion battery. The difference between comparative examples 2a and 2b and example 1 is that the positive electrode active material on the positive electrode sheet does not contain the element T, or the electrolyte does not contain nitrile compounds, while the internal proportions of other materials remain unchanged. See Table 1 for details.

[0075] Comparative Example 3 Groups

[0076] This comparative example group includes comparative examples 3a to 3f, each providing a lithium-ion battery. The difference between these and Example 1 is that the positive electrode active material on the positive electrode sheet contains element T (specifically cobalt), and the electrolyte contains nitrile compounds. However, the ratio of element T content A, cobalt content B, positive electrode sheet resistance R, positive electrode sheet porosity D, and nitrile compound content C in the electrolyte cannot simultaneously satisfy the following conditions: 0.002≤A / B≤0.01, 0.1%≤C≤1%, 15≤R*D / A≤110, 30≤B*R / (A+C)≤100. See Table 1 for details. The lithium-ion batteries in Comparative Examples 3a to 3b were prepared in accordance with Example 1, except that the molar ratio of lithium cobalt oxide to tantalum carbonate in the preparation process of the positive electrode active material in Comparative Examples 3a to 3b and 3d was adjusted from 1:0.007 in Example 1 to 1:0.0016, 1:0.013 and 1:0.0036, respectively, thereby adjusting the tantalum content A in the positive electrode active material.

[0077] Table 1

[0078] Performance testing

[0079] (1) Cyclic life test

[0080] The lithium-ion battery was placed in a constant temperature environment of 45℃ and charged and discharged at a rate of 1.0C / 1.0C. The charging cutoff voltage was 4.5V and the discharging cutoff voltage was 3.0V. The battery was charged and discharged 500 times. The cycle discharge capacity was recorded and divided by the discharge capacity of the first cycle to obtain the cycle capacity retention rate.

[0081] (2) Low-temperature discharge test

[0082] The lithium-ion battery was placed at room temperature and subjected to 5 charge-discharge cycles at a 1C rate. Then, it was charged at a 1C rate to 4.5V, and the 1C charging capacity Q1 was recorded. The fully charged battery was then placed at -20℃ for 4 hours and discharged at a 0.2C rate to 3.0V, and the discharge capacity Q2 was recorded. The low-temperature discharge capacity retention rate can be obtained by calculating Q2 / Q1.

[0083] (3) 134℃ hot box test

[0084] The lithium-ion battery is charged at a constant current rate of 0.5C to 4.5V at 25℃, then charged at a constant voltage rate to the cutoff current of 0.025C. After standing for 2 hours, the fully charged battery is placed in a hot box and heated from room temperature to 134℃ at a rate of 5℃ / min and maintained for 60 minutes. If the battery does not explode or catch fire, it can be considered PASS; otherwise, it is FAIL.

[0085] The performance of the lithium-ion batteries in each embodiment and comparative example was tested according to the above method, and the results are shown in Table 2.

[0086] Table 2

[0087] As shown in Table 2 above, compared with the comparative examples, the safety performance, high-temperature cycle capacity retention rate, and low-temperature discharge capacity retention rate of the lithium-ion batteries in each embodiment are significantly improved. This indicates that the T and cobalt elements in the positive electrode active material of the lithium-ion batteries in each embodiment, in synergy with the nitrile compounds in the electrolyte, can effectively limit the side reactions at the interface between the positive electrode active material and the electrolyte, thereby improving the battery's safety performance and high-temperature cycle stability. Simultaneously, thanks to the addition of nitrile compounds in the electrolyte (especially the low-content design of nitrile compounds) and the increased electronic conductivity brought about by T element doping, as well as the constrained relationship between the resistance and porosity of the positive electrode sheet, the low-temperature discharge performance of the battery is significantly improved.

[0088] The above-mentioned lithium-ion batteries can be used in electronic devices. Furthermore, this application also proposes an electronic device, which includes, but is not limited to, laptops, e-book players, portable telephones, portable printers, clocks, game consoles, toys, lighting equipment, calculators, video recorders, radios, portable power supplies, automobiles, motorcycles, and large household batteries.

[0089] The embodiments described above are merely examples of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application.

Claims

1. A lithium-ion battery, wherein, It includes a positive electrode, a separator, a negative electrode, and an electrolyte; the separator is sandwiched between the positive electrode and the negative electrode. The positive electrode sheet includes a positive current collector and a positive electrode material layer disposed on at least one side surface of the positive current collector. The positive electrode material layer includes a positive electrode active material, which contains cobalt and titanium (T). The T element is selected from at least one element in Groups VB and VIB of Periods 4 to 6 of the periodic table. The mass percentage of T element in the positive electrode active material is A, and the mass percentage of cobalt element in the positive electrode active material is B, and A and B satisfy: 0.002 ≤ A / B ≤ 0.

01. The electrolyte contains nitrile compounds; the mass percentage of the nitrile compounds in the electrolyte is C; the porosity of the positive electrode is D; the resistance of the positive electrode at 50% SOC is R; A, B, C, D, and R satisfy: 15≤R*D / A≤110, 30≤B*R / (A+C)≤100.

2. The lithium-ion battery according to claim 1, wherein, A, B, C, D, and R satisfy: 15 ≤ R*D / A ≤ 70, and 30 ≤ B*R / (A+C) ≤ 90.

3. The lithium-ion battery according to claim 1, wherein, A satisfies: 0.5% ≤ A ≤ 0.55%.

4. The lithium-ion battery according to claim 1, wherein, B satisfies: 55% ≤ B ≤ 65%.

5. The lithium-ion battery according to claim 1, wherein, C satisfies: 0.1% ≤ C ≤ 1%.

6. The lithium-ion battery according to claim 1, wherein, D satisfies: 10% ≤ D ≤ 20%.

7. The lithium-ion battery according to claim 1, wherein, R satisfies: 0.5Ω≤R≤1Ω.

8. The lithium-ion battery according to claim 1, wherein, The chemical formula of the positive electrode active material is Li a Co 1-x- y T x N y O b Wherein, 0.90≤a≤1.10, 0.001≤x≤0.05, 0≤y≤0.02, 1.90≤b≤2.10, T is at least one element in subgroups VB and VIB of periods 4 to 6 of the periodic table, and N is at least one of aluminum, magnesium, titanium, zirconium, yttrium, and lanthanum.

9. The lithium-ion battery according to claim 1, wherein, The nitrile compounds are selected from one or more of dinitrile compounds, trinitrile compounds, and tetranitrile compounds.

10. The lithium-ion battery according to claim 9, wherein, The dinitrile compound has the structural formula NC-R. 21 -CN; The structural formula of the trinitrile compound is: The structural formula of the tetranitrile compound is: Among them, R 21 R 22 and R 23 Each is independently selected from halogen-substituted or unsubstituted C1-C10 alkyl, halogen-substituted or unsubstituted C1-C10 alkenyl, halogen-substituted or unsubstituted C1-C10 alkynyl, halogen-substituted or unsubstituted C5-C10 heteroaryl, or halogen-substituted or unsubstituted C6-C10 aryl.

11. The lithium-ion battery according to claim 9, wherein, The dinitrile compound is selected from one or more of succinic anionizer, glutaronitrile, adiponitrile, sebaconitrile, anonadionitrile, dicyanobenzene, terephthalonitrile, pyridine-3,4-dianitrile, 2,5-dicyanopyridine, 2,2,3,3-tetrafluorosuccinic anionizer, 3,3'-[1,2-ethylenedimethylbis(oxy)]bispropionitrile, tetrafluoroterephthalonitrile, 4-tetrahydrothiamethylenemalonium, transbutenedionitrile, ethylene glycol bis(propionitrile) ether, and 1,4,5,6-tetrahydro-5,6-dioxo-2,3-pyrazinedicarboxynitrile.

12. The lithium-ion battery according to claim 9, wherein, The trinitrile compound is selected from one or more of 1,3,6-hexanetrionitrile, 1,3,5-cyclohexanetrionitrile, 1,3,5-phenyltricyanide, 1,2,3-propanetrionitrile, and glyceryltrionitrile.

13. The lithium-ion battery according to claim 9, wherein, The tetranitrile compound is selected from one or more of 1,1,3,3-propanetetracarbonitrile, 1,2,2,3-tetracyanopropane, 1,2,4,5-tetracyanobenzene, 2,3,5,6-pyrazinetetracarbonitrile, 3-methyl-3-propyl-cyclopropane-1,1,2,2-tetracarbonitrile, and 7,7,8,8-tetracyano-p-benzodiquinone dimethylane.

14. The lithium-ion battery according to claim 1, wherein, The electrolyte also includes lithium salt and organic solvent.

15. The lithium-ion battery according to claim 14, wherein, The lithium salt is selected from one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium perchlorate, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium 2-trifluoromethyl-4,5-dicyanimidazolium, lithium difluorooxalate borate, lithium tetrafluorooxalate phosphate, lithium bis(oxalate)borate, lithium bistrifluoromethanesulfonylimide, and lithium bisfluorosulfonylimide.

16. The lithium-ion battery according to claim 14, wherein, The organic solvent is selected from at least one of ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, γ-butyrolactone, 1,3-propanesulfonate lactone, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, propyl propionate, ethyl butyrate, 1,3-dioxolane, and ethylene glycol dimethyl ether.

17. The lithium-ion battery according to claim 1, wherein, The positive electrode material layer also includes a conductive agent and a binder.

18. The lithium-ion battery according to claim 17, wherein, The adhesive is selected from one or more of the following: polyvinylidene fluoride, copolymer of polyvinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polymethyl methacrylate, polyacrylonitrile, polyethylene oxide, styrene-butadiene rubber, and polyacrylate.

19. The lithium-ion battery according to claim 17, wherein, The mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer is 93-99:0.5-5:0.5-2.

20. An electronic device, wherein, The lithium-ion battery includes any one of claims 1 to 19.

Images