Electrochemical device and electronic apparatus

Abstract

The invention provides an electrochemical device and electronic equipment, the electrochemical device comprises a positive pole piece, a negative pole piece and an electrolyte, the negative pole piece comprises a negative current collector and a negative active material layer arranged on at least one surface of the negative current collector, the positive pole piece comprises a positive current collector and a positive active material layer arranged on at least one surface of the positive current collector, the negative pole piece and the positive pole piece are laminated, the negative active material layer comprises an extension region which is not overlapped with the positive active material layer, and the ratio of the area of the extension region to the area of the negative active material layer is a%; the electrolyte comprises a sulfonate-group-containing compound, and the mass percentage content of the sulfonate-group-containing compound in the electrolyte is b%; and 0.0003 < = b / a < = 5. The electrochemical device has good cycle performance.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to an electrochemical device and an electronic device. Background Art

[0002] With the continuous development of electrochemical devices, higher requirements are put forward for their performance. Since side reactions are likely to occur between the electrolyte and the negative electrode in the electrochemical device, the cycle performance of the electrochemical device will deteriorate. Therefore, it is necessary to improve the cycle performance of the electrochemical device. Summary of the Invention

[0003] The present application provides an electrochemical device and an electronic device, and the electrochemical device has good cycle performance.

[0004] In a first aspect, the present application provides an electrochemical device, including a positive electrode plate, a negative electrode plate and an electrolyte. The negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The negative electrode active material layer includes an overhang region that does not overlap with the positive electrode active material layer, that is, the overhang region. The ratio of the area of the overhang region to the area of the negative electrode active material layer is a%; the electrolyte contains a compound containing a sulfonate group, and the mass percentage content of the compound containing a sulfonate group in the electrolyte is b%; a and b satisfy: 0.0003 ≤ b / a ≤ 5.

[0005] Based on the present application, the negative electrode active material layer is provided with an overhang region, that is, the area of the negative electrode active material layer is larger than the area of the positive electrode active material layer, which can improve the risk of active metal deposition at the edge of the negative electrode during charging and can improve the cycle stability of the electrochemical device. During the formation process, since there is no insertion / extraction reaction of active ions in the overhang region of the negative electrode active material layer, a stable SEI film is not easily formed on the surface of the overhang region, and side reactions with the electrolyte are likely to occur. The present application controls the relationship between the content of the compound containing a sulfonate group in the electrolyte and the area ratio of the overhang region in the negative electrode active material layer within the above range. The compound containing a sulfonate group can preferentially and rapidly form a film in the overhang region, effectively reducing the side reaction between the overhang region and the electrolyte, thereby effectively improving the cycle performance of the electrochemical device.

[0006] In some embodiments, 0.005 ≤ b / a ≤ 1.5. Based on the above embodiments, controlling the relationship between the content of the compound containing a sulfonate group in the electrolyte and the area ratio of the overhang region in the negative electrode active material layer within the above range can make the cycle performance of the electrochemical device better.

[0007] In some embodiments, 1 ≤ a ≤ 30. Based on the above embodiments, when the area ratio of the protruding region in the negative electrode active material layer is controlled within the above range, the electrochemical device has better cycling performance.

[0008] Preferably, 2 ≤ a ≤ 20;

[0009] In some embodiments, 0.01 ≤ b ≤ 5. Based on the above embodiments, when the content of the sulfonate group-containing compound in the electrolyte is controlled within the above range, the electrochemical device has better cycling performance. Preferably, 0.1 ≤ b ≤ 3;

[0010] In some embodiments, the compound containing a sulfonate group is selected from at least one of the structures of formula (I), formula (II), or formula (III):

[0011]

[0012] Wherein, R 11 is selected from substituted or unsubstituted C1-C4 alkylene, substituted or unsubstituted C2-C4 alkenylene, substituted or unsubstituted C1-C6 chain heteroalkyl, the number of heteroatoms in the chain heteroalkyl is 1 to 5, and the heteroatoms in the chain heteroalkyl are selected from O, N, P, or S;

[0013] R 21 and R 22 each independently is selected from substituted or unsubstituted C1-C 10 alkyl, substituted or unsubstituted C2-C 10 alkenyl, substituted or unsubstituted C2-C 10 alkynyl, or any one of substituted or unsubstituted C1-C6 chain heteroalkyl, the number of heteroatoms in the chain heteroalkyl is 1 to 5, and the heteroatoms in the chain heteroalkyl are selected from O, N, P, or S; when substituted, each substituent is independently selected from a halogen atom, C1-C3 alkyl, or C2-C4 alkenyl. Based on the above embodiments, the sulfonate group-containing compound satisfying the above formula (I), formula (II), or formula (III) can preferentially and rapidly form a film in the protruding region, and will not deteriorate other properties of the electrochemical device, and the electrochemical device has better cycling performance.

[0014] In some embodiments, the compound represented by formula (I), formula (II), or formula (III) includes at least one of the following compounds:

[0015]

[0016] Based on the above embodiments, the sulfonate group-containing compound of the above type can preferentially and rapidly form a film in the protruding region, and the electrochemical device has better cycling performance.

[0017] In some embodiments, the electrolyte includes a cyclic carbonate compound. The cyclic carbonate compound includes at least one of ethylene carbonate and propylene carbonate. The mass percentage content of the cyclic carbonate compound in the electrolyte is d%, and d and a satisfy: 0.17 ≤ d / a ≤ 45.

[0018] In the above-mentioned some embodiments, the cyclic carbonate compound has a relatively high dielectric constant, which is beneficial to the dissociation of the electrolyte salt, beneficial to improving the rate performance of the electrochemical device, and is more stable to the negative electrode active material than the chain carbonate compound. By controlling the relationship between its content in the electrolyte and the area ratio of the protruding region in the negative electrode active material layer within the above range, the cycle performance of the electrochemical device can be further improved. Preferably, 0.5 ≤ d / a ≤ 20.

[0019] In some embodiments, 10 ≤ d ≤ 45. Based on the above embodiments, due to the relatively high viscosity of the cyclic carbonate, controlling the mass percentage content of the cyclic carbonate compound in the electrolyte within the above range results in better performance of the electrochemical device.

[0020] In some embodiments, the electrolyte includes a lithium salt additive. The lithium salt additive includes at least one of lithium difluorophosphate, lithium difluoro(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, lithium bis(oxalato)borate, lithium tetrafluoroborate, and lithium difluoro(oxalato)borate; the mass percentage content of the lithium salt additive in the electrolyte is 0.005% to 2%. Based on the above embodiments, further adding the above lithium salt additive to the electrolyte and controlling the mass percentage content within the above range can cooperate with the compound containing a sulfonate group to form a protective film in the protruding region, further reducing the side reaction between the negative electrode active material in the protruding region and the electrolyte, and the cycle performance of the electrochemical device is better.

[0021] In some embodiments, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes at least one of natural graphite, artificial graphite, hard carbon, and soft carbon.

[0022] In some embodiments, the electrolyte further contains a carbonate dimer, and the carbonate dimer is selected from at least one of the following formula (IV):

[0023]

[0024] Wherein, R1 and R3 are each independently selected from C1 to C4 alkyl groups, and R2 is selected from C1 to C4 alkylene groups; the mass percentage content of the carbonate dimer in the electrolyte is 0.001% to 5%.

[0025] Based on the above embodiments, further adding the compound shown in formula (IV) to the electrolyte and controlling the mass percentage within the above range can cooperate with the compound containing a sulfonate group to form a protective film in the protruding area, further reducing the side reaction between the negative active material in the protruding area and the electrolyte, and the cycling performance of the electrochemical device is better.

[0026] In a second aspect, the present application provides an electronic device including the electrochemical device according to any one of the embodiments of the first aspect.

[0027] According to the present application, the electronic device includes the electrochemical device of the first aspect, and thus has the corresponding beneficial effects of the first aspect. Specific Embodiments

[0028] In the present specification, the embodiments or implementation manners are described in a progressive manner, and the key point of each embodiment is to illustrate the differences from other embodiments.

[0029] In the description of the present specification, the description with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present application. In the present specification, the schematic expressions of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0030] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0031] In the present specification, "alkyl" refers to a straight-chain or branched-chain saturated hydrocarbon group. "Alkenyl" refers to a straight-chain or branched-chain alkyl group containing one or more carbon-carbon double bonds. "Alkynyl" refers to a straight-chain or branched-chain alkyl group containing one or more carbon-carbon triple bonds. "Chain heteroalkyl" refers to a straight-chain or branched-chain saturated hydrocarbon group containing heteroatoms. "Aryl" refers to an aromatic monocyclic hydrocarbon ring system or a polycyclic system, in which two or more aromatic hydrocarbon rings are fused (i.e., contain shared bonds) together or at least one aromatic monocyclic hydrocarbon ring is fused with one or more cycloalkyl and / or cycloheteroalkyl rings. "Sub-" refers to a group capable of forming covalent bonds with two other moieties.

[0032] In this specification, substituents of compounds are disclosed in groups or ranges. It is explicitly contemplated that such a description includes every individual sub-combination of the members of these groups and ranges. For example, it is explicitly contemplated that the term "alkyl having 1 to 6 carbon atoms" discloses individually C1, C2, C3, C4, C5, C6, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C6, C2-C5, C2-C4, C2-C3, C3-C6, C3-C5, C3-C4, C4-C6, C4-C5, and C5-C6 alkyls.

[0033] Electrochemical device

[0034] In a first aspect, the present application provides an electrochemical device, comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte. The negative electrode active material layer of the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The negative electrode sheet and the positive electrode sheet are stacked. The area of the negative electrode active material layer is larger than the area of the positive electrode active material layer. The negative electrode active material layer comprises an extended region that does not overlap with the positive electrode active material layer. The ratio of the area of the extended region to the area of the negative electrode active material layer is a%. The electrolyte contains a compound containing a sulfonate group, and the mass percentage content of the compound containing a sulfonate group in the electrolyte is b%. a and b satisfy: 0.0003 ≤ b / a ≤ 5.

[0035] Based on the present application, the fact that the area of the negative electrode active material layer is larger than the area of the positive electrode active material layer can improve the risk of lithium deposition at the edge of the negative electrode during charging, and can improve the cycle stability of the electrochemical device. The non-overlapping region between the negative electrode active material layer and the positive electrode active material layer is the extended region. During the formation process, since there is no lithium insertion / extraction reaction in the negative electrode active material layer of the extended region, it is not easy to form a stable SEI film on the surface of the extended region, and it is easy to have side reactions with the electrolyte. In the present application, by adding a compound containing a sulfonate group to the electrolyte and controlling the relationship between its content in the electrolyte and the area ratio of the extended region in the negative electrode active material layer within the above range, the compound containing a sulfonate group can form a film preferentially and rapidly in the extended region, effectively reducing the side reactions between the extended region and the electrolyte, thereby effectively improving the cycle performance of the electrochemical device.

[0036] Specifically, taking a lithium-ion battery as an example, during the charging stage of an electrochemical device, the negative electrode active material undergoes a lithium intercalation reaction. If the charging capacity of the negative electrode active material is lower than the discharging capacity of the positive electrode active material, lithium may precipitate at the edge of the negative electrode plate, and the lithium dendrites formed by the precipitation will significantly deteriorate the cycle stability of the electrochemical device. Therefore, by setting the area of the negative electrode active material layer to be larger than that of the positive electrode active material, the risk of lithium precipitation at the edge of the negative electrode plate can be effectively reduced. However, during the formation process of the electrochemical device, since there is a lithium deintercalation reaction in the non-extending area of the negative electrode active material layer (i.e., the area overlapping with the positive electrode active material layer), film-forming additives, solvents, etc. in the electrolyte will preferentially form a SEI film in the non-extending area. The SEI film can reduce the side reaction between the negative electrode active material and the electrolyte. Since there is no lithium deintercalation reaction in the extending area of the negative electrode active material layer, it is not easy to form a complete SEI film in this area. The negative electrode active material in this area is in direct contact with the electrolyte, and the solvent in the electrolyte may undergo a reduction reaction to generate gas (such as carbon dioxide), which will deteriorate the cycle performance of the electrochemical device. In the present application, a compound containing a sulfonate group is further added to the electrolyte. The inventors found that this compound can preferentially and rapidly form a film in the extending area of the negative electrode active material layer during the formation stage, thereby effectively inhibiting the direct contact between the electrolyte and the negative electrode active material in the extending area and reducing the occurrence of side reactions. The present application further controls the relationship between the content of the compound containing a sulfonate group in the electrolyte and the area ratio of the extending area in the negative electrode active material layer within the above range, so that the electrochemical device has good cycle performance. For example, the value of b / a can be 0.0003, 0.0001, 0.01, 0.242, 0.624, 1.115, 1.319, 1.606, 2.160, 2.456, 3.071, 3.172, 3.635, 3.922, 4.403, 4.930, 5, or within the range composed of any of the above values.

[0037] It should be noted that the extending area can be located in the length direction and / or the width direction of the negative electrode plate.

[0038] In some embodiments, 0.005 ≤ b / a ≤ 1.5. Based on the above embodiments, by controlling the relationship between the content of the compound containing a sulfonate group in the electrolyte and the area ratio of the extending area in the negative electrode active material layer within the above range, the cycle performance of the electrochemical device is better.

[0039] In some embodiments, 1 ≤ a ≤ 30. Based on the above embodiments, by controlling the area ratio of the extending area in the negative electrode active material layer within the above range, the electrochemical device has better cycle performance. For example, the value of a can be 1, 3, 4, 6, 10, 10, 13, 15, 18, 20, 22, 24, 26, 29, 30, or within the range composed of any of the above values. Preferably, 2 ≤ a ≤ 20;

[0040] In some embodiments, 0.01 ≤ b ≤ 5. Based on the above embodiments, when the content of the sulfonate group-containing compound in the electrolyte is controlled within the above range, the electrochemical device has better cycling performance. For example, the value of b can be 0.01, 0.28, 0.75, 1.08, 1.40, 1.55, 1.97, 2.57, 3.07, 3.20, 3.70, 4.00, 4.48, 4.78, 5, or within the range composed of any of the above values.

[0041] Preferably, 0.1 ≤ b ≤ 3;

[0042] In some embodiments, the compound containing a sulfonate group is selected from at least one of the structures of formula (I), formula (II), or formula (III):

[0043]

[0044] Wherein, R 11 is selected from substituted or unsubstituted C1-C4 alkylene, substituted or unsubstituted C2-C4 alkenylene, substituted or unsubstituted C1-C6 chain heteroalkyl, the number of heteroatoms in the chain heteroalkyl is 1 to 5, and the heteroatoms in the chain heteroalkyl are selected from O, N, P, or S; R 21 , R 22 are each independently selected from substituted or unsubstituted C1-C 10 alkyl, substituted or unsubstituted C2-C 10 alkenyl, substituted or unsubstituted C2-C 10 alkynyl, or any one of substituted or unsubstituted C1-C6 chain heteroalkyl, the number of heteroatoms in the chain heteroalkyl is 1 to 5, and the heteroatoms in the chain heteroalkyl are selected from O, N, P, or S; when substituted, each substituent is independently selected from a halogen atom, C1-C3 alkyl, or C2-C4 alkenyl. Based on the above embodiments, the sulfonate group-containing compound satisfying the above formula (I) or formula (II) can preferentially and rapidly form a film in the protruding area and will not deteriorate other properties of the electrochemical device, and the electrochemical device has better cycling performance.

[0045] In addition, it can be understood that for the compounds represented by formula (I), formula (II), formula (III), or the shown compound, the main part that plays the above role in the electrolyte is the sulfonate group, and R 11 , R 21 , R 22 , R 31 , R 32 , R 33 when being the above types of groups, will not deteriorate the performance of the secondary battery. The following lists some compounds represented by formula (I), formula (II), or formula (III) as examples.

[0046] In some embodiments, the compound represented by formula (I), formula (II) or formula (III) includes at least one of the following compounds:

[0047]

[0048]

[0049] Based on the above embodiments, the sulfonate group-containing compound of the above type can form a film preferentially and rapidly in the protruding region, and the electrochemical device has better cycling performance.

[0050] It can be understood that the main component of the sulfonate group-containing compound that plays the above role in the electrolyte is the sulfonate group. Among the compounds other than the compounds with the structures of formula (I), formula (II) or formula (III) known in the art, other sulfonate group-containing compounds are within the protection scope of this application on the premise of not significantly deteriorating other performances of the electrochemical device.

[0051] In some embodiments, the electrolyte includes a cyclic carbonate compound. The cyclic carbonate compound includes at least one of ethylene carbonate and propylene carbonate. The mass percentage content of the cyclic carbonate compound in the electrolyte is d%, and d and a satisfy: 0.17 ≤ d / a ≤ 45.

[0052] In the above some embodiments, the cyclic carbonate compound has a relatively high dielectric constant, which is beneficial to the dissociation of the electrolyte salt, beneficial to improving the rate performance of the electrochemical device, and is more stable to the negative electrode active material than the chain carbonate compound. By controlling the relationship between its content in the electrolyte and the area ratio of the protruding region in the negative electrode active material layer within the above range, the cycling performance of the electrochemical device can be further improved. For example, the value of d / a can be 0.17, 1.01, 2.47, 4.32, 6.05, 7.56, 8.05, 10.11, 11.86, 13.34, 14.55, 16.86, 17.81, 18.97, 20, 45, or within the range composed of any of the above values. Preferably, 0.5 ≤ d / a ≤ 20.

[0053] In some embodiments, 10 ≤ d ≤ 45. Based on the above embodiments, due to the relatively high viscosity of the cyclic carbonate, controlling the mass percentage content of the cyclic carbonate compound in the electrolyte within the above range results in better performance of the electrochemical device. For example, the value of d can be 10, 11, 14, 16, 19, 20, 24, 25, 27, 31, 32, 34, 37, 38, 40, 42, 45, or within the range composed of any of the above values.

[0054] In some embodiments, the electrolyte includes a lithium salt additive, and the lithium salt additive includes at least one of lithium difluorophosphate, lithium difluoro(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, lithium bis(oxalato)borate, lithium tetrafluoroborate, and lithium difluoro(oxalato)borate; the mass percentage content of the lithium salt additive in the electrolyte is 0.005% to 2%. Based on the above embodiments, further adding the above lithium salt additive to the electrolyte and controlling the mass percentage content within the above range can cooperate with the compound containing a sulfonate group to form a protective film in the protruding area, further reducing the side reaction between the negative electrode active material in the protruding area and the electrolyte, and the cycle performance of the electrochemical device is better. For example, the mass percentage content of the lithium salt additive in the electrolyte can be 0.005%, 0.04%, 0.22%, 0.42%, 0.50%, 0.76%, 0.87%, 1.00%, 1.10%, 1.29%, 1.48%, 1.63%, 1.80%, 1.86%, 2%, or within the range composed of any of the above values.

[0055] In some embodiments, LiPF6 is included in the electrolyte.

[0056] In some embodiments, the electrolyte further contains a carbonate dimer, and the carbonate dimer is selected from at least one of the following formula (IV):

[0057]

[0058] wherein, R1 and R3 are each independently selected from C1 to C4 alkyl groups, and R2 is selected from C1 to C4 alkylene groups; the mass percentage content of the carbonate dimer in the electrolyte is 0.001% to 5%.

[0059] Based on the above embodiments, further adding the compound shown in formula (IV) to the electrolyte and controlling the mass percentage content within the above range can cooperate with the compound containing a sulfonate group to form a protective film in the protruding area, further reducing the side reaction between the negative electrode active material in the protruding area and the electrolyte, and the cycle performance of the electrochemical device is better. For example, the mass percentage content of the carbonate dimer in the electrolyte can be 0.001%, 0.01%, 0.06%, 0.48%, 0.84%, 1.48%, 1.61%, 2.00%, 2.58%, 2.95%, 3.40%, 3.53%, 4.04%, 4.52%, 4.89%, 5%, or within the range composed of any of the above values.

[0060] In some embodiments, the compound shown in formula (IV) includes at least one of the following compounds:

[0061]

[0062]

[0063] In some embodiments, by way of example, the electrolyte further includes, but is not limited to, at least one of ethylene methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0064]

Negative electrode sheet

[0065] In some embodiments, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes at least one of natural graphite, artificial graphite, hard carbon, and soft carbon. In some embodiments, the rechargeable capacity of the negative electrode active material is greater than the discharge capacity of the positive electrode active material to prevent lithium metal from being inadvertently deposited on the negative electrode during charging.

[0066] The negative electrode active material layer of the present application further includes a negative electrode binder. The negative electrode binder can improve the binding between the negative electrode active material particles and the binding between the negative electrode active material and the current collector. The type of the negative electrode binder is not particularly limited as long as it is a material stable to the electrolyte or the solvent used in electrode manufacturing. In some embodiments, the negative electrode binder includes a resin binder. Examples of the resin binder include, but are not limited to, fluororesin, polyacrylonitrile (PAN), polyimide resin, acrylic resin, polyolefin resin, etc. When preparing the negative electrode binder slurry using an aqueous solvent, the negative electrode binder includes, but is not limited to, carboxymethyl cellulose (CMC) or its salt, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or its salt, polyvinyl alcohol, etc.

[0067] The negative electrode active 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 the object of the present application can be achieved. For example, the negative electrode conductive agent can be at least one of acetylene black, Ketjen black, carbon nanotubes, carbon fibers, carbon dots, or graphene, and the above carbon nanotubes can include, but are not limited to, at least one of single-walled carbon nanotubes or multi-walled carbon nanotubes.

[0068] The present application places no particular limitation on the negative electrode current collector, as long as the object of the present application can be achieved. For example, the negative electrode current collector may include copper foil, aluminum foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a polymer substrate coated with a conductive metal, etc. 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, ethylene-propylene copolymer, polyethylene terephthalate, poly(ethylene naphthalate), or poly(p-phenylene terephthalamide). In the present application, there is no particular limitation on the thickness of the negative electrode current collector and the negative electrode active layer, as long as the object of the present application can be achieved. 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 active layer is 30 μm to 160 μm. In the present application, the negative electrode active layer may be provided on one surface in the thickness direction of the negative electrode current collector, or may be provided on both surfaces in the thickness direction of the negative electrode current collector. It should be noted that the "surface" here may be the entire area of the negative electrode current collector or a partial area of the negative electrode current collector. The present application places no particular limitation as long as the object of the present application can be achieved.

[0069] The present application places no particular limitation on the tap density of the negative electrode plate, as long as the object of the present application can be achieved. For example, the tap density of the negative electrode plate can be 1.0 g / cm 3 to 1.85 g / cm 3 . The present application places no particular limitation on the cold pressing pressure of the negative electrode plate, as long as the object of the present application can be achieved. For example, the cold pressing pressure of the negative electrode plate can be 3 tons-force to 30 tons-force.

[0070] Optionally, the negative electrode plate may further include a conductive layer, and the conductive layer is located between the negative electrode current collector and the negative electrode material layer. The present application places no particular limitation on the composition of the conductive layer, and it may be a commonly used conductive layer in the art. The conductive layer includes a conductive agent and a binder. The present application places no particular limitation on the conductive agent and the binder in the conductive layer, and they may be at least one of the above-mentioned conductive agents and the above-mentioned binders. The present application places no particular limitation on the mass ratio of the conductive agent and the binder in the conductive layer, and those skilled in the art can select according to actual needs as long as the object of the present application can be achieved. The present application places no particular limitation on the thickness of the conductive layer, as long as the object of the present application can be achieved. For example, the thickness of the conductive layer is 1 μm to 10 μm.

[0071]

Positive Electrode Plate

[0072] The positive electrode active material layer contains a positive electrode active material, and the positive electrode active material layer may be one layer or multiple layers. Each layer in the multiple positive electrode active material layers may contain the same or different positive electrode active materials. The positive electrode active material is any substance that can reversibly intercalate and deintercalate alkali metal ions.

[0073] The positive electrode active material includes a lithium transition metal oxide containing nickel and other transition metals. In the lithium transition metal oxide containing nickel and other transition metals, the amount of nickel may be 60 mol% or more, for example, 75 mol% or more, for example, 80 mol% or more, for example, 85 mol% or more, or for example, 90 mol% or more, relative to the total molar amount of the transition metals.

[0074] In some embodiments, the positive electrode active material includes at least one active material selected from the group consisting of: Li-Ni-Co-Al (NCA), Li-Ni-Co-Mn (NCM), lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMnO2), lithium nickel oxide (LiNiO2), or lithium iron phosphate (LiFePO4).

[0075] In some embodiments, the positive electrode active 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 may include, but are not limited to, carbon blacks such as acetylene black and Super-P; amorphous carbon materials such as needle coke; carbon nanotubes; graphene, etc. The above positive electrode conductive materials can be used alone or in any combination.

[0076] In some embodiments, the positive electrode active material layer includes a positive electrode binder. The type of the positive electrode binder is not particularly limited, and in the case of the coating method, any material that can be dissolved or dispersed in the liquid medium used during electrode manufacturing is acceptable. Examples of the positive electrode binder may 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, or nitrocellulose; rubber-like polymers such as styrene-butadiene rubber (SBR), nitrile rubber (NBR), fluororubber, isoprene rubber, polybutene rubber, or ethylene-propylene rubber; thermoplastic elastomer-like polymers such as styrene-butadiene-styrene block copolymer or its hydride, ethylene-propylene-diene terpolymer (EPDM), styrene-ethylene-butadiene-ethylene copolymer, styrene-isoprene-styrene block copolymer or its hydride; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymer, or propylene-α-olefin copolymer; fluorine-based polymers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, or polytetrafluoroethylene-ethylene copolymer; polymer compositions having ionic conductivity of alkali metal ions, etc. The above positive electrode binders can be used alone or in any combination.

[0077] There is no limitation on the type of solvent used to form the positive electrode paste, as long as it can dissolve or disperse the positive electrode active material, conductive material, positive electrode binder, and thickener (if used as needed). Examples of solvents used to form the positive electrode paste may include any one of aqueous solvents and organic solvents. Examples of aqueous media may include, but are not limited to, a mixed medium of alcohol and water, or water, etc. Examples of organic media may include, but are not limited to, aliphatic hydrocarbons such as hexane; aromatic hydrocarbons such as benzene, toluene, xylene, and methylnaphthalene; heterocyclic compounds such as quinoline and pyridine; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as methyl acetate and methyl acrylate; amines such as diethylenetriamine and N,N-dimethylaminopropylamine; ethers such as diethyl ether, propylene oxide, and tetrahydrofuran; amides such as N-methylpyrrolidone, dimethylformamide, and dimethylacetamide; aprotic polar solvents such as hexamethylphosphoramide or dimethyl sulfoxide, etc.

[0078] The thickener is usually used to adjust the viscosity of the paste. In the case of using an aqueous medium, a thickener and styrene-butadiene rubber latex can be used for pasting. There is no particular limitation on the type of thickener, and its examples may include, but are not limited to, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, or casein and their salts, etc. The above thickeners can be used alone or in any combination.

[0079] There is no particular limitation on the type of positive electrode current collector, and it can be any material known to be suitable for use as a positive electrode current collector. Examples of positive electrode current collectors may include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, or tantalum; materials such as carbon cloth and carbon paper. In some embodiments, the positive electrode current collector is a metal material. In some embodiments, the positive electrode current collector is aluminum.

[0080] In order to reduce the electron contact resistance between the positive electrode current collector and the positive electrode active layer, the surface of the positive electrode current collector may include a conductive aid or a conductive coating. Examples of conductive aids may include, but are not limited to, noble metals such as carbon, gold, platinum, or silver. Examples of conductive coatings may include a mixture layer containing inorganic oxides, conductive agents, and binders.

[0081] Under normal circumstances, the electrochemical device further includes a separator membrane.

[0082]

Separator Membrane

[0083] In this application, a separator membrane is usually provided between the positive electrode sheet and the negative electrode sheet. The separator membrane 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 progress of the electrochemical charge and discharge process.

[0084] This application has no particular limitation on the separator as long as the purpose of this application can be achieved. For example, the material of the separator may include, but is not limited to, at least one of polyolefins (PO) mainly composed of polyethylene (PE) and polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex or aramid; the type of the separator may include at least one of woven film, non-woven film, microporous film, composite film, rolled film or spun film.

[0085] In this application, the separator may include a substrate and a surface treatment layer. The substrate may be a non-woven fabric or a composite film having a porous structure, and the material of the substrate may include at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide. Optionally, 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 may be used. Optionally, a surface treatment layer is provided on at least one surface of the substrate, and the surface treatment layer may 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. This application has no particular limitation on the above inorganic particles. For example, it may include at least one of alumina, silica, magnesia, 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 or barium sulfate. This application has no particular limitation on the above binder. For example, it may be at least one of the foregoing binders. The polymer layer contains a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyvinylpyrrolidone, polyethylene ether, polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0086] The pore size of the separator in this application is 0.01 μm to 1 μm, and the thickness is 5 μm to 50 μm. In some embodiments, the thickness of the separator is 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, the insulation and mechanical strength can be ensured, and the rate performance and energy density of the secondary battery can be ensured.

[0087] The electrochemical device of this application further includes a packaging bag for accommodating the positive electrode plate, the separator, the negative electrode plate and the electrolyte, as well as other components known in the art in the electrochemical device. This application does not limit the above other components. This application has no particular limitation on the packaging bag, and it may be a packaging bag well known in the art as long as the purpose of this application can be achieved.

[0088] Electronic device

[0089] In a second aspect, the present application provides an electronic device including the electrochemical device according to any one of the embodiments of the first aspect.

[0090] According to the present application, the electronic device includes the electrochemical device of the first aspect, and thus has the corresponding beneficial effects of the first aspect.

[0091] The electronic device of the present application is not particularly limited, and it can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptop computers, pen-input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, portable cleaners, portable CD players, minidiscs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, motor-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0092] Examples

[0093] Hereinafter, taking a lithium-ion battery as an example, examples and comparative examples are given to more specifically illustrate the embodiments of the electrochemical device of the present application. Those skilled in the art will understand 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. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0094] <Test Methods>

[0095] (1) Low-temperature short-term performance test Thickness expansion rate test:

[0096] Place the lithium-ion battery in a high and low temperature chamber, adjust the temperature to 25°C, and let it stand for 30 minutes to make the lithium-ion battery reach a constant temperature. Discharge the lithium-ion battery with a constant current of 0.2C until the voltage reaches 2.5V, and record the thickness of the lithium-ion battery, which is denoted as the initial thickness. Then, adjust the temperature of the high and low temperature chamber to -10°C, and let the lithium-ion battery stand for 3 hours to make the temperature consistent with the external temperature. Under the condition of -10°C, charge it with a constant current of 0.5C until the voltage reaches 4.3V, then charge it at a constant voltage of 4.3V until the current is less than or equal to 0.02C, let it stand for 60 minutes, and then discharge it with a constant current of 0.2C until the voltage reaches 2.5V, and let it stand for 60 minutes. This is regarded as one charge-discharge cycle, and repeat the charge-discharge cycle 10 times. Adjust the temperature of the high and low temperature chamber to 25°C, let the lithium-ion battery stand for 3 hours to make the temperature consistent with the external temperature, charge it with a current of 0.3C until the voltage reaches 4.3V, then charge it at a constant voltage of 4.3V until the current is less than or equal to 0.02C, let it stand for 30 minutes, take out the lithium-ion battery and observe and test its thickness, which is denoted as the thickness after testing. Calculate the thickness expansion rate of the lithium-ion battery, and use it as an index to evaluate the low-temperature short-term performance of the lithium-ion battery.

[0097] The thickness expansion rate for low-temperature short-term performance test = (thickness after testing - initial thickness) / initial thickness × 100%.

[0098] (2) Cycle capacity retention rate test:

[0099] Place the lithium-ion battery in a constant temperature test chamber at 25°C, and let it stand for 30 minutes to make the lithium-ion battery reach a constant temperature. Charge the lithium-ion battery with a constant current of 1C until the voltage reaches 4.3V, then charge it at a constant voltage of 4.3V until the current is less than or equal to 0.05C, and then discharge it with a constant current of 1C until the voltage reaches 2.5V. This is one charge-discharge cycle. At this time, the discharge capacity measured is denoted as the first discharge capacity C0. Taking the capacity of the first discharge as 100%, repeat the charge-discharge cycle. When the cycle reaches 1000 times, stop the test and record the discharge capacity of the lithium-ion battery at this time, which is denoted as the discharge capacity C1 after 1000 cycles.

[0100] The cycle capacity retention rate = C1 / C0 × 100%.

[0101] Example 1

[0102] (1) Preparation of the negative electrode: The artificial graphite as the negative electrode active material, Super P as the conductive agent, and sodium carboxymethyl cellulose as the negative electrode binder are mixed according to a mass ratio of 92:2:6, and deionized water is added and stirred evenly to obtain a negative electrode slurry with a solid content of 70 wt%. The negative electrode slurry is evenly coated on one surface of a negative electrode current collector copper foil with a thickness of 8 μm, and then dried at 110 °C. The above steps are repeated on the other surface of the negative electrode current collector, and after cold pressing, a double-sided coated negative electrode plate with a single-sided negative electrode material layer thickness of 150 μm is obtained, and the compaction density of the single-sided negative electrode material layer is 1.6 g / cm 3 , and then the negative electrode plate is die-cut into a negative electrode plate with two or more negative electrode tabs on one side of the negative electrode current collector and a specification of 75 mm × 865 mm.

[0103] (2) Preparation of the positive electrode: The positive electrode active material LiMn 0.6 Fe 0.4 PO4, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are mixed according to a mass ratio of 96:2:2, and N-methylpyrrolidone (NMP) is added as a solvent, and stirred in a vacuum mixer until the system becomes homogeneous and a positive electrode slurry with a solid content of 75 wt% is obtained. The positive electrode slurry is evenly coated on an aluminum foil positive electrode current collector with a thickness of 12 μm and dried at 85 °C. The above steps are repeated on the other surface of the positive electrode current collector, and after cold pressing, a double-sided coated positive electrode plate with a thickness of 100 μm is obtained. The positive electrode plate is die-cut into a positive electrode plate with two or more positive electrode tabs on one side of the positive electrode current collector and a specification of 74 mm × 867 mm.

[0104] a% = (75 mm × 865 mm - 74 mm × 867 mm) × 100% / (75 mm × 865 mm) = 1%.

[0105] (3) Preparation of the electrolyte: In a glove box with an argon atmosphere with a water content < 10 ppm, the organic solvents cyclic carbonate and diethyl carbonate (DEC) are mixed evenly to obtain a basic solvent. The fully dried lithium salt LiPF6, the compound of formula I-6, adiponitrile (ADN), 1,3,6-hexanetricarbonitrile (HTCN), lithium salt additive, fluoroethylene carbonate (FEC), and carbonate dimer are dissolved in the above basic solvent and mixed evenly to obtain an electrolyte. Among them, the mass percentage content of lithium salt LiPF6 is 12.5%, the mass percentage content of the compound of formula I-6 is 5%, the mass percentage content of FEC is 5%, the mass percentage content of ADN is 1%, and the mass percentage content of HTCN is 2%; the types and contents of cyclic carbonate, lithium salt additive, and carbonate dimer are shown in Table 1, and the balance is diethyl carbonate.

[0106] (4) Preparation of the separator: A polyethylene (PE) porous polymer film is used as the separator.

[0107] (5) Preparation of lithium-ion battery: Stack the above-prepared positive electrode sheet, separator, and negative electrode sheet in sequence, with the separator placed in the middle of the positive electrode sheet and the negative electrode sheet to play a role in isolation, and then wind to obtain an electrode assembly. Put the electrode assembly into an aluminum-plastic film packaging bag, place it in a vacuum oven at 85 °C for 12 h to remove moisture, inject the above-prepared electrolyte, and obtain a lithium-ion battery through processes such as vacuum packaging, standing, formation, shaping, capacity testing, and secondary packaging.

[0108] Perform low-temperature short-term performance tests on the above lithium-ion battery, including thickness expansion rate and capacity retention rate tests. The results are shown in Table 1.

[0109] Examples 2 to 37, Comparative Example 1

[0110] Except for adjusting the parameters according to Table 1, the rest are the same as in Example 1.

[0111] The area of the positive electrode sheet remains unchanged, and the value of a is adjusted by controlling the area of the negative electrode sheet.

[0112] Perform low-temperature short-term performance tests on the above lithium-ion battery, including thickness expansion rate and capacity retention rate tests. The results are shown in Table 1.

[0113]

[0114]

[0115]

[0116]

[0117] As can be seen from Table 1, compared with the lithium-ion battery in the comparative example, the thickness expansion rate of the lithium-ion battery in each example is lower during the low-temperature short-term performance test, and the cyclic capacity retention rate is higher. This shows that by adding a compound containing a sulfonate group to the electrolyte and making the content b% of it in the electrolyte satisfy 0.0003 ≤ b / a ≤ 5 with the ratio a% of the area of the protruding region to the negative active material layer, the cyclic performance of the lithium-ion battery can be effectively improved.

[0118] As can be seen from Examples 1 to 15, when any of the conditions of 0.005 ≤ b / a ≤ 1.5, 2 ≤ a ≤ 20, 0.1 ≤ b ≤ 3, 0.5 ≤ d / a ≤ 20, and 10 ≤ d ≤ 45 are satisfied, the cyclic performance of the lithium-ion battery is better.

[0119] As can be seen from Examples 14, 16 to 23, adding different types of compounds containing a sulfonate group to the electrolyte can effectively improve the cyclic performance of the lithium-ion battery.

[0120] As can be seen from Embodiments 14, 24, and 25, the use of different types of cyclic carbonates can effectively improve the cycling performance of lithium-ion batteries.

[0121] As can be seen from Embodiments 14, 26 to 31, further adding a certain content of lithium salt additive to the electrolyte can synergistically make the cycling performance of lithium-ion batteries better in combination with the compound containing a sulfonate group.

[0122] As can be seen from Embodiments 14, 32 to 37, further adding a certain content of carbonate dimer to the electrolyte can synergistically make the cycling performance of lithium-ion batteries better in combination with the compound containing a sulfonate group.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An electrochemical device, characterized in that Including positive electrode sheet, negative electrode sheet and electrolyte, The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The negative electrode active material layer includes a protruding area that does not overlap with the positive electrode active material layer, and the ratio of the area of ​​the protruding area to the area of ​​the negative electrode active material layer is a %; The electrolyte contains a compound containing a sulfonate group, and the mass percentage of the compound containing a sulfonate group in the electrolyte is b%; The a and b satisfy: 0.0003≤b / a≤5.

2. The electrochemical device according to claim 1, characterized in that The electrochemical device satisfies at least one of the following conditions: (1) 0.005≤b / a≤1.5; (2)1≤a≤30； (3)0.01≤b≤5。 3. The electrochemical device according to claim 1, characterized in that The compound containing a sulfonate group is selected from at least one of the structures of formula (I), formula (II) or formula (III): Among them, R 11 is selected from substituted or unsubstituted C1 to C4 alkylene, substituted or unsubstituted C2 to C4 alkenylene, and substituted or unsubstituted C1 to C6 chain heteroalkylene, wherein the number of heteroatoms in the chain heteroalkylene is 1 to 5, and the heteroatoms in the chain heteroalkylene are selected from O, N, P or S; R 21 , R 22 , R 31 , R 33 are independently selected from a halogen atom, a cyano group, a substituted or unsubstituted C1 to C 10 alkyl, substituted or unsubstituted C2 to C 10 alkenyl, substituted or unsubstituted C2 to C 10 The alkynyl group; R 32 is selected from substituted or unsubstituted C1 to C5 alkylene, substituted or unsubstituted C2 to C4 alkenylene; When substituted, each substituent is independently selected from a halogen atom, a C1 to C3 alkyl group or a C2 to C4 alkenyl group.

4. The electrochemical device according to claim 3, characterized in that The electrochemical device satisfies at least one of the following conditions: (1) The compound represented by formula (I) includes at least one of the following compounds: (2) The compound represented by formula (II) includes at least one of the following compounds: (3) The compound represented by formula (III) includes at least one of the following compounds:

5. The electrochemical device according to claim 1, characterized in that The electrolyte includes a cyclic carbonate compound, which includes at least one of ethylene carbonate and propylene carbonate. The mass percentage of the cyclic carbonate compound in the electrolyte is d%, and d and a satisfy: 0.17≤d / a≤45.

6. The electrochemical device according to claim 5, characterized in that The electrochemical device satisfies at least one of the following conditions: (1) 0.5≤d / a≤20; (2)10≤d≤45。 7. The electrochemical device according to claim 1, characterized in that The electrolyte includes a lithium salt additive, which includes at least one of lithium difluorophosphate, lithium difluorobisoxalate phosphate, lithium tetrafluorooxalate phosphate, lithium dioxalate borate, lithium tetrafluoroborate, and lithium difluorooxalate borate; the mass percentage of the lithium salt additive in the electrolyte is 0.005% to 2%.

8. The electrochemical device according to claim 1, characterized in that The negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes at least one of natural graphite, artificial graphite, hard carbon, and soft carbon.

9. The electrochemical device according to claim 1, characterized in that The electrolyte further contains a carbonate dimer, wherein the carbonate dimer is selected from at least one of the following formula (IV): wherein R1 and R3 are independently selected from C1 to C4 alkyl groups, R2 is selected from C1 to C4 alkylene groups, The mass percentage of the carbonate dimer in the electrolyte is 0.001% to 5%.

10. An electronic device, characterized in that: An electrochemical device comprising any one of claims 1 to 9.

Images