Battery

Abstract

The invention provides a battery. The battery comprises a negative electrode and an electrolyte, the electrolyte comprises a cyclic nitrile compound, the mass content of the cyclic nitrile compound is x wt% on the basis of the total mass of the electrolyte, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer on the surface of any side of the negative electrode current collector, the negative electrode active material layer comprises a concave part, and the concave part is arranged between the negative electrode current collector and the negative electrode active material layer. The width of the concave part is d [mu] m, the depth of the concave part is h [mu] m, and the battery meets the condition that (x / d) + (x / h) is greater than or equal to 0.0024 and less than or equal to 2.83. By simultaneously regulating and controlling the composition of the electrolyte and the structure of the negative electrode active material layer, the wettability and the electrolyte retention capacity of the electrolyte and the cycle performance of the battery can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a battery. Background Art

[0002] Currently, to achieve higher energy density in lithium-ion batteries, commercial graphite anodes are continuously developing towards higher areal density and higher compaction density. However, high-component density graphite anodes often have poor electrolyte wettability and relatively low electrolyte retention, which can lead to lithium deposition at the anode interface. This can cause a sudden and significant drop in the reversible capacity of lithium-ion batteries during subsequent cycles, resulting in a charge drop and affecting the battery's cycling performance. Summary of the Invention

[0003] The present invention provides a battery comprising a negative electrode and an electrolyte. The battery of the present invention has good cycle performance.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] The present invention provides a battery comprising a negative electrode and an electrolyte.

[0006] Wherein, the electrolyte comprises a cyclic nitrile compound, and the mass content of the cyclic nitrile compound is x wt% based on the total mass of the electrolyte;

[0007] The negative electrode comprises a negative electrode current collector and a negative electrode active material layer on either side of the negative electrode current collector, wherein the negative electrode active material layer comprises a concave portion, wherein the width of the concave portion is d μm and the depth is h μm;

[0008] The battery satisfies: 0.0024≤(x / d)+(x / h)≤2.83.

[0009] Through the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0010] The present invention regulates the content of cyclic nitrile compounds in the electrolyte and the concave arrangement of the negative electrode active material layer, and controls the relationship between the width and depth of the concave portion contained in the negative electrode active material layer and the content of the cyclic nitrile compound (x / d) + (x / h) within the above-mentioned specific range. This can not only provide the negative electrode with a higher surface density and compaction density, thereby ensuring high energy density and high capacity of the battery, but also effectively improve the wettability of the electrolyte with the negative electrode surface during the charge and discharge process, increase the battery's liquid retention capacity, and thus improve the battery's cycle performance.

[0011] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a SEM schematic diagram of the concave portion of the negative electrode sheet provided in a possible embodiment of the present invention. DETAILED DESCRIPTION

[0013] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0014] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0015] In the present invention, unless otherwise specified, the term "heterocyclic group" refers to a cyclic group containing at least one heteroatom, wherein the heteroatom includes at least one of boron, nitrogen, oxygen, silicon, phosphorus or sulfur. In some embodiments, the heterocyclic group includes at least one of an aliphatic heterocyclic group and an aromatic heterocyclic group.

[0016] In the present invention, unless otherwise specified, the term "alicyclic hydrocarbon group" refers to a cyclic hydrocarbon group with aliphatic properties, which contains a carbon ring in the molecule, for example, cyclopropyl and cyclopentyl.

[0017] In the present invention, an alkylene group is a divalent group formed by an alkyl group losing a hydrogen atom, an alkenylene group is a divalent group formed by an alkenyl group losing a hydrogen atom, an alkynylene group is a divalent group formed by an alkynyl group losing a hydrogen atom, and an arylene group is a divalent group formed by an aryl group losing a hydrogen atom. In the present invention, any subunit structure not explicitly described shall be interpreted in accordance with the description in this paragraph.

[0018] The present invention provides a battery comprising a negative electrode and an electrolyte.

[0019] Wherein, the electrolyte comprises a cyclic nitrile compound, and the mass content of the cyclic nitrile compound is x wt% based on the total mass of the electrolyte;

[0020] The negative electrode comprises a negative electrode current collector and a negative electrode active material layer on either side of the negative electrode current collector, wherein the negative electrode active material layer comprises a concave portion, wherein the width of the concave portion is d μm and the depth is h μm;

[0021] The battery satisfies: 0.0024≤(x / d)+(x / h)≤2.83.

[0022] In the present invention, the substituents of the cyclic nitrile compounds in the electrolyte include cyano groups, which are carbon-nitrogen triple bonds with very high bond energy. They are not easily oxidized in the electrolyte and are relatively stable at the positive electrode. Their antioxidant stability can reach 7V, and they are difficult to decompose in conventional high-voltage lithium-ion batteries, thereby enabling the battery to have a higher operating voltage (up to 4.53V).

[0023] Furthermore, the present invention regulates the content of cyclic nitrile compounds in the electrolyte and the recess setting of the negative electrode active material layer, and controls the relationship between the width and depth of the recess contained in the negative electrode and the content of the cyclic nitrile compound (x / d) + (x / h) within the above-mentioned specific range, which can not only provide the negative electrode with a higher surface density and compaction density to ensure the high energy density and high capacity of the battery, but also increase the reaction sites for lithium ion intercalation and deintercalation, effectively improving the wettability and liquid retention of the electrolyte. Moreover, the cyclic nitrile compound can undergo ring-opening polymerization on the surface of the negative electrode or form a polymer film through π-π interaction. The polymer film can effectively improve the problem of co-intercalation of the electrolyte solvent and the lithium salt in the recess due to the setting of the negative electrode recess, thereby avoiding capacity loss. In addition, the cyclic nitrile compound can assist the electrolyte in forming an SEI film with lower impedance while assisting the desolvation of the electrolyte, thereby avoiding capacity loss of the battery and improving the cycle performance of the battery.

[0024] In one embodiment, (x / d) + (x / h) is 0.0024, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.83, or a range consisting of any two of these values.

[0025] In the present invention, the cyclic nitrile compound includes the compound represented by formula (I),

[0026]

[0027] Wherein, CY is selected from benzene ring or cyclohexane,

[0028] wherein R1 is selected from substituted or unsubstituted C1-C 10 Alkyl, substituted or unsubstituted C2-C 10 alkenyl, substituted or unsubstituted C2-C 10 Alkynyl, substituted or unsubstituted C6-C 10 aryl, substituted or unsubstituted C3-C 10 alicyclic hydrocarbon group, substituted or unsubstituted C1-C 10 wherein, when substituted, the substituents are each independently selected from halogen.

[0029] In one embodiment, m is an integer selected from 0 to 6, and when m is 2 or greater, two or more R1 are the same as or different from each other, and n is an integer selected from 0 to 6; preferably, m+n=6.

[0030] In the present invention, the battery further comprises a positive electrode, wherein the positive electrode active material layer of the positive electrode comprises lithium cobalt oxide. The cyano group of the cyclic nitrile compound in the electrolyte also has a strong coordination ability and can coordinate with the active site Co of lithium cobalt oxide on the surface of the positive electrode. 3+ 、Co 4+ ) combined with the positive electrode can not only maintain the charge balance of the positive electrode, but also reduce the dissolution of cobalt ions, further improving the cycle performance of the battery.

[0031] In one specific embodiment, 0.004≤(x / d)+(x / h)≤0.75. It is understandable that when (x / d)+(x / h) is too high, the content of the cyclic nitrile compound is too high, the width of the negative electrode recess is too short, or the depth of the negative electrode recess is too shallow, which will cause the viscosity of the electrolyte to increase and the conductivity to decrease, thereby increasing the impedance of the battery cycle, and the wettability and liquid retention of the negative electrode are low, affecting its cycle performance. When (x / d)+(x / h) is too low, the content of the cyclic nitrile compound is too low, the width of the negative electrode recess is too long, or the depth of the negative electrode recess is too deep, which will lead to a reduction in the reaction sites for lithium ion intercalation and deintercalation, affecting its cycle performance. Moreover, if the recess is too deep and too long, it will cause excessive loss of negative electrode active material, thereby reducing the capacity of the battery and affecting its energy density. Moreover, the recesses included in the negative electrode of the present invention can usually be formed using a laser, but this will cause the surface of the recess or the surface of the negative electrode material in the area around the recess to be coked, resulting in the surface of some negative electrode materials not having the ability to deintercalate lithium. By controlling the relationship between the content of the cyclic nitrile compound of formula (I) and the width and depth of the negative electrode recess (x / d) + (x / h) within a specific range, the content of the cyclic nitrile compound and the degree of loss of the negative electrode material can be ensured to be appropriate, and the cyclic nitrile compound can form a stable polymer film on the surface of the negative electrode material, thereby avoiding the electrolyte solvent and lithium salt from being co-intercalated on the surface of the coked negative electrode and causing battery capacity loss, thereby enabling the battery to maintain a higher energy density, and the formation of the surface polymer film reduces the increase in membrane impedance during the cycle, thereby improving the first cycle efficiency of the battery, thereby improving the cycle performance of the battery. In a specific embodiment, 0.22≤(x / d)+(x / h)≤0.55.

[0032] In one embodiment, 0.1 wt%≤x wt%≤5 wt%. In one embodiment, x is 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%. t%, 2.6wt%, 2.7wt%, 2.8wt%, 2.9wt%, 3wt%, 3.1wt%, 3.2wt%, 3.3wt%, 3.4wt%, 3.5wt%, 3.6wt%, 3.7wt%, 3.8wt%, 3.9wt%, 4.1wt%, 4.2wt%, 4.3wt%, 4.4wt%, 4.5wt%, 4.6wt%, 4.7wt%, 4.8wt%, 4.9wt%, 5wt% or a range consisting of any two of these values. Cyclic nitrile compounds can form a stable polymer film on the surface of the negative electrode, avoiding the co-intercalation of the electrolyte solvent and the lithium salt on the surface of the coked negative electrode, maintaining a high capacity and energy density, and improving the cycle to a certain extent, but too high a content will increase the impedance, increase the polarization inside the battery, and affect the cycle performance. In a specific embodiment, 0.1wt%≤x wt%≤3wt%.

[0033] In one embodiment, 15 μm ≤ d μm ≤ 240 μm. In one embodiment, d μm is 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, or a range consisting of any two of these values. If the width of the negative electrode recess is too large, it will cause excessive loss of negative electrode active material, resulting in a decrease in battery capacity and affecting its energy density. If the width of the negative electrode recess is too small, it will lead to low wettability and liquid retention of the negative electrode, affecting its cycling performance. In one specific embodiment, 20μm≤dμm≤150μm.

[0034] In one embodiment, 2 μm ≤ h μm ≤ 50 μm. In one embodiment, h μm is 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm, 59 μm, 60 μm, 61 μm, 62 μm, 63 μm, 64 μm, 65 μm, 66 μm, 67 μm, 68 μm, 69 μm, 70 μm, 71 μm, 72 μm, 73 μm, 74 μm, 75 μm, 76 μm, 77 μm, 78 μm, 79 μm, 80 μm, 81 μm, 82 μm, 83 μ 7μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, 35μm, 36μm, 37μm, 38μm, 39μm, 40μm, 41μm, 42μm, 43μm, 44μm, 45μm, 46μm, 47μm, 48μm, 49μm, 50μm, or a range consisting of any two of these values. If the depth of the negative electrode recess is too deep, it will cause excessive loss of negative electrode active material, resulting in a decrease in battery capacity and affecting its energy density. If the depth of the negative electrode recess is too shallow, it will result in low wettability and liquid retention of the high compaction density negative electrode, affecting its cycling performance. In one specific embodiment, 5μm ≤ hμm ≤ 40μm.

[0035] It should be noted that, in the present invention, the recess can be formed by means of a laser. Specifically, a high-energy laser beam is generated by using electric energy to excite a pump source. The laser beam is transmitted through an optical element and irradiated onto the surface of the material. The material absorbs the photons in the laser beam and converts the light energy into heat energy, causing the material in the irradiated area to instantly melt or even vaporize to form the above-mentioned recess. In the present invention, the recess includes a hole and / or a groove. When the recess is a hole, its shape can be a circular hole, an elliptical hole or any irregular pattern. When the recess is a groove, its projected shape can be a linear structure, a tic-tac-toe structure or any irregular pattern structure. When the recess is a hole and a groove, its recess can be composed of the above-mentioned hole-shaped recess structure and the groove-shaped recess structure. No further details will be given here. In addition, for the width of the recess, when the recess is a hole, its width is the length of the diameter of the circular hole (i.e., the aperture), or the length of the major axis of the elliptical hole or the distance between the two farthest points on any irregular figure; when the recess is a groove, its width is the distance between the two parallel groove edges of the groove; for the depth of the recess, when the recess is a hole, its depth is the distance between the plane where the bottom of the hole is located and the surface of the negative electrode; when the recess is a groove, its depth is the distance between the plane where the bottom of the groove is located and the surface of the negative electrode.

[0036] In one embodiment, the cyclic nitrile compound includes a compound represented by formula (I),

[0037]

[0038] Wherein, CY is selected from benzene ring or cyclohexane,

[0039] wherein R1 is selected from substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C2-C6 alkenyl, substituted or unsubstituted C2-C6 alkynyl, wherein, when substituted, the substituents are each independently selected from halogen, wherein m is an integer selected from 0 to 6, and when m is 2 or greater, two or more R1 are the same as or different from each other, and n is an integer selected from 0 to 6;

[0040] Preferably, m+n=6.

[0041] In the present invention, the C1-C6 alkyl group is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl or n-hexyl.

[0042] In the present invention, the C2-C6 alkenyl group is selected from vinyl, allyl, 1-propenyl, isopropenyl, 2-butenyl, 1,3-butadienyl, 3-butenyl, 4-pentenyl, 3-pentenyl, 2-hexenyl or 3-hexenyl.

[0043] In the present invention, the C2-C6 alkynyl group is selected from ethynyl, 1-propynyl, 2-propynyl, 1,1-dimethyl-2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 4-pentynyl, 3-pentynyl, 2-hexynyl or 3-hexynyl.

[0044] In the present invention, halogen is selected from fluorine, chlorine, bromine or iodine.

[0045] In one embodiment, the compound of formula (I) includes at least one of the following compounds of formula (I-1) to formula (I-10):

[0046]

[0047]

[0048] Wherein, R2, R3, and R4 are independently selected from a covalent single bond, a substituted or unsubstituted C1-C 10 Alkylene, substituted or unsubstituted C2-C 10 Alkenylene, substituted or unsubstituted C2-C 10 Alkynylidene, substituted or unsubstituted C6-C 10 arylene, substituted or unsubstituted C3-C 10 Alicyclic hydrocarbon group, substituted or unsubstituted C1-C 10 wherein, when substituted, the substituents are each independently selected from halogen;

[0049] wherein R5, R6, R7, R8, and R9 are each independently selected from hydrogen, halogen, cyano, substituted or unsubstituted C1-C 10 Alkyl, substituted or unsubstituted C1-C 10 Alkoxy, substituted or unsubstituted C2-C 10 of alkenyl.

[0050] It should be noted that the covalent single bond means that R2, R3, and R4 are directly replaced by the σ bond in the covalent bond, and the substituent cyano group on one side is directly connected to the benzene ring or cyclopentane through the covalent single bond.

[0051] In the present invention, the C1-C6 alkylene group is selected from methylene, ethylene, n-propylene, isopropylene, n-butylene, isobutylene, tert-butylene, n-pentylene, isopentylene or n-hexylene.

[0052] In the present invention, the C2-C6 alkenylene group is selected from vinylene, allylene, 1-propenylene, isopropenylene, 2-butenylene, 1,3-butadienylene, 3-butenylene, 4-pentenylene, 3-pentenylene, 2-hexenylene or 3-hexenylene.

[0053] In the present invention, the C2-C6 alkynylene group is selected from ethynylene, 1-propynylene, 2-propynylene, 1,1-dimethyl-2-propynylene, 1-butynylene, 2-butynylene, 3-butynylene, 4-pentynylene, 3-pentynylene, 2-hexynylene or 3-hexynylene.

[0054] In a specific embodiment, the compound of formula (I) includes at least one of the compounds of formula (I-1) to formula (I-5). It is understandable that the cyclic nitrile compound containing a benzene ring is easier to form a polymer film on the surface of the negative electrode due to its own alternating structure of single and double bonds and delocalized π bond, and the benzene ring is better than cyclopentane in chemical stability, because the benzene ring itself is a large conjugated system, and the lone pair of electrons on the carbon forms a delocalized large π bond, which can enhance the stability of the cyclic nitrile compound containing a benzene ring, and can further improve the problem of co-embedding of the electrolyte and the lithium salt in the recess caused by the provision of the recess, avoid battery capacity loss, and thus further improve the cycle performance of the battery.

[0055] In order to further increase the opportunity for complexation and enhance the stability of the polymer film, in one embodiment, the compound of formula (I) comprises at least one of the compounds of formula (I-1) to formula (I-4). The content of cyano groups, which are long substituents of carbon atoms on the benzene ring, should not be too high or too low. This is because the molecular weight of the benzene ring is larger than that of ordinary straight-chain hydrocarbons. If the content of cyano groups, which are long substituents of carbon atoms on the benzene ring, is excessive, it will have a certain impact on the solubility of the additive in the electrolyte. In addition, nitriles with symmetrical structures can reduce the steric hindrance of cyclic nitrile compounds, increase the opportunity for nitrile compounds to complex with positive electrode metal ions in the electrolyte, and enhance the stability of the polymer film.

[0056] In one embodiment, the cyclic nitrile compound includes at least one of the following compounds:

[0057]

[0058]

[0059] In one embodiment, the electrolyte includes ethylene carbonate (EC), and the mass content of the ethylene carbonate is w1 based on the total mass of the electrolyte. In one embodiment, 5wt%≤w1≤30wt%. EC, with its high dielectric constant, first solvates and combines with LiPF6 in the electrolyte. After the LiPF6 is desolvated on the negative electrode surface, a uniform and dense SEI film is formed during the first charge and discharge cycle, thereby maintaining the cycling stability of the electrode. In one embodiment, w1 is 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, or a range consisting of any two of these values. In one embodiment, 10 wt% ≤ w1 ≤ 20 wt%. Furthermore, the cyclic nitrile compound can undergo ring-opening polymerization or form a polymer film through π-π interaction on the surface of the negative electrode. The polymer film helps EC form an SEI film and improves the stability of the SEI film. Therefore, by using a certain amount of EC and the cyclic nitrile compound together, the cycle performance of the battery can be further improved.

[0060] In a specific embodiment, the electrolyte includes propylene carbonate (PC), and the mass content of the propylene carbonate is w2 based on the total mass of the electrolyte. In a specific embodiment, 8wt%≤w2≤30wt%. In a specific embodiment, w2 is 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 20wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt% or a range consisting of any two of these values. In a specific embodiment, 10wt%≤w2≤20wt%.

[0061] PC as a component of the basic electrolyte can enhance the conductivity of the electrolyte, reduce the impedance of the battery cycle, and is beneficial to the improvement of high-rate discharge and cycle performance. However, PC and lithium salts will also undergo solvation, and because the binding strength of PC is too strong, there will be slow desolvation of the negative electrode surface and PC and the electrolyte solvent will be co-embedded on the negative electrode surface, which can easily cause battery capacity loss. The polymer film formed by the cyclic nitrile compound does not participate in the formation of the solvation shell of lithium ions in the electrolyte, and plays a dipole-dipole interaction with the polar solvent PC, weakening the Coulomb attraction between lithium ions and the electrolyte solvent, thereby avoiding the battery capacity loss caused by slow desolvation of PC on the negative electrode surface or co-embedded with the electrolyte solvent. Therefore, by using a certain amount of PC and cyclic nitrile compounds in combination, the battery's requirements for cycle performance and high capacity and high energy density can be met at the same time.

[0062] In one embodiment, the electrolyte includes propyl propionate (PP), and the mass content of propyl propionate is 30-70wt% based on the total mass of the electrolyte. In another embodiment, the mass content of propyl propionate is 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, or a range consisting of any two of these values. PP is an excellent solvent that can dissolve lithium salts and various additives at room temperature. In addition, PP has a low contact angle with materials such as graphite in the negative electrode material, which can further increase the wettability of the electrolyte on the negative electrode surface. In one embodiment, the mass content of propyl propionate is 40-60wt%.

[0063] In a specific embodiment, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes a carbon material and a silicon-based material;

[0064] In a specific embodiment, the carbon material includes one or more of artificial graphite, natural graphite, hard carbon and soft carbon.

[0065] In a specific embodiment, the silicon-based material includes one or more of silicon, silicon alloys, silicon oxides, and silicon carbon compounds.

[0066] In one embodiment, the median particle size Dv50 of the negative electrode active material is 1 to 30 μm. The median particle size Dv50 of the negative electrode active material can be obtained by laser particle size analysis. In one embodiment, the median particle size of the negative electrode active material is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, or a range consisting of any two of these values. By regulating the median particle size of the negative electrode active material, it is beneficial to form a stable interface structure on the negative electrode surface, further improving the cycle performance of the battery. In one embodiment, the median particle size of the negative electrode active material is 6 to 20 μm.

[0067] In one embodiment, the mass content of the carbon material is 65-98 wt % based on the total mass of the negative electrode active material layer. In one embodiment, the mass content of the carbon material is 60 wt %, 65 wt %, 70 wt %, 75 wt %, 80 wt %, 85 wt %, 90 wt %, 95 wt %, 95.5 wt %, 96 wt %, 96.5 wt %, 97 wt %, 97.5 wt %, 98 wt %, or a range consisting of any two of these values. In one embodiment, the mass content of the carbon material is 92-97.5 wt %.

[0068] In one embodiment, the silicon-based material comprises 0.5-30 wt% of the total mass of the negative electrode active material layer. Adding the silicon-based material to the negative electrode active material layer improves the battery's energy density and, by cooperating with the recessed portion of the negative electrode active material layer, further enhances electrolyte wettability on the negative electrode surface, reduces negative electrode expansion, and improves battery cycle performance. In a specific embodiment, the mass content of the silicon-based material is 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, 21wt%, 22wt%, 23wt%, 24wt%, 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt% or a range consisting of any two of these values. In a specific embodiment, the mass content of the silicon-based material is 3-10wt%.

[0069] In one embodiment, the surface density of the negative electrode active material layer is 8-15 mg / cm 2 In one embodiment, the surface density of the negative electrode active material layer is 8 mg / cm 2 、8.1mg / cm 2 , 8.2mg / cm 2 、8.3mg / cm 2 、8.4mg / cm 2 、8.5mg / cm 2 、8.6mg / cm 2 , 8.7mg / cm 2 , 8.8mg / cm 2 、8.9mg / cm 2 , 9mg / cm 2 、10mg / cm 2 , 11mg / cm 2 , 12mg / cm 2 、13mg / cm 2 , 14mg / cm 2 、15mg / cm 2 Or a range consisting of any two of these values. In one embodiment, the surface density of the negative electrode active material layer is 8-12 mg / cm 2 .

[0070] In one embodiment, the compaction density of the negative electrode active material layer is 1.5-2 g / cm 3 In one embodiment, the compaction density of the negative electrode active material layer is 1.5 g / cm 3 , 1.55g / cm 3 , 1.6g / cm 3 , 1.65g / cm 3 , 1.7g / cm 3 , 1.75g / cm 3 , 1.8g / cm 3 , 1.85g / cm 3 , 1.9g / cm 3 , 1.95g / cm 3 , 2g / cm 3 Or a range consisting of any two of these values. In one embodiment, the compaction density of the negative electrode active material layer is 1.7-1.85 g / cm 3 .

[0071] The present invention regulates the content of cyclic nitrile compounds in the electrolyte and the concave setting of the negative electrode active material layer, and controls the relationship between the width and depth of the concave portion contained in the negative electrode and the content of the cyclic nitrile compound (x / d) + (x / h) within the above-mentioned specific range, so that the negative electrode can provide a higher surface density and compaction density. On this basis, the surface density and compaction density range of the negative electrode active material layer are further limited, which can further ensure the high energy density and high capacity of the battery, increase the reaction sites for lithium ion intercalation and deintercalation, further improve the wettability and liquid retention of the electrolyte, and enhance the cycle performance of the battery.

[0072] In a specific embodiment, the thickness of the negative electrode plate is 80-200 μm. In a specific embodiment, the thickness of the negative electrode plate is 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, 150 μm, 155 μm, 160 μm, 165 μm, 170 μm, 175 μm, 180 μm, 185 μm, 190 μm, 195 μm, 200 μm, or a range consisting of any two of these values. In a specific embodiment, the thickness of the negative electrode plate is 85-130 μm. It should be noted that the thickness of the negative electrode plate is the thickness of the plate when a double-sided negative electrode active material layer is provided.

[0073] In some embodiments, the batteries of the present invention comprise lithium-ion batteries.

[0074] The electronic devices or devices of the present invention are not particularly limited. In some embodiments, the electronic devices of the present application include, but are not limited to, laptop computers, pen-type computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, LCD televisions, portable cleaners, portable CD players, mini-discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, power-assisted bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors.

[0075] The battery of the present invention includes, in addition to the negative electrode and the electrolyte, a separator and a positive electrode. The composition of the positive electrode can refer to conventional positive electrodes in the art, and the separator can also be a separator commonly used in the art, such as PP film, PE film, etc.

[0076] The battery of the present invention can be prepared by conventional methods in the art. Specifically, the positive electrode, separator and negative electrode can be stacked in sequence, and then a battery cell can be obtained through a lamination or winding process, and then the battery can be obtained through baking, liquid injection, formation, packaging and other processes.

[0077] Hereinafter, the positive electrode sheet and the lithium-ion battery provided by the present invention will be described in detail through specific embodiments.

[0078] Example 1

[0079] The battery of the present invention is obtained by the following method:

[0080] Cathode sheet preparation

[0081] The commercially purchased positive electrode active material, conductive agent Super P, and binder polyvinylidene fluoride (PVDF) were weighed and dispersed in an appropriate amount of N-methylpyrrolidone (NMP) at a weight ratio of 97.6:1.4:1. The mixture was fully stirred to form a uniform positive electrode slurry. The positive electrode slurry was coated on the positive electrode current collector aluminum foil, and then dried, roll-pressed, and cut to obtain the positive electrode sheet.

[0082] Negative electrode preparation

[0083] Weigh the commercially available negative electrode active material (wherein the mass content ratio of each component in the negative electrode active material is artificial graphite: silicon powder = 95:5, Dv50 = 15 μm), binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) at a weight ratio of 97:2:1, disperse them in an appropriate amount of deionized water, stir them thoroughly to form a uniform negative electrode slurry, and coat the negative electrode slurry on both sides of the negative electrode current collector copper foil, then dry and roll-press to form a negative electrode active material layer (the measured surface density of the negative electrode active material layer is 11 mg / cm2 , compacted density is 1.75g / cm 3 );

[0084] Then, laser drilling was performed (controlling the power of the laser drilling instrument, fixing the hole depth h to 5 μm, the pore diameter d (i.e., the width of the concave portion) to 30 μm, and the number of holes, and the local SEM image of the formed concave portion, as shown in FIG. Figure 1 As shown), cut to obtain a negative electrode sheet with a thickness of 110 μm.

[0085] The laser drilling of the present invention specifically adopts the following method:

[0086] The aperture size can be controlled by adjusting the power of the laser puncher. For example, a 5% power aperture is approximately 30 μm. The number of dots in a single matrix can be determined by setting the dot density. For example, a dot density of 100 μm yields approximately 75,000 dots.

[0087] Preparation of electrolyte

[0088] The electrolyte material of the present invention is obtained in the following manner:

[0089] In a glove box (H2O < 0.01ppm, O2 < 0.01ppm, Ar atmosphere), EC based on the total mass of the electrolyte w1 (wt%), PC w2 (wt%) and PP w3 (wt%) were added and mixed evenly, and then fully dried lithium hexafluorophosphate (LiPF6) was added thereto. After dissolution, an additive of cyclic nitrile compound (I-1-1) with a total mass content of x (wt%) of the electrolyte was added and stirred evenly. After passing the moisture and free acid tests, the required electrolyte was obtained.

[0090] Finally, the positive electrode sheet, negative electrode sheet and separator are wound into a core according to a predetermined process, and then the tabs are welded, the electrolyte is injected, and vacuum sealing, standing, and formation processes are carried out to prepare a lithium-ion battery.

[0091] Example 2 group

[0092] The lithium-ion batteries of the second embodiment were all manufactured using the method of the first embodiment, except that the additive content x was changed.

[0093] Example 3 group

[0094] The lithium-ion batteries of the third group of embodiments were all manufactured using the method of the first embodiment, except that the aperture d of the negative electrode recess was changed.

[0095] Example 4 Group

[0096] The lithium-ion batteries of the fourth embodiment were all manufactured using the method of the first embodiment, except that the hole depth h of the negative electrode recess was changed.

[0097] Example 5 group

[0098] The lithium-ion batteries of the fifth group of embodiments were all manufactured using the method of the first embodiment, except that the mass content percentages of EC, PC, and PP were changed.

[0099] Example 6

[0100] The lithium-ion batteries of the Example 6 group were all manufactured using the method of the Example 1, except that the type of the cyclic nitrile compound was changed.

[0101] Example 7 Group

[0102] The lithium-ion batteries of Example 7 were all manufactured using the method of Example 1, except that the surface density and compaction density of the negative electrode active material layer and the thickness of the negative electrode sheet were changed. Specifically:

[0103] In Example 7-1, the surface density of the negative electrode active material layer is 14 mg / cm 2 The compaction density of the negative electrode active material layer is 1.9 g / cm 3 , at this time the thickness of the negative electrode sheet is 84μm;

[0104] In Example 7-2, the surface density of the negative electrode active material layer is 17 mg / cm 2 The compaction density of the negative electrode active material layer is 2g / cm 3 , at this time the thickness of the negative electrode sheet is 72μm;

[0105] In Example 7-3, the surface density of the negative electrode active material layer is 6 mg / cm 2 The compaction density of the negative electrode active material layer is 1.5 g / cm 3 , at this time the thickness of the negative electrode sheet is 200μm.

[0106] Example 8

[0107] The lithium-ion batteries of Example 8 were all manufactured using the method of Example 1, except that the negative electrode active material did not contain silicon-based materials. In this case, the median particle size Dv50 of the negative electrode active material was 40 μm.

[0108] Comparative Example 1

[0109] The lithium-ion battery of Comparative Example 1 was manufactured using the method of Example 1, except that the electrolyte did not include the cyclic nitrile compound additive, and the negative electrode sheet was not laser-drilled.

[0110] Comparative Example 2

[0111] The lithium-ion battery of Comparative Example 2 was manufactured using the method of Example 1, except that the electrolyte did not include the cyclic nitrile compound additive.

[0112] Comparative Example 3

[0113] The lithium-ion battery of Comparative Example 3 was manufactured using the method of Example 1, except that the negative electrode sheet was not laser-drilled.

[0114] Comparative Example 4

[0115] The lithium-ion battery of Comparative Example 4 was manufactured using the method of Example 1, with the differences being the additive content x, the pore diameter d, and the pore depth h of the concave portion, as shown in Table 1 for details.

[0116] Comparative Example 5

[0117] The lithium-ion battery of Comparative Example 5 was manufactured using the method of Example 1, with the differences being the additive content x, the pore diameter d, and the pore depth h of the concave portion, as shown in Table 1 for details.

[0118] Lithium-ion battery test example

[0119] The lithium-ion batteries obtained in the above examples and comparative examples were tested using the following methods. The test results are recorded in Table 1:

[0120] (1) First lap efficiency test

[0121] The lithium-ion batteries obtained in the above examples and comparative examples were placed at formation temperature and charged at a constant current of 0.02C to the upper voltage limit (4.53V). They were then charged at a constant voltage of 4.53V to 0.05C and allowed to rest for 5 minutes. This cycle was then considered one charge-discharge cycle. The initial charge capacity, Q1, and the discharge capacity, Q2, were recorded. The first-cycle efficiency (%) of the lithium-ion batteries obtained in each set of examples and comparative examples was calculated using the following formula: First-cycle efficiency (%) = Q1 / Q2 × 100%.

[0122] (2) Battery capacity test

[0123] Place the lithium-ion battery at 25°C and charge it at a constant current of 0.2C to the upper limit voltage (4.53V). Then charge it at a constant voltage of 4.53V to 0.05C and let it rest for 5 minutes. Then discharge it at a constant current of 0.5C to 3V and let it rest for 5 minutes. This is one charge and discharge cycle. Charge and discharge in this way, measure the current and time of the battery during the charge and discharge process, and calculate the battery capacity (mAh g) based on the charge and discharge time and current. -1 ).

[0124] (3) Battery cycle performance test

[0125] The lithium-ion batteries obtained in the above examples and comparative examples were placed at 25°C and charged at a constant current of 0.2C to the upper limit voltage (4.53V). They were then charged at a constant voltage of 4.53V to 0.05C and allowed to stand for 5 minutes. The batteries were then discharged at a constant current of 0.5C to 3V and allowed to stand for 5 minutes. This constituted one charge-discharge cycle. The highest discharge capacity of the first three cycles was recorded as the initial capacity Q3. When the cycle reached the required 1000 times, the discharge capacity Q4 of the battery was recorded. The capacity retention rate (%) of the lithium-ion batteries obtained in each group of examples and comparative examples after 1000 cycles was calculated using the cycle capacity retention rate calculation formula: Capacity retention rate (%) = Q4 / Q3 × 100%.

[0126] (4) Battery wettability test

[0127] The residual liquid coefficient is calculated as: residual liquid coefficient = electrolyte retention amount / battery capacity (initial charge capacity Q1). According to the production process, a certain amount of electrolyte is injected. Then, during the battery formation process, some electrolyte is consumed. During the secondary sealing process, the excess electrolyte is extracted and packaged. Specifically, the formula for calculating the residual liquid amount = electrolyte injection amount - electrolyte amount extracted after secondary sealing.

[0128] Table 1

[0129]

[0130]

[0131] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A battery comprising a negative electrode and an electrolyte, characterized in that: The electrolyte comprises a cyclic nitrile compound, and the mass content of the cyclic nitrile compound is x wt% based on the total mass of the electrolyte; The negative electrode comprises a negative electrode current collector and a negative electrode active material layer on either side of the negative electrode current collector, wherein the negative electrode active material layer comprises a concave portion, wherein the width of the concave portion is d μm and the depth is h μm; The battery satisfies: 0.0024≤(x / d)+(x / h)≤2.

83.

2. The battery according to claim 1, characterized in that The cyclic nitrile compounds include compounds represented by formula (I), Wherein, CY is selected from benzene ring or cyclohexane, wherein R1 is selected from substituted or unsubstituted C1-C 10 Alkyl, substituted or unsubstituted C2-C 10 alkenyl, substituted or unsubstituted C2-C 10 Alkynyl, substituted or unsubstituted C6-C 10 aryl, substituted or unsubstituted C3-C 10 alicyclic hydrocarbon group, substituted or unsubstituted C1-C 10 wherein, when substituted, the substituents are each independently selected from halogen, Preferably, m is an integer selected from 0 to 6, and when m is 2 or greater, two or more R1s are the same as or different from each other, and n is an integer selected from 0 to 6.

3. The battery according to claim 1, characterized in that The battery satisfies at least one of conditions (i) to (iv): (i) 0.004≤(x / d)+(x / h)≤0.75, preferably, 0.22≤(x / d)+(x / h)≤0.55; (ii) 0.1 wt%≤x wt%≤5 wt%, preferably, 0.1 wt%≤x≤3 wt%; (iii) 15 μm ≤ d μm ≤ 240 μm, preferably, 20 μm ≤ d μm ≤ 150 μm; (iv) 2 μm ≤ h μm ≤ 50 μm, preferably, 5 μm ≤ h μm ≤ 40 μm.

4. The battery according to claim 1, characterized in that The electrolyte satisfies at least one of conditions (a) to (c): (a) the electrolyte comprises ethylene carbonate, and the mass content of the ethylene carbonate is w1 based on the total mass of the electrolyte, preferably, 5wt%≤w1≤30wt%; (b) the electrolyte comprises propylene carbonate, and the mass content of the propylene carbonate is w2 based on the total mass of the electrolyte, preferably, 8wt%≤w2≤30wt%; (c) The electrolyte includes propyl propionate. Based on the total mass of the electrolyte, the mass content of the propyl propionate is w3. Preferably, 30wt%≤w3≤70wt%.

5. The battery 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 a carbon material and a silicon-based material; Preferably, the carbon material comprises one or more of artificial graphite, natural graphite, hard carbon and soft carbon; Preferably, the silicon-based material includes one or more of silicon, silicon alloys, silicon oxides, and silicon carbon compounds; Preferably, the median particle size Dv50 of the negative electrode active material is 1 to 30 μm.

6. The battery according to claim 5, characterized in that Based on the total mass of the negative electrode active material layer, the mass content of the carbon material is 65-98wt%; And / or, based on the total mass of the negative electrode active material layer, the mass content of the silicon-based material is 0.5-30wt%.

7. The battery according to claim 5, characterized in that The surface density of the negative electrode active material layer is 8-15 mg / cm 2 ; And / or, the compaction density of the negative electrode active material layer is 1.5-2 g / cm 3 ; And / or, the thickness of the negative electrode plate is 80-200 μm.

8. The battery according to claim 1, characterized in that The cyclic nitrile compound includes at least one of the following compounds of formula (I-1) to formula (I-10): wherein R2, R3, and R4 are each independently selected from a covalent single bond, a substituted or unsubstituted C1-C 10 Alkylene, substituted or unsubstituted C2-C 10 Alkenylene, substituted or unsubstituted C2-C 10 Alkynylidene, substituted or unsubstituted C6-C 10 arylene, substituted or unsubstituted C3-C 10 Alicyclic hydrocarbon group, substituted or unsubstituted C1-C 10 wherein, when substituted, the substituents are each independently selected from halogen, wherein R5, R6, R7, R8, and R9 are each independently selected from hydrogen, halogen, cyano, substituted or unsubstituted C1-C 10 Alkyl, substituted or unsubstituted C1-C 10 Alkoxy, substituted or unsubstituted C2-C 10 of alkenyl.

9. The battery according to claim 1, characterized in that The cyclic nitrile compound includes at least one of the following compounds:

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