Lithium-ion battery that takes into account both low-temperature discharge and high-temperature cycling

Abstract

The present invention belongs to the technical field of lithium-ion batteries, and specifically relates to a lithium-ion battery that takes into account both low-temperature discharge and high-temperature cycling, comprising: a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte; the mass percentage of ash in the negative electrode active material of the negative electrode sheet is H, O I The value is D; the electrolyte includes a compound, and the mass percentage of the compound in the electrolyte is C1; the compound forms an SEI film on the surface of the negative electrode active material after the first charging cycle of the lithium ion battery; the ratio of the total mass of the electrolyte to the discharge capacity of the lithium ion battery is N g / Ah; wherein the lithium ion battery satisfies the following relationship: #imgabs0#; wherein R0 is a single bond or a methylene group, and R1 is any one of hydrogen, halogen, a hydrocarbon group with 1 to 5 carbon atoms, or a halogenated hydrocarbon group with 1 to 5 carbon atoms.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a lithium ion battery capable of both low-temperature discharge and high-temperature circulation. Background Art

[0002] Lithium-ion batteries, with their advantages of high specific energy, low self-discharge, no memory effect, and high operating voltage, have been widely used in mobile phones, laptops, smart homes, automotive power batteries, large-scale industrialization, and home energy storage. With the growing demand for electronic products in terms of battery life, power characteristics, and service life, lithium-ion batteries have been developing towards high energy, high safety, and long life.

[0003] Lithium-ion batteries consist of four main components: a positive electrode, a negative electrode, a separator, and an electrolyte. As the application of lithium-ion batteries continues to expand, the electrochemical performance they pursue is also constantly improving, such as discharge characteristics at low temperatures and service life at high temperatures. However, due to the electrolyte's greater reaction with the positive and negative electrode active materials at high temperatures and the resulting higher resistance at low temperatures, currently used lithium-ion batteries generally struggle to achieve both excellent low-temperature discharge characteristics and high-temperature cycling performance.

[0004] Therefore, how to overcome the above-mentioned defect that high and low temperature lithium battery performance cannot be taken into account is a technical problem that urgently needs to be solved in this field.

[0005] It should be noted that the above information disclosed in this background technology section is only used to understand the background technology of the present application concept, and therefore, the above description is not considered to constitute information of the prior art. Summary of the Invention

[0006] The embodiments of the present disclosure at least provide a lithium-ion battery that takes into account both low-temperature discharge and high-temperature cycling.

[0007] In a first aspect, the present disclosure provides a lithium-ion battery comprising: a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte; the mass percentage of ash in the negative electrode active material of the negative electrode sheet is H, O I The electrolyte includes a compound The mass percentage of the compound in the electrolyte is C1; the compound forms an SEI film on the surface of the negative electrode active material after the first charging cycle of the lithium ion battery; the ratio of the total mass of the electrolyte to the discharge capacity of the lithium ion battery is Ng / Ah; wherein the lithium ion battery satisfies the following relationship: Wherein, R0 is a single bond or methylene, R1 is any one of hydrogen, halogen, hydrocarbon group with 1 to 5 carbon atoms or halogenated hydrocarbon group with 1 to 5 carbon atoms, R2, R3 and R4 are independently selected from Any one of the following, and R2, R3, and R4 are not selected at the same time

[0008] In an optional embodiment, R1 includes any one of hydrogen, halogen, methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, halogenated methyl, halogenated ethyl, halogenated n-propyl, halogenated isopropyl, halogenated butyl, halogenated pentyl and halogenated hexyl.

[0009] In an optional embodiment, the compound includes at least one of the following compounds:

[0010]

[0011] In an optional embodiment, the ash content is obtained by calculating the ratio of the mass of the remaining material to the mass of the initial material after the negative electrode active material is kept at 900° C. for 16 hours, and satisfies the following relationship: 0.005≤H≤0.03.

[0012] In an optional embodiment, the mass percentage C1% of the compound in the electrolyte satisfies the following relationship: 0.1%≤C1≤3%.

[0013] In an optional embodiment, the O I The value is obtained by XRD test using the ratio of the (004) diffraction peak intensity to the (110) diffraction peak intensity and satisfies the following relationship: 1≤D≤10.

[0014] In an optional embodiment, the discharge capacity of the lithium-ion battery is obtained by discharging the battery at 0.5C to a cut-off voltage after the battery is fully charged, and the ratio N satisfies the following relationship: 1≤N≤3.

[0015] In an optional embodiment, the mass proportion of sulfur in the SEI film is 0.1% to 0.8%.

[0016] In an optional embodiment, the electrolyte further includes an electrolyte salt, and the mass proportion of the electrolyte salt in the electrolyte is 10% to 20%.

[0017] In an optional embodiment, the electrolyte further includes an additive, and the mass proportion of the additive in the electrolyte is 1% to 10%; the additive includes at least one of vinylene carbonate, methylene disulfonate, 1,3-propane sultone, glycerol trinitrile, succinonitrile, adiponitrile, 1,3,6-hexane trinitrile, fluoroethylene carbonate, lithium bis(fluorooxalatoborate), lithium bis(oxalatoborate), lithium tetrafluoroborate and lithium bis(fluorobis(oxalatophosphate)).

[0018] The beneficial effect of the present invention is that the compound of the lithium-ion battery that takes into account both low-temperature discharge and high-temperature cycling can form an effective SEI film on the surface of the negative electrode active material during the first charge and cycle of the battery under the premise of satisfying various relationship expressions, and has porous and stable characteristics, thereby improving the low-temperature discharge and high-temperature cycling performance of the lithium-ion battery, taking into account the defects at two extreme temperatures, and broadening the application environment of the lithium-ion battery.

[0019] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description.

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail as follows. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] In this context, a single "compound" refers specifically to The specific structures of different substituents thereof can also be referred to as Formula 1 in specific embodiments, and do not refer to all compounds.

[0023] As used herein, the phrases "in one embodiment," "according to one embodiment," "in some embodiments," and the like generally refer to the fact that the particular feature, structure, or characteristic following the phrase may be included in at least one embodiment of the present disclosure. Thus, a particular feature, structure, or characteristic may be included in more than one embodiment of the present disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms "example," "exemplary," and the like are used to "serve as an example, instance, or illustration." Any implementation, aspect, or design described herein as "example" or "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations, aspects, or designs. Instead, the use of the terms "example," "exemplary," and the like is intended to present concepts in a concrete manner.

[0024] As used herein, expressions such as “at least one of,” when following a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, the expression “at least one of a, b, and c” should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0025] The terms used herein are only used to describe specific exemplary configurations and are not intended to be limiting. As used herein, the singular articles "a", "an" and "the" may also be intended to include plural forms, unless otherwise clearly indicated herein. The terms "comprise", "include" and "have" are inclusive and therefore specify the presence of features, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components and / or combinations thereof. The method steps, processes and operations described herein should not be interpreted as necessarily requiring them to be performed in the particular order discussed or shown, unless specifically identified as an execution order. Additional or alternative steps may be adopted.

[0026] The following are some embodiments of the present invention described in detail. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0027] The present disclosure provides a lithium-ion battery comprising: a positive electrode plate, a negative electrode plate, a separator, and an electrolyte; the mass percentage of ash in the negative electrode active material of the negative electrode plate is H, O I The electrolyte includes a compound The mass percentage of the compound in the electrolyte is C1; the compound forms an SEI film on the surface of the negative electrode active material after the first charging cycle of the lithium ion battery; the ratio of the total mass of the electrolyte to the discharge capacity of the lithium ion battery is Ng / Ah; wherein the lithium ion battery satisfies the following relationship: Wherein, R0 is a single bond or methylene, R1 is any one of hydrogen, halogen, hydrocarbon group with 1 to 5 carbon atoms or halogenated hydrocarbon group with 1 to 5 carbon atoms, R2, R3 and R4 are independently selected from Any one of the following, and R2, R3, and R4 are not selected at the same time

[0028] Specifically, this is because N determines the mass of the electrolyte retained in the lithium-ion battery, and C1 determines the mass of the compound within the retained electrolyte mass. Both largely determine the number or quantity of compound molecules present in the lithium-ion battery. H and D, on the other hand, significantly influence the number of compound molecules required to form the SEI film. When the above formula relationship is satisfied, the number of compound molecules in the lithium-ion battery is just enough to form a complete SEI film, while also replenishing the appropriate amount consumed during subsequent high-temperature cycling. As a result, the battery exhibits excellent low-temperature discharge performance and high-temperature cycling performance.

[0029] In some embodiments, specifically, R1 includes any one of hydrogen, halogen, methyl, ethyl, n-propyl, isopropyl, butyl, pentyl, hexyl, halogenated methyl, halogenated ethyl, halogenated n-propyl, halogenated isopropyl, halogenated butyl, halogenated pentyl, and halogenated hexyl. During the initial charge and cycling of the battery, the compound can be reduced on the surface of the negative electrode active material prior to the electrolyte solvent to form an SEI film rich in sulfonate-containing sulfur compounds. The formed SEI film is relatively thin, which facilitates the rapid passage of ions during charge and discharge, resulting in low impedance of the SEI film, thereby effectively improving the kinetic performance of the battery. The formed SEI film is highly stable and can inhibit further decomposition of the electrolyte during charge and discharge at high temperatures, thereby effectively improving the high-temperature cycling performance of the battery.

[0030] In some embodiments, specifically, the compound includes at least one of the following compounds:

[0031]

[0032] In some embodiments, the ash content is calculated as the ratio of the mass of the remaining material after the negative electrode active material is held at 900°C for 16 hours to the mass of the initial material, and satisfies the following relationship: 0.005 ≤ H ≤ 0.03. The ash content of the negative electrode material includes metallic and inorganic impurities, which can catalyze the decomposition of the electrolyte. A higher H content results in more electrolyte consumption, leading to a high-resistance SEI film. Therefore, controlling H content within a certain range can improve the low-temperature discharge performance of the battery.

[0033] In some embodiments, specifically, the mass percentage C1% of the compound in the electrolyte satisfies the following relationship: 0.1% ≤ C1 ≤ 3%; the size of N determines, to a certain extent, the number of molecules of the compound represented by Formula 1 contained in the battery and the concentration of each molecule in the electrolyte. During the first charge, C1 determines the frequency of the compound's appearance on the negative electrode surface. The larger C1, the greater the activity of the compound. The greater the frequency of appearance on the negative electrode surface, the more likely a sulfur-rich SEI film will form on the negative electrode. This SEI film has low impedance and high stability. This allows for both low-temperature discharge performance and high-temperature cycling performance of the battery.

[0034] In some embodiments, specifically, the O I The value is obtained by XRD testing using the ratio of the (004) diffraction peak intensity to the (110) diffraction peak intensity and satisfies the following relationship: 1≤D≤10. The larger D is, the larger the negative electrode surface area is, the larger the contact area with the electrolyte is, and the more compound molecules are required. Therefore, controlling D within a certain range can improve the high-temperature cycling performance of the battery.

[0035] In some embodiments, the discharge capacity of the lithium-ion battery is determined by discharging the battery at 0.5C to a cutoff voltage after fully charging it, with the ratio N satisfying the following relationship: 1≤N≤3. The magnitude of N determines the mass of electrolyte in the battery, which, to a certain extent, determines the mass or molar number of compounds in the electrolyte, which affects the thickness of the SEI film during the first charge of the battery. A larger N leads to a thicker SEI film, significantly improving the battery's low-temperature performance. This can enhance the battery's low-temperature discharge performance.

[0036] In some embodiments, specifically, the mass proportion of sulfur in the SEI film is 0.1% to 0.8%, and the proportion of sulfur is tested by an X-ray photoelectron spectrometer at a sputtering etching time of 0 seconds.

[0037] In some embodiments, specifically, the negative active material of the negative electrode sheet includes graphite or silicon-based materials.

[0038] In some embodiments, specifically, the silicon-based material may include at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, and silicon alloys.

[0039] Specifically, the negative electrode plate further includes a negative electrode current collector, a first adhesive and a first conductive agent.

[0040] In some embodiments, specifically, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer substrate (such as a substrate made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0041] In some embodiments, specifically, the first binder may include at least one of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0042] In some embodiments, specifically, the first conductive agent may include at least one of natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, and graphene.

[0043] In some embodiments, specifically, the mass ratio of the negative electrode active material, the first conductive agent, and the first binder is (90-99):(0-5):(1-10).

[0044] In some embodiments, specifically, the positive electrode active material of the positive electrode plate includes lithium iron phosphate material, nickel-cobalt-manganese ternary material, lithium cobalt oxide material, lithium manganese iron phosphate material, lithium manganese oxide material or lithium nickel manganese oxide material.

[0045] Specifically, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector. The positive electrode active material layer includes at least one of a second binder and a second conductive agent and a positive electrode active material.

[0046] In some embodiments, specifically, the positive electrode current collector may include a metal foil or a composite positive electrode current collector. For example, the metal foil may be aluminum foil. The composite positive electrode current collector may include a polymer material base layer and a metal layer formed on at least one side of the polymer material base layer. For example, the composite negative electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.).

[0047] In some embodiments, specifically, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0048] In some embodiments, specifically, when the battery is a lithium-ion battery, the positive electrode active material includes, but is not limited to, lithium iron phosphate material, LiCoO2 material, LiNiO2, nickel cobalt manganese ternary material (LiNi x Co y Mn z O2 (x + y + z = 1, 0 < x < 1, 0 < y < 1, 0 < z < 1)), lithium-rich manganese-based material (nLi2MnO3(1 - n)LiMO2 (0 < n < 1, M is one, two or three of Ni, Co, Mn)), lithium nickel manganate (LiNi 0.5 Mn 1.5 O4) material, lithium manganese iron phosphate material, lithium manganate material, lithium nickel manganate material, etc. Preferably, the lithium iron phosphate material, nickel cobalt manganese ternary material, lithium cobalt oxide material, lithium manganese iron phosphate material, lithium manganate material or lithium nickel manganate material has excellent cycle performance and high energy density, thereby improving the cycle stability of the battery.

[0049] In some embodiments, specifically, the second conductive agent includes at least one of carbon black, acetylene black, graphene, Ketjen black, and carbon fiber.

[0050] In some embodiments, specifically, the second binder includes at least one of polytetrafluoroethylene, polyvinylidene fluoride (PVDF), polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polymers containing ethylene oxide, polyvinyl pyrrolidone, and polyurethane.

[0051] In some embodiments, specifically, the mass ratio of the positive electrode active material, the second conductive agent, and the second binder is (90 - 99.5):(0.25 - 5):(0.25 - 5).

[0052] In some embodiments, specifically, the electrolyte solvent includes at least one of carbonates (such as cyclic carbonates, chain carbonates), carboxylates (such as cyclic carboxylates, chain carboxylates), ether compounds (such as cyclic ether compounds, chain ether compounds), phosphorus-containing compounds, sulfur-containing compounds, and aromatic fluorine-containing compounds.

[0053] In some embodiments, specifically, the solvent includes at least one of ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), propyl butyrate (PB), ethyl butyrate (EB), propyl propionate (PP), ethyl propionate (EP), methyl propionate (MP), propyl acetate (PA), ethyl acetate (EA), methyl acetate (MA), propyl formate (PF), ethyl formate (EF), methyl formate (MF), and γ-butyrolactone.

[0054] In some embodiments, specifically, the electrolyte further includes an electrolyte salt, and the mass proportion of the electrolyte salt in the electrolyte is 10% to 20%.

[0055] In some embodiments, specifically, the electrolyte salt is preferably a lithium salt, and the lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0056] In some embodiments, specifically, the electrolyte further includes an additive, and the mass proportion of the additive in the electrolyte is 1% to 10%; the additive includes at least one of vinylene carbonate, methylene disulfonate, 1,3-propane sultone, glycerol trinitrile, succinonitrile, adiponitrile, 1,3,6-hexane trinitrile, fluoroethylene carbonate, lithium bis(fluorooxalatoborate), lithium bis(oxalatoborate), lithium tetrafluoroborate and lithium bis(fluorobis(oxalatophosphate)).

[0057] In some embodiments, specifically, the battery further includes a separator, which includes but is not limited to glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride.

[0058] Example 1

[0059] (1) Preparation of electrolyte: Under an inert atmosphere (water <0.1ppm, oxygen <1ppm), ethylene carbonate (EC), propyl propionate (PP) and diethyl carbonate (DEC) were mixed in a mass ratio of EC:PP:DEC = 3:3:4. After mixing evenly, lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6) were added. The mass proportion of LiFSI in the electrolyte was 2wt%, and the mass proportion of LiPF6 in the electrolyte was 15wt%. Then, the compound of formula 1-1 was added. Based on the total mass of the electrolyte, the mass proportion of the compound of formula 1-1 was 2wt%.

[0060] (2) Preparation of positive electrode sheets: Lithium cobalt oxide, acetylene black and poly (vinylidene fluoride) are dispersed in N-methylpyrrolidone (NMP) solvent in a mass ratio of 97:1:2, stirred and mixed to form a uniform positive electrode slurry, and then evenly coated on the positive electrode current collector aluminum foil. After drying, rolling and slitting, the positive electrode sheets are obtained.

[0061] (3) Preparation of negative electrode sheet: Graphite, acetylene black, sodium carboxymethyl cellulose and styrene butadiene rubber (SBR) are dispersed in an appropriate amount of deionized water at a mass ratio of 95:2:2:1. The mixture is stirred thoroughly to form a uniform negative electrode slurry, which is then evenly coated on the negative electrode current collector copper foil. After drying, rolling and cutting, the negative electrode sheet is obtained. The ash content H% of the graphite material is 0.01wt%. I The value D is 2.

[0062] (4) Preparation of a battery: The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator positioned between the positive and negative electrode sheets to provide isolation. The cells are then wound to obtain a bare cell. The bare cell is placed in an outer packaging shell. After drying, the electrolyte prepared in step (1) is injected. The total mass of the electrolyte is 7.7 g. After vacuum packaging, standing, forming, and shaping, the battery is prepared. The rated capacity is 5.5 Ah, and the ratio of the total mass of the electrolyte to the discharge capacity of the battery, Ng / Ah, is 1.4 / Ah. Specifically, the capacity of the battery obtained by fully charging at a current of 0.5 C and then discharging at a current of 0.5 C is 5.5 Ah.

[0063] Example 2

[0064] The difference between Example 2 and Example 1 is that the compound represented by Formula 1 used in Example 2 is Formula 1-2.

[0065] Example 3

[0066] The difference between Example 3 and Example 1 is that the compound represented by Formula 1 used in Example 3 is Formula 1-3.

[0067] Example 4

[0068] The difference between Example 4 and Example 1 is that the compound represented by Formula 1 used in Example 4 is Formula 1-4.

[0069] Example 5

[0070] The difference between Example 5 and Example 1 is that the compound represented by Formula 1 used in Example 5 is Formula 1-5.

[0071] Example 6

[0072] The difference between Example 6 and Example 1 is that the compound represented by Formula 1 used in Example 6 is Formula 1-6.

[0073] Example 7

[0074] The difference between Example 7 and Example 1 is that the compound represented by Formula 1 used in Example 7 is Formula 1-7.

[0075] Example 8

[0076] The difference between Example 8 and Example 1 is that the ratio of the total mass of the electrolyte to the discharge capacity of the battery in Example 8 is 1 g / Ah.

[0077] Example 9

[0078] The difference between Example 9 and Example 1 is that the ratio of the total mass of the electrolyte to the discharge capacity of the battery in Example 9 is 3 g / Ah.

[0079] Example 10

[0080] The difference between Example 10 and Example 1 is that the mass proportion C1 of the compound of formula 1-1 in Example 10 is 0.1 wt %.

[0081] Example 11

[0082] The difference between Example 11 and Example 1 is that the mass proportion C1 of the compound of Formula 1-1 in Example 11 is 3 wt %.

[0083] Example 12

[0084] The difference between Example 12 and Example 1: The graphite of Example 12 has O I The value D is 1.

[0085] Example 13

[0086] The difference between Example 13 and Example 1 is that the graphite of Example 13 has I The value D is 10.

[0087] Example 14

[0088] The difference between Example 14 and Example 1 is that the ash content H% of the graphite in Example 14 is 0.005wt%.

[0089] Example 15

[0090] The difference between Example 15 and Example 1 is that the ash content H% of the graphite in Example 15 is 0.03wt%.

[0091] Example 16

[0092] The difference between Example 16 and Example 1: In the electrolyte of Example 16, 3% of 1,3,6-hexanetricarbonitrile (HTCN) is further added during the preparation of the electrolyte in step (1).

[0093] Example 17

[0094] The difference between Example 17 and Example 1: The positive electrode active material in step (2) of Example 17 is LiNi 0.5 Co 0.2 Mn 0.3 O2.

[0095] Comparative Example 1

[0096] The difference between Comparative Example 1 and Example 1 is that the aforementioned compound is not added to the electrolyte of Comparative Example 1.

[0097] Comparative Example 2

[0098] The difference between Comparative Example 2 and Example 1 is that based on the total mass of the electrolyte, the mass proportion of the above compound C1 is 0.2w%. The ash content H% of the graphite material is 0.03wt%. I The value D is 1. The ratio Ng / Ah of the total mass of the electrolyte to the discharge capacity of the battery is 1 g / Ah.

[0099] Comparative Example 3

[0100] The difference between Comparative Example 3 and Example 1 is as follows: In the electrolyte of Comparative Example 3, the mass proportion of the aforementioned compound C1 is 3 wt% based on the total mass of the electrolyte. The ash content H% of the graphite material is 0.005 wt%, and the O I The value D is 10. The ratio Ng / Ah of the total mass of the electrolyte to the discharge capacity of the battery is 3 g / Ah.

[0101] The electrolytes, negative electrode active materials and positive electrode active materials of Examples 1-17 and Comparative Examples 1-3 are different, as shown in Table 1.

[0102] Table 1

[0103]

[0104]

[0105] The batteries prepared in Examples 1-17 and Comparative Examples 1-3 were subjected to high-temperature cycle tests and low-temperature discharge performance tests. The specific test conditions are as follows:

[0106] High-temperature cycle test: Place the battery at 45°C and perform charge and discharge cycles using a 1C current. Record the maximum capacity of the first three cycles as Q, and select the capacity after 500 cycles as Q2. Calculate the capacity retention rate of the battery after high-temperature cycling using the following formula: Capacity retention rate (%) = Q2 / Q×100.

[0107] Low-temperature discharge performance test: The battery was charged and discharged once at room temperature with a current of 1C, and the discharge capacity, Q3, was recorded. The battery was then fully charged with a current of 1C. The battery was then placed in a -20°C incubator for 4 hours and discharged with a current of 0.5C to the lower voltage limit. The discharge capacity, Q4, was recorded. The battery's low-temperature discharge capacity retention rate was calculated using the following formula: Low-temperature discharge capacity retention rate (%) = Q4 / Q3 × 100.

[0108] The batteries prepared in Examples 1-17 and Comparative Examples 1-3 were disassembled after capacity separation. The negative electrode sheets were cleaned three times with DMC and then vacuum-baked at 60°C for 6 hours. The sulfur content of the negative electrode sheets was tested by X-ray photoelectron spectrometer at a sputtering etching time of 0 seconds to obtain the sulfur content in the SEI film.

[0109] The high temperature cycle test, low temperature discharge performance and sulfur content in the SEI film of the batteries prepared in Examples 1-17 and Comparative Examples 1-3 were tested and the results are shown in Table 2.

[0110] Table 2

[0111]

[0112] From the data in Table 2, it can be seen that the high-temperature cycle retention rate and low-temperature discharge retention rate of the batteries of Examples 1-17 are significantly improved compared with the battery of Comparative Example 1 in which the compound represented by Formula 1 is not added. In particular, although the values ​​calculated by Formula 1 for Comparative Examples 2 and 3 are not between 0.02 and 2.1, the high-temperature cycle retention rate and low-temperature discharge retention rate of the batteries are also much lower than those of Examples 1-20, indicating that not only the aforementioned compounds are added to the electrolyte of the present application, but also the values ​​calculated by the above formula are between 0.02 and 2.1, and the resulting battery has excellent low-temperature discharge performance and high-temperature cycle stability.

[0113] In summary, the compound of the lithium-ion battery that takes into account both low-temperature discharge and high-temperature cycling can form an effective SEI film on the surface of the negative electrode active material during the first charge and cycle of the battery under the premise of satisfying various relationship equations, and has porous and stable characteristics, thereby improving the low-temperature discharge and high-temperature cycling performance of the lithium-ion battery, taking into account the defects at two extreme temperatures, and broadening the application environment of the lithium-ion battery.

[0114] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A lithium-ion battery, characterized in that: include: Positive electrode sheet, negative electrode sheet, separator and electrolyte; The mass percentage of ash in the negative active material of the negative electrode plate is H, O I The value is D; The electrolyte includes a compound, and the mass percentage of the compound in the electrolyte is C1; The compound forms a SEI film on the surface of the negative electrode active material after the first charging cycle of the lithium ion battery; The ratio of the total mass of the electrolyte to the discharge capacity of the lithium-ion battery is N g / Ah; Wherein, the lithium-ion battery satisfies the following relationship: ； The compound includes at least one of the following compounds: ； The ash content is obtained by the ratio of the mass of the remaining material after the negative electrode active material is kept at 900° C. for 16 hours to the mass of the initial material, and satisfies the following relationship: 0.005≤H≤0.03； The mass percentage C1% of the compound in the electrolyte satisfies the following relationship: 0.1%≤C1≤3%； The O I The value is obtained by XRD test using the ratio of the (004) diffraction peak intensity to the (110) diffraction peak intensity and satisfies the following relationship: 1≤D≤10； The discharge capacity of the lithium-ion battery is obtained by discharging the battery to the cut-off voltage at 0.5C after the battery is fully charged, and the ratio N satisfies the following relationship: 1≤N≤3。 2. The lithium-ion battery according to claim 1, wherein The mass proportion of sulfur in the SEI film is 0.1% to 0.8%.

3. The lithium-ion battery according to claim 1, wherein The electrolyte solution further includes an electrolyte salt, and the electrolyte salt accounts for 10% to 20% by mass in the electrolyte solution.

4. The lithium-ion battery according to claim 1, wherein The electrolyte further includes an additive, and the additive accounts for 1% to 10% by mass in the electrolyte; The additive includes at least one of vinylene carbonate, methylene methanedisulfonate, 1,3-propane sultone, glycerol trinitrile, succinonitrile, adiponitrile, 1,3,6-hexane trinitrile, fluoroethylene carbonate, lithium bisfluorooxalatoborate, lithium bisoxalatoborate, lithium tetrafluoroborate and lithium bisfluorobisoxalatophosphate.

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