Lithium ion battery and electric device

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a lithium ion battery, comprising: a positive pole piece comprising a positive current collector and a plurality of positive tabs arranged on the positive current collector, the width B of each positive tab being 2-6 mm along the length direction of the positive current collector, and the length D of the positive tab cut from the initial rolling position of the positive current collector being 15-30 cm; the negative electrode plate comprises a negative electrode current collector and a negative electrode active substance coating coated on the surface of at least one side of the negative electrode current collector, the negative electrode active substance coating comprises a first type of active substance and a silicon-based material, the first type of active substance comprises one or more of artificial graphite, natural graphite, hard carbon and soft carbon, and the silicon-based material comprises a silicon-based material; and the silicon-based material comprises pre-lithium silica. Therefore, the condition of volume expansion of the silicon particles in the charging and discharging process can be effectively relieved, and meanwhile, the overall capacity and the long cycle life of the battery can be improved. The invention further discloses a power utilization device.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, specifically to a lithium-ion battery and an electrical device. Background Technology

[0002] Currently, with the widespread application of lithium-ion batteries in new energy vehicles, energy storage systems, and portable electronic devices, the requirements for their energy density, rate performance, and cycle life are continuously increasing. Among them, commonly used cathode materials such as lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate, and anode materials such as graphite, have all achieved actual capacities close to their theoretical capacities.

[0003] Because silicon-based materials have high theoretical capacity and low delithiation potential, related technologies introduce silicon-based materials as negative electrode active materials to improve battery capacity. For example, a negative electrode is disclosed, comprising a carbon matrix and silicon particles, with at least some of the silicon particles located inside the carbon matrix particles.

[0004] In the process of implementing the embodiments of this disclosure, at least the following problems were found in the related art:

[0005] During charging and discharging, silicon particles expand in volume, which can not only cause damage to the electrode surface, but also lead to electrolyte degradation and side reactions, thus affecting the stability of lithium-ion batteries.

[0006] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0007] To provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. This summary is not intended as a general commentary, nor is it intended to identify key / important components or describe the scope of protection of these embodiments, but rather as a prelude to the detailed description that follows.

[0008] This disclosure provides a lithium-ion battery and an electrical device that can effectively alleviate the volume expansion of silicon particles during charging and discharging, while improving the overall capacity and cycle life of the battery.

[0009] In some embodiments, the lithium-ion battery includes a positive electrode and a negative electrode.

[0010] The positive electrode sheet includes a positive current collector and a plurality of positive tabs disposed on the positive current collector, wherein the width B of each positive tab is 2mm to 6mm along the length direction of the positive current collector, and the length D of the positive tab cut off at the starting roll-up position of the positive current collector is 15cm to 30cm.

[0011] A negative electrode sheet includes a negative current collector and a negative active material coating coated on at least one side of the negative current collector. The negative active material coating includes a first type of active material and a silicon-based material. The first type of active material includes one or more of artificial graphite, natural graphite, hard carbon, and soft carbon. The silicon-based material includes pre-lithium silicon oxide.

[0012] In some embodiments, the silicon-based material further includes one or more of silicon-carbon, silicon-oxygen, and monocrystalline silicon; wherein, when the first type of active material includes artificial graphite and the silicon-based material includes pre-lithium silicon-oxygen, the mass fraction of pre-lithium silicon-oxygen in the negative electrode active material coating is 1% to 20%.

[0013] In some embodiments, the chemical formula of the pre-lithium silicon oxide is Li. x SiO y And 0.1≤x≤4.4, 1≤y≤4.

[0014] In some embodiments, the ratio of the discharge specific capacity of graphite to the discharge specific capacity of silicon in the negative electrode is 1:4 to 4:1.

[0015] In some embodiments, the discharge capacity G of the lithium-ion battery is 5Ah to 6.5Ah; the fast charging rate A of the lithium-ion battery is 2.5C to 10C; wherein, the width B of the positive electrode tab, the length D of the positive electrode tab, the discharge capacity G of the lithium-ion battery, and the fast charging rate A of the lithium-ion battery also satisfy the following condition: 0.048≤GA / BD≤4.99.

[0016] In some embodiments, the negative electrode active material coating further includes a negative electrode conductive agent, a negative electrode dispersant, and a negative electrode binder; the negative electrode active material, conductive agent, dispersant, and binder form a negative electrode slurry with a solid content of 35% to 60% in deionized water; wherein the solid matter in the negative electrode slurry includes 94wt% to 98wt% of negative electrode active material, 1wt% to 2wt% of negative electrode conductive agent, 0.5wt% to 2wt% of negative electrode dispersant, and 0.5wt% to 2wt% of negative electrode binder, and the negative electrode active material includes 1wt% to 30wt% of silicon-based material.

[0017] In some embodiments, the surface of the negative electrode sheet is provided with a recessed area, the length of the recessed area is less than or equal to the width of the negative electrode sheet, and the depth of the recessed area is less than or equal to the thickness of the negative electrode active material coating.

[0018] In some embodiments, the negative electrode sheet satisfies one or more of the following conditions:

[0019] The compaction density of the negative electrode sheet is 1.3 g / cm³. 3 ~1.75g / cm3 ;

[0020] The areal density of the negative electrode sheet is 6 mg / cm³. 2 ~11mg / cm 2 ;

[0021] The areal capacity of the negative electrode is 1.4 mAh / cm². 2 ~4.9mAh / cm 2 ;

[0022] The specific surface area of ​​the negative electrode sheet is 0.1 m². 2 / g~12m 2 / g;

[0023] The porosity of the negative electrode sheet is 21% to 65%;

[0024] The discharge specific capacity of the negative electrode is 400mAh / g to 1000mAh / g;

[0025] The ratio of the discharge specific capacity to the charge specific capacity of the negative electrode is greater than or equal to 1.

[0026] In some embodiments, the positive electrode sheet further includes a positive electrode active material coating coated on at least one side surface of the positive electrode current collector, the positive electrode active material coating comprising a positive electrode active material, the positive electrode active material comprising lithium nickel cobalt manganese oxide (Li... a Ni b Co c Mn d M e O2), wherein 0.8 < a < 1.1, 0.7 < b ≤ 0.95, 0.1 ≤ c < 0.5, 0.05 ≤ d < 0.5, 0 ≤ e ≤ 0.1, and element M includes one or more of Zr, Ti, W, Nb, Al, Mg, Mo and B.

[0027] In some embodiments, the electrical device includes a lithium-ion battery for providing power as described in the foregoing embodiments.

[0028] The lithium-ion battery and power-consuming device provided in this disclosure can achieve the following technical effects:

[0029] On the positive electrode side, the length of the positive electrode tab is cut off by adjusting the width of the positive electrode tab and the starting position of the positive current collector. This avoids deviations, folding, and bending of the positive electrode tab during folding, while improving the liquid injection efficiency and venting efficiency of the battery's central hole, thereby improving its overall conductivity and ultimately improving the battery's cycle performance.

[0030] On the negative electrode side, by optimizing the material ratio of the negative electrode active material coating, combining pre-lithiated silicon-oxygen, type I active material, and silicon-based materials, the theoretical capacity limit of traditional graphite negative electrode materials can be broken, significantly improving the overall battery capacity. Simultaneously, pre-lithiated silicon-oxygen can effectively compensate for the initial irreversible capacity loss before charging and can generate stable Li... x The Si and Li2O structure helps to form a uniform SEI film, thereby effectively alleviating the volume expansion problem of silicon-based materials during charging and discharging, thus improving the structural stability of the electrode and extending the cycle life of the battery.

[0031] Therefore, by simultaneously optimizing the structure of both the positive and negative electrode plates, the optimal balance between high energy density and long cycle life of the battery can be achieved.

[0032] The above general description and the description below are exemplary and illustrative only and are not intended to limit this application. Attached Figure Description

[0033] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations and drawings do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are shown as similar elements. The drawings are not to be scaled. And wherein:

[0034] Figure 1 This is a schematic diagram of the structure of a lithium-ion battery provided in an embodiment of this disclosure;

[0035] Figure 2 This is a schematic diagram of the internal structure of a lithium-ion battery provided in an embodiment of this disclosure;

[0036] Figure 3 This is a schematic diagram of the structure of a positive electrode sheet provided in an embodiment of this disclosure;

[0037] Figure 4 This is a schematic diagram of the structure of a negative electrode sheet provided in an embodiment of this disclosure;

[0038] Figure 5 This is a schematic diagram of a lithium-ion battery provided in an embodiment of this disclosure;

[0039] Figure 6 This is a schematic diagram of another lithium-ion battery provided in an embodiment of this disclosure;

[0040] Figure 7 This is a schematic diagram of the structure of an electrical device provided in an embodiment of this disclosure.

[0041] Figure label:

[0042] 10. Shell; 11. 21. Core; 111. Diaphragm; 112. Center hole;

[0043] 20. Positive terminal; 21. Positive electrode plate; 22. Positive current collector; 23. Positive electrode tab;

[0044] 30. Negative pole; 31. Negative electrode plate; 32. Depressed area. Detailed Implementation

[0045] To provide a more detailed understanding of the features and technical content of the embodiments of this disclosure, the implementation of the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this disclosure. In the following technical description, for ease of explanation, several details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other cases, well-known structures and devices may be simplified in their depiction to simplify the drawings.

[0046] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0047] In this disclosure, the terms "upper," "lower," "inner," "middle," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for better description of the embodiments of this disclosure and their implementations, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to require them to be constructed and operated in a specific orientation. Furthermore, some of the aforementioned terms may be used to indicate other meanings besides orientation or positional relationship; for example, the term "upper" may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in the embodiments of this disclosure according to the specific circumstances.

[0048] Furthermore, the terms "set up," "connect," and "fix" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0049] Unless otherwise stated, the term "multiple" means two or more.

[0050] In this embodiment of the disclosure, the character " / " indicates that the objects before and after it are in an "or" relationship. For example, A / B means: A or B.

[0051] The term "and / or" describes an association between objects, indicating that three relationships can exist. For example, A and / or B means: A or B, or A and B.

[0052] It should be noted that, unless otherwise specified, the embodiments and features described in the present disclosure can be combined with each other.

[0053] Currently, silicon / graphite composite anodes exhibit significantly higher specific capacities than theoretical graphite anodes. However, silicon particles experience volume expansion of up to 300% during charge and discharge. This leads to electrode structural instability, repeated SEI film rupture, and a sharp increase in internal resistance. This not only makes the electrode surface prone to damage but may also trigger electrolyte degradation and side reactions. Therefore, how to maintain the high capacity of silicon-based anodes while improving their structural stability and cycle performance has become a key issue in the development of current lithium-ion battery technology.

[0054] This disclosure provides a lithium-ion battery, including a positive electrode 21 and a negative electrode 31. The positive electrode 21 includes a positive current collector 22 and a plurality of positive tabs 23 disposed on the positive current collector 22. Along the length direction of the positive current collector 22, the width B of each positive tab 23 is 2mm to 6mm, and the length D of the positive tab 23 cut off at the initial rolled-up position of the positive current collector 22 is 15cm to 30cm. The negative electrode 31 includes a negative current collector and a negative active material coating coated on at least one side of the negative current collector. The negative active material coating includes a first type of active material and a silicon-based material. The first type of active material includes one or more of artificial graphite, natural graphite, hard carbon, and soft carbon. The silicon-based material includes pre-lithium silicon oxide.

[0055] Using the lithium-ion battery provided in this embodiment, the length of the positive electrode tab is cut off on the positive electrode side by adjusting the width of the positive electrode tab and the starting position of the positive current collector. This avoids deviations, folding, and bending of the positive electrode tab during folding, while improving the liquid injection efficiency and venting efficiency of the battery's central hole, thereby improving its overall conductivity and ultimately enhancing the battery's cycle performance.

[0056] On the negative electrode side, by optimizing the material ratio of the negative electrode active material coating, combining pre-lithiated silicon-oxygen, type I active material, and silicon-based materials, the theoretical capacity limit of traditional graphite negative electrode materials can be broken, significantly improving the overall battery capacity. Simultaneously, pre-lithiated silicon-oxygen can effectively compensate for the initial irreversible capacity loss before charging and can generate stable Li... xThe Si and Li2O structure helps to form a uniform SEI film, thereby effectively alleviating the volume expansion problem of silicon-based materials during charging and discharging, thus improving the structural stability of the electrode and extending the cycle life of the battery.

[0057] Therefore, by simultaneously optimizing the structure of both the positive and negative electrode plates, the optimal balance between high energy density and long cycle life of the battery can be achieved.

[0058] Combination Figures 1 to 6 As shown in this embodiment, the lithium-ion battery further includes a casing 10, a core 11, and a cover; wherein the casing 10 and the cover together enclose an inner cavity, and the core 11 is disposed in the inner cavity. The top of the lithium-ion battery is the positive terminal 20, and the bottom is the negative terminal 30. A positive electrode post is disposed on the positive terminal 20, and a central hole 112 is disposed in the middle region of the lithium-ion battery to release the gas and heat generated during charging and discharging.

[0059] In this embodiment of the disclosure, by adjusting the width B of the positive electrode tab 23 and the length D of the positive electrode tab 23 cut off at the starting roll-up position of the positive electrode current collector 22, the heat dissipation and exhaust performance of the central hole 112 can be effectively improved, thereby effectively controlling the deformation control and gas management of the lithium-ion battery during the charging and discharging process, thereby further improving the safety and structural stability of the battery.

[0060] In this embodiment of the disclosure, the core 11 includes a core 11 formed by winding a positive electrode 21, a negative electrode 31 and a separator 111 between them, wherein at least one surface of the positive electrode 21 has a positive active material coating, the positive active material coating including positive active material particles, and at least one surface of the negative electrode 31 has a negative active material coating, the negative active material coating including negative active material particles.

[0061] In this embodiment, the welding of the core 11 to the housing 10 can be achieved by first fixing the spatial position of the core 11 and the housing 10 using a tooling fixture, then pressing the core 11 into the housing using a press to ensure reliable contact between the positive end face of the core 11 and the lower inner end face of the housing 10, and finally fixing the core 11 to the housing 10 using a laser welding machine beam. The core 11 is a wound structure, with positive aluminum foil tabs and negative copper foil tabs at both ends. After being flattened and shaped, the positive aluminum foil tabs and negative copper foil tabs form end face tabs, namely the positive end face tabs and the negative end face tabs. Both the positive end face tabs and the negative end face tabs are welded to the cover structure, and one end of the cover structure is an integral structure with the housing 10.

[0062] Combination Figure 3As shown in this embodiment, a metal strip is connected to one side of the positive current collector 22, and the metal strip is used to form a plurality of positive tabs 23 by a cutting and stacking process; wherein, along the length direction of the positive current collector 22, the width B of each positive tab is 2mm to 6mm, and the length D of the positive tab 23 cut off at the starting rolling position of the positive current collector 22 is 15cm to 30cm.

[0063] In some embodiments, the silicon-based material further includes one or more of silicon-carbon, silicon-oxygen, and monocrystalline silicon; wherein, when the first type of active material includes artificial graphite and the silicon-based material includes pre-lithium silicon-oxygen, the mass fraction of pre-lithium silicon-oxygen in the negative electrode active material coating is 1% to 20%.

[0064] In this embodiment of the disclosure, the silicon-based material further includes silicon-carbon. Here, silicon-carbon is formed by depositing small-sized amorphous silicon within a porous carbon framework, with a size <6nm; the carbon framework of the silicon-carbon material can constrain silicon expansion to a certain extent, thereby helping to slow down volume expansion.

[0065] In some specific embodiments, when the first type of active material includes artificial graphite and the silicon-based material includes pre-lithium silicon oxide, the mass fraction of pre-lithium silicon oxide in the negative electrode active material coating is 5% to 20%. This achieves a balance between high energy density and long cycle life in the battery. The artificial graphite includes mesophase carbon microspheres.

[0066] In some embodiments, the chemical formula of the pre-lithium silicon oxide is Li. x SiO y Furthermore, 0.1≤x≤4.4, 1≤y≤4. Here, pre-lithiated silicon oxide can serve as a first-cycle lithium replenishment agent, and its expansion rate is only 80-120%, which can mitigate volume expansion.

[0067] In some embodiments, in the negative electrode, the ratio of the discharge specific capacity of graphite to the discharge specific capacity of silicon is 1:4 to 4:1.

[0068] In some specific embodiments, the ratio of the discharge specific capacity of graphite to that of silicon in the negative electrode is 2:3 to 3:2.

[0069] In some embodiments, the discharge capacity G of the lithium-ion battery is 5Ah to 6.5Ah; the fast charging rate A of the lithium-ion battery is 2.5C to 10C; wherein, the width B of the positive electrode tab, the length D of the positive electrode tab, the discharge capacity G of the lithium-ion battery, and the fast charging rate A of the lithium-ion battery also satisfy the following condition: 0.048≤GA / BD≤4.99.

[0070] In this embodiment of the disclosure, I = GA, where I is the discharge current. Therefore, the value of GA / BD can characterize the fast charging current density carried per unit positive electrode cross-sectional area.

[0071] Here, if the GA / BD value is too small, it indicates that the cross-sectional area of ​​the positive electrode tab is too large. Although the impedance is low, the positive electrode tab occupies a large space, thereby increasing the proportion of inactive materials and reducing energy density; at the same time, the cost of materials and welding processes increases. If the GA / BD value is too large, it indicates that the current density on the cross-sectional area of ​​the positive electrode tab is high during fast charging, which leads to significant heating of the positive electrode tab, increased power, and consequently, local overheating, solder joint annealing, or even failure of the tab-foil connection.

[0072] Therefore, by limiting the width B of the positive electrode tab, the length D of the positive electrode tab, the discharge capacity G of the lithium-ion battery, and the fast charging rate A of the lithium-ion battery to satisfy 0.048≤GA / BD≤4.99, it can be ensured that the current density per unit electrode tab cross-sectional area is within the safe and efficient conduction range under fast charging conditions. This can both reduce resistance heating and avoid the energy density decrease caused by excessively large electrode tab size.

[0073] In some embodiments, the negative electrode active material coating further includes a negative electrode conductive agent, a negative electrode dispersant, and a negative electrode binder; the negative electrode active material, conductive agent, dispersant, and binder form a negative electrode slurry with a solid content of 35% to 60% in deionized water; wherein the solid matter in the negative electrode slurry includes 94wt% to 98wt% of negative electrode active material, 1wt% to 2wt% of negative electrode conductive agent, 0.5wt% to 2wt% of negative electrode dispersant, and 0.5wt% to 2wt% of negative electrode binder, and the negative electrode active material includes 1wt% to 30wt% of silicon-based material.

[0074] Combination Figure 4 As shown, in some embodiments, a recessed region 32 is provided on the surface of the negative electrode sheet. The length of the recessed region 32 is less than or equal to the width of the negative electrode sheet, and the depth of the recessed region 32 is less than or equal to the thickness of the negative electrode active material coating.

[0075] In this embodiment, the recessed area 32 includes an indentation or groove. Here, if both sides of the negative electrode sheet are coated with a negative electrode active material, then recessed areas 32 are provided on both sides, and the recessed areas 32 on both sides are alternately arranged. If only one side of the negative electrode sheet is coated with a negative electrode active material, then the recessed areas 32 on that side are alternately arranged. In this way, by providing recessed areas 32 on the surface of the negative electrode active material coating, the conductivity and interfacial bonding of the negative electrode material can be effectively improved, thereby improving the overall performance and safety of the battery.

[0076] In some embodiments, the compaction density of the negative electrode sheet is 1.3 g / cm³. 3 ~1.75g / cm 3 .

[0077] In some embodiments, the areal density of the negative electrode sheet is 6 mg / cm³. 2~11mg / cm 2 .

[0078] In some embodiments, the areal capacity of the negative electrode is 1.4 mAh / cm². 2 ~4.9mAh / cm 2 .

[0079] In some embodiments, the specific surface area of ​​the negative electrode is 0.1 m². 2 / g~12m 2 / g.

[0080] In some embodiments, the porosity of the negative electrode sheet is 21% to 65%.

[0081] In some embodiments, the discharge specific capacity of the negative electrode is 400mAh / g to 1000mAh / g.

[0082] In some embodiments, the ratio of the discharge specific capacity to the charge specific capacity of the negative electrode is greater than or equal to 1.

[0083] In this embodiment, by adjusting the discharge specific capacity of the negative electrode and the ratio of discharge specific capacity to charge specific capacity, the charge-discharge performance of the lithium-ion battery can be significantly improved. In some specific embodiments, the discharge specific capacity of the negative electrode is 450mAh / g to 600mAh / g; the ratio of discharge specific capacity to charge specific capacity of the negative electrode is greater than or equal to 1.01.

[0084] In some embodiments, the positive electrode sheet further includes a positive electrode active material coating coated on at least one side surface of the positive electrode current collector, the positive electrode active material coating including a positive electrode active material, the positive electrode active material including lithium nickel cobalt manganese oxide (Li... a Ni b Co c Mn d M e O2), wherein 0.8 < a < 1.1, 0.7 < b ≤ 0.95, 0.1 ≤ c < 0.5, 0.05 ≤ d < 0.5, 0 ≤ e ≤ 0.1, and element M includes one or more of Zr, Ti, W, Nb, Al, Mg, Mo and B.

[0085] This disclosure also provides a method for preparing a negative electrode sheet, comprising the following steps:

[0086] The negative electrode active slurry is coated onto the negative electrode current collector and dried to form a negative electrode active coating on the surface of the negative electrode current collector;

[0087] The negative electrode current collector is placed in a cold press and subjected to a first cold press and a second cold press to obtain the negative electrode sheet; the cold pressing temperature is 20℃~60℃; the cold pressing time is 10min~20min; and the cold pressing pressure is 0.8t / cm. 2 ~1.2t / cm 2 .

[0088] Combination Figure 7 As shown, this disclosure provides an electrical device including a lithium-ion battery for providing power as described in this application.

[0089] The present invention will be further explained and illustrated below with reference to embodiments.

[0090] Example 1

[0091] This embodiment 1 provides a method for preparing a lithium-ion battery as follows:

[0092] Preparation of positive electrode sheet: Select positive electrode active material (Li1Ni) 0.8 Co 0.1 Mn 0.1 O2), conductive carbon black, carbon nanotubes, and polyvinylidene fluoride (PVDF) were thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 96:1:1:2 to obtain a positive electrode coating material. The positive electrode coating material was then coated onto an aluminum foil with a thickness of 12 μm. After drying, cold pressing, slitting, and cutting, a positive electrode sheet was obtained. The width of each positive electrode tab on the positive electrode sheet was 2 mm, and the length of the positive electrode tab cut off at the starting position of the aluminum foil was 26 cm.

[0093] Preparation of negative electrode sheet: This includes the preparation of negative electrode active material. Specifically, artificial graphite, hard carbon, pre-lithium silicon oxide (Li4SiO4), and single crystal silicon are mixed in a mass ratio of 40:35:15:10 to obtain negative electrode active material. The above negative electrode active material, acetylene black, sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are mixed evenly in deionized water in a mass ratio of 95:2:1.5:1.5 to obtain a negative electrode coating material with a solid content of 50%.

[0094] The aforementioned negative electrode coating material was coated onto the surface of copper foil, with a coating thickness of 100 μm and a coating areal density of 6 mg / cm³. 2 After drying, it is then subjected to a process at 60℃ with a flow rate of 1 t / cm. 2 The pressure was cold-pressed for 10 minutes; then a second cold-pressing was performed at 1 t / cm. 2 The material was cold-pressed under pressure for 15 minutes, resulting in a compacted density of 1.6 g / cm³. 3 The negative electrode sheet.

[0095] Preparation of the diaphragm: A diaphragm with a high porosity of 40% to 60% is selected. The thickness of the polyethylene (PE) base membrane in the diaphragm is 9.0 μm, the thickness of the ceramic coating on both sides of the base membrane is 1.0 μm, and the thickness of the polyvinylidene fluoride (PVDF) coating is 1.0 μm.

[0096] Assembling the lithium-ion battery: The prepared positive electrode sheet, negative electrode sheet, and substrate are wound using a winding machine, and the outer side of the winding core is wrapped with expansion tape to form a core. The thickness of the substrate film is 9 μm, the thickness of the ceramic coating on both sides of the substrate film is 1 μm, and the thickness of the expansion tape is 120 μm. The core is inserted into an aluminum casing, electrolyte is added, and the aluminum casing is sealed to complete the assembly of the lithium-ion battery. The electrolyte is lithium hexafluorophosphate (LiPF6) with a concentration of 1.5 mol / L, and ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) are mixed in a mass ratio of 1:1:1 to form the electrolyte solvent system.

[0097] The lithium-ion battery was charged and discharged at a rate of 0.5C at a temperature of 25°C, with charge and discharge cutoff voltages of 4.2V and 2.5V, respectively, to obtain a lithium-ion battery with a standard capacity of 5Ah. The maximum safe fast charging rate of the lithium-ion battery was found to be 6C after testing.

[0098] Example 2

[0099] Example 2 provides a lithium-ion battery. The difference between this example and Example 1 is that in the negative electrode active material, artificial graphite, hard carbon, pre-lithium silicon oxide (Li4SiO4), and monocrystalline silicon are mixed in a mass ratio of 48:35:7:10. Everything else is the same as in Example 1.

[0100] Example 3

[0101] Example 3 provides a lithium-ion battery. The difference between this example and Example 1 is that in the negative electrode active material, artificial graphite, hard carbon, pre-lithium silicon oxide (Li4SiO4), and monocrystalline silicon are mixed in a mass ratio of 43:35:12:10. Everything else is the same as in Example 1.

[0102] Example 4

[0103] Example 4 provides a lithium-ion battery. The difference between this example and Example 1 is that in the negative electrode active material, artificial graphite, hard carbon, pre-lithium silicon oxide (Li4SiO4), and monocrystalline silicon are mixed in a mass ratio of 38:35:17:10. Everything else is the same as in Example 1.

[0104] Example 5

[0105] Example 5 provides a lithium-ion battery. The difference between this example and Example 1 is that in the negative electrode coating material, the negative electrode active material, acetylene black, sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are in a mass ratio of 95:2:1:2. Everything else is the same as in Example 1.

[0106] Example 6

[0107] Example 6 provides a lithium-ion battery. The difference between this example and Example 1 is that in the negative electrode coating material, the negative electrode active material, acetylene black, sodium carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) are in a mass ratio of 95:2:2:1. Everything else is the same as in Example 1.

[0108] Example 7

[0109] Example 7 provides a lithium-ion battery. The difference between this example and Example 1 is that the compaction density of the negative electrode sheet is 1.35 g / cm³. 3 Everything else is the same as in Example 1.

[0110] Example 8

[0111] Example 8 provides a lithium-ion battery. The difference between this example and Example 1 is that the compaction density of the negative electrode sheet is 1.7 g / cm³. 3 Everything else is the same as in Example 1.

[0112] Example 9

[0113] Example 9 provides a lithium-ion battery. The difference between this example and Example 1 is that the width of each positive electrode tab is 4 mm. Everything else is the same as in Example 1.

[0114] Example 10

[0115] Example 10 provides a lithium-ion battery. The difference between this example and Example 1 is that the length of the positive electrode tab cut off at the starting roll-up position of the aluminum foil is 30 cm. Everything else is the same as in Example 1.

[0116] Comparative Example 1

[0117] Comparative Example 1 provides a lithium-ion battery. The difference between this comparative example and Example 1 is that the negative electrode active material consists only of artificial graphite. Everything else is the same as in Example 1.

[0118] Comparative Example 2

[0119] Comparative Example 2 provides a lithium-ion battery. The difference between this comparative example and Example 1 is that the compaction density of the negative electrode sheet is 1.8 g / cm³. 3 Everything else is the same as in Example 1.

[0120] Comparative Example 3

[0121] Comparative Example 3 provides a lithium-ion battery. The difference between this comparative example and Example 1 is that the width of each positive electrode tab of the positive electrode is 1 mm. Everything else is the same as Example 1.

[0122] Comparative Example 4

[0123] Comparative Example 4 provides a lithium-ion battery. The difference between this comparative example and Example 1 is that the length of the positive electrode tab cut off at the starting roll-up position of the aluminum foil is 10 mm. Everything else is the same as Example 1.

[0124] The lithium-ion batteries of Examples 1 to 10, as well as Comparative Examples 1 and 2, were tested accordingly.

[0125] This embodiment provides a method for testing the rate performance of lithium-ion batteries. The lithium-ion battery is discharged to 2.5V and placed in a constant temperature chamber at 25°C for 6 hours, and the test is carried out according to the following steps:

[0126] Under a 1C charging rate, constant current and constant voltage charging is performed to 4.2V, with a cutoff current of 0.1C, followed by resting for 30 minutes. The capacity obtained after constant current charging to 4.2V is Q. N1 ;

[0127] Under a discharge rate of 1C, constant current discharge is applied until 2.5V is cut off, with a cutoff current of 0.1C, and the sample is left to stand for 30 minutes.

[0128] Under a 6C charging rate, constant current and constant voltage charging is performed to 4.2V, with a cutoff current of 0.1C, followed by resting for 30 minutes. The capacity obtained after constant current charging to 4.2V is Q. N6 ;

[0129] Under a discharge rate of 1C, constant current discharge is applied until 2.5V is cut off, with a cutoff current of 0.1C, and the sample is left to stand for 30 minutes.

[0130] Here, via Q N1 and Q N6 Calculate the capacity retention rate Q of a lithium-ion battery. NR ;

[0131] Among them, Q NR =Q N6 / Q N1 ×100%.

[0132] This embodiment also provides a method for testing the low-temperature rate performance of lithium-ion batteries. The lithium-ion battery is discharged to 2.5V at a temperature of 25°C, and then placed in a constant temperature chamber at -40°C for 6 hours. The test is carried out according to the following steps:

[0133] Under a 1C charging rate, constant current and constant voltage charging is performed to 4.2V, with a cutoff current of 0.1C, followed by resting for 30 minutes. The capacity obtained after constant current charging to 4.2V is Q. L1 ;

[0134] Under a discharge rate of 1C, constant current discharge is applied until 2.5V is cut off, with a cutoff current of 0.1C, and the sample is left to stand for 30 minutes.

[0135] Under a 5C charging rate, constant current and constant voltage charging is performed to 4.2V, with a cutoff current of 0.1C, followed by resting for 30 minutes. The capacity obtained after constant current charging to 4.2V is Q. L5 ;

[0136] Under a discharge rate of 1C, constant current discharge is applied until 2.5V is cut off, with a cutoff current of 0.1C, and the sample is left to stand for 30 minutes.

[0137] Here, via Q L1 and Q L5 Calculate the capacity retention Q of lithium-ion batteries under low-temperature conditions. LR ;

[0138] Among them, Q LR =Q L5 / Q L1 ×100%.

[0139] This embodiment also provides a method for testing the cycle performance of a lithium-ion battery. The lithium-ion battery is placed in a constant temperature chamber at 25°C for 6 hours, and the test is carried out according to the following steps:

[0140] Charging steps: Under a charging rate of 0.1C, charge at a constant current to 4.2V, then switch to constant voltage charging until the current drops to 0.01C; after charging is complete, let stand for 30 minutes.

[0141] Discharge procedure: Discharge to 2.5V at a discharge rate of 0.1C.

[0142] Repeat the above charging and discharging steps 1000 times.

[0143] The discharge capacities Q1 and Q2 of the battery after 1 cycle and 1000 cycles respectively. 1000 Calculate the capacity decay rate Q of a lithium-ion battery. d Q d =(Q1-Q 1000 )×100%.

[0144] This embodiment also provides a method for testing the fast charging rate performance of lithium-ion batteries. The lithium-ion battery is placed in a constant temperature chamber at 25°C for 6 hours, and the test is carried out according to the following steps:

[0145] Charging steps: Under a charging rate of 0.5C, charge at a constant current to 4.2V, then switch to constant voltage charging until the current drops to 0.01C; after charging is complete, let stand for 10 minutes and observe whether there is obvious lithium plating on the surface of the negative electrode.

[0146] Discharge procedure: Discharge to 2.5V at a discharge rate of 1C.

[0147] Steps to increase the charging rate: Increase the charging rate by 0.5C each time. After charging, observe whether there is obvious lithium plating on the surface of the negative electrode. If lithium plating appears on the surface of the negative electrode during the Nth charge, then the charging rate of the N-1th charge is the fast charging rate A of this application.

[0148] Examples 1 to 10 and Comparative Examples 1 to 4 were subjected to the above tests, and corresponding data were obtained. This includes whether the discharge capacity at a 0.5C rate is greater than 5Ah, with a cutoff voltage of 2.5V to 4.2V; the capacity retention rate at 25°C and 6C charging; the capacity retention rate at -40°C and 5C charging; and the capacity decay rate after 1000 cycles at 1C. The details are shown in Table 1 below.

[0149] Discharge capacity greater than 5Ah 6C charging capacity retention rate 5C charging capacity retention rate Capacity decay rate Example 1 yes 71.5 41.5 15 Example 2 yes 62.90 34.1 14.2 Example 3 yes 65.30 36.6 14.3 Example 4 yes 68.30 40.3 14.8 Example 5 yes 71.30 42.3 15.8 Example 6 yes 69.10 41.1 16.7 Example 7 no 67.00 39.3 19.9 Example 8 yes 67.60 39.8 14.6 Example 9 yes 72.5 42.6 14.1 Example 10 yes 67.3 37.2 16.1 Comparative Example 1 no 62.90 38.4 14.8 Comparative Example 2 yes 60.20 33.7 32.1 Comparative Example 3 yes 56.7 36.3 16.9 Comparative Example 4 yes 53.1 37.4 17.8

[0150] Table 1

[0151] Table 1 shows the experimental data from Examples 1 to 10 and Comparative Examples 1 to 4. It is evident that introducing approximately 15 wt% pre-lithium silicon oxide (Li4SiO4) into the anode material system can effectively compensate for the initial irreversible capacity loss before charging and generate stable Li. x The Si and Li2O structure helps form a uniform SEI film, thereby significantly improving the charge capacity retention rate at 6C rate (>70%) and the charge capacity retention rate at 5C rate under low temperature conditions (>40%). When the content of pre-lithiated silicon oxide is too low, such as below 7%, insufficient lithium replenishment will occur, and the rate decay will be obvious; when the content of pre-lithiated silicon oxide is too high, such as above 17%, expansion and side reactions will be aggravated, leading to a decrease in cycle stability.

[0152] Secondly, adjusting the ratio of sodium carboxymethyl cellulose (CMC) to styrene-butadiene rubber (SBR) can effectively improve the adhesion and flexibility of the negative electrode slurry. Specifically, the negative electrode sheet exhibits optimal structural stability and flexibility when the ratio of CMC to SBR is 1:1. However, excessive CMC will cause the negative electrode sheet to become brittle, leading to SEI film cracking and increased attenuation rate.

[0153] In Table 1, the compaction density of the negative electrode sheet is controlled at 1.6 g / cm³. 3 This ensures a dense electrode structure without excessive porosity, which facilitates ion diffusion and structural stress release, balancing energy density and cycle life. Conversely, when the compaction density of the negative electrode is 1.35 g / cm³... 3 At times, excessively large gaps can lead to substandard capacity; when the compaction density of the negative electrode is 1.8 g / cm³... 3 At that time, although the capacity was qualified, the capacity decreased sharply (>30%) after cycling.

[0154] In Table 1, referring to Comparative Example 1, through the synergistic effect of multiple components including graphite, hard carbon, silicon oxide, and monocrystalline silicon, the composite structure provided in this application offers significantly superior advantages over a single artificial graphite system. Here, Example 1 demonstrates higher rate performance and better capacity retention.

[0155] In Table 1, on the positive electrode side, if the width of the positive electrode tab is too small, the overall conductivity after folding will deteriorate, leading to poor battery cycle performance. If the width of the positive electrode tab is too large, deviations may occur during the folding process, such as folding or bending, resulting in poor conductivity of the entire tab layer of the lithium-ion battery. Furthermore, if the length of the positive electrode tab removed at the initial roll-up position of the positive current collector is too large, the overall length of the positive electrode tab area will be reduced, leading to poor battery cycle performance. If the length of the positive electrode tab removed at the initial roll-up position of the positive current collector is too small, it will block the liquid injection efficiency and venting efficiency of the battery's central hole, also resulting in poor battery cycle performance.

[0156] The foregoing description and accompanying drawings fully illustrate embodiments of the present disclosure to enable those skilled in the art to practice them. Other embodiments may include structural and other changes. The embodiments represent only possible variations. Individual components and functions are optional unless explicitly required, and the order of operation may vary. Parts and features of some embodiments may be included or substituted for parts and features of other embodiments. Embodiments of the present disclosure are not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from its scope. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A lithium-ion battery, characterized in that, include: The positive electrode sheet includes a positive current collector and a plurality of positive tabs disposed on the positive current collector, wherein the width B of each positive tab is 2mm to 6mm along the length direction of the positive current collector, and the length D of the positive tab cut off at the starting roll-up position of the positive current collector is 15cm to 30cm. A negative electrode sheet includes a negative current collector and a negative active material coating coated on at least one side of the negative current collector. The negative active material coating includes a first type of active material and a silicon-based material. The first type of active material includes one or more of artificial graphite, natural graphite, hard carbon, and soft carbon. The silicon-based material includes pre-lithium silicon oxide.

2. The lithium-ion battery according to claim 1, characterized in that, The silicon-based material further includes one or more of silicon-carbon, silicon-oxygen, and monocrystalline silicon; wherein, when the first type of active material includes artificial graphite and the silicon-based material includes pre-lithium silicon-oxygen, the mass fraction of pre-lithium silicon-oxygen in the negative electrode active material coating is 1% to 20%.

3. The lithium-ion battery according to claim 2, characterized in that, The chemical formula of the pre-lithium silicon oxide is Li. x SiO y And 0.1≤x≤4.4, 1≤y≤4.

4. The lithium-ion battery according to claim 3, characterized in that, In the negative electrode, the ratio of the discharge specific capacity of graphite to that of silicon is 1:4 to 4:

1.

5. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, The discharge capacity G of the lithium-ion battery is 5Ah to 6.5Ah; the fast charging rate A of the lithium-ion battery is 2.5C to 10C; wherein, the width B of the positive electrode tab, the length D of the positive electrode tab, the discharge capacity G of the lithium-ion battery, and the fast charging rate A of the lithium-ion battery also satisfy the following condition: 0.048≤GA / BD≤4.

99.

6. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, The negative electrode active material coating further includes a negative electrode conductive agent, a negative electrode dispersant, and a negative electrode binder; the negative electrode active material, conductive agent, dispersant, and binder form a negative electrode slurry with a solid content of 35% to 60% in deionized water; wherein the solid substances in the negative electrode slurry include 94wt% to 98wt% of negative electrode active material, 1wt% to 2wt% of negative electrode conductive agent, 0.5wt% to 2wt% of negative electrode dispersant, and 0.5wt% to 2wt% of negative electrode binder, and the negative electrode active material includes 1wt% to 30wt% of silicon-based material.

7. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, The surface of the negative electrode sheet is provided with a recessed area, the length of the recessed area is less than or equal to the width of the negative electrode sheet, and the depth of the recessed area is less than or equal to the thickness of the negative electrode active material coating.

8. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, The negative electrode sheet satisfies one or more of the following conditions: The compaction density of the negative electrode sheet is 1.3 g / cm³. 3 ~1.75g / cm 3 ; The areal density of the negative electrode sheet is 6 mg / cm³. 2 ~11mg / cm 2 ; The areal capacity of the negative electrode is 1.4 mAh / cm². 2 ~4.9mAh / cm 2 ; The specific surface area of ​​the negative electrode sheet is 0.1 m². 2 / g~12m 2 / g; The porosity of the negative electrode sheet is 21% to 65%; The discharge specific capacity of the negative electrode is 400mAh / g to 1000mAh / g; The ratio of the discharge specific capacity to the charge specific capacity of the negative electrode is greater than or equal to 1.

9. The lithium-ion battery according to any one of claims 1 to 4, characterized in that, The positive electrode sheet further includes a positive electrode active material coating applied to at least one side surface of the positive electrode current collector, the positive electrode active material coating comprising a positive electrode active material, the positive electrode active material comprising lithium nickel cobalt manganese oxide (Li... a Ni b Co c Mn d M e O2), wherein 0.8 < a < 1.1, 0.7 < b ≤ 0.95, 0.1 ≤ c < 0.5, 0.05 ≤ d < 0.5, 0 ≤ e ≤ 0.1, and element M includes one or more of Zr, Ti, W, Nb, Al, Mg, Mo and B.

10. An electrical device, characterized in that, Includes the lithium-ion battery for providing power as described in any one of claims 1 to 9.

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