Lightweight high-energy-density cylindrical lithium-ion battery and electric device

Abstract

This invention discloses a lightweight, high-energy-density cylindrical lithium-ion battery and related electrical devices. This cylindrical lithium-ion battery achieves high mass energy density while maintaining low AC internal resistance by coupling and defining the foil thickness ratio, the apparent single-sided areal capacity of the positive electrode, the capacity balancing coefficient between the positive and negative electrodes, and the ratio of mass energy density to internal resistance energy density. All of these core parameters can be obtained through disassembly and retesting of finished batteries, avoiding the problem of unclear protection targets caused by limiting protection based solely on a single thickness, areal density, or energy density.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a lightweight, high-energy-density cylindrical lithium-ion battery and related electrical equipment. Background Technology

[0002] Cylindrical lithium-ion batteries, used in power tools, lightweight mobility devices, energy storage, and high-power portable devices, need to simultaneously meet the requirements of high mass energy density, low internal resistance, and stable rate output. To improve battery mass energy density, one can typically reduce the thickness of the current collector, increase the areal density of the active material, or increase the specific capacity of the positive and negative electrode active materials. To reduce internal resistance, it is necessary to maintain the current collector's conductive path, electrode channels, and the capacity balance between the positive and negative electrodes within a reasonable range. Focusing solely on thinning the current collector may lead to reduced electrode processing strength and fluctuations in internal resistance; increasing the areal capacity of the positive electrode alone may result in insufficient capacity redundancy or increased polarization of the negative electrode; and if only battery energy density is considered, it is difficult to determine the structural origin from disassembling finished products and to distinguish between high-energy-density but high-internal-resistance solutions.

[0003] Therefore, there is a need for a cylindrical lithium-ion battery that can establish a calculable relationship between the specific capacity of the positive and negative electrodes at the material end, the foil thickness and areal density at the electrode end, and the mass energy density and AC internal resistance at the performance end. Summary of the Invention

[0004] This invention aims to provide a lightweight, high-energy-density cylindrical lithium-ion battery. By coupling and defining the foil thickness ratio, apparent single-sided areal capacity of the positive electrode, capacity balancing coefficient between the positive and negative electrodes, and the ratio of mass energy density to internal resistance energy density, the battery achieves both high mass energy density and low AC internal resistance. All of these core parameters can be obtained through disassembly and retesting of finished batteries, avoiding the problem of unclear protection targets caused by limiting protection to a single thickness, areal density, or energy density.

[0005] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is as follows: The present invention provides a lightweight high-energy-density cylindrical lithium-ion battery, including a positive electrode sheet, a negative electrode sheet, a separator, and a cylindrical shell for accommodating a wound core. The wound core is mainly formed by winding the positive electrode sheet, the separator, and the negative electrode sheet. The positive electrode sheet includes an aluminum current collector and a positive active material layer region and a positive uncoated region disposed on the surface of the aluminum current collector. The negative electrode sheet includes a copper current collector and a negative active material layer region and a negative uncoated region disposed on the surface of the copper current collector. The cylindrical lithium-ion battery satisfies: 3.4 ≤ 1000 α β η / γ≤10.8; Where 0.45≤α≤0.75, 2.45mAh / cm2 ≤β≤3.15mAh / cm 2 , 1.02≤eta≤1.14, 250Wh / kg≤γ≤330Wh / kg; Define the foil thickness ratio as α, where α = t Cu / t Al , where t Cu t represents the thickness of the copper current collector. Al t is the thickness of the aluminum current collector; Cu and t Al The units are all in μm; Define the apparent single-sided areal capacity of the positive electrode as β, where β = M p ×Q p / 1000, where M p The areal density of the positive electrode active material layer region after removing the aluminum current collector is expressed in mg / cm³. 2 Q p The discharge specific capacity of the positive electrode active material obtained from disassembly under 25±2℃ and 0.1C coin cell test is expressed in mAh / g, and β is expressed in mAh / cm. Define the capacity balancing factor as η, where η = C n / C p , where C p =M p ×A p ×Q p / 1000, C n =M n ×A n ×Q n / 1000, M n The average surface density of the negative electrode active material layer region after removing the copper current collector is expressed in mg / cm³. 2 Q n The reversible lithium-depletion capacity of the negative electrode active material obtained from disassembly under 25±2℃ and 0.1C coin cell testing is expressed in mAh / g (A). p A represents the effective reactive coating area of ​​the positive electrode within the same core. n The effective reactive coating area of ​​the negative electrode in the same core; Among them, the effective reactive coating area of ​​the positive electrode refers to the area of ​​the positive electrode active material layer region; the effective reactive coating area of ​​the negative electrode refers to the area of ​​the negative electrode active material layer region. The mass energy density is defined as γ, where γ = 1000E / m, E is the discharge energy obtained by the cylindrical lithium-ion battery at 0.2C at 25±2℃, in Wh, m is the complete battery weight of the cylindrical lithium-ion battery in g, and γ is in Wh / kg.

[0006] Furthermore, the positive electrode active material in the positive electrode active material layer region includes layered lithium transition metal oxide with a nickel content of 88 mol% to 92 mol%, and the negative electrode active material in the negative electrode active material layer region includes graphite material and silicon-carbon material.

[0007] Furthermore, the cylindrical lithium-ion battery satisfies 0.01 mΩ·kg / Wh ≤ δ ≤ 0.0125 mΩ·kg / Wh, and the internal resistance energy density ratio is defined as δ, where δ = R. AC / γ, where R AC The AC internal resistance of the cylindrical lithium-ion battery was measured using a 1kHz AC internal resistance meter at 25±2℃, 30% SOC (state of charge), and after being left to stand for 60 minutes. The unit is mΩ.

[0008] Furthermore, the cylindrical lithium-ion battery satisfies: 0.50 ≤ α ≤ 0.58, 2.75 mAh / cm². 2 ≤β≤3.10mAh / cm 2 , 1.03≤η≤1.07, 270Wh / kg≤γ≤330Wh / kg, and δ≤0.0105mΩ·kg / Wh.

[0009] Furthermore, the thickness of the aluminum current collector is 11 μm to 13 μm, and the thickness of the copper current collector is 5.5 μm to 8.5 μm.

[0010] Furthermore, the thickness of the copper current collector is 5.8 μm to 6.8 μm.

[0011] Furthermore, the areal density of the positive electrode active material layer region is 12.3 mg / cm². 2 Up to 14.2 mg / cm 2 The compaction density of the positive electrode sheet is 3.40 g / cm³. 3 Up to 3.65 g / cm 3 The thickness of the positive electrode sheet is 86 μm to 92 μm.

[0012] Furthermore, the average areal density of the negative electrode active material layer region is 5.35 mg / cm³. 2 Up to 6.10 mg / cm 2 The compaction density of the negative electrode sheet is 1.50 g / cm³. 3 Up to 1.66 g / cm 3 The thickness of the un-etched area of ​​the negative electrode sheet is 84 μm to 90 μm.

[0013] Furthermore, the layered lithium transition metal oxide comprises polycrystalline particles and single-crystal particles, wherein the mass ratio of the polycrystalline particles to the single-crystal particles is 65:35 to 85:15.

[0014] Furthermore, the discharge specific capacity of the positive electrode active material at 25±2℃ and 0.1C coin cell test is 195mAh / g to 225mAh / g.

[0015] Furthermore, the reversible lithium removal capacity of the negative electrode active material at 25±2℃ and 0.1C coin cell test is 500mAh / g to 525mAh / g, and the silicon capacity obtained by voltage range capacity integration of the negative electrode coin cell lithium removal curve is 44% to 47%.

[0016] Furthermore, the cylindrical lithium-ion battery shall satisfy at least one of the following conditions: (1) The 0.2C discharge capacity of the cylindrical lithium-ion battery is 4.95Ah to 5.10Ah; (2) The discharge energy at 0.2C is 17.8Wh to 18.3Wh; (3) The weight of the complete battery is 64g to 71g; (4) The cylindrical lithium-ion battery is a 21650 full-tab cylindrical battery or a 21700 full-tab cylindrical battery. (5) The AC internal resistance R AC ≤3.1mΩ; (6) The diaphragm comprises a polyolefin-based membrane and a single-sided ceramic coating, and the total thickness of the diaphragm is 9 μm to 12 μm.

[0017] Preferably, the AC internal resistance R AC ≤2.8mΩ.

[0018] The cylindrical lithium-ion battery includes a cylindrical shell, a cap, an insulating component, a positive current collector, a negative current collector, the winding core, an electrolyte, and an outer sheath; "complete battery weight" refers to the weight of the complete battery including the cylindrical shell, cap, insulating component, winding core, and electrolyte.

[0019] The 21650 all-tab cylindrical battery has a diameter of 21mm ± 0.2mm and a height of 65mm ± 0.2mm; the 21700 all-tab cylindrical battery has a diameter of 21mm ± 0.2mm and a height of 70mm ± 0.2mm. This application's all-tab cylindrical battery allows for the assembly of higher battery capacity and energy density within a smaller space, improving the battery's long-range performance and high-rate discharge capability, and expanding the battery's application scenarios.

[0020] The cylindrical lithium-ion battery is a full-tab battery. The positive electrode includes an aluminum current collector and a positive active material layer and an uncoated positive electrode area disposed on the surface of the aluminum current collector. An insulating coating is also applied to the surface at the junction of the positive active material layer and the uncoated positive electrode area. The ratio of the area of ​​the uncoated positive electrode area to the area of ​​the positive electrode is between 3.5% and 10%; the ratio of the area of ​​the insulating coating to the area of ​​the positive electrode is between 1.8% and 6.5%. The insulating coating comprises boehmite and PVDF binder. The negative electrode includes a copper current collector and a negative active material layer and an uncoated negative electrode area disposed on the surface of the copper current collector. The ratio of the area of ​​the uncoated negative electrode area to the area of ​​the negative electrode is between 3.2% and 9.8%. The uncoated positive electrode area is the positive tab area, and the uncoated negative electrode area is the negative tab area. Both uncoated areas are formed into full tabs through a flattening or folding process.

[0021] Furthermore, the present invention also provides an electrical device including the aforementioned cylindrical lithium-ion battery.

[0022] The present invention has the following beneficial effects:

[0023] (1) The present invention limits the thickness relationship between the copper current collector and the aluminum current collector by α, so that the negative electrode current collector has both weight reduction effect and retains the necessary conductivity and processing stability.

[0024] (2) The present invention limits the apparent single-sided surface capacity of the positive electrode by β, and unifies the single-sided surface density of the positive electrode and the discharge capacity of the positive electrode into the same calculation parameter, thereby avoiding the protection separation caused by separately limiting the single-sided surface density of the positive electrode or separately limiting the discharge capacity of the positive electrode.

[0025] (3) The present invention limits the capacity balance of the positive and negative electrodes by η, so that the silicon-containing negative electrode system and the high nickel positive electrode maintain reasonable capacity redundancy, thereby reducing the risk of insufficient negative electrode balance caused by the high areal capacity positive electrode.

[0026] (4) This invention limits battery-level performance by combining γ and δ, thus eliminating the single-index optimization route of "high energy density but high internal resistance" or "low internal resistance but insufficient energy density".

[0027] (5) The core parameters of the present invention can be obtained by measuring the thickness of the current collector, the surface density of the electrode, the 0.1C coin cell, the capacity integration of the voltage range, the capacity energy test of 0.2C, and the AC internal resistance test of 1kHz.

[0028] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the battery structure of the present invention; Figure 2 This is a schematic diagram of the structure of the core of the present invention; Figure 3 This is a schematic diagram of the structure of the positive electrode sheet of the present invention; Figure 4 This is a schematic diagram of the negative electrode sheet of the present invention; The attached figures are labeled as follows: 1. Cap; 2. Positive current collector; 3. Core; 4. Negative current collector; 5. Cylindrical shell; Positive electrode 31, positive active material layer region 311, positive uncoated region 312, positive electrode insulating coating region 313, negative electrode 32, negative active material layer region 321, negative uncoated region 322, separator 33; A represents the starting end of winding, and B represents the ending end of winding. Detailed Implementation

[0030] The following specific embodiments illustrate the detailed implementation of the present invention. Those skilled in the art can easily understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented in other different ways, that is, different modifications and changes can be made without departing from the scope disclosed in the present invention.

[0031] I. Definition of Key Terms and Parameters

[0032] Unless otherwise stated, all tests in this invention were conducted at 25±2℃.

[0033] "Complete battery weight" refers to the weight of the complete battery including the cylindrical casing, cap, insulation, core, and electrolyte.

[0034] "Single-sided surface density M of the positive electrode active material layer region" p "" refers to the surface density of the single-sided coating obtained by subtracting the surface density of the aluminum current collector after sampling from the positive electrode sheet, with units of mg / cm³. 2 The "single-sided surface density of the positive electrode active material layer region" can be simply referred to as the "positive electrode single-sided surface density".

[0035] "M" n "" refers to the average surface density of the coating on one side, obtained by taking samples from both working surfaces of the negative electrode and subtracting the surface density of the copper current collector, with units of mg / cm³. 2 The "average surface density of the negative electrode active material layer" can be simply referred to as the "average surface density of the negative electrode".

[0036] Q p"Q" refers to the discharge specific capacity of the positive electrode active material obtained from disassembly under a 0.1C coin cell test (which can be abbreviated as "positive electrode discharge specific capacity"). n "" refers to the reversible lithium removal capacity of the negative electrode active material obtained from disassembly under a 0.1C coin cell test.

[0037] The foil thickness ratio is calculated according to formula (1): α = t Cu / t Al The apparent single-sided areal capacity of the positive electrode is calculated according to formula (2): β = M p × Q p / 1000 The capacity balancing factor is calculated according to formula (3): η = C n / C p C p = M p × A p × Q p / 1000 C n = M n × A n × Q n / 1000 Among them, A p A represents the effective reactive coating area of ​​the positive electrode within the same core. n This refers to the effective reactive coating area of ​​the negative electrode in the same core. For samples with a known design N / P ratio (which is the negative electrode capacity divided by the positive electrode capacity, generally greater than 1), the design N / P ratio can be used as the benchmark value of η, and verified by a 0.1C coin cell test; if the verification deviation does not exceed ±0.03, it should be standardized according to the design N / P ratio.

[0038] Mass energy density is calculated according to equation (4): γ = 1000E / m The internal resistance energy density ratio is calculated according to equation (5): δ = R AC / γ.

[0039] II. Implementation Examples

[0040] Example 1: Example 1 is a preferred sample of the present invention. For example... Figure 1 As shown, the cylindrical lithium-ion battery includes a cylindrical shell 5, a cap 1, an insulating component (not shown in the figure), a positive current collector 2, a negative current collector 4, the core 3, an electrolyte, and an outer sheath. Figure 2As shown, the core 3 includes a positive electrode 31, a negative electrode 32, and a separator 33. The core is formed by winding the positive electrode, the separator, and the negative electrode, and the core is housed in a cylindrical shell.

[0041] like Figure 3 The positive electrode 31 includes an aluminum current collector (not shown in the figure) and a positive active material layer region 311 and a positive uncoated region 312 disposed on the surface of the aluminum current collector; the surface at the connection between the positive active material layer region 311 and the positive uncoated region 312 is also covered with a positive electrode insulating coating region 313.

[0042] like Figure 4 As shown, the negative electrode 32 includes a copper current collector (not labeled) and a negative electrode active material layer region 321 and a negative electrode uncoated region 322 disposed on the surface of the copper current collector.

[0043] Example 1 was prepared according to the following steps.

[0044] Step 1, Preparation of the positive electrode slurry. A layered lithium transition metal oxide with a nickel content of approximately 90 mol% was selected as the positive electrode active material. The positive electrode active material comprises polycrystalline particles and single-crystal particles, with a mass ratio of polycrystalline particles to single-crystal particles of approximately 80:20. Based on a total solid component mass of 100 wt%, the positive electrode active material comprises 97.25 wt%, conductive carbon black 1.50 wt%, carbon nanotubes 0.10 wt%, and PVDF binder 1.15 wt%. The above solid components were dispersed in NMP solvent to obtain the positive electrode slurry.

[0045] Step 2, positive electrode preparation. A thickness t is selected. Al For an aluminum current collector with a thickness of 12 μm, the positive electrode slurry obtained in step 1 is coated on both sides of the aluminum current collector surface. After drying, rolling, and slitting, the surface density M of the positive electrode active material layer region is reduced. p It is 13.77 mg / cm³ 2 The compaction density of the positive electrode sheet is 3.57 g / cm³. 3 The thickness of the positive electrode sheet is 89 μm. The positive electrode active material was disassembled and subjected to a coin cell test at 25±2℃ and 0.1C to obtain Q. p The value is 222.59 mAh / g, from which we obtain β=M p ×Q p / 1000=3.06mAh / cm 2 .

[0046] Step 3, Preparation of negative electrode slurry. Artificial graphite (i.e., the same type of graphite used in graphite materials) and silicon carbon materials are selected as the negative electrode active materials. Based on a total solid component mass of 100 wt%, the composition of the negative electrode slurry is as follows: artificial graphite 82.95 wt%, silicon carbon material 13.50 wt%, conductive carbon black 0.50 wt%, carbon nanotubes 0.25 wt%, carboxymethyl cellulose thickening / binding component 1.10 wt%, and styrene-butadiene rubber binding component 1.70 wt%. The above solid components are dispersed in an aqueous solvent to obtain the negative electrode slurry.

[0047] Step 4, negative electrode preparation. Select a thickness t. Cu For a copper current collector with a thickness of 6 μm, the negative electrode slurry obtained in step 3 is coated on both sides of the copper current collector. After drying, rolling, and slitting, the surface density of each working surface of the negative electrode is 6.00 mg / cm³. 2 and 5.84 mg / cm 2 Average surface density M n It is 5.92 mg / cm 2 The compaction density of the negative electrode sheet is 1.60 g / cm³. 3 The thickness of the unmarked area of ​​the negative electrode is 87 μm. After 0.1C coin cell verification of the negative electrode, η is made consistent with the designed N / P ratio of 1.04.

[0048] Step 5, preparation of the diaphragm and core. A diaphragm composed of a polyolefin-based membrane and a single-sided boehmite ceramic coating (i.e., a single-sided boehmite ceramic coating) is used, with a total diaphragm thickness of approximately 12 μm. For example... Figure 2 As shown, the positive electrode, separator, and negative electrode are wound into a core in the order of positive electrode, separator, negative electrode, and separator, and the alignment of the positive and negative electrode, the extension of the separator, and the outer diameter of the core are controlled to meet the assembly requirements of 21700 cylindrical batteries.

[0049] Step 6, Assembly and Formation. The core is inserted into the cylindrical shell, and the current collector components are connected, grooved, filled with electrolyte, sealed, formed, aged, and capacity tested to obtain the battery of Example 1. In Example 1, α = t Cu / t Al =0.50, β=3.06mAh / cm 2 η=1.04; the battery's 0.2C discharge capacity is 5.051Ah, its 0.2C discharge energy is 18.17Wh, the complete battery weight is 65.86g, and γ is 276Wh / kg; R AC The value is 2.70 mΩ, and the δ value is 0.0098 mΩ·kg / Wh.

[0050] Example 2: Wide-range coverage sample. The difference between this example and Example 1 is that: by using an 8.08μm thick copper current collector instead of a 6μm thick copper current collector, α changes from 0.50 to 0.673; by reducing the positive electrode slurry coating pump speed and coating gap, the single-sided areal density of the positive electrode is reduced from 13.77 mg / cm³. 2 It became 12.70 mg / cm³ 2 Furthermore, by selecting a high-nickel cathode active material with a 0.1C coin discharge capacity of 201.2 mAh / g, the β value was changed to 2.56 mAh / cm². 2 By reducing the amount of negative electrode slurry coating, the average areal density of the negative electrode on one side was reduced to 5.47 mg / cm³. 2 The parameters were set to η to approximately 1.10, with all other conditions remaining the same as in Example 1. Example 2 had a 0.2C discharge capacity of 5.009 Ah, a 0.2C discharge energy of 17.98 Wh, a complete battery weight of 70.05 g, γ of 257 Wh / kg, and R... AC The value is 2.95 mΩ, and the value of δ is 0.0115 mΩ·kg / Wh.

[0051] Example 3: The difference between this example and Example 1 is that a copper current collector with a thickness of 5.5 μm is used instead of a 6 μm copper current collector, while keeping the aluminum current collector thickness, positive electrode coating amount, negative electrode coating amount, rolling pressure and formation process unchanged, so that α changes from 0.50 to 0.46, and the other conditions are the same as in Example 1.

[0052] Example 4: The difference between this example and Example 1 is that an 8.0 μm thick copper current collector is used instead of a 6 μm copper current collector, while keeping the aluminum current collector thickness, positive electrode coating amount, negative electrode coating amount, rolling pressure and formation process unchanged, so that α changes from 0.50 to 0.67, and the other conditions are the same as in Example 1.

[0053] Example 5: The difference between this example and Example 1 is that by reducing the positive electrode slurry coating pump speed and the coating die gap, the single-sided surface density M of the positive electrode is increased. p From 13.77 mg / cm 2 It became 11.60 mg / cm³ 2 And maintain the positive electrode active material Q p The concentration was 222.59 mAh / g, which reduced β from 3.06 mAh / cm². 2 It became 2.58mAh / cm 2 The remaining conditions are the same as in Example 1.

[0054] Example 6: The difference between this example and Example 1 is that by increasing the positive electrode slurry coating pump speed and the coating die gap, the single-sided surface density M of the positive electrode is increased. p From 13.77 mg / cm 2It changed to 14.05 mg / cm³ 2 And maintain the positive electrode active material Q p The concentration was 222.59 mAh / g, which reduced β from 3.06 mAh / cm². 2 It became 3.13mAh / cm 2 The remaining conditions are the same as in Example 1.

[0055] Example 7: The difference between this example and Example 1 is that by reducing the negative electrode slurry coating pump speed and coating gap, the average surface density M of the negative electrode on one side is increased. n From 5.92 mg / cm 2 It changed to 5.86 mg / cm³ 2 And maintain the surface density of the positive electrode on one side and the Q of the negative electrode active material. n With the effective reaction area remaining unchanged, η was changed from 1.04 to 1.03, and the remaining conditions were the same as in Example 1.

[0056] Example 8: The difference between this example and Example 1 is that by increasing the pump speed and coating gap of the negative electrode slurry coating, the average surface density M of the negative electrode on one side is increased. n From 5.92 mg / cm 2 It changed to 6.10 mg / cm³ 2 By keeping the effective coating width of the negative electrode slitting constant and controlling the effective reaction length of the negative electrode winding to 1.03 times that of Example 1, the effective reaction coating area A of the negative electrode is increased. n The ratio was increased to 1.03 times that of Example 1, and η was changed from 1.04 to 1.12, with the remaining conditions the same as in Example 1.

[0057] Example 9: The difference between this example and Example 1 is that by using a lightweight cylindrical shell, a lightweight insulating gasket, and a weight-reduced cap, the weight of the complete battery is reduced from 65.86g to 65.50g; by keeping the positive and negative electrode design and welding process window unchanged, R is measured... AC The Ω is equal to 2.72 mΩ, γ is equal to 277 Wh / kg, and the corresponding δ is 0.0098 mΩ·kg / Wh. The other conditions are the same as in Example 1.

[0058] Example 10: The difference between this example and Example 1 is as follows: By selecting a higher quality cylindrical shell and cap, and appropriately increasing the electrolyte retention, the weight of the complete battery is increased from 65.86g to 70.30g; by keeping the areal density and formulation of the positive and negative electrodes unchanged, and simultaneously controlling the effective coating length of the positive and negative electrodes to approximately 98.0% of that in Example 1, the 0.2C discharge energy is increased to 17.80Wh; by keeping the welding process of the current collector within the acceptable range, the measured R... ACThe value is equal to 3.08 mΩ, γ is equal to 253 Wh / kg, and the corresponding δ is 0.0122 mΩ·kg / Wh. The other conditions are the same as in Example 1.

[0059] Example 11: The difference between this example and Example 1 is that the mass ratio of polycrystalline particles to single-crystal particles in the positive electrode active material feeding is adjusted so that the mass ratio of polycrystalline particles to single-crystal particles changes from 80:20 to 75:25; the amount of silicon-carbon material added in the negative electrode formulation is slightly adjusted from 13.50wt% to 13.30wt%, and the amount of artificial graphite is added accordingly so that the silicon capacity ratio of the negative electrode becomes 44.5%. The other conditions are the same as in Example 1.

[0060] Example 12: The difference between this example and Example 1 is that: by selecting a copper current collector with a thickness of 6.5 μm, α is changed to 0.54; by reducing the amount of positive electrode coating, the areal density of the positive electrode on one side is changed to 13.60 mg / cm³. 2 And it changed β to 3.03 mAh / cm 2 By reducing the amount of negative electrode coating, the average areal density of the negative electrode on one side became 5.88 mg / cm³. 2 The result showed that η was equal to 1.05, and the other conditions were the same as in Example 1.

[0061] III. Comparative Example

[0062] Comparative Example 1: The difference between this comparative example and Example 1 is that: a 10.5 μm thick copper current collector was used instead of a 6 μm thick copper current collector, making α 0.875; the positive electrode slurry coating pump speed and coating gap were reduced, increasing the single-sided surface density M of the positive electrode. p From 13.77 mg / cm 2 It became 10.80 mg / cm³ 2 And measured Q p The concentration was 222.59 mAh / g, and the measured β was 2.40 mAh / cm³. 2 The remaining conditions are the same as in Example 1.

[0063] Comparative Example 2: The difference between this comparative example and Example 1 is that a copper current collector with a thickness of 4.8 μm is used instead of a 6 μm copper current collector, while keeping the aluminum current collector thickness, positive electrode coating amount, negative electrode coating amount, rolling pressure and formation process unchanged, so that α becomes 0.40, and the other conditions are the same as in Example 1.

[0064] Comparative Example 3: The difference between this comparative example and Example 1 is that the positive electrode slurry coating pump speed and coating gap are increased to improve the single-sided surface density M of the positive electrode. p From 13.77 mg / cm 2 It changed to 14.80 mg / cm³ 2 And it changed β to 3.29 mAh / cm2 By reducing the amount of negative electrode slurry coating, the average areal density M on one side of the negative electrode is increased. n It changed to 5.70 mg / cm³ 2 The result showed that η was equal to 1.00, and the other conditions were the same as in Example 1.

[0065] Comparative Example 4: The difference between this comparative example and Example 1 is that the addition of silicon-carbon material was omitted during the preparation of the negative electrode slurry, and artificial graphite was added to make up the corresponding solid component ratio, so that the negative electrode active material changed from a graphite and silicon-carbon composite system to a single artificial graphite system. The 0.1C coin cell reversible lithium extraction capacity Q of the negative electrode was measured. n The concentration was 360 mAh / g, and η was measured to be 0.82. All other conditions were the same as in Example 1.

[0066] Comparative Example 5: The difference between this comparative example and Example 1 is that: by increasing the welding contact resistance of the current collector and the contact resistance of the cap connection, R was measured. AC The value is equal to 3.80 mΩ. By maintaining the coating amount of positive and negative electrode active materials and selecting a structural component combination with a mass of 67.2 g, the 0.2C discharge energy was measured to be equal to 18.15 Wh, γ was equal to 270 Wh / kg, and δ was measured to be equal to 0.0141 mΩ·kg / Wh. The other conditions were the same as in Example 1.

[0067] Comparative Example 6: The difference between this comparative example and Example 1 is that: by selecting a copper current collector with a thickness of 10 μm, α is changed to 0.83; by reducing the amount of positive electrode slurry coating, the surface density M of the positive electrode on one side is increased. p It became 10.90 mg / cm³ 2 And it changed β to 2.43 mAh / cm 2 By selecting higher-quality cylindrical casing and cap, the weight of the complete battery was reduced to 71.0g; by increasing the contact resistance of the current collector, R was measured. AC The Ω value was 3.40 mΩ, and the 0.2C discharge energy was measured to be 17.20 Wh, γ was measured to be 242 Wh / kg, and δ was measured to be 0.0140 mΩ·kg / Wh. The other conditions were the same as in Example 1.

[0068] IV. Performance Testing

[0069] (a) Capacity, energy and weight tests.

[0070] The complete cylindrical battery was left to stand at 25±2℃ for 12 hours, and its weight (m) was measured, including the cylindrical casing, core, electrolyte, cap, and outer film. It was then charged at a constant current of 0.2C to 4.20V, followed by constant voltage charging to a cutoff current of 0.05C, and left to stand for 30 minutes. Finally, it was discharged at a constant current of 0.2C to 2.50V, and the discharge capacity and discharge energy were recorded. The discharge energy (E) was obtained by integrating the voltage and current over time during the discharge process, and the mass energy density was calculated using the formula γ=1000E / m.

[0071] (ii) AC internal resistance test.

[0072] The battery was adjusted to 30% SOC and left to stand at 25±2℃ for 60 minutes. The AC internal resistance was measured using a 1kHz AC internal resistance meter. Each sample was tested three times, and the average value was taken as R. AC According to the formula δ=R AC / γ is used to calculate the internal resistance-energy density ratio.

[0073] (III) Positive electrode tethering test.

[0074] Disassemble the battery in an inert atmosphere, remove the positive electrode, clean it with DMC (dimethyl carbonate) to remove residual electrolyte, and vacuum dry it at 40°C to 60°C. Punch a positive electrode disc of known area and measure its coating areal density M. p A coin cell battery was assembled using lithium metal sheets as the counter electrode. Charge-discharge tests were conducted at 25±2℃ and 0.1C, with a voltage window of 3.0V to 4.3V. The specific discharge capacity was taken as Q. p The apparent single-sided areal capacity β of the positive electrode is calculated as β=M. p ×Q p Calculate using / 1000.

[0075] (iv) Negative electrode tethering test.

[0076] Disassemble the battery in an inert atmosphere, remove the negative electrode sheet, clean it with DMC to remove residual electrolyte, and vacuum dry it at 40°C to 60°C. Punch a negative electrode disc of known area, measure the coating surface density of the two working surfaces, and take the average value M. n A coin cell was assembled using lithium metal sheets as the counter electrode. Lithium insertion and extraction tests were conducted at 0.1C at 25±2℃, with a voltage window ranging from 0.005V to 1.5V. The reversible lithium extraction specific capacity was taken as Q. n .

[0077] (v) Test of the proportion of silicon capacity in the negative electrode.

[0078] The silicon capacity ratio of the negative electrode is obtained by integrating the capacity over the voltage range of the 0.1C coin cell delithiation curve of the negative electrode. Specifically, this includes the following steps: 1. Collect voltage V and capacity Q data during the lithium removal process of the negative electrode coin cell, and remove data points with voltage jumps, contact abnormalities, and capacity rebounds; 2. Establish interval references using graphite and silicon-carbon standard negative electrodes, and use the valley points in the dQ / dV curves to help determine the boundary voltage V between the graphite contribution interval and the silicon contribution interval. b ; 3. When no separate standard sample is established, V b Preferably, the local valley value located between the graphite peak group and the silicon-based broad peak in the dQ / dV curve within the range of 0.28V to 0.32V is selected; 4. From 0.005V to V b The increase in delithiation capacity within the range is denoted as the graphite contribution capacity Q. gr V b The increase in delithiation capacity up to 0.75V is denoted as the silicon contribution capacity Q. si ; 5. When the tail capacity in the 0.75V to 1.5V range is no more than 5% of the total delithiation capacity, this tail capacity is included in the graphite contribution capacity Q. gr When the tail volume is greater than 5%, Q is calculated after subtracting the tail baseline using a graphite standard sample. gr ; 6. Calculate the silicon capacity percentage using the formula: Silicon capacity percentage = Q si / (Q si + Q gr ) × 100% 7. When the calculated results are inconsistent with the Si elemental distribution trend in SEM / EDS (Scanning Electron Microscopy / Energy Dispersive X-ray Spectroscopy), the SEM / EDS results and the total specific capacity of the negative electrode should be used to adjust the V. b Perform correction, and the corrected V b It should still be within the range of 0.25V to 0.35V.

[0079] V. Performance Data

[0080] Table 1 Performance data of the embodiments

[0081] Table 2 Comparative Performance Data

[0082] VI. Performance Explanation

[0083] Comparing Examples 1, 3, and 4 with Comparative Examples 1 and 2, it can be seen that α is used to limit the thickness matching of the copper current collector relative to the aluminum current collector. When α is too low, the lateral conductive cross-sectional area of ​​the copper current collector is insufficient, and the winding tension and welding heat effects are more likely to cause uneven local current collection. Although the weight of the complete cell decreases and the apparent γ increases, R... AC The α value increases and δ tends to deteriorate. When α is too high, the inactive mass of the negative electrode current collector increases, and the proportion of active material that can be contributed per unit mass decreases. In Comparative Example 1, this is further accompanied by a decrease in β, resulting in a significant reduction in capacity and γ. Therefore, limiting α to 0.45 to 0.75 can balance the weight reduction of the negative electrode current collector, electron collection capacity, and winding processing stability.

[0084] Comparing Examples 1, 5, and 6 with Comparative Examples 1 and 3, it can be seen that β reflects the combined effect of the areal density of the positive electrode and the specific capacity of the positive electrode active material. When β is low, the capacity released per unit area of ​​the positive electrode is insufficient, and the core cannot provide enough active lithium storage within the same geometric space, resulting in a decrease in 0.2C capacity, energy, and γ. When β is high, the active material layer of the positive electrode thickens, the tortuosity of the channels and the resistance to liquid phase transport increase, the lithium ion diffusion path inside the high-nickel particles is prolonged, and the polarization of the positive electrode and the interfacial side reactions are aggravated during charging and discharging. AC And δ increases accordingly. Example 6 is still near the upper limit and the performance is acceptable, indicating that β needs to be related to η and R. AC Commonly limited.

[0085] Comparing Examples 1, 7, and 8 with Comparative Examples 3 and 4, it can be seen that η is used to constrain the redundancy of the negative electrode capacity relative to the positive electrode capacity. When η is too low, the lithium intercalation capacity of the negative electrode is insufficient, the negative electrode potential at the end of a full charge is closer to the lithium plating risk region, the local current density increases, and the SEI film (solid electrolyte interface film) continues to thicken, resulting in increased polarization under cycling and rate conditions. When η is too high, the areal density or effective area of ​​the negative electrode coating is too large. Although this can increase safety redundancy, it will introduce more unnecessary active materials and binders, increase the channel transport burden, and reduce mass utilization efficiency. Examples 7 and 8 show that when η is maintained between 1.02 and 1.14, a balance can be achieved between lithium plating prevention redundancy, mass energy density, and low internal resistance.

[0086] Comparing Examples 1, 2, and 11 with Comparative Example 4, it can be seen that the positive electrode particle gradation and Q... p Q nThe capacity of a material is largely determined by its proportion of silicon. In high-nickel layered cathodes, a higher proportion of polycrystalline particles promotes higher compaction and capacity release due to the secondary structure of the particles. However, an excessively high proportion can lead to grain boundary microcracks under cyclic stress and increase electrolyte side reactions. Increasing the proportion of single-crystal particles improves structural stability, but may decrease the available specific surface area and rate response. Silicon-carbon materials in the anode improve Q... n And γ, but the volume change of the silicon phase consumes electrolyte and promotes SEI reconstruction, requiring a graphite framework to share the burden of electron conduction and mechanical buffering. Comparative Example 4: Q after removing silicon and carbon n The energy density dropped to 360 mAh / g, indicating that a single graphite anode is insufficient to support the high energy density window of this case.

[0087] Comparing Examples 1, 9, and 10 with Comparative Examples 5 and 6, it can be seen that γ and δ are used to evaluate the combined relationship between battery-grade energy output and internal resistance. Example 9 maintains R by reducing the mass of structural components. AC Stability, with both γ and δ within their preferred ranges, indicates that lightweighting must be predicated on maintaining conductive connections and electrode transport without disruption. While Example 10 still falls within the broad scope of the claims, γ is significantly reduced due to increased weight and decreased energy. Comparative Example 5 shows R at γ reaching 270 Wh / kg. AC The energy density increased to 3.80 mΩ, and δ exceeded the limit, indicating that high energy density cannot alone represent low heat generation and high power capability. Comparative Example 6 deviated from α, β, γ, and δ simultaneously, demonstrating the role of multiple parameter constraints in eliminating inefficient circumvention schemes.

[0088] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure made using the content of the present invention specification, or any direct or indirect application in other related technical fields, shall also be included within the patent protection scope of the present invention.

Claims

1. A lightweight, high-energy-density cylindrical lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and a cylindrical shell for housing a wound core, wherein the wound core is mainly formed by winding the positive electrode, the separator, and the negative electrode; characterized in that: The positive electrode includes an aluminum current collector and a positive active material layer region and a positive uncoated region disposed on the surface of the aluminum current collector; the negative electrode includes a copper current collector and a negative active material layer region and a negative uncoated region disposed on the surface of the copper current collector. This cylindrical lithium-ion battery meets the following requirement: 3.4 ≤ 1000 α β η / γ≤10.8; Where 0.45≤α≤0.75, 2.45mAh / cm 2 ≤β≤3.15mAh / cm 2 , 1.02≤eta≤1.14, 250Wh / kg≤γ≤330Wh / kg; Define the foil thickness ratio as α, where α = t Cu / t Al , where t Cu t represents the thickness of the copper current collector. Al t represents the thickness of the aluminum current collector. Cu and t Al The units are all in μm; Define the apparent single-sided areal capacity of the positive electrode as β, where β = M p ×Q p / 1000, where M p The areal density of the positive electrode active material layer region after removing the aluminum current collector is expressed in mg / cm³. 2 Q p The discharge specific capacity of the positive electrode active material obtained from disassembly under 25±2℃ and 0.1C coin cell testing is expressed in mAh / g, and β is expressed in mAh / cm². 2 ; Define the capacity balancing factor as η, where η = C n / C p , where C p =M p ×A p ×Q p / 1000, C n =M n ×A n ×Q n / 1000, M n The average surface density of the negative electrode active material layer region after removing the copper current collector is expressed in mg / cm³. 2 Q n The reversible lithium-depletion capacity of the negative electrode active material obtained from disassembly under 25±2℃ and 0.1C coin cell testing is expressed in mAh / g (A). p A represents the effective reactive coating area of ​​the positive electrode within the same core. n The effective reactive coating area of ​​the negative electrode in the same core; The mass energy density is defined as γ, where γ = 1000E / m, E is the discharge energy obtained by the cylindrical lithium-ion battery at 0.2C at 25±2℃, in Wh, m is the complete battery weight of the cylindrical lithium-ion battery in g, and γ is in Wh / kg.

2. The cylindrical lithium-ion battery according to claim 1, characterized in that: The positive electrode active material in the positive electrode active material layer region includes layered lithium transition metal oxide with a nickel content of 88 mol% to 92 mol%, and the negative electrode active material in the negative electrode active material layer region includes graphite material and silicon-carbon material.

3. The cylindrical lithium-ion battery according to claim 1, characterized in that: The cylindrical lithium-ion battery satisfies 0.01 mΩ·kg / Wh ≤ δ ≤ 0.0125 mΩ·kg / Wh, and the internal resistance energy density ratio is defined as δ, where δ = R. AC / γ, where R AC The AC internal resistance of the cylindrical lithium-ion battery was measured using a 1kHz AC internal resistance meter after being placed at 25±2℃, 30% SOC, and for 60 minutes. The unit is mΩ.

4. The cylindrical lithium-ion battery according to claim 3, characterized in that: The cylindrical lithium-ion battery satisfies: 0.50≤α≤0.58, 2.75 mAh / cm². 2 ≤β≤3.10mAh / cm 2 , 1.03≤η≤1.07, 270Wh / kg≤γ≤330Wh / kg, and δ≤0.0105mΩ·kg / Wh.

5. The cylindrical lithium-ion battery according to claim 1, characterized in that: The thickness of the aluminum current collector is 11 μm to 13 μm, and the thickness of the copper current collector is 5.5 μm to 8.5 μm.

6. The cylindrical lithium-ion battery according to claim 5, characterized in that: The thickness of the copper current collector is 5.8 μm to 6.8 μm.

7. The cylindrical lithium-ion battery according to claim 1, characterized in that: The areal density of the positive electrode active material layer is 12.3 mg / cm³. 2 Up to 14.2 mg / cm 2 The compaction density of the positive electrode sheet is 3.40 g / cm³. 3 Up to 3.65 g / cm 3 The thickness of the positive electrode sheet is 86 μm to 92 μm.

8. The cylindrical lithium-ion battery according to claim 1, characterized in that: The average areal density of the negative electrode active material layer region is 5.35 mg / cm³. 2 Up to 6.10 mg / cm 2 The compaction density of the negative electrode sheet is 1.50 g / cm³. 3 Up to 1.66 g / cm 3 The thickness of the un-etched area of ​​the negative electrode sheet is 84 μm to 90 μm.

9. The cylindrical lithium-ion battery according to claim 2, characterized in that: The layered lithium transition metal oxide comprises polycrystalline particles and single-crystal particles, wherein the mass ratio of the polycrystalline particles to the single-crystal particles is 65:35 to 85:

15.

10. The cylindrical lithium-ion battery according to claim 1, characterized in that: The discharge specific capacity of the positive electrode active material at 25±2℃ and 0.1C coin cell test is 195mAh / g to 225mAh / g.

11. The cylindrical lithium-ion battery according to claim 1, characterized in that: The reversible lithium removal capacity of the negative electrode active material at 25±2℃ and 0.1C coin cell test is 500mAh / g to 525mAh / g, and the silicon capacity obtained by voltage range capacity integration of the negative electrode coin cell lithium removal curve is 44% to 47%.

12. The cylindrical lithium-ion battery according to claim 3, characterized in that: The cylindrical lithium-ion battery must satisfy at least one of the following conditions: (1) The 0.2C discharge capacity of the cylindrical lithium-ion battery is 4.95Ah to 5.10Ah; (2) The discharge energy at 0.2C is 17.8Wh to 18.3Wh; (3) The weight of the complete battery is 64g to 71g; (4) The cylindrical lithium-ion battery is a 21650 full-tab cylindrical battery or a 21700 full-tab cylindrical battery; (5) The AC internal resistance R AC ≤3.1mΩ; (6) The diaphragm comprises a polyolefin-based membrane and a single-sided ceramic coating, and the total thickness of the diaphragm is 9 μm to 12 μm.

13. An electrical appliance, characterized in that: Including the cylindrical lithium-ion battery according to any one of claims 1-12.

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