21650 full tab cylindrical lithium ion battery and screening method of 21650 full tab cylindrical lithium ion battery suitable for pulse high power application scenarios

Abstract

The application discloses a 21650 full-tab cylindrical lithium ion battery and a screening method of the 21650 full-tab cylindrical lithium ion battery suitable for a pulse high-power application scene, the nominal capacity of the cylindrical lithium ion battery is C Ah, and the following characteristics one to three are met; characteristic one, the voltage drop of the cylindrical lithium ion battery is less than or equal to 0.5 V when the cylindrical lithium ion battery is discharged at a 50*C rate pulse for 10 s at 25 DEG C and 50% SOC; characteristic two, the voltage drop of the cylindrical lithium ion battery is less than or equal to 0.8 V when the cylindrical lithium ion battery is discharged at a 70*C rate pulse for 5 s at 25 DEG C and 50% SOC; characteristic three, the maximum surface temperature rise of the cylindrical lithium ion battery is less than or equal to 15 DEG C / 10 s in the process of discharging at a 50*C rate pulse for 10 s at 25 DEG C and 50% SOC. The cylindrical lithium ion battery in the application can meet the demand of the pulse high-power application scene.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a screening method for 21650 full-tab cylindrical lithium-ion batteries and 21650 full-tab cylindrical lithium-ion batteries suitable for pulse high-power applications. Background Technology

[0002] With the rapid iteration and large-scale application of electric aircraft such as drones and eVTOL, various flight scenarios are placing more stringent and specialized demands on the comprehensive performance of their power batteries. Electric aircraft operate under complex and variable conditions. During critical flight phases such as takeoff and climb, attitude adjustments, and sudden acceleration, batteries need to deliver high-intensity power instantaneously to ensure the stability of the aircraft's power response and flight control. Unlike traditional new energy storage and vehicle batteries, aircraft power batteries do not require long-term stable discharge; they prioritize short-term, high-intensity power output. Therefore, providing a battery that meets the requirements of electric aircraft is of paramount importance.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a 21650 all-tab cylindrical lithium-ion battery and a screening method for 21650 all-tab cylindrical lithium-ion batteries suitable for pulse high-power applications, overcoming the problem that existing batteries cannot meet the needs of electric aircraft.

[0005] This invention is implemented as follows: In a first aspect, the present invention provides a 21650 all-tab cylindrical lithium-ion battery, wherein the negative electrode active material in the cylindrical lithium-ion battery comprises artificial graphite and silicon-carbon composite material, wherein the mass fraction of silicon-carbon composite material in the negative electrode active material is 15-20 wt%, and the mass fraction of silicon in the silicon-carbon composite material is 10-20%; The positive electrode active material in the cylindrical lithium-ion battery includes LiNi. x Co y Mn z M j O2, where 0.80≤x≤0.94, 0.01≤y, z, j≤0.1, x+y+z+j=1; the nominal capacity of the cylindrical lithium-ion battery is C Ah, and it satisfies the following characteristics one to three; Feature 1: The cylindrical lithium-ion battery has a voltage drop of ≤0.5V when pulsed discharged at a rate of 50*C for 10s at 25℃ and 50% SOC. Feature 2: The cylindrical lithium-ion battery has a voltage drop of ≤0.8V when pulsed discharged at a rate of 70*C for 5s at 25℃ and 50% SOC. Feature 3: The cylindrical lithium-ion battery, at 25°C and 50% SOC, experiences a maximum surface temperature rise of ≤15°C / 10s during a 50*C pulse discharge.

[0006] In an optional embodiment, the cylindrical lithium-ion battery has a voltage drop of ≤0.6V when pulsed discharged at a rate of 30*C for 30s at 25°C and 50% SOC. And / or, the voltage drop of the cylindrical lithium-ion battery at 0°C, 50% SOC, and a pulse discharge rate of 20*C for 10s is ≤0.7V.

[0007] In an optional embodiment, the maximum continuous discharge current of the cylindrical lithium-ion battery is ≥70A; wherein the maximum continuous discharge current is: at 25°C and 50% SOC, the maximum continuous discharge current is the maximum current value at which the cylindrical lithium-ion battery can maintain the cutoff voltage for 30 minutes without thermal runaway. And / or, the maximum pulse discharge current is ≥250A, wherein the maximum pulse discharge current is: at 25℃ and 50% SOC, a 3s pulse discharge is performed with a stepped increasing current, with a 60s cooling interval between each pulse. The maximum pulse discharge current is the maximum current value of the cylindrical lithium-ion battery that meets the 3s discharge time requirement, the voltage does not drop to the cutoff voltage after discharge, and there is no thermal runaway. In an optional embodiment, the maximum surface temperature of the cylindrical lithium-ion battery during the pulse discharge process is ≤85°C.

[0008] In an optional embodiment, the cylindrical lithium-ion battery includes a full-tab core, the two end faces of which are a positive full-tab flattened layer and a negative full-tab flattened layer, respectively, and the average thickness of the positive full-tab flattened layer and the negative full-tab flattened layer are respectively between 0.2-1.0 mm.

[0009] In an optional embodiment, the cylindrical lithium-ion battery retains ≥90% of its capacity after 500 pulse discharge cycles. Each pulse discharge cycle includes: pulse discharge at 25°C for 10 seconds at a rate of 50*C, resting for 5 minutes, then charging to full charge at a constant current and constant voltage of 0.5*C, and resting for 10 minutes.

[0010] In an optional embodiment, the electrolyte of the cylindrical lithium-ion battery includes LiPF6 and LiFSI, wherein the concentration of LiPF6 in the electrolyte is 0.8-1.2 mol / L and the concentration of LiFSI is 0.05-0.2 mol / L.

[0011] In an optional embodiment, the cylindrical lithium-ion battery has an outer diameter of 20.8-21.8 mm and a height of 64.8-66.2 mm.

[0012] Secondly, the present invention provides a screening method for 21650 all-tab cylindrical lithium-ion batteries suitable for pulse high-power application scenarios, wherein the nominal capacity of the cylindrical lithium-ion battery is C Ah, and cylindrical lithium-ion batteries that meet the following characteristics one to four are screened. Feature 1: The cylindrical lithium-ion battery has a voltage drop of ≤0.5V when pulsed discharged at a rate of 50*C for 10s at 25℃ and 50% SOC. Feature 2: The cylindrical lithium-ion battery has a voltage drop of ≤0.8V when pulsed discharged at a rate of 70*C for 5s at 25℃ and 50% SOC. Feature 3: The cylindrical lithium-ion battery, at 25°C and 50% SOC, experiences a maximum surface temperature rise of ≤15°C / 10s during a 10s pulse discharge at a 50*C rate. Feature 4: The cylindrical lithium-ion battery retains ≥90% of its capacity after 500 pulse discharge cycles. Each pulse discharge cycle includes: pulse discharge at 25°C for 10 seconds at a rate of 50*C, rest for 5 minutes, then charge at 0.5C constant current and constant voltage to full charge, and rest for 10 minutes.

[0013] In an optional embodiment, the cylindrical lithium-ion battery has a voltage drop of ≤0.6V when pulsed discharged at a rate of 30*C for 30s at 25°C and 50% SOC. And / or, the cylindrical lithium-ion battery has a voltage drop of ≤0.7V when pulsed discharged at a rate of 20*C for 10s at 0℃ and 50% SOC. And / or, the maximum continuous discharge current of the cylindrical lithium-ion battery is ≥70A; wherein the maximum continuous discharge current is: at 25℃ and 50% SOC, the maximum continuous discharge current is the maximum current value at which the cylindrical lithium-ion battery can maintain the discharge without reaching the cutoff voltage and without thermal runaway for 30 minutes. And / or, the maximum pulse discharge current is ≥250A, wherein the maximum pulse discharge current is: at 25℃ and 50% SOC, a 3s pulse discharge is performed with a stepped increasing current, with a 60s cooling interval between each pulse. The maximum pulse discharge current is the maximum current value of the cylindrical lithium-ion battery that meets the 3s discharge time requirement, the voltage does not drop to the cutoff voltage after discharge, and there is no thermal runaway. And / or, the maximum surface temperature of the cylindrical lithium-ion battery during the pulse discharge process is ≤85°C.

[0014] The present invention has the following beneficial effects: This application achieves coordinated performance limitations of pulse voltage drop, pulse temperature rise, and cycle capacity retention by synergistically defining the power, thermal, and life characteristics of the battery cell. This ensures the output stability of the cylindrical lithium-ion battery under different pulse conditions by meeting the conditions of ≤0.5V voltage drop at 50*C / 10s and ≤0.8V voltage drop at 70*C / 5s. Surface temperature rise ≤15℃ / 10s and maximum surface temperature ≤85℃ can prevent the risk of thermal runaway under extreme power conditions, thus meeting the needs of high-power pulse applications. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of the 21650 cylindrical lithium-ion battery in Example 1 of this embodiment; Figure 2 This is a voltage-time curve of the 21650 cylindrical lithium-ion battery in Example 1 during a 10s pulse discharge at 50°C. Figure 3 This is a comparison graph showing the voltage drop of the 21650 cylindrical lithium-ion batteries in Examples 1-3 and Comparative Examples 1-3 after a 50*C / 10s pulse discharge. Figure 4 This is a comparison of the surface temperature rise of the 21650 cylindrical lithium-ion batteries in Examples 1-3 and Comparative Examples 1-3 after a 50*C / 10s pulse discharge. Figure 5 The graph shows a comparison of the capacity retention of 21650 cylindrical lithium-ion batteries in Examples 1-3 and Comparative Examples 1-3 after 500 pulse cycles.

[0017] Illustration: 100 - Core; 200 - Housing; 300 - End face of the full electrode tab. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0019] The applicant's research found that if the discharge performance of power batteries used in electric aircraft such as drones and eVTOL is limited to the conventional rate, it will make it easy for competitors to achieve instantaneous high power by sacrificing voltage stability; if the Joule heat and polarization heat under high rate pulse cannot be effectively controlled, the risk of cell thermal runaway will increase sharply.

[0020] Therefore, embodiments of the present invention provide a 21650 all-tab cylindrical lithium-ion battery. The negative electrode active material in the cylindrical lithium-ion battery includes artificial graphite and silicon-carbon composite material. The mass fraction of the silicon-carbon composite material in the negative electrode active material is 15-20 wt%, for example, 15.0 wt%, 15.5 wt%, 16.0 wt%, 16.5 wt%, 17.0 wt%, 17.5 wt%, 18.0 wt%, 18.5 wt%, 19.0 wt%, 19.5 wt%, and 20.0 wt%. The mass fraction of silicon in the silicon-carbon composite material is 10-20%, for example, 10.0%, 11.0%, 12.0%, 13.0%, 14.0%, 15.0%, 16.0%, 17.0%, 18.0%, 19.0%, and 20.0%. The positive electrode active material in the cylindrical lithium-ion battery includes LiNi. x Co y Mn z M j O2, where 0.80≤x≤0.94, for example 0.800, 0.814, 0.828, 0.842, 0.856, 0.870, 0.884, 0.898, 0.912, 0.926, 0.940, 0.01≤y, z, j≤0.1, x+y+z+j=1; the nominal capacity of the cylindrical lithium-ion battery is C Ah, and it satisfies the following characteristics one to three; Feature 1: The cylindrical lithium-ion battery, at 25°C and 50% SOC, experiences a voltage drop of ≤0.5V during a 10s pulse discharge at a 50*C rate, for example, 0.50V, 0.45V, 0.40V, 0.35V, 0.30V, 0.25V, 0.20V, 0.15V, 0.10V, or 0.05V. Feature 2: The cylindrical lithium-ion battery, at 25°C and 50% SOC, has a voltage drop ≤0.8V when pulsed discharged at a rate of 70*C for 5s, for example, 0.80V, 0.72V, 0.64V, 0.56V, 0.48V, 0.40V, 0.32V, 0.24V, 0.16V, or 0.08V. Feature 3: When the cylindrical lithium-ion battery is pulsed at a rate of 50*C for 10s at 25℃ and 50% SOC, the maximum surface temperature rise is ≤15℃ / 10s, for example 15℃ / 10s, 13℃ / 10s, 11℃ / 10s, 9℃ / 10s, 7℃ / 10s, 5℃ / 10s, 3℃ / 10s, 1℃ / 10s.

[0021] This application achieves coordinated performance limitations of pulse voltage drop, pulse temperature rise, and cycle capacity retention by synergistically defining the power, thermal, and life characteristics of the battery cell. This ensures the output stability of the cylindrical lithium-ion battery under different pulse conditions by meeting the conditions of ≤0.5V voltage drop at 50*C / 10s and ≤0.8V voltage drop at 70*C / 5s. Surface temperature rise ≤15℃ / 10s and maximum surface temperature ≤85℃ can prevent the risk of thermal runaway under extreme power conditions, thus meeting the needs of high-power pulse applications.

[0022] It should be noted that the silicon-carbon composite material may include a silicon-carbon material matrix and a carbon coating layer. In some embodiments, the mass fraction of the carbon coating layer in the silicon-carbon composite material may be 2-10%.

[0023] In an optional embodiment, the cylindrical lithium-ion battery has a voltage drop of ≤0.6V when pulsed discharged at a rate of 30*C for 30s at 25℃ and 50% SOC, for example, 0.60V, 0.54V, 0.48V, 0.42V, 0.36V, 0.30V, 0.24V, 0.18V, 0.12V, or 0.06V; this is beneficial for ensuring the stability of the system power supply under continuous high-power conditions such as takeoff / hovering.

[0024] And / or, the cylindrical lithium-ion battery has a voltage drop of ≤0.7V when pulsed discharged at a rate of 20*C for 10s at 0℃ and 50% SOC, for example 0.70V, 0.63V, 0.56V, 0.49V, 0.42V, 0.35V, 0.28V, 0.21V, 0.14V, or 0.07V, at low temperatures, to enhance low-temperature pulse response capability and solve the risk of power interruption caused by sudden voltage drop in eVTOL during winter take-off and landing or in high-altitude low-temperature scenarios.

[0025] In an optional embodiment, the maximum continuous discharge current of the cylindrical lithium-ion battery is ≥70A, for example, 70A, 72A, 74A, 76A, 78A, 80A, 82A, 84A, 86A, 88A, or 90A; wherein the maximum continuous discharge current is defined as the maximum current value at 25°C and 50% SOC, with constant current discharge in a stepped manner, each step lasting 30 minutes, and the maximum current value at which the cylindrical lithium-ion battery can maintain its cutoff voltage for 30 minutes without thermal runaway. This meets the steady-state high-load requirements of drone cruise, eVTOL horizontal forward flight, etc., ensuring that the output does not decay over a long period of time and avoiding power interruption caused by heat accumulation.

[0026] And / or, the maximum pulse discharge current is ≥250A, such as 250A, 255A, 260A, 265A, 270A, 275A, 280A, 285A, 290A, 300A, where the maximum pulse discharge current is: at 25℃ and 50% SOC, a 3s pulse discharge is performed with a stepped increasing current, with a 60s cooling interval between each pulse. The maximum pulse discharge current is the maximum current value that meets the 3s discharge duration of a cylindrical lithium-ion battery, the voltage does not drop to the cutoff voltage after discharge, and there is no thermal runaway; supporting transient peak power requirements such as vertical take-off and landing and emergency avoidance.

[0027] In an optional embodiment, the maximum surface temperature of the cylindrical lithium-ion battery during the pulse discharge process is ≤85°C, for example, 85°C, 80°C, 75°C, 70°C, 65°C, 60°C, 55°C, 50°C, 45°C, or 40°C, which helps to avoid thermal runaway.

[0028] In an optional embodiment, the cylindrical lithium-ion battery includes a full-tab core 100, the two end faces of which are a positive full-tab flattened layer and a negative full-tab flattened layer, respectively. The average thickness of the positive and negative full-tab flattened layers is between 0.2-1.0 mm, for example, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, and 1.0 mm. The full-tab flattened layer increases the number of current collection points and reduces the single-point current density, which is beneficial for suppressing ohmic polarization and local Joule heating.

[0029] In an optional embodiment, the cylindrical lithium-ion battery retains a capacity of ≥90% after 500 pulse discharge cycles, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 100%. Each pulse discharge cycle includes: pulse discharge at 25°C for 10 seconds at a rate of 50*C, resting for 5 minutes, then charging at 0.5C constant current and constant voltage to full charge, and resting for 10 minutes. A capacity retention of ≥90% after 500 pulse cycles ensures the structural stability of the cell under long-term pulse abuse.

[0030] In an optional embodiment, the electrolyte of the cylindrical lithium-ion battery comprises LiPF6 and LiFSI, wherein the concentration of LiPF6 in the electrolyte is 0.8-1.2 mol / L, for example 0.80 mol / L, 0.84 mol / L, 0.88 mol / L, 0.92 mol / L, 0.96 mol / L, 1.00 mol / L, 1.04 mol / L, 1.08 mol / L, 1.12 mol / L, 1.16 mol / L. The concentrations of LiFSI are 0.05-0.2 mol / L, such as 0.050 mol / L, 0.067 mol / L, 0.083 mol / L, 0.100 mol / L, 0.117 mol / L, 0.133 mol / L, 0.150 mol / L, 0.167 mol / L, 0.183 mol / L, and 0.200 mol / L. The dual salts are beneficial for synergistically reducing interfacial impedance.

[0031] This application reduces the current density and ohmic polarization in the tab region through a full-tab structure, combined with a high-nickel cathode to provide a high-specific-capacity ion source, a silicon-carbon anode to provide high lithium intercalation capacity and low polarization characteristics, and a LiPF6. 6 The / LiFSI dual lithium salt electrolyte system optimizes high and low temperature ion conduction, resulting in a systematic cylindrical lithium-ion battery suitable for pulsed high-power applications, encompassing structure, materials, and electrolyte.

[0032] In an optional embodiment, the outer diameter of the cylindrical lithium-ion battery casing 200 is 20.8-21.8 mm, for example 20.80 mm, 20.84 mm, 20.88 mm, 20.92 mm, 20.96 mm, 21.00 mm, 21.04 mm, 21.08 mm, 21.12 mm, 21.16 mm, 21.20 mm, 21.50 mm, 21.80 mm, and the height is 64.8-66.2 mm, for example 64.80 mm, 64.84 mm, 64.88 mm, 64.92 mm, 64.96 mm, 65.00 mm, 65.04 mm, 65.08 mm, 65.12 mm, 65.16 mm, 65.20 mm, 65.50 mm, 65.80 mm, 66.00 mm, 66.20 mm.

[0033] The present invention also provides a screening method for cylindrical lithium-ion batteries suitable for pulse high-power applications, wherein the nominal capacity of the cylindrical lithium-ion batteries is C Ah, and cylindrical lithium-ion batteries that meet the following characteristics one to four are screened. Feature 1: The cylindrical lithium-ion battery has a voltage drop of ≤0.5V when pulsed discharged at a rate of 50*C for 10s at 25℃ and 50% SOC. Feature 2: The cylindrical lithium-ion battery has a voltage drop of ≤0.8V when pulsed discharged at a rate of 70*C for 5s at 25℃ and 50% SOC. Feature 3: The cylindrical lithium-ion battery, at 25°C and 50% SOC, experiences a maximum surface temperature rise of ≤15°C / 10s during a 10s pulse discharge at a 50*C rate. Feature 4: The cylindrical lithium-ion battery retains ≥90% of its capacity after 500 pulse discharge cycles. Each pulse discharge cycle includes: pulse discharge at 25°C for 10 seconds at a rate of 50*C, rest for 5 minutes, then charge at 0.5C constant current and constant voltage to full charge, and rest for 10 minutes.

[0034] In an optional embodiment, the cylindrical lithium-ion battery has a voltage drop of ≤0.6V when pulsed discharged at a rate of 30*C for 30s at 25°C and 50% SOC. And / or, the cylindrical lithium-ion battery has a voltage drop of ≤0.7V when pulsed discharged at a rate of 20*C for 10s at 0℃ and 50% SOC. And / or, the maximum continuous discharge current of the cylindrical lithium-ion battery is ≥70A; wherein the maximum continuous discharge current is: at 25℃ and 50% SOC, the maximum continuous discharge current is the maximum current value at which the cylindrical lithium-ion battery can maintain the discharge without reaching the cutoff voltage and without thermal runaway for 30 minutes. And / or, the maximum pulse discharge current is ≥250A, wherein the maximum pulse discharge current is: at 25℃ and 50% SOC, a 3s pulse discharge is performed with a stepped increasing current, with a 60s cooling interval between each pulse. The maximum pulse discharge current is the maximum current value of the cylindrical lithium-ion battery that meets the 3s discharge time requirement, the voltage does not drop to the cutoff voltage after discharge, and there is no thermal runaway. And / or, the maximum surface temperature of the cylindrical lithium-ion battery during the pulse discharge process is ≤85°C.

[0035] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0036] Example 1 This embodiment provides a method for preparing a cylindrical lithium-ion battery, specifically including: Positive electrode preparation: LiNiO2 is used. 85 Co0. 075 Mn0. 075 O2 (NCM85), conductive carbon black Super P, carbon nanotubes (CNTs) and polyvinylidene fluoride (PVDF) are dispersed in NMP at a mass ratio of 96.0:1.5:1.0:1.5, coated on an aluminum foil current collector, dried and rolled to obtain a positive electrode sheet.

[0037] Negative electrode preparation: Artificial graphite and silicon-carbon composite material (silicon mass fraction 15%, containing carbon coating layer with carbon coating layer mass fraction of 5%) are mixed at a mass ratio of 82:18, and then mixed with conductive carbon black, sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) at a mass ratio of 95.0:2.0:1.5:1.5 to form a slurry. The slurry is coated on copper foil current collector, dried and rolled to obtain the negative electrode.

[0038] Preparation of core 100: Using the full-tab core 100 structure, the positive electrode sheet, negative electrode sheet and ceramic coated diaphragm are wound into an electrode group. The positive and negative electrodes are respectively led out from both ends of the electrode group and flattened to form the full-tab end face 300. The average thickness of the flattened layer of the positive electrode full tab and the flattened layer of the negative electrode full tab are 0.76mm and 0.63mm, respectively.

[0039] Electrolyte preparation: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 20:50:30. 1.0 mol / L LiPF6 and 0.10 mol / L LiFSI are added as a double lithium salt system. 2% by mass of vinylene carbonate (VC) is added as a film-forming additive.

[0040] Battery assembly: The core 100 is placed into a cylindrical shell 200 with an outer diameter of 21.0 mm and a height of 65.0 mm, the electrolyte is injected, and then the shell is sealed to obtain the desired battery assembly. Figure 1 The battery shown was subjected to capacity testing after formation, and its nominal capacity was measured to be C = 4.8 Ah.

[0041] Example 2 This embodiment provides a method for preparing a cylindrical lithium-ion battery, which differs from Embodiment 1 only in that NCM85 is replaced with LiNi0. 90 Co0. 05 Mn0. 05 O2 (NCM90), silicon mass fraction in silicon-carbon composite material is 12%. Electrolyte concentration is 1.2 mol / L LiPF6, LiFSI concentration is 0.15 mol / L. Nominal capacity C = 5.0 Ah was measured.

[0042] Example 3 This embodiment provides a method for preparing a cylindrical lithium-ion battery, which differs from Embodiment 1 only in that NCM85 is replaced with LiNi0. 88 Co0. 06 Mn0. 06 O2 (NCM88), silicon-carbon composite material with a silicon mass fraction of 18%. The electrolyte contains 0.9 mol / L LiPF6 and 0.08 mol / L LiFSI. The measured nominal capacity C = 4.5 Ah.

[0043] Comparative Example 1 This embodiment provides a method for preparing a cylindrical lithium-ion battery, differing from Embodiment 1 only in that it employs a traditional single-tab core 100 structure (two tabs leading out from one side), and the electrolyte does not contain LiFSI. The nominal capacity was measured to be C = 4.8 Ah.

[0044] Comparative Example 2 This embodiment provides a method for preparing a cylindrical lithium-ion battery, which differs from Embodiment 1 only in that NCM85 is replaced with LiNi0. 50 Co0. 20 Mn0. 30 O2 (NCM523, x=0.50, not in the range of 0.80~0.94), the negative electrode active material is artificial graphite (without silicon-carbon composite material), and the electrolyte does not contain LiFSI. The nominal capacity was measured to be C=4.8Ah.

[0045] Comparative Example 3 This embodiment provides a method for preparing a cylindrical lithium-ion battery, which differs from Embodiment 1 only in that NCM85 is replaced with LiNi0. 92 Co0. 04Mn0. 04 O2 (NCM92, x=0.92) was used as the negative electrode. The silicon-carbon composite material contained 25% silicon by mass and had no carbon coating. The electrolyte contained 1.5 mol / L LiPF6 and did not contain LiFSI. The nominal capacity was measured to be C=4.5Ah.

[0046] The performance of the cylindrical lithium-ion batteries prepared in the above embodiments and comparative examples was tested under the following conditions: 1. Nominal capacity C: At 25℃, charge at a constant current and constant voltage of 0.33C to full charge, then discharge at a constant current of 0.33C to the cutoff voltage, and record the discharge capacity.

[0047] 2. Pulse discharge voltage drop: Under an environment of 25℃ (or 0℃) and 50% SOC, a constant current pulse discharge is performed at a specified rate (e.g., 50*C, 70*C, 30*C, 20*C) for a specified duration (10s, 5s, 30s). The difference ΔV (V) between the discharge start voltage and the discharge cutoff voltage is recorded.

[0048] 3. Surface temperature rise during pulse discharge: At 25℃ and 50% SOC, during a 10s pulse discharge at a rate of 50*C, a K-type thermocouple attached to the middle of the battery casing 200 was used to monitor the surface temperature in real time and record the difference (℃) between the highest surface temperature of the battery and the ambient temperature during the pulse cycle.

[0049] 4. Maximum continuous discharge current: At 25℃ and 50% SOC, constant current discharge is performed with step-increasing current, each step lasting 30 minutes. The maximum current value (A) that the battery can maintain for 30 minutes without reaching the cutoff voltage and without thermal runaway is recorded.

[0050] 5. Maximum pulse discharge current: At 25℃ and 50% SOC, a 3-second pulse discharge was performed with a stepped increasing current. Each pulse was cooled for 60 seconds. The maximum current (A) that the battery could withstand for more than 3 seconds without reaching the cutoff voltage and without thermal runaway was recorded.

[0051] 6. Pulse discharge cycle: At 25℃, each cycle consists of: pulse discharge at a rate of 50*C for 10s, rest for 5min, then charge at a constant current and constant voltage of 0.5C to full charge, and rest for 10min; repeat this cycle 500 times, and calculate the ratio of the discharge capacity after the 500th cycle to the discharge capacity of the first cycle.

[0052] 7. Maximum surface temperature: Record the highest absolute temperature (°C) of the battery casing surface during all the pulse tests described above.

[0053] The battery structure, materials, and other parameters of each embodiment and comparative example are summarized in Table 1. Some test results are shown in [Table 1]. Figure 2-5 .

[0054] Table 1 Comparison of Battery Structure and Material Design Parameters

[0055] The high-power pulse performance and cycle test results of the batteries in each embodiment and comparative example are summarized in Table 2.

[0056] Table 2 High-power pulse performance and cycle test results

[0057] Note: Comparative Example 1 suffers from excessive current density in the tab region due to its monotab structure, resulting in severe polarization and overheating of the tab; Comparative Example 2 suffers from insufficient ion transport kinetics due to its low nickel content, lack of silicon and carbon, and absence of LiFSI in the positive electrode; Comparative Example 3 suffers from runaway expansion of the high-silicon uncoated negative electrode and increased viscosity of the high-concentration electrolyte, leading to a sharp deterioration in cycle performance.

[0058] As can be seen from Tables 1 and 2, Examples 1-3 meet the requirements for extreme pulse power applications. Comparative Example 1 demonstrates that the traditional single-tab structure cannot meet the voltage drop and temperature rise requirements of extreme pulses above 50°C, and the capacity retention rate after 500 pulse cycles is only 72% (<90%). During the cycle, the diaphragm shrinks due to overheating of the tab, and the internal resistance increases sharply. Comparative Example 2 demonstrates that without the synergistic effect of high-nickel cathode, silicon-carbon anode, and LiFSI, the cell power density and low-temperature performance deteriorate significantly, and the specific capacity and rate performance are insufficient. Without the high rate support of silicon-carbon anode and LiFSI, the overall power output deteriorates significantly. Comparative Example 3 demonstrates that when the silicon content of the anode is too high and there is no carbon coating, and the electrolyte concentration is too high, although the initial capacity is high, the cycle stability and thermal safety are severely deteriorated. Although the high-nickel cathode provides a high initial capacity, the volume expansion of the high-silicon uncoated anode under extreme pulses is severe (>35%), leading to particle breakage and continuous thickening of the SEI film. At the same time, the excessively high concentration of LiPF6 causes an increase in electrolyte viscosity and interfacial impedance, both of which together lead to a rapid decline in cycle performance.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A 21650 all-tab cylindrical lithium-ion battery, characterized in that, The negative electrode active material in the cylindrical lithium-ion battery includes artificial graphite and silicon-carbon composite material, wherein the mass fraction of silicon-carbon composite material in the negative electrode active material is 15-20 wt%, and the mass fraction of silicon in the silicon-carbon composite material is 10-20%. The positive electrode active material in the cylindrical lithium-ion battery includes LiNi. x Co y Mn z M j O2, where 0.80≤x≤0.94, 0.01≤y, z, j≤0.1, x+y+z+j=1; the nominal capacity of the cylindrical lithium-ion battery is C Ah, and it satisfies the following characteristics one to three; Feature 1: The cylindrical lithium-ion battery has a voltage drop of ≤0.5V when pulsed discharged at a rate of 50*C for 10s at 25℃ and 50% SOC. Feature 2: The cylindrical lithium-ion battery has a voltage drop of ≤0.8V when pulsed discharged at a rate of 70*C for 5s at 25℃ and 50% SOC. Feature 3: The cylindrical lithium-ion battery, at 25°C and 50% SOC, experiences a maximum surface temperature rise of ≤15°C / 10s during a 50*C pulse discharge.

2. The 21650 all-tab cylindrical lithium-ion battery according to claim 1, characterized in that, The cylindrical lithium-ion battery has a voltage drop of ≤0.6V when pulsed discharged at a rate of 30*C for 30s at 25℃ and 50% SOC. And / or, the voltage drop of the cylindrical lithium-ion battery at 0°C, 50% SOC, and a pulse discharge rate of 20*C for 10s is ≤0.7V.

3. The 21650 all-tab cylindrical lithium-ion battery according to claim 1, characterized in that, The maximum continuous discharge current of the cylindrical lithium-ion battery is ≥70A; wherein the maximum continuous discharge current is: at 25℃ and 50% SOC, constant current discharge with step-increasing current, each step lasting 30min, the maximum continuous discharge current is the maximum current value at which the cylindrical lithium-ion battery can maintain the cutoff voltage for 30min without thermal runaway. And / or, the maximum pulse discharge current is ≥250A, wherein the maximum pulse discharge current is: at 25℃ and 50% SOC, a 3s pulse discharge is performed with a stepped increasing current, with a 60s cooling interval between each pulse. The maximum pulse discharge current is the maximum current value of the cylindrical lithium-ion battery that meets the 3s discharge duration requirement, the voltage does not drop to the cutoff voltage after discharge, and there is no thermal runaway.

4. The 21650 all-tab cylindrical lithium-ion battery according to claim 1, characterized in that, The maximum surface temperature of the cylindrical lithium-ion battery during the pulse discharge process is ≤85℃.

5. The 21650 all-tab cylindrical lithium-ion battery according to claim 1, characterized in that, The cylindrical lithium-ion battery includes a full-tab core, and the two end faces of the full-tab core are a positive full-tab flattened layer and a negative full-tab flattened layer, respectively. The average thickness of the positive full-tab flattened layer and the negative full-tab flattened layer are respectively between 0.2-1.0 mm.

6. The 21650 all-tab cylindrical lithium-ion battery according to claim 1, characterized in that, The cylindrical lithium-ion battery retains ≥90% of its capacity after 1000 pulse discharge cycles. Each pulse discharge cycle includes: pulse discharge at 25°C for 10 seconds at a rate of 50*C, rest for 5 minutes, then charge at 0.5*C at constant current and constant voltage to full charge, and rest for 10 minutes.

7. The 21650 all-tab cylindrical lithium-ion battery according to claim 1, characterized in that, The electrolyte of the cylindrical lithium-ion battery includes LiPF6 and LiFSI, wherein the concentration of LiPF6 in the electrolyte is 0.8-1.2 mol / L and the concentration of LiFSI is 0.05-0.2 mol / L.

8. The 21650 all-tab cylindrical lithium-ion battery according to claim 1, characterized in that, The cylindrical lithium-ion battery has an outer diameter of 20.8-21.8 mm and a height of 64.8-66.2 mm.

9. A method for screening 21650 all-tab cylindrical lithium-ion batteries suitable for pulsed high-power applications, characterized in that, The nominal capacity of the cylindrical lithium-ion battery is C Ah. Cylindrical lithium-ion batteries that meet the following characteristics one to four are selected. Feature 1: The cylindrical lithium-ion battery has a voltage drop of ≤0.5V when pulsed discharged at a rate of 50*C for 10s at 25℃ and 50% SOC. Feature 2: The cylindrical lithium-ion battery has a voltage drop of ≤0.8V when pulsed discharged at a rate of 70*C for 5s at 25℃ and 50% SOC. Feature 3: The cylindrical lithium-ion battery, at 25°C and 50% SOC, experiences a maximum surface temperature rise of ≤15°C / 10s during a 10s pulse discharge at a 50*C rate. Feature 4: The cylindrical lithium-ion battery retains ≥90% of its capacity after 500 pulse discharge cycles. Each pulse discharge cycle includes: pulse discharge at 25°C for 10 seconds at a rate of 50*C, rest for 5 minutes, then charge at 0.5*C at constant current and constant voltage until fully charged, and rest for 10 minutes.

10. The screening method for 21650 all-tab cylindrical lithium-ion batteries suitable for pulsed high-power applications according to claim 9, characterized in that, The cylindrical lithium-ion battery has a voltage drop of ≤0.6V when pulsed discharged at a rate of 30*C for 30s at 25℃ and 50% SOC. And / or, the cylindrical lithium-ion battery has a voltage drop of ≤0.7V when pulsed discharged at a rate of 20*C for 10s at 0℃ and 50% SOC. And / or, the maximum continuous discharge current of the cylindrical lithium-ion battery is ≥70A; wherein the maximum continuous discharge current is: at 25℃ and 50% SOC, the maximum continuous discharge current is the maximum current value at which the cylindrical lithium-ion battery can maintain the discharge without reaching the cutoff voltage and without thermal runaway for 30 minutes. And / or, the maximum pulse discharge current is ≥250A, wherein the maximum pulse discharge current is: at 25℃ and 50% SOC, a 3s pulse discharge is performed with a stepped increasing current, with a 60s cooling interval between each pulse. The maximum pulse discharge current is the maximum current value of the cylindrical lithium-ion battery that meets the 3s discharge time requirement, the voltage does not drop to the cutoff voltage after discharge, and there is no thermal runaway. And / or, the maximum surface temperature of the cylindrical lithium-ion battery during the pulse discharge process is ≤85°C.

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