High-rate lithium ion battery

Abstract

The invention relates to the technical field of battery preparation, and particularly discloses a high-rate lithium ion battery, which improves the rate performance, cycle performance and thermal safety of the battery by controlling the relation among the infiltration time t of an electrolyte on a negative plate, the weight of a solid electrolyte interface film (SEI film) and the capacity c of a positive plate. The capacity retention ratio of the prepared battery after 500 times of charge and discharge cycles at the rate of 0.2 C / 10C is 81% or above, the capacity retention ratio of charge and discharge at the rate of 0.2 C / 15C is 85% or above, and the temperature rise rate of discharge at the rate of 15C is 0.6-0.9 DEG C / (s * Ah); and meanwhile, by controlling the infiltration time of the electrolyte on the negative plate, the high-rate discharge performance of the battery is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery preparation, and in particular to a high-rate lithium-ion battery. Background Art

[0002] Lithium-ion batteries, due to their high specific energy, long cycle life, and rechargeability, are widely used in a variety of fields, including power tools, automobiles, energy storage, and aerospace. With the continuous advancement of technology, the market performance requirements for lithium-ion batteries are becoming increasingly diverse and stringent. In the power tool field, these batteries must not only have high energy density and rapid charge and discharge capabilities (i.e., high power), but also exhibit excellent cycle performance to ensure stable performance during long-term use.

[0003] However, achieving high power often leads to a decrease in cycle performance. This is because the rate of chemical reactions within the battery increases during high power output, accelerating the aging of electrode materials and the decomposition of the electrolyte. Furthermore, high-power operation can cause a significant increase in battery temperature, which not only affects the cycle life but also poses a threat to the battery's overall safety. Therefore, developing new materials and battery designs to improve the battery's chemical stability under high-power operation has become a current research hotspot. With the advancement of related technologies, future lithium-ion batteries are expected to achieve both high power output and a balance between cycle life and safety, providing a more reliable solution for applications such as power tools.

[0004] Chinese patent document CN202111252288.8 discloses a battery comprising a positive electrode sheet, a negative electrode sheet, a separator disposed between the positive electrode sheet and the negative electrode sheet, and a non-aqueous electrolyte; the non-aqueous electrolyte comprises a non-aqueous organic solvent, wherein the non-aqueous organic solvent comprises at least ethyl propionate; the content of ethyl propionate in the non-aqueous electrolyte is AEP (unit %), the contact area between the separator and the negative electrode is S negative electrode (unit m 2 ), the battery capacity is C (unit Ah), then AEP, S negative electrode, and C need to satisfy the following relationship: 0.5≤AEP / (S negative electrode / C)≤60. By rationally designing the content of ethyl propionate in the electrolyte, the contact area between the diaphragm and the negative electrode, and the battery capacity, the adhesion between the diaphragm and the negative electrode can be improved, the cycle life of the battery can be improved, the battery cycle expansion can be reduced, and the low-temperature performance of the battery can be taken into account. However, the cycle performance of the prepared battery still needs to be further improved. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a high-rate lithium-ion battery.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A high-rate lithium-ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. A solid electrolyte interface film is formed on the surface of the negative electrode active material layer. The high-rate lithium-ion battery satisfies the relationship: |t-(783m-0.55c+110)|≤10;

[0008] Wherein, t represents the electrolyte infiltration time on the negative electrode sheet, in seconds;

[0009] m represents the weight of the solid electrolyte interface film, in mg / cm 2 ;

[0010] c represents the positive electrode capacity, in mA·h / g.

[0011] In the technical solution disclosed in the present invention, the high-rate lithium-ion battery satisfies the relationship: |t-(783m-0.55c+110)|≤5.

[0012] In the technical solution disclosed in the present invention, the infiltration time t of the electrolyte on the negative electrode sheet satisfies the relationship: 100s≤t≤200s. For example, 100s, 110s, 120s, 130s, 140s, 150s, 160s, 170s, 180s, 190s, and 200s can be selected, but are not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0013] The soaking time t reflects the rate of electrolyte transfer through the electrode pores. A too low soaking time t indicates too low pore impedance in the negative electrode. This leads to excessively high porosity or large pore size in the electrode material, which can reduce the electrode's mechanical strength and structural stability, making the electrode structure looser. During charge and discharge, the volume expansion and contraction of the electrode material can lead to collapse of the electrode structure and easy shedding of active materials, resulting in rapid capacity decay and shortened cycle life. Furthermore, the contact area between the electrode and the electrolyte can be excessively large, increasing the probability of side reactions and reducing battery safety. A too high soaking time t increases the transport resistance of lithium ions through the electrode pores, slowing ion diffusion. During charge and discharge, lithium ions have difficulty quickly entering and exiting the electrode material, limiting the battery's charge and discharge rate and reducing its rate performance. It also leads to uneven lithium ion concentration distribution on the electrode surface, increasing the electrode's polarization. This not only prevents the battery from fully utilizing the active materials at high rates, reducing energy density, but also causes the battery to heat more easily during high-rate charge and discharge, affecting its efficiency and safety.

[0014] In the technical solution disclosed in the present invention, the weight m of the solid electrolyte interface film satisfies the relationship: 0.160 mg / cm 2 ≤m≤0.260mg / cm 2 For example, you can choose 0.160mg / cm 2 , 0.170mg / cm 2 , 0.175mg / cm 2 、0.180mg / cm 2 , 0.190mg / cm 2 , 0.200mg / cm 2 , 0.215mg / cm 2 , 0.230mg / cm 2 , 0.235mg / cm 2 , 0.250mg / cm 2 、0.260mg / cm 2 , but not limited to the listed values, other unlisted values within the numerical range are also applicable.

[0015] The SEI film protects the negative electrode interface. When the SEI film is too small or incomplete, it cannot effectively isolate the electrolyte, leading to more side reactions, consuming more lithium ions and electrolyte, and generating more gas, which affects battery safety. Moreover, without sufficient SEI film protection, the negative electrode material is more susceptible to electrolyte corrosion during the charge and discharge process. During the charge and discharge process, the electrode material structure may change, resulting in a decrease in the electrode's mechanical and electrochemical properties, affecting the overall stability of the battery. Excessive SEI film means that more lithium ions are consumed during its formation, resulting in increased irreversible capacity loss of the battery, reducing the battery's initial capacity and charge and discharge efficiency. At the same time, the battery's internal resistance will increase significantly, causing severe heat generation during high current charge and discharge, and reducing energy conversion efficiency. Furthermore, excessive SEI film will undermine the structural stability of the electrode material, resulting in poor battery cycle stability and increasing the risk of safety issues such as thermal runaway, which will seriously affect the battery's overall performance and service life.

[0016] In the technical solution disclosed in the present invention, the positive electrode capacity c satisfies the relationship: 200mA·h / g≤c≤220mA·h / g. For example, 200mA·h / g, 205mA·h / g, 208mA·h / g, 210mA·h / g, 212mA·h / g, 215mA·h / g, 218mA·h / g, and 220mA·h / g can be selected, but are not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0017] The capacity c of the positive electrode reflects the overall reversible capacity of the battery. If the positive electrode capacity is too low, the overall battery capacity will be insufficient and unable to meet the designed energy output requirements, thus affecting the battery's endurance. At the same time, too low a positive electrode capacity is accompanied by increased irreversible capacity loss, which may be caused by irreversible reactions such as structural changes in the electrode material, the formation of the SEI film, or electrolyte decomposition. These reactions will accelerate the capacity decay of the battery and shorten the cycle life. If the positive electrode capacity is too high, it will lead to capacity imbalance between the electrodes. The negative electrode side may precipitate metallic lithium due to a lack of sufficient active material. This will not only reduce the amount of cyclable lithium in the battery, but also increase the battery's internal resistance, affecting the rate performance. At the same time, it may cause the electrolyte to undergo oxidation reactions during the charging process, generating byproducts that clog the electrode micropores and hinder lithium ion migration. In addition, too high a positive electrode capacity may also be due to the fact that the battery loses less active lithium during the first charge, failing to form a stable interface film, resulting in poor interface stability, which in turn leads to a significant decrease in cycle performance.

[0018] In the technical solution disclosed in the present invention, the single-sided coating thickness d of the negative electrode active material layer satisfies the relationship: 39μm≤d≤51μm. For example, 39μm, 40μm, 41μm, 42μm, 43μm, 44μm, 45μm, 46μm, 47μm, 48μm, 49μm, 50μm, and 51μm can be selected, but are not limited to the listed values. Other values not listed within the numerical range are also applicable.

[0019] If the negative electrode coating is too thick, the lithium ion diffusion path will become longer, increasing the internal resistance and reducing the battery's rate performance and charge-discharge efficiency. It may also lead to a decrease in the utilization of active materials, affecting the battery's energy density and cycle life. In addition, if the coating is too thick, it may cause uneven current distribution, leading to local overheating or lithium dendrite growth, increasing the risk of short circuit and thermal runaway. If the negative electrode coating is too thin, the battery capacity will be reduced due to the reduction of active material. It will be prone to rupture due to volume changes during the charge and discharge process, reducing mechanical strength and affecting battery life and safety. It may also increase local current density, accelerate lithium dendrite growth, and cause short circuit or thermal runaway risks.

[0020] In the technical solution disclosed in the present invention, the positive electrode active material layer includes a positive electrode active material, a conductive agent and a binder.

[0021] Wherein, the mass ratio of the positive electrode active material, the conductive agent and the binder is 94-98:1-3:1-3.

[0022] Wherein, the positive electrode active material is selected from lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide or ternary positive electrode material, wherein the molecular formula of the ternary positive electrode material is LiNi x Co y M zO2, wherein 0.8≤x≤0.9, 0.1≤y≤0.2, 0.01≤z≤0.1; M is selected from any one or more of Mn, Al, Mg, Zr, and Ti.

[0023] In the technical solution disclosed in the present invention, the negative electrode active material layer includes a negative electrode active material, a conductive agent, a thickener and a binder.

[0024] The mass ratio of the negative electrode active material, the conductive agent, the thickener and the binder is 91-95:0.5-3:0.5-3:1-3.

[0025] The negative electrode active material is composed of graphite and silicon oxide material, wherein the content of graphite is 90-95wt%.

[0026] In the technical solution disclosed in the present invention, the electrolyte includes a solvent, a lithium salt and an additive, wherein the solvent is a mixture of ethylene carbonate, dimethyl carbonate and ethyl acetate, wherein the content of ethylene carbonate is 20-30wt%, the content of dimethyl carbonate is 70-80wt%, and the content of ethyl acetate is 0-10wt%; the additive is selected from fluoroethylene carbonate or vinyl ethylene carbonate; and the lithium salt is selected from LiPF6.

[0027] The present invention also provides a method for preparing the high-rate lithium-ion battery, comprising the following steps:

[0028] S1. Preparation of positive electrode sheet: The positive electrode active material, conductive agent, and binder are mixed in a certain mass ratio, and then NMP is added to the mixture as a solvent. The mixture is stirred under the action of a vacuum mixer until the system becomes uniform to obtain a positive electrode slurry. The obtained positive electrode slurry is evenly coated on the positive electrode collector, and after drying, it is cold pressed and cut into positive electrode sheets;

[0029] S2. Preparation of negative electrode sheets: The negative electrode active material, conductive agent, thickener, and binder are mixed in a certain mass ratio, and deionized water is added to the mixture as a solvent. The mixture is stirred in a vacuum mixer until the system becomes uniform to obtain a negative electrode slurry. The obtained negative electrode slurry is evenly coated on the negative electrode current collector, dried, cold pressed, and cut into negative electrode sheets.

[0030] S3. Preparation of electrolyte: Ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl acetate (EA) are mixed uniformly in a certain mass ratio to obtain a solvent, and then an additive, fluoroethylene carbonate (FEC) and a lithium salt are added to the solvent and mixed uniformly to obtain an electrolyte;

[0031] S4. Battery assembly: The positive electrode sheet, separator, and negative electrode sheet are stacked in order and wound into a core, which is placed in a steel shell and welded and fixed. The electrolyte is injected into it and packaged. After the electrolyte is completely infiltrated, it is then subjected to formation, aging, and constant capacity to obtain a high-rate lithium-ion battery.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The present invention improves the rate performance, cycle performance and thermal safety of the battery by controlling the relationship between the electrolyte infiltration time t on the negative electrode sheet, the weight of the solid electrolyte interface film (SEI film), and the positive electrode sheet capacity c. The prepared battery has a capacity retention rate of more than 81% after 500 charge and discharge cycles at a 0.2C / 10C rate, a capacity retention rate of more than 85% at a 0.2C / 15C rate, and a temperature rise rate of 0.6-0.9°C / (s*Ah) during discharge at a 15C rate.

[0034] (2) The present invention further improves the high-rate discharge performance of the battery by controlling the infiltration time of the electrolyte on the negative electrode sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a performance diagram of Example 1 of the present invention and Comparative Example 1 after 500 cycles at 25°C and 10°C. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below through specific preferred embodiments, but the present invention is not limited to the following embodiments.

[0037] It should be noted that, unless otherwise specified, all chemical reagents involved in the present invention were purchased through commercial channels.

[0038] The present invention provides a method for preparing a high-rate lithium-ion battery, comprising the following steps:

[0039] S1. Preparation of positive electrode sheet: LiNi 0.88 Co 0.1 Al 0..02 O2, conductive agent SP, and binder PVDF were mixed in a mass ratio of 96:2:2, and then NMP was added to the mixture as a solvent in portions. The mixture was stirred under the action of a vacuum mixer until the system was uniform to obtain a positive electrode slurry with a solid content of 72% ± 1%. The positive electrode slurry was evenly coated on both sides of the positive electrode current collector aluminum foil and dried in an oven to obtain a single-side surface density of 12.7-14.5 g / cm 2 The positive electrode sheet is then cold pressed and cut, and the coating thickness of the final positive electrode sheet is in the range of 37-44μm;

[0040] S2. Preparation of the negative electrode sheet: Mix the negative electrode active materials (95% graphite, 5% SiO x , where 0 < x < 2, the graphite material is purchased from Shanghai杉杉, and the silicon oxide material is purchased from贝特瑞), conductive agent SP, thickening agent CMC, and binder SBR in a mass ratio of 96:1:0.5:2.5. Then, add deionized water as a solvent to the mixed materials in portions, and stir under a vacuum mixer until the system becomes homogeneous to obtain a negative electrode slurry with a solid content of 50.5% ± 1%. Coat the negative electrode slurry evenly on both sides of the negative electrode current collector copper foil, dry it in an oven, and obtain a negative electrode sheet with a single-sided surface density of 6.7 - 7.8 g / cm 2 . Then, cold press and slit the electrode sheet. The final coating thickness of the negative electrode sheet ranges from 39 - 51 μm;

[0041] S3. Preparation of the electrolyte: Mix EC, DMC, and EA in a mass ratio of 2:7:1 as a solvent, add 7 wt% FEC as an additive to the solvent, and then add LiPF6 as a lithium salt. The concentration of the lithium salt in the electrolyte is 1 mol / L;

[0042] S4. Assembly of the battery: Stack the positive electrode sheet, separator, and negative electrode sheet in sequence and wind them into a core. Place the core in a steel shell and weld it in place. Inject 6 g of electrolyte into it and seal it. Let it stand for 4 h to allow the electrolyte to fully infiltrate. Then, through formation, aging, and constant volume, a high-rate lithium-ion battery is obtained;

[0043] The high-rate lithium-ion battery satisfies the relationship: |t - (783m - 0.55c + 110)| ≤ 10;

[0044] where t represents the infiltration time of the electrolyte on the negative electrode sheet, with the unit of s;

[0045] m represents the weight of the solid electrolyte interface film, with the unit of mg / cm 2 ;

[0046] c represents the capacity of the positive electrode sheet, with the unit of mA·h / g.

[0047] To prove the feasibility of the content provided by the present invention, relevant performance tests were carried out on the present invention. The specific experimental steps are as follows:

[0048] 1) Test method for the capacity c of the positive electrode sheet: After fully discharging the battery after formation and constant volume, disassemble it. Cut the positive electrode sheet into small round pieces, make a button cell with a lithium sheet as the negative electrode, and in a constant temperature oven at 25°C, charge it at a constant current and constant voltage of 0.1C, with a cut-off voltage of 4.25V and a cut-off current of 0.1A. Test its charging capacity, and conduct the experiment 3 times synchronously. Take the average value as c.

[0049] 2) Solid electrolyte interface film (SEI film) weight m test method: SEI film will decompose at a certain temperature, so the weight lost by the negative electrode after high-temperature calcination is the weight of the SEI film. The specific process is: the battery after being fully discharged after being converted to a fixed capacity is disassembled, and the negative electrode plate is cut into 2cm×2cm square pieces, and the initial weight m1 is measured. It is placed in a muffle furnace and calcined at 200℃ for 1h. After cooling, it is taken out and its weight m2 is measured, m=m1-m2. The experiment is carried out simultaneously for 5 times and the average value is taken.

[0050] 3) Test method for negative electrode sheet wetting time t: After the battery has been fully discharged after being formed and fixed in capacity, it is disassembled. In an environment with a dew point of -30°C, 0.1g of electrolyte (the electrolyte prepared in step S3) is dripped onto the electrode until the liquid penetrates the electrode and there is no obvious mark on the surface of the electrode. The time is recorded. The experiment is repeated three times and the average value is taken.

[0051] 4) Rate discharge performance test: Take a cylindrical battery, place it in a 25℃ constant temperature box for more than 4 hours, and test it according to the following steps:

[0052] ①Discharge the battery at a constant current of 0.1C to 2.5V cutoff, and let it stand for 5 minutes;

[0053] ② Charge the battery at a constant current of 0.2C to a cutoff of 4.2V, and at a constant voltage of 0.05C to a cutoff, and let it rest for 5 minutes;

[0054] ③Discharge the battery at a constant current of 0.2C to a cutoff of 2.5V, let it stand for 5 minutes, and read the capacity value C0 at this time;

[0055] ④ Charge the battery at a constant current of 0.2C to 4.2V, and charge it at a constant voltage of 0.05C, and let it stand for 5 minutes;

[0056] ⑤Discharge the battery at a constant current of 15C until the voltage is cut off at 2.5V, let it stand for 5 minutes, and read the capacity value C at this time. 15 , discharge time t1, battery temperature increment ΔT (measured by a thermocouple on the battery surface);

[0057] ⑥C 15 / C0 is the capacity retention rate of the battery at 15C discharge; ΔT / (t1*C 15 ) is the temperature rise rate of the battery when discharged at 15C.

[0058] 5) Cycling performance test: Take a cylindrical battery, place it in a 25°C constant temperature box for more than 4 hours, and test it according to the following steps:

[0059] ①Discharge the battery at a constant current of 0.1C to 2.5V cutoff, and let it stand for 5 minutes;

[0060] ② Charge the battery at a constant current of 0.2C to a cutoff of 4.2V, and at a constant voltage of 0.05C to a cutoff, and let it rest for 5 minutes;

[0061] ③Discharge the battery at a constant current of 0.2C to a cutoff of 2.5V, let it stand for 5 minutes, and read the capacity value C0 at this time;

[0062] ④ Charge the battery at a constant current of 0.2C to 4.2V, and charge it at a constant voltage of 0.05C, and let it stand for 5 minutes;

[0063] ⑤Discharge the battery at a constant current of 10C to 2.5V cutoff, and let it stand for 5 minutes;

[0064] ⑥ Repeat steps ④ and ⑤ 500 times;

[0065] ⑦ The rate cycle performance of a single battery, i.e., the capacity retention rate, is obtained by calculating the ratio of the 500th discharge capacity to the first discharge capacity in steps ④ and ⑤.

[0066] The test results of Examples 1-10 and Comparative Examples 1-4 are shown in Table 1.

[0067] Table 1 Test results of Examples 1-10 and Comparative Examples 1-4

[0068]

[0069]

[0070] Comparing Examples 1-10 and Comparative Examples 1-4 in the table, it can be seen that when the relationship between the negative electrode sheet infiltration time t, the SEI film weight m, and the positive electrode capacity c meets the condition |t-(783m-0.55c+110)|≤10, the lithium-ion battery has better rate discharge performance and thermal safety. In Examples 1-10, the lithium-ion battery achieved a discharge capacity retention rate of over 81% at 15C, and exhibited a low heating rate, low heat release, and was less susceptible to thermal runaway, thus providing higher safety. The cycle life graph shows that the battery cycle life steadily decreases during discharge cycles at a rate of 10C, but after 500 cycles, it still maintained over 85% of its capacity, demonstrating excellent cycle stability. In comparative examples 1-4, however, |t-(783m-0.55c+110)|>10, and an imbalance occurs between the transport of lithium ions within the negative electrode sheet and the electrolyte layer on the negative electrode surface, resulting in difficulty in the deintercalation of lithium ions from the negative electrode sheet. The battery produces a large polarization during high-rate charge and discharge, and the rate discharge performance is greatly reduced. After 300 cycles, the battery interface stability is destroyed and the capacity retention rate decreases rapidly. In addition, the heating rate increases during discharge, and the heat generated by the battery increases, resulting in reduced safety of the lithium-ion battery.

[0071] Furthermore, by comparing Examples 1-6 with Examples 7-10, the倍率循环性能 of Examples 1-6 reaches 87% and maintains a倍率放电容量 of more than 85% on this basis, and the comprehensive performance under倍率放电 is better; it shows that the preferred range of the relationship between the negative electrode soaking time t, the SEI film weight m, and the positive electrode capacity c is |t-(783m - 0.55c + 110)|≤5.

[0072] From the negative electrode soaking time t and倍率性能 in Examples 1-10 in Table 1, it is found that when

[0073] |t-(783m - 0.55c + 110)|≤10 and the negative electrode soaking time satisfies 110s < t < 160s, the lithium-ion battery has better high-倍率性能 and thermal stability; the reason is that a smaller t value indicates that the pores of the negative electrode have lower diffusion impedance, and lithium ions can be transported faster within the negative electrode, thus improving the倍率性能 of the lithium-ion battery; at the same time, it makes the heat generation during the discharge process of the lithium-ion battery lower, with higher thermal stability, and improves the safety of the lithium-ion battery under high-倍率放电.

[0074] By comparing Examples 1-10 with Comparative Example 2 and Comparative Example 4, it is found that when the weight of the SEI film is controlled between 0.160mg / cm 2 -0.260mg / cm 2 it will not lead to a decrease in interfacial stability due to the too thin SEI film, nor will it increase the transport impedance of lithium ions in the SEI film due to the too thick SEI film, and the lithium-ion battery has better倍率性能 and safety performance.

[0075] Furthermore, when the SEI film weight is between 0.175mg / cm 2 -0.230mg / cm 2 it has a higher capacity retention rate after high-倍率放电循环. Within this range, the negative electrode surface has better interfacial stability, and thus has better倍率循环性能.

[0076] In Examples 1-10 and Comparative Examples 1-4, the coating thickness of the negative electrode is controlled within 39μm ≤ d ≤ 51μm to prevent the graphite particles from cracking due to excessive compaction caused by too thin coating, which reduces the stability of the electrode during charge and discharge; too thick coating leads to an increase in the lithium ion transport path, reduces the insertion and extraction speed, and generates more heat. Therefore, controlling the coating thickness of the negative electrode can enable the lithium-ion battery to maintain a high specific energy while ensuring that lithium ions can be quickly inserted and extracted within the negative electrode, achieving a common consideration of high specific energy, high power, high cycle stability, and high safety of the lithium-ion battery.

[0077] In addition, from Figure 1It can be seen that the capacity retention rate of Example 1 is significantly better than that of Comparative Example 1. In the initial stage of the cycle, the capacity retention rate shows a slowly decreasing trend. The capacity retention rate in Example 1 is slightly higher than that in Comparative Example 1, indicating that Example 1 has better interface stability and less active lithium loss during the charge and discharge process. After 300 charge and discharge cycles, the capacity retention rate of Comparative Example 1 drops rapidly, indicating that the negative electrode structure and interface are damaged, and the interface stability deteriorates. The negative electrode active particles rupture after multiple lithium insertion and deinsertion expansions, forming a new interface, the SEI film is damaged and reconstructed, and the electrolyte is in direct contact with the active surface to undergo redox reactions, resulting in more lithium loss; while in Example 1, as the number of cycles increases, the capacity retention rate of the battery continues to slowly decrease, the negative electrode interface is not additionally damaged, and has better cycle stability.

[0078] Finally, it should be noted that the above embodiments do not limit the present invention in any form. Those skilled in the art will appreciate that modifications and improvements can be made based on the present invention. Therefore, any modifications or improvements made without departing from the spirit of the present invention are intended to fall within the scope of protection claimed in the present invention.

Claims

1. A high-rate lithium-ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, characterized in that: The positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, a solid electrolyte interface film is formed on the surface of the negative electrode active material layer, and the high-rate lithium-ion battery satisfies the relationship: |t-(783m-0.55c+110)|≤10; Wherein, t represents the electrolyte infiltration time on the negative electrode sheet, in seconds; m represents the weight of the solid electrolyte interface film, in mg / cm 2 ; c represents the positive electrode capacity, the unit is mA·h / g.

2. The high rate lithium ion battery according to claim 1, characterized in that: The high-rate lithium-ion battery satisfies the relationship: |t-(783m-0.55c+110)|≤5.

3. The high rate lithium ion battery according to claim 1, characterized in that: The electrolyte infiltration time t on the negative electrode sheet satisfies the relationship: 100s≤t≤200s.

4. The high rate lithium ion battery according to claim 3, characterized in that: The electrolyte infiltration time t on the negative electrode sheet satisfies the relationship: 110s≤t≤160s.

5. The high rate lithium ion battery according to claim 1, characterized in that: The weight m of the solid electrolyte interface film satisfies the relationship: 0.160 mg / cm 2 ≤m≤0.260mg / cm 2 .

6. The high rate lithium ion battery according to claim 5, characterized in that: The weight m of the solid electrolyte interface film satisfies the relationship: 0.175 mg / cm 2 ≤m≤0.230mg / cm 2 .

7. The high rate lithium ion battery according to claim 1, characterized in that: The capacity c of the positive electrode sheet satisfies the relationship: 200mA·h / g≤c≤220mA·h / g.

8. The high rate lithium ion battery according to claim 1, characterized in that: The single-side coating thickness d of the negative electrode active material layer satisfies the relationship: 39 μm≤d≤51 μm.

9. The high rate lithium ion battery according to claim 1, characterized in that: The positive electrode active material layer comprises a positive electrode active material, a conductive agent and a binder, and the mass ratio of the positive electrode active material, the conductive agent and the binder is 94-98:1-3:1-3.

10. The high rate lithium ion battery according to claim 9, characterized in that: The positive electrode active material is selected from lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide or a ternary positive electrode material, wherein the molecular formula of the ternary positive electrode material is LiNi x Co y M z O2, wherein 0.8≤x≤0.9, 0.1≤y≤0.2, 0.01≤z≤0.1; M is selected from any one or more of Mn, Al, Mg, Zr, and Ti.

11. The high rate lithium ion battery according to claim 1, characterized in that: The negative electrode active material layer comprises a negative electrode active material, a conductive agent, a thickener and a binder, and the mass ratio of the negative electrode active material, the conductive agent, the thickener and the binder is 91-95:0.5-3:0.5-3:1-3.

12. The high rate lithium ion battery according to claim 11, characterized in that: The negative electrode active material is composed of graphite and silicon-oxygen material, wherein the content of graphite is 90-95wt%.

13. The high rate lithium ion battery according to claim 1, characterized in that: The electrolyte includes a solvent, a lithium salt and an additive, wherein the solvent is a mixture of ethylene carbonate, dimethyl carbonate and ethyl acetate, wherein the content of ethylene carbonate is 20-30wt%, the content of dimethyl carbonate is 70-80wt%, and the content of ethyl acetate is 0-10wt%; the additive is selected from fluoroethylene carbonate or vinyl ethylene carbonate; and the lithium salt is selected from LiPF6.

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