Lithium ion battery using method and lithium ion battery
By adding lithium replenishment additives to lithium iron phosphate batteries and combining a step-by-step lithium replenishment mechanism of low-voltage formation and high-voltage activation, the problem of increased negative electrode redundancy is solved, thereby improving battery energy density and cycle life.
Patent Information
- Application Number
- CN202512043973.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-04-10
AI Technical Summary
In existing lithium iron phosphate batteries, the low initial coulombic efficiency of the negative electrode leads to excessive lithium-ion consumption, increasing the redundancy of the negative electrode, occupying space and reducing energy density. Existing lithium replenishment additives have failed to effectively improve the overall performance of the battery.
A lithium-ion battery with lithium replenishment additives added to the positive electrode sheet, and a step-by-step lithium replenishment mechanism of low-voltage formation and high-voltage activation, combined with specific lithium replenishment additives and low-voltage formation, avoids a large amount of lithium loss during the first charge, releases lithium ions gradually as needed, and replenishes irreversible losses through high-voltage activation.
It reduces the internal space and weight of the battery, increases the battery energy density, extends cycle life, and significantly improves battery performance.
Smart Images
Figure CN121839943A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of lithium-ion battery manufacturing technology, specifically to a method of using a lithium-ion battery and a lithium-ion battery. Background Technology
[0002] As a core energy storage device in the new energy field, lithium-ion batteries have become a key development direction for the industry due to their high energy density, long cycle life, and high safety. Among them, lithium iron phosphate batteries have been widely used in key areas such as electric vehicles and large-scale energy storage due to their excellent safety performance and cycle stability, and have become one of the important types of commercially available lithium-ion batteries.
[0003] The core system of existing commercial lithium iron phosphate (LFP) batteries is "lithium iron phosphate cathode - graphite anode". In this system, the initial coulombic efficiency of the lithium iron phosphate cathode material is typically between 96% and 99%, while the initial coulombic efficiency of the graphite anode material is only 90% to 93%. Because the initial coulombic efficiency of the anode is significantly lower than that of the cathode, the anode consumes more active lithium ions during the first charge and discharge cycle. To avoid lithium plating due to excessive lithium ion insertion at the anode during charging, which could lead to safety hazards, current battery designs generally adopt an N / P ratio greater than 1, i.e., using a redundant anode to accommodate lithium ion consumption. However, the presence of a redundant anode not only further increases irreversible lithium ion consumption but also occupies internal battery space and increases the overall weight of the battery, thus limiting the improvement of battery energy density.
[0004] To compensate for the irreversible loss of lithium ions during cycling and improve battery cycle performance, cathode lithium replenishment additives have been widely researched and applied in lithium-ion battery R&D and production. However, the use of lithium replenishment additives in existing technologies still has significant limitations: lithium replenishment additives release a large number of lithium ions during the first charge. To ensure that the N / P ratio is within a safe range and to avoid lithium plating on the negative electrode, the redundancy of the negative electrode needs to be further increased. However, more negative electrode redundancy will cause additional irreversible lithium ion consumption, and the addition of lithium replenishment additives does not improve the initial coulombic efficiency of the negative electrode, but only matches the performance of the negative electrode by reducing the initial coulombic efficiency of the positive electrode. Ultimately, the residual inactive lithium replenishment agent after the first charge and discharge and the newly added negative electrode redundancy not only fail to effectively improve the overall battery performance, but also increase the battery weight and occupy internal battery space, resulting in room for optimization in existing battery design and manufacturing processes. Summary of the Invention
[0005] In view of the technical problems mentioned in the background art, such as increased negative electrode redundancy, increased battery weight, and occupation of internal battery space caused by the use of positive electrode lithium supplementation additives, the purpose of this invention is to provide a method of using a lithium-ion battery and a lithium-ion battery.
[0006] To achieve the objectives of this invention, the technical solution provided by this invention is as follows:
[0007] A method of using a lithium-ion battery includes the following: adding a lithium-ion additive to the positive electrode and performing low-voltage formation.
[0008] Further, the low-voltage formation includes the following: constant current charging to the first charging cutoff voltage V1, maintaining the V1 voltage constant voltage charging until the current is less than 0.05C, resting for 10 minutes, constant current discharging to the first discharge cutoff voltage, and recording the discharge capacity C0; resting for 10 minutes, constant current charging to the second charging cutoff voltage V2, maintaining the V2 voltage constant voltage charging until the current is less than 0.05C.
[0009] Furthermore, the first charging cutoff voltage V1 is 3V to 3.8V, the first discharging cutoff voltage is 2.0V to 2.5V, the second charging cutoff voltage V2 is 3V to 3.8V, the charging current when constant current charging to the second charging cutoff voltage V2 is 0.02C to 2C, and the discharging current when constant current discharging to the first discharging cutoff voltage is 0.02C to 2C.
[0010] Furthermore, a standard capacity test is performed, and when the capacity decay of the lithium-ion battery meets the judgment criteria, high-voltage activation is carried out.
[0011] Furthermore, the process of standardizing the capacity involves performing high-voltage activation when the lithium-ion battery capacity decay meets the determination criteria. Specifically, this process includes:
[0012] Perform standardization and record the discharge capacity Cn in the nth charge-discharge cycle. When the capacity loss rate (C1-Cn) / C1 > the judgment value D, the battery is activated at high voltage. Wherein, the judgment value D = the percentage of high-voltage activation delithiation capacity to the initial capacity * safety factor, the safety factor > 1, and C1 is the discharge capacity in the first charge-discharge cycle.
[0013] Further, the high-voltage activation includes the following: constant current charging to the third charging cutoff voltage V3, maintaining the V3 voltage constant voltage charging until the current is less than 0.05C, resting for 10 minutes, constant current discharging to the second discharge cutoff voltage, resting for 10 minutes, constant current charging to the fourth charging cutoff voltage V4, maintaining the V4 voltage constant voltage charging until the current is less than 0.05C.
[0014] Furthermore, the third charging cutoff voltage V3 is 3.8V to 4.8V, the second discharging cutoff voltage is 2.0V to 2.5V, and the fourth charging cutoff voltage V4 is 3V to 3.8V; wherein, V1 < V3; the charging current when constant current charging to the fourth charging cutoff voltage V4 is 0.02C to 2C, and the discharging current when constant current discharging to the second discharging cutoff voltage is 0.02C to 2C.
[0015] Furthermore, the process of standardizing capacity involves performing high-voltage activation once or multiple times, depending on the usage of the lithium-ion battery, when the capacity decay of the lithium-ion battery meets the determination criteria.
[0016] It should be noted that, provided that the set voltage and current range is not exceeded, the above standard capacity determination-high voltage activation process can be performed once or multiple times depending on the battery usage.
[0017] Second aspect
[0018] This invention provides a lithium-ion battery manufactured using the aforementioned lithium-ion battery usage method. The lithium-ion battery includes a cell and a battery casing encapsulating the cell. The cell includes a positive electrode and a negative electrode. The positive electrode active material in the positive electrode is lithium iron phosphate (LiFePO4), and a lithium replenishing additive is added to the positive electrode. The lithium replenishing additive has a delithiation potential higher than that of the positive electrode active material. The negative electrode active material in the negative electrode is graphite.
[0019] Furthermore, the lithium supplementation additive is one or a mixture of several of Li2NiO2, Li5FeO4, and Li2O; the areal density of the positive electrode sheet is 25–45 mg / cm³. 2 The areal density of the negative electrode is 12–23 mg / cm³. 2 .
[0020] N / P = (Specific capacity of negative electrode active material * Anode areal density * Anode active material content ratio) / (Specific capacity of positive electrode active material * Anode areal density * Anode active material content ratio). When calculating the N / P ratio, the positive electrode active material includes the positive electrode material and the lithium supplement. The specific capacity of the positive electrode active material refers to the specific capacity it exhibits at a specified formation voltage V1.
[0021] The lithium-ion battery further includes a separator and an electrolyte. The separator is one of the following: a PP separator, a PE separator, a PP and PE composite separator, a PP separator with ceramic and adhesive coating, a PE separator with ceramic and adhesive coating, or a PP and PE composite separator with ceramic and adhesive coating. The electrolyte includes ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc.; commonly used lithium electrolyte salts mainly include lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), etc.
[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0023] (1) This invention uses a combination of adding specific lithium-replenishing additives to the positive electrode and low-voltage formation to avoid the lithium-replenishing additives from delithitolining during the first charge, thus eliminating the need to increase the redundancy of the negative electrode to prevent lithium plating. This reduces the internal space and overall weight of the battery, and at the same time, it increases the charging capacity of the positive electrode without increasing the load on the negative electrode, ultimately effectively improving the actual energy density of the battery and breaking the limitation of existing lithium-replenishing technologies on energy density;
[0024] (2) This invention employs a stepwise lithium replenishment mechanism that uses low-voltage formation and capacity decay to trigger high-voltage activation, where lithium ions in the lithium replenishment additive are released gradually as needed. When the battery capacity loss rate reaches the threshold, high-voltage activation precisely replenishes the irreversibly lost lithium ions during the cycle, enhancing the pre-charge effect and mitigating the impact of lithium loss on battery performance from the root, thus significantly extending the battery cycle life. Attached Figure Description
[0025] Figure 1 A comparison chart showing the cycle capacity retention rates of different embodiments and comparative examples in pouch cells;
[0026] Figure 2 This is a comparison chart showing the cycle capacity retention rates of different embodiments and comparative examples of square batteries. Detailed Implementation
[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0028] Example 1
[0029] The method of using the lithium-ion battery provided in this embodiment is as follows:
[0030] (1) Selecting lithium-ion batteries with lithium supplementation additives added to the positive electrode:
[0031] Experiments were conducted using a 4360143 type soft-pack battery. The positive electrode active material was selected as lithium iron phosphate + lithium replenishment additive. The corresponding capacities at different delithiation voltages are shown in Table 1. The positive electrode mass percentage was: positive electrode active material: lithium replenishment additive: conductive carbon black: conductive carbon nanotubes: binder = 96.6:0.3:0.8:0.4:1.9, and the positive electrode coating amount was set to 35.8 mg / cm³. 2The experiment used artificial graphite as the negative electrode active material, with a charge capacity of 380 mAh / g. The negative electrode mass percentage was: negative electrode active material: conductive carbon black: binder: thickener = 96:1:2:1, and the negative electrode coating amount was set to 17 mg / cm³. 2 The formation voltage V1 is set to 3.65V. According to the N / P ratio formula for lithium-ion batteries, the actual N / P ratio of this battery is 1.120.
[0032] The positive electrode sheet is prepared as follows: 85,000g of lithium iron phosphate material, 264g of lithium supplementation additive, 28,878g of polyvinylidene fluoride (PVDF) slurry (1,672g of effective material), 704g of conductive carbon black, 12,577g of conductive carbon nanotube slurry (352g of effective material) and 8,724g of solvent NMP are stirred and dispersed evenly to form a mixed slurry. The prepared slurry is coated on a 12μm aluminum foil according to the designed coating amount. After drying, rolling and punching, the positive electrode sheet is obtained.
[0033] The negative electrode sheet is prepared as follows: 45,000g of artificial graphite material, 468.75g of conductive carbon black, 2,343.75g of binder SBR slurry (937.5g of effective substance), 31,250g of thickener CMC slurry (468.75g of effective substance) and 16,523g of solvent deionized water are mixed to form a slurry. The prepared slurry is coated on a 5μm copper foil according to the designed coating amount. After drying, rolling and punching, the negative electrode sheet is obtained.
[0034] The assembly of lithium-ion secondary batteries involves stacking positive electrode sheets, separators, and negative electrode sheets to form an electrode assembly, which is then placed in an aluminum-plastic encapsulation shell. After processes such as electrolyte injection and encapsulation, a lithium-ion secondary battery is obtained. The battery is then left to stand at room temperature for 36 hours before entering the low-voltage formation process.
[0035] (2) Formation: After the battery has been filled with electrolyte and allowed to stand, charge it to 3.65V at 0.2C, then charge it at a constant voltage of 3.65V to 0.05C. Let it stand for 10 minutes, then discharge it to 2V at 0.2C, let it stand for 10 minutes, then charge it to 3.2V at 0.2C, and finally charge it at a constant voltage of 3.2V to 0.05C. Calculate the energy density based on the discharge data.
[0036] (3) Cyclic performance test: Charge at 1C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C cutoff, let stand for 10 minutes, discharge at 1C to 2V, and let stand for 10 minutes. Repeat this charge and discharge cycle and record the capacity of each cycle. The discharge capacity of the nth cycle is set as Cn.
[0037] (4) Standard Capacity Determination: As shown in Appendix 1, for batteries in the 3.65V-4.2V range, the percentage of delithiation capacity to initial capacity is 2.2%. The determination value D = 2.2% * safety factor. In this embodiment, the safety factor is 2. Therefore, when the capacity loss rate (C1-Cn) / C1 > determination value D (4.4%), high-voltage activation is performed. In this embodiment, 900 cycles meet the standard capacity determination condition, and high-voltage activation is performed.
[0038] (5) High voltage activation: Cycle the battery until it meets the judgment conditions, perform high voltage activation, charge at 0.2C to 4.2V, charge at 4.2V constant voltage to 0.05C cutoff, let stand for 10min, discharge at 0.2C to 2V, let stand for 10min, charge at 0.2C to 3.2V, charge at 3.2V constant voltage to 0.05C cutoff.
[0039] (6) After high-voltage activation, the battery continues to undergo cycle performance testing according to the method in step (3).
[0040] Example 2
[0041] The method of using the lithium-ion battery provided in this embodiment is as follows:
[0042] (1) Selecting lithium-ion batteries with lithium supplementation additives added to the positive electrode:
[0043] In this embodiment, the battery design, positive electrode preparation, negative electrode preparation, lithium-ion secondary battery assembly, formation, and cycle performance testing are exactly the same as in Example 1.
[0044] (2) Standard Capacity Judgment 1: As shown in Appendix 1, for batteries in the 3.65V-4.0V range, the percentage of delithiation capacity to initial capacity is 1.2%. The judgment value D = 1.2% * safety factor. In this embodiment, the safety factor is taken as 2. Therefore, when the capacity loss rate (C1-Cn) / C1 > judgment value D (2.4%), high-voltage activation is performed. In this embodiment, 500 cycles meet the condition of standard capacity judgment 1, and high-voltage activation 1 is performed.
[0045] (3) High-voltage activation 1: After cycling the battery until it meets the judgment conditions, perform high-voltage activation: charge to 4V at 0.2C, then charge at 4V constant voltage to 0.05C cutoff, let stand for 10 minutes, discharge to 2V at 0.2C, let stand for 10 minutes, charge to 3.2V at 0.2C, and charge at 3.2V constant voltage to 0.05C cutoff. After high-voltage activation, the battery continues to undergo cycle performance testing according to the original method.
[0046] (4) Standard Capacity Judgment 2: As shown in Appendix 1, for batteries in the 3.65V-4.2V range, the percentage of delithiation capacity to initial capacity is 2.2%. The judgment value D = 2.2% * safety factor. In this embodiment, the safety factor is 2. Therefore, when the capacity loss rate (C1-Cn) / C1 > judgment value D (4.4%), a second high-voltage activation is performed. In this embodiment, 1000 cycles meet the conditions for standard capacity judgment 2, and high-voltage activation 2 is performed.
[0047] (5) High voltage activation 2: Cycle the battery until it meets the judgment conditions, perform high voltage activation, charge at 0.2C to 4.2V, charge at 4.2V constant voltage to 0.05C cutoff, let stand for 10min, discharge at 0.2C to 2V, let stand for 10min, charge at 0.2C to 3.2V, charge at 3.2V constant voltage to 0.05C cutoff.
[0048] (6) After high-voltage activation, the battery continues to undergo cycle performance testing according to the original standard.
[0049] Example 3
[0050] The method of using the lithium-ion battery provided in this embodiment is as follows:
[0051] (1) Selecting lithium-ion batteries with lithium supplementation additives added to the positive electrode:
[0052] The experiment was conducted using a 2714897 type square battery. The positive electrode active material was selected as lithium iron phosphate + lithium replenishment additive. The corresponding capacity at different delithiation voltages is shown in Appendix Table 1. The mass percentage of the positive electrode was: positive electrode active material: lithium replenishment additive: conductive carbon black: conductive carbon nanotubes: binder = 96.6:0.3:0.8:0.4:1.9. The positive electrode coating amount was set to 35.8 mg / cm³. 2 The experiment used artificial graphite as the negative electrode active material, with a charge capacity of 380 mAh / g. The negative electrode mass percentage was: negative electrode active material: conductive carbon black: binder: thickener = 96:1:2:1, and the negative electrode coating amount was set to 17 mg / cm³. 2 The formation voltage V1 is set to 3.65V. According to the N / P ratio formula for lithium-ion batteries, the actual N / P ratio of this battery is 1.120.
[0053] The preparation of the positive electrode sheet involves mixing and dispersing 85,000g of lithium iron phosphate material, 264g of lithium supplementation additive, 28,878g of polyvinylidene fluoride (PVDF) slurry (1,672g of effective material), 704g of conductive carbon black, 12,577g of conductive carbon nanotube slurry (352g of effective material), and 8,724g of solvent NMP to form a mixed slurry. The prepared slurry is then coated onto a 12μm aluminum foil according to the designed coating amount. The positive electrode sheet is obtained through processes such as drying, rolling, and laser cutting.
[0054] The preparation of the negative electrode sheet involves mixing 45,000g of artificial graphite material, 468.75g of conductive carbon black, 2,343.75g of SBR binder slurry (937.5g of effective substance), 31,250g of CMC thickener slurry (468.75g of effective substance), and 16,523g of deionized water as solvent to form a slurry. The slurry is then coated onto a 5μm copper foil according to the designed coating amount. The negative electrode sheet is obtained through processes such as drying, rolling, and laser cutting.
[0055] The assembly of lithium-ion secondary batteries involves winding positive electrode sheets, separators, and negative electrode sheets into an electrode assembly, placing it into a square aluminum shell, injecting electrolyte, and encapsulating it to obtain a lithium-ion secondary battery. The battery is then left to stand at room temperature for 36 hours before entering the formation process.
[0056] (2) Formation: After the battery has been filled with electrolyte and allowed to stand, charge it to 3.65V at 0.2C, then charge it at a constant voltage of 3.65V to 0.05C. Let it stand for 10 minutes, then discharge it to 2V at 0.2C, let it stand for 10 minutes, then charge it to 3.2V at 0.2C, and finally charge it at a constant voltage of 3.2V to 0.05C. Calculate the energy density based on the discharge data.
[0057] (3) Cyclic performance test: Charge at 1C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C cutoff, let stand for 10 minutes, discharge at 1C to 2V, and let stand for 10 minutes. Repeat this charge and discharge cycle and record the capacity of each cycle. The discharge capacity of the nth cycle is set as Cn.
[0058] (4) Standard Capacity Determination: As shown in Appendix 1, for batteries in the 3.65V-4.2V range, the percentage of delithiation capacity to initial capacity is 2.2%. The determination value D = 2.2% * safety factor. In this embodiment, the safety factor is 2. Therefore, when the capacity loss rate (C1-Cn) / C1 > determination value D (4.4%), high-voltage activation is performed. In this embodiment, 900 cycles meet the standard capacity determination condition, and high-voltage activation is performed.
[0059] (5) High voltage activation: Cycle the battery until it meets the judgment conditions, perform high voltage activation, charge at 0.2C to 4.2V, charge at 4.2V constant voltage to 0.05C cutoff, let stand for 10min, discharge at 0.2C to 2V, let stand for 10min, charge at 0.2C to 3.2V, charge at 3.2V constant voltage to 0.05C cutoff.
[0060] (6) After high-voltage activation, the battery continues to undergo cycle performance testing according to the method in step (3).
[0061] Example 4
[0062] The method of using the lithium-ion battery provided in this embodiment is as follows:
[0063] (1) Selecting lithium-ion batteries with lithium supplementation additives added to the positive electrode:
[0064] In this embodiment, the battery design, positive electrode preparation, negative electrode preparation, lithium-ion secondary battery assembly, formation, and cycle performance testing are exactly the same as in Example 3.
[0065] (2) Standard Capacity Judgment 1: As shown in Appendix 1, for batteries in the 3.65V-4.0V range, the percentage of delithiation capacity to initial capacity is 1.2%. The judgment value D = 1.2% * safety factor. In this embodiment, the safety factor is taken as 2. Therefore, when the capacity loss rate (C1-Cn) / C1 > judgment value D (2.4%), high-voltage activation is performed. In this embodiment, 400 cycles meet the condition of standard capacity judgment 1, and high-voltage activation 1 is performed.
[0066] (3) High-voltage activation 1: After cycling the battery until it meets the judgment conditions, perform high-voltage activation: charge to 4V at 0.2C, then charge at 4V constant voltage to 0.05C cutoff, let stand for 10 minutes, discharge to 2V at 0.2C, let stand for 10 minutes, charge to 3.2V at 0.2C, and charge at 3.2V constant voltage to 0.05C cutoff. After high-voltage activation, the battery continues to undergo cycle performance testing according to the original method.
[0067] (4) Standard Capacity Judgment 2: As shown in Appendix 1, for batteries in the 3.65V-4.2V range, the percentage of delithiation capacity to initial capacity is 2.2%. The judgment value D = 2.2% * safety factor. In this embodiment, the safety factor is 2. Therefore, when the capacity loss rate (C1-Cn) / C1 > judgment value D (4.4%), a second high-voltage activation is performed. In this embodiment, 1100 cycles meet the conditions for standard capacity judgment 2, and high-voltage activation 2 is performed.
[0068] (5) High voltage activation 2: Cycle the battery until it meets the judgment conditions, perform high voltage activation, charge at 0.2C to 4.2V, charge at 4.2V constant voltage to 0.05C cutoff, let stand for 10min, discharge at 0.2C to 2V, let stand for 10min, charge at 0.2C to 3.2V, charge at 3.2V constant voltage to 0.05C cutoff.
[0069] (6) After high-voltage activation, the battery continues to undergo cycle performance testing according to the original standard.
[0070] Comparative Example 1:
[0071] (1) Select lithium-ion batteries without lithium supplementation additives:
[0072] The experiment was conducted using a 4360143 type soft-pack battery. Lithium iron phosphate was selected as the positive electrode active material, without the addition of any lithium-replenishing additives. The positive electrode mass percentage was: positive electrode active material: conductive carbon black: conductive carbon nanotubes: binder = 96.9:0.8:0.4:1.9, and the positive electrode coating amount was set to 35.83 mg / cm³. 2 The experiment used artificial graphite as the negative electrode active material, with a charge capacity of 380 mAh / g. The negative electrode mass percentage was: negative electrode active material: conductive carbon black: binder: thickener = 96:1:2:1, and the negative electrode coating amount was set to 17 mg / cm³. 2 The formation voltage V1 is set to 3.65V. According to the N / P ratio formula for lithium-ion batteries, the actual N / P ratio of this battery is 1.120.
[0073] Preparation of the positive electrode sheet: 85264g of lithium iron phosphate material, 28878g of polyvinylidene fluoride (PVDF) slurry (1672g of effective material), 704g of conductive carbon black, 12577g of conductive carbon nanotube slurry (352g of effective material) and 8724g of solvent NMP were stirred and dispersed evenly to prepare a mixed slurry. The prepared slurry was coated on a 12μm aluminum foil according to the designed coating amount. After drying, rolling and punching, the positive electrode sheet was obtained.
[0074] The preparation of the negative electrode sheet and the assembly of the lithium-ion secondary battery in this comparative example are exactly the same as in Example 1.
[0075] (2) Formation: After the battery has been filled with electrolyte and allowed to stand, charge it to 3.65V at 0.2C, then charge it at a constant voltage of 3.65V to 0.05C. Let it stand for 10 minutes, then discharge it to 2V at 0.2C, let it stand for 10 minutes, then charge it to 3.2V at 0.2C, and finally charge it at a constant voltage of 3.2V to 0.05C. Calculate the energy density based on the discharge data.
[0076] (3) Cyclic performance test: Charge at 1C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C cutoff, let stand for 10 minutes, discharge at 1C to 2V, and let stand for 10 minutes. Repeat this charge and discharge cycle and record the capacity of each cycle. The discharge capacity of the nth cycle is set as Cn.
[0077] Comparative Example 2
[0078] (1) Selecting lithium-ion batteries with lithium supplementation additives added to the positive electrode:
[0079] Experiments were conducted using a 4360143 type soft-pack battery. The positive electrode active material was selected as lithium iron phosphate + lithium replenishment additive. The corresponding capacities at different delithiation voltages are shown in Appendix Table 1. The mass percentage of the positive electrode was: positive electrode active material: lithium replenishment additive: conductive carbon black: conductive carbon nanotubes: binder = 96.6:0.3:0.8:0.4:1.9, and the positive electrode coating amount was set to 35.02 mg / cm³. 2 The experiment used artificial graphite as the negative electrode active material, with a charge capacity of 380 mAh / g. The negative electrode mass percentage was: negative electrode active material: conductive carbon black: binder: thickener = 96:1:2:1, and the negative electrode coating amount was set to 17 mg / cm³. 2 The formation voltage V1 is set to 4.2V. According to the N / P ratio formula for lithium-ion batteries, the actual N / P ratio of this battery is 1.120.
[0080] The preparation of the positive electrode, the preparation of the negative electrode, and the assembly of the lithium-ion secondary battery in this comparative example are exactly the same as in Example 1.
[0081] (2) Formation: After the battery has been filled with electrolyte and allowed to stand, charge it to 4.2V at 0.2C, then charge it at a constant voltage of 4.2V to 0.05C and let it stand for 10 minutes. Discharge it to 2V at 0.2C, let it stand for 10 minutes, then charge it to 3.2V at 0.2C and charge it at a constant voltage of 3.2V to 0.05C and let it stand for 10 minutes. Calculate the energy density based on the discharge data.
[0082] (3) Cyclic performance test: Charge at 1C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C cutoff, let stand for 10 minutes, discharge at 1C to 2V, and let stand for 10 minutes. Repeat this charge and discharge cycle and record the capacity of each cycle. The discharge capacity of the nth cycle is set as Cn.
[0083] Comparative Example 3
[0084] (1) Selecting lithium-ion batteries with lithium supplementation additives added to the positive electrode:
[0085] Experiments were conducted using a 4360143 type soft-pack battery. The positive electrode active material was selected as lithium iron phosphate + lithium replenishment additive. The corresponding capacities at different delithiation voltages are shown in Appendix Table 1. The mass percentage of the positive electrode was: positive electrode active material: lithium replenishment additive: conductive carbon black: conductive carbon nanotubes: binder = 96.6:0.3:0.8:0.4:1.9, and the positive electrode coating amount was set to 35.8 mg / cm³. 2 The experiment used artificial graphite as the negative electrode active material, with a charge capacity of 380 mAh / g. The negative electrode mass percentage was: negative electrode active material: conductive carbon black: binder: thickener = 96:1:2:1, and the negative electrode coating amount was set to 17 mg / cm³. 2The formation voltage V1 is set to 4.2V. According to the N / P ratio formula for lithium-ion batteries, the actual N / P ratio of this battery is 1.096.
[0086] The preparation of the positive electrode, the preparation of the negative electrode, and the assembly of the lithium-ion secondary battery in this comparative example are exactly the same as in Example 1.
[0087] (2) Formation: After the battery has been filled with electrolyte and allowed to stand, charge it to 4.2V at 0.2C, then charge it at a constant voltage of 4.2V to 0.05C. Let it stand for 10 minutes, then discharge it to 2V at 0.2C, let it stand for 10 minutes, then charge it to 3.2V at 0.2C, and finally charge it at a constant voltage of 3.2V to 0.05C. Calculate the energy density based on the discharge data;
[0088] (3) Cyclic performance test: Charge at 1C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C cutoff, let stand for 10 minutes, discharge at 1C to 2V, and let stand for 10 minutes. Repeat this charge and discharge cycle and record the capacity of each cycle. The discharge capacity of the nth cycle is set as Cn.
[0089] Comparative Example 4
[0090] (1) Selecting lithium-ion batteries with lithium supplementation additives added to the positive electrode:
[0091] The design, preparation of the positive electrode, preparation of the negative electrode, and assembly of the lithium-ion secondary battery in this comparative example are exactly the same as those in Comparative Example 3. The formation voltage is set to 3.65V, and the actual N / P ratio of this battery is 1.120.
[0092] (2) Formation: After the battery has been injected and allowed to stand, charge it to 3.65V at 0.2C, then charge it at a constant voltage of 3.65V to 0.05C. Allow it to stand for 10 minutes, then discharge it to 2V at 0.2C, allow it to stand for 10 minutes, then charge it to 3.2V at 0.2C, and finally charge it at a constant voltage of 3.2V to 0.05C. Calculate the energy density based on the discharge data.
[0093] (3) Cyclic performance test: Charge at 1C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C cutoff, let stand for 10 minutes, discharge at 1C to 2V, and let stand for 10 minutes. Repeat this charge and discharge cycle and record the capacity of each cycle. The discharge capacity of the nth cycle is set as Cn.
[0094] Comparative Example 5
[0095] (1) Select a lithium-ion battery with no lithium-additive on the positive electrode:
[0096] The experiment was conducted using a 2714897 type square battery. Lithium iron phosphate was selected as the positive electrode active material, without the addition of any lithium-replenishing additives. The positive electrode mass percentage was: positive electrode active material: conductive carbon black: conductive carbon nanotubes: binder = 96.9:0.8:0.4:1.9, and the positive electrode coating amount was set to 35.83 mg / cm³. 2 The experiment used artificial graphite as the negative electrode active material, with a charge capacity of 385 mAh / g. The negative electrode mass percentage was: negative electrode active material: conductive carbon black: binder: thickener = 96:1:2:1, and the negative electrode coating amount was set to 17 mg / cm³. 2 The formation voltage V1 is set to 3.65V. According to the N / P ratio formula for lithium-ion batteries, the actual N / P ratio of this battery is 1.120.
[0097] Preparation of the positive electrode sheet: 85264g of lithium iron phosphate material, 28878g of polyvinylidene fluoride (PVDF) slurry (1672g of effective material), 704g of conductive carbon black, 12577g of conductive carbon nanotube slurry (352g of effective material) and 8724g of solvent NMP were stirred and dispersed evenly to prepare a mixed slurry. The prepared slurry was coated on a 12μm aluminum foil according to the designed coating amount. After drying, rolling and laser cutting, the positive electrode sheet was obtained.
[0098] The preparation of the negative electrode sheet in this comparative example and the assembly of the lithium-ion secondary battery are exactly the same as in Example 3;
[0099] (2) Formation: After the battery has been injected and allowed to stand, charge it to 3.65V at 0.2C, then charge it at a constant voltage of 3.65V to 0.05C. Allow it to stand for 10 minutes, then discharge it to 2V at 0.2C, allow it to stand for 10 minutes, then charge it to 3.2V at 0.2C, and finally charge it at a constant voltage of 3.2V to 0.05C. Calculate the energy density based on the discharge data.
[0100] (3) Cyclic performance test: Charge at 1C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C cutoff, let stand for 10 minutes, discharge at 1C to 2V, and let stand for 10 minutes. Repeat this charge and discharge cycle and record the capacity of each cycle. The discharge capacity of the nth cycle is set as Cn.
[0101] Comparative Example 6
[0102] (1) Selecting lithium-ion batteries with lithium supplementation additives added to the positive electrode:
[0103] Experiments were conducted using a 2714897 type square battery. The positive electrode active material was selected as lithium iron phosphate + lithium replenishment additive. The corresponding capacities at different delithiation voltages are shown in Appendix Table 1. The mass percentage of the positive electrode was: positive electrode active material: lithium replenishment additive: conductive carbon black: conductive carbon nanotubes: binder = 96.6:0.3:0.8:0.4:1.9, and the positive electrode coating amount was set to 35.02 mg / cm³. 2 The experiment used artificial graphite as the negative electrode active material, with a charge capacity of 380 mAh / g. The negative electrode mass percentage was: negative electrode active material: conductive carbon black: binder: thickener = 96:1:2:1, and the negative electrode coating amount was set to 17 mg / cm³. 2 The formation voltage V1 is set to 4.2V. According to the N / P ratio formula for lithium-ion batteries, the actual N / P ratio of this battery is 1.120.
[0104] The preparation of the positive electrode, the preparation of the negative electrode, and the assembly of the lithium-ion secondary battery in this comparative example are exactly the same as in Example 3.
[0105] (2) Formation: After the battery has been filled with electrolyte and allowed to stand, charge it to 4.2V at 0.2C, then charge it at a constant voltage of 4.2V to 0.05C. Let it stand for 10 minutes, then discharge it to 2V at 0.2C, let it stand for 10 minutes, then charge it to 3.2V at 0.2C, and finally charge it at a constant voltage of 3.2V to 0.05C. Calculate the energy density based on the discharge data;
[0106] (3) Cyclic performance test: Charge at 1C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C cutoff, let stand for 10 minutes, discharge at 1C to 2V, and let stand for 10 minutes. Repeat this charge and discharge cycle and record the capacity of each cycle. The discharge capacity of the nth cycle is set as Cn.
[0107] Comparative Example 7
[0108] (1) Selecting lithium-ion batteries with lithium supplementation additives added to the positive electrode:
[0109] Experiments were conducted using a 2714897 type square battery. The positive electrode active material was selected as lithium iron phosphate + lithium replenishment additive. The corresponding capacities at different delithiation voltages are shown in Appendix Table 1. The positive electrode mass percentage was: positive electrode active material: lithium replenishment additive: conductive carbon black: conductive carbon nanotubes: binder = 96.6:0.3:0.8:0.4:1.9, and the positive electrode coating amount was set to 35.8 mg / cm³. 2 The experiment used artificial graphite as the negative electrode active material, with a charge capacity of 380 mAh / g. The negative electrode mass percentage was: negative electrode active material: conductive carbon black: binder: thickener = 96:1:2:1, and the negative electrode coating amount was set to 17 mg / cm³. 2The formation voltage V1 is set to 4.2V. According to the N / P ratio formula for lithium-ion batteries, the actual N / P ratio of this battery is 1.096.
[0110] The preparation of the positive electrode, the preparation of the negative electrode, and the assembly of the lithium-ion secondary battery in this comparative example are exactly the same as in Example 3.
[0111] (2) Formation: After the battery has been filled with electrolyte and allowed to stand, charge it to 4.2V at 0.2C, then charge it at a constant voltage of 4.2V to 0.05C and let it stand for 10 minutes. Discharge it to 2V at 0.2C, let it stand for 10 minutes, then charge it to 3.2V at 0.2C and charge it at a constant voltage of 3.2V to 0.05C and let it stand for 10 minutes. Calculate the energy density based on the discharge data.
[0112] (3) Cyclic performance test: Charge at 1C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C cutoff, let stand for 10 minutes, discharge at 1C to 2V, and let stand for 10 minutes. Repeat this charge and discharge cycle and record the capacity of each cycle. The discharge capacity of the nth cycle is set as Cn.
[0113] Comparative Example 8
[0114] (1) Selecting lithium-ion batteries with lithium supplementation additives added to the positive electrode:
[0115] The comparative battery design, positive electrode preparation, negative electrode preparation, and lithium-ion secondary battery assembly are exactly the same as in Example 3.
[0116] (3) Formation: After the battery has been filled with electrolyte and allowed to stand, charge it to 3.65V at 0.2C, then charge it at a constant voltage of 3.65V to 0.05C. Let it stand for 10 minutes, then discharge it to 2V at 0.2C, let it stand for 10 minutes, then charge it to 3.2V at 0.2C, and finally charge it at a constant voltage of 3.2V to 0.05C. Calculate the energy density based on the discharge data.
[0117] (3) Cyclic performance test: Charge at 1C to 3.65V, then charge at a constant voltage of 3.65V to 0.05C cutoff, let stand for 10 minutes, discharge at 1C to 2V, and let stand for 10 minutes. Repeat this charge and discharge cycle and record the capacity of each cycle. The discharge capacity of the nth cycle is set as Cn.
[0118] The energy densities of the various embodiments and comparative examples in the pouch cell are compared in Appendix Table 2. The data in the table show that Embodiments 1 and 2, using positive electrode lithium supplementation additives, a low-voltage formation process, and a reasonable negative electrode redundancy design, achieve higher energy densities than Comparative Examples 1 and 2.
[0119] The energy densities of the various embodiments and comparative examples in the prismatic cells are compared in Appendix Table 3. The data in the table show that Embodiments 3 and 4, using positive electrode lithium supplementation additives, a low-voltage formation process, and a reasonable negative electrode redundancy design, achieve higher energy densities than Comparative Examples 5 and 6.
[0120] Table 1 shows the specific capacity performance of lithium iron phosphate and lithium replenishment additives under different delithiation voltages, as detailed below:
[0121] Table 1
[0122]
[0123] Table 2 shows the energy density of various embodiments and comparative examples of the pouch cell, as detailed below:
[0124] Table 2
[0125]
[0126]
[0127] Table 3 shows the energy density of various embodiments and comparative examples of the square battery, as detailed below:
[0128] Table 3
[0129]
[0130] like Figure 1 The figure shows a comparison of the cycle capacity retention rates of different embodiments and comparative examples in pouch cells. The data in the figure shows that Embodiment 1, after standard capacity testing, underwent one high-voltage activation after 900 cycles, while Embodiment 2, after standard capacity testing, underwent two high-voltage activations at 500 and 1000 cycles respectively. Overall, the two embodiments show better cycle performance than the four comparative examples, and high-voltage activation significantly improves the battery's cycle capacity.
[0131] Figure 2 This chart compares the cycle capacity retention of different embodiments and comparative examples of prismatic batteries. The data shows that, after standard capacity testing, Embodiment 3 underwent one high-voltage activation after 900 cycles, while Embodiment 4 underwent two high-voltage activations at 400 and 1100 cycles, respectively. Overall, the two embodiments outperform the four comparative examples in terms of cycle performance, and high-voltage activation significantly improves the battery's cycle capacity.
[0132] Finally, it should be noted that the above embodiments are merely illustrative and explanatory of the present invention, and are not intended to limit the present invention to the scope of the described embodiments. Furthermore, those skilled in the art will understand that the present invention is not limited to the above embodiments, and many more variations and modifications can be made based on the teachings of the present invention, all of which fall within the scope of protection claimed by the present invention.
Claims
1. A method of using a lithium-ion battery, comprising: The lithium ion battery including a lithium supplement additive in a positive electrode sheet is subjected to low-voltage formation.
2. The method of claim 1, wherein the lithium-ion battery is used for, The low-voltage formation includes: constant current charging to a first charging cut-off voltage V1, maintaining V1 voltage constant voltage charging to a current less than 0.05C, standing for 10 min, constant current discharging to a first discharging cut-off voltage, and recording discharging capacity C0. The first charging cut-off voltage V1 is 3V-3.8V, the first discharging cut-off voltage is 2.0V-2.5V, the second charging cut-off voltage V2 is 3V-3.8V, the charging current when constant current charging to the second charging cut-off voltage V2 is 0.02C-2C, and the discharging current when constant current discharging to the first discharging cut-off voltage is 0.02C-2C.
3. The method of claim 2, wherein the lithium-ion battery is used for, When the capacity attenuation of the lithium ion battery meets a determination condition, the battery is subjected to high-voltage activation.
4. The method of using a lithium-ion battery according to any one of claims 1-3, wherein, The process of performing standard capacity and high-voltage activation when the capacity attenuation of the lithium ion battery meets a determination condition is as follows:
5. The method of claim 4, wherein the lithium-ion battery is used for, When the capacity attenuation of the lithium ion battery meets a determination condition, the battery is subjected to high-voltage activation. The process of performing standard capacity and high-voltage activation when the capacity attenuation of the lithium ion battery meets a determination condition is as follows:
6. The method of claim 4, wherein the lithium-ion battery is used for, When the capacity attenuation of the lithium ion battery meets a determination condition, the battery is subjected to high-voltage activation.
7. The method of claim 6, wherein the lithium-ion battery is used for, The process of performing high-voltage activation includes: constant current charging to a third charging cut-off voltage V3, maintaining V3 voltage constant voltage charging to a current less than 0.05C, standing for 10 min, constant current discharging to a second discharging cut-off voltage, standing for 10 min, constant current charging to a fourth charging cut-off voltage V4, and maintaining V4 voltage constant voltage charging to a current less than 0.05C.
8. The method of claim 4, wherein the lithium-ion battery is used for, The third charging cut-off voltage V3 is 3.8V-4.8V, the second discharging cut-off voltage is 2.0V-2.5V, and the fourth charging cut-off voltage V4 is 3V-3.8V; wherein V1V3; the charging current when constant current charging to the fourth charging cut-off voltage V4 is 0.02C-2C, and the discharging current when constant current discharging to the second discharging cut-off voltage is 0.02C-2C.
9. A lithium ion battery for use in accordance with the method for use of a lithium ion battery as claimed in any one of claims 1 to 8, characterised in that, The process of performing standard capacity and high-voltage activation when the capacity attenuation of the lithium ion battery meets a determination condition is performed once or multiple times according to the use of the lithium ion battery. The lithium ion battery includes a cell and a battery shell packaging the cell, the cell includes a positive electrode sheet and a negative electrode sheet, the material of the positive electrode active material in the positive electrode sheet is lithium iron phosphate LiFePO4, a lithium supplement additive is added in the positive electrode sheet, the lithium supplement additive has a higher delithiation potential than the positive electrode active material, and the material of the negative electrode active material in the negative electrode sheet is graphite.
10. The lithium-ion battery of claim 9, wherein, The lithium supplement additive is one or a mixture of several of Li2NiO2, Li5FeO4 and Li2O; the surface density of the positive electrode sheet is 25-45 mg / cm 2 , and the surface density of the negative electrode sheet is 12-23 mg / cm 2 .