Long-circulation lithium ion battery and charge-discharge control method

Abstract

The invention discloses a long-circulation lithium ion battery and a charging and discharging control method. The long-circulation lithium ion battery comprises a positive plate, a negative plate and a diaphragm, the positive plate and the negative plate are separated through the diaphragm, the N / P ratio of the long-circulation lithium ion battery is at least 1.1, the positive plate and / or the negative plate contains a lithium supplement agent, a lithium storage layer is pre-constructed on the surface, far away from the positive plate, of the negative plate, and the lithium storage layer is a lithium storage layer. The lithium storage layer does not participate in charging and discharging in the initial cycle process. The lithium storage layer is constructed on the negative electrode side by adding excessive negative electrode materials on the negative electrode side and combining the lithium supplementing technology, and the lithium storage layer does not participate in charging and discharging in the initial cycle process; meanwhile, by controlling the lower limit cut-off voltage of discharge in the battery circulation process, the capacity capability and the service life level of the battery cell are fully exerted, and the longer the cycle life of the battery is, the longer the cycle life is.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a long-cycle lithium-ion battery and a charging and discharging control method. Background Technology

[0002] Lithium-ion batteries, with their advantages of high safety, low cost, and long cycle life (over 3000 cycles), have become the mainstream technology in the fields of new energy vehicles and energy storage, especially lithium iron phosphate batteries, which play an irreplaceable role in these areas. However, with technological advancements, more stringent requirements have been placed on the cycle life of lithium-ion batteries. To address this, lithium battery companies have introduced strategies such as lithium replenishment and electrolyte replenishment to improve the cycle life of the cells, which can increase the cycle life to around 10,000 cycles. However, this method has limited effect on improving the cycle life of lithium batteries, and a more efficient cycle life enhancement technology is urgently needed.

[0003] CN114784401A proposes a design that introduces a high-capacity alloy-type anode material as a lithium storage agent in the negative electrode of a lithium battery. It compensates for active lithium loss by gradually reducing the discharge cutoff voltage, further achieving a slow lithium release effect and improving the cell's cycle life. However, this method suffers from significant capacity sacrifice and high cost. Furthermore, it lacks a clear strategy for controlling the discharge cutoff voltage and its rationality, and it is not universally applicable to other systems. This invention achieves improved cycle life by adjusting the positive and negative electrode capacity ratio and the amount of lithium storage agent material in the cell. It does not require the addition of a high-capacity alloy-type anode material, has minimal impact on capacity and cost, and its charge / discharge control strategy is universally applicable to different systems and designs.

[0004] CN117038938A proposes a lithium replenishing agent material with higher air stability and its application in lithium-ion batteries to improve their initial coulombic efficiency and cycle life. However, this patent does not involve constructing a lithium-release layer to further improve cycle life. This invention constructs a lithium-release layer in the battery cell based on lithium replenishing agents and N / P ratio regulation, which can more effectively improve the cell's cycle capability.

[0005] CN111384428B discloses a core-shell structured lithium replenishing agent material and a lithium-ion battery. This patent improves the cell's cycle life by achieving a slow-release effect of the lithium replenishing agent through the dissolution of the outer shell. This technology achieves the slow-release effect of lithium on the positive electrode and separator components. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings and defects of existing technologies and provide an ultra-long cycle life lithium-ion battery and a charge-discharge control method that can extend cycle life. This invention achieves the effect of constructing a lithium slow-release layer on the negative electrode by designing a suitable N / P ratio and the amount of lithium replenishing agent, and by proposing a reasonable and efficient charge-discharge management strategy to achieve the effect of active lithium slow release, resulting in greater controllability.

[0007] One object of the present invention is to provide a long-cycle lithium-ion battery, comprising a positive electrode, a negative electrode, and a separator, wherein the positive electrode and the negative electrode are separated by the separator, the N / P ratio of the long-cycle lithium-ion battery is at least 1.1, the positive electrode and / or the negative electrode contains a lithium replenishing agent, and a lithium storage layer is pre-constructed on the surface of the negative electrode away from the positive electrode, wherein the lithium storage layer does not participate in charging and discharging during the initial cycle.

[0008] Preferably, the lithium replenishment capacity of the positive and / or negative electrode is 0.1 mAh / cm². 2 -1.16mAh / cm 2 .

[0009] Preferably, the lithium replenishing agent is a positive electrode lithium replenishing agent and / or a negative electrode lithium replenishing agent.

[0010] Preferably, the positive electrode active material of the positive electrode sheet is selected from one or more of lithium iron phosphate, nickel-cobalt-manganese ternary lithium, nickel-manganese binary lithium, lithium manganese oxide, lithium cobalt oxide, and lithium-rich manganese.

[0011] Preferably, the negative electrode active material of the negative electrode sheet is selected from one or more of artificial graphite, hard carbon, soft carbon, silicon oxide, and silicon carbon.

[0012] Preferably, the long-cycle lithium-ion battery is a stacked battery or a wound battery.

[0013] Preferably, the long-cycle lithium-ion battery is a pouch battery, a square aluminum-cased battery, a cylindrical battery, or a button battery.

[0014] Preferably, the mass of the lithium replenishing agent is 0.3%-5.6% of the mass of the positive electrode active material / negative electrode active material.

[0015] Another objective of this invention is to provide a charge / discharge control method for a long-cycle lithium-ion battery, used for charge / discharge control of the battery, wherein the discharge voltage of the battery is managed in the battery management system (BMS) using the following strategy:

[0016] A preset discharge lower limit cutoff voltage is provided, which is dynamically adjusted according to the battery's SOH state. The charge and discharge control of the long-cycle-life lithium-ion battery is based on this discharge lower limit cutoff voltage, which is expressed as: U 截止 =U 空电态正极初始 -f-1 (f(U 空电态负极初始 )- f(U 满电态负极初始 )+f(U 满电态负极实时 ));

[0017] Among them, U 截止 U is the lower limit cutoff voltage for discharge during the cyclic process. 空电态正极初始 U represents the positive electrode potential of a fresh, uncharged battery cell in its open state. 空电态负极初始 U represents the negative electrode potential of a fresh, uncharged battery cell. 满电态负极初始 For a fresh battery cell in its fully charged negative electrode potential, U 满电态负极实时 Let f(x) be the negative electrode potential of the cell in a fully charged state during the cyclic process, and f(x) be the function of the negative electrode potential and negative electrode capacity of the cell.

[0018] Preferably, a function U is provided to relate the lower discharge cutoff voltage to the state of state (SOH). 截止 =g(SOH), based on the relationship function between the lower discharge cutoff voltage and the SOH state, the discharge cutoff voltage can be dynamically adjusted according to the SOH state of the battery;

[0019] The relationship between the discharge lower limit cutoff voltage and the SOH state is obtained by performing cycle tests on lithium-ion batteries, collecting the fully charged negative electrode potential value of the cell at each SOH aging stage, and correcting the discharge lower limit cutoff voltage for the next stage, ultimately obtaining the SOH-U. 截止 The functional relationship.

[0020] This invention constructs a lithium storage layer on the negative electrode side by adding an excess of negative electrode material and combining it with lithium replenishment technology (including positive electrode lithium replenishment technology and negative electrode lithium replenishment technology). This lithium storage layer does not participate in charging and discharging during the initial cycle. At the same time, by controlling the lower limit of discharge cutoff voltage during battery cycling, the capacity and lifespan of the battery cell are fully utilized, thereby achieving a longer cycle life. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the cell structure of the long cycle life lithium-ion battery of the present invention. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0023] This invention constructs a lithium-releasing slow-release layer inside the battery cell by increasing the N / P ratio (CB value) of the positive and negative electrodes and the content of lithium replenishing agent. Through advanced charge and discharge management strategies, it achieves the technical effect of ultra-long cycle life of lithium-ion batteries, and can also effectively improve the energy density and power performance of the battery cell.

[0024] See Figure 1 As shown in the exemplary embodiment of this application, the long cycle life lithium-ion battery includes a positive electrode 10, a negative electrode 20, a separator 30, an electrolyte, and a lithium replenishing agent, with an N / P ratio of at least 1.1. The positive electrode and / or the negative electrode contains a lithium replenishing agent, and a lithium storage layer 21 is pre-constructed on the surface of the negative electrode away from the positive electrode. The lithium storage layer 21 does not participate in charging and discharging during the initial cycle.

[0025] According to the present invention, the lithium replenishment surface capacity of the positive electrode and / or negative electrode is 0.58 mAh / cm². 2 -1.16mAh / cm 2 It can be any of these values, such as 0.58mAh / cm³. 2 0.68mAh / cm 2 0.78mAh / cm 2 0.88mAh / cm 2 0.98mAh / cm 2 1.00mAh / cm 2 1.02mAh / cm 2 1.08mAh / cm 2 1.10mAh / cm 2 1.10mAh / cm 2 1.13mAh / cm 2 1.12mAh / cm 2 1.14mAh / cm 2 1.16mAh / cm 2 ,

[0026] According to the present invention, the lithium replenishing agent is a positive electrode lithium replenishing agent and / or a negative electrode lithium replenishing agent, that is, for positive electrode lithium replenishment it is a positive electrode lithium replenishing agent, such as Li5FeO4, and for negative electrode lithium replenishment it is a negative electrode lithium replenishing agent.

[0027] According to the present invention, the positive electrode is composed of a positive electrode active material, a conductive agent, a binder and a current collector, wherein the positive electrode active material includes one or more lithium-containing active materials such as lithium iron phosphate, nickel-cobalt-manganese ternary lithium, nickel-manganese binary lithium, lithium manganese oxide, lithium cobalt oxide, and lithium-rich manganese.

[0028] In an exemplary embodiment, the negative electrode is composed of a negative electrode active material, a conductive agent, a binder, a dispersant, and a current collector, wherein the negative electrode active material includes one or more of lithium-intercalable active materials such as artificial graphite, hard carbon, soft carbon, silicon oxide, and silicon carbon.

[0029] In this application, the N / P ratio of the battery is designed to be ≥1.1, and a lithium replenishing agent is further applied to replenish the lithium insertion amount of the negative electrode, so that the negative electrode potential of the cell under full charge is consistent with the negative electrode potential of the reference group cells under full charge.

[0030] In this application, the increased N / P ratio during cell design leads to a significant overload of the negative electrode, resulting in insufficient lithium intercalation. Therefore, a lithium replenishment technique is further applied to supplement the lithium intercalation of the negative electrode, ensuring that the negative electrode potential of the cell in its fully charged state is consistent with that of the reference group cells. At this point, the empty-state negative electrode potential of the improved cell obtained by the method of this application will be lower than that of the control group (batteries without lithium replenishment), i.e., U... 空电态负极改善组 <U 空电态负极对照组 When the discharge cutoff voltage is continuously reduced, the empty-state negative electrode potential of the improved group's cells will increase. When its potential is equal to that of the control group, the discharge cutoff potential reaches a reasonable limit and is no longer reduced. U appears. 空电态负极改善组 =U 空电态负极对照组 Previously, the discharge lower limit cutoff voltage was managed according to the following relationship:

[0031] U 截止 =U 空电态正极初始 -f -1 (f(U 空电态负极初始 (-Active lithium loss); Active lithium loss = f(U) 满电态负极初始 )-f(U 满电态负极实时 By combining the two relations, the final management strategy of this application is obtained:

[0032] U 截止 =U 空电态正极初始 -f -1 (f(U 空电态负极初始 )- f(U 满电态负极初始 )+f(U 满电态负极实时 ))

[0033] Among them, U 截止 U is the lower limit cutoff voltage for discharge during the cyclic process. 空电态正极初始 To improve the open-state positive electrode potential of the fresh cells in the group, U 空电态负极初始 To improve the open-state negative electrode potential of the fresh cells in the group, U 满电态负极初始 To improve the negative electrode potential of the fresh cells in the group when fully charged, U 满电态负极实时 To improve the negative electrode potential of the fully charged cell during the cycling process, the function f(x) is a function of the negative electrode potential and negative electrode capacity of the cell in the improvement group.

[0034] As can be seen from the above, the lithium-ion battery provided in this application has its discharge lower limit cutoff voltage controlled by the battery management system (BMS) and controlled according to the preset discharge lower limit cutoff management strategy of this application, including: a preset discharge lower limit cutoff voltage dynamically adjusted according to the battery's state of equilibrium (SOH); and charge / discharge control of the long-cycle-life lithium-ion battery based on the discharge lower limit cutoff voltage. The discharge lower limit cutoff voltage is expressed as: U 截止 =U 空电态正极初始 -f -1 (f(U 空电态负极初始 )- f(U 满电态负极初始 )+f(U 满电态负极实时 )); where U 截止 U is the lower limit cutoff voltage for discharge during the cyclic process. 空电态正极初始 U represents the positive electrode potential of a fresh, uncharged battery cell in its open state. 空电态负极初始 U represents the negative electrode potential of a fresh, uncharged battery cell. 满电态负极初始 For a fresh battery cell in its fully charged negative electrode potential, U 满电态负极实时 Let f(x) be the negative electrode potential of the cell in a fully charged state during the cyclic process, and f(x) be the function of the negative electrode potential and negative electrode capacity of the cell.

[0035] In an exemplary embodiment of this application, a relationship function U between the lower discharge cutoff voltage and the SOH state is provided. 截止 =g(SOH), based on the relationship function between the lower discharge cutoff voltage and the SOH state, the discharge cutoff voltage can be dynamically adjusted according to the SOH state of the battery;

[0036] The relationship between the discharge lower limit cutoff voltage and the SOH state is obtained by performing cycle tests on lithium-ion batteries, collecting the fully charged negative electrode potential value of the cell at each SOH aging stage, and correcting the discharge lower limit cutoff voltage for the next stage, ultimately obtaining the SOH-U. 截止 The functional relationship is as follows. Specifically, a three-electrode method can be used to perform cycle testing on lithium batteries and collect the fully charged negative electrode potential value of the cell at each SOH aging stage. This data is then used to correct the discharge lower limit cutoff voltage for the next stage, further obtaining the SOH-discharge lower limit cutoff voltage U. 截止 The functional relationship g is denoted as U. 截止 =g(SOH), and applying this management strategy to the BMS to manage the battery discharge voltage can maximize the battery's cycle life.

[0037] Example 1

[0038] (1) Preparation of positive electrode sheet

[0039] The positive electrode active material LFP, conductive agent SP, and binder PVDF were uniformly mixed and dispersed in NMP solvent at a certain mass ratio to obtain a homogeneous slurry. The solid components of the slurry included 95 wt% positive electrode active material LFP, 2 wt% conductive agent SP, and 3 wt% binder PVDF. Then, lithium supplementer Li5FeO4 was added to the homogeneous slurry to obtain a positive electrode mixed slurry, with the amount of lithium supplementer added being 2.8% of the amount of LFP. The positive electrode mixed slurry was uniformly coated on both sides of an aluminum foil, and the areal capacity of the positive electrode active material was controlled to be 6.2 mAh / cm². 2 The lithium-ion battery capacity is 0.58 mAh / cm². 2 The positive electrode P1 was obtained. The reversible capacity of the positive electrode active material LFP is 145 mAh / g, and the lithium replenishment capacity of the lithium replenishing agent Li5FeO4 is 485 mAh / g.

[0040] (2) Preparation of negative electrode sheet

[0041] Artificial graphite (Gr), conductive agent (SP), binder (SBR), and dispersant (CMC) were uniformly mixed and dispersed in pure water at a specific mass ratio to obtain a homogeneous negative electrode slurry. The solid components of this slurry included 95 wt% of the negative electrode active material (Gr), 2 wt% of the conductive agent (SP), 1.8 wt% of the binder (SBR), and 1.2 wt% of the dispersant (CMC). The negative electrode slurry was uniformly coated on both sides of a copper foil, and the areal capacity of the negative electrode active material was controlled to be 7.45 mAh / cm². 2 A negative electrode N1 was obtained, in which the reversible capacity of the negative electrode active material Gr was 350 mAh / g.

[0042] (3) Preparation of lithium-ion batteries

[0043] The positive electrode P1 and negative electrode N1 are stacked with a separator and packaged into a cell. Then, electrolyte is added, and after aging, formation, aging, secondary sealing and sorting processes, lithium-ion battery C1 is obtained. The designed N / P ratio of C1 cell is 1.2, and after lithium replenishment, the N / P ratio is improved to 1.1.

[0044] Example 2

[0045] (1) Preparation of positive electrode sheet

[0046] A homogeneous positive electrode slurry was prepared by uniformly mixing and dispersing the positive electrode active material (LFP), conductive agent (SP), and binder (PVDF) in a specific mass ratio in NMP solvent. The slurry contained 95 wt% LFP, 2 wt% SP, and 3 wt% PVDF. Lithium supplementer (Li5FeO4) was then added to the slurry to obtain a mixed positive electrode slurry, with the amount of lithium supplementer added being 5.6% of the LFP amount. The mixed positive electrode slurry was then uniformly coated onto both sides of an aluminum foil, and the areal capacity of the positive electrode active material was controlled to be 6.2 mAh / cm².2 The lithium-filled surface capacity is 1.16 mAh / cm². 2 The positive electrode P2 was obtained. The reversible capacity of the positive electrode active material LFP is 145 mAh / g, and the lithium replenishment capacity of the lithium replenishing agent Li5FeO4 is 485 mAh / g.

[0047] (2) Preparation of negative electrode sheet

[0048] Artificial graphite (Gr), conductive agent (SP), binder (SBR), and dispersant (CMC) were uniformly mixed and dispersed in pure water at a specific mass ratio to obtain a homogeneous negative electrode slurry. The solid components of this slurry included 95 wt% of the negative electrode active material (Gr), 2 wt% of the conductive agent (SP), 1.8 wt% of the binder (SBR), and 1.2 wt% of the dispersant (CMC). The negative electrode slurry was uniformly coated on both sides of a copper foil, and the areal capacity of the negative electrode active material was controlled to be 8.08 mAh / cm². 2 The negative electrode N2 was obtained, in which the reversible capacity of the negative electrode active material Gr was 350 mAh / g.

[0049] (3) Preparation of lithium-ion batteries

[0050] The positive electrode P2 and negative electrode N2 are stacked with a separator and packaged into a cell. Then, electrolyte is added, and after aging, formation, secondary sealing, and sorting processes, lithium-ion battery C2 is obtained. The designed N / P ratio of the C2 cell is 1.3, which is improved to 1.1 after lithium replenishment.

[0051] Comparative Example 1

[0052] (1) Preparation of positive electrode sheet

[0053] The positive electrode active material LFP, conductive agent SP, and binder PVDF were uniformly mixed and dispersed in NMP solvent at a certain mass ratio to obtain a uniform positive electrode slurry. The solid components of the slurry consisted of 95 wt% positive electrode active material LFP, 2 wt% conductive agent SP, and 3 wt% binder PVDF, without the addition of lithium supplementer Li5FeO4. The positive electrode slurry was uniformly coated on both sides of an aluminum foil, and the areal capacity of the positive electrode active material was controlled to be 6.2 mAh / cm². 2 The positive electrode P3 was obtained. The reversible capacity of the positive electrode active material LFP is 145 mAh / g.

[0054] (2) Preparation of negative electrode sheet

[0055] Artificial graphite (Gr), conductive agent (SP), binder (SBR), and dispersant (CMC) were uniformly mixed and dispersed in pure water at a specific mass ratio to obtain a homogeneous negative electrode slurry. The solid components of this slurry included 95 wt% of the negative electrode active material (Gr), 2 wt% of the conductive agent (SP), 1.8 wt% of the binder (SBR), and 1.2 wt% of the dispersant (CMC). The negative electrode slurry was uniformly coated on both sides of a copper foil, and the areal capacity of the negative electrode active material was controlled to be 7.45 mAh / cm². 2 A negative electrode N1 was obtained, in which the reversible capacity of the negative electrode active material Gr was 350 mAh / g.

[0056] (3) Preparation of lithium-ion batteries

[0057] The positive electrode P3 and negative electrode N1 are stacked with a separator and packaged into a cell. Then, electrolyte is added, and after aging, formation, aging, secondary sealing and sorting processes, lithium-ion battery C3 is obtained. The designed N / P ratio of C3 cell is 1.2. Since no lithium replenishment agent is used to improve it, the actual N / P ratio of C3 cell is still 1.2.

[0058] Comparative Example 2

[0059] (1) Preparation of positive electrode sheet

[0060] The positive electrode active material LFP, conductive agent SP, and binder PVDF were uniformly mixed and dispersed in NMP solvent at a certain mass ratio to obtain a uniform positive electrode slurry. The solid components of the slurry consisted of 95 wt% positive electrode active material LFP, 2 wt% conductive agent SP, and 3 wt% binder PVDF, without the addition of lithium supplementer Li5FeO4. The positive electrode slurry was uniformly coated on both sides of an aluminum foil, and the areal capacity of the positive electrode active material was controlled to be 6.2 mAh / cm². 2 The positive electrode P3 was obtained. The reversible capacity of the positive electrode active material LFP is 145 mAh / g.

[0061] (2) Preparation of negative electrode sheet

[0062] Artificial graphite (Gr), conductive agent (SP), binder (SBR), and dispersant (CMC) were uniformly mixed and dispersed in pure water at a specific mass ratio to obtain a homogeneous negative electrode slurry. The solid components of this slurry included 95 wt% of the negative electrode active material (Gr), 2 wt% of the conductive agent (SP), 1.8 wt% of the binder (SBR), and 1.2 wt% of the dispersant (CMC). The negative electrode slurry was uniformly coated on both sides of a copper foil, and the areal capacity of the negative electrode active material was controlled to be 6.85 mAh / cm². 2 The negative electrode N3 was obtained, in which the reversible capacity of the negative electrode active material Gr was 350 mAh / g.

[0063] (3) Preparation of lithium-ion batteries

[0064] The positive electrode P3 and negative electrode N3 are stacked with a separator and packaged into a cell. Then, electrolyte is added, and after aging, formation, aging, secondary sealing and sorting processes, lithium-ion battery C4 is obtained. The designed N / P ratio of C3 cell is 1.1. Since no lithium replenishment agent is used to improve it, the actual N / P ratio of C3 cell is also 1.1.

[0065] For ease of understanding, the key information regarding the above-mentioned battery cell design is summarized in the table below:

[0066] Table 1 summarizes the lithium-ion battery cell design information for the embodiments and comparative examples.

[0067] Cell Name LFP formulation percentage Lithium supplementation as a percentage of LFP weight <![CDATA[Positive electrode surface capacity (mAh / cm 2 )]]> <![CDATA[Lithium supplement surface capacity (mAh / cm 2 )]]> <![CDATA[Negative electrode surface capacity (mAh / cm 2 )]]> Design NP ratio Cyclic NP ratio Example 1 C1 95% 2.80% 6.20 0.58 7.45 1.20 1.10 Example 2 C2 95% 5.60% 6.20 1.16 8.08 1.30 1.10 Comparative Example 1 C3 95% 0.00% 6.20 0.00 7.45 1.20 1.20 Comparative Example 2 C4 95% 0.00% 6.20 0.00 6.85 1.10 1.10

[0068] C1 of the examples and comparative examples ~ The C4 battery's 0.5C cycle performance was tested at room temperature using two charge / discharge management strategies. The number of cycles in the table represents the number of cycles the cell has completed when its capacity reaches 70% of its initial capacity.

[0069] Table 2 summarizes the cycle performance test results of lithium-ion battery cells from the examples and comparative examples.

[0070] Cell Name At 25℃, the fixed cutoff voltage Ucutoff of 1C / 1C is 2.0V. 25℃ 1C / 1C Intelligent Advanced Management Strategy U Cutoff = g(SOH) Example 1 C1 7850 times 9200 times Example 2 C2 8970 times 12400 times Comparative Example 1 C3 4730 times 4730 times Comparative Example 2 C4 6200 times 6200 times

[0071] As can be seen from the table above, the intelligent advanced management strategy based on the lithium replenishment system in this application can effectively improve the cycle life of the battery cell. A comparison of Examples 1 and 2 reveals that the intelligent advanced management strategy of this application significantly improves cycle capability in deeply lithium-replenished battery cells, thus proving that the technology of this application can effectively enhance the cycle capability of lithium-replenished battery cell systems without causing cost changes, and possesses high market value. This invention improves the cycle capability of the battery cell by adjusting the positive and negative electrode capacity ratio (CB value) and the amount of lithium replenishing agent material, thereby enhancing the effect of constructing a lithium slow-release layer. This results in a more effective improvement in cycle life without the need for additional high-capacity alloy anode materials, having minimal impact on capacity and cost. Furthermore, it employs a reasonable and efficient charge-discharge control strategy to achieve the effect of active lithium slow release, offering greater controllability and applicability to different systems and designs.

[0072] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description, and therefore all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

[0073] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A long-cycle lithium-ion battery, comprising a positive electrode, a negative electrode, and a separator, wherein the positive electrode and the negative electrode are separated by the separator, characterized in that, The long-cycle lithium-ion battery has an N / P ratio of at least 1.1, the positive and / or negative electrode contains a lithium replenishing agent, and a lithium storage layer is pre-constructed on the surface of the negative electrode away from the positive electrode. The lithium storage layer does not participate in charging and discharging during the initial cycle.

2. The long-cycle lithium-ion battery according to claim 1, characterized in that, The lithium replenishment capacity of the positive and / or negative electrode is 0.1-1.16 mAh / cm². 2 .

3. The long-cycle lithium-ion battery according to claim 1, characterized in that, The lithium replenishing agent is a positive electrode lithium replenishing agent and / or a negative electrode lithium replenishing agent.

4. The long-cycle lithium-ion battery according to claim 1, characterized in that, The positive electrode active material of the positive electrode sheet is selected from one or more of lithium iron phosphate, nickel-cobalt-manganese ternary lithium, nickel-manganese binary lithium, lithium manganese oxide, lithium cobalt oxide, and lithium-rich manganese.

5. The long-cycle lithium-ion battery according to claim 1, characterized in that, The negative electrode active material of the negative electrode sheet is selected from one or more of artificial graphite, hard carbon, soft carbon, silicon oxide, and silicon carbon.

6. The long-cycle lithium-ion battery according to claim 1, characterized in that, The long-cycle lithium-ion battery is a stacked battery or a wound battery.

7. The long-cycle lithium-ion battery according to claim 1, characterized in that, The long-cycle lithium-ion battery is a pouch battery, a square aluminum-cased battery, a cylindrical battery, or a button battery.

8. The long-cycle lithium-ion battery according to claim 1, characterized in that, The mass of the lithium supplement is 0.3%-5.6% of the mass of the positive electrode active material / the negative electrode active material.

9. A method for controlling the charge and discharge of a long-cycle lithium-ion battery, used for controlling the charge and discharge of the long-cycle lithium-ion battery according to any one of claims 1-8, characterized in that, The following strategies are used to manage the discharge voltage of the battery in the battery management system (BMS): A preset discharge lower limit cutoff voltage is provided, which is dynamically adjusted according to the battery's SOH state. The long-cycle-life lithium-ion battery is then charged and discharged based on this discharge lower limit cutoff voltage, which is expressed as: U 截止 =U 空电态正极初始 -f -1 (f(U 空电态负极初始 )- f(U 满电态负极初始 )+f(U 满电态负极实时 )); Among them, U 截止 U is the lower limit cutoff voltage for discharge during the cyclic process. 空电态正极初始 U represents the positive electrode potential of a fresh, uncharged battery cell in its open state. 空电态负极初始 U represents the negative electrode potential of a fresh, uncharged battery cell. 满电态负极初始 For a fresh battery cell in its fully charged negative electrode potential, U 满电态负极实时 Let f(x) be the negative electrode potential of the cell in a fully charged state during the cyclic process, and f(x) be the function of the negative electrode potential and negative electrode capacity of the cell.

10. The charging and discharging control method for a long-cycle lithium-ion battery according to claim 9, characterized in that, A function U is set to relate the lower discharge cutoff voltage to the state of state (SOH). 截止 =g(SOH), based on the relationship function between the lower discharge cutoff voltage and the SOH state, the discharge cutoff voltage can be dynamically adjusted according to the SOH state of the battery; The relationship between the discharge lower limit cutoff voltage and the SOH state is obtained by performing cycle tests on lithium-ion batteries, collecting the fully charged negative electrode potential value of the cell at each SOH aging stage, and correcting the discharge lower limit cutoff voltage for the next stage, ultimately obtaining the SOH-U. 截止 The functional relationship.

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