Lithium ion battery, lithium supplementing method and preparation method

Abstract

The invention discloses a lithium ion battery, a lithium supplementing method and a preparation method, the lithium ion battery comprises: a housing, the inner wall of which is provided with a lithium supplementing layer, and the material of the lithium supplementing layer comprises a lithium supplementing agent; the positive electrode assembly comprises a voltage dividing piece, a positive electrode post and a positive electrode material, the positive electrode post is electrically connected with the shell through the voltage dividing piece, and the positive electrode material is connected with the positive electrode post; the negative electrode assembly comprises a negative electrode post and a negative electrode material which are connected, and the negative electrode post is in insulated connection with the shell; wherein the resistance value of the voltage dividing piece is determined based on the difference value between the complete activation voltage of the lithium supplementing agent and the overcharge cut-off voltage of the positive electrode material; and the larger the difference value between the complete activation voltage of the lithium supplement agent and the overcharge cut-off voltage of the positive electrode material is, the larger the resistance value of the voltage divider is. According to the lithium ion battery, the lithium supplementing method and the preparation method, the lithium supplementing efficiency can be improved, the formation time can be shortened, and the lithium supplementing effect and the gram capacity exerting value of the positive electrode material can be improved.

Description

Technical Field

[0001] The present invention relates to a lithium ion battery, a lithium replenishing method and a preparation method. Background Art

[0002] With the rapid development of new energy vehicles and energy storage technologies, higher requirements are constantly being placed on the various performance of lithium-ion batteries, among which extending cycle performance and improving calendar life are the most urgent. Currently, one of the main reasons affecting the cycle or storage performance of lithium-ion batteries is that in order to repair the damaged SEI film (solid electrolyte interface film) of the negative electrode particles inside the battery cell, the active lithium inside the material system needs to be continuously consumed, resulting in a large loss of capacity. To address this problem, the industry mainly adds lithium supplements to the positive or negative electrode system to compensate for the earlier loss of active lithium, thereby improving the cycle life.

[0003] Taking positive electrode lithium replenishment as an example, traditional methods involve adding a lithium replenisher to the slurry during the homogenization of the cathode material, followed by formation through a low current, gradually supplying lithium ions to the system. However, these lithium replenishers are highly alkaline, making the slurry gel easily a problem during the homogenization process, impacting production and leading to abnormal battery performance.

[0004] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the Invention

[0005] The object of the present invention is to provide a lithium-ion battery, a lithium replenishment method and a preparation method, which can improve the lithium replenishment efficiency, shorten the formation time, and improve the lithium replenishment effect and the gram capacity utilization value of the positive electrode material.

[0006] To achieve the above object, a specific embodiment of the present invention provides a lithium-ion battery, comprising:

[0007] The outer shell has a lithium supplement layer on its inner wall, wherein the material of the lithium supplement layer includes a lithium supplement agent;

[0008] A positive electrode assembly, comprising a voltage divider, a positive electrode post, and a positive electrode material, wherein the positive electrode post is electrically connected to the housing via the voltage divider, and the positive electrode material is connected to the positive electrode post;

[0009] A negative electrode assembly, comprising a connected negative electrode post and a negative electrode material, wherein the negative electrode post is insulated from the housing;

[0010] The resistance value of the voltage divider is determined based on the difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material; and the greater the difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material, the greater the resistance value of the voltage divider.

[0011] In one or more embodiments of the present invention, the difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material is 0.15 to 0.2 V, and the resistance of the voltage divider is 10 to 500 Ω; and / or,

[0012] The difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material is 0.2 to 0.6 V, and the resistance of the voltage divider is 500 to 3000 Ω; and / or,

[0013] The difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material is 0.6 to 1.0 V, and the resistance of the voltage divider is 3000 to 30000 Ω; and / or,

[0014] The difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material is 1.0 to 1.15 V, and the resistance of the voltage divider is 30,000 to 100,000 Ω.

[0015] In one or more embodiments of the present invention, the material of the lithium replenishing layer further includes a conductive agent and an adhesive.

[0016] In one or more embodiments of the present invention, the conductive agent includes at least one of conductive carbon black and carbon nanotubes; and / or,

[0017] The adhesive comprises at least one of polyvinylidene fluoride, polymethyl methacrylate and polytetrafluoroethylene; and / or,

[0018] The lithium supplement includes at least one of Li5FeO4, Li2NiO2, Li2O2, Li2O, Li2MnO3, Li6CoO4, Li6MnO4 and Li3P.

[0019] In one or more embodiments of the present invention, the mass ratio of the lithium replenishing agent to the positive electrode material in the lithium replenishing layer is (1-10):100.

[0020] In one or more embodiments of the present invention, the voltage divider is a sealing ring, the positive electrode assembly includes a positive electrode top cover mounted on the outer shell, and the positive electrode column is connected to the positive electrode top cover through the sealing ring.

[0021] A specific embodiment of the present invention provides a lithium replenishing method for a lithium ion battery, which is applied to the above-mentioned lithium ion battery. The lithium replenishing method for a lithium ion battery comprises the following steps:

[0022] The positive electrode of the formation equipment is electrically connected to the shell of the lithium-ion battery, and the negative electrode of the formation equipment is electrically connected to the negative electrode post of the lithium-ion battery to perform battery formation.

[0023] In one or more embodiments of the present invention, based on the voltage divider, during the battery formation process, the voltage difference between the positive electrode column and the shell is equal to the difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material.

[0024] In one or more embodiments of the present invention, battery formation includes:

[0025] Performing initial formation at a first formation voltage not exceeding a preset voltage;

[0026] The second formation voltage is higher than the preset voltage and lower than the fully activated voltage of the lithium supplement.

[0027] In one or more embodiments of the present invention, a standard voltage for initial formation is set, and the preset voltage is the sum of the absolute value of the difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material and the standard voltage.

[0028] In one or more embodiments of the present invention, battery formation includes:

[0029] After charging at 0.05-0.1C for 55-65 minutes, charge at 0.2-0.5C to the preset voltage, and the initial formation is complete.

[0030] Charge to the fully activated voltage under 0.1-0.5C conditions to complete the re-formation.

[0031] A specific embodiment of the present invention provides a method for preparing the lithium-ion battery as described above, comprising the following steps:

[0032] preparing a lithium supplement slurry containing a lithium supplement agent;

[0033] Evenly coating the lithium replenishing slurry on the inner wall of the shell preform to form a lithium replenishing layer;

[0034] cutting the shell preform into a plurality of shells;

[0035] Assembling and injecting liquid on the shell to obtain a semi-finished battery;

[0036] The lithium-ion battery is obtained by replenishing lithium in the semi-finished battery product using the lithium replenishment method of the lithium-ion battery as described above.

[0037] Compared with the prior art, the lithium ion battery, lithium replenishment method and preparation method of the present invention have the following beneficial effects:

[0038] (1) By placing the lithium supplement agent on the inner wall of the housing, the existing technology (the solution of adding the lithium supplement agent to the positive electrode material) can avoid the processing problems such as increased viscosity of the slurry gel and abnormal screening caused by adding the high-alkalinity lithium supplement agent during the positive electrode homogenization process, thereby improving the battery production efficiency and battery output yield;

[0039] (2) By selecting the resistance value of the voltage divider between the positive electrode column and the shell, the boundary voltage between the positive electrode column and the shell is adjusted, and the shell and the negative electrode column are charged during formation. In this way, the lithium supplement agent can fully release active lithium in a higher voltage window, and at the same time, excessive lithium release from the positive electrode material can be avoided during formation, which causes structural collapse. In particular, for high-nickel ternary positive electrode materials, the structural damage caused by excessive lithium release is obvious. In addition, compared with lithium iron phosphate system batteries, when overcharged, the polarization is severe and it is easy to reach the charging cut-off voltage (also called the overcharge cut-off voltage), and a small current (<0.05C) must be used for formation charging. However, since there is a voltage difference between the shell and the positive electrode column (or positive electrode material), the lithium ion battery of the present invention can continue to be charged with a larger current of 0.1 to 0.5C to allow the lithium supplement agent to continue to fully release active lithium, shortening the formation time, improving the lithium supplement effect and the gram capacity of the positive electrode material;

[0040] (3) During the later stages of cycling and full-charge storage, due to the voltage difference between the outer shell and the positive electrode (or positive electrode material), the lithium replenisher in the lithium replenisher layer on the outer shell is always at a lower voltage, which can effectively inhibit the side reaction between the electrolyte and the lithium replenisher, reduce gas production and electrolyte consumption, and effectively improve the cycling performance and full-charge storage of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments described in the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0042] Figure 1 This is a flow chart of the formation steps in a lithium replenishment method for a lithium-ion battery in one example of the present invention;

[0043] Figure 2 is a flow chart of a method for preparing a lithium-ion battery in an example of the present invention;

[0044] Figure 3 is a perspective view of a lithium-ion battery in an example of the present invention;

[0045] Figure 4 FIG. 4 is a cross-sectional view of a lithium-ion battery in an example of the present invention.

[0046] Description of main reference numerals:

[0047] 1. Outer shell; 11. Lithium replenishing layer; 2. Positive electrode assembly; 21. Voltage divider; 22. Positive electrode column; 23. Positive electrode material; 24. Positive electrode top cover; 31. Negative electrode material; 4. Diaphragm. DETAILED DESCRIPTION

[0048] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0049] like Figure 3 and 4 As shown, a lithium-ion battery in an example of the present invention includes a shell 1, a positive electrode assembly 2 and a negative electrode assembly. A lithium replenishing layer 11 is provided on the inner wall of the shell 1, and the material of the lithium replenishing layer 11 includes a lithium replenishing agent; the positive electrode assembly 2 includes a voltage divider 21, a positive electrode post 22 and a positive electrode material 23, the positive electrode post 22 is electrically connected to the shell 1 through the voltage divider 21, and the positive electrode material 23 is connected to the positive electrode post 22; the negative electrode assembly includes a connected negative electrode post and a negative electrode material 31, and the negative electrode post is insulated from the shell 1; wherein the resistance value of the voltage divider 21 is determined based on the difference between the full activation voltage of the lithium replenishing agent and the cut-off voltage of the positive electrode material 23; and the greater the difference between the full activation voltage of the lithium replenishing agent and the overcharge cut-off voltage of the positive electrode material 23, the greater the resistance value of the voltage divider 21.

[0050] It should be noted that when the lithium-ion battery is assembled to obtain a semi-finished battery, it is generally necessary to undergo a lithium replenishment process. That is, as described in the background art, the traditional positive electrode lithium replenishment method is to add a lithium replenisher during the homogenization process of the positive electrode material 23, and then form it through a small current to gradually provide lithium ions to the system. However, the alkalinity of these lithium replenishers is relatively high, so it is easy for slurry gel abnormalities to occur during the homogenization process of the positive electrode material 23, affecting production and causing abnormal battery performance. In the present invention, the full activation voltage of the lithium replenisher is greater than the overcharge cut-off voltage of the positive electrode material 23, that is, the difference between the full activation voltage of the lithium replenisher and the overcharge cut-off voltage of the positive electrode material 23 is the value of the full activation voltage of the lithium replenisher minus the overcharge cut-off voltage of the positive electrode material 23, and this value is greater than 0.

[0051] The lithium-ion battery of the present invention arranges the lithium supplement agent on the inner wall of the shell 1 to form a lithium supplement layer 11, which can avoid the processing problems such as increased viscosity and abnormal screening of the slurry gel caused by the addition of high-alkaline lithium supplement agents during the positive electrode slurrying process in traditional technologies, thereby improving the battery production efficiency and battery output yield.

[0052] The lithium-ion battery in this example may be a blade battery.

[0053] Preferably, the difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material 23 is 0.15 to 1.15V.

[0054] Specifically, the difference between the full activation voltage of the lithium supplement agent and the overcharge cut-off voltage of the positive electrode material 23 is 0.15 to 0.2 V, and the resistance of the voltage divider 21 is 10 to 500 Ω; the difference between the full activation voltage of the lithium supplement agent and the overcharge cut-off voltage of the positive electrode material 23 is 0.2 to 0.6 V, and the resistance of the voltage divider 21 is 500 to 3000 Ω; the difference between the full activation voltage of the lithium supplement agent and the overcharge cut-off voltage of the positive electrode material 23 is 0.6 to 1.0 V, and the resistance of the voltage divider 21 is 3000 to 30000 Ω; the difference between the full activation voltage of the lithium supplement agent and the overcharge cut-off voltage of the positive electrode material 23 is 1.0 to 1.15 V, and the resistance of the voltage divider 21 is 30000 to 100000 Ω.

[0055] Taking the resistance of the voltage divider as 10-500Ω as an example, when the resistance of the voltage divider 21 is too small (the resistance of the voltage divider 21 is less than 10Ω), that is, the voltage difference between the positive electrode column 22 and the housing 1 is small, the positive electrode material 23 is easily overcharged when the lithium replenishment method of the lithium ion battery of the present invention is used to form the battery; when the resistance of the voltage divider 21 is too large (the resistance of the voltage divider 21 is greater than 500Ω), that is, the voltage difference between the positive electrode column 22 and the housing 1 is large, the actual charging voltage of the positive electrode material 23 (that is, the voltage allocated to the positive electrode material during the formation process) is low when the lithium replenishment method of the lithium ion battery of the present invention is used to form the battery, resulting in unstable battery formation. It is understandable that when the resistance of the voltage divider is within the remaining value range, the above principle is the same.

[0056] In this example, the material of the lithium replenishing layer 11 may also include a conductive agent and an adhesive; the conductive agent serves to improve the conductivity of the lithium replenishing layer 11, and the adhesive gives the lithium replenishing layer 11 a certain viscosity, so that the lithium replenishing layer 11 can be bonded to the inner wall of the shell 1.

[0057] Specifically, the lithium supplement includes at least one of Li5FeO4, Li2NiO2, Li2O2, Li2O, Li2MnO3, Li6CoO4, Li6MnO4, and Li3P. The conductive agent includes a common commercially available conductive agent, for example, at least one of conductive carbon black and carbon nanotubes. The adhesive includes a common commercially available adhesive, for example, at least one of polyvinylidene fluoride, polymethyl methacrylate, and polytetrafluoroethylene.

[0058] Preferably, the mass ratio of the lithium replenishing agent in the lithium replenishing layer 11 to the positive electrode material 23 is (1-10): 100. This ratio range is intended to meet the lithium loss amount consumed by the negative electrode material 31 during the SEI film formation process.

[0059] It should be noted that the positive electrode material 23 generally includes a lithium-containing material, a conductive agent, and a binder. The conductive agent in the positive electrode material 23 includes commonly available commercially available agents, such as at least one of conductive carbon black and carbon nanotubes. The binder in the positive electrode material 23 includes commonly available commercially available agents, such as at least one of polyvinylidene fluoride, polymethyl methacrylate, and polytetrafluoroethylene. The specific compositions of the conductive agent and binder in the positive electrode material 23 may be the same as or different from those in the lithium replenishing layer 11.

[0060] It is understood that the positive electrode material 23 can also be called a positive electrode sheet. The negative electrode material 31 can also be called a negative electrode sheet, which is installed in the shell 1. The shell 1 can also be provided with a separator 4 and an electrolyte (or electrolyte solution).

[0061] The lithium-containing material in the positive electrode material 23 can generally be lithium iron phosphate, nickel-cobalt-manganese / nickel-cobalt-aluminum ternary material, lithium cobaltate, spinel lithium manganese oxide, etc. The overcharge cutoff voltage of the positive electrode material 23 can be determined by the type of lithium-containing material.

[0062] In one specific example, the voltage divider 21 is a sealing ring. The positive electrode assembly 2 includes a positive electrode top cover 24 mounted on the housing 1. The positive electrode post 22 is connected to the positive electrode top cover 24 via the sealing ring. The housing 1, the positive electrode top cover 24, and the positive electrode post 22 are all made of existing conductive materials, such as conductive metals, specifically aluminum. In other examples, the voltage divider 21 can be other components, and the voltage divider 21 can also be composed of a sealing ring and other components.

[0063] In this example, the positive electrode material 23, the negative electrode material 31 and the separator 4 can together constitute an electrode group, and the electrode group also includes a positive electrode tab electrically connected to the positive electrode material 23, and a negative electrode tab electrically connected to the negative electrode material 31. The positive electrode column 22 can be electrically connected to the positive electrode tab through a positive electrode bracket or other components, and the negative electrode column can be electrically connected to the negative electrode tab through a negative electrode bracket or other components; thereby realizing the electrical connection between the positive electrode column 22 and the positive electrode material 23, and the electrical connection between the negative electrode column and the negative electrode material 31.

[0064] It should be noted that in the electrode assembly, the positive electrode material 23 can be evenly coated on the aluminum foil, and then the portion of the aluminum foil not coated with the positive electrode material 23 can be die-cut into the positive electrode tab, thereby achieving electrical connection between the positive electrode material 23 and the positive electrode tab. The negative electrode material 31 can be evenly coated on the copper foil, and then the portion of the copper foil not coated with the negative electrode material 21 can be die-cut into the negative electrode tab, thereby achieving electrical connection between the negative electrode material 31 and the negative electrode tab.

[0065] A specific example of the present invention provides a lithium replenishing method for a lithium ion battery, which is applied to the above-mentioned lithium ion battery. The lithium replenishing method for a lithium ion battery comprises the following steps:

[0066] The positive electrode of the formation equipment is electrically connected to the shell of the lithium-ion battery, and the negative electrode of the formation equipment is electrically connected to the negative electrode post of the lithium-ion battery to perform battery formation.

[0067] It should be noted that formation is a key process in battery manufacturing, primarily involving the activation of the battery cell after it has been injected with electrolyte. This process, through charge and discharge, causes a chemical reaction within the cell to form the SEI (solid electrolyte interface) film, ensuring the safety, reliability, and long cycle life of the cell during subsequent charge and discharge cycles.

[0068] The formation process is an energy conversion process that achieves the initial chemical conversion of the battery through charging and discharging, activating the active materials in the battery cell. The principles of formation and capacity conversion of lithium battery cells are relatively complex, but it is also a very important process that affects battery performance.

[0069] It should be noted that the full activation voltage can be considered as the voltage required for the lithium replenishing agent in the lithium replenishing layer to completely release the active lithium inside the lithium replenishing agent during the formation process.

[0070] The full activation voltage of a lithium supplement depends on the type of supplement. For example, if the supplement is Li5FeO4, the full activation voltage is 4.4V. This means that during the formation process, the Li5FeO4 needs to be charged to 4.4V to fully release the active lithium within it. If the supplement is Li2NiO2, the full activation voltage is 4.2V. This means that during the formation process, the Li2NiO2 needs to be charged to 4.2V to fully release the active lithium within it.

[0071] The formation voltage is the charge and discharge voltage during the formation process. The formation process is the process in which the film-forming additive forms the SEI film on the surface of the active material particles. The process of forming the SEI film is an irreversible reaction process. Therefore, it is only necessary to set the formation voltage above the potential at which the film-forming additive reacts completely so that the film-forming reaction can proceed fully.

[0072] The overcharge cut-off voltage of the positive electrode material is determined based on the type of lithium-containing material in the positive electrode material; for example, when the lithium-containing material is lithium iron phosphate, the overcharge cut-off voltage of the positive electrode material is 3.65V; when the lithium-containing material is a high-nickel ternary positive electrode material LiNi 0.8 Co 0.1 Mn 0.1 When O2 is used, the overcharge cut-off voltage of the positive electrode material is 4.25V.

[0073] In this example, based on the voltage divider, the voltage difference between the positive electrode post and the shell during the battery formation process is equal to the difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material.

[0074] It can be understood that due to the selection of lithium-containing substances in the lithium replenisher and the positive electrode material, there is a difference between the full activation voltage of the lithium replenisher and the overcharge cut-off voltage of the positive electrode material (the default difference is a non-negative number). By selecting the voltage divider, the voltage difference between the positive electrode column and the shell can be made equal to the difference between the full activation voltage of the lithium replenisher and the overcharge cut-off voltage of the positive electrode material, so as to achieve the formation process of the present invention. That is, during the formation process, due to the voltage difference between the shell and the positive electrode column, the formation charge can continue to be carried out at a larger current of 0.1 to 0.5C, allowing the lithium replenisher to continue to fully release active lithium, shortening the formation time, and improving the lithium replenishment effect and the gram capacity of the positive electrode material.

[0075] Preferably, Figure 1 As shown, the battery formation includes:

[0076] S11, performing initial formation at a first formation voltage not exceeding a preset voltage;

[0077] S12, performing formation again at a second formation voltage that exceeds the preset voltage but does not exceed the full activation voltage of the lithium supplement.

[0078] That is, during the formation process, when the voltage between the outer shell and the negative electrode (i.e., the first formation voltage) is less than or equal to the preset voltage, the initial formation is carried out, and when the voltage between the outer shell and the negative electrode (i.e., the second formation voltage) exceeds the preset voltage but does not exceed the full activation voltage, the secondary formation is carried out. The above formation can be considered as the charging process of the lithium-ion battery.

[0079] During the initial formation process, the voltage value of the first formation voltage in the formation process varies. During the secondary formation process, the voltage value of the second formation voltage in the formation process varies.

[0080] The standard voltage for the initial formation can be manually set. The preset voltage is the sum of the absolute value of the difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material and the standard voltage. That is, the standard voltage can be set according to actual needs. For example, the standard voltage can be considered to be the formation voltage during the initial formation in existing formation technology. Existing formation technology can be considered to be a formation process in which the positive electrode of the formation device is connected to the positive electrode post of the lithium-ion battery, and the negative electrode of the formation device is connected to the negative electrode post of the lithium-ion battery.

[0081] Preferably, the battery formation process may include:

[0082] After charging at 0.05-0.1C for 55-65 minutes, charge at 0.2-0.5C to the preset voltage, and the initial formation is complete.

[0083] Charge to the fully activated voltage under 0.1-0.5C conditions to complete the re-formation.

[0084] like Figure 2 As shown, a specific example of the present invention provides a method for preparing a lithium-ion battery as described above, comprising the following steps:

[0085] S21, preparing a lithium supplement slurry containing a lithium supplement agent;

[0086] S22, evenly coating the lithium replenishing slurry on the inner wall of the shell preform to form a lithium replenishing layer;

[0087] S23, cutting the shell preform into a plurality of shells;

[0088] S24, performing assembly and liquid injection processing on the outer shell to obtain a semi-finished battery;

[0089] S25. Use the above-mentioned lithium replenishment method for lithium-ion batteries to replenish lithium on the semi-finished battery product to obtain a lithium-ion battery.

[0090] The shell preform can be considered as a cylinder or frame with a length greater than the length of the lithium-ion battery shell. Then, according to the length of the shell, the shell preform is cut in its length direction to obtain a shell of the required length. Compared with the traditional aluminum shell (shell) with fixed size, the length c (such as Figure 3 As shown in the figure, it can be adjusted according to the subsequent process requirements. It only needs to cut the aluminum shell (housing prefabricated part) with a total length L according to the corresponding length c.

[0091] The method for preparing a lithium-ion battery further includes: performing cell aging and capacity separation on the obtained lithium-ion battery, which are steps known in the prior art.

[0092] The lithium ion battery, lithium replenishment method and preparation method of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0093] Example 1

[0094] In an environment with a humidity of less than 2%, Li5FeO4, SP (conductive carbon black) and PVDF (polyvinylidene fluoride) are uniformly mixed in a mass ratio of 98:1:1 and dispersed in N-methylpyrrolidone solvent to obtain a lithium supplement slurry;

[0095] The lithium replenishing slurry is evenly coated on the inner wall of the incoming aluminum shell to form a lithium replenishing layer, wherein the mass content of Li5FeO4 is 1wt% of the positive electrode material of the lithium ion battery;

[0096] Then the metal aluminum shell coated with the lithium supplement layer is cut into a battery shell that meets the requirements (dimensions are thickness a, height b, and length c);

[0097] Since Li5FeO4 needs to be charged to 4.4V to release the active lithium inside, in order to avoid overcharging (3.65V) of the positive electrode (the lithium-containing substance in the positive electrode material is lithium iron phosphate) during formation, the voltage difference ΔV between the positive electrode post and the shell is 0.75V, that is, a sealing ring with a resistance of 5000~7000Ω is selected;

[0098] Assemble and inject liquid to obtain a semi-finished battery;

[0099] The positive electrode probe of the formation device is brought into contact with the outer shell of the semi-finished battery product, and the negative electrode probe of the formation device is brought into contact with the negative electrode post of the semi-finished battery product to perform formation;

[0100] First, charge at 0.05C for 60 minutes, then charge at 0.3C to 4.2V. At this point, the voltage between the positive and negative poles of the cell is 4.2-ΔV, which equals 3.45V. Then charge at 0.1C between 4.2 and 4.4V to form the cell, and end at 4.4V.

[0101] After the cell is aged and the capacity is divided, the lithium-ion battery of the present invention is obtained.

[0102] Example 2

[0103] In an environment with a humidity of less than 2%, Li2NiO2, SP (conductive carbon black) and PVDF (polyvinylidene fluoride) are uniformly mixed in a mass ratio of 98:1:1 and dispersed in N-methylpyrrolidone solvent to obtain a lithium supplement slurry;

[0104] The lithium replenishing slurry is evenly coated on the inner wall of the incoming aluminum shell to form a lithium replenishing layer, wherein the mass content of Li2NiO2 is 3wt% of the positive electrode material of the lithium ion battery;

[0105] Then the metal aluminum shell coated with the lithium supplement layer is cut into a battery shell that meets the requirements (dimensions are thickness a, height b, and length c);

[0106] Since Li2NiO2 needs to be charged to 4.2V to release the active lithium inside, in order to avoid overcharging the positive electrode (the lithium-containing substance in the positive electrode material is lithium iron phosphate) (3.65V) during formation, the voltage difference ΔV between the positive electrode column and the shell is 0.55V, that is, a sealing ring with a resistance of 600-800Ω is selected; assembly and injection are carried out to obtain a semi-finished battery;

[0107] The positive electrode probe of the formation device is brought into contact with the outer shell of the semi-finished battery product, and the negative electrode probe of the formation device is brought into contact with the negative electrode post of the semi-finished battery product to perform formation;

[0108] First, charge at 0.05C for 60 minutes, then charge at 0.3C to 4.0V. At this point, the voltage between the positive and negative poles of the cell is 4.0-ΔV, which equals 3.45V. Then charge at 0.5C between 4.0 and 4.2V to form the cell, and end at 4.2V.

[0109] After the cell is aged and the capacity is divided, the lithium-ion battery of the present invention is obtained.

[0110] Example 3

[0111] In an environment with a humidity of less than 2%, Li2MnO3, SP (conductive carbon black) and PVDF (polyvinylidene fluoride) are uniformly mixed in a mass ratio of 98:1:1 and dispersed in N-methylpyrrolidone solvent to obtain a lithium supplement slurry;

[0112] The lithium replenishing slurry is evenly coated on the inner wall of the incoming aluminum shell to form a lithium replenishing layer, wherein the mass content of Li2MnO3 is 10wt% of the positive electrode material of the lithium ion battery;

[0113] Then the metal aluminum shell coated with the lithium supplement layer is cut into a battery shell that meets the requirements (dimensions are thickness a, height b, and length c);

[0114] Since Li2MnO3 needs to be charged to 4.7V to release the active lithium inside, in order to avoid overcharging (3.65V) of the positive electrode (the lithium-containing substance in the positive electrode material is lithium iron phosphate) during formation, the voltage difference ΔV between the positive electrode post and the shell is 1.05V, that is, a sealing ring with a resistance of 50,000 to 70,000Ω is selected;

[0115] Assemble and inject liquid to obtain a semi-finished battery;

[0116] The positive electrode probe of the formation device is brought into contact with the outer shell of the semi-finished battery product, and the negative electrode probe of the formation device is brought into contact with the negative electrode post of the semi-finished battery product to perform formation;

[0117] First, charge at 0.05C for 60 minutes, then charge at 0.3C to 4.5V. At this point, the voltage between the positive and negative poles of the cell is 4.5-ΔV, which equals 3.45V. Then charge at 0.1C between 4.5 and 4.7V to form the cell, and end at 4.7V.

[0118] After the cell is aged and the capacity is divided, the lithium-ion battery of the present invention is obtained.

[0119] Example 4

[0120] In an environment with a humidity of less than 2%, Li5FeO4, SP (conductive carbon black) and PVDF (polyvinylidene fluoride) are uniformly mixed in a mass ratio of 98:1:1 and dispersed in N-methylpyrrolidone solvent to obtain a lithium supplement slurry;

[0121] The lithium replenishing slurry is evenly coated on the inner wall of the incoming aluminum shell to form a lithium replenishing layer, wherein the mass content of Li5FeO4 is 1wt% of the positive electrode material of the lithium ion battery;

[0122] Then the metal aluminum shell coated with the lithium supplement layer is cut into a battery shell that meets the requirements (dimensions are thickness a, height b, and length c);

[0123] Since Li5FeO4 needs to be charged to 4.4V to release the internal active lithium, in order to avoid the positive electrode (the lithium-containing material in the positive electrode material is LiNi 0.8 Co 0.1 Mn 0.1 O2) Overcharge (4.25V), the voltage difference ΔV between the positive electrode and the shell is 0.15V, that is, the sealing ring with a resistance of 10~500Ω is selected;

[0124] Assemble and inject liquid to obtain a semi-finished battery;

[0125] The positive electrode probe of the formation device is brought into contact with the outer shell of the semi-finished battery product, and the negative electrode probe of the formation device is brought into contact with the negative electrode post of the semi-finished battery product to perform formation;

[0126] First, charge at 0.05C for 60 minutes, then charge at 0.3C to 4.15V. At this point, the voltage between the positive and negative poles of the cell is 4.15-ΔV, which equals 4.0V. Then charge at 0.1C between 4.15 and 4.4V to form the cell, and end at 4.4V.

[0127] After the cell is aged and the capacity is divided, the lithium-ion battery of the present invention is obtained.

[0128] Comparative Example 1

[0129] During the positive electrode homogenization process, the lithium supplement Li5FeO4 is added to the lithium iron phosphate system positive electrode slurry, and the positive electrode sheet is obtained according to the normal process, wherein the mass content of Li5FeO4 is 1wt% of the positive electrode material;

[0130] Obtain an aluminum shell with a thickness a, a height b, and a length c;

[0131] Assemble and inject liquid to obtain a semi-finished battery;

[0132] The positive electrode probe of the formation device contacts the positive electrode post of the semi-finished battery, and the negative electrode probe of the formation device contacts the negative electrode post of the semi-finished battery to carry out formation.

[0133] First, charge at 0.05C for 60 minutes, then charge at 0.3C until V1 reaches 3.45V. If the voltage exceeds 3.45V and is between 3.45 and 4.4V, charge at a low current of 0.03C to slowly release the active lithium of Li5FeO4.

[0134] After the battery cells age and their capacity is divided, lithium-ion batteries are obtained.

[0135] Comparative Example 2

[0136] This comparative example provides a method for preparing a blade battery with lithium replenishment function that was tested during the research process, including the following steps:

[0137] During the positive electrode homogenization process, the lithium supplement Li5FeO4 is added to LiNi 0.8 Co 0.1 Mn 0.1 In the O2 system positive electrode slurry, a positive electrode sheet is obtained according to a normal process, wherein the mass content of Li5FeO4 is 1wt% of the positive electrode material;

[0138] Obtain an aluminum shell with a thickness a, a height b, and a length c;

[0139] Assemble and inject liquid to obtain a semi-finished battery;

[0140] The positive electrode probe of the formation device contacts the positive electrode post of the semi-finished battery, and the negative electrode probe of the formation device contacts the negative electrode post of the semi-finished battery to perform formation;

[0141] First, charge at 0.05C for 60 minutes, then charge at 0.3C until V1 reaches 4.0V. If the voltage exceeds 4.0V and is between 4.0 and 4.4V, charge at a low current of 0.03C to slowly release the active lithium of Li5FeO4.

[0142] After the battery cells age and their capacity is divided, lithium-ion batteries are obtained.

[0143] Comparative Example 3

[0144] In an environment with a humidity of less than 2%, Li5FeO4, SP and PVDF are uniformly mixed in a mass ratio of 98:1:1 and dispersed in N-methylpyrrolidone solvent to obtain a lithium supplement slurry;

[0145] The lithium replenishing slurry is evenly coated on the inner wall of the incoming aluminum shell to form a lithium replenishing layer, that is, a metal aluminum shell is obtained, wherein the mass content of Li5FeO4 is 1wt% of the positive electrode material;

[0146] Obtain an aluminum shell with a thickness a, a height b, and a length c;

[0147] Assemble and inject liquid to obtain a semi-finished battery, in which the positive electrode is directly connected to the aluminum shell without voltage difference;

[0148] The positive electrode probe of the formation device contacts the positive electrode post of the semi-finished battery, and the negative electrode probe of the formation device contacts the negative electrode post of the semi-finished battery to perform formation;

[0149] First, charge at 0.05C for 60 minutes, then charge at 0.3C until V1 reaches 3.45V. If the voltage exceeds 3.45V and is between 3.45 and 4.4V, charge at a low current of 0.03C to slowly release the active lithium of Li5FeO4.

[0150] After the battery cells age and their capacity is divided, lithium-ion batteries are obtained.

[0151] The assembly steps in Examples 1 to 4 and Comparative Examples 1 to 4 are to assemble the various components of the battery (which may include welding, clamping, etc.).

[0152] Examples 1, 2, 3 and Comparative Examples 1 and 3 are all lithium iron phosphate system lithium ion batteries. Example 4 and Comparative Example 2 are ternary system lithium ion batteries.

[0153] The processing conditions during the positive electrode slurrying process, overall formation time, and specific capacity of the positive electrode material during the lithium-ion battery manufacturing process of Examples 1-4 and Comparative Examples 1-3 were recorded. The lithium-ion batteries prepared in Examples 1-4 and Comparative Examples 1-3 were also tested for their room temperature 1C cycling performance and full-charge storage at 55°C, as shown in Tables 1, 2, 3, and 4.

[0154] Table 1: Processing conditions during the positive electrode homogenization process

[0155] Slurry viscosity (mPa.s) Is gel present? Screening conditions Example 1 9300 no normal Example 2 9500 no normal Example 3 9250 no normal Example 4 9920 no normal Comparative Example 1 14000 yes Disaster Comparative Example 2 11500 no Disaster Comparative Example 3 9400 no normal

[0156] Table 2: Overall formation time and cathode material capacity utilization

[0157]

[0158] Table 3: Cycling performance data

[0159]

[0160]

[0161] Table 4: Fully charged storage at 55°C

[0162] 7-day battery cell thickness expansion rate 7-day ACR growth rate 7-day battery cell discharge capacity retention rate Example 1 2.5％ 15.5％ 99.8％ Example 2 2.9％ 18.8％ 99.5％ Example 3 2.3％ 14.3％ 99.2％ Example 4 3.5％ 20.3％ 98.9％ Comparative Example 1 8.5％ 32.7％ 97.8％ Comparative Example 2 9.6％ 46.8％ 96.9％ Comparative Example 3 8.2％ 31.8％ 98.1％

[0163] The data of Examples 1 to 4 and Comparative Examples 1 to 3 in Table 1 indicate that, in the lithium-ion battery preparation method of the present invention, since the lithium supplement is disposed in the lithium supplement layer on the inner wall of the battery housing, there is no need to add the lithium supplement during the homogenization of the positive electrode material as in the prior art. Consequently, the viscosity of the positive electrode material during the homogenization process may suffer from adverse conditions such as gelation due to the mixing of the lithium supplement.

[0164] The data from Examples 1-4 and Comparative Examples 1-3 in Table 2 indicate that the lithium replenishment method for a lithium-ion battery of the present invention shortens the formation time due to adjustments to the connection between the formation equipment and the lithium-ion battery, the design and selection of the lithium-ion battery, and the lithium replenishment method. This is primarily due to the ability to charge (form) with a large amount of electricity during the secondary formation process, thereby shortening the formation time. Furthermore, the performance of the lithium-ion battery of the present invention is superior, as can be seen from the specific capacity of the positive electrode material.

[0165] It can be seen from the data of Examples 1 to 4 and Comparative Examples 1 to 3 in Tables 3 and 4 that the lithium ion battery prepared by the preparation method of the lithium ion battery of the present invention has significantly better performance in various aspects than the lithium ion battery prepared by the prior art.

[0166] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0167] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A lithium-ion battery, characterized in that: include: The outer shell has a lithium supplement layer on its inner wall, wherein the material of the lithium supplement layer includes a lithium supplement agent; A positive electrode assembly, comprising a voltage divider, a positive electrode post, and a positive electrode material, wherein the positive electrode post is electrically connected to the housing via the voltage divider, and the positive electrode material is connected to the positive electrode post; A negative electrode assembly, comprising a connected negative electrode post and a negative electrode material, wherein the negative electrode post is insulated and connected to the housing; The resistance value of the voltage divider is determined based on the difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material; and the greater the difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material, the greater the resistance value of the voltage divider.

2. The lithium-ion battery according to claim 1, wherein The difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material is 0.15 to 0.2 V, and the resistance of the voltage divider is 10 to 500 Ω; and / or, The difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material is 0.2 to 0.6 V, and the resistance of the voltage divider is 500 to 3000 Ω; and / or, The difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material is 0.6 to 1.0 V, and the resistance of the voltage divider is 3000 to 30000 Ω; and / or, The difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material is 1.0 to 1.15 V, and the resistance of the voltage divider is 30,000 to 100,000 Ω.

3. The lithium-ion battery according to claim 1, wherein The materials of the lithium supplement layer also include a conductive agent and an adhesive.

4. The lithium-ion battery according to claim 3, characterized in that The conductive agent includes at least one of conductive carbon black and carbon nanotubes; and / or, The adhesive comprises at least one of polyvinylidene fluoride, polymethyl methacrylate and polytetrafluoroethylene; and / or, The lithium supplement includes at least one of Li5FeO4, Li2NiO2, Li2O2, Li2O, Li2MnO3, Li6CoO4, Li6MnO4 and Li3P.

5. The lithium-ion battery according to claim 1, wherein The mass ratio of the lithium replenishing agent to the positive electrode material in the lithium replenishing layer is (1-10):

100.

6. The lithium-ion battery according to claim 1, wherein The voltage divider is a sealing ring, the positive electrode assembly includes a positive electrode top cover installed on the shell, and the positive electrode column is connected to the positive electrode top cover through the sealing ring.

7. A lithium replenishing method for a lithium ion battery, applied to the lithium ion battery according to any one of claims 1 to 6, characterized in that: The lithium replenishment method of the lithium ion battery comprises the following steps: The positive electrode of the formation equipment is electrically connected to the shell of the lithium-ion battery, and the negative electrode of the formation equipment is electrically connected to the negative electrode post of the lithium-ion battery to perform battery formation.

8. The lithium replenishing method for a lithium ion battery according to claim 7, characterized in that: Based on the voltage divider, during the battery formation process, the voltage difference between the positive electrode column and the shell is equal to the difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material.

9. The lithium replenishing method for a lithium ion battery according to claim 7, characterized in that: Battery formation, including: Performing initial formation at a first formation voltage not exceeding a preset voltage; The second formation voltage is higher than the preset voltage and lower than the fully activated voltage of the lithium supplement.

10. The lithium replenishing method for a lithium ion battery according to claim 7, characterized in that: The standard voltage for initial formation is set, and the preset voltage is the sum of the absolute value of the difference between the full activation voltage of the lithium supplement and the overcharge cut-off voltage of the positive electrode material and the standard voltage.

11. The lithium replenishing method for a lithium ion battery according to claim 9, characterized in that: Battery formation, including: After charging at 0.05-0.1C for 55-65 minutes, charge at 0.2-0.5C to the preset voltage, and the initial formation is complete. Charge to the fully activated voltage under 0.1-0.5C conditions to complete the re-formation.

12. A method for preparing a lithium-ion battery according to any one of claims 1 to 6, characterized in that: The following steps are involved: preparing a lithium supplement slurry containing a lithium supplement agent; Evenly coating the lithium replenishing slurry on the inner wall of the shell preform to form a lithium replenishing layer; cutting the shell preform into a plurality of shells; Assembling and injecting liquid on the shell to obtain a semi-finished battery; A lithium-ion battery is obtained by replenishing lithium on a semi-finished battery product using the lithium replenishment method for a lithium-ion battery as claimed in any one of claims 7 to 11.

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