Lithium ion battery, lithium supplementing method and preparation method

Abstract

The application discloses a lithium ion battery, a lithium supplement method and a preparation method. The lithium ion battery comprises a shell, a lithium supplement layer is arranged on the inner wall of the shell, and the material of the lithium supplement layer comprises a lithium supplement agent; a positive electrode assembly comprises a voltage divider, a positive electrode pole and a positive electrode material, the positive electrode pole is electrically connected with the shell through the voltage divider, and the positive electrode material is connected with the positive electrode pole; a negative electrode assembly comprises a negative electrode pole and a negative electrode material connected with each other, and the negative electrode pole is insulatively connected with the shell; the resistance value of the voltage divider is determined based on the difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material; and the greater the difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material, the greater the resistance value of the voltage divider. The lithium ion battery, the lithium supplement method and the preparation method can improve the lithium supplement efficiency, shorten the formation time, improve the lithium supplement effect and the specific capacity of the positive electrode material.

Description

TECHNICAL FIELD

[0001] The lithium ion battery belongs to the field, and particularly relates to a lithium ion battery, a lithium supplement method and a preparation method. BACKGROUND

[0002] With the rapid development of new energy vehicles and energy storage technologies, higher requirements are constantly put forward for various performances of lithium ion batteries, among which prolonging the cycle performance and improving the calendar life are the most urgent. At present, one of the main reasons affecting the cycle or storage performance of the lithium ion battery is that in order to repair the damaged negative electrode particle SEI (solid electrolyte interface film), the active lithium inside the material system needs to be continuously consumed, resulting in a large capacity loss. In view of this problem, the industry mainly adds a lithium supplement agent to the positive electrode or negative electrode system to make up for the early loss of active lithium and thus improve the cycle life.

[0003] Taking the positive electrode lithium supplement method as an example, the traditional positive electrode lithium supplement method is to add a lithium supplement agent during the homogenization of the positive electrode material, and then gradually provide lithium ions to the system through small current formation. However, the alkalinity of these lithium supplement agents is high, and abnormal slurry gelation is prone to occur during the homogenization process, which affects production and causes abnormal battery performance.

[0004] The information disclosed in this BACKGROUND section is only for the purpose of increasing the understanding of the background of the present application and should not be taken as an acknowledgment or any form of suggestion that this information forms prior art that is publicly known. SUMMARY

[0005] The purpose of the present application is to provide a lithium ion battery, a lithium supplement method and a preparation method, which can improve the lithium supplement efficiency, shorten the formation time, and improve the lithium supplement effect and the specific capacity of the positive electrode material.

[0006] In order to achieve the above-mentioned purpose, a specific embodiment of the present application provides a lithium ion battery, comprising:

[0007] A shell, an inner wall of which is provided with a lithium supplement layer, the material of the lithium supplement layer comprising a lithium supplement agent;

[0008] A positive electrode assembly comprising a voltage dividing piece, a positive electrode pole and a positive electrode material, the positive electrode pole being electrically connected to the shell through the voltage dividing piece, and the positive electrode material being connected to the positive electrode pole;

[0009] A negative electrode assembly comprising a negative electrode pole and a negative electrode material connected to each other, the negative electrode pole being insulatively connected to the shell;

[0010] The resistance value of the voltage dividing piece is determined based on the difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material; and the greater the difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material, the greater the resistance value of the voltage dividing piece.

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

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

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

[0014] The difference between the full activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material is 1.0-1.15V, and the resistance of the voltage divider is 30000-100000Ω.

[0015] In one or more embodiments of the present application, the material of the lithium supplement layer further comprises a conductive agent and a binder.

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

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

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

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

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

[0021] One specific embodiment of the present application provides a lithium supplement method for a lithium ion battery, which is applied to the above-mentioned lithium ion battery, and comprises the following steps:

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

[0023] In one or more embodiments of the present application, based on the voltage divider, the voltage difference between the positive pole and the shell in the battery formation process is equal to the difference between the full activation voltage of the lithium supplement and the overcharge cutoff voltage of the positive electrode material.

[0024] In one or more embodiments of the present application, the battery formation comprises:

[0025] The first formation is performed at a first formation voltage not exceeding the preset voltage;

[0026] The second formation is performed at a second formation voltage exceeding the preset voltage and not exceeding the full activation voltage of the lithium supplement.

[0027] In one or more embodiments of the present application, the standard voltage of the first 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 cutoff voltage of the positive electrode material and the standard voltage.

[0028] In one or more embodiments of the present application, the battery formation comprises:

[0029] After charging for 55-65 min under the condition of 0.05-0.1 C, the first formation is ended by charging to the preset voltage under the condition of 0.2-0.5 C;

[0030] The second formation is completed by charging to the full activation voltage under the condition of 0.1-0.5 C.

[0031] One specific embodiment of the present application provides a preparation method of the lithium ion battery as described above, comprising the following steps:

[0032] The lithium supplement slurry containing the lithium supplement is configured;

[0033] The lithium supplement slurry is uniformly coated on the inner wall of the shell preform to form a lithium supplement layer;

[0034] The shell preform is cut into a plurality of shells;

[0035] The assembly and liquid injection treatment are performed on the shell to obtain a battery semi-product;

[0036] After the lithium supplement is performed on the battery semi-product by using the lithium supplement method of the lithium ion battery as described above, the lithium ion battery is obtained.

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

[0038] (1) By setting the lithium supplement agent on the inner wall of the shell, the viscosity increase and sieving abnormality of the slurry gel caused by the addition of the high-alkaline lithium supplement agent in the positive electrode homogenate process in the prior art (a scheme of adding the lithium supplement agent to the positive electrode material) can be avoided, and the battery production efficiency and battery yield are improved;

[0039] (2) By selecting the resistance value of the voltage divider between the positive electrode post and the shell, the edge voltage of the positive electrode post and the shell is adjusted, and the shell and the negative electrode post are charged during formation. In this way, the lithium supplement agent can be fully released under a higher voltage window, and the structure collapse caused by excessive lithium release in the positive electrode material during formation can be avoided. In particular, for high-nickel ternary positive electrode materials, the structure damage caused by excessive lithium release is obvious. In addition, compared with lithium iron phosphate system batteries, polarization is serious during overcharging, and the charging cutoff voltage (also known as overcharge cutoff voltage) can be easily reached, so small current (<0.05C) must be used for formation charging. However, since there is a voltage difference between the shell and the positive electrode post (or the positive electrode material) in the lithium ion battery of the present application, the formation charging can continue with a larger current of 0.1-0.5C to allow the lithium supplement agent to continue to release active lithium, thereby shortening the formation time and improving the lithium supplement effect and the specific capacity of the positive electrode material;

[0040] (3) During the later cycle and full-charge storage, the lithium supplement agent in the lithium supplement layer on the shell is always in a low voltage state due to the voltage difference between the shell and the positive electrode post (or the positive electrode material), which can effectively inhibit the side reactions of the electrolyte and the lithium supplement agent, reduce gas production and electrolyte consumption, and effectively improve the cycle performance and full-charge storage performance of the lithium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0042] Figure 1 The flow chart of the formation step in the lithium supplement method of the lithium ion battery in an example of the present application;

[0043] Figure 2 The flow chart of the preparation method of the lithium ion battery in an example of the present application;

[0044] Figure 3 The perspective view of the lithium ion battery in an example of the present application;

[0045] Figure 4 The cross-sectional view of the lithium ion battery in an example of the present application.

[0046] Explanation of key figure labels:

[0047] 1. Outer shell; 11. Lithium replenishment layer; 2. Positive electrode assembly; 21. Voltage divider; 22. Positive electrode post; 23. Positive electrode material; 24. Positive electrode top cover; 31. Negative electrode material; 4. Separator. Detailed Implementation

[0048] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0049] like Figure 3 and 4 As shown, an example of the lithium-ion battery of the present invention includes a casing 1, a positive electrode assembly 2, and a negative electrode assembly. A lithium replenishment layer 11 is provided on the inner wall of the casing 1, and the material of the lithium replenishment 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 casing 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 negative electrode post and a negative electrode material 31 connected to each other, and the negative electrode post is insulated from the casing 1. 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 overcharge cutoff voltage of the positive electrode material 23. The greater the difference between the full activation voltage of the lithium replenishing agent and the overcharge cutoff voltage of the positive electrode material 23, the greater the resistance value of the voltage divider 21.

[0050] It should be noted that when lithium-ion batteries are assembled to obtain a semi-finished battery, a lithium replenishment process is generally required. As described in the background art, the traditional method for replenishing lithium in the positive electrode involves adding a lithium replenishing agent during the homogenization process of the positive electrode material 23, followed by formation with a small current to gradually provide lithium ions to the system. However, these lithium replenishing agents are highly alkaline, making it easy for abnormal slurry gelation to occur during the homogenization process of the positive electrode material 23, affecting production and leading to abnormal battery performance. In this invention, the full activation voltage of the lithium replenishing agent is greater than the overcharge cutoff voltage of the positive electrode material 23. Specifically, the difference between the full activation voltage of the lithium replenishing agent and the overcharge cutoff voltage of the positive electrode material 23 is the full activation voltage of the lithium replenishing agent minus the overcharge cutoff voltage of the positive electrode material 23, and this value is greater than 0.

[0051] The lithium ion battery of the present application is provided with the lithium supplement agent on the inner wall of the shell 1 to form the lithium supplement layer 11, which can avoid the viscosity increase and abnormal screening of the slurry gel caused by the addition of the high-alkaline lithium supplement agent in the positive electrode slurry process in the prior art, and improve the battery production efficiency and the battery yield.

[0052] The lithium ion battery in the present example can be a blade battery.

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

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

[0055] For example, when the resistance of the voltage dividing member is 10-500Ω, if the resistance of the voltage dividing member 21 is too small (the resistance of the voltage dividing member 21 is less than 10Ω), i.e. the voltage difference between the positive electrode pole 22 and the shell 1 is too small, the positive electrode material 23 is prone to overcharge when the battery is formed according to the lithium supplement method of the lithium ion battery of the present application; and if the resistance of the voltage dividing member 21 is too large (the resistance of the voltage dividing member 21 is greater than 500Ω), i.e. the voltage difference between the positive electrode pole 22 and the shell 1 is too large, the actual charging voltage of the positive electrode material 23 (i.e. the voltage to which the positive electrode material is distributed during the formation process) is too low when the battery is formed according to the lithium supplement method of the lithium ion battery of the present application, which results in unstable battery formation. It can be understood that the principle is the same as above when the resistance of the voltage dividing member is in the other ranges.

[0056] In the present example, the material of the lithium supplement layer 11 can further include a conductive agent and a binder; the conductive agent serves to improve the conductivity of the lithium supplement layer 11, and the binder makes the lithium supplement layer 11 have certain adhesion, so that the lithium supplement layer 11 can be bonded to the inner wall of the shell 1.

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

[0058] Preferably, the mass ratio of the lithium supplement agent in the lithium supplement layer 11 to the positive electrode material 23 is (1-10):100. The ratio range aims to meet the lithium loss amount consumed by the negative electrode material 31 in the SEI film forming 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 a common conductive agent on the market, for example, the conductive agent includes at least one of conductive carbon black and carbon nanotubes. The binder in the positive electrode material 23 includes a common binder on the market, for example, the binder includes at least one of polyvinylidene fluoride, polymethyl methacrylate, and polytetrafluoroethylene. The specific components of the conductive agent and the binder in the positive electrode material 23 can be the same as or different from those of the conductive agent and the binder in the lithium supplement layer 11.

[0060] It can be understood that the positive electrode material 23 can also be referred to as a positive electrode sheet. The negative electrode material 31 can also be referred to as a negative electrode sheet, which is installed in the shell 1, and the shell 1 can also be provided with a separator 4 and an electrolyte (or an 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 manganate, etc. The overcharge cutoff voltage of the positive electrode material 23 can be considered to be determined according to the type of the lithium-containing material.

[0062] In a specific example, the voltage dividing piece 21 is a sealing ring, and the positive electrode assembly 2 includes a positive electrode top cover 24 installed on the shell 1, and the positive electrode post 22 is connected to the positive electrode top cover 24 through the sealing ring. The materials of the shell 1, the positive electrode top cover 24, and the positive electrode post 22 are existing conductive materials, for example, conductive metals, and specifically can be aluminum materials. In other examples, the voltage dividing piece 21 can be other components, and the voltage dividing piece 21 can also be composed of a sealing ring and other components.

[0063] In the present example, the positive electrode material 23, the negative electrode material 31 and the separator 4 can collectively constitute a pole group, the pole group further comprising a positive electrode tab electrically connected with the positive electrode material 23, and a negative electrode tab electrically connected with the negative electrode material 31, the positive electrode post 22 can be electrically connected with the positive electrode tab through a positive electrode support or other components, and the negative electrode post can be electrically connected with the negative electrode tab through a negative electrode support or other components; so as to realize the electrical connection between the positive electrode post 22 and the positive electrode material 23, and the electrical connection between the negative electrode post and the negative electrode material 31.

[0064] It should be noted that in the pole group, the positive electrode material 23 can be uniformly coated on the aluminum foil, and then the part of the aluminum foil which is not coated with the positive electrode material 23 can be die-cut into a positive electrode tab, so as to realize the electrical connection between the positive electrode material 23 and the positive electrode tab. The negative electrode material 31 can be uniformly coated on the copper foil, and then the part of the copper foil which is not coated with the negative electrode material 21 can be die-cut into a negative electrode tab, so as to realize the electrical connection between the negative electrode material 31 and the negative electrode tab.

[0065] A specific example of the present application provides a lithium ion battery lithium supplement method applied to the above lithium ion battery, the lithium supplement method of the lithium ion battery comprising the following steps:

[0066] The positive electrode of the formation equipment is electrically connected with the shell of the lithium ion battery, the negative electrode of the formation equipment is electrically connected with the negative electrode post of the lithium ion battery, and the battery formation is carried out.

[0067] It should be noted that formation is an important process in the battery manufacturing process, mainly involving the process of activating the battery after liquid injection (electrolyte). This process forms a SEI film (solid electrolyte interface film) in the battery through charging and discharging, which ensures the safety, reliability and long cycle life of the battery in the subsequent charging and discharging cycle.

[0068] The formation process realizes the initial activation of the battery through charging and discharging, activates the active material of the battery, and is an energy conversion process. The formation and capacity principle of lithium battery is relatively complex, but it is also an important process that affects the performance of the battery.

[0069] It should be noted that the complete activation voltage can be considered as the voltage required for the active lithium inside the lithium supplement agent to be released completely in the formation process.

[0070] The complete activation voltage of the lithium supplement agent is determined based on the type of the lithium supplement agent; for example, when the lithium supplement agent is Li5FeO4, the complete activation voltage is 4.4V; that is, in the formation process, the internal active lithium of Li5FeO4 needs to be released completely by charging to 4.4V. When the lithium supplement agent is Li2NiO2, the complete activation voltage is 4.2V; that is, in the formation process, the internal active lithium of Li2NiO2 needs to be released completely by charging to 4.2V.

[0071] The formation voltage is the charge-discharge voltage during the formation process, the formation process is the process of forming SEI film on the surface of active material particles by the film-forming additive, and the process of forming SEI film is an irreversible reaction process, therefore, only the formation voltage is set to be higher than the potential at which the film-forming additive is completely reacted, and the film-forming reaction is fully carried out.

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

[0073] In the present example, based on the voltage divider, the voltage difference between the positive electrode pole and the shell during the formation process of the battery is equal to the difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material.

[0074] It can be understood that, due to the selection of the lithium supplement agent and the lithium-containing substance in the positive electrode material, there is a difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material (the default difference is a non-negative number), and through the selection of the voltage divider, the voltage difference between the positive electrode pole and the shell can be equal to the difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material, so that the formation process of the present application can be realized, that is, during the formation process, due to the voltage difference between the shell and the positive electrode pole, the formation charging with a large current of 0.1-0.5 C can continue to be carried out to allow the lithium supplement agent to continue to release active lithium sufficiently, thereby shortening the formation time and improving the lithium supplement effect and the specific capacity of the positive electrode material.

[0075] Preferably, as shown in the following table, the battery formation includes: Figure 1

[0076] S11, primary formation is carried out at a first formation voltage not exceeding a preset voltage;

[0077] S12, secondary formation is carried out at a second formation voltage exceeding the preset voltage and not exceeding the complete activation voltage of the lithium supplement agent.

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

[0079] ​In the initial formation process, the voltage value of the first formation voltage in the formation process is variable. In the re-formation process, the voltage value of the second formation voltage in the formation process is variable.

[0080] The standard voltage of the initial formation can be artificially set, and the preset voltage is the sum of the absolute value of the difference between the full activation voltage of the lithium supplement agent and the overcharge cutoff 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 as the formation voltage in the initial formation in the existing formation technology. The existing formation technology can be considered as a formation process in which the positive electrode of the formation device is connected with the positive electrode pole of the lithium ion battery, and the negative electrode of the formation device is connected with the negative electrode pole of the lithium ion battery.

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

[0082] After charging for 55-65 min under the condition of 0.05-0.1 C, charging to the preset voltage under the condition of 0.2-0.5 C, and the initial formation is completed;

[0083] Charging to the full activation voltage under the condition of 0.1-0.5 C, and the re-formation is completed.

[0084] As shown in the specific example of the present application, a preparation method of a lithium ion battery is provided, which comprises the following steps: Figure 2

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

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

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

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

[0089] S25, using the lithium supplement method of the lithium ion battery as described above to supplement lithium to the battery semi-finished product to obtain a lithium ion battery.

[0090] The shell preform can be considered as a cylinder or a frame with a length greater than the length of the shell of the lithium ion battery. Then, according to the length of the shell, the shell preform is cut in the length direction to obtain a shell with the required length. Compared with the traditional aluminum shell (shell) with a fixed size, the length c (as shown in Figure 3 of the lithium ion battery shell (shell) of the present application can be adjusted according to the subsequent process requirements, and only needs to be cut on the aluminum shell (shell preform) with a total length L according to the corresponding length c. ​

[0091] The preparation method of the lithium ion battery further comprises: performing cell aging and capacity grading on the obtained lithium ion battery, which is a step known in the prior art.

[0092] The lithium ion battery, lithium supplement method and preparation method of the present application will be described in detail below with specific examples and comparative examples.

[0093] Example 1

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

[0095] The above lithium supplement slurry is uniformly coated on the inner wall of the incoming aluminum shell to form a lithium supplement 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 meeting the requirements (size: thickness a, height b, length c);

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

[0098] Assembling and liquid injection are performed to obtain a battery semi-finished product;

[0099] The positive electrode probe of the formation device is in contact with the shell of the battery semi-finished product, and the negative electrode probe of the formation device is in contact with the negative electrode pole of the battery semi-finished product, and formation is performed;

[0100] First, 0.05C charging is performed for 60min, and then 0.3C charging is performed to 4.2V, at which time the voltage between the positive and negative electrode poles is 4.2-ΔV equal to 3.45V. Then 0.1C charging is performed between 4.2-4.4V, and the charging is ended at 4.4V;

[0101] After cell aging and capacity grading, the lithium ion battery of the present application is obtained.

[0102] Example 2

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

[0104] The above lithium supplement slurry is uniformly coated on the inner wall of the incoming aluminum shell to form a lithium supplement 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 meeting the requirements (size: thickness a, height b, length c);

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

[0107] The positive electrode probe of the formation device is in contact with the shell of the battery semi-finished product, and the negative electrode probe of the formation device is in contact with the negative electrode pole of the battery semi-finished product, and formation is performed;

[0108] Firstly, 0.05C charging is performed for 60min, and then 0.3C charging is performed to 4.0V, at which time the voltage between the positive and negative electrode poles of the battery is 4.0-ΔV equal to 3.45V. Then, 0.5C charging is performed between 4.0-4.2V, and the charging is ended at 4.2V;

[0109] The battery is aged, and after capacity grading, a lithium ion battery of the application is obtained.

[0110] Example 3

[0111] In a separate environment with humidity 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 an N-methyl pyrrolidone solvent to obtain a lithium supplement slurry;

[0112] The above lithium supplement slurry is uniformly coated on the inner wall of the incoming aluminum shell to form a lithium supplement 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 meeting the requirements (size: thickness a, height b, length c);

[0114] Since Li2MnO3 needs to be charged to 4.7V to release the internal active lithium completely, in order to avoid overcharging (3.65V) of the positive electrode (lithium-containing substance in the positive electrode material is lithium iron phosphate) during formation, the voltage difference ΔV between the positive electrode pole and the shell is 1.05V, that is, the sealing ring with a resistance of 50000-70000Ω is selected;

[0115] Assembly, liquid injection, and a battery semi-finished product are obtained;

[0116] The positive probe of the formation device is contacted with the shell of the battery semi-product, and the negative probe of the formation device is contacted with the negative pole of the battery semi-product, and formation is performed;

[0117] First, 0.05C charging for 60 min, and then 0.3C charging to 4.5V, at which time the voltage between the positive and negative poles of the battery is 4.5-ΔV equal to 3.45V. Then, 0.1C charging is performed at 4.5-4.7V, and the charging is ended at 4.7V;

[0118] The battery is aged, and after the capacity is distributed, the lithium ion battery of the application is obtained.

[0119] Example 4

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

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

[0122] Then, the metal aluminum shell coated with the lithium supplement layer is cut into a battery shell meeting the requirements (size: thickness a, height b, length c);

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

[0124] Assembling and liquid injection are performed to obtain a battery semi-product;

[0125] The positive probe of the formation device is contacted with the shell of the battery semi-product, and the negative probe of the formation device is contacted with the negative pole of the battery semi-product, and formation is performed;

[0126] First, 0.05C charging for 60 min, and then 0.3C charging to 4.15V, at which time the voltage between the positive and negative poles of the battery is 4.15-ΔV equal to 4.0V. Then, 0.1C charging is performed at 4.15-4.4V, and the charging is ended at 4.4V;

[0127] The battery is aged, and after the capacity is distributed, the lithium ion battery of the application is obtained.

[0128] Comparative Example 1

[0129] In the positive electrode slurry 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% to the positive electrode material;

[0130] An aluminum shell with thickness a, height b, and length c is obtained.

[0131] Assembly and liquid injection are performed to obtain a battery semi-finished product.

[0132] The positive electrode probe of the formation device contacts the positive electrode pole of the battery semi-finished product, and the negative electrode probe of the formation device contacts the negative electrode pole of the battery semi-finished product, and formation is performed.

[0133] First, charge at 0.05C for 60 min, then charge at 0.3C to V1 of 3.45V, and charge at a small current of 0.03C to slowly release the active lithium of Li5FeO4 when exceeding 3.45V and between 3.45-4.4V;

[0134] The battery cell is aged, and after capacity grading, a lithium ion battery is obtained.

[0135] Comparative Example 2

[0136] This comparative example provides a preparation method of a blade battery with lithium supplement function tested in the research process, including the following steps:

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

[0138] An aluminum shell with thickness a, height b, and length c is obtained.

[0139] Assembly and liquid injection are performed to obtain a battery semi-finished product.

[0140] The positive electrode probe of the formation device contacts the positive electrode pole of the battery semi-finished product, and the negative electrode probe of the formation device contacts the negative electrode pole of the battery semi-finished product, and formation is performed.

[0141] First, charge at 0.05C for 60 min, then charge at 0.3C to V1 of 4.0V, and charge at a small current of 0.03C to slowly release the active lithium of Li5FeO4 when exceeding 4.0V and between 4.0-4.4V;

[0142] The battery cell is aged, and after capacity grading, a lithium ion battery is obtained.

[0143] Comparative Example 3

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

[0145] The above lithium supplement slurry is uniformly coated on the inner wall of the incoming aluminum shell to form a lithium supplement layer, thereby obtaining a metal aluminum shell, wherein the mass content of Li5FeO4 is 1wt% of the positive electrode material;

[0146] An aluminum shell with thickness a, height b and length c is obtained;

[0147] Assembling and liquid injection are performed to obtain a battery semi-finished product, wherein the positive electrode pole is directly connected with the aluminum shell without voltage difference;

[0148] The positive electrode probe of the formation device contacts the positive electrode pole of the battery semi-finished product, and the negative electrode probe of the formation device contacts the negative electrode pole of the battery semi-finished product, and formation is performed;

[0149] Firstly, 0.05C charging is performed for 60 min, then 0.3C charging is performed until V1 is 3.45V, and when the voltage exceeds 3.45V and is between 3.45V and 4.4V, small current 0.03C charging is required to slowly release the active lithium of Li5FeO4;

[0150] The cell is aged, and after capacity grading, a lithium ion battery is obtained.

[0151] Among them, the assembling steps in Examples 1-4 and Comparative Examples 1-4 are to assemble the various components of the battery (which may include welding, clamping and other steps).

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

[0153] The processing conditions in the positive electrode slurry process, the overall formation time and the positive electrode material gram capacity development during the lithium ion battery manufacturing process of Examples 1-4 and Comparative Examples 1-3 are counted respectively. The normal temperature 1C cycle performance and full charge storage at 55℃ high temperature environment of the lithium ion batteries prepared from Examples 1-4 and Comparative Examples 1-3 are tested, as shown in Tables 1, 2, 3 and 4.

[0154] Table 1: Processing conditions in the positive electrode slurry process

[0155] Slurry viscosity (mPa.s) Gelation Sieve 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 Difficult Comparative Example 2 11500 No Difficult Comparative Example 3 9400 No Normal

[0156] Table 2: Overall formation time and positive electrode material gram capacity development

[0157]

[0158] Table 3: Cycle performance data

[0159]

[0160]

[0161] Table 4: Full charge storage at 55°C high temperature environment

[0162] 7-day cell thickness expansion rate 7-day ACR growth rate 7-day 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] As can be seen from the data of Examples 1-4 and Comparative Examples 1-3 in Table 1, in the preparation method of the lithium ion battery of the present application, since the lithium supplement agent is provided in the lithium supplement layer on the inner wall of the battery shell, there is no need to add the lithium supplement agent in the homogenization process of the positive electrode material as in the prior art, so the viscosity of the slurry in the homogenization process of the positive electrode material does not appear the gelation and other adverse conditions caused by mixing the lithium supplement agent.

[0164] As can be seen from the data of Examples 1-4 and Comparative Examples 1-3 in Table 2, in the lithium supplement method of the lithium ion battery of the present application, since the connection mode of the formation equipment and the lithium ion battery, the design and selection of the lithium ion battery, and the adjustment of the lithium supplement method are improved, the formation time is shortened. The main reason is that the charging (formation) can be carried out with large current during the re-formation, so the formation time can be improved, and the performance of the lithium ion battery of the present application is better according to the capacity of the positive electrode material.

[0165] As can be seen from the data of Examples 1-4 and Comparative Examples 1-3 in Table 3 and Table 4, the performance of the lithium ion battery prepared by the preparation method of the lithium ion battery of the present application is obviously better than that of the lithium ion battery prepared by the prior art.

[0166] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and this application can be carried out in other specific forms without departing from the spirit or essential characteristics of the application. Therefore, it should be understood that the embodiments are illustrative only and the application is not limited in scope by the foregoing description, but rather in accordance with the appended claims and their equivalents. Any reference signs in the claims should not be construed as limiting the claims to the figures in which the reference signs are used.

[0167] Furthermore, it should be understood that although the specification is described in terms of embodiments, not every embodiment includes every feature or implementation described herein. The specification can include implicit combinations of explicitly mentioned features and / or implicit combinations of implicitly mentioned features. Such combinations are also expressly included within the scope of the specification and an embodiment.

Claims

1. A lithium-ion battery, characterized by, The lithium ion battery comprises: a shell, an inner wall of which is provided with a lithium supplement layer, a material of the lithium supplement layer comprising a lithium supplement agent; a positive electrode assembly comprising a voltage divider, a positive electrode post and a positive electrode material, the positive electrode post being electrically connected to the shell through the voltage divider, and the positive electrode material being connected to the positive electrode post; a negative electrode assembly comprising a negative electrode post and a negative electrode material connected to each other, the negative electrode post being insulatedly connected to the shell; wherein a resistance value of the voltage divider is determined based on a difference between a complete activation voltage of the lithium supplement agent and an overcharge cutoff voltage of the positive electrode material; and the greater the difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material, the greater the resistance value of the voltage divider.

2. The lithium-ion battery of claim 1, wherein, The difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material is 0.15-0.2V, and the resistance of the voltage divider is 10-500Ω; and / or, The difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material is 0.2-0.6V, and the resistance of the voltage divider is 500-3000Ω; and / or, The difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material is 0.6-1.0V, and the resistance of the voltage divider is 3000-30000Ω; and / or, The difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material is 1.0-1.15V, and the resistance of the voltage divider is 30000-100000Ω.

3. The lithium-ion battery of claim 1, wherein, The material of the lithium supplement layer further comprises a conductive agent and a binder.

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

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

100.

6. The lithium-ion battery of claim 1, wherein, The voltage divider is a sealing ring, the positive electrode assembly comprises a positive electrode top cover mounted on the shell, and the positive electrode post is connected to the positive electrode top cover through the sealing ring.

7. A lithium supplement method of a lithium ion battery, applied to the lithium ion battery of any one of claims 1-6, characterized in that, The lithium supplement method of the lithium ion battery comprises the following steps: electrically connecting a positive electrode of a formation device to the shell of the lithium ion battery and electrically connecting a negative electrode of the formation device to a negative electrode post of the lithium ion battery, and performing battery formation. 8.The lithium-ion battery lithium supplementing method of claim 7, wherein, Based on the voltage divider, the voltage difference between the positive electrode post and the shell during the battery formation is equal to the difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material. 9.The lithium-ion battery lithium supplementing method of claim 7, wherein, The battery formation comprises: performing primary formation at a first formation voltage not exceeding a preset voltage; and performing secondary formation at a second formation voltage exceeding the preset voltage and not exceeding the complete activation voltage of the lithium supplement agent. 10.The lithium-ion battery lithium supplementing method of claim 7, wherein, The standard voltage of the primary formation is set, and the preset voltage is the sum of the absolute value of the difference between the complete activation voltage of the lithium supplement agent and the overcharge cutoff voltage of the positive electrode material and the standard voltage. 11.The lithium-ion battery lithium supplementing method of claim 9, wherein, The battery formation comprises: after charging for 55-65min under the condition of 0.05-0.1C, charging to the preset voltage under the condition of 0.2-0.5C, and ending the primary formation; and after charging for 55-65min under the condition of 0.05-0.1C, charging to the preset voltage under the condition of 0.2-0.5C, and ending the primary formation. Charging to full activation voltage at 0.1-0.5C, complete re-formation.

12. A method of producing a lithium ion battery as claimed in any one of claims 1 to 6, characterized in that, The method comprises the following steps: A lithium supplement slurry containing a lithium supplement agent is prepared; The lithium supplement slurry is uniformly coated on the inner wall of the shell preform to form a lithium supplement layer; The shell preform is cut into a plurality of shells; Assembly and liquid injection are performed on the shells to obtain a battery semi-product; The lithium ion battery is obtained by supplementing lithium to the battery semi-product by the lithium supplement method of any one of claims 7-11.

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