Preparation method of battery and battery

Abstract

The preparation method mainly comprises the following steps: step S21, applying a first pulse current with a positive plate as a positive electrode and a second reference electrode as a negative electrode at the pulse frequency of 1-10kHz, so as to obtain a second pulse current with the pulse frequency of 1-10kHz; the current density of the first pulse current is in a range of 10 [mu] A / cm < 2 >-50 [mu] A / cm < 2 >, and the duty ratio of the first pulse current is in a range of 30%-70%; step S22, the negative plate is used as a positive electrode, the second reference electrode is used as a negative electrode, a second pulse current is applied, the pulse frequency of the second pulse current is within the range of 1 kHz to 10 kHz, the current density of the second pulse current is within the range of 10 microamperes / cm < 2 > to 50 microamperes / cm < 2 >, the duty ratio of the second pulse current is within the range of 30% to 70%, and the second reference electrode is used as a negative electrode. And the compactness and thickness uniformity of the lithium layer on the surface of the second conductive end are relatively good.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a method for preparing a battery and a battery. Background Art

[0002] Four-electrode batteries typically include a reference electrode with a lithium layer plated on the conductive end. In related technologies, the lithium layer formed on the conductive end suffers from poor density and thickness uniformity, making it prone to shedding from loose and weak areas, resulting in a short cycle life for the reference electrode. Summary of the Invention

[0003] One object of the present invention is to provide a method for preparing a battery, which can improve the density and thickness uniformity of the lithium layer on the surface of the conductive end.

[0004] Another object of the present invention is to provide a battery that is prepared using the aforementioned preparation method and has a longer cycle life.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] In a first aspect, a method for preparing a battery is provided, comprising:

[0007] Step S1: providing a cell assembly placed in a packaging structure and immersed in an electrolyte, the cell assembly comprising a first reference electrode, a second reference electrode, a positive electrode sheet, a negative electrode sheet, and a separator, the positive electrode sheets and the negative electrode sheets being alternately stacked, with spaces formed between adjacent positive electrode sheets and negative electrode sheets, the separator being disposed in all of the spaces, the first conductive end of the first reference electrode and the second conductive end of the second reference electrode being respectively disposed in two different spaces, and the first conductive end and the second conductive end being separated from the adjacent positive electrode sheet and the negative electrode sheet by the separator;

[0008] Step S2, perform step S21 and step S22 respectively;

[0009] In step S21, the positive electrode sheet is used as the positive electrode and the second reference electrode is used as the negative electrode, and a first pulse current is applied to plate lithium on the surface of the positive electrode sheet with the second conductive end facing the adjacent second conductive end, wherein the pulse frequency of the first pulse current is in the range of 1kHz to 10kHz, and the current density of the first pulse current is in the range of 10μA / cm 2 ~50μA / cm 2 , and the duty cycle of the first pulse current is in the range of 30% to 70%;

[0010] Step S22: With the negative electrode sheet as the positive electrode and the second reference electrode as the negative electrode, a second pulse current is applied to plate lithium on the surface of the negative electrode sheet with the second conductive end facing the adjacent negative electrode sheet, wherein the pulse frequency of the second pulse current is in the range of 1kHz to 10kHz, and the current density of the second pulse current is in the range of 10μA / cm 2 ~50μA / cm 2 , and the duty cycle of the second pulse current is in the range of 30% to 70%.

[0011] As a preferred technical solution of the battery preparation method, step S21 includes:

[0012] Step S210: With the second conductive end as the negative electrode and the positive electrode sheet adjacent to the second conductive end as the positive electrode, the first pulse current is intermittently applied multiple times to plate lithium on the surface of the second conductive end facing the positive electrode sheet, wherein the current density of each applied first pulse current decreases sequentially;

[0013] And / or, step S22 includes:

[0014] Step S220: With the second conductive end as the negative electrode and the negative electrode sheet adjacent to the second conductive end as the positive electrode, the second pulse current is intermittently applied multiple times to plate lithium on the surface of the second conductive end facing the negative electrode sheet, wherein the current density of the second pulse current applied each time decreases successively.

[0015] As a preferred technical solution of the battery preparation method, step S21 includes:

[0016] Step S210a: With the second conductive end as the negative electrode and the positive electrode sheet adjacent to the second conductive end as the positive electrode, the first pulse current is applied, wherein the current density of the first pulse current is 40 μA / cm 2 ~50μA / cm 2 within the scope of

[0017] Step S210b, suspending application of the first pulse current;

[0018] Step S210c: With the second conductive end as the negative electrode and the positive electrode sheet adjacent to the second conductive end as the positive electrode, the first pulse current is applied, wherein the current density of the first pulse current is 20 μA / cm 2 ~40μA / cm 2 within the scope of

[0019] Step S210d, suspending application of the first pulse current;

[0020] Step S210e: With the second conductive end as the negative electrode and the positive electrode sheet adjacent to the second conductive end as the positive electrode, the first pulse current is applied, wherein the current density of the first pulse current is 10 μA / cm 2 ~20μA / cm 2 within the range.

[0021] As a preferred technical solution of the battery preparation method, step S22 includes:

[0022] Step S220a: With the second conductive end as the negative electrode and the negative electrode sheet adjacent to the second conductive end as the positive electrode, apply the second pulse current, wherein the current density of the second pulse current is 40 μA / cm 2 ~50μA / cm 2 within the scope of

[0023] Step S220b, suspending application of the second pulse current;

[0024] Step S220c: With the second conductive end as the negative electrode and the negative electrode sheet adjacent to the second conductive end as the positive electrode, apply the second pulse current, wherein the current density of the second pulse current is 20 μA / cm 2 ~40μA / cm 2 within the scope of

[0025] Step S220d, suspending application of the second pulse current;

[0026] Step S220e: With the second conductive end as the negative electrode and the negative electrode sheet adjacent to the second conductive end as the positive electrode, apply the second pulse current, wherein the current density of the second pulse current is 10 μA / cm 2 ~20μA / cm 2 within the range.

[0027] As a preferred technical solution of the battery preparation method, the pulse frequency, current density and duty cycle of the first pulse current and the second pulse current are the same.

[0028] As a preferred technical solution of the battery preparation method, step S11, providing the first reference electrode and the second reference electrode, the first reference electrode including a first metal wire having one end connected to a first electrode tab, the other end of the first metal wire being the first conductive end, and the surface of the first conductive end being covered with the active coating, the second reference electrode including a second metal wire having one end connected to a second electrode tab, the other end of the first metal wire being the second conductive end;

[0029] Step S12: providing the positive electrode sheet, the negative electrode sheet, and the separator, alternately stacking the positive electrode sheets and the negative electrode sheets, forming spaces between adjacent positive electrode sheets and negative electrode sheets, placing the separator in all the spaces, placing the first conductive end and the second conductive end in two different spaces, and separating the first conductive end and the second conductive end from the adjacent positive electrode sheet and the negative electrode sheet by the separator, to obtain the battery cell assembly;

[0030] Step S13: providing a packaging structure, placing the battery cell assembly into the packaging structure, and injecting electrolyte into the packaging structure.

[0031] As a preferred technical solution of the battery preparation method, along the extension direction of the first metal wire, the first conductive end has a length L1, 0.5mm≤L1≤2mm; and / or,

[0032] Along the extending direction of the second metal wire, the second conductive end has a length L2, 0.5 mm ≤ L2 ≤ 2 mm.

[0033] As a preferred technical solution of the battery preparation method, the first metal wire and the second metal wire are made of the same material; and / or,

[0034] The diameter of the first metal wire is within a range of 20 μm to 100 μm, and / or the diameter of the second metal wire is within a range of 20 μm to 100 μm, and / or the diameter of the first metal wire is equal to the diameter of the second metal wire; and / or,

[0035] The first metal wire has a porous structure, and / or the second metal wire has a porous structure.

[0036] As a preferred technical solution of the battery preparation method, step S11 includes:

[0037] Step S111: providing two metal wires, and welding one end of the two metal wires to the tabs;

[0038] Step S112: one of the two metal wires is the first metal wire, and the other is the second metal wire; the electrode tab welded to the first metal wire is the first electrode tab, and the electrode tab welded to the second metal wire is the second electrode tab;

[0039] An active coating is coated on the surface of the first conductive end, and an acid pickling treatment is performed on the surface of the second conductive end to remove an oxide layer on the surface of the second conductive end.

[0040] As a preferred technical solution of the battery preparation method, after step S112, step S11 further includes:

[0041] Step S113a, covering at least part of the outer surface of the first metal wire except the first conductive end with an insulating structure; and / or, step S113b, covering at least part of the outer surface of the second metal wire except the second conductive end with an insulating structure.

[0042] As a preferred technical solution of the battery preparation method, the active coating includes lithium titanate and carbon nanotubes.

[0043] As a preferred technical solution of the battery preparation method, after step S12, the first conductive end is arranged facing the middle portion of the adjacent positive electrode sheet along the extension direction of the first metal wire; and / or,

[0044] After step S12, the second conductive end is arranged facing the middle portion of the adjacent positive electrode sheet along the extending direction of the second metal wire.

[0045] As a preferred technical solution of the battery preparation method, after step S2, the preparation method further includes:

[0046] Step S31: With the positive electrode sheet as the positive electrode and the first reference electrode as the negative electrode, a first current is applied to insert lithium into the surface of the first conductive end facing the adjacent positive electrode sheet through the active coating on the surface of the first conductive end, wherein the current density of the first current is 10 μA / cm 2 ~50μA / cm 2 until the potential between the first reference electrode and the second reference electrode stabilizes;

[0047] Step S32: With the negative electrode sheet as the negative electrode and the first reference electrode as the positive electrode, a second current is applied to insert lithium into the surface of the negative electrode sheet with the first conductive end facing the adjacent negative electrode sheet through the active coating, and the current density of the second current is 10 μA / cm 2 ~50μA / cm 2 until the potential between the first reference electrode and the second reference electrode stabilizes.

[0048] In a second aspect, a battery is provided, which is prepared by the battery preparation method as described above, and the battery comprises:

[0049] A cell assembly, the cell assembly comprising a positive electrode sheet, a negative electrode sheet, a diaphragm, a first reference electrode and a second reference electrode, the positive electrode sheets and the negative electrode sheets are alternately stacked, and a spacing space is formed between adjacent positive electrode sheets and negative electrode sheets, and the diaphragm is provided in all the spacing spaces to separate any adjacent positive electrode sheets from the negative electrode sheets through the diaphragm, the first reference electrode comprises a first metal wire and a first pole ear, one end of the first metal wire is welded to the first pole ear, the other end of the first metal wire is a first conductive end, and the first conductive end is located at a The first conductive end is located in the separation space, and is separated from the adjacent positive electrode sheet and the negative electrode sheet by the diaphragm, the surface of the first conductive end is covered with an active coating, the second reference electrode includes a second metal wire and a second electrode tab, one end of the second metal wire is welded to the second electrode tab, the other end of the second metal wire is a second conductive end, the second conductive end is located in another of the separation spaces, and is separated from the adjacent positive electrode sheet and the negative electrode sheet by the diaphragm, and the surface of the second conductive end is covered with a lithium layer; and,

[0050] A packaging structure is provided with the battery core assembly and is filled with electrolyte.

[0051] The beneficial effects of the present invention are:

[0052] By performing steps S21 and S22 respectively, the second conductive end can be plated with lithium from two opposite sides of the second conductive end respectively, thereby compensating for the thickness difference of the lithium layer on the two opposite sides of the second conductive end when lithium is plated on one side, so as to make the lithium layer on the surface of the conductive end more uniform.

[0053] Furthermore, by making the pulse frequencies of the first pulse current and the second pulse current within the range of 1kHz to 10kHz, the frequencies of the first pulse current and the second pulse current can be made higher, so as to shorten the pulse time and suppress concentration polarization, so as to improve the density of the lithium layer formed by plating, and the pulse frequencies of the first pulse current and the second pulse current will not be too high, which will lead to excessively high requirements on the precision of the electroplating equipment applying the first pulse current and the second pulse current during the electroplating process, so that the difficulty of implementing step S2 will not be too great, and by making the current density of the first pulse current and the second pulse current within the range of 10μA / cm 2 ~50μA / cm 2Within the range of , the current of the first pulse current and the density of the second pulse current can be made larger, so that the crystallinity of the lithium layer is larger, the grain size is smaller, and the density of the lithium layer is better. At the same time, it will not be too large to cause excessive internal stress of the lithium layer and easy cracking. By making the duty cycle of the first pulse current and the second pulse current within the range of 30% to 70%, so that the duty cycle is moderate, it can be avoided that the duty cycle is too small and the current density increases too much instantaneously, thereby causing the structure of the lithium layer to be loose. At the same time, it can be avoided that the duty cycle is too large and the concentration polarization is too large, and the deposition rate is too low and the structure of the lithium layer is loose.

[0054] It can be understood that by making the pulse frequency, current density and duty cycle of the first pulse current and the second pulse current meet the aforementioned ranges at the same time, the density of the lithium layer obtained by electroplating can be significantly improved through the combined effect of the pulse frequency, current density and duty cycle of the first pulse current and the second pulse current. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0056] Figure 1 Schematic diagram of the structure of the battery cell assembly described in the embodiment.

[0057] Figure 2 Schematic diagram of the partial cross-sectional structure of the first reference electrode and the positive electrode sheet in the embodiment.

[0058] Figure 3 Schematic diagram of the partial cross-sectional structure of the second reference electrode and the positive electrode sheet in the embodiment.

[0059] In the picture:

[0060] 100. Battery cell assembly; 1. First reference electrode; 11. First metal wire; 111. First conductive end; 112. Active coating; 12. First electrode tab; 2. Second reference electrode; 21. Second metal wire; 211. Second conductive end; 212. Lithium layer; 22. Second electrode tab; 3. Positive electrode sheet; 4. Negative electrode sheet; 5. Spacing space; 6. Diaphragm; 7. Insulation structure. DETAILED DESCRIPTION

[0061] To make the technical problems solved, the technical solutions adopted, and the technical effects achieved by the present invention more clearly understood, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the described embodiments are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0062] In the description of the present invention, unless otherwise expressly specified or limited, the terms "connected," "connected," and "fixed" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention in specific circumstances.

[0063] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0064] The present invention provides a battery, which is prepared by the battery preparation method described below, specifically, Figures 1 to 3 As shown, the battery includes a cell assembly 100 and a packaging structure, the cell assembly 100 includes a first reference electrode 1, a second reference electrode 2, a positive electrode sheet 3, a negative electrode sheet 4 and a diaphragm 6, the positive electrode sheets 3 and the negative electrode sheets 4 are alternately stacked, and a spacing space 5 is formed between adjacent positive electrode sheets 3 and negative electrode sheets 4, and all spacing spaces 5 are provided with a diaphragm 6 to separate any adjacent positive electrode sheets 3 and negative electrode sheets 4 through the diaphragm 6, the first reference electrode 1 includes a first metal wire 11 and a first pole ear 12, one end of the first metal wire 11 is welded to the first pole ear 12, and the other end of the first metal wire 11 is a first conductive end 111, the first conductive end 111 is located in a spacing space 5, and the first conductive end 111 and the adjacent positive electrode sheets 3 and negative electrode sheets 4 are connected by The first conductive end 111 is separated by a diaphragm 6, and the surface of the first conductive end 111 is covered with an active coating 112. The second reference electrode 2 includes a second metal wire 21 and a second pole ear 22. One end of the second metal wire 21 is welded to the second pole ear 22, and the other end of the second metal wire 21 is a second conductive end 211. The second conductive end 211 is located in another spacing space 5, and the second conductive end 211 is separated from the adjacent positive electrode sheet 3 and the negative electrode sheet 4 by the diaphragm 6. The surface of the second conductive end 211 is covered with a lithium layer 212. The battery cell assembly 100 is arranged in the packaging structure and is filled with electrolyte. Since it is prepared by using the preparation method described below, the thickness uniformity and density of the lithium layer 212 can be better, so the cycle life of the battery can be longer.

[0065] For the convenience of observation, Figure 1 The negative electrode sheet 4 is filled with oblique lines, and the interval 5 formed between the positive electrode sheet 3 and the negative electrode sheet 4 is enlarged. It can be understood that Figure 1 It is only used to illustrate the stacking relationship of the positive electrode sheet 3 , the negative electrode sheet 4 , the separator 6 , the first reference electrode 1 and the second reference electrode 2 , and does not mean that the actual battery cell assembly 100 has the larger spacing space 5 shown in the figure.

[0066] Optionally, the positive electrode sheet 3 can be connected to the positive electrode on the packaging structure so that the positive electrode sheet 3 can be connected to an external circuit through the positive electrode on the packaging structure, and the negative electrode sheet 4 can be connected to the negative electrode on the packaging structure so that the negative electrode sheet 4 can be connected to an external circuit through the negative electrode on the packaging structure.

[0067] When using a battery, a four-electrode system test can be performed on the battery using the positive electrode, the negative electrode, the first reference electrode 1, and the second reference electrode 2. Specifically, the positive electrode and the first reference electrode 1 are connected to a voltmeter as the positive and negative electrodes to detect the first potential, the negative electrode and the first reference electrode 1 are connected to a voltmeter as the positive and negative electrodes to detect the second potential, the first reference electrode 1 and the second reference electrode 2 are connected to a voltmeter as the positive and negative electrodes to detect the correction potential, the positive electrode standard potential curve can be obtained by subtracting the correction potential from the first potential, the negative electrode standard potential curve can be obtained by subtracting the correction potential from the second potential, the positive electrode and the negative electrode are connected to a voltmeter as the positive and negative electrodes to detect the positive and negative potentials, and thus the full battery curve can be used. Through the positive electrode standard potential curve, the negative electrode standard potential curve, and the full battery curve, the standard potential ratio changes of each electrode of the battery can be learned, and then the capacity of each electrode of the battery, the lithium plating situation, and the impedance change can be further analyzed.

[0068] The present invention also provides a method for preparing a battery. Figures 1 to 3 The structure shown in the figure, the preparation method of the battery includes:

[0069] Step S1, provide a battery cell assembly 100 placed in a packaging structure and immersed in an electrolyte, the battery cell assembly 100 includes a first reference electrode 1, a second reference electrode 2, a positive electrode sheet 3, a negative electrode sheet 4 and a separator 6, the positive electrode sheets 3 and the negative electrode sheets 4 are alternately stacked, and a separation space 5 is formed between adjacent positive electrode sheets 3 and negative electrode sheets 4, and a separator 6 is set in all the separation spaces 5, the first conductive end 111 of the first reference electrode 1 and the second conductive end 211 of the second reference electrode 2 are respectively arranged in two different separation spaces 5, and the first conductive end 111 and the second conductive end 211 are separated from the adjacent positive electrode sheet 3 and negative electrode sheet 4 by the separator 6.

[0070] Optionally, step S1 may include: step S11, providing a first metal wire 11 and a second metal wire 21, one end of the first metal wire 11 is connected to a first pole ear 12, the other end of the first metal wire 11 is a first conductive end 111, the surface of the first conductive end 111 is covered with an active coating 112, one end of the second metal wire 21 is connected to a second pole ear 22, and the other end of the first metal wire 11 is a second conductive end 211.

[0071] Optionally, the active coating 112 may include lithium titanate and carbon nanotubes, so that a conductive network structure can be formed by the carbon nanotubes to enhance the conductivity of the active coating 112 and reduce the impedance of the active coating 112 .

[0072] Along the extension direction of the first metal wire 11, the first conductive end 111 has a length L1. If the length L1 of the first conductive end 111 is too small, the electrolyte path between the first reference electrode 1 and the working electrode (i.e., the positive electrode sheet 3 and the negative electrode sheet 4) will be shortened, and the local current density will increase, thereby increasing the ohmic drop and causing the potential measured using the first reference electrode 1 to deviate from the true value. However, if the length L1 of the first conductive end 111 is too long, it will hinder the ion transmission in the electrolyte, increase the local concentration gradient, and cause uneven distribution of ohmic drop and reaction current, which will interfere with the potential measurement. Therefore, the length L1 cannot be too long. Based on this, optionally, the length L1 of the first conductive end 111 can satisfy: 0.5mm≤L1≤2mm. For example, the length L1 of the first conductive end 111 can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm or 2mm, etc.

[0073] Along the extension direction of the second metal wire 21, the second conductive end 211 has a length L2. If the length L2 of the second conductive end 211 is too small, the electrolyte path between the second reference electrode 2 and the working electrode (i.e., the positive electrode sheet 3 and the negative electrode sheet 4) will be shortened, and the local current density will increase, thereby causing the ohmic drop to increase, causing the potential measured using the second reference electrode 2 to deviate from the true value. However, if the length L2 of the second conductive end 211 is too large, it will hinder the ion transmission in the electrolyte, increase the local concentration gradient, and cause uneven distribution of the ohmic drop and reaction current, which will interfere with the potential measurement. Therefore, the length L2 cannot be too large. Based on this, optionally, the length L2 of the second conductive end 211 can satisfy: 0.5mm≤L2≤2mm. For example, the length L2 of the second conductive end 211 can be 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm or 2mm, etc.

[0074] Optionally, the first metal wire 11 and the second metal wire 21 are made of the same material, so that the resistivity difference between the first metal wire 11 and the second metal wire 21 is small, which can make the battery correction potential detected by the first metal wire 11 and the second metal wire 21 more accurate. For example, the first metal wire 11 and the second metal wire 21 can both be made of a metal material with good electrical conductivity, such as copper, platinum, or nickel.

[0075] Optionally, the diameter of the first metal wire 11 is equal to the diameter of the second metal wire 21 , so that the resistance difference between the first metal wire 11 and the second metal wire 21 is small, which can make the battery correction potential detected by the first metal wire 11 and the second metal wire 21 more accurate.

[0076] If the diameter of the first metal wire 11 is too large, it will occupy the electrolyte channel, hindering the transmission of lithium ions between the positive electrode sheet 3 and the negative electrode sheet 4, and may even form a "shielded area" inside the battery cell assembly 100, resulting in abnormal local current density and aggravated polarization. However, if the diameter of the first metal wire 11 is too small, the tensile strength of the first metal wire 11 will be too low. During the battery assembly or charging and discharging process, it is easy to break due to mechanical stress (such as winding tension, electrolyte flow impact), causing the first reference electrode 1 to fail. In addition, when lithium is plated on the surface of the first metal wire 11 with a diameter that is too small, due to the excessively high local current density, dendrites or loose plating are easily formed, resulting in potential drift. Based on this, optionally, the diameter of the first metal wire 11 may be in the range of 20μm to 100μm. For example, the diameter of the first metal wire 11 may be 20μm, 22μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm or 100μm, etc.

[0077] Optionally, the first metal wire 11 may have a porous structure, so that the electrolyte wettability at the first conductive end 111 of the first metal wire 11 is better, thereby further reducing the impedance of the first metal wire 11. Exemplarily, when the first metal wire 11 is made of copper, the first metal wire 11 may have a foam copper structure.

[0078] If the diameter of the second metal wire 21 is too large, it will occupy the electrolyte channel, hindering the transmission of lithium ions between the positive electrode sheet 3 and the negative electrode sheet 4. It may even form a "shielded area" within the battery cell assembly 100, resulting in abnormal local current density and exacerbated polarization. However, if the diameter of the second metal wire 21 is too small, the tensile strength of the second metal wire 21 will be too low. During battery assembly or charging and discharging, it is easy to break due to mechanical stress (such as winding tension, electrolyte flow impact), causing the second reference electrode 2 to fail. In addition, when lithium is plated on the surface of the second metal wire 21 with an excessively small diameter, the local current density is too high, which can easily form dendrites or loose plating, resulting in potential drift. Based on this, optionally, the diameter of the second metal wire 21 is in the range of 20μm to 100μm. For example, the diameter of the second metal wire 21 may be 20μm, 22μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm or 100μm, etc.

[0079] Optionally, the second metal wire 21 may have a porous structure, so that the electrolyte wettability at the second conductive end 211 of the second metal wire 21 is better, thereby further reducing the impedance of the second metal wire 21. Exemplarily, when the second metal wire 21 is made of copper, the second metal wire 21 may have a foam copper structure.

[0080] Preferably, the material, size and structural shape of the first metal wire 11 and the second metal wire 21 can be the same, so that the resistance difference between the first metal wire 11 and the second metal wire 21 can be minimized, so that the battery correction potential detected by the first metal wire 11 and the second metal wire 21 can be more accurate.

[0081] Furthermore, the material, size, and structural shape of the first and second tabs 12, 22 can also be identical, so that the resistance difference between the first reference electrode 1 formed by connecting the first metal wire 11 and the first tab 12 and the second reference electrode 2 formed by connecting the second metal wire 21 and the second tab 22 is minimized, thereby making the battery calibration potential detected by the first and second reference electrodes 1 and 2 more accurate. Exemplarily, the first and second tabs 12, 22 can both be nickel-plated copper sheets. In other embodiments, the first and second tabs 12, 22 can also include, but are not limited to, platinum or nickel.

[0082] When the first metal wire 11 and the second metal wire 21 have the same material, size, and structural shape, and the first electrode tab 12 and the second electrode tab 22 also have the same material, size, and structural shape, optionally, step S11 may include:

[0083] Step S111: provide two metal wires, and weld one end of the two metal wires to the tabs.

[0084] In step S112 , one of the two metal wires is the first metal wire 11 and the other is the second metal wire 21 . The tab welded to the first metal wire 11 is the first tab 12 , and the tab welded to the second metal wire 21 is the second tab 22 .

[0085] An active coating 112 is coated on the surface of the first conductive end 111 , and an acid pickling treatment is performed on the surface of the second conductive end 211 to remove the oxide layer on the surface of the second conductive end 211 .

[0086] Thus, the same step S111 can be used to preliminarily manufacture the first metal wire 11 welded with the first electrode tab 12 and the second metal wire 21 welded with the second electrode tab 22. In other words, when performing step S111, there is no need to distinguish two production lines for the first reference electrode 1 and the second reference electrode 2. Instead, the same production line can be used to batch manufacture metal wires welded with electrode tabs, thereby reducing the manufacturing costs of the first reference electrode 1 and the second reference electrode 2.

[0087] Optionally, after step S112, step S11 may further include:

[0088] Step S113 a : Covering an insulating structure 7 on at least a portion of the outer surface of the first metal wire 11 except the first conductive end 111 .

[0089] This prevents the first metal wire 11 from being directly exposed to the electrolyte, thereby reducing the corrosion effect of the electrolyte on the first metal wire 11 during the use of the battery.

[0090] Illustratively, the insulating structure 7 may include but is not limited to insulating tape and insulating coating.

[0091] Optionally, after step S112, step S11 may further include:

[0092] Step S113b: Covering an insulating structure 7 on at least a portion of the outer surface of the second metal wire 21 except the second conductive end 211 .

[0093] This prevents the second metal wire 21 from being directly exposed to the electrolyte, thereby reducing the corrosion effect of the electrolyte on the second metal wire 21 during the use of the battery.

[0094] Illustratively, the insulating structure 7 may include but is not limited to insulating tape and insulating coating.

[0095] When, as described in the aforementioned technical solution, step S11 also includes step S113a, there is no need to limit the order in which step S113a and step S113b are performed, that is, step S113a and step S113b can be performed simultaneously, or step S113a can be performed first and then step S113b, or step S113b can be performed first and then step S113a.

[0096] Step S12: Provide positive electrode sheets 3, negative electrode sheets 4 and separators 6, alternately stack the positive electrode sheets 3 and negative electrode sheets 4, form separation spaces 5 between adjacent positive electrode sheets 3 and negative electrode sheets 4, set separators 6 in all separation spaces 5, and set the first conductive end 111 and the second conductive end 211 in two different separation spaces 5 respectively, and the first conductive end 111 and the second conductive end 211 are separated from the adjacent positive electrode sheets 3 and negative electrode sheets 4 by the separator 6 to obtain a battery cell assembly 100.

[0097] It can be understood that the stacking arrangement of the positive electrode sheet 3, the negative electrode sheet 4 and the separator 6 can be any stacking arrangement of the positive electrode sheet 3, the negative electrode sheet 4 and the separator 6 of an existing battery cell.

[0098] Optionally, the first conductive end 111 is arranged opposite the middle part of the adjacent positive electrode sheet 3 along the extension direction of the first metal wire 11, so that the first reference electrode 1 can more stably collect the electric potential in the interval space 5 where the first reference electrode 1 is located through the first conductive end 111.

[0099] Optionally, the second conductive end 211 is arranged opposite the middle part of the adjacent positive electrode sheet 3 along the extension direction of the second metal wire 21, so that the first reference electrode 1 can more stably collect the electric potential in the spacing space 5 where the second reference electrode 2 is located through the second conductive end 211.

[0100] Step S14: providing a packaging structure, placing the battery cell assembly 100 into the packaging structure, and injecting electrolyte into the packaging structure.

[0101] Alternatively, the packaging structure may include a flexible package to form the battery into a soft pack battery, or the packaging structure may include a hard shell package to form the battery into a hard shell battery.

[0102] In addition, the positive electrode sheet 3 can be connected to the positive electrode on the packaging structure so that the positive electrode sheet 3 can be connected to the external circuit through the positive electrode on the packaging structure, and the negative electrode sheet 4 can be connected to the negative electrode on the packaging structure so that the negative electrode sheet 4 can be connected to the external circuit through the negative electrode on the packaging structure.

[0103] Step S2, perform step S21 and step S22 respectively;

[0104] In step S21, the positive electrode sheet 3 is used as the positive electrode and the second reference electrode is used as the negative electrode, and a first pulse current is applied to the surface of the second conductive end 211 facing the adjacent positive electrode sheet 3 to perform lithium plating, wherein the pulse frequency of the first pulse current is in the range of 1kHz to 10kHz, and the current density of the first pulse current is in the range of 10μA / cm 2 ~50μA / cm 2 and the duty cycle of the first pulse current is in the range of 30% to 70%.

[0105] Step S22: With the negative electrode 4 as the positive electrode and the second reference electrode as the negative electrode, a second pulse current is applied to plate lithium on the surface of the negative electrode 4 with the second conductive end 211 facing the adjacent negative electrode, wherein the pulse frequency of the second pulse current is in the range of 1kHz to 10kHz, and the current density of the second pulse current is in the range of 10μA / cm 2 ~50μA / cm 2 and the duty cycle of the second pulse current is in the range of 30% to 70%.

[0106] By performing steps S21 and S22 respectively, part of the lithium included in the active materials on the positive electrode sheet 3 and the negative electrode sheet 4 can be plated to the second conductive end 211, and the second conductive end 211 can be plated with lithium by the positive electrode sheet 3 and the negative electrode sheet 4 respectively located on two opposite sides of the second conductive end 211, thereby compensating for the thickness difference of the lithium layer 212 on the two opposite sides of the second conductive end 211 when lithium is plated on one side, so as to make the lithium layer 212 on the surface of the second conductive end 211 more uniform.

[0107] Furthermore, by making the pulse frequencies of the first pulse current and the second pulse current range from 1kHz to 10kHz, the frequencies of the first pulse current and the second pulse current can be higher, so as to shorten the pulse time, suppress concentration polarization, and improve the density of the lithium layer 212 formed by plating, and the pulse frequencies of the first pulse current and the second pulse current will not be too high, which will lead to excessively high requirements on the precision of the electroplating equipment for applying the first pulse current and the second pulse current during the electroplating process, so that the implementation difficulty of step S2 will not be too great. For example, the pulse frequencies of the first pulse current and the second pulse current can be 1kHz, 1.5kHz, 2kHz, 2.5kHz, 3kHz, 3.5kHz, 4kHz, 4.5kHz, 5kHz, 5.5kHz, 6kHz, 6.5kHz, 7kHz, 7.5kHz, 8kHz, 8.5kHz, 9kHz, 9.5kHz or 10kHz, etc.

[0108] By setting the current density of the first pulse current and the second pulse current to 10 μA / cm 2 ~50μA / cm2 Within the range of , the current density of the first pulse current and the second pulse current density can be made larger, so that the crystallinity of the lithium layer 212 is larger, the grain size is smaller, and the density of the lithium layer 212 is better. At the same time, it will not be too large to cause excessive internal stress of the lithium layer 212 and easy cracking. For example, the current density of the first pulse current and the second pulse current can be 10μA / cm 2 , 15μA / cm 2 , 20μA / cm 2 , 25μA / cm 2 、30μA / cm 2 、35μA / cm 2 , 40μA / cm 2 , 45μA / cm 2 or 50μA / cm 2 wait.

[0109] By making the duty cycle of the first pulse current and the second pulse current within the range of 30% to 70%, the duty cycle is moderate, which can avoid the duty cycle being too small, resulting in an excessive increase in the instantaneous current density, and thus causing the structure of the lithium layer 212 to be loose. At the same time, it can avoid the duty cycle being too large, resulting in excessive concentration polarization, and the deposition rate being too small, resulting in a loose structure of the lithium layer 212. Exemplarily, the duty cycles of the first pulse current and the second pulse current can be 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68% or 70%, etc.

[0110] It can be understood that by making the pulse frequency, current density and duty cycle of the first pulse current and the second pulse current meet the aforementioned ranges at the same time, the density of the lithium layer 212 obtained by electroplating can be significantly improved through the combined effect of the pulse frequency, current density and duty cycle of the first pulse current and the second pulse current.

[0111] In addition, it can be understood that the order of performing steps S21 and S22 has no effect on the plating effect of the lithium layer 212 on the surface of the second conductive end 211 in step S2. In other words, step S21 can be performed first and then step S22, or step S22 can be performed first and then step S21.

[0112] Optionally, the pulse frequency, current density and duty cycle of the first pulse current and the second pulse current are the same, so that the density and thickness consistency of the lithium layer 212 plated on the second conductive end 211 from the two opposite sides of the second conductive end 211 in step S21 and step S22 are good, which can make the overall density and thickness of the lithium layer 212 formed on the surface of the second conductive end 211 more uniform.

[0113] It should be noted that the performance parameters of the first pulse current and the second pulse current are the same. Specifically, when a performance parameter of the first pulse current is a certain value, the performance parameter of the second pulse current is also the same value. When a performance parameter of the first pulse current is a value that changes with the action time of the first pulse current, the performance parameter of the second is also a value that changes in the same way with the action time of the second pulse current. That is, the pulse frequency, current density and duty cycle of the first pulse current and the second pulse current can be the same fixed values, or can be values ​​that change in the same way with the action time of the pulse current.

[0114] In other embodiments, the pulse frequency, current density and duty cycle of the first pulse current and the second pulse current may not be exactly the same, that is, at least one of the pulse frequency, current density and duty cycle of the first pulse current and the second pulse current may be different.

[0115] Optionally, step S21 may include:

[0116] Step S210: With the second conductive end 211 as the negative electrode and the positive electrode sheet 3 adjacent to the second conductive end 211 as the positive electrode, a first pulse current is intermittently applied multiple times to plate lithium on the surface of the second conductive end 211 facing the positive electrode sheet 3, wherein the current density of the first pulse current applied each time decreases successively.

[0117] This can gradually reduce the current density during electroplating, and when the gaps between applying the first pulse current multiple times stop, it can provide time for the lithium ions in the electrolyte to diffuse, so as to significantly reduce the polarization effect, avoid the loosening or dendrite growth of the lithium layer 212 caused by the sudden change in current density, and enable the lithium ions to diffuse more evenly at the interface, so as to further improve the density and bonding strength of the lithium layer 212.

[0118] Preferably, the gap stop time between multiple applications of the first pulse current can be approximately 30 minutes, so that the lithium ions in the electrolyte can be more fully diffused, and the gap stop time will not be too long. Exemplarily, the gap stop time can be 20 minutes, 22 minutes, 25 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 35 minutes, 37 minutes or 40 minutes, etc.

[0119] Optionally, the first pulse current may be applied intermittently three times to make the structure of the lithium layer 212 obtained by electroplating more compact while reducing the number of steps included in step S21 and making step S21 less complex. In this case, for example, step S21 may specifically include:

[0120] Step S210a: With the second conductive end 211 as the negative electrode and the positive electrode sheet 3 adjacent to the second conductive end 211 as the positive electrode, a first pulse current is applied, wherein the current density of the first pulse current is 40 μA / cm 2 ~50μA / cm 2 within the range.

[0121] For example, in step S210a, the current density of the first pulse current may be 40 μA / cm 2 , 41μA / cm 2 , 42μA / cm 2 , 43μA / cm 2 , 44μA / cm 2 , 45μA / cm 2 , 46μA / cm 2 , 47μA / cm2, 48μA / cm 2 , 49μA / cm 2 or 50μA / cm 2 wait.

[0122] Step S210b: suspend applying the first pulse current.

[0123] Step S210c: With the second conductive end 211 as the negative electrode and the positive electrode sheet 3 adjacent to the second conductive end 211 as the positive electrode, a first pulse current is applied, wherein the current density of the first pulse current is 20 μA / cm 2 ~40μA / cm 2 within the range.

[0124] For example, in step S210c, the current density of the first pulse current may be 20 μA / cm 2 , 22μA / cm 2 , 25μA / cm 2 , 27μA / cm 2 、30μA / cm 2 、32μA / cm 2 、35μA / cm 2 、37μA / cm 2 or 40μA / cm 2 wait.

[0125] Step S210d: suspend applying the first pulse current.

[0126] Step S210e: With the second conductive end 211 as the negative electrode and the positive electrode sheet 3 adjacent to the second conductive end 211 as the positive electrode, a first pulse current is applied, wherein the current density of the first pulse current is 10 μA / cm 2 ~20μA / cm 2 within the range.

[0127] For example, in step S210e, the current density of the first pulse current may be 10 μA / cm 2 , 11μA / cm 2 , 12μA / cm 2 , 13μA / cm 2 , 14μA / cm 2 , 15μA / cm 2 , 16μA / cm 2 , 7μA / cm 2 , 18μA / cm 2 、19μA / cm 2 or 20μA / cm 2 wait.

[0128] Optionally, step S22 may include:

[0129] In step S220, the second conductive end 211 is used as the negative electrode and the negative electrode sheet 4 adjacent to the second conductive end 211 is used as the positive electrode. A second pulse current is applied intermittently multiple times to plate lithium on the surface of the second conductive end 211 facing the negative electrode sheet 4, wherein the current density of the second pulse current applied each time decreases successively.

[0130] This can gradually reduce the current density during electroplating, and when the intervals between applying the second pulse current multiple times stop, it can provide time for the lithium ions in the electrolyte to diffuse, so as to significantly reduce the polarization effect, avoid the loosening or dendrite growth of the lithium layer 212 caused by the sudden change in current density, and enable the lithium ions to diffuse more evenly at the interface, so as to further improve the density and bonding strength of the lithium layer 212.

[0131] Preferably, the interval stop time between multiple applications of the second pulse current can be approximately 30 minutes, so that the lithium ions in the electrolyte can be more fully diffused, and the interval stop time will not be too long. Exemplarily, the interval stop time can be 20 minutes, 22 minutes, 25 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, 31 minutes, 32 minutes, 33 minutes, 35 minutes, 37 minutes or 40 minutes, etc.

[0132] Optionally, the second pulse current may be applied intermittently three times to make the structure of the lithium layer 212 obtained by electroplating more compact while reducing the number of steps included in step S22 and making step S22 less complex. In this case, for example, step S22 may specifically include:

[0133] Step S220a: With the second conductive end 211 as the negative electrode and the negative electrode sheet 4 adjacent to the second conductive end 211 as the positive electrode, a second pulse current is applied, wherein the current density of the second pulse current is 40 μA / cm 2 ~50μA / cm2 within the range.

[0134] For example, in step S220a, the current density of the second pulse current may be 40 μA / cm 2 , 41μA / cm 2 , 42μA / cm 2 , 43μA / cm 2 , 44μA / cm 2 , 45μA / cm 2 , 46μA / cm 2 , 47μA / cm 2 , 48μA / cm 2 , 49μA / cm 2 or 50μA / cm 2 wait.

[0135] Step S220b: suspend applying the second pulse current.

[0136] Step S220c: With the second conductive end 211 as the negative electrode and the negative electrode sheet 4 adjacent to the second conductive end 211 as the positive electrode, a second pulse current is applied, wherein the current density of the second pulse current is 20 μA / cm 2 ~40μA / cm 2 within the range.

[0137] For example, in step S220c, the current density of the second pulse current may be 20 μA / cm 2 , 22μA / cm 2 , 25μA / cm 2 , 27μA / cm 2 、30μA / cm 2 、32μA / cm 2 、35μA / cm 2 、37μA / cm 2 or 40μA / cm 2 wait.

[0138] Step S220d: suspend applying the second pulse current.

[0139] Step S220e: With the second conductive end 211 as the negative electrode and the negative electrode sheet 4 adjacent to the second conductive end 211 as the positive electrode, a second pulse current is applied, wherein the current density of the second pulse current is 10 μA / cm 2 ~20μA / cm 2 within the range.

[0140] For example, in step S220e, the current density of the second pulse current may be 10 μA / cm 2 , 11μA / cm 2, 12μA / cm 2 , 13μA / cm 2 , 14μA / cm 2 , 15μA / cm 2 , 16μA / cm 2 , 7μA / cm 2 , 18μA / cm 2 、19μA / cm 2 or 20μA / cm 2 wait.

[0141] When, as described in the above-mentioned technical solution, the pulse frequency, current density and duty cycle of the first pulse current are the same as those of the second pulse current, step S21 includes steps S210a, S210b, S210c, S210d and S210e, and step S22 includes steps S220a, S220b, S220c, S220d and S220e, it can be understood that the pulse frequency, current density and duty cycle of the first pulse current in step S210a and the second pulse current in step S220a are the same, the pulse frequency, current density and duty cycle of the first pulse current in step S210c and the second pulse current in step S220c are the same, and the pulse frequency, current density and duty cycle of the first pulse current in step S210e and the second pulse current in step S220e are the same.

[0142] Optionally, after step S2, the battery preparation method may further include:

[0143] Step S31: With the positive electrode 3 as the positive electrode and the first reference electrode 1 as the negative electrode, a first current is applied to insert lithium into the surface of the first conductive end 111 facing the adjacent positive electrode 3 through the active coating on the surface of the first conductive end 111. The current density of the first current is 10 μA / cm 2 ~50μA / cm 2 until the potential between the first reference electrode 1 and the second reference electrode 2 stabilizes.

[0144] Step S32: With the negative electrode 4 as the negative electrode and the first reference electrode 1 as the positive electrode, a second current is applied to insert lithium into the surface of the first conductive end 111 toward the adjacent negative electrode 4 through the active coating 112. The current density of the second current is 10 μA / cm 2 ~50μA / cm 2 until the potential between the first reference electrode 1 and the second reference electrode 2 stabilizes.

[0145] Thus, lithium is inserted into the surface of the first conductive end 111 through the active coating 112 , and the first reference electrode 1 and the second reference electrode 2 are activated at the same time.

[0146] By sequentially performing steps S31 and S32, a portion of the lithium contained in the active coating 112 can be embedded in the first conductive terminal 111 from the first reference electrode 1 toward the two opposite sides of the adjacent positive electrode sheet 3 and the negative electrode sheet 4, respectively. This can compensate for the difference in thickness of the lithium embedded on the two opposite sides of the first conductive terminal 111 when lithium is embedded on one side, thereby improving the uniformity of the lithium embedded on the first conductive terminal 111.

[0147] For example, the current density of the first current may be 10 μA / cm 2 , 15μA / cm 2 , 20μA / cm 2 , 25μA / cm 2 、30μA / cm 2 、35μA / cm 2 , 40μA / cm 2 , 45μA / cm 2 or 50μA / cm 2 The current density of the second current can be 10 μA / cm 2 , 15μA / cm 2 , 20μA / cm 2 , 25μA / cm 2 、30μA / cm 2 、35μA / cm 2 , 40μA / cm 2 , 45μA / cm 2 or 50μA / cm 2 wait.

[0148] In the description herein, it should be understood that the terms "upper," "lower," "left," "right," and other orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely for ease of description and simplified operation. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first" and "second" are used solely for descriptive purposes and have no special meaning.

[0149] In this specification, reference to terms such as "one embodiment" or "example" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example.

[0150] 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.

[0151] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are intended solely to illustrate the principles of the present invention and are not to be construed in any way as limiting the scope of protection of the present invention. Based on the explanations herein, those skilled in the art will readily conceive of other specific embodiments of the present invention without inventive effort, and such embodiments will fall within the scope of protection of the present invention.

Claims

1. A method for preparing a battery, characterized in that: include: Step S1, providing a cell assembly (100) placed in a packaging structure and immersed in an electrolyte, the cell assembly (100) comprising a first reference electrode (1), a second reference electrode (2), a positive electrode sheet (3), a negative electrode sheet (4) and a separator (6), the positive electrode sheets (3) and the negative electrode sheets (4) being alternately stacked, a separation space (5) being formed between adjacent positive electrode sheets (3) and negative electrode sheets (4), the separator (6) being arranged in all the separation spaces (5), the first conductive end (111) of the first reference electrode (1) and the second conductive end (211) of the second reference electrode (2) being respectively arranged in two different separation spaces (5), and the first conductive end (111) and the second conductive end (211) being separated from the adjacent positive electrode sheet (3) and the negative electrode sheet (4) by the separator (6); Step S2, perform step S21 and step S22 respectively; In step S21, the positive electrode sheet (3) is used as the positive electrode, the second reference electrode (2) is used as the negative electrode, and a first pulse current is applied to plate lithium on the surface of the positive electrode sheet (3) adjacent to the second conductive end (211), wherein the pulse frequency of the first pulse current is within the range of 1kHz to 10kHz, and the current density of the first pulse current is within the range of 10μA / cm 2 ~50μA / cm 2 , and the duty cycle of the first pulse current is in the range of 30% to 70%; Step S22: With the negative electrode sheet (4) as the positive electrode and the second reference electrode (2) as the negative electrode, a second pulse current is applied to plate lithium on the surface of the negative electrode sheet (4) with the second conductive end (211) facing the adjacent side, wherein the pulse frequency of the second pulse current is within the range of 1kHz to 10kHz, and the current density of the second pulse current is within the range of 10μA / cm 2 ~50μA / cm 2 , and the duty cycle of the second pulse current is in the range of 30% to 70%.

2. The method for preparing a battery according to claim 1, wherein: The step S21 includes: Step S210: using the second conductive end (211) as the negative electrode and the positive electrode sheet (3) adjacent to the second conductive end (211) as the positive electrode, applying the first pulse current intermittently multiple times to plate lithium on the surface of the second conductive end (211) facing the positive electrode sheet (3), wherein the current density of each application of the first pulse current decreases successively; And / or, step S22 includes: Step S220: With the second conductive end (211) as the negative electrode and the negative electrode sheet (4) adjacent to the second conductive end (211) as the positive electrode, the second pulse current is applied intermittently multiple times to plate lithium on the surface of the second conductive end (211) facing the negative electrode sheet (4), wherein the current density of the second pulse current applied each time decreases successively.

3. The method for preparing a battery according to claim 2, wherein: The step S21 includes: Step S210a: With the second conductive end (211) as the negative electrode and the positive electrode sheet (3) adjacent to the second conductive end (211) as the positive electrode, the first pulse current is applied, wherein the current density of the first pulse current is 40 μA / cm 2 ~50μA / cm 2 within the scope of Step S210b, suspending application of the first pulse current; Step S210c: With the second conductive end (211) as the negative electrode and the positive electrode sheet (3) adjacent to the second conductive end (211) as the positive electrode, the first pulse current is applied, wherein the current density of the first pulse current is 20 μA / cm 2 ~40μA / cm 2 within the scope of Step S210d, suspending application of the first pulse current; Step S210e: With the second conductive end (211) as the negative electrode and the positive electrode sheet (3) adjacent to the second conductive end (211) as the positive electrode, the first pulse current is applied, wherein the current density of the first pulse current is 10 μA / cm 2 ~20μA / cm 2 within the range.

4. The method for preparing a battery according to claim 2, wherein: The step S22 includes: Step S220a: With the second conductive end (211) as the negative electrode and the negative electrode sheet (4) adjacent to the second conductive end (211) as the positive electrode, the second pulse current is applied, wherein the current density of the second pulse current is 40 μA / cm 2 ~50μA / cm 2 within the scope of Step S220b, suspending application of the second pulse current; Step S220c: With the second conductive end (211) as the negative electrode and the negative electrode sheet (4) adjacent to the second conductive end (211) as the positive electrode, the second pulse current is applied, wherein the current density of the second pulse current is 20 μA / cm 2 ~40μA / cm 2 within the scope of Step S220d, suspending application of the second pulse current; Step S220e: With the second conductive end (211) as the negative electrode and the negative electrode sheet (4) adjacent to the second conductive end (211) as the positive electrode, the second pulse current is applied, wherein the current density of the second pulse current is 10 μA / cm 2 ~20μA / cm 2 within the range.

5. The method for preparing a battery according to any one of claims 1 to 4, characterized in that: The first pulse current and the second pulse current have the same pulse frequency, current density and duty cycle.

6. The method for preparing a battery according to any one of claims 1 to 4, characterized in that: The step S1 comprises: Step S11, providing the first reference electrode (1) and the second reference electrode (2), wherein the first reference electrode (1) comprises a first metal wire (11) having one end connected to a first electrode tab (12), the other end of the first metal wire (11) being the first conductive end (111), and the surface of the first conductive end (111) being covered with the active coating (112); and the second reference electrode (2) comprises a second metal wire (21) having one end connected to a second electrode tab (22), the other end of the first metal wire (11) being the second conductive end (211); Step S12, providing the positive electrode sheet (3), the negative electrode sheet (4) and the separator (6), alternately stacking the positive electrode sheet (3) and the negative electrode sheet (4), forming a separation space (5) between adjacent positive electrode sheets (3) and negative electrode sheets (4), setting the separator (6) in all the separation spaces (5), setting the first conductive end (111) and the second conductive end (211) in two different separation spaces (5), and separating the first conductive end (111) and the second conductive end (211) from the adjacent positive electrode sheet (3) and the negative electrode sheet (4) by the separator (6), to obtain the battery cell assembly (100); Step S13: providing a packaging structure, placing the battery cell assembly (100) into the packaging structure, and injecting electrolyte into the packaging structure.

7. The method for preparing a battery according to claim 6, wherein: Along the extension direction of the first metal wire (11), the first conductive end (111) has a length L1, 0.5 mm ≤ L1 ≤ 2 mm; and / or, Along the extending direction of the second metal wire (21), the second conductive end (211) has a length L2, 0.5 mm ≤ L2 ≤ 2 mm.

8. The method for preparing a battery according to claim 6, wherein: The first metal wire (11) and the second metal wire (21) are made of the same material; and / or, The diameter of the first metal wire (11) is within the range of 20 μm to 100 μm, and / or the diameter of the second metal wire (21) is within the range of 20 μm to 100 μm, and / or the diameter of the first metal wire (11) is equal to the diameter of the second metal wire (21); and / or, The first metal wire (11) is a porous structure, and / or the second metal wire (21) is a porous structure.

9. The method for preparing a battery according to claim 6, wherein: The step S11 includes: Step S111: providing two metal wires, and welding one end of the two metal wires to the tabs; Step S112: Of the two metal wires, one is the first metal wire (11) and the other is the second metal wire (21); the electrode tab welded to the first metal wire (11) is the first electrode tab (12); and the electrode tab welded to the second metal wire (21) is the second electrode tab (22); An active coating (112) is coated on the surface of the first conductive end (111), and an acid pickling treatment is performed on the surface of the second conductive end (211) to remove an oxide layer on the surface of the second conductive end (211).

10. The method for preparing a battery according to claim 9, wherein: After step S112, step S11 further includes: Step S113a, covering at least a portion of the outer surface of the first metal wire (11) except the first conductive end (111) with an insulating structure (7); and / or, step S113b, covering at least a portion of the outer surface of the second metal wire (21) except the second conductive end (211) with an insulating structure (7).

11. The method for preparing a battery according to claim 7, wherein: The active coating (112) includes lithium titanate and carbon nanotubes.

12. The method for preparing a battery according to claim 7, wherein: After step S12, the first conductive end (111) is arranged facing the middle portion of the adjacent positive electrode sheet (3) along the extension direction of the first metal wire (11); and / or, After step S12, the second conductive end (211) is arranged opposite to the middle portion of the adjacent positive electrode sheet (3) along the extension direction of the second metal wire (21).

13. The method for preparing a battery according to any one of claims 1 to 4, characterized in that: After step S2, the preparation method further comprises: Step S31: With the positive electrode sheet (3) as the positive electrode and the first reference electrode (1) as the negative electrode, a first current is applied to insert lithium into the surface of the first conductive end (111) toward the adjacent positive electrode sheet (3) through the active coating (112) on the surface of the first conductive end (111), wherein the current density of the first current is 10 μA / cm 2 ~50μA / cm 2 until the potential between the first reference electrode (1) and the second reference electrode (2) stabilizes; Step S32: With the negative electrode sheet (4) as the negative electrode and the first reference electrode (1) as the positive electrode, a second current is applied to insert lithium into the surface of the negative electrode sheet (4) adjacent to the first conductive end (111) through the active coating (112), wherein the current density of the second current is 10 μA / cm 2 ~50μA / cm 2 until the potential between the first reference electrode (1) and the second reference electrode (2) stabilizes.

14. A battery, characterized in that: The battery is prepared by the method for preparing a battery according to any one of claims 1 to 13, wherein the battery comprises: A cell assembly (100), the cell assembly (100) comprising a positive electrode sheet (3), a negative electrode sheet (4), a diaphragm (6), a first reference electrode (1) and a second reference electrode (2), the positive electrode sheets (3) and the negative electrode sheets (4) being alternately stacked, a separation space (5) being formed between adjacent positive electrode sheets (3) and negative electrode sheets (4), the diaphragm (6) being provided in all the separation spaces (5), so as to separate any adjacent positive electrode sheets (3) and negative electrode sheets (4) through the diaphragm (6), the first reference electrode (1) comprising a first metal wire (11) and a first pole ear (12), one end of the first metal wire (11) being welded to the first pole ear (12), the other end of the first metal wire (11) being a first conductive end (111), the first conductive end (111) being located at a The first conductive end (111) is located in the separation space (5), and the first conductive end (111) is separated from the adjacent positive electrode sheet (3) and the negative electrode sheet (4) by the diaphragm (6); the surface of the first conductive end (111) is covered with an active coating (112); the second reference electrode (2) includes a second metal wire (21) and a second pole tab (22); one end of the second metal wire (21) is welded to the second pole tab (22); the other end of the second metal wire (21) is a second conductive end (211); the second conductive end (211) is located in another separation space (5), and the second conductive end (211) is separated from the adjacent positive electrode sheet (3) and the negative electrode sheet (4) by the diaphragm (6); the surface of the second conductive end (211) is covered with a lithium layer (212); and, A packaging structure is provided in which the battery core assembly (100) is arranged and filled with electrolyte.

Images