Negative electrode sheet assembly, battery cell, and method for manufacturing same, and laminated battery

Abstract

The application provides a negative electrode sheet assembly, an electric cell and a preparation method thereof, and a laminated battery. The negative electrode sheet assembly comprises a plurality of negative electrode sheets, each of which comprises a copper foil sheet, a negative electrode tab and an auxiliary electrode tab, the negative electrode tab and the corresponding auxiliary electrode tab are connected with the corresponding copper foil sheet, the negative electrode tabs of the plurality of negative electrode sheets are connected in layers, and the auxiliary electrode tabs of the plurality of negative electrode sheets are connected in layers. The negative electrode sheet assembly can reduce the internal thermal runaway of the lithium electric cell, thereby improving the use safety of the lithium battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery, in particular to a negative plate assembly, a battery cell and a preparation method thereof, and a laminated battery. BACKGROUND

[0002] Lithium batteries have the advantages of high energy density, good cycle performance and long service life, and are widely used in electric devices, electrical appliances and intelligent machines. However, lithium batteries have a serious safety problem, that is, lithium batteries have internal short circuits, causing thermal runaway of the battery cell. Especially, the internal of the battery cell of the lithium battery is constantly undergoing electrochemical reactions, and the occurrence of electrochemical reactions is accompanied by heat release. The temperature rise at the tab position is the most serious. During the preparation of the lithium battery, the tab is prone to breakage due to external interference. If part of the tab breaks, a rapid oxidation-reduction reaction will occur in the internal of the battery cell, causing the temperature to rise rapidly, further exacerbating the thermal runaway problem of the lithium battery, and there is a great potential safety hazard. SUMMARY

[0003] The purpose of the present application is to overcome the deficiencies in the prior art, and to provide a negative plate assembly, a battery cell and a preparation method thereof, and a laminated battery which can reduce the thermal runaway of the internal of the battery cell and improve the safety of the lithium battery.

[0004] The purpose of the present application is achieved by the following technical solutions:

[0005] A negative plate assembly comprises a plurality of negative plates, each of which comprises a copper foil, a negative tab and an auxiliary tab. The negative tab and the corresponding auxiliary tab are connected to the corresponding copper foil. The negative tabs of the plurality of negative plates are connected in layers, and the auxiliary tabs of the plurality of negative plates are connected in layers.

[0006] In one embodiment, the negative tabs of the plurality of negative plates are welded together in layers.

[0007] In one embodiment, the auxiliary tabs of the plurality of negative plates are welded together in layers.

[0008] In one embodiment, the negative plate assembly further comprises a plurality of nickel layers, each of which is connected to the negative tab of the corresponding negative plate, and each of which is wrapped around the negative tab of the corresponding negative plate.

[0009] In one embodiment, the negative tab and the auxiliary tab are arranged on the same side of the copper foil.

[0010] In one embodiment, the negative tab and the auxiliary tab are arranged on opposite sides of the copper foil.

[0011] An electric core, comprising the negative electrode sheet assembly of any one of the above embodiments, further comprising a separator and a plurality of positive electrode sheets, the copper foil sheet of each of the plurality of negative electrode sheets and the positive electrode sheet are alternately and correspondingly stacked, and the separator is arranged between the copper foil sheet of each of the positive electrode sheets and the adjacent negative electrode sheet.

[0012] In one of the embodiments, each of the positive electrode sheets comprises an aluminum foil sheet and a positive electrode tab, the positive electrode tabs of the plurality of positive electrode sheets are connected in layers, the aluminum foil sheet of each of the plurality of positive electrode sheets and the copper foil sheet of each of the plurality of negative electrode sheets are alternately and correspondingly stacked, and the separator is arranged between the aluminum foil sheet of each of the positive electrode sheets and the copper foil sheet of the adjacent negative electrode sheet.

[0013] A preparation method of an electric core, used for preparing the electric core of any one of the above embodiments, the preparation method of the electric core comprises the following steps:

[0014] Obtaining a to-be-processed copper foil sheet, a separator and a positive electrode sheet;

[0015] Cutting the to-be-processed copper foil sheet to form a negative electrode tab and an auxiliary electrode tab on the copper foil sheet to obtain a negative electrode sheet;

[0016] Stacking the separator, the plurality of negative electrode sheets and the plurality of positive electrode sheets to alternately and correspondingly stack the copper foil sheet of each of the plurality of negative electrode sheets and the positive electrode sheet, and arrange the separator between the copper foil sheet of each of the positive electrode sheets and the adjacent negative electrode sheet to obtain an electric core semi-finished product;

[0017] Connecting the tabs of the electric core semi-finished product to obtain an electric core.

[0018] A laminated battery, comprising the electric core of any one of the above embodiments, further comprising an electrolyte and a shell, the electrolyte is filled in the shell, the electric core is arranged in the shell, and the electric core is soaked in the electrolyte.

[0019] Compared with the prior art, the present application has at least the following advantages:

[0020] In the negative electrode assembly of the present invention, both the negative electrode tab and the corresponding auxiliary electrode tab are connected to the corresponding copper foil. The negative electrode tabs of multiple negative electrode sheets are stacked and connected, and the auxiliary electrode tabs of multiple negative electrode sheets are stacked and connected. When the negative electrode tab of a part of the negative electrode sheet breaks, the presence of the auxiliary electrode tab on the negative electrode sheet ensures that the copper foil of the negative electrode sheet remains connected to the entire negative electrode assembly. This avoids the copper foil of the part of the negative electrode sheet being at a high potential and oxidizing. In other words, it avoids the copper foil being at a high potential after the negative electrode tab of a part of the negative electrode sheet breaks, which would cause the copper foil to be oxidized and thus cause a short circuit inside the battery, leading to thermal runaway of the cell. This effectively reduces the thermal runaway of the cell containing the negative electrode assembly, thereby effectively improving the safety of the cell containing the negative electrode assembly. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of a negative electrode assembly according to an embodiment of the present invention;

[0023] Figure 2 for Figure 1 A schematic diagram of the negative electrode structure of the negative electrode assembly shown.

[0024] Figure 3 for Figure 1 Another structural schematic diagram of the negative electrode of the negative electrode assembly shown;

[0025] Figure 4 This is a schematic diagram of the structure of a battery cell according to an embodiment of the present invention;

[0026] Figure 5 This is a schematic diagram of the structure of a battery cell according to another embodiment of the present invention;

[0027] Figure 6 This is a flowchart of a method for preparing a battery cell according to an embodiment of the present invention. Detailed Implementation

[0028] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0029] It should be noted that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements can also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements can also be present. As used herein, the terms "vertical", "horizontal", "left", "right", and the like are merely used for the purpose of explanation and are not intended to be limiting.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0031] The application provides a negative electrode sheet assembly. The negative electrode sheet assembly comprises a plurality of negative electrode sheets, each of the negative electrode sheets comprises a copper foil, a negative tab and an auxiliary tab, the negative tab and the corresponding auxiliary tab are connected to the corresponding copper foil, the negative tabs of the plurality of negative electrode sheets are connected in layers, and the auxiliary tabs of the plurality of negative electrode sheets are connected in layers.

[0032] The negative electrode sheet assembly, the negative tab and the corresponding auxiliary tab are connected to the corresponding copper foil, the negative tabs of the plurality of negative electrode sheets are connected in layers, and the auxiliary tabs of the plurality of negative electrode sheets are connected in layers. When the negative tab of a part of the negative electrode sheets is broken, the copper foil of the negative electrode sheet is still connected together with the entire negative electrode sheet assembly due to the existence of the auxiliary tab on the negative electrode sheet, thereby avoiding the copper foil of the part of the negative electrode sheets from being oxidized at a high potential, i.e. avoiding the corresponding copper foil being oxidized at a high potential when the negative tab of a part of the negative electrode sheets is broken, thereby causing the copper foil to be short-circuited inside the battery and leading to thermal runaway of the battery cell, effectively reducing the thermal runaway of the battery cell containing the negative electrode sheet assembly, and thereby effectively improving the safety of the battery cell containing the negative electrode sheet assembly.

[0033] Please refer to Figure 1 , Figure 2 and Figure 3 , in order to better understand the negative electrode sheet assembly 10 of the application, the negative electrode sheet assembly 10 of the application is further explained as follows. The negative electrode sheet assembly 10 of an embodiment comprises a plurality of negative electrode sheets 100, each of the negative electrode sheets 100 comprises a copper foil 110, a negative tab 120 and an auxiliary tab 130, the negative tab 120 and the corresponding auxiliary tab 130 are connected to the corresponding copper foil 110, the negative tabs 120 of the plurality of negative electrode sheets 100 are connected in layers, and the auxiliary tabs 130 of the plurality of negative electrode sheets 100 are connected in layers.

[0034] The negative tab assembly 10, the negative tab 120 and the corresponding auxiliary tab 130 are connected with the corresponding copper foil 110. The negative tabs 120 of the plurality of negative tabs 100 are connected in layers. The auxiliary tabs 130 of the plurality of negative tabs 100 are connected in layers. When the negative tab 120 of the partial negative tab 100 is broken, the copper foil 110 of the negative tab 100 is still connected together with the whole negative tab assembly 10 due to the existence of the auxiliary tab 130 on the negative tab 100, thereby avoiding the copper foil 110 of the partial negative tab 100 in a high potential and being oxidized. That is, when the negative tab 120 of the partial negative tab 100 is broken, the corresponding copper foil 110 is in a high potential, which causes the copper foil 110 to be oxidized, thereby causing the internal short circuit of the battery and leading to the thermal runaway of the battery cell. The thermal runaway of the battery cell containing the negative tab assembly 10 is effectively reduced, thereby effectively improving the use safety of the battery cell containing the negative tab assembly 10.

[0035] It should be noted that, since the auxiliary tab does not play a role in electrical connection with external components, the auxiliary tab can be directly arranged in the shell of the battery, thereby avoiding the problem that the auxiliary tab is broken due to external interference, effectively ensuring the electrical connection of each negative tab in the negative tab assembly, and better ensuring that when the negative tab of the partial negative tab is broken, the corresponding copper foil is in a high potential, which causes the copper foil to be oxidized, thereby causing the internal short circuit of the battery and leading to the thermal runaway of the battery cell. The thermal runaway of the battery cell containing the negative tab assembly is effectively reduced, thereby effectively improving the use safety of the battery cell containing the negative tab assembly.

[0036] Please refer to Figure 1 In one embodiment, the negative tabs 120 of the plurality of negative tabs 100 are welded together in layers, thereby better ensuring the stable and effective connection of each negative tab 100 with components.

[0037] Please refer to Figure 1 In one embodiment, the auxiliary tabs 130 of the plurality of negative tabs 100 are welded together in layers, thereby better ensuring the stable and firm connection of the negative tab 120 of each negative tab 100, thereby effectively reducing the thermal runaway of the battery cell containing the negative tab assembly 10, and effectively improving the use safety of the battery cell containing the negative tab assembly 10.

[0038] In one embodiment, the negative tab assembly further comprises a plurality of nickel layers, the plurality of nickel layers are connected one by one with the negative tabs of the plurality of negative tabs, and each nickel layer is arranged around the corresponding negative tab, which can effectively reduce the electrochemical polarization at the negative tab, slow down the temperature rise of the battery cell containing the negative tab assembly, and thus improve the safety performance of the battery cell containing the negative tab assembly.

[0039] Please refer to Figure 1 andFigure 2 In one embodiment, the negative tab 120 and the auxiliary tab 130 are arranged on the same side of the copper foil 110. It can be understood that if the positive tab and the negative tab 120 are arranged on the same side of the battery cell, the auxiliary tab 130 and the negative tab 120 are arranged on the same side of the battery cell, which reduces the difficulty of packaging the battery cell, thereby increasing the packaging efficiency of the battery cell.

[0040] Referring to Figure 3 In one embodiment, the negative tab 120 and the auxiliary tab 130 are arranged on the same side of the copper foil 110. It can be understood that if the positive tab and the negative tab 120 are arranged on the same side of the battery cell, the auxiliary tab 130 and the negative tab 120 are arranged on the same side of the battery cell, which reduces the difficulty of packaging the battery cell, thereby increasing the packaging efficiency of the battery cell.

[0041] Referring to Figure 4 and Figure 5 The application also provides a battery cell 10A. The battery cell 10A described above includes the negative tab assembly 10 of any of the embodiments described above, and further includes a separator 20 and a plurality of positive tabs 30. The copper foil 110 of the plurality of negative tabs 100 and the plurality of positive tabs 30 are arranged alternately one by one. The separator 20 is arranged between each positive tab 30 and the copper foil 110 of the adjacent negative tab 100. In this embodiment, the negative tab assembly 10 includes a plurality of negative tabs 100. Each negative tab 100 includes a copper foil 110, a negative tab 120, and an auxiliary tab 130. The negative tab 120 and the corresponding auxiliary tab 130 are connected to the corresponding copper foil 110. The negative tabs 120 of the plurality of negative tabs 100 are connected in layers. The auxiliary tabs 130 of the plurality of negative tabs 100 are connected in layers.

[0042] The above-mentioned battery cell 10A adopts the negative tab assembly 10, the negative tab 120 and the corresponding auxiliary tab 130 in the negative tab 100 are connected with the corresponding copper foil 110, the negative tabs 120 of the plurality of negative tabs 100 are connected in layers, the auxiliary tabs 130 of the plurality of negative tabs 100 are connected in layers, the copper foils 110 of the plurality of negative tabs 100 are alternately and correspondingly arranged with the plurality of positive tabs 30, and the diaphragm 20 is arranged between each positive tab 30 and the copper foil 110 of the adjacent negative tab 100, so as to effectively realize the reduction of the thermal runaway of the battery cell 10A, and further effectively improve the use safety of the battery cell 10A containing the negative tab assembly 10.

[0043] Please refer to Figure 4 and Figure 5 In one embodiment, each positive tab 30 includes an aluminum foil and a positive tab 310, the positive tabs 310 of the plurality of positive tabs 30 are connected in layers, the aluminum foils of the plurality of positive tabs 30 are alternately and correspondingly arranged with the copper foils 110 of the plurality of negative tabs 100, and the diaphragm 20 is arranged between the aluminum foil of each positive tab 30 and the copper foil 110 of the adjacent negative tab 100. It can be understood that the aluminum foils of the plurality of positive tabs 30 are alternately and correspondingly arranged with the copper foils 110 of the plurality of negative tabs 100, and the diaphragm 20 is arranged between the aluminum foil of each positive tab 30 and the copper foil 110 of the adjacent negative tab 100, which ensures the insulating layer arrangement of the negative tab 120 and the positive tab 30, and further ensures the quality of the battery cell 10A.

[0044] Please refer to Figure 4 and Figure 5 In one embodiment, the battery cell further includes a negative tab rubber 40, the negative tab rubber 40 is sleeved on the periphery of the negative tab 120, and the negative tab rubber 40 is used to be clamped between the negative tab 120 and the shell. It can be understood that the negative tab rubber 40 plays a role in promoting the insulating connection of the negative tab 120 and the battery shell, and the negative tab 120 is used to assist the packaging of the battery cell 10A.

[0045] In one embodiment, the negative tab rubber includes insulating rubber and heat-conducting silicone rubber. It can be understood that the resistance of the region near the tab is small, the current density of the tab is large during the charging and discharging of the battery, the electrochemical polarization is large, that is, the temperature at the negative tab rises quickly, and in order to promote the insulating connection of the negative tab and the shell of the battery, the negative tab rubber needs to be arranged on the periphery of the negative tab, and the negative tab rubber generally has poor heat conductivity, which further aggravates the rapid temperature rise at the negative tab. Therefore, in the present application, the negative tab rubber includes insulating rubber and heat-conducting silicone rubber, the heat conductivity of the negative tab rubber is increased, the rapid heat dissipation at the negative tab is effectively realized, and the charging and discharging rate of the battery is effectively improved.

[0046] Please refer to Figure 4 andFigure 5 In one embodiment, the battery cell includes a positive electrode tab adhesive 50, which is sleeved around the positive electrode tab 310 and sandwiched between the positive electrode tab 310 and the outer casing, ensuring an insulating connection between the positive electrode tab 310 and the battery casing, thereby ensuring the quality of the battery.

[0047] In one embodiment, the positive electrode sheet further includes a positive electrode substrate and a positive electrode slurry, with the positive electrode slurry coated on the positive electrode substrate and the positive electrode tab connected to the positive electrode substrate. It is understood that adjusting the cell structure alone to mitigate thermal runaway has limited effect on improving the cell's charge / discharge rate and cycle performance. However, focusing on the electrode slurry can significantly improve the cell's charge / discharge rate and cycle performance. In particular, adjusting the positive electrode slurry in conjunction with the cell structure can more effectively improve the cell's charge / discharge rate and cycle performance while mitigating thermal runaway.

[0048] In one embodiment, the positive electrode slurry includes a positive electrode active material, a conductive agent, a binder, a solvent, and nano-silicone powder, wherein the mass percentage of the nano-silicone powder is [missing information]. It is understandable that the mass percentage content is... When nano-silica powder is mixed with the positive electrode active material and combined with a conductive agent, it effectively improves the conductivity of the positive electrode slurry, which is beneficial for lithium ion insertion and extraction, thereby increasing the charge and discharge rate of the lithium battery and facilitating rapid wetting of the positive electrode slurry; in addition, the mass percentage is The nano-silica powder, by utilizing its own high porosity and the porosity of the positive electrode active material, can offset its own thermal expansion and also provide support for the positive electrode slurry, reducing the collapse of the positive electrode slurry during lithium ion intercalation and deintercalation, thereby improving the cycle performance of lithium batteries.

[0049] In one embodiment, the conductive agent is at least one of carbon black, Ketjen black, carbon fiber, and carbon nanotubes. It is understood that carbon black, Ketjen black, carbon fiber, and carbon nanotubes can effectively form point, line, and surface-type lithium ion transfer sites and provide more binding sites for lithium ions, which is beneficial for lithium ion insertion / extraction and thus improves the charge / discharge rate of the lithium battery.

[0050] In one embodiment, the binder is at least one selected from polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, styrene-butadiene rubber, sodium carboxymethyl cellulose, nitrile rubber, and silicone. It is understood that using at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, styrene-butadiene rubber, sodium carboxymethyl cellulose, nitrile rubber, and silicone as a binder for the positive electrode slurry ensures the adhesion strength of the positive electrode slurry to the positive electrode substrate.

[0051] In one embodiment, the solvent is N-methylpyrrolidone. It is understood that N-methylpyrrolidone has good compatibility with the positive electrode active material in the positive electrode slurry and is easily removed during the drying of the positive electrode sheet, thus better ensuring the stability of the positive electrode slurry.

[0052] In one embodiment, the positive electrode active material is a nickel-cobalt-manganese ternary composite positive electrode material. It can be understood that the nickel-cobalt-manganese ternary composite positive electrode material and... The combination of nano-silica powder effectively ensures that the positive electrode slurry has good electrolyte retention capacity, as well as good charge / discharge rate and cycle performance.

[0053] In one embodiment, the positive electrode active material is LiNi. 1 / 3 Co 1 / 3-x / 3 Mn 1 / 3-x / 3 Mg x / 3 V x / 3 O 2-2y F y Where 0 < x ≤ 0.01, 0 < y ≤ 0.05. It can be understood that the positive electrode active material is LiNi. 1 / 3 Co 1 / 3-x / 3 Mn 1 / 3-x / 3 Mg x / 3 V x / 3O 2-2y F y It possesses good layered structure and electrochemical performance, and when used in cathode slurry, it is compatible with... The combination of nano-silica powder effectively ensures the structural stability of the layered structure of the positive electrode slurry coating layer on the surface of the positive electrode substrate during the lithium-ion deintercalation and intercalation process. This reduces the collapse of the positive electrode slurry during lithium-ion deintercalation and intercalation and the expansion of the positive electrode slurry coating layer on the surface of the positive electrode substrate that would otherwise damage the layered structure, thereby improving the cycle performance, charge / discharge rate and capacity retention of the lithium battery.

[0054] It can be understood that the nano silica powder is nano-sized silicon dioxide. Although the thermal expansion of silicon dioxide is lower than the thermal expansion coefficient of the silicon-based negative electrode material, the positive electrode slurry coating layer on the surface of the positive electrode substrate is relatively thin. Even if the thermal expansion coefficient of silicon dioxide is low, if the positive electrode slurry contains a large amount of silicon dioxide, specifically, when the silicon content is greater than 0.5%wt, the positive electrode slurry will still expand and shrink during the charging and discharging process of the lithium battery, thereby affecting the structural stability of the positive electrode slurry coating layer on the surface of the positive electrode substrate. Therefore, in the present application, in order to ensure the electrolyte retention capacity of the positive electrode slurry and ensure the wicking effect and conductivity of the positive electrode slurry, the use of silicon dioxide is retained, and the amount of silicon dioxide used is optimized from the overall formula of the positive electrode slurry. Specifically, it is found that when the amount of silicon dioxide used is in the range of , the charging and discharging rate of the lithium battery is better ensured, and the rapid wicking of the positive electrode slurry is facilitated, the electrolyte retention capacity of the positive electrode slurry is improved, and the collapse of the positive electrode slurry during lithium ion deintercalation is reduced, thereby improving the cycle performance of the lithium battery.

[0055] In one embodiment, x = 0.01; y = 0.05. It can be understood that when the positive electrode active material LiNi 1 / 3Co 1 / 3-x / 3 Mn 1 / 3-x / 3 Mg x / 3 V x / 3 O 2-2y F y x = 0.01 and y = 0.05, the positive electrode active material has a relatively stable layered structure and good electrochemical performance, thereby better ensuring the cycle performance, charging and discharging rate, and capacity retention rate of the lithium battery.

[0056] In one embodiment, the preparation method of the positive electrode active material includes the following steps:

[0057] Mixing and dissolving the lithium salt, nickel salt, cobalt salt, manganese salt, vanadium salt, and organic acid in deionized water to obtain a metal mixed solution;

[0058] Heating the metal mixed solution to obtain a metal sol;

[0059] Performing calcination treatment on the metal sol;

[0060] Performing crushing operation on the metal sol after calcination treatment to obtain the positive electrode active material.

[0061] The preparation method of the positive electrode active material ensures the sufficient mixed dissolution of the lithium salt, the nickel salt, the cobalt salt, the manganese salt and the vanadium salt, and further ensures the uniformity of the lithium salt, the nickel salt, the cobalt salt, the manganese salt and the vanadium salt, and further ensures the uniformity of each substance in the positive electrode active material obtained after the heating operation on the metal mixed solution and the calcination treatment, and further ensures the stability of the layered structure of the formed positive electrode active material and the excellent electrochemical performance, and further improves the electrochemical performance and the cycle performance of the lithium battery.

[0062] In one embodiment, the preparation method of the positive electrode active material comprises the following steps:

[0063] The lithium nitrate, the nickel nitrate, the cobalt nitrate, the manganese nitrate, the vanadium nitrate and the citric acid are mixed and dissolved in the deionized water to obtain a metal mixed solution;

[0064] The metal mixed solution is heated to obtain a metal sol;

[0065] The metal sol is subjected to a calcination treatment;

[0066] The metal sol after the calcination treatment is crushed to obtain the positive electrode active material.

[0067] The preparation method of the positive electrode active material ensures the stability of the formation of the layered structure of the positive electrode active material, and further ensures the cycle performance and the electrochemical performance of the lithium battery.

[0068] In one of the embodiments, the pH of the metal mixed solution is 0.8-1.2. It can be understood that the pH of the metal mixed solution has a great influence on the electrochemical performance of the positive active material, in particular, on the cycle performance stability and charge-discharge capacity retention rate of the lithium battery with the positive active material. In the case of higher or lower pH, it is difficult to ensure that the cycle performance and capacity retention rate are good at the same time. Therefore, in the present application, the pH of the metal mixed solution is 0.8-1.2, so that the lithium battery with the positive active material has good cycle performance stability and charge-discharge capacity retention rate at the same time.

[0069] In one of the embodiments, the pH of the metal mixed solution is 1.0, which better ensures that the lithium battery with the positive active material has good cycle performance stability and charge-discharge capacity retention rate at the same time.

[0070] In one of the embodiments, the molar ratio of the sum of the nickel salt, the cobalt salt, the manganese salt and the vanadium salt to the lithium salt is 1:(1.2-1.6). It can be understood that when the molar ratio of the sum of the nickel salt, the cobalt salt, the manganese salt and the vanadium salt to the lithium salt is 5 / 6-5 / 8, it is beneficial to form a positive active material with good lithium ion deintercalation and intercalation capacity, thereby better ensuring the initial specific discharge capacity and cycle performance of the lithium battery.

[0071] In one of the embodiments, the molar ratio of the sum of the nickel salt, the cobalt salt, the manganese salt and the vanadium salt to the lithium salt is 1:1.5. It can be understood that when the molar ratio of the sum of the nickel salt, the cobalt salt, the manganese salt and the vanadium salt to the lithium salt is 1:1.5, it is better to ensure that the formed positive active material has good lithium ion deintercalation and intercalation capacity, thereby better ensuring the initial charge-discharge specific capacity and cycle performance of the lithium battery.

[0072] In one of the embodiments, the molar ratio of the nickel salt, the cobalt salt, the manganese salt and the vanadium salt is 0.1:0.2:0.4:0.2. It can be understood that when the molar ratio of the nickel salt, the cobalt salt, the manganese salt and the vanadium salt is 0.1:0.2:0.4:0.2, the positive slurry discharge specific capacity reaches 200 mAh / g, and it is beneficial to the stable formation of the positive active material with good layered structure and electrochemical performance.

[0073] In one embodiment, the molar ratio of the sum of the nickel salt, the cobalt salt, the manganese salt, the vanadium salt and the lithium salt to the citric acid is 1.8-2.5. It can be understood that when the content of the citric acid is high, the groups in the citric acid will interfere with the internal structure of the active material, causing the generated positive electrode active material to have a disordered layered structure and internal group aggregation, i.e., the structure of the positive electrode active material is in a disordered state, which causes the discharge specific capacity and the cycle stability of the lithium battery using the positive electrode slurry to decrease. Therefore, in the present application, the molar ratio of the sum of the nickel salt, the cobalt salt, the manganese salt, the vanadium salt and the lithium salt to the citric acid is 1.8-2.5, which preferably ensures the stable and orderly layered structure of the positive electrode active material, and further ensures the discharge specific capacity and the cycle stability of the lithium battery containing the positive electrode slurry.

[0074] In one embodiment, the molar ratio of the sum of the nickel salt, the cobalt salt, the manganese salt, the vanadium salt and the lithium salt to the citric acid is 2. It can be understood that when the molar ratio of the sum of the nickel salt, the cobalt salt, the manganese salt, the vanadium salt and the lithium salt to the citric acid is 2, the stable and orderly layered structure of the positive electrode active material is more preferably ensured, and further ensures the discharge specific capacity and the cycle stability of the lithium battery containing the positive electrode slurry.

[0075] In one embodiment, the temperature for the heating operation of the metal mixed solution is 80-90°C. It can be understood that the purpose of the heating operation of the metal mixed solution is to reduce the content of the solvent in the metal mixed solution, which is beneficial to the calcination of the metal mixed solution. The heating of the metal mixed solution at 80-90°C is beneficial to ensuring the orderly and stable layered structure of the positive electrode active material formed after calcination.

[0076] In one embodiment, the calcination treatment of the metal sol includes the following steps: pre-calcination treatment of the metal sol;

[0077] secondary calcination treatment of the pre-calcination treated metal sol;

[0078] tertiary calcination treatment of the secondary calcination treated metal sol.

[0079] The above calcination treatment of the metal sol contains citric acid and vanadium nitrate in the metal sol, i.e., has a carbon source. When the vanadium nitrate is calcined, the high-valence oxides of vanadium will sublimate and be consumed at a lower temperature, and then a three-stage calcination method is required, i.e., the valence of vanadium is first kept at a lower level at a lower temperature, and then the temperature is increased for further calcination, which is beneficial to the stable generation of the vanadium-doped ternary composite material.

[0080] In one of the embodiments, the temperature for the pre-calcination of the metal sol is 400-500 DEG C, and the time is 2-3 hours. It can be understood that the calcination at 400-500 DEG C for 2-3 hours effectively ensures the rapid removal of the solvent and the stability of the substances in the metal sol.

[0081] In one of the embodiments, the temperature for the secondary calcination of the pre-calcined metal sol is 600-700 DEG C, and the time is 3-5 hours. It can be understood that the continued calcination at 600-700 DEG C for 3-5 hours effectively ensures the reduction of the valence of the high-valence oxide of vanadium and the stable formation of the vanadium-doped ternary composite material.

[0082] In one of the embodiments, the temperature for the tertiary calcination of the secondary-calcined metal sol is 800-1350 DEG C, and the time is 6-8 hours. It can be understood that the continued calcination at 800-1350 DEG C for 6-8 hours effectively ensures the stable formation of the positive electrode active material with a good layered structure and electrochemical performance.

[0083] The application also provides a preparation method of the battery cell, which is used for preparing the battery cell in any of the above embodiments. The preparation method of the battery cell includes the following steps: obtaining a copper foil sheet to be processed, a separator and a positive electrode sheet; performing a cutting operation on the copper foil sheet to be processed, so that the negative electrode tab and the auxiliary electrode tab are integrally formed on the copper foil sheet to obtain a negative electrode sheet; performing a layering and connecting operation on the separator, the plurality of negative electrode sheets and the plurality of positive electrode sheets, so that the copper foil sheets of the plurality of negative electrode sheets are alternately and correspondingly arranged with the plurality of positive electrode sheets, and the separator is arranged between each positive electrode sheet and the copper foil sheet of the adjacent negative electrode sheet to obtain a battery cell semi-finished product; and performing a tab connecting operation on the battery cell semi-finished product to obtain a battery cell.

[0084] The preparation method of the battery cell adjusts the structure of the negative electrode sheet based on the copper foil sheet to be processed, that is, performs a cutting operation on the copper foil sheet to be processed, so that the negative electrode tab and the auxiliary electrode tab are integrally formed on the copper foil sheet, thereby ensuring the connection stability of the negative electrode tab and the auxiliary electrode tab with the copper foil sheet. The arrangement of the auxiliary electrode tab ensures that the copper foil sheets of the negative electrode sheet are still connected together in the entire negative electrode sheet assembly, thereby avoiding the oxidation of the copper foil sheets of some negative electrode sheets at a high potential, that is, avoiding the copper foil sheets at a high potential due to the fracture of the negative electrode tab of some negative electrode sheets, thereby causing the copper foil sheets to be oxidized and further causing the internal short circuit of the battery to lead to thermal runaway of the battery cell, effectively reducing the thermal runaway of the battery cell containing the negative electrode sheet assembly, and further effectively improving the use safety of the battery cell containing the negative electrode sheet assembly. In addition, the negative electrode sheet, the separator and the positive electrode sheet are alternately and sequentially arranged before the layering and connecting of the negative electrode tab and the auxiliary electrode tab of the negative electrode sheet, which is conducive to improving the alternating layering speed of the negative electrode sheet, the separator and the positive electrode sheet, and further improving the preparation efficiency of the battery cell.

[0085] Referring to Figure 6 In order to better understand the method for preparing the battery cell, the method for preparing the battery cell of the present application is further explained as follows. The method for preparing the battery cell of an embodiment comprises the following steps:

[0086] S100, a copper foil sheet to be processed, a separator and a positive electrode sheet are obtained. It can be understood that the temperature rise of the tab position is the most serious, and in the preparation process of the lithium battery, the tab is prone to breakage due to external interference. If part of the tab breaks, especially in the case of negative tab breakage, the internal negative electrode sheet of the lithium battery will undergo a sharp oxidation-reduction reaction, causing the temperature to rise rapidly, further exacerbating the thermal runaway problem of the lithium battery, and there is a great potential safety hazard. Therefore, based on the copper foil sheet to be processed, the negative electrode sheet structure is adjusted to reduce the thermal runaway of the lithium battery.

[0087] S200, the copper foil sheet to be processed is cut to form the negative tab and the auxiliary tab on the copper foil sheet to obtain the negative electrode sheet. It can be understood that the copper foil sheet to be processed is cut to form the negative tab and the auxiliary tab on the copper foil sheet, which ensures the stability of the connection between the negative tab, the auxiliary tab and the copper foil sheet. The setting of the auxiliary tab ensures that the copper foil sheet of the negative electrode sheet is still connected together as a whole, avoiding the oxidation of the copper foil sheet of part of the negative electrode sheet at a high potential. That is, when part of the negative tab of the negative electrode sheet breaks, the corresponding copper foil sheet is at a high potential, causing the copper foil sheet to be oxidized, which in turn causes an internal short circuit of the battery, leading to thermal runaway of the battery cell. This effectively reduces the thermal runaway of the battery cell containing the negative electrode sheet assembly, thereby effectively improving the safety of the battery cell containing the negative electrode sheet assembly.

[0088] S300, the separator, the plurality of negative electrode sheets and the plurality of positive electrode sheets are connected in layers to alternately and correspondingly stack the copper foil sheets of the plurality of negative electrode sheets and the plurality of positive electrode sheets, and the separator is arranged between each positive electrode sheet and the copper foil sheet of the adjacent negative electrode sheet to obtain a battery cell semi-finished product. It can be understood that the negative electrode sheet, the separator and the positive electrode sheet are sequentially and alternately stacked before the negative tab and the auxiliary tab of the negative electrode sheet are connected in layers, which is conducive to improving the speed of alternately and correspondingly stacking the negative electrode sheet, the separator and the positive electrode sheet, thereby improving the preparation efficiency of the battery cell.

[0089] S400, the tab connection operation is performed on the battery cell semi-finished product to obtain a battery cell. It can be understood that the tab connection operation is performed on the battery cell semi-finished product, i.e., the positive tab of the positive electrode sheet in the battery cell is connected in layers, the negative tab of the negative electrode sheet in the battery cell is connected in layers, and the auxiliary tab of the negative electrode sheet in the battery cell is connected in layers, thereby achieving the preparation of the battery cell. After the negative electrode sheet, the separator and the positive electrode sheet are sequentially and alternately stacked, the tab connection operation is performed on the battery cell semi-finished product, which is conducive to improving the preparation efficiency of the battery cell.

[0090] The preparation method of the above-mentioned battery cell is based on the copper foil to be processed, and the negative tab structure is adjusted, that is, the copper foil to be processed is cut to make the negative tab and the auxiliary tab integrally formed on the copper foil, thereby ensuring the connection stability of the negative tab and the auxiliary tab with the copper foil. The setting of the auxiliary tab makes the copper foil of the negative tab still connected together in the entire negative tab assembly, avoiding the oxidation of the copper foil of part of the negative tab at high potential, that is, avoiding the copper foil at high potential due to the fracture of the negative tab of part of the negative tab, causing the copper foil to be oxidized, thereby causing internal short circuit of the battery and leading to thermal runaway of the battery cell. The thermal runaway of the battery cell containing the negative tab assembly is effectively reduced, thereby effectively improving the use safety of the battery cell containing the negative tab assembly. In addition, before the negative tab and the auxiliary tab of the negative tab are connected in layers, the negative tab, the separator and the positive tab are alternately and sequentially stacked, which is conducive to improving the alternating stacking speed of the negative tab, the separator and the positive tab, thereby improving the preparation efficiency of the battery cell.

[0091] In one embodiment, before the step of cutting the copper foil to be processed, the preparation method of the battery cell further includes the step of preheating the copper foil to be processed to soften the copper foil to be processed. It can be understood that when the copper foil to be processed is cut, that is, when the copper foil to be processed is cut by a punch, burrs will appear at the cutting position of the cut copper foil. The existence of the burrs makes the negative tab easily pierce the separator, causing micro-short circuit in the battery cell, thereby further aggravating the thermal runaway of the battery cell. Therefore, in order to reduce the thermal runaway of the battery cell caused by the negative tab piercing the separator, the copper foil to be processed is preheated before the cutting step. The copper foil to be processed after preheating is softened, and the hardness of the softened copper foil to be processed is low. When the copper foil to be processed with low hardness is cut, the amount of burrs at the cutting position of the copper foil to be processed is greatly reduced, effectively reducing the burrs of the negative tab, thereby reducing the thermal runaway of the battery cell caused by the negative tab piercing the separator, and effectively improving the use safety of the battery cell containing the negative tab assembly.

[0092] In one embodiment, the preheating temperature of the copper foil to be processed is 400-550°C. It can be understood that when the preheating temperature of the copper foil to be processed is 400-550°C, the softening of the copper foil to be processed is effectively ensured, and when the copper foil to be processed with low hardness is cut, the amount of burrs at the cutting position of the copper foil to be processed is greatly reduced, effectively reducing the burrs of the negative tab, thereby reducing the thermal runaway of the battery cell caused by the negative tab piercing the separator, and effectively improving the use safety of the battery cell containing the negative tab assembly.

[0093] In one of the embodiments, the temperature of the preheating treatment of the copper foil to be processed is 500 DEG C, which better controls the softening degree of the copper foil to be processed, so that when the copper foil to be processed with low hardness is cut, the burr amount of the cut copper foil to be processed is greatly reduced, the burr of the negative plate is effectively reduced, and the negative plate pierces the separator to further aggravate the thermal runaway in the battery cell, thereby effectively improving the use safety of the battery cell containing the negative plate assembly.

[0094] In one of the embodiments, the cutting operation of the copper foil to be processed is specifically that the copper foil to be processed is fixed, and the fixed copper foil to be processed is integrally punched and formed by a punching machine to obtain the negative plate. It can be understood that the cutting of the fixed copper foil to be processed effectively ensures the consistency of the formation of the negative plate, thereby ensuring the quality of the battery cell.

[0095] In one of the embodiments, before the step of obtaining the negative plate and after the step of cutting the copper foil to be processed, the preparation method of the battery cell further comprises the following steps:

[0096] The copper foil to be processed after the cutting operation is spliced;

[0097] The spliced copper foil to be processed is reinforced;

[0098] The copper foil to be processed after the reinforcement is coated with negative slurry.

[0099] In the above preparation method of the battery cell, the copper foil to be processed after the cutting operation is spliced, that is, the negative plate and the residual copper foil of the copper foil to be processed are spliced, and then the spliced copper foil to be processed is reinforced, that is, the spliced negative plate and the residual copper foil of the copper foil to be processed are fixed, which is beneficial to the subsequent uniform and rapid coating of the negative slurry on the negative plate, that is, the simultaneous coating of multiple negative plates can be realized by coating the copper foil to be processed after the reinforcement with negative slurry, which effectively increases the preparation efficiency of the negative plate and ensures the consistency of the negative plate, thereby improving the quality of the battery cell.

[0100] In one of the embodiments, after the step of coating the copper foil to be processed after the reinforcement with negative slurry and before the step of obtaining the negative plate, the preparation method of the battery cell further comprises the following step: drying and rolling the copper foil to be processed after the negative slurry coating treatment. It can be understood that the drying and rolling of the negative plate coated with the negative slurry is the drying and rolling of the negative slurry, and the drying and rolling of multiple negative plates is unified, which effectively improves the consistency of the negative plate and thereby improves the quality of the battery cell.

[0101] The application further provides a laminated battery. The laminated battery comprises the battery cell of any of the above embodiments, and further comprises electrolyte and a shell, the electrolyte being filled in the shell, the battery cell being arranged in the shell, and the battery cell being soaked in the electrolyte.

[0102] The laminated battery described above adopts the battery cell, the electrolyte being filled in the shell, the battery cell being arranged in the shell, and the battery cell being soaked in the electrolyte, so that the thermal runaway of the battery is effectively reduced, and the use safety of the battery is effectively improved.

[0103] Compared with the prior art, the application has at least the following advantages:

[0104] The negative tab assembly, the negative tab and the corresponding auxiliary tab are connected with the corresponding copper foil sheet, the negative tabs of the plurality of negative tabs are connected in layers, the auxiliary tabs of the plurality of negative tabs are connected in layers, and when the negative tab of a part of the negative tabs is broken, the copper foil sheet of the negative tab is still connected together with the whole negative tab assembly due to the existence of the auxiliary tab on the negative tab, so that the copper foil sheet of the part of the negative tabs is prevented from being oxidized due to being at a high potential, that is, the copper foil sheet corresponding to the part of the negative tabs is prevented from being at a high potential due to the broken negative tab, so that the copper foil sheet is prevented from being oxidized, and the internal short circuit of the battery is prevented from being caused, so that the thermal runaway of the battery containing the negative tab assembly is effectively reduced, and the use safety of the battery containing the negative tab assembly is effectively improved.

[0105] Some specific embodiments are listed below. It should be noted that the following embodiments do not exhaust all possible cases, and the materials used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0106] Embodiment 1

[0107] The copper foil sheet is preheated at a temperature of 400 DEG C to soften the copper foil sheet, then the softened copper foil sheet is cut to obtain a negative tab with the negative tab and the auxiliary tab integrally formed on the copper foil sheet, then the negative tab obtained by cutting is spliced and fixed, and the negative paste is applied on the spliced and fixed negative tab, then the roll drying is performed, then the separator, the plurality of negative tabs and the plurality of positive tabs are alternately and sequentially stacked, so that the positive tabs and the negative tabs are separated by the separator, then the positive tab is welded, and the negative tab and the auxiliary tab are welded respectively, to obtain the battery cell, and the battery cell is subjected to formation treatment.

[0108] Embodiment 2

[0109] The copper foil is preheated at a temperature of 500°C to soften the copper foil, then the softened copper foil is cut to obtain a negative tab and an auxiliary tab integrally formed on the copper foil, then the cut negative tab is spliced and fixed, and the negative electrode slurry is coated on the spliced and fixed negative tab, then roll drying is performed, then the separator, a plurality of the obtained negative tabs and a plurality of positive tabs are alternately stacked one by one, so that the positive tabs and the negative tabs are separated by the separator, then the positive tabs of the positive tabs are welded, and the negative tabs and the auxiliary tabs of the negative tabs are welded respectively, to obtain a battery cell, and the battery cell is subjected to formation treatment.

[0110] Example 3

[0111] The copper foil is preheated at a temperature of 550°C to soften the copper foil, then the softened copper foil is cut to obtain a negative tab and an auxiliary tab integrally formed on the copper foil, then the cut negative tab is spliced and fixed, and the negative electrode slurry is coated on the spliced and fixed negative tab, then roll drying is performed, then the separator, a plurality of the obtained negative tabs and a plurality of positive tabs are alternately stacked one by one, so that the positive tabs and the negative tabs are separated by the separator, then the positive tabs of the positive tabs are welded, and the negative tabs and the auxiliary tabs of the negative tabs are welded respectively, then the battery cell is assembled, and the battery cell is subjected to formation treatment.

[0112] The battery cells obtained in Examples 1-3 are subjected to short circuit detection, 1000 battery cells prepared in Examples 1-3 are taken for detection, specifically, the battery cells in Examples 1-3 are subjected to 100 constant current charge and discharge, and then subjected to detection.

[0113] Table 1: Short circuit detection pass rate of battery cells in Examples 1-3

[0114] Example 1 Example 2 Example 3 Pass rate (%) 99.90 99.98 99.92

[0115] After the battery cell is subjected to 100 constant current charge and discharge, short circuit caused by tab breakage inside the battery cell, or short circuit caused by membrane puncture, or other short circuit conditions may exist, and from Table 1, it can be seen that the short circuit detection pass rate of the battery cells prepared in Examples 1-3 after multiple constant current charge and discharge is high, all exceeding 99.90%, indicating that the probability of the battery cells prepared in the present application existing the above internal short circuit conditions is low, and further indicating that the battery cells prepared in the present application have less risk of thermal runaway.

[0116] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. An electric cell, characterized by, The negative sheet assembly includes a plurality of negative sheets, each of which includes a copper foil sheet, a negative tab, and an auxiliary tab, the negative tab and the corresponding auxiliary tab are connected to the corresponding copper foil sheet, the negative tabs of the plurality of negative sheets are connected in layers, the auxiliary tabs of the plurality of negative sheets are connected in layers, and the copper foil sheets of the plurality of negative sheets are alternately and correspondingly arranged with the plurality of positive sheets, and the separator is arranged between each positive sheet and the copper foil sheet of the adjacent negative sheet. The positive sheet includes an aluminum foil sheet and a positive tab, the positive tabs of the plurality of positive sheets are connected in layers, the aluminum foil sheets of the plurality of positive sheets are alternately and correspondingly arranged with the copper foil sheets of the plurality of negative sheets, and the separator is arranged between the aluminum foil sheet of each positive sheet and the copper foil sheet of the adjacent negative sheet. The positive electrode sheet further comprises a positive electrode substrate and a positive electrode slurry, the positive electrode slurry is coated on the positive electrode substrate, the positive electrode tab is connected with the positive electrode substrate, the positive electrode slurry comprises a positive electrode active material, a conductive agent, a binder, a solvent and nano silica gel powder, the mass percentage of the nano silica gel powder is The positive electrode active material is LiNi 1 / 3 Co 1 / 3-x / 3 Mn 1 / 3-x / 3 Mg x / 3 V x / 3 O 2-2y F y 0 < x < 0.01, and 0 < y < 0.

05.

2. The electric cell of claim 1, wherein, The negative tabs of the plurality of negative sheets are welded together in layers.

3. The electric cell of claim 1, wherein, The auxiliary tabs of the plurality of negative sheets are welded together in layers.

4. The electric cell of claim 1, wherein, The negative sheet assembly further includes a plurality of nickel layers, the plurality of nickel layers are connected to the negative tabs of the plurality of negative sheets in one-to-one correspondence, and each nickel layer is arranged around the negative tab of the corresponding negative sheet.

5. The electric cell of claim 1, wherein, The negative tab and the auxiliary tab are arranged on the same side of the copper foil sheet.

6. The electric cell of claim 1, wherein, The negative tab and the auxiliary tab are arranged on opposite sides of the copper foil sheet.

7. A method of making an electrochemical cell, characterized by, The method for preparing the battery cell of any one of claims 1 to 6 comprises the following steps: Obtaining a copper foil sheet to be processed, a separator, and a positive sheet; Cutting the copper foil sheet to be processed to form a negative tab and an auxiliary tab on the copper foil sheet to obtain a negative sheet; Stacking the separator, the plurality of negative sheets, and the plurality of positive sheets to arrange the copper foil sheets of the plurality of negative sheets and the plurality of positive sheets in one-to-one correspondence and alternately in layers, and to arrange the separator between each positive sheet and the copper foil sheet of the adjacent negative sheet to obtain a battery cell semi-product; Connecting the tabs of the battery cell semi-product to obtain a battery cell.

8. A stacked battery, characterized by The battery cell of any one of claims 1 to 6 further includes an electrolyte and a housing, the electrolyte is filled in the housing, the battery cell is arranged in the housing, and the battery cell is soaked in the electrolyte.

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