Secondary battery and electronic device

Abstract

The invention provides a secondary battery and an electronic device. The secondary battery comprises an electrode assembly, the electrode assembly comprises a positive pole piece, a negative pole piece and a third pole piece, the third pole piece and the negative pole piece are connected through a one-way electronic conduction switching device, and the third pole piece comprises a third pole piece current collector and a third pole piece material layer arranged on at least one surface of the third pole piece current collector; the third pole piece material layer comprises a third pole piece active material; the potential of the negative pole piece is V1V when the secondary battery is at a discharge cut-off voltage, the corresponding potential of the negative pole piece is V4V when the secondary battery begins over-discharge gas production, the voltage platform of the active material of the third pole piece is V2V when electrochemical reaction is carried out for lithium removal, V2 is less than V4, the electron conduction voltage of the one-way electron conduction switching device is V3V, and V3 is more than V1-V2 and less than V4-V2. According to the invention, the risk of gas production of the secondary battery under low voltage can be reduced, and the energy density and the safety are improved.

Description

Technical Field

[0001] The present application relates to the field of electrochemistry technology, and particularly to a secondary battery and an electronic device. Background Art

[0002] Secondary batteries, such as lithium-ion batteries, are widely used in fields such as smart phones, wearable devices, consumer drones, and electric vehicles due to their advantages such as long cycle life and no memory effect. With the wide application of lithium-ion batteries in the above fields, higher requirements are put forward for the energy density of lithium-ion batteries. Although the application of silicon-containing anode active materials can improve the energy density of lithium-ion batteries, the discharge cut-off voltage of current silicon-based lithium-ion batteries is generally still above 3.0V, resulting in ineffective utilization of the energy density in the low voltage range. The reason is that even when the lithium-ion battery is not in use, there is still a tiny leakage current, causing the voltage to continuously drop. When the voltage of the lithium-ion battery drops to a certain threshold (gas generation voltage), gas will be generated, posing a safety hazard. Therefore, usually the discharge cut-off voltage of the lithium-ion battery needs to be higher than the gas generation voltage to reduce the risk of gas generation due to voltage drop during long-term storage. If the gas generation problem of the lithium-ion battery at low voltage can be solved, the energy density of the silicon-based lithium-ion battery can be improved, but there is currently no effective solution to the above problem. Summary of the Invention

[0003] The purpose of the present application is to provide a secondary battery and an electronic device to reduce the risk of gas generation of the secondary battery at low voltage and improve the energy density and safety of the secondary battery. The specific technical solutions are as follows:

[0004] A first aspect of the present application provides a secondary battery, which includes an electrode assembly. The electrode assembly includes a positive electrode tab, a negative electrode tab, and a third electrode tab. The third electrode tab is connected to the negative electrode tab through a unidirectional electron conduction switch device. The third electrode tab includes a third electrode tab current collector and a third electrode tab material layer provided on at least one surface of the third electrode tab current collector. The third electrode tab material layer includes a third electrode tab active material; the potential of the negative electrode tab at the discharge cut-off voltage of the secondary battery is V1 V, the potential of the negative electrode tab corresponding to the start of over-discharge gas generation in the secondary battery is V4 V, and the voltage plateau when the third electrode tab active material undergoes an electrochemical reaction to de-lithiate is V2 V, where V2 < V4. The electron conduction voltage of the unidirectional electron conduction switch device is V3 V, and V1 - V2 < V3 < V4 - V2. By introducing a third electrode tab into the secondary battery and providing a unidirectional electron conduction switch device between the third electrode tab and the negative electrode tab, such that both V2 < V4 and V1 - V2 < V3 < V4 - V2 are satisfied. During abnormal continuous discharge or long-term storage of the secondary battery, the potential of the negative electrode tab continuously rises (less than the gas generation potential of the negative electrode tab at this time). When the potential difference between the potential of the negative electrode tab and the third electrode tab reaches the conduction voltage of the unidirectional electron conduction switch device, the third electrode tab functions to de-lithiate and provide electrons. The electrons flow from the third electrode tab to the negative electrode tab through the unidirectional electron conduction switch device, which can reduce the rise of the potential of the negative electrode tab and reduce the decomposition of the solid electrolyte interface film (SEI film) in the negative electrode tab, thereby reducing the risk of gas generation in the secondary battery at low voltage and improving the energy density and safety of the secondary battery.

[0005] In some embodiments of the present application, the discharge cut-off voltage of the secondary battery is U V, where 2.5 ≤ U ≤ 3.0. When the discharge cut-off voltage U of the secondary battery is within the above range, it is beneficial to improve the energy density of the secondary battery. At the same time, the secondary battery has a lower risk of gas generation at low voltage and better safety.

[0006] In some embodiments of the present application, the third electrode tab active material includes at least one of lithium metal, lithium alloy, silicon-containing material, graphite, hard carbon, or lithium titanate. By selecting the above third electrode tab active material, the third electrode tab can de-lithiate and provide electrons, reducing the rise of the potential of the negative electrode tab and reducing the decomposition of the SEI film in the negative electrode tab, thereby facilitating the reduction of the risk of gas generation in the secondary battery at low voltage and improving the energy density and safety of the secondary battery.

[0007] In some embodiments of the present application, based on the mass of the third electrode material layer, the mass percentage content of the active lithium element in the third electrode material layer is 20% to 100%. By controlling the mass percentage content of the active lithium element in the third electrode material layer within the above range, the third electrode can de-lithiate and provide electrons, reducing the increase in the potential of the negative electrode sheet and the decomposition of the SEI film in the negative electrode sheet, thereby facilitating the reduction of the risk of gas generation in the secondary battery at low voltages and improving the energy density and safety of the secondary battery.

[0008] In some embodiments of the present application, the capacity provided by the voltage plateau when the third electrode active material undergoes an electrochemical reaction to de-lithiate is Q mAh, where 5 ≤ Q ≤ 600. By controlling the value of Q within the above range, it is beneficial to reduce the risk of gas generation in the secondary battery at low voltages and improve the energy density and safety of the secondary battery.

[0009] In some embodiments of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The negative electrode material layer includes a negative electrode active material, and the negative electrode active material includes a silicon-containing material. The silicon-containing material includes at least one of a silicon-carbon composite material, a silicon-oxygen composite material, or elemental silicon. Selecting the above negative electrode active material is beneficial to reduce the risk of gas generation in the secondary battery at low voltages and improve the energy density and safety of the secondary battery.

[0010] In some embodiments of the present application, the negative electrode active material further includes at least one of graphite, hard carbon, tin, or zinc. Selecting the above negative electrode active material is beneficial to improve the electrochemical performance (such as cycle performance, etc.) of the secondary battery while the secondary battery has a high energy density and good safety.

[0011] In some embodiments of the present application, the unidirectional electron conduction switch device includes at least one of a polarity diode, a unidirectional transistor, or a chip with a unidirectional conduction function. The above device has a unidirectional electron conduction function. Selecting the above unidirectional electron conduction switch device is beneficial to reduce the risk of gas generation in the secondary battery at low voltages and improve the energy density and safety of the secondary battery.

[0012] In some embodiments of the present application, the positive electrode of the unidirectional electron conduction switch device is connected to the negative electrode sheet, and the negative electrode of the unidirectional electron conduction switch device is connected to the third electrode. With the above connection method between the unidirectional electron conduction switch device and the negative electrode sheet and the third electrode, it is beneficial to realize the unidirectional electron conduction function of the unidirectional electron conduction switch device, thereby facilitating the reduction of the risk of gas generation in the secondary battery at low voltages and improving the energy density and safety of the secondary battery.

[0013] In some embodiments of the present application, the secondary battery satisfies any one of the following characteristics: (1) The secondary battery further includes a housing, and the third electrode sheet is disposed on the outer surface of the electrode assembly and adjacent to the housing; (2) The electrode assembly is a wound structure, and the third electrode sheet is disposed in the inner empty foil area of the electrode assembly; (3) The third electrode sheet is disposed between the positive electrode sheet and the negative electrode sheet. The third electrode sheet is disposed at the above positions, which is beneficial to reducing the risk of gas generation in the secondary battery at low voltages and improving the energy density and safety of the secondary battery.

[0014] The second aspect of the present application provides an electronic device, which includes the secondary battery provided by the first aspect of the present application. The electronic device of the present application has a long service life and good performance.

[0015] Advantages of the present application:

[0016] The present application provides a secondary battery and an electronic device. The secondary battery includes an electrode assembly, the electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a third electrode sheet. The third electrode sheet is connected to the negative electrode sheet through a unidirectional electron conduction switch device. The third electrode sheet includes a third electrode current collector and a third electrode material layer disposed on at least one surface of the third electrode current collector. The third electrode material layer includes a third electrode active material; the potential of the negative electrode sheet at the discharge cut-off voltage of the secondary battery is V1 V, the potential of the negative electrode sheet corresponding to the start of over-discharge gas generation in the secondary battery is V4 V, and the voltage plateau when the third electrode active material undergoes an electrochemical reaction to de-lithiate is V2 V, V2 < V4, and the electron conduction voltage of the unidirectional electron conduction switch device is V3 V, V1 - V2 < V3 < V4 - V2. By introducing a third electrode sheet into the secondary battery and disposing a unidirectional electron conduction switch device between the third electrode sheet and the negative electrode sheet in the present application, such that it simultaneously satisfies V2 < V4 and V1 - V2 < V3 < V4 - V2. During abnormal continuous discharge or long-term placement of the secondary battery, the potential of the negative electrode sheet continuously rises (less than the gas generation potential of the negative electrode sheet at this time). When the potential difference between the potential of the negative electrode sheet and the third electrode sheet reaches the conduction voltage of the unidirectional electron conduction switch device, the third electrode sheet plays a role in de-lithiating and providing electrons. The electrons flow from the third electrode sheet to the negative electrode sheet through the unidirectional electron conduction switch device, which can reduce the rise of the potential of the negative electrode sheet and reduce the decomposition of the SEI film in the negative electrode sheet, thereby reducing the risk of gas generation in the secondary battery at low voltages and improving the energy density and safety of the secondary battery.

[0017] Of course, it is not necessary for any product or method implementing the present application to simultaneously achieve all the above-mentioned advantages. Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other embodiments can also be obtained based on these drawings.

[0019] Figure 1 Schematic diagram of the structure of a secondary battery according to an embodiment of the present application;

[0020] Figure 2 Schematic diagram of the structure of the secondary battery of Comparative Example 1.

[0021] Reference numerals: positive electrode plate 1, separator 2, negative electrode plate 3, external electronic device 4, third electrode plate 5, one-way electron conduction switch device 6. Detailed implementation manners

[0022] The following will clearly and completely describe the technical solutions in the present application in conjunction with the embodiments and drawings of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application fall within the protection scope of the present application.

[0023] It should be noted that in the specific implementation manners of the present application, a lithium-ion battery is used as an example of the secondary battery to explain the present application. However, the secondary battery of the present application is not limited to lithium-ion batteries.

[0024] The first aspect of the present application provides a secondary battery, which includes an electrode assembly. The electrode assembly includes a positive electrode plate, a negative electrode plate, and a third electrode plate. The third electrode plate is connected to the negative electrode plate through a one-way electron conduction switch device. The third electrode plate includes a third electrode current collector and a third electrode material layer provided on at least one surface of the third electrode current collector. The third electrode material layer includes a third electrode active material. The potential of the negative electrode plate when the secondary battery is at the discharge cut-off voltage is V1 V, the potential of the negative electrode plate corresponding to the start of over-discharge gas generation in the secondary battery is V4 V, the voltage plateau when the third electrode active material undergoes an electrochemical reaction to de-lithiate is V2 V, V2 < V4, the electron conduction voltage of the one-way electron conduction switch device is V3 V, and V1 - V2 < V3 < V4 - V2.

[0025] The reason for gas generation in a secondary battery when the discharge cut-off voltage is too low usually lies in that the continuously rising potential of the negative electrode plate causes the solid electrolyte interface film (SEI film) to undergo an oxidation reaction and decompose to generate gas. In this application, a third electrode plate is introduced into the secondary battery, and a unidirectional electron conduction switch device is arranged between the third electrode plate and the negative electrode plate. The unidirectional electron conduction switch device has an electron conduction voltage V3. When the voltage difference across the unidirectional electron conduction switch device is less than V3, electrons cannot conduct in the unidirectional electron conduction switch device; when the voltage difference across the unidirectional electron conduction switch device is greater than or equal to V3, the unidirectional electron conduction switch device realizes electron conduction, and electrons can only flow from the third electrode plate through the unidirectional electron conduction switch device to the negative electrode plate and cannot flow from the negative electrode plate through the unidirectional electron conduction switch device to the third electrode plate. The third electrode plate has the ability to deintercalate lithium and can provide electrons, and satisfies V2 < V4, which can realize the above-mentioned unidirectional electron conduction function of the unidirectional electron conduction switch device, enabling electrons to only flow from the third electrode plate to the negative electrode plate, and the third electrode plate can play a role before the secondary battery starts to generate gas, reducing the risk of gas generation in the secondary battery at low voltage and improving the energy density and safety of the secondary battery.

[0026] At the same time, the secondary battery of this application satisfies V1 - V2 < V3. During the normal cycling of the secondary battery when discharging to the discharge cut-off voltage, the potential of the negative electrode plate is relatively low, and the potential difference between the potential of the negative electrode plate and the third electrode plate does not reach the electron conduction voltage of the unidirectional electron conduction switch device, so electrons cannot pass through the unidirectional electron conduction switch device, and the third electrode plate does not participate in the electrochemical reaction in the secondary battery, which can reduce the risk of premature consumption of the capacity of the third electrode plate. During the abnormal continuous discharge or long-term placement process of the secondary battery, the voltage of the secondary battery continuously decreases, and the potential of the negative electrode plate continuously rises (less than the gas generation potential of the negative electrode plate at this time). When the potential difference between the potential of the negative electrode plate and the third electrode plate reaches the electron conduction voltage of the unidirectional electron conduction switch device, the third electrode plate plays a role in deintercalating lithium and providing electrons, and the electrons flow from the third electrode plate to the negative electrode plate through the unidirectional electron conduction switch device, which can reduce the further rise of the potential of the negative electrode plate. The potential of the negative electrode plate corresponding to the start of over-discharge gas generation in the secondary battery is V4 V. The secondary battery satisfies V3 < V4 - V2, which can enable the unidirectional electron conduction switch device to realize electron conduction before the secondary battery starts to generate gas, the third electrode plate plays a role, reducing the rise of the potential of the negative electrode plate and reducing the oxidation decomposition reaction of the SEI film, thereby reducing the risk of gas generation in the secondary battery at low voltage and improving the energy density and safety of the secondary battery.

[0027] When the value of V2 is too large, for example, V2≥V4, the potential of the negative electrode plate of the secondary battery has reached the gas generation potential during the discharge process, and the secondary battery starts to generate gas, but the third electrode plate still does not play a role. While reducing the energy density of the secondary battery, it is also impossible to reduce the risk of gas generation in the secondary battery at low voltages and improve the safety of the secondary battery. When the value of V3 is too small, for example, V3≤V1 - V2, the electron conduction voltage of the unidirectional electron conduction switch device is too low. Before the secondary battery is normally discharged to the discharge cut-off voltage or before being discharged to the discharge cut-off voltage, the unidirectional electron conduction switch device has been turned on, and the third electrode plate starts to de-lithiate, resulting in premature consumption of the capacity of the third electrode plate. When the secondary battery is in an over-discharge state and the voltage continues to decrease and starts to generate gas, the third electrode plate can no longer play a role, so it is impossible to reduce the risk of gas generation in the secondary battery at low voltages and improve the energy density and safety of the secondary battery. When the value of V3 is too large, for example, V3≥V4 - V2, when the negative electrode plate reaches the gas generation potential (V4 V), the unidirectional electron conduction switch device is still not turned on. While reducing the energy density of the secondary battery, the third electrode plate cannot play a role, and it is also impossible to reduce the risk of gas generation in the secondary battery at low voltages and improve the safety of the secondary battery.

[0028] Therefore, in this application, by introducing a third electrode plate into the secondary battery, and setting a unidirectional electron conduction switch device between the third electrode plate and the negative electrode plate, and simultaneously satisfying V2<V4 and V1 - V2<V3<V4 - V2, it is possible to reduce the risk of gas generation in the secondary battery at low voltages and improve the energy density and safety of the secondary battery. In this application, the above-mentioned low voltage refers to the voltage of the secondary battery being lower than the rated discharge cut-off voltage. There is no electron path between the third electrode plate and the positive electrode plate; except for the unidirectional electron conduction switch device, there is no other electron path between the third electrode plate and the negative electrode plate.

[0029] Exemplarily, as Figure 1 shown, the electrode assembly includes a positive electrode plate 1, a separator 2, a negative electrode plate 3, and a third electrode plate 5. A separator 2 is provided between the positive electrode plate 1 and the negative electrode plate 3, a separator 2 is provided between the negative electrode plate 3 and the third electrode plate 5, an external electronic device 4 is connected between the positive electrode plate 1 and the negative electrode plate 3, and the third electrode plate 5 and the negative electrode plate 3 are connected through a unidirectional electron conduction switch device 6.

[0030] In some embodiments of the present application, the discharge cut-off voltage of the secondary battery is U V, where 2.5 ≤ U ≤ 3.0. For example, the value of U can be 2.50, 2.55, 2.60, 2.65, 2.70, 2.75, 2.80, 2.85, 2.90, 2.95, 3.00 or a range composed of any two of these values. When the discharge cut-off voltage U of the secondary battery is within the above range, lithium ions in the negative electrode material layer can be removed as much as possible to contribute to the capacity, which is beneficial to improving the energy density of the secondary battery. At the same time, the risk of gas generation in the secondary battery at low voltage is relatively low, and the safety is good.

[0031] In some embodiments, 0.8 ≤ V1 < 1.3. For example, the value of V1 can be 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, 1.20, 1.25, 1.29 or a range composed of any two of these values. When the value of V1 is within the above range, it is beneficial to improve the energy density of the secondary battery. At the same time, the risk of gas generation in the secondary battery at low voltage is relatively low, and the safety is good.

[0032] In some embodiments, 0 ≤ V2 < 1.3, optionally, 0 ≤ V2 < 0.5. For example, the value of V2 can be 0, 0.20, 0.40, 0.50, 0.60, 0.80, 1.00, 1.10, 1.20, 1.28, 1.29 or a range composed of any two of these values.

[0033] In some embodiments, 1.2 ≤ V4 ≤ 1.6. For example, the value of V4 can be 1.20, 1.25, 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, 1.60 or a range composed of any two of these values.

[0034] In some embodiments of the present application, the active material of the third electrode includes at least one of lithium metal, lithium alloy, silicon-containing material, graphite, hard carbon or lithium titanate. Among them, the lithium alloy can include at least one of lithium aluminum alloy, lithium magnesium alloy, lithium tin alloy, lithium zinc alloy, lithium iron alloy, lithium indium alloy or lithium silver alloy, and the silicon-containing material can include at least one of silicon-carbon composite material, silicon-oxygen composite material or elemental silicon, and the graphite can include at least one of artificial graphite or natural graphite. By selecting the above active material of the third electrode, when the potential difference between the negative electrode potential and the third electrode reaches the electron conduction voltage of the unidirectional electron conduction switch device, the third electrode can play a role in de-lithiation and providing electrons, reducing the rise of the negative electrode potential and the decomposition of the SEI film in the negative electrode, thereby being beneficial to reducing the risk of gas generation in the secondary battery at low voltage and improving the energy density and safety of the secondary battery.

[0035] In the present application, the third electrode active material can participate in the electrochemical reaction and provide electrons. The voltage plateau V2 of the third electrode active material can be a single plateau or multiple plateaus, as long as V2 < V4 is satisfied. The value of the voltage plateau V2 can be determined by assembling the third electrode with a separator and a lithium metal into a half-cell and then charging to delithiate the third electrode active material, and using the obtained curve of voltage versus capacity.

[0036] In some embodiments of the present application, based on the mass of the third electrode material layer, the mass percentage of the active lithium element in the third electrode material layer is 20% to 100%. For example, the mass percentage of the active lithium element in the third electrode material layer can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100% or any range composed of any two of these values. By adjusting the mass percentage of the active lithium element in the third electrode material layer within the above range, when the potential difference between the negative electrode potential and the third electrode reaches the electron conduction voltage of the unidirectional electron conduction switch device, the third electrode can function to delithiate and provide electrons, reducing the elevation of the negative electrode potential and the decomposition of the SEI film in the negative electrode, thereby facilitating the reduction of the risk of gas generation in the secondary battery at low voltage and improving the energy density and safety of the secondary battery.

[0037] In the present application, when the third electrode active material is at least one of a silicon-containing material, graphite, hard carbon, or lithium titanate, before preparing the secondary battery, the third electrode needs to be pre-lithiated to pre-embed lithium ions into the third electrode material layer. The present application does not particularly limit the method of the above pre-lithiation treatment, as long as the purpose of the present application can be achieved. For example, the method of pre-lithiation treatment can be lithium powder lithium supplementation, lithium strip lithium supplementation, and electrochemical lithium supplementation. By adjusting the time of the pre-lithiation treatment, the mass percentage of the active lithium element in the third electrode material layer can be adjusted. When other conditions remain unchanged, the longer the pre-lithiation treatment time, the greater the mass percentage of the active lithium element in the third electrode material layer; the shorter the pre-lithiation treatment time, the smaller the mass percentage of the active lithium element in the third electrode material layer.

[0038] In some embodiments of the present application, when the third electrode active material undergoes an electrochemical reaction to de-lithiate, the capacity provided by the voltage plateau is Q mAh, where 5 ≤ Q ≤ 600. For example, the value of Q can be 5, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, or a range composed of any two of these numerical values. By regulating the value of Q within the above range, when the potential difference between the negative electrode potential and the third electrode reaches the electron conduction voltage of the unidirectional electron conduction switch device, the third electrode can provide more electrons, which is beneficial to reducing the rise of the negative electrode potential and the decomposition of the SEI film in the negative electrode, thereby facilitating the reduction of the risk of gas generation in the secondary battery at low voltages and improving the energy density and safety of the secondary battery.

[0039] The present application has no particular limitation on the method of regulating the value of Q, as long as the purpose of the present application can be achieved. For example, the value of Q can be regulated by controlling the type of the third electrode active material, the size of the third electrode material layer, the content of active lithium elements, the coating surface density, and the number of the third electrodes. When other conditions remain unchanged, as the size of the third electrode material layer increases, the value of Q increases; as the size of the third electrode material layer decreases, the value of Q decreases. When other conditions remain unchanged, as the content of active lithium elements in the third electrode material layer increases, the value of Q increases; as the content of active lithium elements in the third electrode material layer decreases, the value of Q decreases. When other conditions remain unchanged, as the coating surface density of the third electrode material layer increases, the value of Q increases; as the coating surface density of the third electrode material layer decreases, the value of Q decreases. When other conditions remain unchanged, as the number of the third electrodes increases, the value of Q increases; as the number of the third electrodes decreases, the value of Q decreases.

[0040] In some embodiments, based on the mass of the third electrode material layer, the mass percentage of the third electrode active material can be 85% to 100%. For example, the mass percentage of the third electrode active material can be 85%, 88%, 90%, 92%, 94%, 96%, 98%, 100%, or a range composed of any two of these numerical values. By regulating the mass percentage of the third electrode active material within the above range, it is beneficial to obtain a larger value of Q, thereby facilitating the reduction of the risk of gas generation in the secondary battery at low voltages and improving the energy density and safety of the secondary battery.

[0041] The third electrode material layer of the present application may further include a third electrode conductive agent and a third electrode binder. Based on the mass of the third electrode material layer, the mass percentage content of the third electrode conductive agent is 0% to 8%, and the mass percentage content of the third electrode binder is 0% to 8%. For example, the mass percentage content of the third electrode conductive agent may be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or a range composed of any two of these values, and the mass percentage content of the third electrode binder may be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or a range composed of any two of these values. The present application does not particularly limit the types of the third electrode conductive agent and the third electrode binder, as long as the purpose of the present application can be achieved. For example, the third electrode conductive agent may include, but is not limited to, at least one of conductive carbon black, carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metal materials or conductive polymers, and the conductive carbon black may include, but is not limited to, at least one of acetylene black or Ketjen black. The above carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and / or nanofibers. The above metal materials may include, but are not limited to, metal powders and / or metal fibers. Specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum or silver. The above conductive polymers may include, but are not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole. The third electrode binder may include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyimide, polyamideimide, styrene-butadiene rubber or polyvinylidene fluoride.

[0042] In the present application, the third electrode includes a third electrode current collector and a third electrode material layer provided on at least one surface of the third electrode current collector. The provision of the third electrode current collector is beneficial to the processing and preparation of the secondary battery of the present application. On the one hand, it can support the third electrode material layer, and on the other hand, it is beneficial to realize the connection between the third electrode, the unidirectional electron conduction switch device and the negative electrode. The above "third electrode material layer provided on at least one surface of the third electrode current collector" means that the third electrode material layer may be provided on one surface of the third electrode current collector along its own thickness direction, or may be provided on two surfaces of the third electrode current collector along its own thickness direction. It should be noted that the "surface" here may be the entire area of the third electrode current collector or a partial area of the third electrode current collector. The present application does not have a particular limitation, as long as the purpose of the present application can be achieved.

[0043] The present application has no particular limitation on the current collector of the third electrode sheet, as long as the purpose of the present application can be achieved. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or composite current collector. Exemplarily, the composite current collector may be a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector or a titanium-copper composite current collector, etc.

[0044] The present application has no particular limitation on the thickness of the current collector of the third electrode sheet and the material layer of the third electrode sheet, as long as the purpose of the present application can be achieved. For example, the thickness of the current collector of the third electrode sheet may be 4 μm to 15 μm, and the thickness of the material layer of the third electrode sheet may be 5 μm to 100 μm.

[0045] The present application has no particular limitation on the position of the third electrode sheet in the secondary battery, as long as it is electronically insulated from the positive electrode sheet and the negative electrode sheet. The above-mentioned way of maintaining electronic insulation may be to provide a separator film between the third electrode sheet and the adjacent positive electrode sheet or negative electrode sheet. The present application has no particular limitation on the size of the third electrode sheet, and it can be selected according to the Q value required by the secondary battery design.

[0046] In some embodiments of the present application, the secondary battery further includes a housing, and the third electrode sheet is disposed on the outer surface of the electrode assembly and adjacent to the housing. At this time, the electrode assembly may be a wound structure or a stacked structure. The third electrode sheet may be disposed at a position where the gap between the outer surface of the electrode assembly and the housing is relatively large to reduce the impact on the energy density of the secondary battery. By disposing the third electrode sheet at the above position, the redundant space in the housing can be utilized to reduce the increase in the volume of the secondary battery, thereby facilitating reducing the risk of gas generation in the secondary battery at low voltage and improving the energy density and safety of the secondary battery.

[0047] In some embodiments of the present application, the third electrode sheet is disposed between the positive electrode sheet and the negative electrode sheet. Specifically, the third electrode sheet may be disposed between any adjacent positive electrode sheet and negative electrode sheet. At this time, the electrode assembly may be a wound structure or a stacked structure. By disposing the third electrode sheet at the above position, the distance between the third electrode sheet and the negative electrode sheet and the positive electrode sheet can be shortened, accelerating the transmission of lithium ions, thereby facilitating reducing the risk of gas generation in the secondary battery at low voltage and improving the energy density and safety of the secondary battery.

[0048] In some embodiments of the present application, the electrode assembly has a wound structure, and the third electrode tab is disposed in the inner empty foil area of the electrode assembly. The above-mentioned inner empty foil area refers to the current collector area where no active material is provided starting from the starting position of the electrode tab winding. Specifically, the third electrode tab can be disposed in the inner positive current collector empty foil area of the electrode assembly or in the inner negative current collector empty foil area of the electrode assembly. By disposing the third electrode tab in the above positions, the redundant space inside the housing can be utilized to reduce the increase in the volume of the secondary battery, which is beneficial to reducing the risk of gas generation in the secondary battery at low voltages and improving the energy density and safety of the secondary battery.

[0049] In some embodiments of the present application, the unidirectional electron conduction switch device includes at least one of a polarity diode, a unidirectional transistor, or a chip with a unidirectional conduction function. The above device has a unidirectional electron conduction function. By selecting the above unidirectional electron conduction switch device, when the potential of the negative electrode tab continuously rises during abnormal continuous discharge or long-term storage of the secondary battery, the unidirectional electron conduction switch device can achieve electron conduction, the third electrode tab can play a role, reduce the rise of the potential of the negative electrode tab, and reduce the decomposition of the SEI film in the negative electrode tab, which is beneficial to reducing the risk of gas generation in the secondary battery at low voltages and improving the energy density and safety of the secondary battery. In the present application, the unidirectional electron conduction switch device can be obtained by purchase, and the chip with a unidirectional conduction function can be realized by diode integration, circuit design, etc.

[0050] The present application does not particularly limit the types of the polarity diode and the unidirectional transistor, as long as the purpose of the present application can be achieved. For example, the polarity diode can include at least one of, but not limited to, a PN silicon diode, a germanium diode, or a selenium diode, and the above polarity diode can include at least one of, but not limited to, a Zener diode, a tunnel diode, or a cross-flow diode; the unidirectional transistor can include, but not limited to, an NPN silicon transistor, and the above unidirectional transistor can include, but not limited to, a field effect transistor.

[0051] In some embodiments of the present application, the positive electrode of the unidirectional electron conduction switch device is connected to the negative electrode tab, and the negative electrode of the unidirectional electron conduction switch device is connected to the third tab. When the unidirectional electron conduction switch device is connected to the negative electrode tab and the third tab in the above manner, when the potential difference between the potential of the negative electrode tab and the third tab reaches the electron conduction voltage of the unidirectional electron conduction switch device, electrons can only flow from the third tab through the unidirectional electron conduction switch device to the negative electrode tab, and cannot flow from the negative electrode tab through the unidirectional electron conduction switch device to the third tab, reducing the rise of the potential of the negative electrode tab and reducing the decomposition of the SEI film in the negative electrode tab. Therefore, it is beneficial to reduce the risk of gas generation in the secondary battery at low voltage and improve the energy density and safety of the secondary battery. The present application does not particularly limit the connection manner between the unidirectional electron conduction switch device and the negative electrode tab, as long as the purpose of the present application can be achieved. For example, the unidirectional electron conduction switch device and the negative electrode tab can be fixedly connected by welding.

[0052] In the present application, the electron conduction voltage V3 that meets the scope of the present application can be obtained by adjusting the number and connection manner (such as series connection) of the unidirectional electron conduction switch devices. For example, multiple unidirectional electron conduction switch devices can be connected in series, and the sum of the electron conduction voltages of each unidirectional electron conduction switch device is V3.

[0053] In some embodiments of the present application, the negative electrode tab includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The negative electrode material layer includes a negative electrode active material. The negative electrode active material includes a silicon-containing material. The silicon-containing material includes at least one of a silicon-carbon composite material, a silicon-oxygen composite material, or elemental silicon. The above elemental silicon can include at least one of micron silicon or nano silicon. Selecting the above negative electrode active material is beneficial to reducing the risk of gas generation in the secondary battery at low voltage and improving the energy density and safety of the secondary battery. The present application does not particularly limit the mass percentage content of the silicon-containing material in the negative electrode active material, as long as the purpose of the present application can be achieved. In some embodiments, based on the mass of the negative electrode active material, the mass percentage content of the silicon-containing material can be 5% to 100%. For example, the mass percentage content of the silicon-containing material can be 5%, 20%, 40%, 50%, 60%, 80%, 100%, or a range composed of any two of these values.

[0054] In some embodiments of the present application, the negative electrode active material further includes at least one of graphite, hard carbon, tin, or zinc, and the graphite may include at least one of artificial graphite or natural graphite. Selecting the above negative electrode active material is beneficial to improving the electrochemical performance (such as cycle performance, etc.) of the secondary battery while the secondary battery has a high energy density and good safety. The present application does not particularly limit the mass percentage of the above negative electrode active material in the negative electrode active material, as long as the purpose of the present application can be achieved. In some embodiments, based on the mass of the negative electrode active material, the mass percentage of the above negative electrode active material may be 0% to 95%. For example, the mass percentage of the above negative electrode active material may be 0%, 20%, 40%, 50%, 60%, 80%, 95%, or a range composed of any two of these values.

[0055] In the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector. The above "the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector" means that the negative electrode material layer may be provided on one surface of the negative electrode current collector along its thickness direction, or may be provided on both surfaces of the negative electrode current collector along its thickness direction. It should be noted that the "surface" here may be the entire area of the surface of the negative electrode current collector, or may be a partial area of the surface of the negative electrode current collector. The present application does not have a particular limitation, as long as the purpose of the present application can be achieved.

[0056] The present application does not particularly limit the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, it may include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, or a composite current collector. Exemplarily, the composite current collector may be a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, or a titanium-copper composite current collector, etc.

[0057] The negative electrode material layer of the present application may further include a negative electrode conductive agent and a negative electrode binder. The present application does not particularly limit the negative electrode conductive agent and the negative electrode binder in the negative electrode material layer, as long as the purpose of the present application can be achieved. For example, the negative electrode conductive agent may include, but is not limited to, at least one of the above third electrode sheet conductive agents, and the negative electrode binder may include, but is not limited to, at least one of the above third electrode sheet binders. The present application does not particularly limit the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder in the negative electrode material layer. Those skilled in the art can select according to actual needs, as long as the purpose of the present application can be achieved.

[0058] The present application does not particularly limit the thickness of the negative electrode material layer and the thickness of the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, the thickness of the single-sided negative electrode material layer may be 30 μm to 100 μm, and the thickness of the negative electrode current collector may be 4 μm to 15 μm.

[0059] Optionally, the negative electrode tab can further include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. The present application has no particular limitation on the composition of the conductive layer, and it can be a commonly used conductive layer in the art. For example, the conductive layer includes a conductive agent for the conductive layer and a binder for the conductive layer. The present application has no particular limitation on the conductive agent for the conductive layer and the binder for the conductive layer in the conductive layer. For example, the conductive agent for the conductive layer can be at least one of the above-mentioned conductive agents for the third electrode tab, and the binder for the conductive layer can be at least one of the above-mentioned binders for the third electrode tab.

[0060] In the present application, the electrode assembly includes a positive electrode tab. The positive electrode tab includes a positive electrode current collector and a positive electrode material layer provided on at least one surface of the positive electrode current collector. The above-mentioned "positive electrode material layer provided on at least one surface of the positive electrode current collector" means that the positive electrode material layer can be provided on one surface of the positive electrode current collector along its own thickness direction, or can be provided on two surfaces of the positive electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of the positive electrode current collector or a partial area of the positive electrode current collector. The present application has no particular limitation as long as the purpose of the present application can be achieved.

[0061] The present application has no particular limitation on the positive electrode current collector as long as the purpose of the present application can be achieved. For example, it can include aluminum foil, aluminum alloy foil, or a composite current collector (such as an aluminum-carbon composite current collector), etc.

[0062] The positive electrode material layer of the present application includes a positive electrode active material, and the positive electrode active material includes a substance capable of reversibly inserting and extracting active ions such as lithium ions. The positive electrode material layer can be one layer or multiple layers, and each layer in the multiple positive electrode material layers can include the same or different positive electrode active materials. The present application has no particular limitation on the positive electrode active material as long as the purpose of the present application can be achieved. For example, the positive electrode active material can include, but is not limited to, at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium iron phosphate, lithium-rich manganese-based material, lithium cobalt oxide (LiCoO2), lithium manganese oxide, lithium manganese iron phosphate, or lithium titanate. The above-mentioned lithium nickel cobalt manganese oxide can include LiNi 0.95 Co 0.03 Mn 0.02 O2 (Ni95), LiNi 0.91 Co 0.03 Mn 0.06 O2 (Ni91), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.5 Co 0.2Mn 0.3 O2 (NCM523) or LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM111).

[0063] The positive electrode material layer of the present application further includes a positive electrode conductive agent and a positive electrode binder. The present application places no particular limitation on the positive electrode conductive agent and the positive electrode binder in the positive electrode material layer, as long as the objectives of the present application can be achieved. For example, the positive electrode conductive agent can be at least one of the above-mentioned third electrode conductive agents, and the positive electrode binder can be at least one of the above-mentioned third electrode binders. The present application places no particular limitation on the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder in the positive electrode material layer, and those skilled in the art can select according to actual needs as long as the objectives of the present application can be achieved.

[0064] The present application places no particular limitation on the thickness of the positive electrode current collector, as long as the objectives of the present application can be achieved. For example, the thickness of the positive electrode current collector can be 6 μm to 25 μm. The present application places no particular limitation on the thickness of the positive electrode material layer, as long as the objectives of the present application can be achieved. For example, the thickness of the single-sided positive electrode material layer can be 50 μm to 150 μm.

[0065] Optionally, the positive electrode tab may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode material layer. The present application places no particular limitation on the composition of the conductive layer, and it can be a commonly used conductive layer in the art. For example, the conductive layer includes a conductive layer conductive agent and a conductive layer binder. The present application places no particular limitation on the conductive layer conductive agent and the conductive layer binder in the conductive layer. For example, the conductive layer conductive agent can be at least one of the above-mentioned third electrode conductive agents, and the conductive layer binder can be at least one of the above-mentioned third electrode binders.

[0066] In the present application, the electrode assembly includes a separator membrane. The present application places no particular limitation on the separator membrane, as long as the objectives of the present application can be achieved. For example, the material of the separator membrane can include, but is not limited to, at least one of polyolefins (PO) based on polyethylene (PE) and polypropylene (PP), polyester (for example, polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of the separator membrane can include at least one of a woven membrane, a non-woven membrane, a microporous membrane, a composite membrane, a rolled membrane, or a spun membrane.

[0067] In some embodiments, the separator membrane may include a substrate layer and a surface treatment layer. The substrate layer may be a non-woven fabric or a composite membrane having a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene non-woven fabric, a polyethylene non-woven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used.

[0068] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer, and the surface treatment layer may be a polymer layer, an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance.

[0069] In some embodiments, the inorganic layer includes ceramic particles and an inorganic layer binder. There are no particular limitations on the ceramic particles in this application. For example, the ceramic particles may include at least one of silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. There are no particular limitations on the inorganic layer binder in this application. For example, the inorganic layer binder may be at least one of the above-mentioned third electrode binders. In some embodiments, the polymer layer includes a polymer, and the material of the polymer may include but is not limited to at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene ether, polyvinylidene fluoride, or poly(vinylidene fluoride-hexafluoropropylene).

[0070] In this application, there are no particular limitations on the thickness of the separator membrane, as long as the object of this application can be achieved. For example, the thickness of the separator membrane may be 3 μm to 20 μm.

[0071] In this application, the secondary battery further includes an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent.

[0072] There are no particular limitations on the lithium salt in this application, as long as the object of this application can be achieved. For example, the lithium salt may include but is not limited to at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, Li2SiF6, lithium bis(oxalato)borate (LiBOB), or lithium difluoroborate. There are no particular limitations on the content of the lithium salt in the electrolyte in this application, as long as the object of this application can be achieved.

[0073] There are no particular limitations on the non-aqueous solvent in this application, as long as the object of this application can be achieved. For example, the non-aqueous solvent may include but is not limited to at least one of carbonate compounds, carboxylate compounds, ether compounds, or other organic solvents.

[0074] The above-mentioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, or fluorinated carbonate compounds. The above-mentioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC). The above-mentioned cyclic carbonate compounds may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinylene ethylene carbonate (VEC). The above-mentioned fluorinated carbonate compounds may include, but are not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethyl ethylene carbonate. The above-mentioned carboxylate compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolide, valerolactone, or caprolactone. The above-mentioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The above-mentioned other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate. The present application does not particularly limit the content of the non-aqueous solvent in the electrolyte, as long as the object of the present application can be achieved.

[0075] The secondary battery further includes a housing for accommodating the positive electrode sheet, the separator, the negative electrode sheet, the third electrode sheet, and the electrolyte, as well as other components known in the field of secondary batteries. The present application does not limit the above-mentioned other components. The present application does not particularly limit the housing, and it may be a housing well-known in the art, as long as the object of the present application can be achieved. For example, the housing may be a hard shell housing or a flexible housing. The material of the hard shell housing may be metal. The present application does not limit the type of metal, and a metal hard shell housing known in the art may be used, as long as the object of the present application can be achieved. The flexible housing may be a metal plastic film, such as an aluminum plastic film, a steel plastic film, etc.

[0076] The secondary battery of the present application is not particularly limited, and it can include any device that undergoes an electrochemical reaction. In some embodiments, the secondary battery can include, but is not limited to: lithium-ion secondary batteries (lithium-ion batteries), lithium polymer secondary batteries, or lithium-ion polymer secondary batteries, etc.

[0077] The present application does not particularly limit the preparation process of the secondary battery, as long as the purpose of the present application can be achieved. For example, the preparation process of the secondary battery can include, but is not limited to, the following steps: stacking the positive electrode sheet, separator, negative electrode sheet, and separator in sequence, and winding, folding, etc. as needed to obtain a wound body with a wound structure. A third electrode sheet is arranged at a suitable position of the wound body, and a unidirectional electron conduction switch device is connected between the third electrode sheet and the negative electrode sheet to obtain an electrode assembly. Then, the electrode assembly is placed in a housing, electrolyte is injected into the housing and sealed to obtain a secondary battery; or, the positive electrode sheet, separator, negative electrode sheet, and separator are stacked in sequence, and then the four corners of the entire laminated structure are fixed with tape to obtain a laminated body with a laminated structure. A third electrode sheet is arranged at a suitable position of the laminated body, and a unidirectional electron conduction switch device is connected between the third electrode sheet and the negative electrode sheet to obtain an electrode assembly. Then, the electrode assembly is placed in a housing, electrolyte is injected into the housing and sealed to obtain a secondary battery. In addition, an overcurrent protection element, a guide plate, etc. can also be placed in the housing as needed to prevent the pressure inside the secondary battery from rising and overcharging and discharging.

[0078] The second aspect of the present application provides an electronic device, which includes the secondary battery provided in the first aspect of the present application. The electronic device of the present application has a long service life and good performance.

[0079] The electronic device of the present application is not particularly limited, and it can be any electronic device known in the prior art. In some embodiments, the electronic device can include, but is not limited to, laptop computers, pen-input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted stereo headphones, video recorders, liquid crystal televisions, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, motorized bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries, and lithium-ion capacitors, etc.

[0080] Examples

[0081] Hereinafter, examples and comparative examples are given to more specifically illustrate the embodiments of the present application. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0082] Testing method and device:

[0083] V1 Value Test

[0084] Take a copper wire about 10 cm in length, wind one side around the bottom end of the third tab, and leave a 2-cm length of copper wire on the other side. Take a copper foil close to the width of the third tab, wrap the bottom end of the third tab and the copper wire wound thereon, perform ultrasonic welding, and wrap the welding area with high-temperature insulating tape. Soak and clean the reserved copper wire with isopropyl alcohol. Prepare two separator films, stack and wrap the copper wire from both sides with the separator films, and fix the relative positions of the separator films with tape for standby. In a ventilated and dry environment, remove the outer aluminum-plastic film of the lithium-ion battery, uncover the outermost electrode tab, place the previously prepared copper wire wetted with the electrolyte between the uncovered outermost electrode tab and the separator film, cover the original electrode tab back, and fix the position of the copper wire electrode with tape. Then place the lithium-ion battery in the aluminum-plastic film and re-seal it. The above-mentioned third tab is additionally introduced and has the same size and material as the negative electrode tab of the lithium-ion battery, constituting the third tab of the three-electrode battery.

[0085] Lithium plating is carried out on the reference electrode of the assembled three-electrode battery with a lithium plating current of 25 μA for 10 h. Connect the above-mentioned lithium-ion battery to an electrochemical workstation, connect the negative electrode tab to the working electrode, the positive electrode tab to the counter electrode, and the copper wire to the reference electrode. Discharge the lithium-ion battery to the discharge cut-off voltage of each example and comparative example, and record the potentials of the positive electrode tab and the negative electrode tab of the lithium-ion battery at different voltages through the electrochemical workstation to obtain the potential V1 of the negative electrode tab when the lithium-ion battery is at the discharge cut-off voltage.

[0086] V2 Value and Q Value Test

[0087] After discharging the lithium-ion battery to 3 V at 0.2C, disassemble it to obtain the third electrode tab. Clean the third electrode tab with dimethyl carbonate (DMC) and dry it at 60 °C. Stack the third electrode tab, the separator film, and lithium metal in sequence in a dry environment, inject the electrolyte, and seal it to obtain a half-cell. Then charge it at a constant current of 0.2C to 2.5 V, record the change curve of the lithium-ion battery voltage with capacity, and obtain the voltage plateau V2 value when the active material of the third electrode tab undergoes an electrochemical reaction to de-lithiate according to the above curve. Read the charging capacity of the lithium-ion battery in the voltage plateau region, which is the capacity Q provided by the voltage plateau when the active material of the third electrode tab undergoes an electrochemical reaction to de-lithiate.

[0088] V4 Value Test

[0089] Take a copper wire about 10 cm in length, wind one side around the bottom end of the third tab, and leave a 2-cm length of copper wire on the other side. Take a copper foil close to the width of the third tab, wrap the bottom end of the third tab and the copper wire wound thereon, perform ultrasonic welding, and wrap the welding area with high-temperature insulating tape. Soak and clean the remaining copper wire with isopropyl alcohol. Prepare two separator films, stack and wrap the copper wire from both sides with the separator films, and fix the relative positions of the separator films with tape for standby. In a ventilated and dry environment, remove the outer aluminum-plastic film of the lithium-ion battery, uncover the outermost electrode tab, place the prepared copper wire wetted with electrolyte between the uncovered outermost electrode tab and the separator film, cover the original electrode tab back, and fix the position of the copper wire electrode with tape. Place the lithium-ion battery in the aluminum-plastic film and re-seal it. The above-mentioned third tab is additionally introduced and has the same size and material as the negative electrode tab of the lithium-ion battery, constituting the third tab of the three-electrode battery.

[0090] Lithium plating is carried out on the assembled three-electrode battery with a lithium plating current of 25 μA for 10 h. Connect the above-mentioned lithium-ion battery to an electrochemical workstation, connect the negative electrode tab to the working electrode, the positive electrode tab to the counter electrode, and the copper wire to the reference electrode. Record the potentials of the positive electrode tab and the negative electrode tab of the lithium-ion battery at different voltages through the electrochemical workstation. Let the above-mentioned lithium-ion battery stand still in an environment of 25 °C ± 3 °C for 30 min, charge it at a constant current of 1C to 4.53 V, then charge it at a constant voltage of 4.53 V until the current reaches 0.05C and stop. After standing still for 30 min, discharge the lithium-ion battery at 0.5C to the discharge cut-off voltage U, stand still for 30 min, and cycle 200 times according to the above charge-discharge steps. Test the thickness of the lithium-ion battery at this time. Then start discharging at a current of 10 mA until the voltage of the lithium-ion battery drops to 0.1 V. During this period, record the change in the thickness of the lithium-ion battery, record it every 100 ms. When 50 consecutive thickness recording points are all larger than the previous point, it is determined that the lithium-ion battery starts to over-discharge and generate gas. Record the voltage when the lithium-ion battery starts to over-discharge and generate gas, and obtain the potential V4 corresponding to the negative electrode tab when the lithium-ion battery starts to over-discharge and generate gas.

[0091] Test on the mass percentage content of active lithium element in the third electrode tab material layer

[0092] After discharging the lithium-ion battery at 0.2C until 3V, disassemble it to obtain the third electrode sheet. After cleaning the third electrode sheet with dimethyl carbonate (DMC), dry it at 60°C. Punch the dried third electrode sheet to obtain a third electrode sheet wafer with a diameter of 1.5 mm, and weigh it to obtain the mass m1 g of the third electrode sheet wafer. Stack the punched third electrode sheet wafer with a diameter of 1.5 mm, the separator, and lithium metal in sequence in a dry environment, inject the electrolyte, and seal it to obtain a half-cell. Then charge it at a constant current of 0.2C to 2.5V, and record the charging capacity Q1 mAh. Remove the third electrode material layer on the surface of the third electrode sheet to obtain the third electrode current collector, and similarly punch it to obtain a third electrode current collector wafer with a diameter of 1.5 mm, and weigh it to obtain the mass m2 g of the third electrode current collector wafer. The mass percentage of active lithium element in the third electrode material layer can be calculated by the following formula: Mass percentage of active lithium element in the third electrode material layer (%) = Q1 / 3860 / (m1 - m2).

[0093] Time test of lithium-ion battery from full discharge state to gas generation start

[0094] Let the lithium-ion battery stand in an environment of 25°C ± 3°C for 30 min, charge it at a constant current of 1C to 4.53V, then charge it at a constant voltage of 4.53V until the current reaches 0.05C and stop. After standing for 30 min, discharge the lithium-ion battery at 0.5C to the discharge cut-off voltage U, stand for 30 min, and cycle 200 times according to the above charge-discharge steps. Test the thickness of the lithium-ion battery at this time, and record this state as the full discharge state. Then start discharging at a current of 300 μA, discharge to 2.5V, and then continue to discharge at a current of 10 μA to 0.1V. During this period, record the change in the thickness of the lithium-ion battery, record it every 100 ms. When 50 consecutive thickness recording points are all larger than the previous point, it is determined that the lithium-ion battery starts to generate gas, and record the time from the start of discharge to the start of gas generation of the lithium-ion battery, which is recorded as the time of the lithium-ion battery from the full discharge state to the start of gas generation. Characterize the safety of the lithium-ion battery by the time of the lithium-ion battery from the full discharge state to the start of gas generation. The longer the time of the lithium-ion battery from the full discharge state to the start of gas generation, the better the safety performance of the lithium-ion battery; the shorter the time of the lithium-ion battery from the full discharge state to the start of gas generation, the worse the safety performance of the lithium-ion battery.

[0095] Energy density test

[0096] At 25 °C, the lithium-ion battery is charged at a constant current of 0.2C to 4.53V, and then charged at a constant voltage of 4.53V to 0.05C. After the charging step is completed, the length L, width W, and height H of the lithium-ion battery are measured with a laser thickness gauge, and the volume V of the lithium-ion battery is obtained as V = L×W×H. Then, it is discharged at a constant current of 0.2C to the discharge cut-off voltage U. The energy of the above discharge process is denoted as the discharge energy E1. The energy density of the lithium-ion battery is calculated by the following formula: Energy density (Wh / L) = E1 / V.

[0097] Example 1

[0098] <Preparation of the third electrode sheet>

[0099] A lithium-copper composite tape is used as the third electrode sheet, where a lithium metal layer with a thickness of 10 μm is used as the third electrode sheet material layer, and a copper foil with a thickness of 6 μm is used as the third electrode sheet current collector. The third electrode sheet material layer is disposed on one surface of the third electrode sheet current collector. The size of the third electrode sheet material layer is 100 mm × 40 mm, and the V2 value and Q value are shown in Table 1.

[0100] <Preparation of the negative electrode sheet>

[0101] The negative electrode active material artificial graphite, the negative electrode active material silicon-carbon composite material (mass ratio of silicon element to carbon element is 1:1), the negative electrode binder polyacrylic acid, and the negative electrode conductive agent acetylene black are mixed according to a mass ratio of 77.6:19.4:2.8:0.2, and deionized water is added as a solvent to prepare a slurry with a solid content of 45 wt%. After being stirred evenly by a vacuum mixer, a negative electrode slurry is obtained. The negative electrode slurry is uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 6 μm and dried at 80 °C to obtain a negative electrode sheet with a single-sided coated negative electrode material layer. Then, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coated negative electrode material layer. After drying at 80 °C, it is cold-pressed, and then cut into pieces and welded with electrode tabs to obtain a negative electrode sheet with a specification of 78 mm × 875 mm for use. Among them, the thickness of the single-sided negative electrode material layer is 31 μm, and the compaction density of the negative electrode material layer is 1.7 g / cm 3 。

[0102] <Preparation of the positive electrode sheet>

[0103] The positive electrode active material lithium cobalt oxide (LiCoO2), the positive electrode conductive agent conductive carbon black (Super P), and the positive electrode binder polyvinylidene fluoride are mixed in a mass ratio of 97.8:1.4:0.8, and N-methylpyrrolidone (NMP) is added as a solvent to prepare a slurry with a solid content of 75wt%, and the positive electrode slurry is obtained after vacuum stirring. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10μm, and dried at 90°C to obtain a positive electrode sheet with a single-sided positive electrode material layer. Then repeat the above steps on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode material layer. After drying at 90°C, cold pressing is performed, and then cutting and welding of the pole ears are performed to obtain a positive electrode sheet with a specification of 74mm×867mm for standby use. Among them, the thickness of the single-sided positive electrode material layer is 42μm, and the compaction density of the positive electrode material layer is 4.3g / cm 3 .

[0104] <Isolation film>

[0105] A polyethylene porous polymer film with a thickness of 5 μm (manufacturer: Celgard Membrane Co., Ltd., USA) was used as a separator.

[0106] <Preparation of Electrolyte>

[0107] In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) are uniformly mixed at a mass ratio of 10:30:60 to obtain a base solvent, and lithium salt LiPF6 is added and stirred to obtain an electrolyte. Among them, based on the total mass of the electrolyte, the mass percentage of lithium salt LiPF6 is 12.5%, and the remainder is the base solvent.

[0108] <Preparation of lithium-ion batteries>

[0109] The positive electrode sheet, the separator, the negative electrode sheet, and the separator are stacked in order, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then they are wound to obtain a wound body. The third electrode sheet is placed on the outer surface of the above-mentioned wound body, and a separator is placed between the third electrode sheet and the wound body to separate them. A one-way electron conduction switching device is connected between the third electrode sheet and the negative electrode sheet to obtain an electrode assembly, wherein the positive electrode of the one-way electron conduction switching device is welded and fixed to the pole ear of the negative electrode sheet, and the negative electrode of the one-way electron conduction switching device is welded and fixed to the third electrode sheet. The number, connection method and electron conduction voltage V3 of the one-way electron conduction switching device are shown in Table 1. The electrode assembly is placed in an aluminum-plastic film packaging bag, and the moisture is removed at 80°C, and the prepared electrolyte is injected. After vacuum packaging, standing, formation, and shaping processes, a lithium-ion battery (structure reference Figure 1), where the formation upper limit voltage is 4.53 V, the formation temperature is 85 °C, and the formation time is 60 min.

[0110] Examples 2 to 3

[0111] Except for adjusting the discharge cut-off voltage U and preparation parameters of the lithium-ion battery according to Table 1, the rest are the same as in Example 1.

[0112] Example 4

[0113] Except for adjusting the corresponding preparation parameters according to Table 1 and using the following preparation method for <Preparation of the third electrode>, the rest are the same as in Example 1.

[0114] <Preparation of the third electrode>

[0115] Mix the active material artificial graphite of the third electrode, the binder polyacrylic acid of the third electrode, and the conductive agent acetylene black of the third electrode in a mass ratio of 97:2.8:0.2, add deionized water as a solvent, and formulate it into a slurry with a solid content of 45 wt%. After stirring evenly with a vacuum mixer, the slurry of the third electrode material layer is obtained. The slurry of the third electrode material layer is evenly coated on one surface of a third electrode current collector copper foil with a thickness of 6 μm, dried at 80 °C and then cold-pressed, and then cut into pieces and welded with pole ears to obtain a third electrode with a specification of 100 mm × 40 mm for use. Among them, the thickness of the third electrode material layer is 117 μm, and the compaction density of the third electrode material layer is 1.8 g / cm 3 . Perform prelithiation treatment in a dry environment. Stack the third electrode, the separator, and lithium metal in sequence, inject the electrolyte and seal to obtain a half-cell, and discharge at 0.1C for 10 h to intercalate lithium into the third electrode. Among them, based on the mass of the third electrode material layer, the mass percentage content of active lithium elements, V2 value, and Q value in the third electrode material layer are shown in Table 1.

[0116] Example 5

[0117] Except for adjusting the corresponding preparation parameters according to Table 1, the rest are the same as in Example 4. Among them, the mass percentage content of active lithium elements in the third electrode material layer is regulated by controlling the prelithiation treatment time, and at the same time, the capacity Q provided by the voltage platform when the active material of the third electrode undergoes an electrochemical reaction to deintercalate lithium is adjusted by adjusting the size of the third electrode material layer as shown in Table 1.

[0118] Examples 6 to 16

[0119] Except for adjusting the corresponding preparation parameters according to Table 1, the rest are the same as in Example 1. Among them, the capacity Q provided by the voltage platform when the active material of the third electrode undergoes an electrochemical reaction to deintercalate lithium is regulated by controlling the size of the third electrode material layer.

[0120] Example 17

[0121] Except that the preparation method of <Preparation of Lithium-Ion Battery> is as follows, the rest is the same as in Example 1.

[0122] <Preparation of Lithium-Ion Battery>

[0123] Except that the third electrode sheet is disposed in the empty foil area of the positive current collector and is located in the inner empty foil area of the electrode assembly after winding, the rest is the same as in Example 1.

[0124] Example 18

[0125] Except that the corresponding preparation parameters are adjusted according to Table 1, the rest is the same as in Example 1. Among them, the mass ratio of silicon element to oxygen element in the silicon-oxygen composite material is 1:1.5.

[0126] Comparative Example 1

[0127] Except that <Preparation of the Third Electrode Sheet> is not included and the preparation method of <Preparation of Lithium-Ion Battery> is as follows, the rest is the same as in Example 1.

[0128] <Preparation of Lithium-Ion Battery>

[0129] Stack the positive electrode sheet, separator, negative electrode sheet, and separator in sequence, with the separator in the middle of the positive electrode sheet and the negative electrode sheet to play a role in isolation, and wind to obtain an electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag, dehydrated at 80 °C, injected with the prepared electrolyte, and a lithium-ion battery is obtained through vacuum packaging, standing, formation, and shaping processes. Among them, the upper limit voltage of formation is 4.53 V, the formation temperature is 85 °C, and the formation time is 60 min. The structure of the prepared lithium-ion battery refers to Figure 2 , and the electrode assembly includes a positive electrode sheet 1, a separator 2, and a negative electrode sheet 3, and a separator 2 is disposed between the positive electrode sheet 1 and the negative electrode sheet 3.

[0130] Comparative Examples 2 to 3

[0131] Except that the discharge cut-off voltage U of the lithium-ion battery is adjusted according to Table 1, the rest is the same as in Comparative Example 1.

[0132] Comparative Examples 4 to 5

[0133] Except that the corresponding preparation parameters are adjusted according to Table 1, the rest is the same as in Example 1.

[0134] Comparative Example 6

[0135] Except that the corresponding preparation parameters are adjusted according to Table 1, the rest is the same as in Example 4. Among them, the capacity Q provided by the voltage platform when the active material of the third electrode sheet undergoes an electrochemical reaction to de-lithiate is as shown in Table 1 by adjusting the size of the third electrode sheet material layer.

[0136] The preparation parameters and performance parameters of each example and comparative example are shown in Table 1.

[0137]

[0138]

[0139] It can be seen from Examples 1 to 18 and Comparative Examples 1 to 6 that in this application, by introducing a third electrode into the lithium-ion battery and setting a unidirectional electron conduction switch device between the third electrode and the negative electrode, such that V2 < V4 and V1 - V2 < V3 < V4 - V2 are satisfied simultaneously, the time from the fully discharged state of the lithium-ion battery to the start of gas production is longer and the energy density is higher, indicating that this application can reduce the risk of gas production in the lithium-ion battery at low voltages and improve the energy density and safety of the lithium-ion battery. For the lithium-ion batteries of Comparative Examples 1 to 3, the third electrode is not included, and for the lithium-ion batteries of Comparative Examples 4 to 6, V2 < V4 and V1 - V2 < V3 < V4 - V2 are not satisfied simultaneously. The time from the fully discharged state of the lithium-ion battery to the start of gas production is shorter and the energy density is lower, indicating that they cannot reduce the risk of gas production in the lithium-ion battery at low voltages and improve the energy density and safety of the lithium-ion battery.

[0140] The value of the discharge cut-off voltage U affects the gas production situation and energy density of the lithium-ion battery. It can be seen from Examples 1 to 3 that when the value of the discharge cut-off voltage U is within the scope of this application, the time from the fully discharged state of the lithium-ion battery to the start of gas production is longer and the energy density is higher, indicating that this application can reduce the risk of gas production in the lithium-ion battery at low voltages and improve the energy density and safety of the lithium-ion battery.

[0141] The type of active material of the third electrode affects the gas production situation and energy density of the lithium-ion battery. It can be seen from Example 1 and Examples 4 to 5 that by selecting the active material of the third electrode within the scope of this application, the time from the fully discharged state of the lithium-ion battery to the start of gas production is longer and the energy density is higher, indicating that this application can reduce the risk of gas production in the lithium-ion battery at low voltages and improve the energy density and safety of the lithium-ion battery.

[0142] The mass percentage content of active lithium element in the third electrode material layer affects the gas production situation and energy density of the lithium-ion battery. It can be seen from Example 1 and Examples 4 to 5 that when the mass percentage content of active lithium element in the third electrode material layer is within the scope of this application, the time from the fully discharged state of the lithium-ion battery to the start of gas production is longer and the energy density is higher, indicating that this application can reduce the risk of gas production in the lithium-ion battery at low voltages and improve the energy density and safety of the lithium-ion battery.

[0143] The value of the capacity Q provided by the voltage plateau when the third electrode active material undergoes an electrochemical reaction to de-lithiate affects the gas generation situation and energy density of the lithium-ion battery. It can be seen from Example 1, Examples 6 to 9 that when the value of the capacity Q provided by the voltage plateau when the third electrode active material undergoes an electrochemical reaction to de-lithiate is within the scope of this application, the time from the full discharge state of the lithium-ion battery to the start of gas generation is longer and the energy density is higher, indicating that this application can reduce the risk of gas generation in the lithium-ion battery at low voltages and improve the energy density and safety of the lithium-ion battery.

[0144] The type of the unidirectional electron conduction switch device affects the gas generation situation and energy density of the lithium-ion battery. It can be seen from Example 1, Examples 10 to 16 that when the unidirectional electron conduction switch device within the scope of this application is selected, the time from the full discharge state of the lithium-ion battery to the start of gas generation is longer and the energy density is higher, indicating that this application can reduce the risk of gas generation in the lithium-ion battery at low voltages and improve the energy density and safety of the lithium-ion battery.

[0145] The position of the third electrode affects the gas generation situation and energy density of the lithium-ion battery. It can be seen from Example 1 and Example 17 that when the position of the third electrode is within the scope of this application, the time from the full discharge state of the lithium-ion battery to the start of gas generation is longer and the energy density is higher, indicating that this application can reduce the risk of gas generation in the lithium-ion battery at low voltages and improve the energy density and safety of the lithium-ion battery.

[0146] The type of the negative electrode active material affects the gas generation situation and energy density of the lithium-ion battery. It can be seen from Example 1 and Example 18 that when the negative electrode active material within the scope of this application is selected, the time from the full discharge state of the lithium-ion battery to the start of gas generation is longer and the energy density is higher, indicating that this application can reduce the risk of gas generation in the lithium-ion battery at low voltages and improve the energy density and safety of the lithium-ion battery.

[0147] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method or article including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method or article.

[0148] Each embodiment in this specification is described in a related manner. For the same or similar parts between each embodiment, reference can be made to each other. The key point of each embodiment is to illustrate the differences from other embodiments.

[0149] The foregoing are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the scope of protection of the present application.

Claims

1. A secondary battery, comprising an electrode assembly, the electrode assembly including a positive electrode tab, a negative electrode tab, and a third electrode tab, the third electrode tab being connected to the negative electrode tab through a unidirectional electron conduction switch device, the third electrode tab including a third electrode current collector and a third electrode material layer provided on at least one surface of the third electrode current collector, the third electrode material layer including a third electrode active material; The potential of the negative electrode tab at the discharge cut-off voltage of the secondary battery is V1 V, the potential of the negative electrode tab corresponding to the start of over-discharge gas generation of the secondary battery is V4 V, the voltage plateau when the third electrode active material undergoes an electrochemical reaction to de-lithiate is V2 V, V2 < V4, the electron conduction voltage of the unidirectional electron conduction switch device is V3 V, V1 - V2 < V3 < V4 - V2.

2. The secondary battery according to claim 1, wherein, The discharge cut-off voltage of the secondary battery is U V, 2.5 ≤ U ≤ 3.

0.

3. The secondary battery according to claim 1, wherein, The third electrode active material includes at least one of lithium metal, lithium alloy, silicon-containing material, graphite, hard carbon, or lithium titanate.

4. The secondary battery according to claim 1, wherein, Based on the mass of the third electrode material layer, the mass percentage content of active lithium element in the third electrode material layer is 20% to 100%.

5. The secondary battery according to any one of claims 1 to 4, wherein, The capacity provided by the voltage plateau when the third electrode active material undergoes an electrochemical reaction to de-lithiate is Q mAh, 5 ≤ Q ≤ 600.

6. The secondary battery according to any one of claims 1 to 4, wherein, The negative electrode tab includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector, the negative electrode material layer including a negative electrode active material, the negative electrode active material including a silicon-containing material, the silicon-containing material including at least one of a silicon-carbon composite material, a silicon-oxygen composite material, or elemental silicon.

7. The secondary battery according to claim 6, wherein, The negative electrode active material further includes at least one of graphite, hard carbon, tin, or zinc.

8. The secondary battery according to any one of claims 1 to 4, wherein, The unidirectional electron conduction switch device includes at least one of a polar diode, a unidirectional transistor, or a chip with a unidirectional conduction function.

9. The secondary battery according to any one of claims 1 to 4, wherein, The positive electrode of the unidirectional electron conduction switch device is connected to the negative electrode tab, and the negative electrode of the unidirectional electron conduction switch device is connected to the third electrode tab.

10. The secondary battery according to any one of claims 1 to 4, wherein, The secondary battery satisfies any one of the following characteristics: (1) The secondary battery further includes a housing, and the third electrode tab is disposed on the outer surface of the electrode assembly, adjacent to the housing; (2) The electrode assembly is a wound structure, and the third electrode tab is disposed in the inner layer empty foil area of the electrode assembly; (3) The third electrode tab is disposed between the positive electrode tab and the negative electrode tab.

11. An electronic device, comprising the secondary battery according to any one of claims 1 to 10.

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