Pre-lithiation pole piece and preparation method thereof, secondary battery and electric device

Abstract

The present application relates to the technical field of secondary batteries, and in particular to a pre-lithiation pole piece and a preparation method thereof, a secondary battery and an electrical device. The pre-lithiation pole piece includes a current collector and an active material layer disposed on at least one surface of the current collector; a lithium replenishing layer is disposed between the current collector and at least one active material layer; wherein the surface roughness of the current collector is 2μm to 5μm, and the active material layer is a porous structure. By adopting a current collector with a certain surface roughness, it is possible to carry the lithium replenishing material to form a lithium replenishing layer. Without changing the traditional battery cell structure, the active lithium can be released through the pores of the active material layer to replenish the lithium of the battery. The pre-lithiation pole piece has a simple structure and can be produced using the existing pole piece preparation process. No new equipment is required, which can effectively reduce production costs.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a pre-lithiation electrode and a preparation method thereof, a secondary battery and an electrical device. Background Art

[0002] During the first charge of a lithium-ion battery, the formation of the solid electrolyte interface (SEI) film will permanently consume a large amount of lithium from the positive electrode, resulting in a low coulombic efficiency (ICE) of the first cycle, which reduces the capacity and energy density of the lithium-ion battery. In order to solve this problem and further improve the capacity and energy density of lithium-ion batteries, people have developed "pre-lithiation technology", which is to add lithium to the battery before the lithium-ion battery works to replenish lithium ions, also known as "pre-lithiation technology" or "lithium replenishment technology", thereby offsetting the lithium loss caused by the formation of the SEI film and avoiding the reduction of battery performance. However, since most lithium replenishers have poor stability in the air, pre-lithiation often requires major changes to the traditional electrode structure and preparation process to avoid the inactivation of the lithium replenisher, which greatly increases the production cost. Summary of the invention

[0003] Based on this, it is necessary to provide a pre-lithiation electrode sheet and its preparation method, a secondary battery and an electrical device having a simple structure and capable of being produced using an existing electrode preparation process.

[0004] In a first aspect of the present application, a pre-lithiation electrode is provided, which comprises a current collector and an active material layer disposed on at least one surface of the current collector; a lithium supplement layer is disposed between the current collector and at least one of the active material layers;

[0005] The surface roughness of the current collector is 2 μm to 5 μm, and the active material layer is a porous structure.

[0006] By using a current collector with a certain surface roughness, it is possible to carry lithium replenishment materials and form a lithium replenishment layer. Without changing the traditional battery cell structure, active lithium can be released through the pores of the active material layer to replenish lithium for the battery. The pre-lithiation pole piece has a simple structure and can be produced using existing pole piece preparation processes. No new equipment is required, which can effectively reduce production costs.

[0007] In some embodiments, the Dv50 particle size of the lithium supplement agent in the lithium supplement layer is ≤2 μm. The appropriate particle size enables the lithium supplement agent to be better embedded in the pits on the rough surface of the current collector, and the formed lithium supplement layer has better adhesion to the current collector, and the surface is flat without mottled spots that affect the coating of subsequent film layers.

[0008] In some embodiments, the amount of the lithium replenisher in the lithium replenishing layer is 1% to 5% of the mass of the active material in the active material layer. The amount of the lithium replenisher is controlled within a suitable range, while meeting the basic lithium replenishment requirements of the battery, the proportion of active materials will not be reduced too much, and the reduction of the volume capacity of the battery is avoided.

[0009] In some embodiments, the thickness of the lithium replenishment layer is 1 μm to 2 μm. The appropriate thickness of the lithium replenishment layer can meet the lithium replenishment requirements while avoiding excessive collapse of the pole piece after lithium replenishment is completed, and will not occupy too much space on the pole piece, resulting in a reduction in battery volume and capacity.

[0010] In some embodiments, the porosity of the active material layer is 20% to 40%. The porosity of the active material layer is slightly larger than that of the active material layer in a conventional electrode, which can enable better migration of active lithium and prevent the lithium replenishment speed from being too fast, causing adverse effects such as lithium precipitation.

[0011] In some embodiments, the pre-lithiation electrode is a positive electrode, and the porosity of the active material layer is 20% to 30%. Since the oxidation voltage on the positive electrode side is relatively high, the lithium replenishing material is easy to release active lithium, and setting the porosity to be relatively small is conducive to controlling the lithium replenishing rate.

[0012] In some embodiments, the pre-lithiation electrode is a negative electrode, and the porosity of the active material layer is 30% to 40%. The reduction voltage of the negative electrode is low, and the lithium replenishment material is released slowly, so a larger porosity is required to increase the lithium replenishment rate to a more suitable range.

[0013] In some embodiments, the pre-lithiation electrode is a positive electrode, and the lithium replenisher in the lithium replenishing layer includes Li 1+x Ni 0.5 Mn 1.5 O4, Li2NiO2, Li5FeO4, LiF, Li2S, Li2C2O4, LiMn2O4; one or more of Li2O2, Li2O and Li3N, wherein the value of x is selected from any value between 0 and 1.

[0014] In some embodiments, the pre-lithiated electrode is a negative electrode, and the lithium replenishing agent in the lithium replenishing layer includes one or more of lithium powder and pre-lithiated graphite.

[0015] In some embodiments, a conductive layer is provided between at least one of the lithium replenishment layers and the active material layer, and the conductive layer is a porous structure. The introduction of the conductive layer can better passivate the lithium replenishment agent and prevent the lithium replenishment agent from being deactivated due to contact with water and oxygen; in addition, after the lithium replenishment is completed, the conductive layer can play a supporting role to prevent the pole piece from collapsing and demolding; further, the provision of the conductive layer can also make the active material layer more evenly coated, balance the contact resistance between the pole pieces, and prevent the active material from being released unevenly.

[0016] In some embodiments, the porosity of the conductive layer is 40% to 50%. The appropriate porosity of the conductive layer can not only achieve the regulation of the lithium replenishment rate, but also make the conductive layer have a certain rigidity, can provide support, and avoid the collapse of the pole piece after the lithium replenishment is completed.

[0017] In some embodiments, the pre-lithiation electrode is a positive electrode, and the porosity of the conductive layer is 40% to 45%. Since the oxidation voltage on the positive electrode side is relatively high, the lithium replenishing material is easy to release active lithium, and setting the porosity to be relatively small is conducive to controlling the lithium replenishing rate.

[0018] In some embodiments, the pre-lithiation electrode is a negative electrode, and the porosity of the conductive layer is 45% to 50%. The reduction voltage of the negative electrode is low, and the lithium replenishment material is released slowly, so a larger porosity is required to increase the lithium replenishment rate to a more suitable range.

[0019] In some embodiments, the thickness of the conductive layer is 1 μm to 2 μm. The thickness of the conductive layer also needs to be controlled within a suitable range to better achieve the aforementioned support, control the lithium replenishment rate and uniform contact resistance, while not occupying too much space and causing a decrease in the volume capacity of the battery.

[0020] In some embodiments, the conductive layer includes a conductive agent and a binder.

[0021] In some embodiments, the conductive agent includes one or more of conductive graphite, conductive carbon black, carbon fiber, carbon nanotube, and graphene.

[0022] In some embodiments, the binder includes one or more of acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, polyacrylic acid, polytetrafluoroethylene, and polyvinylidene fluoride. A suitable binder can provide sufficient bonding force and make the conductive agent disperse evenly without agglomeration, so as to better play the role of the conductive layer.

[0023] In some embodiments, the mass ratio of the conductive agent to the binder is 1:(0.03-0.07). A suitable ratio of the conductive agent to the binder can make the conductive agent disperse evenly, not agglomerate, have good adhesion and not release from the mold, and at the same time, can make the electrode have a smaller resistance.

[0024] In some embodiments, the conductive layer further includes inorganic nanoparticles.

[0025] In some embodiments, the inorganic nanoparticles include one or more of Au, Sn, ZnO, MoS2, and Al2O3. The introduction of suitable types of inorganic nanoparticles can increase the migration rate of active lithium, and combined with the control of parameters such as porosity, the overall balance and regulation of the lithium replenishment rate can be achieved.

[0026] In some embodiments, the mass ratio of the conductive agent to the inorganic nanoparticles is 1:(0.001-0.01). The appropriate ratio of the conductive agent to the inorganic nanoparticles can balance the conductivity and lithium affinity of the conductive layer, thereby improving the conductivity without affecting the transmission of active lithium.

[0027] In a second aspect of the present application, a method for preparing a pre-lithiation electrode is provided, which comprises the following steps:

[0028] Providing a current collector having a surface roughness of 2 μm to 5 μm, and preparing a lithium replenishing layer on at least one surface of the current collector;

[0029] An active material layer having a porous structure is prepared on the lithium replenishing layer.

[0030] In a third aspect of the present application, a secondary battery is provided, which includes the pre-lithiation electrode sheet described in one or more of the aforementioned embodiments.

[0031] In a fourth aspect of the present application, a battery module is provided, which includes the aforementioned secondary battery.

[0032] In a fifth aspect of the present application, a battery pack is provided, which includes the aforementioned battery module.

[0033] In a sixth aspect of the present application, there is provided an electrical device comprising one or more of the aforementioned secondary battery, battery module and battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of a secondary battery according to one embodiment of the present application.

[0035] Figure 2 yes Figure 1 An exploded view of a secondary battery according to an embodiment of the present application is shown.

[0036] Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0037] Figure 4 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0038] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0039] Figure 6 FIG. 1 is a schematic diagram of an electric device using a secondary battery according to an embodiment of the present application as a power source.

[0040] Description of reference numerals:

[0041] 1: battery pack; 2: upper box; 3: lower box; 4: battery module; 5: secondary battery; 51: shell; 52: electrode assembly; 53: cover plate; 6: power-consuming device. DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0043] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the invention, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of the present application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0045] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0046] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0047] The percentage contents involved in this application, unless otherwise specified, refer to mass percentage for solid-liquid mixing and solid-solid mixing, and refer to volume percentage for liquid-liquid mixing.

[0048] The percentage concentrations mentioned in this application, unless otherwise specified, refer to the final concentration, which refers to the percentage of the added component in the system after the addition of the component.

[0049] The temperature parameters in this application, unless otherwise specified, allow for both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range of instrument control.

[0050] Due to the formation of SEI film, some lithium ions will be consumed, which will increase the irreversible capacity of the battery's first charge and discharge, and reduce the charge and discharge efficiency and cycle performance of the electrode material. In order to replenish these consumed lithium ions, the pole piece needs to be treated with lithium replenishment. However, in traditional technology, in order to achieve lithium replenishment, the pole piece structure often needs to be redesigned, which is quite different from the existing pole piece structure, and it is inconvenient to use existing processing equipment for processing, which greatly increases the production cost. In addition, traditional technology rarely involves the regulation of the lithium replenishment rate, and it is impossible to achieve long-term lithium replenishment, which has limited effect on improving the battery life.

[0051] Based on the above background, the first aspect of the present application provides a pre-lithiation electrode, which includes a current collector and an active material layer disposed on at least one surface of the current collector; a lithium supplement layer is disposed between the current collector and the at least one active material layer;

[0052] The surface roughness of the current collector is 2 μm to 5 μm, and the active material layer is a porous structure.

[0053] By using a current collector with a certain surface roughness, it is possible to carry lithium replenishment materials and form a lithium replenishment layer. Without changing the traditional battery cell structure, active lithium can be released through the pores of the active material layer to replenish lithium for the battery. The pre-lithiation pole piece has a simple structure and can be produced using existing pole piece preparation processes. No new equipment is required, which can effectively reduce production costs.

[0054] The surface roughness of the current collector is preferably 2μm to 3.5μm, and the surface roughness of the current collector can also be 2.5μm, 3μm, 3.5μm, 4μm or 4.5μm; the appropriate roughness can enable the current collector to have sufficient adhesion to the lithium replenisher, while avoiding excessive roughness that causes poor infiltration of the lithium replenisher electrolyte deep in the pits and affects the release.

[0055] In some embodiments, the Dv50 particle size of the lithium supplement agent in the lithium supplement layer is ≤2μm. Optionally, the Dv50 particle size of the lithium supplement agent can be, for example, 300nm to 2μm, or 500nm, 750nm, 1μm, 1.25μm, 1.5μm or 1.75μm. The appropriate particle size can make the lithium supplement agent better embedded in the pits on the rough surface of the current collector, and the formed lithium supplement layer has better adhesion with the current collector, and the surface is flat, and there will be no mottled effect on the coating of subsequent film layers.

[0056] In this application, Dv50 particle size refers to the particle size corresponding to the cumulative volume distribution number of particles reaching 50% in the volume cumulative distribution curve of particle size. Its physical meaning is that the volume of particles with a particle size less than (or greater than) this particle size value accounts for 50%. As an example, Dv50 can be conveniently measured by a laser particle size analyzer with reference to GB / T 19077-2016 particle size distribution laser diffraction method, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK.

[0057] In some embodiments, the amount of the lithium replenisher in the lithium replenishing layer is 1% to 5% of the mass of the active material in the active material layer, and the amount of the lithium replenisher can also be, for example, 2%, 3% or 4%. The amount of the lithium replenisher is controlled within a suitable range, while meeting the basic lithium replenishment requirements of the battery, the proportion of active materials will not be reduced too much, and the reduction of the volume capacity of the battery is avoided.

[0058] In some embodiments, the thickness of the lithium replenishment layer is 1 μm to 2 μm. Optionally, the thickness of the lithium replenishment layer can also be, for example, 1.25 μm, 1.5 μm or 1.75 μm. The appropriate thickness of the lithium replenishment layer can meet the lithium replenishment requirements while avoiding excessive collapse of the pole piece after the lithium replenishment is completed, and will not occupy too much space on the pole piece, resulting in a reduction in the volume and capacity of the battery.

[0059] In some embodiments, the porosity of the active material layer is 20% to 40%. Optionally, the thickness of the active material layer may be, for example, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36% or 38%. The porosity of the active material layer is slightly larger than that of the active material layer in a conventional pole piece, which enables better migration of active lithium and prevents the lithium replenishment speed from being too fast, causing adverse effects such as lithium precipitation.

[0060] In some embodiments, the pre-lithiation electrode is a positive electrode, and the porosity of the active material layer is 20% to 30%. Since the oxidation voltage on the positive electrode side is high, the lithium replenishing material is easy to release active lithium, and setting the porosity to be smaller is conducive to controlling the lithium replenishing rate.

[0061] In some embodiments, the pre-lithiation electrode is a negative electrode, and the porosity of the active material layer is 30% to 40%. The reduction voltage of the negative electrode is low, and the lithium replenishment material is released slowly, so a larger porosity is required to increase the lithium replenishment rate to a more suitable range.

[0062] In some embodiments, the pre-lithiation electrode is a positive electrode, and the lithium replenishing agent in the lithium replenishing layer includes Li 1+ x Ni 0.5 Mn 1.5 O4, Li2NiO2, Li5FeO4, LiF, Li2S, Li2C2O4, LiMn2O4; one or more of Li2O2, Li2O and Li3N, wherein the value of x is selected from any value between 0 and 1, and optionally, x is 0, 0.5 or 1.

[0063] In some embodiments, the pre-lithiated electrode is a negative electrode, and the lithium replenishing agent in the lithium replenishing layer includes one or more of lithium powder and pre-lithiated graphite.

[0064] In some embodiments, a conductive layer is provided between at least one lithium replenishment layer and the active material layer, and the conductive layer is a porous structure. The introduction of the conductive layer can better passivate the lithium replenishment agent and prevent the lithium replenishment agent from being deactivated due to contact with water and oxygen; in addition, after the lithium replenishment is completed, the conductive layer can play a supporting role to prevent the pole piece from collapsing and demolding; further, the provision of the conductive layer can also make the active material layer more evenly coated, balance the contact resistance between the pole pieces, and prevent the active material from being released unevenly.

[0065] It can be understood that the lithium supplement electrode in the present application can have any of the following structures:

[0066] (1) Active material layer A + lithium supplement layer A + current collector;

[0067] (2) Active material layer A + lithium supplement layer A + current collector + active material layer B;

[0068] (3) Active material layer A + lithium replenishing layer A + current collector + lithium replenishing layer B + active material layer B;

[0069] (4) active material layer A + conductive layer A + lithium supplement layer A + current collector;

[0070] (5) active material layer A + conductive layer A + lithium replenishing layer A + current collector + active material layer B;

[0071] (6) Active material layer A+conductive layer A+lithium replenishing layer A+current collector+lithium replenishing layer B+conductive layer B+active material layer B.

[0072] In some embodiments, the porosity of the conductive layer is 40% to 50%. Optionally, the thickness of the conductive layer may be, for example, 42%, 44%, 46% or 48%. The appropriate porosity of the conductive layer can not only achieve the regulation of the lithium replenishment rate, but also make the conductive layer have a certain rigidity, can provide support, and avoid the collapse of the pole piece after the lithium replenishment is completed.

[0073] In some embodiments, the pre-lithiation electrode is a positive electrode, and the porosity of the conductive layer is 40% to 45%. Since the oxidation voltage on the positive electrode side is high, the lithium replenishing material is easy to release active lithium, and setting the porosity to be smaller is conducive to controlling the lithium replenishing rate.

[0074] In some embodiments, the pre-lithiation electrode is a negative electrode, and the porosity of the conductive layer is 45% to 50%. The reduction voltage of the negative electrode is low, and the lithium replenishment material is released slowly, so a larger porosity is required to increase the lithium replenishment rate to a more suitable range.

[0075] In some embodiments, the thickness of the conductive layer is 1 μm to 2 μm. Optionally, the thickness of the conductive layer may be, for example, 1.25 μm, 1.5 μm or 1.75 μm. The thickness of the conductive layer also needs to be controlled within a suitable range, so as to better achieve the aforementioned support, control the lithium replenishment rate and uniform contact resistance, while not occupying too much space and causing a decrease in the volume capacity of the battery.

[0076] In some embodiments, the conductive layer includes a conductive agent and a binder.

[0077] In some embodiments, the conductive agent includes one or more of conductive graphite, conductive carbon black, carbon fiber, carbon nanotube and graphene. Preferably, the carbon fiber is chopped carbon fiber, and the length of the chopped carbon fiber is 2 mm to 4 mm.

[0078] In some embodiments, the binder includes one or more of acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, polyacrylic acid, polytetrafluoroethylene, and polyvinylidene fluoride. A suitable binder can provide sufficient bonding force and enable the conductive agent to be evenly dispersed without agglomeration, so as to better play the role of the conductive layer.

[0079] Preferably, the weight average molecular weight of the polyacrylic acid is 2000 Da to 3000 Da.

[0080] Preferably, the weight average molecular weight of polytetrafluoroethylene is 3w Da to 5w Da.

[0081] Preferably, the weight average molecular weight of the polyvinylidene fluoride is 40w Da to 50w Da.

[0082] In some embodiments, the mass ratio of the conductive agent to the binder is 1:(0.03-0.07). Optionally, the mass ratio of the conductive agent to the binder can also be, for example, 1:0.04, 1:0.05 or 1:0.06. A suitable ratio of the conductive agent to the binder can make the conductive agent dispersed evenly, not agglomerated, and have good adhesion without demolding, and at the same time, can make the electrode have a smaller resistance.

[0083] In some embodiments, the conductive layer further includes inorganic nanoparticles.

[0084] In some embodiments, the inorganic nanoparticles include one or more of Au, Sn, ZnO, MoS2, and Al2O3. The introduction of suitable types of inorganic nanoparticles can increase the migration rate of active lithium, and combined with the control of parameters such as porosity, the overall balance and regulation of the lithium replenishment rate can be achieved.

[0085] In some embodiments, the mass ratio of the conductive agent to the inorganic nanoparticles is 1:(0.001-0.01). Optionally, the mass ratio of the conductive agent to the inorganic nanoparticles can also be, for example, 1:0.002, 1:0.004, 1:0.006 or 1:0.008. A suitable ratio of the conductive agent to the inorganic nanoparticles can balance the conductivity and lithium affinity of the conductive layer, thereby achieving an improvement in conductivity without affecting the transmission of active lithium.

[0086] In a second aspect of the present application, a method for preparing a pre-lithiation electrode is provided, which comprises the following steps:

[0087] Providing a current collector with a surface roughness of 2 μm to 5 μm, and preparing a lithium replenishing layer on at least one surface of the current collector;

[0088] An active material layer having a porous structure is prepared on the lithium replenishing layer.

[0089] It can be understood that in the present application, preparing or forming the target layer B on a certain layer A includes preparing or forming the target layer B directly on this layer A, and also includes preparing or forming layer B on other layers C, D, etc. on this layer A. For example, "preparing an active material layer with a porous structure on the lithium replenishing layer" means: the active material layer can be directly prepared on the surface of the lithium replenishing layer, or other film layers, such as a conductive layer, can be first prepared on the surface of the lithium replenishing layer, and then the active material layer can be prepared on the surface of the conductive layer.

[0090] It can be understood that in the present application, the film layers prepared on the two surfaces of the current collector are independent of each other and are not affected. For example, a lithium replenishing layer and an active material layer can be prepared in sequence on one surface of the current collector, and only an active material layer can be prepared on the other surface; for another example, a lithium replenishing layer, a conductive layer and an active material layer can be prepared in sequence on one surface of the current collector, and only an active material layer can be prepared on the other surface, or a lithium replenishing layer and an active material layer can be prepared in sequence. Of course, the two surfaces can also be symmetrically distributed, with the film layers having the same structure.

[0091] In some embodiments, the lithium replenishing layer is prepared by a dry method. When the pre-lithiated electrode is a negative electrode, the lithium replenishing layer is preferably prepared by a dry method, and the lithium replenishing agent is pressed into the pits on the surface of the current collector by direct rolling.

[0092] In some embodiments, the lithium replenishing layer is prepared by wet coating. When the pre-lithiation electrode is a positive electrode, the lithium replenishing layer is preferably prepared by wet coating, and the lithium replenishing agent can be prepared into a dispersion with solvents such as N-methylpyrrolidone (NMP), ethanol, propylene glycol, and water, and then coated to prepare the lithium replenishing layer.

[0093] In a third aspect of the present application, a secondary battery is provided, which includes a pre-lithiation electrode according to one or more of the aforementioned embodiments.

[0094] In a fourth aspect of the present application, a battery module is provided, which includes the aforementioned secondary battery.

[0095] In a fifth aspect of the present application, a battery pack is provided, which includes the aforementioned battery module.

[0096] In a sixth aspect of the present application, there is provided an electrical device comprising one or more of the aforementioned secondary battery, battery module and battery pack.

[0097] In addition, the secondary battery, battery module, battery pack, and electric device of the present application will be described below with reference to the drawings as appropriate.

[0098] In one embodiment of the present application, a secondary battery is provided.

[0099] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0100] At least one of the positive electrode sheet and the negative electrode sheet of the secondary battery provided in the present application is the pre-lithiation electrode sheet provided in the first aspect of the present application. For example, the positive electrode sheet adopts the pre-lithiation electrode sheet provided in the first aspect of the present application, and the negative electrode sheet adopts the conventional negative electrode sheet, or the negative electrode sheet adopts the pre-lithiation electrode sheet provided in the first aspect of the present application, and the positive electrode sheet adopts the conventional positive electrode sheet. The structure, material, etc. of the conventional positive electrode sheet or negative electrode sheet are as follows:

[0101] Positive electrode

[0102] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.

[0103] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0104] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0105] In some embodiments, the positive electrode active material may adopt a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds, etc. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0106] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0107] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0108] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0109] Negative electrode

[0110] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0111] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0112] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0113] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0114] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0115] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0116] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0117] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0118] Electrolytes

[0119] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0120] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0121] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0122] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0123] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0124] Isolation film

[0125] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0126] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0127] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0128] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0129] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0130] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Figure 1 The secondary battery 5 is a square structure as an example.

[0131] In some embodiments, reference Figure 2 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0132] In some embodiments, secondary batteries may be assembled into a battery module. The number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0133] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0134] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0135] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0136] Figure 4 and Figure 5 1 is a battery pack 1 as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0137] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto. Among them, the mobile device may be, for example, a mobile phone, a laptop computer, etc.; the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc., but are not limited thereto.

[0138] As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

[0139] Figure 6 The power consumption device 6 is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the power consumption device's requirements for high power and high energy density of secondary batteries, a battery pack or a battery module can be used.

[0140] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

[0141] The present application is further described in detail below in conjunction with specific examples and comparative examples. Experimental parameters not specified in the following specific examples are preferably referred to the instructions given in the present application documents, and may also refer to the experimental manual of the art or other experimental methods known in the art, or refer to the experimental conditions recommended by the manufacturer. It is understandable that the instruments and raw materials used in the following examples are more specific, and in other specific embodiments, they may not be limited thereto; the weight of the relevant components mentioned in the embodiments of the present application specification may not only refer to the specific content of each component, but may also represent the proportional relationship of the weight between the components, therefore, as long as the content of the relevant components of the present application specification is proportionally enlarged or reduced, it is within the scope disclosed in the embodiments of the present application specification. Specifically, the weight described in the present application embodiment specification may be mass units known in the chemical and chemical fields such as μg, mg, g, and kg.

[0142] Example 1

[0143] (1) Preparation of positive electrode sheet

[0144] a. Li5FeO4 (Dv50 particle size 1.5μm, amount of 5% of the positive electrode active material) was selected as the lithium replenisher, and the lithium replenisher was divided into two equal parts, pressed on both sides of an aluminum current collector with a roughness of 3μm to obtain a lithium replenisher current collector comprising two lithium replenisher layers with a thickness of 1μm;

[0145] b. The conductive carbon, methyl acrylate, and nano-Sn particles are dispersed in N-methylpyrrolidone (NMP) in a mass ratio of 1:0.05:0.005, and coated on both sides of the lithium replenishment current collector prepared in step a to obtain a conductive lithium replenishment current collector comprising two conductive layers having a thickness of 1 μm;

[0146] c. NCM622, PVDF (polyvinylidene fluoride), and SP (conductive carbon) are mixed in a mass ratio of 80:10:10 to obtain a positive electrode active material; the positive electrode active material is dissolved in NMP (N-methylpyrrolidone) to prepare a positive electrode slurry, which is applied to both sides of the conductive lithium supplement current collector prepared in step b, and then dried and cold pressed to obtain a positive electrode sheet;

[0147] In the obtained positive electrode sheet, the porosity of the conductive layer is 40%, and the porosity of the positive electrode active material layer is 25%;

[0148] (2) Preparation of negative electrode sheet:

[0149] Graphite, SBR (styrene-butadiene rubber), and SP (conductive carbon) are mixed in a mass ratio of 90:5:5, then dissolved in deionized water, stirred evenly to obtain a negative electrode slurry, and coated on the surface of copper foil. After drying, it is cold pressed to obtain a negative electrode sheet.

[0150] (3) The positive electrode sheet, the separator, and the negative electrode sheet are wound, hot pressed, injected, and packaged to obtain a lithium-ion battery, and then subjected to formation (0.1C constant current charging to 3.0V, 0.2C constant current charging to 3.75V) and first-cycle lithium source activation (0.33C constant current charging to 4.50V, constant voltage charging to 0.05C, and 0.33C constant current discharge to 2.5V).

[0151] Example 2

[0152] The method is basically the same as that of Example 1, except that in step (1) a, the roughness of the aluminum current collector is 2 μm, and the thickness of the formed single-sided lithium replenishing layer is 1.1 μm.

[0153] Example 3

[0154] The method is basically the same as that of Example 1, except that in step (1) a, the roughness of the aluminum current collector is 5 μm, and the thickness of the formed single-sided lithium replenishing layer is 0.8 μm.

[0155] Example 4

[0156] The method is basically the same as Example 1, except that in step (1)a, the Dv50 particle size of Li5FeO4 is 3.5 μm, and the thickness of the single-sided lithium supplement layer is 3.5 μm.

[0157] Example 5

[0158] The method is basically the same as Example 1, except that in step (1) a, the Dv50 particle size of Li5FeO4 is 0.5 μm, and the thickness of the single-sided lithium supplement layer is 0.5 μm.

[0159] Example 6

[0160] The method is basically the same as that of Example 1, except that in step (1)a, the thickness of the single-sided conductive layer is 3 μm.

[0161] Example 7

[0162] The method is basically the same as Example 1, except that the porosity of the conductive layer of the positive electrode sheet obtained in step (1) is 35%.

[0163] Example 8

[0164] The method is basically the same as that of Example 1, except that the porosity of the conductive layer of the positive electrode sheet obtained in step (1) is 55%.

[0165] Example 9

[0166] The method is basically the same as that of Example 1, except that the porosity of the active material layer of the positive electrode sheet obtained in step (1) is 15%.

[0167] Example 10

[0168] The method is basically the same as Example 1, except that the porosity of the active material layer of the positive electrode sheet obtained in step (1) is 45%.

[0169] Embodiment 11

[0170] The method is basically the same as Example 1, except that step (1) b is not included, and the obtained positive electrode plate does not contain a conductive layer.

[0171] Example 12

[0172] The method is basically the same as Example 1, except that in step (1)a, the amount of lithium supplement agent used is 10% of the positive electrode active material.

[0173] Example 13

[0174] The method is basically the same as Example 1, except that in step (1) b, the mass ratio of conductive carbon, methyl acrylate and nano-Sn particles in the raw materials of the conductive layer is 1:0.01:0.005.

[0175] Embodiment 14

[0176] The method is basically the same as Example 1, except that in step (1) b, the mass ratio of conductive carbon, methyl acrylate and nano-Sn particles in the raw materials of the conductive layer is 1:0.1:0.005.

[0177] Embodiment 15

[0178] The method is basically the same as Example 1, except that in step (1) b, the mass ratio of conductive carbon, methyl acrylate and nano-Sn particles in the raw materials of the conductive layer is 1:0.05:0.02.

[0179] Example 16

[0180] The method is basically the same as Example 1, except that in step (1) a, the roughness of the aluminum current collector is 2 μm, and the amount of the lithium supplement agent is 3% of the positive electrode active material.

[0181] Embodiment 17

[0182] The method is basically the same as Example 1, except that in step (1)a, the lithium supplement is replaced by an equal mass of Li2O.

[0183] Embodiment 18

[0184] It is basically the same as Example 1, except that in step (1)a, the roughness of the aluminum current collector is 3.5 μm, and the lithium supplement is replaced by an equal mass of Li2NiO2.

[0185] Embodiment 19

[0186] (1) Preparation of positive electrode sheet

[0187] NCM622, PVDF (polyvinylidene fluoride), and SP (conductive carbon) are mixed in a mass ratio of 80:10:10 to obtain a positive electrode active material; the positive electrode active material is dissolved in NMP (N-methylpyrrolidone) to prepare a positive electrode slurry, which is coated on both sides of an aluminum current collector, dried, and then cold pressed to obtain a positive electrode sheet;

[0188] (2) Preparation of negative electrode sheet:

[0189] a. Lithium powder (Dv50 particle size 1.5 μm, amount of 1% of the negative electrode active material) was selected as the lithium replenisher, and the lithium replenisher was divided into two equal parts, pressed on both sides of a copper current collector with a roughness of 3 μm, to obtain a lithium replenisher current collector comprising two lithium replenisher layers with a thickness of 1 μm;

[0190] b. Conductive carbon, polytetrafluoroethylene (weight average molecular weight 40000Da), and nano ZnO particles are dispersed in N-methylpyrrolidone (NMP) in a mass ratio of 1:0.05:0.005, and coated on both sides of the lithium replenishment current collector prepared in step a to obtain a conductive lithium replenishment current collector comprising two conductive layers with a thickness of 1 μm;

[0191] c. Graphite, SBR (styrene-butadiene rubber), and SP (conductive carbon) were mixed in a mass ratio of 90:5:5, then dissolved in deionized water, stirred evenly to obtain a negative electrode slurry, applied to both sides of the conductive lithium supplement current collector prepared in step b, dried, and cold pressed to obtain a negative electrode sheet;

[0192] In the obtained negative electrode sheet, the porosity of the conductive layer is 45%, and the porosity of the positive electrode active material layer is 35%;

[0193] (3) The positive electrode sheet, the separator, and the negative electrode sheet are wound, hot pressed, injected, and packaged to obtain a lithium-ion battery, and then subjected to formation (0.1C constant current charging to 3.0V, 0.2C constant current charging to 3.75V) and first-cycle lithium source activation (0.33C constant current charging to 4.50V, constant voltage charging to 0.05C, and 0.33C constant current discharge to 2.5V).

[0194] Comparative Example 1

[0195] The method is basically the same as Example 11, except that step (1)a is not included, and the obtained positive electrode plate does not contain a lithium replenishing layer and a conductive layer.

[0196] Comparative Example 2

[0197] The method is basically the same as Example 1, except that in step (1) a, the Dv50 particle size of Li5FeO4 is 2 μm, the roughness of the aluminum current collector is 1 μm, and the thickness of the formed single-sided lithium replenishing layer is 1.3 μm.

[0198] Comparative Example 3

[0199] The method is basically the same as Example 1, except that in step (1) a, the Dv50 particle size of Li5FeO4 is 2 μm, the roughness of the aluminum current collector is 6 μm, and the thickness of the formed single-sided lithium replenishing layer is 0.7 μm.

[0200] Characterization Tests:

[0201] The batteries prepared in the above embodiments and comparative examples were subjected to the following performance tests:

[0202] (1) Battery first cycle capacity test:

[0203] The lithium-ion secondary battery was placed in a thermostat at 25°C, and charged at room temperature at a constant current of 0.5C until the voltage was higher than 4.35V, and further charged at a constant voltage of 4.35V until the current was lower than 0.05C, so that it was in a fully charged state of 4.35V, and then the lithium-ion secondary battery was discharged at a constant current of 0.33C until the voltage was 2.5V (cut-off voltage), which was one cycle. The discharge capacity D was recorded; the first-cycle discharge capacity D0 of the comparative example 1 without lithium supplementation was used as the benchmark, and the improvement of the first-cycle capacity of each embodiment relative to the comparative example 1 was calculated as (D-D0) / D0.

[0204] (2) Cycle life test:

[0205] Place the lithium-ion secondary battery in a 25°C constant temperature box, charge it at a constant current of 0.5C at room temperature until the voltage is higher than 4.35V, and further charge it at a constant voltage of 4.35V until the current is lower than 0.05C, so that it is in a fully charged state of 4.35V, and then discharge the lithium-ion secondary battery at a constant current of 0.33C until the voltage is 2.5V (cut-off voltage), which is 1 cycle. Repeat the cycle, record the discharge capacity D2 of each cycle, and stop the test when D2 / D1=80% and record the number of cycles.

[0206] Table 1

[0207]

[0208]

[0209] Analyzing the data in Table 1, compared with Example 1, the surface roughness of the current collector in Example 2 is smaller, the thickness of the lithium replenishing layer formed by the same amount of lithium replenishing agent is slightly increased, the adhesion to the lithium replenishing layer is slightly weaker, and the cycle performance is affected to a certain extent; the surface roughness of the current collector in Example 3 is larger, although the adhesion to the lithium replenishing layer is better, but part of the lithium replenishing agent deep in the pits on the surface of the current collector may not be released, so the cycle performance is also slightly reduced; in Example 4, the particle size of the lithium replenishing agent is too large, and the roughness of the current collector is poorly matched, so the adhesion is also poor, affecting the cycle performance; in Example 5, the particle size of the lithium replenishing agent is too small, and the lithium replenishing layer formed is too thin. Because the particles are too small, part of the lithium replenishing agent is buried deep in the pits of the current collector and cannot be released, which also affects the battery performance; in Example 6, the conductive layer is too thick, occupying more positions of the pole piece, affecting the pole piece In Example 7, the porosity of the conductive layer is relatively low, and part of the lithium supplement cannot be released well, which also affects the cycle performance to a certain extent; in Example 8, the porosity of the conductive layer is relatively high, and the lithium is released too quickly, which is not conducive to long-term lithium supplementation, so the cycle performance is reduced; Examples 9 and 10 are similar to the trends of Examples 7 and 8, and the cycle performance will also decrease; In Example 11, no conductive layer is included, and problems of demolding and too-fast lithium release are prone to occur; In Example 12, the amount of lithium supplement agent used is too high, which will lead to lithium precipitation and affect the proportion of active materials, thereby affecting the cycle performance; In Example 13, the amount of binder used in the conductive layer is relatively small, and there is a risk of demolding; In Example 14, the amount of binder used in the conductive layer is too much, which will increase the electrode impedance; In Example 15, the amount of lithium-philic inorganic nanoparticles used is relatively large, resulting in too-fast lithium release.

[0210] In Comparative Example 1, there is no lithium replenishing layer and conductive layer, and the cycle performance is greatly reduced; in Comparative Examples 2 and 3, the surface roughness is not within the preset range, which seriously affects the adhesion of the current collector surface to the lithium replenishing layer and the release of the lithium replenishing agent. Compared with the various embodiments, the cycle performance is also significantly reduced.

[0211] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0212] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims, and the description and drawings may be used to interpret the contents of the claims.

Claims

1. A pre-lithiation electrode, characterized in that: It comprises a current collector and an active material layer disposed on at least one surface of the current collector; a lithium supplement layer is disposed between the current collector and at least one of the active material layers; The surface roughness of the current collector is 2 μm to 5 μm, the active material layer is a porous structure, and the porosity of the active material layer is 20% to 40%.

2. The pre-lithiation electrode according to claim 1, characterized in that: The Dv50 particle size of the lithium supplement agent in the lithium supplement layer is ≤2 μm.

3. The pre-lithiation electrode according to claim 1, characterized in that: The amount of the lithium replenishing agent in the lithium replenishing layer is 1% to 5% of the mass of the active material in the active material layer.

4. The pre-lithiation electrode according to claim 1, characterized in that: The thickness of the lithium supplement layer is 1 μm to 2 μm.

5. The pre-lithiation electrode according to any one of claims 1 to 4, characterized in that: The pre-lithiation pole piece is a positive pole piece, and the porosity of the active material layer is 20% to 30%.

6. The pre-lithiation electrode according to any one of claims 1 to 4, characterized in that: The pre-lithiation pole piece is a negative pole piece, and the porosity of the active material layer is 30% to 40%.

7. The pre-lithiation electrode according to any one of claims 1 to 4, characterized in that: The pre-lithiation electrode is a positive electrode. The lithium replenisher in the lithium replenishing layer includes Li 1+x Ni 0.5 Mn 1.5 O4, Li2NiO2, Li5FeO4, LiF, Li2S, Li2C2O4, LiMn2O4; one or more of Li2O2, Li2O and Li3N, wherein the value of x is selected from any value between 0 and 1.

8. The pre-lithiation electrode according to any one of claims 1 to 4, characterized in that: The pre-lithiated electrode is a negative electrode, and the lithium replenishing agent in the lithium replenishing layer includes one or more of lithium powder and pre-lithiated graphite.

9. The pre-lithiation electrode according to any one of claims 1 to 4, characterized in that: A conductive layer is disposed between at least one of the lithium replenishing layers and the active material layer, and the conductive layer has a porous structure.

10. The pre-lithiation electrode according to claim 9, characterized in that: The porosity of the conductive layer is 40% to 50%.

11. The pre-lithiation electrode according to claim 9, characterized in that: The pre-lithiation pole piece is a positive pole piece, and the porosity of the conductive layer is 40% to 45%.

12. The pre-lithiation electrode according to claim 9, characterized in that: The pre-lithiation pole piece is a negative pole piece, and the porosity of the conductive layer is 45% to 50%.

13. The pre-lithiation electrode according to claim 9, characterized in that: The thickness of the conductive layer is 1 μm to 2 μm.

14. The pre-lithiation electrode according to claim 9, characterized in that: The conductive layer includes a conductive agent and a binder.

15. The pre-lithiation electrode according to claim 14, characterized in that: The conductive agent includes one or more of conductive graphite, conductive carbon black, carbon fiber, carbon nanotube and graphene.

16. The pre-lithiation electrode according to claim 14, characterized in that: The binder includes one or more of acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, polyacrylic acid, polytetrafluoroethylene and polyvinylidene fluoride.

17. The pre-lithiation electrode according to claim 14, characterized in that: The mass ratio of the conductive agent to the binder is 1:(0.03-0.07).

18. The pre-lithiation electrode according to claim 17, characterized in that: The conductive layer also includes inorganic nanoparticles.

19. The pre-lithiation electrode according to claim 18, characterized in that: The inorganic nanoparticles include one or more of Au, Sn, ZnO, MoS2 and Al2O3.

20. The pre-lithiation electrode according to claim 18, characterized in that: The mass ratio of the conductive agent to the inorganic nanoparticles is 1:(0.001-0.01).

21. A method for preparing a pre-lithiation electrode, characterized in that: The following steps are involved: Providing a current collector having a surface roughness of 2 μm to 5 μm, and preparing a lithium replenishing layer on at least one surface of the current collector; An active material layer with a porous structure is prepared on the lithium supplement layer, and the porosity of the active material layer is 20% to 40%.

22. A secondary battery, characterized in that: It comprises the pre-lithiation electrode sheet as described in any one of claims 1 to 20.

23. An electrical device, characterized in that: Includes the secondary battery as claimed in claim 22.

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