WO2024016891A1

WO2024016891A1 - Pre-lithiated electrode plate and preparation method therefor, secondary battery, and electric device

Info

Publication number: WO2024016891A1
Application number: PCT/CN2023/099576
Authority: WO
Inventors: 王绍衫; 何建福; 刘倩; 叶永煌
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2022-07-19
Filing date: 2023-06-12
Publication date: 2024-01-25
Also published as: CN115842096A

Abstract

The present application relates to the technical field of secondary batteries, and in particular relates to a pre-lithiated electrode plate and a preparation method therefor, a secondary battery and an electric device. The pre-lithiated electrode plate comprises a current collector and an active material layer, which is arranged on at least one surface of the current collector; and a lithium supplementing layer is arranged between the current collector and the at least one active material layer, wherein the surface roughness of the current collector is 2-5 μm, and the active material layer has a porous structure. By using the current collector having a certain surface roughness, the lithium supplementing material can be loaded thereon so as to form a lithium supplementing layer; and the release of active lithium can be achieved through the pores of the active material layer so as to supplement lithium to the battery, without the need for changing the traditional battery cell structure. The pre-lithiated electrode plate has a simple structure, and can be produced by using an existing electrode plate preparation process, no new equipment is required, and the production cost can be effectively reduced.

Description

Pre-lithiated pole piece and preparation method thereof, secondary battery and electrical device

This application requires the priority of the Chinese patent application submitted to the China Patent Office on July 19, 2022, with the application number 2022108465552 and the invention name "Pre-lithiated pole piece and its preparation method, secondary battery and electrical device", The entire contents of which are incorporated herein by reference.

Technical field

The present application relates to the technical field of secondary batteries, and in particular to a prelithiated pole piece and its preparation method, secondary batteries and electrical devices.

Background technique

During the first charging process of a lithium-ion battery, due to the formation of the solid electrolyte interface (SEI) film, a large amount of lithium from the positive electrode will be permanently consumed, causing the Coulombic efficiency (ICE) of the first cycle to be low, reducing the performance of the lithium-ion battery. capacity and energy density.

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 means to add lithium to the interior of the battery before the lithium-ion battery operates to achieve lithium ion replenishment, also known as "Pre-embedded lithium technology" or "lithium replenishment technology" can offset the lithium loss caused by the formation of SEI film and avoid the reduction of battery performance.

However, since most lithium supplementation agents have poor stability in the air, prelithiation often requires major changes to the traditional pole piece structure and preparation process to avoid the deactivation of the lithium supplementation agent, which greatly improves the efficiency of the lithium supplementation agent. Cost of production.

Contents of the invention

This application was made in view of the above-mentioned issues, and one of its purposes is to provide a pre-lithiated pole piece, which has a simple structure, can be produced using existing pole piece preparation processes, and has a low production cost.

In order to achieve the above objects, a first aspect of the present application provides a pre-lithium pole piece, which includes a current collector and an active material layer disposed on at least one surface of the current collector; the current collector and at least one A lithium replenishing layer is provided between the active material layers;

Wherein, the surface roughness of the current collector is 2 μm to 5 μm, and the active material layer has a porous structure.

By using a current collector with a certain surface roughness, it can carry lithium-replenishing materials and form a lithium-replenishing layer. Without changing the traditional cell structure, active lithium can be released through the pores of the active material layer to replenish lithium for the battery. The pre-lithiated pole piece has a simple structure and can be produced using existing pole piece preparation processes without the need for new equipment, which can effectively reduce production costs.

In some embodiments, the Dv50 particle size of the lithium replenishing agent in the lithium replenishing layer is ≤2 μm. Appropriate particle size can enable the lithium replenishing agent to be better embedded in the pits on the rough surface of the current collector. The formed lithium replenishing layer has better adhesion with the current collector, and the surface is smooth, and will not appear mottled and affect subsequent film layers. of coating.

In some embodiments, the amount of lithium replenishing agent in the lithium replenishing layer is 1% to 5% of the mass of the active material in the active material layer. Controlling the dosage of lithium replenishing agent within an appropriate range can meet the basic lithium replenishing needs of the battery without excessively reducing the proportion of active materials and avoiding a reduction in battery volume and capacity.

In some embodiments, the thickness of the lithium supplement layer is 1 μm to 2 μm. The appropriate thickness of the lithium replenishment layer can not only meet the needs of lithium replenishment, but also avoid excessive collapse of the pole piece after the lithium replenishment is completed, and will not occupy too much position of the pole piece, resulting in a reduction in battery volume and capacity.

In some embodiments, the active material layer has a porosity of 20% to 40%. The porosity of the active material layer is slightly larger than that of the active material layer in conventional pole pieces, which allows active lithium to migrate better without replenishing lithium too quickly, causing adverse effects such as lithium precipitation.

In some embodiments, the prelithiated electrode piece is a positive electrode piece, and the porosity of the active material layer is 20% to 30%. Since the oxidation voltage on the cathode side is high, the lithium replenishment material easily releases active lithium. Setting the porosity smaller is beneficial to controlling the lithium replenishment rate.

In some embodiments, the prelithiated electrode piece is a negative electrode piece, and the porosity of the active material layer is 30% to 40%. The reduction voltage on the negative electrode side is low and the lithium replenishment material releases slowly, so a larger porosity is needed to increase the lithium replenishment rate to a more appropriate range.

In some embodiments, the prelithiated electrode piece is a positive electrode piece, and the lithium replenishing agent in the lithium replenishing layer includes Li _1+x Ni _0.5 Mn _1.5 O ₄ , Li ₂ NiO ₂ , Li ₅ FeO ₄ , One or more of LiF, Li ₂ S, Li ₂ C ₂ O ₄ , LiMn ₂ O ₄ ; Li ₂ O ₂ , Li ₂ O and Li ₃ N, where the value of x is selected from 0 to 1 any value.

In some embodiments, the pre-lithium electrode piece is a negative electrode piece, and the lithium supplement layer in the lithium supplement layer The agent includes one or more of lithium powder and prelithiated graphite.

In some embodiments, a conductive layer is provided between at least one of the lithium replenishing layers and the active material layer, and the conductive layer has a porous structure. The introduction of the conductive layer can better passivate the lithium replenishing agent and prevent the lithium replenishing agent from being deactivated due to contact with water and oxygen; in addition, after the lithium replenishing is completed, the conductive layer can play a supporting role to avoid the collapse and demoulding of the pole piece; Furthermore, the arrangement of the conductive layer can also make the active material layer more uniformly coated, balance the contact resistance between the layers of the pole piece, and prevent the active material from being released evenly.

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

In some embodiments, the prelithiated electrode piece is a positive electrode piece, and the porosity of the conductive layer is 40% to 45%. Since the oxidation voltage on the cathode side is high, the lithium replenishment material easily releases active lithium. Setting the porosity smaller is beneficial to controlling the lithium replenishment rate.

In some embodiments, the prelithiated electrode piece is a negative electrode piece, and the porosity of the conductive layer is 45% to 50%. The reduction voltage on the negative electrode side is low and the lithium replenishment material releases slowly, so a larger porosity is needed to increase the lithium replenishment rate to a more appropriate range.

In some embodiments, the conductive layer has a thickness of 1 μm to 2 μm. The thickness of the conductive layer also needs to be controlled within an appropriate range, which can better achieve the aforementioned support, control the lithium replenishment rate and uniform contact resistance, without occupying too much space and causing a decrease in the volume capacity of the battery.

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

In some embodiments, the conductive agent includes one or more of conductive graphite, conductive carbon black, carbon fiber, carbon nanotubes, and graphene.

In some embodiments, the binder includes acrylic, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, polyacrylic acid, polytetrafluoroethylene and one or more of polyvinylidene fluoride. A suitable adhesive can provide sufficient bonding force, and at the same time enable the conductive agent to be dispersed evenly without agglomeration, allowing it to better function as a conductive layer.

In some embodiments, the mass ratio of the conductive agent and the binder is 1:(0.03-0.07). The appropriate dosage ratio of conductive agent and binder can make the conductive agent disperse evenly, not agglomerate, have good adhesion and not be demolded, and at the same time, it can make the pole piece have smaller resistance.

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

In some embodiments _, the inorganic nanoparticles include one or more of Au, Sn, ZnO, _MoS2 , and _Al2O3 . The introduction of appropriate types of inorganic nanoparticles can increase the migration rate of active lithium. Combined with the control of parameters such as porosity, the overall balance and regulation of the lithium replenishment rate can be achieved.

In some embodiments, the mass ratio of the conductive agent and the inorganic nanoparticles is 1:(0.001-0.01). The appropriate dosage ratio of conductive agent and inorganic nanoparticles can balance the conductivity and lithophilicity of the conductive layer, which can improve the conductivity without affecting the transport of active lithium.

A second aspect of this application provides a method for preparing pre-lithiated pole pieces, which includes the following steps:

Provide a current collector with a surface roughness of 2 μm to 5 μm, and prepare 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.

A third aspect of the present application provides a secondary battery, which includes the pre-lithiated electrode piece described in one or more of the aforementioned embodiments.

A fourth aspect of the present application provides a battery module, which includes the aforementioned secondary battery.

A fifth aspect of the present application provides a battery pack, which includes the aforementioned battery module.

A sixth aspect of the present application provides an electrical device, which includes one or more of the aforementioned secondary batteries, battery modules, and battery packs.

Description of drawings

To better describe and illustrate embodiments and/or examples of the present application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the figures should not be construed as limiting the scope of any of the disclosed applications, the embodiments and/or examples presently described, and the best mode currently understood of these applications.

Figure 1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

Figure 2 is an exploded view of the secondary battery according to an embodiment of the present application shown in Figure 1;

Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application;

Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application;

Figure 5 is an exploded view of the battery pack according to an embodiment of the present application shown in Figure 4;

FIG. 6 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.

Explanation of reference symbols:
1: Battery pack; 2: Upper box; 3: Lower box; 4: Battery module; 5: Secondary battery; 51:
Shell; 52: electrode assembly; 53: cover plate; 6: electrical device.

Detailed ways

In order to facilitate 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 shown in the accompanying drawings. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that a thorough understanding of the disclosure of the present application will be provided.

In addition, the terms “first” and “second” are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Therefore, features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the invention, "a plurality" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise expressly and specifically limited.

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

In this application, the technical features described in open format include closed technical solutions composed of the listed features, and also include open technical solutions including the listed features.

In this application, when it comes to numerical intervals, unless otherwise specified, the above numerical interval is considered to be continuous and includes the minimum value and maximum value of the range, as well as every value between such minimum value and maximum value. Further, when a range refers to an integer, every integer between the minimum value and the maximum value of the range is included. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to include any and all subranges subsumed therein.

The percentage contents involved in this application, unless otherwise stated, are for solid-liquid mixing and solid-phase Phase mixing refers to mass percentage, and for liquid-liquid phase mixing, it refers to volume percentage.

The percentage concentrations mentioned in this application refer to the final concentration unless otherwise specified. The final concentration refers to the proportion of the added component in the system after adding the component.

The temperature parameters in this application, unless otherwise specified, allow for constant temperature treatment or treatment within a certain temperature range. The thermostatic treatment described allows the temperature to fluctuate within the accuracy of the instrument control.

Due to the formation of the SEI film, part of the lithium ions will be consumed, which increases the irreversible capacity of the battery for the first charge and discharge and reduces the charge and discharge efficiency and cycle performance of the electrode material. In order to replenish this part of the consumed lithium ions, the electrode piece needs to be replenished with lithium. 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. 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 lithium replenishment rate, cannot achieve long-term lithium replenishment, and has limited improvement in battery life.

Based on the above background, the first aspect of the present application provides a pre-lithium pole piece, which includes a current collector and an active material layer disposed on at least one surface of the current collector; between the current collector and at least one active material layer It is equipped with a lithium supplement layer;

Among them, the surface roughness of the current collector is 2 μm to 5 μm, and the active material layer has a porous structure.

The surface roughness of the current collector is preferably 2 μm to 3.5 μm. The surface roughness of the current collector can also be 2.5 μm, 3 μm, 3.5 μm, 4 μm or 4.5 μm; appropriate roughness can make the current collector have sufficient resistance to the lithium replenishing agent. Adhesion, and at the same time, it can avoid excessive roughness, which will lead to poor infiltration of the lithium replenishing agent electrolyte deep in the pits and affect the release.

In some embodiments, the Dv50 particle size of the lithium replenishing agent in the lithium replenishing layer is ≤2 μm. Alternatively, the Dv50 particle size of the lithium supplement may be, for example, 300 nm to 2 μm, or may be 500 nm, 750 nm, 1 μm, 1.25 μm, 1.5 μm or 1.75 μm. Appropriate particle size can enable the lithium replenishing agent to be better embedded in the pits on the rough surface of the current collector. The formed lithium replenishing layer has better adhesion with the current collector, and the surface is smooth, and will not appear mottled and affect subsequent film layers. of coating.

In this application, Dv50 particle size refers to the particle size corresponding to when the cumulative volume distribution number of particles reaches 50% in the volume cumulative distribution curve of particle size. Its physical meaning is that the particle size is smaller (or larger) than this particle size. The volume proportion of the particles is 50%. As an example, Dv50 can be easily measured using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Co., Ltd. in the UK, referring to the GB/T19077-2016 particle size distribution laser diffraction method.

In some embodiments, the amount of lithium replenishing agent in the lithium replenishing layer is 1% to 5% of the mass of the active material in the active material layer. The amount of lithium replenishing agent may also be, for example, 2%, 3%, or 4%. Controlling the dosage of lithium replenishing agent within an appropriate range can meet the basic lithium replenishing needs of the battery without excessively reducing the proportion of active materials and avoiding a reduction in battery volume and capacity.

In some embodiments, the thickness of the lithium supplement layer is 1 μm˜2 μm. Optionally, the thickness of the lithium replenishing layer can be, for example, 1.25 μm, 1.5 μm, or 1.75 μm. The appropriate thickness of the lithium replenishment layer can not only meet the needs of lithium replenishment, but also avoid excessive collapse of the pole piece after the lithium replenishment is completed, and will not occupy too much position of the pole piece, resulting in a reduction in battery volume and capacity.

In some embodiments, the active material layer has a porosity of 20% to 40%. Alternatively, the thickness of the active material layer may also 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 conventional pole pieces, which allows active lithium to migrate better without replenishing lithium too quickly, causing adverse effects such as lithium precipitation.

In some embodiments, the prelithiated electrode piece is a positive electrode piece, and the lithium replenishing agent in the lithium replenishing layer includes Li _1+x Ni _0.5 Mn _1.5 O ₄ , Li ₂ NiO ₂ , Li ₅ FeO ₄ , LiF, Li ₂ One or more of S, Li ₂ C ₂ O ₄ , LiMn ₂ O ₄ ; Li ₂ O ₂ , Li ₂ O and Li ₃ N, where the value of x is selected from any value between 0 and 1, Optionally, x is 0, 0.5 or 1.

In some embodiments, the prelithiated electrode piece is a negative electrode piece, and the lithium replenishing agent in the lithium replenishing layer includes one or more of lithium powder and prelithiated graphite.

In some embodiments, a conductive layer is provided between at least one lithium supplement layer and the active material layer, and the conductive layer has a porous structure. The introduction of the conductive layer can better passivate the lithium replenishing agent and prevent the lithium replenishing agent from being deactivated due to contact with water and oxygen; in addition, after the lithium replenishing is completed, the conductive layer can play a supporting role to avoid the collapse and demoulding of the pole piece; Furthermore, the arrangement of the conductive layer can also make the active material layer more uniformly coated, balance the contact resistance between the layers of the pole piece, and prevent the active material from being released evenly.

It can be understood that the lithium-replenishing pole piece in this application can have any of the following structures:

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

(2) Active material layer A + lithium replenishing layer A + current collector + active material layer B;

(3) Active material layer A + lithium supplement layer A + current collector + lithium supplement layer B + active material layer B;

(4) Active material layer A + conductive layer A + lithium supplement layer A + current collector;

(5) Active material layer A + conductive layer A + lithium replenishing layer A + current collector + active material layer B;

(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.

In some embodiments, the conductive layer has a porosity of 40% to 50%. Alternatively, the thickness of the conductive layer may also be, for example, 42%, 44%, 46% or 48%. Appropriate porosity of the conductive layer can not only control the lithium replenishment rate, but also make the conductive layer have a certain rigidity, which can provide support and avoid the collapse of the pole piece after the lithium replenishment is completed.

In some embodiments, the conductive layer has a thickness of 1 μm to 2 μm. Alternatively, the thickness of the conductive layer may also 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 an appropriate range, which can better achieve the aforementioned support, control the lithium replenishment rate and uniform contact resistance, without occupying too much space and causing a decrease in the volume capacity of the battery.

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

In some embodiments, the binder includes acrylic, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, polyacrylic acid, polytetrafluoroethylene, and poly(tetrafluoroethylene). One or more types of vinylidene fluoride. A suitable adhesive can provide sufficient bonding force, and at the same time enable the conductive agent to be dispersed evenly without agglomeration, allowing it to better function as a conductive layer.

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

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

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

In some embodiments, the mass ratio of the conductive agent and the binder is 1:(0.03~0.07). Optionally, the mass ratio of the conductive agent and the binder can also be, for example, 1:0.04, 1:0.05 or 1:0.06. The appropriate dosage ratio of conductive agent and binder can make the conductive agent disperse evenly, not agglomerate, have good adhesion and not be demolded, and at the same time, it can make the pole piece have smaller resistance.

In some embodiments, inorganic nanoparticles are also included in the conductive layer.

In some embodiments, the mass ratio of the conductive agent and the inorganic nanoparticles is 1:(0.001～0.01). Alternatively, the mass ratio of the conductive agent and the inorganic nanoparticles can also be, for example, 1:0.002, 1:0.004, 1:0.006 or 1:0.008. The appropriate dosage ratio of conductive agent and inorganic nanoparticles can balance the conductivity and lithophilicity of the conductive layer, which can improve the conductivity without affecting the transport of active lithium.

It can be understood that in this 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 other layers C, Layer B is prepared or formed on D... For example, "preparing an active material layer with a porous structure on the lithium supplement layer" means that the active material layer can be directly prepared on the surface of the lithium supplement layer, or other film layers, such as conductive layers, can be prepared on the surface of the lithium supplement layer first. layer, and then prepare an active material layer on the surface of the conductive layer.

It can be understood that in this 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 sequentially prepared 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 sequentially prepared on one surface of the current collector. , only the active material layer is prepared on the other surface, or the lithium supplement layer and the active material layer are prepared in sequence. Of course, the two surfaces can also be symmetrically distributed and have film layers with the same structure.

In some embodiments, the lithium replenishing layer is prepared using a dry method. When the prelithiated electrode piece is a negative electrode piece, it is preferable to prepare the lithium replenishing layer by a dry method, and press the lithium replenishing agent into the pits on the surface of the current collector by direct rolling.

In some embodiments, the lithium replenishing layer is prepared by wet coating. When the pre-lithiated electrode piece is a positive electrode piece, wet coating is preferably used to prepare the lithium replenishing layer. The lithium replenishing agent can be prepared into a dispersion with solvents such as N-methylpyrrolidone (NMP), ethanol, propylene glycol, and water. Then coating is performed to prepare a lithium replenishing layer.

A third aspect of the present application provides a secondary battery, which includes the pre-lithium pole piece of one or more of the aforementioned embodiments.

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

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

Typically, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator. During the charging and discharging process of the battery, active ions are inserted and detached back and forth between the positive and negative electrodes. The electrolyte plays a role in conducting ions between the positive and negative electrodes. The isolation film is set between the positive electrode piece and the negative electrode piece. It mainly plays the role of preventing the positive and negative electrodes from short-circuiting, and at the same time, it can make the ions pass.

At least one of the positive electrode piece and the negative electrode piece of the secondary battery provided by this application is the pre-lithiated electrode piece provided by the first aspect of this application. For example, the positive electrode piece adopts the prelithiated electrode piece provided in the first aspect of the application, and the negative electrode piece uses a conventional negative electrode piece, or the negative electrode piece uses the prelithiated electrode piece provided in the first aspect of the application, and the positive electrode piece Use conventional positive pole pieces. The structure and materials of conventional positive electrode pieces or negative electrode pieces are as follows:

Positive electrode piece

The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector. The positive electrode film layer includes the positive electrode active material of the first aspect of the present application.

As an example, the positive electrode current collector has two surfaces facing each other in its own 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.

In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can 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 base layer. Composite current collectors can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the cathode active material may be a cathode active material known in the art for batteries. As an example, the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, 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 of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO ₂ ), lithium nickel oxides (such as LiNiO ₂ ), lithium manganese oxides (such as LiMnO ₂ , LiMn ₂ O ₄ ), 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 O ₂ (also referred to as NCM ₃₃₃ ), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (can also be abbreviated to NCM ₅₂₃ ), LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (can also be abbreviated to NCM ₂₁₁ ), LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (can also be abbreviated to NCM ₆₂₂ ), LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM ₈₁₁ ), lithium nickel cobalt aluminum oxide (such as LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) and their modifications At least one of the compounds, etc. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO ₄ (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄ ), phosphoric acid At least one of a composite material of lithium manganese and carbon, a composite material of lithium manganese iron phosphate, or a composite material of lithium manganese iron phosphate and carbon.

In some embodiments, the positive electrode film layer optionally further includes a binder. As examples, the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

In some embodiments, the positive electrode film layer optionally further includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.

Negative pole piece

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, where the negative electrode film layer includes a negative electrode active material.

As an example, the negative electrode current collector has two opposite surfaces in its own 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.

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 can 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 base material. The composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the negative active material may be a negative active material known in the art for batteries. As an example, the negative 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 and 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 battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.

In some embodiments, the negative electrode film layer optionally further includes a binder. The binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyacrylic acid sodium (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

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

In some embodiments, the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.

In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.

electrolyte

The electrolyte plays a role in conducting ions between the positive and negative electrodes. There is no specific restriction on the type of electrolyte in this application, and it can be selected according to needs. For example, the electrolyte can be liquid, gel, or completely solid.

In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes electrolyte salts and solvents.

In some embodiments, the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.

In some embodiments, the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

In some embodiments, the electrolyte optionally further includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

Isolation film

In some embodiments, the secondary battery further includes a separator film. There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.

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 film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.

In some embodiments, the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer packaging. The outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.

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 bag, such as a bag-type soft bag. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.

This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. For example, FIG. 1 shows a square-structured secondary battery 5 as an example.

In some embodiments, referring to FIG. 2 , the outer package may include a housing 51 and a cover 53 . The housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity. The positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the containing cavity. The electrolyte soaks into 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.

In some embodiments, secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.

Figure 3 is a battery module 4 as an example. Referring to FIG. 3 , in the battery module 4 , a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 . Of course, it can also be arranged in any other way. Furthermore, the plurality of secondary batteries 5 can be fixed by fasteners.

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

In some embodiments, the above-mentioned battery modules can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.

Figures 4 and 5 show the battery pack 1 as an example. Referring to FIGS. 4 and 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 2 and a lower box 3 . The upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 . Multiple battery modules 4 can be arranged in the battery box in any manner.

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 by the present application. The secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device. The electrical devices may include mobile equipment, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto. Among them, mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc. , but not limited to this.

As the power-consuming device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

FIG. 6 shows an electrical device 6 as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the secondary battery for the electrical device, a battery pack or battery module can be used.

As another example, the device may be a mobile phone, a tablet, a laptop, etc. The device is usually required to be thin and light, and a secondary battery can be used as a power source.

The present application will be further described in detail below in conjunction with specific examples and comparative examples. For experimental parameters not specified in the following specific examples, priority is given to the guidelines given in the application documents. You can also refer to experimental manuals in the field or other experimental methods known in the field, or refer to the experimental conditions recommended by the manufacturer. It can be understood that the instruments and raw materials used in the following examples are relatively specific, and in other specific examples, they may not be limited thereto; the weight of relevant components mentioned in the examples of this application does not only refer to the specific content of each component. , can also represent the proportional relationship between the weights of each component. Therefore, as long as the content of the relevant components is scaled up or down according to the embodiments of this application, it is within the scope disclosed in the embodiments of this application. Specifically, the weight described in the description of the embodiments of this application may be mass units well known in the field of chemical engineering such as μg, mg, g, kg, etc.

Example 1

(1) Preparation of positive electrode pieces

a. Use Li ₅ FeO ₄ (Dv50 particle size 1.5 μm, dosage is 5% of the cathode active material) as the lithium replenishing agent. Divide the lithium replenishing agent into two equal parts and press them on two aluminum current collectors with a roughness of 3 μm. On the side, a lithium-replenishing current collector containing two lithium-replenishing layers with a thickness of 1 μm is obtained;

b. Mix and disperse conductive carbon, methyl acrylate, and nano-Sn particles in N-methylpyrrolidone (NMP) at a mass ratio of 1:0.05:0.005, and coat them on both sides of the lithium-replenishing current collector prepared in step a. , obtaining a conductive lithium-supplemented current collector containing two conductive layers with a thickness of 1 μm;

c. Mix NCM622, PVDF (polyvinylidene fluoride), and SP (conductive carbon) according to the mass ratio of 80:10:10 to obtain the positive active material; dissolve the positive active material in NMP (N-methylpyrrolidone), Make the positive electrode slurry, apply it on both sides of the conductive lithium replenishing current collector prepared in step b, dry it and then cold-press it to obtain the positive electrode piece;

In the obtained positive electrode sheet, the porosity of the conductive layer was 40%, and the porosity of the positive active material layer was 40%. is 25%;

(2) Preparation of negative electrode plate:

Mix graphite, SBR (styrene-butadiene rubber), and SP (conductive carbon) at a mass ratio of 90:5:5, then dissolve in deionized water, stir evenly to obtain anode slurry, and coat it on the surface of the copper foil and dry it Afterwards, cold pressing is performed to obtain the negative electrode piece.

(3) Wind the positive electrode sheet, separator film, and negative electrode sheet, hot-press, inject liquid, and package to obtain a lithium-ion battery, and conduct chemical formation (constant current charging to 3.0V at a rate of 0.1C, and charging at a rate of 0.2C Constant current charging to 3.75V) and first cycle lithium source activation (constant current charging to 4.50V at a rate of 0.33C, constant voltage charging to 0.05C, constant current discharge to 2.5V at a rate of 0.33C).

Example 2

It 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 thickness of the single-sided lithium supplement layer formed is 1.1 μm.

Example 3

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

Example 4

It is basically the same as Example 1, except that in step (1)a, the Dv50 particle size of Li ₅ FeO ₄ is 3.5 μm, and the thickness of the lithium supplement layer on one side is 3.5 μm.

Example 5

It is basically the same as Example 1, except that in step (1)a, the Dv50 particle size of Li ₅ FeO ₄ is 0.5 μm, and the thickness of the lithium supplement layer on one side is 0.5 μm.

Example 6

It is basically the same as Example 1, except that in step (1)a, the thickness of the conductive layer on one side is 3 μm.

Example 7

It is basically the same as Example 1, except that the porosity of the conductive layer of the positive electrode piece obtained in step (1) is 35%.

Example 8

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

Example 9

It 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 15%.

Example 10

It 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%.

Example 11

It is basically the same as Example 1, except that step (1) b is not included, and the obtained positive electrode piece does not contain a conductive layer.

Example 12

It is basically the same as Example 1, except that in step (1)a, the amount of lithium replenishing agent is 10% of the positive electrode active material.

Example 13

It 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.

Example 14

It 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.

Example 15

It 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.

Example 16

It 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 lithium replenishing agent is 3% of the positive electrode active material.

Example 17

It is basically the same as Example 1, except that in step (1)a, the lithium replenishing agent is replaced by an equal mass of Li ₂ O.

Example 18

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 replenishing agent is replaced by Li ₂ NiO ₂ of equal mass.

Example 19

(1) Preparation of positive electrode pieces

Mix NCM622, PVDF (polyvinylidene fluoride), and SP (conductive carbon) at a mass ratio of 80:10:10 to obtain a positive active material; dissolve the positive active material in NMP (N-methylpyrrolidone) to make The positive electrode slurry is coated on both sides of the aluminum current collector, dried and then cold pressed to obtain the positive electrode piece;

(2) Preparation of negative electrode plate:

a. Use lithium powder (Dv50 particle size 1.5 μm, dosage is 1% of the negative active material) as the lithium supplement agent, divide the lithium supplement agent into two equal parts, and press it on both sides of the copper current collector with a roughness of 3 μm. A lithium-replenishing current collector containing two lithium-replenishing layers with a thickness of 1 μm was obtained;

b. Mix and disperse conductive carbon, polytetrafluoroethylene (weight average molecular weight 40,000 Da), and nano-ZnO particles in N-methylpyrrolidone (NMP) according to a mass ratio of 1:0.05:0.005, and coat them in step a. On both sides of the lithium-supplemented current collector, a conductive lithium-supplemented current collector containing two conductive layers with a thickness of 1 μm is obtained;

c. Mix graphite, SBR (styrene-butadiene rubber), and SP (conductive carbon) at a mass ratio of 90:5:5, then dissolve in deionized water, stir evenly to obtain anode slurry, and apply it to the preparation in step b Both sides of the conductive lithium-replenishing current collector are dried and then cold-pressed to obtain the negative electrode piece;

In the obtained negative electrode piece, the porosity of the conductive layer was 45%, and the porosity of the positive active material layer was 35%;

Comparative example 1

It is basically the same as Example 11, except that step (1)a is not included, and the obtained positive electrode sheet does not include a lithium replenishing layer and a conductive layer.

Comparative example 2

It is basically the same as Example 1, except that in step (1)a, the Dv50 particle size of Li ₅ FeO ₄ is 2 μm, the roughness of the aluminum current collector is 1 μm, and the thickness of the single-sided lithium supplement layer formed is 1.3 μm.

Comparative example 3

It is basically the same as Example 1, except that in step (1)a, the Dv50 particle size of Li ₅ FeO ₄ is 2 μm, the roughness of the aluminum current collector is 6 μm, and the thickness of the single-sided lithium supplement layer formed is 0.7 μm.

Characterization test:

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

(1)Battery first cycle capacity test:

Put the lithium ion secondary battery in a constant temperature box at 25°C, charge it at room temperature with a constant current at a rate of 0.5C until the voltage is higher than 4.35V, and further charge at a constant voltage of 4.35V until the current is lower than 0.05C, so that it is 4.35V full charge state, and then discharge the lithium-ion secondary battery at a constant current of 0.33C rate until the voltage is 2.5V (cut-off voltage). This is one cycle. Record the discharge capacity D; based on the first-cycle discharge capacity D0 of Comparative Example 1 without lithium supplementation, calculate the improvement in the first-cycle capacity of each embodiment relative to Comparative Example 1: (D-D0)/D0.

(2) Cycle life test:

Put the lithium ion secondary battery in a constant temperature box at 25°C, charge it at room temperature with a constant current at a rate of 0.5C until the voltage is higher than 4.35V, and further charge at a constant voltage of 4.35V until the current is lower than 0.05C, so that it is 4.35V full charge state, and then discharge the lithium-ion secondary battery at a constant current of 0.33C rate until the voltage is 2.5V (cut-off voltage). This is one cycle. Repeat this cycle and record the discharge capacity D2 of each cycle. When D2/D1=80%, stop the test and record the number of cycles.

Table 1

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 supplement layer formed by the same amount of lithium supplement agent is slightly increased, and the adhesion to the lithium supplement layer is slightly weaker. , has a certain impact on the cycle performance; the surface roughness of the current collector in Example 3 is relatively large, and although it adheres better to the lithium replenishing layer, part of the lithium replenishing agent deep in the pits on the current collector surface may not be released, so the cycle The performance also decreased slightly; in Example 4, the particle size of the lithium replenishing agent was too large and poorly matched with the roughness of the current collector, so the adhesion was also poor, affecting the cycle performance; in Example 5, the particle size of the lithium replenishing agent Too small, and the formed lithium replenishing layer is too thin. Because the particles are too small, part of the lithium replenishing agent is buried deep in the current collector pits. cannot be released, which also affects the battery performance; in Example 6, the conductive layer is too thick, occupying more positions of the pole pieces, affecting the cycle performance of the pole pieces; in Example 7, the porosity of the conductive layer is low, and part of the The lithium agent cannot be released well, so it also affects the cycle performance to a certain extent; in Example 8, the porosity of the conductive layer is high and the lithium is released too fast, which is not conducive to long-term lithium replenishment, so the cycle performance is reduced; Example The trends of Examples 9 and 10 are similar to those of Examples 7 and 8, and the cycle performance will also decrease; in Example 11, there is no conductive layer, which is prone to problems of demolding and excessive lithium release; in Example 12, lithium supplementation If the dosage of the agent is too high, it will lead to lithium precipitation and affect the proportion of active materials, thus affecting the cycle performance; in Example 13, the amount of binder in the conductive layer is small, which risks demolding; in Example 14, the conductive layer If the amount of layer binder is too much, the resistance of the electrode piece will be increased; in Example 15, the amount of lithiophilic inorganic nanoparticles is too much, resulting in too rapid release of lithium.

In Comparative Example 1, there is no lithium replenishing layer and conductive layer, and the cycle performance has dropped significantly. In Comparative Examples 2 and 3, the surface roughness is not within the preset range, which seriously affects the ability of the current collector surface to the lithium replenishing layer. Adhesion, as well as the release of lithium supplement, and cycle performance were also significantly reduced relative to the examples.

It should be noted that the present application is not limited to the above-described embodiment. The above-mentioned embodiments are only examples. Within the scope of the technical solution of the present application, embodiments that have substantially the same structure as the technical idea and exert the same functions and effects are included in the technical scope of the present application. In addition, within the scope that does not deviate from the gist of the present application, various modifications to the embodiments that can be thought of by those skilled in the art, and other forms constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application. .

Claims

A pre-lithiated pole piece, characterized in that it includes a current collector and an active material layer disposed on at least one surface of the current collector; a lithium replenishing layer is provided between the current collector and at least one of the active material layers. layer;

Wherein, the surface roughness of the current collector is 2 μm to 5 μm, and the active material layer has a porous structure.
The prelithiated pole piece according to claim 1, wherein the Dv50 particle size of the lithium replenishing agent in the lithium replenishing layer is ≤2 μm.
The prelithiated electrode piece according to claim 1 or 2, characterized in that the amount of lithium replenishing agent in the lithium replenishing layer is 1% to 5% of the mass of the active material in the active material layer.
The prelithiated electrode piece according to any one of claims 1 to 3, characterized in that the thickness of the lithium replenishing layer is 1 μm to 2 μm.
The prelithiated pole piece according to any one of claims 1 to 4, wherein the active material layer has a porosity of 20% to 40%.
The prelithiated electrode piece according to any one of claims 1 to 5, characterized in that the prelithiated electrode piece is a positive electrode piece, and the porosity of the active material layer is 20% to 30%.
The prelithiated electrode piece according to any one of claims 1 to 6, characterized in that the prelithiated electrode piece is a negative electrode piece, and the porosity of the active material layer is 30% to 40%.
The prelithiated pole piece according to any one of claims 1 to 7, characterized in that the prelithiated pole piece is a positive pole piece, and the lithium replenishing agent in the lithium replenishing layer includes Li 1+x Ni 0.5 Mn 1.5 O 4 , Li 2 NiO 2 , Li 5 FeO 4 , LiF, Li 2 S, Li 2 C 2 O 4 , LiMn 2 O 4 ; one of Li 2 O 2 , Li 2 O and Li 3 N or multiple types, where the value of x is selected from any value between 0 and 1.
The prelithiated pole piece according to any one of claims 1 to 8, characterized in that the prelithiated pole piece is a negative pole piece, and the lithium replenishing agent in the lithium replenishing layer includes lithium powder and prelithium One or more types of graphite.
The pre-lithiated electrode piece according to any one of claims 1 to 9, characterized in that a conductive layer is provided between at least one of the lithium replenishing layers and the active material layer, and the conductive layer has a porous structure.
The prelithiated electrode piece according to claim 10, wherein the porosity of the conductive layer is 40% to 50%.
The prelithiated pole piece according to claim 10 or 11, characterized in that the prelithiated pole piece is a positive pole piece, and the porosity of the conductive layer is 40% to 45%.
The prelithiated pole piece according to any one of claims 10 to 12, wherein the prelithiated pole piece is a negative pole piece, and the porosity of the conductive layer is 45% to 50%.
The prelithiated pole piece according to any one of claims 10 to 13, wherein the thickness of the conductive layer is 1 μm to 2 μm.
The prelithiated pole piece according to any one of claims 10 to 14, characterized in that the conductive layer includes a conductive agent and a binder.
The prelithiated pole piece according to claim 15, wherein the conductive agent includes one or more of conductive graphite, conductive carbon black, carbon fiber, carbon nanotubes and graphene.
The prelithiated pole piece according to claim 15 or 16, characterized in that the binder includes acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, methyl methacrylate, One or more of ethyl methacrylate, polyacrylic acid, polytetrafluoroethylene and polyvinylidene fluoride.
The prelithiated pole piece according to any one of claims 15 to 17, characterized in that the mass ratio of the conductive agent and the binder is 1: (0.03-0.07).
The prelithiated pole piece according to any one of claims 15 to 18, wherein the conductive layer further includes inorganic nanoparticles.
The prelithiated pole piece according to claim 19, characterized in that the inorganic nanoparticles include one or more of Au, Sn, ZnO, MoS 2 and Al 2 O 3 .
The prelithiated pole piece according to claim 19 or 20, characterized in that the mass ratio of the conductive agent and the inorganic nanoparticles is 1: (0.001~0.01).
A method for preparing prelithiated pole pieces, which is characterized by including the following steps:

Provide a current collector with a surface roughness of 2 μm to 5 μm, and prepare 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.
A secondary battery, characterized by comprising the pre-charged battery according to any one of claims 1 to 21 Lithium electrode piece.
An electrical device, characterized by comprising the secondary battery according to claim 23.