WO2022226814A1

WO2022226814A1 - Electrode pole piece, electrochemical apparatus containing same, and electronic device

Info

Publication number: WO2022226814A1
Application number: PCT/CN2021/090393
Authority: WO
Inventors: 李大光; 陈茂华; 谢远森
Original assignee: 宁德新能源科技有限公司
Priority date: 2021-04-28
Filing date: 2021-04-28
Publication date: 2022-11-03
Also published as: CN114375511B; CN114375511A

Abstract

The present application relates to the technical field of energy storage, and specifically relates to an electrode pole piece, an electrochemical apparatus containing same, and an electronic device. The electrode pole piece of the present application comprises: a current collector; a conductive layer, which comprises a conductive network structure formed from conductive fibers; and an insulating layer, which comprises an insulating network structure formed from insulating fibers and insulating particles disposed in the insulating network structure. The conductive layer is located between the current collector and the insulating layer. The diameter of the conductive fibers is greater than the diameter of the insulating fibers. In the present application, the problem of volume expansion of an electrode pole piece during a cycle process of an electrochemical apparatus can be ameliorated, thereby reducing the risk of the electrochemical apparatus short-circuiting. Furthermore, the cycle performance of the electrochemical apparatus can be improved.

Description

Electrode pole piece and electrochemical device and electronic equipment containing the same

technical field

The present application relates to the technical field of energy storage, and in particular, to an electrode pole piece and an electrochemical device and electronic device including the same.

Background technique

Electrochemical devices (eg, lithium-ion batteries) have the advantages of large specific energy (>200Wh/kg), high operating voltage (>3.5V), low self-discharge rate, small size, and light weight, and have a wide range of applications in the field of consumer electronics. application. With the rapid development of mobile electronic devices and electric vehicles, people have higher and higher requirements for energy density, cycle performance, and safety of batteries. Among them, volume energy density and mass energy density are an important parameter to measure battery performance.

Lithium metal is the metal with the smallest relative atomic mass (about 6.94) and the lowest standard electrode potential (-3.045V) among all metal elements, and its theoretical gram capacity can reach 3860mAh/g. Therefore, using lithium metal as the negative electrode material of the battery, with some high energy density positive electrode materials, can greatly improve the energy density of the battery (>400Wh/kg) and the working voltage of the battery (>4.5V). However, if lithium metal as a negative electrode material is truly commercialized, there are some problems that need to be solved: 1) Li metal itself is very active, especially the freshly formed lithium metal, which is very easy to electrolyze with existing small organic molecules. A series of side reactions occur between the solvent and lithium salt in the liquid system, resulting in the consumption of lithium metal and the electrolyte at the same time, and the circulating Coulomb efficiency is generally less than 99.5%. Graphite anode system (>99.9%). 2) During the charging process of lithium metal batteries, lithium will be deposited on the surface of the negative electrode current collector; due to the uneven distribution of current density and the non-uniformity of lithium ion concentration in the electrolyte at different positions, some problems will occur during the deposition process. The phenomenon that the site deposition rate is too fast, and then the sharp dendrite structure is formed. The presence of lithium dendrites can lead to a large decrease in the deposition density. The true density of lithium metal is about 0.534g/cc, while the actual deposition density can only reach about 0.2g/cc, which reduces the energy density of lithium metal batteries by more than 100Wh/L. In severe cases, the diaphragm may be pierced to form a short circuit, causing safety problems. 3) With the charging-discharging of the lithium metal negative electrode, the thickness of the negative electrode pole piece will undergo severe expansion-shrinkage. The thickness of the expansion and contraction is related to the amount of active material per unit area of the pole piece and the gram capacity of the active material, and is also related to lithium. The density of deposition is related to the volume of side reaction products. According to the general design of lithium ion batteries in the related art, the thickness of the negative electrode usually varies from 8 μm to 200 μm. This will cause the interface between the negative pole piece and the less flexible inorganic protective coating to peel off (that is, the good physical contact between the two will be lost), and the protective effect will be lost.

Therefore, there is a need for improvement in related art electrode pads and electrochemical devices using the same.

SUMMARY OF THE INVENTION

The inventor of the present application has carried out a lot of research, aiming to improve the traditional electrode plate, so that it can reduce the side reaction with the electrolyte, reduce the polarization, slow down the volume expansion, alleviate the interface peeling and protection caused by the expansion-contraction process The problem of layer breakage can be solved, thereby providing an electrochemical device that can take into account better cycle performance and good comprehensive electrochemical performance at the same time.

Therefore, the primary purpose of the present application is to propose an electrode pad in an attempt to at least to some extent solve at least one of the problems existing in the related art. The purpose of the second application of the present application is to propose an electrochemical device and an electronic device including the electrode pole piece.

According to a first aspect of the present application, an electrode pole piece is provided, the electrode pole piece includes: a current collector; a conductive layer, the conductive layer includes a conductive network structure formed by conductive fibers; and an insulating layer, the insulating layer The layer includes an insulating network structure formed by insulating fibers and insulating particles placed in the insulating network structure; wherein the conductive layer is located between the current collector and the insulating layer; the diameter of the conductive fibers is larger than the diameter of the the diameter of the insulating fiber.

In the above-mentioned electrode pole piece, the electrode pole piece satisfies at least one of the conditions (a) to (b): (a) the diameter of the conductive fiber is 5 μm to 10 μm; (b) the diameter of the insulating fiber is 10 nm to 1000nm.

In the above electrode pole piece, the volume percentage of the insulating particles is 1% to 10% based on the volume of the insulating layer.

In the above electrode pole piece, the electrode pole piece satisfies at least one of the conditions (c) to (d): (c) the porosity of the conductive layer is 20% to 90%; (d) the porosity of the insulating layer The porosity is 20% to 90%.

In the above-mentioned electrode pole piece, the electrode pole piece satisfies at least one of the conditions (e) to (g): (e) the thickness of the conductive layer is 20 μm to 100 μm; (f) the thickness of the insulating layer is 10 μm to 100 μm; (g) the thickness of the electrode pole piece is 0.03 mm to 2 mm.

In the above-mentioned electrode pole piece, the electrode pole piece satisfies at least one of the conditions (h) to (j): (h) the conductive fibers include metal material fibers and/or carbon-based material fibers; (i) the The insulating fibers include mineral fibers and/or organic fibers; (j) the insulating particles include inorganic particles.

In the above electrode pole piece, the metal material in the metal material fiber includes aluminum, copper, molybdenum, zinc, nickel, iron, platinum, titanium, aluminum alloy, copper alloy, molybdenum alloy, zinc alloy, nickel alloy or titanium alloy At least one of; the carbon-based material fibers include carbon fibers.

In the above electrode pole piece, the mineral fiber includes at least one of glass fiber, rock fiber or quartz fiber; and the organic fiber includes cellulose fiber.

In the above-mentioned electrode pole piece, the inorganic particles include aluminum oxide, silicon dioxide, magnesium oxide, titanium oxide, ceria, tin oxide, calcium oxide, zirconium dioxide, nickel oxide, zinc oxide, yttrium oxide or LLZO at least one of.

In the above-mentioned electrode and pole piece, the conductive layer and/or the insulating layer includes a lithium-replenishing agent, and the addition amount of the lithium-replenishing agent is 0.25 mg/cm ² to 25 mg/cm ² .

According to a second aspect of the present application, an electrochemical device is provided, which includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode and/or the negative electrode include the electrode sheet according to the first aspect of the present application.

In the above electrochemical device, the negative electrode is the electrode plate described in the first aspect of the application.

According to a third aspect of the present application, there is provided an electronic device comprising the electrochemical device as described in the second aspect of the present application.

In the electrode sheet provided by the present application, a conductive layer and an insulating layer are provided on the surface of the current collector, wherein the conductive layer includes a conductive network structure formed by conductive fibers with relatively large diameters (insulating fibers), and the insulating layer It includes an insulating network structure formed by insulating fibers having a relatively small diameter (conductive fibers) and insulating particles arranged in the insulating network structure. In this way, the pore utilization rate of the structured electrode sheet can be improved through the conductive fibers of larger diameter, and the surface of the skeleton structure built by the conductive fibers of the larger diameter can be covered with the skeleton structure built by the insulating fibers of the smaller diameter to prevent the large diameter fibers from stinging Passing through the separator leads to a short circuit of the battery. Further, in order to ensure the structural integrity of the upper insulating layer, doping insulating particles in the insulating network structure built by insulating fibers can improve the structural strength of the upper structured layered structure. Therefore, the electrode plate can slow down the volume expansion of the battery during the cycle, reduce polarization, inhibit the growth of lithium dendrites, and improve the cycle performance, safety performance or rate performance of the battery, so that the electrochemical cell containing the electrode plate can be improved. The device has good cycling performance, which reduces the risk of short circuits.

The electronic device of the present application includes the electrochemical device provided by the present application, and thus has at least the same advantages as the electrochemical device.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present application more clearly, the following briefly introduces the accompanying drawings that need to be used in the embodiments of the present application. For those of ordinary skill in the art, without creative work, the Additional drawings can be obtained from these drawings.

FIG. 1 shows a schematic structural diagram of an electrode pole piece provided by an embodiment of the present application.

FIG. 2 shows a schematic structural diagram of an electrode pole piece provided by another embodiment of the present application.

FIG. 3 shows a schematic structural diagram of an electrode pole piece provided by another embodiment of the present application.

Description of main component symbols

10- collector;

20-conductive network structure;

30 - Insulation network structure;

40 - insulating particles;

50 - Lithium is deposited.

Detailed ways

In order to make the invention purpose, technical solution and beneficial technical effect of the present application clearer, the present application will be described in further detail below in conjunction with the embodiments. It should be understood that the embodiments described in this specification are only for explaining the present application, but not for limiting the present application.

For the sake of brevity, only some numerical ranges are expressly disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with any other lower limit to form an unspecified range, and likewise any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, every point or single value between the endpoints of a range is included within the range, even if not expressly recited. Thus, each point or single value may serve as its own lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.

In the Detailed Description and the Claims, a list of items joined by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean the listed items any combination of . For example, if items A, B are listed, the phrase "at least one of A, B" means A only; B only; or A and B. In another example, if items A, B, C are listed, the phrase "at least one of A, B, C" means A only; or B only; C only; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements. The term "and/or" or "/" used in this article is only an association relationship to describe related objects, indicating that there can be three kinds of relationships, for example, A and/or B, which can indicate that A exists alone, and A exists at the same time and B, there are three cases of B alone.

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. Herein, the terms used in the specification of the present application are for the purpose of describing specific embodiments only, and are not intended to limit the present application. The above summary of this application is not intended to describe each disclosed embodiment or every implementation in this application. The following description illustrates exemplary embodiments in more detail. In various places throughout this application, guidance is provided through a series of examples, which examples can be used in various combinations. In various instances, the enumeration is merely a representative group and should not be construed as exhaustive.

In the related art, lithium metal negative electrodes or current structured electrode sheets such as structured negative electrodes still have more or less defects. In order to reduce the side reaction between lithium metal and the electrolyte, inhibit the growth of lithium dendrites, or solve the problems of interfacial peeling and breakage of the protective layer caused by the expansion-shrinkage process, in order to realize the commercial application of lithium metal anodes, related technologies usually adopt solutions to The methods include: 1) the method of early protection, that is, before the battery is assembled, one or more stable protective layer structures are deposited on the surface of the lithium metal negative electrode by a physical method or a chemical method. This protective layer is stable to lithium, conducts lithium ions, and isolates the electrolyte from direct contact with lithium metal, thereby reducing side reactions. If the protective layer has high mechanical strength, the growth of lithium dendrites can also be suppressed. However, the disadvantage of this method is that due to the rapid volume change of the negative electrode during the charging and discharging process, the materials with higher hardness covering the negative electrode surface will be greatly displaced with it. If the lithium metal is powdered and loses its support, it will easily rupture, resulting in a continuous reduction in effectiveness. 2) The method of generating the protective layer in situ, that is, adding some special additives, such as FEC or VC to the electrolyte, so that it can chemically react with lithium metal to form a more stable SEI film and prevent further side reactions. occur. However, the disadvantage of this method is that in general, due to the rapid volume change of lithium metal, it is difficult for the SEI to maintain the overall stability, and the continuous existence of destruction and regeneration will lead to the continuous loss of additives during the charging and discharging process. Since the additive content is relatively small (generally less than 10%) relative to the other components of the electrolyte, it is also easier to be depleted. When the additive is depleted, its protective effect will disappear, and the SEI component that is regenerated after destruction will no longer be the reaction product containing the additive, and the stability of the SEI film may also deteriorate accordingly. 3) Negative skeleton, that is, using 3D current collectors, porous negative skeleton, etc. However, the disadvantage of this method is that only the framework material of a single structure cannot fully exert the effect of improving the volume expansion of the structured negative electrode and inhibiting the growth of dendrites under the condition of ensuring the preparation rate. Alternatively, the existing single-structure skeleton, which is built with nanofibers, has a loose structure and can be compressed under a relatively small pressure, resulting in a reduction in thickness and a loss of pores; in addition, the existing single-structure skeleton is also The effect of fiber diameter on the utilization of the internal space of the structured pole piece and the excellent rate of battery preparation is not mentioned.

In addition, currently commonly used anode materials for lithium-ion batteries, such as graphite, exist in the form of intercalation in the graphite layer structure during charging, and the graphite layer is similar to the skeleton structure, providing storage space for lithium. For pure lithium metal electrodes, there is no such skeleton structure, so there will be a dramatic volume change during the charging and discharging process, resulting in a series of problems affecting the performance of the battery such as cycling. Or in some lithium metal batteries, due to the non-uniformity of current density and lithium ion concentration in the electrolyte, the deposition rate of certain sites will be too fast during the deposition process, resulting in the formation of sharp dendrite structures. The presence of lithium dendrites will greatly reduce the deposition density, resulting in lower energy density. Lithium dendrites may also pierce the separator to form a short circuit, causing safety issues. By constructing the framework with metal or carbon or insulating polymers, the above two problems can be effectively improved because: first, during battery discharge (lithium metal is stripped from the negative electrode and intercalated into the positive electrode material), the framework can maintain The shape of itself remains unchanged, so the volume of the negative electrode sheet itself will not decrease; during the lithium deposition process, lithium can be stored in the pores of the framework material, thereby maintaining volume stability. Second, the framework can disperse the current and reduce the local current density, thereby improving the deposition morphology and increasing the deposition density.

In the electrode pole piece, the advantage of using a conductive skeleton is that the local current density can be reduced by increasing the specific surface area, but it is also necessary to control the pore structure and tortuosity. If the pore structure is too complex, lithium metal will be deposited on the surface of the framework, and the framework will not function as a structured pole piece. Generally, the larger the fiber diameter used, the simpler the skeleton pore structure and the smoother the lithium ion transport path. However, the larger diameter of the fibers will also lead to the phenomenon that the separator is easily pierced by the fibers and the battery is short-circuited when the battery is assembled.

At least based on the above insights into the prior art, and in view of the critical impact of electrode plates on the electrochemical performance of electrochemical devices, the present application conducts further extensive research on the structural properties of electrode plates with a view to improving electrochemical devices. The electrochemical performance, especially the improvement of the cycle performance and safety performance of the electrochemical device, is devoted to obtaining an electrochemical device with better electrochemical performance.

The electrode sheet, electrochemical device and electronic device of the present application will be described in detail below with reference to the accompanying drawings and specific embodiments.

1. Electrode pads

In one aspect of the present application, the present application provides an electrode pole piece, which, compared with the traditional electrode pole piece, adopts the upper and lower fiber layers as the structured pole piece, both of which can accommodate the deposition of metal (such as lithium metal), and can To improve the volume expansion of the battery during cycling, since the lithium metal is deposited inside the framework, it can also inhibit the growth of lithium dendrites, thereby improving the cycle performance and safety performance of the electrochemical device.

FIG. 1 schematically shows an electrode pad as an example. Referring to FIG. 1 , the electrode pole piece includes: a current collector 10; a conductive layer, which includes a conductive network structure 20 formed by conductive fibers; and an insulating layer, which includes a conductive network structure formed by insulating fibers The insulating network structure 30 and the insulating particles 40 placed in the insulating network structure 30; wherein the conductive layer is located between the current collector and the insulating layer; the diameter of the conductive fiber is larger than that of the insulating fiber diameter.

In the embodiments of the present application, the network structure may also be referred to as a skeleton, so the conductive network structure may also be referred to as a conductive skeleton, and the insulating network structure may also be referred to as an insulating skeleton.

In the electrode pole piece of the embodiment of the present application, the surface of the skeleton built by the larger-diameter conductive fibers is covered with a layer of the upper-layer skeleton built by the smaller-diameter insulating fibers; and, in order to ensure that the upper-layer skeleton built by the smaller-diameter insulating fibers is not damaged under pressure Compression leads to loss of porosity, and a certain number of insulating particles are added to the upper skeleton, which can ensure that the conductive skeleton plays the role of a structured pole piece in the actual use process, and improve the battery preparation rate. As a new type of structured pole piece, the electrode pole piece contains conductive layers and insulating layers formed by different diameters and different fiber materials, which can improve the volume change during the cycle of the electrochemical device, such as the deposition of 7mAh/ ^cm2 of lithium, the volume The change can be reduced from 400% to 0%.

Specifically, the electrode piece covers a conductive layer on the surface of the current collector, which can play a conductive role, and covers an insulating layer on the surface of the conductive layer, which can play an insulating role and has a good protective effect on the conductive layer. Further, in the embodiment of the present application, a conductive network structure is formed by using a conductive fiber with a larger diameter, an insulating network structure is formed by using an insulating fiber with a smaller diameter, and insulating particles are doped in the insulating network structure, and the conductive network structure of the conductive layer is used to play the role of The effect of increasing the specific surface area and reducing the local current density, and at the same time, the larger diameter of the conductive fiber builds the larger diameter of the skeleton hole, which can reduce the tortuosity of the path in the process of lithium ion transmission, thereby accommodating the lithium transmitted from the positive electrode to the greatest extent. Metal. The fine fibers of the insulating layer are relatively soft, and the insulating network structure built by them can prevent the conductive fibers of the conductive layer from piercing the separator, resulting in a short circuit of the battery. In addition, the purpose of building the insulating network structure with insulating fibers is that if the skeleton is built with small conductive fibers, the lithium ion transport channel is too tortuous, and it is easy to precipitate on the surface of the skeleton before reaching the current collector. The effect of doping insulating particles in the insulating network structure is to improve the mechanical strength of the skeleton. Since the skeleton structure built by the fine fibers is loose, it can be compressed under a small pressure (>100g), resulting in closed pores and lithium deposition on the surface. Therefore, the structured pole piece can not only inhibit the volume expansion and lithium dendrite growth during the battery cycle, thereby improving the cycle performance of the battery, but also improve the battery preparation rate and safety performance (for example, the short-circuit rate can be 8/10). down to 0/10).

Therefore, the embodiment of the present application protects the conductive skeleton built by the large-diameter conductive fibers in the conductive layer by using the insulating skeleton built by the insulating layer doped with the insulating particles of fine insulating fibers, which solves the problem of volume generation during the cycle of electrochemical devices such as lithium metal batteries. The problem of change is improved, the cycle performance of the battery is improved, and the problem of short circuit of the battery caused by the large diameter fiber piercing the separator is solved, and the safety performance of the battery is improved. In addition, the use of the structured pole piece can also improve the rate performance of lithium batteries, because the structured pole piece can inhibit the formation of lithium dendrites, reduce polarization, and slow down volume expansion, thereby improving the cycle performance and rate performance of lithium batteries. Effect.

In some embodiments, the conductive fibers have a diameter of 5 μm to 10 μm, and the diameter of the conductive fibers is larger than the diameter of the insulating fibers. In some embodiments, the conductive fibers have a diameter of 5 μm to 8 μm. In some embodiments, the diameter of the conductive fibers can be listed as 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, or any combination of these values scope.

In some embodiments, the diameter of the insulating fibers is 10 nm to 1000 nm, and the diameter of the insulating fibers is smaller than the diameter of the conductive fibers. In some embodiments, the insulating fibers have a diameter of 50 nm to 1000 nm. In some embodiments, the insulating fibers have a diameter of 100 nm to 800 nm. In some embodiments, the diameter of the insulating fibers can be listed as 10 nm, 20 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, or a range of any two of these values .

According to the embodiments of the present application, the diameter of the conductive fibers may be in the order of micrometers, and the diameter of the insulating fibers may be in the order of nanometers or submicrometers. The skeleton structure built by the larger diameter conductive fibers (such as 5μm-10μm) has smooth pores and facilitates ion transport. It is verified that lithium can be deposited inside the skeleton, and its internal pores can be utilized to the greatest extent. However, too large fiber diameter leads to high fiber hardness, and it is easy to pierce the separator during the battery assembly process, resulting in a short circuit of the battery, resulting in a greatly reduced yield rate. Therefore, it is necessary to apply protection on the surface of the conductive skeleton. Using nano-insulating fibers doped with insulating particles (such as 10nm-1000nm) as the skeleton of the insulating layer can reduce the short-circuit rate of the battery (such as from 8/10 to 0/10), and the insulating skeleton itself is also a part of the structured pole piece. It can accommodate lithium metal, maximize the overall space utilization of the structured pole piece, give full play to the advantages of the structured pole piece, inhibit the formation of lithium dendrites and volume expansion, and improve the safety and cycle performance of electrochemical devices.

In addition, the deposition position of lithium in the conductive framework is affected by the internal pore structure and tortuosity of the framework. The skeleton structure built by the smaller diameter fibers usually has complex pores, and the transport path of lithium ions in it is too complicated. Often, before the lithium ions reach the surface of the current collector, electrons are preferentially exchanged with the fiber surface and are reduced, which leads to the blockage of the pores. , Li metal begins to deposit on the surface of the framework and loses its role as a structured anode. The skeleton structure built by larger diameter fibers usually has better lithium ion transport pathways, which can maximize the use of internal pores for lithium metal storage. Nano-scale insulating fibers are usually soft, and as the insulating layer of the structured pole piece, covering the surface of the structured pole piece can effectively improve the short-circuit situation of the battery. However, the skeleton structure built by nanofibers is loose and can be compressed under a small pressure (>100 g), resulting in the loss or even closure of pores. The insulating particles can play a structural support role, and by doping them into the nanofiber skeleton, the structural strength can be improved.

In some embodiments, the volume percentage of the insulating particles is 1% to 10% based on the volume of the insulating layer. In some embodiments, the volume percentage of the insulating particles is 3% to 10% based on the volume of the insulating layer. In some embodiments, the volume percentage of the insulating particles is 5% to 10% based on the volume of the insulating layer. In some embodiments, based on the volume of the insulating layer, the volume percentage of the insulating particles can be listed as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or a range of any two of these values.

Adding insulating particles to the insulating layer can improve the structural strength of the structured pole piece. However, if the content of the added insulating particles is too small (for example, less than 1%), the insulating particles have limited support for the skeleton structure, and may also The structure is compressed to a certain extent, reducing the effect of reducing volume expansion. If the content of the added insulating particles is too large (for example, more than 10%), the insulating particles will occupy too much the pore structure of the insulating framework, resulting in a decrease in the overall porosity of the framework and a decrease in the lithium storage capacity.

In the embodiments of the present application, methods known in the art can be used to test or calculate the content of insulating particles. As an example, the method for testing and calculating the content of insulating particles in the insulating layer specifically includes: the electrode pole piece used needs to be the original pole piece (without lithium supplementation), and the electrode pole piece after lithium supplementation can be pre-prepared with an aqueous solution. Dry after lithium supplementation is removed. During the test, the upper layer (insulating layer) skeleton and the lower layer (conducting layer) skeleton are first separated by mechanical methods. The lower layer skeleton is generally a conductive carbon material, and the upper layer skeleton is generally an insulating organic material or a ceramic material. , use a mercury porosimeter or a true density tester to measure the _porosity V of the upper skeleton, and use an electronic balance to measure the weight m of the upper skeleton, and use the following formula to calculate the volume fraction of insulating particles:

Among them, V _p is the volume fraction of insulating particles in the insulating layer, that is, the volume percentage; ρ _f is the density of the insulating fiber material used in the insulating layer; ρ _p is the density of the insulating particle material used in the insulating layer; V _table is the insulating layer. Layer skeleton apparent volume.

The types of elements contained in the framework material can be obtained by ICP, EDS and other testing methods, and the specific phase can be reversed by XRD.

In some embodiments, the conductive layer has a porosity of 20% to 90%. In some embodiments, the conductive layer has a porosity of 40% to 90%. In some embodiments, the conductive layer has a porosity of 60% to 85%. In some embodiments, the porosity of the conductive layer can be listed as 20%, 30%, 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 82%, 85% %, 88%, 90%, or a range of any two of these values.

In some embodiments, the insulating layer has a porosity of 20% to 90%. In some embodiments, the insulating layer has a porosity of 40% to 90%. In some embodiments, the insulating layer has a porosity of 60% to 85%. In some embodiments, the porosity of the insulating layer can be listed as 20%, 30%, 40%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 82%, 85% %, 88%, 90%, or a range of any two of these values.

In the electrode sheet, on the one hand, the skeleton structure built by the conductive fibers of the conductive layer can provide a stable space during charging, so that lithium metal is deposited in a large number of pores (the porosity can range from 20% to 90%) During discharge, the skeleton can form a stable structure and internal space in the process of the continuous reduction of lithium in the negative electrode, so that the negative electrode will not undergo severe shrinkage (<50%). On the other hand, the skeleton structure has good ionic and electronic conductivity to provide conductive channels, coupled with its high specific surface area, it can effectively disperse the current during the charging and discharging process, reduce the current density, And form a more uniform electric field, thereby improving the uniformity of lithium deposition and inhibiting the growth of lithium dendrites. Therefore, the porosity of the conductive layer and the porosity of the insulating layer are within the above appropriate ranges, which can slow down the volume expansion of the battery during charging and discharging, and improve the structural stability of the pole piece, which is beneficial to improve the cycle performance and rate of the battery. performance.

In some embodiments, the thickness of the conductive layer is 20 μm to 100 μm. In some embodiments, the thickness of the conductive layer is 20 μm to 80 μm. In some embodiments, the conductive layer has a thickness of 25 μm to 50 μm. In some embodiments, the thickness of the conductive layer can be listed as 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or a range of any two of these values.

In some embodiments, the insulating layer has a thickness of 10 μm to 100 μm. In some embodiments, the insulating layer has a thickness of 10 μm to 60 μm. In some embodiments, the insulating layer has a thickness of 15 μm to 40 μm. In some embodiments, the thickness of the insulating layer can be listed as 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or any two of these values. range.

In some embodiments, the electrode pads have a thickness of 0.03 mm to 2 mm. In some embodiments, the electrode pads have a thickness of 0.03 mm to 1.5 mm. In some embodiments, the electrode pads have a thickness of 0.06 mm to 1.2 mm. In some embodiments, the thickness of the electrode pad can be listed as 0.03mm, 0.04mm, 0.05mm, 0.06mm, 0.08mm, 0.1mm, 0.2mm, 0.4mm, 0.5mm, 0.6mm, 0.8mm, 1mm , 1.2mm, 1.5mm, 1.6mm, 1.8mm, 2mm or a range of any two of these values.

In the electrode piece, the overall thickness and porosity of the electrode piece determine the amount of lithium that the pole piece can store. If the thickness of the electrode piece is too low, the thickness of the skeleton will be too low, which will reduce the lithium metal Storage or deposition density in the skeleton, so the thickness of the skeleton should not be too low. If the thickness of the electrode plate is too large, the volume energy density of the battery will be greatly reduced. Therefore, the thickness of the electrode plate is in the range of 0.03mm to 2mm, especially when it is in the range of 30μm to 50μm, which can ensure the volume energy of the battery. In the case of density, increase the amount of stored lithium. In the electrode pole piece, the thickness of the insulating layer is in the range of 10 μm to 100 μm, especially when the thickness of the insulating layer is greater than 20 μm, the protection effect caused by the too low thickness of the insulating layer can be avoided, and the large diameter of the conductive layer can be reduced. There is a risk that the fibers will penetrate the insulation and increase the short-circuit rate of the battery. In the electrode and pole piece, the thickness of the conductive layer is in the range of 20 μm to 100 μm, which can fully play the role of lithium storage and current density of the conductive layer.

In some embodiments, the conductive fibers include at least one of metallic fibers or carbon-based fibers.

In some embodiments, the metal material in the metal material fiber comprises aluminum, copper, molybdenum, zinc, nickel, iron, platinum, titanium, aluminum alloy, copper alloy, molybdenum alloy, zinc alloy, nickel alloy or titanium alloy at least one of. In some embodiments, the carbon-based material fibers comprise carbon fibers (CF).

According to the embodiment of the present application, the conductive fiber material can be a metal and its alloy that do not react violently with lithium, including but not limited to the above-mentioned Cu, Mo, Al, Zn, Ni, Fe, Pt, etc., and the conductive fiber can also be carbon, etc. Conductive inorganic non-metallic materials. For the sake of clarity and simplicity of description, the present application discusses only a few of them, such as Cu, Al, Zn or CF, as exemplary examples.

In some embodiments, the conductive fibers may be Cu.

In some embodiments, the conductive fibers may be Al.

In some embodiments, the conductive fibers may be CF.

According to the embodiment of the present application, the insulating layer is constructed of insulating fibers doped with insulating particles, and the insulating fibers may be inorganic materials or organic materials.

In some embodiments, the insulating fibers include one of mineral fibers or organic fibers.

In some embodiments, the mineral fibers comprise at least one of glass fibers (GF), rock fibers, or quartz fibers. Wherein the quartz fibers may be fibers comprising greater than 96% by weight of quartz. In some embodiments, the organic fibers comprise cellulose fibers.

In some embodiments, the insulating particles comprise inorganic particles.

In some embodiments, the inorganic particles include alumina (Al ₂ O ₃ ), silica, magnesia, titania, ceria, tin oxide, calcia, zirconia, nickel oxide, zinc oxide, At least one of yttrium oxide or LLZO.

In some embodiments, the conductive layer and/or the insulating layer includes a lithium supplement, and the added amount of the lithium supplement is 0.25 mg/cm ² to 25 mg/cm ² . In some embodiments, a lithium supplement is added to the conductive layer, and the amount of the lithium supplement is 0.25 mg/cm ² to 25 mg/cm ² . In some embodiments, the conductive layer and/or the insulating layer includes a lithium supplement, and the added amount of the lithium supplement is 0.5 mg/cm ² to 20 mg/cm ² .

According to the embodiments of the present application, when the electrode sheet is used as a negative electrode, lithium may or may not be pre-supplemented in the conductive framework. When pre-supplementing lithium, the method of supplementing lithium can be the melting method, PVD method, electrochemical method, etc. commonly used in the field, and the amount of pre-supplementing lithium can be between 0.25 mg/cm ² and 25 mg/cm ² .

In some embodiments, the current collector can be a common current collector in the art. As an example, the current collector may be metals such as copper, nickel, titanium, molybdenum, iron, zinc and their alloys, or the current collector may also be a conductive inorganic material such as carbon.

Unless otherwise specified, various parameters involved in this specification have general meanings known in the art, and can be determined by methods known in the art, and will not be described in detail here.

FIG. 2 and FIG. 3 respectively schematically show electrode pads as another example. Please refer to FIG. 2 and FIG. 3, the electrode pole piece includes: a current collector 10; a conductive layer, the conductive layer includes a conductive network structure 20 formed by conductive fibers; and an insulating layer, the insulating layer includes The insulating network structure 30 and the insulating particles 40 placed in the insulating network structure 30; wherein the conductive layer is located between the current collector and the insulating layer; the diameter of the conductive fiber is greater than the diameter of the insulating fiber; the electrode pole piece is also provided with deposited lithium 50 . It can be understood that in some cases, as shown in FIG. 2 , the deposition position of the deposited lithium 50 is outside the insulating framework; in other cases, as shown in FIG. 3 , the deposition position of the deposited lithium 50 is inside the conductive layer framework, Or inside the skeleton of the conductive layer and inside the skeleton of the insulating layer.

2. Electrochemical device

A second aspect of the present application provides an electrochemical device, which includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode and/or the negative electrode include the electrode sheet described in the first aspect of the present application.

The electrode sheet of the present application can be used for the preparation of positive electrode/negative electrode. Among them, the electrode sheet of the present application is particularly preferable as a negative electrode of a secondary battery.

The electrochemical device of the present application can be a lithium ion battery or a lithium metal battery, and can also be any other suitable electrochemical device. For example, without departing from the content disclosed in the present application, the electrochemical device in the embodiments of the present application includes any device that undergoes an electrochemical reaction, and specific examples thereof include all kinds of primary batteries, secondary batteries, fuel cells, Solar cells or capacitors. In particular, the electrochemical device is a lithium secondary battery including, but not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery. The electrochemical device of the present application is an electrochemical device including a positive electrode having a positive electrode active material capable of occluding and releasing metal ions, and a negative electrode having a negative electrode active material capable of absorbing and releasing metal ions. of any of the above electrode pads. Therefore, since the electrochemical device of the embodiments of the present application includes the above-mentioned electrode and pole pieces, it can alleviate the problem of the volume expansion of the electrode piece or the easy short circuit during the cycle process of the existing electrochemical device, and improve the cycle performance of the electrochemical device. , reducing the risk of short circuits.

In some embodiments, the positive electrode includes a positive electrode current collector and a positive electrode active material layer coated on the surface of the positive electrode current collector. Further, the positive electrode active material layer contains a positive electrode active material, a conductive agent and a binder.

In some embodiments, the positive electrode active material layer may include a positive electrode active material known in the art, capable of reversible intercalation/deintercalation of ions. For example, a positive electrode active material for a lithium ion secondary battery may include a lithium transition metal composite oxide, wherein the transition metal may be among Mn, Fe, Ni, Co, Cr, Ti, Zn, V, Al, Zr, Ce, and Mg one or more of. The lithium transition metal composite oxide can also be doped with elements with large electronegativity, such as one or more of S, F, Cl and I. This enables cathode active materials with high structural stability and electrochemical performance. As an example, the lithium transition metal composite oxide may be selected from LiMn ₂ O ₄ , LiNiO ₂ , LiCoO ₂ , LiNi _1-y Co _y O ₂ , LiNi _a Co _b Al _1-ab O ₂ , LiMn _1-mn Ni _m Co _n O ₂ (0<m<1, 0<n<1, 0<m+n<1), LiNi _0.5 Mn _1.5 O ₄ , LiMPO ₄ (M can be one or more of Fe, Mn, Co ) or one or more of Li ₃ V ₂ (PO ₄ ) ₃ .

In some embodiments, the conductive agent may include any conductive material as long as it does not cause unwanted chemical changes. As an example, the conductive agent may be selected from one or more of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

In some embodiments, by way of example, the binder may be selected from styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), water-based acrylic resin, polytetrafluoroethylene (PTFE) , one or more of ethylene-vinyl acetate copolymer (EVA), polyvinyl alcohol (PVA) or polyvinyl butyral (PVB).

The binder and the conductive agent in the above-mentioned positive electrode active material layer, as well as the types and contents of the two are not specifically limited, and can be selected according to actual needs.

In some embodiments, the positive electrode current collector may be a positive electrode current collector commonly used in the art. The positive electrode current collector is metal, such as but not limited to aluminum foil or nickel foil.

In some embodiments, the structure of the positive electrode is a positive electrode structure known to those skilled in the art that can be used in electrochemical devices. In some embodiments, the method of making the positive electrode is known to those skilled in the art as a method of making a positive electrode that can be used in an electrochemical device.

In some embodiments, the negative electrode may include the electrode pole piece provided in any of the above embodiments of the present application. That is, in an electrochemical device such as a lithium secondary battery, the above-mentioned electrode pole piece as a structured pole piece or a structured pole piece after lithium supplementation can be directly used as a negative electrode.

In some embodiments, the electrolytes that can be used in embodiments of the present application may be electrolytes known in the art. Electrolytes can be divided into aqueous electrolytes and non-aqueous electrolytes. Compared with aqueous electrolytes, electrochemical devices using non-aqueous electrolytes can work in a wider voltage window, thereby achieving higher energy density. In some embodiments, the non-aqueous electrolyte includes an organic solvent and an electrolyte.

Electrolytes that can be used in the electrolyte of the embodiments of the present application include, but are not limited to: inorganic lithium salts, such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiSO ₃ F, LiN(FSO ₂ ) ₂ , etc.; Fluorine-containing organolithium salts such as LiCF ₃ SO ₃ , LiN(FSO ₂ )(CF ₃ SO ₂ ), LiN(CF ₃ SO ₂ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , cyclic 1,3- Lithium hexafluoropropanedisulfonimide, cyclic lithium 1,2-tetrafluoroethanedisulfonimide, LiPF ₄ (CF ₃ ) ₂ , LiN(CF ₃ SO ₂ )(C ₄ F ₉ SO ₂ ) , LiC(CF ₃ SO ₂ ) ₃ , LiPF ₄ (CF ₃ SO ₂ ) ₂ , LiPF ₄ (C ₂ F ₅ ) ₂ , LiPF ₄ (C ₂ F ₅ SO ₂ ) ₂ , LiBF ₂ (CF ₃ ) ₂ , LiBF ₂ (C ₂ F ₅ ) ₂ , LiBF ₂ (CF ₃ SO ₂ ) ₂ , LiBF ₂ (C ₂ F ₅ SO ₂ ) ₂ ; lithium salts containing dicarboxylic acid complexes, such as lithium bis(oxalato)borate , Lithium difluorooxalatoborate, tris (oxalato) lithium phosphate, difluorobis (oxalato) lithium phosphate, tetrafluoro (oxalato) lithium phosphate, etc. In addition, the said electrolyte may be used individually by 1 type, and may use 2 or more types together.

The organic solvent that can be used in the electrolyte in the embodiments of the present application can be any organic solvent known in the prior art. In some embodiments, organic solvents include, but are not limited to, carbonate compounds, ester-based compounds, ether-based compounds, ketone-based compounds, alcohol-based compounds, aprotic solvents, or combinations thereof. Among them, examples of the carbonate compound include, but are not limited to, a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof. In some embodiments, the organic solvent includes ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate At least one of ester, propyl propionate or ethyl propionate.

In order to prevent short circuit, a separator is usually provided between the positive electrode and the negative electrode. In this case, the electrolyte solution is usually used by permeating the separator.

In some embodiments, the isolation membrane may be any material suitable for the isolation membrane of electrochemical energy storage devices in the art, for example, may be including but not limited to polyethylene, polypropylene, polyvinylidene fluoride, aramid, polypara A combination of one or more of ethylene phthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fibers.

There is no particular limitation on the material and shape of the separator in the embodiments of the present application, and any well-known porous-structure separator with electrochemical stability and chemical stability can be selected. In some embodiments, the release film is, for example, a single layer or multiple layers of one or more of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride (PVDF). film.

3. Electronic equipment

A third aspect of the present application provides an electronic device comprising the electrochemical device as described above.

According to the electrode pole piece of the embodiment of the present application, the volume expansion problem of the existing electrode pole piece can be alleviated, the formation of lithium dendrite can be suppressed, and the cycle performance and safety performance of the electrochemical device can be improved, so that the electrochemical device manufactured therefrom is suitable for use in Electronic equipment in various fields. The use of the electrochemical device of the present application is not particularly limited, and it can be used in any electronic device known in the art. Electrochemical devices can be used as power sources for electronic devices and as energy storage units for electronic devices.

In some embodiments, electronic devices of the present application include, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, head-mounted stereos Headphones, VCRs, LCD TVs, Portable Cleaners, Portable CD Players, Mini CDs, Transceivers, Electronic Notepads, Calculators, Memory Cards, Portable Recorders, Radios, Backup Power, Motors, Automobiles, Motorcycles, Power-assisted Bicycles, Bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.

As an example, the electronic device may be a mobile phone, a tablet computer, a notebook computer, and the like. This electronic device is generally required to be thin and light, and a secondary battery can be used as a power source.

The following examples more specifically describe the present disclosure, these examples are for illustrative purposes only, and the present application is not limited to these examples, as it is within the scope of the present disclosure, as long as it does not depart from the gist thereof. Various modifications and changes will be apparent to those skilled in the art. Unless otherwise stated, all reagents used in the following examples and comparative examples are either commercially available or synthesized according to conventional methods, and can be used directly without further processing, and the instruments used in the examples are commercially available get.

Fourth, the embodiment

Preparation of Lithium Secondary Batteries

In order to facilitate the preparation and testing, the preparation of the half-cell was carried out, and the performance test of the half-cell was carried out. It can be understood that, in a half-cell, the above-mentioned electrode piece serves as a positive electrode, while in an actual full cell, the above-mentioned electrode piece can serve as a negative electrode.

(1) Preparation of positive electrode (electrode pole piece): carbon fiber (CF) of suitable diameter is used as conductive fiber, and a conductive layer containing a conductive network structure is formed on the surface of the current collector; glass fiber (GF) is used as insulating fiber, and An insulating layer containing an insulating network structure is formed on the surface of the conductive layer, insulating particles of a certain volume percentage are doped in the insulating network structure, and a positive electrode is obtained through processes such as cutting pieces. The diameter of the obtained positive electrode was 18 mm.

(2) Preparation of negative electrode: A metal lithium sheet with a diameter of 18 mm and a thickness of 0.5 mm was used as the negative electrode.

(3) Preparation of separator: a polyethylene (PE) porous membrane was used as the separator, and the thickness of the separator was 15 μm.

(4) Preparation of electrolyte: organic solvent ethylene carbonate (EC) and 1,1,2,2-tetrafluoro-3-(1,1,2,2-tetrafluoroethoxy)propane (TTE) Mix with mass ratio EC:TTE=2:3, then add fluoroethylene carbonate (FEC), fluorodimethyl carbonate (FEMC) and lithium salt lithium hexafluorophosphate (LiPF ₆ ) to the organic solvent to dissolve and mix uniformly to obtain The concentration of lithium salt is 1.0M electrolyte. The electrolyte contains 20% FEC+30% FEMC+20% EC+30% TTE.

(5) Assembly of lithium secondary battery: 2430 button battery model is selected. The lithium secondary battery is obtained by assembling the negative electrode shell, shrapnel, gasket, negative lithium sheet, electrolyte, separator, electrolyte, positive electrode, Cu foil, and positive electrode shell in sequence from bottom to top.

Pole Piece Expansion Test

Before assembling the battery, the thickness of the structured electrode pole piece was measured by SEM, and the thickness at this time was recorded as the initial thickness of the pole piece. The assembled button battery was placed in a constant temperature room at 25°C for 12 hours to allow the electrolyte to fully infiltrate the separator and structured pole pieces. After that, the battery was discharged on a Neware machine at a current density of 0.2 mA/cm ² for 35 hours (7 mAh/cm ² ). The battery discharged to the specified capacity was disassembled, and the thickness of the pole piece after discharge was recorded by SEM, which was recorded as the thickness of the pole piece after lithium deposition. Calculate the thickness expansion rate of the electrode pole piece as follows:

Thickness expansion ratio=(the thickness of the pole piece after lithium deposition-the initial thickness of the pole piece)÷the initial thickness of the pole piece×100%.

Short circuit rate test

The short circuit of the battery is characterized by the open circuit voltage (OCV) of the battery after 24 hours. The OCV is measured by a multimeter. If the OCV of the battery is less than 2.0V, the short circuit of the battery cell is determined. Calculate the short-circuit rate as follows:

Battery short-circuit rate = OCV<2.0V number of cells ÷ (OCV<2.0V number of cells + OCV≥2.0V number of cells).

Lithium deposition site test

Lithium deposition sites, characterized by CP-SEM testing. The battery after lithium deposition was disassembled, the structured pole piece was taken out, and the residual lithium salt was removed by soaking in DMC for 10 minutes. The structured pole piece section was polished with a Leica EM TIC 3X ion cutter with a cutting voltage of 5V. The polished sections of the samples were characterized by a ZEISS Supra55 field emission scanning electron microscope to characterize the deposition sites of lithium in the structured pole pieces.

The specific embodiments of the electrode pads provided in the present application, as well as the performance test results of each embodiment and comparative example will be described in detail below.

Example 1 to Example 9

Example 1: Preparation of positive electrode (electrode pole piece): carbon fiber (CF) was used as the conductive fiber, and a conductive layer comprising a conductive network structure was formed on the surface of the current collector, the thickness of the conductive layer was 30 μm, and the porosity was 82%, The diameter of the conductive fiber is 5 μm; glass fiber (GF) is used as the insulating fiber, and an insulating layer containing an insulating network structure is formed on the surface of the conductive layer, and the insulating network structure is doped with 10% by volume of insulating particles Al ₂ O ₃ particles, the thickness of the insulating layer is 20 μm, the porosity is 82%, the diameter of the insulating fiber is 1000 nm, and the positive electrode is obtained by cutting pieces and other processes. The diameter of the obtained positive electrode was 18 mm.

Example 2: The difference from Example 1 is that the thickness of the conductive layer is 35 μm, and the thickness of the insulating layer is 15 μm.

Example 3: The difference from Example 1 is that the thickness of the conductive layer is 40 μm, and the thickness of the insulating layer is 10 μm.

Example 4: The difference from Example 1 is that the insulating particles are LLZO particles.

Example 5: The difference from Example 1 is that cellulose is used as the insulating fiber.

Example 6: The difference from Example 1 is that the volume percentage of the insulating particles Al ₂ O ₃ particles is 5%.

Example 7: The difference from Example 1 is that the volume percentage of the insulating particles Al ₂ O ₃ particles is 1%.

Example 8: The difference from Example 1 is that the porosity of the conductive layer is 40%; the porosity of the insulating layer is 40%.

Example 9: The difference from Example 1 is that Ni fiber is used as the conductive fiber.

Comparative Example 1 to Comparative Example 4

Comparative Example 1: The difference from Example 1 is that the thickness of the conductive layer is 50 μm, and the insulating layer is not provided.

Comparative Example 2: The difference from Example 1 is that the conductive layer adopts a carbon nanotube (CNT) skeleton doped with Al ₂ O ₃ particles with a volume percentage of 10%, the diameter of the CNT is 100 nm, and no insulating layer is provided.

Comparative Example 3: The difference from Example 1 is that the glass fibers (GF) in the insulating layer are replaced with carbon nanotubes (CNT), that is, a CNT skeleton with conductive properties is formed.

Comparative Example 4: The difference from Example 1 is that no insulating particles are added to the insulating layer.

Table 1 shows the relevant performance parameters of the positive electrodes in each embodiment and the comparative example, and the performance test results of the corresponding batteries.

Table 1:

As can be seen from the data in Table 1, in Example 1, Example 4 and Example 5, the conductive layer adopts a CF skeleton with a thickness of 30 μm and a porosity of 82%; the insulating layer adopts an insulating skeleton with a thickness of 20 μm and a porosity of 82%. By doping insulating particles, the short-circuit rate of the prepared electrode pole piece and the battery is lower, the expansion of the pole piece is better suppressed, and the cycle performance of the battery is improved. From the comparison of Example 1, Example 4 and Example 5, under the premise of ensuring insulation, replacing the type of skeleton fiber and insulation particle type of the insulation layer has almost no effect on the realization of the technical effect. In addition, it can be seen from the comparison between Example 1 and Example 9 that, on the premise of ensuring basic properties such as conductivity, changing the type of skeleton fibers in the conductive layer has little effect on the realization of technical effects. The comparison of Example 1, Example 2 and Example 3 shows that the thickness of the upper skeleton has a great influence on reducing the short-circuit rate of the battery. When the thickness of the insulating layer is 20 μm, the short-circuit rate of the battery is 0/10. At this time, it is meaningless to increase the thickness of the insulating layer skeleton. Instead, it will reduce the overall conductive part of the skeleton and affect the effect of reducing the local current density.

From the results of Example 6 and Example 7, it is shown that the amount of insulating particles added has a certain influence on the expansion of the battery. When the amount added is small, the supporting effect of the insulating particles on the skeleton structure is limited, and the structure will still be to a certain extent. is compressed, resulting in lithium spillage. It can also be seen from the comparison between Example 1 and Example 8 that reducing the porosity of the conductive layer and the insulating layer will make the internal space insufficient to accommodate 7mAh/cm ² Lithium is completely deposited inside, which will increase the expansion rate of the pole piece.

From the results of Comparative Example 1, it is shown that the battery is very easy to short-circuit by simply using a large-diameter conductive fiber as the skeleton. From the results of Comparative Example 2, it is shown that with the use of small-diameter conductive fibers, lithium cannot be deposited into the interior of the skeleton, and the battery expansion is still very serious. The results of Comparative Example 3 show that when the upper layer (insulating layer) in the structured pole piece adopts a conductive skeleton, lithium cannot be deposited on the lower conductive layer skeleton, and the battery expansion is still very serious. The results of Comparative Example 4 show that even if insulating fibers are used in the upper insulating layer skeleton, if insulating particles are not added as a structural support, the upper conductive layer skeleton will lose or close a lot of pores under pressure (introduced during the battery preparation process), and lithium is deposited in the On the surface of the upper skeleton, the battery swelling is still very serious.

Although illustrative embodiments have been shown and described, it should be understood by those skilled in the art that the above-described embodiments are not to be construed as limitations of the application, and changes may be made in the embodiments without departing from the spirit, principles and scope of the application , alternatives and modifications.

Claims

An electrode pole piece, characterized in that the electrode pole piece comprises:

collector;

a conductive layer comprising a conductive network structure formed by conductive fibers; and

an insulating layer, the insulating layer comprising an insulating network structure formed by insulating fibers and insulating particles disposed in the insulating network structure; wherein the conductive layer is located between the current collector and the insulating layer;

The diameter of the conductive fibers is larger than the diameter of the insulating fibers.
The electrode pole piece according to claim 1, wherein the electrode pole piece satisfies at least one of the conditions (a) to (b):

(a) the diameter of the conductive fiber is 5 μm to 10 μm;

(b) The insulating fiber has a diameter of 10 nm to 1000 nm.
The electrode pole piece according to claim 1, wherein, based on the volume of the insulating layer, the volume percentage of the insulating particles is 1% to 10%.
The electrode pole piece according to claim 1, wherein the electrode pole piece satisfies at least one of the conditions (c) to (d):

(c) the porosity of the conductive layer is 20% to 90%;

(d) The insulating layer has a porosity of 20% to 90%.
The electrode pole piece according to claim 1, wherein the electrode pole piece satisfies at least one of the conditions (e) to (g):

(e) the thickness of the conductive layer is 20 μm to 100 μm;

(f) the thickness of the insulating layer is 10 μm to 100 μm;

(g) The thickness of the electrode pole piece is 0.03 mm to 2 mm.
The electrode pole piece according to any one of claims 1 to 5, wherein the electrode pole piece satisfies at least one of the conditions (h) to (j):

(h) the conductive fibers include metal material fibers and/or carbon-based material fibers;

(i) the insulating fibers include mineral fibers and/or organic fibers;

(j) The insulating particles include inorganic particles.
The electrode pole piece according to claim 6, wherein the metal material in the metal material fiber comprises aluminum, copper, molybdenum, zinc, nickel, iron, platinum, titanium, aluminum alloy, copper alloy, molybdenum alloy, At least one of zinc alloy, nickel alloy or titanium alloy;

The carbon-based material fibers include carbon fibers.
The electrode pole piece according to claim 6, wherein the mineral fiber comprises at least one of glass fiber, rock fiber or quartz fiber;

The organic fibers include cellulose fibers.
The electrode piece according to claim 6, wherein the inorganic particles comprise alumina, silica, magnesia, titania, ceria, tin oxide, calcium oxide, zirconia, nickel oxide, At least one of zinc oxide, yttrium oxide or LLZO.
The electrode pole piece according to any one of claims 1 to 5, wherein the conductive layer and/or the insulating layer comprises a lithium-replenishing agent, and the addition amount of the lithium-replenishing agent is 0.25 mg/cm 2 to 25 mg /cm 2 .
An electrochemical device, characterized in that it comprises a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode and/or the negative electrode comprise the electrode pole piece according to any one of claims 1 to 10.
The electrochemical device according to claim 11, wherein the negative electrode is the electrode plate according to any one of claims 1 to 10.
An electronic device, characterized by comprising the electrochemical device according to any one of claims 11 to 12.