CN115810718A - Negative pole piece and secondary battery comprising same - Google Patents
Negative pole piece and secondary battery comprising same Download PDFInfo
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- CN115810718A CN115810718A CN202211464280.2A CN202211464280A CN115810718A CN 115810718 A CN115810718 A CN 115810718A CN 202211464280 A CN202211464280 A CN 202211464280A CN 115810718 A CN115810718 A CN 115810718A
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The application provides a secondary battery, which comprises a negative pole piece, wherein the negative pole piece comprises a negative pole lug, a main body area and a thinning area, the thinning area is an edge area which is adjacently arranged on the negative pole lug, and the thinning area comprises a first coating; the body region comprises a second coating, the first coating and the second coating comprising different negative active materials; the thickness of the thinning area is smaller than that of the main body area, and the thickness difference is larger than 5um; by adopting the secondary battery, the negative influence caused by lithium precipitation of the negative electrode plate of the secondary battery can be reduced, so that the safety, the energy density and the cycle performance of the secondary battery are improved.
Description
Technical Field
The application relates to the technical field of batteries, in particular to a negative pole piece and a secondary battery comprising the same.
Background
In recent years, the application field of the secondary battery is more and more extensive, and the secondary battery is widely applied to the field of new energy automobiles. Lithium ion batteries are the first choice for high endurance vehicles.
However, in the production process of the secondary battery pole piece, the edge thinning process is usually adopted to solve the edge thick edge phenomenon of the pole piece, and the thinning area of the negative pole piece corresponds to the non-thinning area of the positive pole piece due to the adoption of the process of forming the tabs at two sides of the secondary battery with high power and high energy density, and lithium ions extracted from the non-thinning area of the positive pole piece cannot be completely embedded into the thinning area of the negative pole piece, so that lithium precipitation occurs in the thinning area of the negative pole piece. The lithium separation not only reduces the performance of the battery and greatly shortens the cycle life, but also limits the quick charge capacity of the battery and possibly causes disastrous results such as combustion, explosion and the like, so the lithium separation in the thinning region of the negative electrode plate is a problem to be solved urgently.
Disclosure of Invention
In order to achieve the above object, a first aspect of the present application provides a negative electrode tab, including a negative electrode tab, a main body region, and a thinning region current collector, where the thinning region is an edge region adjacently disposed on the negative electrode tab, and the thinning region includes a first coating; the body region comprises a second coating, the first and second coatings comprising different negative active materials; the regional thickness of thinning is less than the main part is regional, and the thickness difference is greater than 5um.
The assembly of different sides of the positive electrode lug and the negative electrode lug of the secondary battery can lead the non-skived area of the positive electrode lug to be opposite to the skived area of the negative electrode lug, and lead the capacity of the skived area of the negative electrode lug relative to the non-skived area of the positive electrode lug to be too small, so that lithium ions released from the positive electrode can not be completely embedded into the negative electrode, and part of the lithium ions deposit metal lithium on the surface of the negative electrode lug to cause lithium precipitation. Excessive lithium precipitation affects the capacity and safety of the battery. Therefore, the negative pole piece is applied to the secondary battery, the phenomenon that the negative pole piece of the secondary battery is thinned to separate lithium can be improved, and the safety, the energy density and the cycle performance of the secondary battery are further improved.
In any embodiment, the negative pole piece comprises a negative pole tab, a main body region and a thinning region, wherein the thinning region is an edge region adjacently arranged on the negative pole tab, and the thinning region comprises a first coating; the body region comprises a second coating, the first coating and the second coating comprising different negative active materials; the thickness in the thinning area is smaller than the thickness of the main body area, and the thickness difference is larger than 5um.
In any embodiment, the first coating comprises one or more of a first negative electrode active material and a second negative electrode active material; the first negative electrode active material comprises one or more of a silicon-based material, a tin-based material and hard carbon, and the second negative electrode active material comprises one or more of a titanium-based material and a metal oxide material.
In any embodiment, the second coating is disposed adjacent to a surface of the first coating.
In any embodiment, the second coating comprises a graphite material selected from one or more of artificial graphite or natural graphite.
In any embodiment, the second coating layer is disposed on a surface of the first coating layer on a side away from the anode tab.
In any embodiment, the second coating thickness is d2; the first coating thickness is d1; d2/d1 is more than or equal to 2 and less than or equal to 10.
In any embodiment, the second coating has a thickness of 30-60um.
In any embodiment, the first coating has a width of 2 to 20mm; the width of the overlapping area of the first coating and the second coating is 1-3mm.
In any embodiment, the first coating comprises a first coating active material, a conductive agent, a dispersant and a binder, wherein the first coating active material accounts for 90-98% of the mass of the first coating; the conductive agent accounts for 1% -5% of the mass of the first coating; the dispersant accounts for 1% -5% of the mass of the first coating; the mass of the binder is 1% -5% of that of the first coating.
In any embodiment, the negative electrode sheet is required to satisfy at least one of the following (1) to (3),
(1) The first coating adhesive is selected from one or more of styrene-butadiene rubber, polyacrylic acid, polyacrylamide and polyurethane;
(2) The first coating dispersing agent is selected from one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, carboxymethyl cellulose amine and sodium alginate;
(3) The first coating conductive agent is selected from one or more of conductive carbon black, ketjen black, graphene, carbon nano tubes, nano gold and nano silver materials.
In any embodiment, the porosity of the first coating is 25% to 45%.
A second aspect of the present application provides a secondary battery comprising the negative electrode tab provided by the first aspect of the present application.
A third aspect of the present application provides an electric device including the secondary battery of the second aspect of the present application.
Drawings
In order to more clearly illustrate the technical solutions of the present application, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
Fig. 1 is one of schematic structural diagrams of a negative electrode sheet provided in an embodiment of the present application;
fig. 2 is a second schematic structural diagram of a negative electrode sheet according to an embodiment of the present application;
fig. 3 is a secondary battery having a square structure according to an embodiment of the present application;
fig. 4 is a secondary battery having a cylindrical structure according to an embodiment of the present disclosure;
fig. 5 is an exploded view of a secondary battery having a cylindrical structure according to an embodiment of the present disclosure;
fig. 6 is a schematic diagram of an electric device in which a secondary battery according to an embodiment of the present application is used as a power source.
Description of the reference numerals:
203 a negative electrode tab; 202 thinning the area; 201 a body region;
303, a negative pole tab; 302 a first coating layer; 301 a second coating.
Detailed Description
Hereinafter, embodiments of the negative electrode sheet, the secondary battery, and the electric device according to the present application are specifically disclosed in detail with reference to the drawings as appropriate. But detailed description thereof will be omitted unnecessarily. For example, detailed descriptions of already known matters and repetitive descriptions of actually the same configurations may be omitted. This is to avoid unnecessarily obscuring the following description, and to facilitate understanding by those skilled in the art. The drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.
The "ranges" disclosed herein are defined in terms of lower limits and upper limits, with a given range being defined by a selection of one lower limit and one upper limit that define the boundaries of the particular range. Ranges defined in this manner may or may not include endpoints and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Further, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise stated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 to 5" have been listed herein, and "0 to 5" is simply an abbreviated representation of the combination of these numbers. In addition, when a parameter is an integer of 2 or more, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, or the like.
All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, if not specifically stated.
All technical and optional features of the present application may be combined with each other to form new solutions, if not otherwise specified.
All steps of the present application may be performed sequentially or randomly, preferably sequentially, if not specifically stated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, and may also comprise steps (b) and (a) performed sequentially. For example, reference to the process further comprising step (c) means that step (c) may be added to the process in any order, for example, the process may comprise steps (a), (b) and (c), may also comprise steps (a), (c) and (b), may also comprise steps (c), (a) and (b), etc.
The terms "comprises" and "comprising" as used herein mean either open or closed unless otherwise specified. For example, the terms "comprising" and "comprises" may mean that other components not listed may also be included or included, or that only listed components may be included or included.
In this application, the term "or" is inclusive, if not otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or not present); a is false (or not present) and B is true (or present); or both a and B are true (or present).
[ negative electrode sheet ]
The negative pole piece includes the negative pole mass flow body and sets up the negative pole rete on the negative pole mass flow body at least one surface, the negative pole rete includes negative pole active material.
As an example, the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two surfaces opposite to the negative electrode current collector.
In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used.
One embodiment of the present application provides a negative electrode tab, referring to fig. 1 and fig. 2, including a negative electrode tab 203, a main body region 201, and a skived region 202, where the skived region 202 is an edge region adjacently disposed on the negative electrode tab 203, and the skived region 202 includes a first coating 302; the body region 201 comprises a second coating 301, the first and second coatings comprising different negative active materials; the thickness of the thinning area 202 is smaller than that of the main body area 201, and the thickness difference is larger than 5um.
The negative electrode sheet generally refers to an electrode sheet having a high potential containing an active material that undergoes a reduction reaction upon discharge. In some embodiments, the negative electrode current collector may employ 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 base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a base material of a polymer material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). The copper foil is taken as a carrier of a negative active material and also as a negative electron collecting and conducting body at a negative electrode, and the copper foil is used for collecting current generated by a battery active substance to generate larger output current. Meanwhile, in the coating process in the manufacturing process of the lithium ion battery negative pole piece, the edge thick edge phenomenon often occurs, namely the edge of the pole piece has the appearance of suddenly increased thickness. The thick limit phenomenon in edge can exert an influence to the technological process of battery and the uniformity of battery performance, be unexpected appearance, specifically speaking, coating edge thickness can be than the thick several microns of normal region to tens of microns, when the rolling of coating drying back, hundreds of thousands of layers of pole pieces are received into a roll, the protruding line of coating side edge thickness accumulates into several millimeters, lead to the pole piece to roll up and produce the drum limit phenomenon, can cause the pole piece fracture when serious, produce extremely bad influence to coating rolling regularity and subsequent handling. Therefore, an edge thinning process is usually adopted in the production and coating processes of the secondary battery electrode plate to solve the problem of thick edges of the electrode plate, and the assembly of different sides of the positive electrode tab and the negative electrode tab of the secondary battery can lead to the situation that the non-thinned area of the positive electrode plate is over against the thinned area of the negative electrode plate, and lead to the situation that the capacity of the thinned area of the negative electrode plate relative to the non-thinned area of the positive electrode area is too small, so that lithium ions released from the positive electrode can not be completely embedded into the negative electrode, and the lithium precipitation phenomenon of the lithium ions deposited on the surface of the negative electrode plate can be aggravated. Excessive lithium separation can cause internal shorting of the battery and related safety issues. The lithium precipitation refers to the deposition of lithium metal on the negative electrode and the local dead lithium caused by the deposition, the dead lithium is irreversible, the deterioration of the cycle life of the secondary battery is accelerated, and the cycle water-skipping is caused even if the lithium is seriously precipitated. Taking a cylindrical battery as an example, the cylindrical battery adopts a special structure with lugs at two sides, and a stacking mode that a thinning area of a negative pole piece corresponds to an un-thinning area of a positive pole piece can occur in the winding process. In the charging process, lithium ions can be extracted from the positive electrode and inserted into the negative electrode, and the non-thinning area of the positive electrode plate contains more active substances, so that the lithium ions extracted from the positive electrode plate cannot be completely inserted into the thinning area of the negative electrode plate, and the lithium precipitation phenomenon is easily caused in the thinning area of the negative electrode plate, namely the lithium ions can only be precipitated on the surface of the negative electrode to form a layer of gray lithium substance. One embodiment of the present application provides a negative electrode tab, referring to fig. 1 and 2, comprising a negative electrode tab 203, a main body region 201, and a skived region 202, the skived region 202 comprising a first coating 302; the body region 201 comprises a second coating 301; the thinning area 202 is an edge area which is adjacently arranged on a negative pole tab 203; the thickness of the thinned region 202 is at least 5um less than the thickness of the main body region 201; the first coating 302 includes one or more of a first negative active material and a second negative active material. The first coating is arranged in the thinning area of the negative pole piece and is opposite to the non-thinning area of the positive pole piece. The first coating can reduce the characteristic of lithium precipitation through the first negative electrode active material and the second negative electrode active material, and the phenomenon of lithium precipitation of the negative electrode plate is relieved.
One embodiment of the present application provides a negative electrode tab, referring to fig. 2, comprising a first coating 302; the first coating 302 includes one or more of a first negative active material and a second negative active material. The first negative electrode active material is a high-dynamic anode material and comprises one or more of a silicon-based material, a tin-based material and hard carbon, the silicon-based material is taken as an example, the theoretical specific capacity of the silicon-based negative electrode material is high, and the theoretical specific capacity of a simple substance silicon negative electrode is up to 4200mAh/g and is 10 times higher than that of a graphite negative electrode material. The theoretical specific capacity of the silicon oxide negative electrode material reaches 2600mAh/g, which is much higher than that of a graphite negative electrode. The average grain diameter of the silicon electrode material is 500nm-30um, and the specific surface area is 1-4m 2 (ii)/g; the tin-based material has high theoretical specific capacity, sn is 990mAh/g, and SnO 2 1494mAh/g, moderate de-intercalation voltage and average grain diameter of 15nm-20um. The first charge gram capacity of the hard carbon can reach 800mAh/g, the average grain diameter is 5um-15um, the interlayer spacing d002 is more than 0.37nm (graphite is 0.3354 nm), and the large interlayer spacing is beneficial to the intercalation and deintercalation of lithium ions, so the hard carbon has excellent charge and discharge performance. In summary, the high-dynamic anode material, such as SiOx material, has a high specific capacity, and can provide a lithium insertion space for lithium ions, which is larger than that of the conventional negative active material, such as graphite material, thereby improving the surface dynamics of the negative electrode and solving the risk of lithium precipitation of the anode corresponding to the non-thinned region of the cylindrical battery cathode. The second negative active material is a high-potential anode material which comprises one or more of a titanium-based material and a metal oxide material; the titanium-based material such as lithium titanate has a spinel structure, a voltage platform of 1.5V, a three-dimensional ion diffusion channel, stable crystal lattice and theoretical specific capacity of 176mAh/g. The product has high safety, high multiplying power, long service life, and high ion diffusivity. The high potential characteristic of the lithium ion battery enables lithium ions to be incapable of carrying out lithium metal deposition reaction on a negative electrode, and is beneficial to improving the phenomenon of lithium precipitation of the anode.
One embodiment of the present application provides a negative electrode tab, referring to fig. 2, comprising a second coating layer 301; the second coating 301 is disposed adjacent to a surface of the first coating 302.
The second coating 301 is disposed on the surface of the first coating 302 on the side away from the anode tab 303 or the first coating 302 is disposed on the surface of the second coating 301 on the side away from the anode tab 303.
One embodiment of the present application provides a negative electrode tab, as shown in fig. 2, wherein the second coating 301 comprises a graphite material, and the graphite material is selected from one or more of artificial graphite or natural graphite.
The second coating 301 is made of a conventional negative electrode material, including graphite materials, which in turn include natural graphite and artificial graphite. The graphite material has high temperature resistance, corrosion resistance, good electrical conductivity, thermal conductivity and stable chemical properties, has a good layered structure, is suitable for repeated intercalation and deintercalation of lithium ions, and is the most widely applied and technically mature cathode material at present. In general, graphite has the advantages of high electronic conductivity, small volume change of a layered structure before and after lithium intercalation, high lithium intercalation capacity, low lithium intercalation potential and the like.
The second coating 301 is made of a widely used negative electrode material such as graphite and is disposed adjacent to the first coating 302. The first coating 302 provides a specific capacity which is several times that of the traditional graphite negative electrode, reduces the lithium precipitation of the negative electrode piece, simultaneously exerts good conductive performance of the negative electrode piece, and can also effectively reduce the phenomena of expansion and insufficient strength of the electrode piece.
One embodiment of the present application provides a negative electrode tab, see fig. 2, with a second coating 301 disposed on the surface of the first coating on the side away from the negative electrode tab.
In this embodiment, the second coating 301 is provided on the surface of the first coating 302 on the side away from the anode tab 303. In the charging process of the secondary battery, the resistance of the area of the negative pole lug 303 is small, the passing current is large, the first coating 302 and the negative pole lug 303 are arranged adjacently, and because the theoretical specific capacity of the active material of the first coating 302 is high, the channels for the lithium ions to be embedded and separated can be provided from all directions, the reaction kinetics is fast, the hidden danger of lithium analysis can be reduced, and the lithium ions which cannot be completely embedded into the negative pole piece during charging can be prevented from being separated out from the surface of the negative pole piece to the greatest extent.
One embodiment of the present application provides a negative electrode tab, see fig. 2, wherein the second coating 301 has a thickness d2; and the first coating 302 has a thickness d1; d2/d1 is more than or equal to 2 and less than or equal to 10.
The second coating layer 301 mainly contains graphite material and other conventional negative electrode materials of secondary batteries, such as graphite. The gram capacity of graphite is generally 372mAh/g, if the high-dynamic negative electrode material, such as a silicon-based material, is used in the present embodiment, the theoretical gram capacity is 4200mAh/g, which is about ten times the gram capacity of graphite, and therefore, when the thickness d1 of the first coating 302 is in the range of one tenth to one half of the thickness d2 of the second coating 301, a good capacity matching effect can be achieved, and meanwhile, compared with a negative electrode plate coating completely using a conventional negative electrode material, such as a graphite material, the negative electrode plate provided in this embodiment has a thinner overall thickness, which is beneficial to increase the overall energy density of the secondary battery while effectively preventing lithium precipitation.
When the thickness ratio of the second coating thickness d2 to the first coating thickness d1 is controlled to be not less than 2 and not more than d2/d1 and not more than 10, the first coating can achieve a good capacity matching effect, so that lithium precipitation is effectively prevented, meanwhile, the overall thickness of the negative pole piece is not too thick, the expansion force and rebound phenomenon of the pole piece are reduced to a certain extent, lithium precipitation is reduced, the service life of the secondary battery is not influenced, and meanwhile, the improvement of energy density is facilitated.
One embodiment of the present application provides a negative electrode tab, see fig. 2, with a second coating 301 having a thickness between 30-60um.
In the manufacturing process of the lithium ion battery negative pole piece, the coating thickness is determined by the capacity of the designed battery and the gram capacity of the active material. In practical application, the thickness of the graphite layer of the negative pole piece of the lithium ion battery is generally set to be about 30-60um.
In this embodiment, the thickness of the second coating 301 of the secondary battery negative electrode plate is limited within 30-60um, and the thickness of the first coating 302 is within a range from one tenth to one half of the second coating, and correspondingly, the thickness of the first coating 302 is between 3um and even 30um, compared with the lithium ion secondary battery negative electrode plate without the first coating 302, the thickness of the secondary battery negative electrode plate with the first coating 302 is thinner, which is beneficial to improving the energy density of the secondary battery while preventing lithium precipitation, and also can not cause the phenomena of expansive force and rebound of the electrode plate due to over-thickness.
One embodiment of the present application provides a negative electrode tab, see fig. 2, wherein the width of the first coating 302 is 2-20mm; the width of the overlapping area of the first coating 302 and the second coating 301 is 1-3mm.
The width of the first coating 302 varies according to the model parameters of different secondary battery negative electrode plates, and ranges from 2mm to 20mm, and specifically may include 4mm, 6mm, 8mm, 10mm, 12mm, 14mm, 16mm, and 18mm. The width of the overlapping area of the first coating layer 302 and the second coating layer 301 is 1-3mm, so that the coating of the first coating layer 302 and the second coating layer 301 on the current collector is divided coating, the overlapping area of the first coating layer 302 and the second coating layer 301 is small (the width of the overlapping area in the width direction of the current collector is 1-3 mm), and the divided coating can avoid the problem of large internal interface resistance caused by overlapping of the first coating layer 302 and the second coating layer 301 due to non-divided coating.
The first coating 302 is consistent in length with the thinning area of the negative electrode plate of the secondary battery, and completely replaces the original thinning area, so that the purpose of preventing lithium precipitation can be achieved. Due to different cell designs, the widths of the thinning areas are different, and when the overlapping area of the first coating 302 and the second coating 301 is smaller (the width of the overlapping area along the width direction of the current collector is between 1 mm and 3 mm), the problem of larger internal interface impedance caused by overlapping the first coating 302 and the second coating 301 can be avoided, which is beneficial to improving the conductivity of the negative pole piece.
One embodiment of the present application provides a negative electrode plate, see fig. 2, wherein a first coating 302 comprises a first coating active material, a conductive agent, a dispersant, and a binder, and the first coating active material accounts for 90% to 98% of the mass of the first coating 302; the conductive agent accounts for 1% -5% of the mass of the first coating 302; the dispersant accounts for 1-5% of the mass of the first coating 302; the binder accounts for 1-5% of the mass of the first coating 302.
Wherein the first coating active material comprises one or more of a first negative electrode active material or a second negative electrode active material; the first negative electrode active material comprises at least one of a silicon-based material, a tin-based material and hard carbon, wherein the theoretical specific capacity of the silicon-based material reaches 4200mAh/g, higher gram capacity can be provided, reaction kinetics are fast, and the effect of reducing lithium precipitation is excellent; the second anode active material includes at least one of a titanium-based material and a metal oxide material; the first coating active material is a silicon-based material, and comprises one or more of silicon, silicon oxide (silicon monoxide and silicon dioxide) and silicon alloy, wherein the mass of the first coating active material accounts for 90-98% of that of the first coating, so that a better lithium precipitation inhibition effect can be achieved. (ii) a The conductive agent of the first coating 302 comprises one or more of conductive carbon black, ketjen black, graphene, carbon nano tubes, nano gold and nano silver materials, and accounts for 1-5% of the mass of the first coating; the dispersant of the first coating 302 comprises one or more of sodium carboxymethylcellulose, lithium carboxymethylcellulose, carboxymethylcellulose amine and sodium alginate, and accounts for 1-5% of the mass of the first coating; the binder of the first coating 302 comprises one or more of styrene butadiene rubber, polyacrylic acid, polyacrylamide and polyurethane, and accounts for 1% -5% of the mass of the first coating.
One embodiment of the present application provides a negative electrode sheet, referring to fig. 2, satisfying at least one of the following requirements (1) to (3), (1) the first coating binder is selected from one or more of styrene-butadiene rubber, polyacrylic acid, polyacrylamide, and polyurethane; (2) The first coating dispersing agent is selected from one or more of sodium carboxymethylcellulose, lithium carboxymethylcellulose, carboxymethyl cellulose amine and sodium alginate (3), and the first coating conductive agent is selected from one or more of conductive carbon black, ketjen black, graphene, carbon nano tubes, nano gold and nano silver materials.
The conductive agent of the first coating 302 includes one or more of conductive carbon black, ketjen black, graphene, carbon nanotube, nanogold, and nano silver material, wherein when the conductive agent of the first coating adopts a high-dynamics conductive agent including CNT, graphene, mxene, and graphite alkyne, the electronic impedance can be reduced, which is beneficial to the transmission of electrons in the pole piece. The dispersant of the first coating 302 comprises one or more of sodium carboxymethylcellulose, lithium carboxymethylcellulose, carboxymethylcellulose amine and sodium alginate, wherein when the dispersant of the first coating adopts a high-dynamic dispersant, the dispersant of the first coating comprises CMC-Li and PAA-Li, so that the transmission speed of lithium ions in the pole piece can be increased, the ionic impedance can be reduced, and the improvement of the kinetics of the lithium ions in the pole piece is facilitated. The binder of the first coating 302 comprises one or more of styrene-butadiene rubber, polyacrylic acid, polyacrylamide and polyurethane.
The high-dynamic conductive agent mainly comprises two-dimensional conductive agents such as CNT (carbon nano tube), graphene and the like and conductive carbon black which can form a conductive network of points, lines and surfaces, so that a negative pole piece has higher electron conduction capability, and an electrochemical reaction mechanism of lithium ions on a negative pole can be promoted to rapidly occur.
One embodiment of the present application provides a negative electrode tab, see fig. 2, having a porosity of 25% to 45% of the first coating 302.
The porosity is the volume fraction of the pores in the electrode, and is determined by the actual density of the active material, the conductive agent, the dispersing agent and the binder and the pressure of cold pressing after coating. The electrolyte is filled in the pores of the porous electrode, lithium ions are conducted in the pores through the electrolyte, and the conduction characteristic is closely related to the porosity. The larger the porosity is, the higher the volume fraction of the electrolyte phase is, the more sufficient the electrolyte is wetted, the larger the effective lithium ion conductivity is, and the transmission of lithium ions in the pole piece is facilitated. However, too high porosity will affect the contact between the electrode plate particles, resulting in too high interface contact resistance, reduced electron transmission capability, and reduced service life of the electrode plate. Therefore, the electrode sheet of the electrode needs a proper porosity, and the porosity is designed to be inconsistent according to different active materials and different particle sizes. The design is generally 25% to 45%, preferably 35% to 40%.
In some embodiments, the negative electrode sheet can be prepared by: dispersing the components for preparing the negative electrode plate, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (such as deionized water) to form negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and drying, cold pressing and the like to obtain the negative electrode pole piece.
[ Positive electrode sheet ]
The positive electrode plate generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.
As an example, the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two surfaces opposite to the positive electrode current collector.
In some embodiments, additives described herein above may be included in the positive electrode film layer. The mass fraction of the additive in the positive electrode film layer can be 0.01-10%, and can be 0.05-8%.
In some embodiments, the positive electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a base material of a polymer material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some embodiments, the positive active material may employ a positive active material for a battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates of olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material of a battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) 2 ) Lithium nickel oxides (e.g., liNiO) 2 ) Lithium manganese oxide (e.g., liMnO) 2 、LiMn 2 O 4 ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) 1/3 Co 1/3 Mn 1/3 O 2 (may also be abbreviated as NCM) 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (may also be abbreviated as NCM) 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (may also be abbreviated as NCM) 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (may also be abbreviated as NCM) 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (may also be abbreviated as NCM) 811 ) Lithium nickel cobalt aluminum oxides (e.g., liNi) 0.85 Co 0.15 Al 0.05 O 2 ) And modified compounds thereof, and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO) 4 (also referred to as LFP for short)), a composite material of lithium iron phosphate and carbon, and lithium manganese phosphate (e.g., liMnPO) 4 ) At least one of a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroacrylate resin.
In some embodiments, the positive electrode film layer further optionally 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 may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive active material, the additives previously described herein, the conductive agent, the binder, and any other components in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and the like to obtain the positive electrode piece.
[ electrolyte ]
The kind of the electrolyte is not particularly limited and may be selected as desired. For example, the electrolyte may be liquid, gel, or all solid.
In some embodiments, additives as described herein above may be included in the electrolyte. The mass fraction of the additive in the electrolyte may be 0.01-10%, optionally 0.01-5%.
In some embodiments, the electrolyte is in a liquid state and includes an electrolyte salt and a solvent.
In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium dioxaoxalato borate, lithium difluorooxalato phosphate, and lithium tetrafluorooxalato phosphate.
In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.
In some embodiments, the sodium salt and the potassium salt are also not particularly limited and may be selected according to actual needs.
In some embodiments, the electrolyte further optionally includes an additive. By way of example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives capable of improving certain properties of the battery, such as additives that improve the overcharge properties of the battery, additives that improve the high-or low-temperature properties of the battery, and the like.
[ isolation film ]
In some embodiments, a separator is further included in the secondary battery. The type of the separator is not particularly limited, and any known separator having a porous structure and good chemical and mechanical stability may be used.
In some embodiments, the material of the isolation film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.
In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.
[ Secondary Battery ]
A secondary battery is also called a rechargeable battery or a secondary battery, and refers to a battery that can be continuously used by activating an active material by means of charging after the battery is discharged. In general, a secondary battery includes a positive electrode tab, a negative electrode tab, a separator, and an electrolyte. In the process of charging and discharging the battery, active ions (such as lithium ions) are inserted and extracted back and forth between the positive pole piece and the negative pole piece. The isolating membrane is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the short circuit of the positive pole and the negative pole, and can enable active ions to pass through. The electrolyte is arranged between the positive pole piece and the negative pole piece and mainly plays a role in conducting active ions.
One embodiment of the present application provides a secondary battery including the negative electrode tab according to one embodiment of the present application.
In some embodiments, the secondary battery may include an exterior package. The exterior package may be used to enclose the electrode assembly and electrolyte.
In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The outer package of the secondary battery may also be a pouch, such as a pouch-type pouch. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
The shape of the secondary battery is not particularly limited, and may be a cylindrical shape, a square shape, or any other arbitrary shape. For example, fig. 3 is a secondary battery of a square structure as an example. Fig. 4 is a secondary battery of a cylindrical structure as an example. Fig. 5 is an exploded view of a secondary battery of a cylindrical structure as an example.
In addition, this application still provides an electric installation, electric installation includes the secondary battery that this application provided. The secondary battery may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The powered device may include, but is not limited to, a mobile device (e.g., a mobile phone, a laptop computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, and a satellite, an energy storage system, etc.
As the electricity utilization device, a secondary battery, a battery module, or a battery pack may be selected according to its use requirements.
Fig. 6 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. In order to meet the demand of the electric device for high power and high energy density of the secondary battery, a battery pack may be used.
[ examples ]
Hereinafter, examples of the present application will be described. The following description of the embodiments is merely exemplary in nature and is in no way intended to limit the present disclosure. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
Preparation of examples
Comparative example:
(1) Preparation of positive pole piece
Lithium iron phosphate (LiFePO) as positive electrode active material 4 ) The polyvinylidene fluoride (PVDF) and the conductive carbon black (SP) are mixed according to the weight ratio: 96%:2%:2 percent of the solution is dissolved in N-methyl pyrrolidone (NMP) and evenly coated on an aluminum foil, and the positive plate is prepared by drying, rolling and cutting. Wherein the positive electrode active material may be Nickel Cobalt Manganese (NCM), lithium cobaltate (LiCO) 2 ) And the like are commonly used positive electrode active materials.
(2) Preparation of negative pole piece
The preparation of the negative pole piece, in order to prevent edge burst, the coating process is to thin the area near the edge of the pole piece, which is called thin area, the width of the thin area is 14mm, and the thickness is at least 5um thinner than the main area. The method comprises the following steps of mixing artificial graphite, conductive carbon black (Super P), styrene Butadiene Rubber (SBR) and sodium carboxymethylcellulose (CMC-Na) in a weight ratio of 95%:1.7%:1.2%: adding 2.1 percent of the mixture into deionized water, uniformly stirring to prepare negative electrode slurry, uniformly coating the prepared negative electrode slurry on a current collector carbon-coated copper foil with a negative electrode of 6 mu m, and drying and rolling to prepare a negative electrode plate. Wherein the coating surface density is 6.45mg/cm < 2 >, the compaction density is 1.6g/cm < 3 >, and the thickness of the single-surface coating after rolling is 41 mu m.
(3) Preparation of the electrolyte
The lithium salt used in the electrolyte of the embodiment of the present application is lithium hexafluorophosphate (LiPF 6) having a concentration of 1M, and the organic solvent is Ethylene Carbonate (EC), dimethyl carbonate (DMC), and Ethyl Methyl Carbonate (EMC) in a mass ratio of 1:1:1 ratio of the mixture prepared.
(4) Preparation of the separator
Polypropylene film was used as the separator.
(5) Preparation of secondary battery
The prepared lithium ion negative pole piece, the polypropylene porous diaphragm and the positive pole piece are sequentially overlapped to prepare a battery roll core through a winding process, and the battery roll core is prepared into the conventional winding type cylindrical lithium ion battery through the procedures of packaging, liquid injection, formation, sorting and the like.
Example 1:
(4) Preparation of positive pole piece
Lithium iron phosphate (LiFePO) as a positive electrode active material 4 ) The polyvinylidene fluoride (PVDF) and the conductive carbon black (SP) are mixed according to the weight ratio: 96%:2%:2 percent of the solution is dissolved in N-methyl pyrrolidone (NMP) and evenly coated on an aluminum foil, and the positive plate is prepared by drying, rolling and cutting. Wherein the positive electrode active material may be Nickel Cobalt Manganese (NCM), lithium cobaltate (LiCO) 2 ) And the like are commonly used positive electrode active materials.
(5) Preparation of negative pole piece
Preparing a negative pole piece, wherein the artificial graphite, the conductive carbon black (Super P), the Styrene Butadiene Rubber (SBR) and the sodium carboxymethylcellulose (CMC-Na) are mixed according to the weight ratio of 95%:1.7%:1.2%:2.1 percent of the graphite powder is added into deionized water and evenly stirred to prepare the cathode graphite slurry. The SiOx/C composite active material, conductive carbon black (Super P), carbon Nano Tubes (CNT), lithium polyacrylate and sodium carboxymethyl cellulose (CMC-Na) are mixed according to the mass ratio of 95%:1.2%:0.5%:2.0%: adding 1.3 percent of the mixture into deionized water, and uniformly stirring to prepare the active material cathode silicon-based slurry. Referring to fig. 2, the prepared negative electrode silicon-based material was coated on the thinned region of the negative electrode current collector in the comparative example to form a first coating 302; the prepared negative electrode graphite slurry is coated on the first coating layer 302 to form a second coating layer 301. The negative current collector adopts 6um copper foil. Wherein the coating surface density of the second coating layer 301 is 6.45mg/cm 2 The compacted density is 1.6g/cm 3 The thickness of the single-side coating after rolling was 41 μm. The coating surface density of the first coating layer 302 is 6.45mg/cm 2 The compacted density is 1.6g/cm 3 And the thickness of the single surface after rolling is 27um, and the width of the coating is 8mm.
(6) Preparation of the electrolyte
The lithium salt used in the electrolyte of the examples of the present application was lithium hexafluorophosphate (LiPF 6) at a concentration of 1M, and the organic solvent was Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC) in a mass ratio of 1:1:1 ratio of the mixture prepared.
(4) Preparation of the separator
Polypropylene film was used as the separator.
(5) Preparation of secondary battery
The prepared lithium ion negative pole piece, the polypropylene porous diaphragm and the positive pole piece are sequentially overlapped to prepare a battery roll core through a winding process, and the battery roll core is prepared into the conventional winding type cylindrical lithium ion battery through the procedures of packaging, liquid injection, formation, sorting and the like.
Example 2:
the only difference between the second embodiment and the first embodiment is that the coating width of the first coating layer 302 (see fig. 2) is 14mm.
Example 3:
the only difference between the third embodiment and the first embodiment is that the coating width of the first coating layer 302 (see fig. 2) is 16mm.
Example 4:
the only difference between the fourth embodiment and the second embodiment is that the coating thickness of the first coating 302 (see fig. 2) is rolled to a single-sided thickness of 22um.
Example 5:
(1) Preparation of positive pole piece
Lithium iron phosphate (LiFePO) as positive electrode active material 4 ) The polyvinylidene fluoride (PVDF) and the conductive carbon black (SP) are mixed according to the weight ratio: 96%:2%:2 percent of the solution is dissolved in N-methyl pyrrolidone (NMP) and evenly coated on an aluminum foil, and the positive plate is prepared by drying, rolling and cutting. Wherein the positive electrode active material can be Nickel Cobalt Manganese (NCM), lithium cobaltate (LiCO) 2 ) And the like are commonly used positive electrode active materials.
(2) Preparation of negative pole piece
Preparing a negative pole piece, wherein the artificial graphite, the conductive carbon black (Super P), the Styrene Butadiene Rubber (SBR) and the sodium carboxymethylcellulose (CMC-Na) are mixed according to the weight ratio of 95%:1.7%:1.2%:2.1 percent of the graphite powder is added into deionized water and evenly stirred to prepare the cathode graphite slurry. The SiOx/C composite active material, conductive carbon black (Super P), carbon Nano Tubes (CNT), styrene Butadiene Rubber (SBR) and carboxymethyl cellulose lithium (CMC-Li) are mixed according to the mass ratio of 95%:1.2%:0.5%:2.0%: adding 1.3 percent of the mixture into deionized water, and uniformly stirring to prepare the active material cathode silicon-based slurry. Coating the prepared negative electrode graphite slurry on the thinning area and the main body area of the negative electrode current collector in the comparative example, wherein the coating surface density is 6.45mg/cm 2 The compacted density was 1.6g/cm3 and the thickness of the single-side coating after rolling was 41 μm, see fig. 2, to form a graphite coating of the second coating 301 and the first coating 302. Then, a silicon negative electrode coating with a thickness of 5um and a coating width of 14mm was coated on the graphite coating of the first coating 302, to form a lithium deposition-free coating of the first coating 302.
(3) Preparation of the electrolyte
The lithium salt used in the electrolyte of the examples of the present application was lithium hexafluorophosphate (LiPF 6) at a concentration of 1M, and the organic solvent was Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC) in a mass ratio of 1:1:1 ratio of the mixture prepared.
(4) Preparation of the separator
Polypropylene film was used as the separator.
(5) Preparation of secondary battery
The prepared lithium ion negative pole piece, the polypropylene porous diaphragm and the positive pole piece are sequentially overlapped to prepare a battery roll core through a winding process, and the battery roll core is packaged, injected with liquid, formed, sorted and the like to prepare the conventional winding type cylindrical lithium ion battery.
Example 6:
the only difference between the sixth embodiment and the fifth embodiment is that the lithium elution preventing coating of the first coating 302 is a Li4Ti5O12 negative electrode coating.
Example 7:
the only difference between the seventh embodiment and the fifth embodiment is that the non-lithiating coating of the first coating 302 was a mixed composite active material negative electrode coating prepared (50% li4ti5o12 active material +50% siox/C).
Test method
1. Normal temperature lithium extraction test
The lithium evolution condition of the 25 ℃ battery after 20 charge-discharge cycles was tested: charging to 3.65V at a constant current of 0.5C, and then charging at a constant voltage until the current is reduced to 0.05C; the discharge process is to discharge to 2.5V at a constant current of 0.5C; and finally, fully charging at 0.5C, disassembling the battery and fully charging the battery core, and checking the lithium precipitation condition of the negative electrode plate, specifically, observing whether the grey-white lithium deposition appears on the surface of the negative electrode by naked eyes. If continuous off-white lithium deposition occurs on the surface of the pole piece and an area is formed, which can be measured by a measuring tool to a certain value, the lithium is seriously analyzed. If the grey lithium deposition appears on the surface of the pole piece in a point or linear shape and a certain numerical area cannot be measured by a measuring tool, the method is called slight lithium analysis. If no off-white lithium deposition is observed on the surface of the pole piece, it is said that no lithium is separated out.
2. Battery energy density calculation
When the capacity of the battery after capacity division is denoted as C, the weight of the battery is W, and the voltage is denoted as V, the energy density of the battery = C × V/W.
3. 25 ℃,1C/1C,1000 times of capacity retention rate cycle test
Charging the lithium ion secondary battery to 3.65V at a constant current of 1C at 25 ℃, then charging to a cut-off current of 0.05C at a constant voltage, standing for 5min, discharging to 3.0V at a constant current of 1C, and repeating the process for 1000 times. Capacity retention (%) of the battery after 1000 cycles = discharge capacity after 1000 cycles/discharge capacity after the first cycle × 100%.
The results of the relevant performance tests are shown in the following table:
according to the results, the energy density of all experimental groups is greatly improved compared with that of the comparative group; according to the conventional winding type battery, after the anode corresponding to the cathode non-thinning area is coated with the SiOx material, the energy density of the battery is increased, and meanwhile, the anode lithium risk corresponding to the cathode non-thinning area is reduced, mainly because the SiOx material has the characteristic of high specific capacity, a lithium insertion space which is 10 times more than that of a graphite material can be provided for lithium ions, and the surface dynamics of the cathode is improved. The risk of lithium precipitation of the anode corresponding to the non-thinning area of the cathode of the cylindrical battery can be solved. Examples 5, 6 and 7, the first coating 302 was on the original stone compared to the second coating 301On the basis of the ink coating, the thickness of a non-graphite coating with the thickness of 5um is coated, mainly for improving lithium precipitation, and the improvement of energy density is not facilitated. The comparison of the capacity retention ratio of the examples shows that: referring to FIG. 2, the first coating 302 improves lithium extraction, which is beneficial for improved cycling performance, particularly where the first coating 302 contains Li 4 Ti 5 O 12 Mainly due to Li 4 Ti 5 O 12 No strain during charging and discharging.
The present application is not limited to the above embodiments. The above embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exhibiting the same operation and effect within the technical scope of the present application are all included in the technical scope of the present application. In addition, various modifications that can be conceived by those skilled in the art are applied to the embodiments and other embodiments are also included in the scope of the present application, in which some of the constituent elements in the embodiments are combined and constructed, without departing from the scope of the present application.
Claims (13)
1. The negative pole piece is characterized by comprising a negative pole lug, a main body area and a thinning area, wherein the thinning area is an edge area which is adjacently arranged on the negative pole lug, and the thinning area comprises a first coating; the body region comprises a second coating, the first coating and the second coating comprising different negative active materials; the thickness in the thinning area is smaller than the thickness of the main body area, and the thickness difference is larger than 5um.
2. The negative pole piece of claim 1, wherein the first coating comprises one or more of a first negative active material and a second negative active material; the first negative active material comprises one or more of a silicon-based material, a tin-based material and hard carbon, and preferably the silicon-based material; the second negative active material comprises one or more of a titanium-based material and a metal oxide material.
3. The negative electrode tab of any one of claims 1-2, wherein the second coating is disposed adjacent to a surface of the first coating.
4. The negative electrode plate as claimed in any one of claims 1 to 3, wherein the second coating comprises a graphite material selected from one or more of artificial graphite and natural graphite.
5. The negative electrode plate as claimed in any one of claims 1 to 4, wherein the second coating layer is disposed on the surface of the first coating layer on the side away from the negative electrode tab.
6. The negative electrode tab of any one of claims 1-5, wherein the second coating has a thickness d2; the first coating thickness is d1; d2/d1 is more than or equal to 2 and less than or equal to 10.
7. The negative electrode sheet of any one of claims 1 to 6, wherein the thickness of the second coating layer is 30 to 60um.
8. The negative electrode tab of any one of claims 1 to 7, wherein the width of the first coating layer is 2 to 20mm; the width of the overlapping area of the first coating layer and the second coating layer is 1-3mm.
9. The negative electrode plate as claimed in any one of claims 1 to 8, wherein the first coating comprises a first coating active material, a conductive agent, a dispersant and a binder, and the first coating active material accounts for 90 to 98 percent of the mass of the first coating; the conductive agent accounts for 1% -5% of the mass of the first coating; the dispersant accounts for 1% -5% of the mass of the first coating; the mass of the binder is 1% -5% of that of the first coating.
10. The negative electrode tab according to any one of claims 1 to 9, wherein at least one of the following (1) to (3) is satisfied:
(1) The first coating adhesive is selected from one or more of styrene-butadiene rubber, polyacrylic acid, polyacrylamide and polyurethane;
(2) The first coating dispersing agent is selected from one or more of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, carboxymethyl cellulose amine and sodium alginate;
(3) The first coating conductive agent is selected from one or more of conductive carbon black, ketjen black, graphene, carbon nanotubes, nanogold and nano silver materials.
11. The negative electrode tab of any one of claims 1-10, wherein the porosity of the first coating is 25% to 45%.
12. A secondary battery comprising the negative electrode tab according to any one of claims 1 to 11.
13. An electric device comprising the secondary battery according to claim 12.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116525766A (en) * | 2023-06-27 | 2023-08-01 | 宁德时代新能源科技股份有限公司 | Secondary battery and electricity utilization device |
| CN117293274A (en) * | 2023-11-23 | 2023-12-26 | 宁德时代新能源科技股份有限公司 | Negative electrode plate, preparation method thereof, battery and power utilization device |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116525766A (en) * | 2023-06-27 | 2023-08-01 | 宁德时代新能源科技股份有限公司 | Secondary battery and electricity utilization device |
| CN116525766B (en) * | 2023-06-27 | 2023-09-26 | 宁德时代新能源科技股份有限公司 | Secondary battery and electricity utilization device |
| CN117293274A (en) * | 2023-11-23 | 2023-12-26 | 宁德时代新能源科技股份有限公司 | Negative electrode plate, preparation method thereof, battery and power utilization device |
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