Negative pole piece and battery with same

Abstract

The utility model relates to the technical field of batteries, in particular to a negative pole piece and a battery with the same. The utility model provides a negative pole piece. The negative pole piece comprises a current collector, a positive pole piece and a negative pole piece, the first carbon material layer is arranged on the surface of at least one side of the current collector; the second carbon material layer is arranged on the surface of one side, deviating from the current collector, of the first carbon material layer; the protective layer is arranged on the surface of one side, deviating from the first carbon material layer, of the second carbon material layer; wherein the porosity of the first carbon material layer is smaller than that of the second carbon material layer. The utility model also provides a battery comprising the negative pole piece. According to the invention, the length of lithium dendrites can be reduced, the safety performance of the cathode-free battery is improved, and the cycle life of the battery can be prolonged.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, and in particular to a negative electrode sheet and a battery having the same. Background Art

[0002] In recent years, in order to achieve lithium metal batteries with higher energy density, lithium metal-free anode-free lithium batteries represent one of the most advanced technologies in the field of lithium batteries. Although anode-free batteries will increase the energy density of the battery, anode-free batteries also have the problem of lithium dendrites. For example, lithium dendrites are easily formed during the lithium deposition / stripping process. Uncontrollable lithium dendrite growth will pierce the diaphragm, deteriorate performance, and cause battery short circuit and thermal runaway, causing safety problems. In other words, due to the existence of the lithium dendrite problem, it is easy to cause safety hazards in the battery. In addition, lithium metal easily reacts with the electrolyte to cause the loss of active lithium, thereby affecting the cycle life of the battery. Therefore, it is necessary to develop an effective solution to alleviate the problem of lithium dendrites, and then alleviate the above problems.

[0003] In view of this, the present utility model is proposed. Utility Model Content

[0004] In view of this, the utility model aims to solve one of the technical problems in the related art to at least a certain extent. To this end, the utility model provides a negative electrode plate and a battery having the same, which can reduce the length of lithium dendrites, improve the safety performance of negative electrode-free batteries, and also improve the cycle life of the battery.

[0005] In order to solve the above technical problems, this application is implemented as follows:

[0006] According to one aspect of the present application, an embodiment of the present application provides a negative electrode plate, the negative electrode plate comprising:

[0007] current collector;

[0008] a first carbon material layer, the first carbon material layer being disposed on at least one side surface of the current collector;

[0009] a second carbon material layer, the second carbon material layer being disposed on a surface of the first carbon material layer facing away from the current collector;

[0010] A protective layer, the protective layer being disposed on a surface of the second carbon material layer facing away from the first carbon material layer;

[0011] The porosity of the first carbon material layer is smaller than the porosity of the second carbon material layer.

[0012] In addition, the negative electrode sheet according to the present application may also have the following additional technical features:

[0013] In some embodiments, the porosity of the second carbon material layer is 20% to 70%.

[0014] In some embodiments, the porosity of the first carbon material layer is less than 10%.

[0015] In some embodiments, the thickness of the first carbon material layer is 1 μm to 2 μm.

[0016] In some embodiments, the second carbon material layer has a thickness of 1 μm to 10 μm.

[0017] In some of the embodiments, the current collector is copper foil;

[0018] The negative electrode plate further includes a lithium supplement layer, and the lithium supplement layer is arranged between the copper foil and the first carbon material;

[0019] The coating area of ​​the lithium replenishing layer on the copper foil is greater than 50%.

[0020] In some of the embodiments, the copper foil has a thickness of 4 μm to 50 μm;

[0021] The thickness of the lithium supplement layer is 5 μm to 20 μm.

[0022] In some of the embodiments, the thickness of the protective layer is 1 μm to 10 μm;

[0023] The protective layer includes an inorganic ceramic layer.

[0024] In some of the embodiments, the first carbon material layer is a graphene layer;

[0025] The second carbon material layer is any one of carbon nanotubes, graphene, conductive carbon black or porous carbon.

[0026] According to another aspect of the present application, an embodiment of the present application provides a battery, the battery comprising:

[0027] A positive electrode sheet, a negative electrode sheet as described above, and an electrolyte.

[0028] The implementation of the technical solution of the utility model has at least the following beneficial effects:

[0029] In an embodiment of the present application, the negative electrode plate provided includes a current collector, a first carbon material layer, a second carbon material layer and a protective layer arranged in a stacked manner, wherein the porosity of the first carbon material layer is less than the porosity of the second carbon material layer. Thus, by arranging a first carbon material layer with a relatively small porosity on the surface of the current collector, it is possible to isolate the further reaction of air and the current collector, and by arranging a second carbon material layer with a relatively large porosity on the surface of the first carbon material layer, the pores or gaps of the second carbon material layer can be used as a space for lithium deposition, thereby reducing or avoiding the deposition of lithium dendrites on the surface, thereby reducing the length of lithium dendrites or eliminating lithium dendrites, and improving the safety performance of the battery. At the same time, the second carbon material layer or the first carbon material layer has a certain conductivity, and can also play a role in improving the conductivity of the negative electrode plate. In addition, the pores of the second carbon material layer can also adsorb electrolyte, thereby improving the liquid retention of the battery cell, and can reduce the deposition of lithium ions on the surface of the pole piece due to the lack of electrolyte. By arranging a protective layer on the second carbon material layer, the protective layer can be used to prevent or avoid the formed lithium dendrites from piercing the isolation membrane and causing the safety failure of the battery cell, thereby playing a role in safety protection.

[0030] Additional aspects and advantages of the present application will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other purposes, features and advantages of the present invention will become more apparent by describing the embodiments of the present invention in more detail in conjunction with the accompanying drawings. The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings, the same reference numerals generally represent the same components or steps.

[0032] Figure 1 The figure shows a schematic diagram of the structure of a negative electrode sheet provided by an embodiment of the utility model;

[0033] Figure 2 Shown is a schematic structural diagram of another negative electrode sheet provided in an embodiment of the utility model.

[0034] Description of reference numerals:

[0035] 10-current collector;

[0036] 11- copper foil;

[0037] 12-lithium replenishing layer;

[0038] 20-a first carbon material layer;

[0039] 30- a second carbon material layer;

[0040] 40-Protective layer. DETAILED DESCRIPTION

[0041] The present application is further described below in conjunction with specific embodiments. It should be understood that these embodiments of the present application are only used to illustrate the present application and are not used to limit the scope of the present application.

[0042] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0043] Below, the embodiments of the negative electrode plate, battery, etc. of the present application are specifically disclosed with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0044] If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0045] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0046] Generally speaking, a negative electrode-free battery refers to a battery "without negative electrode active material". By not using negative electrode active materials, the negative electrode-free battery can improve the energy density of the battery. The technical principle of a negative electrode-free battery is to deposit the lithium in the positive electrode on the negative electrode current collector through formation charging or during the first charging of the battery. However, the interaction between the negative electrode structure or the negative electrode current collector and lithium in the related art is weak, resulting in uneven lithium deposition. Uncontrollable lithium deposition will form dendrites, deteriorate performance, and cause safety hazards. That is, the existing negative electrode-free batteries mainly have the problem of lithium dendrites, which leads to safety hazards in the battery. In addition, lithium metal easily reacts with the electrolyte, resulting in the loss of active lithium, thereby affecting the cycle life of the battery cell.

[0047] In view of this, the technical solution of the embodiment of the present application provides an improved negative electrode plate, which can be a negative electrode plate without negative electrode active material, and the negative electrode plate can be used in a negative electrode-free battery. The technical solution of the embodiment of the present application can alleviate the problem of lithium dendrites in existing negative electrode-free batteries, thereby reducing the length of lithium dendrites and improving the safety performance and cycle life of negative electrode-free batteries. The specific technical solution is described below.

[0048] See also Figure 1 to Figure 2 As shown, an embodiment of the present application provides a negative electrode sheet, which includes a current collector 10, a first carbon material layer 20, a second carbon material layer 30 and a protective layer 40 that are stacked;

[0049] The first carbon material layer 20 is disposed on at least one side surface of the current collector 10;

[0050] The second carbon material layer 30 is disposed on a surface of the first carbon material layer 20 facing away from the current collector 10;

[0051] The protective layer 40 is disposed on a surface of the second carbon material layer 30 facing away from the first carbon material layer 20;

[0052] The porosity of the first carbon material layer 20 is smaller than the porosity of the second carbon material layer 30 .

[0053] The above “the first carbon material layer 20 is disposed on at least one side surface of the current collector 10” means that the first carbon material layer 20 can be disposed on one surface of the current collector 10 along its thickness direction, or on two surfaces of the current collector 10 along its thickness direction. The “surface” here can be the entire area of ​​the current collector 10, or a partial area of ​​the current collector 10, and there is no particular limitation in this application, as long as the purpose of this application can be achieved.

[0054] Optionally, in this embodiment, the current collector 10 has two surfaces opposite to each other in its own thickness direction, and the first carbon material layer 20 is disposed on the two opposite surfaces of the current collector 10. Further, the first carbon material layer 20, the second carbon material layer 30 and the protective layer 40 are sequentially stacked on one surface of the current collector 10, and the first carbon material layer 20, the second carbon material layer 30 and the protective layer 40 are sequentially stacked on the other surface of the current collector 10. It is understood that in other embodiments, the first carbon material layer 20 can also be stacked on any one of the two surfaces of the current collector 10.

[0055] In this embodiment, the porosity of the first carbon material layer 20 and the second carbon material layer 30 are different. The porosity of the first carbon material layer 20 is smaller than that of the second carbon material layer 30. For example, the first carbon material layer 20 may be a dense carbon layer, and the second carbon material layer 30 may be a porous carbon layer.

[0056] It should be explained that in the embodiments of the present application, porosity has a well-known meaning in the art and can be tested using methods and instruments known in the art. Usually, the porosity of the first carbon material layer refers to the ratio of the volume of all pores in the first carbon material layer to the total volume of the first carbon material layer; similarly, the porosity of the second carbon material layer refers to the ratio of the volume of all pores in the second carbon material layer to the total volume of the second carbon material layer. In the embodiments of the present application, the porosity of the first carbon material layer and the second carbon material layer can be monitored by a charge-coupled device (CCD); alternatively, the porosity can be measured by a gas displacement method in accordance with GB / T24586.

[0057] Therefore, based on the above configuration, the technical solution provided in the embodiment of the present application is adopted, a first carbon material layer 20 is arranged on the surface of the current collector 10, a second carbon material layer 30 is arranged on the surface of the first carbon material layer 20, and a protective layer 40 is arranged on the surface of the second carbon material layer 30. Optionally, the protective layer 40 is preferably an inorganic protective layer. By arranging a first carbon material layer 20 with a relatively small porosity, such as a dense carbon layer, on the surface of the current collector 10, it can play a role in isolating the further reaction of air and the current collector 10. By arranging a second carbon material layer 30 with a relatively large porosity, such as a porous carbon layer, on the surface of the first carbon material layer 20, the pores or gaps of the second carbon material layer 30 can be used as a space for lithium deposition, thereby reducing or avoiding the deposition of lithium dendrites on the surface, thereby reducing the length of lithium dendrites or eliminating lithium dendrites, and improving the safety performance of the battery. At the same time, the second carbon material layer 30 or the first carbon material layer 20 has a certain conductivity, and can also play a role in improving the conductivity of the negative electrode sheet. In addition, the pores of the second carbon material layer 30 can also absorb electrolyte, thereby improving the liquid retention of the battery cell and reducing the deposition of lithium ions on the surface of the pole piece due to lack of electrolyte. In addition, there are certain gaps in the second carbon material layer 30, which can be used as a space for lithium ion deposition, thereby reducing the deposition of lithium ions on the surface of the carbon layer. By providing a protective layer 40 on the second carbon material layer 30, the protective layer 40 can be used to prevent or avoid the formed lithium dendrites from piercing the isolation membrane and causing the safety failure of the battery cell, thereby playing a role in safety protection.

[0058] In some embodiments, the porosity of the second carbon material layer 30 is 20% to 70%. When the porosity of the second carbon material layer 30 is within the above range, it helps to provide sufficient lithium ion deposition sites, that is, it can provide space for the deposition of lithium ions, optimize the deposition of lithium ions inside, thereby reducing the deposition of lithium ions on the surface of the current collector 10, reducing the deposition and formation of lithium dendrites on the surface, thereby reducing the length of lithium dendrites and improving the safety performance of the battery. At the same time, when the porosity of the second carbon material layer 30 is within the above range, it can reduce the impact on the energy density of the battery cell, that is, it helps to improve the energy density of the battery cell. In addition, when the porosity of the second carbon material layer 30 is within the above range, the second carbon material layer 30 can also adsorb electrolyte, thereby improving the liquid retention of the battery cell, thereby reducing the deposition of lithium ions on the surface of the electrode due to lack of electrolyte. Illustratively, the porosity of the second carbon material layer 30 may be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or a range consisting of any two of the above values.

[0059] In some embodiments, the porosity of the first carbon material layer 20 is less than 10%. The second carbon material layer 30 may be a porous carbon layer, while the first carbon material layer 20 is a dense carbon layer, that is, the porosity of the first carbon material layer 20 is relatively small, such as less than 10%. Exemplarily, the porosity of the first carbon material layer 20 may be 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, etc. This embodiment does not limit the specific porosity of the first carbon material layer 20, as long as it is less than the porosity of the second carbon material layer 30, and does not limit the purpose of this application.

[0060] Therefore, the present application can slow down the further reaction between air and the current collector 10 by setting the above-mentioned first carbon material layer 20 and the second carbon material layer 30, and use the holes in the porous carbon layer to provide space for the deposition of lithium ions, thereby reducing the deposition of lithium ions on the surface of the copper current collector 10, thereby reducing the length of lithium dendrites and improving the safety performance of the battery cell; it also plays a role in increasing the liquid retention amount; and can also provide certain protection for the lithium dendrites.

[0061] In some embodiments, the porosity of the second carbon material layer 30 is 25% to 60%. In some embodiments, the porosity of the second carbon material layer 30 is 30% to 50%.

[0062] In some embodiments, the porosity of the first carbon material layer 20 is less than 8%.

[0063] By further increasing the porosity range of the second carbon material layer 30 and the first carbon material layer 20, it helps to further increase the deposition sites for lithium ions, further optimize the internal deposition of lithium ions, and thereby reduce the length of lithium dendrites or eliminate lithium dendrites; it also helps to improve the energy density of the battery while maintaining the strength that meets actual requirements.

[0064] Optionally, the thickness of the first carbon material layer 20 is smaller than the thickness of the second carbon material layer 30 .

[0065] In some embodiments, the thickness of the first carbon material layer 20 is 1 μm to 2 μm. Optionally, in some embodiments, the thickness of the first carbon material layer 20 is 1 μm to 1.8 μm. Optionally, in some embodiments, the thickness of the first carbon material layer 20 is 1 μm to 1.5 μm. Exemplarily, the thickness of the first carbon material layer 20 can be 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.2 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, or a range consisting of any two of the above values.

[0066] When the thickness of the first carbon material layer 20 is within the above range, it is advantageous to manufacture a thin and light negative electrode plate, thereby improving the energy density of the battery cell. In addition, when the thickness of the first carbon material layer 20 is within the above range, it is also possible to provide a certain degree of protection for the surface of the current collector 10, thereby avoiding problems such as increased costs or reduced protective effects caused by the first carbon material layer 20 being too thick or too thin.

[0067] In some embodiments, the thickness of the second carbon material layer 30 is 1 μm to 10 μm. Optionally, in some embodiments, the thickness of the second carbon material layer 30 is 1 μm to 8 μm. Optionally, in some embodiments, the thickness of the second carbon material layer 30 is 1 μm to 5 μm. Exemplarily, the thickness of the second carbon material layer 30 can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range consisting of any two of the above values.

[0068] By making the thickness of the second carbon material layer 30 within the above range, it is beneficial to manufacture a thin and light negative electrode plate, thereby improving the energy density of the battery cell, and also helps to provide sufficient lithium ion deposition sites, reduce the length of lithium dendrites, or inhibit the formation of lithium dendrites, thereby improving safety performance. In addition, by making the thickness of the second carbon material layer 30 within the above range, it is also possible to provide a certain degree of protection for the lithium dendrites on the surface of the current collector 10, thereby avoiding the problems of increased cost, reduced protection performance, or reduced conductivity caused by the carbon material layer being too thick or too thin.

[0069] In some embodiments, the current collector 10 is a copper foil 11 ; the negative electrode plate further includes a lithium replenishing layer 12 , and the lithium replenishing layer 12 is disposed between the copper foil 11 and the first carbon material.

[0070] Optionally, in this embodiment, the current collector 10 has two surfaces opposite to each other in the thickness direction thereof, and the lithium replenishing layer 12 is disposed on the two opposite surfaces of the current collector 10. Further, the lithium replenishing layer 12, the first carbon material layer 20, the second carbon material layer 30 and the protective layer 40 are sequentially stacked on one surface of the current collector 10, and the lithium replenishing layer 12, the first carbon material layer 20, the second carbon material layer 30 and the protective layer 40 are sequentially stacked on the other surface of the current collector 10. It is understood that in other embodiments, the lithium replenishing layer 12 may also be stacked on any one of the two surfaces of the current collector 10.

[0071] In this embodiment, by providing a lithium supplement layer 12 on the surface of the current collector 10 , the loss of active lithium can be supplemented, thereby improving the cycle performance of the battery cell.

[0072] Optionally, the coating area of ​​the lithium supplement layer 12 on the copper foil 11 is greater than 50%. The lithium supplement layer 12 can be disposed on the copper foil 11 by coating, and the coating area of ​​the lithium supplement layer 12 on the copper foil 11 needs to meet a certain range, such as greater than 50%, so as to effectively supplement the loss of active lithium, thereby facilitating the improvement of the cycle life of the battery. As an example, the coating area of ​​the lithium supplement layer 12 on the copper foil 11 can be 51% to 100%, or 55% to 100%, or 60% to 95%, etc.

[0073] Therefore, by providing the lithium replenishing layer 12, the active lithium loss of the negative electrode plate can be replenished with lithium, thereby increasing the cycle life of the negative electrode-free battery.

[0074] In some embodiments, the thickness of the copper foil 11 is 4 μm to 50 μm, that is, the thickness of the current collector 10 can be 4 μm to 50 μm. Optionally, in some embodiments, the thickness of the copper foil 11 is 5 μm to 40 μm. Optionally, in some embodiments, the thickness of the copper foil 11 is 10 μm to 35 μm. Exemplarily, the thickness of the copper foil 11 can be 4 μm, 5 μm, 6 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 50 μm, or a range consisting of any two of the above values.

[0075] By making the thickness of the copper foil 11 or the current collector 10 within the above range, it is advantageous to manufacture a thin and light negative electrode sheet, thereby improving the energy density of the battery cell. At the same time, by making the thickness of the copper foil 11 within the above range, it is possible to avoid the problem of prolonged preparation time and increased cost caused by excessive thickness of the copper foil 11, and it is also possible to avoid the problem of reduced conductivity and strength caused by excessive thinness of the copper foil 11, thereby affecting the conductivity and strength of the negative electrode sheet.

[0076] In some embodiments, the thickness of the lithium replenishing layer 12 is 5 μm to 20 μm. Optionally, in some embodiments, the thickness of the lithium replenishing layer 12 is 6 μm to 18 μm. Optionally, in some embodiments, the thickness of the lithium replenishing layer 12 is 8 μm to 15 μm. For example, the thickness of the lithium replenishing layer 12 can be 5 μm, 6 μm, 8 μm, 10 μm, 15 ...

[0077] μm, 12μm, 15μm, 18μm, 20μm, or a range consisting of any two of the above values.

[0078] By making the thickness of the lithium replenishing layer 12 within the above range, it is advantageous to manufacture a thin and light negative electrode plate, thereby improving the energy density of the battery cell. At the same time, by making the thickness of the lithium replenishing layer 12 within the above range, it is possible to avoid the problem of prolonged preparation time and increased cost caused by the thickness of the lithium replenishing layer 12 being too thick, and it is also possible to avoid the problem of reduced lithium replenishing effect caused by the thickness of the lithium replenishing layer 12 being too thin.

[0079] In some embodiments, the thickness of the protective layer 40 is 1 μm to 10 μm. Optionally, in some embodiments, the thickness of the protective layer 40 is 1 μm to 8 μm. Optionally, in some embodiments, the thickness of the protective layer 40 is 1 μm to 5 μm. Exemplarily, the thickness of the protective layer 40 can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a range consisting of any two of the above values.

[0080] By making the thickness of the protective layer 40 within the above range, it is beneficial to manufacture thin and light negative electrode plates, thereby improving the energy density of the battery cell. It also helps to provide certain protection for lithium dendrites, preventing lithium dendrites from piercing the diaphragm and causing battery cell failure, thereby improving the safety performance of the battery. It can also avoid problems such as increased costs and reduced protective effects caused by the protective layer 40 being too thick or too thin.

[0081] Optionally, the protective layer 40 is an inorganic protective layer, and further the protective layer 40 is an inorganic ceramic layer. The ceramic layer is any one of aluminum oxide, boehmite, zirconium oxide, magnesium zirconium oxide, silicon oxide or silicon nitride. For example, the ceramic layer can be an aluminum oxide layer, a boehmite layer, a zirconium oxide layer, a magnesium zirconium oxide layer, a silicon oxide layer, a silicon nitride layer, etc.; of course, in other embodiments, other types of ceramic materials can also be used, which will not be repeated here.

[0082] Optionally, the particle size of the ceramic in the inorganic ceramic layer is 2 μm to 7 μm. Optionally, in some embodiments, the particle size of the ceramic in the inorganic ceramic layer is 1 μm to 6 μm. Optionally, in some embodiments, the particle size of the ceramic in the inorganic ceramic layer is 3 μm to 5 μm. Exemplarily, the particle size of the ceramic can be 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, or a range consisting of any two of the above values.

[0083] Optionally, a small amount of binder may be provided in the inorganic ceramic layer, and this embodiment does not limit the specific type of the binder.

[0084] In some embodiments, the first carbon material layer 20 is a graphene layer.

[0085] The second carbon material layer 30 is any one of carbon nanotubes, graphene, conductive carbon black or porous carbon. For example, the second carbon material layer 30 can be a carbon nanotube layer, a graphene layer, a conductive carbon black layer, a porous carbon layer, etc. Of course, in other embodiments, any other similar known carbon material can also be used. The above-mentioned graphene, conductive carbon black, porous carbon, and carbon nanotubes are all materials known in the prior art, and this embodiment does not limit their sources.

[0086] Optionally, in some implementations, a small amount of binder may be provided in the first carbon material layer 20 or the second carbon material layer 30 . The specific type of the binder is not limited in this embodiment.

[0087] Optionally, in some embodiments, the first carbon material layer 20 or the second carbon material layer 30 may be a vapor-deposited carbon layer.

[0088] In some embodiments, the present application provides a battery, comprising: a positive electrode plate, a negative electrode plate as described above, and an electrolyte.

[0089] The battery provided in the present application is a negative electrode-free battery, and compared with conventional lithium-ion batteries or sodium-ion batteries using carbon materials or silicon materials as negative electrode active materials, the energy density of the battery can be greatly improved.

[0090] The battery provided in the present application adopts the negative electrode plate provided in the present application, which can induce uniform lithium deposition, reduce or avoid lithium dendrites, reduce the length of lithium dendrites, provide protection for lithium dendrites, improve the safety performance of the battery, and also improve the cycle performance of the battery.

[0091] In some embodiments, the battery further includes a separator, which is disposed between the positive electrode plate and the negative electrode plate and mainly serves to prevent the positive and negative electrodes from short-circuiting while allowing ions to pass through.

[0092] In this embodiment, the material and shape of the isolation membrane are not particularly limited, and it can be any technology disclosed in the prior art. The present application has no particular restrictions on the type of isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected. As an example, the isolation membrane can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, etc.

[0093] The electrolyte mentioned above may be a solid electrolyte or a liquid electrolyte.

[0094] Optionally, when the electrolyte is a liquid electrolyte, that is, an electrolyte, the electrolyte is composed of a solvent, a lithium salt, and an optional additive. The electrolyte that can be used in the embodiments of the present application can be an electrolyte known in the prior art. The specific type and structure of the electrolyte can be an electrolyte type that can be used for a battery as is known in the art, such as an ester electrolyte or an ether electrolyte, etc., which is not limited and will not be repeated here.

[0095] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on the positive electrode current collector.

[0096] In this embodiment, the specific materials and structures of the positive electrode current collector and the positive electrode material layer in the positive electrode plate are not limited, and the positive electrode plate structure and components that are well known in the art and can be used for batteries can be selected.

[0097] As an example, the positive electrode material layer includes a positive electrode active material, and the positive electrode active material contains lithium. When charging, the lithium element can be released to form lithium ions, and migrate to the negative electrode plate through the electrolyte to be reduced to metallic lithium. The embodiment of the present application does not limit the type and composition of the positive electrode active material, as long as the above principles are met. For example, it can be a lithium battery positive electrode active material, such as lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, nickel cobalt manganese oxide (NCM), nickel cobalt aluminum oxide, etc.

[0098] In some embodiments, the battery may further include a packaging shell, i.e., a shell, which encapsulates a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, as well as other components known in the art in the battery, and this application does not limit the above-mentioned other components. This application does not specifically limit the packaging shell, and it can be a packaging shell known in the art, as long as it can achieve the purpose of this application.

[0099] In this embodiment, the battery can be prepared into batteries of different structures according to the situation, and there is no special limitation. As an example, the battery structure of the present application includes but is not limited to soft-pack batteries, square hard-shell batteries or cylindrical hard-shell batteries. That is, the battery can be cylindrical, flat, rectangular or other shapes.

[0100] The present invention is further described below in conjunction with specific embodiments. The implementation methods described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application.

[0101] Example 1

[0102] 1. Negative electrode

[0103] The negative electrode sheet includes a current collector 10 , a first carbon material layer 20 disposed on both surfaces of the current collector 10 in a thickness direction, a second carbon material layer 30 disposed on the first carbon material layer 20 , and a protective layer 40 disposed on the second carbon material layer 30 .

[0104] Wherein, a copper foil with a thickness of 18 μm is used as the current collector 10. The first carbon material layer 20 is a dense carbon layer, the second carbon material layer 30 is a porous carbon layer, the porosity of the first carbon material layer 20 is less than 10%, the porosity of the second carbon material layer 30 is 40%, the thickness of the first carbon material layer 20 is 1 μm, and the thickness of the second carbon material layer 30 is 2 μm. The protective layer 40 is an inorganic ceramic layer, and the thickness of the protective layer 40 is 3 μm.

[0105] 2. Positive electrode

[0106] The positive electrode sheet includes a positive electrode collector and a positive electrode material layer disposed on both surfaces of the positive electrode collector in a thickness direction.

[0107] Among them, aluminum foil or composite aluminum foil is used as the positive electrode current collector; the positive electrode material layer includes a positive electrode active material, a conductive agent and a binder; the positive electrode active material is a ternary high-nickel material, the conductive agent is one or more of SP, CNTs, and graphene; the binder is PVDF, etc.

[0108] For example, the positive electrode active material is NCM high nickel material, the chemical formula is LiNi 0.8 Co 0.1 Mn 0.1 O 2The conductive agent is CNTs, and the binder is PVDF; the mass ratio of the positive electrode active material, the conductive agent and the binder is 98:1:1.

[0109] The batching process uses existing technology to evenly mix the main positive electrode active material, conductive agent, adhesive and other materials and solvent NMP, and then apply them on the positive electrode collector. The coating can be applied by transfer or extrusion, and then after drying and cold pressing, the positive electrode sheet is obtained, with a compaction density of 3.3-3.6 g / cm 3 (Compacted density 3.4g / cm 3 ).

[0110] 3. The isolation membrane can be made of polyethylene film, polypropylene film, polyvinylidene fluoride film and non-woven fabric.

[0111] For example, the separator film is selected from polyethylene film.

[0112] 4. The electrolyte includes a lithium salt and a solvent. The types of the lithium salt and the solvent are not specifically limited and can be selected according to actual needs. For example, the lithium salt can be LiPF 6 、LiTFSI、LiBF 4 wait.

[0113] For example, LiPF is used as electrolyte 6 Dissolved in a solvent of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate in a ratio of 1:1:1, with a concentration of 1.2 mol / L.

[0114] 5. Battery

[0115] During the cell assembly process, the positive electrode sheet, the separator, and the negative electrode sheet are arranged in sequence by winding. The electrolyte is injected into the dry cell, and a lithium battery is obtained after formation and aging.

[0116] Example 2

[0117] The main difference between Example 2 and Example 1 is:

[0118] In the negative electrode sheet, the thickness of the second carbon material layer 30 is 5 μm.

[0119] The rest are the same as in Example 1.

[0120] Example 3

[0121] The main difference between Example 3 and Example 1 is:

[0122] In the negative electrode sheet, the porosity of the second carbon material layer 30 is 70%.

[0123] The rest are the same as in Example 1.

[0124] Example 4

[0125] The main difference between Example 4 and Example 1 is:

[0126] The negative electrode plate includes a current collector 10, a lithium replenishing layer 12 arranged on two surfaces of the current collector 10 along the thickness direction, a first carbon material layer 20 arranged on the lithium replenishing layer 12, a second carbon material layer 30 arranged on the first carbon material layer 20, and a protective layer 40 arranged on the second carbon material layer 30.

[0127] Among them, a copper foil with a thickness of 18 μm is used as the current collector 10. The thickness of the lithium supplement layer 12 is 5 μm. The first carbon material layer 20 is a dense carbon layer, the second carbon material layer 30 is a porous carbon layer, the porosity of the first carbon material layer 20 is less than 10%, the porosity of the second carbon material layer 30 is 40%, the thickness of the first carbon material layer 20 is 1 μm, and the thickness of the second carbon material layer 30 is 2 μm. The protective layer 40 is an inorganic ceramic layer, and the thickness of the protective layer 40 is 3 μm.

[0128] The rest are the same as in Example 1.

[0129] Example 5

[0130] The main difference between Example 5 and Example 4 is:

[0131] In the negative electrode sheet, the thickness of the lithium replenishing layer 12 is 10 μm.

[0132] The rest is the same as Example 4.

[0133] Comparative Example 1

[0134] The main difference between Comparative Example 1 and Example 1 is:

[0135] In the negative electrode sheet, a common copper foil is used as the current collector (negative electrode sheet), and the thickness of the copper foil is 6 μm.

[0136] The rest are the same as in Example 1.

[0137] Comparative Example 2

[0138] The main difference between Comparative Example 2 and Example 1 is:

[0139] In the negative electrode sheet, foam copper is used as the current collector (negative electrode sheet), the thickness of the foam copper is 18 μm, and the porosity of the foam copper is 40%.

[0140] The rest are the same as in Example 1.

[0141] Performance Testing

[0142] (1) Lithium dendrite length: Take a battery whose capacity has decayed to 80% of its initial capacity, disassemble it, cut the end face of the electrode, and measure the length of the lithium dendrite under an electron microscope (CP test).

[0143] (2) Cycle life test: 25°C, using a battery charge and discharge tester, 1 / 3C constant current charging to 4.25V, constant voltage charging to a cut-off current of 0.05C; let stand for 30 minutes, 1 / 3C constant current discharge to 3V. The cycle life is the number of cycles for the discharge capacity to decay to 80% of the initial capacity.

[0144] The test results are shown in Table 1 below.

[0145] Table 1

[0146] Group Lithium dendrite length (μm) Cycle life (number of turns) Example 1 15 150 Example 2 12 180 Example 3 16 320 Example 4 18 390 Example 5 19 420 Comparative Example 1 50 50 Comparative Example 2 35 75

[0147] It can be seen from the data in Table 1 that the negative electrode plate provided in the embodiment of the present application can reduce the length of lithium dendrites and improve the safety performance and cycle life of the battery.

[0148] The parts of the present invention that are not described in detail are well known to those skilled in the art.

[0149] The basic principle of the present invention is described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, strengths, effects, etc. mentioned in the present invention are only examples and not limitations, and it cannot be considered that these advantages, strengths, effects, etc. are required by each embodiment of the present invention. In addition, the specific details disclosed above are only for the purpose of illustration and ease of understanding, not limitation, and the above details do not limit the present invention to being implemented by adopting the above specific details.

[0150] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the utility model.

Claims

1. A negative electrode plate, characterized in that: The negative electrode plate comprises: current collector; a first carbon material layer, the first carbon material layer being disposed on at least one side surface of the current collector; a second carbon material layer, the second carbon material layer being disposed on a surface of the first carbon material layer facing away from the current collector; A protective layer, the protective layer being disposed on a surface of the second carbon material layer facing away from the first carbon material layer; The porosity of the first carbon material layer is smaller than the porosity of the second carbon material layer.

2. The negative electrode sheet according to claim 1, characterized in that: The porosity of the second carbon material layer is 20% to 70%.

3. The negative electrode sheet according to claim 1, characterized in that: The porosity of the first carbon material layer is less than 10%.

4. The negative electrode sheet according to claim 1, characterized in that: The thickness of the first carbon material layer is 1 μm to 2 μm.

5. The negative electrode sheet according to claim 1, characterized in that: The second carbon material layer has a thickness of 1 μm to 10 μm.

6. The negative electrode sheet according to claim 1, characterized in that: The current collector is copper foil; The negative electrode plate further includes a lithium supplement layer, and the lithium supplement layer is arranged between the copper foil and the first carbon material; The coating area of ​​the lithium replenishing layer on the copper foil is greater than 50%.

7. The negative electrode sheet according to claim 6, characterized in that: The thickness of the copper foil is 4 μm to 50 μm; The thickness of the lithium supplement layer is 5 μm to 20 μm.

8. The negative electrode sheet according to claim 1, characterized in that: The thickness of the protective layer is 1 μm to 10 μm; The protective layer includes an inorganic ceramic layer.

9. The negative electrode sheet according to any one of claims 1 to 8, characterized in that: The first carbon material layer is a graphene layer; The second carbon material layer is any one of carbon nanotubes, graphene, conductive carbon black or porous carbon.

10. A battery, characterized in that: The battery comprises: A positive electrode sheet, a negative electrode sheet as claimed in any one of claims 1 to 9, and an electrolyte.

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