A battery cell without current collector, preparation method thereof and lithium ion battery

Abstract

The present invention discloses a current collector-free battery cell, a method for preparing the same, and a lithium-ion battery. The battery cell comprises at least one battery cell unit, each comprising a positive electrode material layer, a negative electrode material layer, and a separator structure interposed between the positive and negative electrode material layers, the separator structure being in contact with the positive and negative electrode material layers, respectively. The battery cell provided by the present invention, lacking a current collector, improves the battery's energy density and ensures safety during production and use.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy storage, and relates to a current collector-free battery cell, a preparation method thereof, and a lithium-ion battery. Background Art

[0002] In recent years, with the development of economy and the advancement of science and technology, energy and environmental issues have become the focus of everyone's attention. The excessive consumption of fossil fuels and the growth of energy demand have made the development and utilization of clean energy extremely urgent.

[0003] Lithium-ion secondary batteries are currently the preferred power source for digital devices, electric vehicles, and other applications due to their high energy density, high operating voltage, long cycle life, and pollution-free performance. With the increasing popularity of portable smart devices, the development of lightweight, compact, high-energy-density, and highly safe battery cells has recently become a hot topic in both academia and industry. One of the most pressing technical challenges facing portable smart devices is the development of battery cells that meet people's daily needs, specifically how to achieve both a compact size and long battery life.

[0004] CN109888168A discloses a positive electrode, a preparation method thereof, and a battery having the positive electrode. The positive electrode comprises a carbon fiber network structure supported by a positive electrode material and nano-titanium dioxide. The positive electrode preparation method comprises: soaking a paper sheet in a titanate solution, removing and drying to obtain a composite paper sheet; ultrasonically dispersing the positive electrode material and deionized water in a certain proportion to obtain a dispersion of a certain solubility; then mixing the composite paper sheet with the dispersion to undergo a hydrolysis reaction; removing and drying to obtain a composite body supported by titanium dioxide and the positive electrode material; and then heating the composite body at high temperature under a protective gas atmosphere to obtain a structure comprising nano-titanium dioxide and the positive electrode material supported on a carbon fiber network, i.e., a positive electrode, and a battery having the positive electrode. This technical solution is used to prepare a self-supporting flexible positive electrode without a binder or current collector, which can simplify the electrode preparation process, reduce the number of steps, reduce costs, increase energy density, and improve conductivity and safety. However, this invention requires the electrodes to be prepared first and then assembled into a battery, which is a relatively complex process and the electrode structure is not compact enough.

[0005] CN108807958A discloses a tin dioxide-graphene-carbon nanotube flexible negative electrode material and its preparation method and application, the preparation method of which comprises: taking tin salt and dissolving it in pure water, heating it to 90-230℃ and keeping it warm for 3-72 hours, then cooling it to room temperature, adding a sugar substance and stirring and dissolving it, heating it to 90-230℃ and keeping it warm for 1-72 hours, then adding a graphene oxide dispersion, stirring and mixing it evenly, then adding short single-walled carbon nanotubes, styrene-butadiene rubber and hydroiodic acid solution, stirring it evenly and then ultrasonically treating it, the mixed solution is filtered under reduced pressure, and the composite film is obtained and dried. The preparation method of the flexible negative electrode material of the present invention is simple, environmentally friendly and low in cost. The problem of volume expansion of tin dioxide is alleviated by the structure of the three-dimensional carbon skeleton. The addition of SBR improves the mechanical properties of the membrane so that it can be directly used as a flexible electrode material without a current collector and a binder. The prepared composite membrane material has excellent cycle performance, high energy density, high rate performance and long service life. However, the preparation process of the flexible negative electrode of this invention is relatively complicated, and the tightness of the battery after assembly is not good enough.

[0006] In view of the development trend of the above-mentioned lithium-ion battery cells, there is currently no mature technology and process in the industry to produce products that meet the requirements. Most devices are still only in the research stage. If they are to be truly applied in practice, there are still many problems that need to be solved, such as performance not meeting the requirements, low energy density, high preparation cost, and complex preparation process.

[0007] In summary, developing a method that can ensure the energy density of the battery cell while ensuring the safety performance during the production and use of the battery cell and has a simple preparation process has become an urgent problem to be solved. Summary of the Invention

[0008] In view of the above problems, the object of the present invention is to provide a battery cell without a current collector, a preparation method thereof, and a lithium ion battery.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a battery cell without a current collector, the battery cell comprising at least one battery cell unit, the battery cell unit comprising a positive electrode material layer, a negative electrode material layer and an isolation structure filled between the positive electrode material layer and the negative electrode material layer, the isolation structure being in contact with the positive electrode material layer and the negative electrode material layer, respectively.

[0011] In the present invention, the number of battery cell units is at least 1, for example, 1, 2, 3, 5, 6, 8, 10, 12 or 15.

[0012] In the battery cell provided by the present invention, the isolation structure effectively isolates the positive and negative electrodes, and since there is no current collector, the energy density of the battery is improved. Moreover, since the electrode structure is compact, the safety performance of the battery cell during production and use is guaranteed.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0014] Preferably, the battery cell unit is a laminated structure, where the “laminated structure” refers to a structure formed by stacking layers.

[0015] Preferably, the number of the units is at least 2, and the vertical cross-section of the isolation structure is Z-shaped, wherein two parallel sides of the Z-shape are respectively located at the edge of the positive electrode material layer and the edge of the negative electrode material layer.

[0016] Preferably, the Z-shaped angle is 90°.

[0017] Preferably, in the vertical cross-section, the thickness of the portion of the isolation structure located between the positive electrode material layer and the negative electrode material layer is 10 μm-300 μm, for example, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 85 μm, 100 μm, 150 μm, 200 μm, 240 μm, 265 μm or 300 μm, etc., preferably 20 μm-200 μm.

[0018] Preferably, the thickness of the edge portion of the isolation structure located at the positive electrode material layer / negative electrode material layer is independently 100μm-1000μm, for example, 100μm, 150μm, 200μm, 300μm, 400μm, 500μm, 600μm, 650μm, 750μm, 800μm, 900μm or 1000μm, etc., preferably 200μm-500μm.

[0019] In the battery cell of the present invention, the isolation structure can be integrated or partitioned, and the material of the isolation structure can be a single type or multiple types. As long as the effect of isolating the positive and negative electrodes can be achieved, the commonly used insulating materials in the field can be used in the present invention.

[0020] Illustratively, the material of the portion of the isolation structure located between the positive electrode material layer and the negative electrode material layer may be the same as or different from the material of the edge portion of the isolation structure located at the positive electrode material layer / negative electrode material layer. In terms of preparation method, it may be prepared once (e.g., by filling and molding once) or multiple times (e.g., by filling and molding twice).

[0021] The present invention does not limit the specific types of the positive electrode material layer and the negative electrode material layer. Positive electrode material layers and negative electrode material layers commonly used in the art that can achieve the same effect can be used in the present invention.

[0022] Preferably, the positive electrode material layer includes a positive electrode active material, a binder and a conductive agent, and the positive electrode active material includes but is not limited to at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese phosphate, nickel cobalt manganese ternary material and nickel cobalt aluminum ternary material.

[0023] Preferably, the negative electrode material layer comprises a negative electrode active material, a binder, and an optional conductive agent. The negative electrode active material includes, but is not limited to, at least one of lithium titanate, natural graphite, artificial graphite, carbon fiber, soft carbon, hard carbon, mesocarbon microbeads, elemental silicon, silicon oxides, and silicon-carbon composites. The "optional conductive agent" means that the negative electrode material layer may or may not contain a conductive agent. For example, when the other components of the negative electrode material layer already provide good conductivity, no additional conductive agent is required.

[0024] The positive electrode material layer and / or the negative electrode material layer of the present invention may further comprise other additives suitable for preparing the positive electrode material layer and / or the negative electrode material layer, such as a surfactant or a pore former.

[0025] Preferably, the binder in the positive electrode material layer and the negative electrode material layer is independently selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, and polyvinyl alcohol, such as polyvinylidene fluoride, polytetrafluoroethylene, a combination of polyvinylidene fluoride and polyacrylic acid, and a combination of polyvinylidene fluoride, polytetrafluoroethylene, and polyvinyl alcohol. However, the binder is not limited to the above-mentioned binders, and other binders commonly used in the art that can achieve the same effect can also be used in the present invention.

[0026] Preferably, the conductive agent in the positive electrode material layer and the negative electrode material layer is independently selected from at least one of conductive carbon black, acetylene black, Ketjen black, Super P, Super S, carbon nanotubes, graphene, porous carbon and carbon fiber, such as conductive carbon black, Ketjen black, a combination of acetylene black and Super P, a combination of Super P, carbon nanotubes and porous carbon, etc., but is not limited to the conductive agents listed above. Other conductive agents commonly used in the art that can achieve the same effect can also be used in the present invention.

[0027] In the present invention, at least the portion of the isolation structure located between the positive electrode material layer and the negative electrode material layer has lithium ion conductivity, thereby ensuring the transmission of lithium ions between the positive and negative electrodes.

[0028] In the present invention, the materials of the isolation structure can be entirely identical or different, and there is no specific limitation on the materials, as long as they can isolate the positive and negative electrodes to prevent short circuits and ensure that lithium ions can be transferred between the positive and negative electrodes. The materials of the isolation structure include, but are not limited to, at least one of a solid electrolyte, a ceramic dielectric material, and a polyolefin.

[0029] Preferably, at least a portion of the separation structure located between the positive electrode material layer and the negative electrode material layer has pores.

[0030] In order to achieve better isolation of the positive and negative electrodes and lithium ion transmission, the following preferred solutions can be adopted:

[0031] ① Solid electrolytes are directly used as isolation materials to prepare isolation structures. Solid electrolytes include oxide solid electrolytes, sulfide solid electrolytes or polymer solid electrolytes, more specifically LLZO, LLZTO, etc. The actual preparation can be done by pressure coating of solid electrolyte dry powder, granular dry material, or granular impregnated material, such as spraying or 3D printing.

[0032] ② Use a porous polyolefin layer to prepare the isolation structure, such as a porous PP layer or a porous PE layer, etc. The actual preparation can be done by lamination.

[0033] ③ Using ceramic dielectric materials as isolation materials to prepare isolation structures. The actual preparation can be achieved by mixing the ceramic dielectric materials with a binder and a solvent and then applying pressure, such as spraying or 3D printing.

[0034] ④ Use molten or powdered polyolefins mixed with pore-forming agents, which include but are not limited to volatile solvents or metal oxide particles (such as Al2O3, TiO2, SiO2, MgO, CaO, etc.). Among them, metal particles increase the stacking pores and provide lithium ion transmission channels on the one hand, and on the other hand have good thermal stability, which can improve the safety performance of the battery.

[0035] Preferably, the battery cell is further provided with a positive electrode tab and a negative electrode tab.

[0036] For the technical solution with one battery cell unit, the form of the isolation structure is not limited. It can be an isolation layer located between the positive electrode material layer and the negative electrode material layer, or it can include both an isolation layer located between the two and an isolation portion located at the edge of the positive electrode material layer and the negative material layer (whose vertical cross-section is Z-shaped). The positive electrode ear and the negative electrode ear only need to be in contact with the positive electrode material layer and the negative electrode material layer respectively, without any specific position limitation.

[0037] For the technical solution with at least 2 battery cell units, the isolation structure includes both an isolation layer located between the two and an isolation portion located at the edges of the positive electrode material layer and the negative material layer (whose vertical cross-section is Z-shaped). The arrangement of the positive and negative electrode ears must meet the following requirements: conductive layers are respectively arranged on the two edges with the isolation portion to connect at least two positive electrode material layers and be used for positive electrode ear connection, and to connect at least two negative electrode material layers and be used for negative electrode ear connection.

[0038] In a second aspect, the present invention provides a method for preparing a current collector-free battery cell as described in the first aspect, the method comprising the following steps:

[0039] (1) preparing a first mixed material comprising a positive electrode active material, a binder and a conductive agent, and a second mixed material comprising a negative electrode active material, a binder and an optional conductive agent;

[0040] (2) A positive electrode material layer and a negative electrode material layer are prepared using the first mixed material and the second mixed material respectively, and an isolation structure of an integrated structure or a separated structure is prepared using an isolation material. The positive electrode material layer, the negative electrode material layer and the isolation structure are laminated so that the isolation structure is filled between the positive electrode material layer and the negative electrode material layer to obtain a battery cell without a current collector.

[0041] The present invention provides another method for preparing a current collector-free battery cell as described in the first aspect, the method comprising the following steps:

[0042] (1') preparing a first mixed material comprising a positive electrode active material, a binder and a conductive agent, and a second mixed material comprising a negative electrode active material, a binder and an optional conductive agent;

[0043] (2') coating a first polar material layer on a substrate using either the first mixed material or the second mixed material, wherein the first polar material layer is a positive electrode material layer or a negative electrode material layer;

[0044] (3') filling and / or coating a material containing an isolation substance on the surface of the first polar material layer on the substrate to form an isolation material layer;

[0045] (4') Filling and / or coating the surface of the isolation material layer with a mixture having a polarity opposite to that of the mixture used in step (2') to form a second polarity material layer, so that the isolation material layer is filled between the positive electrode material layer and the negative electrode material layer to obtain a battery cell without a current collector.

[0046] This preferred technical solution adopts a layered process, which can obtain multiple battery cells at a time, improves work efficiency, and also realizes the controllable shape and size of the battery cells. The prepared lithium-ion battery has good safety.

[0047] The positive and negative electrodes and the separator material of the present invention are prepared and formed at one time, with a compact structure, higher energy density and safety.

[0048] As a preferred technical solution of the method described in the present invention, the method also includes filling and / or coating the outer side of at least one side of the first polar material layer with a material containing an isolating substance in step (3') to form a first isolating portion, and filling and / or coating the surface of the isolating material layer with a material containing an isolating substance in step (4') to form a second isolating portion, the first isolating portion, the second isolating portion and the isolating material layer are connected to form an isolating structure with a Z-shaped vertical cross-section, and after step (4'), steps (3') and (4') are performed in sequence at least once to form at least two battery cell units and a Z-shaped isolating structure.

[0049] In the present invention, there is no limitation on the form of the first mixture and the second mixture, as long as they can form a compact first polar material layer and a compact second polar material layer by a certain process. For example, they can be dry powder, dry granular material, impregnated granular material or slurry.

[0050] Preferably, the coating in step (2') and step (4') is pressure coating, which refers to a coating method in which the raw material is fixed to the surface of the layer to be coated under a certain pressure, including but not limited to at least one of 3D printing and spraying.

[0051] Preferably, the filling method in step (4') can be a deposition method. Preferably, the coating method in step (3') is a casting method.

[0052] In the method of the present invention, a cell product with a preset number of layers and shape can be directly prepared, or a cell product with a preset number of layers can be first prepared and then cut to obtain the cell product. The cutting method includes but is not limited to laser cutting, wire cutting, and knife cutting.

[0053] The manufacturing process of the present invention is simple to operate, the shape and size of the battery core are controllable, and the safety performance of the battery core during production and use can be guaranteed.

[0054] In a third aspect, the present invention provides a lithium-ion battery, comprising the current collector-free battery cell according to the first aspect.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. The present invention provides a laminated current collector-free lithium-ion battery cell. Since there is no current collector, the cell has a higher energy density.

[0057] 2. The present invention innovatively constructs the battery cell structure through a layered manufacturing process, which not only simplifies the manufacturing process but also effectively improves the battery energy density.

[0058] 3. The lithium-ion battery cell manufactured by the present invention has the characteristics of good safety due to its compact electrode structure.

[0059] 4. The battery cell manufacturing process of the present invention can produce multiple units in one production, thereby improving work efficiency.

[0060] 5. The shape, size and capacity of the battery cell of the present invention are controllable, and commercial application is easy to achieve. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 Schematic diagram of the positive electrode material layer area and surrounding blank area of ​​Example 1;

[0062] Figure 2 Schematic diagram of the negative electrode material layer area and surrounding blank area of ​​Example 1;

[0063] Figure 3 Schematic diagram of a cross-section of a stacked battery cell unit according to the first embodiment;

[0064] Figure 4 Schematic diagram of the positive electrode material layer area and surrounding blank area of ​​Example 2;

[0065] Figure 5 Schematic diagram of the negative electrode material layer area and surrounding blank area in Example 2. DETAILED DESCRIPTION

[0066] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementations, rather than limiting the present invention.

[0067] The present invention will be further described in detail below with reference to the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the scope of protection of the present invention. The specific process parameters and the like in the following examples are merely examples within a suitable range, and those skilled in the art can make appropriate selections based on the description herein, and are not intended to be limited to the specific selections in the following examples.

[0068] First, the basic scheme of the materials used in the embodiments of the present invention is briefly described:

[0069] The present invention provides a laminated current collector-free lithium-ion battery cell and manufacturing process. The manufacturing process for the battery cell comprises the following steps: the raw materials for the positive electrode layer are: a positive electrode active material, a conductive agent, and a binder are mixed to form a dry powder; the raw materials for the negative electrode layer are: a negative electrode active material and a binder are mixed to form a dry powder; and the insulating material is: at least one of a ceramic dielectric material, a solid electrolyte material, and a polyolefin.

[0070] Step 1: Select the positive electrode active material lithium cobalt oxide, the conductive agent acetylene black and the binder polyvinylidene fluoride and mix them to prepare a dry powder. Spray the dry powder on the designated area of ​​the hydrophobic and easily peelable platform to obtain a positive electrode material layer. Figure 1 As shown, it includes a positive electrode material layer area 111 and a surrounding blank area 112;

[0071] Step 2: Spraying the insulating material above the positive electrode material layer and the surrounding blank area. Specifically, the ceramic dielectric material is mixed with a binder and a solvent to form a slurry, which is sprayed to obtain a flat surface covered with the insulating material again.

[0072] Step 3: spray the negative electrode material layer on the designated area above the plane of the above step, the specific area is as follows Figure 2 As shown, it includes the negative electrode material layer area 113 and the surrounding blank area 114. Note that this area is consistent in shape and size with the positive electrode material layer area. The most important thing is that there must be a misalignment between the two material layers.

[0073] Step 4: Use isolation material to spray fill the blank area 114;

[0074] Step five: drying, cutting and peeling the laminated material layer prepared above as a whole, thereby obtaining a laminated current collector-free lithium-ion battery cell of the present invention.

[0075] Note that the cutting process uses a laser cutting machine, which can first cut the laminated material layer into a whole long strip, and then cut it into bare cells of different shapes and sizes according to actual needs. The cross section of the bare cell unit after cutting is as follows: Figure 3 As shown, the entire unit 1 in this embodiment includes a positive electrode material layer 11 , a negative electrode material layer 12 and an isolation material layer 13 .

[0076] This embodiment can produce multiple units in one production, thereby improving work efficiency.

[0077] The shape, size and capacity of the battery cell unit in this embodiment are controllable.

[0078] The embodiment of the present invention further provides a lithium-ion battery, specifically a laminated current collector-free lithium-ion battery, which is made using the bare cell prepared above, and the specific implementation method is as follows:

[0079] First, a layer of silver paste or other conductive material is coated on the cut electrode end surface of the battery cell unit containing the positive electrode material layer, the negative electrode material layer and the separator material layer;

[0080] Then, the battery cell is soaked with electrolyte so that the battery cell isolation material layer is filled with electrolyte;

[0081] Then, the battery cell filled with electrolyte is assembled with a shell of corresponding size to obtain a lithium-ion battery; or, the battery cell is encapsulated with an insulating coating or covering layer, and the tabs are led out to obtain a lithium-ion battery.

[0082] Example 1

[0083] Step 1: Prepare a dry powder by mixing lithium cobalt oxide, acetylene black, and polyvinylidene fluoride as a positive electrode active material, and spray the dry powder on a designated area of ​​a hydrophobic and easily peelable platform to obtain a positive electrode material layer with a thickness of 150 μm and a surface density of 400 g / m 2 Specific areas such as Figure 1 As shown, it includes a positive electrode material layer area 111 and a surrounding blank area 112;

[0084] Step 2: Spray the insulating material above the positive electrode material layer and the surrounding blank area. Specifically, the ceramic dielectric material Al2O3 is mixed with the binder polyvinylidene fluoride and the solvent N-methylpyrrolidone to make a slurry, which is sprayed to obtain a flat surface covered with the insulating material again, with a thickness of 30μm.

[0085] Step 3: Spray a negative electrode material layer on the designated area above the plane of the above step with a thickness of 150 μm and a surface density of 200 g / m 2 Specific areas such as Figure 2 As shown, it includes a negative electrode material layer area 113 and a surrounding blank area 114. Note that this area is consistent in shape and size with the positive electrode material layer area, and is offset by 2 mm in the horizontal direction compared to the positive electrode material layer area.

[0086] Step 4: Use isolation material to spray fill the blank area 114 with a thickness of 150 μm;

[0087] Step five: drying, cutting and peeling the laminated material layer prepared above as a whole, thereby obtaining a laminated current collector-free lithium-ion battery cell of the present invention.

[0088] Note that the cutting process uses a laser cutting machine, wire cutting or knife cutting. First, the laminated material layer can be cut into a whole long strip, and then cut into bare cells of different shapes and sizes according to actual needs. The cross section of the bare cell unit after cutting is as follows Figure 3 As shown, the entire unit 1 in this embodiment includes a positive electrode material layer 11 , a negative electrode material layer 12 and an isolation material layer 13 .

[0089] This embodiment can produce multiple units in one production, thereby improving work efficiency.

[0090] The shape, size and capacity of the battery cell unit in this embodiment are controllable.

[0091] Example 2

[0092] The present invention provides a laminated current collector-free lithium-ion battery cell and a manufacturing process. The manufacturing process of the cell is substantially the same as that of the first embodiment, differing only in specific areas. The specific steps are as follows:

[0093] Step 1: Spray the positive electrode material layer on the designated area of ​​the hydrophobic and easily peelable platform. Figure 4 As shown, it includes a positive electrode material layer area 211 and a surrounding blank area 212;

[0094] Step 2: spraying the insulating material above the positive electrode material layer and the surrounding blank area to obtain a plane covered with the insulating material again;

[0095] Step 3: spray the negative electrode material layer on the designated area above the plane of the above step, the specific area is as follows Figure 5 As shown, it includes a negative electrode material layer area 213 and a surrounding blank area 214. Note that this area is consistent with the shape and size of the positive electrode material layer area, and is offset by 2 mm in the horizontal direction compared to the positive electrode material layer area.

[0096] Step 4: Use isolation material to spray fill the blank area 214;

[0097] Step five: drying, cutting and peeling the laminated material layer prepared above as a whole, thereby obtaining a laminated current collector-free lithium-ion battery cell of the present invention.

[0098] This embodiment can produce multiple units in one production, thereby improving work efficiency.

[0099] In this embodiment, the shape and size of the battery cell unit can be controlled when spraying the material layer.

[0100] In this embodiment, the thickness and surface density of the positive electrode material layer and the negative electrode material layer are the same as those in the first embodiment.

[0101] Example 3

[0102] A laminated current collector-free lithium-ion battery of this embodiment is made using the bare cells prepared in Examples 1 and 2. The specific implementation is as follows:

[0103] First, a layer of silver paste is applied on the cut electrode end surface of the battery cell unit comprising the positive electrode material layer, the negative electrode material layer, and the separator material layer obtained in Example 1 and Example 2;

[0104] Then, the battery cell is soaked with electrolyte so that the battery cell isolation material layer is filled with electrolyte;

[0105] Then, the battery cell filled with electrolyte is assembled with a shell of corresponding size to obtain a lithium-ion battery.

[0106] In this embodiment, the thickness and surface density of the positive electrode material layer and the negative electrode material layer are the same as those in the first embodiment.

[0107] Example 4

[0108] A laminated current collector-free lithium-ion battery of this embodiment is made using the bare cells prepared in Examples 1 and 2. The specific implementation is as follows:

[0109] First, a layer of silver paste is applied on the cut electrode end surface of the battery cell unit comprising the positive electrode material layer, the negative electrode material layer, and the separator material layer obtained in Example 1 and Example 2;

[0110] Then, the battery cell is soaked with electrolyte so that the battery cell isolation material layer is filled with electrolyte;

[0111] Then, an insulating coating or covering layer is used to encapsulate the battery cell, and the tabs are led out to obtain a lithium-ion battery.

[0112] In this embodiment, the thickness and surface density of the positive electrode material layer and the negative electrode material layer are the same as those in the first embodiment.

[0113] Example 5

[0114] Step 1: Select the positive electrode active material lithium cobalt oxide, the conductive agent acetylene black, the binder polyvinylidene fluoride and the solvent N-methylpyrrolidone to mix and prepare a slurry, and 3D print the slurry on the designated area of ​​the hydrophobic and easily peelable platform to obtain a positive electrode material layer with a thickness of 150 μm and an area density of 400 g / m 2 , dry and shape;

[0115] Step 2: Coat the insulating material above the positive electrode material layer and the surrounding blank area. Specifically, the ceramic dielectric material Al2O3 is mixed with the binder polyvinylidene fluoride and the solvent N-methylpyrrolidone to form a slurry. 3D printing is performed to obtain a flat surface covered with the insulating material again. The thickness is 30μm and the slurry is dried and fixed.

[0116] Step 3: Coat the designated area above the plane of the above step with a negative electrode material layer with a thickness of 150 μm and a surface density of 200 g / m 2 , this area is displaced by 2 mm in the horizontal direction compared to the area of ​​the positive electrode material layer;

[0117] Step 4: Fill the blank area with an isolation material with a thickness of 150 μm;

[0118] Step five: drying, cutting and peeling the laminated material layer prepared above as a whole, thereby obtaining a laminated current collector-free lithium-ion battery cell of the present invention.

[0119] The cutting process in this embodiment adopts laser cutting.

[0120] This embodiment can produce multiple units in one production, thereby improving work efficiency.

[0121] The shape, size and capacity of the battery cell unit in this embodiment are controllable.

[0122] Example 6

[0123] Step 1: Prepare a dry powder by mixing lithium cobalt oxide, acetylene black, and polyvinylidene fluoride as a positive electrode active material, and spray the dry powder on a designated area of ​​a hydrophobic and easily peelable platform to obtain a positive electrode material layer with a thickness of 150 μm and a surface density of 400 g / m 2 ,;

[0124] Step 2: Spray the insulating material above the positive electrode material layer and the surrounding blank area. Specifically, the ceramic dielectric material Al2O3 is mixed with the binder polyvinylidene fluoride and the solvent N-methylpyrrolidone to form a slurry, which is sprayed to obtain a flat surface covered with the insulating material again, with a thickness of 40μm.

[0125] Step 3: Spray a negative electrode material layer on the designated area above the plane of the above step with a thickness of 150 μm and a surface density of 200 g / m 2 , this area is displaced by 2 mm in the horizontal direction compared to the area of ​​the positive electrode material layer;

[0126] Step 4: Use isolation material to spray fill the blank area with a thickness of 150 μm;

[0127] Step five: drying, cutting and peeling the laminated material layer prepared above as a whole, thereby obtaining a laminated current collector-free lithium-ion battery cell of the present invention.

[0128] This embodiment can produce multiple units in one production, thereby improving work efficiency.

[0129] The shape, size and capacity of the battery cell unit in this embodiment are controllable.

[0130] Example 7

[0131] Step 1: Select the positive electrode active material lithium manganate, the conductive agent acetylene black and the binder polyvinylidene fluoride and mix them to prepare a dry powder. Spray the dry powder on the designated area of ​​the hydrophobic and easily peelable platform to obtain a positive electrode material layer with a thickness of 150 μm and an area density of 400 g / m 2 ;

[0132] Step 2: Spray the insulating material above the positive electrode material layer and the surrounding blank area. Specifically, a solid electrolyte is directly sprayed to obtain a plane covered with the insulating material with a thickness of 30 μm.

[0133] Step 3: Spray a negative electrode material layer on the designated area above the plane of the above step with a thickness of 150 μm and a surface density of 200 g / m 2 , this area is displaced by 2 mm in the horizontal direction compared to the area of ​​the positive electrode material layer;

[0134] Step 4: Use isolation material to spray fill the blank area with a thickness of 150 μm;

[0135] Step five: drying, cutting and peeling the laminated material layer prepared above as a whole, thereby obtaining a laminated current collector-free lithium-ion battery cell of the present invention.

[0136] This embodiment can produce multiple units in one production, thereby improving work efficiency.

[0137] The shape, size and capacity of the battery cell unit in this embodiment are controllable.

[0138] Comparative Example 1

[0139] Step 1: prepare a dry powder by mixing lithium cobalt oxide, a conductive agent acetylene black, and a binder polyvinylidene fluoride into a positive electrode active material, and spray the dry powder onto a designated area of ​​a hydrophobic and easily peelable platform to obtain a positive electrode material layer with a thickness of 150 μm.

[0140] Step 2: Spray the insulating material above the positive electrode material layer and the surrounding blank area. Specifically, the ceramic dielectric material Al2O3 is mixed with the binder polyvinylidene fluoride and the solvent N-methylpyrrolidone to make a slurry, which is sprayed to obtain a flat surface covered with the insulating material again, with a thickness of 30μm.

[0141] Step 3: Spray a negative electrode material layer with a thickness of 150 μm on the designated area above the plane in the above step. Note that this area is completely aligned with the area of ​​the positive electrode material layer without misalignment.

[0142] Step 4: Use isolation material to spray fill the blank area with a thickness of 150 μm;

[0143] Step five: drying, cutting and peeling the laminated material layer prepared above as a whole, thereby obtaining a laminated current collector-free lithium-ion battery cell of the present invention.

[0144] The battery cell prepared in this embodiment has structural defects, and the tabs cannot be drawn out, so it cannot form a lithium-ion battery.

[0145] Comparative Example 2

[0146] The positive electrode active material, conductive agent and binder of the same type and content as those in Example 1 were used to prepare a positive electrode slurry, which was coated on the surface of the aluminum foil and dried to obtain a positive electrode sheet.

[0147] A negative electrode slurry was prepared, applied to the surface of the copper foil, and dried to obtain a negative electrode plate. The composition of the negative electrode material layer in the negative electrode plate was the same as that in the first embodiment.

[0148] A positive electrode sheet and a negative electrode sheet are used, separated by a diaphragm, and stacked to obtain a battery cell.

[0149] Effect analysis:

[0150] First, high energy density and good electrochemical performance:

[0151] In a typical existing battery cell structure, such as in Comparative Example 2, the weight ratio of copper foil and aluminum foil to the active material of the positive and negative electrodes is approximately 1:5 (about 1:8 for the positive electrode and about 1:2 for the negative electrode). However, the copper foil and aluminum foil do not contribute energy.

[0152] In the embodiments of the present application, there is no copper foil or aluminum foil. Under the same ratio of conductive agent to binder, the weight of the battery cell is reduced and the energy density of the battery cell is increased.

[0153] Even if the proportion of conductive agent and adhesive is increased, the capacity and energy density of the battery cell can be improved while ensuring that the increased proportion is lower than the proportion of copper foil and aluminum foil in the existing battery cell structure (for example, the increased proportion does not exceed 5%). The weight of the battery cell can be reduced by about 15%, which is converted into energy density, that is, the energy density increases by about 15%.

[0154] Second, good safety:

[0155] Compared with the existing battery cell structure, the traditional PP / PE material diaphragm is eliminated and replaced with an inorganic oxide material. It does not shrink or burn at high temperatures, thereby improving safety.

[0156] The foregoing is merely a typical embodiment of the present invention, and various other changes are susceptible to being made without departing from the precise scope of the invention as described in the claims.

[0157] The applicant states that the present invention is intended to illustrate the detailed methods of the present invention through the above-described embodiments, but the present invention is not limited to the above-described detailed methods, that is, it does not mean that the present invention must rely on the above-described detailed methods in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for various raw materials in the products of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A battery cell without a current collector, characterized in that: The battery core includes at least two battery core units, each of which includes a positive electrode material layer, a negative electrode material layer, and an isolation structure filled between the positive electrode material layer and the negative electrode material layer, wherein the isolation structure is in contact with the positive electrode material layer and the negative electrode material layer respectively; The battery cell unit is a laminated structure; the vertical cross-section of the isolation structure is Z-shaped, wherein the two parallel sides of the Z-shape are located at the edge of the positive electrode material layer and the edge of the negative electrode material layer respectively; At least a portion of the isolation structure located between the positive electrode material layer and the negative electrode material layer has pores; The positive electrode material layer includes a positive electrode active material, a binder and a conductive agent, and the negative electrode material layer includes a negative electrode active material, a binder and an optional conductive agent; The conductive agents in the positive electrode material layer and the negative electrode material layer are independently selected from at least one of conductive carbon black, acetylene black, Ketjen black, Super P, Super S, carbon nanotubes, graphene, porous carbon and carbon fibers.

2. The current collector-free battery cell according to claim 1, characterized in that: The included angle of the Z-shape is 90°.

3. The current collector-free battery cell according to claim 1, characterized in that: In the vertical cross section, the thickness of a portion of the isolation structure located between the positive electrode material layer and the negative electrode material layer is 10 μm to 300 μm.

4. The current collector-free battery cell according to claim 3, characterized in that: In the vertical cross section, the thickness of a portion of the isolation structure located between the positive electrode material layer and the negative electrode material layer is 20 μm to 200 μm.

5. The current collector-free battery cell according to claim 1, characterized in that: The thickness of the portion of the separator located at the edge of the positive electrode material layer / the negative electrode material layer is independently 100 μm to 1000 μm.

6. The current collector-free battery cell according to claim 5, characterized in that: The thickness of the portion of the separator located at the edge of the positive electrode material layer / the negative electrode material layer is independently 200 μm to 500 μm.

7. The current collector-free battery cell according to claim 1, characterized in that: The positive electrode active material includes at least one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese phosphate, nickel-cobalt-manganese ternary material and nickel-cobalt-aluminum ternary material.

8. The battery cell without current collector according to claim 1, characterized in that: The negative electrode active material includes at least one of lithium titanate, natural graphite, artificial graphite, carbon fiber, soft carbon, hard carbon, mesocarbon microbeads, elemental silicon, silicon oxides, and silicon-carbon composites.

9. The battery cell without current collector according to claim 1, characterized in that: The binder in the positive electrode material layer and the negative electrode material layer is independently selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid and polyvinyl alcohol.

10. The battery cell without current collector according to claim 1, characterized in that: At least a portion of the isolation structure located between the positive electrode material layer and the negative electrode material layer has lithium ion conductivity.

11. The battery cell without current collector according to claim 1, characterized in that: The material of the isolation structure includes at least one of a solid electrolyte, a ceramic dielectric material and a polyolefin.

12. The battery cell without current collector according to claim 1, characterized in that: The battery cell is also provided with a positive electrode tab and a negative electrode tab.

13. The method for preparing a current collector-free battery cell according to any one of claims 1 to 12, wherein: The method comprises the following steps: (1) preparing a first mixed material comprising a positive electrode active material, a binder and a conductive agent, and a second mixed material comprising a negative electrode active material, a binder and an optional conductive agent; (2) A positive electrode material layer and a negative electrode material layer are prepared using the first mixed material and the second mixed material respectively, and an isolation structure of an integrated structure or a separated structure is prepared using an isolation material. The positive electrode material layer, the negative electrode material layer and the isolation structure are laminated so that the isolation structure is filled between the positive electrode material layer and the negative electrode material layer to obtain a battery cell without a current collector.

14. The method for preparing a current collector-free battery cell according to claim 13, wherein: The method comprises the following steps: (1') preparing a first mixed material comprising a positive electrode active material, a binder and a conductive agent, and a second mixed material comprising a negative electrode active material, a binder and an optional conductive agent; (2') coating a first polar material layer on a substrate using either the first mixed material or the second mixed material, wherein the first polar material layer is a positive electrode material layer or a negative electrode material layer; (3') filling and / or coating a material containing an isolation substance on the surface of the first polar material layer on the substrate to form an isolation material layer; (4') Filling and / or coating the surface of the isolation material layer with a mixture having a polarity opposite to that of the mixture used in step (2') to form a second polarity material layer, so that the isolation material layer is filled between the positive electrode material layer and the negative electrode material layer to obtain a battery cell without a current collector.

15. The method according to claim 14, characterized in that The method also includes filling and / or coating the outer side of at least one side of the first polar material layer with a material containing an isolating substance in step (3') to form a first isolating portion, and filling and / or coating the surface of the isolating material layer with a material containing an isolating substance in step (4') to form a second isolating portion, wherein the first isolating portion, the second isolating portion and the isolating material layer are connected to form an isolating structure having a Z-shaped vertical cross-section, and after step (4'), step (3') and step (4') are performed in sequence at least once to form at least two battery cell units and a Z-shaped isolating structure.

16. A lithium ion battery, characterized in that: The lithium-ion battery comprises the current collector-free battery cell according to any one of claims 1 to 12.

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