Electrode for secondary battery and integrated battery

Abstract

The utility model relates to the technical field of battery production, and discloses an electrode for a secondary battery and an integrated battery, which comprise a current collector and an electrode mixture layer which is loaded on the current collector and contains an electrode active material, wherein the electrode mixture layer comprises a plurality of independent electrode mixture bodies, a gap is formed between every two adjacent electrode mixture bodies, and the gaps are used for accommodating an electrolyte to form an expansion buffer layer and enabling the electrolyte to be in contact with the current collector; the volume ratio of the gap in the electrode is Z = W * beta% / a% / b%, W is the width, unit and cm of the electrode mixture body, beta% is the volume expansion rate of the electrode, a% is the porosity of the expansion buffer layer, and b% is the elastic shrinkage rate of the expansion buffer layer. According to the utility model, the power problem and the energy consumption problem caused by transmission resistance can be solved, the intrinsic structural stress problem of the battery core is solved, and the failure risk of the battery is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of battery production, in particular to an electrode and an integrated battery for a secondary battery. Background Art

[0002] As battery applications become more and more widespread, the demand for battery energy density is also increasing. The amount of active material in the lithium-ion battery electrode determines the energy density. The thick electrode design minimizes the proportion of inactive components at the battery cell device level, significantly increases the load of electrode active materials, and provides a good platform for improving the overall energy density of lithium-ion batteries.

[0003] However, due to the increased thickness of the electrode, the transmission path of ions in the thick electrode increases, and the transmission resistance increases, resulting in reduced battery charging and discharging performance. Utility Model Content

[0004] The purpose of the utility model is to overcome the resistance problem caused by the ion transmission channel existing in the prior art and the structural stress problem caused by the intrinsic expansion and contraction of the material, and to provide an electrode and an integrated battery for a secondary battery, which can solve the power problem and energy consumption problem caused by the transmission resistance, solve the intrinsic structural stress problem of the battery cell, and reduce the risk of battery failure.

[0005] In order to achieve the above-mentioned object, the present invention provides an electrode for a secondary battery, wherein the electrode for a secondary battery comprises:

[0006] a current collector; and

[0007] an electrode mixture layer containing an electrode active material loaded on the current collector;

[0008] The electrode mixture layer includes a plurality of independent electrode mixture bodies, and a gap is formed between two adjacent electrode mixture bodies, and the gap is used to accommodate the electrolyte to form an expansion buffer layer and enable the electrolyte to contact the current collector;

[0009] The volume ratio of the gap in the electrode is Z=W*β% / a% / b%, wherein W is the width of the electrode mixture, in cm, β% is the volume expansion rate of the electrode, a% is the porosity of the expansion buffer layer, and b% is the elastic shrinkage rate of the expansion buffer layer.

[0010] A second aspect of the utility model provides an integrated battery, the integrated battery comprising:

[0011] case;

[0012] A positive electrode, a negative electrode and an insulating layer between the positive electrode and the negative electrode are disposed in the housing;

[0013] Wherein, the positive electrode and the negative electrode are the electrodes for the secondary battery described in the utility model.

[0014] Through the above technical scheme, the electrode used in the secondary battery of the utility model reduces the ion transmission resistance, and further solves the structural stress problem caused by the intrinsic expansion and contraction of the material during charging and discharging, increases the battery volume energy density and mass energy density, and reduces the material cost of battery cell manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a front view of an electrode for a secondary battery according to an embodiment of the utility model;

[0016] Figure 2 It is a top view of an electrode for a secondary battery according to one embodiment of the utility model;

[0017] Figure 3 yes Figure 2 Enlarged view of the middle circle T;

[0018] Figure 4 It is a side view of an integrated battery according to one embodiment of the utility model;

[0019] Figure 5 It is a top view of an integrated battery according to one embodiment of the utility model;

[0020] Figure 6 yes Figure 4 Enlarged view of circle K in the middle.

[0021] Description of Reference Numerals

[0022] 1 shell; 2 insulating layer; 3 positive electrode; 4 negative electrode; 5 gap; 6 current collector; I electrode mixture. DETAILED DESCRIPTION

[0023] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0024] 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 and 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.

[0025] In the present invention, unless otherwise specified, directional words such as "up, down, left, right" generally refer to up, down, left, right as shown in the reference drawings; "inside and outside" refer to inside and outside relative to the outline of each component itself.

[0026] like Figure 1-Figure 2 As shown, the utility model discloses an electrode for a secondary battery, and the electrode for the secondary battery comprises:

[0027] a current collector 6; and

[0028] An electrode mixture layer containing an electrode active material loaded on a current collector;

[0029] The electrode mixture layer includes a plurality of independent electrode mixture bodies I, and a gap 5 is formed between two adjacent electrode mixture bodies I, and the gap 5 is used to accommodate the electrolyte to form an expansion buffer layer and enable the electrolyte to contact the current collector 6;

[0030] The volume ratio of gap 5 in the electrode is Z=W*β% / a% / b%, where W is the width of the electrode mixture I, unit: cm, β% is the volume expansion rate of the electrode, a% is the porosity of the expansion buffer layer, and b% is the elastic shrinkage rate of the expansion buffer layer.

[0031] The electrode used in the secondary battery of the utility model is equivalent to dividing the entire electrode mixture layer into a plurality of spaced electrode mixture bodies I, and the gap 5 is filled with electrolyte to form an expansion buffer layer, which can adapt to the conductive ion mass transfer migration requirements of electrodes of different thicknesses, and at the same time improve the expansion and contraction stress of the electrode. Further, an ultra-thick electrode battery with improved performance can be obtained.

[0032] In some embodiments of the present invention, the gap 5 can be formed by, for example, adding hard steel in the step of filling the mixture, and then withdrawing it after cooling to room temperature after hot pressing to form the gap 5 to fill the electrolyte; wherein, Figure 1 As shown, part of the current collector 6 is located in the gap 5, and the filler in the gap 5 should ensure stable chemical properties and be able to form a good infiltration effect with the electrolyte. Specifically, the electrolyte adopts a conventional electrolyte such as a lithium iron phosphate electrolyte; the solid porous filler includes but is not limited to at least one of an insulating porous filler, an insulating porous film or an insulating porous block, wherein the insulating porous filler includes but is not limited to Al 2 O 3 、AlOOH、SiO 2, PVDF or PTFE; the insulating porous membrane includes but is not limited to at least one of PP film, PE film, PET film, PAN film or glass fiber membrane; the insulating porous block includes but is not limited to porous PE block, porous PVDF block or porous PTFE block. When the solid porous filler is used to fill the gap 5, the solid porous filler material does not need to be taken out and normal liquid injection can be performed.

[0033] In this way, the conductive ions can be transferred from the solid phase inside the electrode to the liquid phase, which reduces the ion transmission resistance. Further, it solves the structural stress problem caused by the intrinsic expansion and contraction of the material during charging and discharging, increases the battery volume energy density and mass energy density, and reduces the material cost of battery cell manufacturing.

[0034] In order to evenly distribute the material containing the electrode active material that forms the electrode mixture layer, in some embodiments of the present invention, the shape of the electrode mixture body I is a rectangular parallelepiped.

[0035] In order to further improve the transmission efficiency of conductive ions in the electrode body and solve the intrinsic structural stress problem of the battery cell caused by expansion and contraction on the basis of the above, in some embodiments of the present utility model, Figure 2 As shown, the electrode mixture layer of the electrode has a plurality of electrode mixture bodies I arranged in an N*N form to form a rectangle; and the shape of the electrode mixture body I is also a cuboid, and the width of the cuboid is W, unit, cm; wherein,

[0036] When the electrode is a positive electrode (abbreviated as positive electrode) 3, the volume proportion of the gap 5 in the positive electrode 3 is Z 1 =W*β 1 % / a% / b%, where β 1 % is the volume expansion rate of the positive electrode;

[0037] When the electrode is a negative electrode (abbreviated as negative electrode) 4, the volume proportion of the gap 5 in the negative electrode 4 is Z 2 =W*β 2 % / a% / b%, where β 2 % is the volume expansion rate of the negative electrode.

[0038] It should be noted that when the gap 5 is filled with electrolyte to form an expansion buffer layer, the volume expands in three directions. In some embodiments of the present invention, only one direction is considered, so the expansion in the other two directions needs to be deducted (i.e., divided by 4), that is, the width F of the gap 5 in the positive electrode is Z 1 / 4, the width of the gap 5 in the negative electrode F = Z 2 / 4.

[0039] In some embodiments of the present invention, β 1 % is 0.5%-10%, β2 % is 7%-12%.

[0040] In some embodiments of the present invention, the shape of the current collector 6 is linear, planar mesh, three-dimensional network or formed by a columnar body using an existing technology array. Specifically, the material of the current collector 6 includes but is not limited to one or more of Cu, Ni, Fe, Al, Zn, Ag, Cr, Mo, W, C and their alloys and plated parts; the size of the current collector is designed using existing technology combined with the terminal material and the flow demand. For example, the positive electrode current collector can be an aluminum column array with a diameter of 5 to 100 mm, and the negative electrode current collector can be a copper column current collector array with a diameter of 5 to 50 mm, and the positive and negative electrode current collectors are respectively drawn from both ends.

[0041] The utility model discloses an integrated battery based on the above disclosure, and the integrated battery comprises:

[0042] Shell 1;

[0043] A positive electrode 3, a negative electrode 4 and an insulating layer 2 located between the positive electrode 3 and the negative electrode 4 are arranged in the housing 1;

[0044] The positive electrode 3 and the negative electrode 4 are electrodes for the secondary battery of the present invention.

[0045] In some embodiments of the present invention, Figure 4 As shown, in the shell 1, the positive electrode 3, the insulating layer 2 and the negative electrode 4 are stacked in sequence along the height direction, wherein the insulating layer 2 acts as an electronic insulator filled between the positive electrode and the negative electrode, which can ensure the integrity of the battery cell during operation and prevent damage to the overall structure on the one hand, and on the other hand, this structural form of the utility model serves as a stress buffer structure, which effectively separates the positive electrode and the negative electrode in the phase, alleviates the structural stress changes caused by the increase in the battery cell volume, and prevents the positive and negative battery cells from rupture caused by internal stress.

[0046] The following is an example of an integrated battery manufacturing process of the present invention:

[0047] ① Preparation of a mixture: firstly, the active material and one or more of a conductive agent, a binder, and a solvent (for example, an NMP solvent can be used as an oil-based ingredient, and water can be used as a water-based ingredient) are mixed (the mixing method can be a combination of one or more of stirring, high-speed shearing, ultrasound, kneading, ball milling, sand milling, etc., preferably, the active material and the conductive agent are stirred and mixed, and then the binder is added and mixed at a high speed shearing) to obtain a mixture (for example, a mixed powder or a mixed slurry);

[0048] ② Preparation of electrodes: The mixture in ① is then quantitatively poured (for example, by a screw pump, a metering pump, an air flow conveying method, etc., preferably, the mixture is filled by a screw pump and a heating pipe, and the pipe temperature is set to 150-200° C.) in a shell 1 in which a current collector (for example, a conductive three-dimensional porous current collector or a current collector network composed of Cu, Al, Ni, Fe, Mn, Ti and conductive fibers) is pre-placed, and leveled by a scraper, and compressed and shaped by hot pressing or cold pressing of a metal plate (preferably by hot pressing and shaping by a metal plate, the pressure is set to 0.1-10 MPa, and the hot pressing time can be 0.5-180 min) to obtain an electrode (positive electrode or negative electrode);

[0049] It should be noted that: different from the battery monomer (such as lithium-ion battery monomer) manufacturing process in the prior art, the utility model breaks through the thickness limitation of the existing battery thin electrode production, and greatly simplifies the battery production process. There is no need for complicated electrode coating, rolling, slitting, die cutting, winding (stacking), assembly and other processes. At the same time, the expansion of the monomer scale also reduces the restrictions on the control accuracy of the production equipment.

[0050] In addition, the gap 5 can be formed by, for example, adding hard steel in the step of filling the mixture, and then withdrawing it after cooling to room temperature after hot pressing to form the gap 5 to fill the electrolyte to form an expansion buffer layer. In this way, due to the expansion buffer layer reserved by the electrode itself, the conductive ions are changed from solid-phase transmission inside the thick electrode to liquid-phase transmission, which greatly improves the transmission power of ions inside the electrode body and reduces the power problem and energy consumption problem caused by transmission resistance. In addition, the reserved expansion buffer layer can play a buffering role as the thick electrode expands and contracts during the charging and discharging process, solves the intrinsic structural stress problem of the battery cell, and reduces the risk of battery failure.

[0051] ③ Preparation of integrated battery assembly: Figure 4 As shown, an integrated battery assembly can be obtained in the shell 1 by stacking layers, for example, stacking in the order of negative electrode-insulating layer-positive electrode-insulating layer-negative electrode in the height direction to form an integrated battery, wherein the negative electrode layer, insulating layer, and positive electrode layer can be produced separately by molds and then assembled uniformly, or can be directly loaded and assembled in situ in the inner cavity of the battery shell 1. Preferably, the positive and negative electrodes are assembled in situ in the cavity of the battery shell 1 in the order of negative electrode layer / insulating layer / positive electrode layer / insulating layer, according to the process of loading-scraping-hot pressing.

[0052] ④ Preparation of integrated battery: The integrated battery assembly in ③ is subjected to conventional welding, baking, liquid injection, aging, and formation processes in the prior art, wherein the formation can be open-end formation or closed-end formation. Preferably, after the assembled battery is subjected to multi-current laser welding to lead out the terminals, the dry core is injected with liquid, sealed and nailed, and then aged at 45°C for 24 to 72 hours, and then cooled and subjected to open-end formation at room temperature and negative pressure; finally, the finished battery cell is obtained through the capacity division process.

[0053] The electrode of the utility model can be made into a thick electrode with a thickness greater than 100 microns, and further made into an ultra-thick electrode with a thickness greater than 500 microns, which can not only bring an improvement in the energy density of the battery; but also the expansion buffer layer reserved based on ion kinetic transport and intrinsic material properties can reduce the ion transport resistance and structural stress problems inside the thick electrode, greatly increasing the actual energy efficiency and durability of the battery.

[0054] In some embodiments of the present invention, the shell 1 can be made of metal or insulating material; wherein the metal material is Fe, Al and its alloys, plated parts, composite parts, etc.; the insulating material is one or more of PE, PP, PTFE, PET, PAN. The shape of the shell 1 is set to be cylindrical, rectangular, square or rhombus, and other special-shaped structures designed according to the application scenario. The thickness of the shell 1 of the integrated battery can be 2mm to 200mm.

[0055] In some embodiments of the present invention, the housing 1 is made of stainless steel with a thickness of 5 mm to 100 mm, and the inner wall of the housing 1 has a thickness of 1 mm to 10 mm of Al 2 O 3 The shell 1 is lined with a ceramic layer and retains a top cover plate as a loading operation surface. A current collector outlet is reserved on the side. This structure ensures assembly strength while facilitating the infiltration of the electrolyte.

[0056] In some embodiments of the present invention, Figure 6 As shown, the thickness of the single layer of the insulating layer 2 is E=(Y*β 2 %-X*β 1 %) / a% / b%, where X is the thickness of the single-layer positive electrode 3, cm, and Y is the thickness of the single-layer negative electrode 4, cm. It should be noted that, in general, when the negative electrode of the battery uses graphite or silicon negative electrode, the expansion thickness of the negative electrode will be greater than the expansion thickness of the positive electrode. At this time, the battery charging cell will expand and the battery discharging cell will shrink, so: E=(Y*β 2 %-X*β 1 %) / a% / b%(negative electrode minus positive electrode); however, special cases are not excluded, such as when the positive electrode expands more than the negative electrode, such as when lithium titanate is used as the negative electrode, then E=(X*β1 %-Y*β 2 %) / a% / b%) (positive electrode minus negative electrode).

[0057] In some embodiments of the present invention, the insulating layer 2 is filled between the positive electrode and the negative electrode as an electronic insulator, and the filler in the insulating layer 2 can be selected from at least one of an insulating filler, an insulating porous film, or an insulating porous block; wherein the insulating filler includes but is not limited to Al 2 O 3 、AlOOH、SiO 2 , PVDF, PTFE; the insulating porous membrane includes but is not limited to at least one of PP film, PE film, PET film, PAN film, and glass fiber membrane; the insulating porous block includes but is not limited to one or more of porous PE block, porous PVDF block, and porous PTFE block.

[0058] In order to maintain structural stability, in some embodiments of the present invention, the insulating layer 2 is filled with Al 2 O 3 Powder, filled between the positive and negative electrodes.

[0059] In some embodiments of the present invention, the range of X / Y is 0.1-2.4:1.

[0060] In some embodiments of the present invention, the range of X in the single-layer positive electrode 3 is 0.01-200 mm, and the porosity is 30% to 60%.

[0061] In some embodiments of the present invention, the Y range of the single-layer negative electrode 4 is 0.5 mm to 200 mm, and the porosity is 30% to 60%.

[0062] It can be understood that the integrated battery of the present invention can be a variety of systems such as ternary batteries, lithium iron phosphate batteries and sodium ion batteries. In order to cope with the positive and negative electrode ion transmission kinetics problems and volume expansion and contraction effects, the size of the expansion buffer layer reserved for the positive and negative electrodes can be designed based on the actual electrode thickness changes and material characteristics.

[0063] In some embodiments of the present invention, the electrode mixture layer of the positive electrode contains one or more of a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and a positive electrode functional filler, and the positive electrode current collector is composited in the electrode mixture layer of the positive electrode, wherein the positive electrode active material can be a lithium ion battery positive electrode material (including but not limited to LFP, LFMP, NCM, NCA, NCMA, LMO, LNO, LCO, Li 2 MnO 3 or LiNi 0.5 Mn 1.5 O 2At least one of) or sodium ion positive electrode materials (including but not limited to Prussian white, NaNiFeMnO 2 , NaVP, NVP, NFP 2 O 7 and NFSO); the positive electrode conductive agent includes but is not limited to one or more of graphite powder, carbon black, carbon nanotubes, graphene, polypyrrole, polyaniline, polythiophene, etc.; the positive electrode binder includes but is not limited to one or more of PVDF, PTFE, PEO; the positive electrode functional filler can be a conductive filler (including but not limited to one or more of conductive carbon fiber, conductive carbon rod and conductive carbon tube) and / or an insulating filler (including but not limited to glass fiber, Al 2 O 3 、SiO 2 One or more of); the positive current collector can be a linear, planar network and three-dimensional network structure with Al, Al alloy, Al plating, etc. as the main body. In some embodiments of the utility model, the porosity of the entire positive electrode before compression can be 30% to 80%. Preferably, the positive active material LFP, the positive conductive agent carbon black, and the positive binder PVDF are dry-mixed in a ratio of 80-95%: 2-10%: 3-10% and evenly filled in the three-dimensional porous current collector network with aluminum rod as the skeleton, and then hot-pressed to obtain the positive electrode. After compression, the thickness X of a single positive electrode is 0.5mm to 200mm, and the porosity is 30% to 60%.

[0064] In some embodiments of the present invention, the electrode mixture layer in the negative electrode contains one or more of a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, a negative electrode functional filler, and a negative electrode current collector compounded in the electrode mixture layer of the negative electrode. The negative electrode active material includes but is not limited to graphite, hard carbon, silicon, silicon dioxide, Li 4 Ti 5 O 12 、TiO 2 , Fe 2 O 3 、MoS 2 One or more of; negative electrode conductive agents include but are not limited to conductive graphite, Super P, carbon black, carbon nanotubes, graphene one or more; negative electrode binders include but are not limited to methyl cellulose, styrene-butadiene rubber, polyacrylic acid, sodium alginate, polyimide, polypropylene alcohol one or more; negative electrode functional fillers include but are not limited to conductive fillers and or insulating fillers, conductive fillers include but are not limited to conductive carbon fibers, conductive carbon rods, conductive carbon tubes and insulating fillers such as glass fibers, Al 2 O 3 、SiO 2One or more of; the negative electrode current collector can be a linear, planar network and three-dimensional network structure containing Al, Cu, Ni, Ti and their alloys or plated parts. In some embodiments of the utility model, the porosity of the entire negative electrode before compression can be 30% to 80%. Preferably, the negative electrode active material artificial graphite, the negative electrode conductive agent carbon black, and the negative electrode binder PTFE are dry-mixed in a ratio of 80-95%: 2-10%: 3-10% and evenly filled in the three-dimensional current collector network with copper rod as the skeleton, and then hot-pressed to obtain the negative electrode. After compression, the thickness Y of a single negative electrode is 0.5mm to 200mm, and the porosity is 30% to 60%.

[0065] The integrated battery of the utility model, by reserving the structural form of the expansion buffer layer, breaks through the limitation of the thickness of the pole piece caused by stress shrinkage cracking or failure of the mechanical strength of the pole piece in the traditional membrane electrode manufacturing process, and can achieve normal expansion and contraction of ultra-thick electrodes. At the same time, based on the correlation adjustment of the expansion buffer layer and the thickness of the positive and negative electrodes, the thickness of the expansion buffer layer is changed synchronously while the electrode is thickened, so that the electrolyte can be fully infiltrated, thereby improving the problem of poor lithium ion transmission efficiency in the application process of ultra-thick electrodes.

[0066] It should be noted that the gap 5 and the insulating layer 2 can be filled with the same material. The insulating layer 2 between the positive and negative electrodes is the diaphragm; the expansion buffer layer (gap 5) inside the single layer of the positive or negative electrode plays a buffering role and also plays a role in transporting ions inside the positive or negative electrode.

[0067] The advantages of the present invention will be described below through embodiments, but the present invention is not limited thereto.

[0068] Example 1

[0069] Preparation Figure 1-Figure 5 The integrated battery shown, specifically:

[0070] ① Mix lithium iron phosphate powder, conductive agent Super P, and binder PVDF at a mass ratio of 90%:5%:5% at a speed of 50-100rmp by low-speed ball milling to obtain positive electrode active material powder; mix artificial graphite powder, conductive agent carbon black, and binder PVDF at a mass ratio of 95%:2%:3% at a speed of 50-100rmp by low-speed ball milling to obtain negative electrode active powder; 2 O 3 The powder and the binder PVDF are mixed by low-speed ball milling at a mass ratio of 95%:5% at a rotation speed of 50-100 rpm to obtain an insulating layer powder;

[0071] ② First, a single block is constructed: the positive and negative active powders and insulating powders are poured layer by layer into the iron metal shell 1 lined with insulation treatment in the manner of copper current collector-negative active powder-insulating powder-aluminum current collector-positive active powder. The negative current collector adopts a three-dimensional copper mesh with a pore size of 1×1×1cm woven from copper wire with a diameter of 0.5mm, and the positive current collector adopts a three-dimensional four-layer aluminum mesh with a pore size of 1×1×1cm woven from aluminum wire with a diameter of 1mm. After the negative electrode layer is flattened, it is hot pressed to a layer thickness Y of 2.74cm; after the positive electrode layer is flattened, it is hot pressed to a layer thickness X of 3.52cm; after the insulating layer is flattened, it is hot pressed to a layer thickness E=(2.74*10%-3.52*5.6%) / 50% / 50%=0.307cm. The entire battery cell consists of 6 layers of negative electrode + 5 layers of positive electrode + 10 layers of insulating layer;

[0072] ③ In the step of filling the mixture, hard steel is added, and after hot pressing and cooling to room temperature, it is extracted to form a gap 5; after each flattening, it is baked and shaped to form 5*5 electrode mixture bodies I assembled and filled into the complete iron metal shell. The volume proportion of the gap 5 in the positive and negative electrodes is calculated according to the volume expansion rate of the negative electrode, and its maximum expansion buffer layer volume proportion, that is, Z 1 =Z 2 =10cm*10% / 50% / 50% Prepare the expansion buffer layer (the volume expands in three directions. In this embodiment, only one direction is considered, so the expansion in the other two directions needs to be deducted, that is, divided by 4. Therefore, the width F of the gap 5 in the positive and negative electrodes is Z 1 / 4=Z 2 / 4=1cm), after the complete battery core is formed, the cover plate is welded. In this embodiment, W is 10cm, β 1 % is 5.6%, β 2 % is 10%;

[0073] ④ After baking, the electrolyte is injected, and the electrolyte is a conventional lithium iron phosphate electrolyte.

[0074] ⑤Perform normalized capacity test on the battery cells.

[0075] The test methods and test results are shown below.

[0076] Example 2

[0077] The difference from Example 1 is:

[0078] ① The hot pressing thickness X of the positive electrode single layer is 7.04 cm;

[0079] ②The hot pressing thickness Y of the negative electrode single layer is 4.91cm;

[0080] ③The single-layer hot pressing thickness E of the insulation layer is 0.387cm;

[0081] ④ The entire battery cell is composed of 5*5 electrode composite bodies I, and the entire battery cell includes 3 layers of positive electrodes + 4 layers of negative electrodes + 6 layers of insulation layers. The width F of the gap 5 remains 1 cm and is filled with an expansion buffer layer;

[0082] The test methods and test results are as follows.

[0083] Comparative Example 1

[0084] The difference from the first embodiment is that the gap 5 is not provided, that is, there is no expansion buffer layer in the electrode.

[0085] The test results are shown in the following table.

[0086] Electrochemical performance test

[0087] The battery of the embodiment is subjected to a simulated charge and discharge test using an electrochemical charge and discharge test cabinet to verify the feasibility of the charge and discharge work of the integrated battery of the utility model. Specifically, for the embodiment and the comparative example, a simulated constant current charge and discharge test is performed at a voltage range of 2.0-3.65V using a test current of 1000A at room temperature (25±3°C) to obtain the electrical performance data of the monomer.

[0088] The specific test results are shown in Table 1:

[0089] Table 1

[0090]

[0091] The results of simulated charge and discharge tests on integrated batteries with different electrode thicknesses show that adjusting the expansion buffer layer while increasing the electrode thickness can improve the volume expansion problem caused by the electrode thickening and achieve cycle efficiency at a small rate. At the same time, it also improves the battery stress accumulation problem caused by structural expansion, solves the problem of internal rupture caused by structural stress in the integrated battery, and significantly improves the charge and discharge efficiency of the battery cell. Improving the internal stress problem of thick electrode batteries is of great significance to the practical application of integrated thick electrode batteries.

[0092] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various specific technical features in any appropriate manner. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. An electrode for a secondary battery, characterized in that: The electrode for the secondary battery comprises: a current collector (6); and an electrode mixture layer containing an electrode active material loaded on the current collector; The electrode mixture layer comprises a plurality of independent electrode mixture bodies (I), a gap (5) is formed between two adjacent electrode mixture bodies (I), and the gap (5) is used to accommodate an electrolyte to form an expansion buffer layer and enable the electrolyte to contact the current collector (6); The volume ratio of the gap (5) in the electrode is Z=W*β% / a% / b%, wherein W is the width of the electrode mixture (I), unit, cm, β% is the volume expansion rate of the electrode, a% is the porosity of the expansion buffer layer, and b% is the elastic shrinkage rate of the expansion buffer layer.

2. The electrode for a secondary battery according to claim 1, characterized in that: The electrode mixture body (I) is in the shape of a cuboid; and / or A plurality of the electrode mixture bodies (I) are arrayed in the form of N*N to form the rectangular electrode.

3. The electrode for a secondary battery according to claim 1 or 2, characterized in that: When the electrode is a positive electrode (3), the volume ratio of the gap (5) in the positive electrode (3) is Z1=W*β1% / a% / b%, wherein β1% is the volume expansion rate of the positive electrode; When the electrode is a negative electrode (4), the volume ratio of the gap (5) in the negative electrode (4) is Z2=W*β2% / a% / b%, wherein β2% is the volume expansion rate of the negative electrode.

4. The electrode for a secondary battery according to claim 3, characterized in that: β1% is 0.5%-10%; and / or β2% is 7%-12%.

5. The electrode for a secondary battery according to claim 1, characterized in that: The shape of the current collector (6) is linear, planar mesh, three-dimensional network or formed by a columnar array.

6. An integrated battery, characterized in that: The integrated battery comprises: Housing (1); A positive electrode (3), a negative electrode (4) and an insulating layer (2) located between the positive electrode (3) and the negative electrode (4) arranged in the housing (1); Wherein, the positive electrode (3) and the negative electrode (4) are electrodes for secondary batteries as claimed in any one of claims 1 to 5.

7. The integrated battery according to claim 6, characterized in that: In the shell (1), the positive electrode (3), the insulating layer (2) and the negative electrode (4) are stacked in sequence along a height direction; and / or The shape of the shell (1) is set to be cylindrical, rectangular or rhombus.

8. The integrated battery according to claim 6, characterized in that: The thickness of a single layer of the insulating layer (2) is E=(Y*β2%-X*β1%) / a% / b%, wherein X is the thickness of a single layer of the positive electrode (3), in cm, and Y is the thickness of a single layer of the negative electrode (4), in cm; and / or The thickness E of the insulating layer (2) is 0.01 to 200 mm.

9. The integrated battery according to claim 8, characterized in that: The range of X / Y is 0.1 to 2.4:1; and / or The width F of the gap (5) in the single-layer positive electrode (3) and / or the single-layer negative electrode (4) is 0.01-200 mm.

10. The integrated battery according to claim 9, characterized in that: The X range of the single-layer positive electrode (3) is 0.5 mm to 200 mm, and the porosity is 30% to 60%; and / or The range of Y in the single-layer negative electrode (4) is 0.5 mm to 200 mm, and the porosity is 30% to 60%.

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