CN115394952A

CN115394952A - Thick electrode and manufacturing method and application thereof

Info

Publication number: CN115394952A
Application number: CN202211073068.3A
Authority: CN
Inventors: 孙伟兵; 刘范芬; 苑丁丁; 张�林
Original assignee: Hubei Eve Power Co Ltd
Current assignee: Hubei Eve Power Co Ltd
Priority date: 2022-09-02
Filing date: 2022-09-02
Publication date: 2022-11-25

Abstract

The invention provides a thick electrode and a manufacturing method and application thereof, wherein an active layer of the thick electrode comprises a first active stripe and a second active stripe which are sequentially and horizontally arranged in an alternating manner; the particle size of the active main material in the first active stripe is smaller, but the thickness of the active main material is the same as that of the second active stripe, so that the porosity of the first active stripe is lower than that of the second active stripe, and the width of the first active stripe is kept to be 5-20 times of that of the second active stripe. On the basis, the active main material in the second active stripe has larger grain size, and after roll forming, the active main material has larger porosity and is distributed in a gap formed by the first active stripe in a narrower width, so that the infiltration rate and the infiltration degree of the electrolyte along with the whole active layer can be obviously improved, the internal resistance of the battery can be reduced, and the rate capability of the thick electrode can be improved.

Description

Thick electrode and manufacturing method and application thereof

Technical Field

The invention belongs to the field of lithium ion batteries, and relates to a thick electrode and a manufacturing method and application thereof.

Background

At present, with the rapid development and continuous enlargement of the scale of new energy automobiles, the market demand for high-energy and high-power batteries is also continuously increased. In order to improve the energy density of the power battery, various new materials and new technologies are continuously emerging, and currently, the main strategies for improving the energy density of the power battery are as follows: (1) developing high-capacity anode and cathode materials, such as a high-nickel material, a lithium-rich anode, a silicon cathode, a metal lithium cathode and the like; (2) developing a high-voltage positive electrode material; (3) developing a high-performance electrolyte; (4) developing a high-performance binder; (5) thick electrode development, etc.

In the direction of battery technology, thick electrode development is the most direct method for improving the energy density of a battery, but the thick electrode technology has some problems to be solved, such as that with the increase of the thickness of an electrode, although the proportion of inactive materials is significantly reduced, the stripping force of a pole piece is simultaneously reduced, the infiltration rate of electrolyte is slowed, the internal resistance of the battery is increased, and finally the rate capability and the cycle life of the battery are significantly deteriorated. A large number of researches show that the electrolyte liquid phase transmission in the electrochemical reaction process of the thick electrode is a speed control step, the electrolyte liquid phase transmission is closely related to the pore structure, the porosity and the like in the electrode, and the rate capability of the thick electrode can be improved based on the optimization of the speed control step.

For example, CN102655229B adopts a pore-forming agent solvent to coat the surface of the pole piece, volatilizes the solvent during baking, allows the pore-forming agent to permeate into the inside of the membrane and recrystallize to occupy a certain position, and then bakes at a temperature higher than the sublimation or decomposition temperature of the pore-forming agent to form pores, so that pores are left on the membrane, thereby obtaining a thick electrode with high porosity; julie Bilaud et al (Nature Energy,2016,1 (8), 1-6.) modify a graphite cathode by adopting a magnetic substance, control the orientation of graphite particles by using an external magnetic field in a homogenizing stage to obtain a low-tortuosity graphite thick electrode, and improve the performance of a battery only by changing the internal structure of the electrode, so that the lithium storage capacity of the electrode at the actual charging rate is improved by 1.6-3 times; junsupark (Journal of Industrial and Engineering Chemistry,2019,70, 178-185) adopts laser to etch the groove to obtain an array groove thick electrode, thereby obviously improving the dynamic performance of the battery; however, the above methods for manufacturing thick electrodes have the following problems:

1) When the pore-forming agent is used for pore-forming, the thermal decomposition temperature of the pore-forming agent is incompatible with the electrode baking temperature, harmful gas is easily formed by the thermal decomposition of the pore-forming agent, and the pore-forming efficiency is low;

2) The orientation of the particles controlled by the external physical field is difficult to maintain an oriented structure in subsequent rolling, the compatibility with the current roll-to-roll process is poor, and the material modification cost is high;

3) The laser pore-forming has high destructiveness to the coating, is easy to form substances such as molten beads, dust and the like, has high self-discharge of the battery, and obviously reduces the capacity of the thick electrode surface and the energy density.

It can be seen that there is no new technical solution which is simpler and more feasible and more compatible with the electrode process, and the states of the pore structure, porosity and the like in the thick electrode can be adjusted to optimize the electrolyte liquid phase transmission, so that the thick electrode with high energy, high power and long cycle life meeting the market demand is obtained.

Disclosure of Invention

In view of the problems in the prior art, the present invention aims to provide a thick electrode, a manufacturing method thereof and an application thereof, wherein an active layer of the thick electrode comprises a first active stripe and a second active stripe which are horizontally and alternately arranged in sequence; the particle size of the active main material in the first active stripe is smaller, but the thickness of the first active stripe is the same as that of the second active stripe, so that the porosity of the first active stripe is lower than that of the second active stripe, and the width of the first active stripe is kept 5-20 times of that of the second active stripe. On the basis, the active main material in the second active stripe has larger grain size, and after roll forming, the active main material has larger porosity and is distributed in a gap formed by the first active stripe in a narrower width, so that the infiltration rate and the infiltration degree of the electrolyte along with the whole active layer can be obviously improved, the internal resistance of the battery can be reduced, and the rate capability of the thick electrode can be improved.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a thick electrode, including a current collector and an active layer on the current collector, where the active layer includes first active stripes and second active stripes that are horizontally and alternately arranged in sequence; the first active stripes comprise active main materials, conductive agents and binders, and the component materials of the second active stripes are the same as those of the first active stripes; the particle size of the active main material in the first active stripe is smaller than that of the active main material in the second active stripe; the thickness of the first active stripes is the same as that of the second active stripes; the porosity of the first active stripes is lower than the porosity of the second active stripes; the width of the first active stripe is 5-20 times of the width of the second active stripe.

According to the invention, the stripe type active layer is arranged, and the first active stripe is controlled to have larger width so as to ensure the high capacity and high power of the thick electrode, on the basis, the particle size of the active main material in the second active stripe is larger, the porosity is larger after roll forming, and the active main material is distributed in the gap formed by the first active stripe in a narrower width, so that the effect of a fast channel is mainly played, the infiltration rate and infiltration degree of electrolyte along with the whole active layer can be obviously improved, and the internal resistance of the battery can be reduced, thereby improving the rate capability of the thick electrode.

In the electrode, along with the increase of the thickness of the electrode, the main factor limiting the rate performance of the electrode is the liquid phase transmission process of electrolyte, and the liquid phase transmission process can be influenced because the particle size of the active main material can obviously influence the pore structure of the electrode; the bigger the active main material particles are, bigger pores can be formed among the particles, so that the transmission of electrolyte in the thickness direction of the electrode is facilitated, however, the too big active main material particles lead to the undersize of the compaction density of a thick electrode, the promotion of energy density is not facilitated, and in addition, the too big active main material particles also can obviously reduce the solid phase diffusion coefficient of the thick electrode, and the concentration polarization is obviously aggravated. In the thick electrode, the macropores formed by the large-particle active main material coated in an array mode are beneficial to rapid infiltration and diffusion of electrolyte in the thick electrode, and therefore the dynamic performance of the thick electrode is remarkably improved. However, the second active stripe region formed by the large particles is not too large, otherwise, on one hand, the compaction density of the thick electrode is easily reduced remarkably, the energy density of the battery is seriously attenuated, on the other hand, the large particles are not beneficial to solid-phase lithium ion diffusion, and the multiplying power performance of the thick electrode is remarkably attenuated due to the wider second active stripe region of the large particles.

The following technical solutions are preferred technical solutions of the present invention, but not limited to the technical solutions provided by the present invention, and technical objects and advantageous effects of the present invention can be better achieved and achieved by the following technical solutions.

In a preferred embodiment of the present invention, the width of the first active stripes is 0.5 to 50mm, for example, 0.5mm, 1mm, 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, or 50mm, but the width is not limited to the above-mentioned values, and other values not listed in the above-mentioned value range are also applicable.

Preferably, the first active stripes have a porosity of 20 to 50%, such as 20%, 25%, 30%, 35%, 40%, 45%, or 50%, but not limited to the recited values, and other unrecited values within the above range of values are equally applicable.

Preferably, the active layer is disposed on a surface of one or both sides of the current collector.

In a preferred embodiment of the present invention, the thickness of the first active stripes and the thickness of the second active stripes are 150 to 350 μm, for example, 150 μm, 180 μm, 210 μm, 240 μm, 270 μm, 300 μm, 330 μm, or 350 μm, but the thickness is not limited to the above-mentioned values, and other values not listed in the above-mentioned value range are also applicable.

In a preferred embodiment of the present invention, the particle size of the active material in the first active stripe is 20 to 80%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80% of the particle size of the active material in the second active stripe, but the present invention is not limited to the above-mentioned values, and other values not listed in the above-mentioned numerical range are also applicable.

Preferably, the active main material includes a positive electrode main material or a negative electrode main material.

Preferably, the positive electrode base material comprises any one of, or a combination of at least two of, lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, or lithium nickel cobalt aluminate, typical but non-limiting examples of which include a combination of lithium cobaltate and lithium manganate, a combination of lithium cobaltate and lithium nickelate, a combination of lithium manganate and lithium nickelate, and a combination of lithium manganate and lithium nickel cobalt aluminate.

Preferably, the negative electrode main material includes any one of graphite, hard carbon, soft carbon, silicon carbon, or tin, or a combination of at least two thereof, and typical but non-limiting examples thereof include a combination of graphite and soft carbon, a combination of graphite and hard carbon, a combination of graphite and tin, a combination of hard carbon and tin, a combination of soft carbon and tin, a combination of silicon and tin, and a combination of silicon carbon and tin.

As a preferred embodiment of the present invention, the conductive agent includes any one or a combination of at least two of carbon black, carbon fiber, carbon nanotube, or graphene, and typical but non-limiting examples of the combination include a combination of carbon black and carbon fiber, a combination of carbon black and carbon nanotube, a combination of carbon black and graphene, a combination of carbon fiber and carbon nanotube, a combination of carbon fiber and graphene, and a combination of carbon nanotube and graphene.

As a preferable embodiment of the present invention, the content of the binder in the first active stripe is lower than the content of the binder in the second active stripe.

Preferably, the binder comprises any one or a combination of at least two of sodium hydroxymethyl cellulose, styrene butadiene rubber, polyvinylidene fluoride or polyacrylic acid, typical but non-limiting examples of which include sodium hydroxymethyl cellulose in combination with styrene butadiene rubber, sodium hydroxymethyl cellulose in combination with polyvinylidene fluoride, sodium hydroxymethyl cellulose in combination with polyacrylic acid, styrene butadiene rubber in combination with polyvinylidene fluoride, styrene butadiene rubber in combination with polyacrylic acid, and polyvinylidene fluoride in combination with polyacrylic acid.

In a second aspect, the present invention provides a method for manufacturing a thick electrode according to the first aspect, the method comprising the following steps:

(1) Respectively selecting an active main material, a conductive agent and a binder which are made of the same material, and respectively preparing a first slurry and a second slurry; the particle size of the active main material in the first slurry is smaller than that of the active main material in the second slurry;

(2) Coating the first slurry obtained in the step (1) on a current collector to form first slurry stripes with gaps; the width of the first slurry stripe is 5-20 times of the gap;

(3) Coating the second slurry obtained in the step (1) in the gap obtained in the step (2) to form second slurry stripes;

(4) And sequentially baking and rolling to enable the first slurry stripes to form first active stripes and the second slurry stripes to form second active stripes, controlling the thickness of the first active stripes to be equal to that of the second slurry stripes, enabling the porosity of the first active stripes to be lower than that of the second active stripes, and sequentially and alternately arranging the first active stripes and the second active stripes to form active layers to obtain the thick electrode.

Note that the widths of the first active stripe and the second active stripe formed after the first slurry stripe and the second slurry stripe are rolled, respectively, are not changed, that is, the active stripes are not spread in the actual width direction, and thus the final width is the same as the width at the time of coating.

In a preferred embodiment of the present invention, the content of the binder in the first slurry is 30 to 90% of the content of the binder in the second slurry, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%, but is not limited to the above-mentioned values, and other values not listed in the above-mentioned numerical range are also applicable.

The invention preferably ensures that the content of the binder in the second slurry is higher, which is beneficial to the dispersion of the binder from the second slurry stripe to the first slurry stripe in the baking and rolling processes, obviously improves the migration of the binder, improves the distribution uniformity of the binder in the thick electrode and improves the peeling strength.

Preferably, the binder is contained in an amount of 1 to 3wt%, for example, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, or 3% based on 100wt% of the total mass of the active host material, the conductive agent, and the binder in the first slurry, but is not limited to the enumerated values, and other unrecited values within the above numerical range are also applicable.

Preferably, the first and second slurry stripes each have a thickness of 200 to 450 μm, for example 200 μm, 225 μm, 250 μm, 275 μm, 300 μm, 325 μm, 350 μm, 375 μm, 400 μm, 425 μm or 450 μm, but are not limited to the recited values, and other values within the above range of values are also applicable.

As a preferable technical scheme of the invention, the manufacturing method comprises the following steps:

(1) Respectively selecting an active main material, a conductive agent, a binder and a solvent which are the same in material quality, stirring and dispersing to respectively prepare a first slurry and a second slurry; controlling the particle size of the active main material in the first slurry to be 20-80% of the particle size of the active main material in the second slurry; the active main material comprises a positive electrode main material or a negative electrode main material; the anode main material comprises any one or the combination of at least two of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate or lithium nickel cobalt aluminate; the main material of the negative electrode comprises any one or the combination of at least two of graphite, hard carbon, soft carbon, silicon carbon or tin;

the content of the binder is 1 to 3 weight percent based on the total mass of the active main material, the conductive agent and the binder in the first slurry as 100 weight percent; controlling the content of the binder in the first slurry to be 30-90% of the content of the binder in the second slurry; the binder comprises any one or the combination of at least two of sodium carboxymethylcellulose, styrene butadiene rubber, polyvinylidene fluoride or polyacrylic acid; the conductive agent comprises any one of carbon black, carbon fiber, carbon nano tube or graphene or a combination of at least two of the carbon black, the carbon fiber, the carbon nano tube and the graphene;

(2) Coating the first slurry obtained in the step (1) on a current collector to form first slurry stripes with gaps; the gap is 0.5-50 mm, and the width of the first slurry stripe is 5-20 times of the gap; the thickness of the first slurry stripes is 200-450 mu m;

(3) Coating the second slurry obtained in the step (1) in the gap obtained in the step (2) to form a second slurry stripe with the thickness equal to that of the first slurry stripe;

(4) Sequentially baking and rolling to enable the first slurry stripes to form first active stripes and enable the second slurry stripes to form second active stripes, and sequentially and alternately arranging to form active layers; the thickness of the first active stripes is equal to that of the second active stripes, the first active stripes and the second active stripes are 150-350 mu m, the porosity of the first active stripes is controlled to be 20-50%, and the porosity of the second active stripes is higher than that of the first active stripes, so that the thick electrode is obtained.

In a third aspect, the invention provides a use of the thick electrode of the first aspect or the thick electrode obtained by the manufacturing method of the second aspect, wherein the use comprises using the thick electrode in a lithium ion battery.

Compared with the prior art, the invention at least has the following beneficial effects:

(1) On the basis, the second active stripe containing the active main material with large particle size has high porosity and large aperture after being rolled, is distributed in the gaps of the first active stripe and is alternately arranged with the first active stripe to form a stripe type active layer, so that the infiltration rate and the infiltration of electrolyte in the whole active layer can be obviously improved, the internal resistance of the battery is effectively reduced, and the rate capability is improved;

(2) Compared with the prior art for carrying out pore-forming on the thick electrode, the existence of the second active stripes can obviously improve the energy density of the thick electrode, and in addition, the poor problems of pole piece wrinkling and the like during thick electrode coating and rolling can be effectively relieved; compared with the manufacturing process of the pore-forming thick electrode, the manufacturing method has the advantages of simple process, high production efficiency and remarkably reduced manufacturing cost of the thick electrode;

(3) The content of the binder in the second slurry is higher than that of the binder in the first slurry, so that the binder in the second slurry stripe can be diffused into the first slurry stripe in a peripheral radiation manner during coating and baking, the migration condition of the binder is obviously improved, the distribution uniformity of the whole thick electrode binder is improved, and the peeling strength is effectively improved.

Drawings

Fig. 1 is a schematic top view of a thick lithium iron phosphate electrode obtained in embodiment 1 of the present invention;

FIG. 2 isbase:Sub>A schematic sectional view taken along the line A-A in FIG. 1;

in the figure: 1-first active stripe, 2-second active stripe, 3-current collector.

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

The embodiment provides a lithium iron phosphate thick electrode, and a manufacturing method of the lithium iron phosphate thick electrode comprises the following steps:

(1) Stirring and dispersing carbon black, PVDF (polyvinylidene fluoride) and lithium iron phosphate with the median particle size D50 of 0.5 mu m in NMP (N-methyl pyrrolidone), wherein the content of the PVDF is 2wt%, so as to obtain uniform first slurry; stirring and dispersing carbon black, PVDF and lithium iron phosphate with the median particle size D50 of 1.2 mu m in NMP, wherein the content of the PVDF is 3wt%, so as to obtain uniform second slurry;

(2) Coating the first slurry obtained in the step (1) on an aluminum current collector to form an array formed by first slurry stripes with the gaps of 2mm and the widths of 20mm, wherein the thickness of the first slurry stripes is 300 micrometers;

(4) Sequentially baking and rolling to enable the first slurry stripes to form first active stripes and enable the second slurry stripes to form second active stripes; the thickness of the first active stripes is equal to that of the second active stripes, the first active stripes and the second active stripes are 200 micrometers, and the first active stripes and the second active stripes are sequentially and alternately arranged to form active layers, so that the lithium iron phosphate thick electrode is obtained.

The structural schematic diagram of the lithium iron phosphate thick electrode in this embodiment is shown in fig. 1 and fig. 2, and the lithium iron phosphate thick electrode includes a current collector 3 formed of an aluminum foil, and an active layer formed by sequentially horizontally and alternately arranging first active stripes 1 and second active stripes 2 on the current collector 3; the width of the first active stripe 1 is 20mm, the width of the second active stripe 2 is 2mm, and the thickness of the first active stripe 1 and the second active stripe 2 are both 200 μm.

Example 2

(1) Stirring and dispersing carbon black, PVDF and lithium iron phosphate with the median particle size D50 of 0.8 mu m in NMP, wherein the content of the PVDF is 2wt%, so as to obtain uniform first slurry; stirring and dispersing carbon black, PVDF and lithium iron phosphate with the median particle size D50 of 1.5 mu m in NMP, wherein the content of the PVDF is 3wt%, so as to obtain uniform second slurry;

(2) Coating the first slurry obtained in the step (1) on an aluminum current collector to form an array formed by first slurry stripes with gaps of 4mm and widths of 25mm, wherein the thickness of the first slurry stripes is 300 micrometers;

(3) Coating the second slurry obtained in the step (1) in the gap obtained in the step (2) to form a second slurry stripe with the same thickness as the first slurry stripe;

(4) Sequentially baking and rolling to enable the first slurry stripes to form first active stripes and enable the second slurry stripes to form second active stripes; the thickness of the first active stripes is equal to that of the second active stripes, the first active stripes and the second active stripes are 200 mu m, and the first active stripes and the second active stripes are sequentially and alternately arranged to form active layers, so that the lithium iron phosphate thick electrode is obtained.

Example 3

(2) Coating the first slurry obtained in the step (1) on an aluminum current collector to form an array formed by first slurry stripes with gaps of 5mm and widths of 50mm, wherein the thickness of the first slurry stripes is 400 microns;

(4) Sequentially baking and rolling to enable the first slurry stripes to form first active stripes and enable the second slurry stripes to form second active stripes; the thickness of the first active stripes is equal to that of the second active stripes, the first active stripes and the second active stripes are 300 mu m, and the first active stripes and the second active stripes are sequentially and alternately arranged to form active layers, so that the lithium iron phosphate thick electrode is obtained.

Example 4

The embodiment provides a thick graphite electrode, and a manufacturing method of the thick graphite electrode comprises the following steps:

(1) Taking carbon black as a conductive agent, taking CMC (sodium carboxymethylcellulose) and SBR (styrene butadiene rubber) as a binder and graphite with a median particle size D50 of 6 mu m, and stirring and dispersing the carbon black and the graphite in NMP, wherein the content of the CMC and the SBR is 2.5wt%, so as to obtain uniform first slurry; taking carbon black as a conductive agent, taking CMC and SBR as a binder and graphite with a median particle size D50 of 15 mu m, and stirring and dispersing the carbon black and the graphite in NMP, wherein the content of the CMC and the SBR is 3.2wt%, so as to obtain uniform second slurry;

(2) Coating the first slurry obtained in the step (1) on an aluminum current collector to form an array formed by first slurry stripes with gaps of 2.5mm and widths of 20mm, wherein the thickness of the first slurry stripes is 200 microns;

(4) Sequentially baking and rolling to enable the first slurry stripes to form first active stripes and enable the second slurry stripes to form second active stripes; the thickness of the first active stripes is equal to that of the second active stripes, the first active stripes and the second active stripes are 150 micrometers, and the first active stripes and the second active stripes are sequentially and alternately arranged to form active layers, so that the thick graphite electrode is obtained.

Example 5

(1) Taking carbon black as a conductive agent, taking CMC and SBR as a binder and graphite with the median particle size D50 of 2.4 mu m, and stirring and dispersing the carbon black and the graphite in NMP, wherein the content of the CMC and the SBR is 1wt%, so as to obtain uniform first slurry; taking carbon black as a conductive agent, taking CMC and SBR as a binder and graphite with the median particle size D50 of 12 mu m, and stirring and dispersing the carbon black and the graphite in NMP, wherein the content of the CMC and the SBR is 3.33wt%, so as to obtain uniform second slurry;

(2) Coating the first slurry obtained in the step (1) on an aluminum current collector to form an array formed by first slurry stripes with gaps of 5mm and widths of 40mm, wherein the thickness of the first slurry stripes is 250 micrometers;

(4) Sequentially baking and rolling to form a first active stripe on the first slurry stripe and a second active stripe on the second slurry stripe; the thickness of the first active stripes is equal to that of the second active stripes, the first active stripes and the second active stripes are all 180 micrometers, and the first active stripes and the second active stripes are sequentially and alternately arranged to form active layers, so that the thick graphite electrode is obtained.

Example 6

(1) Taking carbon black as a conductive agent, taking CMC and SBR as a binder and graphite with a median particle size D50 of 4 mu m, and stirring and dispersing the carbon black and the graphite in NMP, wherein the content of the CMC and the SBR is 3wt%, so as to obtain uniform first slurry; taking carbon black as a conductive agent, taking CMC and SBR as binders and graphite with the median particle size D50 of 10 mu m, and stirring and dispersing the carbon black and the graphite in NMP, wherein the content of the CMC and the SBR is 3.33wt%, so as to obtain uniform second slurry;

(2) Coating the first slurry obtained in the step (1) on an aluminum current collector to form an array formed by first slurry stripes with gaps of 6mm and widths of 50mm, wherein the thickness of the first slurry stripes is 450 micrometers;

(4) Sequentially baking and rolling to form a first active stripe on the first slurry stripe and a second active stripe on the second slurry stripe; the thickness of the first active stripes is equal to that of the second active stripes, the first active stripes and the second active stripes are 350 mu m, and the first active stripes and the second active stripes are sequentially and alternately arranged to form active layers, so that the thick graphite electrode is obtained.

Example 7

The embodiment provides a thick lithium iron phosphate electrode, and the manufacturing method of the thick lithium iron phosphate electrode is completely the same as that of the embodiment 1 except that in the step (1), carbon black, PVDF and lithium iron phosphate with a median particle size D50 of 10 μm are stirred and dispersed in NMP, wherein the content of PVDF is 3wt%, and a uniform second slurry is obtained.

Example 8

The embodiment provides a thick lithium iron phosphate electrode, and the manufacturing method of the thick lithium iron phosphate electrode is completely the same as that of the embodiment 1 except that in the step (1), carbon black, PVDF and lithium iron phosphate with a median particle size D50 of 5 μm are stirred and dispersed in NMP, wherein the content of PVDF is 3wt%, and a uniform second slurry is obtained.

Example 9

The embodiment provides a thick lithium iron phosphate electrode, and the manufacturing method of the thick lithium iron phosphate electrode is completely the same as that of the embodiment 1 except that in the step (1), carbon black, PVDF and lithium iron phosphate with a median particle size D50 of 0.625 μm are stirred and dispersed in NMP, wherein the content of PVDF is 3wt%, and a uniform second slurry is obtained.

Example 10

The embodiment provides a thick lithium iron phosphate electrode, and the manufacturing method of the thick lithium iron phosphate electrode is completely the same as that of the embodiment 1 except that carbon black, PVDF and lithium iron phosphate with a median particle size D50 of 0.56 μm are stirred and dispersed in NMP in the step (1), wherein the content of PVDF is 3wt%, so as to obtain a uniform second slurry.

Example 11

The present embodiment provides a thick lithium iron phosphate electrode, and the conditions of the method for manufacturing the thick lithium iron phosphate electrode are completely the same as those in example 1 except that in step (1), carbon black, PVDF, and lithium iron phosphate having a median particle size D50 of 10 μm are stirred and dispersed in NMP, where the content of PVDF is 8wt%, to obtain a uniform second slurry.

Example 12

The embodiment provides a thick lithium iron phosphate electrode, and the manufacturing method of the thick lithium iron phosphate electrode is completely the same as that of the embodiment 1 except that in the step (1), carbon black, PVDF and lithium iron phosphate with a median particle size D50 of 10 μm are stirred and dispersed in NMP, wherein the content of PVDF is 6.6wt%, and a uniform second slurry is obtained.

Example 13

The embodiment provides a thick lithium iron phosphate electrode, and the manufacturing method of the thick lithium iron phosphate electrode is completely the same as that of the embodiment 1 except that in the step (1), carbon black, PVDF and lithium iron phosphate with a median particle size D50 of 10 μm are stirred and dispersed in NMP, wherein the content of PVDF is 2.23wt%, and a uniform second slurry is obtained.

Example 14

The present embodiment provides a thick lithium iron phosphate electrode, and the conditions of the method for manufacturing the thick lithium iron phosphate electrode are completely the same as those in example 1 except that in step (1), carbon black, PVDF, and lithium iron phosphate having a median particle size D50 of 10 μm are stirred and dispersed in NMP, where the content of PVDF is 2wt%, to obtain a uniform second slurry.

Example 15

The present embodiment provides a thick lithium iron phosphate electrode, and the manufacturing method of the thick lithium iron phosphate electrode is completely the same as that in embodiment 1 except that in step (2), the first slurry is coated on an aluminum current collector to form an array formed by first slurry stripes having a gap of 4mm and a width of 20 mm.

Example 16

The present embodiment provides a thick lithium iron phosphate electrode, and the conditions of the manufacturing method of the thick lithium iron phosphate electrode are completely the same as those in embodiment 1 except that in step (2), the first slurry is coated on an aluminum current collector to form an array formed by first slurry stripes with a gap of 1mm and a width of 20 mm.

Comparative example 1

The comparative example provides a lithium iron phosphate thick electrode, and the manufacturing method of the lithium iron phosphate thick electrode comprises the following steps:

stirring and dispersing carbon black, PVDF and lithium iron phosphate with the median particle size D50 of 0.5 mu m in NMP, wherein the content of the PVDF is 2wt%, so as to obtain uniform slurry; coating the slurry on an aluminum current collector to form a slurry layer with the thickness of 300 mu m; and sequentially baking and rolling to form an active layer with the thickness of 200 mu m, thereby obtaining the lithium iron phosphate thick electrode.

Comparative example 2

stirring and dispersing carbon black, PVDF and lithium iron phosphate with the median particle size D50 of 0.8 mu m in NMP, wherein the content of PVDF is 2wt%, so as to obtain uniform slurry; coating the slurry on an aluminum current collector to form a slurry layer with the thickness of 300 mu m; and sequentially baking and rolling to form an active layer with the thickness of 200 mu m, thereby obtaining the lithium iron phosphate thick electrode.

Comparative example 3

stirring and dispersing carbon black, PVDF and lithium iron phosphate with the median particle size D50 of 0.8 mu m in NMP, wherein the content of the PVDF is 2wt%, so as to obtain uniform slurry; coating the slurry on an aluminum current collector to form a slurry layer with the thickness of 400 mu m; and sequentially baking and rolling to form an active layer with the thickness of 300 mu m, thereby obtaining the lithium iron phosphate thick electrode.

Comparative example 4

The comparative example provides a thick graphite electrode, and the manufacturing method of the thick graphite electrode comprises the following steps:

taking carbon black as a conductive agent, taking CMC and SBR as a binder and graphite with a median particle size D50 of 6 mu m, and stirring and dispersing the carbon black and the graphite in NMP, wherein the content of the CMC and the SBR is 2.5wt%, so as to obtain uniform slurry; coating the slurry on an aluminum current collector to form a slurry layer with the thickness of 200 mu m; and sequentially baking and rolling to form an active layer with the thickness of 150 mu m, thereby obtaining the graphite thick electrode.

Comparative example 5

The method for manufacturing the lithium iron phosphate thick electrode is completely the same as the method in the embodiment 1 except that in the step (1), carbon black, PVDF and lithium iron phosphate with the median particle size D50 of 0.5 mu m are stirred and dispersed in NMP, wherein the content of PVDF is 3wt%, and a uniform second slurry is obtained.

Comparative example 6

The manufacturing method of the lithium iron phosphate thick electrode is completely the same as that of the embodiment 1 except that the first slurry is coated on the aluminum current collector in the step (2) to form an array formed by first slurry stripes with the gaps of 10mm and the widths of 20 mm.

Comparative example 7

The manufacturing method of the lithium iron phosphate thick electrode is completely the same as that of the embodiment 1 except that the first slurry is coated on the aluminum current collector in the step (2) to form an array formed by first slurry stripes with the gaps of 0.5mm and the widths of 20 mm.

Comparative example 8

The manufacturing method of the lithium iron phosphate thick electrode is completely the same as that of the embodiment 1 except that the first slurry is coated on the aluminum current collector in the step (2) to form an array formed by first slurry stripes with the gaps of 0.2mm and the widths of 20 mm.

The capacity retention ratios of the batteries prepared in the test example and the comparative example at different multiplying factors are tested at 25 ℃, the voltage interval of the battery with the electrode active material being lithium iron phosphate is 2.5-3.65V, the voltage interval of lithium cobaltate and lithium nickel cobalt manganese oxide is 2.5-4.2V, the voltage interval of graphite is 2.5-3.65V, the multiplying factors are 0.5C, 1C, 2C and 3C respectively, the capacity retention ratio is calculated by dividing the capacity of XC by the capacity of 0.33C (X is 0.5, 1, 2 or 3), so as to obtain the capacity retention ratios at the corresponding multiplying factors, and the obtained results are shown in Table 1.

TABLE 1

As can be seen from table 1:

(1) Comparing example 1 with comparative example 1, it was found that: compared with the conventional thick electrode preparation method, the thick electrode preparation method provided by the invention can obviously improve the rate capability of the thick electrode; the second active stripes and the first active stripes which are formed by large particles distributed in an array can obviously reduce the internal resistance of a thick electrode, so that the multiplying power performance of the battery is improved;

(2) Comparing example 1 with examples 7-10 and comparative example 5, it was found that: the active material median diameter size in the second active stripe has a significant influence on the rate capability of the thick electrode, the second active coating median diameter is too large, the lithium ion solid phase diffusion path is significantly increased, the concentration polarization is aggravated, in addition, the second active particle median diameter is too large, the surface binder content is increased, the electrode resistance is increased, and therefore the second active particle which is too large is not beneficial to the improvement of the rate capability of the thick electrode. On the contrary, if the median particle size of the second active particles is too small, the pores of the corresponding second active stripes are small, and the infiltration of the electrolyte in the thick electrode cannot be effectively improved, so that the thick electrode has high internal resistance and poor rate capability. The particle size of the active main material in the optimized first slurry is 20-80% of the particle size of the active main material in the second slurry.

(3) Comparing example 1 with examples 11-14, it was found that: the content of the binder of the second active stripes is higher than that of the binder of the first active stripes, so that the rate capability of the thick electrode can be effectively improved. When the second active stripe binder is low, the binder migrates to the surface of the electrode when the thick electrode is coated and baked, the distribution is uneven, meanwhile, the content of the binder at the interface of the active coating and the current collector is low, so that the stripping force is obviously reduced, the interface resistance is obviously increased, the internal resistance of the thick electrode is increased, and the rate performance is obviously attenuated. When the second active stripe adhesive is too high, on one hand, the high adhesive blocks the pores of the electrode and cannot realize the rapid absorption and infiltration of the electrolyte in the second active stripe, and on the other hand, the high adhesive content causes the resistivity of the second active stripe to be obviously increased and the internal resistance of the thick electrode to be also obviously increased, so that the rate capability of the battery is obviously attenuated. Therefore, the content of the binder in the first slurry optimally proposed by the invention is 30-90% of the content of the binder in the second slurry.

(4) Comparing example 1 with examples 15-16 and comparative examples 6-8, it was found that: too large or too small a ratio of the first active stripe width to the second active stripe width will result in a degradation of the rate capability of the thick electrode. When the second active stripe is too small, the absorption rate of the electrolyte is low, and meanwhile, the quantity of the second active stripe binder is small, so that the problems of reduction of the stripping force and increase of the internal resistance caused by migration of the first active stripe binder are difficult to effectively relieve. Similarly, too high a width of the second active stripe results in a significant decrease in the effective compacted density of the thick electrode, while too much binder in the second active stripe will also significantly increase the resistivity of the thick electrode, resulting in an increase in the internal resistance of the thick electrode and a significant deterioration in rate performance. Based on experimental results, the width of the first active stripes is preferably 5 to 20 times of the width of the second active stripes.

The present invention is described in detail with reference to the above embodiments, but the present invention is not limited to the above detailed structural features, that is, the present invention is not meant to be implemented only by relying on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. The thick electrode is characterized by comprising a current collector and an active layer positioned on the current collector, wherein the active layer comprises a first active stripe and a second active stripe which are sequentially and horizontally arranged in an alternating manner; the first active stripes comprise active main materials, conductive agents and binders, and the component materials of the second active stripes are the same as those of the first active stripes; the particle size of the active main material in the first active stripe is smaller than that of the active main material in the second active stripe; the thickness of the first active stripes is the same as that of the second active stripes; the width of the first active stripe is 5 to 20 times of the width of the second active stripe.

2. The thick electrode of claim 1, wherein the width of the first active stripes is 0.5-50 mm;

preferably, the porosity of the first active stripes is 20-50%;

3. The thick electrode of claim 1 or 2, wherein the thickness of each of the first active stripes and the second active stripes is 150-350 μm.

4. The thick electrode according to any one of claims 1 to 3, wherein the particle size of the active host material in the first active stripe is 20 to 80% of the particle size of the active host material in the second active stripe;

preferably, the active main material includes a positive electrode main material or a negative electrode main material;

preferably, the positive electrode main material comprises any one of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate or lithium nickel cobalt aluminate or a combination of at least two of the above materials;

preferably, the negative electrode main material comprises any one of graphite, hard carbon, soft carbon, silicon carbon or tin or a combination of at least two of the graphite, the hard carbon, the soft carbon, the silicon carbon and the tin.

5. The thick electrode of any one of claims 1-4, wherein the conductive agent comprises any one of carbon black, carbon fibers, carbon nanotubes, or graphene, or a combination of at least two thereof.

6. The thick electrode of any one of claims 1-5, wherein the binder content in the first active stripes is lower than the binder content in the second active stripes;

preferably, the binder comprises any one of or a combination of at least two of sodium carboxymethylcellulose, styrene butadiene rubber, polyvinylidene fluoride or polyacrylic acid.

7. A method for fabricating a thick electrode according to any one of claims 1 to 6, wherein the method comprises the steps of:

8. The method for manufacturing a thick electrode according to claim 7, wherein the content of the binder in the first paste is 30 to 90% of the content of the binder in the second paste;

preferably, the content of the binder is 1 to 3wt% based on 100wt% of the total mass of the active main material, the conductive agent and the binder in the first slurry;

preferably, the thickness of the first slurry stripe and the second slurry stripe is 200-450 μm.

9. The method for fabricating a thick electrode according to claim 7 or 8, wherein the method comprises the steps of:

(1) Respectively selecting an active main material, a conductive agent, a binder and a solvent which are the same in material quality, stirring and dispersing to respectively prepare a first slurry and a second slurry; controlling the particle size of the active main material in the first slurry to be 20-80% of the particle size of the active main material in the second slurry; the active main material comprises a positive electrode main material or a negative electrode main material; the positive electrode main material comprises any one or the combination of at least two of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate or lithium nickel cobalt aluminate; the main material of the negative electrode comprises any one or the combination of at least two of graphite, hard carbon, soft carbon, silicon carbon or tin;

the content of the binder is 1-3 wt% based on 100wt% of the total mass of the active main material, the conductive agent and the binder in the first slurry; controlling the content of the binder in the first slurry to be 30-90% of the content of the binder in the second slurry; the binder comprises any one or the combination of at least two of sodium carboxymethylcellulose, styrene butadiene rubber, polyvinylidene fluoride or polyacrylic acid; the conductive agent comprises any one or a combination of at least two of carbon black, carbon fiber, carbon nanotube or graphene;

10. Use of a thick electrode according to any one of claims 1 to 6 or obtained by the method of manufacture according to any one of claims 7 to 9, in a lithium ion battery.