阅读说明：本技术 一种极片及锂电池 (Pole piece and lithium battery ) 是由 田奎 邹浒 何志佳 王清辉 朱威 肖良 曹昊楠 于 2021-08-17 设计创作，主要内容包括：一种极片及锂电池,所述极片包括：极片集流体以及设置于所述极片集流体表面的活性物质；所述极片集流体上设置有至少一个存储孔,所述存储孔内填充有可导电多孔物质,所述可导电多孔物质存储有电解液。本发明极片集流体上设置任意形状的孔洞,并在孔洞里填充可导电多孔物质,将所填充的可导电多孔物质作为电解液的储存仓,电池注液后,可导电多孔物质可以吸收并存储部分电解液,提高了电池的保液量,被可导电多孔物质存储的电解液在电池使用循环过程中逐渐析出,为电池补充循环过程中的电解液消耗,从而提升电池的循环寿命。(A pole piece and a lithium battery, the pole piece comprising: the electrode plate current collector comprises an electrode plate current collector and an active substance arranged on the surface of the electrode plate current collector; the pole piece current collector is provided with at least one storage hole, the storage hole is filled with a conductive porous substance, and the conductive porous substance stores electrolyte. The pole piece current collector is provided with the holes in any shape, the holes are filled with the conductive porous substance, the filled conductive porous substance is used as a storage bin of the electrolyte, after the battery is injected with the electrolyte, the conductive porous substance can absorb and store part of the electrolyte, the liquid retention amount of the battery is improved, the electrolyte stored by the conductive porous substance is gradually separated out in the use cycle process of the battery, the electrolyte consumption in the supplement cycle process of the battery is realized, and the cycle life of the battery is prolonged.)

1. A pole piece, comprising: the electrode plate current collector comprises an electrode plate current collector and an active substance arranged on the surface of the electrode plate current collector; the method is characterized in that:

the pole piece current collector is provided with at least one storage hole, the storage hole is filled with a conductive porous substance, and the conductive porous substance stores electrolyte.

2. The pole piece of claim 1, wherein: the total area of the storage holes is 5-60% of the area of the pole piece current collector.

3. The pole piece of claim 1, wherein: the total area of the storage holes is 20-35% of the area of the pole piece current collector.

4. The pole piece of claim 1, wherein: and a plurality of storage holes which are uniformly distributed are formed in the pole piece current collector.

5. The pole piece of claim 1, wherein: the conductive porous substance is a metal or a non-metal.

6. The pole piece of claim 5, wherein: the conductive porous substance is one or more of carbon nano-tubes, graphene, conductive fiber fabric, conductive rubber fibers and conductive plastic fibers.

7. The pole piece of claim 5, wherein: the conductive porous substance is copper or aluminum or silver or an alloy thereof.

8. The pole piece of claim 1, wherein: the conductive porous material contains lithium powder.

9. The pole piece of claim 8, wherein: the addition amount of the lithium powder is 5-30% of the mass of the conductive porous substance.

10. Lithium cell, including positive plate, negative pole piece and set up in diaphragm between positive plate and the negative pole piece, its characterized in that: the positive and/or negative electrode tab is as claimed in any one of claims 1 to 9.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium battery with a long cycle life and a pole piece used by the lithium battery.

Background

In recent years, with the application and development of the device industry such as consumer electronics, electric vehicles, aerospace, and the like, a higher demand has been made for long cycle performance of batteries used therein. The service life of the battery is prolonged, and the replacement frequency of the battery is reduced, so that the use cost of the battery is inevitably reduced. Colleges and universities, scientific research institutions and lithium battery manufacturers invest a large amount of manpower and material resources, and the long-cycle long-life battery is one of the most popular research directions in the field of lithium batteries at present.

The long-cycle battery is mainly characterized in that the long-cycle performance of the battery is improved by developing a novel material system and a novel structure so as to meet the requirements of customers on the electrical performance and the safety performance of the battery. The thick electrode of the battery comprises a current collector and an electrode diaphragm which is distributed on the current collector and contains active substances and conductive substances, wherein the electrode diaphragm contains electrolyte conductive substances used for transmitting or storing electrolyte, and the electrolyte conductive substances are added into the electrode diaphragm so as to effectively transmit the electrolyte, so that the problem that the wettability of the local electrolyte is poor due to the increase of the thickness of the electrode diaphragm is avoided. However, in the battery having such a structure, since the electrolyte conductive material is added to the electrode membrane, the amount of the active material in the electrode membrane is inevitably reduced, and the energy density performance and the long cycle performance of the battery cannot be simultaneously achieved.

Disclosure of Invention

The invention aims to provide a pole piece capable of improving the long cycle performance of a battery and a lithium battery using the pole piece.

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

a pole piece, comprising: the electrode plate current collector comprises an electrode plate current collector and an active substance arranged on the surface of the electrode plate current collector; the pole piece current collector is provided with at least one storage hole, the storage hole is filled with a conductive porous substance, and the conductive porous substance stores electrolyte.

Further, the total area of the storage holes is 5-60% of the area of the pole piece current collector.

Furthermore, the total area of the storage holes is 20-35% of the area of the pole piece current collector.

Furthermore, a plurality of storage holes which are uniformly distributed are formed in the pole piece current collector.

Further, the conductive porous substance is a metal or a non-metal.

Further, the conductive porous substance is one or more of carbon nanotubes, graphene, conductive fiber fabric, conductive rubber fiber, and conductive plastic fiber.

Further, the conductive porous substance is copper or aluminum or silver or an alloy thereof.

Further, the conductive porous material contains lithium powder.

Furthermore, the addition amount of the lithium powder is 5-30% of the mass of the conductive porous substance.

The invention also provides a lithium battery which comprises a positive plate, a negative plate and a diaphragm arranged between the positive plate and the negative plate, wherein the positive plate and/or the negative plate are/is the above-mentioned plates.

According to the technical scheme, the holes in any shape are formed in the pole piece current collector, the conductive porous substance is filled in the holes, the filled conductive porous substance is used as a storage bin of the electrolyte, the conductive porous substance can absorb and store part of the electrolyte after the battery is injected with the electrolyte, the electrolyte stored by the conductive porous substance is gradually separated out in the use cycle process of the battery, the electrolyte consumption in the cycle process of the battery is supplemented, the cycle life of the battery is prolonged, the replacement frequency of the battery is reduced, the use cost of the battery is reduced, and the market competitiveness of a product is improved. In addition, the conductive porous substance of the electrolyte is compositely stored on the pole piece current collector, the load capacity of the active substance of the current collector is not influenced, and the improvement of the long cycle life performance is realized.

Drawings

In order to illustrate the embodiments of the present invention more clearly, the drawings that are needed in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings can be obtained by those skilled in the art without inventive effort.

Fig. 1 is a schematic structural diagram of a pole piece according to an embodiment of the present invention.

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

Detailed Description

The invention will be described in detail below with reference to the accompanying drawings, wherein for the purpose of illustrating embodiments of the invention, the drawings showing the structure of the device are not to scale but are partly enlarged, and the schematic drawings are only examples, and should not be construed as limiting the scope of the invention. It is to be noted, however, that the drawings are designed in a simplified form and are not to scale, but rather are to be construed in an attempt to more clearly and concisely illustrate embodiments of the present invention.

As shown in fig. 1, the pole piece of the present invention includes a pole piece current collector 1, at least one storage hole 1a is formed in the pole piece current collector 1, the storage hole 1a is used for storing a conductive porous substance 2, and the conductive porous substance 2 is used for absorbing and storing an electrolyte. The pole piece current collector 1 is coated with an active material 3. In a specific application, the conductive porous substance 2 may be carbon nanotubes, graphene, conductive fiber fabric, conductive rubber fiber, conductive plastic fiber, copper, aluminum, silver, and other metals, alloys, or non-metal substances. Through compounding the porous material that can lead to on the pole piece mass flow body to the pole piece can absorb and store partial electrolyte in the porous material that can lead to after the battery annotates the liquid, can supply the electrolyte that the battery consumed in the cyclic process to the electrolyte that can lead to storing in the porous material, in order to promote the cyclicity ability of battery. In addition, lithium powder can be added into the conductive porous substance, so that a lithium supplementing function can be provided for the battery. Furthermore, the addition amount of the lithium powder is 5-30% of the mass of the conductive porous substance, and the lithium powder can be specifically prepared according to requirements.

The storage hole 1a may be formed in the pole piece current collector 1 by cutting or punching, and the shape of the storage hole 1a is not limited, and may be circular, rectangular, triangular, polygonal, etc., as long as the function of storing the conductive porous substance 3 is achieved. The number, the area, the distribution mode and the density of the storage holes 1a can be correspondingly set according to production requirements, but in order to ensure that the stress of the pole piece current collector is uniform, the storage holes 1a are preferably uniformly distributed on the pole piece current collector 1. The total area of the storage holes 1a on the pole piece current collector 1 accounts for 5-60% of the area of the pole piece current collector 1. When the area of storage hole 1a is less than 5%, the porous material 3 that can lead to among the pole piece mass flow body 1 is less, the electrolyte that can lead to the absorption of porous material 3 is limited, can't play obvious improvement effect to the cycle performance of battery, when the area of storage hole 1a is greater than 60%, can influence the tensile strength of pole piece mass flow body 1, can lead to the tensile strength of pole piece mass flow body 1 to obviously reduce, the fracture easily takes place under the effect of tensile force at the in-process pole piece mass flow body 1 of coating active material, cause the production difficulty. Preferably, the total area of the storage holes 1a accounts for 20-35% of the area of the pole piece current collector 1.

The positive active material can adopt lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel manganese cobaltate, lithium nickel manganese cobalt aluminate, lithium nickel cobalt aluminate, lithium rich manganese and the like; the negative active material can be lithium titanate, lithium powder, aluminum powder, metal oxide, artificial graphite, natural graphite, silicon alloy, sulfur alloy, silicon carbon and the like. The formula and the preparation process of the anode slurry and the cathode slurry are conventional processes, and the existing formula and preparation process of the anode slurry and the cathode slurry are not required to be improved. The thickness of the pole piece coated with the active substance is 5-600 mu m, and the surface density of the pole piece is 1-300 mg/cm²。

The following is a description of the method of making a lithium battery of the present invention by way of specific examples.

Example 1

Step one, preparing a pole piece current collector; in the embodiment, an aluminum foil and a copper foil are respectively used as a pole piece current collector of a positive plate and a pole piece current collector of a negative plate, and storage holes are respectively prepared on the copper foil and the aluminum foil in a punching mode, wherein the total area of the storage holes is 20% of the area of the pole piece current collector; the storage hole is filled with a conductive porous substance, the conductive porous substance adopted by the embodiment is a carbon nanotube, and the conductive porous substance is used as an electrolyte storage bin;

step two, preparing a positive plate; firstly, preparing positive electrode slurry, namely preparing slurry from 97% of lithium cobaltate (positive electrode active substance), 2% of polyvinylidene fluoride (binder) and 1% of acetylene black (conductive agent), wherein the solid content of the prepared slurry is 75%; coating the positive electrode slurry on the surface of a pole piece current collector of a positive plate, and then drying and rolling the coated pole piece current collector to obtain the positive plate;

preparing a negative plate, namely preparing a negative slurry, preparing a slurry from graphite (a negative active substance), polyvinylidene fluoride (a binder) and acetylene black (a conductive agent) in a ratio of 96% to 2%, wherein the solid content of the prepared slurry is 45%, coating the negative slurry on the surface of a polar current collector of the negative plate, and drying and rolling the coated negative current collector to prepare the negative plate;

welding tabs on the positive plate and the negative plate, stacking the negative plate, the diaphragm and the positive plate in sequence, and packaging the negative plate, the diaphragm and the positive plate into a battery cell by using an aluminum-plastic film; the pole ear can be welded by ultrasonic welding or laser welding,

and step four, putting the battery core into a drying oven for vacuum drying, wherein the temperature of the drying oven is 60-100 ℃, the vacuum drying time is 3-24 hours, and injecting electrolyte after vacuum drying to obtain the lithium battery. The electrolyte can be conventional or functional electrolyte with low temperature, high multiplying power and the like according to the use requirement.

Example 2

This example differs from example 1 in that: the total area of the storage holes on the pole piece current collector of this embodiment is 30% of the area of the pole piece current collector.

Example 3

This example differs from example 1 in that: the total area of the storage holes on the pole piece current collector of this embodiment is 40% of the area of the pole piece current collector.

Example 4

This example differs from example 1 in that: the total area of the storage holes on the pole piece current collector of this embodiment is 50% of the area of the pole piece current collector.

Example 5

This example differs from example 1 in that: the total area of the storage holes on the pole piece current collector of this embodiment is 60% of the area of the pole piece current collector.

Example 6

This example differs from example 1 in that: the total area of the storage holes on the pole piece current collector of this embodiment is 3% of the area of the pole piece current collector.

Example 7

This example differs from example 1 in that: the total area of the storage holes on the pole piece current collector of this embodiment is 65% of the area of the pole piece current collector.

Example 8

This example differs from example 1 in that: the total area of the storage holes on the pole piece current collector of this embodiment is 70% of the area of the pole piece current collector.

Comparative example 1

Comparative example 1 differs from example 1 in that: the pole piece current collector of comparative example 1 was not provided with a storage hole.

Comparative example 2

Comparative example 2 differs from example 1 in that: the electrode sheet current collector of comparative example 2 was a porous current collector, and the porous current collector used in comparative example 2 was a flexible carbon film having pores disclosed in chinese invention patent application No. 2021101688964.

The batteries prepared in examples 1 to 8 and comparative examples 1 and 2 were subjected to cycle performance testing, the batteries were charged and discharged at a current of 1C, the cycle was performed 500 times, the cycle capacity retention rate of the batteries was calculated according to the capacity after 500 cycles of charging and discharging/the capacity at the 1 st cycle of charging and discharging ═ the capacity retention rate, and the tape breakage of the pole piece current collector during the slurry coating process was also counted, and the coating tape breakage rate was ═ the number of pole piece current collectors with tape breakage/the total number of pole piece current collectors in the same specification batch × 100%. The test results are shown in Table 1.

TABLE 1

	Area ratio of storage hole	Cycle of the cycle	Retention rate of circulating capacity	Coating tape breakage rate
					Example 1	20％	500 weeks	84％	1％
Example 2	30％	500 weeks	86％	1.5％
					Example 3	40％	500 weeks	88％	7％
Example 4	50％	500 weeks	90％	10％
					Example 5	60％	500 weeks	93％	15％
Example 6	3％	500 weeks	80％	0.5％
					Example 7	65％	500 weeks	93.5％	30％
Example 8	70％	500 weeks	94％	50％
					Comparative example 1	/	500 weeks	78％	0.01％
Comparative example 2	/	500 weeks	81％	0.05％

From the test results, after the conductive porous substance capable of storing the electrolyte is compounded in the pole piece current collector, the electrolyte stored in the conductive porous substance can supplement the electrolyte consumed in the use process of the battery, so that the cycle capacity retention rate of the battery is obviously improved, and the cycle capacity retention rate is higher along with the improvement of the area ratio of the storage hole. However, after the storage holes are formed in the pole piece current collector, the strength of the pole piece current collector is affected, the larger the area ratio of the storage holes is, the smaller the area of the foil on the pole piece current collector is, and the lower the strength of the pole piece current collector is, so that the coating tape breakage rate is also high along with the increase of the area ratio of the storage holes in the pole piece current collector, especially when the area ratio of the storage holes exceeds 60%, the breakage rate of the pole piece current collector during coating is increased sharply, the number of defective products with tape breakage is increased, difficulty is brought to production and manufacturing, two factors of the coating tape breakage rate and capacity retention rate are combined, the total area of the storage holes is preferably set to be 20-35% of the area of the pole piece current collector, and therefore the purposes of improving the cycle capacity retention rate and not increasing the production and manufacturing difficulty are achieved.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.