CN216980649U

CN216980649U - Lithium battery and lithium battery pole piece

Info

Publication number: CN216980649U
Application number: CN202123087575.6U
Authority: CN
Inventors: 杜新雨; 李先锋; 曲超; 刘翠连
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2021-12-09
Filing date: 2021-12-09
Publication date: 2022-07-15
Anticipated expiration: 2031-12-09

Abstract

The utility model discloses a lithium battery and a lithium battery pole piece, wherein the lithium battery pole piece comprises a positive pole piece and a negative pole piece, the periphery of each positive pole piece is provided with two or more tabs, and the periphery of each negative pole piece is provided with two or more tabs. The lugs on each positive pole piece are uniformly distributed or are centrosymmetric on the periphery of the positive pole piece, and the lugs on each negative pole piece are uniformly distributed or are centrosymmetric on the periphery of the negative pole piece. The utility model improves the uniformity of the charging and discharging current distribution of the lithium battery by increasing the number of the lugs of each layer of battery pole piece in the lithium battery. The scheme provided by the utility model can effectively improve the distribution of the charge-discharge current in the pole piece, so that the charge-discharge current is more uniformly distributed, the polarization in the charge-discharge process is reduced, the discharge power performance of the battery can be effectively improved, and the charge time is shortened.

Description

Lithium battery and lithium battery pole piece

Technical Field

The utility model belongs to the field of lithium batteries, and particularly relates to a lithium battery and a lithium battery pole piece.

Background

The most important problems in all application fields are to reduce the weight of the battery, increase the energy density of the battery, and obtain a lithium ion battery with higher energy density and higher volume density in order to reduce the overall weight of the battery, which is usually realized by the following ways: (1) adopting positive and negative electrode materials with higher gram capacity, such as using a high-nickel positive electrode material or a high-voltage positive electrode material as a positive electrode, using a silicon-carbon negative electrode as a negative electrode and the like as the negative electrode; (2) the capacity of the single battery core is increased, namely the proportion of auxiliary materials is reduced, and the proportion of positive and negative active materials is increased, so that the overall energy density of the battery is increased; (3) the surface density of the battery pole piece is improved, the weight proportion of the copper-aluminum foil base material can be reduced, and the energy density of the battery is increased. The third measure also causes the current density distribution of the battery to be uneven by increasing the surface density of the pole piece, and increases the diffusion resistance of the battery and lithium ions, especially under the condition of large current, the current density of the part close to the pole piece is greater than that of the part far away from the pole piece, so that the power performance and the charging rate of the battery are influenced.

In order to solve the problems caused by the above improvement measures, in the industry, more proportion of conductive agents or conductive agents with better conductivity such as carbon nanotube graphene and the like are usually introduced into a positive electrode formula and a negative electrode formula, so that the electronic conductivity of a battery pole piece is increased, the internal resistance of the battery is reduced, the current density distribution of the pole piece in the battery is more uniform, and the polarization problem caused by diffusion is reduced.

SUMMERY OF THE UTILITY MODEL

In order to solve the technical problems, the utility model increases the number of the battery tabs by designing the battery tabs in different directions of the battery pole piece, so that the current enters the battery through multiple directions of the pole piece, the current density distribution of the battery is more uniform in the charging and discharging process, and the polarization in the charging and discharging process of the battery is reduced, thereby using larger charging and discharging current, shortening the charging time and increasing the discharging power and multiplying power.

The technical scheme of the utility model is as follows:

on one hand, the utility model provides a lithium battery and a lithium battery pole piece, and aims to improve the current distribution in the lithium battery.

Based on the above scheme, preferably, the tab is formed by extending the positive electrode plate or the negative electrode plate in a direction away from the electrode plate and parallel to the surface of the electrode plate.

Based on the above scheme, preferably, the tabs on each positive electrode plate are uniformly distributed or centrosymmetrically distributed on the periphery of the positive electrode plate, and the tabs on each negative electrode plate are uniformly distributed or centrosymmetrically distributed on the periphery of the negative electrode plate.

Based on the above scheme, preferably, the number of the tabs on each positive electrode plate or each negative electrode plate is 2-6.

In another aspect, the utility model provides a lithium battery, which includes the positive pole piece and the negative pole piece in the above method.

Based on the scheme, the lithium battery structure preferably comprises a square winding structure battery cell and a lamination structure battery cell, and the method for adding the tab can be realized through process control in a tab forming procedure of electrode preparation.

Based on the above scheme, preferably, when the lithium battery is in a winding structure, the number of winding turns of the battery is N, N is an integer greater than or equal to 1, and each turn includes one positive pole piece and one negative pole piece; the pole lugs are positioned on two sides of each pole piece and are centrosymmetric.

Based on the above scheme, preferably, when the lithium battery is in a laminated structure, the positive electrode of the battery is N layers, N is an integer greater than or equal to 2, the negative electrode of the battery is N +1 layers, and each layer comprises one positive electrode piece and one negative electrode piece; the pole lugs are positioned on two sides of each pole piece and are centrosymmetric.

Based on the above scheme, preferably, in the lithium battery with the laminated structure or the winding structure, the tab of each pole piece is located in the diagonal direction of the pole piece, and after the battery is assembled, the tab of the negative pole piece is not overlapped with the tab of the positive pole piece.

Based on the scheme, preferably, the tabs are designed on two sides of the battery pole piece of the square winding battery and are centrosymmetric, so that current flows into the battery through the pole piece in two directions. The pole piece of the laminated battery can be divided into two designs, one of the two designs is consistent with a square winding battery, the pole lugs are designed on the two sides of the pole piece and are in central symmetry, the other design of the pole piece of the laminated battery is that the two pole lugs are respectively designed in the length direction and the width direction of the pole piece, the pole lugs in the length direction are in central symmetry, the pole lugs in the width direction are also in central symmetry, the battery flows into the battery from four directions by a method of increasing the pole lugs of the battery in different directions of the pole piece, the problem of uneven current distribution in the battery is reduced, the internal polarization of the battery is reduced, and the integral charging and discharging multiplying power of the battery is increased.

Based on the above scheme, preferably, when the lithium battery structure is a winding structure, the number of winding turns of the battery is N (N is an integer greater than or equal to 1), and the positive electrode and the negative electrode tab in each winding respectively extend out of 2 tabs, the number of the positive electrode and the negative electrode tab in the full battery after winding is 2 × N, the tabs are located at two opposite ends of the battery, and the 2 positive electrode tabs are respectively distributed at corresponding positions in the length or width direction of the full battery to be centrosymmetric, and the same two negative electrode tabs are also respectively distributed at corresponding positions in the length or width direction of the full battery to be centrosymmetric, after the full battery is assembled, that is, after the tabs of each layer of the electrode tab are welded, the number of the positive electrode tabs of the battery is 2, the number of the negative electrode tabs of the negative electrode is 2, that is 4, as shown in fig. 1, the positive electrode tabs are located at

positions

1 and 4, and the negative electrode tabs are located at

positions

2 and 3, the lug is distributed in such a way, so that the charging and discharging current of the battery can flow in or out from two sides of the battery, and the current is more uniformly distributed in the battery.

Based on the above scheme, preferably, when the lithium battery structure is a laminated structure, the positive electrode of the battery is N layers (N is an integer greater than or equal to 2), the negative electrode is N +1 layers, 2 or 4 tabs respectively extend out of the positive electrode and the negative electrode in each layer, the number of the tabs of the positive electrode is 2 × N or 4 × N, the number of the tabs of the negative electrode is 2 × (N +1) or 4 × (N +1), after the full battery is assembled, that is, after the tabs of each layer of electrode are welded, the number of the tabs of the positive electrode is 2 or 4, the number of the tabs of the negative electrode is 2 or 4, and the number of the tabs of the corresponding full battery is 4 or 8; the electrode lug of the positive pole piece or the electrode lug of the negative pole piece are respectively in central symmetry.

When the number of the positive electrode tabs and the negative electrode tabs is 2, the positive electrode tabs are centrosymmetric, the negative electrode tabs are also centrosymmetric, as shown in fig. 2, the tab structure of the full-cell is consistent with the winding structure in the above direction, as shown in fig. 3, the negative electrode tabs are located at the position No. 1 and the position No. 4, and the positive electrode tabs are located at the position No. 2 and the position No. 3 respectively.

When the positive pole piece and the negative pole piece both have 4 tabs, the positive pole piece structure diagram and the negative pole piece structure diagram are shown in fig. 4, the tabs are respectively provided with two tabs in the length direction and the width direction of the pole pieces, the two tabs in the length direction are centrosymmetric, the two tabs in the width direction are also centrosymmetric, the positive pole and the negative pole are assembled into a full battery in a lamination mode, after the tabs are welded, the full battery is provided with 4 positive pole tabs, 4 negative pole tabs and 8 tabs in total, the full battery and the tab structure diagram are shown in fig. 5, the negative pole tabs are positioned at the position No. 1, the position No. 3, the position No. 5 and the position No. 7, the positive pole tabs are respectively positioned at the position No. 2, the position No. 3, the position No. 5 and the position No. 7, the tabs are distributed as shown in fig. 5, so that the charging and discharging current of the battery can flow into or out of the battery from the tab positions in the upper, lower, left and right directions of the battery, and the current can be more uniformly distributed in the battery, the problem of polarization caused by partial nonuniformity of current is reduced.

Advantageous results of the utility model

The utility model can effectively improve the distribution condition of current in the pole piece in the charging and discharging process by increasing the number of the pole lugs of the laminated or wound full battery, so that the charging and discharging current flowing through the battery is distributed more uniformly, the current density of each part of the pole piece in the charging and discharging process tends to be consistent, the reaction polarization caused by nonuniform current part is reduced, the reduction of polarization can effectively improve the discharging power of the battery and can also charge the battery by using larger current, and the charging time of the battery is reduced.

Drawings

Fig. 1 is a schematic diagram of a 4-tab wound battery and the distribution of battery tabs, wherein "1" and "4" represent negative electrode tabs; "2" and "3" represent positive electrode tabs.

Fig. 2 is a schematic view of the tab distribution of the positive electrode tab or the negative electrode tab of the 2-tab.

Fig. 3 is a schematic diagram of a full cell with a 4-tab lamination structure and tab distribution, wherein "1" and "4" represent negative tabs; "2" and "3" represent positive electrode tabs.

Fig. 4 is a schematic view of the tab distribution of the positive electrode tab or the negative electrode tab of the 4-tab.

Fig. 5 is a schematic diagram of a full cell and a tab distribution in an 8-tab lamination structure, wherein "1", "3", "5" and "7" represent negative tabs; "2", "4", "6" and "8" denote positive electrode tabs.

Fig. 6 is a schematic view of a bipolar tab laminated battery structure, wherein "1" represents the positive tab; "2" represents a positive electrode tab.

Detailed Description

The present invention is further illustrated by the following examples. Unless otherwise specified, the raw materials used in the following examples and comparative examples are all commercially available conventional raw materials.

Preparing anode slurry and cathode slurry according to a certain proportion, coating the anode slurry on an aluminum foil, coating the cathode slurry on a copper foil, drying and cold-pressing a pole piece, and then carrying out die cutting, wherein if the designed battery is in a winding structure, tabs are required to be reserved on the upper side and the lower side of the anode pole piece and the cathode pole piece, so that the wound battery has 2 anode tabs and 2 cathode tabs, if the designed battery is a laminated structure battery, the die-cut anode piece has 2 or 4 anode tabs, and the die-cut cathode pole piece has 2 or 4 cathode tabs. And (3) laminating the die-cut pole pieces according to the sequence of the negative pole, the diaphragm and the positive pole, and assembling the full battery, wherein the assembled full battery is provided with 4 lugs or 8 lugs.

Example 1

The positive electrode is made of a lithium cobaltate material, the formula of the positive electrode is 95% of the lithium cobaltate material, 2% of polyvinylidene fluoride and 3% (conductive carbon black) SP, the formula of the negative electrode is graphite, the formula of the negative electrode is 95% of the graphite, 2% of styrene butadiene rubber, 2% of sodium carboxymethylcellulose and 1% (conductive carbon black) SP, the diaphragm is made of a Polyethylene (PE) diaphragm, the electrolyte is lmol/L lithium hexafluorophosphate, EC (ethylene carbonate), DEC (diethyl carbonate) and DMC (dimethyl carbonate) mixed solvent (the volume ratio is 3: 4: 3), the whole assembled battery is tested, the size of the positive electrode plate is 85 mm-106 mm, the size of the negative electrode plate is 86 mm-108 mm, the assembled battery is a lamination process, the battery is divided into an A group and a B group, wherein the A group is a comparison group, the battery structure is a laminated 2-tab battery structure, namely only one positive electrode plate and one negative electrode plate are arranged, the tab sizes are all 13mm × 18mm (length × width), the schematic diagram of the assembled full battery is shown in fig. 6, the group B is a multi-tab battery structure battery (4 tab battery, each positive electrode plate and negative electrode plate is provided with two tabs), the tab sizes are all 13mm × 18mm (length × width), as shown in fig. 3, the capacities of the A, B two groups of batteries are all about 1.2Ah, and the group a battery and the group B battery have completely the same design information except the tab structure.

A, B two groups of batteries are compared and tested, A, B two groups of batteries are respectively tested for multiplying power characteristics under different discharge currents, the discharge multiplying power is selected from 10C, 30C and 50C, after discharge, the capacity retention rate of the battery under the corresponding multiplying power is calculated, and the result is shown in table 1. Wherein, under the discharge rate of 10C, the capacity retention rate of the group B is 3% higher than that of the group A, the capacity retention rate of the group B is 6% higher than that of the group A under the discharge rate of 30C, and the capacity retention rate of the group B is 8% higher than that of the group A under the discharge rate of 50C, and under the same discharge rate, the discharge capacity retention rate of the group B battery (group B) is higher than that of the group A battery (group B) to indicate that the capacity of the internal polarization loss of the group B battery is smaller, mainly because the positive electrode and the negative electrode of the group B battery are respectively provided with two lugs at two ends of the battery, the currents of the positive electrode and the negative electrode can simultaneously diffuse in the battery through the lugs at two sides of the battery, the distribution of the current on the pole piece in the battery is more uniform, the polarization in the battery is reduced, and because the positive electrode and the negative electrode of the group A battery only have one lug respectively, the current is preferentially distributed at one end close to the lug, the current at one end far away from the lug has a hysteresis effect, so that the internal reaction polarization of the battery is increased, and the discharge capacity retention rate of the B group is increased in proportion to the increase of the discharge retention rate of the A group battery along with the increase of the discharge rate, mainly because the discharge current of the battery is gradually increased along with the increase of the discharge rate, the distribution of the current density becomes a main influence factor of the internal reaction of the battery, and because the quantity of the B group battery is one time larger than that of the A group battery and is distributed at two ends of the battery, the current of the B group battery is more uniformly distributed in the battery than that of the A group battery, namely, the polarized B group battery caused by the current is far smaller than the A group battery, the B group battery can release more capacity under high current density.

TABLE 1 comparison of battery characteristics of two tab structures at different discharge rates

Item	10C	30C	50C
				Group A (contrast group)	95％	91％	88％
Group B (Experimental group)	98％	97％	96％

Claims

1. A lithium battery pole piece comprises a positive pole piece and a negative pole piece, and is characterized in that the periphery of each positive pole piece is provided with two or more tabs, and the periphery of each negative pole piece is provided with two or more tabs; the tab on each positive pole piece is symmetrical to the center of the positive pole piece, and the tab on each negative pole piece is symmetrical to the center of the negative pole piece.

2. The pole piece of lithium battery as claimed in claim 1, wherein the tab is formed by extending the positive pole piece or the negative pole piece away from the pole piece and parallel to the surface of the pole piece.

3. The lithium battery pole piece of claim 1, wherein each positive pole piece or negative pole piece has 2-6 tabs.

4. A lithium battery comprising a lithium battery electrode sheet according to any one of claims 1 to 3.

5. The lithium battery of claim 4, wherein the lithium battery is in a winding structure, the number of winding turns of the battery is N, N is an integer greater than or equal to 1, and each turn comprises one positive pole piece and one negative pole piece; the pole lugs are positioned on two sides of each pole piece and are centrosymmetric.

6. The lithium battery of claim 4, wherein the lithium battery is a laminated structure, the positive electrode of the battery is N layers, N is an integer greater than or equal to 2, the negative electrode of the battery is N +1 layers, and each layer comprises one positive pole piece and one negative pole piece; the pole lugs are positioned on two sides of each pole piece and are centrosymmetric.

7. The lithium battery as claimed in claim 5 or 6, wherein the tab of each pole piece is located in a diagonal direction of the pole piece, and the tab of the negative pole piece is not overlapped with the tab of the positive pole piece after the battery is assembled.