CN109904517B

CN109904517B - Lithium ion battery and preparation method thereof

Info

Publication number: CN109904517B
Application number: CN201910167274.2A
Authority: CN
Inventors: 王宏栋
Original assignee: Qinxin Group Tianjin New Energy Technology Research Institute Co ltd
Current assignee: Qinxin Group Tianjin New Energy Technology Research Institute Co ltd
Priority date: 2019-03-06
Filing date: 2019-03-06
Publication date: 2021-06-29
Anticipated expiration: 2039-03-06
Also published as: CN109904517A

Abstract

The lithium ion battery comprises a positive plate, a negative plate, a diaphragm and electrolyte; the positive plate consists of a first positive material layer, a first liquid absorbing layer, a positive current collector, a second liquid absorbing layer and a second positive material layer which are sequentially stacked; the negative plate consists of a first ceramic layer, a first negative material layer, a negative current collector, a second negative material layer and a second ceramic layer which are sequentially stacked; the first liquid absorbing layer and the second liquid absorbing layer comprise a positive electrode active material and a ceramic material in a mass ratio of 100: 1-3; the first ceramic layer and the second ceramic layer comprise a ceramic material. According to the invention, the surface of the positive pole piece is coated with the liquid absorbing layer and the ceramic layer, and the surface of the negative pole piece is coated with the ceramic layer structure, so that after the battery is assembled, the electrolyte is locked in the liquid absorbing layer through the nano silicon dioxide, the electrolyte is prevented from permeating to the outside of the pole piece, the phenomenon of polarization increase of the pole piece due to lack of the electrolyte is prevented, and further the problems of electrolyte decomposition, gas expansion, battery combustion and explosion are solved, thereby improving the safety of the battery.

Description

Lithium ion battery and preparation method thereof

Technical Field

The invention relates to the field of electrochemistry, in particular to a lithium ion battery and a preparation method thereof.

Background

The lithium ion power battery is widely applied to the field of electric vehicles and energy storage batteries due to the advantages of the lithium ion power battery, and the discovery is found in the test use of a lithium ion power single battery that the capacity of the battery is degraded in a cliff mode in the later period along with the cycle use, particularly a large-capacity square battery, and due to the large area and the weak anti-bulging capacity, the battery is damaged due to deformation, safety accidents occur, the service life of the battery is ended in advance, the use requirements cannot be met, and pressure and hidden dangers are brought to the design and the use of a battery pack. Through the analysis of the dissected single battery, the main reasons are: in the use, along with the going on of battery charge-discharge process, the electrolyte of infiltration in the pole piece, along with the going on of charge-discharge process, electrolyte can permeate out from the pole piece, and the gathering is in the battery case bottom, causes some pole pieces to lack the electrolyte, and along with further use, the polarization increase can appear on the pole piece surface of lacking the electrolyte, and electrolyte takes place to decompose, produces gas, arouses the bulging of casing, and the decay of battery capacity accelerates, arouses the burning and the explosion of battery even.

Disclosure of Invention

In order to overcome the defects, the invention provides a lithium ion battery and a preparation method thereof.

The invention provides a lithium ion battery, which comprises a positive plate, a negative plate, a diaphragm and electrolyte; the positive plate consists of a first positive material layer, a first liquid absorbing layer, a positive current collector, a second liquid absorbing layer and a second positive material layer which are sequentially stacked; the negative plate consists of a first ceramic layer, a first negative material layer, a negative current collector, a second negative material layer and a second ceramic layer which are sequentially stacked; the first liquid absorbing layer and the second liquid absorbing layer comprise a positive electrode active material and a ceramic material in a mass ratio of 100: 1-3; the first ceramic layer and the second ceramic layer comprise a ceramic material.

According to an embodiment of the present invention, the ceramic material is nano-silica, Al₂O₃And ZrO₂One or more of (a).

According to another embodiment of the present invention, the first ceramic layer and the second ceramic layer have a thickness of 2 to 5 μm.

According to another embodiment of the present invention, the separator is formed of ceramic particles having a thickness of 0.5 to 20 μm, which are single-coated or double-coated on a polyolefin porous polymer film or a non-woven fabric.

According to another embodiment of the present invention, the polyolefin porous polymer film is a single-layer or multi-layer composite film of polyethylene or polypropylene.

According to another aspect of the present invention, there is provided a method for manufacturing the above lithium ion battery, wherein the first cathode material layer is formed simultaneously with the first liquid absorbent layer, and/or the second cathode material layer is formed simultaneously with the second liquid absorbent layer; and/or the first ceramic layer and the first anode material layer are formed simultaneously, and/or the second ceramic layer and the second anode material layer are formed simultaneously.

According to an embodiment of the present invention, the first positive electrode material layer and the first liquid absorbent layer, and/or the second positive electrode material layer and the second liquid absorbent layer are formed using the same solvent; and/or

The first ceramic layer and the first anode material layer, and/or the second ceramic layer and the second anode material layer are formed using the same solvent.

According to the invention, the surface of the positive pole piece is coated with the liquid absorbing layer, the surface of the negative pole piece is coated with the ceramic layer structure, after the battery is assembled, the electrolyte is locked inside the liquid absorbing layer through one or more of nano silicon dioxide, nano aluminum oxide or zirconium oxide, so that the electrolyte is prevented from permeating to the outside of the pole piece, the phenomenon of polarization increase of the pole piece due to lack of the electrolyte is prevented, and further the problems of electrolyte decomposition, gas expansion, battery combustion and explosion are solved, thereby improving the safety of the battery.

Drawings

The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.

Fig. 1 is a schematic cross-sectional view of a lithium ion battery of the present invention.

Fig. 2A is a schematic cross-sectional view of a negative electrode sheet of a lithium ion battery of the present invention.

Fig. 2B is a schematic cross-sectional view of the positive electrode sheet of the lithium ion battery of the present invention.

Fig. 3 is a schematic view of a process of forming a negative electrode sheet according to the present invention.

Wherein the reference numerals are as follows:

100: lithium ion battery

101: negative plate

102: positive plate

1: negative current collector

21: a first negative electrode material layer

22: second anode material layer

31: first ceramic layer

32: second ceramic layer

4: positive current collector

51: a first positive electrode material layer

52: second positive electrode material layer

61: first liquid absorbing layer

62: second liquid absorption layer

7: diaphragm

Detailed Description

The present invention will be described in detail with reference to the following embodiments.

As shown in fig. 1, 2A and 2B, the lithium ion battery 100 of the present invention includes a positive electrode tab 102, a negative electrode tab 101, a separator 7, and an electrolyte.

As shown in fig. 2A, the negative electrode sheet 101 is composed of a first ceramic layer 31, a first negative electrode material layer 21, a negative electrode collector 1, a second negative electrode material layer 22, and a second ceramic layer 31, which are sequentially stacked.

The first and second

anode material layers

21 and 22 may employ copper foils as the anode current collector 1. The first anode material layer 21 and the second anode material layer 22 include an anode active material, a binder, a thickener, a conductive agent, and/or the like. The weight ratio of the negative electrode active material, the binder, and/or the conductive agent may be any suitable ratio. The negative active substance can be one or more of artificial graphite, natural graphite, silicon carbon material and lithium titanate. The binder may be Styrene Butadiene Rubber (SBR), vinylidene fluoride (PVDF), or the like. The thickener may be sodium carboxymethylcellulose (CMC) or the like. The conductive agent may be ketjen black, acetylene black, Super-P, Carbon Nanotube (CNT), or the like. An appropriate negative electrode active material, a conductive agent, a binder and/or a thickener are selected and mixed with a solvent to form a slurry, and then a first negative electrode material layer 21 and a second negative electrode material layer 22 are formed on both sides of a copper foil as a negative electrode current collector 1 by coating, such as spraying, blade coating, etc. The solvent may be one or more of water, ethanol, acetone and N-methylpyrrolidone.

The first ceramic layer 31 and the second ceramic layer 32 include a ceramic material, a binder, a thickener, and/or the like. The ceramic material can be nano silicon dioxide and Al₂O₃And ZrO₂And the like. The binder may be SBR, PVDF, etc. The thickener may be CMC or the like. Selecting proper ceramic material, adhesive, thickener, etc. and mixing with solvent to form slurry, and separating the slurryThe first ceramic layer 31 and the second ceramic layer 32 are formed on the first anode material layer 21 and the second anode material layer 22, respectively. The thickness of the first ceramic layer 31 and the second ceramic layer 32 is preferably 2 to 5 μm. The thickness is less than 2 μm, and the liquid absorption effect of the ceramic layer is not good; a thickness greater than 5 μm may result in an excessively thick battery, reducing the energy density of the battery.

Preferably, as shown in fig. 3, the first anode material layer 21 and the first ceramic layer 31 are simultaneously formed, and/or the second anode material layer 22 and the second ceramic layer 32 are simultaneously formed. Wherein "simultaneously formed" means that a preceding coating layer (i.e., an inner layer) is applied to a succeeding coating layer (i.e., an outer layer) without being formed, and the preceding coating layer is exposed to air for a period of time not more than 0.1S. Hereinafter, the "simultaneous formation" is also the same meaning and will not be repeated. The two layers are formed simultaneously, so that the structure of the inner layer (namely the prior coating layer) is not damaged, and the uniformity of the surface of the battery pole piece is good; and the liquid phase interface of the inner layer and the outer layer is fused to a certain extent, so that the internal resistance of the electrode is reduced, and the service life of the battery is prolonged.

Preferably, the solvent for forming the first anode material layer 21 and the first ceramic layer 31 slurry is the same solvent. Since the same solvent is used, the anode material layer 21 and the ceramic layer 31 are more easily diffused into each other at the interface during formation, so that the adhesion between the two layers can be increased. For the same reason, the same solvent may be used for the slurry for forming second anode material layer 22 and second ceramic layer 32.

As shown in fig. 2B, the positive electrode sheet 102 is composed of a first positive electrode material layer 51, a first liquid absorbent layer 61, a positive electrode collector 7, a second liquid absorbent layer 62, and a second positive electrode material layer 52, which are stacked in this order.

The first liquid absorbent layer 61 and the second liquid absorbent layer 62 include a positive electrode active material and a ceramic material in a mass ratio of 100: 1-3. The ceramic material in the

liquid absorbing layers

61,62 functions to hold the electrolyte in the positive electrode sheet 102 and prevent the electrolyte from being lost during charge and discharge. Therefore, if the content of the ceramic material in the liquid-

absorbent layers

61 and 62 is too small, a good liquid-absorbing effect cannot be achieved; if the content of the ceramic material is too large, the energy density of the battery may be reduced. The positive electrode active material in the liquid

absorbent layers

61,62 may be lithium cobaltate, lithium nickel cobalt manganese oxideOne or more of lithium aluminate, lithium manganate, lithium iron phosphate and lithium vanadium phosphate. The ceramic material can be nano silicon dioxide and Al₂O₃And ZrO₂And the like. The first and second liquid

absorbent layers

61 and 62 may further include a binder, a thickener, a conductive agent, and the like. The binder may be SBR, PVDF, etc. The thickener may be CMC or the like. The conductive agent may be ketjen black, acetylene black, Super-P, carbon nanotube CNT, or the like. The slurry is formed by mixing a proper positive electrode active material, a ceramic material, a binder, a thickener, a conductive agent and the like with a solvent. The solvent may be one or more of water, ethanol, acetone, and N-methylpyrrolidone. An aluminum foil was selected as the positive electrode current collector 1. The formation slurry is applied to both sides of the aluminum foil to form the first bank 61 and the second liquid absorbent layer 62, respectively.

The first and second cathode material layers 51 and 52 may be formed by applying a suitable cathode active material, binder, thickener, conductive agent, and the like to the surfaces of the first and second liquid

absorbent layers

61 and 62 in accordance with the solvent-forming slurry.

For the same reason as in the formation of the negative electrode sheet 101, it is preferable to form the first liquid absorbent layer 61 and the first positive electrode material layer 51 at the same time. The second liquid absorbent layer 62 and the second cathode material layer 52 are simultaneously formed. Preferably, the same solvent is used for the slurry forming the first liquid absorbent layer 61 and the first cathode material layer 51. The same solvent is also used for the slurry forming the second liquid absorbent layer 62 and the second cathode material layer 52.

The diaphragm of the lithium ion battery can be a common polyolefin porous polymer film or a non-woven fabric diaphragm, preferably the polyolefin porous polymer film, and can be a single-layer film or a multi-layer composite film formed by polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, polyvinyl alcohol, polyvinylidene fluoride-hexafluoropropylene copolymer or acrylonitrile-methyl methacrylate copolymer. The ceramic membrane, namely the polyolefin porous polymer membrane or the non-woven fabric membrane, can also be formed by single-side coating or double-side coating of ceramic particles with the thickness of 0.5-20 microns. The ceramic particles may be one or more of nano silica, Al2O3, ZrO2, and the like. The ceramic separator may also hold the electrolyte in the cell in the pole piece.

The electrolyte comprises a solution of lithium salt and a solvent, wherein the lithium salt is one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate and lithium bis (oxalate) borate, and the solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

The lithium ion battery of the present invention may also include any other suitable elements, such as a battery case, a safety valve, and the like.

The invention will be further illustrated by the following examples, but is not to be construed as being limited thereto. Unless otherwise specified, all reagents used in the invention are industrially pure.

Example 1

The negative electrode sheet 101 has a multi-layer double-sided structure, as shown in fig. 2A, the negative electrode material layers 21 and 22 are coated on both sides of the copper foil (8 μm), the

ceramic layers

31 and 32 are coated on the outside of the negative electrode material layers, and the ceramic layers 31 and 32(2-3 μm) are composed of 90% (weight ratio) of nano-silica, 3.5% (weight ratio) of CMC, and 6.5% (weight ratio) of SBR. The negative electrode material layers 21,22 were composed of 96% (by weight) of graphite negative electrode material, 1.5% (by weight) of CMC, and 2.5% (by weight) of SBR. The anode material layers 21,22 and the

ceramic layers

31,32 are formed simultaneously. The solvent forming the anode material layer and the ceramic layer slurry is water.

The positive electrode sheet 102 has a multi-layer, double-sided structure, and as shown in fig. 2B, the liquid

absorbent layers

61,62 are coated on both sides of the aluminum foil, and the positive electrode material layers 51,52 are coated on the outer sides of the liquid

absorbent layers

61, 62. The aluminum foil has a thickness of 16 μm, and the positive electrode material layers 51 and 52 contain 96 wt% of the positive electrode material, 1.5 wt% of the conductive agent CNT, and 2.5 wt% of the binder PVDF. The liquid

absorbent layers

61 and 62 include 92 wt% of a positive electrode material, 2.5 wt% of a conductive agent CNT, 4 wt% of a binder PVDF, and 1.5 wt% of nano silica. The positive electrode material layers 51,52 and the liquid

absorbent layers

61,62 are formed simultaneously. The solvent forming the positive electrode material layer and the liquid absorbent layer slurry was NMP.

The diaphragm 7 is a ceramic diaphragm.

The negative electrode sheet 101, the separator 7 and the positive electrode sheet 102 are stacked and wound, and then are placed in a battery case, and then an electrolyte is injected to seal the battery case for standby.

Comparative example 1

The components and the packaging mode except for the positive plate are the same as those in example 1.

The positive plate is of a double-sided structure, and positive material layers are coated on two sides of the aluminum foil. The aluminum foil was 16 μm thick, and the positive electrode material layer contained 96 wt% of the positive electrode material, 1.5 wt% of the conductive agent CNT, and 2.5 wt% of the binder PVDF.

Comparative example 2

The components and the packaging mode except for the negative plate are the same as those in example 1.

The negative plate is of a double-sided structure, the two sides of the copper foil (8 mu m) are coated with negative material layers, and the negative material layers consist of 96 percent (weight ratio) of graphite negative material, 1.5 percent (weight ratio) of CMC and 2.5 percent (weight ratio) of SBR.

The batteries manufactured in example 1 and comparative examples 1-2 were used.

Test experiments

The following experiment was performed on the fabricated batteries of example 1 and comparative examples 1-2:

1. experiment of normal temperature cycle performance

Under the condition of normal temperature (25 ℃), the lithium ion battery is charged to 4.2V under the constant current and the constant voltage of 1C, and then is discharged to 3.0V under the constant current of 1C. After 1000 cycles of charge and discharge, capacity retention rate after 1000 cycles was calculated:

normal temperature capacity retention rate is 1000 th cycle discharge capacity/1 st cycle discharge capacity 2. high temperature cycle performance experiment.

Under the condition of high temperature (45 ℃), the lithium ion battery is charged to 4.2V under the constant current and the constant voltage of 1C, and then is discharged to 3.0V under the constant current of 1C. After 1000 cycles of charge and discharge, capacity retention rate after 1000 cycles was calculated:

high-temperature capacity retention rate is 1000 th cycle discharge capacity/1 st cycle discharge capacity.

3. Internal resistance test

The initial internal resistance before charge-discharge cycles of the batteries manufactured in example 1 and comparative examples 1-2 was measured using an internal resistance tester (R1), the internal resistance of the above lithium ion batteries was measured again after 1000 cycles of charge-discharge at 1C (R2), and the increase rate of the internal resistance after the 1000 th cycle was calculated:

the internal resistance increase rate is (R2-R1)/R1.

4. Acupuncture experiment

After the battery is fully charged, the battery is completely punctured at the position, close to the center, of the maximum plane of the battery by using a stainless steel needle with the diameter of 3mm, the temperature change of the battery is monitored in the experimental process, and when the temperature of the battery is reduced to be about 10 ℃ lower than the peak value, the experiment is ended.

5. Test of dissection

The batteries of example 1 and comparative examples 1-2 were charged and discharged 1000 times, and then cut to examine the presence of electrolyte at the bottom of the battery case.

The results of the above experiments are shown in table 1.

TABLE 1

The test data prove that the lithium ion battery disclosed by the invention has the advantages that the liquid absorbing layer and the ceramic layer are coated on the surface of the positive pole piece, and the ceramic layer structure is coated on the surface of the negative pole piece, so that after the battery is assembled, the electrolyte is locked inside the liquid absorbing layer through the nano silicon dioxide, the electrolyte is prevented from permeating to the outside of the pole piece, the phenomenon that the polarization of the pole piece is increased due to the lack of the electrolyte is prevented, the problems of electrolyte decomposition, gas expansion, battery combustion and explosion are further solved, and the safety of the battery is improved.

The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A lithium ion battery comprises a positive plate, a negative plate, a diaphragm and electrolyte; the positive plate consists of a first positive material layer, a first liquid absorbing layer, a positive current collector, a second liquid absorbing layer and a second positive material layer which are sequentially stacked; the negative plate consists of a first ceramic layer, a first negative material layer, a negative current collector, a second negative material layer and a second ceramic layer which are sequentially stacked;

the first liquid absorbing layer and the second liquid absorbing layer comprise a positive electrode active material and a ceramic material in a mass ratio of 100: 1-3;

the first ceramic layer and the second ceramic layer comprise a ceramic material.

2. The lithium ion battery of claim 1, wherein the ceramic material is nano silica, Al₂O₃And ZrO₂One or more of (a).

3. The lithium ion battery of claim 1, wherein the first ceramic layer and the second ceramic layer have a thickness of 2-5 μ ι η.

4. The lithium ion battery of claim 1, wherein the separator is formed by single-side coating or double-side coating of polyolefin porous polymer film or non-woven fabric with ceramic particles with a thickness of 0.5 to 20 microns.

5. The lithium ion battery of claim 4, wherein the polyolefin porous polymer film is a single or multilayer composite film of polyethylene or polypropylene.

6. A method for manufacturing a lithium ion battery according to claim 1, wherein the first positive electrode material layer is formed simultaneously with the first liquid absorbent layer, and/or the second positive electrode material layer is formed simultaneously with the second liquid absorbent layer; and/or

The first ceramic layer and the first anode material layer are formed at the same time, and/or the second ceramic layer and the second anode material layer are formed at the same time.

7. The production method according to claim 6, wherein the first positive electrode material layer and the first liquid-absorbent layer, and/or the second positive electrode material layer and the second liquid-absorbent layer are formed using the same solvent; and/or