CN115810863A - Separator, method for producing same, secondary battery, battery module, battery pack, and electric device - Google Patents
Separator, method for producing same, secondary battery, battery module, battery pack, and electric device Download PDFInfo
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- CN115810863A CN115810863A CN202111395899.8A CN202111395899A CN115810863A CN 115810863 A CN115810863 A CN 115810863A CN 202111395899 A CN202111395899 A CN 202111395899A CN 115810863 A CN115810863 A CN 115810863A
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- China
- Prior art keywords
- lithium
- coating
- battery
- separator
- secondary battery
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Images
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The application provides an isolating membrane and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electric device, wherein the isolating membrane comprises: a release film substrate and a coating on at least one surface of the release film substrate; the coating comprises an iodine-containing species; wherein the coating on the surface of the side of the separator substrate facing the negative electrode comprises an iodate; and/or the coating on the surface of the side of the separator substrate facing the positive electrode comprises iodide. The application provides an isolating membrane can be changed into active lithium ion with the metal lithium that the negative pole was appeared to lithium dendrite that forms when avoiding appearing lithium pierces through the isolating membrane and causes the inside short circuit of battery, reduces the irreversible decay of battery capacity because of active lithium ion loss causes, promotes secondary battery's stability of performance, life and security performance.
Description
Technical Field
The application relates to the technical field of secondary batteries, in particular to an isolating membrane and a preparation method thereof, a secondary battery, a battery module, a battery pack and an electric device.
Background
In recent years, with the wider application range of secondary batteries, secondary batteries are widely used in energy storage power systems such as hydraulic power, thermal power, wind power, and solar power stations, and in various fields such as electric tools, electric bicycles, electric motorcycles, electric automobiles, military equipment, and aerospace. The secondary battery isolating film is an important component of the battery except for a positive electrode material, a negative electrode material and electrolyte, and plays an important role in isolating the positive electrode and the negative electrode and realizing electronic insulation and ion conduction.
However, during the charging process of the secondary battery, lithium precipitation is easy to occur in the negative electrode, and the current isolating membrane is easy to be pierced by lithium dendrites formed by precipitation, so that the internal short circuit of the battery is caused to cause thermal runaway, and the service life and the safety performance of the secondary battery are seriously influenced. Therefore, the existing barrier films still need to be improved.
Disclosure of Invention
The present invention has been made in view of the above problems, and an object of the present invention is to convert precipitated lithium metal into lithium ions, thereby preventing lithium dendrites formed during lithium precipitation from penetrating a separator to cause a short circuit in a battery, and improving the service life and safety of a secondary battery.
In order to achieve the above objects, the present application provides a separator and a method of manufacturing the same, a secondary battery, a battery module, a battery pack, and an electric device.
A first aspect of the present application provides a separator comprising: a release film substrate and a coating on at least one surface of the release film substrate; the coating comprises an iodine-containing species; wherein the coating on the surface of the side of the separator film substrate facing the negative electrode comprises iodate; and/or the coating on the surface of the side of the separator film substrate facing the positive electrode comprises iodide.
Therefore, the iodine-containing substances are arranged in the coating on at least one surface of the isolating membrane substrate, when the metal lithium is separated out from the negative electrode, the iodine-containing substances and the metal lithium are subjected to a series of reactions to convert the metal lithium into active lithium ions, so that the situation that the lithium dendrite formed during lithium separation pierces the isolating membrane to cause the internal short circuit of the battery can be avoided, and the service life and the safety performance of the secondary battery are improved; in addition, because the metal lithium is converted into active lithium ions, the irreversible attenuation of the battery capacity caused by the loss of the active lithium ions can be reduced, so that the capacity retention rate of the secondary battery is improved, and the performance stability and the service life of the secondary battery are improved.
In any embodiment, both surfaces of the separation film substrate are provided with the coating, wherein the coating on the surface of the side of the separation film substrate facing the positive electrode comprises one or more of iodate and iodide. When the coating on the surface of the side, facing the positive electrode, of the separation film substrate contains iodate, the iodate can react with lithium dendrite in the electrolyte which penetrates through the separation film and reaches the space between the positive electrode and the separation film, so that the lithium dendrite is eliminated, and negative effects caused by lithium precipitation of the negative electrode are reduced.
In any embodiment, the iodate is selected from the group consisting of KIO 3 、Fe(IO 3 ) 3 、NaIO 3 、Ca(IO 3 ) 2 、LiIO 3 And Mg (IO) 3 ) 2 One or more of; the iodide is selected from KI, naI, HI, liI, agI, and AlI 3 、MgI 2 、MnI 2 、ZnI 2 、BiI 3 And NH 4 And (I) one or more of. The iodine-containing substance can convert lithium metal into lithium metal by reacting with lithium metal in seriesActive lithium ions, so that the situation that lithium dendrites formed during lithium precipitation penetrate through the isolating membrane to cause internal short circuit of the battery can be avoided, and the irreversible attenuation of the battery capacity caused by the loss of the active lithium ions is reduced.
In any embodiment, the total amount of iodine-containing species in the coating on the surface of the release film substrate is 65mg/m 2 -1300mg/m 2 . The total dosage of iodine-containing substances is controlled within the range, and the lithium metal can be converted into active lithium ions to a great extent, so that the problems of internal short circuit of the battery, irreversible battery capacity attenuation and the like caused by lithium separation are reduced to a great extent.
The second aspect of the present application also provides a method for producing a separator, including: and coating the coating containing iodine substances on at least one surface of the isolating film substrate, and drying to obtain the isolating film.
Therefore, when the lithium metal is separated out from the negative electrode, iodate or iodide in a coating formed after the coating is dried can convert the lithium metal into active lithium ions through a series of reactions with the lithium metal, so that the situation that lithium dendrites formed during lithium separation penetrate through an isolating membrane to cause internal short circuit of the battery is avoided, and the service life and the safety performance of the secondary battery are improved; and the irreversible attenuation of the battery capacity caused by the loss of active lithium ions can be reduced, so that the capacity retention rate of the secondary battery is improved, and the performance stability and the service life of the secondary battery are improved.
In any embodiment, the coating further comprises a binder, and the mass ratio of the binder to the iodine-containing substance is 1.11: (10-100). The adhesive is used for bonding iodine-containing substances to the surface of the isolating membrane substrate; the usage amount of the adhesive is controlled within the range, iodine-containing substances can be bonded on the surface of the isolation film substrate without falling off, and the coating is ensured not to agglomerate in the coating process.
A third aspect of the present application provides a secondary battery comprising the separator of the first aspect of the present application or the separator prepared according to the method of the second aspect of the present application.
A fourth aspect of the present application provides a battery module including the secondary battery of the third aspect of the present application.
A fifth aspect of the present application provides a battery pack including the battery module of the fourth aspect of the present application.
A sixth aspect of the present application provides an electric device including one or more selected from the group consisting of the secondary battery of the third aspect of the present application, the battery module of the fourth aspect of the present application, and the battery pack of the fifth aspect of the present application.
The beneficial effect of this application:
according to the isolating membrane, the secondary battery, the battery module, the battery pack and the power utilization device, the coating comprising the iodine-containing substances is arranged on the surface of the isolating membrane, and the iodine-containing substances can convert metal lithium separated out from a negative electrode into active lithium ions, so that the situation that lithium dendrites formed during lithium separation penetrate through the isolating membrane to cause short circuit inside the battery is avoided, and the service life and the safety performance of the secondary battery are improved; in addition, metal lithium is converted into active lithium ions, so that the irreversible attenuation of the battery capacity caused by the loss of the active lithium ions can be reduced, the capacity retention rate of the secondary battery is improved, and the performance stability and the service life of the secondary battery are improved.
Drawings
Fig. 1 is a schematic structural diagram of a separation film according to an embodiment of the present application.
Fig. 2 is a schematic view illustrating an operation mechanism of the separator according to an embodiment of the present disclosure.
Fig. 3 is a schematic view of a secondary battery according to an embodiment of the present application.
Fig. 4 is an exploded view of the secondary battery according to the embodiment of the present application shown in fig. 3.
Fig. 5 is a schematic view of a battery module according to an embodiment of the present application.
Fig. 6 is a schematic diagram of a battery pack according to an embodiment of the present application.
Fig. 7 is an exploded view of the battery pack according to the embodiment of the present application shown in fig. 6.
Fig. 8 is a schematic diagram of an electric device in which the secondary battery according to the embodiment of the present application is used as a power source.
Description of reference numerals:
11 a base material of a separation film; 12 coating; 1, a battery pack; 2, putting the box body on the box body; 3, discharging the box body; 4 a battery module; 5 a secondary battery; 51 a housing; 52 an electrode assembly; 53 Top cover Assembly
Detailed Description
Hereinafter, embodiments of the separator and the method of manufacturing the same, the secondary battery, the battery module, the battery pack, and the electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. But a detailed description thereof will be omitted. For example, detailed descriptions of already known matters and repetitive descriptions of actually the same configurations may be omitted. This is to avoid unnecessarily obscuring the following description, and to facilitate understanding by those skilled in the art. The drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.
As disclosed herein, a "range" is defined in terms of lower and upper limits, with a given range being defined by the selection of one lower limit and one upper limit, which define the boundaries of the particular range. Ranges defined in this manner may or may not include endpoints and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Further, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3,4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise stated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 to 5" have been listed herein, and "0 to 5" is only a shorthand representation of the combination of these numbers. In addition, when a parameter is an integer of 2 or more, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, or the like.
All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, if not specifically stated.
All technical and optional features of the present application may be combined with each other to form new solutions, if not specifically mentioned.
All steps of the present application may be performed sequentially or randomly, preferably sequentially, if not specifically stated. For example, the method comprises steps (a) and (b), meaning that the method may comprise steps (a) and (b) performed sequentially, and may also comprise steps (b) and (a) performed sequentially. For example, reference to the process further comprising step (c) means that step (c) may be added to the process in any order, for example, the process may comprise steps (a), (b) and (c), may also comprise steps (a), (c) and (b), may also comprise steps (c), (a) and (b), etc.
The terms "comprises" and "comprising" as used herein mean either open or closed unless otherwise specified. For example, the terms "comprising" and "comprises" may mean that other components not listed may also be included or included, or that only listed components may be included or included.
In this application, the term "or" is inclusive, if not otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or not present); a is false (or not present) and B is true (or present); or both a and B are true (or present).
In the process of researching the secondary battery, the applicant finds that during the charging process of the secondary battery, the lithium precipitation of the negative electrode is easy to occur, and the lithium precipitation of the negative electrode has negative effects on the secondary battery: on one hand, lithium dendrite formed by lithium precipitation easily pierces the isolating membrane, so that internal short circuit of the battery is caused to cause thermal runaway, and the service life and the safety performance of the secondary battery are seriously influenced; on the other hand, active lithium ions are lost because they are converted into metallic lithium, resulting in irreversible degradation of battery capacity and shortened battery life.
In order to avoid that lithium dendrites formed during lithium precipitation penetrate through the separator to cause internal short circuit of the battery and reduce the loss of active lithium ions, the applicant researches and discovers that metal lithium precipitated from the negative electrode can be converted into active lithium ions through chemical reaction. Through intensive research, the following results are found: when the lithium metal is separated out from the negative electrode, the iodate or the iodide can react with the lithium metal to convert the lithium metal into active lithium ions, so that the situation that the lithium dendrite formed during the lithium separation pierces the isolating membrane to cause the internal short circuit of the battery is avoided, and the service life and the safety performance of the secondary battery are improved; and the irreversible attenuation of the battery capacity caused by the loss of active lithium ions can be reduced, so that the capacity retention rate of the secondary battery is improved, and the performance stability and the service life of the secondary battery are improved.
The isolating membrane provided by the application can be used in a secondary battery; the secondary battery may be used in, but not limited to, an electric device for a vehicle, a ship, an aircraft, or the like. The power supply system of the electric device can be formed by the secondary battery and the like, so that the situation that the lithium dendrite formed during lithium separation pierces the isolating membrane to cause short circuit inside the battery is avoided, and the service life and the safety performance of the secondary battery are improved; and the irreversible capacity attenuation of the secondary battery caused by the loss of active lithium ions is reduced, the capacity retention rate of the secondary battery is improved, and the performance stability and the service life of the secondary battery are improved.
The application provides an electric device using a secondary battery as a power supply, wherein the electric device can be but is not limited to a mobile phone, a flat panel, a notebook computer, an electric toy, an electric tool, a battery car, an electric automobile, a ship, a spacecraft and the like. The electric toy may include a stationary or mobile electric toy, such as a game machine, an electric car toy, an electric ship toy, an electric airplane toy, and the like, and the spacecraft may include an airplane, a rocket, a space shuttle, a spacecraft, and the like.
In order to avoid the lithium dendrite that forms when separating out the lithium and impale the barrier film and cause the inside short circuit of battery, reduce active lithium ion's loss, promote secondary battery's life and security performance, this application provides a barrier film and preparation method, secondary battery, battery module, battery package and electric device.
Isolation film
In one embodiment of the present application, the present application provides a separation film, the schematic structural diagram of which is shown in fig. 1, the separation film comprises a separation film substrate 11 and a coating layer 12 on at least one surface of the separation film substrate 11; the coating 12 includes an iodine-containing species; wherein the coating layer 12 on the surface of the side of the separator substrate 11 facing the negative electrode contains iodate; and/or the coating layer 12 on the surface of the separator substrate 11 on the side facing the positive electrode contains iodide.
The applicant has surprisingly found that: according to the lithium ion secondary battery, the iodine-containing substances are arranged in the coating on at least one surface of the isolating membrane substrate, when the metal lithium is separated out from the negative electrode, the iodine-containing substances and the metal lithium are subjected to a series of reactions, and the metal lithium is converted into active lithium ions, so that the situation that the lithium dendrite formed during lithium separation pierces the isolating membrane to cause the internal short circuit of the battery can be avoided, and the service life and the safety performance of the secondary battery are improved; in addition, because the metal lithium is converted into active lithium ions, the irreversible attenuation of the battery capacity caused by the loss of the active lithium ions can be reduced, so that the capacity retention rate of the secondary battery is improved, and the performance stability and the service life of the secondary battery are improved.
The action mechanism of the isolating film provided by one embodiment of the application is schematically shown in fig. 2, and the isolating film comprises an isolating film substrate and a coating layer on the surface of the side, opposite to the negative electrode, of the isolating film substrate; the coating comprises an iodine-containing species which is an iodate.
IO in iodate when metallic lithium (Li) is precipitated from the negative electrode 3 - The electrolyte enters into the electrolyte between the cathode and the isolating film, and reacts with Li as shown in formula (1):
6Li+IO 3 - ＝I - +3Li 2 O。 (1)
i produced by reaction of equation (1) - And (3) entering the electrolyte between the positive electrode and the isolating membrane through the isolating membrane, and carrying out a reaction as shown in the formula (2):
3I - -2e - ＝I 3 - 。 (2)
i produced by reaction of equation (2) 3 - The electrolyte enters the electrolyte between the negative electrode and the isolating film through the isolating film, and reacts with Li precipitated from the negative electrode as shown in formula (3):
2Li+I 3 - ＝2Li + +3I - ； (3)
with Li produced by reaction equation (1) 2 O undergoes a reaction as shown in formula (4):
3Li 2 O+3I 3 - ＝6Li + +IO 3 - +8I - 。 (4)
i produced by reaction of equations (3) and (4) - Can enter into the electrolyte between the anode and the isolating membrane through the isolating membrane, and the reaction shown in the formula (2) occurs, and the cycle is repeated.
As is apparent from the above, the lithium metal precipitated in the negative electrode can be converted into active lithium ions, so that it is possible to prevent lithium dendrites formed during lithium precipitation from penetrating the separator to cause a short circuit inside the battery, and to reduce irreversible capacity degradation due to loss of active lithium ions.
Another embodiment of the present application provides a separator including a separator substrate and a coating layer on a surface of the separator substrate on a side facing a positive electrode; the coating includes an iodide containing species.
When metallic lithium (Li) is precipitated in the negative electrode, I in the iodide - Will enter into the electrolyte between the anode and the isolating membrane, and will take place the reaction as shown in formula (2):
3I - -2e - ＝I 3 - 。 (2)
i produced by reaction of equation (2) 3 - And (3) entering the electrolyte between the negative electrode and the isolating membrane through the isolating membrane, and carrying out a reaction as shown in the formula (3):
2Li+I 3 - ＝2Li + +3I - 。 (3)
i produced by reaction of equation (3) - Can enter into the electrolyte between the anode and the isolating membrane through the isolating membrane to generate the reverse reaction shown in the formula (2)This should be repeated.
As is apparent from the above, the lithium metal precipitated in the negative electrode can be converted into active lithium ions, so that it is possible to prevent lithium dendrites formed during lithium precipitation from penetrating the separator to cause a short circuit inside the battery, and to reduce irreversible capacity degradation due to loss of active lithium ions.
Another embodiment of the present application provides a separator comprising: a release film substrate; a coating is arranged on the surface of one side, opposite to the negative electrode, of the isolation film substrate, and the coating comprises an iodine-containing substance which is iodate; the surface of one side of the isolating membrane substrate, which is opposite to the positive electrode, is provided with a coating, and the coating comprises iodide.
IO in iodate when metallic lithium (Li) is precipitated in the negative electrode 3 - The electrolyte enters into the electrolyte between the cathode and the isolating film, and reacts with Li as shown in formula (1):
6Li+IO 3 - ＝I - +3Li 2 O。 (1)
i produced by reaction of equation (1) - I in the iodide enters the electrolyte between the positive electrode and the isolating membrane through the isolating membrane - Will enter into the electrolyte between the anode and the isolating membrane, and will take place the reaction as shown in formula (2):
3I - -2e - ＝I 3 - 。 (2)
i produced by reaction equation (2) 3 - The electrolyte enters the electrolyte between the cathode and the isolating film through the isolating film, and reacts with Li precipitated from the cathode as shown in formula (3):
2Li+I 3 - ＝2Li + +3I - ； (3)
with Li produced by reaction equation (1) 2 O undergoes a reaction as shown in formula (4):
3Li 2 O+3I 3 - ＝6Li + +IO 3 - +8I - 。 (4)
i produced by reaction of equations (3) and (4) - The positive electrode and the separator are accessible through the separatorIn the electrolyte solution, the reaction as shown in the formula (2) occurs, and the cycle is repeated.
As is apparent from the above, the lithium metal precipitated in the negative electrode can be converted into active lithium ions, so that it is possible to prevent lithium dendrites formed during lithium precipitation from penetrating the separator to cause a short circuit inside the battery, and to reduce irreversible capacity degradation due to loss of active lithium ions.
The present application is not particularly limited as to the kind of the base material of the separation film as long as the object of the present application can be achieved. For example, the base material of the separation film can be directly selected from a bare polymer film, or a ceramic coating (hereinafter abbreviated as CCS layer) and a polymer bonding coating (hereinafter abbreviated as PCS layer) can be sequentially arranged on one side or both sides of the polymer film, wherein the CCS layer is positioned between the polymer film and the PCS layer; wherein the polymer film may be selected from one or more of a polypropylene film and a polyethylene film.
The thickness of the separation film substrate is not limited as long as the object of the present invention can be achieved, and for example, the thickness of the separation film substrate may be 5 μm to 54 μm, and the thickness of the polymer thin film, the thickness of the CCS layer, and the thickness of the PCS layer in the separation film substrate may be 5 μm to 50 μm, the thickness of the CCS layer may be 3 μm, and the thickness of the PCS layer may be 1 μm.
A CCS layer, as used herein, refers to a coating comprising a ceramic material selected from SiO 2 、TiO 2 、ZrO 2 、Al 2 O 3 One or more of MgO and SiC. In some embodiments, the CCS layer optionally further comprises a binder selected from one or more of polyvinylidene fluoride (PVDF), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, polyurethane (PU), styrene acrylic latex (SA).
The PCS layer is a coating layer containing a polymer binder selected from one or more of polyvinylidene fluoride (PVDF), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, polyurethane (PU), and styrene-acrylic latex (SA).
The method for producing the separator substrate is not limited in the present application as long as the object of the present application can be achieved, and for example, a CCS layer may be coated on a polymer thin film, and then a PCS layer may be coated on the CCS layer to obtain the separator substrate. The application of the CCS layer to the polymer film and the PCS layer to the CCS layer are common methods in the art, and are not limited herein.
In some embodiments, both surfaces of the separator are provided with a coating, wherein the coating on the surface of the side of the separator substrate facing the positive electrode comprises one or more selected from iodate and iodide. When the coating on the surface of the separator substrate on the side facing the positive electrode contains iodate, if lithium dendrites formed during lithium separation penetrate through the separator to reach the electrolyte between the positive electrode and the separator, IO in the iodate is 3 - A reaction with Li as shown in formula (1) occurs:
6Li+IO 3 - ＝I - +3Li 2 O。 (1)
therefore, lithium dendrite in the electrolyte between the positive electrode and the separation film can be eliminated in time, and negative influence caused by lithium precipitation of the negative electrode is reduced.
In some embodiments, the iodate is selected from KIO 3 、Fe(IO 3 ) 3 、NaIO 3 、Ca(IO 3 ) 2 、LiIO 3 And Mg (IO) 3 ) 2 One or more of; the iodide is selected from KI, naI, HI, liI, agI, and AlI 3 、MgI 2 、MnI 2 、ZnI 2 、BiI 3 And NH 4 And (I) one or more of. The iodate and the iodide can react with the lithium metal to convert the lithium metal into active lithium ions, so that the situation that the lithium dendrite formed during lithium precipitation pierces the isolating membrane to cause the internal short circuit of the battery can be avoided, and the irreversible attenuation of the battery capacity caused by the loss of the active lithium ions is reduced.
In some embodiments, the total amount of iodine-containing species in the coating on the surface of the release film substrate is 65mg/m 2 -1300mg/m 2 I.e. for each m 2 The total mass of iodine-containing substances in the coatings arranged on the two surfaces of the isolating film is 65-1300 mg. If the total mass of iodine-containing substances of the coating is low, lithium is difficult to effectively eliminate and separated lithium is converted into active lithium ions to a large extent, so that the secondary battery still has a relatively obvious lithium separation condition, and the capacity retention rate and the cycle life are not effectively improved; if the total mass of the iodine-containing substances of the coating is higher, the thickness of the cathode and anode sheets can be increased, so that the number of turns of the electrode sheet wound by the battery cell with the same volume can be reduced, the mass energy density is reduced, and the performances of the battery such as the cruising ability are finally influenced. Therefore, the inventor believes that the use amount of the iodine-containing substance is controlled within the range, the metallic lithium can be effectively converted into active lithium ions to a large extent, the lithium precipitation condition of the secondary battery is obviously improved, and the secondary battery has better first discharge capacity, capacity retention rate and cycle life.
The coating described herein may be disposed on a localized area or all areas on at least one surface of the release film substrate. The coating is arranged in a local area on the surface of the isolating film substrate, iodine-containing substances in the coating can react with the lithium metal to convert the lithium metal into active lithium ions, so that the situation that lithium dendrites formed during lithium precipitation penetrate the isolating film to cause internal short circuit of the battery can be avoided, and irreversible attenuation of the battery capacity caused by loss of the active lithium ions is reduced. The coating is arranged in all areas on the surface of the isolating membrane substrate, iodine-containing substances in the coating can react with the lithium metal more timely and efficiently, and the reaction efficiency can be further improved.
Preparation method of isolating film
In one embodiment, the present application provides a method for preparing a separation film, including: and coating the coating containing iodine substances on at least one surface of the isolating film substrate, and drying to obtain the isolating film.
The iodine-containing substance contains iodate when the surface of the side of the separator substrate facing the negative electrode is coated with a coating; the iodine-containing substance contains an iodide when a coating layer is applied on the surface of the side of the separation film substrate facing the positive electrode; when both surfaces of the separation film substrate are provided with the coating layer, the iodine-containing substance of the coating layer on the surface of the separation film substrate on the side facing the positive electrode contains one or more selected from iodate and iodide.
According to the preparation method, the coating containing iodine is coated on at least one surface of the isolating membrane substrate, the isolating membrane coated with the coating on the surface of the isolating membrane substrate is prepared, when metal lithium is separated out from a negative electrode, the iodine-containing material in the coating can convert the metal lithium into active lithium ions through a series of reactions with the metal lithium, so that the situation that lithium dendrites formed during lithium separation penetrate through the isolating membrane to cause short circuit inside the battery is avoided, the service life of the secondary battery is prolonged, and the safety performance of the secondary battery is improved; and the irreversible attenuation of the battery capacity caused by the loss of active lithium ions can be reduced, so that the capacity retention rate of the secondary battery is improved, and the performance stability and the service life of the secondary battery are improved.
In some embodiments, the coating further comprises a binder, and the mass ratio of the binder to the iodine-containing substance is 1.11: (10-100). The adhesive is capable of bonding iodine-containing substances to the surface of the release film substrate. If the amount of the adhesive is low, the iodine-containing substance is difficult to adhere to the surface of the release film substrate without falling off; if the binder is used in a high amount, agglomeration is easily generated during the coating process, and the mass energy density of the secondary battery may be reduced.
The present application is not particularly limited as long as the object of the present application can be achieved. For example, the adhesive may employ one or more of polyvinylidene fluoride (PVDF), sodium carboxymethylcellulose (CMC), and Styrene Butadiene Rubber (SBR).
The specific preparation method of the coating is not particularly limited, as long as the purpose of the coating can be achieved, for example, the coating can be prepared by dissolving an iodine-containing substance in deionized water, adding a binder, and uniformly stirring. When the coating is prepared, the iodine-containing substances are dissolved by using deionized water, and the using amount of the iodine-containing substances is not particularly limited as long as the purpose of the coating can be achieved.
The method of coating is not particularly limited as long as the object of the present invention can be achieved, and for example, coating may be performed by gravure, extrusion, or spray coating.
The drying is performed to remove the deionized water, and the drying device, the drying time and the drying temperature are not particularly limited as long as the drying device, the drying time and the drying temperature can achieve the purpose of the drying device, for example, the drying temperature is 30-50 ℃.
The secondary battery, the battery module, the battery pack, and the electric device according to the present invention will be described below with reference to the drawings as appropriate.
In one embodiment of the present application, a secondary battery is provided.
In general, a secondary battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. In the process of charging and discharging the battery, active ions are embedded and separated back and forth between the positive pole piece and the negative pole piece. The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The isolating membrane is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the short circuit of the positive pole and the negative pole, and can enable ions to pass through.
[ Positive electrode sheet ]
The positive pole piece comprises a positive pole current collector and a positive pole film layer arranged on at least one surface of the positive pole current collector.
As an example, the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two surfaces opposite to the positive electrode current collector.
In some embodiments, the positive electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a base material of a polymer material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some embodiments, the positive active material may employ a positive active material for a battery, which is well known in the art. As an example, the positive electrode active material may include one or more of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material of a battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) 2 ) Lithium nickel oxide (e.g., liNiO) 2 ) Lithium manganese oxide (e.g., liMnO) 2 、LiMn 2 O 4 ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) 1/3 Co 1/3 Mn 1/3 O 2 (may also be abbreviated as NCM) 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (may also be abbreviated as NCM) 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (may also be abbreviated as NCM) 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (may also be abbreviated as NCM) 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (may also be abbreviated as NCM) 811 ) Lithium nickel cobalt aluminum oxides (e.g., liNi) 0.85 Co 0.15 Al 0.05 O 2 ) And modified compounds thereof, and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO) 4 (also referred to as LFP for short)), a composite material of lithium iron phosphate and carbon, and lithium manganese phosphate (e.g., liMnPO) 4 ) One or more of a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
In some embodiments, the positive electrode film layer further optionally includes a binder. By way of example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymers, tetrafluoroethylene-hexafluoropropylene copolymers, and fluoroacrylate resins.
In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and the like to obtain the positive electrode piece.
[ negative electrode sheet ]
The negative pole piece includes the negative current collector and sets up the negative pole rete on the negative current collector at least one surface, the negative pole rete includes negative active material.
As an example, the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two surfaces opposite to the negative electrode current collector.
In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a base material of a polymer material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some embodiments, the negative active material may employ a negative active material for a battery known in the art. As an example, the negative active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate and the like. The silicon-based material can be one or more selected from elemental silicon, silicon-oxygen compounds, silicon-carbon compounds, silicon-nitrogen compounds and silicon alloys. The tin-based material may be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative active material may also be used. These negative electrode active materials may be used alone or in combination of two or more.
In some embodiments, the anode film layer further optionally includes a binder. The binder may be one or more selected from Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).
In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent can be selected from one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
In some embodiments, the negative electrode film layer may also optionally include other adjuvants, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.
In some embodiments, the negative electrode sheet can be prepared by: dispersing the above components for preparing a negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and drying, cold pressing and the like to obtain the negative electrode pole piece.
[ electrolyte ]
The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The kind of the electrolyte is not particularly limited and may be selected as desired. For example, the electrolyte may be liquid, gel, or all solid.
In some embodiments, the electrolyte is an electrolytic solution. The electrolyte includes an electrolyte salt and a solvent.
In some embodiments, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium dioxaoxalato borate, lithium difluorodioxaoxalato phosphate, and lithium tetrafluorooxalato phosphate.
In some embodiments, the solvent may be selected from one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.
In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives capable of improving certain properties of the battery, such as an additive for improving overcharge properties of the battery, an additive for improving high-temperature or low-temperature properties of the battery, and the like.
[ isolation film ]
In some embodiments, the separator provided herein is further included in a secondary battery.
In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.
In some embodiments, the secondary battery may include an exterior package. The exterior package may be used to enclose the electrode assembly and electrolyte.
In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The outer package of the secondary battery may also be a pouch, such as a pouch-type pouch. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
The shape of the secondary battery is not particularly limited, and may be a cylindrical shape, a square shape, or any other arbitrary shape. For example, fig. 3 is a secondary battery 5 of a square structure as an example.
In some embodiments, referring to fig. 4, the overwrap may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose to form an accommodating cavity. The housing 51 has an opening communicating with the accommodation chamber, and a cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. An electrode assembly 52 is enclosed within the receiving cavity. The electrolyte is impregnated into the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 may be one or more, and those skilled in the art can select them according to the actual needs.
In some embodiments, the secondary batteries may be assembled into a battery module, and the number of the secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
Fig. 5 is a battery module 4 as an example. Referring to fig. 5, in the battery module 4, a plurality of secondary batteries 5 may be arranged in series along the longitudinal direction of the battery module 4. Of course, the arrangement may be in any other way. The plurality of secondary batteries 5 may be further fixed by a fastener.
Alternatively, the battery module 4 may further include a case having an accommodation space in which the plurality of secondary batteries 5 are accommodated.
In some embodiments, the battery modules may be assembled into a battery pack, and the number of the battery modules contained in the battery pack may be one or more, and the specific number may be selected by one skilled in the art according to the application and the capacity of the battery pack.
Fig. 6 and 7 are a battery pack 1 as an example. Referring to fig. 6 and 7, a battery pack 1 may include a battery case and a plurality of battery modules 4 disposed in the battery case. The battery box comprises an upper box body 2 and a lower box body 3, wherein the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. A plurality of battery modules 4 may be arranged in any manner in the battery box.
In addition, the application also provides an electric device, and the electric device comprises one or more of the secondary battery, the battery module or the battery pack provided by the application. The secondary battery, the battery module, or the battery pack may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The powered device may include a mobile device (e.g., a mobile phone, a laptop computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc., but is not limited thereto.
As the electricity-using device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirement thereof.
Fig. 8 is an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle or a plug-in hybrid electric vehicle and the like. In order to meet the demand of the electric device for high power and high energy density of the secondary battery, a battery pack or a battery module may be used.
As another example, the device may be a cell phone, a tablet, a laptop, etc. The device is generally required to be thin and light, and a secondary battery may be used as a power source.
Examples
Hereinafter, examples of the present application will be described. The following description of the embodiments is merely exemplary in nature and is in no way intended to limit the present disclosure. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are conventional products which are commercially available, and are not indicated by manufacturers.
Example 1
< preparation of Positive electrode sheet >
Lithium iron phosphate (LiFePO) as positive electrode active material 4 ) The conductive agent carbon black and the binder polyvinylidene fluoride are 8:1:1, adding N-methyl pyrrolidone (NMP) as a solvent, and stirring the mixture under the action of a vacuum stirrer until the system is uniform to obtain anode slurry with the solid content of 65%. And uniformly coating the positive electrode slurry on two surfaces of a positive electrode current collector aluminum foil with the thickness of 12 microns, drying at 120 ℃, cold-pressing to obtain a positive electrode piece with the thickness of a positive electrode active material layer of 60 microns, and then carrying out procedures such as tab forming, slitting and the like to obtain the positive electrode piece.
< preparation of negative electrode sheet >
The method comprises the following steps of mixing a negative active material artificial graphite, a conductive agent carbon black and a binder polyacrylic acid according to a weight ratio of 7:1.5:1.5, adding deionized water as a solvent, and stirring the mixture under the action of a vacuum stirrer until the system is uniform to obtain cathode slurry with the solid content of 50%. And uniformly coating the negative electrode slurry on two surfaces of a negative electrode current collector copper foil with the thickness of 8 mu m, drying at 110 ℃, obtaining a negative electrode plate with the thickness of 50 mu m after cold pressing, and then obtaining the negative electrode plate through procedures of tab forming, slitting and the like.
< preparation of electrolytic solution >
Under the environment that the water content is less than 10ppm, non-aqueous organic solvents of ethylene carbonate and dimethyl carbonate are mixed according to the volume ratio of 1:1 to obtain an electrolyte solvent, followed by mixing a lithium salt LiPF 6 Dissolved in the mixed solvent to prepare an electrolyte solution having a lithium salt concentration of 1 mol/L.
< preparation of separator >
The thickness is 20 mu m, the area of a single sheet is 1540.25mm 2 The polypropylene film is a bare film, a CCS layer with the thickness of 3 mu m is coated on the surface of the polypropylene film, and then a PCS layer with the thickness of 1 mu m is coated on the surface of the CCS layer, so that the isolating film substrate is obtained.
Mixing 100mg of KIO 3 Dissolving in 50mL deionized water, adding 2.564mg of polyvinylidene fluoride as binder, stirring uniformly to obtain coating, and coating on the base of isolating membrane by extrusion coating methodControlling KIO in all regions on the surface of the side of the material facing the negative electrode 3 The coating mass is 975mg/m 2 (ii) a And (5) after coating, drying in a drying box to obtain the isolating membrane.
< preparation of lithium ion Battery >
Stacking the positive pole piece, the isolating film and the negative pole piece in sequence to enable the isolating film to be positioned between the positive pole piece and the negative pole piece to play an isolating role, and then winding to obtain an electrode assembly; and (3) placing the electrode assembly in an outer packaging shell, drying, injecting electrolyte, and performing vacuum packaging, standing, formation, shaping and other processes to obtain the lithium ion battery.
Examples 2 to 15
The procedure was as in example 1 except that < preparation of separator > was different from example 1.
The same procedure as in example 1 was repeated except that the type of iodine-containing substance, the coating quality of the iodine-containing substance, and the position of the coating material on the separator substrate were adjusted as shown in table 1.
Comparative example 1
The procedure was as in example 1 except that < preparation of separator > was different from example 1.
< preparation of separator >
The thickness is 20 mu m, the area of a single sheet is 1540.25mm 2 The polypropylene film is a bare film, a CCS layer with the thickness of 3 mu m is coated on the surface of the polypropylene film, and then a PCS layer with the thickness of 1 mu m is coated on the surface of the CCS layer to obtain an isolation film substrate; the base material of the isolation film is directly used as the isolation film.
Comparative examples 2 to 4
The procedure was as in example 1 except that < preparation of separator > was different from example 1.
In that<Preparation of the separator>In addition to those shown in Table 1, other substances ((NH) were used 4 ) 2 CO 3 And/or NH 4 HCO 3 ) The procedure of example 1 was repeated except that the coating quality of the iodine-containing substance was changed and the position of the release film substrate to which the coating material was applied was changed.
Table 1: relevant parameters of examples 1 to 15 and comparative examples 1 to 4
In addition, the lithium ion batteries obtained in examples 1 to 15 and comparative examples 1 to 4 were subjected to a performance test. The test results are shown in table 2 below.
(1) First discharge capacity test and lithium precipitation test
The lithium ion batteries prepared in the examples and comparative examples were charged to 4.35V at a constant current of 1/3C, then charged to 0.05C at a constant voltage, and then discharged to 2.8V at a constant current of 1/3C at a test temperature of 25 deg.C, and the obtained capacity was recorded as a first discharge capacity value C 0 。
And then, charging to 4.35V by adopting a 1/3C constant current, charging to 0.05C by adopting a constant voltage, discharging to 2.8V by adopting a 1/3C constant current, performing 10 cycles, disassembling the lithium ion battery in a drying room with the humidity of less than 5 percent, and checking the state of a negative pole piece.
Judging the lithium separation degree of the lithium ion battery according to the following standards:
no lithium precipitation: no lithium deposition exists on the surface of the negative pole piece;
slight lithium precipitation: the lithium deposition area on the surface of the negative pole piece is less than 10 percent;
moderate lithium precipitation: the lithium deposition area on the surface of the negative pole piece is 10-30%;
severe lithium evolution: the lithium deposition area on the surface of the negative pole piece is more than 30 percent.
(2) Lithium ion battery performance cycle test
The lithium ion batteries prepared in the examples and comparative examples were charged to 4.35V at a constant current of 1/3C, then charged to 0.05C at a constant voltage, and then discharged to 3.3V at a constant current of 1/3C at a test temperature of 25 ℃, the cycle was repeated, the discharge capacity value during the cycle was recorded, and the capacity retention ratio at 1000 cycles was calculated, the capacity retention ratio at N cycle = (discharge capacity at N cycle/first discharge capacity) × 100%. The number of cycles at which the capacity retention rate decreased to 80% was recorded as the cycle life of the battery.
(3) Lithium ion battery mass energy density test
The lithium ion batteries manufactured in each example and comparative example were charged at a test temperature of 25C to 4.35V at a constant current of 1/3C, then charged at a constant voltage to 0.05C, and then discharged at a constant current of 1/3C to 2.8V, and their discharge energies were recorded, and then the 1/3C discharge energy density was calculated according to the following formula: mass energy density (Wh/kg) = discharge energy (Wh)/electrochemical device weight (kg).
Table 2: results of Performance test of examples 1 to 15 and comparative examples 1 to 4
From the above results, it can be seen that the separators of the lithium ion batteries of examples 1 to 11 included a coating layer on at least one surface of the separator substrate, the kind of iodine-containing substances in the coating layer was controlled within the range of the present application, and the coating quality was controlled to 65mg/m 2 -1300mg/m 2 Within the range, the lithium precipitation condition of the lithium ion battery is obviously improved, and the lithium ion battery has better first discharge capacity, better capacity retention rate, cycle life and mass energy density.
As can be seen from examples 1 to 3, the coating quality of iodate in the coating on the surface of the side of the separator substrate facing the negative electrode was controlled to 65mg/m 2 -1300mg/m 2 Within the range, the lithium ion Chi Qingwei separates lithium or does not separate lithium, the lithium separation condition is obviously improved, and the lithium ion battery has better first discharge capacity, better capacity retention rate, cycle life and mass energy density.
As can be seen from examples 4 to 6, the coating quality of iodide in the coating layer on the surface of the side of the separator substrate facing the positive electrode was controlled to 65mg/m 2 -1300mg/m 2 In the range of Chi Qingwei, either lithium is separated or not,the lithium precipitation condition is obviously improved, and the lithium-ion battery has better first discharge capacity, capacity retention rate, cycle life and mass energy density.
As can be seen from examples 1 and 4, the capacity retention rate and the cycle life of example 1 are superior to those of example 4, and the inventors of the present application do not limit any theory, and believe that when a negative pole lithium precipitation occurs in a battery cell, iodate can directly react with lithium metal to convert lithium metal into lithium ions, so that the problem of lithium precipitation can be solved in time, and the negative effects of lithium metal on the safety and performance of a battery can be reduced; iodide is required to consume the metallic lithium through charging and ion transmission processes, and the efficiency of removing the metallic lithium is influenced by ion diffusion and charge-discharge cycles, so that the effect of using iodate is better than that of using iodide.
As can be seen from examples 7 to 11, the release film substrate was coated on both sides, and the total coating mass of iodate in the coating on the surface of the release film substrate on the side facing the negative electrode and iodine-containing substance in the coating on the surface of the release film substrate on the side facing the positive electrode was controlled to 65mg/m 2 -1300mg/m 2 Within the range, the lithium ion Chi Qingwei separates lithium or does not separate lithium, the lithium separation condition is obviously improved, and the lithium ion battery has better first discharge capacity, better capacity retention rate, cycle life and mass energy density.
The separator of the lithium ion battery of example 12, although the iodate was included in the coating on the surface of the side of the separator substrate facing the negative electrode, was 32.5mg/m due to its low coating mass 2 The precipitated metal lithium is not enough to be converted into lithium ions as much as possible, so that the lithium ion battery still has medium precipitated lithium, and the capacity retention rate and the cycle life are not effectively improved.
The separators of the lithium ion batteries of examples 13 to 15, although including iodine-containing substances in the coating layer on one or both sides of the separator substrate, were 1950mg/m due to their high coating quality 2 Resulting in a decrease in mass energy density, and a further increase in capacity retention rate and cycle life is difficult. Is not limited to anyTheoretically, the inventor of the application thinks that the coating quality of the iodine-containing substances is higher, the thickness of the cathode and anode plates is increased, the number of turns of the wound pole piece of the battery cell with the same volume is reduced, and the mass energy density is reduced; in addition, the lithium ion battery has an upper limit on the amount of lithium separated, so that the required iodine-containing substance also has an upper limit, and when the coating quality of the iodine-containing substance is too high, the capacity retention rate and the cycle life cannot be further obviously improved, but the iodine-containing substance is wasted, and the production cost is increased.
On the contrary, the isolating membrane of the lithium ion battery of the comparative example 1 does not include a coating containing iodine, the lithium ion battery has serious lithium precipitation, the capacity retention rate after 1000 cycles is only 85.1%, the cycle life is only 1320 circles, and the requirement of many application scenes on the service life of the lithium ion battery is difficult to meet.
The coating layer of the separation film of the lithium ion batteries of comparative examples 2 to 4 includes (NH) 4 ) 2 CO 3 And/or NH 4 HCO 3 However, the lithium ion battery does not contain iodine-containing substances, the problem of lithium analysis cannot be effectively solved due to the fact that lithium ion batteries have serious lithium analysis, the capacity retention rate after 1000 cycles does not exceed 84.3%, the cycle life does not exceed 1260 circles, and the requirement of many application scenes on the service life of the lithium ion battery cannot be met.
The present application is not limited to the above embodiments. The above embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exhibiting the same operation and effect within the technical scope of the present application are all included in the technical scope of the present application. In addition, various modifications that can be conceived by those skilled in the art are applied to the embodiments and other embodiments are also included in the scope of the present application, in which some of the constituent elements in the embodiments are combined and constructed, without departing from the scope of the present application.
Claims (10)
1. A separator, comprising: a release film substrate and a coating on at least one surface of the release film substrate; the coating comprises an iodine-containing species;
wherein the coating on the surface of the side of the separator substrate facing the negative electrode comprises an iodate; and/or
The coating layer on the surface of the separator substrate on the side facing the positive electrode contains iodide.
2. The separator of claim 1, wherein both surfaces of the separator substrate are provided with the coating, wherein the coating on the surface of the separator substrate on the side facing the positive electrode comprises one or more of iodate and iodide.
3. The separator according to claim 1 or 2, wherein said iodate is selected from the group consisting of KIO 3 、Fe(IO 3 ) 3 、NaIO 3 、Ca(IO 3 ) 2 、LiIO 3 And Mg (IO) 3 ) 2 One or more of; the iodide is selected from KI, naI, HI, liI, agI, and AlI 3 、MgI 2 、MnI 2 、ZnI 2 、BiI 3 And NH 4 And (I) one or more of.
4. The separator of claim 1, wherein the total amount of iodine-containing species in the coating on the surface of the separator substrate is 65mg/m 2 -1300mg/m 2 。
5. A method for producing the separator according to any one of claims 1 to 4, comprising: and coating a coating containing iodine-containing substances on at least one surface of the isolating film substrate, and drying to obtain the isolating film.
6. The method for preparing the release film according to claim 5, wherein the coating material further comprises a binder, and the mass ratio of the binder to the iodine-containing substance is 1.11: (10-100).
7. A secondary battery comprising the separator according to any one of claims 1 to 4 or the separator produced by the method for producing a separator according to claim 5 or 6.
8. A battery module characterized by comprising the secondary battery according to claim 7.
9. A battery pack comprising the battery module according to claim 8.
10. An electric device comprising one or more selected from the group consisting of the secondary battery according to claim 7, the battery module according to claim 8, and the battery pack according to claim 9.
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