CN112952291A - Lithium ion diaphragm containing lithium carbonate coating and preparation method thereof - Google Patents
Lithium ion diaphragm containing lithium carbonate coating and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a lithium ion diaphragm containing a lithium carbonate coating and a preparation method thereof. Mainly comprises a base film and a safety coating coated on the surface of the base film; the safety coating mainly comprises mixed glue, an auxiliary agent and water; the safe coating comprises the following raw material components in addition: by percentage, 90-93% of mixed glue, 5.5-6.5% of auxiliary agent and the balance of water; the mixed rubber mainly comprises a high-molecular rubber material and lithium carbonate; the addition amount of lithium carbonate in the mixed rubber is 0.5-2% of that of the polymer rubber. The lithium carbonate-containing coating diaphragm can quickly provide gas molecules at the early stage of thermal runaway inside a battery, so that the time for a safety structure to reach critical pressure is shortened, and the safety performance of the battery is improved; the special coating diaphragm coating material containing the lithium carbonate component has the advantages of simple preparation process and low cost, can obviously improve the safety of the battery, can realize industrial generation, and has high economic value and practical value.
Description
Technical Field
The invention relates to the technical field of lithium ion diaphragms, in particular to a lithium ion diaphragm containing a lithium carbonate coating and a preparation method thereof.
Background
Nowadays, the application range of lithium ion batteries is more and more extensive, the number of safety events of the lithium ion batteries is also continuously increased, and the safety performance of the lithium ion batteries also becomes the main technical key of lithium battery manufacturers. Particularly, for a square aluminum shell battery, as the assembly structure adopts an aluminum metal shell, once thermal runaway occurs, the lithium battery can be subjected to serious safety events such as explosion, fire and the like. For the safety of the aluminum-shell battery, a top cover structure of an aluminum-shell is provided with a first SSD turnover sheet (the pressure resistance range of the SSD turnover sheet is 0.40-0.70 MPa); secondly, a safety explosion-proof valve (which generally resists the pressure of 0.85-0.95 MPa); and thirdly, an aluminum shell (the pressure resistance of the aluminum shell is generally more than or equal to 1.0 MPa).
When the thermal runaway inside the battery violently reacts to generate gas to form high pressure, the pressure value can reach the critical value of the SSD turnover piece, the SSD turnover piece is triggered to turn over, and the external short circuit fuses the battery core tab inside the battery to block the thermal runaway during turning over, so that the effect of improving the safety of the battery is realized. However, the gas production required to reach the critical pressure needs to reach a higher voltage or a middle and later thermal runaway stage, and sufficient gas cannot be generated in time to trigger a safety structure.
Therefore, there is a need for a lithium ion separator capable of triggering a safety structure in time to solve the problems suggested in the background.
Disclosure of Invention
The invention aims to provide a lithium ion diaphragm containing a lithium carbonate coating and a preparation method thereof, so as to solve the problems in the background technology.
A lithium ion separator comprising a lithium carbonate coating consisting essentially of: a base film and a safety coating coated on the surface of the base film; the safety coating mainly comprises mixed glue, an auxiliary agent and water.
Further, the addition amount of each raw material component in the safety coating is as follows: by percentage, 90-93% of mixed glue, 5.5-6.5% of auxiliary agent and the balance of water.
Further, the mixed rubber mainly comprises a high-molecular rubber material and lithium carbonate; the addition amount of lithium carbonate in the mixed rubber is 0.5-2% of that of the polymer rubber.
Further, the polymer size includes, but is not limited to, polyvinylidene fluoride glue, and may also be one or more of polyvinyl alcohol glue, polymethyl methacrylate glue, and AFL glue (e.g., modified acrylic colloidal particle or polyacrylic acid modified colloidal particle).
Furthermore, the auxiliary agent mainly comprises an anti-settling agent, an adhesive, a binder and a wetting agent.
Further, the anti-settling agent includes, but is not limited to, sodium carboxymethyl cellulose; the adhesive is one or more of styrene-butadiene latex, cinnamic acid, polyacrylamide, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, modified paraffin resin, carbomer resin, polyacrylic acid, polyurethane acrylate, polyacrylate copolymer emulsion, polyurethane and carbamate; the binder is an acrylic acid type binder; the wetting agent comprises one or more of organic silicon ether surfactants, anionic surfactants and nonionic surfactants; the anionic surfactant is one or more of alkyl aryl sodium sulfonate, butyl naphthalene sodium sulfonate, hydroxyethyl sodium sulfonate or sodium dodecyl sulfonate; the nonionic surfactant is one or more of long-chain fatty alcohol-polyoxyethylene ether, alkylphenol ethoxylate, polyoxyethylene alkylolamide or fatty alcohol-polyoxyethylene ether.
Further, the base film is one of a PE film and a ceramic coating film.
A preparation method of a lithium ion diaphragm containing a lithium carbonate coating comprises the following steps:
s1, preparing safety coating slurry;
s2, coating the safety coating slurry on the surface of the base film;
and S3, drying the base film obtained in the step S2 at 65-75 ℃ to obtain the lithium ion diaphragm containing the lithium carbonate coating.
Further, the step s1. includes the specific operation processes: adding a high molecular rubber material and lithium carbonate into a kneading machine, carrying out dry mixing and kneading, controlling the stirring speed at 150-.
Further, the coating mode in the step S2 is one of micro-gravure coating, spraying and spot coating; s2, the surface density of the middle coating slurry on the base film is 0.7-0.8g/m2。
The main purpose of the research of the invention is to enable the lithium battery to generate a large amount of gas in advance, trigger a safety mechanism, avoid the problem of overlarge internal voltage of the battery or thermal runaway and improve the safety of the battery.
In order to achieve the above object, the present invention specifically adds lithium carbonate to the lithium ion separator coating layer.
The lithium carbonate is decomposed under the heating condition, and a large amount of gas is generated; the specific reaction process is as follows:
the theoretical decomposition voltage of the lithium carbonate is 3.82V; under the passivation effect of an SEI film of the lithium battery, when the battery is overcharged, once the voltage reaches 4.8V, lithium carbonate in a lithium ion diaphragm starts to decompose; or when the heating temperature in the battery cell is higher than 120 ℃, the SEI film starts to be heated and decomposed to release a large amount of gas, and the safety structure is triggered in advance; because the main inorganic components in the SEI film are lithium carbonate, LiF and other organic alkanes, the SEI film can generate a large amount of gas even under the conditions of low temperature and low pressure due to the existence of the components, and the internal air pressure of the square aluminum-shell battery can quickly reach the critical air pressure value of the safety structural member, so that the early-stage prevention effect of thermal runaway is achieved.
Compared with the prior art, the invention has the following beneficial effects:
1. the coating diaphragm containing the lithium carbonate can quickly provide gas molecules at the early stage of thermal runaway inside the battery, quickens the time of a safety structure reaching critical pressure, and improves the safety performance of the battery.
2. The lithium carbonate contains a large amount of Li in the molecular structure+A source capable of providing Li for SEI film forming process of lithium ion battery+The lithium ion capacity is effectively improved, and the cycle life is prolonged.
3. Lithium carbonate is a precursor of the battery positive electrode material and has no harmful effect on the battery.
4. The special coating diaphragm coating material containing the lithium carbonate component has the advantages of simple preparation process and low cost, can obviously improve the safety of the battery, can realize industrial generation, and has high economic value and practical value.
Drawings
FIG. 1 is a process flow diagram of a lithium ion separator containing a lithium carbonate coating;
FIG. 2 is a graph showing the relationship between the capacity retention rate and the number of cycles of a lithium ion separator battery.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
S1, adding a high-molecular rubber material and lithium carbonate into a kneading machine, carrying out dry mixing and kneading, controlling the stirring speed at 150r/min to obtain mixed rubber, adding an anti-settling agent, an adhesive and water, stirring and wetting, sucking into a sand mill, sanding for 1h, continuously adding a binder and a wetting agent, and stirring and mixing for 10min to obtain the safe coating slurry.
S2, coating the safety coating slurry on the surface of the base film;
and S3, drying the base film obtained in the step S2 at 65 ℃ to obtain the lithium ion diaphragm containing the lithium carbonate coating.
A lithium ion diaphragm containing a lithium carbonate coating mainly comprises a base film and a safety coating coated on the surface of the base film; the safety coating mainly comprises mixed glue, an auxiliary agent and water.
The safe coating comprises the following raw material components in addition: 86 percent of mixed glue, 6.5 percent of auxiliary agent and the balance of water.
The mixed rubber mainly comprises a high-molecular rubber material and lithium carbonate; the addition amount of lithium carbonate in the mixed rubber is 0.5 percent of that of the polymer rubber.
S2, the surface density of the intermediate coating slurry on the base film is 0.7g/m2。
The base film is a PE film.
The polymer sizing material is polyvinylidene fluoride glue.
The auxiliary agent mainly comprises an anti-settling agent, an adhesive, a binder and a wetting agent.
The wetting agent is an alkyl aryl sodium sulfonate anionic surfactant; the anti-settling agent is sodium carboxymethyl cellulose; the adhesive is styrene-butadiene latex.
The proportion of the mixed glue in the safe coating slurry in the embodiment 1 is less than 90% of the amount specified by the invention; the addition amount of lithium carbonate in polyvinylidene fluoride is the minimum value specified in the invention.
And (3) performance testing: the lithium ion diaphragm prepared in the embodiment 1 is assembled into a battery cell, a square aluminum shell assembly mode is adopted for assembly, and the safety performance of the battery is tested after liquid injection and formation. The safety performance test method refers to GB-T31485-.
And (3) testing results:
(1)500 cycle life, capacity retention (1C/1C, 100% DOD): the charge-discharge efficiency of the lithium ion battery is 98.04%.
(2) And (3) overcharging test: the battery is blown out and broken when overcharged voltage is 5.2V, and the battery is not ignited and not exploded; and (3) short-circuiting the lithium ion battery for 10min, wherein the battery is subjected to air blowing, short-circuiting, non-ignition and non-explosion, and the highest temperature is not more than 150 ℃.
In this embodiment, because the polyvinylidene fluoride colloid has a low content in the safety coating and the water content in the safety coating is high, the adhesion of the safety coating to the PE base film is reduced, that is, the load rate of lithium carbonate on the PE base film is low; the lithium ion diaphragm prepared by the embodiment has less gas production in the test process, is difficult to trigger the safety structure in advance, and has poor effect of improving the safety performance of the lithium battery.
Example 2
S1, adding a high-molecular rubber material and lithium carbonate into a kneading machine, carrying out dry mixing and kneading, controlling the stirring speed at 150r/min to obtain mixed rubber, adding an anti-settling agent, an adhesive and water, stirring and wetting, sucking into a sand mill, sanding for 1h, continuously adding a binder and a wetting agent, and stirring and mixing for 10min to obtain the safe coating slurry.
S2, coating the safety coating slurry on the surface of the base film;
and S3, drying the base film obtained in the step S2 at 65 ℃ to obtain the lithium ion diaphragm containing the lithium carbonate coating.
A lithium ion diaphragm containing a lithium carbonate coating mainly comprises a base film and a safety coating coated on the surface of the base film; the safety coating mainly comprises mixed glue, an auxiliary agent and water.
The safe coating comprises the following raw material components in addition: 86 percent of mixed glue, 6.5 percent of auxiliary agent and the balance of water.
The mixed rubber mainly comprises a high-molecular rubber material and lithium carbonate; the addition amount of lithium carbonate in the mixed rubber is 2% of that of the high-molecular rubber material.
S2, the surface density of the intermediate coating slurry on the base film is 0.7g/m2。
The base film is a PE film.
The polymer sizing material is polyvinylidene fluoride glue.
The auxiliary agent mainly comprises an anti-settling agent, an adhesive, a binder and a wetting agent.
The wetting agent is an alkyl aryl sodium sulfonate anionic surfactant; the anti-settling agent is sodium carboxymethyl cellulose; the adhesive is styrene-butadiene latex.
This example differs from example 1 in that the amount of lithium carbonate added to polyvinylidene fluoride in example 2 is the maximum value specified in the scheme of the present invention.
And (3) performance testing: the lithium ion diaphragm prepared in the embodiment 2 is assembled into a battery cell, a square aluminum shell assembly mode is adopted for assembly, and the safety performance of the battery is tested after liquid injection and formation. The safety performance test method refers to GB-T31485-.
And (3) testing results:
(1)500 cycle life, capacity retention (1C/1C, 100% DOD): the charge-discharge efficiency of the lithium ion battery is 98.64 percent.
(2) And (3) overcharging test: the battery is blown out and broken when overcharged voltage is 4.8V, and the battery is not ignited and not exploded; and (3) short-circuiting the lithium ion battery for 10min, wherein the battery is subjected to air blowing, short-circuiting, non-ignition and non-explosion, and the highest temperature is not more than 160 ℃.
In the embodiment, because the polyvinylidene fluoride colloid has a small content in the safety coating and a large amount of water in the safety coating, the adhesion of the safety coating on the PE base film is reduced; in this example, the load rate of lithium carbonate on the PE base film was increased compared to that in example 1, but the overall increase was not large; the lithium ion diaphragm prepared by the embodiment has less gas production in the test process, is difficult to trigger the safety structure in advance, and has poor effect of improving the safety performance of the lithium battery.
Example 3
S1, adding a high-molecular rubber material and lithium carbonate into a kneading machine, carrying out dry mixing and kneading, controlling the stirring speed at 150r/min to obtain mixed rubber, adding an anti-settling agent, an adhesive and water, stirring and wetting, sucking into a sand mill, sanding for 1h, continuously adding a binder and a wetting agent, and stirring and mixing for 10min to obtain the safe coating slurry.
S2, coating the safety coating slurry on the surface of the base film;
and S3, drying the base film obtained in the step S2 at 65 ℃ to obtain the lithium ion diaphragm containing the lithium carbonate coating.
A lithium ion diaphragm containing a lithium carbonate coating mainly comprises a base film and a safety coating coated on the surface of the base film; the safety coating mainly comprises mixed glue, an auxiliary agent and water.
The safe coating comprises the following raw material components in addition: the adhesive comprises, by percentage, 90% of mixed glue, 5.5% of an auxiliary agent and the balance of water.
The mixed rubber mainly comprises a high-molecular rubber material and lithium carbonate; the addition amount of lithium carbonate in the mixed rubber is 0.5 percent of that of the polymer rubber.
S2, the surface density of the intermediate coating slurry on the base film is 0.7g/m2。
The base film is a PE film.
The polymer sizing material is polyvinylidene fluoride glue.
The auxiliary agent mainly comprises an anti-settling agent, an adhesive, a binder and a wetting agent.
The wetting agent is an alkyl aryl sodium sulfonate anionic surfactant; the anti-settling agent is sodium carboxymethyl cellulose; the adhesive is styrene-butadiene latex.
And (3) performance testing: and assembling the lithium ion diaphragm prepared in the embodiment 3 into a battery cell, assembling the battery cell by adopting a square aluminum shell assembly mode, and testing the safety performance of the battery after liquid injection and formation. The safety performance test method refers to GB-T31485-.
And (3) testing results:
(1)500 cycle life, capacity retention (1C/1C, 100% DOD): the charge-discharge efficiency of the lithium ion battery is 99.74 percent.
(2) And (3) overcharging test: the battery is blown out and broken when overcharged voltage is 5.1V, and the battery is not ignited and not exploded; and (3) short-circuiting the lithium ion battery for 10min, wherein the battery is subjected to air blowing, short-circuiting, non-ignition and non-explosion, and the highest temperature is not more than 175 ℃.
Example 4
S1, adding a high-molecular rubber material and lithium carbonate into a kneading machine, carrying out dry mixing and kneading, controlling the stirring speed at 200r/min to obtain mixed rubber, adding an anti-settling agent, an adhesive and water, stirring and wetting, sucking into a sand mill, sanding for 1.5h, continuously adding a binder and a wetting agent, stirring and mixing for 15min, and obtaining the safe coating slurry.
S2, coating the safety coating slurry on the surface of the base film;
and S3, drying the base film obtained in the step S2 at 70 ℃ to obtain the lithium ion diaphragm containing the lithium carbonate coating.
A lithium ion diaphragm containing a lithium carbonate coating mainly comprises a base film and a safety coating coated on the surface of the base film; the safety coating mainly comprises mixed glue, an auxiliary agent and water.
The safe coating comprises the following raw material components in addition: 92 percent of mixed glue, 5.8 percent of auxiliary agent and the balance of water.
The mixed rubber mainly comprises a high-molecular rubber material and lithium carbonate; the addition amount of lithium carbonate in the mixed rubber is 1.0 percent of that of the polymer rubber.
S2, the surface density of the intermediate coating slurry on the base film is 0.75g/m2。
The polymer sizing material is polyvinylidene fluoride glue.
The base film is a PE film.
The mixed glue is polyvinylidene fluoride glue;
the auxiliary agent mainly comprises an anti-settling agent, an adhesive, a binder and a wetting agent.
The wetting agent is an alkyl aryl sodium sulfonate anionic surfactant; the anti-settling agent is sodium carboxymethyl cellulose; the adhesive is styrene-butadiene latex.
And (3) performance testing: the lithium ion diaphragm prepared in the embodiment 4 is assembled into a battery cell, the battery cell is assembled by adopting a square aluminum shell assembly mode, and the safety performance of the battery is tested after liquid injection and formation. The safety performance test method refers to GB-T31485-.
And (3) testing results:
(1)500 cycle life, capacity retention (1C/1C, 100% DOD): the charge-discharge efficiency of the lithium ion battery is 99.59%.
(2) And (3) overcharging test: the battery is blown out and broken when overcharged voltage is 5.0V, and the battery is not ignited and not exploded; and (3) short-circuiting the lithium ion battery for 10min, wherein the battery is subjected to air blowing, short-circuiting, non-ignition and non-explosion, and the highest temperature is not more than 175 ℃.
Example 5
S1, adding a high-molecular rubber material and lithium carbonate into a kneading machine, carrying out dry mixing and kneading, controlling the stirring speed at 250r/min to obtain mixed rubber, adding an anti-settling agent, an adhesive and water, stirring and wetting, sucking into a sand mill, sanding for 2h, continuously adding a binder and a wetting agent, and stirring and mixing for 20min to obtain the safe coating slurry.
S2, coating the safety coating slurry on the surface of the base film;
and S3, drying the base film obtained in the step S2 at 75 ℃ to obtain the lithium ion diaphragm containing the lithium carbonate coating.
A lithium ion diaphragm containing a lithium carbonate coating mainly comprises a base film and a safety coating coated on the surface of the base film; the safety coating mainly comprises mixed glue, an auxiliary agent and water.
The safe coating comprises the following raw material components in addition: 93 percent of mixed glue, 6.5 percent of auxiliary agent and the balance of water.
The mixed rubber mainly comprises a high-molecular rubber material and lithium carbonate; the addition amount of lithium carbonate in the mixed rubber is 2.0 percent of that of the polymer rubber.
S2, the surface density of the intermediate coating slurry on the base film is 0.75g/m2。
The base film is a PE film.
The mixed glue is polyvinylidene fluoride glue;
the auxiliary agent mainly comprises an anti-settling agent, an adhesive, a binder and a wetting agent.
The wetting agent is an alkyl aryl sodium sulfonate anionic surfactant; the anti-settling agent is sodium carboxymethyl cellulose; the adhesive is styrene-butadiene latex.
And (3) performance testing: the lithium ion diaphragm prepared in the embodiment 5 is assembled into a battery cell, the battery cell is assembled by adopting a square aluminum shell assembly mode, and the safety performance of the battery is tested after liquid injection and formation. The safety performance test method refers to GB-T31485-.
And (3) testing results:
(1)500 cycle life, capacity retention (1C/1C, 100% DOD): the charge-discharge efficiency of the lithium ion battery is 99.37%.
(2) And (3) overcharging test: the battery is blown out and broken when overcharged voltage is 4.9V, and the battery does not catch fire or explode; short-circuiting the lithium ion battery for 30min, wherein the battery is aerated, short-circuited, not ignited and not exploded, and the highest temperature is not more than 180 DEG C
In the embodiments 3-5, the addition amounts of the mixed glue, the auxiliary agent and the lithium carbonate are controlled within the requirements of the technical scheme, the charge and discharge efficiency of the prepared lithium ion battery is over 99.0%, the generated gas can trigger a protection mechanism in time to cause power failure, and the safety performance of the battery is greatly improved.
Example 6
S1, adding a high-molecular rubber material and lithium carbonate into a kneading machine, carrying out dry mixing and kneading, controlling the stirring speed at 250r/min to obtain mixed rubber, adding an anti-settling agent, an adhesive and water, stirring and wetting, sucking into a sand mill, sanding for 2h, continuously adding a binder and a wetting agent, and stirring and mixing for 20min to obtain the safe coating slurry.
S2, coating the safety coating slurry on the surface of the base film;
and S3, drying the base film obtained in the step S2 at 75 ℃ to obtain the lithium ion diaphragm containing the lithium carbonate coating. A lithium ion separator comprising a lithium carbonate coating consisting essentially of: a base film and a safety coating coated on the surface of the base film;
a lithium ion diaphragm containing a lithium carbonate coating mainly comprises a base film and a safety coating coated on the surface of the base film; the safety coating mainly comprises mixed glue, an auxiliary agent and water.
The safe coating comprises the following raw material components in addition: 93 percent of mixed glue, 6.5 percent of auxiliary agent and the balance of water.
The mixed rubber mainly comprises a high-molecular rubber material and lithium carbonate; the addition amount of lithium carbonate in the mixed rubber is 5.5% of that of the polymer rubber.
S2, the surface density of the middle coating slurry on the base film is 0.8g/m2。
The base film is a PE film.
The mixed glue is polyvinylidene fluoride glue;
the auxiliary agent mainly comprises an anti-settling agent, an adhesive, a binder and a wetting agent.
The wetting agent is an alkyl aryl sodium sulfonate anionic surfactant; the anti-settling agent is sodium carboxymethyl cellulose; the adhesive is styrene-butadiene latex.
To further test the safety of the lithium ion separator, we increased the addition amount of lithium carbonate in the blend to 5.5% based on the preparation process and parameter settings of reference example 5.
And (3) performance testing: the lithium ion diaphragm prepared in the embodiment 6 is assembled into a battery cell, the battery cell is assembled by adopting a square aluminum shell assembly mode, and the safety performance of the battery is tested after liquid injection and formation. The safety performance test method refers to GB-T31485-.
And (3) testing results:
(1)500 cycle life, capacity retention (1C/1C, 100% DOD): the charge-discharge efficiency of the lithium ion battery is 95.74 percent.
(2) And (3) overcharging test: the battery is blown out and broken when overcharged voltage is 4.7V, and the battery is not ignited and not exploded; and (3) short-circuiting the lithium ion battery for 10min, wherein the battery is subjected to air blowing, short-circuiting, non-ignition and non-explosion, and the highest temperature is not more than 160 ℃.
In the embodiment, because the addition amount of the lithium carbonate in the mixed gel is too high, the gas generated by the lithium ion battery is too much in the testing process, and the performance and the subsequent cycle life of the battery are greatly influenced.
Comparative example:
s1, adding a high-molecular rubber material into a kneading machine, carrying out dry mixing and kneading, controlling the stirring speed at 250r/min to obtain mixed rubber, adding an anti-settling agent, an adhesive and water, stirring and wetting, sucking into a sand mill, sanding for 2 hours, continuously adding a binder and a wetting agent, stirring and mixing for 20 minutes to obtain the safe coating slurry.
S2, coating the safety coating slurry on the surface of the base film;
and S3, drying the base film obtained in the step S2 at 75 ℃ to obtain the lithium ion diaphragm.
A lithium ion diaphragm mainly comprises a base film and a safety coating coated on the surface of the base film; the safety coating mainly comprises mixed glue, an auxiliary agent and water.
The safe coating comprises the following raw material components in addition: 93 percent of mixed glue, 6.5 percent of auxiliary agent and the balance of water.
S2, the surface density of the middle coating slurry on the base film is 0.8g/m2。
The mixed rubber mainly comprises a high-molecular rubber material;
the base film is a PE film.
The mixed glue is polyvinylidene fluoride glue;
the auxiliary agent mainly comprises an anti-settling agent, an adhesive, a binder and a wetting agent.
The wetting agent is an alkyl aryl sodium sulfonate anionic surfactant; the anti-settling agent is sodium carboxymethyl cellulose; the adhesive is styrene-butadiene latex.
The comparative example differs from example 5 in that lithium carbonate is not included in the safety coating slurry.
And (3) performance testing: assembling the lithium ion diaphragm prepared by the comparative example into a battery cell, assembling by adopting a square aluminum shell assembling mode, and testing the safety performance of the battery after liquid injection and formation. The safety performance test method refers to GB-T31485-2015 safety requirements and test methods for power storage batteries for electric vehicles.
And (3) testing results:
(1)500 cycle life, capacity retention (1C/1C, 100% DOD): the charge-discharge efficiency of the lithium ion battery is 97.99%.
(3) And (3) overcharging test: the battery is blown out and broken when overcharged voltage is 5.4V, and the battery is not ignited and not exploded; and (3) short-circuiting the lithium ion battery for 10min, wherein the battery is subjected to air blowing, short-circuiting, non-ignition and non-explosion, and the highest temperature is not higher than 110 ℃.
According to the attached figure 2, the cycle life of the lithium battery can be improved to a certain extent by adding the lithium carbonate, and the cycle life of the lithium battery cannot be influenced.
From the above data and experiments, we can conclude that:
1. the coating diaphragm containing the lithium carbonate can quickly provide gas molecules at the early stage of thermal runaway inside the battery, quickens the time of a safety structure reaching critical pressure, and improves the safety performance of the battery.
2. The lithium carbonate molecular structure contains a large amount of Li + sources, and the Li + sources can be provided for the SEI film forming process of the lithium ion battery, so that the lithium ion capacity is effectively improved, and the cycle life is prolonged.
3. Lithium carbonate is a precursor of the battery positive electrode material and has no harmful effect on the battery.
4. The special coating diaphragm coating material containing the lithium carbonate component has the advantages of simple preparation process and low cost, can obviously improve the safety of the battery, can realize industrial generation, and has high economic value and practical value.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A lithium ion diaphragm containing a lithium carbonate coating is characterized by mainly comprising
A base film and a safety coating coated on the surface of the base film;
the safety coating mainly comprises mixed glue, an auxiliary agent and water.
2. The lithium ion separator comprising a lithium carbonate coating according to claim 1, wherein: the safe coating comprises the following raw material components in addition: by percentage, 90-93% of mixed glue, 5.5-6.5% of auxiliary agent and the balance of water.
3. The lithium ion separator comprising a lithium carbonate coating according to claim 1, wherein: the mixed rubber mainly comprises a high-molecular rubber material and lithium carbonate; the addition amount of lithium carbonate in the mixed rubber is 0.5-2% of that of the polymer rubber.
4. The lithium ion separator comprising a lithium carbonate coating according to claim 2, wherein: the polymer sizing material is polyvinylidene fluoride glue.
5. The lithium ion separator comprising a lithium carbonate coating according to claim 1, wherein: the auxiliary agent mainly comprises an anti-settling agent, an adhesive, a binder and a wetting agent.
6. The lithium ion separator comprising a lithium carbonate coating according to claim 5, wherein: the anti-settling agent is sodium carboxymethyl cellulose; the adhesive is one or more of styrene-butadiene latex, cinnamic acid, polyacrylamide, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene oxide, modified paraffin resin, carbomer resin, polyacrylic acid, polyurethane acrylate, polyacrylate copolymer emulsion, polyurethane and carbamate; the binder is an acrylic acid type binder; the wetting agent comprises one or more of organic silicon ether surfactants, anionic surfactants and nonionic surfactants; the anionic surfactant is one or more of alkyl aryl sodium sulfonate, butyl naphthalene sodium sulfonate, hydroxyethyl sodium sulfonate or sodium dodecyl sulfonate; the nonionic surfactant is one or more of long-chain fatty alcohol-polyoxyethylene ether, alkylphenol ethoxylate, polyoxyethylene alkylolamide or fatty alcohol-polyoxyethylene ether.
7. The lithium ion separator comprising a lithium carbonate coating according to claim 1, wherein: the base film is one of a PE film and a ceramic coating film.
8. A preparation method of a lithium ion diaphragm containing a lithium carbonate coating is characterized by comprising the following steps:
s1, preparing safety coating slurry;
s2, coating the safety coating slurry on the surface of the base film;
and S3, drying the base film obtained in the step S2 at 65-75 ℃ to obtain the lithium ion diaphragm containing the lithium carbonate coating.
9. The method of claim 8, wherein the lithium ion separator comprises a lithium carbonate coating layer, and the method comprises: the step S1. the specific operation process is as follows: adding a high molecular rubber material and lithium carbonate into a kneading machine, carrying out dry mixing and kneading, controlling the stirring speed at 150-.
10. The method of claim 8, wherein the lithium ion separator comprises a lithium carbonate coating layer, and the method comprises: the coating mode in the step S2 is one of micro-gravure coating, spraying and spot coating; s2, the surface density of the middle coating slurry on the base film is 0.7-0.8g/m2。
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114024092A (en) * | 2021-11-09 | 2022-02-08 | 江苏厚生新能源科技有限公司 | Ice crystallization induced self-assembly porous coating diaphragm and preparation process thereof |
| CN114267924A (en) * | 2021-12-17 | 2022-04-01 | 蜂巢能源科技股份有限公司 | Lithium ion battery diaphragm, lithium ion battery and power device |
-
2021
- 2021-01-29 CN CN202110125410.9A patent/CN112952291A/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114024092A (en) * | 2021-11-09 | 2022-02-08 | 江苏厚生新能源科技有限公司 | Ice crystallization induced self-assembly porous coating diaphragm and preparation process thereof |
| CN114267924A (en) * | 2021-12-17 | 2022-04-01 | 蜂巢能源科技股份有限公司 | Lithium ion battery diaphragm, lithium ion battery and power device |
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