CN115051113A - Lithium battery diaphragm with high safety performance and lithium iron phosphate battery for communication base station - Google Patents

Lithium battery diaphragm with high safety performance and lithium iron phosphate battery for communication base station Download PDF

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CN115051113A
CN115051113A CN202210705647.9A CN202210705647A CN115051113A CN 115051113 A CN115051113 A CN 115051113A CN 202210705647 A CN202210705647 A CN 202210705647A CN 115051113 A CN115051113 A CN 115051113A
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polyolefin film
metal layer
copper metal
battery
lithium
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蔡海龙
刘祥哲
聂慧丽
马永岗
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Yueyang Yaoning New Energy Technology Co Ltd
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Yueyang Yaoning New Energy Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/457—Separators, membranes or diaphragms characterised by the material having a layered structure comprising three or more layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/497—Ionic conductivity
    • 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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  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
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  • Inorganic Chemistry (AREA)
  • Materials Engineering (AREA)
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Abstract

The invention relates to the technical field of lithium batteries, and discloses a lithium battery diaphragm with high safety performance, which comprises two polyolefin film layers and a copper metal layer arranged between the two polyolefin film layers, wherein the thickness of the copper metal layer is smaller than that of a single polyolefin film layer, the copper metal layer is deposited on one of the polyolefin film layers through a physical deposition method, and heat and slight short-circuit current generated inside a battery can be timely dispersed and released through the quick heat dissipation and good conductivity of the copper metal layer, so that the thermal runaway inside the battery is avoided, the safety performance and the cycle performance of the lithium battery are improved, and the prepared lithium iron phosphate battery can better meet the use requirements of a communication base station.

Description

Lithium battery diaphragm with high safety performance and lithium iron phosphate battery for communication base station
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a high-safety lithium battery diaphragm and a lithium iron phosphate battery for a communication base station.
Background
The number of domestic communication base stations reaches 996 ten thousand in 2021, and still keeps a high-speed increasing trend, and a large amount of energy storage batteries are required to be used for providing energy supply. The communication base station has the main functions of signal transmission, when the base station causes signal interruption due to battery performance faults such as fire, serious loss is brought, and if signals transmitted by the base station are serviced by military industry, bank information or public security systems, huge compensation and important information loss in the order of tens of millions of times are faced each second, so that the communication base station has high requirements on the safety performance and the cycle performance of the energy storage battery, the service life of a conventional calendar is more than or equal to 10 years, and the cycle number is more than or equal to 4500 times.
Based on safety performance considerations, the energy storage batteries used by communication base stations are mainly lead-acid batteries. However, lead-acid batteries have the disadvantages of short service life, low performance, large content of heavy metal lead and the like, and cause secondary pollution to the environment if the lead-acid batteries are not properly treated after being discarded. Since 2015, iron tower companies in China began to adopt echelon lithium ion batteries or lithium batteries for energy storage to replace lead-acid batteries, and completely stopped purchasing the lead-acid batteries in 2018, so that the lead-acid batteries bring about billions of market capacity to the lithium battery market.
The lithium ion battery has the advantages of high energy density, long cycle life, no memory effect and the like, and is applied to the fields of new energy automobiles, energy storage equipment and the like. However, the lithium ion battery has higher activity than the lead-acid battery, so the safety performance of the lithium ion battery is much lower than that of the lead-acid battery, and safety accidents such as fire, explosion and the like are more likely to occur. The safety accident of the lithium battery is mainly caused by thermal runaway caused by internal short circuit of the battery. The separator is one of the key components of the lithium ion battery, and directly influences the capacity, safety performance and cycle performance of the battery. The common internal short circuit of the battery is caused by the fact that lithium dendrite pierces a diaphragm, chemical energy of the battery after short circuit is rapidly converted into heat energy and cannot be rapidly released to the surface of a battery core, so that the internal energy of the battery core is overstocked, and fire or even explosion occurs. And the common diaphragm is mainly polyolefin diaphragm such as polyethylene, polypropylene and the like, and also has the defects of poor thermal stability, poor voltage resistance, poor battery cycle performance and the like, thereby affecting the performance of the lithium battery. Chinese patent No. cn201710074882.x discloses a lithium ion battery, wherein heat-resistant coatings with stable chemical properties are respectively disposed on two sides of a diaphragm, so that when a slight short circuit occurs, a short circuit contact point is a heat-resistant coating, and a thermal runaway phenomenon can be avoided within a certain range. But when the thermal effect exceeds the tolerance range of the heat-resistant coating, thermal runaway will inevitably occur.
For the above reasons, the current lithium battery cannot fully meet the safe use requirement of the communication base station.
Disclosure of Invention
Aiming at the problems that the current lithium battery diaphragm is poor in thermal stability and is easy to generate thermal runaway after being punctured and short-circuited, the invention aims to provide the lithium battery diaphragm with high safety performance, which can rapidly dissipate heat and disperse current, protect a battery core, improve the safety performance of the lithium battery and meet the application of the lithium battery on a communication base station.
The invention also aims to provide a lithium iron phosphate battery for the communication base station, which has higher safety performance and is suitable for the communication base station.
The invention provides the following technical scheme:
a lithium battery diaphragm with high safety performance comprises two polyolefin film layers and a copper metal layer arranged between the two polyolefin film layers, wherein the thickness of the copper metal layer is smaller than that of a single polyolefin film layer, and the copper metal layer is deposited on one of the polyolefin film layers through a physical deposition method.
The lithium battery diaphragm comprises conventional polyolefin film layers, wherein the polyolefin film layers can be polyethylene films, polypropylene films and the like, the preferred single-layer thickness is 3-5 mu m, a copper metal layer is deposited on the surface of one polyolefin film layer through a physical deposition method, and the thickness of the copper metal layer is smaller than that of the single polyolefin film layer, preferably 1-2 mu m. The physical deposition method can select a relatively common magnetron sputtering method, a vacuum coating method or an ion coating method and the like, and can realize single-sided deposition. The copper metal layer has higher strength, and more importantly, the copper metal layer has excellent heat-conducting property and electric conductivity. When slight internal short circuit or puncture occurs in the battery core of the lithium battery, after the diaphragm layer is punctured, short circuit current and heat can be instantly dissipated by the copper metal layer, so that the battery core is protected, explosion caused by thermal runaway of the battery core is avoided, and the safety performance of the battery core is improved.
As the optimization of the invention, the copper metal layer comprises 2n +1 sub-layers, n is a natural number, when n is larger than or equal to 1, the thickness of the sub-layers from two sides to the middle is gradually increased, and the deposition rate of copper forming the sub-layers is gradually increased. The copper metal layer is arranged into odd number of sublayers, the thickness of the middle sublayers is controlled to be the largest, the deposition rate of copper is controlled to be the largest, the bending stress generated by the copper metal layer when the diaphragm is wound is increased from two sides to the middle in a gradient mode, so that the bending stress on the two sides is smaller, the diaphragm is not easy to break or fall off from the diaphragm, the bending stress in the middle of the diaphragm can be buffered and released outwards, and the stability of the copper metal layer is improved. Even if the intermediate layer is slightly cracked due to excessive stress, the state of the surface is not affected.
Preferably, n is 1 or 2. The deposition difficulty is increased by setting the number of the sub-layers to be too large, and the practical number of the layers is 3 or 5, and the 3 is more preferable.
Preferably, the physical deposition method is a magnetron sputtering method, and the magnetron sputtering process is as follows: taking copper as a target material, placing a polyolefin film in a magnetron sputtering chamber, wherein the distance between the polyolefin film and the target material is 60-100 mm, and vacuumizing to 5 multiplied by 10 - 4 Pa～8×10 -4 Pa, then introducing sputtering atmosphere with the air inlet rate of 20-40 mL/min, adjusting the sputtering working pressure to 0.5-2.0 Pa, the sputtering power to 20-80W and the voltage to 100-300V. The magnetron sputtering can be realized at low temperature, and is friendly to the polyolefin film. The deposition rate of copper atoms and the thickness of a magnetron sputtering layer can be regulated and controlled by controlling sputtering power, the distance between a target material and a substrate, working air pressure, time and the like, and the sputtering time for obtaining a copper metal layer with the thickness of 1-2 mu m is 5-40 min under the working conditions.
Preferably, the sputtering atmosphere is argon.
Preferably, a buffer coating is further arranged between the copper metal layer and the polyolefin film layer, and the buffer coating is coated on the surface of the polyolefin film layer and comprises the following components in parts by weight:
10-20 parts of polymer of dimethyl (siloxane and polysiloxane) and phenyl silsesquioxane, 3-8 parts of isopropyl n-silicate, 2-5 parts of tetra (2-methoxyethoxy) silane, 0.5-1 part of tetrabutyl titanate and 80-100 parts of diluent.
The buffer film layer is a silicon resin film layer, so that the adhesive force of the copper metal layer on the polyolefin film layer can be increased, more importantly, the good flexibility and elasticity of the silicon resin layer can endow the copper metal layer with bending flexibility, and the copper metal layer is easier to wind and bend.
Preferably, the diluent is n-hexane or petroleum ether.
Preferably, the outer side surfaces of the two polyolefin film layers are sequentially provided with a ceramic coating and a polyvinylidene fluoride coating.
The ceramic coating and the polyvinylidene fluoride coating can be coated in a roll coating mode, the thickness of the ceramic coating is 0.7-1 mu m, so that the thermal stability and the mechanical capacity of the diaphragm are guaranteed, the coating thickness of the polyvinylidene fluoride coating is 1-2 mu m, the coating of the polyvinylidene fluoride can effectively guarantee the bonding capacity between the diaphragm and a pole piece, and rebound space and stress release are provided for long-term circulation of the battery.
A lithium iron phosphate battery comprising the lithium battery diaphragm. The lithium iron phosphate battery has the advantages in service life, can meet the requirement of the market on the 10-year service life (calendar) of the battery, and has higher safety performance and cycle performance by using the lithium battery diaphragm on the basis, so that the lithium iron phosphate battery can meet the use requirement of a communication base station.
As a preferred aspect of the present invention,
coating an aerosol layer on the surface of a shell of the lithium iron phosphate battery;
the thickness of the aerosol layer is 0.2-0.3 mm, wherein the aerosol layer is a solid fire extinguishing agent which mainly comprises N 2 A small amount of CO 2 And metal salt solid particles, which are conventional products in the market. When the thermal runaway occurs in the battery core, the gas sol layer can effectively prevent the heat of the battery coreAnd (4) diffusion.
The invention has the following beneficial effects:
according to the lithium battery diaphragm provided by the invention, through the rapid heat dissipation and good conductive capability of the copper metal layer, heat and slight short-circuit current generated inside the battery can be dispersed and released in time, thermal runaway inside the battery is avoided, the safety performance and the cycle performance of the lithium battery are improved, and the prepared lithium iron phosphate battery can better meet the use requirements of a communication base station.
Drawings
Fig. 1 is a structural view of a lithium battery separator of example 1.
Fig. 2 is a structural view of a lithium battery separator of example 5.
In the figure, 1, a polyethylene film layer, 2, a copper metal layer, 3, an alumina ceramic coating, 4, a polyvinylidene fluoride coating, 5 and a buffer coating.
Detailed Description
The following further describes the embodiments of the present invention.
The starting materials used in the present invention are commercially available or commonly used in the art, unless otherwise specified, and the methods in the following examples are conventional in the art, unless otherwise specified.
The lithium battery diaphragm with high safety performance comprises two polyolefin film layers and a copper metal layer arranged between the two polyolefin film layers, wherein the polyolefin film layers are polyethylene film layers or polypropylene film layers, the thickness of the copper metal layer is smaller than that of a single polyolefin film layer, and the copper metal layer is deposited on one of the polyolefin film layers through a physical deposition method. The relatively thin copper metal layer facilitates adhesion of the copper metal layer to the polyolefin film layer and also facilitates avoidance of handling bending cracks or peeling during winding bending.
In the embodiment of the invention, the copper metal layer can be arranged into a plurality of sub-layers, the thicknesses or deposition rates are different, the deposition rate and the thicknesses influence the compactness, and the larger the deposition rate is, the larger the compactness is. The dispersion effect of the bending stress changes along with the change of the arrangement mode of the sub-layers, under certain arrangement conditions, for example, the density gradually increases when a polyolefin film layer attached to the copper metal layer is transited to another polyolefin film layer, the improvement effect is not outstanding, and for example, when the thickness is only gradually increased, the adverse phenomena of bending cracks and the like also occur at the thickest sub-layer, but the overall effect is still better than that of the non-copper metal layer.
In the embodiment of the present invention, a more preferable scheme for disposing the sublayers of the copper metal layer is to dispose 2n +1 sublayers, where n is a natural number, for example, n is 1 or 2; when n is larger than or equal to 1, the thickness of the sub-layer from two sides to the middle is gradually increased, and the deposition rate of copper forming the sub-layer is gradually increased, so that the stress dispersion during bending is more prominent.
In the embodiment of the invention, a magnetron sputtering method is adopted to deposit a copper metal layer on the surface of the polyolefin film layer, and the magnetron sputtering process is as follows: taking copper as a target material, placing a polyolefin film in a magnetron sputtering chamber, wherein the distance between the polyolefin film and the target material is 60-100 mm, and vacuumizing to 5 multiplied by 10 -4 Pa～8×10 -4 Pa, then introducing sputtering atmosphere with the air inlet rate of 20-40 mL/min, adjusting the sputtering working pressure to 0.5-2.0 Pa, the sputtering power to 20-80W, the voltage to 100-300V, and sputtering for 5-40 min; an alternative sputtering atmosphere is 99.999% high purity argon.
In the embodiment of the invention, a buffer coating is further arranged between the copper metal layer and the polyolefin film layer, and the buffer coating is coated on the surface of the polyolefin film layer and comprises the following components in parts by weight:
10-20 parts of polymer of dimethyl (siloxane and polysiloxane) and phenyl silsesquioxane, 3-8 parts of isopropyl n-silicate, 2-5 parts of tetra (2-methoxyethoxy) silane, 0.5-1 part of tetrabutyl titanate and 80-100 parts of diluent, wherein the diluent is n-hexane or petroleum ether.
The buffer coating can be arranged on the polyolefin film layer in advance by means of spraying or rolling coating, and then the copper metal layer is deposited.
In the embodiment of the invention, the outer side surfaces of the two polyolefin film layers are further provided with a ceramic coating and a polyvinylidene fluoride coating in sequence. The ceramic coating and the polyvinylidene fluoride coating may be provided via roll coating.
Further, the invention provides a lithium iron phosphate battery comprising the lithium battery diaphragm.
In the embodiment of the invention, the surface of the shell of the lithium iron phosphate battery is coated with an aerosol layer;
the thickness of the aerosol layer is 0.2-0.3 mm.
Example 1
The utility model provides a lithium battery diaphragm of high security performance, as shown in figure 1, by two-layer polyethylene rete 1 with set up the copper metal level 2 between two polyolefin rete and constitute, the thickness of two single polyethylene rete is 3.5 mu m, the lateral surface of two polyethylene rete still is equipped with alumina ceramic coating 3 and polyvinylidene fluoride coating 4 in proper order, thickness is 0.7 mu m, 1 mu m in proper order, the copper metal level passes through the deposition of magnetron sputtering method on one of them polyolefin rete, the magnetron sputtering process is as follows:
taking copper as a target material, placing a polyolefin film in a magnetron sputtering chamber, wherein the distance between the polyolefin film and the target material is 80mm, and vacuumizing to 5 multiplied by 10 -4 Pa, then introducing argon with the purity of 99.999 percent, regulating the gas inlet rate to be 30mL/min, regulating the sputtering working pressure to be 1.0Pa, the sputtering power to be 60W, and the working voltage to be 200V, and controlling the sputtering time to ensure that the thickness of the copper metal layer is 1.2 mu m.
Example 2
The lithium battery diaphragm with high safety performance is different from the embodiment 1 in that a copper metal layer consists of three sublayers with the thicknesses of 200nm, 400nm and 600nm from an attached polyethylene film layer to the outside, and in the corresponding magnetron sputtering deposition process, the distance between a target and the polyolefin film layer and the sputtering power are as follows in sequence: 100mm/40W, 80mm/60W and 60 mm/80W.
Example 3
The lithium battery diaphragm with high safety performance is different from the embodiment 1 in that a copper metal layer consists of three sublayers with the thickness of 400nm from an attached polyethylene film layer to the outside, and in the corresponding magnetron sputtering deposition process, the distance between a target and a polyolefin film layer and the sputtering power are as follows in sequence: 100mm/40W, 80mm/60W and 60 mm/80W.
Example 4
The lithium battery diaphragm with high safety performance is different from the embodiment 1 in that a copper metal layer consists of three sublayers with the thicknesses of 300nm, 600nm and 300nm from an attached polyethylene film layer to the outside, and in the corresponding magnetron sputtering deposition process, the distance between a target and the polyolefin film layer and the sputtering power are as follows in sequence: 100/40mm, 60mm/80 and 100 nm/40.
Example 5
A lithium battery diaphragm with high safety performance is different from that of the embodiment 1 in that as shown in figure 2, a buffer coating 5 is further arranged between a copper metal layer and two polyethylene film layers, the buffer coating is obtained by coating a spray gun on the polyethylene film layers at 0.3MPa and placing for 1h for solidification, and the spray density is 1g/m 2 The coating thickness is 1.5 mu m and consists of the following components in parts by weight:
10 parts of polymer of dimethyl (siloxane and polysiloxane) and phenyl silsesquioxane (CAS: 73138-88-2), 3 parts of isopropyl n-silicate, 2 parts of tetra (2-methoxyethoxy) silane (CAS: 2157-45-1), 0.5 part of tetrabutyl titanate and 80 parts of normal hexane.
Example 6
A lithium battery diaphragm with high safety performance is different from that of the embodiment 1 in that a buffer coating is further arranged between a copper metal layer and two polyethylene film layers as shown in figure 2, the buffer coating is obtained by coating a spray gun on the polyethylene film layers at 0.3MPa and placing for 1h for solidification, and the spray density is 1g/m 2 The coating thickness is 1.5 mu m and consists of the following components in parts by weight:
20 parts of a polymer of dimethyl (siloxane and polysiloxane) and phenyl silsesquioxane (CAS: 73138-88-2), 8 parts of isopropyl n-silicate, 5 parts of tetra (2-methoxyethoxy) silane (CAS: 2157-45-1), 1 part of tetrabutyl titanate and 100 parts of n-hexane.
Comparative example 1
The difference from example 1 is that there is no copper metal layer.
Comparative example 2
The difference from example 1 is that the thickness of the copper metal layer is 4 μm.
Comparative example 3
The difference from the embodiment 1 is that polyvinylidene fluoride bonding layers are respectively arranged between the copper metal layer and the two polyethylene film layers, and the thickness of the bonding layer is 1.5 mu m.
The lithium iron phosphate batteries prepared in the above examples and comparative examples were respectively wound in a positive-diaphragm-negative manner to obtain lithium iron phosphate batteries, and the safety performance and cycle performance of the diaphragms and the lithium iron phosphate batteries were tested, and in order to maintain consistency, the lithium iron phosphate batteries were as follows: (1) positive plate: the aluminum foil is used as a substrate, and PTC heat-sensitive coatings (the mass composition is that polyvinylidene fluoride and PTC material are 8:92, and PTC is barium titanate) are coated on two sides of the aluminum foil substrate; the positive active material is a lithium iron phosphate material (the grain diameter D50 is less than or equal to 3um), the capacity is 142mAh/g @0.5C @25 ℃, and the compaction density is 2.3g/cm 3 The coating surface density is 350 g/square meter, the mass proportion of the lithium iron phosphate in the positive formula is 95%, the conductive agent is carbon black conductive agent 3%, and the binder is polyvinylidene fluoride 2%; coating an aluminum oxide coating layer with the thickness of 1 mu m on the surface of the positive plate (polyvinylidene fluoride: aluminum oxide: 12: 88);
(2) and (3) negative plate: the negative active material is graphite, the capacity of the negative active material is 350mAh/g, the particle size is 12-16 um, and the compaction density is 1.55g/cm 3 The coating surface density of the negative electrode is 200 g/square meter, and the thickness is 6 mu m;
(3) electrolyte solution: ethylene carbonate and ethyl methyl carbonate (mass ratio is 1:1), lithium hexafluorophosphate concentration is 1.3mol/L, and 0.5 wt% of trimethyl phosphate and 0.5 wt% of diphenyl neo-phosphate are added;
(4) a housing: and (4) an aluminum shell.
The safety performance and cycle performance test indexes are as follows:
(1) battery needling experiment: according to the method, 5 samples in each group are obtained by referring to 6.2.8 parts, phi 5mm steel needles and a cone angle of 45 degrees in GB/T31485-2015, penetrating a battery cell at a speed of 25mm/s, and observing for 1 hour until the phenomena of fire, smoke, explosion and the like do not appear;
(2) the heat resistance of the battery is as follows: after charging, the battery cell does not burn and explode under the environment of 200 ℃ for +1h, and each group comprises 5 samples; (3) the battery cycle performance is as follows: and (3) carrying out a 1C/1C full-filling and discharging cycle test on the battery at a constant normal temperature and 25 ℃, stopping the test when the capacity reaches 80% of the initial capacity, and calculating the cycle times, wherein each group contains 3 samples.
The test results are shown in table 1.
Table 1 performance of lithium iron phosphate batteries prepared by separators of examples and comparative examples
Figure BDA0003705200990000061
Figure BDA0003705200990000071
As can be seen from the above table, in the case that the initial capacities of the batteries are similar, the lithium battery provided in example 1 has a 80% passing rate in the needle punching test, and the passing amplitude is greatly increased, and the cycle number is maintained at 4500 or more. Compared with the embodiment 1, the embodiment 2 has the advantages that the bending stress of the copper metal layer and the polyolefin contact outer layer is strengthened, the cycle number is reduced, compared with the embodiment 1, the probability of passing the needle punching test is not obviously improved in the embodiment 3, but the average cycle number is slightly improved, and the stability of the battery in the same batch is improved. Compared with the embodiment 1, the safety performance and the cycle performance of the embodiment 4 are obviously improved. As can be seen from the comparison between examples 5 and 6 and example 1, the improvement of the average cycle performance is not significant, but the stability of the battery is improved, and the needle penetration test passing rate is further improved. As can be seen from comparison of comparative example 2 with example 1, when the thickness of the copper metal layer is excessively large, the performance of the separator is rather lowered. It can be seen from comparison among comparative example 3, example 1 and example 5 that, when the buffer coating is replaced by the polyvinylidene fluoride layer, the basic performance of the battery is not obviously improved, and we analyze that the polyvinylidene fluoride bonding layer only provides bonding force compared with the buffer coating in example 5, and has little influence on the bending stress relief of the copper metal layer.

Claims (10)

1. A lithium battery diaphragm with high safety performance is characterized in that,
the polyolefin film comprises two polyolefin film layers and a copper metal layer arranged between the two polyolefin film layers, wherein the thickness of the copper metal layer is smaller than that of a single polyolefin film layer, and the copper metal layer is deposited on one of the polyolefin film layers by a physical deposition method.
2. The lithium battery separator as claimed in claim 1, wherein the copper metal layer includes 2n +1 sublayers, n is a natural number, and when n ≧ 1, the thickness of the sublayers from both sides to the middle gradually increases, and the deposition rate of copper forming the sublayers gradually increases.
3. The lithium battery separator according to claim 2, wherein n is 1 or 2.
4. The lithium battery separator according to claim 1, 2 or 3, wherein the physical deposition method is a magnetron sputtering method, and the magnetron sputtering process is as follows: taking copper as a target material, placing a polyolefin film in a magnetron sputtering chamber, wherein the distance between the polyolefin film and the target material is 60-100 mm, and vacuumizing to 5 multiplied by 10 -4 Pa～8×10 -4 Pa, then introducing sputtering atmosphere, and adjusting the sputtering working pressure to be 0.5-2.0 Pa and the sputtering power to be 20-80W.
5. The lithium battery separator according to claim 4, wherein the sputtering atmosphere is argon gas.
6. The lithium battery diaphragm of claim 1, wherein a buffer coating is further arranged between the copper metal layer and the polyolefin film layer, and the buffer coating is coated on the surface of the polyolefin film layer and comprises the following components in parts by weight:
10-20 parts of polymer of dimethyl (siloxane and polysiloxane) and phenyl silsesquioxane, 3-8 parts of isopropyl n-silicate, 2-5 parts of tetra (2-methoxyethoxy) silane, 0.5-1 part of tetrabutyl titanate and 80-100 parts of diluent.
7. The lithium battery separator according to claim 6, wherein the diluent is n-hexane or petroleum ether.
8. The lithium battery separator according to claim 1, wherein the outer side surfaces of the two polyolefin film layers are sequentially provided with a ceramic coating layer and a polyvinylidene fluoride coating layer.
9. A lithium iron phosphate battery comprising a lithium battery separator as claimed in any one of claims 1 to 8.
10. The lithium iron phosphate battery of claim 9,
coating an aerosol layer on the surface of a shell of the lithium iron phosphate battery;
the thickness of the aerosol layer is 0.2-0.3 mm.
CN202210705647.9A 2022-06-21 2022-06-21 Lithium battery diaphragm with high safety performance and lithium iron phosphate battery for communication base station Pending CN115051113A (en)

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CN105161661A (en) * 2015-10-14 2015-12-16 中航锂电（洛阳）有限公司 Composite diaphragm for lithium ion battery, preparation method of composite diaphragm, and lithium ion battery
CN105226226A (en) * 2015-09-22 2016-01-06 东莞市爱思普能源科技有限公司 A kind of lithium ion battery separator and the method with its monitoring battery short circuit
CN110707267A (en) * 2018-07-10 2020-01-17 中国科学院大连化学物理研究所 Composite diaphragm for alkali metal battery and preparation and application thereof
CN111244371A (en) * 2020-01-19 2020-06-05 青岛国轩电池有限公司 Lithium iron phosphate battery cell, high-energy-density lithium iron phosphate battery and preparation method of battery
CN112534635A (en) * 2018-05-10 2021-03-19 赛尔格有限责任公司 Microlayer membranes, battery separators, batteries, and related methods

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CN104269506A (en) * 2014-10-24 2015-01-07 深圳市星源材质科技股份有限公司 Method and device for preparing composite diaphragm of lithium battery in multilayer co-extrusion coating way
CN105226226A (en) * 2015-09-22 2016-01-06 东莞市爱思普能源科技有限公司 A kind of lithium ion battery separator and the method with its monitoring battery short circuit
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