CN114709396A - High-rate and low-temperature high-specific-energy lithium ion battery - Google Patents

High-rate and low-temperature high-specific-energy lithium ion battery Download PDF

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CN114709396A
CN114709396A CN202210390263.2A CN202210390263A CN114709396A CN 114709396 A CN114709396 A CN 114709396A CN 202210390263 A CN202210390263 A CN 202210390263A CN 114709396 A CN114709396 A CN 114709396A
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lithium ion
ion battery
lithium
electrolyte
parts
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CN114709396B (en
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朱敏
朱罗泉
江剑兵
唐垒
朱阳
姜帆
连攀
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Hunan Mengda New Energy Materials Co ltd
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    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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Abstract

The invention discloses a high-rate and low-temperature high-specific energy lithium ion battery, which comprises a positive electrode, a negative electrode, a current collector, a diaphragm and electrolyte, wherein the positive electrode is connected with the current collector; the active material of the positive electrode consists of nickel cobalt aluminum and lithium nickel cobalt manganese oxide, the negative electrode comprises intermediate carbon microsphere graphite and a composite silicon carbon material, and the electrolyte consists of a solute, a solvent and an additive, wherein the solute is lithium hexafluorophosphate, the solvent is a mixed solution consisting of ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, linear carboxylic ester and tetrafluoropropyl ether, and the additive is at least 3 selected from fluoroethylene carbonate, lithium tetrafluoroborate, lithium difluoro (oxalate) borate and propane sultone. According to the invention, through the synergistic effect of the positive electrode, the negative electrode, the current collector, the diaphragm and the electrolyte, the low-temperature rate type lithium ion battery has excellent discharge performance in a low-temperature environment.

Description

High-rate and low-temperature high-specific-energy lithium ion battery
Technical Field
The invention discloses a high-rate and low-temperature high-specific energy lithium ion battery, and belongs to the technical field of lithium ion preparation.
Background
Compared with the traditional storage battery, the lithium ion storage battery has the advantages of high specific energy, long service life, high voltage, low self-discharge rate, no memory effect and the like, so that the lithium ion storage battery becomes the main power supply of the third generation after the cadmium-nickel and hydrogen-nickel storage battery. Previous research on lithium ions has focused on cycle performance and safety performance. However, as the application field is continuously expanded, the low-temperature performance of the lithium ion battery becomes one of the bottlenecks that restrict the development of the lithium ion battery. The traditional lithium ion battery has the working temperature of-20 to +55 ℃, but in the fields of aerospace, war industry, electric vehicles and the like, the battery is required to normally work at the temperature of-40 ℃ 1, and the battery is required to have higher specific energy and stronger environmental adaptability. Therefore, it is very significant to improve the low temperature performance of the lithium ion battery while considering both high rate and specific energy and environmental suitability.
The temperature has an important influence on the lithium ion battery, the performance of the lithium ion battery is reduced due to the excessively low temperature, the lithium ion battery cannot work normally, the phenomenon of lithium precipitation of a negative electrode is caused due to the low-temperature charging, the capacity of the battery is rapidly reduced, and even the short circuit of the positive electrode and the negative electrode is caused under the extreme condition. The characteristics of the lithium ion power battery are relatively obviously influenced by the ambient temperature, the energy and power of the lithium ion power battery are seriously reduced when the practical ambient temperature is low, and the service life of the lithium ion power battery is shortened if the lithium ion power battery is used at the temperature for a long time. The sharp increase of internal resistance of low-temperature charge migration is the main reason of the decline of power performance of the power battery. Specifically, first, the performance of the lithium ion battery in a low temperature environment is related to the electrolyte therein. If the temperature is lower, the conductivity of the electrolyte is reduced, and the environment with low temperature can cause the precipitated lithium metal to easily react with the electrolyte, thereby further deteriorating the performance of the lithium ion power battery. The increase of the resistance of the electrode film in the battery in the low temperature environment is another reason for the deterioration of the performance of the power battery at such temperature.
Disclosure of Invention
In view of the defects of the prior art, the present invention aims to provide a high-rate and low-temperature high-specific energy lithium ion battery, which can have excellent high-rate discharge performance in a low-temperature environment.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention relates to a high-rate and low-temperature high-specific energy lithium ion battery, which comprises a positive electrode, a negative electrode, a current collector, a diaphragm and electrolyte, wherein the positive electrode is connected with the current collector; the active substance of the positive electrode consists of Nickel Cobalt Aluminum (NCA) and nickel cobalt lithium manganate (NCM), the negative electrode comprises intermediate carbon microsphere graphite and a composite silicon carbon material, the electrolyte consists of a solute, a solvent and an additive, wherein the solute is lithium hexafluorophosphate, the solvent is a mixed solution consisting of Ethylene Carbonate (EC), dimethyl carbonate (DMC), methyl ethyl carbonate (EMC), linear carboxylic Ester (EA) and tetrafluoropropyl ether, and the additive is selected from fluoroethylene carbonate (FEC) and lithium tetrafluoroborate (LiBF)4) At least 3 of lithium difluoro (oxalato) borate (LIODFB) and propane sultone (1, 3-PS).
According to the lithium ion battery provided by the invention, the active substance of the positive electrode consists of nickel-cobalt-aluminum and nickel-cobalt-lithium manganese oxide, the negative electrode adopts a material containing middle carbon microsphere graphite and composite silicon carbon, the middle carbon microsphere graphite has relatively high specific capacity, so that the lithium ion battery has the characteristics of excellent conductivity, high cycle stability, high rate performance and the like, and in the electrolyte, a solvent system which is formed by diluting EC, DMC, EMC, linear carboxylic Ester (EA), and then adding 0.5 percent (TTE) of tetrafluoropropyl ether as an inert solvent is adopted, so that the liquid phase process change degree of the electrolyte along with the temperature reduction can be slowed down, and the low-temperature discharge performance of the lithium ion battery is improved. Meanwhile, an additive is added into the electrolyte, the added additive enables the electrolyte to have the best low-temperature conductivity and electrode/electrolyte interface impedance, and the assembled lithium battery has the lowest polarization degree at low temperature and a stable discharge platform. Therefore, the low-temperature rate type lithium ion battery has excellent discharge performance in a low-temperature environment through the synergistic effect of the substances of the positive electrode, the negative electrode, the current collector, the diaphragm and the electrolyte, and the detection shows that the capacity of the lithium ion battery is 2500mAh-2600mAh, and the energy density is as follows: 205-210Wh/kg, the low temperature performance is as follows: under the environment of 25 ℃, current discharge at 10C multiplying power is carried out, and the discharge capacity reaches more than 95 percent of rated capacity; at 25 ℃, the capacity retention rate is more than 87 percent after 500 cycles of 1.6C charge/10C discharge; the capacity retention rate of the monomer battery cell 18650-2.5Ah (10C) is 81% after low-temperature 1C discharge at 40 ℃ below zero to 2.0V, the discharge capacity of the battery in groups (4 in series and 8 in parallel, 14.4V/20Ah) at 40 ℃ below zero reaches 87% of the rated capacity, the safety performance is good, and the safety test requirements of UL and UN38.3 are met.
In a preferable scheme, the mass ratio of nickel cobalt lithium manganate (NCM) to Nickel Cobalt Aluminum (NCA) is 20-40: 60-80.
More preferably, the particle size D50 of the nickel cobalt lithium manganate is 5-8 μm, and the particle size D50 of nickel cobalt aluminum is 10-12 μm.
In a preferred embodiment, the positive electrode comprises the following components in parts by mass: 94.45-94.8 parts of active substance, 1.3-1.55 parts of binder and 3.5-4.2 parts of conductive agent, wherein the conductive agent is carbon black Super-P Li, and the binder is SBR.
The positive electrode material adopts nickel cobalt lithium manganate (NCM) and Nickel Cobalt Aluminum (NCA) as active substances, and the mass ratio of the nickel cobalt lithium manganate (NCM) to the Nickel Cobalt Aluminum (NCA) is controlled to be 20-40: 60-80, the anode material has the optimal discharge performance, in addition, carbon black Super-P Li is used as a conductive agent in the anode material, the carbon black Super-P Li is in a chain shape or grape shape under a scanning electron microscope, and a single carbon black particle has a very large specific surface area. Have better ion and electron conductivity than graphite, the high specific surface area of carbon black granule piles up closely and is favorable to between the granule in close contact with together, has constituteed the conductive network in the electrode, is favorable to the absorption of electrolyte and improves ionic conductivity, in addition, the once granule of charcoal is reunited and is formed the branch chain structure, can form chain conductive structure with active material, helps improving the electronic conductivity of material, and the binder is SBR: SBR is Styrene-Butadiene latex, a water-based binder, which is generated by adding Styrene (Styrene) and Butadiene (Butadiene) monomers into an emulsifier initiator and the like by emulsion polymerization copolymerization by taking water as a medium, and the state of the water emulsion is water emulsion with the solid content of about 41 percent. SBR is a substance in which hydrophilicity and lipophilicity coexist. The water-based group is combined with the surface group of the foil to form binding power, so that the dispersibility and the slurry stability are facilitated, and the oily chain segment is combined with the negative electrode graphite to form the binding power, so that the binding effect is achieved.
In a preferred scheme, the negative electrode comprises the following components in parts by weight: 93-95 parts of mesocarbon microbeads graphite, 5-7 parts of composite silicon carbon material, 1.5-1.8 parts of carbon black SP, 3.5-4.2 parts of SBR and 1.5-1.8 parts of NMP.
The inventors have found that the composition of the negative electrode is controlled to the above-described preferable range, and that the negative electrode has more excellent low-temperature performance.
Preferably, the current collector is made of aluminum foil or copper foil, wherein the thickness of the positive current collector is 15-18 μm, and the thickness of the negative copper foil is 10-12 μm, wherein the negative copper foil is a negative current collector with high tensile strength and high elongation. The inventors have found that the proper use of a slightly thicker current collector reduces the internal resistance, the temperature generated during high rate discharge.
Preferably, the membrane comprises a base membrane and nano-scale boehmite coating layers arranged on the two surfaces of the base membrane, the base membrane is made of polyethylene and has a thickness of 12-13 μm, and the nano-scale boehmite coating layers have a thickness of 1.5-2.0 μm.
The inventor finds that the two surfaces of the base film are respectively coated with a layer of nano boehmite. The excellent thermal conductivity of the material can improve the problem of thermal conductivity of a lithium battery diaphragm, and the flame retardance can prevent the battery from burning in a large range and even exploding; boehmite is a plate-like crystal, and expands when a material abnormally generates heat, closing a conduction hole, thereby blocking current. When the temperature drops, the material shrinks in volume and the current conduction hole is opened again. Therefore, the safety performance of the lithium battery can be improved by using the boehmite, and the possibility of application of a high-energy battery is provided. While controlling the thickness of the nano-sized boehmite coating within the above range, the final properties are optimal.
In a preferred scheme, the solvent of the electrolyte comprises the following components in parts by weight: 15-16 parts of ethylene carbonate, 0.5-1 part of dimethyl carbonate, 0.4-0.8 part of methyl ethyl carbonate, 55-60 parts of linear carboxylic ester and 0.5-1 part of tetrafluoropropyl ether.
The electrolyte provided by the invention adopts the linear carboxylic Ester (EA) with low melting point and low viscosity, which can slow down the change degree of the liquid phase process of the electrolyte when the temperature is reduced, and improve the low-temperature discharge performance of the lithium ion battery, and in addition, tetrafluoropropyl ether is added as an inert solvent for dilution, so that the viscosity is reduced, the conductivity is improved, and the wettability of the electrolyte is increased, however, the ethylene carbonate, the dimethyl carbonate and the methyl ethyl carbonate are added at the same time, under the synergistic action of the formula of the mass parts, the electrolyte of the lithium battery can not be obviously increased under the environment of-40 ℃, and still has excellent discharge performance under the environment of-40 ℃.
In a preferred embodiment, the mass fraction of the lithium hexafluorophosphate in the electrolyte is 17 to 17.5%. .
Preferably, the additive consists of fluoroethylene carbonate, lithium tetrafluoroborate, lithium difluoro (oxalate) borate and propane sultone, wherein the mass fraction of lithium tetrafluoroborate in the electrolyte is 0.5-1%, the mass fraction of lithium difluorooxalate borate in the electrolyte is 0.5-1%, the mass fraction of fluoroethylene carbonate is 8-10%, and the mass fraction of propane sultone is 4-5%.
In the electrolyte, a plurality of additives are added, wherein the added lithium tetrafluoroborate and lithium difluorooxalato borate can enable the battery to show excellent electrochemical performance in a wide temperature range, the fluoroethylene carbonate is beneficial to the reduction of the impedance of an SEI film at low temperature, so that the low-temperature performance of the battery is improved, and the propane sultone can improve the service life and the safety performance of a battery core.
According to the electrolyte disclosed by the invention, the electrolyte formula is obtained through a large number of experiments, and the electrolyte has the optimal low-temperature conductivity and electrode/electrolyte interface impedance under the synergistic action of solute, various solvents and additives, so that the assembled lithium battery has the lowest polarization degree at low temperature and a stable discharge platform.
Advantageous effects
According to the lithium ion battery provided by the invention, the active substance of the positive electrode consists of nickel-cobalt-aluminum and nickel-cobalt-lithium manganese oxide, the negative electrode adopts a material containing middle carbon microsphere graphite and composite silicon carbon, the middle carbon microsphere graphite has relatively high specific capacity, so that the lithium ion battery has the characteristics of excellent conductivity, high cycle stability, high rate performance and the like, and in the electrolyte, a solvent system which is formed by diluting EC, DMC, EMC, linear carboxylic Ester (EA), and then adding 0.5 percent (TTE) of tetrafluoropropyl ether as an inert solvent is adopted, so that the liquid phase process change degree of the electrolyte along with the temperature reduction can be slowed down, and the low-temperature discharge performance of the lithium ion battery is improved. Meanwhile, the additive is added into the electrolyte, so that the electrolyte has the best low-temperature conductivity and electrode/electrolyte interface impedance, and the assembled lithium battery has the lowest polarization degree at low temperature and stable discharge platform. Therefore, the low-temperature rate type lithium ion battery has excellent discharge performance in a low-temperature environment through the synergistic effect of the substances of the positive electrode, the negative electrode, the current collector, the diaphragm and the electrolyte, and the detection shows that the capacity of the lithium ion battery is 2500mAh-2600mAh, and the energy density is as follows: 205-210Wh/kg, the low temperature performance is as follows: under the environment of 25 ℃, current discharge at 10C multiplying power is carried out, and the discharge capacity reaches more than 95 percent of rated capacity; at 25 ℃, the capacity retention rate is more than 87 percent after 500 cycles of 1.6C charge/10C discharge; the capacity retention rate of the monomer battery cell 18650-2.5Ah (10C) is 81% after low-temperature 1C discharge at 40 ℃ below zero to 2.0V, the discharge capacity of the battery in a group (4 series 8 parallel, 14.4V/20Ah) at 40 ℃ below zero reaches 87% of the rated capacity, the safety performance is good, and the safety test requirements of UL and UN38.3 are met.
Drawings
FIG. 1 shows the discharge retention of 18650-2.5Ah cells prepared in example 1 at-40 ℃ and 3.6 ℃ after the cells are assembled into a battery pack (4 strings 8 and 14.4V/20 Ah).
FIG. 2 is a graph showing the decay rate of 1.6C-charge 10C-discharge cycles of 18650-2.5Ah cells prepared in example 1.
FIG. 3 is a comparative graph of the capacity retention% of the monomer cells 18650-2.5Ah (10C) prepared in comparative example 1 discharged at-40 ℃ and low temperature 1C to 2.0V.
Detailed Description
Example 1
The low-temperature multiplying power type lithium ion battery with the rated capacity of 2.5Ah consists of a positive electrode, a negative electrode, a current collector, a diaphragm and electrolyte.
Wherein the active material of the positive electrode is prepared from 523NCM ternary active material (the particle size D50 is 5-8 μm) and positive electrode NCA ternary active material (the particle size D50 is 10-12 μm.) according to the mass ratio of 30: 70, and mixing.
The anode comprises the following components in percentage by mass: 94.61 parts of active substance, 1.5 parts of binder PVDF and 4.2 parts of conductive agent carbon black Super-P Li4.
The cathode comprises the following components in percentage by mass: 93 parts of mesocarbon microbeads graphite, 7 parts of composite silicon-carbon material, 1.6 parts of conductive agent SP, 1.8 parts of binder CMC, 4.15 parts of binder SBR and 1.5 parts of NMP;
aluminum foil is used as a positive current collector, the thickness is 15-18 mu m,
the copper foil is used as a copper foil negative current collector with high tensile strength and high elongation, and the thickness is 10-12 mu m.
The membrane comprises a base membrane and nano boehmite coatings arranged on two surfaces of the base membrane, the thickness of the membrane is 14 mu m, and the thickness of the nano boehmite is 2 mu m.
The electrolyte consists of a solute, a solvent and an additive, wherein the solute is lithium hexafluorophosphate, and the mass fraction of the lithium hexafluorophosphate in the electrolyte is 17%.
The solvent of the electrolyte comprises the following components in parts by weight: 15 parts of ethylene carbonate, 0.5 part of dimethyl carbonate, 0.4 part of methyl ethyl carbonate, 55 parts of linear carboxylic ester and 0.5 part of tetrafluoropropyl ether.
The additive comprises fluoroethylene carbonate, lithium tetrafluoroborate, lithium difluoro (oxalate) borate and propane sultone, wherein the mass fraction of the lithium tetrafluoroborate in the electrolyte is 0.7%, the mass fraction of the lithium difluorooxalate borate in the electrolyte is 0.8%, the mass fraction of the fluoroethylene carbonate is 9%, and the mass fraction of the propane sultone is 4.5%.
18650-2.5Ah batteries are manufactured according to the components, electrochemical performance tests are carried out, as shown in figures 1 and 2, 1.6C charging and 10C discharging of the single batteries are carried out for 500 weeks, the capacity retention rate of the single batteries is 81% when the single batteries are charged at 40 ℃ below zero and discharged at 1C of 18650-2.5Ah (10C), and the discharge retention rate of the single batteries is more than 87% when the single batteries are assembled into a battery pack (4 strings of 8 and 14.4V/20Ah) at 40 ℃ below zero and 3.6C.
Comparative example 1
The other conditions were the same as in example 1 except that EA and tetrafluoropropyl ether were not contained in the solvent. The 18650-2.5Ah single cell is manufactured, an electrochemical performance test is carried out, as shown in figure 3, the preservation ratio of the 2.0V of the single cell discharged at 40 ℃ below zero 1C is 46%, the 18650-2.5Ah cell manufactured by the electrolyte formula disclosed by the invention is tested for the electrochemical performance, as shown in figure 3, the preservation ratio of the 2.0V of the single cell discharged at 40 ℃ below zero 1C is 81%.
Comparative example 2
The other conditions were the same as in example 1 except that fluoroethylene carbonate was not contained in the additive. The cycle performance is degraded because a stable SEI film cannot be formed.
Comparative example 3
The other conditions were the same as in example 1 except that the thickness of the negative electrode current collector was 6 to 8 μm. At the low temperature of-40 ℃, the negative electrode material may fall off to cause potential safety hazards such as capacity reduction, performance reduction, resistance increase, heat generation increase and the like.
Comparative example 4
Other conditions were the same as in example 1 except that the electrolyte contained no lithium tetrafluoroborate additive and the performance was degraded at low temperatures.

Claims (10)

1. A high-rate and low-temperature high-specific energy lithium ion battery is characterized in that: the battery comprises a positive electrode, a negative electrode, a current collector, a diaphragm and electrolyte; the active material of the positive electrode consists of nickel cobalt aluminum and lithium nickel cobalt manganese oxide, the negative electrode comprises intermediate carbon microsphere graphite and a composite silicon carbon material, and the electrolyte consists of a solute, a solvent and an additive, wherein the solute is lithium hexafluorophosphate, the solvent is a mixed solution consisting of ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate, linear carboxylic ester and tetrafluoropropyl ether, and the additive is at least 3 selected from fluoroethylene carbonate, lithium tetrafluoroborate, lithium difluoro (oxalate) borate and propane sultone.
2. The lithium ion battery of claim 1, wherein the lithium ion battery has high rate, low temperature and high specific energy, and is characterized in that:
the mass ratio of the nickel cobalt lithium manganate to the nickel cobalt aluminum is 20-40: 60-80.
3. The lithium ion battery of claim 1, wherein the lithium ion battery has high rate, low temperature and high specific energy, and is characterized in that:
the particle size D50 of the nickel cobalt lithium manganate is 5-8 μm, and the particle size D50 of the nickel cobalt aluminum is 10-12 μm.
4. The lithium ion battery of claim 1, wherein the lithium ion battery has high rate, low temperature and high specific energy, and is characterized in that: the positive electrode comprises the following components in percentage by mass: 94.45-94.8 parts of active substance, 1.3-1.55 parts of binder and 3.5-4.2 parts of conductive agent, wherein the conductive agent is carbon black Super-P Li, and the binder is SBR.
5. The lithium ion battery of claim 1, wherein the lithium ion battery has high rate, low temperature and high specific energy, and is characterized in that: the cathode comprises the following components in parts by weight: 93-95 parts of mesocarbon microbeads graphite, 5-7 parts of composite silicon carbon material, 1.5-1.8 parts of carbon black SP, 3.5-4.2 parts of SBR and 1.5-1.8 parts of NMP.
6. The lithium ion battery of claim 1, wherein the lithium ion battery has high rate, low temperature and high specific energy, and is characterized in that: the current collector is made of aluminum foil or copper foil, wherein the thickness of the positive current collector is 15-18 mu m, and the thickness of the negative current collector is 10-12 mu m.
7. The lithium ion battery of claim 1, wherein the lithium ion battery has high rate, low temperature and high specific energy, and is characterized in that: the diaphragm comprises a base film and a nano boehmite coating layer arranged on the two surfaces of the base film, wherein the base film is made of polyethylene and has a thickness of 12-13 mu m, and the nano boehmite coating layer has a thickness of 1.5-2.0 mu m.
8. The lithium ion battery with high rate and high specific energy at low temperature according to claim 1, wherein: the solvent of the electrolyte comprises the following components in parts by weight: 15-16 parts of ethylene carbonate, 0.5-1 part of dimethyl carbonate, 0.4-0.8 part of methyl ethyl carbonate, 55-60 parts of linear carboxylic ester and 0.5-1 part of tetrafluoropropyl ether.
9. The lithium ion battery of claim 1, wherein the lithium ion battery has high rate, low temperature and high specific energy, and is characterized in that:
the mass fraction of the lithium hexafluorophosphate in the electrolyte is 17-17.5%.
10. The lithium ion battery of claim 1, wherein the lithium ion battery has high rate, low temperature and high specific energy, and is characterized in that:
the mass fraction of the lithium tetrafluoroborate in the electrolyte is 0.5-1%, the mass fraction of the lithium difluorooxalato borate in the electrolyte is 0.5-1%, the mass fraction of the fluoroethylene carbonate in the electrolyte is 8-10%, and the mass fraction of the propane sultone in the electrolyte is 4-5%.
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CN110957476A (en) * 2019-10-30 2020-04-03 深圳市卓能新能源股份有限公司 High-rate lithium ion power battery and manufacturing method thereof
CN112290091A (en) * 2019-07-25 2021-01-29 杉杉新材料（衢州）有限公司 Lithium ion battery electrolyte with high and low temperature performance and lithium ion battery
CN112786964A (en) * 2020-12-30 2021-05-11 惠州亿纬锂能股份有限公司 High-voltage high-energy-density electrolyte and lithium battery thereof

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CN106229477A (en) * 2016-08-12 2016-12-14 中航锂电（洛阳）有限公司 Positive electrode active materials, preparation method and application
CN112290091A (en) * 2019-07-25 2021-01-29 杉杉新材料（衢州）有限公司 Lithium ion battery electrolyte with high and low temperature performance and lithium ion battery
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