CN105932325A - Long-storage life lithium ion storage battery - Google Patents

Abstract

The invention discloses a lithium-ion storage battery with a long storage life, which includes a positive electrode, a negative electrode, a diaphragm, an electrolyte and a shell, and both the positive electrode and the negative electrode are composed of a metal foil current collector and an active material coating coated on the surface thereof, wherein, The surface of the positive electrode active material is coated with metal oxide, and the positive electrode active material is selected from any one or a mixture of lithium cobaltate, lithium manganate, lithium iron phosphate or nickel-cobalt lithium manganate. The lithium ion storage battery produced by the invention has excellent storage performance, and has obvious advantages in the fields of energy storage power supply and combat readiness power supply, such as energy storage power supply for smart grid emergency, energy storage power supply for medium and high orbit satellites, and combat readiness power supply for missiles.

Description

A lithium-ion battery with long storage life

technical field

The invention belongs to the field of lithium ion accumulators, in particular to a lithium ion accumulator with long storage life.

Background technique

Compared with other secondary batteries, lithium-ion batteries not only have higher operating voltage and greater energy density, but also have a longer working life. These excellent properties allow it to meet the complex requirements of ever-evolving equipment. Efforts are underway worldwide to develop existing lithium-ion battery technology and expand its applications beyond portable electronics into other areas such as transportation, energy storage, medical and defense.

Lithium-ion batteries are gradually being used as energy storage power supplies and combat readiness power supplies, such as energy storage power supplies for emergency use in smart grids, energy storage power supplies for medium and high orbit satellites, and combat readiness power supplies for missiles. The characteristic of this type of power supply is that the storage battery is in a storage state for a long time, and it starts charging and discharging and enters the working mode once it is triggered. Taking medium and high-orbit satellites as an example, about 3/4 of the time is in the long-light period every year. During this time, the lithium-ion battery is basically in a state of shelving. The degree of reaction will lead to the decrease of battery voltage, capacity decay, and the inability to complete subsequent tasks.

Long life has always been the goal pursued by lithium-ion battery researchers. With the in-depth application of lithium-ion batteries, in addition to service life, storage life has attracted more and more attention from researchers, and has gradually become a research hotspot.

Contents of the invention

The object of the present invention is to effectively overcome the capacity attenuation problem of the lithium-ion storage battery during long-term storage, and provide a lithium-ion storage battery with a long storage life.

In order to achieve the above object, the present invention provides a lithium ion storage battery with a long storage life, which includes a positive pole, a negative pole, a diaphragm, an electrolyte and a casing, and the positive pole and the negative pole are coated with a metal foil current collector and an active material coated on its surface. layer structure, wherein, the surface of the positive electrode active material is coated with metal oxide, and the positive electrode active material is selected from any one or more of lithium cobalt oxide, lithium manganate, lithium iron phosphate or lithium nickel cobalt manganate mixture of species.

In the aforementioned lithium-ion storage battery with long storage life, the metal oxide is selected from any one or a mixture of Al ₂ O ₃ , MgO, TiO ₂ , and ZrO ₂ .

In the aforementioned lithium-ion storage battery with long storage life, the negative electrode active material is any one or a mixture of natural graphite, mesocarbon microspheres or hard carbon.

In the aforementioned lithium-ion storage battery with long storage life, the surface of the negative electrode active material has a coating layer.

In the aforementioned lithium-ion storage battery with long storage life, the coating layer is selected from one or a mixture of carbon, metal, and polymer.

In the lithium-ion storage battery with long storage life mentioned above, the metal is Ag, Ni, Sn; the polymer is polypyrrole or polyaniline.

In the lithium-ion storage battery with long storage life mentioned above, the diaphragm adopts polyolefin diaphragm.

In the above-mentioned lithium-ion storage battery with long storage life, the surface of the separator is coated with an inorganic nanoparticle layer.

In the aforementioned lithium-ion storage battery with long storage life, the inorganic nanoparticle layer is any one or a mixture of SiO ₂ , TiO ₂ , Al ₂ O ₃ , and ZrO ₂ .

The above-mentioned lithium-ion battery with long storage life, wherein the electrolyte contains a film-forming additive, and the film-forming additive is selected from any one or a mixture of vinyl sulfite, vinylene carbonate and derivatives thereof , which is beneficial to suppress the generation of irreversible capacity and the excessive growth of SEI film on the surface of the negative electrode material.

In the lithium-ion storage battery with a long storage life as described above, both sides of the positive and negative electrode metal foil current collectors are coated with active material coatings.

The present invention is characterized in that the coated positive electrode active material, the coated negative electrode active material, the diaphragm coated with an inorganic nanoparticle layer are selected, and the electrolyte solution of film-forming additives is added to make a lithium ion storage battery, and the obtained lithium ion storage battery Has excellent storage life.

Lithium-ion batteries are stored in a certain state of charge, and a certain amount of lithium ions are released from the crystal lattice of the active material, and the chemical potential is high, and it is in an unstable state. Due to the stress of the material itself, the positive and negative active materials are prone to irreversible deformation, and the active material is in direct contact with the electrolyte, which is prone to side reactions, thereby reducing the number of lithium intercalation sites in the active material, resulting in capacity decay. Coating the outer surface of the active material by chemical or physical methods can not only stabilize the structure of the active material, but also cut off the direct contact with the electrolyte to avoid the loss of the active material.

The separator is in direct contact with the positive and negative electrodes and undergoes redox reactions on the electrode surfaces. Because polyolefin separators have low resistance to oxidation reactions, they are prone to oxidative decomposition during storage. This oxidative decomposition is aggravated at high temperatures, ultimately reducing the battery's lifespan. And as the demand for high-capacity batteries increases, the oxidation resistance of the separator becomes more important. Coating an inorganic nanoparticle layer on the surface of the polyolefin separator can prevent direct contact with the positive and negative electrodes and avoid the influence of redox reactions on the separator.

The present invention has the following positive effects:

(1) In the present invention, the positive and negative active materials are coated, starting from the material itself, to suppress the irreversible deformation caused by the stress of the material itself during the long-term storage process.

(2) The present invention adopts the diaphragm coated with inorganic nanoparticle layer on the surface, and adds the electrolyte solution of film-forming additives to make lithium-ion storage battery, which greatly improves the storage life of the battery.

detailed description

The invention provides a lithium-ion storage battery with long storage life, which includes positive pole, negative pole, diaphragm, electrolyte and shell, and both positive pole and negative pole are composed of metal foil current collector and active material coating coated on the surface. Preferably, both sides of the positive and negative electrode metal foil collectors are coated with a single-layer or double-layer active material coating.

The positive electrode includes a positive electrode active material, a conductive agent, a binder, and a current collector. The mass percentages of each material in the positive electrode coating are: the content of the positive electrode active material is 85% to 95%, the content of the conductive agent is 1% to 10%, The binder content is 1%~10%.

The negative electrode of the present invention includes negative electrode active material, conductive agent, binder and current collector, and the mass percentage content of each material in the negative electrode coating is: negative electrode active material content 85% ~ 95%, conductive agent content 1% ~ 10% %, the binder content is 1%~10%.

The conductive agent can be a conventional negative electrode conductive agent in the field, such as conductive carbon black, superconductive carbon black, acetylene black, flake graphite, carbon nanofiber or a mixture of one or more materials.

The binder can be fluorine-containing resin, polyethylene, polyvinyl alcohol, such as styrene-butadiene rubber (SBR), sodium hydroxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene ( PTFE) in a mixture of one or more materials.

Both the positive electrode coating and the negative electrode coating of the present invention may contain a solvent, and the solvent may be a mixture of one or more materials in N-methylpyrrolidone, dimethylformamide, absolute ethanol, and deionized water.

The surface of the positive electrode active material is coated with metal oxide, and any one or a mixture of several of Al ₂ O ₃ , MgO, TiO ₂ , ZrO ₂ is selected; the positive electrode active material is selected from lithium cobaltate, manganese Lithium oxide, lithium iron phosphate or lithium nickel cobalt manganese oxide or a mixture of several.

The negative active material is any one or a mixture of natural graphite, mesocarbon microspheres or hard carbon; the surface of the negative active material has a coating, the coating is preferably carbon, metal , one or a mixture of several polymers; the metal is preferably Ag, Ni, Sn; the polymer is preferably polypyrrole or polyaniline.

The diaphragm is preferably a polyolefin diaphragm, preferably, the surface of the diaphragm is coated with an inorganic nanoparticle layer; preferably, the inorganic nanoparticle layer is selected from any of SiO ₂ , TiO ₂ , Al ₂ O ₃ , and ZrO ₂ One or a mixture of several.

The electrolyte is composed of an organic solvent and an electrolyte lithium salt. The organic solvent can be one or more mixtures of the following substances. For example, ethyl carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethylformamide, diethylformamide Amide, tetrahydrofuran, methyl acetate, etc. In order to obtain good discharge performance and life of the battery, it is preferable to include ethylene carbonate (EC) in the above-mentioned solvent. The electrolyte lithium salt may include the following single electrolyte lithium salts and mixtures thereof, such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiCF ₃ CO ₂ , LiCF ₃ (CF) ₃ , LiBOB, and the like. In a preferred embodiment, one or more film-forming additives, such as ethylene sulfite (ES), vinylene carbonate (VC) and their derivatives, are added to the electrolyte, which is beneficial to inhibit the irreversible capacity Generation and excessive growth of SEI film on the surface of negative electrode materials.

The shell can be a steel shell, an aluminum shell or an aluminum-plastic packaging film.

The present invention will be further explained and illustrated through specific examples below. These examples are only used to illustrate the present invention, and are not intended to limit the protection scope of the present invention.

Example 1

The lithium ion accumulator provided by the invention includes: positive pole, negative pole, electrolyte, separator and casing.

1. Production of positive electrode sheet

Add NMP (N-methylpyrrolidone) into the mixing tank, then add 3% by weight of binder (PVDF), stir until the white binder is completely dissolved, then add 2.5% of conductive agent, after stirring, we get Conductive colloid, 94.5% of the positive active material mixture is added to the conductive colloid, the positive active material is lithium cobalt oxide coated with ZrO ₂ , the positive electrode slurry is prepared after stirring and mixing, and then evenly coated on the 18μm thick Aluminum foil, and then rolled and sliced to make the positive electrode sheet.

2. Production of negative electrode sheet

Add NMP into the mixing tank, then add 3% by weight of binder (PVDF), stir until the white binder is completely dissolved, then add 2% of conductive agent, and get conductive colloid after stirring, add 95% of the The negative electrode active material is added to the conductive colloid. The negative electrode active material is the mesophase carbon microspheres coated with carbon. After stirring and mixing, the negative electrode slurry is prepared, and then evenly coated on the copper foil with a thickness of 12 μm, and then passed through the roller After pressing and slicing, the negative electrode sheet was made.

3. Production of battery

The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence to form a battery cell with a laminated structure. The separator is a polypropylene separator coated with Al ₂ O ₃ on the surface, the coating thickness is 4 µm, and the diaphragm thickness is 25 µm.

After the battery core is welded to the positive and negative pole lugs, it is then inserted into the shell and laser welded. Inject the electrolyte, the electrolyte is 1mol L ^-1 LiPF ₆ –EC+DEC+DMC (1:1:1, wt%), and add 4% vinylene carbonate (VC), and finally through the formation and volume separation After the process, it is made into an aluminum case lithium-ion battery.

Comparative example 1

The positive electrode active material is uncoated lithium cobalt oxide, the negative electrode active material is uncoated mesophase carbon microspheres, the separator is uncoated PP separator, and the electrolyte is 1 mol L ^-1 LiPF ₆ without additives – EC+DEC+DMC (1:1:1, wt%), and the rest of the materials are the same as those in the examples, and a battery is fabricated according to the method in the examples.

The test method of the lithium-ion accumulator made in embodiment 1 and comparative example 1 is as follows:

Initial capacity: at a room temperature of 25°C, charge the battery at a constant current rate of 0.2C to 4.1V, then charge at a constant voltage with a cut-off current of 0.05C; after leaving it aside for 0.5h, discharge it at a constant current rate of 0.2C to 2.75V to obtain the initial capacity of the battery Discharge capacity C ₀ .

Storage method: At room temperature 25°C, charge the battery at a constant current of 0.2C to 4.1V, and then charge at a constant voltage with a cut-off current of 0.05C. Store the fully charged battery at an ambient temperature of 5°C, and conduct a capacity test on the battery every 135 days (1 storage period).

Capacity test: at room temperature 25°C, charge the battery at a constant current of 0.2C to 4.1V, constant voltage until the current is less than or equal to 0.05C, and discharge it at a constant current of 0.2C to 2.75V after standing aside for 0.5h, to obtain the capacity C of the battery after laying aside _d , Calculate the capacity retention rate of the battery after storage according to the method of L=C _d /C ₀ ×100%.

The experimental results of Comparative Example 1 and Example 1 are shown in Table 1.

Table 1: Capacity test results of Example 1 and Comparative Example 1

As can be seen from Table 1, the lithium-ion accumulator produced in the embodiment has a higher capacity retention rate of more than 97% after 4 shelving periods and 540 days; while the capacity retention rate of the lithium-ion accumulator produced in the comparative example is low, only 94%.

In summary, the present invention uses coated active materials as positive and negative electrode materials. The coating layer can stabilize the structure of active materials and avoid irreversible deformation of positive and negative electrode materials during long-term storage; The separator of the nanoparticle layer can enhance the oxidation resistance of the separator and prevent the oxidative decomposition of the separator during storage; the use of an electrolyte with film-forming additives can inhibit the generation of irreversible capacity and the excessive growth of the SEI film on the surface of the negative electrode material. The lithium ion storage battery produced by the invention has excellent storage performance, and has obvious advantages in the fields of energy storage power supply and combat readiness power supply, such as energy storage power supply for smart grid emergency, energy storage power supply for medium and high orbit satellites, and combat readiness power supply for missiles.

Although the content of the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be considered as limiting the present invention. Various modifications and alterations to the present invention will become apparent to those skilled in the art upon reading the above disclosure. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims (10)

1. the lithium-ions battery of long storage life, it includes positive pole, negative pole, barrier film, electrolyte and shell, positive pole and negative Pole is constituted by metal forming collector and the coating layer of active substance being coated in its surface, it is characterised in that described positive electrode active material Matter Surface coating has metal oxide, described positive active material to select cobalt acid lithium, LiMn2O4, LiFePO4 or nickel cobalt mangaic acid Any one or a few mixture in lithium.

The lithium-ions battery of long storage life the most as claimed in claim 1, it is characterised in that described metal oxide choosing Select Al₂O₃、MgO、 TiO₂、ZrO₂In any one or a few mixture.

The lithium-ions battery of long storage life the most as claimed in claim 1 or 2, it is characterised in that described negative electrode active Material is any one or a few the mixture in native graphite, carbonaceous mesophase spherules or hard carbon.

The lithium-ions battery of long storage life the most as claimed in claim 3, it is characterised in that described negative electrode active material Surface there is clad.

The lithium-ions battery of long storage life the most as claimed in claim 4, it is characterised in that described clad selects The mixture of one or more in carbon, metal, polymer.

The lithium-ions battery of long storage life the most as claimed in claim 5, it is characterised in that described metal select Ag, Ni、Sn；Described polymeric oxidizer polypyrrole or polyaniline.

The lithium-ions battery of long storage life the most as claimed in claim 1, it is characterised in that barrier film use polyolefin every Film, this membrane surface is coated with inorganic nano-particle layer.

The lithium-ions battery of long storage life the most as claimed in claim 7, it is characterised in that described inorganic nano-particle Layer selects SiO₂、TiO₂、Al₂O₃、ZrO₂In any one or a few mixture.

The lithium-ions battery of long storage life the most as claimed in claim 1, it is characterised in that described electrolyte comprises into Film additive, this film for additive select in ethylene sulfite, vinylene carbonate and derivative thereof any one or several The mixture planted.

The lithium-ions battery of long storage life the most as claimed in claim 1, it is characterised in that positive and negative electrode metal forming afflux Body both sides are all coated with coating layer of active substance.