CN106169617A - A kind of space safety high power lithium ion accumulator - Google Patents

Abstract

The invention discloses a safe high-power lithium-ion storage battery for space use, which includes a positive electrode sheet, a negative electrode sheet, a diaphragm separating the positive and negative electrodes, and an electrolyte, and the positive electrode sheet includes a positive electrode collector and a positive electrode coated on the surface of the positive electrode collector Active coating, the positive active coating contains a positive active material, the positive active material is a mixed system composed of component A and component B, component A is lithium cobaltate, lithium nickel cobalt aluminate, nickel cobalt manganese At least one of lithium oxide, the outer surface of the material of component A is covered with a conductive carbon layer, the mass ratio of the conductive carbon layer to component A is (0.1‑2): 100, and the thickness of the carbon layer is nanoscale; The component B is selected from at least one of lithium manganese oxide and lithium iron phosphate; the mass percentage of the component B in the active material of the positive electrode is 5%-50%. Compared with the prior art, the use of the mixed positive electrode system in the present invention can greatly improve the rate performance and safety performance of the space lithium-ion battery, and expand the application of the lithium-ion battery in the space power supply.

Description

A safe high-power lithium-ion battery for space

technical field

The invention belongs to the technical field of lithium ion accumulators, and in particular relates to a safe high-power lithium ion accumulator for hybrid system type space.

Background technique

Compared with lead-acid batteries, nickel-cadmium batteries, and nickel-hydrogen batteries, lithium-ion batteries have the advantages of higher energy density, long cycle life, and lower self-discharge rate. They have been widely used in various electronic products, new energy vehicles, and space In the satellite power subsystem.

At present, lithium-ion batteries used in space energy storage power supply are all high specific energy type, and the specific energy of single battery is high, which is suitable for lightweight and long-life satellite power supply. With the continuous increase of space load on power system power requirements, high specific power lithium-ion batteries have attracted widespread attention due to their high specific power and a certain specific energy. At present, the development of high-power lithium-ion battery technology used in space is relatively slow, and the corresponding technology is still immature. At the same time, because high-power lithium-ion batteries usually generate high heat when they are discharged with large currents, it is also crucial to improve the safety of batteries. important.

For this reason, the present invention starts from improving the electrochemical system of the lithium-ion storage battery, increases the intrinsic safety of the battery while increasing the power density of the battery, and further expands its application field in satellite platforms.

Contents of the invention

The object of the present invention is to solve the above-mentioned technical problems and design a hybrid system high-power lithium-ion storage battery for space. The lithium-ion battery has technical characteristics such as high rate performance and safety performance.

In order to achieve the above object, the present invention provides a safe high-power lithium-ion storage battery for space, including a positive electrode sheet, a negative electrode sheet, a diaphragm separating the positive and negative electrodes, an electrolyte, and a fully sealed casing for the lithium-ion storage battery for space use. The positive electrode sheet includes a positive electrode current collector and a positive electrode active coating coated on the surface of the positive electrode current collector. By mass percentage, the positive electrode active coating includes the following components:

Positive active material: 85%~95%;

Positive electrode conductive agent: 0.1%~10%;

Positive electrode binder: 0.1%~10%;

The positive electrode active material is a mixed system composed of component A and component B, and the component A is at least one of lithium cobalt oxide, lithium nickel cobalt aluminate, and lithium nickel cobalt manganese oxide. Part B is selected from at least one of lithium manganate and lithium iron phosphate;

The component B accounts for 5%-50% by mass of the positive electrode active material. The mass percentage of component B in the positive electrode active material cannot be too high, otherwise the capacity and specific energy of the battery will be reduced, and it should not be too low, otherwise the safety of the battery cannot be improved.

Preferably, the particle diameter D50 of the component A is 5-10um, and the particle diameter D50 of the component B is 4-10um.

In order to improve the rate characteristics of the lithium-ion battery, the outer surface of the material of the component A is covered with a conductive carbon layer, and the mass ratio of the carbon layer to the component A is (0.1-2): 100 , the thickness of the carbon layer is nanoscale.

The positive electrode conductive agent is selected from at least one of conductive super carbon black, carbon nanotubes and graphene.

The positive electrode binder is selected from at least one of polyvinylidene fluoride, styrene-butadiene rubber and polytetrafluoroethylene.

The negative electrode sheet includes a negative electrode current collector and a negative electrode active coating coated on the surface of the negative electrode current collector. By mass percentage, the negative electrode active coating includes the following components:

Negative electrode active material: 80%~95%;

Negative electrode conductive agent: 1%~10%;

Negative electrode binder: 1%~10%;

The negative electrode active material is at least one of artificial graphite, mesocarbon microspheres, hard carbon, and tin metal alloy.

The particle size D50 of the negative electrode active material is 5-10um, the particle size is small, and the particle size distribution of the material is narrow.

The negative electrode conductive agent is selected from at least one of conductive super carbon black, carbon nanotubes and graphene.

As an improvement of the space-safe high-power lithium-ion battery of the present invention, the positive electrode conductive agent and the negative electrode conductive agent are at least one of conductive super carbon black, carbon nanotubes, and graphene. Through the introduction of some two-dimensional and three-dimensional conductive materials to build a three-dimensional conductive network, improve the electrical contact between the active materials of the electrode material, enhance the electrical conductivity of the pole piece and the electrical contact with the current collector. At the same time, the addition of a certain high-efficiency conductive agent can better connect the contact force between the active material and the current collector in series, and enhance the toughness of the electrode sheet.

The negative electrode binder is selected from at least one of polyvinylidene fluoride, styrene-butadiene rubber and polytetrafluoroethylene.

Compared with the prior art, the present invention has the following beneficial effects: the present invention carries out simple physical mixing of component A and component B, not only can take into account lithium cobaltate, lithium nickel cobalt aluminate, lithium nickel cobalt manganate and other materials It has the characteristics of high capacity and high rate, as well as the excellent rate and safety characteristics of lithium manganate and lithium iron phosphate, and the mechanical mixing is simple and easy to realize. Moreover, the conductive carbon layer coated on the outside of the material of component A can improve the discharge capacity of the above-mentioned hybrid battery, make the battery structure more stable, and help improve the cycle performance of the battery. In addition, the materials in the present invention all use small-sized particle materials, the particle size D50 of component A is 5-10um, the particle size D50 of component B is 4-10um, and the particle size distribution of the material is narrow. Materials with small-sized particles have the characteristics of small particle size and large specific surface area, showing the following advantages: (1) Improve the kinetic performance of lithium ion transport. Due to the small particle size and the short diffusion path of lithium ions, the average diffusion time of lithium ions in the solid phase is greatly reduced; the shorter transmission path makes it possible to charge and discharge large currents, and the larger specific surface area reduces the actual current density. The damage to the electrode material is reduced, which is conducive to the maintenance of cycle performance; (2) the internal stress of the lattice generated by the material structure during the charging and discharging process is relieved, showing a high lithium intercalation capacity and a long cycle life.

Description of drawings

FIG. 1 is a schematic diagram of a high-rate discharge in Example 1 of the present invention.

detailed description

The specific implementation manners of the present invention will be further described below in conjunction with the embodiments and the accompanying drawings.

Example 1-3

The lithium ion battery that embodiment 1-3 provides, comprises positive electrode sheet, negative electrode sheet, separator and electrolyte, battery design capacity 4Ah; The fluid is an aluminum foil with a thickness of 20um; the formulation of the positive active coating is shown in Table 1. The negative electrode sheet includes a negative electrode current collector and a negative electrode active coating coated on the surface of the negative electrode current collector. The negative electrode current collector is a copper foil with a thickness of 12um; the formula of the negative electrode active coating is shown in Table 1.

Table 1: The raw material formula of embodiment 1-3 (in parts by mass)

The electrolyte mainly includes organic solvents, additives and lithium salts. The lithium salt is LiFP ₆ with a concentration of 1.2mol/L. The organic solvents are mainly DMC (dimethyl carbonate), EMCEMC (ethyl methyl carbonate), EC (ethylene carbonate ), etc., while adding VC (vinylene carbonate), PS (propylene sulfite), LiODFB and other additives.

The thickness of the diaphragm is PP (polypropylene)/PE (polyethylene)/PP three-layer composite film with a thickness of 25um.

The preparation method of the battery of this embodiment is:

Preparation of positive electrode sheet: Add lithium cobaltate, lithium manganate, carbon black, carbon nanotubes, and polyvinylidene fluoride into NMP and mix them into a slurry, and evenly coat them on aluminum foil. After drying, rolling, and cutting, Get the positive plate;

Preparation of negative electrode sheet: Add artificial graphite, carbon black, and carbon nanotube polyvinylidene fluoride to NMP and mix to form a slurry, which is evenly coated on copper foil, and after drying, rolling, and cutting, the negative electrode sheet is obtained;

The preparation of the cell: the positive electrode sheet, the negative electrode sheet and the diaphragm are made into a cell by Z-shaped laminated sheets, and then the positive electrode tab and the negative electrode tab are ultrasonically welded on the positive electrode sheet and the negative electrode sheet respectively, and finally the cell is placed in the full Seal the shell, bake, and remove the moisture in the battery core;

Injection: Inject a certain amount of the above-mentioned electrolyte into the above-mentioned cell, seal it and let it stand;

Finally, the above-mentioned battery cells are chemically divided into volumes, and after a period of aging, a high-power lithium-ion battery is obtained.

The above 4Ah battery was discharged at a high rate, as shown in Figure 1, which is a schematic diagram of the high rate discharge of the battery prepared in Example 1. The battery can be discharged at a maximum of 200A, and the rate can reach 50C, with excellent rate performance. In Example 2 and Example 3, after the above-mentioned high-rate discharge test, the rate is also as high as 50C, while the rate performance of the lithium-ion storage battery in the prior art is generally 10C-20C. It can be seen that the rate performance of the battery provided by the present invention is greatly improved.

At the same time, the batteries prepared in Examples 1-3 are tested according to national standards and national military standards, and can pass safety tests such as acupuncture, short circuit, overcharge, and overdischarge. They have excellent safety performance and can be used for space power supplies.

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. A safe high-power lithium-ion storage battery for space, comprising a positive electrode sheet, a negative electrode sheet, a diaphragm separating the positive and negative electrodes, an electrolyte, and a fully sealed casing for the lithium-ion storage battery for space, characterized in that: The positive electrode sheet includes a positive electrode current collector and a positive electrode active coating coated on the surface of the positive electrode current collector. The positive electrode active coating contains a positive electrode active material, and the positive electrode active material is composed of component A and component B. Mixed system, component A is at least one of lithium cobalt oxide, lithium nickel cobalt aluminate, and lithium nickel cobalt manganate, and component B is at least one selected from lithium manganate and lithium iron phosphate; The outer surface of the material of component A is covered with a conductive carbon layer, the mass ratio of the conductive carbon layer to the component A is (0.1-2): 100, and the thickness of the carbon layer is on the order of nanometers; The component B accounts for 5%-50% by mass of the positive electrode active material. 2. The safe high-power lithium-ion battery for space use according to claim 1, characterized in that: the particle size D50 of component A is 5-10 um, and the particle size D50 of component B is 4-10 um. 3. The safe high-power lithium-ion storage battery for space according to claim 1, characterized in that: the positive active coating comprises the following components, in mass percent: Positive active material: 85%~95%; Positive electrode conductive agent: 0.1%~10%; Positive electrode binder: 0.1%~10%. 4. The space-use safe high-power lithium-ion storage battery according to claim 3, characterized in that: the positive electrode conductive agent is selected from at least one of conductive super carbon black, carbon nanotubes and graphene. 5. The space-use safe high-power lithium-ion battery according to claim 3, characterized in that: said positive electrode binder is selected from at least one of polyvinylidene fluoride, styrene-butadiene rubber and polytetrafluoroethylene. 6. The safe high-power lithium-ion storage battery for space according to claim 1, characterized in that: the negative electrode sheet includes a negative electrode current collector and a negative electrode active coating coated on the surface of the negative electrode current collector, by mass percentage, the Described negative electrode active coating comprises following component: Negative electrode active material: 80%~95%; Negative electrode conductive agent: 1%~10%; Negative electrode binder: 1%~10%. 7. The space-use safe high-power lithium ion storage battery according to claim 6, characterized in that: said negative electrode active material is at least one of artificial graphite, mesocarbon microspheres, hard carbon, and tin metal alloy. 8. The space-use safe high-power lithium-ion battery according to claim 6, characterized in that: the particle size D50 of the negative electrode active material is 5-10 um. 9. The safe high-power lithium-ion storage battery for space use according to claim 6, characterized in that: the negative electrode conductive agent is selected from at least one of conductive super carbon black, carbon nanotubes and graphene. 10. The safe high-power lithium-ion battery for space use according to claim 6, characterized in that: said negative electrode binder is selected from at least one of polyvinylidene fluoride, styrene-butadiene rubber and polytetrafluoroethylene.