CN216719992U

CN216719992U - Metallic lithium negative electrode and secondary battery

Info

Publication number: CN216719992U
Application number: CN202220224181.6U
Authority: CN
Inventors: 郇庆娜; 孔德钰; 孙兆勇; 陈强; 牟瀚波
Original assignee: China Energy Lithium Co ltd
Current assignee: China Energy Lithium Co ltd
Priority date: 2022-01-27
Filing date: 2022-01-27
Publication date: 2022-06-10
Anticipated expiration: 2032-01-27

Abstract

A metallic lithium anode and a secondary battery are provided. The metal lithium negative electrode comprises a current collector with a sandwich structure and metal lithium/lithium alloy belts positioned on the upper surface and the lower surface of a composite current collector, wherein the sandwich structure of the current collector is composed of a base film layer and copper layers positioned on the two surfaces of the base film layer. The lithium metal cathode can meet the requirement of high specific energy batteries and can be produced in batch.

Description

Metallic lithium negative electrode and secondary battery

Technical Field

The utility model relates to the technical field of energy storage, in particular to a lithium metal cathode for a secondary battery.

Background

The lithium battery has the advantages of high energy density, long cycle life and wide applicable temperature range, so that the lithium battery is widely applied to the fields of aerospace, computers, mobile communication equipment, electric automobiles and the like. With the development of society and the progress of science and technology, the requirements on the energy density and the cycle life of a lithium battery are higher and higher, but the lithium ion battery which only uses graphite as a negative electrode at present cannot meet the social requirements, so that a novel positive and negative electrode material with higher specific capacity needs to be developed. For the negative electrode material, the specific energy of the battery can be effectively improved due to the high specific capacity (3860mAh/g, which is 10 times of that of a graphite negative electrode) and the lowest oxidation-reduction potential (-3.04V VS standard hydrogen potential) of the lithium metal.

In the lithium battery, the anode material uses lithium iron phosphate, lithium cobaltate or high nickel ternary material, the anode material contains lithium, and the cathode uses little metal lithium (the thickness of the metal lithium is less than 50 um); because the metal lithium is soft, if the thickness of the metal lithium is less than 50um, if no supporting film exists, the metal lithium is easy to break adhesion, so the currently used metal lithium negative electrode usually adopts a lithium-copper composite belt, and copper also plays a supporting role as a current collector. At present, the thickness of copper foil used in secondary batteries is 6-8um, the copper foil accounts for about 13% of the total mass of the batteries, and the specific energy of the batteries needs to be further improved.

SUMMERY OF THE UTILITY MODEL

In order to improve the specific energy of the battery, the inventor finds that the light metal lithium cathode can be obtained by adopting high-molecular polymer material vapor deposition copper as a support material of the metal lithium cathode and then compounding a metal lithium/lithium alloy belt. In addition, by controlling the temperature and pressure conditions, a smooth-surfaced metallic lithium negative electrode can be obtained, which can be directly used as a battery.

One aspect of the present invention is directed to a metallic lithium negative electrode including a current collector having a sandwich structure, and metallic lithium/lithium alloy tapes on both upper and lower surfaces of the current collector, wherein the sandwich structure of the current collector is composed of a base film layer and copper layers on both surfaces of the base film layer.

Optionally, the copper layer has a thickness of 100nm-3um, preferably 500nm-2 um.

Optionally, the thickness of the metallic lithium/lithium alloy ribbon is 1-150um, preferably 5-20 um.

Alternatively, the metallic lithium alloy is an alloy of metallic lithium with one or more of Ag, Al, Au, Ba, Be, Bi, C, Ca, Cd, Co, Cr, Cs, Fe, Ga, Ge, Hf, Hg, In, Ir, K, Mg, Mn, Mo, N, Na, Nb, Ni, Pt, Pu, Rb, Rh, S, Se, Si, Sn, Sr, Ta, Te, Ti, Y, V, Zn, Zr, Pb, Pd, Sb and Cu. By adjusting the amount of the alloying element, the amount of metallic lithium (effective lithium) can be controlled without changing the thickness of the lithium-containing layer. The content of metallic lithium in the lithium alloy is generally 10 to 99.9% by weight.

Optionally, the thickness of the base film layer is 3-10 um.

Optionally, the base film layer is formed of a high molecular polymer material. The high polymer material comprises at least one of polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, polydiformyl phenylenediamine, polyvinyl chloride, polystyrene, polytetrafluoroethylene, polyvinylidene fluoride, polyamide, polyimide, polystyrene, polybutylene terephthalate, poly (p-phenylene terephthalamide), acrylonitrile-butadiene-styrene copolymer, aramid fiber, epoxy resin, polyformaldehyde, phenolic resin, silicon rubber, starch and derivatives thereof, cellulose and derivatives thereof, protein and derivatives thereof, polyethylene glycol and cross-linked substances thereof, and polyvinyl alcohol and cross-linked substances thereof.

Optionally, the width of the lithium metal anode is 10-1000mm, preferably 100-500 mm.

Optionally, the surface of the lithium metal negative electrode is flat and free of wrinkles, and the roughness Ra of the surface of the lithium metal negative electrode ranges from 0.5 um to 3 um.

Alternatively, the lithium metal anode may be formed by a method comprising:

(1) drying the coiled high molecular polymer material film layer, and then forming a current collector by vapor deposition of metal copper layers on the upper surface and the lower surface of the high molecular polymer material film layer;

(2) and rolling and compounding the metal lithium/lithium alloy belt on the metal copper layer to obtain the metal lithium cathode.

Alternatively, the vapor deposition may be realized by vacuum evaporation, magnetron sputtering, ion plating, or the like.

Optionally, freezing the current collector prior to step (2), for example at-10 ℃ to-18 ℃; and in the rolling compounding of the step (2), a cold roll is adopted, and the surface temperature of the roll is between 15 ℃ below zero and 5 ℃ below zero.

Alternatively, the roll lamination is carried out in stages, each using a pressure of 1 to 20MPa, preferably 1 to 10MPa, more preferably 1 to 5 MPa. Preferably, the rolling compounding is carried out in two steps, and the pressure of the second rolling compounding is greater than that of the first rolling compounding.

Another aspect of the present invention provides a secondary battery comprising the above-described metallic lithium negative electrode, and a positive electrode/separator/electrolyte or a positive electrode/solid electrolyte.

Alternatively, the metal lithium cathode can be directly used as a cathode of a secondary battery and can be assembled with a positive electrode/electrolyte/diaphragm to form a liquid secondary battery; or can be assembled with a positive electrode/solid electrolyte (with or without electrolyte) to form a semi-solid or solid secondary battery.

Alternatively, the positive electrode active material may be selected from lithium iron phosphate, lithium cobaltate, high nickel ternary material (NCM nickel cobalt manganese ternary or NCA nickel cobalt aluminum ternary), and the like.

Alternatively, the separator may be selected from a polypropylene (PP) film or a polypropylene/polyethylene/polypropylene (PP/PE/PP) three-layer composite film, and may have a ceramic or PVDF (polyvinylidene fluoride) coating thereon.

Alternatively, the solid electrolyte may be selected from the group consisting of a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte (e.g., composed of polyethylene oxide, PVDF, polyacrylonitrile, etc., and lithium salt), a sulfide solid electrolyte and a polymer mixed electrolyte, an oxide solid electrolyte, and a polymer mixed electrolyte.

Optionally, the electrolyte is selected from an ester electrolyte or an ether electrolyte.

Alternatively, the secondary battery is assembled through a lamination or winding process.

The technical scheme of the utility model at least realizes one of the following beneficial effects:

1. and directly compounding the metal lithium/lithium alloy strip on a current collector with a sandwich structure to obtain the light metal lithium cathode.

2. The obtained lithium metal cathode has a flat surface and can be directly used as a battery.

3. The light lithium metal negative electrode can be prepared in batch by two mature processes of vapor deposition and rolling, and can be applied to industrial production.

4. The density of the high molecular polymer material is lower than that of pure copper foil, and the specific energy can be improved by about 10 percent (the density of the copper foil is 8.93 g/cm)³The density of the high molecular polymer material is 0.7-1.4 g/cm³)。

5. The safety is improved, and when the battery is short-circuited, the polymer material in the metal lithium negative electrode material plays a role in insulating and isolating the positive electrode and the negative electrode.

Drawings

Fig. 1 is a schematic structural view of a lithium metal negative electrode product according to the present invention.

Fig. 2 is a photograph of a lithium metal negative electrode product of example 1 of the present invention.

Fig. 3 is a photograph of a lithium metal anode product of comparative example 1 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit the utility model. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Example 1:

metallic lithium negative electrode (example) preparation: using roll BOPP (biaxially oriented polypropylene) film as a base material, the thickness is 4um, firstly drying the roll BOPP film in a vacuum oven at 60 ℃ for 24 hours, and then carrying out vacuum evaporation on the film in a vacuum evaporation device (the vacuum degree is 10)^-3pa, the temperature is 800 ℃) and copper layers are evaporated on the upper surface and the lower surface of the rolled BOPP film, the thickness of the copper layer is 1um, and the current collector with the metal copper layer is obtained. And packaging the current collector by adopting a dried aluminum plastic bag, placing the current collector in a freezer, and performing freezing storage at a temperature of between 10 ℃ below zero and 18 ℃ below zero for more than two hours to prepare the product.

With the help of receive and release the roll system and two roll squeezer placed from beginning to end, two rolls of metal lithium area (thickness 20um) about unreeling, the middle mass flow body that unreels first roll squeezer is compound earlier, and pressure sets up to 1Mpa, and compound through second roll squeezer again, pressure sets up to 2Mpa, obtains the inseparable metal lithium negative pole of three-layer laminating. The surface temperature of the rollers of the first and second roll presses is-10 ℃. The structure of the obtained lithium metal cathode is schematically shown in fig. 1, wherein 1 is a high polymer material film layer, 2 is a copper layer, and 3 is a lithium metal tape. The photo of the lithium metal negative electrode product of example 1 is shown in fig. 2, wherein the surface of the lithium metal is flat, and the surface roughness Ra of the lithium metal negative electrode is 1.82 um.

Comparative example 1:

metallic lithium negative electrode (comparative) preparation: using roll BOPP (biaxially oriented polypropylene) film as a base material with the thickness of 4um, firstly drying the roll BOPP film in a vacuum oven at 60 ℃ for 24 hours, and then performing vacuum evaporation on the film in a vacuum evaporation device (the vacuum degree is 10)^- ³pa, and the temperature is 800 ℃) to steam-plate copper layers on the upper surface and the lower surface of the rolled BOPP film, wherein the thickness of the copper layer is 1um, and thus a current collector is obtained.

With the help of receive and release the roll system and two roll squeezer of placing around, two rolls of metal lithium area (thickness 20um) about unreeling, the middle mass flow body that unreels, compound with the roll squeezer at normal atmospheric temperature, pressure sets up to 2Mpa, obtains the inseparable metal lithium negative pole of three-layer laminating, as shown in figure 3, many folds on metal lithium surface, metal lithium negative pole roughness Ra is 7.2um, can't adorn the battery and use.

Claims

1. A lithium metal anode, comprising:

a current collector having a sandwich structure, and

metallic lithium/lithium alloy ribbons on both upper and lower surfaces of said current collector,

wherein the current collector has a sandwich structure composed of a base film layer and copper layers on both surfaces of the base film layer.

2. The metallic lithium anode of claim 1, wherein the copper layer has a thickness of 100nm-3 um.

3. The lithium metal anode of claim 1, wherein the lithium metal/lithium alloy ribbon has a thickness of 1-150 um.

4. The lithium metal anode of claim 1, wherein the substrate film layer has a thickness of 3-10 um.

5. The lithium metal anode of claim 1, wherein the base film layer is formed from a high molecular polymer material.

6. The lithium metal anode of claim 1, wherein the lithium metal anode has a width of 10-1000 mm.

7. The lithium metal negative electrode of claim 1, wherein the lithium metal negative electrode has a flat surface without wrinkles, and the surface roughness Ra of the lithium metal negative electrode is in a range of 0.5-3 um.

8. A secondary battery comprising the lithium metal anode of any one of claims 1 to 7, and further comprising a positive electrode/separator/electrolyte or a positive electrode/solid electrolyte.