Anisotropic collector for lithium-ion battery, and manufacturing method therefor and application thereof

Abstract

Disclosed are an anisotropic collector for a lithium-ion battery, and a manufacturing method therefor and an application thereof. The collector is made of a resin material added with spherical metal particles. Conductive particles of the collector in an X-Y direction do not form a sufficient conductive network, but form a good conductive network in a Z direction. While a short circuit occurs, the collector is not easy to activate most of active materials in the X-Y direction so that thermal runaway is not easy to occur, but the collector may fully conduct electricity in the Z direction so that the battery may be normally charged and discharged, thereby improving battery safety.

Claims

1. A collector, which is made of a resin material added with spherical metal particles, wherein the spherical metal particles form a conductive path, the width of the conductive path is 500 nm-20 μm, the distance between adjacent conductive paths is 500 nm-20 μm, and the diameter of the spherical metal particles is 500 nm-20 μm.

2. The collector according to claim 1, wherein the spherical metal particles are metals that do not generate an alloying reaction with lithium ions; and preferably, the spherical metal particles is selected from one or a combination of two or more of nickel, gold, silver, platinum, titanium, and copper.

3. The collector according to claim 1, wherein the spherical metal particles is solid, hollow or spherical metal particles having a core-shell structure.

4. The collector according to claim 1, wherein the volume percentage of the spherical metal particles accounting for the collector is 30 wt %-70 wt %.

5. The collector according to claim 1, wherein the resin material is a polyolefin-based material, for example, a copolymer or a mixture of one or a combination of two or more of a high-density polyethylene, a low-density polyethylene, a polypropylene, a polybutene, and a polymethylpentene.

6. The collector according to claim 1, wherein the spherical metal particles and the resin material are distributed at intervals, and in an X-Y direction, the number of the conductive particles forming the conductive paths does not exceed 20% of the total number of the conductive particles.

7. The collector according to claim 1, wherein the thickness of the collector is 5-20 μm; and preferably, the thickness of the collector is less than 20 μm, further preferably less than 15 μm, and more preferably less than 10 μm.

8. The collector according to claim 1, wherein the surface impedance is lower than 15 mohm/sq, preferably lower than 10 mohm/sq.

9. The collector according to claim 1, wherein the density of the collector is 0.3 g/cc-0.8 g/cc.

10. A method for preparing the collector according to claim 1, wherein the method comprises: heating a resin to above the melting temperature, and mixing it with spherical metal particles uniformly; and extruding a molten mixture added with the spherical metal particles into a cooling chamber, rapidly increasing the viscosity of the mixture while cooled to form a film, and then stretching the film to the corresponding thickness and internal structure by a group of stretching rollers.

11. The method according to claim 10, wherein the preheating temperature of a melting furnace is 80° C.; and preferably, the stretching speed of a mechanical drum is 10 m/min-40 m/min, and the stretching tension is 5N-25N.

12. An application of the collector according to claim 1 in preparing a lithium-ion battery.

13. The collector according to claim 2, wherein the spherical metal particles is solid, hollow or spherical metal particles having a core-shell structure.

14. The application according to claim 12, wherein the spherical metal particles are metals that do not generate an alloying reaction with lithium ions; and preferably, the spherical metal particles is selected from one or a combination of two or more of nickel, gold, silver, platinum, titanium, and copper.

15. The application according to claim 12, wherein the volume percentage of the spherical metal particles accounting for the collector is 30 wt %-70 wt %.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a flow diagram of a preparation process of a collector of Embodiment 1.

[0031] FIG. 2 is a schematic diagram of a process for forming an anisotropic collector with a conductive path structure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] In order to have clearer understanding of technical features, purposes and beneficial effects of the present disclosure, technical schemes of the present disclosure are now described in detail below in combination with the drawings and specific embodiments. It should be understood that these embodiments are only used to describe the present disclosure and not to limit a scope of the present disclosure. In the embodiments, experimental methods without specific conditions are conventional methods and conventional conditions well-known in the field, or operated in accordance with conditions suggested by instrument manufacturers.

Contrast Example 1

[0033] Positive electrode: LFP (10 μm)

[0034] Negative electrode: artificial graphite (20 μm)

[0035] Diaphragm: 12 μm PE+2 μm Al.sub.2O.sub.3

[0036] Size: 600 L×300 W×1 Tmm single cell structure

[0037] Collector: positive electrode (Al, 12 μm in thickness); and negative electrode (Cu, 8 μm in thickness)

[0038] Acupuncture experiment: at a temperature of 20±5° C., a battery is in a full point state (SOC100), a steel needle with a diameter of 3 mm is used to penetrate rapidly in a direction perpendicular to an electrode plate, and the steel needle stays in it.

Embodiment 1

[0039] Positive electrode: LFP (10 μm)

[0040] Negative electrode: artificial graphite (20 μm)

[0041] Diaphragm: 12 μm PE+2 μm Al.sub.2O.sub.3

[0042] Size: 600 L*300 W*1 Tmm single cell structure

[0043] Collector: positive electrode (50 wt % nickel ball (5 μm in diameter)+50 wt % PP, 5 μm in thickness); negative electrode (50 wt % nickel ball (5 μm in diameter)+50 wt % PP, 5 μm in thickness). Herein, spherical metal particles form a conductive path, the width of the conductive path is 5 μm, the distance between adjacent conductive paths is 3 μm, and the diameter of the spherical metal particles is 5 μm. In an X-Y direction, the number of the spherical metal particles forming the conductive path is 20% of the total number of the conductive particles. The collector is prepared according to the following steps, as shown in FIG. 1:

[0044] a resin is heated to above the melting temperature, and mixed with the spherical metal particles uniformly, and the preheating temperature of a melting furnace is 80° C.; and

[0045] a molten mixture added with the spherical metal particles is extruded into a cooling chamber, the viscosity of the mixture is rapidly increased to form a film while cooled, and then the film is stretched by a group of stretching rollers (stretching speed: 15 m/min, and the stretching tension is 15 N), to obtain the collector. The thickness is 5 μm, and the surface impedance is 13 mohm/sq.

[0046] Acupuncture experiment: at a temperature of 20±5° C., a battery is in a full point state (SOC100), a steel needle with a diameter of 3 mm is used to penetrate rapidly in a direction perpendicular to an electrode plate, and the steel needle stays in it.

Embodiment 2

[0047] Positive electrode: LFP (10 μm)

[0048] Negative electrode: artificial graphite (20 μm)

[0049] Diaphragm: 12 μm PE+2 μm Al.sub.2O.sub.3

[0050] Size: 600 L×300 W×1 Tmm single cell structure

[0051] Collector: positive electrode (50 wt % nickel ball (10 μm in diameter)+50 wt % PP, 10 μm in thickness); negative electrode (50 wt % nickel ball (10 μm in diameter)+50 wt % PP, 10 μm in thickness). Herein, spherical metal particles form a conductive path, the width of the conductive path is 10 μm, the distance between adjacent conductive paths is 5 μm, and the diameter of the spherical metal particles is 10 μm. In an X-Y direction, the number of the spherical metal particles forming the conductive path is 20% of the total number of the conductive particles. The collector is prepared according to the following steps:

[0052] a resin is heated to above the melting temperature, and mixed with the spherical metal particles uniformly, and the preheating temperature of a melting furnace is 80° C.; and

[0053] a molten mixture added with the spherical metal particles is extruded into a cooling chamber, the viscosity of the mixture is rapidly increased to form a film while cooled, and then the film is stretched by a group of stretching rollers (stretching speed: 10 m/min, and the stretching tension is 15 N), to obtain the collector. The thickness is 10 μm, and the surface impedance is 12 mohm/sq.

[0054] Acupuncture experiment: at a temperature of 20±5° C., a battery is in a full point state (SOC100), a steel needle with a diameter of 3 mm is used to penetrate rapidly in a direction perpendicular to an electrode plate, and the steel needle stays in it.

Embodiment 3

[0055] Positive electrode: LFP (10 μm)

[0056] Negative electrode: artificial graphite (20 μm)

[0057] Diaphragm: 12 μm PE+2 μm Al.sub.2O.sub.3

[0058] Size: 600 L×300 W×1 Tmm single cell structure

[0059] Collector: positive electrode (50 wt % hollow nickel ball (10 μm in diameter)+50 wt % PP, 10 μm in thickness, and the thickness of an shell is 1 μm); negative electrode (50 wt % hollow nickel ball (10 μm in diameter)+50 wt % PP, 10 μm in thickness, and the thickness of an shell is 1 μm). Herein, spherical metal particles form a conductive path, the width of the conductive path is 10 μm, the distance between adjacent conductive paths is 5 μm, and the diameter of the spherical metal particles is 10 μm. In an X-Y direction, the number of the spherical metal particles forming the conductive path is 20% of the total number of the conductive particles. The collector is prepared according to the following steps:

[0060] a resin is heated to above the melting temperature, and mixed with the spherical metal particles uniformly, and the preheating temperature of a melting furnace is 80° C.; and

[0061] a molten mixture added with the spherical metal particles is extruded into a cooling chamber, the viscosity of the mixture is rapidly increased to form a film while cooled, and then the film is stretched by a group of stretching rollers (stretching speed: 15 m/min, and the stretching tension is 10 N), to obtain the collector. The thickness is 10 μm, and the surface impedance is 15 mohm/sq.

[0062] Acupuncture experiment: at a temperature of 20±5° C., a battery is in a full point state (SOC100), a steel needle with a diameter of 3 mm is used to penetrate rapidly in a direction perpendicular to an electrode plate, and the steel needle stays in it.

Embodiment 4

[0063] Positive electrode: LFP (10 μm)

[0064] Negative electrode: artificial graphite (20 μm)

[0065] Diaphragm: 12 μm PE+2 μm Al.sub.2O.sub.3

[0066] Size: 600 L×300 W×1 Tmm single cell structure

[0067] Collector: positive electrode (50 wt % nickel-coated aluminum (core-shell) wrapping spherical particles (10 μm in diameter)+50 wt % PP, 10 μm in thickness; and a coating layer is 1 μm); and negative electrode (50 wt % nickel-coated copper (core-shell) wrapping spherical particles (10 μm in diameter, and a coating layer is 1 μm)+50 wt % PP, 10 μm in thickness). Herein, spherical metal particles form a conductive path, the width of the conductive path is 10 μm, the distance between adjacent conductive paths is 5 μm, and the diameter of the spherical metal particles is 10 μm. In an X-Y direction, the number of the spherical metal particles forming the conductive path is 20% of the total number of the conductive particles. The collector is prepared according to the following steps:

[0068] a resin is heated to above the melting temperature, and mixed with the spherical metal particles uniformly, and the preheating temperature of a melting furnace is 80° C.; and

[0069] a molten mixture added with the spherical metal particles is extruded into a cooling chamber, the viscosity of the mixture is rapidly increased to form a film while cooled, and then the film is stretched by a group of stretching rollers (stretching speed: 10 m/min, and the stretching tension is 10 N), to obtain the collector. The thickness is 10 μm, and the surface impedance is 15 mohm/sq.

[0070] Acupuncture experiment: at a temperature of 20±5° C., a battery is in a full point state (SOC100), a steel needle with a diameter of 3 mm is used to penetrate rapidly in a direction perpendicular to an electrode plate, and the steel needle stays in it.

[0071] The batteries of Contrast example 1 and Embodiments 1˜4 are tested as shown in Table 1, and results are shown in Table 1.

TABLE-US-00001 TABLE 1 Contrast example 1 Embodiment 1 Embodiment 2 Embodiment 3 Embodiment 4 Positive electrode LFP LFP LFP LFP LFP Negative electrode Artificial Artificial Artificial Artificial Artificial graphite graphite graphite graphite graphite Collector Positive Al, 50 wt % nickel 50 wt % nickel 50 wt % hollow 50 wt % nickel-coated electrode 12 μm in ball (5 μm in ball (10 μm in nickel ball aluminum (core-shell) thickness diameter) + 50 diameter) + 50 (10 μm in wrapping spherical wt % PP, 5 μm wt % PP, 10 μm diameter) + 50 particles (10 μm in in thickness in thickness wt % PP, 10 μm diameter) + 50 wt % in thickness PP, 10 μm in thickness Negative Cu, 50 wt % nickel 50 wt % nickel 50 wt % hollow 50 wt % nickel-coated electrode 8 μm in ball (5 μm in ball (10 μm in nickel ball copper (core-shell) thickness diameter) + 50 diameter) + 50 (10 μm in wrapping spherical wt % PP, 5 μm wt % PP, 10 μm diameter) + 50 particles (10 μm in in thickness in thickness wt % PP, 10 μm diameter) + 50 wt % in thickness PP, 10 μm in thickness Single cell length (mm) 600 600 600 600 600 Single cell width (mm) 300 300 300 300 300 Single cell height (mm) 1 1 1 1 1 Single cell energy 190 210 205 220 203 density (Wh/kg) Single cell energy 390 420 395 395 395 density (Wh/L) Single cell capacity (Ah) 66 66 66 66 66 First effect (%) 94 91 93 93 93 Cycle 2000 1500 2000 2000 2000 EOL DCIR 120%  125%  120%  120%  120%  Pack energy density 152 164 160 178 162 (Wh/kg) Pack energy density 187 250 260 260 260 (Wh/L) 1 C/0.1 C 90% 89% 90% 91% 93% 6 C/0.1 C 71% 67% 69% 70% 75% Acupuncture 5 3 3 3 3 experiment (HL)

[0072] It may be seen from Table 1 that, the resin-based collector of the present disclosure is used, the volume energy density of Pack and the safety performance of the battery are both greatly improved (acupuncture experiment).