Application of metal grid composite current collector based on carbon nanotubes in battery

Abstract

The invention discloses application of a metal grid composite current collector based on carbon nanotubes in a battery, and belongs to the technical field of lithium ion batteries and energy storage devices. According to the invention, the carbon nanotube coating is introduced into the structure of the current collector, and the carbon nanotube coating and the 3D metal grid current collector form a'macroscopic-microscopic-nanometer 'multistage synergistic effect through the unique nanostructure, conductivity and mechanical properties, so that the energy density, the cycle life, the rate capability and the safety of the negative electrode are remarkably improved; and the method is particularly suitable for next-generation high-specific-energy batteries (such as silicon-based negative electrodes and lithium metal batteries) and flexible energy storage devices.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries and energy storage devices, and in particular to the application of a metal grid composite current collector based on carbon nanotubes in batteries. Background Art

[0002] Conventional lithium metal or silicon-based current collectors (such as copper foil and aluminum foil) have the following issues: insufficient conductivity: high-rate charge and discharge increases interfacial resistance, exacerbating polarization effects; poor active material adhesion: volume expansion (>300%) of silicon-based materials can easily cause active layer shedding; dendrite growth risk: non-uniform deposition of lithium metal anodes can easily generate dendrites, causing short circuits; and process limitations: conventional carbon coatings require high-temperature treatment (>600°C) and are incompatible with flexible substrates. Existing improvements, such as 3D porous metal current collectors and electroless lithium-philic coatings, have partially alleviated these issues, but still suffer from low energy density, insufficient mechanical strength (easily shedding), short cycle life, and complex processes. Summary of the Invention

[0003] In order to solve the above problems, the present invention provides an application of a metal grid composite current collector based on carbon nanotubes in a battery.

[0004] The present invention is achieved through the following technical solutions:

[0005] The invention relates to the application of a metal grid composite current collector based on carbon nanotubes in batteries, wherein the metal grid composite current collector based on carbon nanotubes is used as a negative electrode current collector.

[0006] Preferably, the CNTs in the carbon nanotube-based metal grid composite current collector are directly grown on the metal grid surface by slurry coating, spray coating or chemical vapor deposition (CVD).

[0007] Preferably, the carbon nanotube-based metal grid composite current collector is used as the CNT-coated silicon-based negative electrode, and the capacity retention rate can be improved from 70% to 90% after 500 cycles.

[0008] Preferably, a metal grid composite current collector based on carbon nanotubes is used as a silicon-carbon composite negative electrode, and a copper grid current collector coated with CNTs can increase the first coulombic efficiency of the silicon negative electrode from 75% to 85%, and the capacity retention rate is >80% after 1000 cycles.

[0009] Preferably, a metal grid composite current collector based on carbon nanotubes is used as the negative electrode of a lithium metal battery to reduce the lithium deposition overpotential to <50 mV and suppress the short circuit problem caused by dendrites.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] In the present invention, a carbon nanotube coating is introduced into the structure of the current collector. The carbon nanotube coating forms a "macro-micro-nano" multi-level synergistic effect with the 3D metal grid current collector through its unique nanostructure, conductivity and mechanical properties, significantly improving the energy density, cycle life, rate performance and safety of the negative electrode. It is particularly suitable for the next generation of high-energy-density batteries (such as silicon-based negative electrodes, lithium metal batteries) and flexible energy storage devices. DETAILED DESCRIPTION

[0012] The present invention is further described below:

[0013] This method directly grows CNTs onto a metal mesh surface through slurry coating, spraying, or chemical vapor deposition (CVD) to produce a carbon nanotube-based metal mesh composite current collector. The CNTs and 3D metal mesh current collector form a multi-level "macro-micro-nano" synergistic effect, significantly improving the energy density, cycle life, rate capability, and safety of the negative electrode. This approach is particularly suitable for next-generation high-energy-density batteries (such as silicon-based negative electrodes and lithium metal batteries) and flexible energy storage devices.

[0014] The specific principles and advantages are as follows:

[0015] 1. Enhance conductivity and electron transfer efficiency

[0016] Intrinsic high conductivity of carbon nanotubes: CNTs have extremely high electron mobility (about 10 4 –10 5 cm 2 / (V·s)), a three-dimensional conductive network can be formed on the surface of the metal grid, which can significantly reduce the interface resistance between the current collector and the negative electrode active material (such as silicon, graphite), for example, from 0.1Ω·cm 2 Down to 0.02Ω·cm 2 .

[0017] Multi-level conductive channels: The macroscopic conductive framework of the 3D metal grid and the nanoscale conductive network of CNTs work synergistically to achieve rapid electron transfer from the tab to the active material, especially reducing polarization effects during high-rate charge and discharge (such as above 5C).

[0018] 2. Improve active material loading and adhesion

[0019] High specific surface area support: CNT coating forms a nanoporous structure on the surface of the metal grid, and the specific surface area can be increased to 500-1000m 2 / g, significantly increasing the loading amount of negative electrode materials (such as silicon nanoparticles) (for example, from 8 mg / cm 2 Increased to 12mg / cm 2 ).

[0020] Mechanical anchoring effect: The fibrous structure of CNTs forms a physical interlock with the rough surface of the metal grid, combined with chemical bonding, such as the interaction between carboxyl groups and metal oxides, which effectively inhibits the shedding of active materials when the volume expands during charge and discharge (silicon expansion rate is about 300%).

[0021] 3. Buffer volume expansion stress and extend cycle life

[0022] Flexible buffer layer: CNT has excellent mechanical properties: elastic modulus of about 1TPa, tensile strength of 50–200GPa, which can absorb the volume change stress of alloy-type negative electrodes such as silicon, reducing the risk of electrode cracking.

[0023] Inhibit lithium dendrite growth: The uniform conductive network of CNT can guide the uniform deposition of lithium ions, reduce local current density, inhibit the formation of lithium dendrites (especially when used for lithium metal negative electrodes), and improve safety.

[0024] 4. Optimize interfacial chemical stability

[0025] Chemical inertness protection: The chemical stability of CNTs can reduce side reactions between metal current collectors (such as copper) and electrolytes (such as Cu dissolution), especially in high-voltage electrolyte (>4.3V) systems to extend battery life.

[0026] SEI film regulation: Functional groups on the CNT surface (such as -COOH, -OH) can induce the formation of a more stable and uniform solid electrolyte interface (SEI) film, reducing the interfacial impedance, for example, from 25Ω to 10Ω.

[0027] 5. Compatible with flexible and lightweight design

[0028] Lightweight and high strength properties: The density of CNT (about 1.3g / cm 3 ) is much lower than metal. After coating, the performance can be improved without significantly increasing the weight, and it is suitable for flexible devices (such as foldable batteries).

[0029] Bending resistance: The composite structure of CNT and 3D metal grid has a resistance change of less than 2% when bent (curvature radius <5mm), which is better than traditional foil (>10% change).

[0030] 6. Process compatibility and cost-effectiveness

[0031] Low-temperature coating process: CNTs can be grown directly on the metal grid surface through slurry coating, spraying or chemical vapor deposition (CVD), without the need for high-temperature annealing (traditional carbon coatings require >600°C), and are compatible with heat-sensitive substrates (such as PI films).

[0032] Reducing metal usage: By enhancing conductivity through CNTs, the thickness or line width of the metal grid can be reduced, for example, the line width can be reduced from 20μm to 15μm, further reducing material costs.

[0033] Practical application cases

[0034] Silicon-carbon composite anode: The CNT-coated copper grid current collector can increase the initial Coulombic efficiency of the silicon anode from 75% to 85%, and the capacity retention rate is >80% after 1,000 cycles.

[0035] Lithium metal batteries: CNT coating reduces the lithium deposition overpotential to <50mV and suppresses the short circuit problem caused by dendrites.

[0036] Experiments show that the capacity retention rate of the CNT-coated silicon-based negative electrode can be increased from 70% to more than 90% after 500 cycles.

[0037] In summary, the present invention introduces a carbon nanotube coating into the structure of the current collector. The carbon nanotube coating forms a "macro-micro-nano" multi-level synergistic effect with the 3D metal grid current collector through its unique nanostructure, conductivity and mechanical properties, significantly improving the energy density, cycle life, rate performance and safety of the negative electrode. It is particularly suitable for the next generation of high-energy-density batteries (such as silicon-based negative electrodes, lithium metal batteries) and flexible energy storage devices.

[0038] In summary, the above is only a preferred embodiment of the present invention and is not intended to limit the scope of implementation of the present invention. All equivalent changes and modifications of the shape, structure, characteristics and spirit described in the scope of the claims of the present invention should be included in the scope of the claims of the present invention.

Claims

1. Application of a carbon nanotube-based metal grid composite current collector in a battery, characterized by: A carbon nanotube-based metal grid composite current collector is used as the negative electrode current collector.

2. The use of the carbon nanotube-based metal grid composite current collector in a battery according to claim 1, characterized in that: The CNTs in the carbon nanotube-based metal grid composite current collector are directly grown on the metal grid surface by slurry coating, spray coating or chemical vapor deposition (CVD).

3. The use of the carbon nanotube-based metal grid composite current collector in a battery according to claim 1, characterized in that: The carbon nanotube-based metal grid composite current collector as the CNT-coated silicon-based negative electrode can increase the capacity retention rate from 70% to 90% after 500 cycles.

4. The use of the carbon nanotube-based metal grid composite current collector in a battery according to claim 1, characterized in that: A metal grid composite current collector based on carbon nanotubes is used as a silicon-carbon composite negative electrode, and a copper grid current collector coated with CNTs can increase the first coulombic efficiency of the silicon negative electrode from 75% to 85%, and the capacity retention rate is >80% after 1,000 cycles.

5. The use of the carbon nanotube-based metal grid composite current collector in a battery according to claim 1, characterized in that: The carbon nanotube-based metal grid composite current collector is used as the negative electrode of the lithium metal battery, which reduces the lithium deposition overpotential to <50mV and suppresses the short circuit problem caused by dendrites.