Carbon coated aluminum foil industry study-reasons for large scale production expansion

Carbon coated aluminum foil industry study-reasons for large scale production expansion

Table of Contents

In the current lithium battery industry, lithium-ion batteries have been widely used in portable electronic devices, new energy vehicles and energy storage power plants, etc. In addition to the important four main materials, the set Fluid is an important part of lithium battery, accounting for 10% to 13% of the total weight, its thickness weight, surface performance will affect the performance of lithium batteries.

Among them, aluminum foil as the cathode collector fluid, with the continued growth of power battery shipments and large-scale expansion of production capacity, the market demand has maintained a significant growth trend. Since this year, major lithium battery companies and foil companies have begun to carry out large-scale expansion of high-end composite aluminum foil, that is, carbon coated aluminum foil.

Advantages of carbon coated aluminum foil

The passivation layer on the surface of aluminum foil can avoid corrosion of electrolyte during charging and discharging, and it is often used as a cathode collector to match LiCoO2, lithium manganate, ternary materials and LiFePO4, etc.

However, conventional aluminum foil usually has the following limitations.

● Limited contact area with positive material in the electrode sheet, affecting the internal resistance of the positive electrode sheet.

● Limited bonding strength with binder and active material, which leads to loose bonding between particle materials and easy powder dropping due to constant changes in electrode volume during cyclic charging and discharging, resulting in rapid decay of battery capacity and cycle life.

● The oxidation decomposition products of electrolyte occur on the surface of the electrochemical reaction, leading to and accelerating the corrosion of aluminum foil. Therefore the application trend of high-end batteries, especially ternary lithium battery is the need for modification of aluminum foil.

The main methods of modification of aluminum foil are as follows.

● Surface treatment (chemical etching, electrochemical etching, DC anodizing, corona treatment)

● Conductive coatings (surface coated carbon, graphene coating, carbon nanotube coating, composite coating)

● 3D porous structure (foam structure, nanoribbon structure, nanocone mechanism, fiber weave mechanism).

● Composite modification treatment.

Among them, surface coating of carbon is a common modification method for aluminum foil.

Carbon coated aluminum foil is a material used for lithium-ion battery cathode collector after adding a carbon coating layer to the surface of aluminum foil. The carbon powder is mixed with certain film-forming agents, solvents and auxiliaries to form a slurry and then coated on the surface of aluminum foil, forming a dense carbon coating layer after drying.

Carbon coated aluminum foil is a common modified aluminum foil

Compared to blank aluminum foil, carbon coated aluminum foil improves the electrical conductivity of the positive electrode sheet and can reduce the internal resistance of the battery. For example, lithium iron phosphate itself has poor electrical conductivity and lacks a bridge to transfer electrons between it and the light aluminum foil. After carbon coated treatment, carbon coated aluminum foil can play the role of a bridge to tightly bond the cathode active material to the aluminum foil and embed the particles with each other, thus improving the electrical conductivity of the cathode sheet and ultimately reducing the internal resistance of the battery.

In addition, carbon coated aluminum foil can make the aluminum foil surface uniformly concave and convex, increasing the contact area between the active material in the electrolyte and the cathode collector fluid, thus transferring electrons faster and collecting current when charging and discharging rapidly at high current, which can improve the battery multiplier charging and discharging performance and help lithium batteries improve their efficiency and adapt to large multiplier fast charging.

The advantages are:

● Lowering the interfacial impedance of the collector fluid, reducing polarization and improving cycle life and multiplier performance.

● Improve the adhesion of active material and collector fluid, reduce the amount of binder, and lower the production cost.

● Prevent the collector fluid from corrosion and oxidation, and extend the cell life.

In summary, carbon coated aluminum foil has the ability to improve battery energy density, inhibit battery polarization, reduce battery internal resistance, increase battery cycle life, and is currently mainly used in lithium iron phosphate batteries. In recent years, with the battery energy density requirements to improve, carbon coated aluminum foil market demand continues to release, nearly 90% of the current power lithium batteries have used carbon coated aluminum foil.

Development of carbon coated aluminum foil

The core barrier of carbon coated aluminum foil lies in the formulation of the conductive coating, i.e. the manufacturer needs to produce a functional coating with stable performance, voltage resistance, electrolyte/hydrofluoric acid corrosion resistance, and high electrical conductivity, and coat it uniformly on the surface of the aluminum foil.

The core barriers of carbon coated aluminum foil

Conductive coatings are divided into intrinsic conductive coatings and filler conductive coatings, intrinsic conductive coatings are the use of their own conductive polymer materials, there are processing difficulties, the conjugate structure is vulnerable to damage and manufacturing costs and other shortcomings, it is difficult to large-scale applications; filler conductive coatings are conductive fillers (such as metal fillers, carbon materials) and film-forming agents, solvents and additives and other co-mingled coatings, the current industrialization of the main carbon coatings.

In carbon-based conductive coatings, graphite is used in combination with carbon black for better processing and conductivity; graphene is often added to the coating to improve conductivity and increase scratch resistance and flexibility. In addition, as fillers, usually flake fillers have better conductivity than spherical fillers, while carbon nanotubes with larger aspect ratios have optimal conductivity.

Usually conductive carbon paste consists of carbon materials, film-forming materials, solvents and additives, film-forming agents are acrylic, polyurethane, epoxy, polyester and alkyd resins and other common binders, in order to increase the film-forming properties, film-forming agents are often used in conjunction with the corresponding cross-linking agents; solvents are true solvents of resins, with a certain degree of wettability of the carbon material. And in order to meet the green, safe market demand, water-based conductive pastes become a hot research trend.

Carbon coated aluminum foil market status

In the global market, carbon coated aluminum foil consumer market is mainly concentrated in North America, Europe, China and Japan and other countries and regions with more complete industrial development system, of which China and Japan carbon coated aluminum foil production scale ranks among the global forefront. In recent years, with the economic development of Southeast Asia, as well as the global industry to the east, Malaysia, Indonesia, Thailand and other Southeast Asian countries carbon coated aluminum foil market demand growth rate accelerated, the future market development potential.

Carbon coated aluminum foil will continue to be upgraded

Global carbon coated aluminum foil market concentration is high, currently carbon coated aluminum foil manufacturers are mainly located in Japan, China and other Asia-Pacific region. carbon coated aluminum foil processing costs are high, is the ordinary lithium aluminum foil 2-3 times. In recent years, along with the downstream lithium battery density, the market for carbon coated aluminum foil cost, quality, performance, specifications and other higher requirements, in the relevant enterprises actively improve, carbon coated aluminum foil specifications gradually increased, the function of the richer.

In the long run, the carbon coated aluminum foil industry will continue to diversify, high performance, functionalization, environmental protection direction upgrade, its processing technology to be further optimized, while the upgrading of market demand, will also drive the development of carbon coated aluminum foil to high performance, functionalization direction.

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