Anode plates, as core components in fields such as electrochemistry, metallurgy, and environmental protection, are categorized in various ways. Different types of anode plates have unique performance and application scenarios due to differences in material, structure, or purpose. The following is a detailed explanation from the perspectives of material, process, and function.
Classification by Material: Determinants of Basic Performance
The material of the anode plate directly determines its conductivity, corrosion resistance, and catalytic activity. Common classifications include metal-based, graphite-based, and composite-based.
1. Metal-Based Anode Plates
Metal-based anode plates are primarily made of metals such as lead, titanium, stainless steel, or their alloys and are the most widely used type. Lead alloy anode plates (such as lead-silver and lead-calcium alloys) dominate traditional lead-acid batteries and hydrometallurgy (such as copper and zinc electrolysis) due to their low cost and moderate oxygen evolution overpotential. Titanium-based anode plates (typically coated with precious metal oxides such as ruthenium-titanium or iridium-titanium) have become the mainstream choice in the chlor-alkali industry and wastewater treatment electrolysis due to their excellent corrosion resistance and high catalytic activity. For example, in chlor-alkali production, titanium-coated anodes can increase chlorine evolution efficiency by over 30% and extend their lifespan to over five times that of traditional graphite anodes.
2. Graphite-Based Anode Plates
Graphite has long been used in applications such as water electrolysis for hydrogen production and aluminum electrolysis due to its excellent chemical stability (resistance to acid and alkali corrosion) and moderate conductivity. However, natural graphite is brittle and has low mechanical strength, leading to its gradual replacement by artificial graphite (which achieves density enhancement through high-temperature graphitization). However, graphite anodes are susceptible to oxidation loss in highly oxidizing environments (for example, chlorine in the chlor-alkali industry can corrode the graphite surface). Currently, they are mostly replaced by titanium-coated anodes, remaining in use only in some cost-sensitive, small-scale electrolysis applications.
3. Composite-Based Anode Plates
To address the limitations of single materials, researchers have developed a variety of composite anode plates, such as a "titanium mesh + carbon fiber" composite structure (which combines the strength of titanium with the conductivity of carbon) and a "stainless steel base + rare earth oxide coating" (which reduces cost while improving corrosion resistance). These anode plates, through optimized material combinations, exhibit unique advantages in specific applications (such as seawater electrolysis and electrochemical treatment of high-concentration wastewater).
Classification by Manufacturing Process: Detailed Control of Structure and Performance
The manufacturing process directly influences the anode plate's microstructure (e.g., porosity, coating uniformity) and macromorphology (e.g., plate or mesh), which in turn determines its applicable applications.
1. Rolled Anode Plates
Made by high-temperature rolling of metal sheets (such as lead or titanium), these plates offer a smooth, dense surface and are suitable for applications requiring uniform current distribution (such as in the electrowinning of refined copper). However, their poor flexibility makes them difficult to adapt to complex electrolytic cell shapes.
2. Stamped/Welded Anode Plates
These plates are stamped into specific shapes (such as rectangular plates with holes) and then welded with reinforcing ribs. They are commonly used in large hydrometallurgical electrolytic cells (such as zinc electrowinning cells). Their high structural strength allows them to withstand the pressure of electrolyte erosion and anode slime deposition.
3. Coated/Sintered Anode Plates
For inert substrates such as titanium, an active coating is applied via thermal decomposition (coating a ruthenium or iridium salt solution followed by high-temperature sintering) or electrochemical deposition. The key to this process lies in controlling coating thickness (typically 10-50 microns) and adhesion. For example, the coating on ruthenium-titanium anodes used in the chlor-alkali industry requires multiple sintering cycles (each at 500-600°C) to ensure resistance to peeling in highly corrosive environments.
Classification by Function and Application: Differentiated Design for Scenario Adaptation
Based on actual application requirements, anode plates can be further divided into general-purpose and specialized types.
1. General-purpose Anode Plates
Represented by lead alloy or ordinary titanium-based anodes, these are suitable for conventional electrochemical processes (such as general electroplating and low-concentration wastewater treatment). They are characterized by low cost and mature technology, but are less adaptable to extreme environments (such as high chloride ion concentrations and strong alkaline media).
2. Specialized Anode Plates
Optimized designs are designed for specific scenarios. For example, DSA (Dimensionally Stable Anode) anode plates used in wastewater treatment are coated with iridium-tantalum composite oxides, which efficiently degrade organic matter and produce active chlorine in high-salinity wastewater. Nickel anode plates used in the electroplating industry use a small amount of sulfur to improve anode dissolution uniformity and avoid "burned" coating defects. Lithium metal anode plates used in solid-state batteries in the new energy sector require special coatings (such as ceramic electrolyte composite layers) to inhibit dendrite growth and improve safety.
Conclusion
The classification of anode plates is essentially the result of the coordinated development of materials science, engineering technology, and application needs. From traditional lead plates to modern titanium-based coated anodes, from simple plate structures to multifunctional designs, each refinement of the classification has driven technological progress in related fields. In the future, with the rapid development of the new energy and environmental protection industries, new anode plates that combine high activity, long life, and environmental friendliness (such as bio-based composite anodes) may become a research hotspot, further expanding the application boundaries of anode plates.
