Novel Lead and Carbon Materials and Their Application in Lead-Acid Batteries
High-Capacity Lead-Carbon Batteries
Since the 19th century, lead-acid batteries have seen increasingly widespread use, particularly in electric vehicles where various types of batteries have been employed. However, many still require significant improvement, such as low energy density and insufficient specific capacity. One primary reason lies in the high proportion of alloy plates used (over 25%). Mesh glass-coated lead can replace conventional lead plates, offering significantly lower density (only 1/8th of conventional lead) to reduce the weight and volume of lead-acid batteries while maintaining high energy density. The Advanced Lead-Acid Alliance has also explored this approach, utilizing mesh glass carbon as the positive plate material and alloy grids or coated short-circuit protection as the negative plate. The design has undergone rigorous testing. New materials for busbars in 120V batteries, such as high-conductivity copper (0HO), have also been experimentally evaluated. This CPC material exhibits superior mechanical properties and electrical parameters (low resistance). When used in refined battery structures, it is significantly lighter than traditional lead grids. CPC plates account for only 10-12% of the battery's total mass, while lead plates typically constitute 22-27% of the total mass.
(1) Lead-carbon metal composite
It is well known that lead, as a non-transition element, is chemically inert toward carbon, forming a blunt contact angle on graphite and diamond surfaces. At 1073 K, the contact angle of lead on molten graphite is a blunt angle (130°).
A novel method for producing lead-carbon metal composites relies on direct chemical reactions between carbon ions and molten metallic lead. This reaction occurs at temperatures between 700 and 750°C using melts of oxides or natural salt oxides. The result is the direct one-step synthesis of nano-lead particles within the molten lead composite, bypassing the multi-step synthesis of isolated nano-carbon. At such elevated temperatures, the reaction between carbide ions from the hard alloy and molten graphite particles releases metallic particles in the form of solid solutions, graphite flakes, or graphite crystals with average sizes ranging from 10 to 50 nm. In this composite material, the carbon particle content, particle size, form, type, and concentration are all dependent on the type of metal or non-metallic carbide used.
(2) Novel Structural Carbon-Lead Composites
A novel carbon-coated lead material features a core-shell structure, with lead as the core and carbon as the shell. This material is synthesized via hydrothermal carbonization to prepare carbon-coated lead, with a shell layer thickness of 10–30 nm.
It utilizes highly conductive carbon and poorly conductive PbO or Pb to provide electron conduction pathways, thereby enhancing the material's electrical conductivity. By studying hydrogen evolution curves of several commercial materials and Pb/C composites in H₂SO₄ (d=1.28 g/cm³) solution, it was found that Pb/C composites exhibit the lowest hydrogen evolution current density at the same potential. Linear relationships were also observed among certain kinetic parameters: under constant potential, the overpotential at a hydrogen evolution current density of 1 μA/g indicates the difficulty of the hydrogen evolution reaction. At constant time, the hydrogen evolution reaction rate exhibits a relationship with potential: the data indicate that the hydrogen evolution overpotential for Pb/C composite materials is higher than that of other carbon materials, suggesting Pb/C composites are unlikely to undergo hydrogen evolution. During battery operation, Pb/C batteries also exhibit reduced self-discharge during charging. After 10,000 cycles, voltammetric analysis reveals excellent capacity retention in Pb/C composite batteries, maintaining 94% of initial capacity. This demonstrates the exceptional electrochemical stability of carbon materials.
Lead-carbon batteries incorporate composite materials into the negative electrode active substance during fabrication, differing from traditional lead-acid batteries. Lead-carbon batteries exhibit exceptionally long WRPSoC cycle life, with no accumulation of large Pb5O4 particles on the negative plate after cycling.