Mesocarbon Microspheres (MCMB) are micrometer sized spherical carbon materials with a nematic liquid crystal layered stacking structure generated by thermal condensation of heavy aromatic compounds such as asphalt. Some MCMBs are prepared using petroleum asphalt or coal tar as raw materials.

Structure and Characteristics

The outstanding performance of MCMB is entirely due to its unique physical and chemical structure:

Spherical particle morphology:

Advantages: The particles are perfectly spherical or nearly spherical in shape, with a smooth surface. This form gives it excellent fluidity and compaction density, making it easier to evenly apply when preparing electrode slurries. After compaction, higher energy density electrode sheets can be obtained.

Layered graphitic structure:

Advantages: After high-temperature graphitization treatment, the carbon atoms inside are arranged in a highly ordered layered structure. This structure provides a stable and unobstructed channel for the insertion and extraction of lithium ions, thus possessing excellent rate performance (fast charging and discharging) and long cycle life.

Isotropic:

Advantages: Unlike the anisotropy of ordinary graphite sheet structures, the spherical structure of MCMB means that its properties are the same in all directions. This allows lithium ions to be embedded from any surface of the ball, avoiding the problem of uneven expansion caused by directionality, and the structure is very stable.

Core advantages as a negative electrode material for batteries

Based on the above structure, MCMB negative electrode material exhibits the following high-performance characteristics:

High magnification performance: Very suitable for fast charging applications. Lithium ions can quickly embed and detach spherical particles from various directions, resulting in high capacity retention and low polarization during high current charging and discharging.

Excellent cycle life: The highly graphitized structure and spherical stability result in minimal material volume changes during charge and discharge processes, making the structure less susceptible to damage and able to withstand thousands of cycles.

Good low-temperature performance: Its unique lithium insertion mechanism allows it to maintain relatively good capacity and power output in low-temperature environments.

High safety: The spherical structure has good compatibility with electrolytes, fewer side reactions, and relatively high thermal stability.

Technical preparation process

The preparation of MCMB is a complex and energy intensive process, which directly leads to its high cost. The main steps include:

Precursor treatment: Select suitable coal tar pitch or petroleum pitch as raw materials.

Intermediate phase formation (liquid-phase carbonization): Under an inert atmosphere, the asphalt is heated to about 400 ° C. At this temperature, the large aromatic molecules in the asphalt undergo thermal decomposition, condensation, and rearrangement, forming a liquid crystal state called the "intermediate phase". This type of liquid crystal spontaneously forms micrometer sized spheres under the action of surface tension.

Separation and extraction: The formed MCMB is separated and washed from the remaining asphalt using a solvent such as quinoline.

Carbonization and graphitization: These are the most critical and energy consuming steps. Firstly, carbonization is carried out at around 1000 ° C after non melting treatment, and then heat treatment is carried out in an ultra-high temperature graphitization furnace up to 2800 ° C-3000 ° C to transform the disordered carbon structure into a highly ordered graphite layered structure.

Screening and packaging: Finally, screen according to the particle size range required by the customer.

The ultra-high temperature graphitization during this process is one of the main sources of cost.

Main application areas

Due to its high performance (and of course, high cost), MCMB is often used in fields that require extremely high performance, lifespan, and reliability:

High end consumer electronics products, such as ultra-thin laptops and batteries for high-end smartphones.

Power battery: Especially for electric vehicle batteries that have extremely high requirements for fast charging and cycle life.

Energy Storage System (ESS): Especially for grid energy storage and household energy storage systems that require frequent charging and discharging and long lifespan assurance.

Special purpose batteries: fields such as drones, aerospace, medical equipment, etc. that require extremely high battery performance.