As one of the many approaches under investigation to increase the power density, specific capacity, and cyclic efficiency of rechargeable lithium-ion batteries, researchers are seeking to develop higher-capacity anode materials (such as silicon- or tin-based materials). However, carbon remains the predominant commercial anode material solution at this point.

Researchers at Feng Chia University in Taiwan have developed a procedure to prepare surface-modified mesophase pitch carbon to increase the charge-discharge capacity and cycleability of carbon electrodes for lithium-ion batteries (LIBs).

After high-temperature treatment, GMP40 shows the highest first charge and discharge capacities of 426 and 322 mAh g^-1, respectively, while mesophase pitch carbon shows the first charge and discharge capacities of 237 and 206 mAh g^-1, respectively. A paper on their work appeared online 4 June in the ACS journal Energy & Fuels.

The GMP40 material also showed strong cycling performance, with capacity remaining above 250 mAh g^-1 at the 60^th cycle in comparison to less than 175 mAh g^-1 for

the mesophase pitch carbon.

Carbon materials—currently the predominant anode material for lithium-ion batteries—are categorized into three types, the researchers note: natural graphite, artificial graphite, and graphite-like carbon. Natural graphite is superior to other carbon candidates in terms of high capacity, low irreversible capacity at the first cycle, flat and low potential profile, large amounts of resources, and low cost.

Early studies showed that coke-coated graphite exhibits

some smaller irreversible capacity and better cyclability than

pristine graphite. The coke-coated graphite shows lower capacity than graphite, and it decreases the total reversible capacity for the anode of LIBs. Some studies have demonstrated that carbon coating of graphite improves the anode

performance in LIBs.

Presently, we show a new material for

the modified traditional anode of LIBs. We used mesophase

pitch carbon as a precursor to coat with various concentrations

of phenolic resin for application in the anode of LIBs.

The core material is mesophase pitch carbon, which is highly

crystalline.

—Lin et al.

The team produced seven different materials with different ratios of mesophase pitch carbon and phenolic resin ranging from pure mesophase pitch carbon (MGP) to carbon powder produced from pure phenolic resin (GPR). These were then fabricated into electrodes.

The remarkably improved electrochemical

properties for the coated mesophase pitch carbon

can be mainly attributed to the outer turbostratic structure,

which provided more sites for Li ions. Further studies and

evaluations are needed for commercial exploitation of the

mesophase pitch carbon coated with phenolic resin as negative

current collectors in LIBs.

—Lin et al.

Resources

• Jui-Hsiang Lin, Tse-Hao Ko, Wen-Shyong Kuo and Chia-Hung Wei (2010) Mesophase Pitch Carbon Coated with Phenolic Resin for the Anode of Lithium-Ion Batteries. Energy Fuels, Article ASAP doi: 10.1021/ef1004122