Researchers of the CAS
Key Laboratory of Molecular Nanostructure and Nanotechnology successfully designed
and synthesized a nanocomposite of LiFePO4 nanoparticles embedded in nanoporous
carbon matrix (LFP-NP@NPCM) as a superior cathode material for LIBs. The finding
has been published in the recent issue of Adv. Mater. (2009, 21, 2710-2714).
Amongst all the commercially available power sources, lithium-ion batteries
(LIBs) currently represent the state-of-the-art technology in high energy batteries,
and has occupied a prime position in the market place to power portable electronic
devices such as, laptops, personal digital assistants, and cellular phones.
However, for the use as power supplies of electric vehicles (EVs) and hybrid
electric vehicles (HEVs), it is still a challenge for LIBs to achieve long-term
cycling life and high power density in which supercapacitors currently address
the extremes.
Compared with the commercial LiCoO2, olivine-structural LiFePO4 has attracted
extensive interest as a potential cathode material for LIBs because of its numerous
appealing features such as high theoretical capacity (170 mA h g-1), high safety,
environmental benignity, and low cost.
One of the challenging issues in using it for high power LIBs is to tackle
its sluggish mass and charge transport.
In the present LFP-NP@NPCM, nanometer-sized LiFePO4 particles uniformly embed
in the nanoporous carbon matrix, which own the following virtues: i) Nanometer-sized
LiFePO4 particles could decrease the Li diffusion distance and time, resulting
in much improved power capability; ii) The pores in the porous carbon matrix
serve as electrolyte-containers for high rate charge/discharge process; iii)
The carbon matrix enhances the electronic conductivity of nanocomposite; iv)
The carbon matrix stabilizes the nanoscaled LiFePO4, and then improves the cycling
performance.
Therefore, the LFP-NP@NPCM electrode can be fully charged or discharged within
a period of about 16 seconds, similar to a super capacitor, but with more energy
density. Another excellent property of the LFP-NP@NPCM nanocomposite is the
superior cycling performance. The discharge capacity loss is less than 3% over
700 cycles at a rate of 1.5C (Fig. 2b).
The research is financially supported by the Chinese Academy of Sciences,
Ministry of Science and Technology of the People's Republic of China and China's
National Natural Science Foundation.
Posted August 19th, 2009
