|The new battery features high energy content and high rate capability. Images of anode material (left) and cathode (right). Click to enlarge.
Researchers from the University of Rome Sapienza (Italy) and Hanyang University (S. Korea) are developing a new advanced lithium-ion battery featuring a high capacity Sn-C nanostructured anode and a high rate, high-voltage Li[Ni0.45Co0.1Mn1.45]O4 spinel cathode.
The new chemistry offers excellent performances in terms of cycling life, i.e., around 100 high rate cycles; of rate capability, operating at 5C and still keeping more than 85% of the initial capacity; and of energy density, expected to be of the order of 170 Wh kg-1. These combined features make the battery a very promising energy storage for powering low- or zero-emission HEV or EV vehicles, the team report in a paper published in the Journal of the American Chemical Society.
Enhancements in energy density necessarily require the passage from the present lithium ion technology to novel, advanced chemistries based on high performance electrode materials. Good examples are lithium metal alloy anodes and spinel cathodes. It is expected that advancements in lithium ion battery technology can be achieved by combining these high performance electrode materials in a complete cell configuration.
In a previous paper we described a novel design battery formed by combining a high capacity nanostructured tin-carbon (Sn-C) anode with a high voltage LiNi0.5Mn1.5O4 spinel cathode. The excellent performance in terms of cycle life and rate capability confirmed the validity of the concept, thus encouraging us to extend the approach for obtaining other, advanced lithium ion battery chemistries. In this work we disclose an important example based on a Sn-C anode having an optimized morphology with a high rate, new Li[Ni0.45Co0.1Mn1.45]O4 cathode.—Hassoun et al.
Anode. While Lithium metal alloys (Li-M, M = Sn, Si, Sb, etc.) are very appealing as anode materials due to their higher specific capacity, the authors noted, the large volume expansion-contraction experienced during their electrochemical process in lithium cells has prevented their commercial use.
The researchers had earlier shown that the volume stress issue can be addressed by developing suitable electrode morphologies, such as M-C nanocomposites. The anode in their current work is basically similar to one they previously reported, although considerably upgraded in terms of surface morphology and rate capability. In particular, the issue of large irreversible capacity that affected the original material was addressed by a suitable surface treatment.
The Sn-C electrode was also upgraded in terms of rate capability, they said. Improvement in the morphology allowed the electrode to operate under high current rates.
Cathode. The performance of lithium manganese spinel cathode materials is strongly influenced by the particle size and by the presence of doping metals, they noted. While reduction in the particle size significantly improves the kinetics of the electrochemical lithium insertion/extraction reactions, it also increases reactivity for the electrolyte decomposition.
In this work we have addressed this contradictory issue by doping LiMn2O4 spinel with Ni and Co and, at the same time, by preparing the resulting Li[Ni0.45Co0.1Mn1.45]O4 cathode with particles at micrometric size (in order to avoid electrolyte decomposition) and using a metal ratio that is expected to provide high working voltage and high rate capability.—Hassoun et al.
Full battery. The authors combined the anode and cathode materials in a complete lithium ion battery using an ethylene carbonate:ethyl methyl carbonate, EC: EMC, lithium hexafluorophosphate (LiPF6) electrolyte. Testing showed that the practical working voltage of the battery ranges between 3.9 V and 4.7 V while the specific capacity, related to the cathode mass, is of the order of 125 mAh g-1. In addition, the battery can cycle at 1C with a very stable capacity delivery.
Taking an average voltage of 4.2 V, a top specific energy density value of 500 Wh kg-1 is obtained. Assuming a 1/3 reduction factor associated with the weight of the electrolyte, current collector, and aluminum case in a pouch configuration, we obtain a 170 Wh kg-1 value that still exceeds that offered by conventional lithium ion batteries chemistry.Hassoun et al.
Jusef Hassoun, Ki-Soo Lee, Yang-Kook Sun, Bruno Scrosati (2011) An Advanced Lithium Ion Battery Based on High Performance Electrode Materials. Journal of the American Chemical Society doi: 10.1021/ja110522x