High-capacity, high-rate Li-ion battery for HEV or EVs; mixed oxide cathode and Sn-C anode
04 February 2011
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| 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.
Resources
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
85% at 5C? Isn't that setting the bar kind of low? It is below 0C nearly every morning for 3 months of the year so what kind of loss are we looking for during our morning commutes? I do like the fact that they spoke about both the cathode and anode instead of boasting about gains in one and not the other.
I wish GCC would have a monthly article on what the state of the art in wholesale and retail pricing, weight per kWh and expected life cycles for batteries that are currently being sold. It is useful to see what the universities claim to expect in 2 or 3 years, but it would be even more enlightening to see what the facts on the ground are, and how they have changed over the past few years.
Posted by: Ziv | 04 February 2011 at 05:21 AM
Ziv,
The 5C refers not to temperature but the charging rate:
'The charge and discharge current of a battery is measured in C-rate. Most portable batteries are rated at 1C. This means that a 1000mAh battery would provide 1000mA for one hour if discharged at 1C rate. The same battery discharged at 0.5C would provide 500mA for two hours. At 2C, the 1000mAh battery would deliver 2000mA for 30 minutes. 1C is often referred to as a one-hour discharge; a 0.5C would be a two-hour, and a 0.1C a 10-hour discharge.'
http://batteryuniversity.com/partone-16.htm
So you can charge or discharge this battery in about 12.5 minutes 100 times and still retain 85% of capacity.
Hopefully it's cycle life at 1C to 2C is enough to be useful in an EV, as 100 cycles is not good enough.
Posted by: Davemart | 04 February 2011 at 05:42 AM
Mr. Ziv,
"5C" in this report does not mean a temperature of 5 degrees Celcius. It means the rate of charging (or discharging). A rate of charge/discharge of 5C means you can charge/discharge the battery in question in approximately 60min/5 = 12 minutes.
Posted by: Freddy Torres | 04 February 2011 at 05:50 AM
Ziv,
I like this site partly because there are no ads or popups. If you want analysis, you better do it yourself or read more comments. otherwise GCC will have to hire some analysts and put ads and popups to brainwash us to buy stuff.
100 charges at 5C is not bad, but depends onthe cost of the battery. If it's the same as Altairnano's titanium battery, no deal.
100 quick charges wouldn't be so bad if the cost was low. Most of the time I would slow charge, so they would proably last a few years for me. Many Li-Ion batteries can be quick charged, but it would be nice to compare their lifetimes.
Batteries don't have to be rechargable. I wouldn't mind replacing primary batteries once a week if they were cheap, available, only 20 kg, and safe for the environment.
Posted by: Zhukova | 04 February 2011 at 06:27 AM
"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, a 170 Wh kg-1 value that still exceeds that offered by conventional lithium ion batteries chemistry."
A loss of 330 Wh/kg due to electrolyte & packaging??
Posted by: Reel$$ | 04 February 2011 at 10:08 AM
The authors claim that 100 full quick charges is excellent performance. Probably it is comparable with other batteries. Slow charging probably gives a lifetime of many hundreds. The point is that their's is high specific energy and high current density. Usually, high current density batteries have low energy per kg.
Altairnano's titanium battery has very high current density, but the specific energy is only 47 wh/kg and they cost about $2000/kwh. For that price you can charge at high rate a couple thousand times. But the energy density is so low, they aren't practical in a BEV. The battery in this article doesn't have expensive metals like cobalt or complex manufacturing like nanowires, so it will probably be cost competitive with Li Iron Phosphate batteries, which are popular now, but have only 100 wh/kg.
This battery could be practical if it was not totally discharged every day and quick charging is done only infrequently, like on a twice a year vacation. The motorist who frequently forgets to charge it at night and does it at the quick charge station instead will have to buy a new battery sooner than desired. But, this is true with any battery that is quick charged or is used by someone who is fond of hard accelerating.
Posted by: Zhukova | 05 February 2011 at 04:28 PM
This is not the solution.
Posted by: HarveyD | 05 February 2011 at 06:04 PM
I missed the point by such a huge margin that I am rather embarrassed to return to the scene of my crime. I obviously thought that the 5C was a temperature.
I still wish there was a record of what the price per kWh was every month, if the past few years were documented in a site like this it would give us a better idea of what we could expect in the future.
Posted by: Ziv | 06 February 2011 at 05:32 PM
I'm actually impressed with this battery if it performs as they say. It's nice to have quick charging possible, although it shouldn't be done often. The higher capacity and lack of expensive metals or manufacturing makes it look good.
Even Tesla doesn't recommend more than C/2 charging. That is a two hour charge for them. They actually warn buyers not to use quick charging often because it reduces battery life. They also advise refreining from frequent hard acceleration.
We know that quick charging stations are getting installed and battery and EV makers are saying their batteries can be charged quickly. But this is probably deceptive, because they don't talk about reduced lifetime in the same breath.
This could develope into the same practice as the tobacco companies claiming their products were safe because of research at the American Tobacco Institute. Get people hooked on quick charging and producers sell more batteries because they die quicker. Quick-charge, quick-die! The manufacturers could claim that drivers accelerate too much.
Posted by: Zhukova | 07 February 2011 at 06:35 AM