Hanyang/BMW team develops high-energy density Li-ion battery with carbon-nanotube-Si composite anode and NCM concentration gradient cathode
20 May 2016
Researchers from Hanyang University in Korea and the BMW Group have developed a new fully operational, practical Li-ion rechargeable battery combining high energy density with excellent cycle life. A report on their work is published in the RSC journal Energy & Environmental Science.
A carbon nanotube (CNT)-Si composite anode with extremely stable long-term cycling provides a discharge capacity of 2364 mAh g-1 at a tap density of 1.1 g cm-3; a two-sloped full concentration gradient (TSFCG) Li[Ni0.85Co0.05Mn0.10]O2 cathode, with a Ni-enriched core and Mn-enriched layer, yields a discharge capacity of 221 mAh g-1. The full cell generates an energy density of 350 Wh kg-1 with excellent capacity retention for 500 cycles at 1 C rate—satisfying the energy density limit imposed by the drive range requirement for EVs.
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| Energy density of different LIBs. Comparison of the CNT-Si/TSFCG against the currently developed LIBs. LCO: LiCoO2, NCM333: Li[Ni⅓Co⅓Mn⅓]O2, NCM523: Li[Ni0.5Co0.2Mn0.3]O2, Li[Ni0.85Co0.05Mn0.15]O2. Lee et al. Click to enlarge. |
Li[Ni0.8Co0.1Mn0.1]O2 (NCM) and Li[Ni0.8Co0.15Al0.05]O2 (NCA) in particular are the most promising candidates for EVs among the next-generation of high energy density cells owing to their high capacity, outstanding rate capability, and low cost. Despite the advantages, increasing the Ni fraction in the NCM cathodes negatively impacts the lifetime and safety of the battery, particularly when higher cut-off voltages and high electrode packing densities are pursued. A number of strategies have been explored to increase the stability of the Ni-enriched NCM cathode material by suppressing the parasitic side reactions with the electrolyte.
Among them, a compositionally graded cathode material in which concentrations of the transition metals continuously varied from the particle center to the surface appears to be the most promising since the graded cathodes have demonstrated remarkable improvements over cathodes with single uniform composition, not only in lifetime and safety, but also in battery power due to the superior Li+ diffusion kinetics. However, like conventional NCM cathodes, it is challenging to increase the Ni concentration above 80% even in the compositionally graded NCM cathodes; hence, a NCM cathode that is compositionally graded with multi-level gradients was introduced in this work to maximize the Ni content near the particle core.
Among anode materials for LIB, Si exhibits the highest gravimetric capacity (3579 mAh g-1, when charged to Li15Si4); however, a large volume change during cycling often results in pulverization, electrical contact loss, and constant evolution of the solid-electrolyte interphase (SEI), leading to rapid capacity fading. … The anode strategy proposed in this work is to develop a composite anode consisting of structurally defective Si micro-particles encapsulated by carbon nanotubes, fabricated via the simple ball-milling of nanoporous Si and carbon nanotubes (CNTs).
—Lee et al.
For the full cell configuration, the researchers added vinylene carbonate (VC) to the electrolyte to aid the formation of a stable SEI layer on the CNT-Si anode for long term cycling.
Resources
Joo Hyeong Lee, Chong Seung Yoon, Hwang Jang-Yeon, Sung-Jin Kim, Filippo Maglia, Peter Lamp, Seung-Taek Myung and Yang-Kook Sun (2016) “High-energy-density lithium-ion battery using carbon-nanotube-Si composite anode and compositionally graded Li[Ni0.85Co0.05Mn0.10]O2 cathode” Energy Environ. Sci. doi: 10.1039/C6EE01134A
With more fine tuning, this battery could have the potential to become a 2X unit, good enough for good weather extended range (300 miles) BEVs when equipped with with 100+ kWh batteries.
Could also improve PHEVs e-range to 100 miles or so?
Posted by: HarveyD | 20 May 2016 at 12:46 PM
It's the 200th improved battery article i read here, yet in the street we don't see any bev because peoples don't want to plug all the time instead of putting gas once a week especially in cold climate . At least it take a 10x battery to go mainstream
Posted by: gorr | 20 May 2016 at 05:49 PM
This is twice the energy density of the first generation Nissan Leaf battery...only taken 6 years to get there...can't help but think the Republican-led, fossil fuel interest campaigns against a better battery has been and still is very effective:
http://insideclimatenews.org/news/19052016/house-republicans-assail-climate-fraud-investigations-exxon-lamar-smith
Posted by: Lad | 20 May 2016 at 07:31 PM
Same old same old. The Democrats blame the Republicans and the Republicans blame the Democrats for all that's wrong with the world.
Posted by: Mannstein | 22 May 2016 at 03:10 PM