Sunday, April 5, 2015

Amorphous ALD iron phosphate buffers high capacities at high current densities in Litthium Ion Batteries


Researchers at University of Western Ontario, Canada, shows that by coating LiNi0.5Mn1.5O4 cathode material powders with ultrathin amorphous FePO4 by ALD it is possible to dramatically increase the capacity retention of LiNi0.5Mn1.5O4. The researchers believe that the amorphous FePO4 layer acts as a lithium-ions reservoir and electrochemically active buffer layer during the charge/discharge cycling, helping achieve high capacities in LiNi0.5Mn1.5O4, especially at high current densities. 

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The ALD amorphous FePO4 was deposited using ferrocene (FeCp2), ozone, trimethyl phosphate (TMPO), and water (H2O) in an Ultratech/Cambridge Nanotech Savannah 100 ALD system. 

Please check out all the details in the Open Access article below:

Unravelling the Role of Electrochemically Active FePO4 Coating by Atomic Layer Deposition for Increased High-Voltage Stability of LiNi0.5Mn1.5O4 Cathode Material [OPEN ACCESS] 
Biwei Xiao1, Jian Liu1, Qian Sun1, Biqiong Wang1,2, Mohammad Norouzi Banis1, Dong Zhao2, Zhiqiang Wang2, Ruying Li1, Xiaoyu Cui3, Tsun-Kong Sham2 and Xueliang Sun1,*
Article first published online: 25 MAR 2015, DOI: 10.1002/advs.201500022

Ultrathin amorphous FePO4 coating derived by atomic layer deposition (ALD) is used to coat the 5 V LiNi0.5Mn1.5O4 cathode material powders, which dramatically increases the capacity retention of LiNi0.5Mn1.5O4. It is believed that the amorphous FePO4 layer could act as a lithium-ions reservoir and electrochemically active buffer layer during the charge/discharge cycling, helping achieve high capacities in LiNi0.5Mn1.5O4, especially at high current densities.



Schematic illustrations of a) LNMO-n upon cycling; b) illustration of the electrolyte highest occupied molecular orbital (HOMO) and work functions of FePO4 and LiNi0.5Mn1.5O4.



FESEM images of a) LNMO-0 and b) LNMO-20; c) HRTEM images of LNMO-20 (inset: Electron diffraction patterns of the LNMO-20 along the [110] zone axis).