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 LiNi_0.5Mn_1.5O₄ cathode material powders with ultrathin amorphous FePO₄ by ALD it is possible to dramatically increase the capacity retention of LiNi_0.5Mn_1.5O₄. 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 LiNi_0.5Mn_1.5O₄, especially at high current densities. 

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 LiNi_0.5Mn_1.5O₄.

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).