Synergic Titanium Nitride Coating and Titanium Doping by Atomic Layer Deposition for Stable- and High-Performance Li-Ion Battery

Yan Gao,Xinhua Liang,Jonghyun Park

doi:10.1149/2.0671816jes

Abstract

Atomic layer deposition (ALD) method has emerged as a promising technique to address the dissolution and poor conductivity of electrode materials of lithium ion batteries. In this work, surface modification of LiFePO4 (LFP) was carried out by titanium nitride (TiN) ALD, during which a Ti doping into LFP occurred simultaneously. X-ray photoelectron spectroscopy (XPS) and electrochemical tests were performed to prove the Ti doping, and the composition of TiN layer on the surface of LFP particles was interpreted as a combination of TiN and titanium oxynitride (TiOxNy). Owing to the synergy of TiN coating and Ti doping, the specific capacity of the modified LFP particles increased to ∼159 mAh/g, compared to ∼150 mAh/g of the uncoated one. The modified LFP exhibited a superior cyclic stability with a capacity retention of ∼89% after 1,000 cycles of charge-discharge at a 2C rate at room temperature, whereas the failure of uncoated LFP began after only 500 cycles. A significant reduction of impedance was observed on the TiN ALD-modified LFP, and SEM results showed that this modification restricted severe growth of solid permeable interface layer on the surface of cathode.

Highlights

Synergic Titanium Nitride Coating and Titanium Doping by Atomic Layer Deposition for Stable- and High-Performance LiFePO4
The weight increase in an O2 atmosphere indicated the oxidization of LFP particles, which caused the formation of a secondary phase, Li3Fe2(PO4)3.22 These results indicated that the LFP particles could be unstable at high temperature in an atmosphere of reactive gas, such as TiCl4 vapor during the titanium nitride (TiN) Atomic layer deposition (ALD) process
Due to the reaction between LFP and ALD precursor TiCl4 at 400◦C, Ti cation was doped into LFP during ALD process

Summary

Yan Gao

Follow this and additional works at: https://scholarsmine.mst.edu/mec_aereng_facwork Part of the Chemical Engineering Commons, and the Mechanical Engineering Commons. Coin cell assembly.—A cathode electrode was prepared with slurry using 10 wt% of polymer binder poly(vinylidene fluoride) (PVDF, Alfa Aesar) completely dissolved in N-methyl-2-pyrrolidone (NMP, Sigma-Aldrich) solvent, which was incorporated into a mixture of 80 wt% of uncoated or ALD-modified LFP cathode powders and 10 wt% carbon black (super P conductive, 99+ %, Alfa Aesar). This slurry was cast on an aluminum foil uniformly using a doctor blade and dried at 120◦C for 12 hours in a vacuum oven. The acquired cathode discs were visualized using SEM measurements to investigate the morphology change after 1,000 cycles of charge-discharge test

Results and Discussion

MT i N MT i

The LFP particles were also coated with different thicknesses of

Normalized Discharge Capacity

Conclusions