| AVS 56th International Symposium & Exhibition | |
| Thin Film | Monday Sessions |
| Session TF3-MoA |
| Session: | Energy Applications and Scaling |
| Presenter: | A.S. Cavanagh, University of Colorado at Boulder |
| Authors: | A.S. Cavanagh, University of Colorado at Boulder Y.S. Jung, University of Colorado at Boulder A.C. Dillon, National Renewable Energy Laboratory M.D. Groner, ALD NanoSolutions Inc. S.H. Lee, University of Colorado at Boulder S.M. George, University of Colorado at Boulder |
| Correspondent: | Click to Email |
Lithium ion batteries (LIBs) are emerging as the dominant power source for portable electronics. Improvement in their capacity lifetime during charge-discharge cycles must be achieved before LIBs can be used for plug-in-hybrid and electric vehicles. LiCoO2 has been the dominant cathode material in LIBs. The instability of LiCoO2 particles comprising the cathodes leads to the deterioration of the LIB. Efforts to stabilize LiCoO2 particles have concentrated on nanometer thick coatings of metal oxides, metal fluorides and metal phosphates deposited using sol-gel techniques. In this study, we demonstrate that Al2O3 ALD grown on LiCoO2 particles dramatically enhances their specific discharge capacity.
After coating the LiCoO2 particles with Al2O3 ALD in a rotary reactor, battery cathodes were prepared and cycled against a Li/Li+ anode near the threshold for 50% Li extraction at 1 C-rate after the first two charge-discharge cycles. A control cathode prepared using uncoated LiCoO2 particles was tested for comparison. With respect to the third charge-discharge cycle, the LiCoO2 particles coated with 2 Al2O3 ALD cycles showed a 89% capacity retention after 120 charge-discharge cycles. In comparison, the bare LiCoO2 particles displayed only a 45% capacity retention after 120 charge-discharge cycles.
LiCoO2 particles coated with 6 and 10 Al2O3 ALD cycles showed lower specific capacities when run at a 1 C-rate after the first two charge-discharge cycles. This lower capacity is attributed to the slower Li+ diffusion and restricted electron mobility through the insulating Al2O3 ALD layer. We propose two mechanisms by which the Al2O3 ALD may enhance the cycle performance of the LIBs. The Al2O3 film may prevent the LiCoO2 particles from decomposing electrolyte and forming a solid-electrolyte interphase. Alternatively, the Al2O3 film may protect the LiCoO2 particles from corrosion by HF.