Development of surface functionalized ZnO-doped LiFePO4/C composites as alternative cathode material for lithium ion batteries

• Published in: Applied surface science Vol. 394; pp. 25 - 36
• Main Authors: Saroha, Rakesh, Panwar, Amrish K., Sharma, Yogesh, Tyagi, Pawan K., Ghosh, Sudipto
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2017
• Subjects: Charge separation; Discharge; Energy density; Energy measurement; Hybrid vehicles; Lithium-ion batteries; Olivine-cathode; Ragone plot; Surface force gradient; Synthesis; Topography; Zinc oxide; ZnO-doping; ZnO-doping; Surface force gradient; Ragone plot; Olivine-cathode; Charge separation
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2016.09.105

[Display omitted] •Pristine LFP and ZnO-doped LFP/C samples have been synthesized using sol-gel assisted ball milling route.•Electronic conductivity of pristine LFP increases to 102-103 orders of magnitude for ZnO doped LFP/C samples.•AFM results indicate the presence of more volumetric charge density at the surface for ZnO-doped LFP/C sample.•LFPZ2.5 shows best cycling and rate performances among all the prepared samples.•Lithium ion diffusion coefficient increases significantly. Surface modified olivine-type LiFePO4/C-ZnO doped samples were synthesized using sol-gel assisted ball-milling route. In this work, the influence of ZnO-doping on the physiochemical, electrochemical and surface properties such as charge separation at solid-liquid interphase, surface force gradient, surface/ionic conductivity of pristine LiFePO4/C (LFP) has been investigated thoroughly. Synthesized samples were characterized using X-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. All the synthesized samples were indexed to the orthorhombic phase with Pnma space group. Pristine LiFePO4 retain its structure for higher ZnO concentrations (i.e. 2.5 and 5.0wt.% of LFP). Surface topography and surface force gradient measurements by EFM revealed that the kinetics of charge carriers, e−/Li+ is more in ZnO-doped LFP samples, which may be attributed to diffusion or conduction process of the charges present at the surface. Among all the synthesized samples LFP/C with 2.5wt.% of ZnO (LFPZ2.5) displays the highest discharge capacity at all C-rates and exhibit excellent rate performance. LFPZ2.5 delivers a specific discharge capacity of 164 (±3) mAhg−1 at 0.1C rate. LFPZ2.5 shows best cycling performance as it provides a discharge capacity of 135 (±3) mAhg−1 at 1C rate and shows almost 95% capacity retention after 50 charge/discharge cycles. Energy density plot shows that LFPZ2.5 offers high energy and power density measured at high discharge rates (5C), proving its usability for hybrid vehicles application.