With electric vehicles (EVs) industry growing at an alarming rate, many kinds of cathode materials were developed so far to satisfy increasing needs for more energy density and cycling lifespan.^[1] Regarding structural stability, nothing but layered transition-metal (TM) oxide cathode materials especially Li[Ni_xCo_yMn_(1-x-y)]O₂ and Li[Ni_xCo_yAl_(1-x-y)]O₂ (0.5 < x < 0.8) so called NCM and NCA are used as a practical lithium ion batteries (LIBs) cathodes for EV applications.^[2] Especially, NCM and NCA with even higher nickel contents (x > 0.8) are getting much attention in these days. At the end of Ni-rich cathode material lies pure LiNiO₂ (LNO), however, the intrinsic structural instability, poor thermal property and complexity on synthesis highly limits its practical application.^[3] By referring to J.-H. Kim et al., in order to increase the energy density of Ni-rich cathode material, it may be advantageous to raise the potential rather than increase the nickel contents further.^[4] In this study, a series of tungsten (0.5 and 1.0 mol%) were incorporated in Ni-rich layered Li[Ni_0.90Co_0.05Mn_0.05]O₂ cathode material to investigate the stabilization role of tungsten especially on higher voltage and thermally aged condition. In situ X-ray diffraction analysis linked with cross-sectional visual imaging were done to demonstrate the effect of tungsten on bulk lattice stabilization. Surface protectivity at upper potential of disordered spinel-like phases which come from tungsten doping was proved through impedance spectroscopy and post-mortem TEM analysis.

References

1. S.-T. Myung, F. Maglia, K.-J. Park, C. S. Yoon, P. Lamp, S.-J. Kim, Y.-K. Sun, ACS Energy Lett. 2017, 2, 196.
2. Teslar Motors, http://www.teslamotors.com/ (accessed: December 2017).
3. C. S. Yoon, D.-W. Jun, S.-T. Myung, Y.-K. Sun, ACS Energy Lett. 2017, 2, 1150.
4. J.-H. Kim, K.-J. Park, S. J. Kim, C. S. Yoon, Y.-K. Sun, J. Mater. Chem. A, 2019, 7, 2694