Ni-rich layered transition-metal (TM) oxides, e.g., Li[Ni_xCo_yMn_1-x-y]O₂ (NCM) and Li[Ni_xCo_yAl_1-x-y]O₂ (NCA), have attracted considerable attention as cathode materials for Li-ion batteries (LIBs) and have been deployed in commercial EVs.¹ In order to increase the energy density and satisfy the target driving range, the Ni content in NCM and NCA cathodes has been progressively increased, from 33% to 85%.^2,3 At the end of this strategy lies LiNiO₂ (LNO), in which all of the Co and Mn is replaced by Ni, yielding a high specific capacity of 250 mAh g^-1 at a relatively low material cost.³ However, it was notoriously difficult to use in practice because LNO undergoes several phase transition during Li⁺ intercalation and deintercalation, which can lead to severe capacity fading.⁴ In addition to the detrimental phase transition occurring in the deeply charged state and the parasitic reactions of reactive Ni⁴⁺ at the surface cause the capacity fading of cathode materials.

In the present study, we investigated the effect of W doping on the structural stabilization during the electrochemical process. To systematically investigate the effect of W doping, a series of W-doped LNO cathodes with 1.0, 1.5, and 2.0 mol% W were synthesized using an optimized co-precipitation process. The structural behavior observed via in situ X-ray diffraction (XRD) was correlated to the electrochemical performance of the W-doped cathodes.

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. H.-J. Noh, S. Youn, C. S. Yoon, Y.-K. Sun, J. Power Sources 2013, 233, 121.
3. H.-H. Sun, W. Choi, J. K. Lee, I.-H. Oh, H.-G. Jung, J. Power Sources 2015, 275, 877.
4. C. S. Yoon, D.-W. Jun, S.-T. Myung, Y.-K. Sun, ACS Energy Lett. 2017, 2, 1150.