Investigation of Fluorine and Nitrogen as Anionic Dopants in Nickel-Rich Cathode Materials for Lithium-Ion Batteries

Abstract

Advanced lithium-ion batteries are of great interest for consumer electronics and electric vehicle applications; however, they still suffer from drawbacks stemming from cathode active material limitations (e.g., insufficient capacities and capacity fading). One approach for alleviating such limitations and stabilizing the active material structure may be anion doping. In this work, fluorine and nitrogen are investigated as potential dopants in Li1.02(Ni0.8Co0.1Mn0.1)0.98O2 (NCM) as a prototypical nickel-rich cathode active material. Nitrogen doping is achieved by ammonia treatment of NCM in the presence of oxygen, which serves as an unconventional and new approach. The crystal structure was investigated by means of Rietveld and pair distribution function analysis of X-ray diffraction data, which provide very precise information regarding both the average and local structure, respectively. Meanwhile, time-of-flight secondary-ion mass spectroscopy was used to assess the efficacy of dopant incorporation within the NCM structure. Moreover, scanning electron microscopy and scanning transmission electron microscopy were conducted to thoroughly investigate the dopant influences on the NCM morphology. Finally, the electrochemical performance was tested via galvanostatic cycling of half- and full-cells between 0.1 and 2 C. Ultimately, a dopant-dependent modulation of the NCM structure was found to enable the enhancement of the electrochemical performance, thereby opening a route to cathode active material optimization.

Review on Synthesis, Characterization, and Electrochemical Properties of Fluorinated Nickel‐Cobalt‐Manganese Cathode Active Materials for Lithium‐Ion Batteries

“…To prove the chemical composition of CAMs containing lithium and transition‐metal ions, those were determined by inductively coupled plasma (ICP), inductively coupled plasma optical emission spectrometry (ICP‐OES), and atomic absorption spectroscopy (AAS) measurements. The additional presence of fluoride in the fluorinated CAMs was confirmed by IC,, ICP‐MS, ICP‐OES, electron microprobe, distillation‐thorium nitrate titration volumetric method, and F‐ion selective electrode measurements, but also ICP titration and microprobe …”

“…For all CAMs described herein, the pXRD diffraction patterns of the synthesized samples could be indexed based on the α‐NaFeO 2 ‐type structure ( ) . It was observed that surface modification using the F‐sources: [NH 4 ]FHF, [NH 4 ]F, LiF, PTFE, PVDF, Li[PF 6 ], NaF, and F 2 did not alter the crystal structure and/or produce other secondary phases in the main layered structure of the pristine materials. Other authors reported an impurity of the material by the fluorination of the NCM CAMs, using LiF and NiF 2 as a F‐sources.…”

An Overview on the Advances of LiCoO2 Cathodes for Lithium‐Ion Batteries

“…Aside from cations doping, doping anions is another approach to modify the electrode materials. [ 94 ] Zhou et al investigated halogen instead of oxygen of LiCoO 2 by means of DFT calculations. [ 95 ] Results show that the halogen species enlarge the lithium slabs, which improves the lithium storage capacity, increases the lithium diffusion, and decreases the lattice and volume change during the (de)lithiation process.…”

Research Progress on the Surface of High-Nickel Nickel–Cobalt–Manganese Ternary Cathode Materials: A Mini Review

“…Figure 1 shows the processing of high nickel NCM ternary cathode material, which is due to cation mixed discharge caused by structural changes (Wang et al, 2017 ). Many studies believe that heterogeneous ions can be inserted into the lattice through doping, thereby changing the bond energy and lattice parameters and suppressing the deterioration of the internal structure of the lattice (Binder et al, 2018 ; Yu et al, 2020 ).…”