Tuning of Ni, Mn, and Co (NMC) Content in 0.4(LiNi_xMn_yCo_zO₂)·0.4(Li₂MnO₃) toward Stable High-Capacity Lithium-Rich Cathode Materials

Abstract

Li-rich cathode materials can offer a high specific capacity of ≥250 mA h g −1 ; however, the major issues are their structural instability, capacity degradation, and voltage decay upon prolonged cycling. Herein, we have shown that an increase in Ni content with a concomitant reduction in Mn and Co content in Li-rich cathode materials can help to alleviate structural and electrochemical instability to a considerable extent. In this regard, we have carried out a systematic investigation of tuning the Ni, Mn, and Co (NMC) content in the Li-rich phase, Li 1.2 (Ni x Mn y Co z )O 2 (where x + y + z = 0.8). In the composite notion, these Li-rich phases can also be written as 0.4(LiNi x Mn y Co z O 2 )•0.4(Li 2 MnO 3 ), where the layered oxide components LiNi x Mn y Co z O 2 (x + y + z = 1) are generally termed as NMC-333, NMC-442, NMC-532, NMC-622, and NMC-811, depending upon the concentration of metal constituents. The electrochemical studies reveal that the higher Ni-containing phase 0.4(LiNi 0.8 Mn 0.1 Co 0.1 O 2 )•0.4(Li 2 MnO 3 ) or Li 1.2 Ni 0.32 Co 0.04 Mn 0.44 O 2 shows the least voltage decay of about 0.4 V and a higher capacity retention of 85% after 100 cycles compared to those of the low Ni-containing composition 0.4(LiNi 0.33 Mn 0.33 Co 0.33 O 2 )•0.4(Li 2 MnO 3 ) or Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 , which shows a higher voltage decay of 1.0 V with a 69% capacity retention after 100 cycles at a 0.2 C rate.

Radiation effects on lithium metal batteries

“…Li + /Ni 2+ mixing is also detrimental to the electrochemical performance of NCM811. According to the CV curves of NCM811-0 and NCM811-20 ( Figure S20 A), oxidation of Ni 2+ to Ni 3+ /Ni 4+ is represented by the oxidation peaks in the voltage range of 3.6–4.0 V, while oxidation of Co 3+ to Co 4+ is shown at 4.2 V. 38 The NCM811-20 redox peak seems faint and broad, indicating poor ion transport kinetics of Li + /Ni 2+ mixing. The potential difference of NCM811-20 is also greater than that of NCM811-0, which also supports the idea that gamma ray-induced ion mixing worsens the electrochemical characteristics by increasing polarization.…”

Properties of Layered TMDC Superlattices for Electrodes in Li-Ion and Mg-Ion Batteries

“…Following the work of Whittingham , and Goodenough , in the 1970s and 1980s and the recent isolation of graphene by Novoselov and Geim, , materials which possess a layered structure have received a lot of attention for energy storage. Materials such as NMC and its variants, − the TMDCs, − and the MXenes − all demonstrate ideal electrode properties owing to the fact that their intrinsic structures possess van der Waals (vdW) gaps and provide natural channels for intercalated ions to occupy and travel through during the cycling of a cell. However, many of these materials possess voltages that lie outside ideal anode/cathode ranges, slow charging rates, and low capacities.…”