Electrochemical performance of overlithiated Li1+xNi0.8Co0.2O2: structural and oxidation state studies

Abstract

Pure, layered compounds of overlithiated Li 1+x Ni 0.8 Co 0.2 O 2 (x = 0.05 and 0.1) were successfully prepared by a modified combustion method. XRD studies showed that cell parameters of the material decreased with increasing the lithium content. SEM revealed that the morphology of particles changed from rounded polyhedral-like crystallites to sharp-edged polyhedral crystals with more doped lithium. EDX showed that the stoichiometries of Ni and Co agrees with calculated synthesized values. Electrochemical studies revealed the overlithiated samples have improved capacities as well as cycling behavior. The sample with x = 0.05 shows the best performance with a specific capacity of 113.29 mA•h•g -1 and the best capacity retention of 92.2% over 10 cycles. XPS results showed that the binding energy of Li 1s is decreased for the Li doped samples with the smallest value for the x = 0.05 sample, implying that Li + ions can be extracted more easily from Li 1.05 Ni 0.8 Co 0.2 O 2 than the other stoichiometries accounting for the improved performance of the material. Considerations of core level XPS peaks for transition metals reveal the existence in several oxidation states. However, the percentage of the +3 oxidation state of transition metals for the when x = 0.1 is the highest and the availability for charge transition from the +3 to +4 state of the transition metal during deintercalation is more readily available.

Prelithiation: A Crucial Strategy for Boosting the Practical Application of Next-Generation Lithium Ion Battery

“…However, this overlithiation process was sensitive to air and moisture, and the reaction needed to be kept at a low temperature all the time with the addition of dry ice, which is not suitable for large-scale applications. Analogously, overlithiated Li 1+ x (Ni z Co 1–2 z Mn z ) 1– x O 2 ( z = 0.1–0.4 and x = 0.0–0.1) and Li 1+ x (Ni 1/3 Co 1/3 Mn 1/3 ) 1– x O 2 materials (0 ≤ x ≤ 0.17) with α-NaFeO 2 structure and layered compounds of overlithiated Li 1+ x Ni 0.8 Co 0.2 O 2 ( x = 0.05 and 0.1) and Li-rich (1 – x )­LiMO 2 · x Li 2 MnO 3 have also been investigated to store additional lithium ions to compensate for the initial irreversible capacity of anodes.…”

Practical evaluation of prelithiation strategies for next‐generation lithium‐ion batteries

“…Compared with the use of prelithiation agents to lithiate the as‐prepared active materials, integration of the prelithiation step into the synthesis simplifies the preparation procedure. For instance, overlithiated Li 1+ x (Ni z Co 1−2 z Mn z ) 1− x O 2 34 and Li 1+ x (Ni 1/3 Co 1/3 Mn 1/3 ) 1− x O 2 35 were synthesized using the spray‐drying method, overlithiated Li 1+ x Ni 0.8 Co 0.2 O 2 36 was synthesized using the combustion/annealing method, and lithium‐rich x Li 2 MnO 3 ·(1− x )Li[Mn y Ni z Co 1− y − z ]O 2 37 was synthesized using the co‐precipitation method.…”

Opportunities and Challenges of Li2C4O4 as Pre‐Lithiation Additive for the Positive Electrode in NMC622||Silicon/Graphite Lithium Ion Cells

“…[ 12 ] While many of the early studies on over‐lithiated cathode materials focused on the over‐lithiation of spinel oxides, such as Li 1+ x Mn 2 O 4 and Li 1+ x Ni 0.5 Mn 1.5 O 4 , [ 12b–e ] recent works have also reported the possible over‐lithiation of SOTA LiNi x Mn y Co z O 2 (NMC‐ xyz , x + y + z = 1) layered oxides, yet precise control is required to avoid irreversible phase transitions. [ 11b,12a,13 ] In both cases, either an additional production step is necessary or the use of an inert atmosphere is needed to handle the utilized chemicals and reaction conditions, raising safety concerns.…”