Structural Evolution and High-Voltage Structural Stability of Li(Ni_xMn_yCo_z)O₂Electrodes

Abstract

Positive electrode materials remain a limiting factor for the energy density of lithium-ion batteries (LIBs). Improving the structural stability of these materials over a wider potential window presents an opportune path to higher energy density LIBs. Herein, operando neutron diffraction is used to elucidate the relationship between the structural evolution and electrochemical behavior for a series of Li-ion pouch cells containing Li(Ni x Mn y Co z )O 2 (x + y + z = 1) electrode chemistries. The structural stability of these electrodes during charge and discharge cycling across a wide potential window is found to be influenced by the ratio of transition-metal atoms in the material. Of the electrodes investigated in this study, the Li(Ni 0.4 Mn 0.4 Co 0.2 )O 2 composition exhibits the smallest magnitude of structural expansion and contraction during cycling while also providing favorable structural stability at high voltage. Greater structural change was observed in electrodes with a higher Ni content, while decreasing inversely to the Ni and Co content in the positive electrode. The combination of structural and electrochemical characterization of a wide range of NMC compositions provides useful insight for the design and application of ideal electrode compositions for long-term cycling and structural stability during storage at the charged state.

Surface/Interface Structure Degradation of Ni‐Rich Layered Oxide Cathodes toward Lithium‐Ion Batteries: Fundamental Mechanisms and Remedying Strategies

“…Reproduced with permission . Copyright 2019, Elsevier Ltd. b) Change in the c lattice parameter (Δ c %) as a function of atomic composition after potentiostatic hold at 4.7 V. Reproduced with permission . Copyright 2019, American Chemical Society.…”

“…Sharma and co-workers demonstrate that ratio of TM ions can be controlled to influence the magnitude of structural evolution during cycling and structural stability at high cutoff voltage, according to the investigation in the variation in the c lattice parameter as a function of atomic composition after potentiostatically hold at 4.7 V (Figure 7b). [43] Similarly, a comparative study in the electrochemical and structural properties of a series of NCM cathodes with x = 1/3, 0.5, 0.6, 0.7, 0.8, and 0.85 to identify the optimum composition for the optimized energy density and stability is purposefully performed by Brezesinski and co-workers. (Figure 7c).…”

“…Therefore, within the past decades, worldwide efforts focusing on the surface/interface modifications have been devoted to regulate the chemical and/or physical properties of the cathodes. [35][36][37][38] More significantly, microstructure degradation during accelerated calendar aging [39,40] structural evolution under high voltages [41][42][43][44][45][46] and elevated temperature conditions [41,[47][48][49][50] and oxygen release phenomenon [1,46,[51][52][53][54] as well as several new insights into the cation disorder [55][56][57] concerning the Ni-rich cathodes have been lately uncovered by various means. A comprehensive summary of the advancements in the field of Ni-rich cathodes has been reported recently, [2,6,12,14,16,36,[58][59][60][61][62] but an overview of the fundamental origins governing these surface/interface behaviors has yet to be completely realized.…”

High‐Voltage Layered Ternary Oxide Cathode Materials: Failure Mechanisms and Modification Methods†

“…used operando neutron diffraction to elucidate the structure evolution of LiNi x Co y Mn z O 2 under high voltage. [ 98 ] Figure 7b shows the evolution of the NMC111 lattice parameters throughout a charge−discharge cycle. The “a” lattice parameter was noted to expand and contract in an approximately opposite manner to the “c” lattice parameter.…”

Strategies of Removing Residual Lithium Compounds on the Surface of Ni‐Rich Cathode Materials†

“…have been widely applied in LIBs. [ 19‐21 ] Owing to their high reversible capacity and low cost, [ 22‐24 ] the Ni‐rich cathode materials (LiNi m Co n M 1– m – n O 2 , x ≥0.6, M = Mn, Al) have been a research hotspot in the past years, and increasing the nickel content of them is a common method to obtain higher reversible capacity. [ 25‐27 ] For example, Kim and Zhang et al .…”