Low-Temperature Synthesis, Structural Characterization, and Electrochemistry of Ni-Rich Spinel-like LiNi_2–yMn_yO₄ (0.4 ≤ y ≤ 1)

Abstract

The thermal conversion of chemically delithiated layered Li 0.5 Ni 1−y Mn y O 2 (0.2 ≤ y ≤ 0.5) into spinel-like LiNi 2−y Mn y O 4 (0.4 ≤ y ≤ 1) has been systematically investigated. The formed spinel-like phases are metastable and cannot be accessed by a conventional high-temperature solid-state method. The layered-to-spinel transformation mechanism has been studied by the Rietveld refinement of in situ neutron diffraction as a function of temperature (25− 300 °C). In particular, the ionic diffusion of Li and M ions is quantified at different temperatures. Electrochemistry of the metastable spinel-like phases obtained has been studied in lithium-ion cells. A bond valence sum map has been performed to understand the ionic diffusion of lithium ions in the Ni-rich layered, spinel, and rock-salt structures. The study can aid the understanding of the possible phases that could be formed during the cycling of Ni-rich layered oxide cathodes.

A reflection on lithium-ion battery cathode chemistry

“…This is because of the difficulty of stabilizing the highly oxidized M 3+/4+ oxidation states by conventional high-temperature synthesis. 19,[29][30][31] . However, such attempts result in either incomplete transformation at low enough temperatures or loss of oxygen and formation of a mixture of spinel-like phases and reduced Co 3 O 4 or NiO phases due to the instability of Co 3+/4+ and Ni 3+/4+ at high enough temperatures.…”

Critical Role of pH Evolution of Electrolyte in the Reaction Mechanism for Rechargeable Zinc Batteries

“…For zinc metal, an additional advantage exists in that an aqueous electrolyte can be employedt oa chieveahighly reversible electrodeposition/stripping reactiono nt he negative electrode without dendrite formation. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] The detailed reactionm echanism of these manganese dioxide structures with zinc ions in aqueous solution is still cryptic but wasc onventionally explained by the intercalation of zinc ions into the tunnelstructures. This is certainly advantageous compared to conventional cells employing Zn metal and alkaline electrolytes, which suffer from poor coulombic efficiency and dangerousd endrite formation,a lthough many advances have been made recently.…”

“…[25,26] For positive electrodes, manganese dioxide with various tunnel structuresh ave been exploreds o far because they are inexpensive and exhibit reversible reactions with plateau potentials around 1.3 V, delivering discharge capacities of 100-300mAh g À1 .T he manganese dioxide polymorphsw ith various tunnels tructures investigateds of ar span from b-MnO 2 (1 1), a-MnO 2 (2 2), g-MnO 2 and d-MnO 2 (1 1), and l-MnO 2 (1 3) to todorokite (3 3). [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] The detailed reactionm echanism of these manganese dioxide structures with zinc ions in aqueous solution is still cryptic but wasc onventionally explained by the intercalation of zinc ions into the tunnelstructures. [14][15][16][17][18][19][20] This is rather surprising, considering that electrode materials reported to reversibly intercalate aconsiderable amount of multivalent cationsi nto their structures are extremely rare.…”

Origin of Structural Phase Transitions in Ni-Rich LixNi0.8Co0.1Mn0.1O2 with Lithiation/Delithiation: A First-Principles Study

“…The first drawback is related to the low operating voltage (∼4.3 V) as well as specific capacity. , The reason for the constrained voltage is a structural instability (i.e., severe phase transition) induced by the extraction of more than half of the Li contents during charging. − The O3 → O1 phase transition at low Li contents decreases the Li diffusivity leading to the capacity fading upon cycling . In recent years, a large number of layered cathode materials in which Co was replaced by other active transition metals (TMs) has been investigated. − Substitution of Co by Ni and Mn cations to form LiNi x Co y Mn 1‑x‑y O 2 (NCMxy1-x-y) materials is one of the most interesting and practical approach to improve the capacity as well as energy density of cathodes. Moreover, Ni and Mn are cheaper than Co, thus reducing the overall price of LIBs.…”