Abstract
Lithium-rich layered oxides (LRLOs) are opening unexplored frontiers for high-capacity/high-voltage positive electrodes in Li-ion batteries (LIBs) to meet the challenges of green and safe transportation as well as cheap and sustainable stationary energy storage from renewable sources. LRLOs exploit the extra lithiation provided by the Li1.2TM0.8O2 stoichiometries (TM = a blend of transition metals with a moderate cobalt content) achievable by a layered structure to disclose specific capacities beyond 200–250 mA h g–1 and working potentials in the 3.4–3.8 V range versus Li. Here, we demonstrate an innovative paradigm to extend the LRLO concept. We have balanced the substitution of cobalt in the transition-metal layer of the lattice with aluminum and lithium, pushing the composition of LRLO to unexplored stoichiometries, that is, Li1.2+x(Mn,Ni,Co,Al)0.8–xO2−δ. The fine tuning of the composition of the metal blend results in an optimized layered material, that is, Li1.28Mn0.54Ni0.13Co0.02Al0.03O2−δ, with outstanding electrochemical performance in full LIBs, improved environmental benignity, and reduced manufacturing costs compared to the state-of-the-art.
Highlights
In the last decades, a wide variety of new electrode materials have been developed and demonstrated for innovative lithiumion battery (LIB) formulations to push performance beyond the state-of-the-art.[1,2] the massive change in the societal needs from the beginning of the century to present is leading to a remarkable energetic demand increase, beyond short-term fluctuations, calling for more efficient, cheap, and more sustainable energy storage technologies such as batteries.[3]
We demonstrate experimentally a strategy to extend the concept of Lithium-rich layered oxides (LRLOs) to unexplored stoichiometries, landing to an optimized sample with stoichiometry
The morphology and composition of the materials were investigated by JEOL JSM-7500FA scanning electron microscopy (SEM), with a cold-field emission gun, equipped with an energy-dispersive X-ray (EDX) spectroscopy system based on an Oxford X-Max silicon-drift detector (80 mm[2] active area)
Summary
A wide variety of new electrode materials have been developed and demonstrated for innovative lithiumion battery (LIB) formulations to push performance beyond the state-of-the-art.[1,2] the massive change in the societal needs from the beginning of the century to present is leading to a remarkable energetic demand increase, beyond short-term fluctuations, calling for more efficient, cheap, and more sustainable energy storage technologies such as batteries.[3]. Lithium-rich layered oxides (LRLOs) are a well-known wide family of mixed metal oxides with general formula Li1+xM1−xO2, where M is a blend of transition metals, typically containing manganese and cobalt These materials can supply capacities in the order of 200−250 mA h g−1 and operating potentials in the range 3.4−3.8 V versus Li, overcoming conventional layered oxide cathode materials.[4−6] The peculiar crystal structure of LRLOs, made up of a coexistence of two lattices partially sharing crystal symmetries [i.e., the α-NaFeO2 lrahtotimcebso],h7e−d9raalllo(whRs 1fo2r)aarneddothxeacLtiiv2MitynoOri3gimnaotneodcbliyniocx(idmaCtio2n4/) reduction of transition-metal ions and above 4.2 V by the partially reversible O22−/O24− couple on the anion sublattices.[10,11] This last lithium exchange mechanism leads, on charge, to irreversible molecular oxygen release at high potentials.[12] the accumulation of oxygen vacancies and subsequent rearrangements on the cation sublattice promote lattice distortions upon cycling resulting in the long term to wide structural transition into a spinel lattice.[13,14] These structural changes lead to a monotonic mean redox potential decay and capacity fading.[15,16] the search of innovative LRLO with tailored transition-metal blends and doping is rushing,[17,18] aimed at reducing the cobalt content of this class of materials but, at the same time, ameliorating performances. Cobalt is a strategic commodity traded with rising prices on the international markets, and its minimization in a battery formulation substantially leads to the reduction of energy storage costs, in terms of $ kW h−1 .21−23
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