High Performance LiMn_1.9Al_0.1O₄ Porous Microspheres Rapidly Self‐Assembled through an Acetylene‐Black‐Assisted Solid‐State Approach

Abstract

We present a novel approach for preparing porous LiMn 1.9 Al 0.1 O 4 microspheres with diameters of about 2 μm through direct calcination of solid monolith-like precursors formed by simply mixing acetylene black and nitrate. The introduction of aluminium not only causes lattice doping of manganese but also plays an indispensable role in the formation of the porous microsphere structure assisted by acetylene black as both a solution absorbent and a pore-forming agent. Porous LiMn 1.9 Al 0.1 O 4 microspheres with an optimized aluminium concen-tration demonstrate a superior rate capability of 121 mAh g À 1 at 1 C and 94 mAh g À 1 at 40 C, and an excellent cyclic performance with a capacity retention of 82 % at 1 C after 700 cycles. The excellent electrochemical performance results from the unique porous microspheres assembled by nanoparticles and the doping of Al. The approach proposed herein is facile, inexpensive, and environmentally friendly and could also be extended to the mass production of other electrode materials.[a] X.

Surface Magnesium Substitution at Spinel Lithium Manganate 8a Tetrahedral Sites for Suppressed Manganese Dissolution and Enhanced Cycle Stability

“…This concept was applied to LIBs by Thackeray in 1994 . With an average manganese oxidation number of +3.5, most studies attribute Mn dissolution to trace amounts of water in electrolytes, which may contribute to an acidic environment in cells. , Previous modification strategies have been built on this disproportionation mechanism, focusing on partial substitution of Mn 3+ or reducing Mn 3+ sites exposed to electrolytes. , Replacing Mn 3+ with guest ions, such as Al 3+ , B 3+ , Mg 2+ , Li + , etc., can enhance crystal structure stability. − As most doped atoms are electrochemically inert, such a method of improving the cycle stability results in a substantial loss of the initial specific capacity. The surface coating has also been widely employed to increase the stability of the electrode and electrolyte interface against the attack of hydrogen fluoride.…”