Core-shell structure of LiMn2O4 cathode material reduces phase transition and Mn dissolution in Li-ion batteries

Abstract

Although the LiMn2O4 cathode can provide high nominal cell voltage, high thermal stability, low toxicity, and good safety in Li-ion batteries, it still suffers from capacity fading caused by the combination of structural transformation and transition metal dissolution. Herein, a carbon-coated LiMn2O4 cathode with core@shell structure (LMO@C) was therefore produced using a mechanofusion method. The LMO@C exhibits higher cycling stability as compared to the pristine LiMn2O4 (P-LMO) due to its high conductivity reducing impedance growth and phase transition. The carbon shell can reduce direct contact between the electrolyte and the cathode reducing side reactions and Mn dissolution. Thus, the cylindrical cell of LMO@C//graphite provides higher capacity retention after 900 cycles at 1 C. The amount of dissoluted Mn for the LMO@C is almost 2 times lower than that of the P-LMO after 200 cycles. Moreover, the LMO@C shows smaller change in lattice parameter or phase transition than P-LMO, indicating to the suppression of λ-MnO2 phase from the mixed phase of Li1-δMn2O4 + λ-MnO2 when Li-delithiation at highly charged state leading to an improved cycling reversibility. This work provides both fundamental understanding and manufacturing scale demonstration for practical 18650 Li-ion batteries.

Improved electrochemical performance of spinel LiMn2O4 derived from manganese-based metal–organic frameworks by organic ligands

“…The electrochemical performance of LiMn 2 O 4 cathode materials published in recent years is compared in Table 2. 32–41 When compared to other batteries, the battery described in this study performs exceptionally well. High stability and capacity are simultaneously attained.…”

Lithium-Ion Conductivity Epitaxial Layer Contributing to the Structure and Cycling Stability of LiMn2O4 Cathodes

“…In addition, although the diffraction peaks of the two electrodes after cycling were basically the same and did not disappear, the MAT electrode showed a splitting of the (400) peak after cycling, indicating that a phase change may have occurred during the cycling process. The phase changes resulting from the lithium manganate cycling are mainly by-products such as Li 2 CO 3 from the loss of active material due to manganese dissolution, and surface phase changes that increase cathode impedance, such as the formation of the surface Mn 3 O 4 phase. ,− Combined with the above various analyses of the electrodes after cycling, it shows that the surface-coated Li 3 PO 4 layer protects the internal structure from electrolyte erosion and reduces the occurrence of side reactions.…”

Li-ion and Na-ion intercalation in layered MnO2 cathodes enabled by using bismuth as a cation pillar

“…64 However, the cycling behavior revealed the 4.9 Å peak was LMO spinel, due to the peak shiing observed: d-spacing expanded during electrochemical insertion of Li + and contracted on extraction. 65,66 For Li x MnO 2 material, the opposite trend would be expected: d-spacing contraction during electrochemical insertion of Li + . However, it should be noted the LMO reaction (∼3.5 V) was small in differential capacity plots, suggesting it was a small fraction of the overall capacity.…”