Morphological evolution and electrochemical properties of cathode material LiAl0.08Mn1.92O4 single crystal particles
Combined with the element doping and morphology controlling strategies,the LiAl0.08Mn1.92O4 cathode material was synthesized by solid-state combustion method and dealt with at different calcination temperatures(600,650,700,and 750 ℃).The experimental results showed that the phase structure of LiMn2O4 was not changed by Al doping and the change of calcination temperature.With the increase in temperature,the crystallinity of the sample increased and the particle size enlarged.The calcination temperature of 650 ℃ was the key temperature for the for-mation of truncated octahedral single crystal particle morphology,and 750 ℃ was the abrupt temperature of the par-ticles that suddenly became larger.The LiAl0.08Mn1.92O4 material with an optimized calcination temperature of 650 ℃ formed a relatively complete truncated octahedral single crystal morphology particle containing(111),(110),and(100)crystal planes,and showed excellent electrochemical and kinetic performance.The initial discharge capacity was 112.0 mAh·g-1 at 1C,and the capacity retention rate was 72.9％after 500 cycles.The initial discharge capaci-ties were 107.1 and 100.4 mAh·g-1 at 5C and 10C,and the capacity retention rates were 52.2％and 53.5％after 2 000 cycles,respectively.It had the minimum redox peak potential difference(ΔEp2=0.109 and 0.114 V before and after cycling respectively),the minimum charge transfer resistance(Rct=106.49 and 125.49 Ω before and after cycling respectively),and the large lithium-ion diffusion coefficient(DLi+=1.72×10-16 cm2·s-1).The Al doping and single crystal truncated octahedral particle morphology not only effectively inhibited the Jahn-Teller effect of LiMn2O4 but also relieved the dissolution of Mn,and improved the rate performance and long cycle life of the materi-als.
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