Limits...
Mechanochemical synthesis of Li₂MnO₃ shell/LiMO₂ (M = Ni, Co, Mn) core-structured nanocomposites for lithium-ion batteries.

Noh JK, Kim S, Kim H, Choi W, Chang W, Byun D, Cho BW, Chung KY - Sci Rep (2014)

Bottom Line: Core/shell-like nanostructured xLi2MnO3·(1-x)LiMO2 (M = Ni, Co, Mn) composite cathode materials are successfully synthesized through a simple solid-state reaction using a mechanochemical ball-milling process.The detrimental surface effects arising from the high Ni-content are countered by the Li2MnO3 shell, which stabilizes the nanoparticles.The electrochemical performances and thermal stabilities of the synthesized nanocomposites are compared with those of bare LiMO2.

View Article: PubMed Central - PubMed

Affiliation: 1] Center for Energy Convergence, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil-5, Seongbuk-gu, Seoul 136-197, Republic of Korea [2] Department of Materials Science and Engineering, Korea University, Anam-dong 5-1, Seongbuk-gu, Seoul 136-701, Republic of Korea [3].

ABSTRACT
Core/shell-like nanostructured xLi2MnO3·(1-x)LiMO2 (M = Ni, Co, Mn) composite cathode materials are successfully synthesized through a simple solid-state reaction using a mechanochemical ball-milling process. The LiMO2 core is designed to have a high-content of Ni, which increases the specific capacity. The detrimental surface effects arising from the high Ni-content are countered by the Li2MnO3 shell, which stabilizes the nanoparticles. The electrochemical performances and thermal stabilities of the synthesized nanocomposites are compared with those of bare LiMO2. In particular, the results of time-resolved X-ray diffraction (TR-XRD) analyses of xLi2MnO3·(1-x)LiMO2 nanocomposites as well as their differential scanning calorimetry (DSC) profiles demonstrate that the Li2MnO3 shell is effective in stabilizing the LiMO2 core at high temperatures, making the nanocomposites highly suitable from a safety viewpoint.

No MeSH data available.


Related in: MedlinePlus

TR-XRD patterns of the (a) LiNi0.5Co0.2Mn0.3O2 and (b) 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 samples heat treated at 1000°C (the temperature was raised to 600°C after being charged to 4.8 V vs. Li/Li+).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4007074&req=5

f8: TR-XRD patterns of the (a) LiNi0.5Co0.2Mn0.3O2 and (b) 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 samples heat treated at 1000°C (the temperature was raised to 600°C after being charged to 4.8 V vs. Li/Li+).

Mentions: The thermal stabilities of the 0.5Li2MnO3·0.5LiMO2 and LiNi0.5Co0.2Mn0.3O2 nanocomposites after they had been charged to 4.8 V were compared using differential scanning calorimetry (DSC) in a manner similar to that employed by Park et al.36 For 0.5Li2MnO3·0.5LiMO2, the sample heat treated at 1000°C was selected because this sample had exhibited the best electrochemical performance. It can be observed from Figure 7 that the 4.8-V-charged LiNi0.5Co0.2Mn0.3O2 sample, whose particles did not have an outer Li2MnO3 coating, exhibited exothermic peaks corresponding to a two-step dissociation reaction. The temperatures corresponding to the 1st and 2nd exothermic peaks were 228.68 and 268.52°C, respectively; this result indicated that the dissociation of the material occurred through a two-step process36. The total heat generated during the dissociation reaction was 461.5 J g−1. However, only one exothermic peak was observed for the 4.8-V-charged 0.5Li2MnO3·0.5LiMO2 sample, indicating a one-step dissociation reaction. The peak was positioned at 248.30°C, and the total heat generated during the reaction was 239.2 J g−1, which was lower than that for the bare sample. This result is very similar to those reported by other research groups, who have reported that AlF3 or FePO4-coated LiMO2 can stabilize the cathode surface and start to decompose only at high temperatures3738. Thus, in addition to exhibiting a higher capacity and improved cyclability (see Figs. 5 and 6), the core/shell-like structured 0.5Li2MnO3·0.5LiMO2 sample also exhibited a reduction in the total heat generated and an increase in the dissociation temperature. Therefore, the fact that a greater number of Ni ions were present in the bulk of the electrode resulted in a higher capacity, while the Li2MnO3 shell improved the overall thermal stability of the Li2MnO3-coated materials37. The results of the time-resolved (TR) XRD analyses were in good agreement with the DSC results and provided additional information regarding the changes induced in the various nanocomposite samples after heating. Figures 8 (a) and (b) present the TR-XRD patterns of the LiNi0.5Co0.2Mn0.3O2 and 0.5Li2MnO3·0.5LiMO2 samples heat treated at 1000°C in the absence of an electrolyte; the samples were subsequently heated from room temperature to 600°C and then charged to 4.8 V. The initial TR-XRD data were collected at 38°C because the X-ray generator required more than a few minutes to initialize.


Mechanochemical synthesis of Li₂MnO₃ shell/LiMO₂ (M = Ni, Co, Mn) core-structured nanocomposites for lithium-ion batteries.

Noh JK, Kim S, Kim H, Choi W, Chang W, Byun D, Cho BW, Chung KY - Sci Rep (2014)

TR-XRD patterns of the (a) LiNi0.5Co0.2Mn0.3O2 and (b) 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 samples heat treated at 1000°C (the temperature was raised to 600°C after being charged to 4.8 V vs. Li/Li+).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4007074&req=5

f8: TR-XRD patterns of the (a) LiNi0.5Co0.2Mn0.3O2 and (b) 0.5Li2MnO3·0.5LiNi0.5Co0.2Mn0.3O2 samples heat treated at 1000°C (the temperature was raised to 600°C after being charged to 4.8 V vs. Li/Li+).
Mentions: The thermal stabilities of the 0.5Li2MnO3·0.5LiMO2 and LiNi0.5Co0.2Mn0.3O2 nanocomposites after they had been charged to 4.8 V were compared using differential scanning calorimetry (DSC) in a manner similar to that employed by Park et al.36 For 0.5Li2MnO3·0.5LiMO2, the sample heat treated at 1000°C was selected because this sample had exhibited the best electrochemical performance. It can be observed from Figure 7 that the 4.8-V-charged LiNi0.5Co0.2Mn0.3O2 sample, whose particles did not have an outer Li2MnO3 coating, exhibited exothermic peaks corresponding to a two-step dissociation reaction. The temperatures corresponding to the 1st and 2nd exothermic peaks were 228.68 and 268.52°C, respectively; this result indicated that the dissociation of the material occurred through a two-step process36. The total heat generated during the dissociation reaction was 461.5 J g−1. However, only one exothermic peak was observed for the 4.8-V-charged 0.5Li2MnO3·0.5LiMO2 sample, indicating a one-step dissociation reaction. The peak was positioned at 248.30°C, and the total heat generated during the reaction was 239.2 J g−1, which was lower than that for the bare sample. This result is very similar to those reported by other research groups, who have reported that AlF3 or FePO4-coated LiMO2 can stabilize the cathode surface and start to decompose only at high temperatures3738. Thus, in addition to exhibiting a higher capacity and improved cyclability (see Figs. 5 and 6), the core/shell-like structured 0.5Li2MnO3·0.5LiMO2 sample also exhibited a reduction in the total heat generated and an increase in the dissociation temperature. Therefore, the fact that a greater number of Ni ions were present in the bulk of the electrode resulted in a higher capacity, while the Li2MnO3 shell improved the overall thermal stability of the Li2MnO3-coated materials37. The results of the time-resolved (TR) XRD analyses were in good agreement with the DSC results and provided additional information regarding the changes induced in the various nanocomposite samples after heating. Figures 8 (a) and (b) present the TR-XRD patterns of the LiNi0.5Co0.2Mn0.3O2 and 0.5Li2MnO3·0.5LiMO2 samples heat treated at 1000°C in the absence of an electrolyte; the samples were subsequently heated from room temperature to 600°C and then charged to 4.8 V. The initial TR-XRD data were collected at 38°C because the X-ray generator required more than a few minutes to initialize.

Bottom Line: Core/shell-like nanostructured xLi2MnO3·(1-x)LiMO2 (M = Ni, Co, Mn) composite cathode materials are successfully synthesized through a simple solid-state reaction using a mechanochemical ball-milling process.The detrimental surface effects arising from the high Ni-content are countered by the Li2MnO3 shell, which stabilizes the nanoparticles.The electrochemical performances and thermal stabilities of the synthesized nanocomposites are compared with those of bare LiMO2.

View Article: PubMed Central - PubMed

Affiliation: 1] Center for Energy Convergence, Korea Institute of Science and Technology (KIST), Hwarangno 14-gil-5, Seongbuk-gu, Seoul 136-197, Republic of Korea [2] Department of Materials Science and Engineering, Korea University, Anam-dong 5-1, Seongbuk-gu, Seoul 136-701, Republic of Korea [3].

ABSTRACT
Core/shell-like nanostructured xLi2MnO3·(1-x)LiMO2 (M = Ni, Co, Mn) composite cathode materials are successfully synthesized through a simple solid-state reaction using a mechanochemical ball-milling process. The LiMO2 core is designed to have a high-content of Ni, which increases the specific capacity. The detrimental surface effects arising from the high Ni-content are countered by the Li2MnO3 shell, which stabilizes the nanoparticles. The electrochemical performances and thermal stabilities of the synthesized nanocomposites are compared with those of bare LiMO2. In particular, the results of time-resolved X-ray diffraction (TR-XRD) analyses of xLi2MnO3·(1-x)LiMO2 nanocomposites as well as their differential scanning calorimetry (DSC) profiles demonstrate that the Li2MnO3 shell is effective in stabilizing the LiMO2 core at high temperatures, making the nanocomposites highly suitable from a safety viewpoint.

No MeSH data available.


Related in: MedlinePlus