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Relevance of LiPF6 as Etching Agent of LiMnPO4 Colloidal Nanocrystals for High Rate Performing Li-ion Battery Cathodes.

Chen L, Dilena E, Paolella A, Bertoni G, Ansaldo A, Colombo M, Marras S, Scrosati B, Manna L, Monaco S - ACS Appl Mater Interfaces (2016)

Bottom Line: We report here an effective surface etching process (using LiPF6) on colloidally synthesized LiMnPO4 NCs that makes the NCs dispersible in the aqueous glucose solution used as carbon source for the carbon coating step.Also, it is likely that the improved exposure of the NC surface to glucose facilitates the formation of a conductive carbon layer that is in intimate contact with the inorganic core, resulting in a high electronic conductivity of the electrode, as observed by us.The rate capability here reported for the carbon coated etched LiMnPO4 nanocrystals represents an important result, taking into account that in the electrode formulation 80% wt is made of the active material and the adopted charge protocol is based on reasonable fast charge times.

View Article: PubMed Central - PubMed

Affiliation: IREQ - Institut de Recherche d'Hydro-Québec , 1800 Boulevard Lionel Boulet, Varennes, QC J3X 1S, Canada.

ABSTRACT
LiMnPO4 is an attractive cathode material for the next-generation high power Li-ion batteries, due to its high theoretical specific capacity (170 mA h g(-1)) and working voltage (4.1 V vs Li(+)/Li). However, two main drawbacks prevent the practical use of LiMnPO4: its low electronic conductivity and the limited lithium diffusion rate, which are responsible for the poor rate capability of the cathode. The electronic resistance is usually lowered by coating the particles with carbon, while the use of nanosize particles can alleviate the issues associated with poor ionic conductivity. It is therefore of primary importance to develop a synthetic route to LiMnPO4 nanocrystals (NCs) with controlled size and coated with a highly conductive carbon layer. We report here an effective surface etching process (using LiPF6) on colloidally synthesized LiMnPO4 NCs that makes the NCs dispersible in the aqueous glucose solution used as carbon source for the carbon coating step. Also, it is likely that the improved exposure of the NC surface to glucose facilitates the formation of a conductive carbon layer that is in intimate contact with the inorganic core, resulting in a high electronic conductivity of the electrode, as observed by us. The carbon coated etched LiMnPO4-based electrode exhibited a specific capacity of 118 mA h g(-1) at 1C, with a stable cycling performance and a capacity retention of 92% after 120 cycles at different C-rates. The delivered capacities were higher than those of electrodes based on not etched carbon coated NCs, which never exceeded 30 mA h g(-1). The rate capability here reported for the carbon coated etched LiMnPO4 nanocrystals represents an important result, taking into account that in the electrode formulation 80% wt is made of the active material and the adopted charge protocol is based on reasonable fast charge times.

No MeSH data available.


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Electrochemicalcharacterization of neLMP/C and etchLMP/C-basedcells. (a) Cyclic voltammetry performed at scan rate of 30 μVs–1 in the 3.5–4.5 voltage range with currentnormalized to the active material mass. (b) Electrochemical impedancespectra (Nyquist plot) of the fully charged (4.5 V, full squares)and discharged (2.5 V, empty dots) cells. Inset: scheme of the equivalentcircuit that better fits the impedance data of the fully charged cells.(c) Voltage profiles upon the first galvanostatic charge/dischargecycle at C-rate of C/10.
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fig3: Electrochemicalcharacterization of neLMP/C and etchLMP/C-basedcells. (a) Cyclic voltammetry performed at scan rate of 30 μVs–1 in the 3.5–4.5 voltage range with currentnormalized to the active material mass. (b) Electrochemical impedancespectra (Nyquist plot) of the fully charged (4.5 V, full squares)and discharged (2.5 V, empty dots) cells. Inset: scheme of the equivalentcircuit that better fits the impedance data of the fully charged cells.(c) Voltage profiles upon the first galvanostatic charge/dischargecycle at C-rate of C/10.

Mentions: As preliminary electrochemicaltest, we investigated the behavior of the etchLMP/C and neLMP/C NCsby CVs. Figure 3a comparesthe CVs (normalized to the mass of active material) of the two systems.Both samples were characterized by an anodic peak A at 4.23 V whichis related to Mn2+/Mn3+ oxidation, and a cathodicpeak C at 3.93 V attributed to the reverse redox process. The maindifference between the two systems is that the value of the normalizedcurrent of the peaks for the etched sample (blue line) was almost8 times higher than that of the neLMP/C (red line). This behaviorcan indicate a superior conductivity of the former electrode.


Relevance of LiPF6 as Etching Agent of LiMnPO4 Colloidal Nanocrystals for High Rate Performing Li-ion Battery Cathodes.

Chen L, Dilena E, Paolella A, Bertoni G, Ansaldo A, Colombo M, Marras S, Scrosati B, Manna L, Monaco S - ACS Appl Mater Interfaces (2016)

Electrochemicalcharacterization of neLMP/C and etchLMP/C-basedcells. (a) Cyclic voltammetry performed at scan rate of 30 μVs–1 in the 3.5–4.5 voltage range with currentnormalized to the active material mass. (b) Electrochemical impedancespectra (Nyquist plot) of the fully charged (4.5 V, full squares)and discharged (2.5 V, empty dots) cells. Inset: scheme of the equivalentcircuit that better fits the impedance data of the fully charged cells.(c) Voltage profiles upon the first galvanostatic charge/dischargecycle at C-rate of C/10.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4759613&req=5

fig3: Electrochemicalcharacterization of neLMP/C and etchLMP/C-basedcells. (a) Cyclic voltammetry performed at scan rate of 30 μVs–1 in the 3.5–4.5 voltage range with currentnormalized to the active material mass. (b) Electrochemical impedancespectra (Nyquist plot) of the fully charged (4.5 V, full squares)and discharged (2.5 V, empty dots) cells. Inset: scheme of the equivalentcircuit that better fits the impedance data of the fully charged cells.(c) Voltage profiles upon the first galvanostatic charge/dischargecycle at C-rate of C/10.
Mentions: As preliminary electrochemicaltest, we investigated the behavior of the etchLMP/C and neLMP/C NCsby CVs. Figure 3a comparesthe CVs (normalized to the mass of active material) of the two systems.Both samples were characterized by an anodic peak A at 4.23 V whichis related to Mn2+/Mn3+ oxidation, and a cathodicpeak C at 3.93 V attributed to the reverse redox process. The maindifference between the two systems is that the value of the normalizedcurrent of the peaks for the etched sample (blue line) was almost8 times higher than that of the neLMP/C (red line). This behaviorcan indicate a superior conductivity of the former electrode.

Bottom Line: We report here an effective surface etching process (using LiPF6) on colloidally synthesized LiMnPO4 NCs that makes the NCs dispersible in the aqueous glucose solution used as carbon source for the carbon coating step.Also, it is likely that the improved exposure of the NC surface to glucose facilitates the formation of a conductive carbon layer that is in intimate contact with the inorganic core, resulting in a high electronic conductivity of the electrode, as observed by us.The rate capability here reported for the carbon coated etched LiMnPO4 nanocrystals represents an important result, taking into account that in the electrode formulation 80% wt is made of the active material and the adopted charge protocol is based on reasonable fast charge times.

View Article: PubMed Central - PubMed

Affiliation: IREQ - Institut de Recherche d'Hydro-Québec , 1800 Boulevard Lionel Boulet, Varennes, QC J3X 1S, Canada.

ABSTRACT
LiMnPO4 is an attractive cathode material for the next-generation high power Li-ion batteries, due to its high theoretical specific capacity (170 mA h g(-1)) and working voltage (4.1 V vs Li(+)/Li). However, two main drawbacks prevent the practical use of LiMnPO4: its low electronic conductivity and the limited lithium diffusion rate, which are responsible for the poor rate capability of the cathode. The electronic resistance is usually lowered by coating the particles with carbon, while the use of nanosize particles can alleviate the issues associated with poor ionic conductivity. It is therefore of primary importance to develop a synthetic route to LiMnPO4 nanocrystals (NCs) with controlled size and coated with a highly conductive carbon layer. We report here an effective surface etching process (using LiPF6) on colloidally synthesized LiMnPO4 NCs that makes the NCs dispersible in the aqueous glucose solution used as carbon source for the carbon coating step. Also, it is likely that the improved exposure of the NC surface to glucose facilitates the formation of a conductive carbon layer that is in intimate contact with the inorganic core, resulting in a high electronic conductivity of the electrode, as observed by us. The carbon coated etched LiMnPO4-based electrode exhibited a specific capacity of 118 mA h g(-1) at 1C, with a stable cycling performance and a capacity retention of 92% after 120 cycles at different C-rates. The delivered capacities were higher than those of electrodes based on not etched carbon coated NCs, which never exceeded 30 mA h g(-1). The rate capability here reported for the carbon coated etched LiMnPO4 nanocrystals represents an important result, taking into account that in the electrode formulation 80% wt is made of the active material and the adopted charge protocol is based on reasonable fast charge times.

No MeSH data available.


Related in: MedlinePlus