| 1. |
- Capone, Isaac, et al.
(författare)
-
Effect of the Particle-Size Distribution on the Electrochemical Performance of a Red Phosphorus-Carbon Composite Anode for Sodium-Ion Batteries
- 2019
-
Ingår i: Energy & Fuels. - : AMER CHEMICAL SOC. - 0887-0624 .- 1520-5029. ; 33:5, s. 4651-4658
-
Tidskriftsartikel (refereegranskat)abstract
- Red phosphorus (RP) is a promising candidate as an anode for sodium-ion batteries because of its low potential and high specific capacity. It has two main disadvantages. First, it experiences 490% volumetric expansion during sodiation, which leads to particle pulverization and substantial reduction of the cycle life. Second, it has an extremely low electronic conductivity of 10(-14) S cm(-1). Both issues can be addressed by ball milling RP with a carbon matrix to form a composite of electronically conductive carbon and small RP particles, less susceptible to pulverization. Through this procedure, however, the resulting particle-size distribution of the RP particles is difficult to determine because of the presence of the carbon particles. Here, we quantify the relationship between the RP particle-size distribution and its cycle life for the first time by separating the ball-milling process into two steps. The RP is first wet-milled to reduce the particle size, and then the particle-size distribution is measured via dynamic light scattering. This is followed by a dry-milling step to produce RP-graphite composites. We found that wet milling breaks apart the largest RP particles in the range of 2-10 mu m, decreases the Dv90 from 1.85 to 1.26 mu m, and significantly increases the cycle life of the RP. Photoelectron spectroscopy and transmission electron microscopy confirm the successful formation of a carbon coating, with longer milling times leading to more uniform carbon coatings. The RP with a Dv90 of 0.79 mu m mixed with graphite for 48 h delivered 1354 mA h g(-1) with high coulombic efficiency (>99%) and cyclability (88% capacity retention after 100 cycles). These results are an important step in the development of cyclable, high-capacity anodes for sodium-ion batteries.
|
|
| 2. |
- Munoz-Garcia, Ana Belen, et al.
(författare)
-
Structural evolution of disordered LiCo(1/3)Fe(1/3)Mn(1/3)PO(4)in lithium batteries uncovered
- 2020
-
Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7496 .- 2050-7488. ; 8:37, s. 19641-19653
-
Tidskriftsartikel (refereegranskat)abstract
- In this study we address the Li-ion de-insertion/insertion mechanisms from/into the lattice of the mixed olivine LiCo1/3Fe1/3Mn1/3PO4(LCFMP). This mechanism is driven by a subtle interplay of structural, electronic and thermodynamic features. We aim at dissecting this complex landscape that is tightly connected to the long-term electrochemical performance of this material as a positive electrode in lithium-ion cells. To this end, we report advanced structural characterization, based onex situsynchrotronradiation diffraction on samples at different lithium contents. We couple this analysis with first-principles simulations, for a directvis-a-viscomparison. Our results show that (1) the mixing of the three transition-metal (TM) cations in the olivine lattice leads to a solid solution, providing the olivine lattice with the necessary flexibility to retain its single-phase structure during cell operation; (2) the electronic features of the three TMs are responsible for the observed electrochemical performance; (3) the de-lithiation of the olivine lattice is a thermodynamically driven process. Last but not least, our integrated experimental and theoretical results reveal the subtle features behind the formation of antisite defects that selectively involve Li-Co couples. In conclusion, our study provides the necessary scientific foundations to understand the structure-property-function relationships in LCFMP olivines, paving the way for further development and optimization of this material for application in Li-ion batteries.
|
|
