The cells in a and b were charged at 0.04 C to 4.5 V, followed by holding the potential until current flowed below one hundredth of the charging current. The intensities were normalized by that of the (002) peak of the corresponding material. b) Comparison of d-spacing values and domain sizes. Three different bands (G, D and D') are indicated by dashed lines. b) Comparison of Raman shifts at peaks of the G band.
The same colors of the corresponding samples were used in (a). c) Comparison between EG* and EG by normalizing the intensities with those of the D-band. Electrochemical impedance spectra of the bare graphite (dashed lines) and EG (solid lines) measured in situ during galvanostatic delithiation at 0.1 C.
Introduction
Lithium-ion Batteries (LIBs)
- Principle of LIBs
- Characteristics of LIBs
- Cathode materials
- Anode materials
It has good thermal stability compared to LiCoO2 and is cheap due to the manganese element. Phospho-olivine structural materials, LiMPO4 (M=Fe, Mn), were created because of its structural stability. Due to the intrinsic properties of Mn, its ionic and electrical conductivities are much lower than those of LiFePO4.
Lithium metal is considered an anode material because of its high energy density, high voltage, and high energy density. Carbon was favored as the anode material due to its low cost and lower reduction potential that is close to the reduction potential of Li/Li+.
Strategies to Improve the Kinetics of LIBs
- Ionic Transport
- Li Solid-State Diffusion
- Electron transport
LiFePO4, the most representative member of the phosphoolivine family, shows an energy density of 585 Wh kg-1, which is a lower value than that of LiMn2O4 spinel (607 Wh kg-1). The main cause of LiFePO4's inferior energy density is its low working potential of 3.45 versus ~4.1 V for LiMn2O4). The stage behavior of the bare graphite was clearly observed in the differential capacitance curve (dQ/dV) (Figure 5.9c). EG involved a smaller resistivity (semicircle size) the first time (once delithiation started) compared to that of the bare graphite.
Enhanced anode performance of the three-dimensional Fe3O4-carbon-rGO composite in lithium ion batteries. Hollow versus non-hollow: the electrochemical preference in a case study of the conversion reaction of Fe3O4”.
Research purpose
Restricted growth of LiMnPO 4 nanoparticles evolved from a precursor seed
- Introduction
- Experiments
- Preparation
- Cell construction
- Results and discussion
- Preparation
- Electrochemical performances
- Conclusion
Formation of the second precipitate Mn3(PO4)2 is followed with the lower value of solubility product Ksp2:56. A trace of hollow spheres still observed in insets of Figure 2.2e and f confirms that the nanoparticles originate from the wall of the hollow structure. More abundant loss of mass before the second precipitation leads to the weakening of a structural support of the hollow secondary structure.
The products from each step of the surface-confined precipitation were also identified by XRD. A line mapping of the constituents of a single carbon-coated LMP particle at the same scale of (a).
Hollow versus non-hollow: The electrochemical preference in a case study of the
- Introduction
- Experiments
- Preparation
- Electrochemical analysis
- Results and discussion
- Morphological evolution of hollow structure
- Electrochemical preference of hollowness to non-hollowness
- Conclusion
1 g of CBall, dried at 70 oC overnight, was again ultrasonically dispersed in 200 ml of ethanol for 1 hour. A 70:20:10 mixture of active material (h-Fe3O4@C), conductive agent (Super P) and PAA/CMC (1:1, polyacrylic acid: carboxymethyl cellulose) as a binder was used as the working electrode. used, which is stuck on Cu foil. The main peak indicator (311) corresponds to the spacing of 0.252 nm of the crystal lattice edge shown in the TEM image (Figure 3.2l).
Pore size distributions calculated from nitrogen adsorption isotherms confirm the morphology revealed by electron microscopy and provide more detailed information on the morphology of the shells of hollow samples (Figure 3.4c). It is likely that micropores of approximately 1.2 nm have been developed in the shell of the hollow particles, accounting for 5.0% or 9.4%. Most of the surface area and pore volume comes from the inner and outer surfaces of the shell of the hollow particles, while the porous morphology of coated carbon layers contributed to the additional increase in micropores.
The relative cavity to non-void SBET ratio is 2.05, which is at least roughly consistent with the value calculated based on the above geometry (2.65). The deviation from the calculated values comes from the fact that a part of the non-hollow nanoparticles has dimensions smaller than the size of the solid spheres having the equivalent mass to that of h-Fe2O3 or h-Fe3O4@C. The kinetic advantage of the hollow structure would become more and more pronounced as the discharge rate increased.
The electrode composites consisted of a 70:20:10 mixture of the active material (h-Fe3O4@C or nh-Fe3O4@C), a conductive agent (Super P) and PAA/CMC (1: 1, polyacrylic acid/ .carboxymethyl cellulose) as a binder. The ∼80 nm diameter cavity accommodated volume expansion during charging, while the porous shell structure enabled easy Li+ ion transfer and improved surface accessibility of the active material. The carbon coating layer of the h-Fe3O4@C also improved electrical conductivity, which is believed to be partly responsible for suppressing the pulverization of the metal oxide.
- Introduction
- Experiments
- Electrochemical measurements
- Results and discussion
- Conclusion
Preparation of Co3O4 electrode materials with different microstructures through pseudomorphic conversion of Co-based organic metal. Here, we report the synthesis of two types of Co3O4 nanomaterials through pseudomorphic conversion where the macroscopic morphologies of the parent MOFs were preserved. The electrochemical properties of p-Co3O4 and r-Co3O4 were characterized using coin-type cells (CR2032) mounted in an Ar-filled glove box.
1 C was defined as 890 mA g-1, taking into account the theoretical capacity calculated based on the conversion reaction of Co3O4 to Co and Li2O (890 mAh g-1). As shown in the TEM images (Figures 4.1b and e), primary Co3O4 particles in both materials are observed as approx. As shown in Figure 4.1c and f, p-Co3O4 was composed of secondary particles with no integrity between primary particles, r-Co3O4 secondary particles.
Electrochemical characteristics of p-Co3O4 and r-Co3O4 in the left and right columns, respectively. a and b) Possible profiles during lithiation and delithiation in the first and second cycles. c and d) Capacity retention during repeated charge and discharge cycles at 0.1 C for 100 cycles. e and f) Dependence of capacity on discharge rates. In the Li2O matrix, the conversion reaction of Co3O4 to Co metal proceeded at a well-defined reduction potential, 1 V, which is responsible for the reversible electrochemical capacities. Conversely, its rod-shaped counterpart (r-Co3O4) was observed to be much more stable, providing an improved cyclability (with a capacity of ~800 mAh g-1), while the capacity of p-Co3O4 decreased at ~300 mAh g. -1 after 100 cycles (Figure 4.4d).
In addition to cyclic stability, the kinetics of the conversion reaction of r-Co3O4 was superior to that of p-Co3O4 (Figure 4.4e and f). In conclusion, we successfully synthesized two types of Co3O4 nanomaterials through the pseudomorphic conversion of two Co-based MOFs constructed with the same building blocks. These different higher levels of Co3O4 architectures were used as electrodes in LIB and their electrochemical properties were studied comparatively.
Enlarging the d-spacing of graphite and polarizing its surface charge for driving
- Introduction
- Experiments
- Mild oxidation of graphite to EG* and subsequent thermal reduction of EG* to EG
- Characterization
- Results and discussion
- Conclusion
The d-spacing distribution is responsible for the width of the (002) peak of EG* and its shoulder to its left between 20o and 25o. After subsequent thermal reduction, the 2 location and width of the (002) peak and its left shoulder were not significantly changed. Even in terms of the capacity values in mAh g-1, EG* and EG overcame their disadvantages of low initial capacities of 30 C and 40 C, respectively.
The available capacity (assumed to be Q0.1C) of the expanded graphites inferior to the bare graphite can be explained by several reasons. The thickness of the SEI layer was characterized by depth profiles by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). A dramatic increase in the atomic concentration of carbon is detected at the interface between the SEI layer and graphite.
The intensity of the carbon-related XPS peak of EG* and EG gradually increased after 10 min of sputtering (Figure 5.7). The depth profile from TOF-SIMS supports the development of the thinner SEI layer of EG* and EG more clearly (Figure 5.8). The capacity of both EG* and EG was maintained to be higher than 95% of the capacity at the first cycle even after 100 cycles.
Lithiation of bare graphite proceeds step by step (Figure 5.9c).23 Lithium ions are inserted into the empty space layers where the intercalation energy barriers are minimized. The dependence on the C rate of the lithiation processes also confirmed the asymmetric behavior of the EG overpotential (Figure 5.10). As delithiation proceeds, the effects of the larger d-spacing of the expanded graphite on the kinetics decrease.
Summary
The effect of different types of nano-carbon conductive additives in lithium ion batteries on the resistance and electrochemical behavior of the LiCoO 2 composite cathodes. Synthesis of hierarchical hollow-structured single-crystalline magnetite (Fe3O4) microspheres: the high-performance storage versus lithium as an anode for lithium-ion batteries. Manganese oxide nanoparticle-loaded porous carbon nanofibers as anode materials for high-performance lithium-ion batteries.
Graphene-wrapped Fe3O4 anode material with improved reversible capacity and cycling stability for lithium-ion batteries. Fe3O4 nanoparticles encapsulated in mesocellular carbon foam for high-performance anode materials for lithium-ion batteries. Controlled synthesis of α-Fe2O3 nanostructures and their size-dependent electrochemical properties for lithium-ion batteries.
Graphene-encapsulated hollow Fe(3)O(4) nanoparticle aggregates as a high-performance anode material for lithium-ion batteries. Magnetite/graphene nanosheet composites: interaction interaction and its impact on the durable high-speed performance in lithium-ion batteries. Conversion of cobalt oxide subunits in cobalt metal-organic framework into agglomerated Co3O4 nanoparticles as an electrode material for lithium ion battery.
Large-scale reversible lithium storage of graphene nanosheet families for use in rechargeable lithium-ion batteries. Graphene sheets as anode materials for Li-ion batteries: preparation, structure, electrochemical properties and lithium storage mechanism. Reactivity and safety aspects of carbon anodes used in lithium-ion batteries - Correlation of structural parameters and reactivity.
Acknowledgement
그리고 수많은 동기들과 선배, 후배들에게도 감사의 말씀을 전하고 싶습니다. 종이에 다 표현하지 못한 마음을 평생 갚으며 살겠습니다. 리튬이온 배터리용 Si/Cu 1D 나노와이어의 3D 얽힘 및 교차 연결 아키텍처를 기반으로 한 올인원 어셈블리”입니다.
Ju-Myung Kim, Han-Saem Park, Jang-Hoon Park, Tae-Hee Kim, Hyun-Kon Song*, Sang-Young Lee*. Conduction of polymer-skinned electroactive materials of lithium-ion batteries: Ready for single-component electrodes without additional binders and conducting agents”. Tae-Hee Kim‡, Eun Kyung Jeon‡, Younghoon Ko, Bo Yun Jang, Byeong-Su Kim, Hyun-Kon Song*.
Catalytic Carbonization of a Non-Carbonizing Precursor by Transition Metals in Olivine Cathode Materials of Lithium Ion Batteries. Tae-Hee Kim, Jeong-Seok Park, Sung Kyun Chang, Seungdon Choi*, Ji Heon Ryu*, Hyun-Kon Song*. Myeong-Hee Lee, Tae-Hee Kim, Young-Soo Kim, Jeong-Seok Park, Hyun-Kon Song*.
Tae-Hee Kim, Han-Saem Park, Myeong-Hee Lee, Sang-Young Lee*, Hyun-Kon Song*. Geun Gi Min, Younghoon Ko, Tae-Hee Kim, Hyun-Kon Song, Seung Bin Kim, Su- Moon Park*. Nanostructured and nanocomposite one-dimensional (1D) LiFePO4: its prospective advantages for lithium-ion battery cathode materials”.
