1,720,980 research outputs found
Surface modification of the Co-free LiNi0.5 Mn1.5O4-δ positive electrode material for high-voltage lithium-ion batteries
No full textThe aim of this thesis was to modify the surface of the LNMO powder to improve
its electrochemical performance as a high-voltage lithium-ion battery positive
electrode material. Different types of LNMO powders, synthesis routes and surface
modification materials were explored to achieve this target.
The Ti-containing surface modification materials were shown to be effective in
improving the LNMO electrochemical performance:
Ti surface doped LNMO nanopowders synthesized via the hydrolysiscondensation approach improved the LNMO cyclic stability, Coulombic
efficiency and rate performance compared to bare LNMO
Amorphous-LTO surface modified LNMO micron-powders synthesized via the
solution-gel approach improved the LNMO rate performance, reduced the cell
impedance during cycling and improved the cyclic stability
Returning to the questions introduced in the scope of the thesis in Section 1.12:
A too high LNMO surface area results in low capacities due to a high amount
of side reactions for the LNMO commercial nanopowders, as in Chapter 2. A
micron-sized LNMO composed of large, irregular aggregates is not ideal either,
as in Chapter 3. Optimizing the pre-calcination conditions during the aqueous
solution-gel synthesis route in Chapter 3 enabled synthesis of an optimum
LNMO particle size and morphology with good electrochemical performance.
To reach an optimum electrode preparation protocol and electrochemical
performance with a specific powder, the solvent concentration and slurry
mixture viscosity, therefore the electrode morphology, should be optimized.
Several electrode preparation parameters were studied in Chapter 4 and an
optimum preparation protocol is obtained.
Materials of strong metal-oxygen bonds are interesting candidates for surface
modification, to improve the LNMO surface stability at high voltages. Surface
doping occurs instead of surface coating, especially if high synthesis
temperatures are used. The surface doping approach is an effective way to
improve the electrochemical performance. Interesting candidates also include
amorphous oxides. The amorphous oxides seem to increase the side reactions
at the beginning of cycling. However, as the cycling continues, they might be
providing a more stable, compact CEI layer, since the cell resistance drops
and cycle life improves.
Two different synthesis approaches provide successful surface modifications
for the nano/micron-sized LNMO powders and improve the electrochemical
performance: The hydrolysis-condensation approach (Section 1.9.3.2) coupled with
LNMO nanopowders in Chapter 2. It provides uniformly doped LNMO
nanopowder surfaces. An electrostatic adsorption mechanism is
proposed to take place during synthesis. Electrically charged LNMO
surfaces apply electrostatic forces to ions/nanoparticles in the solution
over large distances and loosely bind them to their surface.
o The solution-gel approach (Section 1.9.4) coupled with LNMO micronpowders in Chapter 5. The solution-gel approach allows synthesis of
multi-metal ion surface modification materials with controlled
stoichiometry. It provides coatings/islands or surface dopants on
LNMO micron-powders. A surface complex formation mechanism is
proposed to take place during synthesis.
Possible reasons for the electrochemical performance improvements with the
Ti-based surface modification materials are:
o Surface structure stabilization by incorporation of the strong Ti-O
bonds
o Increased LNMO surface area after the surface modification leading to
lower polarization and improved rate performance
o A more favorable CEI layer formation on the electrode during cycling
The findings of this thesis are summarized below in further detail:
The thesis started with the use of commercial, nano-sized LiNi0.5Mn1.5O4-δ powder
in Chapter 2. A hydrolysis-condensation approach was used for surface
modification, followed by annealing. The surface of the LNMO powder was
modified by Ti cation doping over 2-4 nm depth, while maintaining the initial spinel
structure, using a hydrolysis-condensation approach followed by 500oC anneal.
Particle size and surface area of the bare and surface modified LNMO remained
similar after 500oC anneal and the Ti doped surface remained intact. Although the
initial discharge capacity was slightly reduced, cycle life, Coulombic efficiency and
rate performance were improved for Ti surface doped LNMO annealed at 500oC
compared to bare LNMO also annealed at 500oC. The improvement is probably
due to surface structure stabilization by the stronger Ti-O bonds, which reduces
the manganese dissolution. On the other hand, during an 800oC anneal, Ti diffused
from the surface towards the core of LNMO, causing a secondary LiNi0.5-xMn1.5-
yTizO4 phase formation and particle size growth. Mn-Ni ordering in the lattice
increased with 800oC annealing in oxygen for both bare and surface modified
LNMO samples, compared to 500oC annealed samples in oxygen. However, no
significant improvement was observed in cycle life or Coulombic efficiency of Ti
surface modified LNMO annealed at 800oC compared to bare LNMO also annealed
at 800oC. This is probably because the Ti doped surface layer of LNMO was in this
case not well preserved during Ti diffusion and particle size growth. The Ti surfacedoped LNMO annealed at 500oC, having a well preserved spinel surface structure
and a disordered Mn-Ni distribution, could be an interesting candidate as a
cathode material for lithium-ion battery applications requiring both good cycle life
and rate performance. The thesis continued with the synthesis of LNMO powders to achieve an optimum
particle size, morphology and electrochemical performance in Chapter 3. The
LNMO particle size and morphology were controlled using aqueous solution-gel
synthesis with different pre-calcination temperatures, times and oven types.
Crystalline LNMO powder morphology and particle sizes were shown to depend on
the organic residue in the LNMO precursor powder before the 900oC calcination
step. Calcining the LNMO precursor gel at 200oC for 40 h in a forced convection
oven (LNMO-4) started a vigorous decomposition reaction and resulted in a
voluminous, foam-like precursor powder morphology. The amount of organic
residues before crystallization was minimized in the LNMO-4 precursor powder,
enabling a small particle size after the 900oC calcination step with well-defined
facets. LNMO-4 provided the highest initial discharge capacity of 121 mAh/g at
0.2 C compared to other LNMO powders. On the other hand, organic removal was
probably incomplete with 170oC, 24 h, natural-convection oven pre-calcination
during LNMO-1 precursor powder synthesis, resulting in large aggregates with
non-uniform size distribution and poor electrochemical performance. The
carboxylates or carbonaceous residues present in LNMO-1 precursor powder
possibly adsorb on the surface of small metal oxide nuclei cause agglomeration
and prevent formation of well-defined facets during the 900oC calcination step.
Ball-milling of crystalline LNMO powder (LNMO-3) reduced the agglomeration and
particle size, increased the disordering, Mn3+ concentration and lattice parameter.
However, the initial discharge capacities of LNMO-3 were lower compared to
LNMO-4, which was linked to the increased surface area, Mn3+ concentration and
side-reactions. LNMO particle size optimization via controlling the pre-calcination
conditions is more advantageous compared to size reduction via ball-milling, in
terms of preserving well-defined facets, a high capacity and high Coulombic
efficiency.
The synthesized LNMO powders in Chapter 3 were used to optimize the electrode
properties in Chapter 4, which also has an important influence on the
electrochemical properties. An optimized electrode preparation protocol was
proposed for the synthesized LNMO active material of ~30 μm average aggregate
and ~3.5 μm average primary particle size, after individually examining the
effects of composite electrode processing parameters on the electrochemical
performance of the Li|LNMO cells. A good rate performance was obtained for
LNMO electrodes made using a 150 μm wet thickness, 3 wt. % PVDF-NMP mixture
and C65 carbon black. The use of C45 carbon black can improve the initial
discharge capacity, reduce the amount of parasitic side reactions and improve the
cyclability compared to C65. However, the application of C65 should be preferred,
if a higher rate performance is desired. Thinky planetary mixing method coupled
with a LNMO-carbon black dry mixing step could be preferred over ball-milling to
homogeneously distribute the carbon black particles and increase porosity while
eliminating LNMO particle size, crystalline structure or morphology changes. A
calendering step should be applied to optimize the porosity, improve the electrical
contact and reduce the cell impedance. However, LNMO particle size and shape
should be considered while calendering and excessive forces should be avoided
since LNMO particles could break apart during calendering resulting in a lower
capacity.
The optimized LNMO synthesis and electrode making routes in Chapters 3 and 4
were used to explore the influence of amorphous LTO surface modification of
LNMO on the electrochemical performance in Chapter 5. LNMO surface was
modified with amorphous LTO material (LNMO@LTO-200oC) via a solution-gel
route, resulting in Ti-rich amorphous coatings/islands or Ti-rich spinel surfaces
mostly on the {001} surfaces of LNMO. Transition metal ions on LNMO powder
surfaces partly dissolved into the aqueous, citric acid LTO precursor solution
during the LNMO@LTO-200oC synthesis. The dissolved TM ions precipitated
together with the Ti ions in the LTO precursor solution during the water removal
step and formed the Ti-Ni-Mn-O containing amorphous nanoparticles inside the
LNMO@LTO-200oC powder. Upon 500oC annealing in dry air flow (LNMO@LTO500oC), the amorphous matter crystallized into spinel or rock salt nanoparticles
depending on the composition. Amorphous LTO surface modification slightly
increased the Mn3+ concentration in LNMO based on the capacity curve
measurements and dQ/dV plots, but the electronic or bulk ionic conductivities
were not improved. Amorphous LTO surface modification increased the LNMO
surface area by ~4 times. The rate performance and cyclability were improved for
LNMO@LTO-200oC compared to bare LNMO, while crystallized LNMO@LTO-500oC
showed similar rate performance and cyclabilites compared to its bare
counterpart. The cell impedance increased more rapidly for the bare LNMO
compared to LNMO@LTO-200oC, while the dry air annealed samples had similar
impedances after 1000 cycles. Amorphous coating-HF scavenging reactions might
be occuring slowly on the LNMO@LTO-200oC powder surfaces during cycling,
providing a more favorable CEI layer formation on the electrode surface compared
to bare LNMO.
ZrO2-SiO2 surface modification materials were explored for LNMO in Chapter 6 via
the hydrolysis-condensation approach. ZrO2 surface modified LNMO was
synthesized using different ZrO2 loadings. A too thick, tetragonal ZrO2 coating
layer was probably synthesized on LNMO using 0.2 mL NH3 (25 wt. %) and 4 h
annealing time, which impedes the Li+ transport and causes a large capacity drop.
ZrO2 coating made using 0.1 mL NH3 (25 wt. %) and 4 h annealing time on the
other hand provided probably a more optimum coating thickness, a slightly
improved initial capacity but a deteriorated cyclic stability. The cyclic stability was
improved using a longer anneal time of 10 h, which probably promotes Zr ion
doping into the LNMO surface structure and improves the CEI layer stability during
cycling at room temperature. Cycling temperature was increased to 55oC to
increase the amount of side-reactions and to observe the influence of the ZrO2
surface modification layer better. Improved Coulombic efficiency values were
recorded for the surface modified LNMO compared to the bare LNMO. This could
be explained by a HF-scavengering mechanism where Zr cations react with HF to
form a more stable, ZrF4 containing CEI layer.
SiO2 was incorporated on the LNMO surface together with the ZrO2. Lower or
higher temperatures were used to synthesize ZrO2-SiO2 coated or Zr-Si doped
LNMO surfaces. Neither showed an important improvement in the rate
performance. However, when also coupled with different cooling rates, important
variations in the Ni/Mn disordering were observed for the bare/ZrO2-SiO2 coated
LNMO powders, which greatly influenced the electrochemical performances. The
700oC annealed, slow cooled (1oC/min) bare/ZrO2-SiO2 surface modified LNMO
powders showed a drastic increase in the Ni/Mn ordering and better
electrochemical performance compared to the 500oC annealed, furnace cooled
bare/surface modified LNMO powders. Increased ordering is probably caused by
the slower cooling rate in oxygen flow. The higher temperature used on the other
hand could be introducing more oxygen vacancies in the structures, because of
the temperature dependent O2 evolution reaction. As a result, a more optimum
amount of oxygen vacancies and Ni/Mn ordering were probably achieved in the
bare/ZrO2-SiO2 surface modified LNMO powders with the 700oC annealing and
1°C/min heating/cooling rates, which helped improve the electrochemical
performance
Surface modification of the Co-free LiNi0.5 Mn1.5O4-δ positive electrode material for high-voltage lithium-ion batteries
No full textThe aim of this thesis was to modify the surface of the LNMO powder to improve
its electrochemical performance as a high-voltage lithium-ion battery positive
electrode material. Different types of LNMO powders, synthesis routes and surface
modification materials were explored to achieve this target.
The Ti-containing surface modification materials were shown to be effective in
improving the LNMO electrochemical performance:
Ti surface doped LNMO nanopowders synthesized via the hydrolysiscondensation approach improved the LNMO cyclic stability, Coulombic
efficiency and rate performance compared to bare LNMO
Amorphous-LTO surface modified LNMO micron-powders synthesized via the
solution-gel approach improved the LNMO rate performance, reduced the cell
impedance during cycling and improved the cyclic stability
Returning to the questions introduced in the scope of the thesis in Section 1.12:
A too high LNMO surface area results in low capacities due to a high amount
of side reactions for the LNMO commercial nanopowders, as in Chapter 2. A
micron-sized LNMO composed of large, irregular aggregates is not ideal either,
as in Chapter 3. Optimizing the pre-calcination conditions during the aqueous
solution-gel synthesis route in Chapter 3 enabled synthesis of an optimum
LNMO particle size and morphology with good electrochemical performance.
To reach an optimum electrode preparation protocol and electrochemical
performance with a specific powder, the solvent concentration and slurry
mixture viscosity, therefore the electrode morphology, should be optimized.
Several electrode preparation parameters were studied in Chapter 4 and an
optimum preparation protocol is obtained.
Materials of strong metal-oxygen bonds are interesting candidates for surface
modification, to improve the LNMO surface stability at high voltages. Surface
doping occurs instead of surface coating, especially if high synthesis
temperatures are used. The surface doping approach is an effective way to
improve the electrochemical performance. Interesting candidates also include
amorphous oxides. The amorphous oxides seem to increase the side reactions
at the beginning of cycling. However, as the cycling continues, they might be
providing a more stable, compact CEI layer, since the cell resistance drops
and cycle life improves.
Two different synthesis approaches provide successful surface modifications
for the nano/micron-sized LNMO powders and improve the electrochemical
performance: The hydrolysis-condensation approach (Section 1.9.3.2) coupled with
LNMO nanopowders in Chapter 2. It provides uniformly doped LNMO
nanopowder surfaces. An electrostatic adsorption mechanism is
proposed to take place during synthesis. Electrically charged LNMO
surfaces apply electrostatic forces to ions/nanoparticles in the solution
over large distances and loosely bind them to their surface.
o The solution-gel approach (Section 1.9.4) coupled with LNMO micronpowders in Chapter 5. The solution-gel approach allows synthesis of
multi-metal ion surface modification materials with controlled
stoichiometry. It provides coatings/islands or surface dopants on
LNMO micron-powders. A surface complex formation mechanism is
proposed to take place during synthesis.
Possible reasons for the electrochemical performance improvements with the
Ti-based surface modification materials are:
o Surface structure stabilization by incorporation of the strong Ti-O
bonds
o Increased LNMO surface area after the surface modification leading to
lower polarization and improved rate performance
o A more favorable CEI layer formation on the electrode during cycling
The findings of this thesis are summarized below in further detail:
The thesis started with the use of commercial, nano-sized LiNi0.5Mn1.5O4-δ powder
in Chapter 2. A hydrolysis-condensation approach was used for surface
modification, followed by annealing. The surface of the LNMO powder was
modified by Ti cation doping over 2-4 nm depth, while maintaining the initial spinel
structure, using a hydrolysis-condensation approach followed by 500oC anneal.
Particle size and surface area of the bare and surface modified LNMO remained
similar after 500oC anneal and the Ti doped surface remained intact. Although the
initial discharge capacity was slightly reduced, cycle life, Coulombic efficiency and
rate performance were improved for Ti surface doped LNMO annealed at 500oC
compared to bare LNMO also annealed at 500oC. The improvement is probably
due to surface structure stabilization by the stronger Ti-O bonds, which reduces
the manganese dissolution. On the other hand, during an 800oC anneal, Ti diffused
from the surface towards the core of LNMO, causing a secondary LiNi0.5-xMn1.5-
yTizO4 phase formation and particle size growth. Mn-Ni ordering in the lattice
increased with 800oC annealing in oxygen for both bare and surface modified
LNMO samples, compared to 500oC annealed samples in oxygen. However, no
significant improvement was observed in cycle life or Coulombic efficiency of Ti
surface modified LNMO annealed at 800oC compared to bare LNMO also annealed
at 800oC. This is probably because the Ti doped surface layer of LNMO was in this
case not well preserved during Ti diffusion and particle size growth. The Ti surfacedoped LNMO annealed at 500oC, having a well preserved spinel surface structure
and a disordered Mn-Ni distribution, could be an interesting candidate as a
cathode material for lithium-ion battery applications requiring both good cycle life
and rate performance. The thesis continued with the synthesis of LNMO powders to achieve an optimum
particle size, morphology and electrochemical performance in Chapter 3. The
LNMO particle size and morphology were controlled using aqueous solution-gel
synthesis with different pre-calcination temperatures, times and oven types.
Crystalline LNMO powder morphology and particle sizes were shown to depend on
the organic residue in the LNMO precursor powder before the 900oC calcination
step. Calcining the LNMO precursor gel at 200oC for 40 h in a forced convection
oven (LNMO-4) started a vigorous decomposition reaction and resulted in a
voluminous, foam-like precursor powder morphology. The amount of organic
residues before crystallization was minimized in the LNMO-4 precursor powder,
enabling a small particle size after the 900oC calcination step with well-defined
facets. LNMO-4 provided the highest initial discharge capacity of 121 mAh/g at
0.2 C compared to other LNMO powders. On the other hand, organic removal was
probably incomplete with 170oC, 24 h, natural-convection oven pre-calcination
during LNMO-1 precursor powder synthesis, resulting in large aggregates with
non-uniform size distribution and poor electrochemical performance. The
carboxylates or carbonaceous residues present in LNMO-1 precursor powder
possibly adsorb on the surface of small metal oxide nuclei cause agglomeration
and prevent formation of well-defined facets during the 900oC calcination step.
Ball-milling of crystalline LNMO powder (LNMO-3) reduced the agglomeration and
particle size, increased the disordering, Mn3+ concentration and lattice parameter.
However, the initial discharge capacities of LNMO-3 were lower compared to
LNMO-4, which was linked to the increased surface area, Mn3+ concentration and
side-reactions. LNMO particle size optimization via controlling the pre-calcination
conditions is more advantageous compared to size reduction via ball-milling, in
terms of preserving well-defined facets, a high capacity and high Coulombic
efficiency.
The synthesized LNMO powders in Chapter 3 were used to optimize the electrode
properties in Chapter 4, which also has an important influence on the
electrochemical properties. An optimized electrode preparation protocol was
proposed for the synthesized LNMO active material of ~30 μm average aggregate
and ~3.5 μm average primary particle size, after individually examining the
effects of composite electrode processing parameters on the electrochemical
performance of the Li|LNMO cells. A good rate performance was obtained for
LNMO electrodes made using a 150 μm wet thickness, 3 wt. % PVDF-NMP mixture
and C65 carbon black. The use of C45 carbon black can improve the initial
discharge capacity, reduce the amount of parasitic side reactions and improve the
cyclability compared to C65. However, the application of C65 should be preferred,
if a higher rate performance is desired. Thinky planetary mixing method coupled
with a LNMO-carbon black dry mixing step could be preferred over ball-milling to
homogeneously distribute the carbon black particles and increase porosity while
eliminating LNMO particle size, crystalline structure or morphology changes. A
calendering step should be applied to optimize the porosity, improve the electrical
contact and reduce the cell impedance. However, LNMO particle size and shape
should be considered while calendering and excessive forces should be avoided
since LNMO particles could break apart during calendering resulting in a lower
capacity.
The optimized LNMO synthesis and electrode making routes in Chapters 3 and 4
were used to explore the influence of amorphous LTO surface modification of
LNMO on the electrochemical performance in Chapter 5. LNMO surface was
modified with amorphous LTO material (LNMO@LTO-200oC) via a solution-gel
route, resulting in Ti-rich amorphous coatings/islands or Ti-rich spinel surfaces
mostly on the {001} surfaces of LNMO. Transition metal ions on LNMO powder
surfaces partly dissolved into the aqueous, citric acid LTO precursor solution
during the LNMO@LTO-200oC synthesis. The dissolved TM ions precipitated
together with the Ti ions in the LTO precursor solution during the water removal
step and formed the Ti-Ni-Mn-O containing amorphous nanoparticles inside the
LNMO@LTO-200oC powder. Upon 500oC annealing in dry air flow (LNMO@LTO500oC), the amorphous matter crystallized into spinel or rock salt nanoparticles
depending on the composition. Amorphous LTO surface modification slightly
increased the Mn3+ concentration in LNMO based on the capacity curve
measurements and dQ/dV plots, but the electronic or bulk ionic conductivities
were not improved. Amorphous LTO surface modification increased the LNMO
surface area by ~4 times. The rate performance and cyclability were improved for
LNMO@LTO-200oC compared to bare LNMO, while crystallized LNMO@LTO-500oC
showed similar rate performance and cyclabilites compared to its bare
counterpart. The cell impedance increased more rapidly for the bare LNMO
compared to LNMO@LTO-200oC, while the dry air annealed samples had similar
impedances after 1000 cycles. Amorphous coating-HF scavenging reactions might
be occuring slowly on the LNMO@LTO-200oC powder surfaces during cycling,
providing a more favorable CEI layer formation on the electrode surface compared
to bare LNMO.
ZrO2-SiO2 surface modification materials were explored for LNMO in Chapter 6 via
the hydrolysis-condensation approach. ZrO2 surface modified LNMO was
synthesized using different ZrO2 loadings. A too thick, tetragonal ZrO2 coating
layer was probably synthesized on LNMO using 0.2 mL NH3 (25 wt. %) and 4 h
annealing time, which impedes the Li+ transport and causes a large capacity drop.
ZrO2 coating made using 0.1 mL NH3 (25 wt. %) and 4 h annealing time on the
other hand provided probably a more optimum coating thickness, a slightly
improved initial capacity but a deteriorated cyclic stability. The cyclic stability was
improved using a longer anneal time of 10 h, which probably promotes Zr ion
doping into the LNMO surface structure and improves the CEI layer stability during
cycling at room temperature. Cycling temperature was increased to 55oC to
increase the amount of side-reactions and to observe the influence of the ZrO2
surface modification layer better. Improved Coulombic efficiency values were
recorded for the surface modified LNMO compared to the bare LNMO. This could
be explained by a HF-scavengering mechanism where Zr cations react with HF to
form a more stable, ZrF4 containing CEI layer.
SiO2 was incorporated on the LNMO surface together with the ZrO2. Lower or
higher temperatures were used to synthesize ZrO2-SiO2 coated or Zr-Si doped
LNMO surfaces. Neither showed an important improvement in the rate
performance. However, when also coupled with different cooling rates, important
variations in the Ni/Mn disordering were observed for the bare/ZrO2-SiO2 coated
LNMO powders, which greatly influenced the electrochemical performances. The
700oC annealed, slow cooled (1oC/min) bare/ZrO2-SiO2 surface modified LNMO
powders showed a drastic increase in the Ni/Mn ordering and better
electrochemical performance compared to the 500oC annealed, furnace cooled
bare/surface modified LNMO powders. Increased ordering is probably caused by
the slower cooling rate in oxygen flow. The higher temperature used on the other
hand could be introducing more oxygen vacancies in the structures, because of
the temperature dependent O2 evolution reaction. As a result, a more optimum
amount of oxygen vacancies and Ni/Mn ordering were probably achieved in the
bare/ZrO2-SiO2 surface modified LNMO powders with the 700oC annealing and
1°C/min heating/cooling rates, which helped improve the electrochemical
performance
Eliminating cobalt from lithium-ion batteries: which improvements can be enabled by the use of wet chemical routes?
No full textLithium-ion batteries (LIBs) are considered an important technology for the mobility sector’s green energy transition by enabling the breakthrough of electric vehicles (EVs). The forecasted explosive growth of the EV market implies that the demand for LIB materials will show a steep increase over the following years. This will put considerable strain on the sourcing of the critical raw materials needed for LIB production. The mining, refining, and processing of cobalt pose a number of challenges, ranging from social and environmental impacts to supply shortages. One way to tackle these challenges is to use battery active materials which contain (almost) no cobalt. This again requires extensive research to ensure high cycle life and thermal stability. In the Horizon 2020 COBRA project, we aim to completely eliminate cobalt from the positive electrode, while reaching an adequate energy density (750 Wh/L) and cycle life (>2000 cycles) with fast charging (3 C). COBRA aims to reach competitive cost targets (< 90 €/kWh at pack level).
Here, an overview will be given of our recent studies on Co-free and Co-poor materials for LIBs. Our research relies on the use of wet chemical routes, either to synthesize the active materials, or to form a shell on pre-existing active material core particles. The developed wet chemical synthesis routes allow a careful control over the synthesis parameters, and enable us to accurately control the particle size/morphology of cobalt-free LiNi0.5Mn1.5O4 (LNMO) particles.[1] The electrochemical performance of LNMO core particles could be further improved by coating them with shells of TiOx or amorphous Li4Ti5O12.[2] Cores of LiNi0.6Mn0.2Co0.2O2 (NMC-622, a nickel-rich, cobalt-poor layered oxide) were similarly modified with TiOx shells, improving its rate capability and energy density.[3] Wet chemical routes are ideal for inserting dopants into materials. For instance, the replacement of Mn4+ by Sn4+ in lithium- and manganese-rich (and cobalt-poor) NMC was studied in an effort to mitigate the voltage fade which is typically observed in such materials.[4] Whereas cobalt is ubiquitous in today’s LIBs, current research efforts strive toward a reduction and even elimination of cobalt in future LIBs. As shown here, our research contributes to the improvements required to make these novel materials competitive with the materials that are currently used in LIBs.
[1] F. Ulu Okudur, S. K. Mylavarapu, M. Safari, D. De Sloovere, J. D’Haen, B. Joos, P. Kaliyappan, A. S. Kelchtermans, P. Samyn, M. K. Van Bael, A. Hardy, J. Alloys Compd. 892 (2022) 162175.
[2] F. Ulu Okudur, J. D’Haen, T. Vranken, D. De Sloovere, M. Verheijen, O. M. Karakulina, A. M. Abakumov, J. Hadermann, M. K. Van Bael, A. Hardy, RSC Adv. 8 (2018) 7287-7300.
[3] S. K. Mylavarapu, F. Ulu Okudur, S. Yari, D. De Sloovere, J. D’Haen, A. Shafique, M. K. Van Bael, M. Safari, A. Hardy, ACS Appl. Energy Mater. 4 (2021) 10493-10504.
[4] A. Paulus, M. Hendrickx, M. Bercx, O. M. Karakulina, M. A. Kirsanova, D. Lamoen, J. Hadermann, A. M. Abakumov, M. K. Van Bael, A. Hardy, Dalt. Trans. 49 (2020) 10486-10497.
The Horizon 2020 LCBAT-5 COBRA project 875568 is acknowledged for financial support
Eliminating cobalt from lithium-ion batteries: which improvements can be enabled by the use of wet chemical routes?
No full textLithium-ion batteries (LIBs) are considered an important technology for the mobility sector’s green energy transition by enabling the breakthrough of electric vehicles (EVs). The forecasted explosive growth of the EV market implies that the demand for LIB materials will show a steep increase over the following years. This will put considerable strain on the sourcing of the critical raw materials needed for LIB production. The mining, refining, and processing of cobalt pose a number of challenges, ranging from social and environmental impacts to supply shortages. One way to tackle these challenges is to use battery active materials which contain (almost) no cobalt. This again requires extensive research to ensure high cycle life and thermal stability. In the Horizon 2020 COBRA project, we aim to completely eliminate cobalt from the positive electrode, while reaching an adequate energy density (750 Wh/L) and cycle life (>2000 cycles) with fast charging (3 C). COBRA aims to reach competitive cost targets (< 90 €/kWh at pack level).
Here, an overview will be given of our recent studies on Co-free and Co-poor materials for LIBs. Our research relies on the use of wet chemical routes, either to synthesize the active materials, or to form a shell on pre-existing active material core particles. The developed wet chemical synthesis routes allow a careful control over the synthesis parameters, and enable us to accurately control the particle size/morphology of cobalt-free LiNi0.5Mn1.5O4 (LNMO) particles.[1] The electrochemical performance of LNMO core particles could be further improved by coating them with shells of TiOx or amorphous Li4Ti5O12.[2] Cores of LiNi0.6Mn0.2Co0.2O2 (NMC-622, a nickel-rich, cobalt-poor layered oxide) were similarly modified with TiOx shells, improving its rate capability and energy density.[3] Wet chemical routes are ideal for inserting dopants into materials. For instance, the replacement of Mn4+ by Sn4+ in lithium- and manganese-rich (and cobalt-poor) NMC was studied in an effort to mitigate the voltage fade which is typically observed in such materials.[4] Whereas cobalt is ubiquitous in today’s LIBs, current research efforts strive toward a reduction and even elimination of cobalt in future LIBs. As shown here, our research contributes to the improvements required to make these novel materials competitive with the materials that are currently used in LIBs.
[1] F. Ulu Okudur, S. K. Mylavarapu, M. Safari, D. De Sloovere, J. D’Haen, B. Joos, P. Kaliyappan, A. S. Kelchtermans, P. Samyn, M. K. Van Bael, A. Hardy, J. Alloys Compd. 892 (2022) 162175.
[2] F. Ulu Okudur, J. D’Haen, T. Vranken, D. De Sloovere, M. Verheijen, O. M. Karakulina, A. M. Abakumov, J. Hadermann, M. K. Van Bael, A. Hardy, RSC Adv. 8 (2018) 7287-7300.
[3] S. K. Mylavarapu, F. Ulu Okudur, S. Yari, D. De Sloovere, J. D’Haen, A. Shafique, M. K. Van Bael, M. Safari, A. Hardy, ACS Appl. Energy Mater. 4 (2021) 10493-10504.
[4] A. Paulus, M. Hendrickx, M. Bercx, O. M. Karakulina, M. A. Kirsanova, D. Lamoen, J. Hadermann, A. M. Abakumov, M. K. Van Bael, A. Hardy, Dalt. Trans. 49 (2020) 10486-10497.
The Horizon 2020 LCBAT-5 COBRA project 875568 is acknowledged for financial support
Innovative battery materials: it’s all about chemistry!
No full textBatteries are ubiquitous in our society and can be used in many applications, such as electric vehicles and stationary energy storage. Further progress in the development of batteries relies on the synergy between concepts from chemistry, physics and engineering. Creative chemical synthesis processes for the electrodes and electrolyte are a key factor in improving the functionality of battery technologies and pave the way toward a more sustainable future. This presentation will showcase a number of selected examples, where chemical approaches were used to improve the electrochemical performance and/or sustainability of current and upcoming battery chemistries.
Although commonly used in lithium-ion batteries (LIBs), the mining, refining, and processing of cobalt causes a range of detrimental societal and environmental impacts. Therefore, extensive research was performed within the Horizon 2020 COBRA project to produce a positive electrode material for LIBs that does not contain any cobalt but still reaches a high energy/power density and cycle life at a competitive cost. In a different research path, core particles of positive electrode materials were coated with a shell of a material with high conductivity, thereby enhancing their energy and power density. The synthesis of core-shell particles can also enable an improved battery cycle life.1,2 Creative chemical approaches were also used to synthesize durable negative electrode materials for sodium-ion batteries (SIBs), making use of a carbothermal reduction reaction to form a phase which can otherwise only be formed in a cumbersome synthesis method.3
The electrolyte component of batteries should have a high conductivity for ions. Conventional electrolytes are highly flammable, limiting the safety of battery operation. To improve the safety, a nonflammable class of liquid electrolyte was developed for SIBs. The combination of experimental and computational studies allowed the optimization of the coordination structure of deep eutectic solvents (DESs) as viable electrolyte alternatives. They can offer a more durable electrochemical performance compared to conventional electrolytes.4 The development of solid electrolytes for battery applications may enable the safe use of metallic anodes, thereby offering the possibility to drastically improve the energy density. Therefore, DESs were incorporated into inorganic and polymeric backbone structures, compatible with high-energy density electrode materials. This new class of solid electrolyte for battery applications was termed eutectogel and consists of inexpensive and mechanically optimized electrolytes for next-generation solid-state batteries.5,6
This work was supported by Horizon 2020 LCBAT-5 COBRA project 875568 and by Research Foundation Flanders in several projects and mandates. Furthermore, the work received the support of the European Union, the European Regional Development Fund ERDF, Flanders Innovation & Entrepreneurship and the Province of Limburg (project 936).
(1) Ulu Okudur, F. et al. Ti surface doping of LiNi0.5Mn1.5O4-δ positive electrodes for lithium ion batteries. RSC Adv. 8, p7287–7300 (2018).
(2) Mylavarapu, S. K. et al. Effect of TiOx Surface Modification on the Electrochemical Performances of Ni-Rich (NMC-622) Cathode Material for Lithium-Ion Batteries. ACS Appl. Energy Mater. 4, p10493–10504 (2021).
(3) De Sloovere, D. et al. Reduced Na2+xTi4O9/C Composite: A Durable Anode for Sodium-Ion Batteries. Chem. Mater. 30, p8521–8527 (2018).
(4) De Sloovere, D. et al. Deep Eutectic Solvents as Nonflammable Electrolytes for Durable Sodium‐Ion Batteries. Adv. Energy Sustain. Res. 3, p2100159 (2022).
(5) Joos, B. et al. Eutectogels: A New Class of Solid Composite Electrolytes for Li/Li-Ion Batteries. Chem. Mater. 30, p655–662 (2018).
(6) Joos, B. et al. Polymeric Backbone Eutectogels as a New Generation of Hybrid Solid-State Electrolytes. Chem. Mater. 32, p3783–3793 (2020).This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 875568.
The complete DESINe group
Technical personnel at UH
All coauthor
Innovative battery materials: it’s all about chemistry!
No full textBatteries are ubiquitous in our society and can be used in many applications, such as electric vehicles and stationary energy storage. Further progress in the development of batteries relies on the synergy between concepts from chemistry, physics and engineering. Creative chemical synthesis processes for the electrodes and electrolyte are a key factor in improving the functionality of battery technologies and pave the way toward a more sustainable future. This presentation will showcase a number of selected examples, where chemical approaches were used to improve the electrochemical performance and/or sustainability of current and upcoming battery chemistries.
Although commonly used in lithium-ion batteries (LIBs), the mining, refining, and processing of cobalt causes a range of detrimental societal and environmental impacts. Therefore, extensive research was performed within the Horizon 2020 COBRA project to produce a positive electrode material for LIBs that does not contain any cobalt but still reaches a high energy/power density and cycle life at a competitive cost. In a different research path, core particles of positive electrode materials were coated with a shell of a material with high conductivity, thereby enhancing their energy and power density. The synthesis of core-shell particles can also enable an improved battery cycle life.1,2 Creative chemical approaches were also used to synthesize durable negative electrode materials for sodium-ion batteries (SIBs), making use of a carbothermal reduction reaction to form a phase which can otherwise only be formed in a cumbersome synthesis method.3
The electrolyte component of batteries should have a high conductivity for ions. Conventional electrolytes are highly flammable, limiting the safety of battery operation. To improve the safety, a nonflammable class of liquid electrolyte was developed for SIBs. The combination of experimental and computational studies allowed the optimization of the coordination structure of deep eutectic solvents (DESs) as viable electrolyte alternatives. They can offer a more durable electrochemical performance compared to conventional electrolytes.4 The development of solid electrolytes for battery applications may enable the safe use of metallic anodes, thereby offering the possibility to drastically improve the energy density. Therefore, DESs were incorporated into inorganic and polymeric backbone structures, compatible with high-energy density electrode materials. This new class of solid electrolyte for battery applications was termed eutectogel and consists of inexpensive and mechanically optimized electrolytes for next-generation solid-state batteries.5,6
This work was supported by Horizon 2020 LCBAT-5 COBRA project 875568 and by Research Foundation Flanders in several projects and mandates. Furthermore, the work received the support of the European Union, the European Regional Development Fund ERDF, Flanders Innovation & Entrepreneurship and the Province of Limburg (project 936).
(1) Ulu Okudur, F. et al. Ti surface doping of LiNi0.5Mn1.5O4-δ positive electrodes for lithium ion batteries. RSC Adv. 8, p7287–7300 (2018).
(2) Mylavarapu, S. K. et al. Effect of TiOx Surface Modification on the Electrochemical Performances of Ni-Rich (NMC-622) Cathode Material for Lithium-Ion Batteries. ACS Appl. Energy Mater. 4, p10493–10504 (2021).
(3) De Sloovere, D. et al. Reduced Na2+xTi4O9/C Composite: A Durable Anode for Sodium-Ion Batteries. Chem. Mater. 30, p8521–8527 (2018).
(4) De Sloovere, D. et al. Deep Eutectic Solvents as Nonflammable Electrolytes for Durable Sodium‐Ion Batteries. Adv. Energy Sustain. Res. 3, p2100159 (2022).
(5) Joos, B. et al. Eutectogels: A New Class of Solid Composite Electrolytes for Li/Li-Ion Batteries. Chem. Mater. 30, p655–662 (2018).
(6) Joos, B. et al. Polymeric Backbone Eutectogels as a New Generation of Hybrid Solid-State Electrolytes. Chem. Mater. 32, p3783–3793 (2020).This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 875568.
The complete DESINe group
Technical personnel at UH
All coauthor
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Conventional and less conventional solution-based synthesis of battery materials: Cathodes, anodes and electrolytes
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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