Supplementary Information for “New High Capacity Cathode Materials for Rechargeable
Li-ion Batteries: Vanadate-Borate Glasses”
By Semih Afyona, Frank Krumeicha, Christian Mensinga, Andreas Borgschulteb, Reinhard
Nespera
Table S1: Elemental analysis results and the expected theoretical values for V2O5 – LiBO2 glass; results
of the quantification in weight (g/kg) permil and the relative standard deviations (RSD %).
Sample
Li ‰
RSD %
B‰
RSD %
V‰
RSD %
SA310
27.28
0.25
40.16
0.29
449.89
1.92
Theoretical 27.72
-----
43.18
-----
448.83
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Supplementary Figure S1. Differential thermal analysis (DTA) of the V2O5 – LiBO2 glass.
Supplementary Figure S2. Electron diffraction pattern of V2O5 – LiBO2 glass lacking any reflection
further supporting the glassy nature of the material.
Supplementary Figure S3. Transmission electron microscopy images (TEM) of the V2O5 – LiBO2 glass
indicating nano-crystallites of LixV2O5 phases embedded in the amorphous glass matrix, and lattice
fringes with a spacing of ~ 9.5 Å.
Supplementary Figure S4. XRD powder patterns for the RGO / V2O5 – LiBO2 glass composite produced
at 205-210 o C and the LixV2O5 phases (e.g. Li0.3V2O5 (ICSD 166482) and Li0.667V2O5 (ICSD 25383)).
Very broad diffraction peaks occurring at 2Θ ~ 26.5, 12.2 and 9.3, when the V2O5 –
LiBO2 glass is annealed above the glass transition temperature, might be attributed to trace
amounts of the LixV2O5 phases. These broad reflections were also found to be present in XRD
powder pattern of some samples. Thus, crystalline LixV2O5 phases are obviously formed when
the quenching rate was too low.
Supplementary Figure S5. Transmission electron microscopy (TEM) image of the RGO / V 2O5 – LiBO2
glass composite (obtained at 205 oC) indicating a fine coating of reduced graphite oxide (RGO) and
embedded LixV2O5 nano-crystallites.
In accordance with the XRD powder pattern of the sample annealed above the glass
transition temperature, it can be concluded that these nano-crystallites grew in number and
become more readily noticeable in TEM images.
Supplementary Figure S6. Scanning electron microscopy (SEM) images of the RGO / V 2O5 – LiBO2
glass composite.
Supplementary Figure S7. Transmission electron microscopy (TEM) images of the RGO / V2O5 –
LiBO2 glass composite displaying a) particle agglomerates b) RGO flakes on the rim of particles.
Supplementary Figure S8. Transmission electron microscopy (TEM) image of showing RGO flakes on
the rim of glass particles and the interlayer distance for RGO (zoomed in region from Fig. S7-b)
The interlayer distance found for the flocculated RGO, 4.3Å, provides further evidence for
the partial reduction of graphite oxide and the formation of RGO on glass particle surfaces (Fig.
S8). This finding is in agreement with other investigations, where the partial reduction of
graphite oxide at 200 oC was demonstrated1.
Supplementary Figure S9. Temperature dependence of magnetic susceptibility for the V2O5 – LiBO2
glass at a field strength of 100 Oe showing a simple paramagnetic behavior.
The glass material synthesized at 900 oC has a greenish-brown-yellow color indicating to a
lowering of oxidation state of some of the vanadium centers to V4+. Magnetic measurements
provide further evidence for this assumption. For V2O5 a diamagnetic behavior is expected, yet
the V2O5 – LiBO2 glass material shows a paramagnetic behavior by a logarithmic decrease of χ
(magnetic susceptibility) with increasing temperature (Fig. S9). Oxygen loss during annealing at
high temperatures in an open system could have caused a partial reduction of V5+ species to V4+
species.
Figure S10 XPS overview of the V2O5 – LiBO2 glass (SA467, blue) the RGO / V2O5 – LiBO2 glass
composite (SA478, red) (the energy of the O1s peak was re-calibrated to 530 eV giving a C1s peak
at 284.5 eV).
The XPS-measurements confirm the existence of new phases other than the starting
materials (Fig. S10 & S11). The strong C1s peak in SA478 originates from reduced graphite
oxide (and possibly from C-based adsorbed impurities for the plain V2O5 – LiBO2 glass
(SA467)) and confirms the presence of RGO in the composite glass material. A fit of the C1s
peaks of the sample with reduced graphene oxide reveals the typical contributions of states to be
expected for this compound2,3.
Figure S11 XPS plots of the V2O5 reference sample, V2O5 – LiBO2 glass (SA467) and the RGO / V2O5 –
LiBO2 glass composite (SA478). (the energy of the O1s peak was re-calibrated to 530 eV giving a
C1s peak at 284.5 eV)
Fig. S11 shows the XPS graphs of aV2O5 reference sample, V2O5 – LiBO2 glass (SA467)
and the RGO / V2O5 – LiBO2 glass composite (SA478), all measured under identical conditions.
The resulting chemical shifts of the V2O5 – LiBO2 samples to plain V2O5 of 0.1 eV and 0.2 eV,
respectively, indicate a partial reduction of the V(5)-state towards lower oxidation states that is
in agreement with the findings from bulk characterization, electrochemical properties and
magnetic measurements. ((E(V2O5 2p3/2) = 517.4 eV4) and E(VO2 2p3/2) = 516.4 eV5).
Figure S12 The first five charge/discharge curves of the RGO / V 2O5 – LiBO2 glass composite in a
potential window of 4.5 – 1.5 V, and the first delithiation resulting in a first charge capacity of ~ 20
mAh/g (zoomed in region).
Figure S13 Discharge capacity vs. cycle number for the RGO / V2O5 – LiBO2 glass composite within 4.5
– 1.5 V.
If the cell is charged to 4.5 V first, the glass material can be also delithiated resulting a
first charge capacity of ~ 20-25 mAh/g, however, the cycling stability is found to be rather poor
in the large potential window (Figure S12 & S13). The electrochemical activity in the first
charge indicates the partial reduction of V5+ species to V4+ species.
Figure S14 XRD powder pattern of an electrode of the RGO / V2O5 – LiBO2 glass composite in the
charged and discharged states.
XRD powder pattern of an electrode of the RGO / V2O5 – LiBO2 glass composite in the charged
(to 4.0 V) and discharged states (to 1.5 V) are displayed in Figure S10. The amorphous nature of the
glass electrodes is also largely preserved upon lithium insertion and extraction (Fig. S14);
however, further investigations that are beyond the scope of this current work could be
performed to deeply understand the lithiation/delithiation processes.
References for Supplementary Information
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