V. Focused Fundamental Research - EERE - U.S. Department of ...

Zhang, Liu – PNNL
V.B.10 Development of High Energy Cathode (PNNL)
Specific Capacity (mAh/g)
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0
C/10
C/20
C/5
P15AQS
P18AQS
C/2 1C 2C
5C
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Cycle number
Figure V - 56: Comparison of the rate capabilities of novel organic cathodes
with more than one redox center.
Conclusions and Future Directions
Different Li contents were used to synthesize
Li x MnPO 4 (0.5≤ x ≤1.2) materials, which then were
systematically investigated in terms of structure,
morphology, electrochemical behaviors, and magnetic
properties along with an XAS study. We found that pure
LiMnPO 4 forms within the whole range of 0.5≤ x ≤1.2
while Mn 2 P 2 O 7 and/or Li 3 PO 4 impurities coexist in the
non-stoichiometric compositions. For Li 0.5 MnPO 4 and
Li 0.8 MnPO 4 , a gradual increase in the reversible capacity
with cycling was observed, which may be related to
interactions between Mn 2 P 2 O 7 and LiMnPO 4 . Among all
the samples, Li 1.1 MnPO 4 exhibits the most stable cycling
probably because of the Li 3 PO 4 coating on the surface of
LiMnPO 4 nano-particles that functions as a solid
electrolyte to facilitate ion transport. This observation
provides important clues on the activation and stabilization
of phosphate-based cathode materials.
We investigated the phase transformations and
thermal stabilities of the electrochemically charged MnPO 4
cathode. The MnPO 4 reduction to Mn 2 P 2 O 7 with oxygen
evolution was observed at 490°C, which coincides with the
phase changes in MnPO 4 H 2 O. The charged MnPO 4
undergoes amorphization changes at temperatures 180°C,
and there is no oxygen released between 180 and 490°C.
Although the kinetics of the LiMnPO 4 cathode needs to be
improved, LiMnPO 4 can be a safe alternative to other
high-voltage cathodes if its power can be further improved
A cost-effective approach has been developed for
synthesizing the high-voltage spinel LiNi 0.5 Mn 1.5 O 4 . After
Cr substitution, the cycling performance was greatly
improved because of the increased concentration of Mn 3+
ions. The influence of Mn 3+ concentration on performance
will be investigated further next year. The addition of a
low concentration of LiBOB (0.25%) improves the
Coulombic efficiency especially for the first cycle.
Cathode pans and separator membranes are now being
evaluated with high-voltage cathode materials.
We also prepared a new renewable organic cathode
based on quinonyl group, P18AQ. We found that the
substitution position that results in less steric stress on the
backbone is critical for designing a high-performance
organic cathode. To improve the energy density and
cycling stability of these high-capacity cathodes, novel
organic cathode with other functional groups on the ring
will be further investigated.
FY 2011 Publications/Presentations
1. D. Choi, J. Xiao, Y. J. Choi, J. S. Hardy, V.
Murugesan, J. Liu, W. Wang, W. Xu, J.-G. Zhang, Z.
Yang and G. L. Graff. “Thermal Stability of
Electrochemically Charged/Discharged LiMnPO 4
Nanoplate Cathode for Li-ion Battery”, Energy
Environ.Sci. 4, 4560(2011). (Back cover article)
2. J. Xiao, N. A. Chernova, S. Upreti, X. Chen, Z. Li, Z.
Deng, D. Choi, W. Xu, Z. Nie, G. L. Graff, J. Liu, M.
S. Whittingham and J.-G. Zhang, “Electrochemical
Performances of LiMnPO 4 Synthesized from Non-
Stoichiometric Li/Mn Ratio”, Phys. Chem. Chem.
Phys., 13, 18099(2011).
3. A. Pan, D. Choi, J.-G. Zhang, S. Liang, G. Cao, Z.
Nie, B. W. Arey, and J. Liu, “High-rate cathodes
based on Li 3 V 2 (PO 4 ) 3 nanobelts prepared via
surfactant-assisted fabrication”, J. Power Sources,
196, 3646 (2011).
4. A. Pan, J. Liu, J.-G. Zhang, G. Cao, W. Xu, Z. Nie, X.
Jie, D. Choi, B. W. Arey, C. Wang, and S. Liang,
“Template free synthesis of LiV 3 O 8 nanorods as a
cathode material for high-rate secondary lithium
batteries”, J. Mater. Chem., 21, 1153 (2011).
5. A. Pan, J.-G. Zhang, G. Cao, S. Liang, C. Wang, Z.
Nie, B. W. Arey, W. Xu, D. Liu, J. Xiao, G. Li, and J.
Liu, “Nanosheet-structured LiV 3 O 8 with high capacity
and excellent stability for high energy lithium
batteries”, J. Mater. Chem., 21, 10077 (2011).
6. D. Wang, J. Xiao, W. Xu, Z. Ni, C. Wang, G.L. Graff,
J.-G. Zhang. “Preparation and Electrochemical
Investigation of Li 2 CoPO 4 F Cathode Material for
Lithium-Ion Batteries”, Journal of Power Sources
196, 2241–2245 (2011).
7. J. Yu, K. M. Rosso, J.-G. Zhang and J. Liu, Ab initio
study of lithium transition metal fluorophosphate
cathodes for rechargeable batteries, J. Mater. Chem.,
21, 12054(2011).
8. A. Pan, J. Liu, J.-G. Zhang, W. Xu, G. Cao, Z. Nie
“Nano-Structured Li 3 V 2 (PO 4 ) 3 /Carbon Composite for
High-Rate Lithium-Ion Batteries”, Electrochem.
Commun., 12, 1674-1677 (2010).
FY 2011 Annual Progress Report 517 Energy Storage R&D