Supporting Information
Copper Phosphate as a Cathode Material for Rechargeable Li
Batteries and Its Electrochemical Reaction Mechanism
Guiming Zhong†, Jingyu Bai†,‡, Paul N. Duchesne§, Matthew J. McDonald†, Qi Li†, Xu Hou†, Joel A.
Tang‖, Yu Wang△, Wengao Zhao¶, Zhengliang Gong¶, Peng Zhang§, Riqiang Fu‖, Yong Yang*,†,¶
†
State Key Lab of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy
Materials and Department of Chemistry and ¶School of Energy Research, Xiamen University, Xiamen, Fujian 361005,
China
‡
Shanghai Institute of Space Power-Sources, No. 2965 Dongchuan Road, Shanghai 200245, China
§
Department of Chemistry, Dalhousie University, Halifax B3H4R2, Canada
‖
National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, United states
△Shanghai
Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Science,
Shanghai 201204, China
1. Electrochemistry
Figure S1. Cycling performance of carbon-coated crystalline and amorphous Cu3(PO4)2 under 400
mA/g.
2. Ex situ XRD
Figure S2. (a) Ex situ XRD patterns of crystalline Cu3(PO4)2/C electrodes. (b) Partial enlargement of
the ex situ patterns to show detail.
3. 7Li MAS NMR
Figure S3. 7Li MAS NMR spectra of crystalline Cu3(PO4)/C materials at different states during the
second discharge process. The spinning frequency was 60 kHz. The inset is an enlarged view of the
data. The intensity of the -13 ppm peak clearly increases when the voltage reaches 2.7, and begins to
decrease when the voltage exceeds 2.5 V.
4. 31P NMR
Figure S4. Mass-normalized spin-echo mapping
31
P NMR spectra of crystalline Cu3(PO4)2/C, collected
during the first discharge process. The spectra were acquired under the spinning frequency of 25 kHz. A
recycle delay of 0.05 s was applied here so that the intensity of the resonance signal of Li3PO4 (0 ppm) cannot
be compared, due to the very long 31P T1 of Li3PO4.
Figure S5. Spin-echo mapping
31
P MAS NMR spectrum of amorphous copper phosphate. A very
broad peak between 4000 and -500 ppm can be observed.
Figure S6. Normalized spin-echo
31
P MAS NMR spectra of crystalline Cu3(PO4)2/C during (a) the
first discharge, (b) the second charge and (c) the second discharge processes. The spectra were
acquired under a spinning frequency of 60 kHz. A recycle delay of 60 s was applied for fully
relaxation of spin. Figure S6 (d) compares
31
P NMR spectra of material charged to 4.0 V acquired
under different recycle delays. The actual integral ratio of the broad peak between 3000 and – 500
ppm and 9 ppm was calculated to be 3.77. Finally, the spin-spin relaxation times of Li3PO4,
amorphous LixCu(II)PO4 and copper phosphate were tested to be 17 ms, 643 us and 356 us,
respectively.
5. X-ray absorption fine-structure
Figure S7. In situ XANES spectra of a Cu3(PO4)2/Li battery during (a) the 1st discharge process, (b) the 2nd
charge process and (c) the 2nd discharge process.
Figure S8. First derivative curves of XANES spectra from a Cu3(PO4)2/Li battery during (a) the 1st discharge
process, (b) the 2nd charge process and (c) the 2nd discharge process.
Figure S9. Fitted (red solid lines) and experimental (circles) Fourier transforms of k3-weighted
EXAFS spectra from a Cu3(PO4)2/Li battery during cycling.
6. TEM
Figure S10. TEM image of carbon coated amorphous material, showing the particle size of the
sample was around 50-200 nm.
Figure S11. TEM image of carbon coated crystalline material, showing the particle size of the
crystalline sample was around 50-200 nm, which was similar to the amorphous sample.