Supporting Informations

New liquid carbon dioxide based strategy for high energy/power density

LiFePO4

By Jieun Hwang, Ki Chun Kong, Wonyoung Chang, Eunmi Jo, Kyungwan Nam, Jaehoon Kim

Fig. S1 Schematic of the hFMC apparatus. CV (coating vessel), SV (solution vessel), G (gas communication line), L (liquid communication line).

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Fig. S2 (a) SEM images, (b) N2 adsorption-desorption isotherm, and (c) XRD pattern of the LFP precursor.

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(a)

Table S1. Calculated structural analysis and lattice parameter data obtained by XRD Rietveld refinement.

Crystal system Space group

C-LFP-SOrthorhombic

PnmaAtom x y z Occ Biso

Li 0 0 0 1 1.334Fe 0.283 0.250 0.975 1 0.530P 0.096 0.250 0.420 1 0.422

O1 0.090 0.250 0.747 1 0.663O2 0.454 0.250 0.207 1 0.641O3 0.164 0.054 0.282 1 0.660

Rwp (%) 12.7X2 0.1

Sample a (Å) b (Å) c (Å)H-LFP 10.3243 6.0049 4.6916

C-LFP-S 10.3228 6.0039 4.6903

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Fig. S3 FT-IR spectrum of the LFP precursor.

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Fig. S4 Digital camera images of the H-LFP and the C-LFP-S samples containing 1 g of each sample. The volumes of the samples were measured to estimate the tap density values.

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Fig. S5 (a) Dependence of middle discharge voltages and (b) polarization on the C rate (0.1–30 C). The middle discharge voltage was the discharge voltage at half of the maximum discharge capacity.

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Fig. S6 (a) High-rate capability and (b) voltage profiles of the C-LFP-S electrode at a constant charge rate of 0.1 C and different discharge rates from 0.1 to 100 C.

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Fig. S7 Comparison of high-rate performances.

[1] Z.-X. Chi, W. Zhang, F.-Q. Cheng, J.-T. Chen, A.-M. Cao, L.-J. Wan, Optimizing the carbon coating on

LiFePO4 for improved battery performance, RSC Adv. 4 (2014) 7795-7798.

[2] Q. Zhang, S.-Z. Huang, J. Jin, J. Liu, Y. Li, H.-E. Wang, L.-H. Chen, B.-J. Wang, B.-L. Su, Engineering 3D

bicontinuous hierarchically macro-mesoporous LiFePO4/C nanocomposite for lithium storage with high rate

capability and long cycle stability, Sci. Rep. 6 (2016) 25942.

[3] J. Song, B. Sun, H. Liu, Z. Ma, Z. Chen, G. Shao, G. Wang, Enhancement of the Rate Capability of LiFePO4

by a New Highly Graphitic Carbon-Coating Method, ACS Appl. Mater. Interfaces. 8 (2016) 15225-15231.

[4] B. Wang, T. Liu, A. Liu, G. Liu, L. Wang, T. Gao, D. Wang, X.S. Zhao, A Hierarchical Porous

C@LiFePO4/Carbon Nanotubes Microsphere Composite for High-Rate Lithium-Ion Batteries: Combined

Experimental and Theoretical Study, Adv. Energy Mater. (2016) n/a-n/a.

[5] R. Muruganantham, M. Sivakumar, R. Subadevi, Enhanced rate performance of multiwalled carbon nanotube

encrusted olivine type composite cathode material using polyol technique, J. Power Sources 300 (2015) 496-506.

[6] B. Wang, W. Al Abdulla, D. Wang, X. Zhao, A three-dimensional porous LiFePO 4 cathode material

modified with a nitrogen-doped graphene aerogel for high-power lithium ion batteries, Energy Environmen. Sci. 8

(2015) 869-875

[7] K. Zhang, J.-T. Lee, P. Li, B. Kang, J.H. Kim, G.-R. Yi, J.H. Park, Conformal coating strategy comprising N-

doped carbon and conventional graphene for achieving ultrahigh power and cyclability of LiFePO4, Nano Lett. 15

(2015) 6756-6763.

[8] R. Mo, S.O. Tung, Z. Lei, G. Zhao, K. Sun, N.A. Kotov, Pushing the Limits: 3D Layer-by-Layer-Assembled

Composites for Cathodes with 160 C Discharge Rates, ACS Nano 9 (2015) 5009-5017.

[9] Y. Zhao, L. Peng, B. Liu, G. Yu, Single-crystalline LiFePO4 nanosheets for high-rate Li-ion batteries, Nano

Lett. 14 (2014) 2849-2853.

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Fig. S8 (a) Charge current and capacity of C-LFP-S as a function of time for fast-charging (100 C) performance, and (b) voltage profiles during the fast charge (100 C) and discharge (1 C).

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28.5 29.0 29.5 30.0 30.5 31.0 31.5

data fit

16 20 24 28 32 36 40

s0030 s

120 s

(200)

(210

)

(020

)

(311

)

60 s90 s

180 s

150 s

210 s240 s

(a) (b)

2θ (λ=1.54 Å)

s00

10s

120s130s140s

110s100s90s80s70s60s50s40s30s20s

LiFePO4

FePO4

Fig. S9 (a) In situ time-resolved XRD patterns of a C-LFP-S electrode measured every 10 s under constant voltage charging at 4.2 V. (b) Fitting of the (020) peaks using a Gaussian function to determine the phase fractions of each LFP and FP phase with time.

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Fig. S10 Cyclic voltammograms of (a) H-LFP and (b) C-LFP-S with different scan rates and (c) response of the peak current (Ip) as a function of the square root of scanning rate (v).

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Fig. S11 Electrochemical performance of C-LFP-S at various temperatures; (a) cycling stability at 60 °C and 1 C, (b) rate capability at various charge-discharge rates from 0.1–30 C and at temperatures of -20, 25, and 60 °C, (c) charge-discharge profiles at -20 °C and 60 °C and at various charge-discharge rates, and (d) charge-discharge profiles at temperatures of -20, 25, and 60 °C at 1 C.

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Fig. S12 Corrosion and dissolution test results in the presence or absence of water. (a) Charge-discharge profiles at 0.1 and 1 C, (b) cycling stability at 0.1 C, (c) charge-discharge profiles at various C rates, and (d) rate capabilities at 0.1–30 C.

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Fig. S13 Oxidation test results. (a) Charge-discharge profiles 0.1 and 1 C, (b) cycling stability at 0.1 C, and (c) long-term cyclability at 10 C after five cycle activation at 0.1 C.

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Fig. S14 Electrochemical performances of C-LFP-S with different mass loadings: (a) Charge-discharge profiles at 0.1 and 1 C and (b) charge-discharge profiles at various C rates

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Fig. S15 Electrochemical performance of the C-LFP-S electrode in the absence of carbon black. The electrode consisted of 95 wt% C-LFP-S and 5 wt% PVDF. (a) Cycling stability at 0.1 and 1 C with the corresponding Coulombic efficiency, (b) charge-discharge profiles at 0.1 and 1 C, and (c) rate capabilities at various C rates from 0.1–1 C.

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Fig. S16 Effect of carbon content on the discharge capacities of the C-LFP-S electrodes.

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Fig. S17 Electrochemical performance of the C-LFP-E electrode prepared using PEG250 as the carbon precursor. (a) Cycling stability at 0.1 C and the corresponding Coulombic efficiency, (b) charge-discharge profiles at 0.1 and 1 C, (c) charge-discharge profiles at various C rates from 0.1–30 C, (d) rate capabilities at various C rates from 0.1–30 C, and (e) ultra-long-term cycling performance combined with Coulombic efficiency at 10 C.

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Fig. S18 (a) SEM images, (b) N2 adsorption-desorption isotherm, and (c) XRD pattern of the H2O-LFP sample prepared using water as the coating solvent.

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Fig. S19 Electrochemical performance of the H2O-LFP electrode. (a) Cycling stability at 0.1 C and the corresponding Coulombic efficiency, (b) charge-discharge profiles at 0.1 and 1 C, (c) charge-discharge profiles at various C rates from 0.1–30 C, (d) rate capabilities at various C rates from 0.1–30 C, and (e) ultra-long-term cycling performance combined with Coulombic efficiency at 10 C.

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