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Cite this: Chem. Commun., 2014, 50, 7011 Received 13th February 2014, Accepted 15th April 2014
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TPPi as a flame retardant for rechargeable lithium batteries with sulfur composite cathodes† Hao Jia,a Jiulin Wang,*a Fengjiao Lin,a Charles W. Monroe,b Jun Yanga and Yanna NuLia
DOI: 10.1039/c4cc01151a www.rsc.org/chemcomm
Triphenyl phosphite (TPPi) is adopted as a flame retardant to improve the safety of rechargeable lithium batteries with sulfur composite cathodes. The thermal stability of the electrolyte is greatly enhanced after the addition of TPPi, which also has a positive impact on the electrochemical performance of the Li–S batteries. TPPi facilitates the formation of SEI, resulting in a smaller interfacial impedance and a better rate performance. The addition of about 5 wt% TPPi greatly reduces the polarization voltage, stabilizing the cycle performance of the battery. This indicates that an optimized addition of TPPi is a favorable additive in conventional liquid electrolytes for rechargeable Li–S batteries with high performances and good safety.
Lithium ion batteries demonstrate promising power sources for electrical vehicles and energy storage devices for smart grid, solar and wind stations. Because of the active electrode materials and the flammable organic electrolyte, the safety of lithium ion batteries is a very important issue for their practical applications. Recently secondary lithium–sulfur (Li–S) batteries, one of most promising types of battery, have been investigated intensively due to their high theoretical capacity, low cost and non-toxicity.1 However, Li–S batteries suffer more serious safety issues compared to lithium ion batteries. Three main factors influencing the safety performances of Li–S batteries are as follows: the formation of lithium dendrites in batteries using the inevitable lithium anode, which are the causes of battery dysfunction and heat emission;2,3 liquid electrolytes used in batteries are highly volatile and inflammable, and at high temperatures the electrolytes tend to react with both the anode and cathode, generating even more heat in the battery and causing thermo runaways;4 and insulator sulfur with conductive agents (usually acetylene black) are combustible, bringing hazards to the system.5 a
School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China. E-mail: [email protected]; Fax: +86-21-54747667; Tel: +86-21-54745887 b Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA † Electronic supplementary information (ESI) available. See DOI: 10.1039/ c4cc01151a
This journal is © The Royal Society of Chemistry 2014
In our previous work, the safety of sulfur cathodes has been significantly improved by combining elemental sulfur with nonflammable polyacrylonitrile (PAN).6 However, traditional electrolytes with carbonates or ethers are highly flammable and might cause safety hazards when the cells are misused. In traditional lithium ion batteries, the thermal stabilities and electrochemical performances of conventional electrolytes have been enhanced by flame retardants. The most explored flame retardants used in batteries can be categorized into the following groups: alkyl phosphates,7–9 fluorinated alkyl phosphates,10 ionic liquids,11 and phosphazenes.12 Most of these flame retardants were found to greatly enhance the safety of lithium ion batteries. However, flame retardants also have a negative impact to some extent on lithium ion batteries’ electrochemical performances, for example they can destroy the cycling stability or deteriorate the power rate properties. Ideal flame retardants which completely resolve the safety issues of batteries and at the same time have no negative impact on the electrochemical performances are still under investigations. Triphenyl phosphite (TPPi) is a chemical compound with the formula P(OC6H5)3, as shown in Fig. S1 (ESI†). This colorless liquid with a viscosity of 17.7 mm2 s 1 at 20 1C is the ester of phosphorous acid and phenol, and generates phosphates and retards combustion when heated. In this work, TPPi was adopted as a flame retardant additive into the traditional electrolyte 1 M LiPF6/EC + DMC (1 : 1, v/v) which not only enhanced the carbonates’ thermal properties but also improved the electrochemical performances of rechargeable Li–S batteries. The thermal properties of the blank electrolyte and the functional electrolytes with different doses of TPPi were characterized via DSC as shown in Fig. 1(a). For the blank electrolyte, the thermolysis temperature was about 266 1C, which shifted to about 275 1C after 10 wt% TPPi addition. The thermal stability of the electrolytes coupled with the cathode as a whole was also investigated as shown in Fig. 1(b). The thermolysis temperature was pushed 20 1C higher, demonstrating an enhanced thermal stability. DSC studies carried out in a sealed pan without pinholes showed similar results (Fig. S2, ESI†). Since such a small dose of TPPi is incapable of bringing significant changes
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Fig. 1 (a) DSC profiles of the electrolytes, in which the black line indicates the blank electrolyte 1 M LiPF6/EC + DMC (1 : 1, v/v) and the red line indicates the blank electrolyte with 10 wt% TPPi additive; (b) DSC profiles of the electrolytes with fully charged sulfur cathodes, in which the black line indicates the blank electrolyte and the red line indicates the blank electrolyte with 10 wt% TPPi additive. The electrolytes were sealed in an aluminum pan in the glove box. A pinhole was punched on the pan prior to the DSC testing.
to the heat capacity of the system, the change in the heat flow indicates that the pyrolysis reaction is efficiently suppressed by TPPi. When heated above the pyrolysis temperature, TPPi generates free radicals (such as PO ), which are able to actively capture other free radicals emitted by the burning electrolyte (usually H and OH) to retard the reaction.12 Additionally, metaphosphoric acid and polyvinylidene acid, along with other phosphorous compounds produced in this process form an oxygen-proof layer that helps distinguish the flame on the surface of the combustible materials.13 The influence of TPPi on the conductivity is shown in Fig. 2(a). The conductivity of the electrolytes decreased as the concentration of TPPi increased due to its high viscosity. With three equivalent phenyl groups in the molecule, the polarity of TPPi is weak. This hinders the dissociation of LiPF6, resulting in a lower conductivity. However, electrolytes with TPPi demonstrated lower interfacial impedances. After being fully charged in the 2nd cycle at 0.1 C, the electrochemical impedances of these batteries were tested by AC impedance. As is shown in Fig. 2(b), the impedances of the electrolytes diminished after adding TPPi. This is possibly attributed to the electron-rich phenyl structure of TPPi, which could facilitate the formation of SEI,14 enabling a faster lithium ion transportation.15 The mechanism concerning the formation of SEI is still not thoroughly elucidated as it varies in different systems. It is commonly accepted that SEI formation in all these systems involves a reductive decomposition of the electrolyte components (solvents, salts, additives).14 TPPi consists of three reductive phenoxy groups, which probably promote the formation of SEI and induce a lower interfacial impedance. The addition of TPPi does not affect the electrochemical windows
7012 | Chem. Commun., 2014, 50, 7011--7013
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Fig. 2 (a) Effects of TPPi addition on SET and ionic conductivity; (b) impedance spectra (at the fully charged state) of the cells with electrolytes containing 0, 5 and 10 wt% TPPi.
of the electrolyte, and the benefits to the plating/stripping of the Li metal on the anode. Fig. 3(a) presents a comparison of batteries using electrolytes with different TPPi contents. It should be noted that the sulfur content in the composite materials was ca. 45 wt%, as determined by elemental analysis. The specific capacities in this paper were calculated based on the whole weight of the composite materials including the pyrolyzed PAN matrix and the pure sulfur, and this is noted in the units of (mA h g 1)(composite) and (mA h g 1)(sulfur) in the figures, respectively. After 45 cycles, the capacity retention rates of these batteries were 90.4% for the normal electrolyte, 94.5% for the functional electrolyte containing 5 wt% TPPi and 94.2% for the functional electrolyte containing 10 wt% TPPi. The batteries using electrolytes with 20 wt% TPPi demonstrated relatively lower capacities. When the concentration of TPPi reached 20 wt%, the high viscosity of TPPi decreased the ionic conductivity of the electrolyte, and even influenced the intimate contact between the electrolyte and the cathode material. As a result, the Li+ transfer at the interface deteriorated. Fig. 3(b) shows the polarization voltage profiles after the TPPi additions. The battery using an electrolyte doped with 5 wt% TPPi manifested the smallest polarization voltage. It can be inferred that when the concentration of TPPi is constrained to around 5 wt%, the contradictory effects brought by TPPi in the electrolyte conductivity and interface impedance reach an optimal level. The rate performance of the S–PAN cathode also benefits from the presence of TPPi. The batteries with different TPPi contents were recharged and discharged at different rates varying from 0.2 C to 5 C. The battery with blank electrolyte was more sensitive to rate variations. As shown in Fig. 4(a), in low rate zone (o1 C), the differences among three electrolytes are negligible. Significant discrepancies emerged in the high
This journal is © The Royal Society of Chemistry 2014
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Fig. 3 (a) Cycle performances at 0.5 C, except for the cell with 20 wt% TPPi which was initially activated at 0.06 C for 3 cycles, then 0.5 C for the following cycles; and (b) charge–discharge profiles for the 40th cycle of the cells with electrolytes containing 0, 5 and 10 wt% TPPi at 0.1 C.
rate zone, where the capacity of the battery with a blank electrolyte faded to 160 mA h g 1 (5 C), while the 5 wt% TPPi doped battery maintained a capacity of 400 mA h g 1 (5 C). The 5% TPPi doped battery illustrates the best rate performance, a fact which coincides with the recharge–discharge pattern which shows that the 5 wt% TPPi battery reduces the polarization
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voltage most significantly. Similar to the battery with the blank electrolyte, the battery with 10 wt% TPPi additive also suffers a rapid capacity loss at a high rate. As the current increases, the rate performance of the batteries is primarily determined by the transportation of the lithium ions in the electrode, interface, and electrolyte. The electrolyte with 10 wt% TPPi possesses a high viscosity, which hinders fast lithium ion transportation in the electrolyte and therefore deteriorates the rate performance. All batteries with TPPi addition recovered well from the high rate test, indicating that the reversibility of the electrodes is well preserved by TPPi. The effect of 5 wt% TPPi addition on the discharge voltage at different rates is shown in Fig. 4(b). Under the same rate, the PAN–S cathode demonstrates a higher discharge voltage and a larger capacity when doping with TPPi. The initial voltage of the regular battery decreased from 2.1 V (0.1 C) to 1.7 V (2 C) (Fig. S2, ESI†), whereas the voltage values of the batteries with additives were sustained at 1.85 V, as shown in Fig. 4(b), since they benefited from the formation of SEI with less impedance. Since the interface is enhanced, lithium is able to more readily enter the internal structure of the electrodes, resulting in a low polarization voltage and insensitivity to rate variation. In summary, safety is a very important issue for rechargeable batteries and in this work TPPi was successfully adopted as a flame retardant in rechargeable lithium batteries with a PAN–S composite cathode. Despite its disadvantages such as high viscosity and weak polarity, TPPi is applicable as an additive in the traditional electrolyte to enhance its thermal stability and improve the electrochemical performance of Li–S batteries. The optimal content of TPPi is around 5 wt%, with which the batteries show the small polarization voltage, a good rate performance and stable cycle performances. This work is financially supported by the National Natural Science Foundation of China (51272156, 21333007) and the SJTU-UM joint research project.
Notes and references
Fig. 4 (a) Rate performances of the cells with and without the TPPi additive; (b) discharge profiles for the PAN–S composite electrodes at different rates with the blank electrolyte and the electrolyte with 5 wt% TPPi.
This journal is © The Royal Society of Chemistry 2014
1 P. G. Bruce, S. A. Freunberger, L. J. Hardwick and J.-M. Tarascon, Nat. Mater., 2011, 11, 19. 2 O. Crowther and A. C. West, J. Electrochem. Soc., 2008, 155, A806. 3 C. Monroe and J. Newman, J. Electrochem. Soc., 2003, 150, A1377. 4 T. Ohsaki, T. Kishi, T. Kuboki, N. Takami, N. Shimura, Y. Sato, M. Sekino and A. Satoh, J. Power Sources, 2005, 146, 97. 5 J. Wang, J. Chen, K. Konstantinov, L. Zhao, S. Ng, G. Wang, Z. Guo and H. Liu, Electrochim. Acta, 2006, 51, 4634. 6 F. J. Lin, J. L. Wang, H. Jia, C. W. Monroe, J. Yang and Y. N. NuLi, J. Power Sources, 2013, 223, 18. 7 X. Xia, P. Ping and J. R. Dahn, J. Electrochem. Soc., 2012, 159, A1834. 8 R. Shibutani and H. Tsutsumi, J. Power Sources, 2012, 202, 369. 9 Y. Shigematsu, M. Ue and J. Yamaki, J. Electrochem. Soc., 2009, 156, A176. 10 G. Nagasubramanian and C. J. Orendorff, J. Power Sources, 2011, 196, 8604. 11 J. Choi, Y.-K. Sun, E.-G. Shim, B. Scrosati and D.-W. Kim, Electrochim. Acta, 2011, 56, 10179. 12 T. Tsujikawa, K. Yabuta, T. Matsushita, T. Matsushima, K. Hayashi and M. Arakawa, J. Power Sources, 2009, 189, 429. 13 E. P. Roth and C. J. Orendorff, Electrochem. Soc. Interface, 2012, 45, summer. 14 M. Inaba, Y. Kawatate, A. Funabiki, S.-K. Jeong, T. Abe and Z. Ogumi, Electrochim. Acta, 1999, 45, 99. 15 M. Winter and R. J. Brodd, Chem. Rev., 2004, 104, 4245.
Chem. Commun., 2014, 50, 7011--7013 | 7013
Published on 15 April 2014. Downloaded by Michigan Technological University on 21/10/2014 22:21:32.
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Cite this: Chem. Commun., 2014, 50, 7011 Received 13th February 2014, Accepted 15th April 2014
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TPPi as a flame retardant for rechargeable lithium batteries with sulfur composite cathodes† Hao Jia,a Jiulin Wang,*a Fengjiao Lin,a Charles W. Monroe,b Jun Yanga and Yanna NuLia
DOI: 10.1039/c4cc01151a www.rsc.org/chemcomm
Triphenyl phosphite (TPPi) is adopted as a flame retardant to improve the safety of rechargeable lithium batteries with sulfur composite cathodes. The thermal stability of the electrolyte is greatly enhanced after the addition of TPPi, which also has a positive impact on the electrochemical performance of the Li–S batteries. TPPi facilitates the formation of SEI, resulting in a smaller interfacial impedance and a better rate performance. The addition of about 5 wt% TPPi greatly reduces the polarization voltage, stabilizing the cycle performance of the battery. This indicates that an optimized addition of TPPi is a favorable additive in conventional liquid electrolytes for rechargeable Li–S batteries with high performances and good safety.
Lithium ion batteries demonstrate promising power sources for electrical vehicles and energy storage devices for smart grid, solar and wind stations. Because of the active electrode materials and the flammable organic electrolyte, the safety of lithium ion batteries is a very important issue for their practical applications. Recently secondary lithium–sulfur (Li–S) batteries, one of most promising types of battery, have been investigated intensively due to their high theoretical capacity, low cost and non-toxicity.1 However, Li–S batteries suffer more serious safety issues compared to lithium ion batteries. Three main factors influencing the safety performances of Li–S batteries are as follows: the formation of lithium dendrites in batteries using the inevitable lithium anode, which are the causes of battery dysfunction and heat emission;2,3 liquid electrolytes used in batteries are highly volatile and inflammable, and at high temperatures the electrolytes tend to react with both the anode and cathode, generating even more heat in the battery and causing thermo runaways;4 and insulator sulfur with conductive agents (usually acetylene black) are combustible, bringing hazards to the system.5 a
School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China. E-mail: [email protected]; Fax: +86-21-54747667; Tel: +86-21-54745887 b Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA † Electronic supplementary information (ESI) available. See DOI: 10.1039/ c4cc01151a
This journal is © The Royal Society of Chemistry 2014
In our previous work, the safety of sulfur cathodes has been significantly improved by combining elemental sulfur with nonflammable polyacrylonitrile (PAN).6 However, traditional electrolytes with carbonates or ethers are highly flammable and might cause safety hazards when the cells are misused. In traditional lithium ion batteries, the thermal stabilities and electrochemical performances of conventional electrolytes have been enhanced by flame retardants. The most explored flame retardants used in batteries can be categorized into the following groups: alkyl phosphates,7–9 fluorinated alkyl phosphates,10 ionic liquids,11 and phosphazenes.12 Most of these flame retardants were found to greatly enhance the safety of lithium ion batteries. However, flame retardants also have a negative impact to some extent on lithium ion batteries’ electrochemical performances, for example they can destroy the cycling stability or deteriorate the power rate properties. Ideal flame retardants which completely resolve the safety issues of batteries and at the same time have no negative impact on the electrochemical performances are still under investigations. Triphenyl phosphite (TPPi) is a chemical compound with the formula P(OC6H5)3, as shown in Fig. S1 (ESI†). This colorless liquid with a viscosity of 17.7 mm2 s 1 at 20 1C is the ester of phosphorous acid and phenol, and generates phosphates and retards combustion when heated. In this work, TPPi was adopted as a flame retardant additive into the traditional electrolyte 1 M LiPF6/EC + DMC (1 : 1, v/v) which not only enhanced the carbonates’ thermal properties but also improved the electrochemical performances of rechargeable Li–S batteries. The thermal properties of the blank electrolyte and the functional electrolytes with different doses of TPPi were characterized via DSC as shown in Fig. 1(a). For the blank electrolyte, the thermolysis temperature was about 266 1C, which shifted to about 275 1C after 10 wt% TPPi addition. The thermal stability of the electrolytes coupled with the cathode as a whole was also investigated as shown in Fig. 1(b). The thermolysis temperature was pushed 20 1C higher, demonstrating an enhanced thermal stability. DSC studies carried out in a sealed pan without pinholes showed similar results (Fig. S2, ESI†). Since such a small dose of TPPi is incapable of bringing significant changes
Chem. Commun., 2014, 50, 7011--7013 | 7011
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Fig. 1 (a) DSC profiles of the electrolytes, in which the black line indicates the blank electrolyte 1 M LiPF6/EC + DMC (1 : 1, v/v) and the red line indicates the blank electrolyte with 10 wt% TPPi additive; (b) DSC profiles of the electrolytes with fully charged sulfur cathodes, in which the black line indicates the blank electrolyte and the red line indicates the blank electrolyte with 10 wt% TPPi additive. The electrolytes were sealed in an aluminum pan in the glove box. A pinhole was punched on the pan prior to the DSC testing.
to the heat capacity of the system, the change in the heat flow indicates that the pyrolysis reaction is efficiently suppressed by TPPi. When heated above the pyrolysis temperature, TPPi generates free radicals (such as PO ), which are able to actively capture other free radicals emitted by the burning electrolyte (usually H and OH) to retard the reaction.12 Additionally, metaphosphoric acid and polyvinylidene acid, along with other phosphorous compounds produced in this process form an oxygen-proof layer that helps distinguish the flame on the surface of the combustible materials.13 The influence of TPPi on the conductivity is shown in Fig. 2(a). The conductivity of the electrolytes decreased as the concentration of TPPi increased due to its high viscosity. With three equivalent phenyl groups in the molecule, the polarity of TPPi is weak. This hinders the dissociation of LiPF6, resulting in a lower conductivity. However, electrolytes with TPPi demonstrated lower interfacial impedances. After being fully charged in the 2nd cycle at 0.1 C, the electrochemical impedances of these batteries were tested by AC impedance. As is shown in Fig. 2(b), the impedances of the electrolytes diminished after adding TPPi. This is possibly attributed to the electron-rich phenyl structure of TPPi, which could facilitate the formation of SEI,14 enabling a faster lithium ion transportation.15 The mechanism concerning the formation of SEI is still not thoroughly elucidated as it varies in different systems. It is commonly accepted that SEI formation in all these systems involves a reductive decomposition of the electrolyte components (solvents, salts, additives).14 TPPi consists of three reductive phenoxy groups, which probably promote the formation of SEI and induce a lower interfacial impedance. The addition of TPPi does not affect the electrochemical windows
7012 | Chem. Commun., 2014, 50, 7011--7013
ChemComm
Fig. 2 (a) Effects of TPPi addition on SET and ionic conductivity; (b) impedance spectra (at the fully charged state) of the cells with electrolytes containing 0, 5 and 10 wt% TPPi.
of the electrolyte, and the benefits to the plating/stripping of the Li metal on the anode. Fig. 3(a) presents a comparison of batteries using electrolytes with different TPPi contents. It should be noted that the sulfur content in the composite materials was ca. 45 wt%, as determined by elemental analysis. The specific capacities in this paper were calculated based on the whole weight of the composite materials including the pyrolyzed PAN matrix and the pure sulfur, and this is noted in the units of (mA h g 1)(composite) and (mA h g 1)(sulfur) in the figures, respectively. After 45 cycles, the capacity retention rates of these batteries were 90.4% for the normal electrolyte, 94.5% for the functional electrolyte containing 5 wt% TPPi and 94.2% for the functional electrolyte containing 10 wt% TPPi. The batteries using electrolytes with 20 wt% TPPi demonstrated relatively lower capacities. When the concentration of TPPi reached 20 wt%, the high viscosity of TPPi decreased the ionic conductivity of the electrolyte, and even influenced the intimate contact between the electrolyte and the cathode material. As a result, the Li+ transfer at the interface deteriorated. Fig. 3(b) shows the polarization voltage profiles after the TPPi additions. The battery using an electrolyte doped with 5 wt% TPPi manifested the smallest polarization voltage. It can be inferred that when the concentration of TPPi is constrained to around 5 wt%, the contradictory effects brought by TPPi in the electrolyte conductivity and interface impedance reach an optimal level. The rate performance of the S–PAN cathode also benefits from the presence of TPPi. The batteries with different TPPi contents were recharged and discharged at different rates varying from 0.2 C to 5 C. The battery with blank electrolyte was more sensitive to rate variations. As shown in Fig. 4(a), in low rate zone (o1 C), the differences among three electrolytes are negligible. Significant discrepancies emerged in the high
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Fig. 3 (a) Cycle performances at 0.5 C, except for the cell with 20 wt% TPPi which was initially activated at 0.06 C for 3 cycles, then 0.5 C for the following cycles; and (b) charge–discharge profiles for the 40th cycle of the cells with electrolytes containing 0, 5 and 10 wt% TPPi at 0.1 C.
rate zone, where the capacity of the battery with a blank electrolyte faded to 160 mA h g 1 (5 C), while the 5 wt% TPPi doped battery maintained a capacity of 400 mA h g 1 (5 C). The 5% TPPi doped battery illustrates the best rate performance, a fact which coincides with the recharge–discharge pattern which shows that the 5 wt% TPPi battery reduces the polarization
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voltage most significantly. Similar to the battery with the blank electrolyte, the battery with 10 wt% TPPi additive also suffers a rapid capacity loss at a high rate. As the current increases, the rate performance of the batteries is primarily determined by the transportation of the lithium ions in the electrode, interface, and electrolyte. The electrolyte with 10 wt% TPPi possesses a high viscosity, which hinders fast lithium ion transportation in the electrolyte and therefore deteriorates the rate performance. All batteries with TPPi addition recovered well from the high rate test, indicating that the reversibility of the electrodes is well preserved by TPPi. The effect of 5 wt% TPPi addition on the discharge voltage at different rates is shown in Fig. 4(b). Under the same rate, the PAN–S cathode demonstrates a higher discharge voltage and a larger capacity when doping with TPPi. The initial voltage of the regular battery decreased from 2.1 V (0.1 C) to 1.7 V (2 C) (Fig. S2, ESI†), whereas the voltage values of the batteries with additives were sustained at 1.85 V, as shown in Fig. 4(b), since they benefited from the formation of SEI with less impedance. Since the interface is enhanced, lithium is able to more readily enter the internal structure of the electrodes, resulting in a low polarization voltage and insensitivity to rate variation. In summary, safety is a very important issue for rechargeable batteries and in this work TPPi was successfully adopted as a flame retardant in rechargeable lithium batteries with a PAN–S composite cathode. Despite its disadvantages such as high viscosity and weak polarity, TPPi is applicable as an additive in the traditional electrolyte to enhance its thermal stability and improve the electrochemical performance of Li–S batteries. The optimal content of TPPi is around 5 wt%, with which the batteries show the small polarization voltage, a good rate performance and stable cycle performances. This work is financially supported by the National Natural Science Foundation of China (51272156, 21333007) and the SJTU-UM joint research project.
Notes and references
Fig. 4 (a) Rate performances of the cells with and without the TPPi additive; (b) discharge profiles for the PAN–S composite electrodes at different rates with the blank electrolyte and the electrolyte with 5 wt% TPPi.
This journal is © The Royal Society of Chemistry 2014
1 P. G. Bruce, S. A. Freunberger, L. J. Hardwick and J.-M. Tarascon, Nat. Mater., 2011, 11, 19. 2 O. Crowther and A. C. West, J. Electrochem. Soc., 2008, 155, A806. 3 C. Monroe and J. Newman, J. Electrochem. Soc., 2003, 150, A1377. 4 T. Ohsaki, T. Kishi, T. Kuboki, N. Takami, N. Shimura, Y. Sato, M. Sekino and A. Satoh, J. Power Sources, 2005, 146, 97. 5 J. Wang, J. Chen, K. Konstantinov, L. Zhao, S. Ng, G. Wang, Z. Guo and H. Liu, Electrochim. Acta, 2006, 51, 4634. 6 F. J. Lin, J. L. Wang, H. Jia, C. W. Monroe, J. Yang and Y. N. NuLi, J. Power Sources, 2013, 223, 18. 7 X. Xia, P. Ping and J. R. Dahn, J. Electrochem. Soc., 2012, 159, A1834. 8 R. Shibutani and H. Tsutsumi, J. Power Sources, 2012, 202, 369. 9 Y. Shigematsu, M. Ue and J. Yamaki, J. Electrochem. Soc., 2009, 156, A176. 10 G. Nagasubramanian and C. J. Orendorff, J. Power Sources, 2011, 196, 8604. 11 J. Choi, Y.-K. Sun, E.-G. Shim, B. Scrosati and D.-W. Kim, Electrochim. Acta, 2011, 56, 10179. 12 T. Tsujikawa, K. Yabuta, T. Matsushita, T. Matsushima, K. Hayashi and M. Arakawa, J. Power Sources, 2009, 189, 429. 13 E. P. Roth and C. J. Orendorff, Electrochem. Soc. Interface, 2012, 45, summer. 14 M. Inaba, Y. Kawatate, A. Funabiki, S.-K. Jeong, T. Abe and Z. Ogumi, Electrochim. Acta, 1999, 45, 99. 15 M. Winter and R. J. Brodd, Chem. Rev., 2004, 104, 4245.
Chem. Commun., 2014, 50, 7011--7013 | 7013
