1. The low-temperature chemical synthesis of Li 4 Ti 5 O 12 powder for Li-ion battery anodes ChemCYS 2016 – Blankenberge – 17/03/2016 D. De Sloovere, N. Peys, C. De Dobbelaere, M.K. Van Bael, A. Hardy

2. Contents  Why Li 4 Ti 5 O 12 ?  Low-temperature processing  Precursor synthesis  Results  Conclusion 2

3. Why Li 4 Ti 5 O 12 ? 3 Cheng, F., Liang, J., Tao, Z., Chen, J. (2011). Functional Materials for Rechargeable batteries. Adv. Mater., 23, 1695-1715.

4. Why Li 4 Ti 5 O 12 ?  Li-ion batteries offer high energy density  Quick commercialization after introduction of graphite as anode material  Increased safety because of lower volume expansion  Problem at the end of Li insertion Tarascon & Armand (2001). Issues and challenges facing rechargeable lithium batteries. Nature, 414, 359-367. 4

5. Why Li 4 Ti 5 O 12 ?  Advantages of LTO as anode  Extremely flat working potential at 1.55 V  Avoids reduction of electrolyte on anode surface  Circumvents formation SEI  Zero-strain insertion material  Good cycling stability  Theoretical capacity of 175 mAh g -1 5

6. Why Li 4 Ti 5 O 12 ?  Solid-state synthesis + Easy -Irregular and inhomogeneous products -600 – 1000 °C  Sol-gel synthesis + Molecular mixing: homogeneity -Up to 800 °C 6 Han, S. W., Ryu, J. H., Jeong, J. & Yoon, D. H. Solid-state synthesis of Li4Ti5O12 for high power lithium ion battery applications. J. Alloys Compd. 570, 144–149 (2013). Zhang, S. S. The effect of the charging protocol on the cycle life of a Li-ion battery. J. Power Sources 161, 1385–1391 (2006).

7. Contents  Why Li 4 Ti 5 O 12 ?  Low-temperature processing  Precursor synthesis and processing  Results  Conclusion 7

8. Low-temperature processing  Combustion synthesis  Self-sustainable reaction leading to internal temperature build-up  High temperatures in sample vs. low processing temperature  By exothermic reaction between fuel and oxidizer 8 Patil, K.C. et al., Chemistry of nanocrystalline oxide materials, 2008, world scientific, Singapore

9. Low-temperature processing  Advantages  Cheap  Fast  Low processing temperatures  Disadvantages  Complex mechanism  Properties of the product depend on processing parameters  Gas flow rate  Atmosphere 9

10. Low-temperature processing Previous literature Solution combustion synthesis, but not low- temperature Prakash et al. (2010). Solution-Combustion Synthesized Nanocrystalline Li 4 Ti 5 O 12 As High-Rate Performance Li- Ion Battery Anode. Chem. Mater., 22, 2857-2863. LiNO 3 GlycineLTO precTiO(NO 3 ) 2 800 °C 10

11. Contents  Why Li 4 Ti 5 O 12 ?  Low-temperature processing  Precursor synthesis  Results  Conclusion 11

12. Precursor synthesis and processing H2OH2OH2OH2O LiNO 3 in H 2 O Hydrated Ti-oxide Reflux 80 o C Ti in H 2 O NH 3 NH 4 NO 3 pH = 7 Lactic acid 12

13. Contents  Why Li 4 Ti 5 O 12 ?  Low-temperature processing  Precursor synthesis  Results  Conclusion 13

14. TGA-DSC Sudden mass loss process High-temperature degradation TA instruments Q600, 100 ml min -1 dry air, 10 o C min -1 14

15. TGA-DSC: Theoretically optimized NH 4 NO 3 amount TA instruments Q600, 100 ml min -1 dry air, 10 o C min -1 Exothermic and endothermic reactions NH 4 NO 3 degrades endothermically at high heating rates Biamino, S. & Badini, C. (2004). Combustion synthesis of lanthanum chromite starting from water solutions: Investigation of process mechanism by DTA-TGA-MS. J. Eur. Cer. Soc., 24, 3021-3034. 15

16. TGA-DSC: Reduced NH 4 NO 3 amount TA instruments Q600, 100 ml min -1 dry air, 10 o C min -1 NH 4 NO 3 is both necessary for and detrimental to combustion reaction! Larger exothermicity Evolved gases? 16

17. TGA-IR: analysis of evolved gases N2ON2O H2OH2O NO 2 CO 2 NH 3 240 o C NH 3 : Endothermic NH 4 NO 3 degradation CO 2 : Exothermic fuel-oxidizer reaction NO 2 : Partial combustion or endothermic NH 4 NO 3 degradation 90 ml min -1 dry air, 10 o C min -1 N 2 O: Partial combustion or exothermic NH 4 NO 3 degradation Biamino, S. & Badini, C. (2004). Combustion synthesis of lanthanum chromite starting from water solutions: Investigation of process mechanism by DTA-TGA-MS. J. Eur. Cer. Soc., 24, 3021-3034. 17

18. FTIR and XRD Shu, J. (2008). Study of the Interface Between Li 4 Ti 5 O 12 Electrodes and Standard Electrolyte Solution in 0.0-5.0 V. Electrochem. Solid-State Lett., 11, A238-A240. Ti-O stretching: LTO N-O strech: NO 3 - H-O-H bending OH - strech There are still nitrates present after combustion LTO Li 2 TiO 3 * * Si substrate Rutile Anatase Presence of impurity phases 18

19. Electrochemistry  Voltage plateaus of LTO, anatase  Sloped profile due to amorphous material LTO Anatase Discharge capacity of 161 mAh/g 0,2 C 19

20. Contents  Why Li 4 Ti 5 O 12 ?  Low-temperature processing  Precursor synthesis  Results  Conclusion 20

21. Conclusion  NH 4 NO 3 reacts in exothermic reaction with fuel but degrades endothermically  Careful optimization required  LTO can be succesfully synthesized at 300 °C, albeit with impurities  The synthesized sample is electrochemically active 21

22. Acknowledgements  This research was supported by the FWO, the Research Foundation Flanders  XRD: Ken Elen  TG-IR: Wouter Marchal  Other colleagues of the IPC group 22