A tidy laboratory means a lazy chemist Jöns Jacob Berzelius (Swedish chemist, )

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1 A tidy laboratory means a lazy chemist Jöns Jacob Berzelius (Swedish chemist, )

2 6. SEC-Jahrestreffen, Mai 2016 in Münster (GER) Vernachlässigt, vergessen oder unwichtig? - Inaktivmaterialien für Lithium-Ionen Batterien B. Streipert, E. Krämer, L. Terborg, V. Kraft, J. Menzel, D. Gallus, I. Cekic-Laskovic, S. Nowak, T. Placke und M. Winter MEET Battery Research Center, Institute of Physical Chemistry, Univ. of Muenster, GER, martin.winter@uni-muenster.de & Helmholtz Institute Muenster; Ionics in Energy Storage, IEK-12 of Forschungszentrum Juelich m.winter@fz-juelich.de

3 Acknowledgements (General) Federal Ministry of Economics and Technology (BMWi) Federal Ministry for the Environment, Nature Conservation & Nuclear Safety (BMU) Federal Ministry of Education and Research (BMBF) North-Rhine-Westphalia (NRW) University of Muenster (WWU) Helmholtz Association (HGF) and Forschungszentrum Jülich

4 Acknowledgements (Specific) German Ministry of Education and Research (BMBF) within the project Elektrolytlabor 4 E Cabot Corporation

5 Acknowledgements None of us is as smart as all of us

6 Lithium Ion Battery (LIB): Active and Inactive Materials Have Functions Active Anode and Cathode Materials: Determine capacity and voltage energy Inactive Materials: Additional mass + volume decrease energy Electrolyte: inside ion conduction, interfaces Separator: safety, electrode separation Inactive cell and electrode components: Can/Pouch, Headers, Terminals, Vents, etc. Current collector: electron conduction, connection to the outside Conductive additive: porosity, inside electron current distribution Binder: The glue, that holds everything together Processing solvents (often disregarded)

7 From the Beginning: Inactive Materials Determine Performance: Volta-Pile (1791); Zn/Cu; NaCl aq as Electrolyte Volta-Cell (open to O 2 from air) O 2 reacts with Cu forming CuO at the surface. (Volta-Pile is a kind of Zinc/Air Battery) Salt water 1.1 V: (Anode) Zn Zn e - (Cathode) CuO + 2H + + 2e - Cu + H 2 O Cu reacts with O 2, regen. CuO Closed 0.76V (Anode) Zn Zn e - (Cathode) 2 H + + 2e - H 2 on inert Cu Failure mechanism of the Volta-Pile: Drying out, because of H 2 O evaporation Technology progress: Pile Electrolyte reservoirs or crown of cups

8 Lithium Ion Battery Name given by Mr. Keizaburo TOZAWA, Chief Executive Officer, Sony Energytec, Inc. Based on intercalation research in Europe/US. # Realized by Sony, 1990/1991*: I. Use coating technique: audio/video tapes II. Assemble cell in the discharge state and then do formation III. Right electrolyte IV. LiPF 6 as HF-Generator for Al passivation # V. Microporous PE-separator # Impresses by an infinite variety of materials, designs and applications The established Allrounder # Personal discussions with pioneering scientists *T. Nagaura, Progress in Batteries & Solar Cells, 10, 218 (1991)

9 Active and Inactive Materials in LIB Parallel electron & lithium ion movement Active Materials: Host electrodes (i) Graphite at the negative electrode (ii) LiMO 2 or LiMPO 4 (M = Co, Ni, Mn, Fe, etc.) at the positive electrode = Li + -packaging materials Per Li + : Two electrode sites are needed (= double electrode packaging per charge) * Inactive Materials necessary for cell reaction: electrolyte, separator and electrode formulation: additives, binders, collectors *Winter, M.; Besenhard, J. O. Chemie in unserer Zeit 1999, 33, Inactive materials: Packaging, vents, etc.

10 18650: The Standard Cylindrical Cell: Notebook Computers and Power Tools Depending on chemistry and technology: 30 to >50 grams Case typically: stainless steel, Al + 65 mm 617 mm 18.0 mm Anode 60 mm Cathode Separator 57 mm 57 mm - 2 x 600 mm = 1200 mm

11 Mass Distribution in an cell: 5 Main Groups of Components g / t h ig e W Anode Total Cathode Total Electrolyte Separator Case, Vents, etc cell: 45g; based on graphite anode and lithium iron phosphate (LiFePO 4 ) cathode

12 Mass Distribution in an cell: Component Details cell: 45g; based on graphite anode and lithium iron phosphate (LiFePO 4 ) cathode g / t h ig e W Current Collector (Cu) Binder (Anode) Conductive Agent (Anode) Graphite Current Collector (Al) Binder (Cathode) Conductive Agent (Cathode) LiFePO4 Electrolyte Separator Case, Vents, etc.

13 Mass Distribution in an cell: Summary: Active vs. Inactive Materials g / t h ig e W wt.% Active Mat. Cathode Act. Mat. Anode Act. Mat. Inactive wt.% Inactive cell: 45g; based on graphite anode and lithium iron phosphate (LiFePO 4 ) cathode

14 Mass Distribution in an cell: Lithium Ion Battery is Sham Li Active: 0.52g (= 1.16 wt.%): mobile Li from Cathode Material Li Inactive: 0.21g (= 0.27 wt.%): Li Loss from Cathode Material + Li in Electrolyte Rest: 44.37g (= wt.%) cell: 45g; based on graphite anode and lithium iron phosphate (LiFePO 4 ) cathode

15 4.5 Ah Cylindrical Cell: Material Costs* Material costs on cell level: Active: 61.8% Inactive: 38.2% *Source: Total Battery Consulting, 2015

16 42 Ah Pouch EV Cell Material Costs* Material costs on cell level: Active: 55.2% Inactive: 44.8% *Source: Total Battery Consulting, 2015

17 34 Ah Metal can EV Cell Material Costs* Material costs on cell level: Active: 46.9% Inactive: 53.1% *Source: Total Battery Consulting, 2015

18 5 Ah HEV Cell, 200k Packs per Year Material Costs* 5-Ah, 500-W HEV Cell 216 MWh Plant NMC/graphite, Metal Can, 12 Million HEV Cells / year Units Amount $/unit $/cell Cathode Active Materials Anode Active Materials Electrolyte Separator Copper Foil Can, Headers & Terminals Other kg kg kg m kg cell cell Material costs on cell level: Active: 25.6% Inactive: 74.4 % Total Materials Per kwh Per kw *Source: Total Battery Consulting

19 An Example for an Inactive, but not Passive Material: TheElectrolyte Salt LiPF 6 : Unwanted, but Indispensable Typical range of LiPF 6 in non-aqu. electrolyte is 0.8 to 1.2 molar (10-15% by weight) wt. %: organic carbonate solvents + eventual electrolyte additives Electrolyte contributes ca. 5 to 10 % to the overall lithium ion battery material costs. With a mass fraction of <15%, the LiPF 6 costs are up to 90% of the electrolyte costs. Pros: Instability SEI passivation film forming agent Al current collector protection (!!!) Cons: Instability Thermal and chemical (hydrolysis) HF and other toxic compounds (fluorophosphates and organophosphates) HF promotes cathode dissolution LiPF 6 is the worst electrolyte salt you can imagine,...except for all the others.

20 Current Collectors: Requirements for LIB* Excellent electronic conductivity: Ag, Cu, Au, Al, Low cost: X X Ag, Cu, Au, Al Electrochemically stable within the electrode operation potentials: Metals that alloy with Li He B C N O F Ne Al Si P S Cl Ar Fe Co Ni Cu Zn Ga Ge As Se Br Kr Ru Rh Pd Ag Cd In Sn Sb Te I Xe Os Ir Pt Au Hg Tl Pb Bi Po At Rn Al alloys with Li at carbon anode potentials Cu is oxidized at > 3.5V vs. Li/Li + (= cathode potentials), surface impurities Cu anode, Al (!) cathode (LiPF 6 necessary!) Processing to thin foils (in the µm range) possible Rel. light weight Chemically and thermally stable/inert *Considerations are valid for lithium ion cells with carbonaceous anode and 4-V cathode!

21 Al: Anodic Oxidation Dissolution Mechanisms in the Presence of LiPF 6 vs. LiTFSI* Al PF 6 - PF 5 1 µm Al 2 O 3 Al z O y F z Solvated PF 6 - HF after 1,000 cycles Oxidation Al TFSI- TFSI - = N(SO Al 2 O 2 CF 3 ) Solvated TFSI Al µm Oxidation after 3 cycles *E. Krämer, MW, et al., J. Electrochem. Soc. 2013, 160 (2), A356-A360; E. Krämer, MW, et al., ECS Lett.,2012, 1(5), C1 - C3;

22 High Voltage LIB High Voltage is Relative Lightning: Several Volts High voltage grid: Several Volts Static electricity: Several 10,000 Volts Humans: Up to Volts Sr/Sr + Li/Li + SHE F 2 /HF OF 2 Possible: <8V Batteries: Practical: <5 V * 3.294* E / V vs. SHE Typical: 1.2 4V *(in acidic solution)

23 Towards High Energy Density LIB with High Voltage (HV) Cathodes Potential vs. Li/Li + 5 V 4 V 3 V 2 V 1 V 0 V? HV Cathodes NMC at NMC HV Graphite E = C V Cathode Cathode Anode Energy density can be elevated by: higher specific capacity and higher cell voltage (via cathode potential increase) The use of high voltage cathodes materials presents a major challenge to the oxidation stability of the electrolyte e.g., organic carbonate solvents: > V

24 LiNi 0.33 Mn 0.33 Co 0.33 O 2 ( 1/3-NMC ) at HV: Enhanced Potential and Capacity B. Xu, D. Qian, Z. Wang, Y.S. Meng, Materials Science and Engineering: R: Reports 2012, 73, NMC can be charged to different upper cut-off potentials Higher cut-off potential HV application higher specific energy 48% 68% Li + Li +

25 High Voltage Application of NMC Use of LiPF 6 in Electrolyte at HV Metal Dissolution (Promoted by HF) 2000 Specific capacity / mah g WE: NMC, CE, RE: Li Upper cut-off potential vs. Li/Li V 4.4 V 4.6 V LiPF Cycle number Concentration / µg L Ni Co Mn NMC storage in electrolyte for 28 days Electrode potential vs. Li/Li + / V Enhanced average discharge potential Electrolyte: 1M LiPF 6 in EC/DMC (1:1) Higher specific capacity Ni, Co, and Mn dissolution Lower Coulombic Efficiency Large dissolution at 4.6 V vs. Li/Li + Insufficient cycle life D.R. Gallus, MW, et al., Electrochimica Acta, 134 (2014)

26 New HF (and H 2 O) Scavenging Electrolyte Additives: TMS (Trimethylsilyl-) Based **Mechanism S.S. Zhang, J Power Sources, 162 (2006) Patent Claim by Saidi et al.*: TMS diethylamine can reduce HF induced transition metal dissolution* Proposal of mechanism by Zhang** Diethylamine = Leaving group (LG) However: Not stable at high cathode potentials Mn concentration / µg L NMC storage at 4.6V vs. Li/Li + for 28 days** 1/100 1M LiPF 6 in EC/DMC + 1wt% TMS diethylamine Current density / ma cm M LiPF 6 in EC/DMC (1/1) + 1 wt% TMS diethylamine Potential vs. Li/Li + / V *M.Y. Saidi, F. Gao, J. Barker, C. Scordilis-Kelley, U.S. Patent 5,846,673 (1998) WE: LMO; CE, RE: Li Scan rate: 0.1 mv s -1

27 Effect of TMS Additives on NMC Cycling at HV* Specific capacity / mah g WE: NMC; CE, RE: Li; V vs. Li 1 st -3 rd cycle: 0.2C; 4 th -50 th cycle: 1C 1M LiPF 6 in EC/DMC (1/1) + 1wt-% TMS diethylamine + 1wt-% TMS trifluoroacetate Cycle number Coulombic efficiency / % M LiPF 6 in EC/DMC (1/1) + 1wt-% TMS diethylamine + 1wt-% TMS trifluoroacetate Cycle number TMS diethyl amine: Better capacity retention Low Coulombic efficiency Oxid. decomposition during cycling TMS trifluoro acetate: Better capacity retention Higher Coulombic efficiency Enables HV application *D. Gallus, MW, et al., Electrochimica Acta, 2015, 184,

28 Al Passivation in TMS Electrolyte in the Presence of Smaller HF Amounts Sufficient amounts of HF in the electrolyte are beneficial in order to passivate the Al current collector* TMS reduces amount of HF in the electrolyte Al : Constant 4.6 V vs. Li/Li +, 24 h a b c SEM of Al foils after polarization to 4.6 V vs. Li/Li + for 24 h a.) 1M LiPF 6 in EC/DMC, b.) + 1 wt.-% TMS trifluoro acetate, c.) 1M LiTFSI in EC/DMC *E. Krämer, et al., J. Electrochem. Soc. 2013, 160 (2), A356-A360 E. Krämer, et al., ECS Lett.,2012, 1(5), C1 - C3.

29 The Ancestor of Li + Ion Transfer Cells: The HSO 4- Ion Transfer Cell* ) - negative electrode electrolyte + positive electrode C X 2n discharge charge C X 2n C n C X n *W. Rüdorff, U. Hofmann, Z. Anorg. Allg. Chem., 238 (1938) 1. Page 29

30 Carbon Black: Small Amount, but Influential Spherical paracrystalline carbon (10~100 nm) with concentrically oriented graphitic domains. [*] Carbon black: High contact surface area High electronic conductivity High thermal conductivity Thermal Treatment to Remove Surface Groups CB-N: non-treated CB-SG: 1500 C in Ar (slightly graphitized) CB-HG: 2000 C in Ar (highly graphitized) *R.D. Heidenreich, W.M. Hess, L.L. Ban, J. Appl. Cryst. 1968, 1, 1-19.

31 CB Graphitization Degree: Anion intercalation into CB WE: 80 wt.% CB, 20 wt.% PVdF binder; CE/RE: Li Electrolyte: 1M LiPF 6 in EC/DMC (1:1) 1. Constant current cycling Specific current 10 ma g Cyclic voltammetry Potential range: V vs. Li/Li + Scan rate: 20 mv s -1

32 Anion Intercalation into Carbon Black Leads to Extra Capacity [1] Balancing of cathode and anode capacity is crucial for safety and life Extra capacity at the cathode has to be considered when balancing the anode capacity Anion intercalation may damage the electrolyte and the conductive additive [1] X. Qi, B. Blizanac, A. DuPasquier, P. Meister, T. Placke, M. Oljaca, J. Li, M. Winter, Phys. Chem. Chem. Phys., 2014, 16,

33 Dual-Ion Cell Example: Metallic Li-Electrode Metallic Lithium DISCHARGE Graphite X - Li + Lithium metal X - Li + X - Li + X - Li e + - Li + X - Li + X - Li + X - Negative Electrode Electrolyte Positive Electrode Placke, T.; Bieker, P.; Lux, S.F.; Fromm, O.; Meyer, H.-W.; Passerini, S.; Winter, M.; Zeitschrift für Physikalische Chemie, 2012, 226,

34 Long-Term Cycling Stability: Effect of Temperature* 140 met. Li vs. KS6 graphite; Cut-off: 5.0 V discharge capacity / mah g C 40 C 60 C Li vs. KS6; CMC Pyr 14 TFSI, 0.3M LiTFSI Cut-off: 3.4V 5.0V Current: 50mA/g cycle number *Placke, T.; Fromm, O.; Lux, S.F.; Bieker, P.; Rothermel, S.; Meyer, H.-W.; Passerini, S.; Winter, M. Journal of the Electrochemical Society, 159, 2012, A1755-A1765.*

35 Summary LiPF 6 is a good inactive material, as the reaction products with water and protons (H + ) allow to combine an Al collector with org. carbonate solvents. Alternative electrolyte salts such as LiTFSI (= LiN(SO 2 CF 3 ) 2 ) Al dissolution. LiPF 6 is an essential electrolyte component. LiPF 6 is a bad inactive material, as the reaction products with water and protons (H + ) induce the formation of (hopefully not?) highly toxic compounds. In any case, reducing the amount of inactive materials will reduce the amount of dead mass and dead volume of the cell. The wish: A cell chemistry without any inactive materials. Slide 35

36 Inactive Materials: Even Small Amounts Make a Big Difference g / 30.0 t h ig e 22.5 W Current Collector (Cu) Binder (Anode) Conductive Agent (Anode) Graphite Current Collector (Al) Binder (Cathode) Conductive Agent (Cathode) LiFePO4 Electrolyte Separator Case, Vents, etc cell: 45g; graphite anode and lithium iron phosphate (LiFePO 4 ) cathode Total cost per cell: Total amount of CB: 1.58 g Costs of CB/cell: (10 kg -1 ) 85 wt.% LiNi 0.5 Mn 1.5 O 4 ; 10 wt.% CB; 5 wt.% PVdF

37 An investment in knowledge pays the best interest. ---Benjamin Franklin (American Publisher, Inventor and Scientist, )