Progress in rechargeable Li ion batteries.

Transcription

1 Progress in rechargeable Li ion batteries. Doron Aurbach Department of Chemistry, Bar-Ilan University, Ramat-Gan 529, Israel At Bar Ilan University: Elena Markevich Gregory Salitra Ella Zinigrad Boris Markovsky Mikhail Levi At Merck KGaA: Guenter Semrau Michael Schmidt At HPL Ivan Exnar At GM Ion Halalay At Sion Power Charlie s. Kelley At Tadiran Herzel Yamin At ETV Arie Neitav & Shalom Luski Support: ISF, Israel Science Foundation. Chief Scientist (MAGNETON programs). ETV,TAMI (Israel) Merck KGaA (Germany), LG Korea). GM, Sion Power (USA). In collaboration with UBE Industries, Japan.

2

3 Outline Introductory remarks. On polar aprotic solutions for Li ion batteries. On the use of ionic liquids for rechargeable Li electrodes: 5 V cathodes, Li-Graphite, Li-Si. Comparative study of cathode materials: LiMn 1.5 Ni.5 O 4 spinel LiNi.5 Mn.5 O 2 LiNi.33 Mn.33 Co.33 O 2 LiNi.4 Mn.4 Co.2 O 2 LiNi.8 Co.15 Al.5 O 2 LiMnPO 4 two generations. Aging, stability, rate capability, cycle life and surface chemistry. Conclusion.

4 Solvents for Li batteries Choice of salts LiAsF 6 toxic LiClO 4 explosive LiBF 4 poor passivation LiBOB limited anodic stability Li(NSO 2 CF 3 ) 2 poor passivation LiPF 6 The best compromise Side products: LiF, PF 5,HF, POF 3 LiPF 6 LiF + PF 5 PF 5 + H 2 O 2HF + PF 3 O Interesting additives (UBE Industries) Surface reactive compounds that polymerize on both anodes and cathodes VC PMS Donor # density gr/cc viscosity C p (γ) Dielectric ε b.p. C m.p. C Mw [g/mol] Solution ( 4c ) EC PC DMC DEC THF EMC

5 Rechargeable Li sulfur cells: The highest energy density due to the high electrodes capacity Ethereal solvents such as 1-3 Dioxolane + an electrolyte such as LiN(SO 2 CF 3 ) 2 A major problem: limited capacity of the sulfur cathode due to shuttle mechanism. Voltage profiles of Li-S cells based on dioxolane & LiN(SO 2 CF 3 ) 2 solutions Solution containing LiNO 3 Impedance spectra of Li electrodes prepared fresh in dioxolane LiTFSI solutions : with no additives ; with LiNO 3 ; with Li 2 S 6 and with LiNO 3 + Li 2 S V vs. Li Shuttle mechanism, Low capacity Due to poly-sulfide a reduction on the Li anode and their repeated oxidation on the cathode b -"Z/ohm cm DOL+LiTFSI+LiNO 3 DOL+LiTFSI+ PS+LiNO 3 DOL+LiTFSI +PS 'Z/ohm cm 2 DOL+LiTFSI Capacity [mah/g] Sulfur XPS spectra of Li electrodes prepared and stored in 1,3-dioxolane solutions Solution containing only Li 2 S 6 Solution containing both Li 2 S 6 and LiNO 3 Note the high oxidation state of Li surface sulfur due to the presence of LiNO 3 The passivation of Li is due to the formation of various Li-S-O compounds

6 Low-temperature electrolytes for Li-batteries 2 Conductivity results obtained for different electrolytes at various temperatures. EC:DMC(1:2)1.5m LiPF 6 Standard Kansai coke graphite NG15 in standard electrolyte EC:DMC 1.5M LiPF 6. Inset graph shows the Voltage Vs Discharge capacity at 3 and -3 o C temperature. ms EC:DEC:DMC:EMC(1:1:1:2)1m LiPF 6 EC:DEC:DMC:EMC(3:5:4:1)1m LiPF 6 EC:DMC:EMC (15:37:48)1m LiTFSI EC:DEC:DMC:BL(1:1:1:1)1m LiPF 6 EC:DMC:EMC (15:37:48)1m LiPF 6 EC:DEC:DMC:EB(1:1:1:1)1m LiPF 6 EC:EMC (3:7)1m LiBF 4 PC:EC:EMC (1:1:3)1m LiBF 4 Discharge Capacity (mah/g) Voltage (V) o C 1 st Cycle Discharge Capacity (mah/g) Voltage (V) o C 1 st Cycle Discharge Capacity (mah/g) Temperature ( o C) Temperature ( o C) Performance of different graphite materials in two different electrolytes at various temperatures. Discharge Capacity (mah/g) 6 EC:DMC:EMC-1M LiPF 6 +1% VC Kansai Coke N15 Conoco Philips G5 Timcal SLP Temperature o C Discharge Capacity (mah/g) EC:DMC:EMC-1M LiTFSI +1% VC Kansai Coke N15 Conoco Philips G5 Timcal SLP Temperature o C

7 Discharge Capacity (mah/g) Voltage (V) Low temperature performance of different cathode and anode materials in various electrolytes Lithium Titanate (Li 4 Ti 5 O 12 ) 2 NMC (LiNi 1/3 Mn 1/3 Co 1/3 O 2 ) 18 EC:DMC:EMC-1M LiPF 6 + 1% VC EC:DMC:EMC-1M LiTFSI + 1% VC EC:DMC:EMC-.9M LiTFSI +.1M LiBOB +1% VC EC:DEC:DMC:BL-1M LiPF 6 +1% VC EC:DEC:DMC:EB- 1M LiPF 6 +1% VC Temperature o C Temperature o C Voltage Vs Discharge capacity curve of Li 4 Ti 5 O 12 and LiNi 1/3 Mn 1/3 Co 1/3 O 2 at various temperature in different electrolytes. 3 deg. -red (1) deg. -green (4) -1 deg. -blue (6) deg. -cyan (9) -3 deg. -Magenta (1) -4 deg. -Purple (12) deg. -wine (15) (repeat after low temperature measurement) Voltage (v) 2. Discharge Capacity (mah/g) 3 deg. -red (1) 4.5 deg. -green (5) -1 deg. -blue (7) -2 deg. -cyan (9) -3 deg. -Magenta ( deg. -Purple(13) 3 deg. -wine (16)(repeat after low temperature measurement) Voltage (V) deg. -red (1) 3 deg. -green (2) deg. -blue (8) -1 deg. -cyan (13) -2 deg. -Magenta (21) -3 deg. -dark yellow (33) -4 deg. -wine (48) 3 deg. pink (59)(repeat after low temperature measurement) Voltage (V) EC:DMC:EMC-1M LiPF 6 + 1% VC EC:DMC:EMC-1M LiTFSI + 1% VC EC:DMC:EMC-.9M LiTFSI +.1M LiBOB +1% VC EC:DEC:DMC:BL-1M LiPF 6 +1% VC EC:DEC:DMC:EB- 1M LiPF 6 +1% VC Li 4 Ti 5 O 12 LiNi 1/3 Mn 1/3 Co 1/3 O 2 3 deg. -red (1) 3 deg. -green (2) deg. -blue (8) -1 deg. -cyan (11) -2 deg. -Magenta (18) -3 deg. -dark yellow (28) -4 deg. -wine (4) 3 deg. (49)(repeat after low temperature measurement) Discharge Capacity (mah/g) Discharge capacity (mah/g) Discharge capacity (mah/g) Discharge capacity (mah/g) EC:DMC:EMC-1mLiPF 6 +1%VC EC:DMC:EMC-1mLiTFSI +1%VC EC:DMC:EMC-1mLiPF 6 +1%VC EC:DEC:DMC:EB- 1mLiPF 6 +1%VC

8 i / A Why Ionic Liquids (Ils)? Wide electrochemical window Safety The electrochemical stability window of LiTFSI in MPPpTFSI electrolyte Pt and LiNi.5 Mn 1.5 O 2 electrodes.2m.15m.1m.5m I, μa LiNi.5 Mn 1.5 O 2 electrodes in 1.5M LiPF 6 EC/EMC 1:2 and in IL solution.5m LiTFSI in MPPpTFSI N C 3 H 7 N(SO 2 CF 3 ) E, V 2 1 side parasitic oxidation processes in standard electrolytes not in Ils -.5m -.1m E / V vs. Li/Li+ Kinetics is slower in the ionic liquid electrolyte LiNi.5 Mn 1.5 O 2 /Li 5V cells demonstrate stable cycling with IL electrolyte solutions : elaboration of real 5V rechargeable Li batteries may be feasible.

9 LiNi.5 Mn 1.5 O 4 electrodes in standard & IL solutions μV/s, 2C Capacity/mA H g I/μA E/V `.5M LiTFSI in BMPTFSI.5M LiTFSI in MPPpTFSI 1.5M LiPF 6 in EC/EMC 1:2 2 4 Cycle number Charge and discharge capacity obtained for the galvanostatic cycling of LiNi.5 Mn 1.5 O 2 electrodes (C/16). Upper curves are discharge proesses and the lower curves are the charging processes. Note the much lower irreversible capacity obtained with the ILs electrolytes. V. Burgel et Al, J. Power Sources (28) In press

10 A comparative study of the behavior of different kinds of graphite electrodes in solutions based on ionic liquids IL + Li salt 4 2 Cycle 3 IL + Li salt Cycle 3 Cycle 2 Cycle 1 Synthetic flakes, 4 micron I, μa -2 Cycle Cycle 1 Natural graphite Natural graphite E, V 5-5 I, μa E, V Synthetic flakes NG Graphite in pure IL (MPPpTFSI): no Li ions, no passivation, irreversible IL intercalation

11 Attenuation of thermal activity by use of ILs as additives DSC response of Li.5 CoO 2 + solutions exo.5 W/g of Li.5 CoO ºC Standard solution+1 % BMPFAP 667 J/g N + N(SO 2 CF 3 ) 2 C 4 H ºC Standard solution+1 % BMPTFSI 286 J/g N + PF 3 (C 2 F 5 ) 3 C 4H 9 Heat flow 186 J/g 156 ºC Standard solution EC-DMC LiPF 6 1M Li.5 CoO 2 no solution 33 J/g 254 ºC Temperature, ºC

12 Synthesis Single-step sucrose-aided Self-Combustion Reaction for production of layered compounds of nanosized lithiated oxides LiNO Ni(NO 3 ) 2.6H 2 O +.5 Mn(NO 3 ) 2.4H 2 O C 12 H 22 O O 2 LiNi.5 Mn.5 O CO H 2 O + 3 N 2 Then, calcination provides the final structure. The temp. & time of calcination determine the particle size. 25 nm Number (%) Number, (%) OXIDIZER Metal Nitrates REDUCER (FUEL) Sucrose (C 12 H 22 O 11 ) PRODUCT Nanosized + Gases Material (CO 2, N x O y ) Solution Syrupy mass Foam Self-ignition % 5 Particle size, μm 9 (22 hours) 7 o C for 22h 9 o C for 22h ParticleSize(µm) size, μm Particle size, µm

13 Intensity/ counts.s e-6 1e Nano-sized LiNi.5 Mn vs. Micro-sized LiNi.5 Mn W=.17 W=.32 XRD W=.18 W= Micro-particles Nano-particles 2-Theta - Scale Ni 2+ Ni 3+ We have synthesized nano particles of the right material, it behaves indeed faster! Micro-sized particles W=.25 W= Nano-sized particles Ni 3+ Ni 4+ Intensity/ a.u. Up to 14 mah/g Hundreds of cycles 5 5 w=75 w= w= w=19 5 w= w= Raman shift/ cm -1 Raman Nano-sized particles Micro-sized particles I/ A.g -1 2e-6 1e-6 P ris tin e p a rtic le s P a rtic le s a g e d in s o lu tio n (7 C) 4.71 V 4.76 V -1e-6 Ni 2+ Ni 3+ Ni 3+ Ni 4+ ν=3 μvs -1, T=3 C -2e E/ V I / A.cm -2-1e-6 7 C 4.72 V Scan rate 1 μ V/s 4.69 V -2e E / V vs. L i/l i +

14 LiNi.5 Mn.5 O 2 Electrodes: 6 C, E=3.9 V Micro-particles Nano-particles Z'' / Ohm.cm Hz -4 2 Hz 1.25 Hz 316 mhz mhz mhz 2.5 Hz days cycling/ageing 2 mhz 5 Hz Z' / Ohm.cm 2 5 days cycling/ageing Z'' / Ohm.cm 2 Initial (steady-state) -4 2 Hz 2.5 Hz 5 mhz Hz 1 Hz -2 5 mhz week ageing Hz 1 Hz 5 mhz weeks ageing Z' / Ohm.cm 2

15 Electrochemical behavior of electrodes prepared from micro-, submicron or nano-particles in Li cells, DMC-EC/LiPF 6 solutions Capacity / mah.g -1 Discharge capacity / mahg Total charge (CC-CV) capacity Discharge capacity C/ C/5 3C C/5 Submicron- Submicron- 8C C/2 LiNi.5 Mn.5 O Aging at 3 C for 1 week every 1 cycles 3C 1 C Submicron- LiNi.33 Mn.33 Co.33 O Cycle number 3C Cycle number Capacity / mah.g -1 Discharge capacity / mahg C/5 2 C/1 Total charge (cc-cv) capacity Discharge capacity C/4 C/2 Total charge (CC-CV) capacity Discharge capacity LiNi.5 Mn.5 O 2 Very good cyclability C Cycle number 2C 7.5C Cycle number C/7 Discharge capacity / mahg Capacity / mahg C/2.5 1C 2C 6C C/5 Submicron- LiNi.4 Mn.4 Co.2 O 2 Very fast material Submicron- LiNi.33 Mn.33 Co.33 O 2 6C Cycle number Total charge (CC-CV) capacity 2 C/15 Discharge capacity C/1 C/1 C/5 C/2 1 C 2 C Submicron- LiNi.8 Co.15 Al.5 O 2 4 C Cycle number

16 Voltage profile for LiNi.5 Mn.5 O 2, NCA and C-coated LiMnPO 4 composite electrodes at various discharge rates at 3 o C 4.5 NCA LiNi.5 Mn.5 O 2 Cell voltage (V) C/15 C/1 Cell voltage (V) C 2C C C/2 C/ Discharge capacity (mahg -1 ) 2.5 3C C C/2 C/5 C/ Discharge capacity (mahg -1 ) Cell voltage / V C-coated LiMnPO 4 C/25 C/1 5C 2C C C/2 C/ Discharge capacity / mahg -1

17 Comparison of cycling behavior at various rates of discharge for Gen 1 and Gen 2 electrodes at 3 o C Discharge capacity / mahg C/2 C/1 C/5 C/2 Gen 1 (2.7 V V) Gen 2 (2.7 V-4.25 V) 1C 1C 3C C Cycle number 5C

18 Cycling behavior at C/5 rate of discharge for Gen 2 electrodes at 3 o C 4 35 Total charge (CC-CV) capacity Discharge capacity Capacity / mahg C/2 4.4 V-2.7V EC-DMC/LiPF 6 electrolyte C/5 1 5 C/ Cycle number

19 Comparison of capacity at various discharge rates for the electrodes comprising LiNi.5 Mn.5 O 2, LiNi.33 Mn.33 Co.33 O 2, LiNi.8 Co.15 Al.5 O 2, (NCA), LiNi.4 Mn.4 Co.2 O 2, LiMnPO 4 (Gen 1)and Gen 2 Olivine particles Discharge capacity / mahg min 3 min 2 min 12 min 1 min LiNi.5 Mn.5 O 2 LiMnPO 4 LiNi.33 Mn.33 Co.33 O 2 LiNi.4 Mn.4 Co.2 O 2 LiNi.8 Co.15 Al.5 O 2 Gen 2 Olivine 7.5 min 6 min 2C 4C 6C 8C 1C Rates of discharge

20 DSC response for different cathodes in EC-DMC/ LiPF 6 Solution PRISTINE SOC x=.5 ( half delithiated) SOC x=.5 ( fully delithiated) exo Heat flow.25 W/g of cathode 242 ºC Li Ni.5 Mn.5 O 2 LiCo.2 Ni.4 Mn.4 O ºC LiNi.8 Co.15 Al.5 O ºC 24 ºC LiCo 1/3 Ni 1/3 Mn 1/3 O 2 LiMnPO 4 25 ºC 232 ºC Li Ni.5 Mn 1.5 O J/g 153 J/g 192 J/g 12 J/g 35 J/g 5 J/g.25 W/g of cathode Li.5 Ni.5 Mn.5 O ºC 197 ºC Li.5 MnPO 4 Li.5 MnPO ºC Li.5 Co.2 Ni.4 Mn.4 O 2 Li.5 Ni.8 Co.15 Al.5 O ºC 211 ºC 122 J/g 1315 J/g 181 J/g Li.5 Co 1/3 Ni 1/3 Mn 1/3 O 2 86 J/g 85 J/g W/g of cathode 64 J/g 67 J/g 21 ºC 82 J/g 25 ºC 116 J/g 195 ºC 55 J/g 23 ºC Li.5 Ni.5 Mn.5 O ºC Li.5 Co.2 Ni.4 Mn.4 O 2 Li.5 Ni.8 Co.15 Al.5 O 2 Li.5 Co 1/3 Ni 1/3 Mn 1/3 O 2 Li.5 MnPO Temperature/ ºC

21 Comparison between surface active and non active cathode materials Absorbance week Pronounced changes No significant changes 7 week.6.5 Pristin e Wavenumbers (cm-1) Wave numbers (cm - LiNi.5 Mn.5 O Absorbance Li 2 CO Pristine Wavenumbers (cm-1) 1) Wave numbers (cm - 1) LiMnPO

22 Li [MnNiCo]O 2 Pristine powder + ROCO 2 R LiPF 6 Surface chemistry PF 5,HF,H 2 O ROCO 2 Li ROLi [ROCO 2 ] n MFx, LiF Li[NiMnCo]O 2 Nucleophilic reactions polymerization Other oxides Cobalt 2p 2/3 Manganese 2p 2/3 Nickel 2p 2/3 Li[NiMnCo]O 2 Powder aged Li x [NiMnCo]O 2 Electrode charged

23 Ni Pristine XPS spectra of nano-lini.5 Mn.5 O 2 particles Ni Surface chemistry Aged at 6 C peaks at 855 ev and at ev : formation of surface species containing Ni of higher oxidation state than 2 +. Oxygen F Oxygen F peak at ev: nickel (III) oxide and manganese oxides. a satellite peak at ev: organic species with carbonyl groups peak at 686 ev: LiF, MnF 2, NiF 2 Ageing in solution Changes in surface chemistry and passivation

24 Absorbance Nano-LiNi.5 Mn.5 O 2 EC-DMC (1:2)/1.5 M LiPF 6 Ni O Mn O Li 2 CO 3 Li 2 CO Pristin e FTIR spectroscopy deciphers the surface chemistry. O O C O υ C O Polycarbonate Li x PF y aged at 6 C Solution spectrum P F Wavenumbers (cm -1 ) 5

25 Summary: Main Demonstrations 1. Ionic liquids can work well with all relevant electrodes materials. The anodes passivation can be controlled by additives. 2. LiNi.5 Mn 1.5 O 4, LiNi.5 Mn.5 O 2 and Li[NiMnCo]O 2 nanomaterials can be apparently chemically stable in standard electrolyte solutions, even at high temperatures. 3.These materials develop unique surface chemistry in standard solutions that leads to their efficient passivation. 4. A maximal practical capacity up to 2 mah/g can be from both LiNi.5 Mn.5 O 2 and LiNi.8 Co.15 Al.5 O 2.The former one is a slow material. 5. The fastest material is LiNi.33 Mn.33 Co.33 O 2 however the practical capacity is around 16 mah/g. 6. LiMnPO 4 produced by HPL is the least surface reactive of all the cathode materials studied, what is well expressed in very good cycleability. Its rate capability is better than that of LiNi.5 Mn.5 O 2 and LiNi.8 Co.15 Al.5 O 2