Aqueous Rechargeable Lithium Batteries (ARLBs) of High Energy Density. Prof. Dr. Yuping Wu

Transcription

1 Aqueous Rechargeable Lithium Batteries (ARLBs) of High Energy Density Prof. Dr. Yuping Wu New Energy and Materials Laboratory (NEML), Department of Chemistry, Fudan University, Shanghai Tel/Fax: th US-China Electric Vehicles and Battery Technology Workshop, Boston August, 2012

2 Motto of NEML 4E + E Electrochemical technologies Solve Energy problem Reduce Environmental pollution Enjoy life To cultivate Elites for the society.

3 1. Chemical Power Sources Supercapacitors Polysulfide bromide battery (PSB) Zn/Br battery Vanadium redox couples (VRC) Sodium sulfur battery (Na/S) Lead acid battery Metal-air battery Ni-MH Lithium ion battery Safety Rate capability Energy density Energy efficiency Cycling life Maintenance Capital cost for kwh Per-cycle cost Aqueous rechargeable lithium battery (ARLB) 2 nd Symposium on Energy Storage and Power Batteries, Chengdu, Nov., 2007

4 Lithium Ion Batteries Characteristics of lithium ion batteries: High output voltage (average 3.6V) and power High energy density (UR18650: >500 Wh/dm 3, >200Wh/kg) Low self discharge (<10%/month) No memory effect Long cycle life (>1000 times) High rate capability (1C) High coulomb efficiency (near 100% except in the 1st cycle) Easy to measure the residual capacity Maintenance free No environmental pollution (green battery) Wide work temperature ( o C, extended to o C)

5 Main Materials for Lithium Ion Batteries Energy Storage Inner safety Electrolyte Anode material Cathode material Electrolyte Separator Anode Cathode Separator

6 Field Failure Manufacturing defects Loose connection, separator damage, foreign debris Can develop into an internal short circuit Can lead to overheating and thermal runaway Abuse Failure Mechanical crush, nail penetration Electrical short circuit, overcharge Thermal thermal ramp, simulated fire Safety during Abuse A123: PHEV (Jun. 2008) (April. 2011)

7 One th China-U.S. Electric Vehicle and Battery Technology Workshop Safety & reliability for lithium ion batteries is the challenging problems for electric vehicles. Gel lithium ion batteries (GLIBs) is surely the true choice as power source for EVs. Safety time: Another importance GMs: Self-distinguishing Full charge and then put on electric oven: at least 1 min and 10 seconds (even for C//LiCoO 2 ) to escape when EVs are on fire.

8 Li//Air Challenging problems Conductors of low ionic conductivity Low stability: reaction with Li 2 O 2 Low O 2 solubility Low Li 2 O 2 solubility Narrow temperature High overpotentials Low energy efficiency Low practical energy density Sensitive to the environment Prof. Deyang th China-U.S. Electric Vehicle and Battery Technology Workshop, April, 2012

9 Li//S Li??? Nobody should forget the story of MoLi Company (Li//MoS 2 ). Some facts: MoS 2 is more reliable than S. Lithium dendrite is the main safety issue instead of S. Low volumetric energy density. There is still quite some distance to go.

10 New Power sources Cheap: Lead acid has the largest market Green: The ultimate goal of electrochemists Power density: Very high Neutral aqueous solutions.

11 Definition: What is ARLB? Lithium intercalation compound(s) as one or both electrodes Redox reactions instead of absorption/ desorption Aqueous lithium-containing solution as electrolyte Why not called as aqueous lithium ion batteries: Misunderstanding: Aqueous to replace organic??? Scope: Very narrow

12 2. Aqueous rechargeable lithium battery (ARLB) LiMn 2 O 4 //VO 2 (B) Possibility and availability. Poor cycling. W. Li, J. R. Dahn, D. Wainwright, Science, 264, 1115 (1994).

13 Comments Since our first publication on ARLBs in Angew. Chem. Int. Edi. in 2007, Stanford Univ., Kyushu Univ. and the like show great interest. J. Glanz, Science, 264, 1084 (1994). Our reply: not maybe but sure.

14 2.1 Cathode: LiCoO 2 Current (ma) mV/s Lithium Extraction 0.71V 0.87V 0.95V 1.06V 0.90V 1.01V Potential (V) Lithium Insertion Current (ma) Scan rate 0.1mV/s Lithium Extraction Lithium Insertion 4.14V 4.03V 3.83V Potential (V) 4.08V 4.13V (a) In saturated Li 2 SO 4 aqueous (b) In organic LIB 315 De-intercalation and intercalation of LiCoO 2 in aqueous and organic solutions. Similar behavior including phase transitions. D Li+ = x cm 2 /s Wu et al., Angew. Chem. Int. Ed., 46, 295 (2007); Electrochim. Acta, 52, 4911 (2007). 4.21V

15 Nanostructured LiCoO 2 Our nano LiCoO 2 LiCoO 2 from traditional solidstate reaction in aqueous electrolytes: Results from Stanford University. Fast kinetics Very good charge-discharge behavior for high power density. Full charge: < 1 min. Wu et al., Electrochem. Commun. 11 (2010) 1524.

16 Current (ma) (a) Scan rate: 2 mv s mv s mv s LiMn 2 O 4 : cheap 3.94V 4.08V Lithium insertion Lithium extraction 4.19V 4.07V Potential (V vs Li + /Li) Current (A) (b) 1 mv s -1 2 mv s -1 4 mv s -1 6 mv s -1 8 mv s -1 Fast kinetics Potential (V vs SCE) (a)in organic LIB 315 (b) In 2 M Li 2 SO 4 aqueous Similar intercalation and deintercalation behavior in organic and aqueous electrolytes. Satisfactory at high scan rate, indicating great promise for application at high current density for aqueous electrolyte. Wu et al., Funt. Mater. Lett., 3 (2010) 151.

17 PS template (1) Macroporous (a) (b) (c) 700 Intensity (a. u.) 600 (d) 500 Solid LiMn2O4 Porous LiMn2O nm (2) Nanograin Theta (degree) 70 (3) High crystallinity Wu et al., Energ. Environ. Sci., 2011, (Feature article).

18 CVs in 0.5 mol l -1 Li 2 SO 4 aqueous solution. Ultra-fast kinetics Current (A) a: Solid LiMn 2 O mv/s 1 mv/s 2 mv/s 3 mv/s 5 mv/s Current (A) b: Porous LiMn 2 O 4 1 mv/s 5 mv/s 10 mv/s 15 mv/s 20 mv/s Potential (V vs. SCE) Potential (V vs. SCE) (a) Solid-LiMn 2 O 4 (b) Porous-LiMn 2 O 4 Electrode: 80% active material, 10% conductive agent and 10% binder.

19 The transportation process in porous LiMn 2 O 4 electrode will be more facile. Porous LiMn 2 O 4 : 118 mah/g Solid LiMn 2 O 4 : 85 mah/g -Z'' (Ohm) Solid LiMn 2 O 4 Porous LiMn 2 O Z' (Ohm) Fig. Nyquist plots by using Ni mesh as the counter electrodes. Potential ( V vs. SCE) 1.0 Porous LiMn 2 O st 2nd 3rd Solid LiMn 2 O 4 1st 2nd 3rd Specific capacity ( mah g -1 ) Fig. Charge-discharge curves at 100 ma/g for the initial 3 cycles.

20 Potential (V vs. SCE) Potential (V vs. SCE) (a) Solid LiMn 2 O ma g ma g ma g ma g ma g Specific capacity (mah g -1 ) ma g -1 (b) Porous LiMn 2 O ma g ma g ma g ma g Specific Capacity (mah g -1 ) Fig. Charge-discharge at different current density. Specific capacity (mah g -1 ) In the case of porous LiMn 2 O 4, capacity retention is 76% at the charge current density of ma/g Porous LiMn 2 O Solid LiMn 2 O Open: charge Solid: discharge Unit: ma g Cycle number Fig. Capacity at different current density.

21 Porous LiMn 2 O 4 Potential (V vs. SCE) Specific Capacity (mah/g) 100 ma/g ma/g Potential ( V vs. SCE) The discharge curves of porous when it was fully charged at 100 ma/g): Capacity retention of 95% at ma/g mag ma g -1 Capacity: 118 mah g Time (min) Charge at ma/g and then kept at 1.29 V (NHE) until current goes to 100 ma/g. Full charge: < 2.4 mins. Ultra-fast kinetics: much faster than in organic electrolytes.

22 Good crystal, nano grain and porous structure No acid: ph ~7 Specific capacity (mah g-1) Excellent cycling behavior 150 (b) 120 Porous LiMn2O Solid LiMn2O Cycle number 100 nm TEM of porous LiMn2O4 after cycles. Stable morphology and crystal structure after cycles. Oxygen: not removed

23 Nanochain LiMn 2 O 4 : Super-fast charge capability Potential / V vs.sce SEM 150C charge 1.5C discharge 24 seconds: 84.1% Time / min. 84.1% 92.6mAh/g Potential / V vs.sce mA/g charge 500mA/g discharge 1000mA/g charge 1000mA/g discharge 5000mA/g charge 5000mA/g discharge 10000mA/g charge 10000mA/g discharge Capacity(mAh/g) Charge/discharge curves at different current densities Super-fast charge performance Wu et al., Electrochem. Commun., 13 (2011) 205.

24 Potential / V vs.sce (b) LiMn 2 O 4 nanorod : Super-fast SEM Charge and discharge current: 500mA/g 1000mA/g 5000mA/g 10000mA/g NEML, Fudan Capacity Uni. / mah/g charge capability Current / A (a) Scan rate: 1 mv/s; 5 mv/s; 10 mv/s; 15 mv/s; 20 mv/s; 30 mv/s; 50 mv/s; 100 mv/s; 150 mv/s Potential / V vs.sce CVs at different scan rate Charge/discharge curves at different current densities Super-fast charge kinetics: 40 sec (90%) Wu et al., Electrochem. Commun., 13, 1159 (2011).

25 2.2 Anode: 2 O 5 +CNTs) SEM micrograph of the virginal hybrid of V 2 O 5 with MWCNTs and TEM micrographs of the coated hybrid.

26 Wu et al., J. Mater. Chem., 2012, 22, in press Electrochemical performance of the virginal and the coated hybrids and the prepared ARLB: (a) cyclic voltammograms, (b) charge and discharge curves, (c) charge and discharge curves of the ARLB together with those of LiMn 2 O 4 and the coated hybrid, and (d) cycling behavior.

27 Anode: 3 (a) (b) (a) Scan rate: 1 mv/s LiMn 2 O 4 (c) 8. 44nm 100 nm (d) Current / A V V Nanocomposite of MoO 3 with PPy coating Current / A 20 nm (b) 1 mv/s 5 mv/s 10mV/s 30 mv/s 50 mv/s 80 mv/s 100 mv/s 50 nm Nanocomposite of MoO 3 with PPy coating Potential / V vs. SCE Potential / V vs. SCE

28 3 //LiMn 2 O 4 Potential / V vs. SCE Energy density / Wh/kg (a) Charge Charge LiMn 2 O 4 MoO 3 ARLB: MoO 3 //LiMn 2 O 4 Discharge Discharge Charge Discharge (c) Capacity / mah/g Super-fast: < 36 sec 10 Nanocomposite/Li 2 SO 4 /LiMn 2 O 4 Virginal MoO 3 /Li 2 SO 4 /LiMn 2 O Power density W/kg Voltage / V Coulombic efficiency / % (b) Coulombic efficiency for the ARLB from the nanocomposite Cycling of the nanocomposite//limn 2 O 4 Cycling of the virginal MoO 3 //LiMn 2 O Cycle number Capacity / mah/g 40 for 20 0 LiMn2O4 The energy density of this ARLB is 45 Wh/kg (lower than the estimated value, about 55 Wh/kg) at 350 W/kg and even maintains at 38 Wh/kg at 6 kw/kg. This kind of excellent rate capability can be compared with supercapacitors. Wu et al., Energy Environ. Sci., 5, 6909 (2012). (Top 10 most-read EES article)

29 Comparison of Filling (charge) Time Filling gasoline Filling natural gas 1-3 mins (Full) 3-5 mins (full, fast) Lithium ion batteries > 10 min (<80%) ARLBs < 1 min (>90%) Note: For average size vehicle.

30 Easy to produce 2.3 Advantages of ARLBs Good availability of lithium salts High ionic conductivity, about 1-2 orders of magnitude higher than organic electrolyte, suitable for charge and discharge at high rate High power density Good safety, no combustibility or explosion Low cost for production due to no requirements on the content of moisture Low requirements on separators especially the shut-down performance Friendly to environment, completely GREEN Satisfactory energy density Wh/kg for the total electrodes Super-fast charge capability Excellent cycling behavior Good promising for energy storage, HEVs, assistance for EVs and rangeextenders.

31 3. New ARLBs: EVs for long distance High voltage cathode??? Li-rich cathode??? Si anode??? P.G. Bruce et al., Nat. Mater., 11, 19 (2012).??? No idea so far

32 Li metal is not stable in water!!! Li + H 2 O = LiOH + H 2 Metal ( 金 ) Earth( 土 ) LiMO x Water( 水 ) Lithium Fire( metal 火 ) Wood( 木 ) Incompatible Compatible Traditional Theory of the Five Elements

33 To make fire compatible with water Fire( 火 ) Wood( 木 ) Water( 水 ) Lithium metal GPE + LISICON LiMn 2 O 4 Target: Polymers No LISICON (earth)

34 ARLBs of High Energy Density Li + deintercalation from LiMn 2 O 4 Current / ma Li + intercalation into LiMn 2 O Potential / V vs. Li + /Li CN Patent Application No: , PCT is under way.

35 ARLB of Li//LiMn 2 O 4 Capacity / mah/g Voltage / V (a) Charge Discharge (b) Capacity / mah/g Cycle number Coulomb effeciency/ % Fast kinetics: Small overpotential High energy/power efficiency: >95% (very rare) Good cycling: No evident capacity fading Stable lithium metal: No chance of lithium dendrite

36 High energy density ARLB Calculated energy density 50% utilization based on LIBs Possible practical energy density Li//LiMn 2 O Wh/kg 50% > 220 Wh/kg Li//NCM > 600 Wh/g 50% > 300 Wh/kg In aqueous electrolyte: At least 3 times thicker electrode pellets.

37 Advantage of the New ARLBs Good safety and reliability: an effective (close contact with the anode) cooling system (aqueous) Benign to environment: much green (no LiPF 6 ) High energy density: > 600 Wh/kg based on the mass of the electrode materials, and > 300 Wh/kg for practical value High coulomb efficiency: near 100% except for the initial cycles Fast redox kinetics for the electrodes: small overpotentials & superfast charge High energy/power efficiency: > 95% No memory effects Excellent cycling life: > cycles Low cost

38 4. Summary Nanomaterials greatly promote the development of ARLBs (aqueous rechargeable lithium batteries) including reversible capacity, rate capability and cycling behavior. New designed ARLBs open a great future for energy storage including EVs and smart grids in the near future. Social sciences are good to develop natural sciences: life enjoyment can lead to new ideas. We are developing new rechargeable aqueous battery systems with energy density > 500 Wh/kg (estimated practical value).

39 Acknowledgment Financial sponsors and collaborators: National Basic Research Program of China (973 Program No: 2007CB209702) Natural Science Foundation Committee of China Ministry of Science and Technology of China Science and Technology Commission of Shanghai Municipality Alexander von Humboldt Foundation (Partnership Program) Sanyo Chemical

40 Twice Study Tours to Shanghai Expo (2010) for our NEML Study Tour to Xi An (2011) (The top of Hua Mountain to watch sunrise)

41 Thanks for your kind attention!