Novel Electrolyte Additives for Enhanced Li-ion Battery Performance, Lecture notes of Chemistry

Download Novel Electrolyte Additives for Enhanced Li-ion Battery Performance and more Lecture notes Chemistry in PDF only on Docsity! Novel Electrolytes and Additives Project Id: ES023 D.P. Abraham Gang Cheng Vehicle Technologies Program Annual Merit Review Washington DC, May 9-13, 2011 This presentation does not contain any proprietary or confidential information 2 Overview Timeline • Start date: FY10 • End date: On-going • Percent complete: - project on-going Budget • Total project funding - 100% DOE • FY10: $300K • FY11: $300K Barriers • Performance • Calendar/Cycle Life • Abuse tolerance Partners • Argonne colleagues • Purdue University • University of Rhode Island • Kang Xu, ARL • JPL colleagues • Industrial collaborators 5 Technical Accomplishments and Progress  Identified new family of heteroaromatics substituted carboxylic ester- based compounds as electrolyte additives  Determined effects on cell performance and calendar life  Argonne filed a USA Patent Application based on these compounds (ANL-376, Cheng, G.; Abraham, D.P., 2010, September 23)  Recommended list of electrolyte additive compounds for scale-up  Investigating the relationship of additive structure to characteristics of surface films at both positive and negative electrodes  Currently examining the effect of SEI composition/morphology on interactions with Li-ion.  Designed and synthesized various GC-derivative compounds including alkyl ethers, carboxylic esters, and alkyl carbonates  Examined performance/cycling behavior of these compounds, both as co- solvents and as electrolyte additives  Argonne filed a USA Patent Application (ANL-368, Serial No. 12/910,549) and is in the process of filing another non-provisional patent application (ANL-382, Argonne Invention No. ANL-10-093) based on data from these compounds 6  Positive Electrode: – 84% Fuji CA1505 (NCA) – 4% SFG-6 + 4% carbon black – 8% PVDF binder (KF1100)  Negative Electrode: – 92% Mag-10 Graphite (Gr) – 8% PVDF binder (Kureha#C)  Baseline Electrolyte (Gen2): – 1.2 M LiPF6 in EC/EMC (3:7)  Typical cycling range: – Positive: 3 – 4.3V vs. Li – Negative: 2 – 0 vs. Li – Full Cell: 3 – 4.1V Baseline Chemistry used for electrolyte evaluation 7 Examples of heteroaromatic compounds examined as electrolyte additives for Lithium Batteries N O O O O N O O O N O O Methyl Picolinate (MP) N O O Ethyl Nicotinate (EN) N O O Methyl Isonicotinate (MIN) 3,4-diethyl pyridine Carboxylate (3,4-DEPC) 3,4-pyridinedicarboxylic anhydride (3,4-PyDCA) N O O Methyl-1-methylpyrrole- 2-carboxylate (MMPC) O O O O O O S O O 2-Ethyl furoate (2-EF) 3-Ethyl furoate (3-EF) 2-Ethyl thiophenecarboxylate (2-ETC) USA Patent Application, ANL-376, Cheng, G.; Abraham, D.P., 2010 10 Initial Cycling Behavior of NCA+/Gr- cell: Effect of Formation Cycle (0.3wt% MP in baseline electrolyte) Cells with 0.3 wt% MP in baseline electrolyte show relatively lower initial capacity when formation is conducted at 30 C. The initial capacity is significantly higher when formation is conducted at 55°C. 80 90 100 110 120 130 140 150 160 170 0 10 20 30 40 50 Cycle Number D is ch ar ge C ap ac ity , m A h/ g Gen2 Baseline 0.3wt%MP-formation cycle at 30degC 0.3wt%MP-formation cycle at 55degC 55°C formation 30°C formation 1st 2 cycles at C/12 rate Next 50 cycles at C/4 rate ~35mAh/g difference 0 2 4 6 8 10 12 14 0 5 10 15 20 25 Z (Re), ASI Z (Im g) , A SI 104 Hz 30°C formation 55°C formation Baseline electrolyte 1Hz 1Hz 1Hz MP N O O For cells with the MP electrolyte additive, the one formed at 55°C shows a lower impedance than the one formed at 30°C. 11 Mechanistic Hypothesis N O O Li N Li N O O LiN O O O O Li N O O Li Intramolecular bidentate binding offers strongest solvent Interaction with Li-ion Intermolecular bidentate interaction is weaker Monodentate binding has the weakest interaction in this group The SEI generated by the various additives is expected to bear signatures of the corresponding lithium-additive complexes. Stronger SEI/Li+ interaction may cause higher impedance. The “initial induction period” reflects changes in SEI characteristics during cycling. MP MN MIN 12 Initial Cycling behavior of NCA+/Gr- cells - Effects of Intramolecular bidentate binding 90 100 110 120 130 140 150 160 170 0 10 20 30 40 50 Cycle Number D is ch ar ge C ap ac ity , m A h/ g Gen2 Baseline, Disch 0.3wt% MP+Gen2, Disch 0.3wt%MMPC+Gen2, Disch 0.3wt%2-ETC+Gen2, DisCh 0.3wt%2-EF+ Gen2, Disch N O O O O O N O O S O O All additives with possible intramolecular bidentate binding site for Li-ion exhibit a long “initial induction period” during cycling Different heteroatoms have different binding affinities to the Li-ion; N and S binding to the Li-ion appears stronger than O 1st 2 cycles at C/12 rate Next 50 cycles at C/4 rate 2-EF MP 2-ETC MMPC 15 Philosophy Behind Study of GC derivatives - A Good System to Explore Novel Electrolytes  What is Glycerol Carbonate (GC)? Glycerol Carbonate is just an oxygen-substituted Propylene Carbonate! O O O OH O O O H H H H H + O Propylene Carbonate Glycerol Carbonate  What makes GC a good system to study? GC can be easily derivatized/modified. Therefore, it provides an excellent platform to study bi-/multi-functional electrolytes. O O O OH O O O X Note: X can be any functional group thanks to modern organic synthesis techniques Note: PC cannot be cycled with graphite anode but GC can.  Why its important to study bi-/multi-functional electrolyte systems? SEI formed by EC is good but not perfect, therefore electrolyte additives are often required. It is reasonable to believe that a better SEI can be achieved by introducing extra functionalities into the molecule. 16 Previously reported - GC and GCME data O O O OH Glycerol Carbonate O O O O O Glycerine carbonate methyl ester • Cell containing 1.2M LiPF6 in GC:DMC=2:8 can be cycled with graphite anode. • Surface film formation at the first cycle on oxide electrode indicates oxidation of GC. 0 0.4 0.8 1.2 1.6 2 0 100 200 300 400 Graphite vs. Li/Li+ C/15 rate, 2-0 V 1st cycle 2nd cycle 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 0 100 200 300 400 NCA (+) vs. Li/Li+ C/30 rate, 3-4.3 V 1st cycle 2nd cycle Surface film formation 0.0 0.5 1.0 1.5 2.0 2.5 0 100 200 300 400 1st cycle Graphite vs. Li/Li+ C/15 rate, 2-0 V 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 0 50 100 150 200 250 NCA(+) vs. Li/Li+ C/30 rate, 3-4.3 V 1st cycle 2nd cycle •Cell containing 1.2M LiPF6 in GCME:DMC=2:8 can be cycled with both graphite and oxide electrodes. 17 Evolution towards Glycerine Carbonate Methyl Carbonate (GCMC) O O O O O O O O O OH Glycerol Carbonate O O O O O Glycerine carbonate methyl ester • GC can be cycled with graphite anode without exfoliation! • However, oxidation potential of GC is low due to the free hydroxyl group. • Protection of free hydroxyl group in GC improves the cathodic stability significantly. O O O O O O Glycerine carbonate methyl carbonate (GCMC) O O O O O O O O O + O O O Ethylene carbonate (EC) Dimethyl carbonate (DMC) GCMC 20 GCMC can also be used as an electrolyte additive – data below is from NCA+/Gr- cells with 5wt% GCMC in baseline electrolyte O O O O O O 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14 16 18 20 Z (Real) Z (I m g ) Gen2 50 cycles Gen2+5wt%GCMC 50 cycles Gen2 150cycles Gen2+5%GCMC 150cycles 60 80 100 120 140 160 0 25 50 75 100 125 150 Cycle Number C ap ac ity , m A h/ g Gen2+5%GCMC Gen2 Baseline 30°C 3-4.1 V 1st 2 cycles at C/12 rate Next 50 cycles at C/4 rate Then 100 cycles at C/1 rate C/12 C/4 1C Impedance measured at 30 oC Cells with GCMC additive show improved capacity retention AC impedance data show that impedance of GCMC-bearing cells is similar to that of cells with baseline electrolyte during the first 50 cycles – the impedance is higher after longer term cycling (150 cycles) 21 Other promising GC derivatives are also being examined as electrolyte additives – data below is from NCA+/Gr- cells Cells containing 3wt% of additives A and B showed almost no capacity loss after 50 cycles at C/4 rate. Long-term cycling is in progress. 80 90 100 110 120 130 140 150 160 170 0 10 20 30 40 50 Cycle Number D is ch ar ge C ap ac ity , m A h/ g Gen2 Baseline, Disch 3wt%A+Gen2, Disch 3wt%B+Gen2, Disch 1st 3 cycles at C/12 rate Next 50 cycles at C/4 rate 30°C 3-4.1 V 0 2 4 6 8 10 12 0 2 4 6 8 10 12 14 16 18 Z (Real) Z (Im g) Gen2 50cycles 3wt%A+Gen2 initial 3wt%A+Gen2 50cycles 3wt%B+Gen2 initial 3wt%B+Gen2 50cycles Impedance measured at 30 oC C/12 C/4 The additive-containing cells have a slightly higher impedance than the baseline cells. However, cell impedance is unchanged after 50 cycles at C/4 rate. 22 Collaborations  Partners – Purdue University (A. Wei et al.) • Collaboration to synthesize derivatives of glycerol carbonate and other promising electrolyte additive compounds – University of Rhode Island (B. Lucht et al.) • Collaboration to determine changes at the electrode-electrolyte interface using surface analysis techniques. – Colleagues at Labs (ARL, JPL) • Collaboration to evaluate electrolyte additives or solvents to facilitate/accelerate the development process. – Industry Colleagues • Collaborations to evaluate novel compounds in ABR cells  Technology Transfer – Knowledge generated during the course of our studies is shared with colleagues in US battery industry through presentations, articles, and reports