Thermal runaway inhibiting electrolytes

Transcription

1 Thermal runaway inhibiting electrolytes Surya Moganty, PhD CT HMs Technologies Y-BEST Energy Storage Technology Conference

2 utline Li-ion battery- Safety challenges Liquid electrolyte systems HMs functional materials Electrolyte design- abuse tolerance Case study- Consumer battery LC-Graphite chemistry High voltage cycle life Mechanical Abuse tests Summary HMs Confidential 2

3 ano rganic Hybrid Materials HMs started in 2010 from Cornell University US Government Support S, US Air orce, ASA, DARPA, IH, USABC/DE and YSERDA Venture Capital Phoenix Venture Partners and Solvay Ventures Corporate partnerships business model Joint Development (JDA) with automotive, battery, and chemical companies Access to development tools at Kodak, including chemical and roll-to-roll pilot manufacturing plant. HMs Confidential 3

4 Li-ion Battery Safety: A Concern HMs Confidential 4

5 Thermal run away Causes of high temperature in the battery cell: 1. External short circuit (impact) 2. Internal short circuit 3. vercharge (abuse) 4. ver discharge (abuse) 5. External heating 6. ver heating by self-heating Heat dissipation < Heat generation Thermal runaway Venting, rupture ire/explosion Elevated temperature Generation of gas and more heat Heat dissipation > Heat generation Safe utcome HMs Confidential 5

6 Li-ion Electrolyte- the fuel Lithium Hexafluorophosphate Conducting Salt Thermally unstable Decomposes to corrosive acids (H) Ethylene Carbonate (EC) orms SEI on graphite anodes, conducts Li + Solid at room temperature Precipitates at low temperatures (MP 34 o C) Linear Carbonates (DMC, DEC, EMC) Solvates conducting salt and EC Highly flammable Unstable at high voltages (> 4.2V) luorinated solvents unctional additives HMs unctional Ionic Liquids C 3 S Si P Si B Si HMs Confidential R R S S R R S S 6

7 HMs functional materials Ionic liquids Salts with melting point below 100 o C Bulky cation, anion: Ionic Conductivity Wide redox stabilities Ultralow vapor pressure Thermally stable many have liquid ranges > 300 o C Reasonable viscosity range ~ cp Designer Solvents :Task specific nature! Viscosity and hydrophilicity can be adjusted by suitable choice of cation and anion n G n Hetro-cyclic Cation family containing a functional group S S TSI Anion HMs Confidential 7

8 HMs functional Ionic liquids n S S G n Hetro-cyclic Cation family TSI Anion containing a functional group 2 Decomposition Temp >300 o C Conductivity (ms/cm) Temperature ( o C) EC:EMC 3:7 1MLiP6 HMs HVE36 HMs HVE133 HMs HVE137 HMs HVE HMs Confidential 8

9 Charging to higher voltages Lithium-cobalt-oxide (LC) cathode materials are used in li-ion battery for mobile electronics. LC stores 30% more capacity when charged to high voltage. However, today s electrolytes have limited voltage and temperature stability Voltage V Energy Wh/L Voltage_V V 4.4V 4.45V 4.5V Capacity_mAh HMs Confidential *Cell phone battery 9

10 High voltage sensitivity- Cycle life 4.4V 4.2V 4.5V HMs designed electrolytes showed showed excellent high voltage stability against LC cathodes. Capacity (Ah) Charged to 4.2V Charged to 4.2V Charged to 4.45V Charged to 4.45V 20% more capacity Graphite-LC 5 Ah Pouch cells C/2 Rate Room Temp Cycles HMs Confidential 10

11 Challenges with high energy ully charged LC cathode releases oxygen upon abuse (mechanical, electrical and thermal) Thermal runaway results in fire and explosion 11 HMs Confidential

12 Abuse tolerant electrolytes Electrolyte Composition 1MLiP 6 Viscosity cp Discharge Ah icl % Base line EC:EMC 3: anolyte_1 HMs (>12%) anolyte_2 HMs (>12%) anolyte_3 HMs (>35%) HMs designed electrolytes showed decent transport properties and similar discharge capacities and icls during formation Discharge capacity LC charged to 4.4V HMs Confidential 12

13 Abuse test- ail puncture test HMs electrolyte Base line electrolyte HMs Confidential 13

14 Abuse test- Cell temperature RD571 HMs anolyte 01 HMs anolyte 02 HMs anolyte 03 Temp ( C) Time (s) HMs designed electrolytes showed excellent abuse tolerance All three electrolytes did not show an event and the temperature raise is below 100 o C HMs Confidential 14

15 Summary Electrolyte plays critical role in dictating the life and use of Li-ion batteries Electrolyte is the fuel in the battery. During abuse conditions temperature of the cell increases and causes thermal runaway, which leads to fire and explosion HMs designed electrolyte families that over come thermal runaway challenges in high energy Li-ion battery chemistries Developing electrolytes for other chemistries MC, CA, LP, LM for automotive applications (PHEVs and EVs) Electrolyte for safe, long lasting, and low cost lithium ion battery. HMs Confidential 15