Green Materials & Processes of Lithium-Ion Battery

Transcription

1 Nano and Advanced Materials Institute (NAMI) Green Materials & Processes of Lithium-Ion Battery Paul Ho 1

2 Content NAMI Lithium-ion Battery Researches Green Materials & Processes for Lithiumion Battery Sustainable and Biodegradable Polymeric Separator Non-fluorinated Binding Materials for Battery Electrode Green Manufacturing Process for Lithiumion Battery Summary 2

3 NAMI: An Applied Research Centre NAMI established in 2006 by Hong Kong Government to be an integral part of Hong Kong s Applied Research Eco-system Applied Research Eco-system Applied R&D Centres Academia, Universities Industry, Startups Ideas Research Bench-top Prototypes Technology Development Scale-up Manufacturing Refinement Traditional Research, Development & Implementation Cycle 3

4 The Promise of NAMI NAMI s mission is to develop competencies on advanced materials to support industries with technology upgrade while developing talents Developing core competencies on advanced materials Providing technology upgrade to local enterprises Training researchers for HK s talent pool 4

5 Market Sector & Core Competence Sustainable Energy Bio & Healthcare Solid State Lighting & Display Environmental Technologies Construction Materials 5

6 NAMI Talents Academic Qualification Develop talent pool Degree 17% Establish a network of professionals NAMI Mentoring Program Provide motivation Master 32% PhD 51% Share the skills, knowledge, experience and insight Areas of Research Offer support Chemistry/Chemical Engineering/Biochemistry Material Science/Materials Engineering Physics Mechanical/Electrical/Electronic Engineering/Civil Engineering Biochemistry/Biotechnology/Environmental Engineering Overseas Graduate 15% Mainland Graduate 11% HK Graduate 74% ~150+ experts conduct materials R&D for industries 6

7 NAMI Lithium-ion Battery Researches 7

8 Rechargeable Lithium-ion Battery Market Lithium-ion battery is growing rapidly because of the excellent energy density and reasonable cost The market is ~ $22 billion in 2012 and will grow to ~ $78 billion in Growth is expected in all segments, with significant growth in renewable energy storage and HEVs/EVs. We are concurrently running more than 10 Lithium-ion battery applied research projects for our industrial sponsors Global Lithium-based Battery Market (in USD Billion), Source: International Information Technology

9 NAMI s Lithium-ion Battery Materials Cathode Anode Electrolyte Separator Doped nano-lmo with high power density Doped nano- LTO with high power density LTO-coated graphite with good lowtemperature performance Additives offers thermal protection Additives offers overcharge protection Electrospun PVDF with high porosity Li-rich NMC with high energy capacity Core@shell Si with high energy density High voltage electrolyte formulation Ceramic-coated separator

10 Products and Applications from NAMI s Lithium-ion Battery Materials Fast-Charging High Power Safe Extreme Temperature Wearable Devices

11 Green Materials & Processes for Lithium-ion Battery 11

12 Lithium-ion Battery Manufacturing Steps for Lithium-ion Battery Manufacturing Electrode Coating: The active electrode materials are coated on metallic foils Cell Assembly: Separator is sandwiched between the anode and the cathode and assembled into casing Formation: Activate the battery materials and transforming them into a cell ready to be used Mixing Coating Pressing Assembly Formation Aging Products

13 Lithium-ion Battery Manufacturing Challenges for Environment and Sustainability Conventional Organic solvent-based slurry for electrode preparation Issues: 100% recycled required, high energy consumption due to high boiling point Fluorinated polymer as binder for electrode materials Issues: Waste and pollution Synthetic polymer as separator Issues: Waste and pollution

14 Lithium-ion Battery Manufacturing NAMI Green Materials & Processes NAMI Green LIB Water as Solvent for both cathode and anode electrodes preparation Non-fluorinated Water Soluble Binder Natural Polymer derived separator

15 Separators Characteristics and Structures Requirements for separator in Lithium-ion Battery Chemically and electrochemically stable even under repeated cycles of charging-discharging No release of impurities over time Compatible with corrosive electrolyte at elevated temperatures Structure of separators Microporous membrane separators (Fig. 1) Modified microporous membrane separators (Fig. 2) Non-woven mat separators (Fig. 3) Fig. 1 Fig. 2 Fig. 3

16 Typical Separator Materials Base Materials for Common Separators in Lithium-ion Battery Microporous membrane separators, e.g. poly(propylene (PP), poly(ethylene) (PE), poly(vinylidene fluoride) (PVDF), poly(acrylonitrile) (PAN) and poly(methyl methacrylate) (PMMA) Modified microporous membrane separators, e.g. PP, PE and PVDF Non-woven mat separators, e.g. PVDF, PAN and poly(imide) (PI) Impacts to Environment All are non-biodegradable polymers The production of these polymers emits greenhouse gases PVDF is a fluorinated polymer and will emit fluorinated gas during incineration PP PE PVDF PAN PMMA PI

17 Sustainable Polymeric Materials Green Separators A sustainable polymer is a plastic material that addresses the needs of consumers without damaging our environment The feedstock for sustainable plastics are renewable, such as plants. Cellulose in plants is one of sustainable and renewable feedstock as the base materials for the separator in lithium-ion battery Cellulose-based Composite Nonwoven Separator Nonwoven separator has higher porosity and thus higher conductivity and better rate capability and capacity retention Good electrolyte wettability High thermal stability due to low shrinkage Needs to functionalize to improve stability Cellulose A SEM image of cellulose-based composite nonwoven separator

18 Typical Binder and Solvent Requirements for Binders used in Lithium-ion Battery Chemically and electrochemically stable, under repeated charging-discharging cycles Compatible with electrolyte at elevated temperatures PVDF NMP Common Electrode Binder and solvent Poly(vinylidene fluoride) or PVDF is widely adopted as binder for both the anode and cathode slurries Organic solvent N-methyl-2-pyrrolidone or NMP is used to dissolve PVDF for the preparation of slurry in the electrode coating step. Impacts to Environment PVDF is a non-biodegradable fluorinated polymers, which release fluorinated gas during incineration NMP is an organic solvent which needs to be 100% recovered Impacts to Lithium-ion Battery Cost and Performance PVDF and NMP are relative expensive Fluorinated compound from PVDF degradation can shorten the battery lifespan

19 Green Binder Materials Candidates include sodium carboxymethyl cellulose (CMC) / styrene-butadiene rubber (SBR), polyvinyl pyrrolidone (PVP) and polyethyleneimine (PEI) and their derivatives They allow the use of water as solvent (water soluble binders) and create less environmental problem Ease of processing NMP has a boiling point of > 200 C and thus reduce energy cost of drying Reduce burden on exhaust and humidity control Use of natural polymer will further enhance the sustainability CMC SBR Sodium Alginate

20 Typical Cell Manufacturing Process Mixing of the electrode materials Coating of the substrate and drying of the NMP organic solvent Minimization of porosity by means of compression Film cutting, cell stacking and electrolyte filling Activation by specific charging-discharging program Mixing Coating Pressing Assembly Formation Aging Products

21 Green Cell Manufacturing Process Water is used as solvent comparing to the use of expensive and harmful organic solvent NMP Green binder that is soluble in water will be used, natural and/or fluorinefree polymer will be used Ease of process control (humidity), no VOC issue, save energy for the drying process Water Vapor to be removed instead of NMP

22 Comparison Table Conventional lithium-ion battery Green lithium-ion battery Binder for electrode fabrication Binders soluble in organic solvent only (e.g. PVDF) Water-soluble binders Solvent for electrode fabrication N-methyl-2-pyrrolidone (NMP) Water Solvent toxicity High Nil Operational / material costs Processing energy for electrode coating Waste treatment / Exhaust or solvent recovery High NMP, ~US$ 25/L PVDF, ~US$ 20/kg High NMP b.p. > 200 C Complicated Low Deionized water, ~US$ 0.015/L Water-based binder, ~US$ 5.6 /kg Low Water b.p. 100 C Simple

23 Green Cell Manufacturing Process in NAMI Anode Slurry Anode Coating Cathode Slurry Cathode Coating Anode drying Cathode drying Coating steps of anode and cathode electrodes

24 Capacity Retention / % Green Lithium-ion Battery Cell Performance NMP-based Process (PVDF binder) Water-based Process (water-based binder) Battery cell: Anode: graphite Cathode: LCO Separator: ceramic coated nonwoven PET Cycle number For comparison, same cathode and anode formulations were used except the binders The first cycle efficiency is virtually the same between the two batch of cells made by the two different binders shown The impedances of the two cells are comparable There is no difference in cycling performance

25 Summary Green materials and processes can be used in Lithium-ion battery manufacturing without impacting the cell performance The overall manufacturing is more sustainable and the cost can be reduced More research and development is needed to formulate and functionalize new materials to allow the use of these green materials and processes 25

26 ENERGY GENERATION ENERGY STORAGE ENERGY SAVING 26