Project

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Synthetic Solid Electrolyte Interphase on Carbon Electrodes for Lithium-Ion Batteries

English title Synthetic Solid Electrolyte Interphase on Carbon Electrodes for Lithium-Ion Batteries
Applicant Novák Petr
Number 124695
Funding scheme Project funding
Research institution Labor für Elektrochemie Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Physical Chemistry
Start/End 01.04.2009 - 31.07.2012
Approved amount 163'883.00
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All Disciplines (2)

Discipline
Physical Chemistry
Inorganic Chemistry

Keywords (12)

Interfaces; In situ methods; Synthesis; Characterization; Non-aqueous electrolytes; Electrochemical energy storage; Lithium-ion batteries; energy storage devices; batteries; carbon electrodes; interface electrochemistry; infrared spectroscopy

Lay Summary (English)

Lead
Lay summary
The challenge of this project is the characterization of surface films formed on carbon negative electrodes of lithium-ion batteries and the preparation of such films by chemical synthesis. In more detail, all the electrolytes used today in lithium-ion batteries are thermodynamically unstable at the very negative potential of lithiated graphite electrodes. Reductive decomposition of the electrolyte at the electrode surface leads to formation of a surface film - the Solid Electrolyte Interphase (SEI) - which prevents further degradation of the electrolyte. While the SEI is of key importance for the function of lithium-ion batteries, many questions about its composition remain unresolved. In this project we address these open scientific questions by chemical synthesis of SEI components and subsequent deposition of SEI-like layers on carbon materials. Electrochemical properties and analytical data of electrodes covered with synthetic layers will be compared with data obtained from real electrodes. Thereby the goal is to prove or disprove the different models for the structure of the SEI proposed in the past.The project is divided into two tasks, namely the synthesis of products mimicking the surface layers on negative electrode materials, and the development of novel analytical tools for the characterization thereof.The SEI layers are made up of two main compound classes - inorganic lithium salts and polymeric products stemming from the degradation of electrolyte solvents. Chemical synthesis of these compounds will be done in our laboratory, and they will be deposited onto carbon materials. At a later stage, polymers will be covalently grafted to the surface of graphite powders. Composite electrodes containing this graphite will be prepared and tested in battery cells. Due to the particular properties of the SEI - a very thin film consisting of a variety of inorganic, organic, and polymeric molecules - special analytical methods are needed for its characterization. In situ methods for the spectroscopic and electrochemical characterization of battery materials are already established in our laboratory, and will be used to study the newly synthesized materials. A new advanced in situ cell for infrared spectroscopy will be tested and used to investigate the influence of electrolyte additives. Pre-coating of graphite electrodes with synthetic SEI layers could ultimately lead to a reduced irreversible charge capacity in the first charging cycles of lithium-ion batteries and therefore to higher energy densities. Once the identity and function of the different SEI components is cleared, tailor-made layers for specific applications can be prepared.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Formation of Artificial Solid Electrolyte Interphase by Grafting for Improving Li-Ion Intercalation and Preventing Exfoliation of Graphite
Verma Pallavi, Novák Petr (2012), Formation of Artificial Solid Electrolyte Interphase by Grafting for Improving Li-Ion Intercalation and Preventing Exfoliation of Graphite, in Carbon, 50(7), 2599-2614.
Surface Layer Formation on Li1+xMn2O4-δ Thin Film Electrodes during Electrochemical Cycling
Simmen Franziska, Foelske-Schmitz Annette, Verma Pallavi, Horisberger Michael, Lippert Thomas, Novák Petr, Schneider Christof Walter, Wokaun Alexander (2011), Surface Layer Formation on Li1+xMn2O4-δ Thin Film Electrodes during Electrochemical Cycling, in Electrochim. Acta, (56), 8539-8544.
A Review of the Features and Analyses of the Solid Electrolyte Interphase in Li-Ion Batteries
Verma Pallavi, Maire Pascal, Novák Petr (2010), A Review of the Features and Analyses of the Solid Electrolyte Interphase in Li-Ion Batteries, in Electrochim. Acta, 55(22), 6332-6341.
Concatenation of Electrochemical Grafting with Chemical or Electrochemical Modification for Preparing Electrodes with Specific Surface Functionality
Verma Pallavi, Maire Pascal, Novák Petr (2010), Concatenation of Electrochemical Grafting with Chemical or Electrochemical Modification for Preparing Electrodes with Specific Surface Functionality, in Electrochim. Acta, 56(10), 3555-3561.
Chemical Surface Treatments for Decreasing Irreversible Charge Loss and Preventing Exfoliation of Graphite in Li-Ion Batteries
Verma Pallavi, Sasaki Tsuyoshi, Novák Petr, Chemical Surface Treatments for Decreasing Irreversible Charge Loss and Preventing Exfoliation of Graphite in Li-Ion Batteries, in Electrochim. Acta.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
14th International Union of Pure and Applied Chemistry Conference on Polymers and Organic Chemistry (POC 2012) Talk given at a conference SEI modification of graphite 08.01.2012 Doha, Qatar, Qatar Novák Petr;
EMPA PhD Students’ Symposium 2010 Talk given at a conference SEI modification of graphite 07.10.2011 Dübendorf, Switzerland Verma Pallavi;
International Society of Electrochemistry Annual Meeting 2010 Talk given at a conference SEI modification of graphite 26.09.2011 Nice, France, France Verma Pallavi;
62nd ISE Annual Meeting Talk given at a conference SEI modification of graphite 12.09.2011 Niigata, Japan, Japan Novák Petr;
Lithium Batteries Discussion 2011 Talk given at a conference SEI modification of graphite 12.06.2011 Arcachon, France, France Novák Petr;
27th One-Day-Symposium of the Electrochemistry Laboratory on Electromobility Talk given at a conference SEI modification of graphite 11.05.2011 Villigen, Switzerland Verma Pallavi;
General Energy Department Seminar Individual talk SEI modification of graphite 07.04.2011 Villigen, Switzerland Verma Pallavi;
EMPA PhD Students’ Symposium 2009 Talk given at a conference SEI modification of graphite 09.11.2009 Dübendorf, Switzerland Verma Pallavi;


Knowledge transfer events

Active participation

Title Type of contribution Date Place Persons involved
Fährt das Auto der Zukunft mit Batterien? Talk 31.03.2011 Böttstein, Switzerland Novák Petr;
GreentechEvent Talk 25.10.2010 Windisch, Switzerland Novák Petr;


Associated projects

Number Title Start Funding scheme
129508 New Oxyphosphates as High Specific Charge Electrode Materials for Lithium-Ion Batteries 01.04.2010 Project funding
103715 Synthesis and Characterization of Advanced Electroactive Materials for Electrodes of Rechargeable Lithium-Ion Batteries 01.04.2004 Project funding
117607 Advanced materials for efficient portable energy supplies 01.10.2007 Project funding

Abstract

SummaryThe great scientific challenge of this project is the characterization of surface films formed on carbon negative electrodes of lithium-ion batteries and especially the preparation of such films by chemical synthesis. In more detail, all the electrolytes used today in lithium-ion batteries are thermodynamically unstable at the very negative potential of lithiated graphite electrodes. Reductive decomposition of the electrolyte at the electrode surface leads to formation of a surface film - the Solid Electrolyte Interphase (SEI) - which prevents further degradation of the electrolyte. The SEI is of key importance for the function of lithium-ion batteries, and its formation and composition have been the objects of many scientific studies in the past. Despite these efforts, many scientific questions about the SEI composition remain unresolved. Herein we propose to address these open scientific questions by chemical synthesis of SEI components and subsequent deposition of SEI-like layers on carbon materials. Electrochemical properties and analytical data of electrodes covered with synthetic layers shall be compared with data obtained from real electrodes. Thereby the goal is to prove or disprove the different models for the structure of the SEI proposed in the past.The project is divided into two tasks, namely the synthesis of products mimicking the surface layers on negative electrode materials, and the development of novel analytical tools for the characterization thereof. The two interrelated tasks will be tackled in parallel, in order to benefit from mutual synergy effects and to verify continuously whether the spectroscopic and electrochemical properties of the synthesized materials are identical to those of the “natural” SEI.The SEI layers are made up of two main compound classes - inorganic lithium salts and polymeric products stemming from the reductive degradation of carbonate solvents. While the former are mostly commercially available, the synthesis of the polymeric products will be done in our laboratory using modern synthesis tools like transition metal catalyzed reactions and radical reactions. A special focus will be on polymers resembling the products originating from film forming additives like vinylene carbonate. The polymers will be deposited from solutions onto carbon materials either in pure form or as (stratified) layers together with other SEI components. At a later stage polymers will be covalently grafted to the surface of graphite powders and other carbon materials. Selected polymers will be further modified, e.g. by crosslinking or co-polymerization with other monomers in order to prepare hybrid materials acting as SEI and binder. Composite electrodes will be prepared using these polymers. Due to the particular properties of the SEI - a very thin film consisting of a variety of highly air sensitive inorganic, organic, and polymeric molecules - special analytical methods are needed for its characterization. In situ methods for the spectroscopic and electrochemical characterization of battery materials are already established in our laboratory and will be used to study the newly synthesized materials. An advanced in situ cell for infrared spectroscopy with the possibility to exchange the electrolyte will be tested and used to investigate the influence of electrolyte additives. To avoid the common drawback of in situ cells for infrared spectroscopy, i.e. the strong absorption of infrared light by the electrolyte, a completely new setup based on optically transparent carbon electrodes will be tested. An ATR-crystal coated with a nanolayer of graphitized carbon will serve as model electrode. Surface films formed electrochemically on top of this electrode can then be monitored from the backside, with less interference of the electrolyte solvents. Supporting synchrotron based methods like infrared microscopy shall be used to investigate the homogeneity of SEI layers on graphite powders. Pre-coating of graphite electrodes with synthetic SEI layers will ultimately lead to a reduced irreversible charge capacity in the first charging cycles of lithium-ion batteries and therefore to higher energy densities. Once the identity and function of the different SEI components is clarified, tailor-made layers for specific applications can be prepared. Layers with better high temperature stability could improve the safety and lifetime of lithium-ion batteries, and layers with reduced resistance could lead to batteries with higher power capability.
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