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ELECTRODE MATERIALS FOR LITHIUM BATTERIES.

Objective

INVESTIGATION OF THE PERFORMANCE (CYCLABILITY, STABILITY KINETICS; CAPACITY AND ENERGY CONTENT) OF NEGATIVE ELECTRODES (LI-RICH COMPOUNDS) AND POSITIVE ELECTRODES (INTERCALATION COMPOUNDS, P-DOPED SEMICONDUCTING POLYMERS) IN LITHIUM ORGANIC ELECTROLYTE BATTERIES.
An investigation has taken place of the kinetics of negative and positive electrodes of interest for the development of solid state, polymer electrolyte, lithium batteries.
The electrode materials considered were: metal lithium, vanadium bronze lithium intercalation compounds and redox etherocyclic polymers (eg polypyrrole). These electrodes were characterized in terms of electrochemical and chemical stability, reversibility and cyclability in solid state cells using polyethylene oxide (PEO), PEO-lithium salt complexes as model polymer electrolytes.

The experimental techniques used for this characterization were mainly: cyclic voltammetry, impedance spectroscopy, galvanostatic and potentiostatic cycling. The results clearly indicate that the electrode materials selected, such as chain modified polypyrroles and of amorphous lithium and sodium bronzes, are very promising for the realization of high energy, long life, rechargeable lithium batteries. Preliminary performance tests carried out in small laboratory cell prototypes have indeed confirmed that these batteries may offer energy densities of the order of 100 Wh kg{-1} and cycle lifes of the order of several hundred cycles.
THE DEVELOPMENT OF RECHARGEABLE LITHIUM BATTERIES HAS NOT BEEN COMPARABLY FAST, MAINLY BECAUSE OF ELECTRODE CYCLABILITY PROBLEMS. IN PARTICULAR THE LITHIUM ELECTRODE SUFFERS OF POOR CYCLABILITY DUE TO UNAVOIDABLE REACTIONS WITH THE ELECTROLYTE SYSTEMS, WHILE THE POSITIVE ELECTRODES, GENERALLY OF THE INTERCALATION TYPE, SUFFER OF VOLUME CHANGES DURING THE CYCLING LIFE.

THESE PROBLEMS HAVE BEEN FACED WITH THE CHARACTERIZATION OF 'OPTIMIZED' ELECTROLYTES SYSTEMS (BOTH IN THE LIQUID AND IN THE SOLID STATE) AND WITH THE USE OF IMPROVED ELECTRODE MATERIALS.

HOWEVER IT SEEMS THAT FOR REACHING THE STATE OF VAST COMMERCIAL PRODUCTION, IS STILL NECESSARY TO DEVOTE CONSISTENT ATTENTION TO THE ELECTRODE MATERIALS, IN ORDER TO OBTAIN OVERALL ELECTROCHEMICAL SYSTEMS WHICH CAN ADEQUATELY EXPLOIT THE EXCELLENT CAPABILITIES OF THE NEW ELECTROLYTE MATERIALS (SOLID OR LIQUID). IN PARTICULAR, NEGATIVE ELECTRODES WITH HIGHER CYCLABILITY THAN PURE LITHIUM METAL AND POSITIVE ELECTRODES WITH BETTER STRUCTURE RETENTION THAN THE MOST COMMON INTERCALATION COMPOUNDS, WOULD BE GREATLY WELCOME AT THIS STAGE.

THE FOLLOWING RESEARCH PROGRAMME RELATED TO NEGATIVE AND POSITIVE ELECTRODES IN LIQUID ORGANIC ELECTROLYTE LI BATTERIES IS PROPOSED.

A.- NEGATIVE ELECTRODES:
A.1. INVESTIGATION OF THE PERFORMANCE (CYCLABILITY AND STABILITY) OF LI METAL ELECTRODES IN LIQUID ORGANIC AND SOLID POLYMERIC ELECTROLYTES.

A.2. CHARACTERIZATION OF NEGATIVE ELECTRODES ALTERNATIVE TO LI METAL, IE LI-RICH COMPOUNDS AND INVESTIGATION OF THEIR CYCLABILITY, OPERATIONAL VOLTAGE, KINETICS, CAPACITY AND ENERGY CONTENTS.

B.- POSITIVE ELECTRODES.
B.1. CHARACTERIZATION OF INTERCALATION COMPOUNDS WITH PARTICULAR CONCERN TO CAPACITY, SPECIFIC ENERGY AND STRUCTURE RETENTION UPON CYCLING.

B.2. EVALUATION OF THE PROPERTIES (COULOMBIC EFFICIENCY, STABILITY, SPECIFIC ENERGY) OF P-DOPED SEMICONDUCTOR POLYMERS.

THE BODIES INVOLVED IN THE PROJECT ARE THE UNIVERSITIES OF ROMA " LA SAPIENZA ", " TOR VERGATA ", OF BOLOGNA AND OF CAMERINO.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Università degli Studi di Camerino
Address
Via Sant'agostino
62032 Camerino
Italy

Participants (3)

UNIVERSITY OF BOLOGNA
Italy
Address
Via Francesco Selmi 2
40126 Bologna
UNIVERSITY OF ROME "LA SAPIENZA"
Italy
Address
2,Piazzale Aldo Moro 5
00185 Roma
UNIVERSITÀ DEGLI STUDI DI ROMA TOR VERGATA
Italy
Address
Via Della Ricerca Scientifica 1 Edificio Sogene
00133 Roma