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Electrochemical Flash Sintering as a new tool to obtain all solid-state batteries in few seconds – FLASHBAT

Submission summary

Today, a considerable effort is being made worldwide to develop inorganic all solid-state batteries (ASSB) that provide greater safety and energy density than conventional Li-ion batteries. The development of such ASSBs is limited by the processing of the inorganic active materials (AM), electrolyte and electronic additives. Indeed, the electrodes are composites that must be compact with intimate and stable interfaces between the different materials to allow a reversible charge transfer, which is generally realized by high temperature sintering process. In addition, a full battery is composed of two composite electrodes sandwiching the ceramic electrolyte with again the need of forming low impedance interfaces. Therefore, the direct realization of inorganic ASSB corresponds to the assembly of multi-materials by co-sintering which must take into account several locks: compatible materials in terms of "sintering windows" (chemical compatibility, sintering temperature and coefficient of thermal expansion); cohesive and intimate interfaces between the materials to ensure a good mechanical hold and to get low resistance for the interfacial charge transfer; finally a self-supported batteries with high areal capacity. In this context, our main objective is to demonstrate the feasibility of assembling a functional prototype of Li-ion ASSB based on a new ultra-fast sintering method called (Electrochemical) Flash Sintering (EFS) that allows a full preform sintering in few seconds, which would renew the field and open new paths for the development of such safe and high energy density technology.
Flash Sintering brings a different perspective to the selection of materials for sintering of a multi-layer material. Indeed, the first criterion for flash sintering is the electrical behavior, in particular the conductivity of each material, which determines the sintering conditions. This project proposes the development of a promising process through a fundamental approach coupling the preselection and synthesis of the materials, understanding of the electrochemical and physicochemical mechanisms governing heating, interface formation and densification. Before obtaining operational prototype of Li-ion ASSB that operates reversibly for 100 cycles at RT with at least an areal capacity of 5 mAh/cm2, several challenges have to be tackled. They concern 1/ the choice of the materials, 2/ the optimization of the EFS process parameters together with the formulation of the composite electrodes and the geometrical parameters of the ASSB, 3/ the reversibility of the electroactive interfaces together with their mechanical integrity along cycling. To solve these issues we have planned 4 WPs that corresponds to the different skills of the partners:

- WP1: Materials synthesis and characterization. Different types of active materials and electrolytes with as first criteria of choice the thermal stability and the compatibility of the structures will be synthetized by CRISMAT.

- WP 2: Flash electrochemical sintering. This central WP will be dedicated to the manufacturing of ASSB in a single step by EFS, controlling the flash phenomenon (thermal runaway) and exploring the relationship between temperature, microstructure, conductivity and thermal production by Joule effect by relying on the great expertise of two partners LEPMI and SIMAP on this technique.

- WP3: Modeling densification along EFS. Modeling of heating and sintering under electric current will be carried out at SIMAP using COMSOL finite element code at macroscopic scale. This will help to optimize the electrode formulation, the AASB geometrical parameters, and the process parameters.

- WP4: Advanced electrochemical characterizations. A new methodology will be developed to analyze operando the charge transfer processes trough the compact along the flash. The electrochemical behavior and the performance of the ASSB produced in WP2 will be deeply characterized thanks to the LEPMI facilities.

Project coordination

Renaud Bouchet (Laboratoire d'Electrochimie et de Physico-chimie des Matériaux et des Interfaces)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

LEPMI Laboratoire d'Electrochimie et de Physico-chimie des Matériaux et des Interfaces
SIMaP Sciences et Ingénierie, Matériaux, Procédés
CRISMAT LABORATOIRE DE CRISTALLOGRAPHIE ET SCIENCES DES MATERIAUX

Help of the ANR 393,660 euros
Beginning and duration of the scientific project: January 2021 - 42 Months

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