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All-Solid-state litHium sulfUr Battery with a poLymer Electrolyte – SHUTTLE

All-solid-state lithium sulfUr battery with a polymer electrolyte

High energy density, low cost, and safe battery devices are a need to promote the energy transition. To answer this challenge, all-solid-state Li-sulfur batteries are a promising solution. However, achieving an efficient combination between a sulfur cathode and a Li anode remains a challenge. The proposed solution is to design an adapted polymer electrolyte acting as battery separator and cathode binder stable with Li metal and blocking the polysulfide redow shuttle.

Main objective: mitigate polysuldife redox shutlle in solid-state Li-sulfur comprising a functionnalized polymer electrolyte

Li metal is the best negative electrode due to its low electrochemical potential and high capacity, at least 10 times higher than that of graphite in Li-ion battery. However, the uneven Li electrodeposition onto metallic Li produces dendrites limiting the battery coulombic efficiency and which may grow until a short. To overcome this safety issue, a solution is to replace the conventional flammable liquid electrolyte by an inherently non-flammable solid polymer electrolyte (SPE). Among the SPE families, single-ion conducting block copolymer electrolytes are of interest as their cationic transference number of unity avoids ionic gradient concentration during battery operation which favors dendrite growth.<br />On the positive electrode, the most attractive active material is sulfur (S8) thanks to its low cost, low toxicity, recycling possibilities, and high capacity (1675 mAh/g) roughly ten times higher than transition-metal oxides. However, the reduction products, lithium polysulfides onset a redox shuttle when dissolved in the electrolyte leading to low coulombic efficiency and collapse of the electrode microstructure. The delivered capacity of the positive electrode is also a fraction of the theoretical one due to the insulating nature of the final product (Li2S) that precipitates at the electrode surface. The use of a functionalized polymer electrolyte may help to prevent these issues.

The SHUTTLE project belongs to the ANR Young Researcher call, so the project is decomposed is different main tasks with a management task and three scientific tasks. SHUTTLE is a multidisciplinary project that connects the dots between the fields of polymer science (synthesis and characterizations), electrochemistry (electrodes, electrolytes, interfaces) and materials science (characterizations by X-ray and Neutron tomography).

The main results are listed below:

• Task 1: polymer characterizations
Polymers were successfully produced at Institut de Chimie Radicalaire (Aix Marseille University).

• Task 2: Characterizations of the materials and interfaces
Sulfur based composite electrode were formulated to be tested in Li metal battery.

• Task 3: operando characterization
An article was published as open-access in Frontiers in Energy Research (DOi: 10.3389/fenrg.2021.657712) in June 2021. This wok is a proof-of-concept of the use of Neutron tomography to study Li electrodeposits by taking advantage if the difference in Neutron attenuation between natural Li and 6Li isotope. The electrochemical cell imaged by Neutron tomography was also imaged by X-ray tomogrpahy at a laboratory (SIMAP, Grenoble) and at the SOLEIL synchrotron (Gif-sur-Yvette).

As perspective, each task of the project will be pushed forward before being connected in order to develop an original battery assembly. In this context, a electrochemical cell adapted for solid-state battery will be designed and optimized to be compatible with tomography apparatus (laboratory X-ray scanner, synchrotron X-ray, Neutron source). These non-invasive technics permit to probe the materials and hidden interfaces during cycling. At last, through this instrumental development a tomography lab setup will be created and, after optimization, open to the scientific community interested in collaboration in materials for energy devices.

1. L. Magnier et al., Frontiers in Energy Research 9 (2021) 266. (DOI:: 10.3389/fenrg.2021.657712, open access)

Energy production and storage are great challenges to ensure the energetic transition. High energy density, low cost, with extended cycle life batteries must be developed to promote renewable stationary applications (solar and wind farm) and electrified transport. Since their market introduction in 1991, lithium (Li)-ion batteries are the dominant solutions to power small electronic portable devices and are now used in most of the modern hybrid and full electric cars. However, for all of these applications this accumulator is not fully adequate because its energy density should be increased by factor two at minimum to answer the demand of the market whereas their energy levels off at about 250 Wh/kg due to their maturity. In addition, the presence of flammable liquid electrolyte is a strong safety issue (fire, explosion). To overcome these limitations a solution is to replace the unsafe liquid electrolyte by an inherently non-flammable solid polymer electrolyte. In addition to safety, the other advantage of polymer electrolytes resides in their chemical and electrochemical stability toward metallic Li. This material is ideally suited as negative electrode because of its high specific capacity (3860 mAh/g). At the positive electrode side, an interesting active material is sulfur (S8). The specific capacity of sulfur is important (1675 mAh/g) and permits to envision Li-S8 batteries with a specific energy density in the order of 500 Wh/kg, roughly twice that of conventional Li-ion accumulator. However, many hurdles remain to be solved to favor this battery technology such as the lithium polysulfides dissolution in to the electrolyte upon cycling (redox shuttle effect) which impairs the delivered capacity and the faradaic efficiency, and the prevention of dendrite growth at the negative electrode leading to short-cut issues. In this context, the project proposes to design an all-Solid-state litHium sulfUr baTTery with a poLymer Electrolyte (SHUTTLE). The goal is to develop a reliable device based on a new generation of sulfur based accumulator in order to increase in the energy density and cyclability. One of the originality of the project corresponds to the investigation of the functioning and failure modes by operando analysis of batteries in order to optimize the positive electrode texture and the polymer electrolyte properties, and to deeply understand the dendrite growth processes at the negative electrode. As a perspective, the project will develop a test bench of microstructural and topological analysis of electrochemical energy storage devices during cycling by X-ray and Neutron tomography.

Project coordination

Didier Devaux (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

Help of the ANR 209,974 euros
Beginning and duration of the scientific project: January 2020 - 48 Months

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