Electrochemical energy storage is one of the main societal challenges of this century. The performances of classical lithium-ion technology based on liquid electrolytes have made great advances in ...the past two decades, but the intrinsic instability of liquid electrolytes results in safety issues. Solid polymer electrolytes would be a perfect solution to those safety issues, miniaturization and enhancement of energy density. However, as in liquids, the fraction of charge carried by lithium ions is small (<20%), limiting the power performances. Solid polymer electrolytes operate at 80 °C, resulting in poor mechanical properties and a limited electrochemical stability window. Here we describe a multifunctional single-ion polymer electrolyte based on polyanionic block copolymers comprising polystyrene segments. It overcomes most of the above limitations, with a lithium-ion transport number close to unity, excellent mechanical properties and an electrochemical stability window spanning 5 V versus Li(+)/Li. A prototype battery using this polyelectrolyte outperforms a conventional battery based on a polymer electrolyte.
Safety is one of the most important criteria for electrochemical energy storage devices used in large scale applications such as wind or solar farms. In this context, solid polymer electrolytes based ...on nanostructured block copolymer electrolytes (BCEs) are promising because their properties can be finely tuned by adjusting simultaneously their block chemistries and polymer architectures. However, there is a need to rationalize the different properties of BCE that are optimal for battery applications. We produced by controlled radical polymerization a large number of BCEs based on either (1) linear poly(ethylene oxide) (PEO) or (2) comb PEO as the ionic conductor block, and polystyrene as the structural block. We varied the molecular weight of the PEO-based block, the composition, and the architecture (diblock vs triblock). We performed a systematic analysis of their thermodynamic, ionic transport, and mechanical properties. To verify the potential of BCEs as electrolytes, we evaluated their electrochemical stabilities. Laboratory scale batteries comprising the best BCEs and LiFePO4 as a positive active material were cycled at different rates and temperatures. This process allows the selection of the best architectures and compositions that had been successfully tested in battery prototypes and cycled for more than 600 cycles at high rates without any dendritic growth.
Due to its high theoretical specific capacity, the lithium/sulfur battery is one of the most promising candidates for replacing current lithium-ion batteries. In this work, we investigate both ...chemical and morphological changes in the electrodes during cycling, by coupling operando spatially resolved X-ray diffraction and absorption tomography to characterize Li/S cells under real working conditions. By combining these tools, the state of the active material in the entire cell was correlated with its electrochemical behavior, leading to a deeper understanding of the performance limiting degradation phenomena in Li/S batteries. Highly heterogeneous behavior of lithium stripping/plating was observed in the anode, while the evolution of sulfur distribution in the cathode depth was followed during cycling.
A new path for the design of safe and efficient, all‐solid‐state Li‐ion batteries by spark plasma sintering (SPS) is considered. To reach a good electrochemical performance from such batteries, ...several parameters are investigated, such as the composite‐electrode formulation (active material/electrolyte/carbon ratio) and the influence of the sintering parameters on their compactness. The formulation is optimized to ensure good ionic and electronic percolation through the composite electrode's volume. The compactness has to be sufficient to guarantee a good mechanical aspect, while the residual porosity in the composite electrode allows electrode‐volume changes upon insertion and deinsertion, preserving the electrode/electrolyte interfaces, which are crucial in such technology. Based on these investigations, an all‐solid‐state battery with a surface capacity of 2.2 mA h cm−2 is assembled by SPS, displaying a promising electrochemical performance at 80 °C.
By controlling and optimizing the formulation of a composite electrode, as well as the sintering parameters (temperature, pressure) that affect the compactness of both the electrolyte and the composite electrode, an efficient and safe solid‐state Li‐ion battery can be assembled in a one‐step process by spark plasma sintering (SPS). The first prototype shows good cycling and a promising electrochemical performance.
Bulk‐type all‐solid‐state inorganic Li‐ion batteries can be prepared in one step in few minutes using spark plasma sintering. The self‐supported cells display thick composite electrodes of up to 800 ...μm, which offer high surface capacities of up to 10 mAh.cm−2. Such technology is safer than classical Li‐ion batteries and offers good electrochemical properties at temperatures above 100 °C.
The energy conversion and storage are great challenges for our society. Despite the progress accomplished by the Lithium(Li)-ion technology based on flammable liquid electrolyte, their intrinsic ...instability is the strong safety issue for large scale applications. The use of solid polymer electrolytes (SPEs) is an adequate solution in terms of safety and energy density. To increase the energy density (resp. specific energy) of the batteries, the positive electrode thickness must be augmented. However, as for Li-ion liquid electrolyte, the cationic transference number of SPEs is low, typically below 0.2, which limits their power performance because of the formation of strong gradient of concentration throughout the battery. Thus, for a given battery system a compromise between the energy density and the power has to be found in a rapid manner. The goal of this study is to propose a simple efficient methodology to optimize the thickness of the SPE and the positive electrode based on charge transport parameters, which allows to determine the effective limiting Li+ diffusion coefficient. First, we rapidly establish the battery power performance thanks to a specific discharge protocol. Then, by using an approach based on the Sand equation a limiting current density is determined. A unique mother curve of the capacity as a function of the limiting current density is obtained whatever the electrode and electrolyte thicknesses. Finally, the effective limiting diffusion coefficient is estimated which in turn allows to design the best electrode depending on electrolyte thickness.
New single-ion hybrid electrolytes have been synthetized via an original and simple synthetic approach combining Michael addition, epoxidation, and sol-gel polycondensation. We designed an organic ...PEO network as a matrix for the lithium transport, mechanically reinforced thanks to crosslinking inorganic (SiO
) sites, while highly delocalized anions based on lithium vinyl sulfonyl(trifluoromethane sulfonyl)imide (VSTFSILi) were grafted onto the inorganic sites to produce single-ion hybrid electrolytes (HySI). The influence of the electrolyte composition in terms of the inorganic/organic ratio and the grafted VSTFSILi content on the local structural organization, the thermal, mechanical, and ionic transport properties (ionic conductivity, transference number) are studied by a variety of techniques including SAXS, DSC, rheometry, and electrochemical impedance spectroscopy. SAXS measurements at 25 °C and 60 °C reveal that HySI electrolyte films display locally a spatial phase separation with domains composed of PEO rich phase and silica/VSTFSILi clusters. The size of these clusters increases with the silica and VSTFSILi content. A maximum ionic conductivity of 2.1 × 10
S·cm
at 80 °C has been obtained with HySI having an EO/Li ratio of 20. The Li
ion transfer number of HySI electrolytes is high, as expected for a single-ion electrolyte, and comprises between 0.80 and 0.92.
X-ray and neutron imaging are widely employed for battery materials, thanks to the possibility to perform noninvasive
in situ
and
in operando
analyses. X-ray tomography can be performed either in ...synchrotron or in laboratory facilities and is particularly well-suited to analyze bulk materials and electrode/electrolyte interfaces. Several post-lithium-ion (Li-ion) devices, such as Li–sulfur, Li–O
2
, or all-solid-state Li batteries, have an anode made of metallic Li in common. The main failure mode of Li batteries is the inhomogeneity of the Li electrodeposits onto the Li anode during charge steps, leading to dendrite growth and low Coulombic efficiency. X-ray tomography is a powerful tool for studying dendrites as it provides useful information about their locations, dynamics, and microstructures. So far, the use of neutron tomography is scarcely reported for Li deposit analysis due to the difficulty in reaching sufficient image resolution to capture the deposit microstructure, that is, typically below 10–20 µm. The very different interactions of X-rays and neutrons with Li, which has significantly different opacity in the two cases, make the two techniques highly complementary. Notably, the capacity of neutrons to discern different Li isotopes is pivotal to getting an insight into the composition of Li deposits by distinguishing between Li originating from an electrode (
6
Li in this study) and Li originating from the Li salt electrolyte (mainly in
7
Li here). Indeed, the theoretical linear neutron attenuation coefficient of
6
Li is about 15 and 2,000 times larger than that of natural Li and
7
Li, respectively. Therefore, a high imaging contrast difference is obtained between
6
Li (high attenuation) and natural Li and
7
Li (lower attenuations), which could allow a better understanding of the origin of the Li comprising the electrodeposits. In this work, we report, as a proof of concept, an
in situ
neutron tomography imaging of Li electrodeposits in a cycled Li symmetric cell. The electrochemical cell comprises a natural Li electrode, a
6
Li electrode, and a deuterated liquid electrolyte. The neutron tomographies are compared with X-ray tomography images of the same electrochemical cell acquired both at an X-ray synchrotron beamline and at a laboratory X-ray tomograph. Neutron tomography is shown to be compatible with
in situ
analysis and capable of capturing the overall morphology of the Li deposits in good accordance with X-ray tomography analyses.
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