Li-ion batteries presently operate on inorganic insertion compounds. The abundance and materials life-cycle costs of such batteries may present issues in the long term with foreseeable large-scale applications. To address the issue of sustainability of electrode materials, a radically different approach from the conventional route has been adopted to develop new organic electrode materials. The oxocarbon salt Li2C6O6 is synthesized through potentially low-cost processes free of toxic solvents and by enlisting the use of natural organic sources (CO2-harvesting entities). It contains carbonyl groups as redox centres and can electrochemically react with four Li ions per formula unit. Such battery processing comes close to both sustainable and green chemistry concepts, which are not currently present in Li-ion cell technology. The consideration of renewable resources in designing electrode materials could potentially enable the realization of green and sustainable batteries within the next decade.

The fundamental challenge of the 21 st century that mankind has to face is definitely energy supply, its storage and conversion in a way that necessarily protects the environment. For 250 years, the tremendous development of humanity has been founded on the harnessing of fossil fuels (coal, crude oil then natural gas) as primary energy due to their high energy density values and the easiness of access. However, this global pattern of energy supply and use is unsustainable. Global warming and finite fossil-fuel supplies call for a radical change in the energy mix to favour renewable energy sources. Without being exhaustive, we tackle in this article the tricky energy question and associated environmental issues as personally perceived. The eminent role of electric energy produced from decarbonized sources in a future sustainable economy is particularly highlighted as well as the issues of its needed storage. The possible and foreseen hindrances of electrochemical energy storage devices, focusing on the lithium-ion technology, are presented in parallel with the possible pathways to make such a technology greener in synergy with the rise of a biomass-based industry.

The use of lithiated redox organic molecules containing electrochemically active C=O functionalities, such as lithiated oxocarbon salts, is proposed. These represent alternative electrode materials to those used in current Li-ion battery technology that can be synthesized from renewable starting materials. The key material is the tetralithium salt of tetrahydroxybenzoquinone (Li(4)C(6)O(6)), which can be both reduced to Li(2)C(6)O(6) and oxidized to Li(6)C(6)O(6). In addition to being directly synthesized from tetrahydroxybenzoquinone by neutralization at room temperature, we demonstrate that this salt can readily be formed by the thermal disproportionation of Li(2)C(6)O(6) (dilithium rhodizonate phase) under an inert atmosphere. The Li(4)C(6)O(6) compound shows good electrochemical performance vs Li with a sustained reversibility of approximately 200 mAh g(-1) at an average potential of 1.8 V, allowing a Li-ion battery that cycles between Li(2)C(6)O(6) and Li(6)C(6)O(6) to be constructed.

Meeting the ever-growing demand for electrical storage devices requires both superior and “greener” battery technologies. Nearly 40 years after the discovery of conductive polymers, long cycling stability in lithium organic batteries has now been achieved. However, the synthesis of high-voltage lithiated organic cathode materials is rather challenging, so very few examples of all-organic lithium-ion cells currently exist. Herein, we present an inventive chemical approach leading to a significant increase of the redox potential of lithiated organic electrode materials. This is achieved by tuning the electronic effects in the redox-active organic skeleton thanks to the permanent presence of a spectator cation in the host structure exhibiting a high ionic potential (or electronegativity). Thus, substituting magnesium (2,5-dilithium-oxy)-terephthalate for lithium (2,5-dilithium-oxy)-terephthalate enables a voltage gain of nearly +800 mV. This compound being also able to act as negative electrode via the carboxylate functional groups, an all-organic symmetric lithium-ion cell exhibiting an output voltage of 2.5 V is demonstrated.

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Li-ion batteries (LIBs) appear nowadays as flagship technology able to power an increasing range of applications starting from small portable electronic devices to advanced electric vehicles. Over the past two decades, the discoveries of new metal-based host structures, together with substantial technical developments, have considerably improved their electrochemical performance, particularly in terms of energy density. To further promote electrochemical storage systems while limiting the demand on metal-based raw materials, a possible parallel research to inorganic-based batteries consists in developing efficient and low-polluting organic electrode materials. For a long time, this class of redox-active materials has been disregarded mainly due to stability issues but, in recent years, progress has been made demonstrating that organics undeniably exhibit considerable assets. On the basis of our ongoing research aiming at elaborating lithiated organic cathode materials, we report herein on a chemical approach that takes advantage of the positive potential shift when switching from para to ortho-position in the dihydroxyterephthaloyl system. In practice, dilithium (2,3-dilithium-oxy)-terephthalate compound (Li4C8H2O6) was first produced through an eco-friendly synthesis scheme based on CO2 sequestration, then characterized, and finally tested electrochemically as lithiated cathode material vs. Li. This new organic salt shows promising electrochemical performance, notably fast kinetics, good cycling stability and above all an average operating potential of 2.85 V vs. Li(+)/Li(0) (i.e., +300 mV in comparison with its para-regioisomer), verifying the relevance of the followed strategy.

Pyromellitic diimide dilithium salt was selected to complete our database on redox-active polyketones with a N-cyclic structure. Although never reported to date, such a lithiated salt was readily synthesized making its electrochemical evaluation in a Li battery possible. Preliminary data show that this novel material reversibly inserts two Li per formula unit at a relatively low potential giving a stable capacity value of 200 mAh g(-1).

International audienceCation insertion reactions in inorganic host frameworks are well-established phenomena. Over the last 40 years, a myriad of examples have been documented, which have given rise to key applications such as for electrochemical storage devices. By contrast, materials able to reversibly insert anions into their host lattice are rare, and consist essentially of graphite intercalation compounds (GICs), thus limiting their potential use. Organic materials, conversely, if properly designed, could pave the way for future developments in anionic insertion electrochemistry, by virtue of the rational incorporation of p-type redox-active organic moieties. Here, we report the discovery of a p-type organic host lattice based on a simple crystallized aromatic diamine. The reversible anion insertion process relies on the electrochemical activity of neutral secondary amino groups incorporated into a robust terephthalate backbone. XRD, TEM and EELS studies reveal the attainment of a unique lamellar structure conducive to the oxidative insertion of anions (including the bulky TFSI-). In a dual-ion cell configuration using lithium as the negative electrode, this organic structure can react reversibly at high operating potential (hEi z 3.22 V vs. Li+/Li) with good cycling performance even without carbon addition, hence generating further avenues for the development of organic batteries and more generally, the field of intercalation chemistry.