The rapid growth, demand, and production of batteries to meet various emerging applications, such as electric vehicles and energy storage systems, will result in waste and disposal problems in the next few years as these batteries reach end-of-life. Battery reuse and recycling are becoming urgent worldwide priorities to protect the environment and address the increasing need for critical metals. As a review article, this paper reveals the current global battery market and global battery waste status from which the main battery chemistry types and their management, including reuse and recycling status, are discussed. This review then presents details of the challenges, opportunities, and arguments on battery second-life and recycling. The recent research and industrial activities in the battery reuse domain are summarized to provide a landscape picture and valuable insight into battery reuse and recycling for industries, scientific research, and waste management.

At first glance, the combination of the lightest, most electropositive metal (lithium) with a safe, abundant (and reasonably light) non-metal (sulfur) makes good sense as a prospective battery. However, while the lithium–sulfur battery offers a very high theoretical specific energy (∼2600 W h kg⁻¹) the actual performance delivered is proving to be severely limited—in many cases, this is directly related to the role of the electrolyte. The fundamental issue is that the reduction of sulfur proceeds through a series of polysulfide species, which are for the most part soluble in common organic solvents, including those employed in battery electrolyte solutions. So, despite the fact that the ultimate product (Li₂S) is essentially insoluble, the intermediate stages of discharge see a migration of redox-active species out of the cathode, from where they can react with the lithium anode, which sets in train a series of equilibria that cause both a loss of charging efficiency and a gradual loss of discharge capacity. In the last decade, a major stream of the research to overcome this complex situation has focused on minimizing the solubility of polysulfides. From this we now have a range of media in which the lithium–sulfur system can operate with much improved charge–discharge characteristics: ionic liquids (and blends with organic media); super-saturated salt-solvent mixtures; polymer-gelled organic media; solid polymers; solid inorganic glasses. Underlining the multi-faceted nature of interactions within the lithium–sulfur cell, though, none of these improved electrolytes has been able to bring the performance of this system up to the levels of reliability and capacity maintenance (without sacrificing high specific energy) that are benchmarks in energy storage applications. Our survey indicates that only by combining particular electrolytes with cathode materials that are designed to actively retain sulfur and its reduction products, have a relatively few studies been able to obtain the desired levels of performance. Ultimately the successful development of the lithium–sulfur battery requires careful coordination of the choice of modified electrolyte with the specific nature of the cathode material, underpinned by the assumption that the resulting electrolyte composition will meet established criteria for compatibility with the lithium anode.

Replacement of volatile and combustible electrolytes in conventional lithium batteries is desirable for two reasons: safety concerns and increase in specific energy. In this work we consider the use of an ionic organic plastic crystal material (IOPC), N-ethyl-N-methylpyrrolidinium tetrafluoroborate, [C2mpyr][BF₄], as a solid-state electrolyte for lithium battery applications. The effect of inclusion of 1 to 33 mol% lithium tetrafluoroborate, LiBF₄, into [C2mpyr][BF₄] has been investigated over a wide temperature range by differential scanning calorimetry (DSC), impedance spectroscopy, cyclic voltammetry and cycling of full Li|LiFePO₄ batteries. The increases in ionic conductivity by orders of magnitude observed at higher temperature are most likely associated with an increase in Li ion mobility in the highest plastic phase. At concentrations >5 mol% LiBF₄ the ionic conductivity of these solid-state composites is comparable to the ionic conductivity of room temperature ionic liquids. Galvanostatic cycling of Li|Li symmetrical cells showed that the reversibility of the lithium metal redox reaction at the interface of this plastic crystal electrolyte is sufficient for lithium battery applications. For the first time we demonstrate an all solid state lithium battery incorporating solid electrolytes based on IOPC as opposed to conventional flammable organic solvents.