Practical Cell Design for PTMA-Based Organic Batteries: an Experimental and Modeling Study

Poly(2,2,6,6-tetramethyl-1-piperidinyloxy methacrylate) (PTMA) is one of the most promising organic cathode materials thanks to its relatively high redox potential, good rate performance, and cycling stability. However, being a p-type material, PTMA-based batteries pose additional challenges compared to conventional lithium-ion systems due to the involvement of anions in the redox process. This study presents a comprehensive approach to optimize such batteries, addressing challenges in electrode design, scalability, and cost. Experimental results at a laboratory scale demonstrate high active mass loadings of PTMA electrodes (up to 9.65 mg cm$^{–2}$), achieving theoretical areal capacities that exceed 1 mAh cm$^{–2}$. Detailed physics-based simulations and cost and performance analysis clarify the critical role of the electrolyte and the impact of the anion amount in the PTMA redox process, highlighting the benefits and the drawbacks of using highly concentrated electrolytes. The cost and energy density of lithium metal batteries with such high mass loading PTMA cathodes were simulated, finding that their performance is inferior to batteries based on inorganic cathodes even in the most optimistic conditions. In general, this work emphasizes the importance of considering a broader perspective beyond the lab scale and highlights the challenges in upscaling to realistic battery configurations

Opportunities and Challenges in the Development of Cathode Materials for Rechargeable Mg Batteries

Recent years have seen an intense and renewed interest in the Mg battery research, naming Mg-S the ≫Holy Grail≪ battery, and expectations that Mg battery system will be able to compete and surpass Li-ion batteries in a matter of years. Considerable progress has been achieved in the field of Mg electrolytes, where several new electrolytes with improved electrochemical performance and favorable chemical properties (non-corrosive, non-nucleophilic) were synthesized. Development in the field of cathodes remains a bit more elusive, with inorganic, sulfur, and organic cathodes all showing their upsides and downsides. This review highlights the recent progress in the field of Mg battery cathodes, paying a special attention to the performance and comparison of the different types of the cathodes. It also aims to define advantages and key challenges in the development of each type of cathodes and finally specific questions that should be addressed in the future research

Unveiling true limits of electrochemical performance of organic cathodes in multivalent batteries through cyclable symmetric cells

Multivalent batteries are often hyped as a next-generation high-energy density battery technology, but in reality, both literature reports and practical research are plagued by poor reproducibility of electrochemical results. Within the present work, we take a look at the electrochemical testing of organic cathodes that can be used with a variety of mono- and multivalent cations and propose a cyclable symmetric cell approach, already applied to the field of lithium-ion batteries. By using a model organic system based on poly(anthraquinonyl sulfide) (PAQS) active material, we demonstrate that the symmetric cell approach elegantly removes the limitations of multivalent metal anodes, and for the first time, reveals the full potential of organic cathodes in multivalent batteries. Furthermore, symmetric cells enable reliable EIS measurements on organic cathodes and open a pathway to optimize electrochemical/transport parameters through the design of next generation organic cathode materials and advanced electrode design(s). We suggest that the cyclable symmetric cell approach should be generally applicable in multivalent and all other batteries where electrochemical characterization requires the elimination of the counter electrode contribution.Funding from Slovenian Research Agency through research program P2-0423 and project J2-4462

Quinone Based Materials as Renewable High Energy Density Cathode Materials for Rechargeable Magnesium Batteries

Organic cathode materials are promising cathode materials for multivalent batteries. Among organic cathodes, anthraquinone (AQ) has already been applied to various metal‒organic systems. In this work, we compare electrochemical performance and redox potential of AQ with 1,4-naphthoquinone (NQ) and 1,4-benzoquinone (BQ), both of which offer significantly higher theoretical energy density than AQ and are tested in two different Mg electrolytes. In Mg(TFSI)2-2MgCl2 electrolyte, NQ and BQ exhibit 0.2 and 0.5 V higher potential than AQ, respectively. Furthermore, an upshift of potential for 200 mV in MgCl2-AlCl3 electrolyte versus Mg(TFSI)2-2MgCl2 was confirmed for all used organic compounds. While lower molecular weights of NQ and BQ increase their specific capacity, they also affect the solubility in used electrolytes. Increased solubility lowers long-term capacity retention, confirming the need for the synthesis of NQ and BQ based polymers. Finally, we examine the electrochemical mechanism through ex situ attenuated total reflectance infrared spectroscopy (ATR-IR) and comparison of ex situ cathode spectra with spectra of individual electrode components. For the first time, magnesium anthracene-9,10-bis(olate), a discharged form of AQ moiety, is synthesized, which allows us to confirm the electrochemical mechanism of AQ cathode in Mg battery system