Energy-dense rechargeable batteries have enabled a multitude of applications in recent years. Moving forward, they are expected to see increasing deployment in performance-critical areas such as electric vehicles, grid storage, space, defense, and subsea operations. While this at first glance spells great promise for conventional lithium-ion batteries, all of these use-cases, unfortunately, share periodic and recurring exposures to extremely low-temperature conditions, a performance constraint where the lithium-ion chemistry can fail to perform optimally. Next-generation chemistries employing alternative anodes with increased solvent compatibility or altogether different operating mechanisms could present an avenue for overcoming many of the low-temperature hurdles intrinsic to the lithium-ion battery. In this article, we provide a brief overview of the challenges in developing lithium-ion batteries for low-temperature use, and then introduce an array of nascent battery chemistries that may be intrinsically better suited for low-temperature conditions moving forward. Specifically, we evaluate the prospects of using lithium-metal, lithium-sulfur, and dual-ion batteries for performance-critical low-temperature applications. These three chemistries are presented as prototypical examples of how the conventional low-temperature charge-transfer resistances can be overcome. However, these three chemistries also present their own unique challenges at low temperatures, highlighting the balance between traditional low-temperature electrolyte design and next-generation approaches.

There is a critical need to evaluate lithium-sulfur (Li-S) batteries with practically relevant high sulfur loadings and minimal electrolyte. Under such conditions, the concentration of soluble polysulfide intermediates in the electrolyte drastically increases, which can alter the fundamental nature of the solution-mediated discharge and thereby the total sulfur utilization. In this work, we present an investigation into various high donor number (DN) electrolytes that allow for increased polysulfide dissolution, and demonstrate how this property may in fact be necessary for increasing sulfur utilization at low electrolyte and high loading conditions. The solvents dimethylacetamide, dimethyl sulfoxide, and 1-methylimidazole are holistically evaluated against dimethoxyethane as electrolyte co-solvents in Li-S cells, and they are used to investigate chemical and electrochemical properties of polysulfide species at both dilute and practically relevant conditions. The nature of speciation exhibited by lithium polysulfides is found to vary significantly between these concentrations, particularly in regards to the S species. Furthermore, the extent of the instability in conventional electrolyte solvents and high DN solvents with both lithium metal and polysulfides is thoroughly investigated. These studies establish a basis for future efforts into rationally designing an optimal electrolyte for a lean electrolyte, high energy density Li-S battery.

Nearly all implantable bioelectronics are powered by bulky batteries which limit device miniaturization and lifespan. Moreover, batteries contain toxic materials and electrolytes that can be dangerous if leakage occurs. Herein, an approach to fabricate implantable protein-based bioelectrochemical capacitors (bECs) employing new nanocomposite heterostructures in which 2D reduced graphene oxide sheets are interlayered with chemically modified mammalian proteins, while utilizing biological fluids as electrolytes is described. This protein-modified reduced graphene oxide nanocomposite material shows no toxicity to mouse embryo fibroblasts and COS-7 cell cultures at a high concentration of 1600 μg mL which is 160 times higher than those used in bECs, unlike the unmodified graphene oxide which caused toxic cell damage even at low doses of 10 μg mL. The bEC devices are 1 μm thick, fully flexible, and have high energy density comparable to that of lithium thin film batteries. COS-7 cell culture is not affected by long-term exposure to encapsulated bECs over 4 d of continuous charge/discharge cycles. These bECs are unique, protein-based devices, use serum as electrolyte, and have the potential to power a new generation of long-life, miniaturized implantable devices.

Herein, the synthesis of new quaternary layered Na-based oxides of the type Na Mn Ni FeMgO (0.67≤ ≤ 1.0; 0.5≤ ≤ 0.7; 0.1≤ ≤ 0.3) is described. The synthesis can be tuned to obtain P2- and O3-type as well as mixed P-/O-type phases as demonstrated by structural, morphological, and electrochemical properties characterization. Although all materials show good electrochemical performance, the simultaneous presence of the P- and O-type phases is found to have a synergetic effect resulting in outstanding performance of the mixed phase material as a sodium-ion cathode. The mixed P3/P2/O3-type material, having an average elemental composition of NaMnNiFeMgO, overcomes the specific drawbacks associated with the P2- and O3-type materials, allowing the outstanding electrochemical performance. In detail, the mixed phase material is able to deliver specific discharge capacities of up to 155 mAh g (18 mA g) in the potential range of 2.0-4.3 V. In the narrower potential range of 2.5-4.3 V the material exhibits high average discharge potential (3.4 V versus Na/Na), exceptional average coulombic efficiencies (>99.9%), and extraordinary capacity retention (90.2% after 601 cycles). The unexplored class of P-/O-type mixed phases introduces new perspectives for the development of layered positive electrode materials and powerful Na-ion batteries.

The synthesis of in situ polymer-functionalized anatase TiO particles using an anchoring block copolymer with hydroxamate as coordinating species is reported, which yields nanoparticles (≈11 nm) in multigram scale. Thermal annealing converts the polymer brushes into a uniform and homogeneous carbon coating as proven by high resolution transmission electron microscopy and Raman spectroscopy. The strong impact of particle size as well as carbon coating on the electrochemical performance of anatase TiO is demonstrated. Downsizing the particles leads to higher reversible uptake/release of sodium cations per formula unit TiO (e.g., 0.72 eq. Na (11 nm) vs only 0.56 eq. Na (40 nm)) while the carbon coating improves rate performance. The combination of small particle size and homogeneous carbon coating allows for the excellent electrochemical performance of anatase TiO at high (134 mAh g at 10 C (3.35 A g)) and low (≈227 mAh g at 0.1 C) current rates, high cycling stability (full capacity retention between 2nd and 300th cycle at 1 C) and improved coulombic efficiency (≈99.8%).

The performance of metal oxides as redox materials is limited by their oxygen conductivity and thermochemical stability. Predicting these properties from the electronic structure can support the screening of advanced metal oxides and accelerate their development for clean energy applications. Specifically, reducible metal oxide catalysts and potential redox materials for the solar-thermochemical splitting of CO and HO via an isothermal redox cycle are examined. A volcano-type correlation is developed from available experimental data and density functional theory. It is found that the energy of the oxygen-vacancy formation at the most stable surfaces of TiO, TiO, CuO, ZnO, ZrO, MoO, AgO, CeO, yttria-stabilized zirconia, and three perovskites scales with the Gibbs free energy of formation of the bulk oxides. Analogously, the experimental oxygen self-diffusion constants correlate with the transition-state energy of oxygen conduction. A simple descriptor is derived for rapid screening of oxygen-diffusion trends across a large set of metal oxide compositions. These general trends are rationalized with the electronic charge localized at the lattice oxygen and can be utilized to predict the surface activity, the free energy of complex bulk metal oxides, and their oxygen conductivity.

Biophotovoltaics has emerged as a promising technology for generating renewable energy because it relies on living organisms as inexpensive, self-repairing, and readily available catalysts to produce electricity from an abundant resource: sunlight. The efficiency of biophotovoltaic cells, however, has remained significantly lower than that achievable through synthetic materials. Here, a platform is devised to harness the large power densities afforded by miniaturized geometries. To this effect, a soft-lithography approach is developed for the fabrication of microfluidic biophotovoltaic devices that do not require membranes or mediators. PCC 6803 cells are injected and allowed to settle on the anode, permitting the physical proximity between cells and electrode required for mediator-free operation. Power densities of above 100 mW m are demonstrated for a chlorophyll concentration of 100 μM under white light, which is a high value for biophotovoltaic devices without extrinsic supply of additional energy.

An innovative and environmentally friendly battery chemistry is proposed for high power applications. A carbon-coated ZnFeO nanoparticle-based anode and a LiFePO-multiwalled carbon nanotube-based cathode, both aqueous processed with Na-carboxymethyl cellulose, are combined, for the first time, in a Li-ion full cell with exceptional electrochemical performance. Such novel battery shows remarkable rate capabilities, delivering 50% of its nominal capacity at currents corresponding to ≈20C (with respect to the limiting cathode). Furthermore, the pre-lithiation of the negative electrode offers the possibility of tuning the cell potential and, therefore, achieving remarkable gravimetric energy and power density values of 202 Wh kg and 3.72 W kg, respectively, in addition to grant a lithium reservoir. The high reversibility of the system enables sustaining more than 10 000 cycles at elevated C-rates (≈10C with respect to the LiFePO cathode), while retaining up to 85% of its initial capacity.

Colloidal quantum dot solar cells (CQDSCs) are attracting growing attention owing to significant improvements in efficiency. However, even the best depleted-heterojunction CQDSCs currently display open-circuit voltages (s) at least 0.5 V below the voltage corresponding to the bandgap. We find that the tail of states in the conduction band of the metal oxide layer can limit the achievable device efficiency. By continuously tuning the zinc oxide conduction band position via magnesium doping, we probe this critical loss pathway in ZnO-PbSe CQDSCs and optimize the energetic position of the tail of states, thereby increasing both the (from 408 mV to 608 mV) and the device efficiency.

The temperature dependent aggregation behavior of PffBT4T polymers used in organic solar cells plays a critical role in the formation of a favorable morphology in fullerene-based devices. However, there has been little investigation into the impact of donor/acceptor ratio on morphology tuning, especially for non-fullerene acceptors (NFAs). Herein, the influence of composition on morphology is reported for blends of PffBT4T-2DT with two NFAs, O-IDTBR and O-IDFBR. The monotectic phase behavior inferred from differential scanning calorimetry provides qualitative insight into the interplay between solid-liquid and liquid-liquid demixing. Transient absorption spectroscopy suggests that geminate recombination dominates charge decay and that the decay rate is insensitive to composition, corroborated by negligible changes in open-circuit voltage. Exciton lifetimes are also insensitive to composition, which is attributed to the signal being dominated by acceptor excitons which are formed and decay in domains of similar size and purity irrespective of composition. A hierarchical morphology is observed, where the composition dependence of size scales and scattering intensity from resonant soft X-ray scattering (R-SoXS) is dominated by variations in volume fractions of polymer/polymer rich domains. Results suggest an optimal morphology where polymer crystallite size and connectivity are balanced, ensuring a high probability of hole extraction via such domains.