Cobalt-free composite-structured cathodes with lithium-stoichiometry control for sustainable lithium-ion batteries

A bifunctional catalyst of CoO/NBC composite for high-performance rechargeable flexible zinc-air battery

Rechargeable flexible zinc-air batteries (ZABs) represent a promising energy-supply device for wearable electronics due to their low cost, safety and high energy density, but their electrochemical performance often suffers from the sluggish reaction kinetics of air electrode and poor moisture-retention ability of polymer electrolytes. Here, we report a type of high-performance rechargeable flexible ZABs endowed by an efficient bifunctional catalyst for air electrode and a high moisture-retention hydrogel electrolyte. The designed nitrogen-boron co-doped carbon nanotube arrays loaded with cobalt oxide nanoparticles (CoO/NBC) with abundant catalytic active sites and oriented structure provide its excellent electrochemical catalytic activities for both oxygen reduction reaction and oxygen evolution reaction. Based on the bifunctional catalyst of CoO/NBC, the developed rechargeable ZABs exhibit a high open-circuit voltage of 1.44 V and a high energy density of 920.0 Wh kg-1, which are superior than commercial Pt/C + RuO2 and most reported non-precious metal catalysts. Furthermore, a trehalose modified polyacrylamide hydrogel electrolytes (trehalose/PAAm) with high moisture-retention has been synthesized to construct flexible ZABs, which not only exhibit outstanding electrochemical performance (1.39 V and 824.8 Wh kg-1), but also show excellent stability even after 400 charge/discharge cycles or being bent to any angle.

Enhancing full-field TXM with low emittance synchrotron sources: Mono-capillary condenser shaker optimization

Synchrotron radiation based full-field transmission hard x-ray microscope (TXM) achieves spatial resolutions ranging from a few to tens of nanometers. The field of view (FOV) and resolution are contingent upon the illumination characteristics of the condenser, the zone plate, and the detector. With the technological advancements in synchrotron radiation accelerators, there has been a progressive reduction in the electron beam emittance. The focused spot by the condenser in TXM systems utilizing a mono-capillary condenser has also become smaller, consequently narrowing the TXM's FOV. Additionally, due to slope errors of the mono-capillary condenser, the focused spot is non-uniform, leading to a non-uniform FOV in TXM. To address these issues, a condenser shaker has been implemented. This study presents theoretical analysis, simulations, and experimental data, illustrating the impacts of different amplitudes and frequencies of the condenser shaker on the focused spot, TXM's FOV, and imaging quality. The results indicate that the FOV of TXM increases nearly double when the condenser shaker is optimally applied, compared to its absence. These enhancements signify that the optimization of mono-capillary condenser shaking in the TXM system can expand the FOV and significantly enhance the overall imaging quality. Through this optimization, three-dimensional nano-imaging of a battery particle with a 28 μm diameter and 96 nm micro-structures was successfully achieved.

Cu- and P-co-doped nitrogen-doped hierarchical carbon for enhanced oxygen reduction reaction in zinc-air batteries

High-performance Fe-based nitrogen-doped carbon oxygen reduction catalysts have been widely reported, but the Fenton reaction faced by such catalysts has hindered their practical application in fuel cells. The development of inexpensive, effective, and durable non-Fe nitrogen-doped carbon electrocatalysts is important for advancing fuel cell technology. In this work, we have introduced a molecular coordination chemistry method to synthesize a Cu- and P-co-doped nitrogen-doped hierarchical carbon (Cu-P-N-C) oxygen reduction reaction (ORR) electrocatalyst by pyrolyzing a mixture of phytate and melamine. The refined Cu-P-N-C material showcased a three-dimensional, porous, interconnected nanosheet structure with an ultra-high specific surface area and an abundance of active sites. The Cu-P-N-C catalyst displayed a half-wave potential (E1/2) of 0.86 VRHE, higher than that of commercial Pt/C in 0.1 M KOH. It was also found to maintain an impressive long-term stability, retaining 95.4% of its initial activity after extensive testing. When integrated into zinc-air batteries (ZABs), the Cu-P-N-C electrocatalyst was observed to deliver exceptional performance, achieving a high peak power density of 164.5 mW cm-2, a promising specific capacity of 807 mA h g-1, and remarkable stability. These findings underscore the potential of Cu-P-N-C as a potential candidate for next-generation ORR electrocatalysts in new energy devices.

Tuning Li occupancy and local structures for advanced Co-free Ni-rich positive electrodes

Structure evolution and surface reactivity have long been regarded as the most crucial points for studying Ni-rich positive electrodes for Li-ion batteries. Unfortunately, the influence of Li occupancy as a single factor on electro-chemomechanical stability has been overlooked and is missing, owing to the challenge of Li determination in the lattice. Here, a comprehensive analysis reveals different Li occupancies and related structural domains (Ni/Li exchange, LiaXOb, Li/Mn/X(Ni) ordering domains, X = Nb5+, W6+, and Mo6+) by using a combination of Li-sensitive characterization techniques. By introducing a Li-regulation strategy, the relative ratio of each domain is effectively tuned in the Ni-rich positive electrodes. Through tuning, two specific positive electrodes are designed, exhibiting notable improvement in battery cyclability. The specific Li structural units induce significant changes in redox mechanisms. This Li-occupancy-tuning approach highlights the necessity of focusing on Li distribution and opens up ideas for designing advanced Ni-rich positive electrodes with high durability.

Nano-rods in Ni-rich layered cathodes for practical batteries

Lithium transition metal oxide layers, Li[Ni1-x-yCox(Mn and/or Al)y]O2, are widely used and mass-produced for current rechargeable battery cathodes. Development of cathode materials has focused on increasing the Ni content by simply controlling the chemical composition, but as the Ni content has almost reached its limit, a new breakthrough is required. In this regard, microstructural modification is rapidly emerging as a prospective approach, namely in the production of nano-rod layered cathode materials. A comprehensive review of the physicochemical properties and electrochemical performances of cathodes bearing the nano-rod microstructure is provided herein. A detailed discussion is regarding the structural stability of the cathode, which should be maximized to suppress microcrack formation, the main cause of capacity fading in Ni-rich cathode materials. In addition, the morphological features required to achieve optimal performance are examined. Following a discussion of the initial nano-rod cathodes, which were based on compositional concentration gradients, the preparation of nano-rod cathodes without the inclusion of a concentration gradient is reviewed, highlighting the importance of the precursor. Subsequently, the challenges and advances associated with the nano-rod structure are discussed, including considerations for synthesizing nano-rod cathodes and surface shielding of the nano-rod structure. It goes on to cover nano-rod cathode materials for next-generation batteries (e.g., all-solid-state, lithium-metal, and sodium-ion batteries), inspiring the battery community and other materials scientists looking for clues to the solution of the challenges that they encounter.

In situ Synchrotron X-ray Metrology Boosted by Automated Data Analysis for Real-time Monitoring of Cathode Calcination

Synchrotron X-ray-based in situ metrology is advantageous for monitoring the synthesis of battery materials, offering high throughput, high spatial and temporal resolution, and chemical sensitivity. However, the rapid generation of massive data poses a challenge to on-site, on-the-fly analysis needed for real-time process monitoring. Here, a weighted lagged cross-correlation (WLCC) similarity approach is presented for automated data analysis, which merges with in situ synchrotron X-ray diffraction metrology to monitor the calcination process of the archetypal nickel-based cathode, LiNiO2. The WLCC approach, incorporating variables that account for peak shifts and width changes associated with structural transformations, enables rapid extraction of phase progression within 10 seconds from tens of diffraction patterns. Details are captured, from initial precursors to intermediates and the final layered LiNiO2, providing information for agile on-site adjustments during experiments and complementing post hoc diffraction analysis by offering insights into early-stage phase nucleation and growth. Expanding this data-powered platform paves the way for real time calcination process monitoring and control, which is pivotal to quality control in battery cathode manufacturing.

Closed-Loop Direct Upcycling of Spent Ni-Rich Layered Cathodes into High-Voltage Cathode Materials

Facing the resource and environmental pressures brought by the retiring wave of lithium-ion batteries (LIBs), direct recycling methods are considered to be the next generation's solution. However, the contradiction between limited battery life and the demand for rapidly iterating technology forces the direct recovery paradigm to shift toward "direct upcycling." Herein, a closed-loop direct upcycling strategy that converts waste current collector debris into dopants is proposed, and a highly inclusive eutectic molten salt system is utilized to repair structural defects in degraded polycrystalline LiNi0.83Co0.12Mn0.05O2 cathodes while achieving single-crystallization transformation and introducing Al/Cu dual-doping. Upcycled materials can effectively overcome the two key challenges at high voltages: strain accumulation and lattice oxygen evolution. It exhibits comprehensive electrochemical performance far superior to commercial materials at 4.6 V, especially its fast charging capability at 15 C, and an impressive 91.1% capacity retention after 200 cycles in a 1.2 Ah pouch cell. Importantly, this approach demonstrates broad applicability to various spent layered cathodes, particularly showcasing its value in the recycling of mixed spent cathodes. This work effectively bridges the gap between waste management and material performance enhancement, offering a sustainable path for the recycling of spent LIBs and the production of next-generation high-voltage cathodes.

In Situ Insights into Cathode Calcination for Predictive Synthesis: Kinetic Crystallization of LiNiO2 from Hydroxides

Calcination is a solid-state synthesis process widely deployed in battery cathode manufacturing. However, its inherent complexity associated with elusive intermediates hinders the predictive synthesis of high-performance cathode materials. Here, correlative in situ X-ray absorption/scattering spectroscopy is used to investigate the calcination of nickel-based cathodes, focusing specifically on the archetypal LiNiO2 from Ni(OH)2. Combining in situ observation with data-driven analysis reveals concurrent lithiation and dehydration of Ni(OH)2 and consequently, the low-temperature crystallization of layered LiNiO2 alongside lithiated rocksalts. Following early nucleation, LiNiO2 undergoes sluggish crystallization and structural ordering while depleting rocksalts; ultimately, it turns into a structurally-ordered layered phase upon full lithiation but remains small in size. Subsequent high-temperature sintering induces rapid crystal growth, accompanied by undesired delithiation and structural degradation. These observations are further corroborated by mesoscale modeling, emphasizing that, even though calcination is thermally driven and favors transformation towards thermodynamically equilibrium phases, the actual phase propagation and crystallization can be kinetically tuned via lithiation, providing freedom for structural and morphological control during cathode calcination.

ARGET-ATRP-Mediated Grafting of Bifunctional Polymers onto Silica Nanoparticles Fillers for Boosting the Performance of High-Capacity All-Solid-State Lithium-Sulfur Batteries with Polymer Solid Electrolytes

The shuttle effect in lithium-sulfur batteries, which leads to rapid capacity decay, can be effectively suppressed by solid polymer electrolytes. However, the lithium-ion conductivity of polyethylene oxide-based solid electrolytes is relatively low, resulting in low reversible capacity and poor cycling stability of the batteries. In this study, we employed the activator generated through electron transfer atom transfer radical polymerization to graft modify the surface of silica nanoparticles with a bifunctional monomer, 2-acrylamide-2-methylpropanesulfonate, which possesses sulfonic acid groups with low dissociation energy for facilitating Li+ migration and transfer, as well as amide groups capable of forming hydrogen bonds with polyethylene oxide chains. Subsequently, the modified nanoparticles were blended with polyethylene oxide to prepare a solid polymer electrolyte with low crystallinity and high ion conductivity. The resulting electrolyte demonstrated excellent and stable electrochemical performance, with a discharge-specific capacity maintained at 875.2 mAh g-1 after 200 cycles.