Visualization of Tetrahedral Li in the Alkali Layers of Li-Rich Layered Metal Oxides.

Understanding Li ion diffusion pathways in Li-rich layered transition metal (TM) oxides is crucial for understanding the sluggish kinetics in anionic O redox. Although Li diffusion within the alkali layers undergoes a low-barrier octahedral-tetrahedral-octahedral pathway, it is less clear how Li diffuses in and out of the TM layers, particularly given the complex structural rearrangements that take place during the oxidation of O. Here, we develop simultaneous electron ptychography and annular dark field imaging methods to unlock the Li migration pathways in LiNiMnCoO associated with structural changes in the charge-discharge cycle.

A High Capacity Gas Diffusion Electrode for Li-O Batteries.

The very high theoretical specific energy of the lithium-air (Li-O) battery (3500 Wh kg) compared with other batteries makes it potentially attractive, especially for the electrification of flight. While progress has been made in realizing the Li-air battery, several challenges remain. One such challenge is achieving a high capacity to store charge at the positive electrode at practical current densities, without which Li-air batteries will not outperform lithium-ion.

Achieving Planar Zn Electroplating in Aqueous Zinc Batteries with Cathode-Compatible Current Densities by Cycling under Pressure.

The value of aqueous zinc-ion rechargeable batteries is held back by the degradation of the Zn metal anode with repeated cycling. While raising the operating current density is shown to alleviate this anode degradation, such high cycling rates are not compatible with full cells, as they cause Zn-host cathodes to undergo capacity decay. A simple approach that improves anode performance while using more modest cathode-compatible current densities is required.

Lithium Borate Polycarbonates for High-Capacity Solid-State Composite Cathodes.

Improving composite cathode function is key to the success of the solid-state battery. Maximizing attainable cathode capacity and retention requires integrating suitable polymeric binders that retain a sufficiently high ionic conductivity and long-term chemo-mechanical stability of the cathode active material-solid-electrolyte-carbon mixture. Herein, we report block copolymer networks composed of lithium borate polycarbonates and poly(ethylene oxide) that improved the capacity (200 mAh g at 1.

Trapped O and the origin of voltage fade in layered Li-rich cathodes.

Oxygen redox cathodes, such as LiNiCoMnO, deliver higher energy densities than those based on transition metal redox alone. However, they commonly exhibit voltage fade, a gradually diminishing discharge voltage on extended cycling. Recent research has shown that, on the first charge, oxidation of O ions forms O molecules trapped in nano-sized voids within the structure, which can be fully reduced to O on the subsequent discharge.

Alternatives to fluorinated binders: recyclable copolyester/carbonate electrolytes for high-capacity solid composite cathodes.

Optimising the composite cathode for next-generation, safe solid-state batteries with inorganic solid electrolytes remains a key challenge towards commercialisation and cell performance. Tackling this issue requires the design of suitable polymer binders for electrode processability and long-term solid-solid interfacial stability. Here, -polyester/carbonates are systematically designed as Li-ion conducting, high-voltage stable binders for cathode composites comprising of single-crystal LiNiMnCoO cathodes, LiPSCl solid electrolyte and carbon nanofibres.

Diagnosing the Electrostatic Shielding Mechanism for Dendrite Suppression in Aqueous Zinc Batteries.

Aqueous zinc electrolytes offer the potential for cheaper rechargeable batteries due to their safe compatibility with the high capacity metal anode; yet, they are stymied by irregular zinc deposition and consequent dendrite growth. Suppressing dendrite formation by tailoring the electrolyte is a proven approach from lithium batteries; yet, the underlying mechanistic understanding that guides such tailoring does not necessarily directly translate from one system to the other. Here, it is shown that the electrostatic shielding mechanism, a fundamental concept in electrolyte engineering for stable metal anodes, has different consequences for the plating morphology in aqueous zinc batteries.

A lithium-air battery and gas handling system demonstrator.

The lithium-air (Li-air) battery offers one of the highest practical specific energy densities of any battery system at >400 W h kg. The practical cell is expected to operate in air, which is flowed into the positive porous electrode where it forms LiO on discharge and is released as O on charge. The presence of CO and HO in the gas stream leads to the formation of oxidatively robust side products, LiCO and LiOH, respectively.

The accumulation of LiCO in a Li-O battery with dual mediators.

One of the most important challenges facing long cycle life Li-O batteries is solvent degradation. Even the most stable ethers, such as CHO(CHCHO)CH, degrade to form products including LiCO, which accumulates in the pores of the gas diffusion electrode on cycling leading to polarisation and capacity fading. In this work, we examine the build-up and distribution of LiCO within the porous gas diffusion electrode during cycling and its link to the cell failure.

Dendrite initiation and propagation in lithium metal solid-state batteries.

All-solid-state batteries with a Li anode and ceramic electrolyte have the potential to deliver a step change in performance compared with today's Li-ion batteries. However, Li dendrites (filaments) form on charging at practical rates and penetrate the ceramic electrolyte, leading to short circuit and cell failure. Previous models of dendrite penetration have generally focused on a single process for dendrite initiation and propagation, with Li driving the crack at its tip.

Why charging Li-air batteries with current low-voltage mediators is slow and singlet oxygen does not explain degradation.

Although Li-air rechargeable batteries offer higher energy densities than lithium-ion batteries, the insulating LiO formed during discharge hinders rapid, efficient re-charging. Redox mediators are used to facilitate LiO oxidation; however, fast kinetics at a low charging voltage are necessary for practical applications and are yet to be achieved. We investigate the mechanism of LiO oxidation by redox mediators.

Batteries for wearables.

This perspective article highlights the recent advances and future challenges of battery technologies for wearables.

Buffering Volume Change in Solid-State Battery Composite Cathodes with CO-Derived Block Polycarbonate Ethers.

Polymers designed with a specific combination of electrochemical, mechanical, and chemical properties could help overcome challenges limiting practical all-solid-state batteries for high-performance next-generation energy storage devices. In composite cathodes, comprising active cathode material, inorganic solid electrolyte, and carbon, battery longevity is limited by active particle volume changes occurring on charge/discharge. To overcome this, impractical high pressures are applied to maintain interfacial contact.

Transition metal migration and O formation underpin voltage hysteresis in oxygen-redox disordered rocksalt cathodes.

Lithium-rich disordered rocksalt cathodes display high capacities arising from redox chemistry on both transition-metal ions (TM-redox) and oxygen ions (O-redox), making them promising candidates for next-generation lithium-ion batteries. However, the atomic-scale mechanisms governing O-redox behaviour in disordered structures are not fully understood. Here we show that, at high states of charge in the disordered rocksalt LiMnOF, transition metal migration is necessary for the formation of molecular O trapped in the bulk.

Achieving Ultrahigh-Rate Planar and Dendrite-Free Zinc Electroplating for Aqueous Zinc Battery Anodes.

Despite being one of the most promising candidates for grid-level energy storage, practical aqueous zinc batteries are limited by dendrite formation, which leads to significantly compromised safety and cycling performance. In this study, by using single-crystal Zn-metal anodes, reversible electrodeposition of planar Zn with a high capacity of 8 mAh cm can be achieved at an unprecedentedly high current density of 200 mA cm . This dendrite-free electrode is well maintained even after prolonged cycling (>1200 cycles at 50 mA cm ).

Covalency does not suppress O formation in 4d and 5d Li-rich O-redox cathodes.

Layered Li-rich transition metal oxides undergo O-redox, involving the oxidation of the O ions charge compensated by extraction of Li ions. Recent results have shown that for 3d transition metal oxides the oxidized O forms molecular O trapped in the bulk particles. Other forms of oxidised O such as O or (O-O) with long bonds have been proposed, based especially on work on 4 and 5d transition metal oxides, where TM-O bonding is more covalent.

Temperature Dependence of Lithium Anode Voiding in Argyrodite Solid-State Batteries.

Void formation at the Li/ceramic electrolyte interface of an all-solid-state battery on discharge results in high local current densities, dendrites on charge, and cell failure. Here, we show that such voiding is reduced at the Li/LiPSCl interface at elevated temperatures, sufficient to increase the critical current before voiding and cell failure from <0.25 mA cm at 25 °C to 0.

Visualizing plating-induced cracking in lithium-anode solid-electrolyte cells.

Lithium dendrite (filament) propagation through ceramic electrolytes, leading to short circuits at high rates of charge, is one of the greatest barriers to realizing high-energy-density all-solid-state lithium-anode batteries. Utilizing in situ X-ray computed tomography coupled with spatially mapped X-ray diffraction, the propagation of cracks and the propagation of lithium dendrites through the solid electrolyte have been tracked in a Li/LiPSCl/Li cell as a function of the charge passed. On plating, cracking initiates with spallation, conical 'pothole'-like cracks that form in the ceramic electrolyte near the surface with the plated electrode.

Non-equilibrium metal oxides via reconversion chemistry in lithium-ion batteries.

Binary metal oxides are attractive anode materials for lithium-ion batteries. Despite sustained effort into nanomaterials synthesis and understanding the initial discharge mechanism, the fundamental chemistry underpinning the charge and subsequent cycles-thus the reversible capacity-remains poorly understood. Here, we use in operando X-ray pair distribution function analysis combining with our recently developed analytical approach employing Metropolis Monte Carlo simulations and non-negative matrix factorisation to study the charge reaction thermodynamics of a series of Fe- and Mn-oxides.

Imaging Sodium Dendrite Growth in All-Solid-State Sodium Batteries Using Na -Weighted Magnetic Resonance Imaging.

Two-dimensional, Knight-shifted, -contrasted Na magnetic resonance imaging (MRI) of an all-solid-state cell with a Na electrode and a ceramic electrolyte is employed to directly observe Na microstructural growth. A spalling dendritic morphology is observed and confirmed by more conventional post-mortem analysis; X-ray tomography and scanning electron microscopy. A significantly larger Na for the dendritic growth, compared with the bulk metal electrode, is attributed to increased sodium ion mobility in the dendrite.

Redox Chemistry and the Role of Trapped Molecular O in Li-Rich Disordered Rocksalt Oxyfluoride Cathodes.

In the search for high energy density cathodes for next-generation lithium-ion batteries, the disordered rocksalt oxyfluorides are receiving significant attention due to their high capacity and lower voltage hysteresis compared with ordered Li-rich layered compounds. However, a deep understanding of these phenomena and their redox chemistry remains incomplete. Using the archetypal oxyfluoride, LiMnOF, we show that the oxygen redox process in such materials involves the formation of molecular O trapped in the bulk structure of the charged cathode, which is reduced on discharge.

Imaging Sodium Dendrite Growth in All-Solid-State Sodium Batteries Using Na T -Weighted Magnetic Resonance Imaging.

Two-dimensional, Knight-shifted, T -contrasted Na magnetic resonance imaging (MRI) of an all-solid-state cell with a Na electrode and a ceramic electrolyte is employed to directly observe Na microstructural growth. A spalling dendritic morphology is observed and confirmed by more conventional post-mortem analysis; X-ray tomography and scanning electron microscopy. A significantly larger Na T for the dendritic growth, compared with the bulk metal electrode, is attributed to increased sodium ion mobility in the dendrite.