An Adjustable‐Porosity Plastic Crystal Electrolyte Enables High‐Performance All‐Solid‐State Lithium‐Oxygen Batteries

The limited triple‐phase boundaries (TPBs) in solid‐state cathodes (SSCs) and high resistance imposed by solid electrolytes (SEs) make the achievement of high‐performance all‐solid‐state lithium‐oxygen (ASS Li‐O₂) batteries a challenge. Herein, an adjustable‐porosity plastic crystal electrolyte (PCE) has been fabricated by employing a thermally induced phase separation (TIPS) technique to overcome the above tricky issues. The SSC produced through the in‐situ introduction of the porous PCE on the surface of the active material, facilitates the simultaneous transfer of Li⁺/e^?, as well as ensures fast flow of O₂, forming continuous and abundant TPBs. The high Li⁺ conductivity, softness, and adhesion of the dense PCE significantly reduce the battery resistance to 115 Ω. As a result, the ASS Li‐O₂ battery based on this adjustable‐porosity PCE exhibits superior performances with high specific capacity (5963 mAh g^?1), good rate capability, and stable cycling life up to 130 cycles at 32 °C. This novel design and exciting results could open a new avenue for ASS Li‐O₂ batteries.     

Solvation Structure with Enhanced Anionic Coordination for Stable Anodes in Lithium-Oxygen Batteries

Li-O₂ batteries have garnered much attention due to their high theoretical energy density. However, the irreversible lithium plating/stripping on the anode limits their performance, which has been paid little attention. Herein, a solvation-regulated strategy for stable lithium anodes in tetraethylene glycol dimethyl ether (G4) based electrolyte is attempted in Li-O₂ batteries. Trifluoroacetate anions (TFA⁻) with strong Li⁺ affinity are incorporated into the lithium bis(fluorosulfonyl)imide (LiTFSI)/G4 electrolyte to attenuate the Li⁺-G4 interaction and form anion-dominant solvates. The bisalt electrolyte with 0.5 M LiTFA and 0.5 M LiTFSI mitigates G4 decomposition and induces an inorganic-rich solid electrolyte interphase (SEI). This contributes to decreased desolvation energy barrier from 58.20 to 46.31 kJ mol⁻¹, compared with 1.0 M LiTFSI/G4, for facile interfacial Li⁺ diffusion and high efficiency. It yields extended lifespan of 120 cycles in Li-O₂ battery with a limited Li anode (7 mAh cm⁻²). This work gains comprehensive insights into rational electrolyte design for Li-O₂ batteries.     

Influencing Factors on Li-ion Conductivity and Interfacial Stability of Solid Polymer Electrolytes,Exampled by Polycarbonates,Polyoxalates and Polymalonates

The application of solid polymer electrolytes (SPEs) in all-solid-state(ASS) batteries is hindered by lower Li⁺-conductivity and narrower electrochemical window. Here, three families of ester-based F-modified SPEs of poly-carbonate (PCE), poly-oxalate (POE) and poly-malonate (PME) were investigated. The Li⁺-conductivity of these SPEs prepared from pentanediol are all higher than the counterparts made of butanediol, owing to the enhanced asymmetry and flexibility. Because of stronger chelating coordination with Li⁺, the Li⁺-conductivity of PME and POE is around 10 and 5 times of PCE. The trifluoroacetyl-units are observed more effective than −O−CH₂−CF₂−CF₂−CH₂−O− during the in situ passivation of Li-metal. Using trifluoroacetyl terminated POE and PCE as SPE, the interfaces with Li-metal and high-voltage-cathode are stabilized simultaneously, endowing stable cycling of ASS Li/LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cells. Owing to an enol isomerization of malonate, the cycling stability of Li/PME/NCM622 is deteriorated, which is recovered with the introduce of dimethyl-group in malonate and the suppression of enol isomerization. The coordinating capability with Li⁺, molecular asymmetry and existing modes of elemental F, are all critical for the molecular design of SPEs.     

High-Capacity and Stable Li-O2 Batteries Enabled by a Trifunctional Soluble Redox Mediator

Li-O₂ batteries with ultrahigh theoretical energy densities usually suffer from low practical discharge capacities and inferior cycling stability owing to the cathode passivation caused by insulating discharge products and by-products. Here, a trifunctional ether-based redox mediator, 2,5-di-tert-butyl-1,4-dimethoxybenzene (DBDMB), is introduced into the electrolyte to capture reactive O₂⁻ and alleviate the rigorous oxidative environment of Li-O₂ batteries. Thanks to the strong solvation effect of DBDMB towards Li⁺ and O₂⁻, it not only reduces the formation of by-products (a high Li₂O₂ yield of 96.6 %), but also promotes the solution growth of large-sized Li₂O₂ particles, avoiding the passivation of cathode as well as enabling a large discharge capacity. Moreover, DBDMB makes the oxidization of Li₂O₂ and the decomposition of main by-products (Li₂CO₃ and LiOH) proceed in a highly effective manner, prolonging the stability of Li-O₂ batteries (243 cycles at 1000 mAh g⁻¹ and 1000 mA g⁻¹).     

Realizing Stable Carbonate Electrolytes in Li–O2/CO2 Batteries†

The increasing demand for high-energy storage systems has propelled the development of Li-air batteries and Li-O₂/CO₂ batteries to elucidate the mechanism and extend battery life. However, the high charge voltage of Li₂CO₃ accelerates the decomposition of traditional sulfone and ether electrolytes, thus adopting high-voltage electrolytes in Li-O₂/CO₂ batteries is vital to achieve a stable battery system. Herein, we adopt a commercial carbonate electrolyte to prove its excellent suitability in Li-O₂/CO₂ batteries. The generated superoxide can be captured by CO₂ to form less aggressive intermediates, stabilizing the carbonate electrolyte without reactive oxygen species induced decomposition. In addition, this electrolyte permits the Li metal plating/stripping with a significantly improved reversibility, enabling the possibility of using ultra-thin Li anode. Benefiting from the good rechargeability of Li₂CO₃, less cathode passivation, and stabilized Li anode in carbonate electrolyte, the Li-O₂/CO₂ battery demonstrates a long cycling lifetime of 167 cycles at 0.1 mA·cm^–2 and 0.25 mAh·cm^–2. This work paves a new avenue for optimizing carbonate-based electrolytes for Li-O₂ and Li-O₂/CO₂ batteries.      

A soluble phenolic mediator contributing to enhanced discharge capacity and low charge overpotential for lithium-oxygen batteries

In this study, a phenolic antioxidant of 2,6-di-tert-butyl-hydroxytoluene (BHT) is applied in Li-O₂ batteries to simultaneously improve discharge capacity and reduce charge overpotential. BHT exhibits a redox couple at ~ 3.0 V (vs. Li⁺/Li), which is extremely close to the thermodynamic potential of a Li-O₂ battery (2.96 V). The unique chemical and electrochemical behaviors of BHT contribute to the improvement on both oxygen reduction reaction and oxygen evolution reaction performances. These factors lead to the notable enhancement of discharge capacity (capacity increases by 72%) and the reduction of charge plateau (the plateau is 3.2 V and 4.2 V, respectively, with and without BHT) for Li-O₂ batteries. Furthermore, in-situ X-ray diffraction results confirm that the BHT-mediated formation and decomposition of Li₂O₂, rather than parasitic reactions, dominate the discharge and charge processes. The results provide a new approach for exploiting appropriate soluble mediators for rechargeable Li-O₂ batteries.     

Recent advances in charge mechanism of noble metal-based cathodes for Li-O2 batteries

Lithium-oxygen(Li-O₂ ) batteries are considered as the next generation for energy storages systems due to the higher theoretical energy density than that of Li-ion batteries. However, the high charge overpotential caused by the insulated Li₂O₂ results in low energy efficiency, side reaction from electrolyte and cathode, and therefore poor battery performance. Designing noble metal-based catalysts can be an effective strategy to develop high-performance Li-O_2...     

A Li-ion oxygen battery with Li-Si alloy anode prepared by a mechanical method

Li-O₂ battery is the leading next-generation battery system, which is known for its extremely high theoretic specific energy. However, the Li metal used in Li-O₂ batteries suffers from low Li utilization and safety hazards. In this work, as an alternative to Li anode, Li₂₁Si₅ powders, which are synthesized by an easy mechanical process, are incorporated into a Li-ion oxygen battery. The electrochemical property of the prepared battery and its cycling stability are investigated. Without electrochemical prelithiation, the pursuit of Li-Si alloy anodes in this study provides an easy and scalable strategy for preparing Li-ion oxygen batteries.     

Temperature dependence of charging characteristic of C-free Li2O2 cathode in Li-O2 battery

Charging characteristics of lithium–oxygen (Li-O₂) batteries, using C-free lithium peroxide (Li₂O₂)-based electrodes, have been explored in this paper based on ether-based electrolytes. Charging overpotential can be lowered with the decrease of current density, and the most possible reason behind this may lie in the poor electrical conductivity of Li₂O₂. Meanwhile, high temperature seems beneficial for the charging process indicating Li-O₂ batteries may be promising high-temperature batteries. Charging voltage plateau is about 3.05 V at the test temperature of 343 K and current density of 4.2 mA g^?1, which is the lowest value among the Li-O₂ batteries reported to date.     

Ionic Liquid Electrolyte with Weak Solvating Molecule Regulation for Stable Li Deposition in High-Performance Li−O2 Batteries

Li−O₂ batteries with bis(trifluoromethanesulfonyl)imide-based ionic liquid (TFSI-IL) electrolyte are promising because TFSI-IL can stabilize O₂⁻ to lower charge overpotential. However, slow Li⁺ transport in TFSI-IL electrolyte causes inferior Li deposition. Here we optimize weak solvating molecule (anisole) to generate anisole-doped ionic aggregate in TFSI-IL electrolyte. Such unique solvation environment can realize not only high Li⁺ transport parameters but also anion-derived solid electrolyte interface (SEI). Thus, fast Li⁺ transport is achieved in electrolyte bulk and SEI simultaneously, leading to robust Li deposition with high rate capability (3 mA cm⁻²) and long cycle life (2000 h at 0.2 mA cm⁻²). Moreover, Li−O₂ batteries show good cycling stability (a small overpotential increase of 0.16 V after 120 cycles) and high rate capability (1 A g⁻¹). This work provides an effective electrolyte design principle to realize stable Li deposition and high-performance Li−O₂ batteries.     

Defective TiO2 hollow nanospheres as photo-electrocatalysts for photo-assisted Li-O2 batteries

The large overpotential for conventional Li-O₂ batteries is an enormous challenge, which impedes their practical application. Here, we prepare a defective TiO₂ (Ov-TiO₂) hollow nanosphere as photo-electrocatalyst for photo-assisted Li-O₂ batteries to reduce the overpotential. Under illumination, the oxygen vacancies as a charge separation center contribute to the separation of electrons and holes. The generated electrons could promote reducing O₂ to Li₂O₂ during oxygen reduction reaction (ORR) process, while the generated holes are beneficial to Li₂O₂ decomposition during oxygen evolution reaction (OER) process. Additionally, the proper concentration of oxygen vacancies will decrease the recombination rate between electrons and holes. The photo-assisted Li-O₂ batteries with Ov-TiO₂-650 exhibit advanced performances, such as the low overpotential (0.70 V), the fine rate capability, and the considerable reversibility accompanied with the formation/decomposition of Li₂O₂. We expect that these results could open a new mind to design of highly efficient photo-electrocatalysts for photo-assisted Li-O₂ battery.     

New Reaction Pathway of Superoxide Disproportionation Induced by a Soluble Catalyst in Li-O2 Batteries

Aprotic Li-O₂ battery has attracted considerable interest for high theoretical energy density, however the disproportionation of the intermediate of superoxide (O₂⁻) during discharge and charge leads to slow reaction kinetics and large voltage hysteresis. Herein, the chemically stable ruthenium tris(bipyridine) (RB) cations are employed as a soluble catalyst to alternate the pathway of O₂⁻ disproportionation and its kinetics in both the discharge and charge processes. RB captures O₂⁻ dimer and promotes their intramolecular charge transfer, and it decreases the energy barrier of the disproportionation reaction from 7.70 to 0.70 kcal mol⁻¹. This facilitates the discharge and charge processes and simultaneously mitigates O₂⁻ and singlet oxygen related side reactions. These endow the Li-O₂ battery with reduced discharge/charge voltage gap of 0.72 V and prolonged lifespan for over 230 cycles when coupled with RuO₂ catalyst. This work highlights the vital role of superoxide disproportionation for Li-O₂ battery.     

Enzyme-Inspired Room-Temperature Lithium–Oxygen Chemistry via Reversible Cleavage and Formation of Dioxygen Bonds

Li-O₂ batteries are promising energy storage systems due to their ultra-high theoretical capacity. However, most Li-O₂ batteries are based on the reduction/oxidation of Li₂O₂ and involve highly reactive superoxide and peroxide species that would cause serious degradation of cathodes, especially carbon-based materials. It is important to explore lithium-oxygen reactions and find new Li-O₂ chemistry which can restrict or even avoid the negative influence of superoxide/peroxide species. Here, inspired by enzyme-catalyzed oxygen reduction/oxidation reactions, we introduce a copper(I) complex 3 N-Cu^I (3 N=1,4,7-trimethyl-1,4,7-triazacyclononane) to Li-O₂ batteries and successfully modulate the reaction pathway to a moderate one on reversible cleavage/formation of O−O bonds. This work demonstrates that the reaction pathways of Li-O₂ batteries could be modulated by introducing an appropriate soluble catalyst, which is another powerful choice to construct better Li-O₂ batteries.     

A Rechargeable Li-CO2 Battery with a Gel Polymer Electrolyte

The utilization of CO₂ in Li-CO₂ batteries is attracting extensive attention. However, the poor rechargeability and low applied current density have remained the Achilles’ heel of this energy device. The gel polymer electrolyte (GPE), which is composed of a polymer matrix filled with tetraglyme-based liquid electrolyte, was used to fabricate a rechargeable Li-CO₂ battery with a carbon nanotube-based gas electrode. The discharge product of Li₂CO₃ formed in the GPE-based Li-CO₂ battery exhibits a particle-shaped morphology with poor crystallinity, which is different from the contiguous polymer-like and crystalline discharge product in conventional Li-CO₂ battery using a liquid electrolyte. Accordingly, the GPE-based battery shows much improved electrochemical performance. The achieved cycle life (60 cycles) and rate capability (maximum applied current density of 500 mA g⁻¹) are much higher than most of previous reports, which points a new way to develop high-performance Li-CO₂ batteries.     

A Long-Life Lithium–Air Battery in Ambient Air with a Polymer Electrolyte Containing a Redox Mediator

Lithium–air batteries when operated in ambient air generally exhibit poor reversibility and cyclability, because of the Li passivation and Li₂O₂/LiOH/Li₂CO₃ accumulation in the air electrode. Herein, we present a Li–air battery supported by a polymer electrolyte containing 0.05 m LiI, in which the polymer electrolyte efficiently alleviates the Li passivation induced by attacking air. Furthermore, it is demonstrated that I⁻/I₂ conversion in polymer electrolyte acts as a redox mediator that facilitates electrochemical decomposition of the discharge products during recharge process. As a result, the Li–air battery can be stably cycled 400 times in ambient air (relative humidity of 15 %), which is much better than previous reports. The achievement offers a hope to develop the Li–air battery that can be operated in ambient air.     

Experimental and Computational Analysis of the Solvent‐Dependent O2/Li+‐O2− Redox Couple: Standard Potentials,Coupling Strength,and Implications for Lithium–Oxygen Batteries

Understanding and controlling the kinetics of O₂ reduction in the presence of Li⁺‐containing aprotic solvents, to either Li⁺‐O₂⁻ by one‐electron reduction or Li₂O₂ by two‐electron reduction, is instrumental to enhance the discharge voltage and capacity of aprotic Li‐O₂ batteries. Standard potentials of O₂/Li⁺‐O₂⁻ and O₂/O₂⁻ were experimentally measured and computed using a mixed cluster‐continuum model of ion solvation. Increasing combined solvation of Li⁺ and O₂⁻ was found to lower the coupling of Li⁺‐O₂⁻ and the difference between O₂/Li⁺‐O₂⁻ and O₂/O₂⁻ potentials. The solvation energy of Li⁺ trended with donor number (DN), and varied greater than that of O₂⁻ ions, which correlated with acceptor number (AN), explaining a previously reported correlation between Li⁺‐O₂⁻ solubility and DN. These results highlight the importance of the interplay between ion–solvent and ion–ion interactions for manipulating the energetics of intermediate species produced in aprotic metal–oxygen batteries.     

High-Voltage Rechargeable Alkali–Acid Zn–PbO2 Hybrid Battery

Aqueous rechargeable batteries have attracted attention owning to their advantages of safety, low cost, and sustainability, while the limited electrochemical stability window (1.23 V) of water leads to their failure in competition with organic-based lithium-ion batteries. Herein, we report an alkali–acid Zn–PbO₂ hybrid aqueous battery obtained by coupling an alkaline Zn anode with an acidic PbO₂ cathode. It shows the capability to deliver an impressively high open-circuit voltage (V_oc) of 3.09 V and an operate voltage of 2.95 V at 5 mA cm⁻², thanks to the contribution of expanding the voltage window and the electrochemical neutralization energy from the alkali–acid asymmetric-electrolyte hybrid cell. The hybrid battery can potentially deliver a large area capacity over 2 mAh cm⁻² or a high energy density of 252.39 Wh kg⁻¹ and shows almost no fading in area capacity over 250 charge–discharge cycles.     

Excellent Stability of a Lithium‐Ion‐Conducting Solid Electrolyte upon Reversible Li+/H+ Exchange in Aqueous Solutions

Batteries with an aqueous catholyte and a Li metal anode have attracted interest owing to their exceptional energy density and high charge/discharge rate. The long‐term operation of such batteries requires that the solid electrolyte separator between the anode and aqueous solutions must be compatible with Li and stable over a wide pH range. Unfortunately, no such compound has yet been reported. In this study, an excellent stability in neutral and strongly basic solutions was observed when using the cubic Li₇La₃Zr₂O₁₂ garnet as a Li‐stable solid electrolyte. The material underwent a Li⁺/H⁺ exchange in aqueous solutions. Nevertheless, its structure remained unchanged even under a high exchange rate of 63.6 %. When treated with a 2 M LiOH solution, the Li⁺/H⁺ exchange was reversed without any structural change. These observations suggest that cubic Li₇La₃Zr₂O₁₂ is a promising candidate for the separator in aqueous lithium batteries.     

Intrinsic Stress-strain in Barium Titanate Piezocatalysts Enabling Lithium−Oxygen Batteries with Low Overpotential and Long Life

Rechargeable lithium−oxygen (Li−O₂) batteries with high theoretical energy density are considered as promising candidates for portable electronic devices and electric vehicles, whereas their commercial application is hindered due to poor cyclic stability caused by the sluggish kinetics and cathode passivation. Herein, the intrinsic stress originated from the growth and decomposition of the discharge product (lithium peroxide, Li₂O₂) is employed as a microscopic pressure resource to induce the built-in electric field, further improving the reaction kinetics and interfacial Lithium ion (Li⁺) transport during cycling. Piezopotential caused by the intrinsic stress-strain of solid Li₂O₂ is capable of providing the driving force for the separation and transport of carriers, enhancing the Li⁺ transfer, and thus improving the redox reaction kinetics of Li−O₂ batteries. Combined with a variety of in situ characterizations, the catalytic mechanism of barium titanate (BTO), a typical piezoelectric material, was systematically investigated, and the effect of stress-strain transformation on the electrochemical reaction kinetics and Li⁺ interface transport for the Li−O₂ batteries is clearly established. The findings provide deep insight into the surface coupling strategy between intrinsic stress and electric fields to regulate the electrochemical reaction kinetics behavior and enhance the interfacial Li⁺ transport for battery system.     

Lithium Nitrate Regulated Sulfone Electrolytes for Lithium Metal Batteries

The electrolytes in lithium metal batteries have to be compatible with both lithium metal anodes and high voltage cathodes, and can be regulated by manipulating the solvation structure. Herein, to enhance the electrolyte stability, lithium nitrate (LiNO₃) and 1,1,2,2-tetrafuoroethyl-2′,2′,2′-trifuoroethyl(HFE) are introduced into the high-concentration sulfolane electrolyte to suppress Li dendrite growth and achieve a high Coulombic efficiency of >99 % for both the Li anode and LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) cathodes. Molecular dynamics simulations show that NO₃⁻ participates in the solvation sheath of lithium ions enabling more bis(trifluoromethanesulfonyl)imide anion (TFSI⁻) to coordinate with Li⁺ ions. Therefore, a robust LiN_xO_y−LiF-rich solid electrolyte interface (SEI) is formed on the Li surface, suppressing Li dendrite growth. The LiNO₃-containing sulfolane electrolyte can also support the highly aggressive LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) cathode, delivering a discharge capacity of 190.4 mAh g⁻¹ at 0.5 C for 200 cycles with a capacity retention rate of 99.5 %.