Superior Rechargeability and Efficiency of Lithium–Oxygen Batteries: Hierarchical Air Electrode Architecture Combined with a Soluble Catalyst

The lithium–oxygen battery has the potential to deliver extremely high energy densities; however, the practical use of Li‐O₂ batteries has been restricted because of their poor cyclability and low energy efficiency. In this work, we report a novel Li‐O₂ battery with high reversibility and good energy efficiency using a soluble catalyst combined with a hierarchical nanoporous air electrode. Through the porous three‐dimensional network of the air electrode, not only lithium ions and oxygen but also soluble catalysts can be rapidly transported, enabling ultra‐efficient electrode reactions and significantly enhanced catalytic activity. The novel Li‐O₂ battery, combining an ideal air electrode and a soluble catalyst, can deliver a high reversible capacity (1000 mAh g^?1) up to 900 cycles with reduced polarization (about 0.25 V).     

The Stabilization Effect of CO2 in Lithium–Oxygen/CO2 Batteries

The lithium (Li)–air battery has an ultrahigh theoretical specific energy, however, even in pure oxygen (O₂), the vulnerability of conventional organic electrolytes and carbon cathodes towards reaction intermediates, especially O₂^?, and corrosive oxidation and crack/pulverization of Li metal anode lead to poor cycling stability of the Li‐air battery. Even worse, the water and/or CO₂ in air bring parasitic reactions and safety issues. Therefore, applying such systems in open‐air environment is challenging. Herein, contrary to previous assertions, we have found that CO₂ can improve the stability of both anode and electrolyte, and a high‐performance rechargeable Li–O₂/CO₂ battery is developed. The CO₂ not only facilitates the in situ formation of a passivated protective Li₂CO₃ film on the Li anode, but also restrains side reactions involving electrolyte and cathode by capturing O₂^?. Moreover, the Pd/CNT catalyst in the cathode can extend the battery lifespan by effectively tuning the product morphology and catalyzing the decomposition of Li₂CO₃. The Li–O₂/CO₂ battery achieves a full discharge capacity of 6628 mAh g^?1 and a long life of 715 cycles, which is even better than those of pure Li–O₂ batteries.     

The Stabilization Effect of CO2 in Lithium–Oxygen/CO2 Batteries

The lithium (Li)–air battery has an ultrahigh theoretical specific energy, however, even in pure oxygen (O₂), the vulnerability of conventional organic electrolytes and carbon cathodes towards reaction intermediates, especially O₂⁻, and corrosive oxidation and crack/pulverization of Li metal anode lead to poor cycling stability of the Li-air battery. Even worse, the water and/or CO₂ in air bring parasitic reactions and safety issues. Therefore, applying such systems in open-air environment is challenging. Herein, contrary to previous assertions, we have found that CO₂ can improve the stability of both anode and electrolyte, and a high-performance rechargeable Li–O₂/CO₂ battery is developed. The CO₂ not only facilitates the in situ formation of a passivated protective Li₂CO₃ film on the Li anode, but also restrains side reactions involving electrolyte and cathode by capturing O₂⁻. Moreover, the Pd/CNT catalyst in the cathode can extend the battery lifespan by effectively tuning the product morphology and catalyzing the decomposition of Li₂CO₃. The Li–O₂/CO₂ battery achieves a full discharge capacity of 6628 mAh g⁻¹ and a long life of 715 cycles, which is even better than those of pure Li–O₂ batteries.     

Cation Additive Enabled Rechargeable LiOH-Based Lithium–Oxygen Batteries

Lithium–oxygen (Li–O₂) batteries have attracted extensive research interest due to their high energy density. Other than Li₂O₂ (a typical discharge product in Li–O₂ batteries), LiOH has proved to be electrochemically active as an alternative product. Here we report a simple strategy to achieve a reversible LiOH-based Li–O₂ battery by using a cation additive, sodium ions, to the lithium electrolyte. Without redox mediators in the cell, LiOH is detected as the sole discharge product and it charges at a low charge potential of 3.4 V. A solution-based reaction route is proposed, showing that the competing solvation environment of the catalyst and Li⁺ leads to LiOH precipitation at the cathode. It is critical to tune the cell chemistry of Li–O₂ batteries by designing a simple system to promote LiOH formation/decomposition.     

Core–Shell‐Structured CNT@RuO2 Composite as a High‐Performance Cathode Catalyst for Rechargeable Li–O2 Batteries

A RuO₂ shell was uniformly coated on the surface of core CNTs by a simple sol–gel method, and the resulting composite was used as a catalyst in a rechargeable Li–O₂ battery. This core–shell structure can effectively prevent direct contact between the CNT and the discharge product Li₂O₂, thus avoiding or reducing the formation of Li₂CO₃, which can induce large polarization and lead to charge failure. The battery showed a high round‐trip efficiency (ca. 79 %), with discharge and charge overpotentials of 0.21 and 0.51 V, respectively, at a current of 100 mA g_total^?1. The battery also exhibited excellent rate and cycling performance.     

Integrating a Photocatalyst into a Hybrid Lithium–Sulfur Battery for Direct Storage of Solar Energy

Direct capture and storage of abundant but intermittent solar energy in electrical energy‐storage devices such as rechargeable lithium batteries is of great importance, and could provide a promising solution to the challenges of energy shortage and environment pollution. Here we report a new prototype of a solar‐driven chargeable lithium–sulfur (Li‐S) battery, in which the capture and storage of solar energy was realized by oxidizing S^2? ions to polysulfide ions in aqueous solution with a Pt‐modified CdS photocatalyst. The battery can deliver a specific capacity of 792 mAh g^?1 during 2 h photocharging process with a discharge potential of around 2.53 V versus Li⁺/Li. A specific capacity of 199 mAh g^?1, reaching the level of conventional lithium‐ion batteries, can be achieved within 10 min photocharging. Moreover, the charging process of the battery can proceed under natural sunlight irradiation.     

Lithium Ion Pathway within Li7La3Zr2O12‐Polyethylene Oxide Composite Electrolytes

Polymer–ceramic composite electrolytes are emerging as a promising solution to deliver high ionic conductivity, optimal mechanical properties, and good safety for developing high‐performance all‐solid‐state rechargeable batteries. Composite electrolytes have been prepared with cubic‐phase Li₇La₃Zr₂O₁₂ (LLZO) garnet and polyethylene oxide (PEO) and employed in symmetric lithium battery cells. By combining selective isotope labeling and high‐resolution solid‐state Li NMR, we are able to track Li ion pathways within LLZO‐PEO composite electrolytes by monitoring the replacement of ⁷Li in the composite electrolyte by ⁶Li from the ⁶Li metal electrodes during battery cycling. We have provided the first experimental evidence to show that Li ions favor the pathway through the LLZO ceramic phase instead of the PEO‐LLZO interface or PEO. This approach can be widely applied to study ion pathways in ionic conductors and to provide useful insights for developing composite materials for energy storage and harvesting.     

Highly Rechargeable Lithium‐CO2 Batteries with a Boron‐ and Nitrogen‐Codoped Holey‐Graphene Cathode

Metal‐air batteries, especially Li‐air batteries, have attracted significant research attention in the past decade. However, the electrochemical reactions between CO₂ (0.04 % in ambient air) with Li anode may lead to the irreversible formation of insulating Li₂CO₃, making the battery less rechargeable. To make the Li‐CO₂ batteries usable under ambient conditions, it is critical to develop highly efficient catalysts for the CO₂ reduction and evolution reactions and investigate the electrochemical behavior of Li‐CO₂ batteries. Here, we demonstrate a rechargeable Li‐CO₂ battery with a high reversibility by using B,N‐codoped holey graphene as a highly efficient catalyst for CO₂ reduction and evolution reactions. Benefiting from the unique porous holey nanostructure and high catalytic activity of the cathode, the as‐prepared Li‐CO₂ batteries exhibit high reversibility, low polarization, excellent rate performance, and superior long‐term cycling stability over 200 cycles at a high current density of 1.0 A g⁻¹. Our results open up new possibilities for the development of long‐term Li‐air batteries reusable under ambient conditions, and the utilization and storage of CO₂.     

A Versatile Halide Ester Enabling Li‐Anode Stability and a High Rate Capability in Lithium–Oxygen Batteries

Li‐O₂ batteries are promising candidates for next‐generation high‐energy‐density battery systems. However, the main problems of Li–O₂ batteries include the poor rate capability of the cathode and the instability of the Li anode. Herein, an ester‐based liquid additive, 2,2,2‐trichloroethyl chloroformate, was introduced into the conventional electrolyte of a Li–O₂ battery. Versatile effects of this additive on the oxygen cathode and the Li metal anode became evident. The Li–O₂ battery showed an outstanding rate capability of 2005 mAh g^?1 with a remarkably decreased charge potential at a large current density of 1000 mA g^?1. The positive effect of the halide ester on the rate capacity is associated with the improved solubility of Li₂O₂ in the electrolyte and the increased diffusion rate of O₂. Furthermore, the ester promotes the formation of a solid–electrolyte interphase layer on the surface of the Li metal, which restrains the loss and volume change of the Li electrode during stripping and plating, thereby achieving a cycling stability over 900 h and a Li capacity utilization of up to 10 mAh cm^?2.     

Ambient Lithium–SO2 Batteries with Ionic Liquids as Electrolytes

Li‐SO₂ batteries have a high energy density but bear serious safety problems that are associated with pressurized SO₂ and flammable solvents in the system. Herein, a novel ambient Li‐SO₂ battery was developed through the introduction of ionic liquid (IL) electrolytes with tailored basicities to solvate SO₂ by reversible chemical absorption. By tuning the interactions of ILs with SO₂, a high energy density and good discharge performance with operating voltages above 2.8 V were obtained. This strategy based on reversible chemical absorption of SO₂ in IL electrolytes enables the development of the next generation of ambient Li‐SO₂ 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.     

Rechargeable Room‐Temperature Na–CO2 Batteries

Developing rechargeable Na–CO₂ batteries is significant for energy conversion and utilization of CO₂. However, the reported batteries in pure CO₂ atmosphere are non‐rechargeable with limited discharge capacity of 200 mAh g^?1. Herein, we realized the rechargeability of a Na–CO₂ battery, with the proposed and demonstrated reversible reaction of 3 CO₂+4 Na?2 Na₂CO₃+C. The battery consists of a Na anode, an ether‐based electrolyte, and a designed cathode with electrolyte‐treated multi‐wall carbon nanotubes, and shows reversible capacity of 60000 mAh g^?1 at 1 A g^?1 (≈1000 Wh kg^?1) and runs for 200 cycles with controlled capacity of 2000 mAh g^?1 at charge voltage <3.7 V. The porous structure, high electro‐conductivity, and good wettability of electrolyte to cathode lead to reduced electrochemical polarization of the battery and further result in high performance. Our work provides an alternative approach towards clean recycling and utilization of CO₂.     

NiCo2O4 nanosheets supported on Ni foam for rechargeable nonaqueous sodium–air batteries

NiCo₂O₄ nanosheets supported on Ni foam were synthesized by a solvothermal method. A composite of NiCo₂O₄ nanosheets/Ni as a carbon-free and binder-free air cathode exhibited an initial discharge capacity of 1762 mAh g^− 1 with a low polarization of 0.96 V at 20 mA g^− 1 for sodium–air batteries. Na₂O₂ nanosheets were firstly observed as the discharged product in sodium–air battery. High electrocatalytic activity of NiCo₂O₄ nanosheets/Ni made it a promising air electrode for rechargeable sodium–air batteries.     

High-Performance K–CO2 Batteries Based on Metal-Free Carbon Electrocatalysts

Metal–CO₂ batteries have attracted much attention owing to their high energy density and use of greenhouse CO₂ waste as the energy source. However, the increasing cost of lithium and the low discharge potential of Na–CO₂ batteries create obstacles for practical applications of Li/Na–CO₂ batteries. Recently, earth-abundant potassium ions have attracted considerable interest as fast ionic charge carriers for electrochemical energy storage. Herein, we report the first K–CO₂ battery with a carbon-based metal-free electrocatalyst. The battery shows a higher theoretical discharge potential (E^⊖=2.48 V) than that of Na–CO₂ batteries (E^⊖=2.35 V) and can operate for more than 250 cycles (1500 h) with a cutoff capacity of 300 mA h g⁻¹. Combined DFT calculations and experimental observations revealed a reaction mechanism involving the reversible formation and decomposition of P12₁/c1-type K₂CO₃ at the efficient carbon-based catalyst.     

High‐Performance K–CO2 Batteries Based on Metal‐Free Carbon Electrocatalysts

Metal–CO₂ batteries have attracted much attention owing to their high energy density and use of greenhouse CO₂ waste as the energy source. However, the increasing cost of lithium and the low discharge potential of Na–CO₂ batteries create obstacles for practical applications of Li/Na–CO₂ batteries. Recently, earth‐abundant potassium ions have attracted considerable interest as fast ionic charge carriers for electrochemical energy storage. Herein, we report the first K–CO₂ battery with a carbon‐based metal‐free electrocatalyst. The battery shows a higher theoretical discharge potential (E^?=2.48 V) than that of Na–CO₂ batteries (E^?=2.35 V) and can operate for more than 250 cycles (1500 h) with a cutoff capacity of 300 mA h g^?1. Combined DFT calculations and experimental observations revealed a reaction mechanism involving the reversible formation and decomposition of P12₁/c1‐type K₂CO₃ at the efficient carbon‐based catalyst.     

A novel all-solid-state thin-film-type lithium-ion battery with in situ prepared positive and negative electrode materials

A novel all-solid-state thin-film-type rechargeable lithium-ion battery employing in situ prepared both positive and negative electrode materials is proposed. A lithium-ion conducting solid electrolyte sheet of Li₂O–Al₂O₃–TiO₂–P₂O₅-based glass–ceramic manufactured by OHARA Inc. (OHARA sheet) was used as the solid electrolyte, which was sandwiched by Cu and Mn metal films. The Cu/OHARA sheet/Mn layer became an all-solid-state lithium-ion battery after applying d.c. 16 V to the layer, and the resultant battery operated at 0.3–0.8 V with reversible capacity of 0.45 μAh cm^?2. High voltage battery was successfully prepared by applying the d.c. high voltage to a five-series of Cu/OHARA sheet/Mn layer, resulting in all-solid-state battery operating at 1.5–4.0 V. The proposed fabrication process will become a new technology to develop advanced all-solid-state rechargeable lithium-ion batteries.     

Sulfur-doped LaNiO3 perovskite oxides with enriched anionic vacancies and manipulated orbital occupancy facilitating oxygen electrode reactions in lithium-oxygen batteries

The rational design of effective bifunctional catalysts with enhanced activity toward oxygen reduction reaction and oxygen evolution reaction is of significance to develop high-performance lithium-oxygen (Li–O₂) batteries. Herein, sulfur-doped LaNiO₃ nanoparticles are elaborately synthesized, and their catalytic activity toward oxygen redox reactions in Li–O₂ batteries is comprehensively studied. As confirmed by the density functional theory calculations and experimental results, the substitution of oxygen atoms by sulfur atoms with lower Pauling electronegativity can enhance the covalent feature of bonds, thus increasing electrical conductivity of catalyst. In addition, abundant oxygen vacancies created after sulfur doping are capable of providing concentrated active sites. Simultaneously, sulfur dopants boost the hybridization between Ni 3d orbital and O 2p orbital and increase the covalency of Ni–O bonds due to the increase of Ni³⁺ with the near-unity occupancy of the e_g orbital, thereby increasing the adsorption strength of oxygen-containing intermediates on the surface. Eventually, lowered reaction energy barriers and accelerated reaction kinetics of oxygen electrode reactions are realized, contributing to the optimized electrochemical performance of Li–O₂ battery. The Li–O₂ battery based on sulfur-doped LaNiO₃ with the optimized S-doping level of 2.89 wt% (marked as S_2.89 wt%-LNO) delivers a high specific discharge capacity of 24067 mAh/g, an ultralow overpotential of 0.37 V and extended life of 347 cycles.     

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.     

Advanced High‐Voltage Aqueous Lithium‐Ion Battery Enabled by “Water‐in‐Bisalt” Electrolyte

A new super‐concentrated aqueous electrolyte is proposed by introducing a second lithium salt. The resultant ultra‐high concentration of 28 m led to more effective formation of a protective interphase on the anode along with further suppression of water activities at both anode and cathode surfaces. The improved electrochemical stability allows the use of TiO₂ as the anode material, and a 2.5 V aqueous Li‐ion cell based on LiMn₂O₄ and carbon‐coated TiO₂ delivered the unprecedented energy density of 100 Wh kg^?1 for rechargeable aqueous Li‐ion cells, along with excellent cycling stability and high coulombic efficiency. It has been demonstrated that the introduction of a second salts into the “water‐in‐salt” electrolyte further pushed the energy densities of aqueous Li‐ion cells closer to those of the state‐of‐the‐art Li‐ion batteries.     

Experimental study of the heat generations of Li/SOCl2 and Li/SO2 batteries using a phase-change measurement method

A paraffin phase-change measurement method for the heat generation of spirally wound cylindrical Li/SOCl₂ and Li/SO₂ batteries at different ambient temperatures and discharge currents is proposed. The electrical and thermal insulations of the measurement system have been greatly improved, and the accuracy of the measurement system is 4.6 % based on calibration experiments. Compared with accelerated rate calorimetry, isothermal microcalorimetry, and radiation calorimetry methods, the phase-change measurement method is simpler, but with a high accuracy. The experimental results reveal that the heat generation of the batteries during discharge is weakly dependent on the ambient temperature in the range of 38–50 °C, but strongly affected by the discharge current. As the discharge current increases, the heat generated by the Li/SOCl₂ and Li/SO₂ batteries increases as a quadratic polynomial function. The Li/SO₂ battery generates more heat than the Li/SOCl₂ battery at the same discharge current, which is demonstrated by the qualitative analysis of the internal resistance. Furthermore, the phase-change measurement method for heat generation has a strong universality, and can be applicable for heat generation measurement of various battery types.