Lee Johnson

Lee Johnson
University of Nottingham | Notts · School of Chemistry

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49
Publications
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2,715
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Publications

Publications (49)
Article
Development of sodium anodes, both hard carbon (HC) and metallic, is dependent on the discovery of electrolyte formations and additives able to stabilize the interphase and support Na+ transport. Halogen salt additives are known to lower the energy barrier for the Na-ion charge transfer at the interface and facilitate stable Na plating/stripping in...
Article
The demand for secondary batteries has shown continual and rapid growth, driven by the societal transition to electric and hybrid modes of transportation, with the lithium-ion battery finding extensive application throughout the energy storage industry. 1–3 To attain the energy density, lifetime and reliability required to satiate the needs of soci...
Article
Investigation of lithium-oxygen cells on discharge using a mixture of ¹⁶O¹⁶O and ¹⁸O¹⁸O gases, showed that O–O bond cleavage occurs during disproportionation of LiO2 to O2 and Li2O2, detected by the presence of isotopic ¹⁶O¹⁸O. The formation of singlet oxygen, ¹O2, was also monitored during disproportionation. While only 4.5% of oxygen was found to...
Article
We describe the preparation of hybrid redox materials based on polyoxomolybdates encapsulated within single-walled carbon nanotubes (SWNTs). Polyoxomolybdates readily oxidize SWNTs under ambient conditions in solution, and here we study their charge-transfer interactions with SWNTs to provide a detailed mechanistic insight into the redox-driven enc...
Article
Full-text available
We describe the preparation of hybrid redox materials based on polyoxomolybdates encapsulated within single-walled carbon nanotubes (SWNTs). Polyoxomolybdates readily oxidize SWNTs under ambient conditions in solution, and here we study their charge-transfer interactions with SWNTs to provide a detailed mechanistic insight into the redox-driven enc...
Article
Confinement of molecules within nanocontainers can be a powerful tool for controlling the states of guest-molecules, tuning properties of host-nanocontainers and triggering the emergence of synergistic properties within the host-guest systems. Among nanocontainers, single-walled carbon nanotubes - atomically thin cylinders of carbon, with typical d...
Article
This Tutorial Review describes how the development of dissolved redox-active molecules is beginning to unlock the potential of three of the most promising 'next-generation' battery technologies - lithium-air, lithium-sulfur and redox-flow batteries. Redox-active molecules act as mediators in lithium-air and lithium-sulfur batteries, shuttling charg...
Article
The search for enhanced energy density is fueling global research in battery science and engineering, where applications spanning consumer electronics, electric vehicles, and grid-scale energy storage are stimulating enormous industrial growth. While higher-energy-density batteries will combat range anxiety hampering EV adoption, it is not the only...
Article
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The goal of limiting global warming to 1.5 °C requires a drastic reduction in CO2 emissions across many sectors of the world economy. Batteries are vital to this endeavor, whether used in electric vehicles, to store renewable electricity, or in aviation. Present lithium-ion technologies are preparing the public for this inevitable change, but their...
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Discharge by a surface route at the cathode of an aprotic metal-O2 battery typically results in surface passivation by the non-conducting oxide product. This leads to low capacity and early cell death. Here we investigate the cathode discharge reaction in the potassium-O2 battery and demonstrate that discharge by a surface route is not limited to g...
Article
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Lithium-oxygen cells, in which lithium peroxide forms in solution rather than on the electrode surface, can sustain relatively high cycling rates but require redox mediators to charge. The mediators are oxidised at the electrode surface and then oxidise lithium peroxide stored in the cathode. The kinetics of lithium peroxide oxidation has received...
Article
The Na–air battery, because of its high energy density and low charging overpotential, is a promising candidate for low-cost energy storage, hence leading to intensive research. However, to achieve such a battery, the role of the positive electrode material in the discharge process must be understood. This issue is herein addressed by exploring the...
Article
An understanding of the species generated in the bulk electrolyte in the presence of superoxide anion, O2●-, is of interest due to its close relationship to the nature of the electrode reduction products. The sodium cation concentration in a pyrrolidinium-based ionic liquid has been shown to have a major impact on the nature of the discharge produc...
Article
At the cathode of a Li–O2 battery, O2 is reduced to Li2O2 on discharge, the process being reversed on charge. Li2O2 is an insulating and insoluble solid, leading ultimately to low rates, low capacities and early cell death if formed on the cathode surface. Here we show that when using dual mediators, 2,5-Di-tert-butyl-1,4-benzoquinone [DBBQ] on dis...
Article
Herein we investigate the influence of the sodium salt anion on the performance of Na-O2 batteries. To illustrate the solvent-solute interactions in various solvents, we use 23Na-NMR to probe the electronic environment of Na+ in presence of different anions (ClO4-, PF6-, OTf- or TFSi-). Strong solvation of either the Na+ or the salt anion leads to...
Article
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Discharge in the lithium-O2 battery is known to occur either by a solution mechanism, which enables high capacity and rates, or a surface mechanism, which passivates the electrode surface and limits performance. The development of strategies to promote solution-phase discharge in stable electrolyte solutions is a central challenge for development o...
Article
Full-text available
Discharge in the lithium-O2 battery is known to occur either by a solution mechanism, which enables high capacity and rates, or a surface mechanism, which passivates the electrode surface and limits performance. The development of strategies to promote solution-phase discharge in stable electrolyte solutions is a central challenge for development o...
Article
The reduction of O2 to solid Li2O2, via the intermediates O2- and LiO2, is the desired discharge reaction at the positive electrode of the aprotic Li-O2 batteries. In practice, a plethora of byproducts are identified together with Li2O2 and have been assigned to the side reactions between the reduced oxygen species (O2-, LiO2 and Li2O2) and the bat...
Article
The Na–O2 battery offers an interesting alternative to the Li–O2 battery, which is still the source of a number of unsolved scientific questions. In spite of both being alkali metal–O2 batteries, they display significant differences. For instance, Li–O2 batteries form Li2O2 as the discharge product at the cathode, whereas Na–O2 batteries usually fo...
Article
On discharge, the Li-O2 battery can form a Li2O2 film on the cathode surface, leading to low capacities, low rates and early cell death, or it can form Li2O2 particles in solution, leading to high capacities at relatively high rates and avoiding early cell death. Achieving discharge in solution is important and may be encouraged by the use of high...
Article
On discharge, the Li-O2 battery can form a Li2O2 film on the cathode surface, leading to low capacities, low rates and early cell death, or it can form Li2O2 particles in solution, leading to high capacities at relatively high rates and avoiding early cell death. Achieving discharge in solution is important and may be encouraged by the use of high...
Article
Li-ion and related battery technologies will be important for years to come. However, society needs energy storage that exceeds the capacity of Li-ion batteries. We must explore alternatives to Li-ion if we are to have any hope of meeting the long-term needs for energy storage. One such alternative is the Li-air (O 2 ) battery; its theoretical spec...
Article
Full-text available
There are various reaction mechanisms in the discharge process of a non-aqueous lithium air battery (LAB). Recently, it has been identified that low current rate and high donor number solvents can lead to solution phase reaction, but high current rate and low donor number solvents will cause thin film growth covering the active cathode surface. In...
Article
When lithium-oxygen batteries discharge, O2 is reduced at the cathode to form solid Li2O2. Understanding the fundamental mechanism of O2 reduction in aprotic solvents is therefore essential to realizing their technological potential. Two different models have been proposed for Li2O2 formation, involving either solution or electrode surface routes....
Article
We investigated the use of sulfone-based electrolytes for the Li-O2 battery. The study compared the behavior of three commercially available sulfones: ethyl vinyl sulfone (EVS), tetramethylene sulfone (TMS), also called sulfolane, and ethyl methyl sulfone (EMS). First, we carried out a preliminary investigation of the oxygen reduction reaction and...
Article
Several problems arise at the O2 (positive) electrode in the Li-air battery, including solvent/electrode decomposition and electrode passivation by insulating Li2O2. Progress partially depends on exploring the basic electrochemistry of O2 reduction. Here we describe the effect of complexing-cations on the electrochemical reduction of O2 in DMSO in...
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Full-text available
Oxidation of H2O, CO and CH3OH was investigated at Pt as a function of temperature in the protic ionic liquid diethylmethylammonium trifluoromethanesulfonate. Trace H2O oxidation in the ionic liquid results in coverage of the Pt with adsorbed oxides. Increasing the temperature significantly reduces the potential at which this reaction occurs. CH3OH...
Article
H2 oxidation and O2 reduction have been studied as a function of temperature at Pt electrodes in the protic ionic liquid diethylmethylammonium trifluoromethanesulfonate. Hydrodynamic voltammetry showed that the H2 oxidation reaction (HOR) became hindered at positive potentials (>1.0 V). Electrochemical analysis and X-ray photoelectron spectroscopy...
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Concentric microring-disk tips for scanning electrochemical microscopy (SECM) were fabricated and used in a new “tip generation–substrate collection–tip collection” (TG–SC–TC) mode to determine the activity of an Au electrocatalyst for the oxygen reduction reaction (ORR), while simultaneously monitoring hydrogen peroxide produced during the reactio...
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There is considerable interest in the development of nanostructured metal surfaces for applications in chemical sensing, optics, catalysis and magnetics. For a number of years, the use of templates based on polystyrene nanospheres has been particularly successful for the construction of meso- and macroporous surfaces. We have discovered that redox...
Article
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Pt nanoparticles have been synthesized at relatively low temperatures in aqueous solution from hexachloroplatinic acid using cellulose nanocrystals (CNXLs) from cotton as reducing agents. The Pt nanoparticles were characterised using X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis...
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Crystalline cellulose nanofibrils from cotton were used as reducing agents for the synthesis of nanostructured silver. The hydrothermal synthesis involved heating an AgNO3 solution containing suspended cellulose nanofibrils at 80 °C for 2 h. The formation of metallic silver was verified using UV/Visible spectroscopy, X-ray diffraction and transmiss...
Article
Platinum nanoparticles were formed by reduction of H2PtCl6 using nanocrystalline cellulose from cotton as the reducing agent.
Article
Terminal thiolate ligands on the synthetic Fe-S-based clusters [Fe4S4(SR)4]2- (R = Et or SPh) or [{MoFe3S4(SPh)3}2(mu-SPh)3]3- are replaced by chloride in a reaction with PhCOCl to produce [Fe4S4Cl4]2- and [{MoFe3S4Cl3}2(mu-SPh)3]3-, respectively. Kinetic studies using stopped-flow spectrophotometry show that, in general, the mechanisms of these re...

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