A Gel–Polymer Sn–C/LiMn_0.5Fe_0.5PO₄ Battery Using a Fluorine-Free Salt

Safety and environmental issues, because of the contemporary use of common liquid electrolytes, fluorinated salts, and LiCoO₂-based cathodes in commercial Li-ion batteries, might be efficiently mitigated by employing alternative gel–polymer battery configurations and new electrode materials. Herein we study a lithium-ion polymer cell formed by combining a LiMn_0.5Fe_0.5PO₄ olivine cathode, prepared by simple solvothermal pathway, a nanostructured Sn–C anode, and a LiBOB-containing PVdF-based gel electrolyte. The polymer electrolyte, here analyzed in terms of electrochemical stability by impedance spectroscopy (EIS) and voltammetry, reveals full compatibility for cell application. The LiBOB electrolyte salt and the electrochemically delithiaded Mn_0.5Fe_0.5PO₄ have a higher thermal stability compared to conventional LiPF₆ and Li_0.5CoO₂, as confirmed by thermogravimetric analysis (TGA) and by galvanostatic cycling at high temperature. LiMn_0.5Fe_0.5PO₄ and Sn–C, showing in lithium half-cell a capacity of about 120 and 350 mAh g^–1, respectively, within the gelled electrolyte configuration are combined in a full Li-ion polymer battery delivering a stable capacity of about 110 mAh g^–1, with working voltage ranging from 2.8 to 3.6 V

Ruthenium-Based Electrocatalysts Supported on Reduced Graphene Oxide for Lithium-Air Batteries

Ruthenium-based nanomaterials supported on reduced graphene oxide (rGO) have been investigated as air cathodes in non-aqueous electrolyte Li-air cells using a TEGDME-LiCF₃SO₃ electrolyte. Homogeneously distributed metallic ruthenium and hydrated ruthenium oxide (RuO₂·0.64H₂O), deposited exclusively on rGO, have been synthesized with average size below 2.5 nm. The synthesized hybrid materials of Ru-based nanoparticles supported on rGO efficiently functioned as electrocatalysts for Li₂O₂ oxidation reactions, maintaining cycling stability for 30 cycles without sign of TEGDME-LiCF₃SO₃ electrolyte decomposition. Specifically, RuO₂·0.64H₂O-rGO hybrids were superior to Ru-rGO hybrids in catalyzing the OER reaction, significantly reducing the average charge potential to ∼3.7 V at the high current density of 500 mA g^–1 and high specific capacity of 5000 mAh g^–1

High Capacity O3-Type Na[Li_0.05(Ni_0.25Fe_0.25Mn_0.5)_0.95]O₂ Cathode for Sodium Ion Batteries

In this work we report Na­[Li_0.05(Ni_0.25Fe_0.25Mn_0.5)_0.95]­O₂ layered cathode materials that were synthesized via a coprecipitation method. The Na­[Li_0.05(Ni_0.25Fe_0.25Mn_0.5)_0.95]­O₂ electrode exhibited an exceptionally high capacity (180.1 mA h g^–1 at 0.1 C-rate) as well as excellent capacity retentions (0.2 C-rate: 89.6%, 0.5 C-rate: 92.1%) and rate capabilities at various C-rates (0.1 C-rate: 180.1 mA h g^–1, 1 C-rate: 130.9 mA h g^–1, 5 C-rate: 96.2 mA h g^–1), which were achieved due to the Li supporting structural stabilization by introduction into the transition metal layer. By contrast, the electrode performance of the lithium-free Na­[Ni_0.25Fe_0.25Mn_0.5]­O₂ cathode was inferior because of structural disintegration presumably resulting from Fe³⁺ migration from the transition metal layer to the Na layer during cycling. The long-term cycling using a full cell consisting of a Na­[Li_0.05(Ni_0.25Fe_0.25Mn_0.5)_0.95]­O₂ cathode was coupled with a hard carbon anode which exhibited promising cycling data including a 76% capacity retention over 200 cycles

A Metal-Free, Lithium-Ion Oxygen Battery: A Step Forward to Safety in Lithium-Air Batteries

A preliminary study of the behavior of lithium-ion-air battery where the common, unsafe lithium metal anode is replaced by a lithiated silicon–carbon composite, is reported. The results, based on X-ray diffraction and galvanostatic charge–discharge analyses, demonstrate the basic reversibility of the electrochemical process of the battery that can be promisingly cycled with a rather high specific capacity

Advanced Na[Ni_0.25Fe_0.5Mn_0.25]O₂/C–Fe₃O₄ Sodium-Ion Batteries Using EMS Electrolyte for Energy Storage

While much research effort has been devoted to the development of advanced lithium-ion batteries for renewal energy storage applications, the sodium-ion battery is also of considerable interest because sodium is one of the most abundant elements in the Earth’s crust. In this work, we report a sodium-ion battery based on a carbon-coated Fe₃O₄ anode, Na­[Ni_0.25Fe_0.5Mn_0.25]­O₂ layered cathode, and NaClO₄ in fluoroethylene carbonate and ethyl methanesulfonate electrolyte. This unique battery system combines an intercalation cathode and a conversion anode, resulting in high capacity, high rate capability, thermal stability, and much improved cycle life. This performance suggests that our sodium-ion system is potentially promising power sources for promoting the substantial use of low-cost energy storage systems in the near future

Relevance of LiPF₆ as Etching Agent of LiMnPO₄ Colloidal Nanocrystals for High Rate Performing Li-ion Battery Cathodes

LiMnPO₄ is an attractive cathode material for the next-generation high power Li-ion batteries, due to its high theoretical specific capacity (170 mA h g^–1) and working voltage (4.1 V vs Li⁺/Li). However, two main drawbacks prevent the practical use of LiMnPO₄: its low electronic conductivity and the limited lithium diffusion rate, which are responsible for the poor rate capability of the cathode. The electronic resistance is usually lowered by coating the particles with carbon, while the use of nanosize particles can alleviate the issues associated with poor ionic conductivity. It is therefore of primary importance to develop a synthetic route to LiMnPO₄ nanocrystals (NCs) with controlled size and coated with a highly conductive carbon layer. We report here an effective surface etching process (using LiPF₆) on colloidally synthesized LiMnPO₄ NCs that makes the NCs dispersible in the aqueous glucose solution used as carbon source for the carbon coating step. Also, it is likely that the improved exposure of the NC surface to glucose facilitates the formation of a conductive carbon layer that is in intimate contact with the inorganic core, resulting in a high electronic conductivity of the electrode, as observed by us. The carbon coated etched LiMnPO₄-based electrode exhibited a specific capacity of 118 mA h g^–1 at 1C, with a stable cycling performance and a capacity retention of 92% after 120 cycles at different C-rates. The delivered capacities were higher than those of electrodes based on not etched carbon coated NCs, which never exceeded 30 mA h g^–1. The rate capability here reported for the carbon coated etched LiMnPO₄ nanocrystals represents an important result, taking into account that in the electrode formulation 80% wt is made of the active material and the adopted charge protocol is based on reasonable fast charge times

Influence of Temperature on Lithium–Oxygen Battery Behavior

In this Letter we report an electrochemical and morphological study of the response of lithium–oxygen cells cycled at various temperatures, that is, ranging from −10 to 70 °C. The results show that the electrochemical process of the cells is thermally influenced in an opposite way, that is, by a rate decrease, due to a reduced diffusion of the lithium ions from the electrolyte to the electrode interface, at low temperature and a rate enhancement, due to the decreased electrolyte viscosity and consequent increased oxygen mobility, at high temperature. In addition, we show that the temperature also influences the crystallinity of lithium peroxide, namely of the product formed during cell discharge

An Advanced Lithium-Ion Battery Based on a Graphene Anode and a Lithium Iron Phosphate Cathode

We report an advanced lithium-ion battery based on a graphene ink anode and a lithium iron phosphate cathode. By carefully balancing the cell composition and suppressing the initial irreversible capacity of the anode in the round of few cycles, we demonstrate an optimal battery performance in terms of specific capacity, that is, 165 mAhg^–1, of an estimated energy density of about 190 Wh kg^–1 and a stable operation for over 80 charge–discharge cycles. The components of the battery are low cost and potentially scalable. To the best of our knowledge, complete, graphene-based, lithium ion batteries having performances comparable with those offered by the present technology are rarely reported; hence, we believe that the results disclosed in this work may open up new opportunities for exploiting graphene in the lithium-ion battery science and development

Highly Cyclable Lithium–Sulfur Batteries with a Dual-Type Sulfur Cathode and a Lithiated Si/SiO_<i>x</i> Nanosphere Anode

Lithium–sulfur batteries could become an excellent alternative to replace the currently used lithium-ion batteries due to their higher energy density and lower production cost; however, commercialization of lithium–sulfur batteries has so far been limited due to the cyclability problems associated with both the sulfur cathode and the lithium–metal anode. Herein, we demonstrate a highly reliable lithium–sulfur battery showing cycle performance comparable to that of lithium-ion batteries; our design uses a highly reversible dual-type sulfur cathode (solid sulfur electrode and polysulfide catholyte) and a lithiated Si/SiO_<i>x</i> nanosphere anode. Our lithium–sulfur cell shows superior battery performance in terms of high specific capacity, excellent charge–discharge efficiency, and remarkable cycle life, delivering a specific capacity of ∼750 mAh g^–1 over 500 cycles (85% of the initial capacity). These promising behaviors may arise from a synergistic effect of the enhanced electrochemical performance of the newly designed anode and the optimized layout of the cathode

Study on the Catalytic Activity of Noble Metal Nanoparticles on Reduced Graphene Oxide for Oxygen Evolution Reactions in Lithium–Air Batteries

Among many challenges present in Li–air batteries, one of the main reasons of low efficiency is the high charge overpotential due to the slow oxygen evolution reaction (OER). Here, we present systematic evaluation of Pt, Pd, and Ru nanoparticles supported on rGO as OER electrocatalysts in Li–air cell cathodes with LiCF₃SO₃–tetra­(ethylene glycol) dimethyl ether (TEGDME) salt-electrolyte system. All of the noble metals explored could lower the charge overpotentials, and among them, Ru-rGO hybrids exhibited the most stable cycling performance and the lowest charge overpotentials. Role of Ru nanoparticles in boosting oxidation kinetics of the discharge products were investigated. Apparent behavior of Ru nanoparticles was different from the conventional electrocatalysts that lower activation barrier through electron transfer, because the major contribution of Ru nanoparticles in lowering charge overpotential is to control the nature of the discharge products. Ru nanoparticles facilitated thin film-like or nanoparticulate Li₂O₂ formation during oxygen reduction reaction (ORR), which decomposes at lower potentials during charge, although the conventional role as electrocatalysts during OER cannot be ruled out. Pt-and Pd-rGO hybrids showed fluctuating potential profiles during the cycling. Although Pt- and Pd-rGO decomposed the electrolyte after electrochemical cycling, no electrolyte instability was observed with Ru-rGO hybrids. This study provides the possibility of screening selective electrocatalysts for Li–air cells while maintaining electrolyte stability