Search

The insertion of lithium into lithium manganese oxide spinel (LiMn2O4 (LMO) to Li2Mn2O4 (L2MO)) was used to store light energy as a form of chemical energy in a dye-sensitized photorechargeable bat...

A redox-active mixed ion and electron conductor (redox-active MIEC) is presented as a binder for the lithium titanate anodes of lithium-ion batteries. The redox-active MIEC binder (symbolized by PT*-GmCn) was designed to be (1) electrically conductive along its conjugated thiophene backbone (PT = polythiophene), (2) redox-active from its succinimide moiety (* = redox-active) and (3) ionically conductive by adopting glyme (G) branches. It was superior to the practically used PVdF binder in terms of lithium ion diffusivity and electrical conductivity (1.4× and 15 000×, respectively). High capacity was guaranteed, particularly at high rates due to its MIEC nature of PT*-GmCn, while an additional capacity was achieved from its redox activity.

Although bimetallic materials with various structures have been used as anodes for advanced lithium ion batteries, structural degradation, caused during electrochemical reactions, leads to a shorte...

The concentration polarization, in addition to the activation and ohmic polarizations, limits the fast operation of electrochemical cells such as Li-ion batteries (LIBs). We demonstrate an approach...

Perovskite oxides have received considerable attention as useful electro-catalysts for Li-air batteries due to their properties of excellent catalytic activity, electrical conductivity, and durability. The nanostructure can enhance the electrochemical performance of perovskite oxides by enlarging the catalytic active sites. In this study, nano-size Nd0.67Sr0.33CoO3-δ (NSC) perovskite particles with a particle size of 20–50 nm and a specific surface area of 12.759 m2 g−1 were successfully synthesized by a microemulsion method. The NSC perovskite particles exhibit excellent electrocatalytic activity particularly in the oxygen evolution reaction (OER) with a high limiting current density of 33.68 mA cm-2 at 0.9 V vs. (Hg/HgO). This excellent catalytic activity can be ascribed to the existence of Co3+ and the enlarged surface area. Co3+ provides catalytically active site by forming Co3+/4+ redox couple and the enlarged surface increases active sites for reactants and catalyst particles. In this regard, nano-size NSC particles prepared by the microemulsion route provide excellent and stable electrochemical performance in the hybrid Li-air battery.

We present a metal-ion-chelating organogel electrolyte, thermally gelated within cells, to solve the problems triggered by metal dissolution from cathodes of lithium ion batteries. The organogel significantly improved the capacity retention of lithium manganese oxide spinel during cycling. The organogel mitigated metal deposition on anodes by capturing metal ions (anode protection). Interestingly, the organogel inhibited metal dissolution by keeping dissolved metal ions highly concentrated around the cathode surface (cathode protection by Le Chatelier's principle).

A dendrite-free and chemically stabilized lithium metal anode is required for extending battery life and for the application of high energy density coupled with various cathode systems. However, uneven Li metal growth and the active surface in nature accelerate electrolyte dissipation and surface corrosion, resulting in poor cycle efficiency and various safety issues. Here, the authors suggest a thin artificial interphase using a multifunctional poly(styrene-b-butadiene-b-styrene) (SBS) copolymer to inhibit the electrochemical/chemical side reaction during cycling. Based on the physical features, hardness, adhesion, and flexibility, the optimized chemical structure of SBS facilitates durable mechanical strength and interphase integrity against repeated Li electrodeposition/dissolution. The effectiveness of the thin polymer film enables high cycle efficiency through the realization of a dendrite-free structure and a chemo-resistive surface of Li metal. The versatile anode demonstrates an improvement in the electrochemical properties, paired with diverse cathodes of high-capacity lithium cobalt oxide (3.5 mAh cm

Reactive oxygen species or superoxide (O2-), which damages or ages biological cells, is generated during metabolic pathways using oxygen as an electron acceptor in biological systems. Superoxide dismutase (SOD) protects cells from superoxide-triggered apoptosis by converting superoxide to oxygen and peroxide. Lithium-oxygen battery (LOB) cells have the same aging problems caused by superoxide-triggered side reactions. We transplanted the function of SOD of biological systems into LOB cells. Malonic acid-decorated fullerene (MA-C60) was used as a superoxide disproportionation chemocatalyst mimicking the function of SOD. As expected, MA-C60 as the superoxide scavenger improved capacity retention along charge/discharge cycles successfully. A LOB cell that failed to provide a meaningful capacity just after several cycles at high current (0.5 mA cm-2) with 0.5 mAh cm-2 cutoff survived up to 50 cycles after MA-C60 was introduced to the electrolyte. Moreover, the SOD-mimetic catalyst increased capacity, e.g., more than a 6-fold increase at 0.2 mA cm-2. The experimentally observed toroidal morphology of the final discharge product of oxygen reduction (Li2O2) and density functional theory calculation confirmed that the solution mechanism of Li2O2 formation, more beneficial than the surface mechanism from the capacity-gain standpoint, was preferred in the presence of MA-C60.

Alloys are recently receiving considerable attention in the community of rechargeable batteries as possible alternatives to carbonaceous negative electrodes; however, challenges remain for the practical utilization of these materials. Herein, we report the synthesis of germanium-zinc alloy nanofibers through electrospinning and a subsequent calcination step. Evidenced by in situ transmission electron microscopy and electrochemical impedance spectroscopy characterizations, this one-dimensional design possesses unique structures. Both germanium and zinc atoms are homogenously distributed allowing for outstanding electronic conductivity and high available capacity for lithium storage. The as-prepared materials present high rate capability (capacity of ~ 50% at 20 C compared to that at 0.2 C-rate) and cycle retention (73% at 3.0 C-rate) with a retaining capacity of 546 mAh g−1 even after 1000 cycles. When assembled in a full cell, high energy density can be maintained during 400 cycles, which indicates that the current material has the potential to be used in a large-scale energy storage system., Alloy anode materials are receiving renewed interest. Here the authors show the design of Ge-Zn nanofibers for lithium ion batteries. Featured by a homogeneous composition at the atomic level and other favorable structural attributes, the materials allow for impressive electrochemical performance.

Aprotic lithium-oxygen batteries (LOBs) have been considered as one of the high-energy-density alternatives to replace currently available lithium ion batteries. Highly reactive superoxide as the discharge intermediate of LOBs triggers side reactions to deteriorate LOB performances. Also, high overpotential is required to oxidize the discharge product Li2O2 during charge due to the non-conductive nature of Li2O2. Herein, we present 4-carboxy-(2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO-COOH) as a superoxide dismutase mimetic bifunctional mobile catalyst soluble in electrolytes for improving LOB performances. The role of TEMPO-COOH is two-fold: (1) the chemo-catalyst to catalyze superoxide disproportionation reaction for suppressing the superoxide-triggered side reactions during discharge; and (2) the redox mediator to oxidize Li2O2 in a kinetically effective way for reducing the overpotential during charge. The use of the mobile catalyst in LOB cells resulted in the 4-fold increase in cycle life from 50 cycles to 200 cycles as well as the 4-fold increase in the discharge capacity, significantly reducing the overpotential during charge.

Conversion-reaction-based anode materials for lithium ion batteries (LIBs) such as transition metal oxides have been considered as high-capacity alternatives to graphite. In the conversion reactions, interestingly, microparticles have been known to be superior to nanoparticles in terms of capacity retention along repeated cycles. In this work, a cross-linked two-component binder system of poly(acrylic acid) and carboxymethyl cellulose (PAA/CMC) was used for nanoparticular Co 3 O 4 . The binder was characterized by high modulus and strong bonding to the surface oxide of Co 3 O 4 . Even without carbon coating, the composite electrodes of nanoparticular Co 3 O 4 in the presence of PAA/CMC showed significantly enhanced cycle retention with improved reversibility of the conversion reaction.

Germanium nanoparticles were synthesized and subjected to study as anode materials for lithium ion batteries and sodium ion batteries. Laser pyrolysis of GeH4 was used to produce germanium nanoparticles and the average diameter of these nanoparticles was easily controlled by regulating sensitizer gas flow rates during the process. 60 and 10 nm diameter nanoparticles were synthesized and micron-size powder was purchased and these three pure germanium powder samples were tested as the anode materials of lithium ion batteries and sodium ion batteries in terms of cycle retention, long term cycles and the kinetics of reactions. Experimental results showed that the smallest powder sample which is synthesized, average 10 nm, exhibited excellent performances in both kinds of batteries. According to the results, the characteristics of batteries improved as the size of germanium powder decreased consistently. Pure germanium was thoroughly investigated as an anode of metal-ion batteries with regard to its powder size. The experimental data and synthesis approach of germanium nanoparticles suggested in this research would be a good example for the utilization of elemental germanium in high performance batteries.

Lithium oxygen batteries (LOBs) have been spotlighted as the next generation of rechargeable batteries due to their high theoretical capacity. One of the key issues of LOBs is how effectively lithium peroxide as the discharge product is removed. (2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO) was reported as a charge redox mediator to remove lithium peroxide during charge. TEMPO is oxidized to TEMPO+ at 3.70V vs. Li/Li+ and then withdraw electron from lithium peroxide. In this presentation, we present the effects of functional groups attached to 4'-C of TEMPO on LOB performances. Several TEMPO derivatives improved cycling stability significantly. In addition to redox mediation role on charging, a group of TEMPO derivatives promoted disproportionation reaction of superoxide radical during discharging to change the morphology of lithium peroxide. Another group of TEMPO derivatives improved the cycling stability by forming a protective interface film on lithium metal cathode.

Reactive oxygen species or superoxide (O2 -) to damage or age biological cells is generated during metabolic pathways using oxygen as an electron acceptor in biological systems. Superoxide dismutase (SOD) protects cells from the superoxide-triggered apoptosis by converting superoxide to oxygen and peroxide. Lithium-oxygen battery (LOB) cells have the same aging problems caused by superoxide-triggered side reactions. We transplanted the function of SOD of biological systems into LOB cells. Malonic acid-decorated fullerene (MA-C60) was used as a superoxide disproportionation chemo-catalyst mimicking the function of SOD. As expected, MA-C60 as the superoxide scavenger improved capacity retention along charge/discharge cycles successfully. A LOB cell that failed to provide a meaningful capacity just after several cycles at high current (0.5 mA cm-2) with 0.5 mAh cm-2 cut-off survived up to 50 cycles after MA-C60 was introduced to electrolyte. Moreover, the SOD-mimetic catalyst increased capacity: e.g., more than six-fold increase at 0.2 mA cm-2. Experimentally observed toroidal morphology of the final discharge product of oxygen reduction (Li2O2) and density functional theory calculation confirmed that the solution mechanism of Li2O2 formation, more beneficial than the surface mechanism from the capacity-gain standpoint, was preferred in the presence of MA-C60.

Germanium nanoparticles were synthesized and subjected to study as anode materials for lithium ion batteries and sodium ion batteries. Laser pyrolysis of GeH4 was used to produce germanium nanoparticles and the average diameter of these nanoparticles was easily controlled by regulating sensitizer gas flow rates during the process. 60 and 10 nm diameter nanoparticles were synthesized and micron-size powder was purchased and these three pure germanium powder samples were tested as the anode materials of lithium ion batteries and sodium ion batteries in terms of cycle retention, long term cycles and the kinetics of reactions. Experimental results showed that the smallest powder sample which is synthesized, average 10 nm, exhibited excellent performances in both kinds of batteries. According to the results, the characteristics of batteries improved as the size of germanium powder decreased consistently. Pure germanium was thoroughly investigated as an anode of metal-ion batteries with regard to its powder size. The experimental data and synthesis approach of germanium nanoparticles suggested in this research would be a good example for the utilization of elemental germanium in high performance batteries.

High-theoretical capacity and low working potential make silicon ideal anode for lithium ion batteries. However, the large volume change of silicon upon lithiation/delithiation poses a critical challenge for stable battery operations. Here, we introduce an unprecedented design, which takes advantage of large deformation and ensures the structural stability of the material by developing a two-dimensional silicon nanosheet coated with a thin carbon layer. During electrochemical cycling, this carbon coated silicon nanosheet exhibits unique deformation patterns, featuring accommodation of deformation in the thickness direction upon lithiation, while forming ripples upon delithiation, as demonstrated by in situ transmission electron microscopy observation and chemomechanical simulation. The ripple formation presents a unique mechanism for releasing the cycling induced stress, rendering the electrode much more stable and durable than the uncoated counterparts. This work demonstrates a general principle as how to take the advantage of the large deformation materials for designing high capacity electrode., Maintaining the structural stability during electrochemical cycling remains a big challenge facing the silicon anode material. Here, the authors have developed 2D silicon nanosheets coated with carbon layers, which show a unique mechanism in releasing internal stress by forming ripple structures.

Molecular structures of polysaccharide binders determining mechanical properties were correlated to electrochemical performances of silicon anodes for lithium-ion batteries. Glycosidic linkages (α and β) and side chains (-COOH and -OH) were selected and proven as the major factors of the molecular structures. Three different single-component polysaccharides were compared: pectin for α-linkages versus carboxylic methyl cellulose (CMC) for β-linkages from the linkage's standpoint, and pectin as a COOH-containing polymer and amylose as its non-COOH counterpart from the side chain's standpoint. Pectin was remarkably superior to CMC and amylose in cyclability and rate capability of battery cells based on silicon anodes. The pectin binder allowed volume expansion of silicon electrodes with keeping high porosity during lithiation due to the elastic nature caused by the chair-to-boat conformation in α-linkages of its backbone. Physical integrity of pectin-based electrodes was not challenged during repeated lithiation/delithiation cycles without crack development that was observed in rigid CMC-based electrodes. Covalent bonds formed between carboxylic side chains of pectin and silicon surface oxide prevented active silicon mass from being detached away from electric pathways. However, hydrogen bonds between hydroxyl side chains of amylose and silicon surface oxide were not strong enough to keep the silicon mass electrochemically active after cyclability tests.

Silicon, a promising high-capacity anode material of lithium ion batteries, suffers from its volume expansion leading to pulverization and low conductivities, showing capacity decay during cycling and low capacities at fast charging and discharging. In addition to popular active-material-modifying strategies, building lithium-ion-rich environments around silicon surface is helpful in enhancing unsatisfactory performances of silicon anodes. In this work, we accelerated lithium ion transport to silicon surface by using an organogel binder to utilize the electroactivity of silicon in a more efficient way. The cyanoethyl polymer (PVA-CN), characterized by high lithium ion transference number as well as appropriate elastic modulus with strong adhesion, enhanced cycle stability of silicon anodes with high coulombic efficiency even at high temperature (60 °C) as well as at fast charging/discharging rates.

A crumply and highly flexible lithium-ion battery is realized by using microfiber mat electrodes in which the microfibers are wound or webbed with conductive nanowires. This electrode architecture guarantees extraordinary mechanical durability without any increase in resistance after folding 1000 times. Its areal energy density is easily controllable by the number of folded stacks of a piece of the electrode mat. Deformable lithium-ion batteries of lithium iron phosphate as cathode and lithium titanium oxide as anode at high areal capacity (3.2 mAh cm-2 ) are successfully operated without structural failure and performance loss, even after repeated crumpling and folding during charging and discharging.

Single crystal silicon nanoparticles (Si-NPs) of 20 nm were produced via laser pyrolysis with a virtually complete conversion from SiH4 to Si-NPs. SF6 was used as the photosensitizer to transfer laser beam energy to silicon precursors, dramatically enhancing crystallinity of Si-NPs and their production efficiency. By using their well-developed crystalline structure, the directional volume expansion of Si-NPs was confirmed during lithiation. Lithiation/delithiation kinetics of our Si-NPs was superior to that of their amorphous counterparts due to the footprinted Li+ pathways formed during amorphization.

Rapid growth of mobile and even wearable electronics is in pursuit of high-energy-density lithium-ion batteries. One simple and facile way to achieve this goal is the elimination of nonelectroactive components of electrodes such as binders and conductive agents. Here, we present a new concept of monocomponent electrodes comprising solely electroactive materials that are wrapped with an insignificant amount (less than 0.4 wt %) of conducting polymer (PEDOT:PSS or poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate)). The PEDOT:PSS as an ultraskinny surface layer on electroactive materials (LiCoO2 (LCO) powders are chosen as a model system to explore feasibility of this new concept) successfully acts as a kind of binder as well as mixed (both electrically and ionically) conductive film, playing a key role in enabling the monocomponent electrode. The electric conductivity of the monocomponent LCO cathode is controlled by simply varying the PSS content and also the structural conformation (benzoid-favoring coil structure and quinoid-favoring linear or extended coil structure) of PEDOT in the PEDOT:PSS skin. Notably, a substantial increase in the mass-loading density of the LCO cathode is realized with the PEDOT:PSS skin without sacrificing electronic/ionic transport pathways. We envisage that the PEDOT:PSS-skinned electrode strategy opens a scalable and versatile route for making practically meaningful binder-/conductive agent-free (monocomponent) electrodes.

Non-flammability of electrolyte and tolerance of cells against thermal abuse should be guaranteed for widespread applications of lithium-ion batteries (LIBs). As a strategy to improve thermal stability of LIBs, here, we report on nitrile-based molecular coverage on surface of cathode active materials to block or suppress thermally accelerated side reactions between electrode and electrolyte. Two different series of aliphatic nitriles were introduced as an additive into a carbonate-based electrolyte: di-nitriles (CN-[CH2]n-CN with n = 2, 5, and 10) and mono-nitriles (CH3-[CH2]m-CN with m = 2, 5, and 10). On the basis of the strong interaction between the electronegativity of nitrile functional groups and the electropositivity of cobalt in LiCoO2 cathode, aliphatic mono- and di-nitrile molecules improved the thermal stability of lithium ion cells by efficiently protecting the surface of LiCoO2. Three factors, the surface coverage θ, the steric hindrance of aliphatic moiety within nitrile molecule, and the chain polarity, mainly affect thermal tolerance as well as cell performances at elevated temperature.

The charge/discharge characteristics of lithium ion batteries at low temperature (LT = −20 °C) are enhanced by using ethylene carbonate (EC)-based electrolytes with the help of assistant solvents of nitriles. Conventional liquid electrolytes (e.g. a mixture of EC and dimethyl carbonate (DMC), abbreviated as LED) cannot support a satisfactory capacity at low temperature as well as at high rates even if electric vehicles require low-temperature operation. Introducing propionitrile or butyronitrile (Pn or Bn) into LED (resulting in LEDPn or LEDBn) as a co-solvent increases significantly the high-rate capacities at −20 °C. For example, LEDPn delivers 62% of the available capacity at 1 C and 46% at 3 C with a 2.7 V cut-off while the control LED provides just 6% and 4% at the same rates. Successful operation at −20 °C with nitrile-assistant electrolytes results from high ionic conductivity, low viscosity and freezing point depression caused by the eutectic behavior of the carbonates (EC/DMC) and Pn. Based on the phase diagram of Pn with EC/DMC, we expect a meaningful battery operation up to −110 °C, probably lower, at the eutectic composition.

To develop high-performance nanostructured metal oxide electrodes, it is important to understand their structural effects on electrochemical performances. Thus, the preparation of metal oxide materials that have well-tailored nanostructures is crucial for studies. However, while synthetic strategies to control the size of metal oxide nanoparticles are well-developed, the control of the higher level structures, namely microstructure, is not very well established. Herein, we present the synthesis of the two kinds of Co3O4 nanomaterials through pseudomorphic conversion so that the macroscopic morphologies of parent MOFs, such as plate-like and rod-like shape, are well-maintained. Both Co3O4 nanomaterials are composed of almost identical 10 nm-sized primary nanocrystals but with different nanoporous secondary structures and macroscopic morphologies such as plate and rod shapes. These Co3O4 nanomaterials were utilized as an electrode in lithium ion batteries (LIBs), and their electrochemical properties were comparatively investigated. It was revealed that the different cyclability and rate capability are attributed to their different microstructures. The pseudo-monolithic integration of primary and secondary structures at higher level was the governing factor, which determined the electrochemical performances of the Co3O4 electrode.

Germanium exhibits high charge capacity and high lithium diffusivity, both are the key requirements for electrode materials in high performance lithium ion batteries (LIBs). However, high volume expansion and segregation from the electrode during charge-discharge cycling have limited use of germanium in LIBs. Here, we demonstrate that ZnO decorated Ge nanoparticles (Ge@ZnO NPs) can overcome these limitations of Ge as an LIB anode material. We produced Ge NPs at high rates by laser pyrolysis of GeH4, then coated them with solution phase synthesized ZnO NPs. Half-cell tests revealed dramatically enhanced cycling stability and higher rate capability of Ge@ZnO NPs compared to Ge NPs. Enhancements arise from the core-shell structure of Ge@ZnO NPs as well as production of metallic Zn from the ZnO layer. These findings not only demonstrate a new surface treatment for Ge NPs, but also provide a new opportunity for development of high-rate LIBs.

Delithiation followed by lithiation of Li+-occupied (n-type) tetrahedral sites of cubic LiMn2O4 spinel (LMO) at ~4 $${{\bf{V}}}_{{{\bf{Li}}{\boldsymbol{/}}{\bf{Li}}}^{{\boldsymbol{+}}}}$$ V Li / Li + (delivering ~100 mAh gLMO−1) has been used for energy storage by lithium ion batteries (LIBs). In this work, we utilized unoccupied (p-type) octahedral sites of LMO available for lithiation at ~3 $${{\bf{V}}}_{{{\bf{Li}}{\boldsymbol{/}}{\bf{Li}}}^{{\boldsymbol{+}}}}$$ V Li / Li + (delivering additional ~100 mAh gLMO−1) that have never been used for LIBs in full-cell configuration. The whole capacity of amphi-redox LMO, including both oxidizable n-type and reducible p-type redox sites, at ~200 mAh gLMO−1 was realized by using the reactions both at 4 $${{\bf{V}}}_{{{\bf{Li}}{\boldsymbol{/}}{\bf{Li}}}^{{\boldsymbol{+}}}}$$ V Li / Li + and 3 $${{\bf{V}}}_{{{\bf{Li}}{\boldsymbol{/}}{\bf{Li}}}^{{\boldsymbol{+}}}}$$ V Li / Li + . Durable reversibility of the 3 V reaction was achieved by graphene-wrapping LMO nanoparticles (LMO@Gn). Prelithiated graphite (LinC6, n

As high rate charge and discharge characteristics of energy storage devices become more important with the market of electric vehicles intensively growing, the kinetics of lithiation or delithiation of electrode materials for lithium ion batteries require enhancement. Graphites, the most widely used anode materials, have a limited power density at high discharge rates, while their alternatives, such as silicon and transition metal oxides, show even inferior rate capability. This work was motivated from an idea of what if the edge opening of graphite was zipped more open to lithium ions in the electrolyte. By edge-selective functionalization, the peripheral d-spacing of graphite (d(0)) was locally controlled. Larger values of d(0) led to higher capacity especially at high discharge rates. Around 2-fold enhancement of capacity or energy density was achieved at 50C discharge rate from 110 to 190 mAh g(-1) by exfoliating graphite locally in its edge region. Also, the d(0) dependency of delithiation kinetics confirmed that the electrochemical step of Li(+) influx into or efflux out of the interlayer space of graphite is possibly the rate-determining step of lithiation or delithiation.

Tunable precipitation strategy to control the shape of nanoparticles of a three-component system is presented. The strategy is devised from understanding the effects of precursor addition sequences on the morphology of resultant precipitates. LiFePO4, one of the most potential candidate as a cathode material of lithium ion batteries for electric vehicles, was used as a representative model of the three (Li, Fe, and PO4)-component system. According to the precursor addition sequence, three different precipitation methods were adopted: coprecipitation (Copr) and two different types of sequential precipitations (Seq1 and Seq2). Solubility product (Ksp) of intermediate precipitates (Li3PO4 and Fe3(PO4)2) is the key parameter to help the precipitation processes understood. In Copr, the intermediate precipitates are formed simultaneously under Ksp-governed competition. In Seq1 and Seq2, Li3PO4 precipitates prior to Fe3(PO4)2. When Fe2+ is introduced into the suspension of Li3PO4, the preformed precipitate is sa...

Diversified and extended applications of lithium-ion batteries demand the development of more enhanced materials that can be achieved by sophisticated synthetic methods. Combination of novel materials with strategic design of their shape on the nanometer scale enables a breakthrough to overcome problems experienced by present technologies. In this feature article, an overview is given of Mn-based and polyanion-based cathode materials with nanoscale features for lithium-ion batteries as materials to replace conventional bulk cathode materials. Various synthetic methods coupled with nanostructuring as well as the benefits obtained from the nanostructure are described.

The chemically cross-linked gel polymer electrolytes supported by the microporous polyethylene membrane were prepared for application in lithium-ion polymer cells. The chemical cross-linking by tris(2-(acryloyloxy)ethyl) phosphate enhanced the electrochemical stability of the electrolyte and also promoted strong interfacial adhesion between the electrodes and the membrane. Lithium-ion polymer cells composed of a carbon anode and a lithium–cobalt oxide cathode were assembled by in situ chemical cross-linking, and their charge/discharge cycling performances were evaluated. Effect of the cross-linking agent on cycling performances of the cells has been investigated.

With the increasing demand of cost-effective and high-energy devices, sodium–air (Na–air) batteries have attracted immense interest due to the natural abundance of sodium in contrast to lithium. In particular, an aqueous Na–air battery has fundamental advantage over non-aqueous batteries due to the formation of highly water-soluble discharge product, which improve the overall performance of the system in terms of energy density, cyclic stability and round-trip efficiency. Despite these advantages, the rechargeability of aqueous Na–air batteries has not yet been demonstrated when using non-precious metal catalysts. In this work, we rationally synthesized a binder-free and robust electrode by directly growing urchin-shaped MnO2 nanowires on porous reduced graphene oxide-coated carbon microfiber (MGC) mats and fabricated an aqueous Na–air cell using the MGC as an air electrode to demonstrate the rechargeability of an aqueous Na–air battery. The fabricated aqueous Na–air cell exhibited excellent rechargeability and rate capability with a low overpotential gap (0.7 V) and high round-trip efficiency (81%). We believe that our approach opens a new avenue for synthesizing robust and binder-free electrodes that can be utilized to build not only metal–air batteries but also other energy systems such as supercapacitors, metal–ion batteries and fuel cells. Growing metal nanostructures on graphene-coated electrodes makes batteries that run on salt, water and air more practical to operate. Sodium's abundance gives batteries that use this metal a price advantage over lithium-based cells. Hyunhyub Ko and co-workers in South Korea have developed a way around aqueous sodium-air batteries' Achilles heel – a reliance on precious-metal catalysts for recharging. The team used gas bubbles, which form on a submerged carbon microfibre mat coated with graphene, as templates to transform inexpensive manganese oxide (MnO2) catalysts into ‘sea urchin’-shaped nanostructures. The ion-accessible morphology of the MnO2 urchins, coupled with the highly conductive substrate, boosted the rechargeability and efficiency of a prototype battery. Additionally, this technique's ability to generate catalytic electrodes without binder opens opportunities for devices such as fuel cells that require lightweight materials. We have rationally synthesized a binder-free and robust electrode by directly growing urchin-shaped α-MnO2 nanostructures on porous reduced graphene oxide-coated carbon microfiber (MGC) mats and fabricated an aqueous sodium–air cell using the MGC as an air electrode to demonstrate the rechargeability of an aqueous sodium–air battery. The fabricated aqueous Na–air cell exhibited excellent rechargeability, rate capability and round-trip efficiency.

Silicon anode materials have been developed to achieve high capacity lithium ion batteries for operating smart phones and driving electric vehicles for longer time. Serious volume expansion induced by lithiation, which is the main drawback of silicon, has been challenged by multi-faceted approaches. Mechanically rigid and stiff polymers (e.g. alginate and carboxymethyl cellulose) were considered as the good choices of binders for silicon because they grab silicon particles in a tight and rigid way so that pulverization and then break-away of the active mass from electric pathways are suppressed. Contrary to the public wisdom, in this work, we demonstrate that electrochemical performances are secured better by letting silicon electrodes breathe in and out lithium ions with volume change rather than by fixing their dimensions. The breathing electrodes were achieved by using a polysaccharide (pullulan), the conformation of which is modulated from chair to boat during elongation. The conformational transition of pullulan was originated from its α glycosidic linkages while the conventional rigid polysaccharide binders have β linkages.

Electrode materials having nanometer scale dimensions are expected to have property enhancements due to enhanced surface area and mass/charge transport kinetics. This is particularly relevant to intrinsically low electronically conductive materials such as lithium iron phosphate (LiFePO4), which is of recent research interest as a high performance intercalation electrode material for Li-ion batteries. Many of the reported works on LiFePO4 synthesis are unattractive either due to the high cost of raw materials or due to the complex synthesis technique. In this direction, synthesis of LiFePO4 directly from inexpensive FePO4 shows promise.The present study reports LiFePO4 nanostructures prepared from iron (III) phosphate (FePO4 x 2H2O) by precipitation-hydrothermal method. The sintered powder was characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Inductive coupled plasma-optical emission spectroscopy (ICP-OES), and Electron microscopy (SEM and TEM). Two synthesis methods, viz. bulk synthesis and anodized aluminum oxide (AAO) template-assisted synthesis are reported. By bulk synthesis, micro-sized particles having peculiar surface nanostructuring were formed at precipitation pH of 6.0 to 7.5 whereas typical nanosized LiFePO4 resulted at pH ≥ 8.0. An in-situ precipitation strategy inside the pores of AAO utilizing the spin coating was utilized for the AAO-template-assisted synthesis. The template with pores filled with the precipitate was subsequently subjected to hydrothermal process and high temperature sintering to fabricate compact rod-like structures.

We demonstrate multiscale patterned electrodes that provide surface-area enhancement and strong adhesion between electrode materials and current collector. The combination of multiscale structured current collector and active materials (anodes and cathodes) enables us to make high-performance Li-ion batteries (LIBs). When LiFePO4 (LFP) cathode and Li4 Ti5 O12 (LTO) anode materials are combined with patterned current collectors, their electrochemical performances are significantly improved, including a high rate capability (LiFePO4 : 100 mAh g(-1) , Li4 Ti5 O12 : 60 mAh g(-1) at 100C rate) and highly stable cycling (LiFePO4 : capacity retention of 99.8% after 50 cycles at 10C rate). Moreover, we successfully fabricate full cell system consisting of patterned LFP cathode and patterned LTO anode, exhibiting high-power battery performances [capacity of approximately 70 mAh g(-1) during 1000 cycles at 10C rate (corresponding to charging/discharging time of 6 min)]. We extend this idea to Si anode that exhibits a large volume change during lithiation/delithiation process. The patterned Si electrodes show significantly enhanced electrochemical performances, including a high specific capacity (825 mAh g(-1) ) at high rate of 5C and a stable cycling retention (88% after 100 cycle at a 0.1C rate). This simple strategy can be extended to other cathode and anode materials for practical LIB applications.

Succinonitrile (SN) is investigated as an electrolyte additive for copper corrosion inhibition to provide overdischarge (OD) protection to lithium ion batteries (LIBs). The anodic Cu corrosion, occurring above 3.5 V (vs Li/Li(+)) in conventional LIB electrolytes, is suppressed until a voltage of 4.5 V is reached in the presence of SN. The corrosion inhibition by SN is ascribed to the formation of an SN-induced passive layer, which spontaneously develops on the copper surface during the first anodic scan. The passive layer is composed mainly of Cu(SN)2PF6 units, which is evidenced by Raman spectroscopy and electrochemical quartz crystal microbalance measurements. The effects of the SN additive on OD protection are confirmed by using 750 mAh pouch-type full cells of LiCoO2 and graphite with lithium metal as a reference electrode. Addition of SN completely prevents corrosion of the copper current collector in the full cell configuration, thereby tuning the LIB chemistry to be inherently immune to the OD abuses.

Electrolytes are characterized by their ionic conductivity (sigma(i)). It is desirable that overall si results from the dominant contribution of the ions of interest (e. g. Li+ in lithium ion batteries or LIB). However, high values of cationic transference number (t(+)) achieved by solid or gel electrolytes have resulted in low sigma(i) leading to inferior cell performances. Here we present an organogel polymer electrolyte characterized by a high liquid-electrolyte-level sigma(i) (similar to 10(1) mS cm(-1)) with high t(+) of Li+ (>0.8) for LIB. A conventional liquid electrolyte in presence of a cyano resin was physically and irreversibly gelated at 60 degrees C without any initiators and crosslinkers, showing the behavior of lower critical solution temperature. During gelation, sigma(i) of the electrolyte followed a typical Arrhenius-type temperature dependency, even if its viscosity increased dramatically with temperature. Based on the Li+-driven ion conduction, LIB using the organogel electrolyte delivered significantly enhanced cyclability and thermal stability.

Nanostructured materials have attracted recent research interest as battery materials due to their expected enhancement of properties. The characteristic nanoscale dimension and its structuring guarantees improved charge and mass transfer during charge/discharge processes. Among the potential cathode materials investigated as a substitute to LiCoO(2), one of the most promising materials is LiFePO(4) with olivine structure (LFP). In this perspective article, the current research and development in the synthesis and electrochemical studies of nanostructured LFP are reviewed with a special emphasis on one-dimensional (1D) nanostructures and nanocompositing with 1D conductive materials. In addition to various examples of 1D LFP with detailed synthetic methods, why 1D nanostructures could be meaningful is discussed in terms of a geometric point of view and the anisotropic lithiation/de-lithiation mechanism of LFP.

Herein, we report on catalytic effects of transition metals (Me) in phospho-olivines (LiMePO4) on carbonization of cetyltrimethylammonium bromide (CTAB). Carbon coating is the required process to enhance electronic conductivity of phospho-olivines that are used as cathode materials for lithium ion batteries. Primary particles of phospho-olivines were in situ coated with CTAB and the adsorbed carbon precursor was carbonized to provide an electrically conductive pathway. CTAB was successfully carbonized in a significant amount with Fe in phospho-olivines (LiFexMn1−xPO4 with x = 1 and 0.5) even if CTAB is thermally decomposed around 300 °C without any residual mass in the absence of the phospho-olivines. LiMnPO4 was the most inferior in terms of CTAB adsorption and thermal carbonization. LiNiPO4 and LiCoPO4 showed inefficient conversion of adsorbed CTAB to carbon even if their adsorption ability for CTAB is quite large. Also, the effect of the amount of carbon coating on LiFePO4 was investigated, leading to a conclusion that the carbon thickness balanced between electronic and ionic conductances results in the best electrochemical performances of lithium ion batteries specifically at high discharge rates.

A facile approach to the surface modification of spinel LiNi0.5Mn1.5O4 (LNMO) cathode active materials for high-voltage lithium ion batteries is demonstrated. This strategy is based on nanoarchitectured polyimide (PI) gel polymer electrolyte (GPE) coating. The PI coating layer successfully wrapped a large area of the LNMO surface via thermal imidization of 4-component (pyromellitic dianhydride/biphenyl dianhydride/phenylenediamine/oxydianiline) polyamic acid. In comparison to conventional metal oxide-based coatings, distinctive features of the unusual PI wrapping layer are the highly continuous surface coverage with nanometre thickness (∼10 nm) and the provision of facile ion transport. The nanostructure-tuned PI wrapping layer served as an ion-conductive protection skin to suppress the undesired interfacial side reactions, effectively preventing the direct exposure of the LNMO surface to liquid electrolyte. As a result, the PI wrapping layer played a crucial role in improving the high-voltage cell performance and alleviating the interfacial exothermic reaction between charged LNMO and liquid electrolyte. Notably, the superior cycle performance (at 55 °C) of the PI-wrapped LNMO (PI-LNMO) was elucidated in great detail by quantitatively analyzing manganese (Mn) dissolution, cell impedance, and chemical composition (specifically, lithium fluoride (LiF)) of byproducts formed on the LNMO surface.

Specific design and optimization of the configuration of micro-scale materials can effectively enhance battery performance, including volumetric density. Herein, we employed commercially available low-cost bulk silicon powder to produce multi-dimensional silicon composed of porous nanowires and micro-sized cores, which can be used as anode materials in lithium-ion batteries, by combining a metal deposition and metal-assisted chemical etching process. Nanoporous silicon nanowires of 5–8 μm in length and with a pore size of ∼10 nm are formed in the bulk silicon particle. The silicon electrodes having multi-dimensional structures accommodate large volume changes of silicon during lithium insertion and extraction. These materials show a high reversible charge capacity of ∼2400 mAh g−1 with an initial coulombic efficiency of 91% and stable cycle performance. The synthetic route described herein is simple, low-cost, and mass producible (high yield of 40–50% in tens of gram scale), and thus, provides an effective method for producing high-performance anode materials.

Lithium iron phosphate olivine (LFP) and lithium manganese oxide spinel (LMO) are competitive and complementary to each other as cathode materials for lithium ion batteries, especially for use in hybrid electric vehicles and electric vehicles. Interest in these materials, due to their low cost and high safety, has pushed research and development forward and toward high performance in terms of rate capability and capacity retention or cyclability at a high temperature of around 60 °C. From the view point of basic properties, LFP shows a higher gravimetric capacity while LMO has better conductivities, both electrically and ionically. According to our comparison experiments, depending on the material properties and operational potential window, LFP was favored for fast charging while LMO led to better discharge performances. Capacity fading at high temperatures due to metal dissolution was revealed to be the most problematic issue of LFP and LMO-based cells for electric vehicles (EVs), with thicker electrodes, in the case of no additives in the electrolyte and no coating to prevent metal dissolution on cathode materials. Various strategies to enhance the properties of LFP and LMO are ready for the realization of EVs in the near future.

nanoparticles of two different structures have been investigated as cathode materialsfor lithium ion batteries using real time Fourier transform electrochemical impedance spectroscopy (FTEIS) techniques duringpotentiodynamic charging and discharging cycles. The effects of their nanostructures were examined employing hollow spheresecondary structured LiFePO

Succinonitrile (SN, CN–[CH2]2–CN) is evaluated as an additive for improving thermal stability in ethylene carbonate (EC)-based electrolytes for lithium ion batteries. Without any sacrifice of performance such as cyclability and capacity, the introduction of SN into an electrolyte with a graphite anode and LixCoO2 cathode leads to (1) reducing the amount of gas emitted at high temperature, (2) increasing the onset temperature of exothermic reactions and (3) decreasing the amount of exothermal heat. The improvement in the thermal stability is considered to be due to strong complex formation between the surface metal atoms of LixCoO2 and nitrile (–CN) groups of SN, from spectroscopic studies based on photoelectrons induced by X-rays and by considering that the exothermic heat and gas evolution are caused by interfacial reactions between the electrolyte and cathode.