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Quinones having a fully conjugated cyclic dione structure have been used as redox mediators in electrochemistry. 2,5-Di

High-energy density lithium-oxygen batteries (LOBs) seriously suffer from poor rate capability and cyclability due to the slow oxygen-related electrochemistry and uncontrollable formation of lithium peroxide (Li

Silicon microparticles (SiMPs), which have a high capacity, a high initial Coulombic efficiency, and a low volume-to-surface ratio compared with nanosized materials, are promising anode materials f...

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...

Nickel-rich layered oxides (LiNi1–x–yCoxMnyO2; (1 – x – y) ≥ 0.6), the high-energy-density cathode materials of lithium-ion batteries (LIBs), are seriously unstable at voltages higher than 4.5 V ve...

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...

A carbon electrode was designed to guarantee flexibility of symmetric electric double layer capacitors (EDLCs) based on its architecture. Three different dimensional carbon materials were combined ...

Highly oxygen evolution reaction (OER)-active electrocatalysts often exhibit improved OER durability in the presence of carbon corrosion or oxidation (COR) in the literature. The activity-durability coincidence of OER electrocatalysts was theoretically understood by preferential depolarization in galvanostatic situations. At constant-current conditions for a system involving multiple reactions that are independent and competitive, the overpotential is determined most dominantly by the most facile reaction so that the most facile reaction is responsible for a dominant portion of the overall current. Therefore, higher OER activity improves durability by mitigating the current responsible for COR. The activity-durability coincidence was then proved experimentally by comparing between two catalysts of the same chemical identity (MnCo2O4) in different dimensions (5 and 100 nm in size). Carbon corrosion responsible for inferior durability was suppressed in the smaller-dimension catalyst (MnCo2O4 in 5 nm) having...

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.

Oxygen reduction reaction (ORR) on carbon in lithium-ion-containing nonaqueous electrolytes is supposed to follow a three-step mechanism: oxygen (O20) to superoxide (O2– or LiO2) to peroxide (O22– or Li2O2) to oxide (O2– or Li2O). This work attempts to solve three controversial issues: (1) whether the superoxide is really formed; (2) whether the superoxide can be stable or immediately converts to peroxide; (3) whether the formation of oxide is feasible at the typical discharge potentials of lithium–air battery or the discharge product is only peroxide. ORR on carbon was studied in LiClO4 or LiPF6 containing dimethyl sulfoxide. The staircase cyclic voltammetry combined with Fourier transform electrochemical impedance spectroscopy (SCV-FTEIS) was used for the in situ investigation of ORR during potential scans. Oxygen was quasi-reversibly reduced to superoxide in the first step. Superoxide showed chemical stability in electrolyte. The superoxide was further reduced to surface-adsorbed peroxide, and the redu...

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.

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...

A biopolymer composite consisting of polypyrrole, ABTS, and laccase (PAL) was electrodeposited onto the surface of an electrode and was shown to catalyze the reduction of dioxygen to water under acidic conditions. The catalytic activity of this biopolymer composite is highest at pH 4, decreasing with increasing pH. The activity of laccase immobilized within this polymer composite was found to be higher than laccase dissolved in solution when methanol was present or at elevated temperatures.

Polypyrrole films doped with ABTS {2,2‘-azinobis(3-ethylbenzothiazoline-6-sulfonate)} show multicolor electrochromism: the anodic coloration from brown at 0.0 V to greenish blue at 0.8 V due to oxidation of ABTS to its radical; and the cathodic coloration to yellow (−1.0 V) based on the reduction of polypyrrole itself.