In situ fabrication of lithium polymer battery basing on a novel electro-polymerization technique

Electro-polymerization technology is proposed for the in situ fabrication of polymer lithium secondary battery and exciting results have been obtained. The polymerization starts from a common used electrolyte of 1 M LiTFSI in DOL/DME (2:1 by weight) with no initiator addition through a routine charge–discharge treatment under some appointed current rate. It is found that once an appropriate current is applied in the charging–discharging of Li/1 M LiTFSI in DOL + DME/LiCoO₂ cell, the original liquid electrolyte polymerizes readily during the first several cycles in an irreversible mode, and thus the desired polymer electrolyte obtained. SEM observation indicates that unlike previous report, the designed electro-polymerization does not result in destructive local break and then turnoff of the circuit, just the reverse, it helps to the formation of a smooth polymer layer, which can effectively protect the lithium substrate from corrosion and dendrite growth. Detailed examination shows that the in situ electro-polymerization does not disturb the electrochemical behavior of the cell, the cycleabilty, internal resistance are all comparable to that of a normal Li/LiCoO₂ liquid secondary battery.     

The reactivity of delithiated Li(Ni1/3Co1/3Mn1/3)O2, Li(Ni0.8Co0.15Al0.05)O2 or LiCoO2 with non-aqueous electrolyte

The high temperature reactions of 1 M LiPF₆ EC:DEC and LiCoO₂, Li(Ni_1/3Co_1/3Mn_1/3)O₂ (NCM) or Li(Ni_0.8Co_0.15Al_0.05)O₂ (NCA) charged to 4.2 V and 4.4 V, respectively, were studied by accelerating rate calorimetry (ARC). The results indicate that NCM shows better thermal stability than both LiCoO₂ and NCA. The state-of-the-art NCA sample shows better safety properties than LiCoO₂. The reactivity of the samples depends on the electrolyte:active material ratio used during ARC testing. Electrode materials charged to 4.4 V are more reactive than the electrode materials charged to 4.2 V. These results should be useful for Li-ion battery researchers interested in maximizing the safety of high energy density cells and also as a benchmark for other researchers using ARC.     

Fabrication of solid thin film electrolyte and LiCoO2 by aerosol flame pyrolysis deposition

Aerosol flame pyrolysis deposition method was applied to deposit the oxide glass electrolyte film and LiCoO₂ cathode for thin film type Li-ion secondary battery. The thicknesses of as-deposited porous LiCoO₂ and Li₂O–B₂O₃–P₂O₅ electrolyte film were about 6 μm and 15 μm, respectively. The deposited LiCoO₂ was sintered for 2 min at 700 °C to make partially densified cathode layer, and the deposited Li₂O–P₂O₅–B₂O₃ glass film completely densified by the sintering at 700 °C for 1 h. After solid state sintering process the thicknesses were reduced to approximately 4 μm and 6 μm, respectively. The cathode and electrolyte layers were deposited by continuous deposition process and integrated into a layer by co-sintering. It was demonstrated that Aerosol flame deposition is one of the good candidates for the fabrication of thin film battery.     

Olivine LiCoPO4 phase grown LiCoO2 cathode material for high density Li batteries

Olivine LiCoPO₄ phase grown LiCoO₂ cathode material was prepared by mixing precipitated Co₃(PO₄)₂ nanoparticles and LiCoO₂ powders in distilled water, followed by drying and annealing at 120 °C and 700 °C, respectively, for 5 h. As opposed to ZrO₂ or AlPO₄ coatings that showed a clearly distinguishable coating layer from the bulk materials, Co₃(PO₄)₂ nanoparticles were completely diffused into the surface of the LiCoO₂ and reacted with lithium of LiCoO₂. An olivine LiCoPO₄ phase was grown on the surface of the bulk LiCoO₂, with a thickness of ∼7 nm. The electrochemical properties of the LiCoPO₄ phase, grown in LiCoO₂, had excellent cycle life performance and higher working voltages at a 1C rate than the bare sample. More importantly, Li-ion cells, containing olivine LiCoPO₄, grown in LiCoO₂, showed only 10% swelling at 4.4 V, whereas those containing bare sample showed a 200% increase during storage at 90 °C for 5 h. In addition, nail penetration test results of the cell containing olivine LiCoPO₄, grown in LiCoO₂ at 4.4 V, did not exhibit thermal runaway with a cell surface temperature of ∼80 °C. However, the cell containing bare LiCoO₂ showed a burnt-off cell pouch with a temperature above 500 °C.     

Amorphous silicon thin films as a high capacity anodes for Li-ion batteries in ionic liquid electrolytes

High lithiation capacity at low red-ox potentials in combination with good safety characteristics makes amorphous Si as a very promising anode material for rechargeable Li batteries.Thin film silicon electrodes were prepared by DC magnetron sputtering of silicon on stainless steel substrates. Their behavior as Li insertion/extraction electrodes was studied by voltammetry and chronopotentiometry at room temperature in the ionic liquid (IL) 1-methyl-1-propylpiperidinium bis(trifluoromethylsuphonil)imide containing 1 M Li bis(trifluoromethylsuphonil)imide. Li/Si cells containing this electrolyte showed good performance with a stable Si electrodes capacity of about 3000 mA h g⁻¹ and a relatively low irreversible capacity. Preliminary results on cycling Si–LiCoO₂ cells using this IL electrolyte are also presented.     

A novel process to prepare porous membranes comprising SnO2 nanoparticles and P(MMA-AN) as polymer electrolyte

We have successfully developed a new process to prepare porous poly(methyl methacrylate-co-acrylonitrile) (P(MMA-AN)) copolymer based gel electrolyte. The porous structure in the polymer matrix is achieved by adding SnO₂ nanoparticles which are mostly used as gas sensor materials. The quasi-aromatic solvent, NMP, has an electron-repulsion effect with the space charge layer on the surface of SnO₂ nanoparticles and forms a special gas–liquid phase interface. Once the cast polymer solution is stored at an elevated temperature to evaporate the solvent, gas–liquid phase separation happens and spherical pores are obtained. The ionic conductivity at room temperature of the prepared gel polymer electrolyte based on the porous membrane is as high as 1.54 × 10⁻³ S cm⁻¹ with the electrochemical stability up to 5.10 V (vs. Li/Li⁺). This method presents another promising way to prepare porous polymer electrolyte for practical use.     

Spectroelectrochemical studies on highly polarized LiCoO2 electrode in organic solutions

In situ Raman spectroscopy was conducted on thin film electrodes of pure LiCoO₂ in order to observe the nature of the changes in interfacial structure between LiCoO₂ and organic solutions (propylene carbonate and ethylene carbonate containing 1 M LiClO₄) when LiCoO₂ is scanned up to highly anodic potentials (∼5.0 V Li⁺/Li). Raman spectra and cyclic voltammograms were recorded simultaneously during the potential scan. We observed a sudden increase in the background signals of the Raman spectra at potentials more positive than 4.7 V. The increased background did not change after potential cycling. The change was irreversible, indicating that surface film formation occurred at positive potentials. As organic compounds fluoresce by visible light, the increased background is ascribed to the formation of a film on the LiCoO₂ electrode surface in organic solutions.     

Operando soft x-ray emission spectroscopy of LiMn2O4 thin film involving Li–ion extraction/insertion reaction

We developed an electrochemical in situ cell for soft x-ray emission spectroscopy (XES) to accurately investigate the redox reaction and electronic structure of transition metals in the cathode materials for Li–ion battery. The in situ cell consists of a Li–metal counter electrode, an organic electrolyte solution, and a cathode on a membrane window which separates the liquid electrolyte from high vacuum and can pass the incoming and emitted photons. In this study, the Mn 3d electronic structure of LiMn₂O₄ thin-film electrode was clarified by the operando XES. At the charged state, the XES spectrum changed significantly from the open-circuit-voltage (OCV) state, suggesting oxidation of the Mn^3 + component through Li–ion extraction. Upon discharge up to 3.0 V vs. Li/Li⁺, the XES spectrum almost returned to its profile at the OCV state with small difference, indicating the valence change of Mn: Mn^3.6 + → Mn^4 + → Mn^3.3 + corresponding to the OCV, charged, and discharged states.     

Perfect reversibility of the lithium insertion in FeS2: The combined effects of all-solid-state and thin film cell configurations

All-solid-state thin film batteries based on sputtered pyrite electrodes, a lithium phosphorus oxynitride electrolyte and a lithium anode were prepared and characterized. The successive reduction of both S₂^2 − and Fe^2 + species led to an impressive volumetric discharge capacity, five times higher than the one for LiCoO₂. Excellent reversibility and capacity retention were obtained during the first and the subsequent 800 charge–discharge cycles. A continuous cycling in the low voltage domain was found to be detrimental to the reversibility of the conversion reaction, suggesting a progressive evolution of the phase distribution inside the electrode. The initial capacity was easily recovered after few full oxidation cycles.     

A strategy of tailoring stable electrolyte material for high performance proton-conducting solid oxide fuel cells (SOFCs)

A facile strategy was proposed to synthesize Nb-containing BaCeO₃-based material, which is a potential electrolyte for proton-conducting solid oxide fuel cells (SOFCs), via a wet chemical route while the conventional synthesis of Nb-containing oxides relied on the solid state reaction method due to the unavailability of suitable Nb-precursors such as Nb-nitrates resulting in a less desirable fuel cell performance when used as an electrolyte. The BaCe_0.7Nb_0.1Y_0.2O_3 − δ (BCNY) electrolyte material in this study persisted a good chemical stability against CO₂ and exhibited good performance in the fuel cell application. The fuel cell with BCNY electrolyte film showed a high performance of 533 mW cm^− 2 at 700 °C. This cell performance based on BCNY electrolyte was superior to that of many stable modified BaCeO₃-based proton-conducting SOFCs where the electrolytes were tailored by other strategies. This result indicated that the strategy presented in this study could be an effective way to prepare a stable electrolyte for high performance proton-conducting SOFCs, which could advance the development of proton-conducting SOFCs.     

A novel sandwiched membrane as polymer electrolyte for lithium ion battery

A novel kind of sandwiched polymer membrane was prepared by coating three layers of poly(vinyl difluoride) (PVDF), poly(methyl methacrylate) (PMMA) and PVDF, separately. Its characteristics were investigated by scanning electron microscopy, FT-IR, X-ray diffraction, and differential thermal analysis. It consists of two phases. The outer PVDF layers are porous, and the inner PMMA layer is solid. Since the PMMA has a good compatibility with the carbonate-based liquid electrolyte, the membrane can easily absorb the electrolyte to form a gelled polymer electrolyte (GPE). As a result, the evaporation peak of the liquid electrolyte is increased to 160 °C. Due to very low evaporation of the liquid electrolyte, LiCoO₂ shows good cycling behavior in the range of 4.4–3.0 V when this GPE is used as the separator and polymer electrolyte, and lithium as the counter and reference electrode. This unique sandwiched membrane is promising for application in scale-up lithium ion batteries with high safety and high energy density.     

Nano-LiCoO2 as cathode material of large capacity and high rate capability for aqueous rechargeable lithium batteries

Crystalline nanoparticles of LiCoO₂ are prepared by a sol–gel method at 550 °C and characterized by X-ray diffraction. Their electrochemical behaviors were characterized by cyclic voltammograms, capacity measurement and cycling performance. Results show that the reversible capacity of the nano-LiCoO₂ can be up to 143 mAh/g at 1000 mA/g and still be 133 mAh/g at 10,000 mA/g (about 70C) in 0.5 mol/l Li₂SO₄ aqueous electrolyte. In addition, their cycling behavior is also very satisfactory, no evident capacity fading during the initial 40 cycles. These data present great promise for the application of aqueous rechargeable lithium batteries.     

Carboxylic and sulfonic N-substituted naphthalene diimide salts as highly stable non-polymeric organic electrodes for lithium batteries

Two N-substituted naphthalene tetracarboxylic diimide (NTCDI) ionic compounds, carboxylic and sulfonic sodium salts, were prepared and used as positive electrode active materials in lithium-half cells. The aim of this investigation was to assess the solubility-suppressing effect of two different negatively charged substituent groups on a redox-active organic backbone using a carbonate-based liquid electrolyte. NTCDI derivatives were obtained in high yields from reaction of naphthalene tetracarboxylic dianhydride with neutralized glycine or with neutralized taurine. They were mixed with carbon black and cycled in galvanostatic mode against lithium metal using 1 M LiPF₆ EC/DMC liquid electrolyte. These two NTCDI derivatives exhibit a quite stable electrochemical activity upon cycling at an average potential of 2.3 V vs. Li⁺/Li⁰ giving rise to specific capacity values of 147 mAh·g^− 1 and 113 mAh·g^− 1 for the dicarboxylate and the disulfonate derivative, respectively. This study clearly supports the useful effect of such grafted permanent charges as a general rule on the electrochemical stability of crystallized organic materials based on the assembly of small redox-active units.     

Li2SO4-polyacrylamide polymer electrolytes for 2.0 V solid symmetric supercapacitors

A neutral polymer electrolyte comprised of lithium sulfate (Li₂SO₄) and polyacrylamide (PAM) was developed. The Li₂SO₄-PAM electrolyte film shows an ionic conductivity up to 10 mS cm^− 1 in 45%RH conditions. Solid double layer capacitors were demonstrated using CNT-graphite electrodes and Li₂SO₄-PAM solid electrolytes. The voltage window of the solid cell was about 2.0 V, identical to that of a Li₂SO₄ liquid cell used as baseline. The demonstrated voltage window is significantly larger than that reported for proton- or hydroxyl-conducting electrolytes, suggesting that the Li₂SO₄-PAM electrolyte is a promising system for high energy density supercapacitors. The solid device also demonstrated excellent rate capability (up to 5 V s^− 1) and good cycle life (beyond 10,000 charge/discharge cycles).     

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.     

Microwave-assisted synthesis of multimetal oxygen-evolving catalysts

Oxygen evolution reaction (OER) plays a pivotal role in water-splitting. Here, we report a facile method to synthesize multimetal supported on commercial carbon black via a time-saving microwave process. Crystalline FeNi₃ nanoparticles homogeneously doped with Mo are formed via a microwave treatment and activated to metal oxyhydroxide in-situ during cyclic voltammetry test with overpotential of only 280 mV at 10 mA cm^− 2 for OER in alkaline electrolyte, outperforming RuO₂. Our synthesis methodology is a promising alternative for large-scale production, delivering a valuable contribution to catalyst preparation and electrocatalytic water oxidation research.     

Amphiphilic ruthenium dye as an ideal sensitizer in conversion of light to electricity using ionic liquid crystal electrolyte

The optimization of interfacial charge transfer between the dye and the electrolyte is crucial to the design of dye-sensitized solar cells. In this paper, we address the combined use of an ionic liquid crystal electrolyte and amphiphilic ruthenium dyes in dye-sensitized solar cells. The solar cell with an amphiphilic ruthenium dye [Ru(H₂dcbpy)(tdbpy)(NCS)2] (H₂dcbpy = 4,4′-dicarboxy-2,2′-bipyridine, tdbpy = 4,4′-tridecyl-2,2′-bipyridine), exhibited a short-circuit photocurrent density of 9.1 mA/cm², an open-circuit voltage of 665 mV and a fill factor of 0.58, corresponding to an overall conversion efficiency of 3.51%. We find that increasing dye alkyl chain length to octadecyl from tridecyl results in lower short-circuit photocurrent density and open-circuit voltage, and the suitable dyes for ionic liquid crystal electrolyte differed completely from those used in liquid and ionic liquid electrolyte cells.     

High power LiCoO2 cathode materials with ultra energy density for Li-ion cells

Hydrothermally prepared 100 nm-sized LiCoO₂ with a plate morphology packed in a crucible resulted in 40 μm-sized particles that consisted of aggregated < 1 micron-sized particles after annealing at 900 °C for 3 h. In the condition where the optimized electrode pore volume was 20%, 4.1 g/cc of electrode density was obtained, which corresponded to 3 Wh/cc, which is the highest value among the cathode materials. Furthermore, the LiCoO₂ showed excellent capacity retention of 78% after 290 cycles in a Li-ion cell under 7 C rate cycling.     

Fabrication of a large area cathode-supported thin electrolyte film for solid oxide fuel cells via tape casting and co-sintering techniques

A large area cathode-supported electrolyte film, comprising porous (La_0.8Sr_0.2)_0.95MnO₃ (LSM95) cathode substrate, LSM95/Zr_0.89Sc_0.1Ce_0.01O_2?x (SSZ) cathode active layer, and SSZ electrolyte, has been successfully fabricated by tape casting and co-sintering techniques. The interface reaction between cathode and electrolyte was inhibited by using A-site deficient LSM. A dense enough SSZ thin film with a thickness of ～26 μm was obtained at 1250 °C. By using Pt as anode, the obtained single cell reached the maximum power density of 0.54 W cm^?2 at 800 °C in O₂/humidified H₂, with open circuit voltage (OCV) value of 1.08 V.     

Preparation of nano-sized LiCoO2 powder by the combination of sonication and modified Pechini process

A sonication (ultrasonic processing) and modified Pechini process were combined to fabricate nano-sized LiCoO₂ powder. A composition of precursor solution for fabricating LiCoO₂ was modulated by controlling the molar ratios of lithium acetate to cobalt acetate and ethylene glycol to citric acid, respectively. The sonication was applied on the precursor solution to get highly dispersed transition-metal oxide powder. The sonicated precursor gels pre-dried were calcined in the range of 400 to 800 °C for 10 h. Effect of sonication on the particle size and the morphology of LiCoO₂ prepared by the modified Pechini process was elucidated. After calcination, the unsonicated LiCoO₂ powder had an aggregated-like morphology, as combined loosely and/or firmly, while the sonicated LiCoO₂ was more ultra-finely particulated and presented more mono-dispersed morphology without severe aggregation. The nano-sized LiCoO₂ with high crystallinity and homogeneity could be prepared by the combination of sonication and modified Pechini process.