In Situ Co-O Bond Reinforcement of the Artificial Cathode Electrolyte Interphase in Highly Delithiated LiCoO2 for High-Energy-Density Applications.

Highly delithiated LiCoO2 has high specific capacity (>200 mAh g-1); however, its degradation behavior causes it to have poor electrochemical performance and thermal instability. The degradation of highly delithiated LiCoO2 is mainly induced by oxygen vacancy migration and weakening of oxygen-related interactions, which result in pitting corrosion and fault formation on the surface. In this research, a coupling agent, namely, 3-aminopropyltriethoxysilane (APTES), was grafted onto the surface of LiCoO2 to form a cross-linking structure. Through the aza-Michael addition reaction, an oligomer formed from barbituric acid and bisphenol a diglycidyl ether diacrylate were reacted with the cross-linking APTES to form an artificial cathode electrolyte interphase (ACEI). The highly delithiated LiCoO2 containing the ACEI had considerably less degradation on the surface of the bulk material caused by oxygen release. The formation of the O1 phase was prevented in high delithiation and high-temperature operations. This research revealed that the ACEI reinforced the Co-O bond, which is crucial in preventing gas evolution and O1 phase formation. In addition, the ACEI prevents direct contact between the electrolyte and highly active surface of LiCoO2, thereby preventing the formation of a thick and high impedance traditional cathode electrolyte interphase. According to the present results, highly delithiated LiCoO2 containing the ACEI exhibited outstanding cycle retention and capacity at 55 °C as well as low heat capacity release in the fully delithiated state. The ACEI considerably protected and maintained the electrochemical performance of highly delithiated LiCoO2, which is suitable for high-energy-density applications, such as electric vehicles and power tools.

Controlling Ni2+ from the Surface to the Bulk by a New Cathode Electrolyte Interphase Formation on a Ni-Rich Layered Cathode in High-Safe and High-Energy-Density Lithium-Ion Batteries.

Ni-rich high-energy-density lithium ion batteries pose great risks to safety due to internal short circuits and overcharging; they also have poor performance because of cation mixing and disordering problems. For Ni-rich layered cathodes, these factors cause gas evolution, the formation of side products, and life cycle decay. In this study, a new cathode electrolyte interphase (CEI) for Ni2+ self-oxidation is developed. By using a branched oligomer electrode additive, the new CEI is formed and prevents the reduction of Ni3+ to Ni2+ on the surface of Ni-rich layered cathode; this maintains the layered structure and the cation mixing during cycling. In addition, this new CEI ensures the stability of Ni4+ that is formed at 100% state of charge in the crystal lattice at high temperature (660 K); this prevents the rock-salt formation and the over-reduction of Ni4+ to Ni2+. These findings are obtained using in situ X-ray absorption spectroscopy, operando X-ray diffraction, operando gas chromatography-mass spectroscopy, and X-ray photoelectron spectroscopy. Transmission electron microscopy reveals that the new CEI has an elliptical shape on the material surface, which is approximately 100 nm in length and 50 nm in width, and covers selected particle surfaces. After the new CEI was formed on the surface, the Ni2+ self-oxidation gradually affects from the surface to the bulk of the material. It found that the bond energy and bond length of the Ni-O are stabilized, which dramatically inhibit gas evolution. The new CEI is successfully applied in a Ni-rich layered compound, and the 18650- and the punch-type full cells are fabricated. The energy density of the designed cells is up to 300 Wh/kg. Internal short circuit and overcharging safety tests are passed when using the standard regulations of commercial evaluation. This new CEI technology is ready and planned for future applications in electric vehicle and energy storage.

Interface Interaction Behavior of Self-Terminated Oligomer Electrode Additives for a Ni-Rich Layer Cathode in Lithium-Ion Batteries: Voltage and Temperature Effects.

Self-terminated oligomer additives synthesized from bismaleimide and barbituric acid derivatives improve the safety and performance of lithium-ion batteries (LIBs). This study investigates the interface interaction of these additives and the cathode material. Two additives were synthesized by Michael addition (additive A) and aza-Michael addition (additive B). The electrochemical performances of bare and modified LiNi0.6Mn0.2Co0.2O2 (NMC622) materials are studied. The cycling stability and rate capability of NMC622 considerably improve on surface modification with additive B. According to the differential scanning calorimetry results, the exothermic heat of fully deliathiated NMC622 is dramatically decreased through surface modification with both additives. The electrode surface kinetics and interface interaction phenomena of the additives are determined through surface plasma resonance measurements in operando gas chromatography-mass spectroscopy (GCMS) and in situ soft X-ray absorption spectroscopy (XAS). The binding rate constant of additive B onto NMC622 particles is 1.2-2.3 × 104 M-1 s-1 in the temperature range of 299-311 K, which is ascribed to the strong binding affinity toward the electrode surface. This affinity enhances Li+ diffusion, which allows the electrode modified by additive B to provide high electrochemical performance with superior thermal stability. In operando GCMS reveals that gas evolution due to the electrolyte degradation at the NMC622 surface contributes to safety hazards in the bare NMC622 material. In situ soft XAS indicates the occurrence of structural transformation in the bare NMC622 material after it is fully charged and at elevated temperatures. The NMC622 material is stabilized by incorporating additives. The unique performance of additive B can be attributed to its linear structure that allows superior electrode surface adhesion compared with that of additive A. Therefore, this study presents an optimized working principle of self-terminated oligomers, which can be developed and applied to improve the safety and performance of LIBs.

Comparisons of urodynamic characteristics between female patients with overactive bladder and overactive bladder plus stress urinary incontinence.

OBJECTIVES: To determine and compare the urodynamic characteristics in patients with overactive bladder (OAB) and patients with OAB plus stress urinary incontinence (OAB+SUI). METHODS: A total of 120 patients (60 each in OAB and OAB+SUI groups) who underwent urodynamic study between January and April 2003 were recruited. A detailed history, physical examination, and multichannel urodynamic data, including uroflowmetry, filling and voiding cystometry, stress urethral pressure profile, and 20-minute pad test were obtained for each patient. The urodynamic findings of each patient were analyzed and the results compared between the two groups. RESULTS: The median age of both groups was 51 years (interquartile range 43 to 64) with a parity of 3 (interquartile range 2 to 4); 54% (n = 65) were menopausal. The urodynamic parameters of bladder storage function showed premature filling sensation with decreased bladder capacity. Additionally, 60 (50%) had genuine stress incontinence, 3 (3%) had idiopathic detrusor overactivity, 11 (9%) mixed type incontinence, and 12 (11%) had voiding dysfunction. Among the urodynamic parameters between the two groups, first desire, strong desire, urgency, functional urethral length, maximal urethral pressure, maximal urethral closure pressure, pad test, and percentage of genuine stress incontinence in the OAB+SUI group were significantly lower statistically than those in the OAB group (P <0.03); the differences in age, parity, and percentage of menopausal status were also statistically significant (P <0.03). CONCLUSIONS: Our data showed that patients in the OAB+SUI group had more impaired urodynamic parameters than those in the OAB group. Age, parity, and menopausal status were contributory factors.