Erector Spinae Regional Anesthesia for Robotic Coronary Artery Bypass Surgery Is Not Associated With Reduced Postoperative Opioid Use: A Retrospective Observational Study.

OBJECTIVE: Regional anesthesia techniques are gaining traction in cardiac surgery. The aim of this study was to compare the analgesic efficacy of erector spinae plane block catheters (ESPBC), serratus anterior plane block catheters (SAPBC), and paravertebral single-shot block (PVB) versus no block after robotic minimally invasive direct coronary artery bypass (MIDCAB). DESIGN: This was a retrospective observational study of routinely recorded data. SETTING: The study was performed at a single healthcare system. PARTICIPANTS: All patients underwent robotic MIDCAB. INTERVENTION: Data were analyzed from 346 patients during a 53-month period. The clinical data warehouse was queried for all robotic MIDCAB surgeries. Variables abstracted included type of nerve block, age, sex, use of adjuncts, Society of Thoracic Surgeons predicted short length of stay (PSLOS), total opioid consumption during the 72 hours after surgery, and postoperative hospital length of stay (LOS). The primary outcome was total oral morphine milligram equivalents (MME) consumed during the first 72 hours after surgery. The secondary outcome was hospital LOS. MEASUREMENTS AND MAIN RESULTS: In a model adjusting for PSLOS, the authors did not observe an association between ESPBC and the reduction of total administered oral MME within 72 hours after surgery. There was no significant difference in MME when comparing patients who received PVB to patients with ESPBC. Older age and female sex were associated with significantly lower MME. Patients who received ESPBC had a significantly shorter hospital LOS than patients with SAPBC. CONCLUSIONS: These findings suggested that postoperative pain after MIDCAB surgery might not be completely covered by ESPBC. Prospective studies are needed to further elucidate the value of this technique for robotic MIDCAB.

Review of Acute Treatment of Migraine Trial Results With the New FDA Endpoints: Design Implications for Future Trials.

BACKGROUND: In October 2014, the US Food and Drug Administration released a draft guidance for the development of drugs for the acute treatment of migraine. This guidance offered the option of replacing the previously required 4 co-primary endpoints: pain freedom, freedom from nausea, freedom from photophobia, and freedom from phonophobia, all at 2 hours posttreatment, with 2 co-primary endpoints: pain freedom and freedom from most bothersome symptom (MBS) other than pain, both at 2 hours posttreatment. At the time the new draft guidance was released, no large clinical trials had been undertaken with these 2 co-primary endpoints, posing a challenge in determining the sample size that might be required to achieve statistical significance. As a number of trials have now been completed, we conducted a review of the observed placebo responses, drug effect sizes, and sample sizes to better inform the design of future trials. METHODS: We searched PubMed, Embase, Web of Science, and the Cochrane library for primary publications of phase 3 randomized, placebo-controlled, double-blind acute migraine treatment trials that used pain freedom and MBS freedom as primary or planned secondary endpoints. For each endpoint, placebo response rates were determined and used to generate estimates of sample size, assuming differences between placebo and active treatment groups of 10%, 15%, and 20%. Sample size calculations were based on 80% power using a 2-group continuity corrected chi-square test with a 5% 2-sided significance level. RESULTS: We identified abstracts or full-length papers describing results of 8 clinical trials employing the new co-primary endpoints. The mean placebo response rate for 2-hour pain freedom was 16.75% (range 11.8-21.3%) and treatment effect (difference in response rates between active and placebo groups) ranged from 5.0% to 27.2%. For 2-hour MBS freedom, the mean placebo response rate was 32.8% (range 25.2-48.1%), and the range of treatment effect was 8.9% to 25.4%. Based on a placebo response rate of 17% for pain freedom, the sample sizes that would have been required to achieve statistical significance were n = 269, n = 128, and n = 77, for treatment effect sizes of 10%, 15%, and 20%, respectively. For MBS, assuming a placebo response rate of 33%, the corresponding required sample sizes would have been n = 389, n = 181, and n = 105. CONCLUSIONS: The observed range of placebo response and treatment effect sizes suggests that use of the newly recommended 2 co-primary endpoints could reduce the sample sizes required to achieve significance compared with past trials using 4 primary endpoints (in which mean and median group sizes for recent trials were 375 and 362, respectively). However, the initial trials using the newly recommended co-primary endpoints tended to treat more participants than would have been minimally required. We anticipate that with the growing body of information regarding the use of these new endpoints, samples sizes may be more aligned with treatment efficacy, enabling faster and more cost-effective trials for acute migraine treatment.

Efficacy of ADAM Zolmitriptan for the Acute Treatment of Difficult-to-Treat Migraine Headaches.

OBJECTIVE: To understand the efficacy of zolmitriptan applied with Adhesive Dermally Applied Microarray (ADAM) in treating types of migraine (those with severe headache pain, the presence of nausea, treatment ≥2 hours after migraine onset, or migraine present upon awakening) that are historically considered to be less responsive to oral medications. BACKGROUND: ADAM is an investigational system for intracutaneous drug administration. In a pivotal Phase 2b/3 study (ZOTRIP, N = 321 in the modified intention-to-treat population), ADAM zolmitriptan 3.8 mg provided superior pain freedom and freedom from patients' usual most bothersome associated symptom (MBS), compared with placebo at 2 hours post-dose. We undertook a post hoc analysis of data from the ZOTRIP trial to examine these same outcomes in subsets of patients whose migraine characteristics have been associated with poorer outcomes when treated with oral medications. METHODS: The ZOTRIP trial was a multicenter, randomized, double-blind, placebo-controlled, parallel group Phase 2b/3 study conducted at 36 sites in the United States. Presented here are post hoc subgroup analyses of patients with nausea (n = 110) or severe pain (n = 72) at baseline, those whose treatment was delayed 2 or more hours after onset (n = 75), and those who awoke with migraine (n = 80). The Cochran-Mantel-Haenszel test was used to assess whether patients in the ADAM zolmitriptan 3.8 mg group had superior treatment outcomes compared with placebo. RESULTS: In patients with nausea, 2-hour pain freedom was achieved in 44% (26/59) in the ADAM zolmitriptan 3.8 mg group and 14% (7/51) in the placebo group (P = .005) (odds ratio = 5.11, 95% CI: 1.96-13.30), and 2-hour MBS freedom was achieved in 68% (40/59) in the active treatment group and 45% (23/51) of those receiving placebo (P = .009) (odds ratio = 2.86, 95% CI: 1.28-6.43). For those with severe pain, corresponding pain-free values were 26% (10/39) and 15% (5/33) (P = .249) (odds ratio = 2.14, 95% CI: 0.60-7.62), and MBS-free values were 64% (25/39) and 42% (14/33) (P = .038) (odds ratio = 2.86, 95% CI: 1.05-7.79). Among participants who awoke with migraine, 44% (16/36) and 16% (7/44) were pain-free in the ADAM zolmitriptan 3.8 mg and placebo groups, respectively (P = .006) (odds ratio = 4.29, 95% CI: 1.50-12.31), and 72% (26/36) vs 39% (17/44) were MBS-free, respectively (P = .003) (odds ratio = 4.40, 95% CI: 1.61-12.05). In those whose treatment was delayed ≥2 hours, pain freedom in the active treatment group and placebo group were 33% (12/36) and 10% (4/39), respectively (P = .017) (odds ratio = 4.33, 95% CI: 1.24-15.10), and MBS freedom was achieved in 69% (25/36) and 41% (16/39), respectively, in the delayed treatment group (P = .014) (odds ratio = 3.37, 95% CI: 1.27-8.95). No significant effects (overall interaction P = .353) were observed in logistical regression models of treatment by subgroup interaction. CONCLUSION: Severe pain, delayed treatment, awakening with a headache, and the presence of nausea are factors that predict a poorer response to acute migraine treatment. In these post hoc analyses of subgroups of patients with each of these characteristics in the ZOTRIP trial, participants receiving ADAM zolmitriptan 3.8 mg displayed nearly uniformly better headache responses (2-hour headache freedom and 2-hour MBS freedom) compared with those who received placebo.

Randomized, double-blind, placebo-controlled, parallel-group, multi-center study of the safety and efficacy of ADAM zolmitriptan for the acute treatment of migraine.

Objective To determine the efficacy, tolerability, and safety of ascending doses of Adhesive Dermally-Applied Microarray (ADAM) zolmitriptan versus placebo for acute migraine treatment. Background ADAM is a novel patient-administered system for intracutaneous drug administration. In a phase 1 pharmacokinetic study, zolmitriptan administered using ADAM had much faster absorption than oral administration with higher exposure in the first two hours. Methods This was a multicenter, randomized, double-blind, placebo-controlled, parallel-group Phase 2b/3 study evaluating ADAM zolmitriptan 1 mg, 1.9 mg, and 3.8 mg versus placebo. Co-primary endpoints were pain freedom and freedom from most bothersome other migraine-associated symptom 2 hours post-dose. Results Of patients treated with ADAM zolmitriptan 3.8 mg or placebo, 41.5% and 14.2%, respectively were pain-free 2 hours post-dose ( p = 0.0001) and 68.3% and 42.9% were free from their most bothersome other symptom ( p = 0.0009). Due to the fixed sequential testing methodology, formal statistical significance was not established for secondary endpoints. However, the proportion of patients who were photophobia-free, phonophobia-free, and nausea-free at 2 hours post-dose was higher in the ADAM zolmitriptan 3.8 mg group compared with placebo, as were the percentages of patients who were pain-free, and who experienced pain relief up to 48 hours post-dose. Systemic adverse events were consistent with previous triptan trials, and included dizziness, paresthesia, muscle tightness, and nausea, all of which occurred in < 5% of patients in any group. Application site reactions were generally mild and resolved within 48 hours, although erythema and bruising persisted for longer periods in some patients. Conclusion ADAM zolmitriptan 3.8 mg provides effective relief of migraine headache and associated most bothersome symptoms compared with placebo, and is well-tolerated. ClinicalTrials.gov NCT02745392.

Use of Most Bothersome Symptom as a Coprimary Endpoint in Migraine Clinical Trials: A Post-Hoc Analysis of the Pivotal ZOTRIP Randomized, Controlled Trial.

OBJECTIVE: To better understand the utility of using pain freedom and most bothersome headache-associated symptom (MBS) freedom as co-primary endpoints in clinical trials of acute migraine interventions. BACKGROUND: Adhesive dermally applied microarray (ADAM) is an investigational system for intracutaneous drug administration. The recently completed pivotal Phase 2b/3 study (ZOTRIP), evaluating ADAM zolmitriptan for the treatment of acute moderate to severe migraine, was one of the first large studies to incorporate MBS freedom and pain freedom as co-primary endpoints per recently issued guidance by the US Food and Drug Administration. In this trial, the proportion of patients treated with ADAM zolmitriptan 3.8 mg, who were pain-free and MBS-free at 2 hours post-dose, was significantly higher than for placebo. METHODS: We undertook a post-hoc analysis of data from the ZOTRIP trial to examine how the outcomes from this trial compare to what might have been achieved using the conventional co-primary endpoints of pain relief, nausea, photophobia, and phonophobia. RESULTS: Of the 159 patients treated with ADAM zolmitriptan 3.8 mg or placebo, prospectively designated MBS were photophobia (n = 79), phonophobia (n = 43), and nausea (n = 37). Two-hour pain free rates in those with photophobia as the MBS were 36% for ADAM zolmitriptan 3.8 mg and 14% for placebo (P = .02). Corresponding rates for those with phonophobia as the MBS were 14% and 41% (P = .05). For those whose MBS was nausea, corresponding values were 56% and 16%, respectively (P = .01). Two-hour freedom from the MBS for active drug vs placebo were 67% vs 35% (P < .01) for photophobia, 55% vs 43% (P = .45) for phonophobia, and 89% vs 58% for nausea (P = .04). MBS freedom but not pain freedom was achieved in 28%. Only 1 patient (1%) achieved pain freedom, but not MBS freedom. The proportion with both pain and MBS freedom was highest (56%) among those whose MBS was nausea. CONCLUSION: In this study, the use of MBS was feasible and seemed to compare favorably to the previously required 4 co-primary endpoints.

Sacroiliac joint radiofrequency ablation with a multilesion probe: a case series of 60 patients.

This retrospective case series of patients with refractory sacroiliac joint (SIJ) pain presents our first 77 SIJ radiofrequency ablation (RFA) procedures performed with a multilesion probe. Of these, 16 (20.8%) provided no relief; 55 (71.4%) provided >50% pain relief at 6 weeks; 42 (54.5%, 95% confidence interval, 42.8%-65.8%) provided >50% pain relief at 6 months; and 12 (15.6%) continued to provide >50% pain relief at 1 year. These results compare favorably to those published using other RFA techniques. In conclusion, more than half of our patients with refractory SIJ pain received some pain relief for at least 6 months after RFA.

Self-loathing aspects of depression reduce postoperative opioid cessation rate.

OBJECTIVE: We previously reported that increased preoperative Beck Depression Inventory II (BDI-II) scores were associated with a 47% (95% CI 24%-64%) reduction in the rate of opioid cessation following surgery. We aimed to identify the underlying factors of the BDI-II (affective/cognitive vs somatic) associated with a decreased rate of opioid cessation after surgery. METHODS: We conducted a secondary analysis of the data from a previously reported prospective, longitudinal, observational study of opioid use after five distinct surgical procedures (total hip replacement, total knee replacement, thoracotomy, mastectomy, and lumpectomy) in 107 patients. The primary endpoint was time to opioid cessation. After exploratory factor analysis of the BDI-II, mean summary scores were calculated for each identified factor. These scores were evaluated as predictors of time to opioid cessation using Cox proportional hazards regression. RESULTS: The exploratory factor analysis produced three factors (self-loathing symptoms, motivational symptoms, emotional symptoms). All three factors were significant predictors in univariate analysis. Of the three identified factors of the BDI-II, only preoperative self-loathing symptoms (past failure, guilty feelings, self-dislike, self-criticalness, suicidal thoughts, worthlessness) independently predicted a significant decrease in opioid cessation rate after surgery in the multivariate analysis (HR 0.86, 95% CI 0.75-0.99, P value 0.037). CONCLUSIONS: Our results identify a set of negative cognitions predicting prolonged time to postoperative opioid cessation. Somatic symptoms captured by the BDI-II were not primarily responsible for the association between preoperative BDI-II scores and postoperative prolonged opioid use.

Building regional anesthesia capacity in limited-resource settings: a pilot study evaluating a 4-week curriculum.

Aim: To pilot a 4-week regional anesthesia curriculum for limited-resource settings. Intervention: A baseline needs assessment and knowledge test were deployed. The curriculum included lectures and hands-on teaching, followed by knowledge attainment tests. Results: Scores on the knowledge test improved from a mean of 37.1% (SD 14.7%) to 50.9% (SD 18.6%) (p = 0.017) at 4 weeks and 49% at 24 months. An average of 1.7 extremity blocks per month was performed in 3 months prior to the curriculum, compared with an average of 4.1 per month in 8 months following. Conclusion: This collaborative curriculum appeared to have a positive impact on the knowledge and utilization of regional anesthesia.

A chemically driven insulator-metal transition in non-stoichiometric and amorphous gallium oxide.

Insulator-metal transitions are well known in transition-metal oxides, but inducing an insulator-metal transition in the oxide of a main group element is a major challenge. Here, we report the observation of an insulator-metal transition, with a conductivity jump of seven orders of magnitude, in highly non-stoichiometric, amorphous gallium oxide of approximate composition GaO(1.2) at a temperature around 670 K. We demonstrate through experimental studies and density-functional-theory calculations that the conductivity jump takes place at a critical gallium concentration and is induced by crystallization of stoichiometric Ga(2)O(3) within the metastable oxide matrix-in chemical terms by a disproportionation. This novel mechanism--an insulator-metal transition driven by a heterogeneous solid-state reaction--opens up a new route to achieve metallic behaviour in oxides that are expected to exist only as classic insulators.

Granulation by roller compaction and enteric coated tablet formulation of the extract of the seeds of Glinus lotoides loaded on Aeroperl 300 Pharma.

The purpose of this research was to improve the hygroscopicity and poor flow properties of the crude dry extract of the seeds of Glinus lotoides and improve the disintegration time of the core-tablets for enteric coated formulation thereof. The liquid crude extract of the plant was adsorbed on granulated colloidal silicon dioxide (Aeroperl 300 Pharma) at 30% w/w and the dry extract preparation (DEP) was dry-granulated with roller-compaction using Micro-Pactor. Hygroscopicity, flow property and disintegration time were improved significantly due to the adsorption and granulation processes. Moreover, the DEP does not become mucilaginous even at higher relative humidity levels (above 65%). Oblong tablets (20 x 8.25 mm) containing 947 mg of the granulated DEP (equivalent to the traditional dose), 363 mg of Avicel PH101 and 90 mg of Ac-di-Sol as disintegrant were formulated using an instrumented eccentric tablet machine at 20 kN. The tablets showed a crushing strength of 195 N, a friability of 0.4% and disintegrated within 9 min. The tablets were then enteric coated using polymethacrylate co-polymers (Eudragit L 100-55 and Kollicoat MAE 100P). The coated tablets resisted disintegration or softening in simulated gastric fluid for a minimum of 2 h and disintegrated within 15 min in intestine simulated fluid at pH 6.8. In addition to controlling the release of the active agents, the enteric coating improved the strength and decreased friability of the core-tablets.

Investigation of the glidant properties of compacted colloidal silicon dioxide by angle of repose and X-ray photoelectron spectroscopy.

The optimal flow-enhancing effect of a new compacted, hydrophilic colloidal silicon dioxide (AEROSIL 200 VV Pharma) on microcrystalline cellulose (Avicel PH 101) and pregelatinized starch (Starch 1500) was found to be 0.25% under gentle and 0.125% under strong mixing conditions, as measured by the angle of repose. The effect could be explained by X-ray photoelectron spectroscopy (XPS) investigations. The Si 2p signals of the silicon dioxide indicated that the coverage of the excipient surface with AEROSIL was greater for all mixtures produced under strong mixing conditions and corresponded to a higher degree of de-agglomeration of the AEROSIL aggregates. The more extensive surface coverage of Avicel PH 101 as compared to Starch 1500 could be explained by the particle morphology on the one hand and by the XPS C 1s signals on the other. Due to the different conformation of the two excipients, Avicel PH 101 offers a higher density of hydroxyl groups on its surface which are available for hydrogen bonding with the surface hydroxyl groups of hydrophilic colloidal silicon dioxide.

Quantitative determination of the group of flavonoids and saponins from the extracts of the seeds of Glinus lotoides and tablet formulation thereof by high-performance liquid chromatography.

The total flavonoids and saponins of the seeds of Glinus lotoides in the crude extracts and tablet formulation thereof were quantified by reversed-phase high-performance liquid chromatographic (RP-HPLC) methods with UV detection. The saponins were analyzed after acid hydrolysis in 3 M HCI at 100 degrees C for 1 h. Vicenin-2 and mollugogenol B were isolated and used as reference substances for the quantification of total flavonoids and saponins, respectively. The identity and purity (> 97%) of the standards were confirmed by spectroscopic (UV, MS, and NMR) and chromatographic (HPLC) methods. The flavonoids and saponins of the crude extract of the seeds and tablet formulation were separated by RP-HPLC (Nucleosil RP-18 column, 250 mm x 4.6 mm) using linear gradient elution systems of acetonitrile-water-0.1 M H3PO4 for flavonoids and methanol-water for saponins. Satisfactory separation of the compounds was obtained in less than 30 and 25 min, for the flavonoids and saponins, respectively. The methods were validated for linearity, repeatability, limits of detection (LOD) and limits of quantification (LOQ). Repeatability (inter- and intra-day, n = 6 and 9, respectively) showed less than 2% relative standard deviation (RSD). The LOD and LOQ were found to be 0.075 and 0.225 mg/mL, respectively, for vicenin-2 and 0.027 and 0.082 mg/100 mL, respectively, for mollugogenol B. The content of flavonoids and saponins of six single tablets was between 95 and 103% for flavonoids and 94-98% for saponins. The validated HPLC methods were employed to standardize a fingerprint of a laboratory produced purified extract, which could be used as a secondary standard for the routine quality control. Accordingly, the purified extract was found to contain 21.3% flavonoids (vicenin-2, 10%) and 25.4% saponins (glinuside G, 14.2%).

In vitro availability of kaempferol glycosides from cream formulations of methanolic extract of the leaves of Melilotus elegans.

In Ethiopian traditional medicine, Melilotus elegans Salzm. ex Ser. (Leguminosae) is used for the treatment of haemorrhoids and lacerated wounds. In view of its wide spread use and proven anti-inflammatory activity, 80% methanolic extract of the leaves was formulated into creams. HPLC/UV and MS studies revealed the presence of flavonoids, of which kaempferol was the major aglycone. Quantitative estimation of kaempferol in the hydrolyzed extract as determined by HPLC/UV was found to be 16.3+/-0.93 microg/mg (n=6, range) of extract. The in vitro release profiles of kaempferol glycosides (quantified as kaempferol equivalent) from the cream formulations in a multilayer membrane system indicated that a lipophilic cream of the extract provides higher release of kaempferol glycosides than hydrophilic and amphiphilic ones. Over a study period of 4h, the lipophilic cream released 66+/-5.70% of kaempferol glycosides, while the hydrophilic and amphiphilic creams resulted in 55+/-2.77 and 38+/-2.30% release, respectively.

Quantitation of the enantiomers of ofloxacin by capillary electrophoresis in the parts per billion concentration range for in vitro drug absorption studies.

Ofloxacin, a chiral fluoroquinolone, possesses two optical isomers. The antibacterial activity of S-(-)-ofloxacin is reported to be 8-128 times higher than that of R-(+)-ofloxacin. A capillary zone electrophoresis method has been developed to quantify the enantiomers of ofloxacin in high diluted samples (20-700 ng/ml for each enantiomer). After fluid-fluid extraction of ofloxacin from physiological solution electrokinetic injection was employed to improve the sensitivity. The method was optimised using a central composite design. Four experimental factors were investigated: the background electrolyte concentration, the methyl-beta-cyclodextrin concentration, the buffer pH and the temperature. The amount migrated into the capillary, determined by the peak area, the resolution between the ofloxacin enantiomers, the migration time and the generated current were evaluated as responses. The quantification limit is 11.4 ng/ml for S-ofloxacin and 10.8 ng/ml for R-ofloxacin. The method has shown good validation data in terms of precision and recovery rate.

Quantification of sugars and organic acids in hygroscopic pharmaceutical herbal dry extracts.

Three chromatographic methods have been employed for the determination of hydrophilic compounds, namely carbohydrates and organic acids in herbal dry extracts of Eschscholtzia californica Cham. The hydrophilic compounds were separated from the other components of the dry extracts by solid-phase extraction methods, which were optimised with respect to recovery rates. Carbohydrates were quantified using high-performance anion-exchange chromatography with pulsed amperometric detection. Organic acids were analysed by ion-exclusion chromatography with evaporative light scattering detection and gas chromatography-mass spectrometry. Using the latter method, large amounts of glyceric acid were separated from the extracts of Eschscholtzia californica Cham. This substance together with sugars may be responsible for the increased hygroscopicity and the poor processing behaviour of the extracts.

Enrichment of hyperforin from St. John's wort (Hypericum perforatum) by pilot-scale supercritical carbon dioxide extraction.

St. John's Wort (Hypericum perforatum L.) was extracted with supercritical carbon dioxide using a pilot batch extraction plant. The effects of pressure, temperature, flow rate and extraction time were examined with respect to extraction yield and hyperforin content. Supercritical carbon dioxide showed a high selectivity for phloroglucinols. Extracts were analyzed using an isocratic HPLC method with a mixture of hyperforin/adhyperforin as an external standard. Within the studied range of extraction pressure (90-150 bar) and extraction time (1-5 h), extraction at 90 bar for 3 h and 120 bar for 1 h provided higher hyperforin content (up to 35%) in the resulting extracts. An increase in extraction temperature showed a negative effect, leading to increased degradation of hyperforin into orthoforin. When the total mass of carbon dioxide passing the extraction vessel was kept constant, changes in mass flow rate did not affect the extraction result.

Characterization of supercritical fluid extracts of St. John's wort (Hypericum perforatum L.) by HPLC-MS and GC-MS.

Supercritical fluid extracts (carbon dioxide without modifiers) of St. John's Wort (Hypericum perforatum L., Clusiaceae) were analyzed by GC-MS, HPLC-DAD and HPLC-DAD-MS. Besides the dominating phloroglucinols hyperforin (36.5 +/- 1.1%) and adhyperforin (4.6 +/- 0.1%), the extracts mainly contained alkanes (predominantly nonacosane), fatty acids and wax esters. The apolar components tended to accumulate in a waxy phase resting a top of the hyperforin-enriched phase. No components of higher polarity like naphthodianthrones were found. A set of hyperforin oxidation products was detected and tentatively assigned using HPLC-MS.

Changes in the crystal and electronic structure of LiCoO(2) and LiNiO(2) upon Li intercalation and de-intercalation.

Li(x)CoO(2) and Li(x)NiO(2) (0.5 < x < 1) are used as prototype cathode materials in lithium ion batteries. Both systems show degradation and fatigue when used as cathode material during electrochemical cycling. In order to analyze the change of the structure and the electronic structure of Li(x)CoO(2) and Li(x)NiO(2) as a function of Li content x in detail, we have performed X-ray diffraction studies, photoelectron spectroscopy (PES) investigations and band structure calculations for a series of compounds Li(x)(Co,Ni)O(2) (0 < x < or = 1). The calculated density of states (DOS) are weighted by theoretical photoionization cross sections and compared with the DOS gained from the PES experiments. Consistently, the experimental and calculated DOS show a broadening of the Co/Ni 3d states upon lithium de-intercalation. The change of the shape of the experimental PES curves with decreasing lithium concentration can be interpreted from the calculated partial DOS as an increasing energetic overlap of the Co/Ni 3d and O 2p states and a change in the orbital overlap of Co/Ni and O wave functions.