Dual Modification Strategy for Enhanced Cycling and Rate Performance of Ni-Rich Cathode Materials in Lithium-Ion Batteries.

A great challenge in the commercialization process of layered Ni-rich cathode material LiNixCoyMn1-x-yO2 (NCM, x ≥ 80%) for lithium-ion batteries is the surface instability, which is exacerbated by the increase in nickel content. The high surface alkalinity and unavoidable cathode/electrolyte interface side reactions result in significant decrease for the capacity of NCM material. Surface coating and doping are common and effective ways to improve the electrochemical performance of Ni-rich cathode material. In this study, an in situ reaction is induced on the surface of secondary particles of NCM material to construct a stable lithium sulfate coating, while achieving sulfur doping in the near surface region. The synergistic modification of lithium sulfate coating and lattice sulfur doping significantly reduced the content of harmful residual lithium compounds (RLCs) on the surface of NCM material, suppressed the side reactions between the cathode material surface and electrolyte and the degradation of surface structure of the NCM material, effectively improved the rate capability and cycling stability of the NCM material.

The Time-Effect Relationship between Time to Surgery and In-Hospital Postoperative Pneumonia in Older Patients with Hip Fracture.

INTRODUCTION: Pneumonia is a common and devastating complication following hip fracture surgery in older patients. Time to surgery is a potentially modifiable factor associated with improved prognosis, and we aim to quantify the time-effect relationship between time to surgery and in-hospital postoperative pneumonia (IHPOP) and identify the effect of delayed surgery on the risk of IHPOP. METHODS: We analyzed clinical data of older hip fracture patients (≥60 years) undergoing surgical treatments at a tertiary referral trauma center between 2015 and 2020. Restricted cubic spline (RCS) was used to fit the time-effect relationship between time to surgery and IHPOP. Based on the results of RCS, we divided patients into two groups of "early surgery" and "delayed surgery." A 1:1 propensity score matching (PSM) analysis and multivariate conditional logistic regression analysis were performed to minimize the selection bias and determine the association magnitude. Subgroup analysis was conducted to assess potential interaction effects between delayed surgery and common risk factors for IHPOP. RESULTS: 3,118 eligible patients were included. The RCS curve showed an inverse S-shape trend and the relative risk of IHPOP decreased in the range of days 2-3 and increased on day 1 and day 3 or more post-injury, with the lowest point on day 3. PSM yielded 1,870 matched patients and delayed surgery (>3 days) was identified to be independently associated with IHPOP (relative ratio, 1.66; 95% confidence interval, 1.12-2.46; p value, 0.011). We observed positive interaction effects between delayed surgery and age of 80 years or more, female gender, COPD, heart disease, ASA score ≥3, anemia, and hypoproteinemia. CONCLUSION: The relative risk of IHPOP decreased in the range of 2-3 days and increased on day 1 and day 3 or more post-injury. Delayed surgery (>3 days) was identified to be independently associated with a 1.66-fold increased risk of IHPOP.

Risk factors of preoperative deep vein thrombosis in patients with non-traumatic osteonecrosis of the femoral head.

PURPOSE: This study aims to identify independent risk factors for preoperative lower extremity deep venous thrombosis (DVT) in patients with non-traumatic osteonecrosis of the femoral head (NONFH), and to develop a prediction nomogram. METHODS: Retrospective analysis of prospectively collected data on patients presenting with non-traumatic osteonecrosis of the femoral head between October 2014 and April 2019 was conducted. Duplex ultrasonography (DUS) was routinely used to screen for preoperative DVT of bilateral lower extremities. Data on demographics, chronic comorbidities, preoperative characteristics, and laboratory biomarkers were collected. Univariate analyses and multivariate logistic regression analyses were used to identify the independent risk factors associated with DVT which were combined and transformed into a nomogram model. RESULT: Among 2824 eligible patients included, 35 (1.24%) had preoperative DVT, including 15 cases of proximal thrombosis, and 20 cases of distal thrombosis. Six independent risk factors were identified to be associated with DVT, including Sodium ≤ 137 mmol/L (OR = 2.116, 95% confidence interval [CI]: 1.036-4.322; P = 0.040), AGE ≥ 49 years (OR = 7.598, 95%CI: 1.763-32.735; P = 0.008), D-Dimer > 0.18 mg/L (OR = 2.351, 95%CI: 1.070-5.163; P = 0.033), AT III ≤ 91.5% (OR = 2.796, 95%CI: 1.387-5.634; P = 0.006), PLT ≥ 220.4*109 /L (OR = 7.408, 95%CI: 3.434-15.981; P = 0.001) and ALB < 39 g/L (OR = 3.607, 95%CI: 1.084-12.696; P = 0.042). For the nomogram model, AUC was 0.845 (95%CI: 0.785-0.906), and C-index was 0.847 with the corrected value of 0.829 after 1000 bootstrapping validations. Moreover, the calibration curve and DCA exhibited the tool's good prediction consistency and clinical practicability. CONCLUSION: These epidemiologic data and the nomogram may be conducive to the individualized assessment, risk stratification, and development of targeted prevention programs for preoperative DVT in patients with NONFH.

The effect of distal locking mode on postoperative mechanical complications in intertrochanteric fractures: a retrospective cohort study of five hundred and seven patients.

PURPOSE: The optimal choice of distal locking modes remains a subject due to limited available data, and therefore, this study aims to investigate the relationship between distal locking mode and postoperative mechanical complications in an intertrochanteric fracture (ITF) population who underwent closed reduction and intramedullary fixation with a PFNA-II. METHODS: Patients aged 65 years or older who underwent surgery with PFNA-II fixation in a university teaching hospital between January 2020 and December 2021 were potentially eligible. Based on the distal locking mode, patients were classified into static, dynamic, and limited dynamic groups, among which the differences were tested using univariate analysis. Multivariate logistic regression was used to examine whether the distal locking mode was independently associated with the risk of postoperative one year mechanical complications, adjusting for covariates and potential confounders. Subgroup analyses were performed to evaluate the robustness of the findings. RESULT: Among 507 eligible patients, 33 (6.5%) developed postoperative mechanical complications. In the univariate analysis, sex (P = 0.007), fracture type (P = 0.020), LAT Parker ratio (P = 0.023), and lateral femoral (P = 0.003) wall showed that the differences were significant. Compared to the static group, the limited dynamic group and the dynamic group showed higher odds of postoperative mechanical complications (OR = 3.314, 95% CI: 1.215-9.041; and OR = 3.652, 95% CI: 1.451-9.191, respectively). These associations were robust across a series of analyses, including adjusting for confounders and subgroup analyses. CONCLUSION: Using a distal non-static locking mode significantly increases the risk of postoperative mechanical complications, and static locking could be a preferable option when treating an intertrochanteric fracture.

One-year unplanned readmission after total hip arthroplasty in patients with osteonecrosis of the femoral head: rate, causes, and risk factors.

BACKGROUND: The primary objectives of this study were to focus on one - year unplanned readmissions after THA in ONFH patients and to investigate rates, causes, and independent risk factors. METHODS: Between October 2014 and April 2019, eligible patients undergoing THA were enrolled and divided into unplanned readmission within one year and no readmission in this study. All unplanned readmissions within 1 year of discharge were reviewed for causes and the rate of unplanned readmissions was calculated. Demographic information, ONFH characteristics, and treatment-related variables of both groups were compared and analysed. RESULTS: Finally, 41 out of 876 patients experienced unplanned readmission. The readmission rate was 1.83% in 30 days 2.63% in 90 days, and 4.68% in 1 year. Prosthesis dislocation was always the most common cause at all time points studied within a year. The final logistic regression model revealed that higher risks of unplanned readmission were associated with age > 60 years (P = 0.001), urban residence (P = 0.001), ARCO stage IV (P = 0.025), and smoking (P = 0.033). CONCLUSIONS: We recommend the introduction of a strict smoking cessation program prior to surgery and the development of comprehensive management strategies, especially for the elderly and end-stage ONFH patients, and pay more attention to preventing prosthesis dislocation in the early days after surgery.

A Nanostructured Si/SiOC Composite Anode with Volume-Change-Buffering Microstructure for Lithium-Ion Batteries.

Si/SiOC composites are promising high-capacity anode materials for lithium-ion batteries since the SiOC matrix can effectively buffer the volumetric change of Si during cycling. However, a structure of Si nanoparticles (NPs) enwrapped by a continuous SiOC phase typically shows poor cyclic stability and low charge/discharge rate due to structure failure of bulk SiOC shells derived from carbon-rich organosilicon. To address this issue, in this work, an Si/SiOC nanocomposite with volume-change-buffering microstructure, in which Si NPs are uniformly dispersed in a matrix of SiOC nanospheres, has been synthesized. Our results show that the space between Si and SiOC NPs can accommodate the large volume change of Si during cycling and facilitate infiltration of the electrolyte. The nanostructured SiOC skeleton serves as both a mechanically robust buffer to alleviate the intrinsic expansion of Si and an effective electron conductor. The Si/SiOC NP composite displays significantly increased capacity and cyclic stability compared with pure SiOC, and delivers reversible capacities of around 800 mA h-1 g-1 at a current density of 100 mA g-1 (approximately 100 % capacity retention after 100 cycles) and around 600 mA h-1 g-1 at 500 mA g-1 (capacity retention about 80 % after 500 cycles).

ZIF-8 with Ferrocene Encapsulated: A Promising Precursor to Single-Atom Fe Embedded Nitrogen-Doped Carbon as Highly Efficient Catalyst for Oxygen Electroreduction.

The oxygen reduction reaction (ORR) plays an important role in the fields of energy storage and conversion technologies, including metal-air batteries and fuel cells. The development of nonprecious metal electrocatalysts with both high ORR activity and durability to replace the currently used costly Pt-based catalyst is critical and still a major challenge. Herein, a facile and scalable method is reported to prepare ZIF-8 with single ferrocene molecules trapped within its cavities (Fc@ZIF-8), which is utilized as precursor to porous single-atom Fe embedded nitrogen-doped carbon (Fe-N-C) during high temperature pyrolysis. The catalyst shows a half-wave potential (E1/2 ) of 0.904 V, 67 mV higher than commercial Pt/C catalyst (0.837 V), which is among the best compared with reported results for ORR. Significant electrochemical properties are attributed to the special configuration of Fc@ZIF-8 transforming into a highly dispersed iron-nitrogen coordination moieties embedded carbon matrix.

Comparison of outcomes after total hip arthroplasty between patients with osteonecrosis of the femoral head in Association Research Circulation Osseous stage III and stage IV: a five-year follow-up study.

BACKGROUND: No large cohort study has evaluated the surgical outcomes of THA between different stages of ONFH patients. This study aimed to compare the surgical outcomes of ONFH patients who underwent THA in ARCO stage III versus IV, in terms of operative parameters, one-year hip function assessments and postoperative at least five-year complications, to inform optimized management of ONFH. METHOD: From our prospectively collected database, 876 patients undergoing THA between October 2014 and April 2017 were analyzed and divided into ARCO stage III group (n = 383) and ARCO stage IV group(n = 493). Details of demographics, medical record information, adverse events and clinical scores of both groups were collected and compared. Proper univariate analysis was used for the analysis. RESULT: There were no statistically significant differences in baseline characteristics between the two groups. Compared to ARCO stage IV patients, ARCO stage III patients showed a shorter operative time (p < 0.01), less bleeding (p < 0.01), fewer one-year readmissions (p = 0.026) and complications (p = 0.040), and significantly higher HHS (p < 0.01) one year after THA. In addition, ARCO stage IV patients seem more likely to suffer prosthesis dislocation (p = 0.031). CONCLUSION: Although ARCO stage IV patients in the study cohorts appeared to suffer more one-year complications, no significant difference was observed at long-term follow-up. Enhanced clinical guidance on preventing early prosthesis dislocation may help improve the prognosis of final-stage ONFH patients.

Loss of walking independence one year after primary total hip arthroplasty for osteonecrosis of the femoral head: incidence and risk prediction model.

BACKGROUND: Assessment of postoperative ambulation in osteonecrosis of the femoral head (ONFH) patients treated with total hip arthroplasty (THA) is limited. This study aimed to define the incidence and risk factors for losing walking independence (LWI) at one-year postoperatively in patients with ONFH undergoing primary THA, and to establish and validate a predictive nomogram. METHODS: This was a retrospective analysis of prospective collected data from patients admitted to a tertiary referral hospital with ONFH who underwent primary unilateral THA from October 2014 to March 2018. The Functional Independence Measure-Locomotion scale was used to quantify walking independence and was documented at a one-year continuous postoperative follow-up, which classified patients with a final score below 6 as LWI. Multivariate logistic regression identified independent risk factors for LWI, and a predictive nomogram was constructed based on the analysis results. The stability of the model was assessed using patients from April 2018 to April 2019 as an external validation set. RESULTS: 1152 patients were enrolled in the study, of which 810 were used in the training cohort and the other 342 for the validation cohort. The incidence of LWI was 5.93%. Multivariate analysis revealed that age 62 years or older (odd ratio (OR) = 2.37, 95% confidence interval (CI) 1.07-5.24), Charlson's comorbidity index 3 or higher (OR = 3.64, 95% CI 1.09-12.14), Association Research Circulation Osseous stage IV (OR = 2.16, 95% CI 1.03-4.54), reduced femoral offset (OR = 2.41, 95% CI 1.16-5.03), and a higher controlling nutritional status score (OR = 1.14, 95% CI 1.01-1.30) were independent risk factors of LWI. The nomogram had a concordance index of 0.773 and a Brier score of 0.049 in the training set, with corrected values of 0.747 and 0.051 after internal validation. The receiver-operating characteristic curve, calibration curve, Hosmer-Lemeshow test, and decision curve analysis all performed well in both the training and validation cohorts. CONCLUSIONS: This study reported a 5.93% incidence of LWI and established a risk prediction model in patients undergoing THA for ONFH, supporting targeted screening and intervention to assist surgeons in assessing ambulation capacity and managing rehabilitation.

Association of preoperative nutritional status evaluated by the controlling nutritional status score with walking independence at 180 days postoperatively: a prospective cohort study in Chinese older patients with hip fracture.

BACKGROUND: Malnutrition is significantly associated with unfavorable outcomes, but there is little high-level evidence to elucidate the association of malnutrition with losing walking independence (LWI) after hip fracture surgery. This study aimed to assess the association between preoperative nutritional status evaluated by the Controlling Nutritional Status (CONUT) score and walking independence at 180 days postoperatively in Chinese older hip fracture patients. METHODS: This prospective cohort study included 1958 eligible cases from the SSIOS database. The restricted cubic spline was used to assess the dose-effect relationship between the CONUT score and the recovery of walking independence. Propensity score matching was performed to balance potential preoperative confounders, and multivariate logistic regression analysis was applied to assess the association between malnutrition and LWI with perioperative factors for further adjustment. Furthermore, inverse probability treatment weighting and sensitivity analyses were performed to test the robustness of the results and the Fine and Gray hazard model was applied to adjust the competing risk of death. Subgroup analyses were used to determine potential population heterogeneity. RESULTS: The authors found a negative relationship between the preoperative CONUT score and recovery of walking independence at 180 days postoperatively, and that moderate-to-severe malnutrition evaluated by the CONUT score was independently associated with a 1.42-fold (95% CI, 1.12-1.80; P =0.004) increased risk of LWI. The results were overall robust. And in the Fine and Gray hazard model, the result was still statistically significant despite the apparent decrease in the risk estimate from 1.42 to 1.21. Furthermore, significant heterogeneities were observed in the subgroups of age, BMI, American Society of Anesthesiologists score, Charlson's comorbidity index, and surgical delay ( P for interaction < 0.05). CONCLUSION: Preoperative malnutrition is a significant risk factor for LWI after hip fracture surgery, and nutrition screening on admission would generate potential health benefits.

Long-sequence voltage series forecasting for internal short circuit early detection of lithium-ion batteries.

Accurate early detection of internal short circuits (ISCs) is indispensable for safe and reliable application of lithium-ion batteries (LiBs). However, the major challenge is finding a reliable standard to judge whether the battery suffers from ISCs. In this work, a deep learning approach with multi-head attention and a multi-scale hierarchical learning mechanism based on encoder-decoder architecture is developed to accurately forecast voltage and power series. By using the predicted voltage without ISCs as the standard and detecting the consistency of the collected and predicted voltage series, we develop a method to detect ISCs quickly and accurately. In this way, we achieve an average percentage accuracy of 86% on the dataset, including different batteries and the equivalent ISC resistance from 1,000 Ω to 10 Ω, indicating successful application of the ISC detection method.

Preoperative Risk Factor Analysis and Dynamic Online Nomogram Development for Early Infections Following Primary Hip Arthroplasty in Geriatric Patients with Hip Fracture.

Background: Hip arthroplasty is in increasing demand with the aging of the world population, and early infections, such as pneumonia, surgical site infection (SSI), and urinary tract infection (UTI), are uncommon but fatal complications following hip arthroplasty. This study aimed to identify preoperative risk factors independently associated with early infections following primary arthroplasty in geriatric hip fracture patients, and to develop a prediction nomogram. Methods: Univariate and multivariate logistical analyses were performed to identify the independent risk factors for early infections, which were combined and transformed into a nomogram model. The prediction model was evaluated by using the area under the receiver operating characteristic curve (AUC), Hosmer-Lemeshow test, concordance index (C-index), 1000 bootstrap replications, decision curve analysis (DCA), and calibration curve. Results: One thousand eighty-four eligible patients got included and 7 preoperative variables were identified to be independently associated with early infections, including heart disease (odds ratio (OR): 2.17; P: 0.026), cerebrovascular disease (OR: 2.25; P: 0.019), liver disease (OR: 8.99; P: <0.001), time to surgery (OR: 1.10; P: 0.012), hematocrit (44.52; OR: 2.73; P: 0.047), and high-sensitivity C-reactive protein (HCRP; >78.64mg/L; OR: 3.71; P: <0.001). For the nomogram model, AUC was 0.807 (95% confidence interval (CI): 0.742-0.873), the Hosmer-Lemeshow test demonstrated no overfitting (P = 0.522), and C-index was 0.807 (95% CI: 0.742-0.872) with corrected value of 0.784 after 1000 bootstrapping validations. Moreover, the calibration curve and DCA exhibited the tools' good prediction consistency and clinical practicability. Conclusion: Heart disease, cerebrovascular disease, liver disease, time to surgery, hematocrit, PMR, and HCRP were significant preoperative predictors for early infections following primary arthroplasty in elderly hip fracture patients, and the converted nomogram model had strong discriminatory ability and translatability to clinical application.

Red Cell Distribution Width-to-High-Density Lipoprotein Cholesterol Ratio (RHR): A Promising Novel Predictor for Preoperative Deep Vein Thrombosis in Geriatric Patients with Hip Fracture.

Background: Deep vein thrombosis (DVT) is a devastating complication in geriatric patients before hip fracture surgery, and the predictive value of red cell distribution width (RDW) and high-density lipoprotein cholesterol (HDL-C) for DVTs after hip fracture remains to be established. This study aimed to assess the predictive value of RDW, HDL-C, and RDW-to-HDL-C ratio (RHR) in preoperative DVTs screening. Methods: We retrospectively analyzed the data of geriatric patients (≥65 years old) admitted for hip fracture surgery between 2015 and 2020. The receiver operating characteristic (ROC) curve and related parameters were used to evaluate the predictive value of the biomarkers. Patients were divided into two groups according to the cutoff value of RHR, and propensity score matching (PSM) and subgroup analyses were performed to assess the true correlations between RHR and DVT. Results: Among 2566 eligible patients included, we identified RDW with the area under ROC curve (AUC) of 0.532, cut-off value of 15.89, specificity of 88.2%, sensitivity of 18.2%, HDL-C with AUC of 0.574, cut-off value of 1.20, specificity of 55.6%, sensitivity of 59.3%, and RHR with AUC of 0.578, cut-off value of 13.45, specificity of 71.3%, sensitivity of 43.4%. RHR (>13.45) was independently associated with 1.54-fold risk (95% CI: 1.11-2.14, P=0.011) of DVTs among the post-PSM cohort. And compared with the counterparts, the relative risk of RHR associated with DVT was higher in the subgroups of aged 65-79 years (1.61 vs 1.45), non-hypoproteinemia (2.70 vs 1.29), non-diabetic (1.58 vs 1.41), non-hypertension (2.40 vs 1.06), ASA score I-II (2.38 vs 1.04), and femoral neck fracture (1.70 vs 1.50). Conclusion: RDW, HDL-C and RHR were valuable biomarkers in predicting preoperative DVTs in geriatric patients with hip fracture, and RHR would be more efficient in the subgroups of younger age, better medical condition or femoral neck fracture.

Development and validation of a predictive nomogram for preoperative deep vein thrombosis (DVT) in isolated calcaneal fracture.

The fact that most of the patients with preoperative DVTs after calcaneal fractures are asymptomatic brought challenges to the early intervention, and periodic imaging examinations aggravated the financial burden of the patients in preoperative detumescence period. This study aimed to use routine clinical data, obtained from the database of Surgical Site Infection in Orthopaedic Surgery (SSIOS), to construct and validate a nomogram for predicting preoperative DVT risk in patients with isolated calcaneal fracture. The nomogram was established base on 7 predictors independently related to preoperative DVT. The performance of the model was tested by concordance index (C-index), receiver operating characteristic (ROC) curve, calibration curve, and decision curve analysis (DCA), and the results were furtherly verified internally and externally. 952 patients were enrolled in this study, of which 711 were used as the training set. The AUC of the nomogram was 0.870 in the training set and 0.905 in the validation set. After internal verification, the modified C-index was 0.846. Calibration curve and decision curve analysis both performed well in the training set and validation set. In short, we constructed a nomogram for predicting preoperative DVT risk in patients with isolated calcaneal fracture and verified its accuracy and clinical practicability.

Facile carbon fiber-sewed high areal density electrode for lithium sulfur batteries.

A high sulfur loading cathode strengthened by using carbon fiber (CF) is achieved via a typical coating method. Interlaced fibers and abundant hairline cracks ensure an unobstructed electron transfer path and sufficient Li-ion transport channels. The CF-sewed electrode with sulfur loading up to 10 mg cm-2 delivers a high areal capacity of over 7 mA h cm-2 after 96 cycles with a high coulombic efficiency over 99%.

Understanding the Structural Evolution and Lattice Water Movement for Rhombohedral Nickel Hexacyanoferrate upon Sodium Migration.

Prussian blue analogues (PBAs) have been regarded as prospective cathode materials for sodium-ion batteries due to tunable chemical composition and structure. Herein, a high-performance rhombohedral nickel hexacyanoferrate is synthesized via a controllable low-temperature reaction process. It can deliver impressive capacity retention of 87.8% after 10 000 cycles at 10C and high rate discharge capacity of 53 mAh g-1 at 40C. According to the structural evolution and lattice water movement, superior electrochemical performance is ascribed to small lattice alteration and high reversibility of rhombohedral-cubic transition upon Na+ insertion/extraction. The environment information of local- and long-range structure evolution is revealed by ex situ X-ray absorption spectroscopy (XAS) and in situ X-ray diffraction (XRD). Importantly, lattice water movement during cycling by Fourier transform infrared (FTIR) measurements offers an experimental validation about Na+ nonlinear migration path, as well as the accumulative lattice distortion effect from large-size Na(OH2)+ unit. The revealed mechanism points out the modified path for PBAs.

Layer-by-Layer Engineered Silicon-Based Sandwich Nanomat as Flexible Anode for Lithium-Ion Batteries.

Lithium-ion batteries with high electrochemical performance and stable mechanical compliance are pivotal to propel the advanced wearable electronics forward. Herein, a high-conductive flexible electrode densified from multilayer lamellar unit cells with the silicon-based sandwich structure is rationally designed by molecular engineering. Silicon nanoparticles can be uniformly anchored to the surface of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized bacterial cellulose (TOBC) aerogel through hydrogen bonding, which effectively relaxes the drastic volume expansion of the Si-based anode. The graphite microsheets (GMs) attached on silicon nanoparticles allow the porous aerogel network to maintain excellent electrical connection in all directions, and after being switched to compact film, the conductive network enables a robust contact with silicon nanoparticles. As a result, the Si-based nanomat anode exhibits reliable cycling stability (639.4 mA h g-1 after 400 cycles at 1.0 A g-1) and enhanced rate capability (298.6 mA h g-1 at 1.6 A g-1). Notably, instead of conventional polyolefin separators, TOBC-reinforced silica aerogel is fabricated as an advanced separator to integrate the flexible all-in-one full-cell with freestanding GM/TOBC/silicon (GM/TOBC/Si) anode and GM/TOBC/LiFePO4 cathode. Driven by the unique structure and functional component, the flexible all-in-one lithium-ion batteries showcase exceptional deformation tolerance yet impressive charge/discharge behavior.

Accelerated aging and degradation mechanism of LiFePO4/graphite batteries cycled at high discharge rates.

The effects of discharge rates (0.5C, 1.0C, 2.0C, 3.0C, 4.0C and 5.0C) on the aging of LiFePO4/graphite full cells are researched by disassembling the fresh and aged full cells. The capacity degradation mechanism is analyzed via electrochemical performance, surface morphologies and compositions, and the structure of the anode and cathode electrodes. The capacity fade is accelerated with increasing discharge rates. The irreversible loss of active lithium due to the generation of an SEI film is the primary aging factor for the full cells cycled at low discharge rates. However, when the discharge rate is greater than or equal to 4.0C, the performance degradation of the LiFePO4 electrode is distinct due to structure decay, which is caused by quick and repeated intercalation of lithium ions and elevated temperature during discharging. In addition, the SEI film on the anode tends to be unstable after the rapid extraction of lithium ions at high discharge rates, and this enhances the loss of active lithium. Therefore, it is indicated that the degradation mechanism is changed for the full cells aged at 4.0C and 5.0C. Besides, the high discharge rate also increases the internal resistance of the full cell, which is detrimental to high rate discharge performance.

Free-Standing Sandwich-Type Graphene/Nanocellulose/Silicon Laminar Anode for Flexible Rechargeable Lithium Ion Batteries.

Freely deformable and free-standing electrodes together with high capacity are crucial to realizing flexible Li-ion batteries. Herein, a lamellar graphene/nanocellulose/silicon (GN/NC/Si) film assembled by interpenetrated GN nanosheets is synthesized via a facile vacuum-assisted filtration approach accompanied by the covalent cross-linking effect of glutaraldehyde. The hybrid film consists of the highly conductive GN matrix as an effective current collector, hydroxylated silicon nanoparticles (Si NPs) embedded uniformly within GN interlayer and NC as adhesive to cross-link GN and Si NPs. When applied as anode, the GN/NC/Si film exhibits a high reversible capacity of 1251 mA h g-1 at 100 mA g-1 after 100 cycles and superior rate capability. More importantly, in the stress-strain test, this film represents robust mechanical strength, which not only provides good flexibility but also accommodates volume change of Si during cycling. By coupling with lithium cobalt oxide as the cathode, the full cell successfully powers a light-emitting diode, even bended and folded, indicating the deformation-tolerant GN/NC/Si film electrode for flexible Li-ion batteries. Therefore, the design of layered nanocomposites will offer the possibility closer to the application of flexible batteries.