Non-flammable long chain phosphate ester based electrolyte via competitive solventized structures for high-performance lithium metal batteries

Safety remains a persistent challenge for high-energy-density lithium metal batteries(LMBs).The development of safe and non-flammable electrolytes is especially important in harsh conditions such as high temperatures.Herein,a flame-retardant,low-cost and thermally stable long chain phosphate ester based(tributyl phosphate,TBP)electrolyte is reported,which can effectively enhance the cycling stability of highly loaded high-nickel LMBs with high safety through co-solvation strategy.The interfacial compatibility between TBP and electrode is effectively improved using a short-chain ether(glycol dimethyl ether,DME),and a specially competitive solvation structure is further constructed using lithium borate difluorooxalate(LiDFOB)to form the stable and inorganic-rich electrode interphases.Benefiting from the presence of the cathode electrolyte interphase(CEI)and solid electrolyte interphase(SEI)enriched with LiF and Li_(x)PO_(y)F_(z),the electrolyte demonstrates excellent cycling stability assembled using a 50μm lithium foil anode in combination with a high loading NMC811(15.4 mg cm^(-2))cathode,with 88%capacity retention after 120 cycles.Furthermore,the electrolyte exhibits excellent high-temperature characteristics when used in a 1-Ah pouch cell(N/P=0.26),and higher thermal runaway temperature(238℃)in the ARC(accelerating rate calorimeter)demonstrating high safety.This novel electrolyte adopts long-chain phosphate as the main solvent for the first time,and would provide a new idea for the development of extremely high safety and high-temperature electrolytes.

Effects of conductive agent type on lithium extraction from salt lake brine with LiFePO_(4) electrodes

Electrochemical lithium extraction from salt lakes is an effective strategy for obtaining lithium at a low cost.Nevertheless,the elevated Mg:Li ratio and the presence of numerous coexisting ions in salt lake brines give rise to challenges,such as prolonged lithium extraction periods,diminished lithium extraction efficiency,and considerable environmental pollution.In this work,Li FePO4(LFP)served as the electrode material for electrochemical lithium extraction.The conductive network in the LFP electrode was optimized by adjusting the type of conductive agent.This approach resulted in high lithium extraction efficiency and extended cycle life.When the single conductive agent of acetylene black(AB)or multiwalled carbon nanotubes(MWCNTs)was replaced with the mixed conductive agent of AB/MWCNTs,the average diffusion coefficient of Li+in the electrode increased from 2.35×10^(-9)or 1.77×10^(-9)to 4.21×10^(-9)cm^(2)·s^(-1).At the current density of 20 mA·g^(-1),the average lithium extraction capacity per gram of LFP electrode increased from 30.36 mg with the single conductive agent(AB)to 35.62 mg with the mixed conductive agent(AB/MWCNTs).When the mixed conductive agent was used,the capacity retention of the electrode after 30 cycles reached 82.9%,which was considerably higher than the capacity retention of 65.8%obtained when the single AB was utilized.Meanwhile,the electrode with mixed conductive agent of AB/MWCNTs provided good cycling performance.When the conductive agent content decreased or the loading capacity increased,the electrode containing the mixed conductive agent continued to show excellent electrochemical performance.Furthermore,a self-designed,highly efficient,continuous lithium extraction device was constructed.The electrode utilizing the AB/MWCNT mixed conductive agent maintained excellent adsorption capacity and cycling performance in this device.This work provides a new perspective for the electrochemical extraction of lithium using LFP electrodes.

Unraveling high efficiency multi-step sodium storage and bidirectional redox kinetics synergy mechanism of cobalt-doping vanadium disulfide anode

Sodium-based storage devices based on conversion-type metal sulfide anodes have attracted great atten-tion due to their multivalent ion redox reaction ability.However,they also suffer from sodium polysul-fides(NaPSs)shuttling problems during the sluggish Na^(+) redox process,leading to"voltage failure"and rapid capacity decay.Herein,a metal cobalt-doping vanadium disulfide(Co-VS_(2))is proposed to simulta-neously accelerate the electrochemical reaction of VS_(2) and enhance the bidirectional redox of soluble NaPSs.It is found that the strong adsorption of NaPSs by V-Co alloy nanoparticles formed in situ during the conversion reaction of Co-VS_(2) can effectively inhibit the dissolution and shuttle of NaPSs,and ther-modynamically reduce the formation energy barrier of the reaction path to effectively drive the complete conversion reaction,while the metal transition of Co elements enhances reconversion kinetics to achieve high reversibility.Moreover,Co-VS_(2) also produce abundant sulfur vacancies and unsaturated sulfur edge defects,significantly improve ionic/electron diffusion kinetics.Therefore,the Co-VS_(2) anode exhibits ultrahigh rate capability(562 mA h g^(-1) at 5 A g^(-1)),high initial coulombic efficiency(~90%)and 12,000 ultralong cycle life with capacity retention of 90%in sodium-ion batteries(SIBs),as well as impressive energy/power density(118 Wh kg^(-1)/31,250 W kg^(-1))and over 10.000 stable cycles in sodium-ion hybrid capacitors(SIHCs).Moreover,the pouch cell-type SIHC displays a high-energy density of 102 Wh kg^(-1) and exceed 600 stable cycles.This work deepens the understanding of the electrochemical reaction mechanism of conversion-type metal sulfide anodes and provides a valuable solution to the shuttlingofNaPSs inSIBsandSIHCs.

Adaptive and regulatory mechanisms in aged rats with postoperative cognitive dysfunction

Inflammation may play a role in postoperative cognitive dysfunction. 5＇ Adenosine monophos- phate-activated protein kinase, nuclear factor-kappa B, interleukin-1β, and tumor necrosis factor-a are involved in inflammation. Therefore, these inflammatory mediators may be involved in postoperative cognitive dysfunction. Western immunoblot analysis revealed 5＇ adenosine mo- nophosphate-activated protein kinase and nuclear factor-kappa B in the hippocampus of aged rats were increased 1-7 days after splenectomy. Moreover, interleukin-1β and tumor necrosis fac- tor-α were upregulated and gradually decreased. Therefore, these inflammatory mediators may participate in the splenectomy model of postoperative cognitive dysfunction in aged rats.

Acupuncture preconditioning protects hippocampal neurons from transient ischemia/reperfusion injury

The present study established a model of brain ischemia in aged rats using four-vessel occlusion.We observed hippocampal CA1 neuronal apoptosis and apoptosis-mediated protease caspase-3 expression following preconditioning of electroacupuncture at Baihui（GV 20）.Our results showed that the number of hippocampal CA1 normal neurons was decreased,and degenerated neurons were increased 12 hours to 3 days following cerebral ischemia/reperfusion.The number of hippocampal CA1 apoptotic neurons and caspase-3-positive neurons in rats with cerebral ischemia/reperfusion injury was significantly decreased following acupuncture preconditioning.Acupuncture preconditioning protects aged rats against ischemia/reperfusion injury by regulating caspase-3 protein expression.

Edema and neuronal apoptosis in the hippocampus and cortex of elderly rats following transient cerebral ischemia/reperfusion injury

BACKGROUND： Previous studies of cerebral ischemia have used young animals, with an ischemic time greater than 5 minutes （safe time limit）. Despite an increased understanding of neuronal apoptosis, it remains uncertain whether brief cerebral ischemic events of 5 minutes or less damage brain tissue in elderly rodents. OBJECTIVE： To investigate the effects of transient cerebral ischemia （5 minutes）/reperfusion injury on brain cortical and hippocampal edema, aquaporin-4 （AQP-4） expression, and neuronal apoptosis in aged rats, and to compare ischemic sensitivity between cortex and hippocampus. DESIGN, TIME AND SETTING： A randomized, controlled, animal experiment was performed at the Institute of Cerebrovascular Disease, Qingdao University Medical School from April 2008 to March 2009. MATERIALS： Rabbit anti-AQP-4 polyclonal antibody, TUNEL kit, and SABC immunohistochemistry kit were purchased from Wuhan Boster Bioengineering, China. METHODS： A total of 160 healthy, male, aged 19-21 months, Wistar rats were randomly assigned to 4 groups： sham-surgery, and ischemia 1-, 3-, and 5-minute groups, with 40 rats in each group. The global cerebral ischemia model was established using the Pusinelli four-vessel occlusion, and the three cerebral ischemia groups were subdivided into reperfusion 12-hour, 1-, 2-, 3-, and 7-day subgroups, with 8 rats in each subgroup. The sham-surgery group was subjected to exposure of the first cervical bilateral alar foramina and bilateral common carotid arteries. MAIN OUTCOME MEASURES： The dry-wet weight assay was used to measure brain water content and histopathology of the cortex and hippocampus was observed following hematoxylin-eosin staining. In addition, cortical and hippocampal AQP-4 expression was detected by streptavidin-biotin complex immunohistochemistry, and neuronal apoptosis was detected by the TUNEL method. RESULTS： There was no significant difference in brain water content or AQP-4 expression in the cortex and hippocampus between ischemia 1- and 3-minute groups and the sham-surgery group or brain water content or AQP-4 expression in the cortex between ischemia 5-minute group and sham-surgery group （P 〉 0.05）. However, brain water content and AQP-4 expression in the hippocampus after 5 minutes of cerebral ischemia were significantly increased compared with the sham-surgery group （P 〈 0.05 or P 〈 0.01）. Several TUNEL-positive cells were observed in the cortex and hippocampus of the sham-surgery group and ischemia 1-minute group, as well as in the cortex of the ischemia 3-minute group. In addition, the number of apoptotic neurons in the hippocampus of ischemia 3-minute group and in the cortex and hippocampus of ischemia 5-minute group was significantly increased （P 〈 0.05 or P 〈 0.01 ）. Neuronal apoptosis was increased after 12 hours of ischemia/reperfusion, and it reached a peak by 2 days （P 〈 0.01）. CONCLUSION： Transient cerebral ischemia （5 minutes） resulted in increased hippocampal edema, AQP-4 expression, and neuronal apoptosis. Moreover, cerebral ischemia had a greater effect on neuronal apoptosis than brain edema or AQP-4 expression, and the hippocampus was more sensitive than the cortex.

Kinetic and thermodynamic synergy of organic small molecular additives enables constructed stable zinc anode

An organic small molecule additive zinc formate is introduced to construct stable Zn metal interphase by electrochemical kinetic control and thermodynamic adjustment.It partially forms a water-formate concomitant dipole layer at the internal Helmholtz electrical double layers(HEDLs) under the preferential adsorption function of formate on Zn surface,reducing the occurrence of side reactions at phase interface.Meanwhile,free formate in HEDLs regulates the Zn^(2+) solvation sheath structure to accelerate the desolvation,transference,and deposition kinetics of Zn^(2+).Besides,the hydrolysis reaction of zinc formate increases the hydrogen evolution overpotential,inhibiting the thermodynamic tendency of hydrogen evolution.Consequently,it presents stable cycle for more than 2400 h at 5 mA cm^(-2),as well as an average Coulombic efficiency of 99.8% at 1 A g^(-1) after 800 cycles in the Zn‖VO_(2) full cell.The interphase engineering strategy zinc anode by organic small molecular brings new possibility towards high-performance aqueous zinc-ion batteries.

Concentrated ternary ether electrolyte allows for stable cycling of a lithium metal battery with commercial mass loading high-nickel NMC and thin anodes

A new concentrated ternary salt ether-based electrolyte enables stable cycling of lithium metal battery(LMB)cells with high-mass-loading(13.8 mg cm^(−2),2.5 mAh cm^(−2))NMC622(LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2))cathodes and 50μm Li anodes.Termed“CETHER-3,”this electrolyte is based on LiTFSI,LiDFOB,and LiBF4 with 5 vol%fluorinated ethylene carbonate in 1,2-dimethoxyethane.Commer-cial carbonate and state-of-the-art binary salt ether electrolytes were also tested as baselines.With CETHER-3,the electrochemical performance of the full-cell battery is among the most favorably reported in terms of high-voltage cycling stability.For example,LiNi_(x)Mn_(y)Co_(1-x-y)O_(2)(NMC)-Li metal cells retain 80%capacity at 430 cycles with a 4.4 V cut-off and 83%capacity at 100 cycles with a 4.5 V cut-off(charge at C/5,discharge at C/2).According to simulation by density functional theory and molecular dynamics,this favorable performance is an outcome of enhanced coordination between Li^(+)and the solvent/salt molecules.Combining advanced microscopy(high-resolution transmission electron microscopy,scanning electron microscopy)and surface science(X-ray photoelectron spectroscopy,time-of-fight secondary ion mass spectroscopy,Fourier-transform infrared spectroscopy,Raman spectroscopy),it is demonstrated that a thinner and more stable cathode electrolyte interphase(CEI)and solid electrolyte interphase(SEI)are formed.The CEI is rich in lithium sulfide(Li_(2)SO_(3)),while the SEI is rich in Li_(3)N and LiF.During cycling,the CEI/SEI suppresses both the deleterious transformation of the cathode R-3m layered near-surface structure into disordered rock salt and the growth of lithium metal dendrites.

Strain-sensitive ferromagnetic two-dimensional Cr_(2)Te_(3)

Searching for room temperature magnetic two-dimensional(2D)materials is a charming goal,but the number of satisfied materials is tiny.Strain can introduce considerable deformation into the lattice structure of 2D materials,and thus significantly modulate their intrinsic properties.In this work,we demonstrated a remarkable strain-modulated magnetic properties in the chemical vapor deposited Cr_(2)Te_(3) nanoflakes grown on mica substrate.We found the Curie temperature of Cr_(2)Te_(3) nanoflakes can be positively and negatively modulated under tensile and compressive strain respectively,with a maximum varied value of -40 and-90 K,dependent on the thickness of samples.Besides,the coercive field of Cr_(2)Te_(3) nanoflakes also showed a significant decrease under the applied strain,suggesting the decrease of exchange interaction or the change of the magnetization direction.This work suggests a promise to employ interfacial strain to accelerate the practical application of room temperature 2D magnetics.