How do high-voltage cathode and PEO electrolyte get along well?EIS analysis mechanism&potentiometric control strategy

PEO-based all-solid-state electrolytes are extensively utilized and researched owing to their exceptional safety,low-mass-density,and cost-effectiveness.However,the low oxidation potential of PEO makes the interface problem with the high-voltage cathode extremely severe.In this work,the impedance of PEO-based all-solid-state batteries with high-voltage cathode(NCM811)was studied at different potentials.The Nyquist plots displayed a gyrate arc at low-frequencies for NCM811/PEO interface.Based on the kinetic modeling,it was deduced that there is a decomposition reaction of PEO-matrix in addition to de-embedded reaction of NCM811,and the PEO intermediate product(dehydra-PEO)adsorbed on the electrode surface leading to low-frequency inductive arcs.Furthermore,the distribution of relaxation time shows the dehydra-PEO results in the kinetic tardiness of the charge transfer process in the temporal dimension.Hence,an artificial interface layer(CEI_(x))was modified on the surface of NCM811 to regulate the potential of cathode/electrolyte interface to prevent the high-voltage deterioration of PEO.NCM/CEI_(x)/PEO batteries exhibit capacity retentions of 96.0%,84.6%,and 76.8%after undergoing 100 cycles at cut-off voltages of 4.1,4.2,and 4.3 V,respectively.Therefore,here the failure mechanism of high-voltage PEO electrolyte is investigated by EIS and a proposed solving strategy is presented.

Enhanced High-Temperature Cycling Stability of LiMn<SUB>2</SUB>O<SUB>4</SUB>by LiCoO<SUB>2</SUB>Coating as Cathode Material for Lithium Ion Batteries

LiCoO2 surface layer is proposed and prepared through sol-gel method. The physical and electrochemical performances of pristine LiMn2O4 and LiCoO2-coated LiMn2O4 cathode materials were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, electrochemical measurements respectively. Comparing with the pristine LiMn2O4, the LiCoO2- coated LiMn2O4 phase significantly improved cycling stability, especially at 55°C. Additionally, the thermal safety of LiMn2O4 is greatly enhanced after being coated by LiCoO2. ICP-AES measurement, structural analysis, and impedance experiments indicate that the improved electrochemical property of LiCoO2-coated LiMn2O4 should be attributed to the alleviated dissolution loss of manganese, strengthened structural stability.

Theoretic Diffraction Research on the Order-Disorder Effect of Transition Metal in Li(Ni1/3 Co1/3 Mn1/3)O2

After describing research status of super-structure for Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2,diffraction patterns of Li (Ni_(1/3)Co_(1/3)Mn_(1/3)) O_2 in different order parameters have been researched by Powder-cell program,including crystal structure,X-ray and neutron diffraction pattern,anomalous diffraction pattern and comparison of NiCoMn in different positions. The influence of order parameters on intensity of matrix and super-lattice diffraction lines has also been analyzed and the summarization and prospect have been made lastly.

Effect of VFe addition on hydrogen storage behavior of TiMn_(1.5)-based alloys

The hydrogen absorption and desorption behavior of TiMn_(1.25)Cr_(0.25)alloys with VFe substitution for partial Mn was investigated at 273, 293 and 313 K. It is found thatVFe substitution increases their hydrogen storage capacity, decreases the plateau pressure and thehysteresis factor of their pressure-composition-temperature (PCT) curves. After annealing treatmentat 1223 K for 6 h, TiMn_(0.95)Cr_(0.25)(VFe)_(0.3) alloy exhibits a lower hydrogen desorptionplateau pressure (0.27 MPa at 313 K) and a smaller hysteresis factor (0.13 at 313 K); the maximumand effective hydrogen storage capacities (mass fraction) are 2.03% and 1.12% respectively, whichcan satisfy the demand of hydrogen storage tanks for proton exchange membrane fuel cells (PEMFC).

Synergy effect of regulated Li-plating and functional solid electrolyte interphase on graphite anodes

The growth of Li dendrites poses potential safety hazard to lithium-ion batteries(LIBs),and eliminating Li dendrites thoroughly stills face tough difficulties ahead.Thus,regulating Li-plating is a critical optimization-direction to address the issue.Herein,a“graphite-Li hybrid”anode with high reversibility is realized under the constant-capacity lithiation(CCL).Within CCL,the uniform distribution of Li-plating on the graphite surface is successfully achieved.The evolution in different states of solid electrolyte interphase(SEI)is investigated in detail to study the interaction between the potentials and impedance during the process of Liintercalation and Li-deintercalation.Under the potential below 0 V and the state of charge(SOC)of 110%relative to the theoretical capacity,the F-rich SEI with high stability is constructed to hinder the emergency of Li dendrites and maintain the intact structure of graphite anode under long cycling.The cell presents more than 100%Coulombic efficiency(CE)with the 900 cycles,demonstrating the reversible Li-plating and the utilization of defects.And the CCL half-cell provides a good cycling performance and specific capacity of 900 cycles at 0.5 C,it is attributed to the synergy effect of stable inorganic-rich SEI and regulated active Li-plating.