3D Carbon Frameworks for Ultrafast Charge/Discharge Rate Supercapacitors with High Energy‑Power Density

Carbon-based electric double layer capacitors(EDLCs)hold tremendous potentials due to their high-power performance and excellent cycle stability.However,the practical use of EDLCs is limited by the low energy density in aqueous electrolyte and sluggish diffusion kinetics in organic or/and ionic liquids electrolyte.Herein,3D carbon frameworks(3DCFs)constructed by interconnected nanocages(10-20 nm)with an ultrathin wall of ca.2 nm have been fabricated,which possess high specific surface area,hierarchical porosity and good conductive network.After deoxidization,the deoxidized 3DCF(3DCFDO)exhibits a record low IR drop of 0.064 V at 100 A g^−1 and ultrafast charge/discharge rate up to 10 V s^−1.The related device can be charged up to 77.4%of its maximum capacitance in 0.65 s at 100 A g^−1 in 6 M KOH.It has been found that the 3DCF-DO has a great affinity to EMIMBF4,resulting in a high specific capacitance of 174 F g^−1 at 1 A g^−1,and a high energy density of 34 Wh kg^−1 at an ultrahigh power density of 150 kW kg^−1 at 4 V after a fast charge in 1.11 s.This work provides a facile fabrication of novel 3D carbon frameworks for supercapacitors with ultrafast charge/discharge rate and high energy-power density.

Impact of Updraft on Neutralized Charge Rate by Lightning in Thunderstorms:A Simulation Case Study

The rate of neutralized charge by lightning（RNCL） is an important parameter indicating the intensity of lightning activity.The total charging rate（CR）,the CR of one kind of polarity（e.g.,negative） charge（CROP）,and the outflow rate of charge on precipitation（ORCP） are proposed as key factors impacting RNCL,based on the principle of conservation of one kind of polarity charge in a thunderstorm.In this paper,the impacts of updraft on CR and CROP are analyzed by using a 3D cloud resolution model for a strong storm that occurred in Beijing on 6 September 2008.The results show that updraft both promotes and inhibits RNCL at the same time.（1） Updraft always has a positive influence on CR.The correlation coefficient between the updraft volume and CR can reach 0.96.Strengthening of the updraft facilitates strengthening of RNCL through this positive influence.（2） Strengthening of the updraft also promotes reinforcement of CROP.The correlation coefficient between the updraft volume and CROP is high（about0.9）,but this promotion restrains the strengthening of RNCL because the strengthening of CROP will,most of the time,inhibit the increasing of RNCL.（3） Additionally,increasing of ORCP depresses the strengthening of RNCL.In terms of magnitude,the peak of ORCP is equal to the peak of CR.Because precipitation mainly appears after the lightning activity finishes,the depression effect of ORCP on RNCL can be ignored during the active lightning period.

Adaptive Kalman filter based state of charge estimation algorithm for lithium-ion battery

In order to improve the accuracy of the battery state of charge（SOC） estimation, in this paper we take a lithiumion battery as an example to study the adaptive Kalman filter based SOC estimation algorithm. Firstly, the second-order battery system model is introduced. Meanwhile, the temperature and charge rate are introduced into the model. Then, the temperature and the charge rate are adopted to estimate the battery SOC, with the help of the parameters of an adaptive Kalman filter based estimation algorithm model. Afterwards, it is verified by the numerical simulation that in the ideal case, the accuracy of SOC estimation can be enhanced by adding two elements, namely, the temperature and charge rate.Finally, the actual road conditions are simulated with ADVISOR, and the simulation results show that the proposed method improves the accuracy of battery SOC estimation under actual road conditions. Thus, its application scope in engineering is greatly expanded.

Strategies for Rational Design of High-Power Lithium-ion Batteries

Lithium-ion batteries(LIBs)have shown considerable promise as an energy storage system due to their high conversion efficiency,size options(from coin cell to grid storage),and free of gaseous exhaust.For LIBs,power density and energy density are two of the most important parameters for their practical use,and the power density is the key factor for applications such as fast-charging electric vehicles,high-power portable tools,and power grid stabilization.A high rate of performance is also required for devices that store electrical energy from seasonal or irregular energy sources,such as wind energy and wave energy.Significant efforts have been made over the last several years to improve the power density of LIBs through anodes,cathodes,and electrolytes,and much progress has been made.To provide a comprehensive picture of these recent achievements,this review discusses the progress made in high-power LIBs from 2013 to the present,including general and fundamental principles of high-power LIBs,challenges facing LIB development today,and an outlook for future LIB development.

Charging for the waste dumping of open-pit metal mines

Based on the externality theory and the environmental value theory, the hypothesis of charging for waste dumping of open-pit metal mines was put forth. The charging methods were designed according to the characteristics of waste dumping of openpit metal mines, including charging based on the dumping amount of the total waste, multi-charging factors, exceeding standard punishment charging, and so on. The main charging parameter is based on the dumping area rather than the total amount of waste dumping. The charging model of waste dumping of open-pit mines was formulated, and the charging rate was divided into two parts, i.e., the standard charging rate and the differential charging rate. The standard charging rate was derived using the equilibrium dynamic model, whereas the differential one was obtained by establishing the fuzzy synthesized evaluation model.

Sensitivity analysis of borehole thermal energy storage: examining key factors for system optimization

Borehole thermal energy storage(BTES)systems have garnered significant attention owing to their efficacy in storing thermal energy for heating and cooling applications.Accurate modeling is paramount for ensuring the precise design and operation of BTES systems.This study conducts a sensitivity analysis of BTES modeling by employing a comparative investigation of five distinct parameters on a wedge-shaped model,with implications extendable to a cylindrical configuration.The parameters examined included two design factors(well spacing and grout thermal conductivity),two operational variables(charging and discharging rates),and one geological attribute(soil thermal conductivity).Finite element simulations were carried out for the sensitivity analysis to evaluate the round-trip efficiency,both on a per-cycle basis and cumulatively over three years of operation,serving as performance metrics.The results showed varying degrees of sensitivity across different models to changes in these parameters.In particular,the round-trip efficiency exhibited a greater sensitivity to changes in spacing and volumetric flow rate.Furthermore,this study underscores the importance of considering the impact of the soil and grout-material thermal conductivities on the BTES-system performance over time.An optimized scenario is modelled and compared with the base case,over a comparative assessment based on a 10-year simulation.The analysis revealed that,at the end of the 10-year period,the optimized BTES model achieved a cycle efficiency of 83.4%.This sensitivity analysis provides valuable insights into the merits and constraints of diverse BTES modeling methodologies,aiding in the selection of appropriate modeling tools for BTES system design and operation.

The scaling of charging rate and cycle number of commercial batteries

Health management for commercial batteries is crowded with a variety of great issues,among which reliable cycle-life prediction tops.By identifying the cycle life of commercial batteries with different charging histories in fast-charging mode,we reveal that the average charging rate c and the resulted cycle life N of batteries obey c=c_(0)N^(b),where c_(0) is a limiting charging rate and b is an electrode-dependent constant.This c-N law,resembling the classic stress versus cycle number relationship(the S-N curve or Wohler curve)of solids subject to cyclic loading,could be applicable to most batteries.Such a scaling law,in combination with a physics-augmented machine-learning algorithm,could foster the predictability of battery life with high fidelity.The scaling of charging rate and cycle number may pave the way for cycle-life prediction and the directions of optimization of advanced batteries.

Crystal packing and charge transport in single crystals of chrysene derivatives: Impact of halogenation

Crystal packing has strong influence on the charge mobility for organic semiconductors, so the elucidation of the structure-property relationship is important for the design of high-performance organic semiconductors. Halogen substitution has been shown to be a promising strategy to alter the crystal structure without significantly changing the molecular size in previous reports. This paper studies the influence of halogenation on charge transport in single crystals of chrysene derivatives from a theoretical standpoint. The structure-property relationship is first rationalized by investigating the reorganization energy and electronic coupling from the density functional theory calculations. Based on the Marcus charge transfer theory, the mobilities in the molecular monolayer are then calculated with the random walk simulation technique from which the angular resolution anisotropic mobilities are obtained on the fly. It is shown that the mobilities become much larger for holes than those for electrons in the molecular monolayer when the halogenation occurs. Furthermore, the intra-layer charge transport is little influenced by the inter-layer pathways in the single crystals of the halogenated chrysene derivatives, while the opposite case is shown for the crystal of the nonhalogenated chrysene derivative. The reason for the variations of charge transport is discussed theoretically.

Study of Heat Transfer in Ice-storage Tank

The heat transfer process of ice formation on the outside of coil pipe in the ice storage tank with glycol solution as the second refrigerant was studied in this paper analytically and experimentally. A model was developed for the charging process and the conduction shape factor was applied. Also, the result obtained from the model was compared with the experimental data, both data were in agreement. The simple model is useful for the operation, design and optimization of the ice storage tank.

Novel Conformal Structure-Preserving Algorithms for Coupled Damped Nonlinear Schr odinger System

This paper introduces two novel conformal structure-preserving algorithms for solving the coupled damped nonlinear Schr¨odinger(CDNLS)system,which are based on the conformal multi-symplectic Hamiltonian formulation and its conformal conservation laws.The proposed algorithms can preserve corresponding conformal multi-symplectic conservation lawand conformalmomentum conservation lawin any local time-space region,respectively.Moreover,it is further shown that the algorithms admit the conformal charge conservation law,and exactly preserve the dissipation rate of charge under appropriate boundary conditions.Numerical experiments are presented to demonstrate the conformal properties and effectiveness of the proposed algorithms during long-time numerical simulations and validate the analysis.