A Review on Nanocomposite Materials for Rechargeable Li-ion Batteries

Molecular dynamics simulations are carried out to investigate the structure and capacitance of the electrical double layers (EDLs) at the interface of vertically oriented graphene and ionic liquids [EMIM] + /[BF 4 ] − . The distribution and migration of the ions in the EDL on the rough and non-rough electrode surfaces with different charge densities are compared and analyzed, and the effect of the electrode surface morphology on the capacitance of the EDL is clarified. The results suggest that alternate distributions of anions and cations in several consecutive layers are formed in the EDL on the electrode surface. When the electrode is charged, the layers of [BF 4 ] − anions experience more significant migration than those of [EMIM] + cations. These ion layers can be extended deeper into the bulk electrolyte solution by the stronger interaction of the rough electrode, compared to those on the non-rough electrode surface. The potential energy valley of ions on the neutral electrode surface establishes a potential energy difference to compensate the energy cost of the ion accumulation, and is capable of producing a potential drop across the EDL on the uncharged electrode surface. Due to the greater effective contact area between the ions and electrode, the rough electrode possesses a larger capacitance than the non-rough one. In addition, it is harder for the larger-sized [EMIM] + cations to accumulate in the narrow grooves on the rough electrode, when compared with the smaller [BF 4 ] − . Consequently, the double-hump-shaped C-V curve (which demonstrates the relationship between differential capacitance and potential drop across the EDL) for the rough electrode is asymmetric, where the capacitance increases more significantly when the electrode is positively charged.

Section: Introductionmentioning

confidence: 99%

Structure and Capacitance of Electrical Double Layers at the Graphene–Ionic Liquid Interface

Dai

et al. 2017

“…Li-ion batteries are gradually receiving attention from the industry because of its small size, high energy density, long life cycle, no memory effect and no pollution, low self-discharging, and a high comprehensive efficiency. Additionally, the cost of Li-ion batteries continues to drop due to technology development and material innovation [16]. Figure 1 shows the characteristics of different types of batteries, the Li-ion batteries, therefore, have been selected in this study from the perspective of economy, efficiency, and technology maturity.…”

Section: Ess Type Selectionmentioning

confidence: 99%

Considering the Life-Cycle Cost of Distributed Energy-Storage Planning in Distribution Grids

Zhu

et al. 2018

In the face of the radical revolution of energy systems, there is a gradually held consensus regarding the adoption of distributed renewable energy resources, represented by Photovoltaic (PV) and wind generation. Consequently, the distributed Energy Storage Systems (ESSs) have become increasingly important in the distribution networks, as they provide the arbitrage and ancillary services. Determining the optimal installation site and the capacity of the distributed ESSs will defer the network reinforcements, reduce the investment of ESSs, and improve the reliability, flexibility, and efficiency of distribution grids. In order to investigate the optimal ESS configuration and to solve voltage fluctuations brought by the increased penetration of PV, in this study a two-stage heuristic planning strategy has been proposed, which considers both the economic operation and the lifetime of the distributed ESSs, to determine the optimal sitting and sizing of the ESSs, in the distribution grids. The first stage decides the optimal installation site and the economic scheduling of the ESSs, aiming to minimize the fabricating cost of the distributed ESSs and the network losses. Based on the output of the first stage, the second stage planning is further delivered to achieve the optimal ESS capacity, considering the Life-Cycle Cost (LCC) minimization. Finally, the feasibility and effectiveness of the proposed method is verified on a typical distribution case study network.

“…Given the rapid development of portable electronics, electric vehicles, and smart grids, advanced electrochemical energy storage systems have been investigated extensively [1][2][3][4][5][6][7][8][9][10][11]. Lithium-sulfur (Li-S) batteries are expected to perform a significant role in the field of energy storage owing to its ultrahigh theoretical energy density of 2500 Wh kg −1 , environmental friendliness, and low cost [12][13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Macroporous Activated Carbon Derived from Rapeseed Shell for Lithium–Sulfur Batteries

Zheng

Zhang

et al. 2017

Lithium-sulfur batteries have drawn considerable attention because of their extremely high energy density. Activated carbon (AC) is an ideal matrix for sulfur because of its high specific surface area, large pore volume, small-size nanopores, and simple preparation. In this work, through KOH activation, AC materials with different porous structure parameters were prepared using waste rapeseed shells as precursors. Effects of KOH amount, activated temperature, and activated time on pore structure parameters of ACs were studied. AC sample with optimal pore structure parameters was investigated as sulfur host materials. Applied in lithium-sulfur batteries, the AC/S composite (60 wt % sulfur) exhibited a high specific capacity of 1065 mAh g −1 at 200 mA g −1 and a good capacity retention of 49% after 1000 cycles at 1600 mA g −1 . The key factor for good cycling stability involves the restraining effect of small-sized nanopores of the AC framework on the diffusion of polysulfides to bulk electrolyte and the loss of the active material sulfur. Results demonstrated that AC materials derived from rapeseed shells are promising materials for sulfur loading.