Self-discharge of Rechargeable Hybrid Aqueous Battery

This thesis studies the self-discharge performance of recently developed rechargeable hybrid aqueous batteries, using LiMn2O4 as a cathode and Zinc as an anode. It is shown through a variety of electrochemical and ex-situ analytical techniques that many parts of the composite cathode play important roles on the self-discharge of the battery. It was determined that the current collector must be passive towards corrosion, and polyethylene was identified as the best option for this application. The effect of amount and type of conductive agent was also investigated, with low surface area carbonaceous material giving best performances. It was also shown that the state of charge has strong effects on the extension of self-discharge. More importantly, this study shows that the self-discharge mechanism in the ReHAB system involves the cathode active material and contains a reversible and an irreversible part. The reversible portion is predominant and is due to lithium re-intercalation into the LiMn2O4 spinel framework, and results from Zn dissolution into the electrolyte, which drives the Li+ ions out of the solution. The irreversible portion of the self-discharge occurs as a result of the decomposition of the LiMn2O4 material in the presence of the acidic electrolyte, and is much less extensive than the reversible process

Development of innovative lithium metal-free lithium-ion sulfur battery for renewable energy, electric transport and electronics

Lithium/sulfur (Li/S) battery is a promising candidate for the next generation rechargeable battery since the negative electrode, lithium, and the cathode, sulfur, have the highest theoretical capacities of 3862 and of 1672 mAh/g, respectively, among any other active materials, e.g., graphite (372 mAh/g) or LiCoO2 (274 mAh/g, only about 50% is practically available). However, there are several challenging issues in order to realize the use of this type of next generation battery. First, the lithium metal anode has an intrinsic safety issue, dendrite growth that can result in internal short circuit failure. Second, the sulfur cathode is a very insulating material; therefore, sulfur-based cathodes need a large amount of conducting additives, resulting in the decrease in the practically available gravimetric capacity per the unit mass of cathode composite. Third, lithium polysulfides, reduced (discharged) forms of sulfur, dissolve into an electrolyte solution, resulting in capacity fading. For realistic battery applications, these issues from both the anode and the cathode need to be solved or mitigated. To this end, we integrate three practically possible solutions: (1) manufacture-friendly pre-lithiation of anode or cathode materials, (2) practically optimal choice of conducting agent and of the method for S/conductive-agent integration, and (3) stabilization of discharged forms of the cathode

Development of innovative lithium metal-free lithium-ion sulfur battery for renewable energy, electric transport and electronics

Lithium/sulfur (Li/S) battery is a promising candidate for the next generation rechargeable battery since the negative electrode, lithium, and the cathode, sulfur, have the highest theoretical capacities of 3862 and of 1672 mAh/g, respectively, among any other active materials, e.g., graphite (372 mAh/g) or LiCoO2 (274 mAh/g, only about 50% is practically available). However, there are several challenging issues in order to realize the use of this type of next generation battery. First, the lithium metal anode has an intrinsic safety issue, dendrite growth that can result in internal short circuit failure. Second, the sulfur cathode is a very insulating material; therefore, sulfur-based cathodes need a large amount of conducting additives, resulting in the decrease in the practically available gravimetric capacity per the unit mass of cathode composite. Third, lithium polysulfides, reduced (discharged) forms of sulfur, dissolve into an electrolyte solution, resulting in capacity fading. For realistic battery applications, these issues from both the anode and the cathode need to be solved or mitigated. To this end, we integrate three practically possible solutions: (1) manufacture-friendly pre-lithiation of anode or cathode materials, (2) practically optimal choice of conducting agent and of the method for S/conductive-agent integration, and (3) stabilization of discharged forms of the cathode

High mass-loading of sulfur-based cathode composites and polysulfides stabilization for rechargeable lithium/sulfur batteries

Although sulfur has a high theoretical gravimetric capacity, 1672 mAh/g, its insulating nature requires a large amount of conducting additives: this tends to result in a low massloading of active material (sulfur), and thereby, a lower capacity than expected. Therefore, an optimal choice of conducting agents and of the method for sulfur/conductingagent integration is critically important. In this paper, we report that the areal capacity of 4.9 mAh/cm2 was achieved at sulfur mass loading of 4.1 mg/cm2 by casting sulfur/ polyacrylonitrile/ketjenblack (S/PAN/KB) cathode composite into carbon fiber paper. This is the highest value among published/reported ones even though it does not contain expensive nanosized carbon materials such as carbon nanotubes, graphene, or graphene derivatives, and competitive enough with the conventional LiCoO2-based cathodes (e.g., LiCoO2, <20 mg/cm2 corresponding to <2.8 mAh/cm2). Furthermore, the combination of sulfur/PAN-based composite and PAN-based carbon fiber paper enabled the sulfurbased composite to be used even in carbonate-based electrolyte solution that many lithium/sulfur battery researchers avoid the use of it because of severer irreversible active material loss than in electrolyte solutions without carbonate-based solutions, and even at the highest mass-loading ever reported (the more sulfur is loaded, the more decomposed sulfides deposit at an anode surface)

Development of novel sulfur/carbon cathode composites using spray pyrolysis and study of their electrochemical performance in lithium-sulfur batteries

The eminent global energy crisis and growing ecological concerns in the past two decades have led to intensive development in the fields of green transportation such as electric and hybrid electric vehicles (HEV), as well as clean energy sources such as wind and solar power. These technologies demand low cost, safe, and environmentally friendly energy storage systems. Therefore, development of novel economically feasible and ecologically friendly high performance batteries is crucial. Lithium/ sulfur (Li/S) batteries have the highest energy density (2600 Wh/kg) and theoretical capacity (1672 mAh/g) among all known systems [1,2]

Zinc ion interactions in a two-dimensional covalent organic framework based aqueous zinc ion battery

The two-dimensional structural features of covalent organic frameworks (COFs) can promote the electrochemical storage of cations like H+, Li+, and Na+ through both faradaic and non-faradaic processes. However, the electrochemical storage of cations like Zn2+ ion is still unexplored although it bears a promising divalent charge. Herein, for the first time, we have utilized hydroquinone linked β-ketoenamine COF acting as a Zn2+ anchor in an aqueous rechargeable zinc ion battery. The charge-storage mechanism comprises of an efficient reversible interlayer interaction of Zn2+ ions with the functional moieties in the adjacent layers of COF (−182.0 kcal mol−1). Notably, due to the well-defined nanopores and structural organization, a constructed full cell, displays a discharge capacity as high as 276 mA h g−1 at a current rate of 125 mA g−1

ENHANCEMENT OF THE ELECTROCHEMICAL PERFORMANCE OF THE CATHODE MATERIAL NANI0.5MN0.5-XZRXO2

The development of the cathode material for beyond lithium-ion batteries plays a critical role in advancing technical progress and ensuring the long-term viability of our society. However, because of the poor performance of SIBs, many novel technical solutions are delayed or hindere

Effect of carbon-sulphur bond in a sulphur/dehydrogenated polyacrylonitrile/reduced graphene oxide composite cathode for lithium-sulphur batteries

Abstract A S/DPAN (dehydrogenated polyacrylonitrile) composite shows promising electrode performances as a cathode material for Li-S batteries though its electric conductivity is insufficient for high rate tests. In an attempt to enhance the electric conductivity, the S/DPAN composite is attached on reduced graphene oxide (rGO) sheets via self-assembling modification. As a result, the conductivity improves to ∼10−4 S cm−1, and the S/DPAN/rGO composite thereby delivers approximately 90% of the theoretical capacity of sulphur at a rate of 0.2C (0.34 A g−1) over 700 mAh (g-S)−1 even at 2C (3.4 A g−1). We first report on the CS bond between sulphur and DPAN in a composite that maintains the bond even after an extensive cycling test, as confirmed by time-of-flight secondary-ion mass spectroscopy (ToF-SIMS). These synergistic effects enable facile electron transport such that the S/DPAN/rGO composite electrode is able to maintain superior electrode performances

P-DOPED COFFEE GROUND-DERIVED HARD CARBON FOR BOOSTING SODIUM-ION BATTERIES

The paper proposed the facile and successful preparation of P-doped coffee ground-derived hard carbon using H3PO4 as a dopant material for sodium-ion batteries. The manipulation with 1-3 M of H3PO4, contributed to finding the optimal concentration for the maximum incorporation of phosphorus ions into the carbon framework. The use of 2 M of H3PO4 dopant material for hard carbon as anode for sodium-ion battery delivers promising electrochemical performanc

MAXIMIZING SPECIFIC CAPACITY OF NUTTY HARD CARBON: IMPACT OF TREATMENT CONDITIONS ON STRUCTURAL AND ELECTROCHEMICAL PROPERTIES

Hard carbon (HC) has attracrted tremendous attention in sodium ion batteries (SIBs) as promising negative electrode material due to its low cost, environmental friendliness and stable cyling performance. However, due to the limited capacity and low initial columbic efficiency (ICE), the actual full cell application of HC faces significant obstacles. Therefore, preparation process was optimized to investigate the impact of the pre-treatment conditions and degree of graphitization on electrochemical performance and to resolve abovementioned problems