Engineering topics

Zhang, Jiguang

Publications and source records attributed to Zhang, Jiguang.

24 records · Page 2

DOE OSTI2020

Role of inner solvation sheath within salt–solvent complexes in tailoring electrode/electrolyte interphases for lithium metal batteries

Functional electrolyte is the key to stabilizing the highly reductive lithium (Li) metal anode (LMA) and high voltage cathode for long life, high energy-density rechargeable Li metal batteries (LMBs). However, fundamental knowledge of the interaction principles between reactive electrodes and electrolytes is still limited. Recently localized high-concentration electrolytes (LHCEs) are emerging as promising electrolyte design strategies for LMBs. They can also serve as an ideal platform for understanding the reactivity characteristics of the inner solvation sheath on electrode surfaces due to their unique solvation structures. Here, we study the effects of a series of LHCEs with model electrolyte solvents (carbonate, sulfone, phosphate and ether) in high voltage LMBs. Varied electrode stabilities exhibited in different LHCEs indicate the intricate synergies between the salt and the solvent on electrode surfaces. Experimental and theoretical analyses reveal an intriguing general rule that the strong interactions between the salt and the solvent in the inner solvation sheath promote their intermolecular proton/charge transfer reactions, which dictates the properties of the electrode/electrolyte interphases and thus the battery performances.

Solvation sheath, salt-solvent complex, electrode/↗

DOE OSTI2020

Controlling Ion Coordination Structure and Diffusion Kinetics for Optimized Electrode-Electrolyte Interphases and High Performance Si Anodes

The cycling performance of batteries is largely determined by electrode-electrolyte interphase associated with the chemical and electrochemical properties of electrolyte salts and solvents. In this work, we used a localized high concentration electrolyte (LHCE) that enables high performance of Si anodes as a model system and investigated the scientific mechanism behind the optimization of electrolyte. The correlation between electrode (cathode/anode)-electrolyte interphase and ion coordination structure and diffusion kinetics were elucidated systematically. Among all the LHCEs tested, the one with 1.8M LiFSI concentration and 1:2 molar ratio of carbonate solvents and fluorinated diluents has the highest proportion of solvent-separated ion pairs and contact ion pairs and fastest ion diffusion. It enables the most stable electrode-electrolyte interphase and hence the best Si anode performance. These results reveal the fundamental mechanism behind the stability of LHCEs and provide guidance on the new electrolyte design for Si anodes and other battery systems.

Jia, Haiping↗

DOE OSTI2020

Highly Reversible Sodium Ion Batteries Enabled by Stable Electrolyte-Electrode Interphases

Sodium (Na) ion battery is a very promising technology for the alternative energy storage systems because of the abundance and low cost of Na element in the Earth’s crust. However, the limited cycle life and safety concerns still hinder its large-scale applications. Here, we report a nonflammable localized high concentration electrolyte (sodium bis(fluorosulfonyl)imide - triethyl phosphate/1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (1:1.5:2 in molar ratio)), which enables a very high initial Coulombic efficiency (CE) of 97.8% for Na||Na-CNFM (O3-NaCu1/9Ni2/9Fe1/3Mn1/3O2) cells and stable cycling of Na||hard carbon (HC) cells with a capacity retention of 95.4% after 500 cycles. The HC||Na-CNFM full cells using this electrolyte retain 82.5% capacity after 200 cycles with a CE of ~99.9% compared to 48.4% capacity retention in the carbonate electrolyte (1 M NaPF6/EC+DMC (1:1 in weight)). The extremely high CE and stability of HC||Na-CNFM cells in this electrolyte can be attributed to the stable interphase layers formed on both HC anode and Na-CNFM cathode. These layers minimize undesirable reaction between HC and electrolyte, and block the dissolution of transition metal from cathode. The insight obtained in this work can be used to further improve cycling stability and safety of rechargeable batteries.

Jin, Yan↗

DOE OSTI2020

A lithium-sulfur battery with a solution-mediated pathway operating under lean electrolyte conditions

Lithium-sulfur (Li-S) battery is one of the most promising candidates for the next generation energy storage systems. However, several barriers, including polysulfide shuttle effect, the slow solid-solid surface reaction pathway in the lower discharge plateau, and corrosion of Li anode still limit its practical applications, especially under the lean electrolyte condition required for high energy density applications. Here, we propose a solution-mediated sulfur reduction pathway to improve the capacity and reversibility of the sulfur cathode and suppress dendrite growth on the Li metal anode simultaneously. With this method, a high coulombic efficiency (99%) and stable cycle life over 100 cycles were achieved under application-relevant conditions (S loading: 6.2 mg cm-2; electrolyte to sulfur ratio: 3 mLE gs-1; sulfur weigh ratio: 72 wt%). This result is enabled by a specially designed Li2S4-rich electrolyte, in which Li2S is formed through a chemical disproportionation reaction instead of electrochemical routes. A diglyme solvent was used to obtain electrolytes with the optimum range of Li2S4 concentration. Operando X-ray absorption spectroscopy confirms the solution pathway in a practical Li-S cell. This solution pathway not only introduces a new electrolyte regime for practical Li-S batteries, but also provides a new perspective for bypassing the inefficient surface pathway for other electrochemical processes.

Wang, Hui↗

DOE OSTI2020

Unravelling high-temperature stability of lithium-ion battery with lithium-rich oxide cathode in localized high-concentration electrolyte

Lithium (Li)-rich manganese (Mn)-rich oxide (LMR) cathode materials, despite of the high specific capacity up to 250 mAh g-1 suffer from instability of cathode/electrolyte interfacial layer at high working voltages, causing continuous voltage decay and capacity fading, especially at elevated temperatures. In various battery systems, localized high-concentration electrolytes (LHCEs) have been widely reported as a promising candidate to form effective electrode/electrolyte interphases. Here, an optimized LHCE is studied in graphite (Gr)-based full cells being cycled at 25, 45 and 60 °C with the reference of a conventional LiPF6-based electrolyte. It is revealed that the LHCE can effectively suppress continuous electrolyte decompositions and mitigate the dissolution of Mn ions due to the formation of more protective electrode/electrolyte interphases on both anode and cathode, which, in turn, lead to significantly improved cycling stability and enhanced rate capability under the selected temperatures. The mechanistic understanding on the failure of the conventional LiPF6-containing electrolyte and the function of the LHCE in Gr||LMR cells under high temperatures provides valuable perspectives of electrolyte development for practical application of LMR cathodes in high energy density batteries over a wide temperature range.

Localized high-concentration electrolyte, Lithium-↗

DOE OSTI2020

Understanding and applying coulombic efficiency in lithium metal batteries

Coulombic Efficiency (CE) has been widely used in battery research as a quantifiable monitor to compare the properties and performances of materials, electrolytes, interfaces and the entire electrochemical cells. While CE with ultra high precision effectively predicts the lifespan and health for lithium ion (Li-ion) batteries, it is not necessarily true in rechargeable lithium (Li) metal batteries. A large variation of CE is often seen even from the same materials and electrolytes in Li metal cells. This work discusses the fundamental definition of CE in different configurations of Li metal-based cells. The similarities and differences of CE in Li-ion and Li metal cells have been clarified and used to understand the relevance/irrelevance between CE and cycling. Long-standing goal of this study is to help rational design of cell testing protocols and elaborate electrochemical results. The insights from this work are broadly applicable in many other rechargeable metal cells e.g., Zn, Mg and Na batteries to accelerate reseach innovation.

Xiao, Jie↗