Research Progresses of Liquid Electrolytes in Lithium-Ion Batteries

In recent years, the rapid development of modern society is calling for advanced energy storage to meet the growing demands of energy supply and generation. As one of the most promising energy storage systems, secondary batteries are attracting much attention. The electrolyte is an important part of the secondary battery, and its composition is closely related to the electrochemical performance of the secondary batteries. Lithium-ion battery electrolyte is mainly composed of solvents, additives, and lithium salts, which are prepared according to specific proportions under certain conditions and according to the needs of characteristics. This review analyzes the advantages and current problems of the liquid electrolytes in lithium-ion batteries (LIBs) from the mechanism of action and failure mechanism, summarizes the research progress of solvents, lithium salts, and additives, analyzes the future trends and requirements of lithium-ion battery electrolytes, and points out the emerging opportunities in advanced lithium-ion battery electrolytes development.

Safety Concerns for the Management of End-of-Life Lithium-Ion Batteries

Lithium-ion battery (LIB) usage is growing dramatically worldwide. Relatedly, there is a need for the management of end-of-life (EOL) LIBs. EOL requires closed-loop systems and supply chains. Although many studies related to managing EOL in closed-loop supply chains exist, one especially pernicious issue is overlooked-safety. This study seeks to address this major safety oversight for EOL LIBs using closed-loop supply chains that are critical to a larger circular economy environment. The evaluation is completed along a technology-organization-environment (TOE) framework; potential research directions for mitigating safety issues are part of the analysis of this study. Specific and general research questions pertaining to secure management of EOL LIBs are put forward to help advance academic research. Practical concerns are also described for policymakers and organizations. This study reveals implications of these questions for the intersection of materials science, supply chain management, and fire-protection engineering.

Highly Stable Porous Polyimide Sponge as a Separator for Lithium-metal Secondary Batteries

To inhibit Li-dendrite growth on lithium (Li)-metal electrodes, which causes capacity deterioration and safety issues in Li-ion batteries, we prepared a porous polyimide (PI) sponge using a solution-processable high internal-phase emulsion technique with a water-soluble PI precursor solution; the process is not only simple but also environmentally friendly. The prepared PI sponge was processed into porous PI separators and used for Li-metal electrodes. The physical properties (e.g., thermal stability, liquid electrolyte uptake, and ionic conductivity) of the porous PI separators and their effect on the Li-metal anodes (e.g., self-discharge and open-circuit voltage properties after storage, cycle performance, rate capability, and morphological changes) were investigated. Owing to the thermally stable properties of the PI polymer, the porous PI separators demonstrated no dimensional changes up to 180 °C. In comparison with commercialized polyethylene (PE) separators, the porous PI separators exhibited improved wetting ability for liquid electrolytes; thus, the latter improved not only the physical properties (e.g., improved the electrolyte uptake and ionic conductivity) but also the electrochemical properties of Li-metal electrodes (e.g., maintained stable self-discharge capacity and open-circuit voltage features after storage and improved the cycle performance and rate capability) in comparison with PE separators.

Essential geometric and electronic properties in stage-n graphite alkali-metal-intercalation compounds

The rich and unique properties of the stage-n graphite alkali-metal-intercalation compounds are fully investigated by first-principles calculations.

Evaluation of Present Accelerated Temperature Testing and Modeling of Batteries

Battery manufacturers and device companies often test batteries at high temperature to accelerate the degradation process. The data collected from these accelerated tests are then used to determine battery performance and reliability over specified nominal operating temperatures. In many cases, companies assume an Arrhenius model, or prescribe a decade rule to conduct the data analysis. This paper presents the flaws in accelerated temperature testing of batteries using the Arrhenius model and the decade rule, with the emphasis on lithium-ion batteries. Experimental case studies demonstrate the inaccuracy of the Arrhenius model. Alternative methods based on reliability science are then provided.

Elucidating the Polymeric Binder Distribution within Lithium-Ion Battery Electrodes Using SAICAS

Polymeric binder distribution within electrodes is crucial to guarantee the electrochemical performance of lithium-ion batteries (LIBs) for their long-term use in applications such as electric vehicles and energy-storage systems. However, due to limited analytical tools, such analyses have not been conducted so far. Herein, the adhesion properties of LIB electrodes at different depths are measured using a surface and interfacial cutting analysis system (SAICAS). Moreover, two LiCoO₂ electrodes, dried at 130 and 230 °C, are carefully prepared and used to obtain the adhesion properties at every 10 μm of depth as well as the interface between the electrode composite and the current collector. At high drying temperatures, more of the polymeric binder material and conductive agent appears adjacent to the electrode surface, resulting in different adhesion properties as a function of depth. When the electrochemical properties are evaluated at different temperatures, the LiCoO₂ electrode dried at 130 °C shows a much better high-temperature cycling performance than does the electrode dried at 230 °C due to the uniform adhesion properties and the higher interfacial adhesion strength.

Insight into the capacity fading of layered lithium-rich oxides and its suppression via a film-forming electrolyte additive

The capacity fading of layered lithium-rich oxide (Li_1.2Mn_0.54Ni_0.13Co_0.13O₂, LLO) cathodes greatly hinders their practical application in next generation lithium ion batteries. It has been demonstrated in this work that the slow capacity fading of a LLO/Li cell within 120 cycles is mainly caused by electrolyte oxidation and LLO phase transformation with Ni dissolution. After 120 cycles, the dissolution of Mn becomes worse than that of Ni, leading to structural destruction of the generated spinel phase structure of LLO and fast capacity fading. Tripropyl borate (TPB) is proposed as a film-forming electrolyte additive, which shows a great capability to enhance the cycling stability of LLO/Li, with a capacity retention improvement from 21% to 78% after 250 cycles at 0.5C. Electrochemical and physical characterization demonstrated that the TPB-derived SEI film shows great capability to suppress electrolyte oxidation and the structural destruction of the generated spinel phase of LLO.

The capacity fading of layered lithium-rich oxide (Li_1.2Mn_0.54Ni_0.13Co_0.13O₂, LLO) cathodes greatly hinders their practical application in next generation lithium ion batteries.