Static and Dynamic Studies on LiNi1/3 Co1/3 Mn1/3 O2 -Based Suspensions for Semi-Solid Flow Batteries

Rechargeable Batteries for Grid Scale Energy Storage

Ever-increasing global energy consumption has driven the development of renewable energy technologies to reduce greenhouse gas emissions and air pollution. Battery energy storage systems (BESS) with high electrochemical performance are critical for enabling renewable yet intermittent sources of energy such as solar and wind. In recent years, numerous new battery technologies have been achieved and showed great potential for grid scale energy storage (GSES) applications. However, their practical applications have been greatly impeded due to the gap between the breakthroughs achieved in research laboratories and the industrial applications. In addition, various complex applications call for different battery performances. Matching of diverse batteries to various applications is required to promote practical energy storage research achievement. This review provides in-depth discussion and comprehensive consideration in the battery research field for GSES. The overall requirements of battery technologies for practical applications with key parameters are systematically analyzed by generating standards and measures for GSES. We also discuss recent progress and existing challenges for some representative battery technologies with great promise for GSES, including metal-ion batteries, lead-acid batteries, molten-salt batteries, alkaline batteries, redox-flow batteries, metal-air batteries, and hydrogen-gas batteries. Moreover, we emphasize the importance of bringing emerging battery technologies from academia to industry. Our perspectives on the future development of batteries for GSES applications are provided.

High-Capacity CuSi2P3-Based Semisolid Anolyte for Redox Flow Batteries

Redox flow batteries (RFBs) have attracted more attention due to their ability of decoupling energy and power, but their low energy density has greatly restricted their applications. Semisolid flow batteries (SSFBs) are a kind of RFBs, but they have high energy density. However, there is a lack of research on semisolid anolytes, and thus the application of SSFBs is still in its infancy. In this work, a low-potential (0.6 V vs Li/Li⁺) CuSi₂P₃@C-LiPAA composite is synthesized through a simple high-energy mechanical ball milling and impregnation method based on the CuSi₂P₃ (CSP) compound; then, it is used to prepare a semisolid anolyte, which is able to achieve a high volumetric capacity of 400 Ah L^-1 in static mode and 320 Ah L^-1 in intermittent-flow mode. This is the highest volumetric capacity of anolyte so far. The effect of adding binder to a composite is also discussed for the first time, which makes the connection between the composite particles closer and the semisolid suspension more uniform so as to obtain stable electrochemical performance. At the same time, through pairing respectively with two types of catholytes, liquid 10-methylphenothiazine (MPT) and semisolid LiFePO₄ (LFP), a single-cell voltage of 3 V and more than 100 stable cycles with the Coulombic efficiency of 99% have been achieved by CSP-MPT and CSP-LFP full-cell systems. The result fully demonstrates the applicability of the prepared CSP semisolid anolyte. The synthesis method of adding a binder to the composite in this work also provides a direction for optimizing the suspension for other active materials to be applied to SSFBs in the future.

Trust is good, control is better: a review on monitoring and characterization techniques for flow battery electrolytes

Flow batteries (FBs) currently are one of the most promising large-scale energy storage technologies for energy grids with a large share of renewable electricity generation. Among the main technological challenges for the economic operation of a large-scale battery technology is its calendar lifetime, which ideally has to cover a few decades without significant loss of performance. This requirement can only be met if the key parameters representing the performance losses of the system are continuously monitored and optimized during the operation. Nearly all performance parameters of a FB are related to the two electrolytes as the electrochemical storage media and we therefore focus on them in this review. We first survey the literature on the available characterization methods for the key FB electrolyte parameters. Based on these, we comprehensively review the currently available approaches for assessing the most important electrolyte state variables: the state-of-charge (SOC) and the state-of-health (SOH). We furthermore discuss how monitoring and operation strategies are commonly implemented as online tools to optimize the electrolyte performance and recover lost battery capacity as well as how their automation is realized via battery management systems (BMSs). Our key findings on the current state of this research field are finally highlighted and the potential for further progress is identified.

Contact resistance stability and cation mixing in a Vulcan-based LiNi1/3Co1/3Mn1/3O2 slurry for semi-solid flow batteries

The Semi-Solid Flow Battery (SSFB) is an interesting energy storage system (ESS) for stationary applications but, in spite of the significant work presented on this technology so far, understanding the chemical and physical factors limiting its electrochemical performance is still blurred by measurements under static conditions rather than under real operando conditions. In this study, we have used Vulcan carbon as a conductive additive to formulate LiNi1/3Co1/3Mn1/3O2 (NCM) based slurries as the catholyte to characterize electrical and electrochemical performances using a 3-electrode flow cell by electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCD), respectively. The results are correlated with post-mortem analyses of recovered slurries using Scanning Electron Microscopy (SEM), Raman spectroscopy and Rietveld refinement of the NCM crystal structure. Due to the improved electrochemical cycling stability of the Vulcan-based NCM slurry and cell configuration used for measurements, we have been able to characterize the system in terms of electrical contributions and correlate them with particle degradation as well as detect antisite defect formation on cycling. The electrical stability of the contact resistance and cation mixing are identified as factors limiting the performance of the semi-solid slurry. The latter is frequently reported in porous electrodes for Li-ion batteries but, to our knowledge, it has not been reported for SSFBs to date.

Redox-Targeting-Based Flow Batteries for Large-Scale Energy Storage

Redox-targeting reactions of battery materials by redox molecules are extensively studied for energy storage since the first report in 2006. Implementation of the "redox-targeting" concept in redox flow batteries presents not only an innovative idea of battery design that considerably boosts the energy density of flow-battery system, but also an intriguing research platform applied to a wide variety of chemistries for different applications. Here, a critical overview of the recent progress in redox-targeting-based flow batteries is presented and the development of the technology in the various aspects from mechanistic understanding of the reaction kinetics to system optimization is highlighted. The limitations presently lying ahead for the widespread applications of "redox targeting" are also identified and recommendations for addressing the constraints are given. The adequate development of the redox-targeting concept should provide a credible solution for advanced large-scale energy storage in the near future.