Commercial lithium-ion (Li-ion) batteries suffer from low energy density and do not meet the growing demands of the energy storage market. Therefore, building next-generation rechargeable Li and Li-ion batteries with higher energy densities, better safety characteristics, lower cost and longer cycle life is of outmost importance. To achieve smaller and lighter next-generation rechargeable Li and Li-ion batteries that can outperform commercial Li-ion batteries, several new energy storage chemistries are being extensively studied. In this review, we summarize the current trends and provide guidelines towards achieving this goal, by addressing batteries using high-voltage cathodes, metal fluoride electrodes, chalcogen electrodes, Li metal anodes, high-capacity anodes as well as useful electrolyte solutions. We discuss the choice of active materials, practically achievable energy densities and challenges faced by the respective battery systems. Furthermore, strategies to overcome remaining challenges for achieving energy characteristics are addressed in the hope of providing a useful and balanced assessment of current status and perspectives of rechargeable Li and Li-ion batteries.

Guidelines and trends for next-generation rechargeable lithium and lithium-ion batteries.

The ever-growing demand for advanced rechargeable lithium-ion batteries in portable electronics and electric vehicles has spurred intensive research efforts over the past decade. The key to sustaining the progress in Li-ion batteries lies in the quest for safe, low-cost positive electrode (cathode) materials with desirable energy and power capabilities. One approach to boost the energy and power densities of batteries is to increase the output voltage while maintaining a high capacity, fast charge–discharge rate, and long service life. This review gives an account of the various emerging high-voltage positive electrode materials that have the potential to satisfy these requirements either in the short or long term, including nickel-rich layered oxides, lithium-rich layered oxides, high-voltage spinel oxides, and high-voltage polyanionic compounds. The key barriers and the corresponding strategies for the practical viability of these cathode materials are discussed along with the optimization of electrolytes and other cell components, with a particular emphasis on recent advances in the literature. A concise perspective with respect to plausible strategies for future developments in the field is also provided.

High-voltage positive electrode materials for lithium-ion batteries

Lithium metal (Li0 ) rechargeable batteries (LMBs), such as systems with a Li0 anode and intercalation and/or conversion type cathode, lithium-sulfur (Li-S), and lithium-oxygen (O2 )/air (Li-O2 /air) batteries, are becoming increasingly important for electrifying the modern transportation system, with the aim of sustainable mobility. Although some rechargeable LMBs (e.g. Li0 /LiFePO4 batteries from Bollore Bluecar, Li-S batteries from OXIS Energy and Sion Power) are already commercially viable in niche applications, their large-scale deployment is hampered by a number of formidable challenges, including growth of lithium dendrites, electrolyte instability towards high voltage intercalation-type cathodes, the poor electronic and ionic conductivities of sulfur (S8 ) and O2 , as well as their corresponding reduction products (e.g. Li2 S and Li2 O), dissolution, and shuttling of polysulfide (PS) intermediates. This leads to a short lifecycle, low coulombic/energy efficiency, poor safety, and a high self-discharge rate. The use of electrolyte additives is considered one of the most economical and effective approaches for circumventing these problems. This Review gives an overview of the various functional additives that are being applied and aims to stimulate new avenues for the practical realization of these appealing devices.

Electrolyte Additives for Lithium Metal Anodes and Rechargeable Lithium Metal Batteries: Progress and Perspectives.

Metal oxides have been of great importance to the development of energy conversion and storage technologies including heterojunction solar cells, Li-ion batteries, and electrocatalysts/photocatalys...

Electrochemical Impedance Spectroscopy of Metal Oxide Electrodes for Energy Applications

The lithium- and manganese-rich (LMR) layered structure cathodes exhibit one of the highest specific energies (≈900 W h kg−1) among all the cathode materials. However, the practical applications of LMR cathodes are still hindered by several significant challenges, including voltage fade, large initial capacity loss, poor rate capability and limited cycle life. Herein, we review the recent progress and in depth understandings on the application of LMR cathode materials from a practical point of view. Several key parameters of LMR cathodes that affect the LMR/graphite full-cell operation are systematically analyzed. These factors include the first-cycle capacity loss, voltage fade, powder tap density, and electrode density. New approaches to minimize the detrimental effects of these factors are highlighted in this work. We also provide perspectives for the future research on LMR cathode materials, focusing on addressing the fundamental problems of LMR cathodes while keeping practical considerations in mind.

Li- and Mn-Rich Cathode Materials: Challenges to Commercialization

Designing Low Impedance Interface Films Simultaneously on Anode and Cathode for High Energy Batteries

A novel electrolyte additive, 1-(2-cyanoethyl) pyrrole (CEP), has been investigated to improve the electrochemical performance of graphite/LiNi0.6Co0.2Mn0.2O2 cells cycling up to 4.5 V vs Li/Li+. The 4.5 V cycling results present that after 50 cycles, up to 4.5 V capacity retention of the graphite/LiNi0.6Co0.2Mn0.2O2 cell is improved significantly from 27.4 to 81.5% when adding 1% CEP to baseline electrolyte (1 M LiPF6 in EC/EMC 1:2, by weight). Ex situ characterization results support the mechanism of CEP for enhancing the electrochemical performance. On one hand, the significant enhancement is ascribed to a formed superior cathode interfacial film by preferential oxidation of CEP on the cathode electrode surface suppressing electrolyte decomposition at high voltage. On the other hand, the duo Lewis base functional groups can effectively capture dissociation product PF5 from LiPF6 with the presence of an unavoidable trace amount of water or aprotic impurities in the electrolyte. Thus this mitigates the h...

Constructing Unique Cathode Interface by Manipulating Functional Groups of Electrolyte Additive for Graphite/LiNi0.6Co0.2Mn0.2O2 Cells at High Voltage.

The energy density of commercial Li-ion batteries (LIBs) using LiCoO2 is adversely affected by the limited access to the Li stored in the CoO2 lattice, which is imposed partially by the instability of carbonate-based electrolytes at potentials higher than 4.5 V. In this work, we report a novel approach to fully utilize these extra Li via simultaneously stabilizing anode and cathode interfaces with a designed additive, 4-propyl-[1,3,2]dioxathiolane-2,2-dioxide (PDTD), which strongly coordinates with Co ions dissolved in electrolytes while decomposing to form protective interphases on both cathode and anode surfaces. The Co ions present in the electrolyte deposit on the anode in the form of a coordination complex with PDTD, avoiding the formation of Co metal that will catalyze the reduction decomposition of the additive-free electrolyte. The presence of PDTD in the electrolyte enables a higher charging potential of 4.45 V for LiCoO2/graphite cells, which significantly improves the energy density and cycling stability of this cathode chemistry that has already been used extensively in commercial LIBs.

Stabilizing LiCoO 2 /Graphite at High Voltages with an Electrolyte Additive

Failure mechanism of layered lithium-rich oxide/graphite cell and its solution by using electrolyte additive

Performances of lithium-ion batteries at subambient temperatures are extremely restricted by the resistive interphases originated from electrolyte decomposition, especially on the anode surface. This work reports a novel strategy that an anode interphase of low impedance is constructed by applying an electrolyte additive dimethyl sulfite (DMS). Electrochemical measurements indicate that the as-constructed interphase provides graphite/LiNi0.5Co0.2Mn0.3O2 pouch cells with excellent low-temperature performance, outperforming the interphase constructed by 1,3,2-dioxathiolane 2,2-dioxide (DTD), a common commercially used electrolyte additive. Spectral characterizations in combination with theoretical calculations demonstrate that the improved performance is attributed to the unique molecular structure of DMS, which presents appropriate reduction activity and constructs the more stable and ionically conductive anode interphase due to the weaker combination of its reduction product with lithium ions than DTD. This rational design of interphases via an additive structure has been proven to be a low cost but rather an effective approach to tailor the performances of lithium-ion batteries.

Le Yu

Papers

Designing Low Impedance Interface Films Simultaneously on Anode and Cathode for High Energy Batteries

Constructing Unique Cathode Interface by Manipulating Functional Groups of Electrolyte Additive for Graphite/LiNi0.6Co0.2Mn0.2O2 Cells at High Voltage.

Stabilizing LiCoO 2 /Graphite at High Voltages with an Electrolyte Additive

Failure mechanism of layered lithium-rich oxide/graphite cell and its solution by using electrolyte additive

Tailoring Low-Temperature Performance of a Lithium-Ion Battery via Rational Designing Interphase on an Anode