The tremendous improvement in performance and cost of lithium-ion batteries (LIBs) have made them the technology of choice for electrical energy storage. While established battery chemistries and cell architectures for Li-ion batteries achieve good power and energy density, LIBs are unlikely to meet all the performance, cost, and scaling targets required for energy storage, in particular, in large-scale applications such as electrified transportation and grids. The demand to further reduce cost and/or increase energy density, as well as the growing concern related to natural resource needs for Li-ion have accelerated the investigation of so-called "beyond Li-ion" technologies. In this review, we will discuss the recent achievements, challenges, and opportunities of four important "beyond Li-ion" technologies: Na-ion batteries, K-ion batteries, all-solid-state batteries, and multivalent batteries. The fundamental science behind the challenges, and potential solutions toward the goals of a low-cost and/or high-energy-density future, are discussed in detail for each technology. While it is unlikely that any given new technology will fully replace Li-ion in the near future, "beyond Li-ion" technologies should be thought of as opportunities for energy storage to grow into mid/large-scale applications.

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Promises and challenges of next-generation "beyond Li-ion" batteries for electric vehicles and grid decarbonization

Rechargeable batteries with lithium metal anodes exhibit higher energy densities than conventional lithium-ion batteries. Solid-state electrolytes (SSEs) provide the opportunity to unlock the full potential of lithium metal anodes and fundamentally eliminate safety concerns caused by flammable liquid electrolytes. Up to now, most studies on SSEs have been focused on enhancing the ionic conductivity and improving the interfacial stability. However, the electrolyte thickness, which has received less attention, also plays an important role in determining the energy density and electrochemical performance of all-solid-state lithium batteries (ASSLBs). Recognizing this, our review evaluates SSE studies beyond traditional factors and focuses on a thickness perspective. We systematically analyze the influence of the electrolyte thickness on the energy densities of ASSLB pouch cells, and highlight the strategies that dramatically reduce the thickness of SSE membranes without sacrificing their mechanical properties. Then, we discuss recent advances and challenges of ASSLBs based on high-voltage and high-capacity cathodes, as well as novel configurations such as bipolar and flexible ASSLBs. Finally, we provide perspectives and suggestions towards high energy-density ASSLBs for future commercialization.

Reducing the thickness of solid-state electrolyte membranes for high-energy lithium batteries

Interface issues of lithium metal anode for high-energy batteries: Challenges, strategies, and perspectives

Energy storage materials are finding increasing applications in our daily lives, for devices such as mobile phones and electric vehicles. Current commercial batteries use flammable liquid electrolytes, which are unsafe, toxic, and environmentally unfriendly with low chemical stability. Recently, solid electrolytes have been extensively studied as alternative electrolytes to address these shortcomings. Herein, we report the early history, synthesis and characterization, mechanical properties, and Li+ ion transport mechanisms of inorganic sulfide and oxide electrolytes. Furthermore, we highlight the importance of the fabrication technology and experimental conditions, such as the effects of pressure and operating parameters, on the electrochemical performance of all-solid-state Li batteries. In particular, we emphasize promising electrolyte systems based on sulfides and argyrodites, such as LiPS5Cl and β-Li3PS4, oxide electrolytes, bare and doped Li7La3Zr2O12 garnet, NASICON-type structures, and perovskite electrolyte materials. Moreover, we discuss the present and future challenges that all-solid-state batteries face for large-scale industrial applications.

Sulfide and Oxide Inorganic Solid Electrolytes for All-Solid-State Li Batteries: A Review

Solid-state lithium batteries (SSLBs) are promising next-generation energy storage devices due to their potential for high energy density and improved safety. The properties and physical parameters of the solid-state electrolyte (SSE), as a critical component of the battery, have a significant effect on the electrochemical performance and energy density. In recent years, thick SSEs have been widely used in SSLBs but present several drawbacks in terms of increased internal resistance, additional inactive material content, low practical energy densities, and higher battery manufacturing costs. Reducing the thickness of SSEs and developing high-performance thin SSE-based SSLBs are essential for the commercialization of SSLBs. In this review, we comprehensively summarize the fabrication methods of thin SSEs, their rational design, and their manufacturing processes and applications in different SSLB systems. Moreover, advanced characterization techniques for understanding the Li+ transport kinetics and structural evolution of SSEs at the interface are introduced. Additionally, the gravimetric/volumetric energy densities for various SSLB pouch cells with SSEs less than 100 μm thick are evaluated. Lastly, other cell design parameters are tuned to achieve gravimetric/volumetric energy densities over 300 W h kg−1/500 W h L−1, and the future directions of thin SSEs in SSLBs are speculated upon.

Recent advances and perspectives on thin electrolytes for high-energy-density solid-state lithium batteries

Ceramic oxide electrolytes are outstanding due to their excellent thermostability, wide electrochemical stable windows, superior Li-ion conductivity, and high elastic modulus compared to other electrolytes. To achieve high energy density, all-solid-state batteries require thin solid-state electrolytes that are dozens of micrometers thick due to the high density of ceramic electrolytes. Perovskite-type Li0.34 La0.56 TiO3 (LLTO) freestanding ceramic electrolyte film with a thickness of 25 µm is prepared by tape-casting. Compared to a thick electrolyte (>200 µm) obtained by cold-pressing, the total Li ionic conductivity of this LLTO film improves from 9.6 × 10-6 to 2.0 × 10-5 S cm-1 . In addition, the LLTO film with a thickness of 25 µm exhibits a flexural strength of 264 MPa. An all-solid-state Li-metal battery assembled with a 41 µm thick LLTO exhibits an initial discharge capacity of 145 mAh g-1 and a high capacity retention ratio of 86.2% after 50 cycles. Reducing the thickness of oxide ceramic electrolytes is crucial to reduce the resistance of electrolytes and improve the energy density of Li-metal batteries.

Tape-Casting Li 0.34 La 0.56 TiO 3 Ceramic Electrolyte Films Permit High Energy Density of Lithium-Metal Batteries

Improving diffusion kinetics and phase stability of LiCoO2 via surface modification at elevated voltage

Lithium‐Metal Batteries: Tape‐Casting Li0.34La0.56TiO3 Ceramic Electrolyte Films Permit High Energy Density of Lithium–Metal Batteries (Adv. Mater. 6/2020)

Wenlong Yang

Papers

Tape-Casting Li 0.34 La 0.56 TiO 3 Ceramic Electrolyte Films Permit High Energy Density of Lithium-Metal Batteries

Improving diffusion kinetics and phase stability of LiCoO2 via surface modification at elevated voltage

Lithium‐Metal Batteries: Tape‐Casting Li0.34La0.56TiO3 Ceramic Electrolyte Films Permit High Energy Density of Lithium–Metal Batteries (Adv. Mater. 6/2020)

Ultrathin Graphdiyne Oxide-Intercalated MXene: A New Heterostructure with Interfacial Synergistic Effect for High Performance Lithium-ion Storage