Materials and Interfacial Engineering for High-Performance All-Solid-State Batteries



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Developing advanced energy storage systems may address the increasing concerns of energy shortage and environmental issues. Among many energy storage technologies, electrochemical energy storage systems such as lithium-ion batteries have been widely used in various applications. However, current lithium-ion batteries using flammable liquid electrolytes may cause a safety risk. All-solid-state sodium batteries (ASSSBs) have been attracting considerable attention as safe and low-cost alternatives to Li-ion batteries. However, the performance of ASSSBs falls short of the requirements for commercial applications mainly due to the challenges at the electrode-solid electrolyte interface.

The goal of this dissertation is to develop new materials and interfacial engineering methods for high-performance ASSSBs with favorable electrode-electrolyte interfaces. In this dissertation, I demonstrate three effective strategies to address the interfacial challenges, namely through the use of organic cathode materials, new solid electrolyte development, and interfacial engineering.

First, a high-performance ASSSB can be achieved using organic cathode materials due to their unique properties. Organic cathode materials with a moderate redox potential enable an (electro)chemically reversible cathode-electrolyte interface. The unique elastic properties of organic cathode materials also ensure intimate contact during cycling. The benefits of organic cathode material are reflected in the excellent cell performance.

Second, an oxysulfide solid-state electrolyte (SE) is developed to improve the stability at the anode-electrolyte interface. The oxygen doped SE with more bridging units shows a more interconnected glass structure with less grain boundaries than that of pure oxide or sulfide-based SEs, effectively suppressing the dendrite growth. The stronger bonding of P-O than P-S also improves the chemical stability against Na metal, which may be attributed to the electronic insulating interphase that self-limits the continuous interfacial decomposition in sulfide-based SEs.

Pervious two strategies aim to solve the interfacial challenges between sulfide- based electrolytes and electrodes mainly due to the (electro)chemical instability. Oxide- based solid electrolytes can provide much better (electro)chemical stability but poor interfacial contact against electrodes. The third strategy is to introduce auxiliary wetting agents at the electrode-electrolyte interface to significantly improve the interfacial contact and reduce the interfacial resistance. At the anode-electrolyte interface, an introduced Sn thin film can serve as a buffer layer to react with molten Na, forming a NaSn alloy and improving the interfacial contact. At the cathode-electrolyte interface, poly(ethylene oxide) can serve as a mechanically compliant and ionically conductive agent to form an efficient percolation network, enabling the full utilization of the organic cathode material in the ASSSB.

In summary, the demonstrated three strategies address the key challenges in solid- state batteries. Strategy 1 focuses on new electrode materials; strategy 2 proposes new electrolyte materials; and strategy 3 combines strategies 1 and 2 with new device engineering. I hope these approaches will be useful for building future solid-state batteries with higher energy and longer cycling stability, and eventually for enabling large-scale production.



Solid-state batteries, Cathode materials, Batteries, Electrolytes, Interfacial engineering


Portions of this document appear in: Hao, Fang, Fudong Han, Yanliang Liang, Chunsheng Wang, and Yan Yao. "Architectural design and fabrication approaches for solid-state batteries." MRS Bulletin 43, no. 10 (2018): 775-781. And in: Hao, Fang, Xiaowei Chi, Yanliang Liang, Ye Zhang, Rong Xu, Hua Guo, Tanguy Terlier et al. "Taming Active Material-Solid Electrolyte Interfaces with Organic Cathode for All-Solid-State Batteries." Joule 3, no. 5 (2019): 1349-1359. And in: Chi, Xiaowei, Fang Hao, Jibo Zhang, Xiangwei Wu, Ye Zhang, Saman Gheytani, Zhaoyin Wen, and Yan Yao. "A high-energy quinone-based all-solid-state sodium metal battery." Nano Energy (2019).