Ye Xiang-Yang,Bao Ke-Pan,Luo Sai-Nan,Li Xin,Chen Tai-Qiang,Xia Shui-Xin,Yuan Tao,Pang Yue-Peng,Zheng Shi-You
Composite solid electrolytes (CSEs) containing polymer matrices and inorganic fillers hold promise for the next generation of solid-state batteries. However, the role of residual solvents in CSEs remains controversial. This study investigated the evolution and function of the residual solvent in a polymer-Li 2 B 12 H 12 CSE. A partial reaction occurred between Li 2 B 12 H 12 and solvent N, N-dimethylformamide (DMF), which produced dimethylaminomethanol (DMAM) in the CSE. Density functional theory calculations have revealed that DMAM forms stronger hydrogen bonds with polyvinylidene fluoride chains than DMF, which can have a plasticizing effect on the polymer matrix, leading to lower crystallinity and quicker segment motion. Therefore, this CSE exhibited improved Li-ion conducting properties, enabling the stable cycling of Li||LiFePO 4 solid-state batteries. This study provided insights into the role of residual solvents in CSEs.
Bao Kepan,Pang Yuepeng,Yang Junhe,Sun Dalin,Fang Fang,Zheng Shiyou
Rational composite design is highly important for the development of high-performance composite polymer electrolytes (CPEs) for solid-state lithium (Li) metal batteries. In this work, Li closo-borohydride, Li 2 B 12 H 12 , is introduced to poly(vinylidene fluoride)-Li-bis-(trifluoromethanesulfonyl) imide (PVDF-LiTFSI) with a bound N -methyl pyrrolidone plasticizer to form a novel CPE. This CPE shows superb Li + conduction properties, as evidenced by its conductivity of 1.43 × 10 −4 S cm −1 and Li + transference number of 0.34 at 25°C. Density functional theory calculations reveal that Li 2 B 12 H 12 , which features electron-deficient multicenter bonds, can facilitate the dissociation of LiTFSI and enhance the immobilization of TFSI to improve the Li + conduction properties of the CPE. Moreover, the fabricated CPE exhibits excellent electrochemical, thermal, and mechanical stability. The addition of Li 2 B 12 H 12 can help form a protective layer at the anode/electrolyte interface, thereby preventing unwanted reactions. The above benefits of the fabricated CPE contribute to the high compatibility of the electrode. Symmetric Li cells can be stably cycled at 0.2 mA cm −2 for over 1200 h, and Li∥LiFePO 4 cells can deliver a reversible specific capacity of 140 mA h g −1 after 200 cycles at 1 C at 25°C with a capacity retention of 98%.
Chongyang Zhou,Han Sun,Qian Wang,Jakob B. Grinderslev,Dan Liu,Yigang Yan,Torben R. Jensen
Designing solid electrolytes for all-solid-state lithium batteries that can be compatible with high-voltage cathodes is challenging. Here we report that the nanocomposite Li 2 B 12 H 12 -Al 2 O 3 mechano-chemically treated for 120 h achieves an electrochemical stability window up to ∼ 3.8 V owing to the interfacial interaction via B-O bonds and a high lithium ionic conductivity , σ(Li + ) = 2.73 × 10 −5 S cm −1 at 30 °C. Moreover, this electrolyte shows high compatibility with the lithium metal anode as demonstrated by stable Li plating/stripping for 300 cycles. These electrolyte properties enable the first demonstration of a 3.8 V all-solid-state battery In 1.3 Li 0.3 |Li 2 B 12 H 12 -Al 2 O 3 (25 vol%)|LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) operating for 120 cycles with a rate of 0.2 C and at 30 °C, with a reversible specific capacity of 77.5 mAh g −1 and Coulombic efficiency of 99.8 %. The results demonstrate the potential of hydroborates as electrolyte for all-solid-state lithium batteries.
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