With excellent energy densities and highly safe performance, solid-state lithium batteries (SSLBs) have been hailed as promising energy storage devices. Solid-state electrolyte is the core component of SSLBs and plays an essential role in the safety and electrochemical performance of the cells. Composite polymer electrolytes (CPEs) are considered as one of the most promising candidates among all solid-state electrolytes due to their excellent comprehensive performance. In this review, we briefly introduce the components of CPEs, such as the polymer matrix and the species of fillers, as well as the integration of fillers in the polymers. In particular, we focus on the two major obstacles that affect the development of CPEs: the low ionic conductivity of the electrolyte and high interfacial impedance. We provide insight into the factors influencing ionic conductivity, in terms of macroscopic and microscopic aspects, including the aggregated structure of the polymer, ion migration rate and carrier concentration. In addition, we also discuss the electrode–electrolyte interface and summarize methods for improving this interface. It is expected that this review will provide feasible solutions for modifying CPEs through further understanding of the ion conduction mechanism in CPEs and for improving the compatibility of the electrode–electrolyte interface.
The solid electrolyte interphase (SEI) film is vital to the plating/stripping behavior of lithium metal, while the formation mechanism has not been explained clearly. Here, the formation process of the SEI film is first classified into chemical and electrochemical degradation routes by introducing a LiZn alloy, a chemically inert but electrochemically reactive interphase, as a distinguished research substrate. In a carbonate electrolyte, it is found that the common inorganic matters (such as Li 2 O and LiF) mainly originate from the chemical degradation of the electrolyte; meanwhile, the electrochemical degradation mainly generates organic species such as C-OR and COOR. Based on this understanding, the SEI film can be further accurately regulated, and a heterojunction-type SEI film with a well-defined composition and structure is constructed. This offers us a new perspective to understand and regulate the formation of the SEI film for applicable lithium metal batteries.
Because of uncontrolled plating and stripping behavior, infinite volume expansion, and dendrite formation, Li metal anodes have seriously restricted the practical application of lithium metal batteries (LMBs). In this study, a three-dimensional (3D) Li metal anode host composed of a copper oxide nanowires (CuO NWs) as the substrate with silver nanoparticles (Ag NPs) as the induced deposition sites was prepared (Ag@CuO NWs) by electrochemical machining technology. On the one hand, CuO NWs with a specific 3D structure obtained through an anodic oxidation process can provide enough space for Li deposition and thus would hinder the downside of volume change. On the other hand, Ag NPs, which are evenly distributed on the substrate by electrodeposition method can significantly reduce the nucleation overpotential and induce uniform Li deposition in this whole 3D structure. As a result, Ag@CuO NWs could maintain a capacity retention of 85.6% for 200 cycles at a 1 C rate in carbonate-based electrolytes. This work proposes a strategy that can effectively regulate the Li metal deposition behavior by means of anodic oxidation and electrodeposition.
The safety concerns associated with power batteries have prompted significant interest in all−solid−state lithium batteries (ASSBs). However, the advancement of ASSBs has been significantly impeded due to their unsatisfactory electrochemical performance, which is attributed to the challenging interface between the solid−state electrolyte and the electrodes. In this work, an in situ polymerized composite solid−state electrolyte (LLZTO−PVC) consisting of poly(vinylene carbonate) (PVC) and Li6.4La3Zr1.4Ta0.6O12 (LLZTO) was successfully prepared by a γ−ray irradiation technique. The novel technique successfully solved the problem of rigidity at the interface between the electrode and electrolyte. The LLZTO−PVC electrolyte exhibited a notable ionic conductivity of 1.2 × 10−4 S cm−1 25 °C, along with good mechanical strength and flexibility and an electrochemical window exceeding 4.65 V. It was showed that the LiCoO2(LCO)/LLZTO−PVC/Li battery, which achieved in situ solidification via γ−ray irradiation, can steadily work at a current density of 0.2 C at 25 °C and maintain a retention rate of 92.4% over 100 cycles. The good interfacial compatibility between electrodes and LLZTO−PVC electrolyte designed via in situ γ−ray irradiation polymerization could be attributed to its excellent electrochemical performance. Therefore, the method of in situ γ−ray irradiation polymerization provides a vital reference for solving the interface problem.
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