The anode material largely determines the energy density of all-solid-state lithium battery (ASLB). Silicon (Si) and lithium (Li) metals are the two most attractive anode materials because of their ultra-high theoretical capacity. However, at present, most research focuses on lithium metal, while underestimating the great potential of silicon.

Scholars from Northeastern University in the United States studied the stability, machinability and cost of silicon anode in ASLBS, and compared it with lithium metal. In addition, Li2SiOx was used to stabilize lini0.8co0.1mn0.1o 2 single crystal by an extensible sol-gel method. Lattice energy-level ASLBS with energy density of 285 wh kg-1was obtained through the interlayer silicon negative electrode, thin sulfide solid electrolyte membrane and stable interface lini0.8co0.1o 2. The capacity of the whole battery at C/3 is as high as 145 mAh g- 1, and the stability is maintained as high as 1000 cycles. This work provides a solution for ASLB's large-scale commercial, safe and economical energy storage production line. The related article was published in Advanced Materials, entitled "High-performance confined-base all-solid-state battery enabled by electrochemical-mechanically stable electrodes".

Paper link:

https://doi.org/ 10. 1002/adma.20220040 1

Figure 1. High energy ASLB. (a) schematic diagram of high-energy ASLBS based on silicon composite negative electrode and Li2SiOx@S-NMC composite positive electrode; (b) Advantages of silicon anode and its expanding potential in industrial manufacturing and application.

Figure 2. Comprehensive evaluation of silicon anode and lithium metal anode. The application of sulfide selenium-based ASLBS was compared from the aspects of cost, energy density, interface compatibility and processability.

Figure 3. Half-cell performance of silicon anode. (a) schematic diagram of the preparation process of aslbsie-CB and the configuration scheme of silicon composite cathode. The electron and ion conduction paths are emphatically introduced. (2) The structure and ion conduction path of the positive electrode of lithium ion battery are introduced emphatically. (c) scanning electron microscope images of silicon nanoparticles and (d) silicon selenium CB. (e) X-ray diffraction spectra of Si, Se, Cb and Si-Se-Cb. (f) constant current charge-discharge curve and (g) corresponding dq/dv curve of the first cycle. (h) The rate performance of h)ASLB at current densities of 0. 1, 0.2, 0.5, 1 and 2 milliamperes cm -2. (i) Long-term cycling performance of I)ASLB at a current density of 0.5 mA/cm -2.

Figure 4. Morphology evolution of silicon anode after cycling. The top scanning electron microscope images of the silicon composite anode before cycling at the magnifications of (A) 1kX and (B) 10kX. (c) The cross-sectional image of the silicon composite negative electrode before cycling. (d) Scanning electron microscope images of the silicon composite negative electrode after cycling at D) 1kX and (E) 10kX. (f) The cross-sectional image of the silicon composite negative electrode after cycling. Cross-section and plan view of silicon composite negative electrode (G) before and after cycle (H).

Figure 5. Study on the stability of silicon and lithium metal negative electrodes during cycling. (a) the Nyquist curve of the stack and (b) the electrochemical impedance spectrum results of the silicon negative electrode half cell in different discharge states during the first discharge. (c) superimposing the Nyquist diagram and (d) EIS results of the silicon negative electrode half cell in different charging states in the subsequent charging process. The illustrations in (b) and (d) are equivalent circuits of EIS fitting. (e) Superimposed Nyquist diagram of Li|Se|Li symmetrical battery with different rest time before cycling.

Figure 6. Half-cell performance of li2siox @ s-NMC cathode (a) interface engineering was carried out on single crystal NMC 8 1 1, and Li2SiOx@S-NMC composite anode was prepared by wet chemical coating; (b) configure ASLB with Li2SiOx @S-NMC composite anode and In-Li cathode. (c) scanning electron microscope image of naked NMC and (D) Li2SiOx @S-NMC. EDX element diagram of (E)Ni and (F)Si in Li2SiOx @S-NMC. (g) The EDX spectrum of li2siox @ s-NMC shows the existence of Si.

Figure 7. Full battery performance. (a) A schematic diagram of a full battery using a thin SE film. (b) Scanning electron microscope image of the cross section of the whole battery. (c) EDX element diagram of C)Ni, (D)S and (E)Si on the whole battery section. (f) the constant current charge-discharge curve of the whole battery in the first cycle at the rate of C/20 and the negative load of10 mg cm-2, and (g) the corresponding DQ/DV curve. (h) the rate performance and (i) the long-term cycle performance of the whole battery under the conditions of positive electrode mass loads of 10 and 20 mg cm-2.

Figure 8. Evaluation of battery-level energy density: compared with other reported ASLB using silicon anode at different current densities.

To sum up, the silicon composite anode was successfully prepared by simple ball milling method. When the high capacity of the half battery is 2773 mAh g- 1, 0. 1 mA cm-2, the ice content is 85.6%. After 200 cycles at 0.5 Ma cm-2, the battery still has a high capacity of 2067 mAh g-1. OPANDO AC impedance spectrum test shows that the Si composite negative electrode shows good stability in the cycle process, but SE has a slight decomposition effect on Li2S, and the conductivity of Li2S ion is low, which is beneficial to cycle stability.

In contrast, lithium metal anode and sulfide SE have serious chemical and electrochemical instability. A series of interface engineering on silicon surface, including carbon coating, ionic conductor coating and hybrid coating, will lead to the slow transfer of corresponding charges in silicon composite negative electrode, thus accelerating the decomposition of SE. On the cathode side, a low-cost Li2SiOx layer was prepared on single crystal NMC 8 1 1 to stabilize the interface with sulfide Se. The results show that the horizontal energy density of the battery is 285 Wh kg-1under the high negative mass load of 20 mg cm-2. This work has certain guiding significance for the commercialization of ASLBS, and also promotes the practical application of silicon anode in ASLBS. (text: SSC)