Silicon oxides have been recognized as a promising family of anode materials for high-energy lithium-ion batteries (LIBs) owing to their abundant reserve, low cost, environmental friendliness, easy synthesis, and high theoretical capacity. However, the extended application of silicon oxides is severely hampered by the intrinsically low conductivity, large volume change, and low initial coulombic efficiency. Significant efforts have been dedicated to tackling these challenges towards practical applications. This Review focuses on the recent advances in the synthesis and lithium storage properties of silicon oxide-based anode materials. To present the progress in a systematic manner, this review is categorized as follows: (i) SiO-based anode materials, (ii) SiO₂-based anode materials, (iii) non-stoichiometric SiO_x-based anode materials, and (iv) Si–O–C-based anode materials. Finally, future outlook and our personal perspectives on silicon oxide-based anode materials are presented.

Carbon materials are generally preferred as anodes in supercapacitors; however, their low capacitance limits the attained energy density of supercapacitor devices with aqueous electrolytes. Here, we report a low-crystalline iron oxide hydroxide nanoparticle anode with comprehensive electrochemical performance at a wide potential window. The iron oxide hydroxide nanoparticles present capacitances of 1,066 and 716 F g⁻¹ at mass loadings of 1.6 and 9.1 mg cm⁻², respectively, a rate capability with 74.6% of capacitance retention at 30 A g⁻¹, and cycling stability retaining 91% of capacitance after 10,000 cycles. The performance is attributed to a dominant capacitive charge-storage mechanism. An aqueous hybrid supercapacitor based on the iron oxide hydroxide anode shows stability during float voltage test for 450 h and an energy density of 104 Wh kg⁻¹ at a power density of 1.27 kW kg⁻¹. A packaged device delivers gravimetric and volumetric energy densities of 33.14 Wh kg⁻¹ and 17.24 Wh l⁻¹, respectively.