In recent years, micrometer‐sized Si‐based anode materials have attracted intensive attention in the pursuit of energy‐storage systems with high energy and low cost. However, the significant volume variation during repeated electrochemical (de)alloying processes will seriously damage the bulk structure of SiOx microparticles, resulting in rapid performance fade. This work proposes to address the challenge by preparing in situ magnesium‐doped SiOx (SiMgyOx) microparticles with stable structural evolution against Li uptake/release. The homogeneous distribution of magnesium silicate in SiMgyOx contributes to building a bonding network inside the particle so that it raises the modulus of lithiated state and restrains the internal cracks due to electrochemical agglomeration of nano‐Si. The prepared micrometer‐sized SiMgyOx anode shows high reversible capacities, stable cycling performance, and low electrode expansion at high areal mass loading. A 21700 cylindrical‐type cell based on the SiMgyOx‐graphite anode and LiNi0.8Co0.15Al0.05O2 cathode demonstrates a 1000‐cycle operation life using industry‐recognized electrochemical test procedures, which meets the practical storage requirements for consumer electronics and electric vehicles. This work provides insights on the reasonable structural design of micrometer‐sized alloying anode materials toward realization of high‐performance Li‐ion batteries.

The carbon-coated silicon monoxide (SiO x @C) has been considered as one of the most promising high-capacity anodes for the next-generation high-energy-density lithium-ion batteries (LIBs). However, the relatively low initial Coulombic efficiency (ICE) and the still existing huge volume expansion during repeated lithiation/delithiation cycling remain the greatest challenges to its practical application. Here, we developed a lithium and boron (Li/B) co-doping strategy to efficiently enhance the ICE and alleviate the volume expansion or pulverization of SiO x @C anodes. The in situ generated Li silicates (Li x SiO y ) by Li doping will reduce the active Li loss during the initial cycling and enhance the ICE of SiO x @C anodes. Meanwhile, B doping works to promote the Li + diffusion and strengthen the internal bonding networks within SiO x @C, enhancing its resistance to cracking and pulverization during cycling. As a result, the enhanced ICE (83.28%), suppressed volume expansion, and greatly improved cycling (85.4% capacity retention after 200 cycles) and rate performance could be achieved for the Li/B co-doped SiO x @C (Li/B-SiO x @C) anodes. Especially, the Li/B-SiO x @C and graphite composite anodes with a capacity of 531.5 mA h g −1 were demonstrated to show an ICE of 90.1% and superior cycling stability (90.1% capacity retention after 250 cycles), which is significant for the practical application of high-energy-density LIBs.

Microsized SiO x has been vigorously investigated as an advanced anode material for next-generation lithium-ion batteries. However, its practical application is seriously hampered by its huge volume variation during the repeated (de)­lithiation process, which destroys the microparticle structure and results in rapid capacity fading. Herein, we propose the usage of trans-difluoroethylene carbonate (DFEC) as an electrolyte additive to maintain the structural integrity of microsized SiO x with a uniform carbon layer (SiO x @C). Compared with ethylene carbonate and fluoroethylene carbonate, DFEC has lower lowest unoccupied molecular orbital energy and higher reduction potential, which is easily reduced and promotes the in situ formation of a more stable LiF-rich solid electrolyte interphase (SEI) on the surface of anode materials. The LiF-rich SEI exhibits enhanced mechanical rigidity and ionic conductivity, thus enabling the microsized SiO x @C anodes’ excellent lithium storage stability and high average Coulombic efficiency.

The rational design of graphene-encapsulated nanomaterials is of great significance to the high-rate and long-cycle anode materials in lithium-ion batteries. Herein, composites of three-dimensional reduced graphene oxide-encapsulated SnO 2 nanoparticles (SnO 2 /RGO) have been synthesized by combining hydrothermal treatment with spray drying or freeze drying, and finally calcination. The morphology of a SnO 2 /RGO composite can be controlled and SnO 2 /RGO microspheres obtained by spray drying possess a large specific surface area and abundant inner spaces. Such kinds of morphology and porosity characteristics cannot only provide sufficient interior void to buffer the large volume variation but also provide an effective contacting area of electrolyte with electrode materials and more active sites for a redox reaction, which effectively avoids shedding of active components during lithiation/delithiation. The obtained SnO 2 /RGO shows a high specific capacity of 1592 mA h g −1 after 500 cycles at 500 mA g −1 , and it can maintain 319 mA h g −1 even at 5 A g −1 .