improved LIB performance is in the electrode materials. [ 11 ] Presently, commercial anode materials mainly include graphite, which limits the lithium storage performance in terms of energy and power density due to the low theoretical capacity (LiC 6 , 372 mAh g −1 ) and low Li-ion transport rate. [12][13][14] New anode materials with higher capacities are being looked for including mixed transition metal oxide anodes. Traditional Metal Oxide AnodesNew research is constantly being carried out to reach the high requirements for LIB anodes. Various metal oxide materials such as SnO 2 , [15][16][17][18][19] Co 3 O 4 , [20][21][22][23] NiO, [24][25][26][27] Fe 3 O 4 , [28][29][30] and MnO 2 [31][32][33] are alternative potential anodes for LIBs due to their high theoretical capacities, high power density, and wide usefulness. However, metal oxides inevitably suffer from several major problems: severe volume changes during the alloying-dealloying processes, pulverization and agglomeration of primitive particles, and poor electronic conductivity that hinders the reaction with lithium during electrochemical reactions. Numerous approaches have attempted to address these challenges. One useful method is to develop the metal oxide materials into nanostructures. [ 3 ] The distinct lithium storage mechanisms and the infl uence of unique structures on the lithium storage properties of the metal oxide materials have been reported in detail. [ 5 ] A series of work on the design of various nanostructures of metal oxide materials has been subsequently carried out, for nanomaterials of different dimensions, hollow structures, and hierarchical structures. [ 5 ] Coating or combining the buffering matrix or conductive materials with metal oxide materials is another way to relieve the severe problems. [36][37][38][39][40][41][42] Various carbon materials, especially novel nanocarbon materials like carbon nanotubes and graphene nanosheets, have been widely studied as the buffering and conductive agent for metal oxide anodes. [43][44][45][46] In our previous review, [ 47 ] the signifi cant effects of graphene nanosheets on tin-based anodes were summarized in detail. It has been concluded that graphene not only contributes as a highly conductive network, but also as a fl exible supporting layer, effectively relieving the volume change and particle aggregation. In addition, different metals and metal oxides that are electrochemically active and Mixed transition-metal oxides (MTMOs), including stannates, ferrites, cobaltates, and nickelates, have attracted increased attention in the application of high performance lithium-ion batteries. Compared with traditional metal oxides, MTMOs exhibit enormous potential as electrode materials in lithium-ion batteries originating from higher reversible capacity, better structural stability, and high electronic conductivity. Recent advancements in the rational design of novel MTMO micro/nanostructures for lithium-ion battery anodes are summarized and their energy storage mechanism is compared to transit...

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The exploration of sodium ion batteries (SIBs) is a profound challenge due to the rich sodium abundance and limited supply of lithium on earth. Here, amorphous SnO2/graphene aerogel (a‐SnO2/GA) nanocomposites have been successfully synthesized via a hydrothermal method for use as anode materials in SIBs. The designed annealing process produces crystalline SnO2/graphene aerogel (c‐SnO2/GA) nanocomposites. For the first time, the significant effects of SnO2 crystallinity on sodium storage performance are studied in detail. Notably, a‐SnO2/GA is more effective than c‐SnO2/GA in overcoming electrode degradation from large volume changes associated with charge–discharge processes. Surprisingly, the amorphous SnO2 delivers a high specific capacity of 380.2 mAh g−1 after 100 cycles at a current density of 50 mA g−1, which is almost three times as much as for crystalline SnO2 (138.6 mAh g−1). The impressive electrochemical performance of amorphous SnO2 can be attributed to the intrinsic isotropic nature, the enhanced Na+ diffusion coefficient, and the strong interaction between amorphous SnO2 and GA. In addition, amorphous SnO2 particles with the smaller size better function to relieve the volume expansion/shrinkage. This study provides a significant research direction aiming to increase the electrochemical performance of the anode materials used in SIBs.

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