No abstract

No abstract

ambient temperature inevitably, [4][5][6][7] which build up a significant obstacle to the fast charging of LIBs at low temperatures. In addition, the potential polarization caused by the increased internal resistance at subzero temperature can easily reach the lithium plating during charging for the graphite anode with low operating potential, resulting in small charging capacity, inability to charge and even safety hazards. [8] For the latter, the awkward cycling ability of the anode at elevated temperature is mainly due to the increased instability of the electrolyte, in which the in situ-formed SEI is unable to avoid the oxidative decomposition of the electrolyte at a high potential, resulting in unstable electrode cycling and abnormal consumption of electrolyte. Therefore, to achieve a superior operation at a wide temperature, the electrode material in LIBs needs to have decent Li + conductivity at sub-zero temperature and have stable SEI with fast Li + transport at elevated temperature.Recently, extensive efforts have been committed to promote the low-temperature Li storage capability of the anode materials, including alloying-type Sn-Cu and Sn-C, [9] conversion-type metal oxides, such as V 2 O 5 , [10] Co 3 O 4 , [11] CoFe 2 O 4 , [12] MnO, [13] and metal sulfide MnS. [14] It has been shown that all these anode materials can discharge the LIBs successfully from subzero temperature to −25 °C, however, they cannot maintain cycle stability at high temperatures. At the same time, the reversible capacity of the alloy anodes yielded at low-temperature (≈200 mA h g −1 ) is far below their theoretical capacity. Recently, we have found that the SnO 2 anode can deliver stable and high capacity at subzero temperature. [15] In a commercial propylene carbonate (PC) based electrolyte, throughout 100 cycles at −20 °C, 71% of its 30 °C capacity comes from the moderate operating temperature. It is very significant that the polymorphic transformation of β-Sn to α-Sn at temperature below 13 °C is helpful to build faster transport channels for Li + during de-/ lithiation because the diffusion barrier of Li atoms in the α-Sn is lower than that in the β-Sn. [16][17][18] These show that the SnO 2based anode materials can be excellent candidates for low temperature LIBs.However, there are still great challenges for wide temperature application of SnO 2 -based anode materials. First, pure SnO 2 electrode suffers from inferior cycling stability and reversibility of conversion reaction at room temperature and above Lithium-ion batteries (LIBs) suffer dramatic energy reduction, and are even unable to safely charge below -10 °C, due to sluggish Li + transport kinetics in the anode, electrolyte and solid electrolyte interphase (SEI), as well as large overpotential which causes Li plating on the anode surface. Herein, a SnO 2 -LiF-graphite (SLG) composite anode is developed for wide temperature application. The SLG with a propylene carbonate electrolyte delivers a stable capacity of more than 900 mA h g -1 at 60 °C with 100 mA g -1 , mai...

No abstract

No abstract

Among the promising high‐capacity anode materials, SnO2 represents a classic and important candidate that involves both conversion and alloying reactions toward Li storage. However, the inferior reversibility of conversion reactions usually results in low initial Coulombic efficiency (ICE, ≈60%), small reversible capacity, and poor cycling stability. Here, it is demonstrated that by carefully designing the interface structure of SnO2–Mo, a breakthrough comprehensive performance with ultrahigh average ICE of 92.6%, large capacity of 1067 mA h g−1, and 100% capacity retention after 700 cycles can be realized in a multilayer Mo/SnO2/Mo electrode. Furthermore, high capacity retentions are also achieved in pouch‐type Mo/SnO2/Mo||Li half cells and Mo/SnO2/Mo||LiFePO4 full cells. The amorphous SnO2/Mo interfaces, which are induced by redistribution of oxygen between SnO2 and Mo, can precisely adjust the reversible capacity and cycling stability of the multilayers, while the stable capacities are parabolic with the interfacial density. Theoretical calculations and in/ex situ investigation reveal that oxygen redistribution in SnO2/Mo heterointerfaces boosts Li‐ion transport kinetics by inducing a built‐in electric field and improves the reaction reversibility of SnO2. This work provides a new understanding of interface–performance relationship of metal–oxide hybrid electrodes and pivotal guidance for creating high‐performance Li‐ion batteries.

No abstract

The unstable interfaces between a SnO 2 anode and an electrolyte in a Li-ion battery dramatically impair the reversibility and cycling stability of lithiation and delithiation, resulting in low roundtrip Coulombic efficiency (CE) and fast capacity decay of SnO 2 -based anode materials. Herein, a simple strategy of modifying the solid electrolyte interphase (SEI) is developed to enhance the interfacial stability and lithium storage reversibility of SnO 2 by compositing it with graphite (G) and an inorganic component of the SEI, such as Li 2 CO 3 or LiF, which results in the SnO 2 -Li 2 CO 3 /G and SnO 2 -LiF/G composite anodes with high CEs, large capacities and long cycle lives. Specifically, the SnO 2 -Li 2 CO 3 /G composite anode exhibits an average initial CE of 79.6%, a stable reversible capacity of 927.5 mA h g −1 at a current rate of 0.2 A g −1 , and a charge capacity over 1200 mA h g −1 with a CE >99% after 900 cycles at a higher current rate of 1 A g −1 . It is revealed that Li 2 CO 3 induces the formation of a dense and stable SEI on SnO 2 grains and inhibits the coarsening of nanosized Sn particles generated from the dealloying reaction in the SnO 2 -Li 2 CO 3 /G electrode. Moreover, the CE and cycling stability of other alloying-type (Si) and conversion reaction (MnO 2 and Fe 3 O 4 ) anodes can also be greatly promoted by simply milling with Li 2 CO 3 . Thus, a universal and simple strategy is developed to achieve highly reversible and stable electrodes for large-capacity lithium storage.