Reducing voltage hysteresis of metal oxide anodes to achieve high energy efficiency for Li-ion batteries

In the past two decades,a lot of high-capacity conversion-type metal oxides have been intensively studied as alternative anode materials for Li-ion batteries with higher energy density.Unfortunately,their large voltage hysteresis(0.8-1.2 V) within reversed conversion reactions results in huge round-trip inefficiencies and thus lower energy efficiency(50%-75%) in full cells than those with graphite anodes.This remains a long-term open question and has been the most serious drawback toward application of metal oxide anodes.Here we clarify the origins of voltage hysteresis in the typical SnO2anode and propose a universal strategy to minimize it.With the established in situ phosphating to generate metal phosphates during reversed conversion reactions in synergy with boosted reaction kinetics by the added P and Mo,the huge voltage hysteresis of 0.9 V in SnO_(2),SnO_(2)-Mo,and 0.6 V in SnO2-P anodes is minimized to 0.3 V in a ternary SnO_(2)-Mo-P(SOMP) composite,along with stable high capacity of 936 mA h g^(-1)after 800 cycles.The small voltage hysteresis can remain stable even the SOMP anode operated at high current rate of10 A g^(-1)and wide-range temperatures from 60 to 30℃,resulting in a high energy efficiency of88.5% in full cells.This effective strategy to minimize voltage hysteresis has also been demonstrated in Fe2O3,Co3O4-basded conversion-type anodes.This work provides important guidance to advance the high-capacity metal oxide anodes from laboratory to industrialization.

Plasma assisted synthesis of LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2) cathode materials with good cyclic stability at subzero temperatures

Layered Ni-rich cathode materials,LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622),are synthesized via solid reaction assisted with a plasma milling pretreatment,which is resulted in lowering sintering temperatures for solid precursors.The plasma milling pretreated NCM622 cathode material sintered at 780℃(named as PM-780)demonstrates good cycling stability at both room and subzero temperatures.Specifically,the PM-780 cathode delivers an initial discharge capacity of 171.2 mAh g^(-1) and a high capacity retention of 99.7%after 300 cycles with current rate of 90 mA g^(-1) at 30℃,while stable capacities of 120.3 and 94.0 m Ah g^(-1) can be remained at-10℃and-20℃in propylene carbonate contained electrolyte,respectively.In-situ XRD together with XPS and SEM reveal that the NCM622 cycled at-10℃presented better structural stability and more intact interface than that of cathodes cycled at 30℃.It is also found that subzero temperatures only limit the discharge potential of NCM622 without destroying its structure during cycling since it still exhibits high discharge capacity at 30℃after cycled at subzero temperatures.This work may expand the knowledge about the low-temperature characteristics of layered cathode materials for Li-ion batteries and lay the foundation for its further applications.

Sn Alloy and Graphite Addition to Enhance Initial Coulombic Efficiency and Cycling Stability of SiO Anodes for Li-Ion Batteries

Silicon monoxide(SiO)has aroused increased attention as one of the most promising anodes for high-energy density Li-ion batteries.To enhance the initial Coulombic efficiencies(ICE)and cycle stability of SiO-based anodes,a new facile composition and electrode design strategy have been adapted to fabricate a SiO-Sn-Co/graphite(G)anode.It achieves a unique structure where tiny milled SiO-Sn-Co particles are dispersed among two graphite layers.In this hybrid electrode,Sn-Co alloys promoted Li;extraction kinetics,and the holistic reversibility of SiO and graphite enhanced the electrical conductivity.The SiO-Sn-Co/G electrode delivered an average ICE of 77.6%and a reversible capacity of 640 mAh g^(-1)at 800 mA g^(-1),and the capacity retention was above 98%after 100 cycles,which was much higher than that of the SiO with an ICE of 55.3%and a capacity retention of 50%.These results indicated that this was reliable method to improve the reversibility and cycle ability of the SiO anode.Furthermore,based on its easy and feasible fabrication process,it may provide a suitable choice to combine other alloy anodes with the graphite anode.

Li_(2)CO_(3)诱导生长稳定SEI膜:提升SnO_(2)储锂可逆性和稳定性的有效策略

电极与电解液之间的界面不稳定极大地损害了高比容量的储锂SnO_(2)负极锂化和脱锂过程的可逆性和循环稳定性.本文提出了一种简单的改善固态电解质膜(SEI)不稳定问题的策略.通过将SnO_(2)与石墨和SEI的无机成分(Li_(2)CO_(3)或LiF)复合来增强SnO_(2)的界面稳定性和储锂可逆性,获得了具有高库仑效率、高容量和长寿命的复合电极.其中,SnO_(2)-Li_(2)CO_(3)/G电极在0.2 A g^(-1)的电流密度下具有高达79.6%的首次库仑效率和927.5 mA h g^(-1)的可逆充电比容量,在1 A g^(-1)的电流密度下,经过900次循环仍能得到超过1200 mA h g^(-1)的稳定充电比容量,表现出优异的长循环稳定性能.此外,通过与Li_(2)CO_(3)球磨复合,合金化Si基负极、转化类MnO_(2)、Fe_(3)O_(4)负极的首次库仑效率和循环稳定性也可显著提升.因此,本文中提出的利用SEI膜中稳定成分与负极材料进行复合的策略对于提升大容量储锂电极材料的电化学性能具有普适性.