Low-strain Co-free Li-rich layered cathode with excellent voltage and capacity stability

Owing to the inherent advantages of low cost and high capacity,cobalt(Co)-free lithium(Li)-rich layered oxides have become one of the most promising cathodes for next-generation high-energy lithium-ion batteries.However,these familial cathodes suffer from serious voltage decay due to many reasons,such as oxygen release and transition metal(TM)migration,which are closely related to nanoscale strain evolution.Here,by combining the synergistic effects of surface integration,bulk doping,and concentration gradient,we successfully construct a Co-free Li-rich layered cathode with a very small volumetric strain(1.05%)between 2.0 and 4.8 V,approaching the critical value of zero strain.Various characterizations indicate that the constructed zero-strain cathode can significantly suppress the TM migration,interfacial reactions,and structural degradation including cracks,lattice defects,phase evolution,and nanovoids,leading to improved voltage stability of Co-free Li-rich layered oxides during the prolonged cycles.This work provides a strategy to eliminate the lattice strain of Li-rich layered cathodes and facilitates the up-scaled application of the as-prepared cathode materials.

An almost full reversible lithium-rich cathode: Revealing the mechanism of high initial coulombic efficiency

Low initial Coulombic efficiency (ICE) is an important impediment to practical application of Li-rich layered oxides (LLOs), which is due to the irreversible oxygen release. It is generally considered that surface oxygen vacancies are conducive to the improvement of ICE of LLOs. To reveal the relation of oxygen vacancies and ICE, sample PLO (Li-Mn-Cr-O) and its treated product (TLO) are comprehensive investigated in this work. During the treated process, part of oxygen atoms return to original constructed vacancies. It makes oxygen vacancies in sample TLO much poorer than those in sample PLO, and induces the formation of Li-poor spinel-layered integrated structure. Electrochemical measurement indicates the ICE of sample PLO is only 80.8%, while sample TLO is almost full reversible with the ICE of ~97.1%. In term of high-energy X-ray diffraction, scanning transmission electron microscopy, X-ray photoelectron spectroscopy and synchrotron hard/soft X-ray absorption spectroscopy, we discover that the ICE is difficult to be improved significantly just by building oxygen vacancies. LLOs with high ICE not only have to construct suitable oxygen vacancies, but also require other components with Li-poor structure to stabilize oxygen. This work provides deep insight into the mechanism of high ICE, and will contribute to the design and development of LLOs for next-generation high-energy lithium-ion batteries.

Electrodeposition of a dendrite-free 3D Al anode for improving cycling of an aluminum-graphite battery

Aluminum-metal batteries show great potential as next-generation energy storage due to their abundant resources and intrinsic safety.However,the crucial limitations of metallic Al anodes,such as dendrite and corrosion problems in conventional aluminum-metal batteries,remain challenging and elusive.Here,we report a novel electrodeposition strategy to prepare an optimized 3D Al anode on carbon cloth with an uniform deposition morphology,low local current density,and mitigatory volume change.The symmetrical cells with the 3D Al anode show superior stable cycling(>450 h)and low-voltage hysteresis(~170 mV)at 0.5 mA cm^(−2).High reversibility(~99.7%)is achieved for the Al plating/stripping.The graphite||Al‐4/CC full batteries show a long lifespan of 800 cycles with 54 mAh g^(−1) capacity at a high current density of 1000 mA g^(−1),benefiting from the high capacitive-controlled distribution.This study proposes a novel strategy to design 3D Al anodes for metallic-Al-based batteries by eliminating the problems of planar Al anodes and realizing the potential applications of aluminum-graphite batteries.

双功能氮氧化钛-碳涂层提升高容量锂离子电池用SiO_(x)的储锂性能

非化学计量微米氧化硅(SiO_(x))由于其高理论容量和低成本,有望成为锂离子电池石墨负极材料的替代品.然而,SiO_(x)的实际应用仍然受到其较差的固有导电性和循环过程中明显的体积变化的阻碍.在本工作中,为了同时解决这些问题,我们使用可规模化的溶剂热和热还原方法制备了具有TiO_(1-y)Ny-C涂层的SiO_(x)基负极材料(SiO_(x)@TiON-C).我们通过系统性研究发现,TiO_(1-y)Ny-C涂层可以适应SiO_(x)循环过程中大的体积变化且有效提高其导电性.因此,SiO_(x)@TiON-C负极具有突出的储锂性能.具体而言,SiO_(x)@TiON-C负极可以在500 mA g^(-1)的电流密度下循环500圈后仍保持750.2 mA h g^(-1)的优异可逆容量,75.1%的初始库仑效率和优异的倍率性能.这项工作为促进下一代锂离子电池微米SiO_(x)基负极材料的实际商业化提供了一种很有前途的方法.

Surface reconstruction establishing Mott-Schottky heterojunction and built-in space-charging effect accelerating oxygen evolution reaction

Structural reconstruction of nanomaterials offers a fantastic way to regulate the electronic structure of active sites and promote their catalytic activities.However,how to properly facilitate surface reconstruction to overcome large overpotential that stimulate the surface reconstruction has remained elusive.Herein,we adopt a facile approach to activate surface reconstruction on Ni(OH)_(2) by incorporating F anions to achieve electro-derived structural oxidation process and further boost its oxygen evolution reaction(OER)activity.Ex situ Raman and X-ray photoemission spectroscopy studies indicate that F ions incorporation facilitated surface reconstruction and promotes the original Ni(OH)_(2)transformed into a mesoporous and amorphous F-NiOOH layer during the electrochemical process.Density functional theory(DFT)calculation reveals that this self-reconstructed NiOOH induces a space-charge effect on the p-n junction interface,which not only promotes the absorption of intermediates species(^(*)OH,^(*)O,and^(*)OOH)and charge-transfer process during catalysis,but also leads to a strong interaction of the p-n junction interface to stabilize the materials.This work opens up a new possibility to regulate the electronic structure of active sites and promote their catalytic activities.