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The inherently huge volume expansion during Li uptake has hindered the use of Si‐based anodes in high‐energy lithium‐ion batteries. While some pore‐forming and nano‐architecting strategies show promises to effectively buffer the volume change, other parameters essential for practical electrode fabrication, such as compaction density, are often compromised. Here we propose a new in situ Mg doping strategy to form closed‐nanopore structure into a micron‐sized SiOx particle at a high bulk density. The doped Mg atoms promote the segregation of O, so that high‐density magnesium silicates form to generate closed nanopores. By altering the mass content of Mg dopant, the average radii (ranged from 5.4 to 9.7 nm) and porosities (ranged from 1.4 % to 15.9 %) of the closed pores are precisely adjustable, which accounts for volume expansion of SiOx from 77.8 % to 22.2 % at the minimum. Benefited from the small volume variation, the Mg‐doped micron‐SiOx anode demonstrates improved Li storage performance towards realization of a 700‐(dis)charge‐cycle, 11‐Ah‐pouch‐type cell at a capacity retention of >80 %. This work offers insights into reasonable design of the internal structure of micron‐sized SiOx and other materials that undergo conversion or alloying reactions with drastic volume change, to enable high‐energy batteries with stable electrochemistry. [ABSTRACT FROM AUTHOR]

Silicon oxide‐graphite (SiOx‐G) composites are promising anode materials for building practical high‐energy Li‐ion batteries. To acquire long and safe operation of battery, extensive efforts are made to maintain stable Li storage of SiOx‐G against materials aging and the accompanied performance fade. While previous studies mostly focus on the cycling aging, the calendar aging occurred during battery storage at a high state of charge or high temperature has not received sufficient attention. In this work, a mechanism study on the calendar aging chemistry of fully lithiated SiOx‐G electrodes in half‐cells both at ambient and high temperature (60 °C) is performed. Unmodified SiOx is employed as active materials to inspect the change of thermodynamics properties in the bulk and at interfaces. By excluding the interference from cathode, it is revealed that besides aggravated parasitic reactions happening at interface, Li migration from the lithiated graphite to the vicinal SiOx particles is also responsible for calendar aging of SiOx‐G electrodes, and high‐temperature storage notably accelerates the aging process. This work enriches the fundamental understandings about the multifactor‐coupled aging process of anode materials and sheds lights on rational materials design toward improved calendar life of a high‐energy rechargeable battery. [ABSTRACT FROM AUTHOR]

Micron-sized Si anode promises a much higher theoretical capacity than the traditional graphite anode and more attractive application prospect compared to its nanoscale counterpart. However, its severe volume expansion during lithiation requires solid electrolyte interphase (SEI) with reinforced mechanical stability. Here, we propose a solvent-induced selective dissolution strategy to in situ regulate the mechanical properties of SEI. By introducing a high-donor-number solvent, gamma-butyrolactone, into conventional electrolytes, low-modulus components of the SEI, such as Li alkyl carbonates, can be selectively dissolved upon cycling, leaving a robust SEI mainly consisting of lithium fluoride and polycarbonates. With this strategy, raw micron-sized Si anode retains 87.5% capacity after 100 cycles at 0.5 C (1500 mA g−1, 25°C), which can be improved to >300 cycles with carbon-coated micron-sized Si anode. Furthermore, the Si||LiNi0.8Co0.1Mn0.1O2 battery using the raw micron-sized Si anode with the selectively dissolved SEI retains 83.7% capacity after 150 cycles at 0.5 C (90 mA g−1). The selective dissolution effect for tailoring the SEI, as well as the corresponding cycling life of the Si anodes, is positively related to the donor number of the solvents, which highlights designing high-donor-number electrolytes as a guideline to tailor the SEI for stabilizing volume-changing alloying-type anodes in high-energy rechargeable batteries. The severe volume expansion during the lithiation of micron-sized Si in Li-ion batteries requires a solid electrolyte interphase with reinforced mechanical stability. Here, the authors propose a solvent-induced selective dissolution strategy to regulate the mechanical properties of the interphase. [ABSTRACT FROM AUTHOR]

Ether solvents with superior reductive stability promise excellent interphasial stability with high‐capacity anodes while the limited oxidative resistance hinders their high‐voltage operation. Extending the intrinsic electrochemical stability of ether‐based electrolytes to construct stable‐cycling high‐energy‐density lithium‐ion batteries is challenging but rewarding. Herein, the anion‐solvent interactions were concerned as the key point to optimize the anodic stability of the ether‐based electrolytes and an optimized interphase was realized on both pure‐SiOx anodes and LiNi0.8Mn0.1Co0.1O2 cathodes. Specifically, the small‐anion‐size LiNO3 and tetrahydrofuran with high dipole moment to dielectric constant ratio realized strengthened anion‐solvent interactions, which enhance the oxidative stability of the electrolyte. The designed ether‐based electrolyte enabled a stable cycling performance over 500 cycles in pure‐SiOx||LiNi0.8Mn0.1Co0.1O2 full cell, demonstrating its superior practical prospects. This work provides new insight into the design of new electrolytes for emerging high‐energy density lithium‐ion batteries through the regulation of interactions between species in electrolytes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Poly (poly (ethylene glycol) methacrylate) (PPEGMA) was grafted onto PP separator by N-hydroxyphthalimide (NHPI) catalysis combined with ARGET-ATRP. • Electrolyte wettability of PPEGMA functionalized PP was enhanced evidently compared to that of pristine PP separator. • Rate performance and long cycle ability for cell with the modified PP separator was improved significantly. • The proposed strategy was also applied to modify other polyolefine membranes for advanced applications. Surface modification of polyolefine separators for high performance lithium-ion batteries has been a worthwhile research topic. In this work, poly (poly (ethylene glycol) methacrylate) (PPEGMA) was firstly grafted onto polypropylene (PP) separator based on N-hydroxyphthalimide (NHPI) catalysis and activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP). Bis(2,2,2-trichloroethyl) azodicarboxylate (BTCEAD) was anchored on the surface of PP separators in the presence of NHPI. Then BTCEAD functionalized PP separator initiated the polymerization of PEGMA by ARGET-ATRP. Thus, structure controllable PPEGMA was grafted on the surface of PP separators. The results of contact angle and electrolyte uptake tests demonstrated that electrolyte wettability of PPEGMA functionalized PP separator has been significantly improved. Electrochemical measurements indicated that the ionic conductivity and discharge capacity retention of cells assembled with PPEGMA functionalized PP separators were distinctly higher than that of cells with pristine PP separator. Herein, we presented a new methodology with high efficiency to modify PP separators under mild condition, which was also applied to other polyolefine separator for high performance lithium-ion batteries. The proposed approach might have many other potential applications in membrane modification field. [ABSTRACT FROM AUTHOR]