Silicon (Si) is a promising anode material for lithium-ion batteries but has long been suffering from low conductivity, drastic volume change, poor cycling performance, etc. Adding SiO, Al, etc. to form Si-based binary composite films can improve some properties but have to give up others. Here, we prepared a ternary Si–SiO–Al composite film anode by adding SiO and Al together into Si using magnetron sputtering. This film has an extraordinary combination of conductivity, specific capacity, cycling stability, rate performance, etc., when compared with its binary and unary counterparts. While both SiO and Al can separately mitigate anode cracking resulting from the huge volume expansion during the lithiation/delithiation cycling process, the synergetic effect of adding SiO and Al together to form a ternary composite film can produce much better results. This film maintains an island structure that can efficiently buffer the volume expansion during the cycling process, giving rise to superior cycling performance and excellent rate performance. In addition, the cosputtered Al improves the electrical conductivity of the anode at the same time. This unique combination of anode properties, together with the low cost, suggests that the Si–SiO–Al composite film has the potential to be commercialized as a binder-free anode for lithium-ion batteries. This work also provides an efficient means to modulate the anode properties with more degrees of freedom.

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Nickel-rich layered cathode LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) is the most promising cathode material due to its high specific capacity and lower cost than lithium cobalt oxides. However, NCM811 suffers from structural instability and capacity degradation during charge−discharge cycles. Herein, we report a strategy to construct a conductive network by employing a holistic Ge coating, which interconnects Mg-doped NCM811 particles. Dopant Mg ions, serving as a "pillar" in the Li slab of NCM811, substantially enhance the structural reversibility. The Ge particles are not only coated on the electrode surface but also enter into the electrode pores to form a multidimensional conductive structure, which improves the conductivity of the electrode and slows down the interface side reaction, thus minimizing the irreversible loss of NCM811 upon long cycling. The modified NCM811 electrode delivers a high discharge capacity (∼204 mAh g −1 at 0.1C), excellent rate performance (∼155 mAh g −1 at 10C), and high capacity retention (83% after 200 cycles) even at 4.4 V. Additionally, a cylindrical full battery with graphite/modified NCM811 undergoes 1000 cycles with 86% capacity retention at 2C.

SiO is a promising alternative to Si as the anode material for lithium-ion batteries, but it still suffers from a low initial coulomb efficiency, poor electrical conductivity, unstable cycling performance, etc. Various strategies have been attempted to solve these issues but were left unsolved. In this work, we propose a simple strategy that checks all of the right boxes by presetting a lithium source electrolyte (Li2CO3) into a SiO film using the magnetron sputtering method. The preset lithium source electrolyte provides both the lithium ions and the electrolyte required for the formation of a solid electrolyte interphase and thus significantly improves the initial coulomb efficiency. The lithium source electrolyte also acts as a medium to facilitate the growth of a solid electrolyte interphase inside this composite film in addition to its surfaces. The interior interphase provides an efficient and fast pathway for lithium-ion transmission during the lithiation process and thus improves the anode conductivity and the rate performance. The interior interphase also suppresses the brittle fracture by buffering the dramatic volume change during the lithiation/delithiation process and stabilizes the cycling performance substantially. In addition, this strategy is safe, green, and of low-cost, when compared to others, and provides a feasible way to commercialize the SiO anode for lithium-ion batteries.

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Li-rich Mn-based cathode materials possess a high specific capacity, but their application is hindered by inherent anion activity and surface instability. Herein, we propose a design of a spinel heterogeneous...