Rate-Dependent Failure Mechanisms and Mitigating Strategies of Anode-Free Lithium Metal Batteries.

Anode-free lithium (Li) metal batteries (AFLMBs) could provide a specific energy over 500 Wh/kg, but their cycle life requires improvement. In this work, we propose a new method to calculate the real Coulombic efficiency (CE) of the Li metal during the cycling of AFLMBs. Through this approach, we find low rate discharging unfavorable for Li CE, which is mitigated through electrolyte optimization. In contrast, high rate discharging boosts Li reversibility, indicating AFLMBs to be intrinsically suited for high power use cases. However, AFLMBs still fail rapidly, due to the Li stripping overpotential buildup, which is mitigated by a zinc coating that enables a better electron/ion transferring network. We believe well-targeted strategies need to be better developed to synergize with the intrinsic features of AFLMBs to enable their commercialization in the future.

Adjustable Mixed Conductive Interphase for Dendrite-Free Lithium Metal Batteries.

Lithium (Li) metal batteries with high energy density are of great promise for next-generation energy storage; however, they suffer from severe Li dendritic growth and an unstable solid electrolyte interphase. In this study, a mixed ionic and electronic conductive (MIEC) interphase layer with an adjustable ratio assembled by ZnO and Zn nanoparticles is developed. During the initial cycle, the in situ formed Li2O with high ionic conductivity and a lithiophilic LiZn alloy with high electronic conductivity enable fast Li+ transportation in the interlayer and charge transfer at the ion/electron conductive junction, respectively. The optimized interface kinetics is achieved by balancing the ion migration and charge transfer in the MIEC Li2O-LiZn interphase. As a result, the symmetric cell with MIEC interphase delivers superior cycling stability of over 1200 h. Also, Li||Zn-ZnO@PP||LFP (LFP = LiFePO4) full cells exhibit long cyclic life for 2000 cycles with a very high capacity retention of 91.5% at a high rate of 5 C and stable cycling for 350 cycles at a high LFP loading mass of 13.27 mg cm-2.

Boosting the Electrochemical Performance of Li- and Mn-Rich Cathodes by a Three-in-One Strategy.

There are plenty of issues need to be solved before the practical application of Li- and Mn-rich cathodes, including the detrimental voltage decay and mediocre rate capability, etc. Element doping can effectively solve the above problems, but cause the loss of capacity. The introduction of appropriate defects can compensate the capacity loss; however, it will lead to structural mismatch and stress accumulation. Herein, a three-in-one method that combines cation-polyanion co-doping, defect construction, and stress engineering is proposed. The co-doped Na+/SO42- can stabilize the layer framework and enhance the capacity and voltage stability. The induced defects would activate more reaction sites and promote the electrochemical performance. Meanwhile, the unique alternately distributed defect bands and crystal bands structure can alleviate the stress accumulation caused by changes of cell parameters upon cycling. Consequently, the modified sample retains a capacity of 273 mAh g-1 with a high-capacity retention of 94.1% after 100 cycles at 0.2 C, and 152 mAh g-1 after 1000 cycles at 2 C, the corresponding voltage attenuation is less than 0.907 mV per cycle.