No abstract

No abstract

No abstract

Chemical lithiation using lithium metal dissolved in liquid ammonia is introduced for the first time as a viable, potentially scalable method to overlithiate cathode materials, in this case, the 5 V spinel Li1+x Ni0.5Mn1.5O4. In this formula the value of x represents the amount of extra lithium inserted into the spinel. Such overlithiated cathodes can subsequently be used to prelithiate high-energy anodes in a lithium-ion battery configuration during the first charge step. Lithiated 5 V spinel Li1+x Ni0.5Mn1.5O4 cathode materials prepared by this technique show higher first delithiation capacities, confirming the chemically inserted lithium is electrochemically active. Full cells with a Si–graphite anode and the Li1+x Ni0.5Mn1.5O4 (x = 0.62) cathode show a 23% higher reversible capacity in the first cycle than LiNi0.5Mn1.5O4 baseline cells and improved capacity retention. The extra chemically inserted lithium therefore sacrificially compensates for the loss of lithium at the anode, allowing higher utilization of the cathode capacity in following cycles.

The energy density of lithium-ion batteries can be increased by replacing the traditional graphite anode with a high capacity silicon anode. However, volume changes and interfacial instabilities cause a large irreversible capacity and a continual loss of lithium during cycling, which lead to rapid capacity loss. In this work, we add Li5FeO4 (LFO) to a LiNi0.5Mn0.3Co0.2O2 (NMC) cathode as a pre-lithiation additive, which increases the lithium inventory and extends the cycle life of Si-graphite/NMC full cells, and decreases the NMC particle degradation. LFO delivers a large 764 mAh g−1 LFO capacity below 4.7 V vs Li/Li+. By tuning the LFO content in Si-graphite/LFO-NMC full cells, we show higher capacity, improved retention, lower impedance, and superior rate performance compared to full cells without LFO. Post-test characterizations demonstrate that LFO inclusion in the cathode matrix leads to less NMC secondary particle segregation/cracking and a thinner surface reduced layer on the NMC particles. The beneficial effects of LFO endure after the lithium reserve has been exhausted, highlighting a lasting synergy between the lithium source and electrode active materials. This study introduces a new approach to simultaneously increase lithium inventory and reduce cathode degradation, and makes critical advances toward enabling Si anodes for lithium-ion batteries.