High capacity battery cathode prelithiation to offset initial lithium loss

Loss of lithium in the initial cycles appreciably reduces the energy density of lithium-ion batteries. Anode prelithiation is a common approach to address the problem, although it faces the issues of high chemical reactivity and instability in ambient and battery processing conditions. Here we report a facile cathode prelithiation method that oers high prelithiation ecacy and good compatibility with existing lithium-ion battery technologies. We fabricate cathode additives consisting of nanoscale mixtures of transition metals and lithium oxide that are obtained by conversion reactions of metal oxide and lithium. These nanocomposites aord a high theoretical prelithiation capacity (typically up to 800 mAh g−1 , 2,700 mAh cm−3 ) during charging. We demonstrate that in a full-cell configuration, the LiFePO4 electrode with a 4.8% Co/Li2O additive shows 11% higher overall capacity than that of the pristine LiFePO4 electrode. The use of the cathode additives provides an eective route to compensate the large initial lithium loss of high-capacity anode materials and improves the electrochemical performance of existing lithium-ion batteries.clos

Free-standing Fe2O3 nanomembranes enabling ultra-long cycling life and high rate capability for Li-ion batteries

With Fe(2)O(3) as a proof-of-concept, free-standing nanomembrane structure is demonstrated to be highly advantageous to improve the performance of Li-ion batteries. The Fe(2)O(3) nanomembrane electrodes exhibit ultra-long cycling life at high current rates with satisfactory capacity (808 mAh g(−1) after 1000 cycles at 2 C and 530 mAh g(−1) after 3000 cycles at 6 C) as well as repeatable high rate capability up to 50 C. The excellent performance benefits particularly from the unique structural advantages of the nanomembranes. The mechanical feature can buffer the strain of lithiation/delithiation to postpone the pulverization. The two-dimensional transport pathways in between the nanomembranes can promote the pseudo-capacitive type storage. The parallel-laid nanomembranes, which are coated by polymeric gel-like film and SEI layer with the electrolyte in between layers, electrochemically behave like numerous “mini-capacitors” to provide the pseudo-capacitance thus maintain the capacity at high rate

Visualizing non-equilibrium lithiation of spinel oxide via in situ transmission electron microscopy

Spinel transition metal oxides are important electrode materials for lithium-ion batteries, whose lithiation undergoes a two-step reaction, whereby intercalation and conversion occur in a sequential manner. These two reactions are known to have distinct reaction dynamics, but it is unclear how their kinetics affects the overall electrochemical response. Here we explore the lithiation of nanosized magnetite by employing a strain-sensitive, bright-field scanning transmission electron microscopy approach. This method allows direct, real-time, high-resolution visualization of how lithiation proceeds along specific reaction pathways. We find that the initial intercalation process follows a two-phase reaction sequence, whereas further lithiation leads to the coexistence of three distinct phases within single nanoparticles, which has not been previously reported to the best of our knowledge. We use phase-field theory to model and describe these non-equilibrium reaction pathways, and to directly correlate the observed phase evolution with the battery's discharge performance