Lithium-ion batteries are still the highest-performing commercialized rechargeable batteries, wherein graphite is used as the anode due to its high stability, very low irreversible capacity loss, and low cost. However, being low (372 mAh g-1, LiC6) in theoretical capacity and inability to offer high power, alternate high-capacity anode materials are being sought as potential replacements. Alloying and conversion cum alloying anodes, in this context, become an attractive choice due to their combinatorial ability to deliver high energy and power densities. Given a proper synthetic materialistic understanding, conversion cum alloying anodes can often come up with reversible capacities beyond their theoretical limit. However, deep synthetic, electrochemical and mechanistic understanding in this regard to achieve reversible and reproducible capacities beyond theoretical limits has not been researched to a significant extent. This study offers a detailed mechanistic understanding of how a conversion cum alloying anodic system can deliver a capacity which can go beyond the theoretical limit. This study explored a dedicated synthesis of mix-phase tin oxides (SnII and SnIV oxides) uniformly distributed on an in-situ reduced graphene oxide matrix that could reversibly show a Lithium-ion storage capacity way beyond the theoretical limit. Manipulation of defect density distribution on the reduced graphene oxide matrix in situ reversibly forms Lithium hydroxide which was proven to be the fact of this extra high capacity. The reported material was noted to deliver a high reversible capacity of 2604 mAh g−1 at a current density of 0.1 A g−1 (along with superior rate capability) which is way beyond its theoretical limit. The whole concept was taken further to a practical Li-ion full battery (keeping LiNi0.5Mn0.3Co0.2O2 as the cathodic counterpart) and it could deliver a reversible capacity of f 570 mAh g−1 (based on the anode weight)

Realization and understanding of reversible lithium ion storage capacity beyond theoretical limit in a mix-phase tin-based oxide conversion anode

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