Tailoring the Charge/Discharge Potentials and Electrochemical Performance of SnO₂ Lithium‐Ion Anodes by Transition Metal Co‐Doping

Abstract

It has been shown that the introduction of several transition metal (TM) dopants into SnO2 lithium‐ion battery anodes can overcome the issues associated with the irreversible capacity loss from the conversion reaction of SnO2 and the aggregation of the metallic Sn particles formed upon lithiation. As the choice of the single dopant, however, plays a decisive role for the achievable energy density – precisely its redox potential – we investigate herein TM co‐doped SnO2, prepared by using a readily scalable continuous hydrothermal flow synthesis (CHFS) process, to tailor the dis‐/charge profile and by this the energy density. It is shown that the judicious choice of different elemental doping combinations in samples made via CHFS simultaneously improves the cycling performance and the full‐cell energy density. To support these findings, we realized a lithium‐ion full‐cell incorporating the best performing co‐doped SnO2 as negative electrode and high‐voltage LiNi0.5Mn1.5O4 (LNMO) as positive electrode–to the best of our knowledge, the first full‐cell based on such anode material in combination with LNMO as cathode active material.

The success story of graphite as a lithium-ion anode material – fundamentals, remaining challenges, and recent developments including silicon (oxide) composites

“…For graphite, this difference, also referred to as voltage hysteresis, is relatively small, rendering it additionally favorable compared to most alternatives investigated so far, 111 although some progress has been reported very recently for (pre-lithiated) conversion/alloying-type materials when limiting the de-/ lithiation to a rather narrow potential range. 112 3. Remaining (intrinsic) challenges…”

“…Work on the "electrode pre-lithiation approach", similar to the frequently employed lab-scale approach of rst prelithiating the electrode in half-cell conguration prior to the full-cell assembly (Fig. 14a), 112,[288][289][290][291] was inter alia reported by Kim et al, 292 who developed a scalable roll-to-roll process for the pre-lithiation of the electrode prior to the full-cell assembly by spraying an electrolyte solution onto the electrode tape and bringing it in contact with lithium foil with a separator inbetween ( Fig. 14b), followed by the application of an external short circuit.…”

Overcoming the Challenges of Freestanding Tin Oxide‐Based Composite Anodes to Achieve High Capacity and Increased Cycling Stability

“…[ 2,49 ] Furthermore, a small shoulder at 0.5 V versus Li/Li + and an intense peak at 0.04 V versus Li/Li + can be observed during the first reduction scan, which correspond to the multistep alloying reactions between Sn/Sb and lithium ions with formation of Li 4.4 Sn and Li 3 Sb alloys. [ 2,42,50 ] The peaks at 0.6 and 1.3 V versus Li/Li + observed during the reverse anodic scan correspond to the dealloying reaction and the conversion of Sn/Sb back to ATO. [ 42 ] Similar CV curves are also obtained for the SnO 2 /rGO, SnO 2 /C/rGO, ATO/rGO, and ATO/C‐2/rGO hybrid materials (Figure S17a–d, Supporting Information).…”

“…The improved stability as compared to ATO/rGO can be explained by the newly introduced carbon coating layer which is known to enhance the contact between ATO nanoparticles and rGO sheets upon cycling, thus enabling fast electron transfer, increasing the overall conductivity, stabilizing the large volume changes of the ATO particles during cycling, and also preventing the Sn, Sb, and SnSb nanoparticles from aggregation. [ 11,14,15,50,51 ] Moreover, comparison of the carbon‐coated ATO/C/rGO and SnO 2 /C/rGO composites indicates that antimony doping can lead to higher reversible capacities which may be caused by a better conductivity inside the ATO nanoparticles and an improved reversibility of the electrochemical reactions.…”

Determination of the Volume Changes Occurring for Conversion/Alloying-Type Li-Ion Anodes upon Lithiation/Delithiation

“…Potential alternatives are conversion-type − or alloying-type active materials. , These alternative candidates commonly provide substantially higher specific capacities and, frequently, greater rate capability than graphite. − Nonetheless, both classes of active materials also reveal some fundamental challenges, i.e., a pronounced voltage hysteresis and a rather wide potential window for the complete lithiation/delithiation reaction in the case of conversion-type materials and an extreme volume variation upon lithiation/delithiation in the case of alloying-type compounds. , To overcome these challenges, the synergistic combination of the two reaction mechanisms in one single material has been proposed . Indeed, such conversion/alloying materials (CAMs) provide elevated specific capacities, high energy densities, stabilized long-term cycling, and excellent rate capability. − Very recently, we could also show that full cells incorporating CAMs as an anode may provide substantially enhanced energy efficiencies of up to more than 80% and even more than 90% under certain conditions. ,, …”