Key Factors Controlling the Reversibility of the Reaction of Lithium with SnO2 and Sn2 BPO 6 Glass

Abstract

Tin oxide composite glasses represent a new class of material for the anode of Li-ion cells. Using results of experiments on Li/Sn 2 BPO 6 and Li/SnO 2 cells, we identify those factors which are responsible for good charge-discharge capacity retention, First, the grains (those regions which diffract coherently) which make up the particles of the material should be as small as possible. Then, regions of tin which form are kept small and two-phase coexistence regions between bulk Li-Sn alloys of different composition do not occur. The Sn 2 BPO 6 glass represents the smallest grains possible. Second, the particles themselves should be small so that they can each be well contacted by carbon black during electrode manufacture. Third, the voltage range of cycling must be selected so that the tin atoms do not aggregate into large regions which grow in size. This aggregation is evidenced by the growth of peaks in the differential capacity vs. voltage as a function of cycle number. The peaks represent the coexistence between bulk Li-Sn alloy phases which have substantially different volumes. The coexistence is thought to cause fracturing and loss of contact between the grains. Therefore, materials with small particles, small grains, and smooth sloping voltage profiles which do not change with cycle number (as indicated by a stable differential capacity) give the best cycling performance. The selection of the voltage limits for cycling strongly influences the stability of the voltage profile (as illustrated here), so this must be done with much care.

High reversible capacity of SnO2/graphene nanocomposite as an anode material for lithium-ion batteries

“…Thus, the conversion reaction, SnO 2 + 4Li + + 4e − → 2Li 2 O + Sn, which is usually reported to be irreversible [9,41], can become reversible in the SnO 2 /graphene nanocomposite due to the very small Sn nanoparticles [5,27,[46][47][48][49]. It has been reported that the Sn-Li alloying and dealloying reactions only occur below 1.0 V (vs. (Li/Li + )) [4,10,50] and the Li-O bonds are not stable when the charge potential is above 1.3 V [50]. As shown in Fig.…”

SnO2/graphene composite with high lithium storage capability for lithium rechargeable batteries

“…On further lithiation, the Sn metal nanoparticles alloy with Li to form SnLix as the active component. The inactive Li 2 O matrix helps to buffer the volume change of the SnLix alloy and prevents Sn nanoparticles from being mechanically pulverized or disconnected in repeated charge/discharge processes [19][20][21][22]. However, the electrically insulating characteristics of the Li 2 O matrix formed in the first discharge can cause a problem of poor electronic conductivity in the electrode [10,23], and this problem can cause a severe deterioration in the rate capability of the electrode and gives a low efficiency in energy storage due to the large polarization [24].…”

Lithium Isotope Effect Accompanying Electrochemical Intercalation of Lithium into Graphite

“…The chemical reaction occurring is in principle the redox reaction of lithium between Li 0 and Li + . Tin compounds are studied as substitutes of graphite due to their large capacity for lithium [5].…”