Carbon coating and Al-doping to improve the electrochemistry of Li₂CoSiO₄ polymorphs as cathode materials for lithium-ion batteries

Abstract

Conductive carbon framework, stable polymorphs, and the control of impurity are crucial to achieve advanced performance for insulating Li2CoSiO4.

Prospect and Status of Polyanionic Lithium Cobalt Silicates as High Energy‐Density and Safe Cathode Materials for Lithium‐Ion Batteries

“…Very interesting, through the systematic change of Al‐doping contents, we showed the Si‐site doping can effectively inhibit the formation of TP phase in the process of carbon coating and obtain a high‐purity DP phase. [ 22 ] Our doping on Si sites with P, Al, and V presents the same phenomena. [ 12,22,23 ] But doping on Co site, for example, by Mn, does not have this effect, cf.…”

“…Raman spectroscopy of the coated samples displays two bands around 1352 and 1582 cm −1 corresponding to the typical D (sp 3 type) and G (sp 2 type) bands of carbon. The intensity ratio between D and G bands ( I D / I G ) falls in the range of 1.4–1.5, [ 22 ] which is often the optimized range for good electrical conductivity of polyanionic cathodes, LFP/C, LFSO/C, and LMSO/C nanocomposites. Brunauer−Emmett−Teller (BET) analysis of the isothermal adsorption of N 2 on the surface of particles reveals the mixed type‐II/IV curves and H‐3 hysteresis, [31a] similar to that reported for LFSO, which indicates the presence of mesopores in the ranges of 2–50 nm in our samples.…”

“…Figure 5 compiles the initial charging and discharging profiles of LCSO systems reported in our recent publications. [ 12,22,23,31a,35 ] Spherical (with the secondary particle size ≈900 nm) and low‐dimensional sheet‐like LCSO/C material can deliver charge and discharge capacities at 212/116 and 281/147 mAh g −1 , respectively, between 2 and 4.6 V [31a] . The improved reversibility is largely attributed to the optimal ion transport channel between the electrolyte and nanostructures of the pure LCSO/C materials.…”

“…In addition, we found that using only a small amount of Al doping can achieve similar higher electrochemical reversibility at Li 2 CoSi 0.96 Al 0.04 O 4 at 331 and 140 mAh g −1 for the charge and discharge capacity, respectively. [ 22 ] The underlying mechanism is attributed to the mixture polymorphs of β II and β I phases.…”

“…Previous works reported nearly zero cycling capacity and realized only about %110 mAh g À1 reversible capacity in the first discharging, as shown in Table 2. [16][17][18][19][20][21][22][23] However, one electrochemical character catches our attention. Its discharge voltage plateaus seem be around 4 V, which ideally matches the 4 V window of the commercial organic electrolytes and is also higher than the 3.3 V of LFP.…”