High-rate capability of bamboo-like single crystalline LiFePO₄ nanotubes with an easy access to b-axis 1D channels of olivine structure

Abstract

Bamboo-like vertically standing LFP nanotube bundles enable a better accessibility for Li-ion movement along 1D-channels in b-axis of olivine structure.

Sol/Antisolvent Coating for High Initial Coulombic Efficiency and Ultra-stable Mechanical Integrity of Ni-Rich Cathode Materials

“…The improved lithium-ion diffusion coefficient of the crystalline LiBO 2 coating is further confirmed by CV analysis at varied scan rates from 0.1 to 0.5 mV s –1 in the voltage range of 2.8–4.3 V based on the Randles–Sevcik equation as follows: , where I p is the peak current (A), m is the mass of the active material, R is the gas constant, F is the Faraday constant, and T is the absolute temperature (298.15 K). Li + concentration C is determined referring to one Li + occupying on average a unit cell, i.e., 1.635 × 10 –2 mol cm –3 for NCM with a unit cell volume of 101.58 A ̊ 3 and 1.630 × 10 –2 mol cm –3 for LiBO 2 -coated NCM with a unit cell volume of 101.91 A ̊ 3 based on the cell refinements.…”

Influence of Morphology and Compositional Mixing on the Electrochemical Performance of Li-Rich Layered Oxides Derived from Nanoplatelet-Shaped Transition Metal Oxide–Hydroxide Precursors

“…where D Li is the lithium-ion diffusion coefficient (cm 2 s −1 ), K is a constant, Z′ is the real part of the Nyquist plot (Ω), R is a gas constant, T is room temperature (298 K), A is the electrode surface area (1.76 cm 2 ), n is the number of charges transferred during redox, F is the Faraday constant (96 485 C mol −1 ), C is the lithium-ion concentration in the cathode (mol cm −3 ), and ω is the frequency. Although smaller particles specifically in the nanoscale dimensions are known to shorten the lithium-ion diffusion distance in cathodes, 19,20,39 here, LMNC-06 with micro-sized particles (Figure 5d) exhibits a slightly lower diffusion coefficient. The estimated lithium-ion diffusion coefficient is 7.26 × 10 −18 cm 2 s −1 for the LMNC-06 cathode.…”

“…Finally, the long slope line [Warburg line (W)] of the lower frequency region is attributed to Li + migration in the solid phase. 15,19 The four spectra were fitted with the equivalent circuit, as shown in Figure 9c, and parameters obtained from the fit are given in Table 3. Interestingly, the cathode LMNC-00, which lacks the monoclinic phase, shows a higher R sf resistance of 677 Ω.…”

“…The intercept in Z ′ in the high-frequency (1 MHz) region is related to the solution resistance ( R e ), while the intercepts of the semicircles at the high-to-intermediate frequency region and low-frequency region correspond to the surface film resistance ( R sf ) and charge transfer resistance ( R ct ) in the solid phase, respectively. Finally, the long slope line [Warburg line ( W )] of the lower frequency region is attributed to Li + migration in the solid phase. , The four spectra were fitted with the equivalent circuit, as shown in Figure c, and parameters obtained from the fit are given in Table . Interestingly, the cathode LMNC-00, which lacks the monoclinic phase, shows a higher R sf resistance of 677 Ω.…”

“…Solution-based cathode preparation is one of the best methods to control morphology, with the ability to obtain 1D or 2D microstructures by changing the synthesis conditions. Moreover, this method can yield an atomic level of mixing of transition metals (Ni, Mn, and Co) in the compound, which is vital when two different phases should be mixed uniformly down to an atomic level in a composite. ,,, In the literature, to the best of our knowledge, there is no systematic study made for a wide range of NMC/LMO compositions for the hydrothermally synthesized particles with nanoplatelet morphology. Table S2 of the Supporting Information summarizes few studies that have focused on understanding electrochemical property changes in LLOs made over a wide range of the NMC/LMO ratio using other techniques (like self-combustion, co-precipitation, etc.…”