This study reports the preparation of Al2O3 and TiO2 coatings on the as-prepared LiCoO2 electrodes using atomic layer deposition (ALD). A thin Al2O3 ALD coating was shown to eliminate capacity fading effectively during repeated charging and discharging, whereas a TiO2 coating led to significant improvement only at high cycle numbers. An analysis of the differential capacity versus potential curves suggests that this poorer cycling performance could be related to the participation of the TiO2 thin film in the redox reaction. Graphical representation of the energy levels of the various ALD coatings on LiCoO2 during charging and discharging indicated that the redox current is impeded at the Al2O3–LiCoO2 junction, whereas electrons and holes were energetic enough to flow into the TiO2 because of the smaller band gap energy. The barrier between the valence band maxima of TiO2 and LiCoO2 expands as the charge–discharge cycle number increases, eventually making TiO2 redox-inactive. These conclusions are supported by both XPS spectra and the cycle performance in the established literature references. Our results suggest that large band gap materials should be considered to be potentially useful ALD coatings on cathode materials.

A substantial increase in charging capacity over long cycle periods was made possible by the formation of a flexible weblike network via the combination of Al2O3 atomic layer deposition (ALD) and the electrolyte additive vinylene carbonate (VC). Transmission electron microscopy shows that a weblike network forms after cycling when ALD and VC were used in combination that dramatically increases the cycle stability for the Si composite anode. The ALD-VC combination also showed reduced reactions with the lithium salt, forming a more stable solid electrolyte interface (SEI) absent of fluorinated silicon species, as evidenced by X-ray photoelectron spectroscopy. Although the bare Si composite anode showed only an improvement from a 56% to a 45% loss after 50 cycles, when VC was introduced, the ALD-coated Si anode showed an improvement from a 73% to a 11% capacity loss. Furthermore, the anode with the ALD coating and VC had a capacity of 630 mAh g(-1) after 200 cycles running at 200 mA g(-1), and the bare anode without VC showed a capacity of 400 mAh g(-1) after only 50 cycles. This approach can be extended to other Si systems, and the formation of this SEI is dependent on the thickness of the ALD that affects both capacity and stability.

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Predicting the electrochemical performance of active materials before their assembly in lithium ion batteries would be a path to cutting costs and time for assembling coin cells and running charging and discharging tests. Therefore, it is valuable to establish a statistical model to precisely predict the electrochemical performance of active materials in lithium ion batteries before cell assembly. In this study, we employed LiFePO 4 as the cathode active material. We measured the properties of LiFePO 4 powder, and then prepared cathode electrodes and ran electrochemical experiments. The acquired material property parameters and the electrochemical scores were correlated using multivariate linear regression models. Using these models, we can predict electrochemical performance prior to cell assembly. In this study, we collected 11 different commercial LiFePO 4 powders. We first used XRD, FTIR, and EA techniques to measure the crystal structure, vibration of PO 4 3− functional group, and the carbon content, respectively. Next we made the cathode electrodes using these 11 LiFePO 4 products and assembled them into coin cells, we then ran capacity tests at various current rates and cycleability tests at a 2 C current rate for 1000 cycles. Estimates of the regression coefficients in the regression models were calculated by the least squares method, and thus the regression models were established. We hope the models can act as references for effectively estimating capacity, rate and cycle performances based on the structure, functional groups, and carbon content properties of LiFePO 4 . The regression models can be expanded to consider the effects of additional material properties, and to predict other electrochemical properties. We expect to popularize this powerful material science statistical predictive strategy, to allow future researchers to predict the performance of products in a cost-effective and timely manner.

In this study, two cathode materials were synthesized (Li 2 Mn 0.5 Fe 0.5 SiO 4 and Li 2 Mn 0.2 Fe 0.8 SiO 4 ). The intrinsic characteristics and electrochemical performance of these materials were investigated. These silicate cathode materials have several advantages such as high safety, low cost, low environmental toxicity, and high theoretical energy density. However, they have some drawbacks that must be addressed, including low electronic conductivity and low ionic diffusivity, which limit their practical application in lithium-ion batteries. The Li 2 Mn x Fe 1−x SiO 4 /C composite materials were prepared using the sol-gel method. The X-ray diffraction patterns of the synthesized Li 2 Mn x Fe 1-x SiO 4 /C composite materials exhibited favorable crystallinity. Pitch was coated on the synthesized composite materials to improve their electronic conductivity. Raman spectroscopy confirmed the high graphitization of the carbon coatings. The discharge capacity of the pitch-coated Li 2 Mn 0.2 Fe 0.8 SiO 4 /C (Li 2 Mn 0.2 Fe 0.8 SiO 4 /C/pitch) cathode was 183 mAh g −1 delivered in the first cycle at a rate of 0.1 C. The battery cycle retention was 85% after 30 cycles, demonstrating an excellent cycle life compared with those reported in previous studies. These cathode materials have high potential for application in lithium-ion batteries.