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The electrochemical properties of a Li-excess Li 1.18 Ni 0.15 Co 0.15 Mn 0.52 O 2 cathode material in a lithium difluoro (oxalate) borate (LiDFOB, 20 wt%) and lithium hexafluoride phosphate (LiPF 6 , 80 wt%) dual-salt electrolyte are investigated. The use of a dual-salt electrolyte significantly improves the material's electrochemical performance, especially at elevated temperature. The capacity retention of the electrode increases from 24% to 92% after charging-discharging at 55 °C for 100 cycles. Spectroscopic analysis demonstrates that LiDFOB salt suppressed Mn 2+ dissolution into the electrolyte and improved the electrode's electrochemical kinetic properties. In addition, the thermal safety of the fully-charged electrode is improved by the dual-salt electrolyte, which results in high onset temperature and reduces thermal release. [ABSTRACT FROM AUTHOR]

Li-rich layered oxide Li1.18Ni0.15Co0.15Mn0.52O2 (LNCM) is, for the first time, examined as the positive electrode for hybrid sodium-ion battery and its Na+ storage properties are comprehensively studied in terms of galvanostatic charge-discharge curves, cyclic voltammetry and rate capability. LNCM in the proposed sodium-ion battery demonstrates good rate capability whose discharge capacity reaches about 90 mA h g−1 at 10 C rate and excellent cycle stability with specific capacity of about 105 mA h g−1 for 200 cycles at 5 C rate. Moreover, ex situ ICP-OES suggests interesting mixed-ions migration processes: In the initial two cycles, only Li+ can intercalate into the LNCM cathode, whereas both Li+ and Na+ work together as the electrochemical cycles increase. Also the structural evolution of LNCM is examined in terms of ex situ XRD pattern at the end of various charge-discharge scans. The strong insight obtained from this study could be beneficial to the design of new layered cathode materials for future rechargeable sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Li 3 PO 4 coated Li 1.18 Co 0.15 Ni 0.15 Mn 0.52 O 2 cathode materials were prepared by the precipitation method. The Li 3 PO 4 coating process cleans the Li 2 CO 3 impurity on the surface of the material. In addition, a continuous stacking faults region forms in the near-surface region of the material. Electrochemical studies show that Li 3 PO 4 coating improves the activation of Mn 4+ ions, prohibits the growth of solid electrolyte interface film and facilitates the charge transfer reactions at the electrode/electrolyte interface. As a result, the Li 3 PO 4 coated materials show larger discharge capacities, longer cycle life and better rate capability than the un-coated one. With the coating content as small as 1.0 wt%, the material shows a high discharge capacity of 272.5 mAh g −1 at the 0.4C rate and 121.1 mAh g −1 at the 10C rate. The capacity fading rate at 0.4C is only 0.08 % per cycle. Differential scanning calorimetry shows that the exothermic temperature of the fully charged electrode increases from 203.0 °C to 289.7 °C after Li 3 PO 4 coating. And the thermal release reduces from 832.4 J g −1 to 305.5 J g −1 highlighting the improved thermal stability of the Li 3 PO 4 coated material. [ABSTRACT FROM AUTHOR]

Abstract: Carbon coated monoclinic Li3V2(PO4)3 cathode material was prepared by the carbothermal reduction method. Raman scattering showed the amorphous nature of the residual carbon in the material. HRTEM and XPS showed that a small amount of carbon penetrated into the Li3V2(PO4)3 crystallites to form a surface carbon layer with thickness about 5–10nm. The material showed a reversible discharge capacity of 120mAhg−1 (C/4 rate), 115mAhg−1 (1C rate) and 110mAhg−1 (2C rate) in the voltage window of 3.0–4.3V, which kept excellent cycle stability in 300 cycles. The material suffered from capacity loss in the initial ten charge–discharge cycles. The irreversible capacity loss was mainly related to the progressive formation of a solid electrolyte interface (SEI) film which was clearly observed by HRTEM. FTIR analysis showed that the chemical species of the SEI film mainly contained some organic compounds such as ROCO2Li, RCO2Li, and aliphatic, as well as some inorganic compounds such as Li2CO3, Li x PF y or Li x PO y F z . The SEI film tended to be stabilized in the initial several cycles, which led to excellent electrochemical performance during long term cycling. [Copyright &y& Elsevier]

• Our study shows that the diffusion of potassium ions in the host material is not as slow as people think. On the contrary, the insertion and extraction of potassium ions in Prussian blue are very rapid. • Potassium metal anode is the main culprit that limits the performance of the cathode, and the performance of the cathode material is seriously underestimated by the traditional half-cell test. • The using of alloy/carbon composite counter electrode, the deterioration of metal K can be avoided so that the performance of the positive electrode can be fully exerted. Many efforts were made to modify cathode materials for K-ion batteries to improve their performance. However, the improvements are not so significant. Herein, we show that the performance of host materials are limited by metal K counter electrode, which leads to underestimation of materials. With a potassiated alloy/carbon composite counter electrode, the Prussian blue analogue cathode can show outstanding rate capability at 5000 mA g−1 and operate 1000 cycles without capacity fading. Besides, when the anode utilization increased to 72.7%, the battery parameters, such as lifespan, energy and power density, were also promising. This work offers a new perspective for both fundamental and practical research of K-ion batteries. [Display omitted] [ABSTRACT FROM AUTHOR]