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Lithium ion batteries (LIBs) as the mainstream rechargeable batteries are widely used in industrial production and life. However, it is hard to meet the demand in the future due to the lack of lithium resources. At the same time, increasingly scarce lithium resources will increase the cost of LIBs. In contrast, potassium is abundant in the earth's crust, and available researches suggest that rechargeable potassium ion batteries (KIBs) may be a promising substitute for LIBs. In this paper, the research progress of non-aqueous KIBs is reviewed, including cathode materials, anode materials, electrolytes, binders, opportunities and future challenges. Firstly, cathode and anode materials are summarized according to the different reaction types. Secondly, the application and influence of electrolytes and binders for non-aqueous KIBs are also discussed. Moreover, in order to promote the advancement for non-aqueous KIBs, the main future challenges and some solutions are also proposed. Image 1 • The present situation and advantages of non-aqueous KIBs are discussed. • A review of electrode materials, electrolytes and binders for KIBs. • Challenges and opportunities for KIBs in the future are pointed out. [ABSTRACT FROM AUTHOR]

Layered LiNiCoMnO was synthesized by a citric acid assisted solid-state method. The structure and electrochemical properties of the LiNiCoMnO materials were investigated. XRD analysis indicated the as-synthesized LiNiCoMnO was with the layered α-NaFeO structure. The discharge capacity was about 154 m·Ahg at 0·1 °C rate in the range of 2·0-4·5 V. The kinetics of the LiNiCoMnO materials was investigated by the galvanostatic intermittent titration technique (GITT) method. The lithium ion diffusion coefficient of the LiNiCoMnO was determined in the range of 10 − 10cm· s as a function of voltage of 3·7−4·5 V. [ABSTRACT FROM AUTHOR]

Abstract: Lithium-ion battery cathode material Li1+x V3O8 was synthesized by a tartaric acid assisted sol–gel method and thermally treated at 350°C, 450°C and 550°C for 3h for the formation of Li1+x V3O8 phase. The synthesized samples were fully characterized by FTIR, TG/DTA, XRD and charge–discharge tests. Li1+x V3O8 material synthesized by tartaric acid assisted route, followed by heat treatment at 450°C for 3h shows best electro-chemical performance. It shows a high initial capacity of 249mAhg−1 and still reserves a discharge capacity of 260mAhg−1 after 50 cycles. Moreover, for all tartaric assisted products, no capacity decadence is observed in 50 cycles. The in situ X-ray measurements reveal a two-phase transition mechanism in the lithium intercalation/deintercalation process. During lithium extraction, the structure of the delithiated compound changes from Li4V3O8 (x >3.1) to the original LiV3O8 phase (x <1.4) via the coexistence state of these two phases (1.4< x <3.2). An obvious contraction, especially at Li(3)–Li(4) transition, along a axis and a slight expansion along b axis are also observed. [Copyright &y& Elsevier]

The overdischarge behaviors of LiFePO, LiNiO, and LiMnO are thoroughly studied in different overlithiation voltage limitations. The results showed that LiFePO and LiMnO cathode materials show high structure stability under the overdischarge process to 1.0 V. The microstructure of LiNiO is vulnerable to breakdown under the same testing condition. Fe-based olivine and Mn-based spinel cathode materials show better cyclic calendar life than that of Ni-based layered material. When an extreme overdischarge parameter (down to 0.0 V) is applied, all three samples experience an electrochemically driven irreversible solid-state amorphization process. Due to this overlithiation reaction, the host structure is totally destroyed. Therefore, it is harmful to experience deep overdischarge behaviors for most cathode materials. [ABSTRACT FROM AUTHOR]

Abstract: A series of LiNi0.5Co0.5− x Ti x O2 (0⩽ x ⩽0.5) are prepared by a tartaric acid-assisted sol–gel technique. The phase formation process is observed by TG–DTA. It is found that the target product appears at a temperature higher than 400°C and completes to phase formation at 700°C. The crystal structure and morphology are characterized by XRD, SEM and Raman spectroscopy. XRD patterns show that the as-prepared sample transforms from hexagonal structure into cubic structure with the increase of Ti content in LiNi0.5Co0.5− x Ti x O2. Raman spectra also demonstrate the successive substitution of Ti for Co in the structure with band blue-shift phenomenon. SEM images confirm that the as-prepared sample exhibits narrow and regular particles with the size between 0.5 and 1.5μm. The apparent particle size of sample starts to decrease with x ⩽0.1, and the gradually increases by introducing Ti dopant with higher content (x ⩾0.15). The electrochemical behavior of the sample displays different characteristics after Ti substitution. It is found that the initial working potential increases with the increase of Ti doping content. As a result, the initial lithium storage capacity for trace Ti-doped sample is higher than that delivered by the pristine one. The decrease of reversible capacity for high degree Ti-doped sample is ascribed to the electrochemical inactivity of the cubic compound in the sample. Therefore, trace Ti doping is beneficial to achieve promising cathode material for lithium-ion batteries. [Copyright &y& Elsevier]

Aqueous rechargeable sodium-ion batteries (ARSB) have great potential as large-scale storage devices owing to their low cost, high energy density, safety, and environmental friendliness. Here, micron-sized Na0.7MnO2.05, fabricated by a facile sol–gel method, is reported as a novel cathode material for ARSB and has been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), selected area electron diffraction/energy dispersive spectroscopy (ED/EDS) and X-ray photoelectron spectroscopy (XPS). As revealed, the material is perfectly synthesized. The Na0.7MnO2.05 electrode delivers an initial charge specific capacity of 42.6 mA h g−1 at a current density of 50 mA g−1. Compared with the capacity of 100th cycle (the highest discharge specific capacity of 52 mA h g−1), a capacity retention of 90.1% after 600 cycles is still observed. Good rate performance and excellent long-term cycling capability are also demonstrated. Unique morphology, medium-sized and mono-disperse particles facilitate the diffusion of Na+ in the electrode, which is also beneficial for Na0.7MnO2.05 electrode to exhibit excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

Cathode material 0.5Li 2 MnO 3 ·0.5LiNi 0.5 Mn 0.5 O 2 is successfully synthesized by citrate acid assisted sol–gel method and shows pretty good electro-chemical performance. To elucidate the electro-chemical reactions and charge carrier transportation kinetics in the charge–discharge process, series of electro-chemical impedance spectra for the first and the second charge process are measured on multiple given state of charges. The rapid augmentation of resistance to electronic conduction and ionic conduction within the voltage range 4.45–4.6 V where the removal of Li 2 O from Li 2 MnO 3 component takes place gives us more evidence about the complicated “structurally integrated” feature of this material. The relatively large span of the arc responsible for electronic conduction and the extremely large Mn 3+ related charge transfer resistance at the beginning of the second charging indicate that after one complete charge–discharge cycle, Li 2 MnO 3 and LiNi 0.5 Mn 0.5 O 2 domains still reserve its original structure and will keep its structure for the followed cycles. [ABSTRACT FROM AUTHOR]

Abstract: The electronic property and structural stability of LiMn2O4 and LiNi0.5Mn1.5O4 with Fd m space group are investigated by density functional theory (DFT) plane-wave pseudopotential method. The calculated values of Mn(Ni)–O bond lengths are found to be consistent with the reported experimental values. Due to the Ni doping, the significant shortening of Mn(Ni)–O bond strengthens the structural stability of spinel. The electronic properties of spinel show that the bonding between O and metal (Mn and Ni) is also strengthened due to the Ni doping, and then it improves the structural stability of LiNi0.5Mn1.5O4. Ni-doped spinel has a lower formation enthalpy than that of the pristine, indicating that the Ni doping improves the structural stability of spinel. [ABSTRACT FROM AUTHOR]

In this work, Li 2 NaV 2 (PO 4 ) 3 is successfully synthesized by using a simple solid-state reaction method. Structural analysis shows that this sample is a hybrid product consisted of rhombohedral Li 3 V 2 (PO 4 ) 3 phase and rhombohedral Na 3 V 2 (PO 4 ) 3 phase As a cathode material for lithium ion batteries, Li 2 NaV 2 (PO 4 ) 3 exhibits an initial reversible capacity of 108.9 mAh g −1 at 35 mA g −1 in the potential range between 3.0 and 4.3 V, with an average working potential at 3.75 V. The lithium-ion diffusion coefficient in Li 2 NaV 2 (PO 4 ) 3 is measured to be 1.86–3.27 × 10 −15 cm 2 s −1 . In addition, the electrochemical reaction between Li 2 NaV 2 (PO 4 ) 3 and Li is also investigated by various in-situ and ex-situ techniques. Viewed from the in-situ and ex-situ results, it is concluded that the electrochemical reactions of Li 2 NaV 2 (PO 4 ) 3 with Li are associated with the formation of rhombohedral LiV 2 (PO 4 ) 3 phase and rhombohedral NaV 2 (PO 4 ) 3 phase during the lithium ion extraction process and its reverse lithium insertion process is reversible for structural evolution. The highly stable structure ensures the electrochemical reversibility of Li 2 NaV 2 (PO 4 ) 3 cathode material in lithium ion batteries. [ABSTRACT FROM AUTHOR]

Co 3+ substituted lithium rich cathode material 0.5Li 2 MnO 3 ·0.5LiNi 0.5 Mn 0.5 O 2 , Li(Li 0.3 Ni 0.2 Mn 0.5 Co 0.1 )O 2 , was prepared at strictly controlled pH level realized by a carefully designed feeding system. The as prepared cathode material showed lamellar morphology with clearly shown edges. Less cation mixing and higher hexagonal ordering were observed indicating intact layered structure and good electrochemical performances. The first charge delivered a total capacity of ca. 328 mAh g −1 and the subsequent discharge sent a capacity of 238 mAh g −1 back. Except for the initial several cycles, the fading of the discharge capacity was limited. A discharge capacity of 166 mAh g −1 was still reserved after 50 cycles. The rate performance was also improved. The last cycle of each current density, namely 0.1 C, 0.2 C, 0.5 C, 1 C and 2 C, delivered a capacity of ca. 226 mAh g −1 , ca. 191 mAh g −1 , ca. 160 mAh g −1 , ca. 135 mAh g −1 and ca. 110 mAh g −1 , respectively. When the current density was back to 0.1 C, ca. 80% of the initial discharge capacity, nearly 200 mAh g −1 , was regained. [ABSTRACT FROM AUTHOR]

In this work, triclinic structured LiVPO 4 F is prepared by a simple two-step carbothermal reduction method and subsequently exposed to water under different storage conditions. The impact of exposure on the structure, morphology and electrochemical performance of LiVPO 4 F is investigated in detail. It is found that the effect of exposure at room temperature (20 °C) is slight. In contrast, exposure at 80 °C has great effect on the structure and electrochemical properties of LiVPO 4 F. Li, P and V dissolution into aqueous solution at 80 °C results in the formation of a yellowish solution. Electrochemical tests show that LiVPO 4 F samples aged in water at 80 °C for 3 and 5 days show poorer electrochemical properties than the pristine sample. LiVPO 4 F aged in water at 80 °C for 15 days exhibits higher initial reversible capacity compared with the pristine sample. However, it deteriorates rapidly in the following cycles due to the moisture-sensitive surface, which induces the formation of thick Li 2 CO 3 /Li 3 PO 4 film on the surface and leads to a high charge transfer resistance and the degradation of electrochemical performance. [ABSTRACT FROM AUTHOR]

Abstract: Time domain transients to current step of multiple current densities were calculated to evaluate the polarization and fractional contribution of lithium rich cathode material Li[Li0.2Ni0.2Mn0.6]O2 based on the equivalent circuit determined from the electrochemical impedance spectrum. The calculated data matched the experimental profiles well. The contributions of the individual circuit elements, like charge transfer reaction, lithium transportation across the SEI film and solid-state lithium diffusion process, were successfully differentiated and the importance of each element was fully assessed. The results told us that they should be equally paid attention to and minimized by the optimized preparation method and cell design. [Copyright &y& Elsevier]

In this work, atomistic simulation together with density functional theory (DFT) method is applied to study the concerted motion of lithium ions and the intercalation/deintercalation mechanism in cathode material ε-LiVOPO 4. Two kinds of one dimensional Li + diffusion paths along the direction of → a − → b , that is Li 1-2i O 5 chains and Li 2-2i O 5 chains with an energy barrier of 0.066 eV and 0.35 eV, are revealed by molecular dynamics (MD) and bond-valence-energy-landscape mapping (BVEL). At higher temperature, extra diffusion paths between different Li 1-2i O 5 chains and Li 2-2i O 5 chains are found. MD studies show that Li + migration along a-axis and b-axis own the same energy barrier of 0.128 eV and the estimated diffusion coefficient at room temperature (RT) is 1.4 × 10−6 cm2 s−1 at the fully lithiated state. The lithium mobility is extremely high for the perfect lattice of ε-LiVOPO. In the process of lithium ion deintercalation, the lithium mobility is gradually depressed. The state of charge (SOC) dependency of Li+ diffusion coefficients shows a downward tendency. [Display omitted] • Li + migration mechanism determined by DFT and MD. • The SOC dependency of Li + diffusion coefficients fully revealed. • Li + deintercalation mechanism and phase evolution revealed. [ABSTRACT FROM AUTHOR]