and environmental friendliness of the batteries. As a rare metal element, Li resources in the earth and their accessibility at low cost are a serious concern for upcoming larger-scale EES applications. Therefore, it is greatly needed to develop new batteries that are built up from environmentally benign and sustainable electrode materials. In the development of these new technologies, ambient sodium-ion batteries (SIBs) are revived and actively investigated as promising alternatives to LIBs for the next-generation energy storage devices due to the natural abundance of Na resources and the similar intercalation chemistry of Na + ions to their lithium counterpart. As a "rockingchair" type battery, the charge-discharge reactions of SIBs take place through a reversible Na + -intercalation mechanism, while Na ions move off from the cathode host, pass through the electrolyte and then insert into the anode host during charge, and vice versa during discharge. Meanwhile, electrons move from anode to cathode during charge or from cathode to anode during discharge through the external circuit, thus storing or delivering electric energy in a direct electrochemical manner.Studies on Na-intercalation chemistry can be dated back to the early 1980s, [ 2,3 ] almost in the same period as the development of Li-ion technology. Soon after the fi rst demonstration of lithium intercalation compounds for battery application, [4][5][6] the Na insertion behavior of Na x CoO 2 was also revealed as a cathode host. [ 7,8 ] Earlier pioneering works on earlier development of Na-ion technologies were given in a recent review. [ 9 ] Unfortunately, development of SIBs has almost halted in the past three decades since the successful commercialization of LIBs in the 1990s. A major reason for this embarrassment is the diffi culty to fi nd Na-host materials with comparable high capacities and suitable working potentials as their Li analogues. Because of larger atomic weight and less negative potential of Na than Li, Na-host materials have to suffer from a lower energy density than their Li counterparts. Furthermore, the larger ion radius of Na + (1.02 Å) than that of Li + (0.76 Å) make them kinetically frustrated during their insertion and transport in the host lattices, which further decreases the capacity utilization and rate performance of the materials.In recent years, great efforts have been made to achieve considerable success in understanding the Na + intercalation chemistry and in developing Na-host materials. It is now recognized that Na-host materials cannot simply be duplicated from their lithium analogues. For example, Okada and Sodium-ion batteries (SIBs) are now being actively developed as low cost and sustainable alternatives to lithium-ion batteries (LIBs) for large-scale electric energy storage applications. In recent years, various inorganic and organic Na compounds, mostly mimicked from their Li counterparts, have been synthesized and tested for SIBs, and some of them indeed demonstrate comparable specifi c capacity to the presentl...

As an anode material for sodium-ion batteries (SIBs), hard carbon (HC) presents high specific capacity and favorable cycling performance. However, high cost and low initial Coulombic efficiency (ICE) of HC seriously limit its future commercialization for SIBs. A typical biowaste, mangosteen shell was selected as a precursor to prepare low-cost and high-performance HC via a facile one-step carbonization method, and the influence of different heat treatments on the morphologies, microstructures, and electrochemical performances was investigated systematically. The microstructure evolution studied using X-ray diffraction, Raman, Brunauer–Emmett–Teller, and high-resolution transmission electron microscopy, along with electrochemical measurements, reveals the optimal carbonization condition of the mangosteen shell: HC carbonized at 1500 °C for 2 h delivers the highest reversible capacity of ∼330 mA h g –1 at a current density of 20 mA g –1 , a capacity retention of ∼98% after 100 cycles, and an ICE of ∼83%. Additionally, the sodium-ion storage behavior of HC is deeply analyzed using galvanostatic intermittent titration and cyclic voltammetry technologies.

Figure 3. a) N 1s and b) F 1s XPS spectra of SEI formed on the PDDA-TFSI@Cu, poly(EVIm-TFSI)@Cu, PDMA-TFSI@Cu, and bare Cu electrodes. c) Nucleation overpotentials of Li deposition on bare Cu electrode and the PIL-coated electrodes. d) Coulombic efficiency of Li/Cu half-cells using the bare Cu electrode and the PIL-coated electrodes at 0.5 mA cm −2 with a plating capacity of 1 mAh cm −2. e,f) Potential profiles of various electrodes at the 50th (e) and 100th (f) cycles.

Here, a P2-type layered Na Zn TeO (NZTO) is reported with a high Na ion conductivity ≈0.6×10 S cm at room temperature (RT), which is comparable to the currently best Na Zr Si P O NASICON structure. As small amounts of Ga substitutes for Zn , more Na vacancies are introduced in the interlayer gaps, which greatly reduces strong Na -Na coulomb interactions. Ga-substituted NZTO exhibits a superionic conductivity of ≈1.1×10 S cm at RT, and excellent phase and electrochemical stability. All solid-state batteries have been successfully assembled with a capacity of ≈70 mAh g over 10 cycles with a rate of 0.2 C at 80 °C. Na nuclear magnetic resonance (NMR) studies on powder samples show intra-grain (bulk) diffusion coefficients D on the order of 12.35×10 m s at 65 °C that corresponds to a conductivity σ of 8.16×10 S cm , assuming the Nernst-Einstein equation, which thus suggests a new perspective of fast Na ion conductor for advanced sodium ion batteries.

For reaching a high-performance of electrode materials, it is generally believed that understanding the structure evolution and heterogeneous alignment effect is the key. Presently, a very simple and universal applicable...