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CN(CH2)2Si(CH3)(OCH2CH2OCH3)2 (BNS) is used as electrolyte solvent to improve the safety for LiNi1/3Co1/3Mn1/3O2 (NCM)/graphite battery. BNS increases the thermal stability of the carbonate-based electrolyte with (de) lithiated cathode/anode and the electrochemical stability of coin cells. By using an optimal BNS-based electrolyte formula, 13 Ah NCM/graphite prismatic cell achieves 95.8% retain of capacity at 2 C/3 C (charge/discharge) rate after 600 cycles. Meanwhile, 13 Ah prismatic cell exhibits improved safety performance in the nail penetration test.

Structural hierarchy of porous carbon has been a key role in the sulfur hosts for lithium sulfur (Li-S) batteries. Herein, coral-like hierarchical porous carbon (HPC) is developed by a dual alkaline activation process. The production of HPC is inexpensive and scalable, which gives a great promise as sulfur host for the future application of Li-S batteries. Moreover, the as-prepared material achieves an admirable interconnected conductive network, hierarchical pore size distribution and notably high pore volume. This architecture contributes to ultrafast ion diffusion, rapid mass transport, robust electrode configuration as well as effective physical adsorption for soluble polysulfide, thus enabling a favorable scaffold for Li-S battery cathodes with high sulfur utilization and exceptionally electrochemical stability. As a consequence, the HPC based sulfur cathode manifests high areal capacity of 7.5mAh/cm2 with a high sulfur loading and superb cycling stability over 500 cycles with lower sulfur loading. The classification of alkali significantly affects on the hierarchical porosity of the resultant carbon. And the correlation between the pore size distribution and electrochemical performance is revealed. This work offers a hierarchical material engineering of a sulfur host material for restricting the mobile polysulfide moieties, thus achieving a high efficiency and stable Li-S battery.

Driven by intriguingly high energy density up to 2600 Wh/kg, lithium sulfur (Li-S) battery is considered as one of the most promising energy storage devices compared with conventional lithium ion battery. The main obstructions plaguing Li-S batteries associated with the electrical resistivity of sulfur/lithium sulfides, the dissolution of polysulfides in ether-based electrolyte and the large volume variation, result in poor cycling performance and rate capability. Here, we develop a polymer optimized cathode that is polydopamine layer coated on the surface of sulfur loaded hierarchical porous graphitic carbon composites (HPGC-S-PD) by a simple in-situ polymerization method toward the highly suppressed shuttle effect, thus the significantly improved cell performance. Attributed to the superiorities of the structure engineering including the strengthened polysulfide trapping, accelerated ionic conductivity and stable electrode construction, this cathode can deliver an excellent cycling performance over 700 cycles at 1 C, a high areal capacity of 7.25 mAh/cm2 with raised sulfur loading as high as 5.15 mg/cm2. Meanwhile, the obtained cathode can work well with a lower E/S ratio compared with the non-coated cell, which suggests the immense possibility for yielding a practically Li-S battery with high energy density based on this electrode architecture. Strikingly, the pouch cell with optimized cathode material can realize an energy density of 272 Wh/kg after 40 cycles at 0.1 C. This rational design of sulfur cathode combining HPGC with polymer coating by a scalable strategy provides a comprehensive understanding of the structural engineering for sulfur cathodes in pursuit of practically high performance Li-S batteries.

Aliovalently Ce 3+ -doped Li 4 Ti 5 O 12 (LTO) is firstly synthesized by a sol-gel method using Ce(CH 3 COOH) 3 as the dopant and CH 3 COOLi/(C 4 H 9 O ) 4 Ti as starting materials. The structure and morphology of Ce 3+ -doped LTO with various doping level (Li 4 Ti 5-x Ce x O 12 ; x = 0, 0.05, 0.10, 0.15 and 0.20) are characterized by XRD, EDX, Raman, XPS, SEM and TEM. Pure phase Ce 3+ -doped Li 4 Ti 5 O 12 is obtained when x ≤ 0.10, while CeO 2 impurity is observed when x > 0.10. The Ce 3+ -doped LTO with appropriate content of CeO 2 impurity shows much improved rate capability and specific capacity compared with the pristine and Ce 3+ -doped LTO without CeO 2 impurity. Particularly, the Li 4 Ti 5-x Ce x O 12 (x = 0.15) electrode exhibits the best rate capability and long-term cycling stability among all samples, delivering a capacity of 120.0 mAh g −1 at 5C even after 1000 cycles. This work demonstrates that aliovalently Ce 3+ -doping is an effective approach for enhancing LTO’s rate-performance.

Cyanoethylated carboxymethyl chitosan (CN-CCTS) has been synthesized through a straightforward cyanoethylation reaction by reacting CCTS with acrylonitrile in NaOH aqueous solution. CN-CCTS shows improved adhesion strength of 0.047 N/cm as compared with 0.013 N/cm for CCTS after introducing cyanoethyl group in the chemical structure of CCTS. The electrochemical performances of LiFePO 4 electrode with CN-CCTS binder have been investigated and compared with those using water soluble sodium carboxymethyl cellulose (CMC) and non-aqueous polyvinylidene difluoride (PVDF) binder. LiFePO 4 electrode with CN-CCTS exhibits better cycling stability and rate capability, retaining 56.3% capacity of C/5 at 5C rate as compared with 48.4% and 32.8% for CMC and PVDF, respectively. Cyclic voltammetry and electrochemical impedance spectroscopy measurement reveal that LiFePO 4 electrode with CN-CCTS has a more favorable electrochemical kinetics than that with CMC and PVDF, thus better rate capability.

Carboxymethyl chitosan (C-CTS) was firstly reported as a water soluble binder for LiFePO 4 cathode in Li-ion batteries. The electrochemical performances of LiFePO 4 cathode with C-CTS binder was investigated and compared with the conventional water-soluble sodium carboxymethyl cellulose (CMC) and the commercial non-aqueous polyvinylidene difluoride (PVDF). LiFePO 4 cathode with C-CTS exhibited a comparable cycling performance, but better rate capability than that of CMC and PVDF, retaining 65% capacity of C/5 at 5 C rate as compared with 55.9% and 39.4% for CMC and PVDF, respectively. In addition, LiFePO 4 cathode with C-CTS exhibited excellent cycling performance at 60 °C, retaining 91.8%/62.1% capacity after 80 cycles at 1 C/10 C, respectively.

A novel Si/porous-C composite with buffering voids was prepared by the co-assembly of phenol-formaldehyde resin, SiO 2 and Si nanoparticles, followed by a carbonizing process and subsequent removal of SiO 2 template. Si nanoparticle was coated with a layer of porous carbon shell with rationally designed void in between which provides the accommodating space for the volume change of Si over cycling. The as-prepared composite electrode exhibited good electrochemical performances as an anode material in lithium-ion cells, showing a stable reversible capacity of 980 mAh g −1 over 80 cycles with small capacity fade of 0.17%/cycle and high rate capability (721 mAh g −1 at 2000 mA g −1 ).

Nano-Si/(multi-wall carbon nanotube) (Si/MWCNT) composite paper was prepared as flexible electrode for lithium ion batteries by a simple filtration method using sodium carboxymethyl cellulose (CMC) as a dispersing/binding agent, followed by a thermal sintering process. Scanning electron microscopy (SEM) showed that nanosized Si particles were dispersed homogeneously and intertwined by the MWCNT throughout the whole paper electrode. After thermal sintering, Si/MWCNT paper electrode exhibited a significantly improved flexibility with a high Si content of 35.6 wt% as compared with before sintering, and retained a specific capacity of 942 mAh g −1 after 30 cycles with a capacity fade of 0.46%/cycle.

The electrochemical performance of gel electrolytes based on crosslinked poly[ethyleneoxide-co-2-(2-methoxyethyoxy)ethyl glycidyl ether-co-allyl glycidyl ether] was investigated using graphite/Li1.1[Ni1/3Mn1/3Co1/3]0.9O2 lithium-ion cells. It was found that the conductivity of the crosslinked gel electrolytes was as high as 5.9 mS/cm at room temperature, which is very similar to that of the conventional organic carbonate liquid electrolytes. Moreover, the capacity retention of lithium-ion cells comprising gel electrolytes was also similar to that of cells with conventional electrolytes. Despite of the high conductivity of the gel electrolytes, the rate capability of lithium-ion cells comprising gel electrolytes is inferior to that of the conventional cells. The difference was believed to be caused by the poor wettability of gel electrolytes on the electrode surfaces.