The study of zirconium vanadate as a cathode material for lithium ion batteries

The electrochemical properties of ZrV₂O₇ (ZVO) and ZVO@C were investigated in lithium ion batteries. The first charge (or discharge) specific capacity of ZVO and ZVO@C are 279 mA h g⁻¹, 392 mA h g⁻¹, 208 mA h g⁻¹ and 180 mA h g⁻¹ for 0%, 3%, 5% and 9% of carbon, respectively. The capacity retention rates (with 0% 3%, 5% and 9% carbon content) are 33.0%, 52.5%, 56.4% and 76.1% after ten cycles, respectively. The low inner resistance relates to the good contact of the electrode rather than the high content of carbon, and the specific capacity retention rate increases with the increase of the carbon content.

The carbon content in the electrode is not the only factor that determines the internal resistance. The high capacity of lithium ion batteries is related to high conductivity. The lattice is stable (expect for shrinkage) when Li ions insert into ZVO.     

The influence of different Si : C ratios on the electrochemical performance of silicon/carbon layered film anodes for lithium-ion batteries

With a high specific capacity (4200 mA h g⁻¹), silicon based materials have become the most promising anode materials in lithium-ions batteries. However, the large volume expansion makes the capacity reduce rapidly. In this work, a periodic silicon/carbon (Si/C) multilayer thin film was synthesized by magnetron sputtering method on copper foil. The titanium (Ti) film (about 20 nm) as the transition layer was deposited on the copper foil prior to the deposition of the multilayer film. Superior electrochemical lithium storage performance was obtained by the multilayer thin film. The initial discharge and charge specific capacity of the Si (15 nm)/C (5 nm) multilayer film anode are 2640 mA h g⁻¹ and 2560 mA h g⁻¹ with an initial coulombic efficiency of ∼97%. The retention specific capacity is about 2300 mA h g⁻¹ and there is ∼87% capacity retention after 200 cycles.

With a high specific capacity (4200 mA h g⁻¹), silicon based materials have become the most promising anode materials in lithium-ions batteries.     

Double-layer carbon protected CoS2 nanoparticles as an advanced anode for sodium-ion batteries

Cobalt disulfides with high theoretical capacity are regarded as appropriate anode materials for sodium ion batteries (SIBs), but their intrinsically low conductivity and large volume expansion lead to a poor electrochemical performance. In this work, graphitic carbon coated CoS₂ nanoparticles are encapsulated in bamboo-like carbon nanotubes by pyrolysis and sulfidation process. Graphitic carbon can improve the electrical conductivity and prevent the agglomeration of CoS₂ nanoparticles. Meanwhile, bamboo-like carbon nanotubes can serve as conductive skeleton frames to provide rapid and constant transport pathways for electrons and offer void space to buffer the volume change of CoS₂ nanoparticles. The advanced anode material exhibits a long-term capacity of 432.6 mA h g⁻¹ at 5 A g⁻¹ after 900 cycles and a rate capability of 419.6 mA h g⁻¹ even at 10 A g⁻¹ in the carbonate ester-based electrolyte. This avenue can be applicable for preparing other metal sulfide/carbon anode materials for sodium-ion batteries.

The outstanding electrochemical performance is ascribed to the novel structure design of CoS₂@GC@B-CNT.     

In situ template synthesis of hierarchical porous carbon used for high performance lithium–sulfur batteries

Hierarchical porous carbon (HPC) consists of micropores, mesopores and macrospores which are synthesized by in situ formation of template followed by acid etching. The obtained pores are three-dimensional and interconnected, and evenly distributed in the carbon matrix. By adjusting the ratio of the raw materials, the high specific surface area and large pore volume is afforded. The obtained HPC-3 samples possess graphite flakes and locally graphited-carbon walls, which provide good electrical conductivity. These unique characteristics make these materials suitable cathode scaffolds for Li–S batteries. After encapsulating 61% sulfur into HPC-3 host, the S/HPC-3 composite exhibits excellent cycling stability, high columbic efficiency, and superior rate cycling as a cathode material. The S/HPC-3 composite cathode displays an initial discharge capacity of 1059 mA h g⁻¹, and a reversible capacity of 797 mA h g⁻¹ after 200 cycles at 0.2C. The discharge capacities of the S/HPC-3 composite cathode after every 10 cycles at 0.1, 0.2, 0.5, 1, and 2C are 1119, 1056, 982, 921, and 829 mA h g⁻¹, respectively.

In situ template synthesis of HPCs used for lithium–sulfur batteries, which exhibits excellent cycling stability and superior rate cycling.     

Suppressing self-discharge of Li–B/CoS2 thermal batteries by using a carbon-coated CoS2 cathode

Thermal batteries with molten salt electrolytes are used for many military applications, primarily as power sources for guided missiles. The Li–B/CoS₂ couple is designed for high-power, high-voltage thermal batteries. However, their capacity and safe properties are influenced by acute self-discharge that results from the dissolved lithium anode in molten salt electrolytes. To solve those problems, in this paper, carbon coated CoS₂ was prepared by pyrolysis reaction of sucrose at 400 °C. The carbon coating as a physical barrier can protect CoS₂ particles from damage by dissolved lithium and reduce the self-discharge reaction. Therefore, both the discharge efficiency and safety of Li–B/CoS₂ thermal batteries are increased remarkably. Discharge results show that the specific capacity of the first discharge plateau of carbon-coated CoS₂ is 243 mA h g⁻¹ which is 50 mA h g⁻¹ higher than that of pristine CoS₂ at a current density of 100 mA cm⁻². The specific capacity of the first discharge plateau at 500 mA cm⁻² for carbon-coated CoS₂ and pristine CoS₂ are 283 mA h g⁻¹ and 258 mA h g⁻¹ respectively. The characterizations by XRD and DSC indicate that the carbonization process has no noticeable influence on the intrinsic crystal structure and thermal stability of pristine CoS₂.

Suppressing self-discharge of Li–B/CoS₂ thermal batteries through modifying the CoS₂ cathode with a protective carbon coating layer.     

Role of polyvinylpyrrolidone in the electrochemical performance of Li2MnO3 cathode for lithium-ion batteries

While Li₂MnO₃ as an over-lithiated layered oxide (OLO) shows a significantly high reversible capacity of 250 mA h g⁻¹ in lithium-ion batteries (LIBs), it has critical issues of poor cycling performance and deteriorated high rate performance. In this study, modified OLO cathode materials for improved LIB performance were obtained by heating the as-prepared OLO at different temperatures (400, 500, and 600 °C) in the presence of polyvinylpyrrolidone (PVP) under an N₂ atmosphere. Compared to the as-prepared OLO, the OLO sample heated at 500 °C with PVP exhibited a high initial discharge capacity of 206 mA h g⁻¹ and high rate capability of 111 mA h g⁻¹ at 100 mA g⁻¹. The superior performance of the OLO sample heated at 500 °C with PVP is attributed to an improved electronic conductivity and Li⁺ ionic motion, resulting from the formation of the graphitic carbon structure and increased Mn³⁺ ratio during the decomposition of PVP.

The modified OLO cathode materials for improved LIB performance were obtained by heating the as-prepared OLO in the presence of polyvinylpyrrolidone (PVP) under an N₂ atmosphere.     

From grass to battery anode: agricultural biomass hemp-derived carbon for lithium storage

Biomass-derived carbon, as a low-cost material source, is an attractive choice to prepare carbon materials, thus providing an alternative to by-product and waste management. Herein, we report the preparation of carbon from hemp stem as a biomass precursor through a simple, low-cost, and environment-friendly method with using steam as the activating agent. The hemp-derived carbon with a hierarchically porous structure and a partial graphitization in amorphous domains was developed, and for the first time, it was applied as an anode material for lithium-ion battery. Natural hemp itself delivers a reversible capacity of 190 mA h g⁻¹ at a rate of 300 mA g⁻¹ after 100 cycles. Ball-milling of hemp-derived carbon is further designed to control the physical properties, and consequently, the capacity of milled hemp increases to 300 mA h g⁻¹ along with excellent rate capability of 210 mA h g⁻¹ even at 1.5 A g⁻¹. The milled hemp with increased graphitization and well-developed meso-porosity is advantageous for lithium diffusion, thus enhancing electrochemical performance via both diffusion-controlled intercalation/deintercalation and surface-limited adsorption/desorption. This study not only demonstrates the application of hemp-derived carbon in energy storage devices, but also guides a desirable structural design for lithium storage and transport.

Hemp-derived carbon was prepared by physical activation using only steam, and directly applied as an electrode for lithium storage.     

Performance optimization of freestanding MWCNT-LiFePO4 sheets as cathodes for improved specific capacity of lithium-ion batteries

The typical lithium-ion-battery positive electrode of “lithium-iron phosphate (LiFePO₄) on aluminum foil” contains a relatively large amount of inactive materials of 29 wt% (22 wt% aluminum foil + 7 wt% polymeric binder and graphitic conductor) which limits its maximum specific capacity to 120.7 mA h g⁻¹ (71 wt% LiFePO₄) instead of 170 mA h g⁻¹ (100 wt% LiFePO₄). We replaced the aluminum current-collector with a multi-walled carbon nanotube (MWCNT) network. We optimized the specific capacity of the “freestanding MWCNT-LiFePO₄” positive electrode. Through the optimization of our unique surface-engineered tape-cast fabrication method, we demonstrated the amount of LiFePO₄ active materials can be as high as 90 wt% with a small amount of inactive material of 10 wt% MWCNTs. This translated to a maximum specific capacity of 153 mA h g⁻¹ instead of 120.7 mA h g⁻¹, which is a significant 26.7% gain in specific capacity compared to conventional cathode design. Experimental data of the freestanding MWCNT-LiFePO₄ at a low discharge rate of 17 mA g⁻¹ show an excellent specific capacity of 144.9 mA h g⁻¹ which is close to its maximum specific capacity of 153 mA h g⁻¹. Furthermore, the freestanding MWCNT-LiFePO₄ has an excellent specific capacity of 126.7 mA h g⁻¹ after 100 cycles at a relatively high discharge rate of 170 mA g⁻¹ rate.

We optimized the specific capacity of freestanding MWCNT-LiFePO₄ positive electrode. We demonstrated as high (low) as 90 wt% LiFePO₄ active material (10 wt% MWCNTs inactive material). This corresponded to a maximum specific capacity of 153 mA h g⁻¹.     

Mesoporous carbon prepared by etching halloysite nanotubes (HNTs) with pyrrole as a precursor for a sulfur carrier of superior lithium–sulfur batteries

Using pyrrole as a carbon precursor and halloysite nanotubes (HNT) as a templating agent, mesoporous carbon (MC) was prepared by template etching and combined with sulfur as a composite cathode for lithium–sulfur batteries. The mesoporous carbon/sulfur (MC/S) composite cathode exhibits a first cycle discharge specific capacity of 1355 mA h g⁻¹ at 0.2C, and the utilization rate of active sulfur can reach 80.9%. Even after 500 cycles, the discharge specific capacity still remains at 496.9 mA h g⁻¹ when tested at 0.5C. Furthermore, the hollow groove structure present in the MC/S electrode provides a large number of active sites for electrochemical reactions. The prepared MC/S composite cathode not only has a high discharge specific capacity and good cycle stability, but also increases the energy density of the lithium–sulfur battery. Therefore, this preparation process of MC is more conducive to practical application.

Using pyrrole as a carbon precursor and halloysite nanotubes (HNT) as a templating agent, mesoporous carbon (MC) was prepared by template etching and combined with sulfur as a composite cathode for lithium–sulfur batteries.     

Designing conductive networks of hybrid carbon enables stable and long-lifespan cotton-fiber-based lithium–sulfur batteries

In modern society, flexible rechargeable batteries have become a burgeoning apodictic choice for wearable devices. Conventional lithium–sulfur batteries lack sufficient flexibility because their electrode materials are too rigid to bend. Along with the inherent high theoretical capacity of sulfur, lithium–sulfur batteries have some issues, such as dissolution and shuttle effect of polysulfides, which restricts their efficiency and practicability. Here, a flexible and “dead-weight”-free lithium–sulfur battery substrate with a three-dimensional structure was prepared by a simple strategy. With the cooperative assistance of carbon nanotubes and graphene attached to cotton fibers, the lithium–sulfur battery with 2.0 mg cm⁻² sulfur provided a high initial discharge capacity of 1098.7 mA h g⁻¹ at 1C, and the decay rate after 300 cycles was only 0.046% per cycle. The initial discharge capacity at 2C was 872.4 mA h g⁻¹ and the capacity was maintained 734.4 mA h g⁻¹ after 200 cycles with only a 0.079% per cycle decay rate.

A flexible, “dead weight”-free lithium–sulfur battery substrate was prepared, and batteries using these substrates showed great electrochemical performance.     

An investigation of Li2TiO3–coke composite anode material for Li-ion batteries

Anode material Li₂TiO₃–coke was prepared and tested for lithium-ion batteries. The as-prepared material exhibits excellent cycling stability and outstanding rate performance. Charge/discharge capacities of 266 mA h g⁻¹ at 0.100 A g⁻¹ and 200 mA h g⁻¹ at 1.000 A g⁻¹ are reached for Li₂TiO₃–coke. A cycling life-time test shows that Li₂TiO₃–coke gives a specific capacity of 264 mA h g⁻¹ at 0.300 A g⁻¹ and a capacity retention of 92% after 1000 cycles of charge/discharge.

Anode material Li₂TiO₃–coke was prepared and tested for lithium-ion batteries. The as-prepared material exhibits excellent cycling stability and outstanding rate performance.     

Polyimide-derived carbon nanofiber membranes as free-standing anodes for lithium-ion batteries

Free-standing and flexible carbon nanofiber membranes (CNMs) with a three-dimensional network structure were fabricated based on PMDA/ODA polyimide by combining electrospinning, imidization, and carbonization strategies. The influence of carbonization temperature on the physical-chemical characteristics of CNMs was investigated in detail. The electrochemical performances of CNMs as free-standing electrodes without any binder or conducting materials for lithium-ion batteries were also discussed. Furthermore, the surface state and internal carbon structure had an important effect on the nitrogen state, electrical conductivity, and wettability of CNMs, and then further affected the electrochemical performances. The CNMs/Li metal half-cells exhibited a satisfying charge–discharge cycle performance and excellent rate performance. They showed that the reversible specific capacity of CNMs carbonized at 700 °C could reach as high as 430 mA h g⁻¹ at 50 mA g⁻¹, and the value of the specific capacity remained at 206 mA h g⁻¹ after 500 cycles at a high current density of 1 A g⁻¹. Overall, the newly developed carbon nanofiber membranes will be a promising candidate for flexible electrodes used in high-power lithium-ion batteries, supercapacitors and sodium-ion batteries.

Free-standing and flexible carbon nanofiber membranes (CNMs) with a three-dimensional network structure were fabricated based on PMDA/ODA polyimide by combining electrospinning, imidization, and carbonization strategies.     

Rapid fabrication of porous silicon/carbon microtube composites as anode materials for lithium-ion batteries

Herein, we present a simple and rapid method to synthesize porous silicon/carbon microtube composites (PoSi/CMTs) by adopting a unique configuration of acid etching solution. The CMTs can act as both conductive agent and buffer for Si volume change during the charge and discharge process. The highly reversible capacity and excellent rate capability can be ascribed to the structure, where porous silicon powders are wrapped by a network of interwoven carbon microtubes. The composites show specific capacities of more than 1712 mA h g⁻¹ at a current density of 100 mA g⁻¹, 1566 mA h g⁻¹ at 200 mA g⁻¹, 1407 mA h g⁻¹ at 400 mA g⁻¹, 1177 mA h g⁻¹ at 800 mA g⁻¹, 1107 mA h g⁻¹ at 1000 mA g⁻¹, 798 mA hg⁻¹ at 2000 mA g⁻¹, and 581 mA h g⁻¹ at 3000 mA g⁻¹ and maintain a value of 1127 mA h g⁻¹ after 100 cycles at a current density of 200 mA g⁻¹. Electrochemical impedance spectroscopy (EIS) measurements prove that charge transfer resistance of PoSi/CMT composites is smaller than that of pure PoSi. In this study, we propose a quick, economical and feasible method to prepare silicon-based anode materials for lithium-ion batteries.

We added additives to the acid etching solution and prepared the silicon/carbon microtubes composites using a simple and fast method.     

Enhanced stability of nitrogen doped porous carbon fiber on cathode materials for high performance lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries are considered to be one of the candidates for high-energy density storage systems due to their ultra-high theoretical specific capacity of 1675 mA h g⁻¹. However, problems of rapid capacity decay, sharp expansion in volume of the active material, and the shuttle effect have severely restricted their subsequent development and utilization. Herein, we design a nitrogen-doped porous carbon nanofiber (NPCNF) network as a sulfur host by the template method. The NPCNF shows a feather-like structure. After loading sulfur, the NPCNF/S composite can maintain a hierarchically porous structure. A high discharge capacity of 1301 mA h g⁻¹ is delivered for the NPCNT/S composite at 0.1C. The reversible charge/discharge capacity at 2C is 576 mA h g⁻¹, and 700 mA h g⁻¹ is maintained after 500 cycles at 0.5C. The high electrochemical performance of this NPCNT/S composite is attributed to the synergy effects of abundant N active sites and high electrical conductivity of the material.

The conductive network of nitrogen-doped porous carbon nanofibers was successfully prepared by the template method. The doping of nitrogen and the synergistic effect of mesopores and micropores reduce the energy barrier of Li⁺ migration in the material.     

Hard carbon spheres prepared by a modified Stöber method as anode material for high-performance potassium-ion batteries

The Stöber method is a highly efficient synthesis strategy for homogeneous monodisperse polymer colloidal spheres and carbon spheres. This work delivers an extended Stöber method and investigates the synthesis process. By calcining the precursor under appropriate conditions, solid secondary particles of amorphous carbon (SSAC) and hollow secondary particles of graphitized carbon (HSGC) can be directly synthesized. The two materials have a nano-primary particle structure and a closely-packed sub-micron secondary particle structure, which can be used in energy storage. We find that SSAC and HSGC have high potassium-ion storage capacity with reversible capacities of 274 mA h g⁻¹ and 283 mA h g⁻¹ at 20 mA g⁻¹ respectively. Significantly, SSAC has better rate performance with a specific capacity of 107 mA h g⁻¹ at 1 A g⁻¹.

A modified Stöber method synthesizes resorcinol-formaldehyde resin-based secondary particle hard carbon spheres as anode material for high-performance potassium-ion batteries.     

Catalytic graphitization assisted synthesis of Fe3C/Fe/graphitic carbon with advanced pseudocapacitance

We report an environmentally friendly strategy for the synthesis of Fe₃C/Fe/graphitic carbon based on hydrothermal carbonization and graphitization of carbon spheres with potassium ferrate (K₂FeO₄) at 800 °C. The obtained sample consisting of Fe₃C/Fe nanoparticles and graphitic carbon (FC-1-8) delivered an enhanced pseudocapacitance of 428.0 F g⁻¹ at a current density of 1 A g⁻¹. After removal of the Fe₃C/Fe electroactive materials, the graphitic carbon (FC-1-8-HCl) possessed a large specific surface area (SSA) up to 2813.6 m² g⁻¹ with a capacity of 243.3 F g⁻¹ at 1 A g⁻¹, far outweighing the other amorphous carbon electrodes of FC-0-8 (carbon spheres annealed at 800 °C without the treatment of K₂FeO₄). The graphitic material with a porous structure could offer more electroactive sites and improved conductivity of the sample. This method provided guidelines for the synthesis of superior performance supercapacitors with synchronous graphitic carbon and electroactive species.

We report an environmentally friendly strategy for the synthesis of Fe₃C/Fe/graphitic carbon based on hydrothermal carbonization and graphitization of carbon spheres with potassium ferrate (K₂FeO₄) at 800 °C.     

A germanium and zinc chalcogenide as an anode for a high-capacity and long cycle life lithium battery

High-performance lithium ion batteries are ideal energy storage devices for both grid-scale and large-scale applications. Germanium, possessing a high theoretical capacity, is a promising anode material for lithium ion batteries, but still faces poor cyclability due to huge volume changes during the lithium alloying/dealloying process. Herein, we synthesized an amorphous germanium and zinc chalcogenide (GZC) with a hierarchically porous structure via a solvothermal reaction. As an anode material in a lithium ion battery, the GZC electrode exhibits a high reversible capacity of 747 mA h g⁻¹ after 350 cycles at a current density of 100 mA g⁻¹ and a stable capacity of 370 mA h g⁻¹ after 500 cycles at a current density of 1000 mA g⁻¹ along with 92% capacity retention. All of these outstanding electrochemical properties are attributed to the hierarchically porous structure of the electrode that has a large surface area, fast ion conductivity and superior structural stability, which buffers the volumetric variation during charge/discharge processes and also makes it easier for the electrolyte to soak in, affording more electrochemically active sites.

High-performance lithium ion batteries are ideal energy storage devices for both grid-scale and large-scale applications.     

Enhanced storage behavior of quasi-solid-state aluminum–selenium battery

The current aluminum batteries with selenium positive electrodes have been suffering from dramatic capacity loss owing to the dissolution of Se₂Cl₂ products on the Se positive electrodes in the ionic liquid electrolyte. For addressing this critical issue and achieving better electrochemical performances of rechargeable aluminum–selenium batteries, here a gel-polymer electrolyte which has a stable and strongly integrated electrode/electrolyte interface was adopted. Quite intriguingly, such a gel-polymer electrolyte enables the solid-state aluminum–selenium battery to present a lower self-discharge and obvious discharging platforms. Meanwhile, the discharge capacity of the aluminum–selenium battery with a gel-polymer electrolyte is initially 386 mA h g⁻¹ (267 mA h g⁻¹ in ionic liquid electrolyte), which attenuates to 79 mA h g⁻¹ (32 mA h g⁻¹ in ionic liquid electrolyte) after 100 cycles at a current density of 200 mA g⁻¹. The results suggest that the employment of a gel-polymer electrolyte can provide an effective route to improve the performance of aluminum–selenium batteries in the first few cycles.

A quasi-solid-state aluminum–selenium battery has been established using gel-polymer electrolyte between the Se positive electrode and Al negative electrode which increasing the utilization of the active materials.     

TiO2-decorated porous carbon nanofiber interlayer for Li–S batteries

Lithium–sulfur (Li–S) batteries are the most promising energy storage systems owing to their high energy density. However, shuttling of polysulfides detracts the electrochemical performance of Li–S batteries and thus prevents the commercialization of Li–S batteries. Here, TiO₂@porous carbon nanofibers (TiO₂@PCNFs) are fabricated via combining electrospinning and electrospraying techniques and the resultant TiO₂@PCNFs are evaluated for use as an interlayer in Li–S batteries. TiO₂ nanoparticles on PCNFs are observed from SEM and TEM images. A high initial discharge capacity of 1510 mA h g⁻¹ is achieved owing to the novel approach of electrospinning the carbon precursor and electrospraying TiO₂ nanoparticles simultaneously. In this approach TiO₂ nanoparticles capture polysulfides with strong interaction and the PCNFs with high conductivity recycle and re-use the adsorbed polysulfides, thus leading to high reversible capacity and stable cycling performance. A high reversible capacity of 967 mA h g⁻¹ is reached after 200 cycles at 0.2C. The cell with the TiO₂@PCNF interlayer also delivers a reversible capacity of around 1100 mA h g⁻¹ at 1C, while the cell without the interlayer exhibits a lower capacity of 400 mA h g⁻¹. Therefore, this work presents a novel approach for designing interlayer materials with exceptional electrochemical performance for high performance Li–S batteries.

Lithium–sulfur (Li–S) batteries are the most promising energy storage systems owing to their high energy density.     

The electrochemical performance of fluorinated ketjenblack as a cathode for lithium/fluorinated carbon batteries

The inferior rate capacity of lithium/fluorinated carbon (Li/CF_x) batteries limits their application in the field, requiring large discharge current and high power density. Herein, we report a novel type of fluorinated carbon with superior performance through gas-phase fluorination of ketjenblack. The investigation shows that the F/C ratio of the fluorinated ketjenblack (FKB) increases with the fluorination temperature, whereas the discharge voltage decreases due to the lowered content of semi-ionic C–F bonds. Accordingly, a suitable fluorination temperature of 520 °C was selected, under which the product exhibits the largest specific capacity of 924.6 mA h g⁻¹ with discharge potential exceeding 3.1 V (vs. Li/Li⁺) and the highest energy density of 2544 W h kg⁻¹ with power density of 27 493 W kg⁻¹. This energy density is higher than the theoretical energy density of commercial fluorinated graphite (2180 W h kg⁻¹). In addition, the sample delivers good rate capability demonstrated by a specific capacity retention ratio of 79.5% even at a current density of 20C. Therefore, the FKB material may have very promising practical applications in lithium primary batteries.

Fluorinated kejtenblack as the cathode of Li/CF_x batteries exhibits excellent energy density and power density with high rate capability.