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The development of efficient oxygen evolution reaction (OER) electrocatalysts is of vital importance for acidic water decomposition. Currently, the rutile structured RuO 2 is considered to be the best candidate and has been studied widely. However, the state-of-the-art rutile RuO 2 still suffers from unsatisfactory activity and stability, while other crystalline structures of Ru-based oxides are seldom reported as OER electrocatalysts. The present work, for the first time, successfully synthesizes orthorhombic (Ru, Mn) 2 O 3 electrocatalyst through cation exchange. The orthorhombic (Ru, Mn) 2 O 3 particles exhibit the outstanding electrocatalysis performance as OER electrocatalyst, showing an ultralow overpotential of 168 mV at 10 mA cm−2 in acidic water and good stability in 40 h of OER. The outstanding electrocatalysis performance is attributed to the distinct Ru d -band structure together with the larger surface density of Ru active site, which reduces the free energy of the rate-limiting step during OER. [Display omitted] • Orthorhombic (Ru, Mn) 2 O 3 is synthesized through cation exchange. • Orthorhombic (Ru, Mn) 2 O 3 exhibits outstanding OER performance. • The distinct Ru d -band structure reduces the free energy of the rate-limiting step during OER. [ABSTRACT FROM AUTHOR]

The relentless development and modularization of electronics have urgently required the all-round improvement of performance, flexibility, safety, miniaturization and integration of micro-batteries. However, traditional cell design in stacked geometry fails to meet these comprehensive demands, especially high-temperature performance. Herein, we report the prototype construction of all-solid-state planar lithium ion micro-batteries (LIMBs), with characteristics of superior volumetric energy density, exceptional flexibility, extraordinary high-temperature performance, and outstanding integration of bipolar cells. The planar LIMBs were manufactured based on the interdigital patterns of lithium titanate nanospheres/graphene as anode and lithium iron phosphate microspheres/graphene as cathode, free of polymer binder and separator, working in ionogel electrolyte. The resulting LIMBs deliver ultrahigh volumetric energy density of 125.5 mWh cm −3 , ultralong-term cyclability without capacity loss after 3300 times at room temperature, and outstanding rate capability due to the multi-directional Li-ion diffusion mechanism. Furthermore, our micro-batteries present exceptional flexibility without capacity decay under repeated bending, remarkable high-temperature performance up to 1000 cycles operated at 100 °C, superior miniaturization and simplified modularization of constructing intergrated LIMBs that readily control over the output voltage and capacity, all of which can’t be simultaneously achieved by the conventional techniques. Therefore, our planar LIMBs hold tremendous opportunities for future miniaturized and integrated electronics. [ABSTRACT FROM AUTHOR]

Bismuth (Bi), a uniquely stable pnictogen element, is deemed a promising anode material for lithium-ion batteries owing to its high volumetric capacity, moderate operating voltage and environmental friendliness. However, the application of Bi as anode is hindered by its low conductivity and large volume change during cycling. Herein, we introduce an advanced surface engineering strategy to construct Bi@C-TiO x microspheres encapsulated by ultra-large graphene interfacial layer. Ultrafine Bi nanoparticles are confined and uniformly dispersed inside the C-TiO x matrix, which is the pyrolysis derivative of the newly developed Bi-Ti-EG bimetal organic frameworks, with the aid of a selective graphene interfacial barrier. A three-dimensional (3D) long-range conductive network is successfully constructed by the ultra-large graphene and the carbonized derivative of Bi-Ti-EG. Additionally, the 3D carbon network and the in-situ formed TiO x coupled with a porous structure act as soft buffer and hard suppressor to alleviate the huge volume change of Bi during cycling, and they also are the important electrochemically active components. Thanks to the synergistic effects intrigued by the aforementioned interfacial engineering strategy, the newly developed ultra-large graphene encapsulated Bi@C-TiO x microspheres exhibit an exceptional superpower and outstanding cycle stability (namely, 333.3, 275 and 225 mAh g −1 at 1, 5 and 10 A g −1 , respectively, with remarkable capacity retention upon 5000 cycles), surpassing other reported Bi-based anode materials so far. This study underpins that the nanoscale surface design of electrode materials for batteries is an effective approach to significantly enhance the power capability, capacity and cyclic stability of new metal anodes. [ABSTRACT FROM AUTHOR]

The severe lithium polysulfide (LiPS) shuttling and self-discharge behavior of lithium-sulfur (Li-S) batteries remarkably hinder their practical application. The construction of interlayer is an effective strategy to obstruct the diffusion of LiPS. However, the simplex physical block or chemical absorption of monotonous interlayer is difficult to reuse sulfur species, reduce impedance and restrain self-discharge of the Li-S battery simultaneously. In this study, a multicomponent sandwich-type interlayer was integrated by vanadium disulfide and carbon nanotubes composite (VS 2 /CNT), carbon nanofibers (CNF) substrate and graphene coating layer. The VS 2 /CNT presented strong affinity towards LiPS and effectively restrained the self-discharge of Li-S batteries. The CNF substrate as supporting framework increased the wettability of electrolyte and reduced the diffusion impedance of lithium ion. The graphene coating layer acting as the second collector effectively recovered the inactivated sulfur species. The multiple components of VS 2 /CNT adsorbent, CNF substrate and graphene coating layer exhibited favorable synergetic effects to suppress the LiPS shuttling and self-discharge of Li-S batteries. Besides, this interlayer endowed Li-S batteries with boosted redox kinetics and outstanding rate performance. The specific capacities at 0.1, 1 and 10 C were 1525, 834 and 621 mAh g −1 , respectively. More importantly, the Li-S batteries with this multicomponent interlayer performed a high residual capacity of 605 mAh g −1 after 1145 cycles at 1 C. Even at a high sulfur loading of 5.6 mg cm −2 , the cell still had high capacity of 1150 mAh g −1 and 750 mAh g −1 at 0.1 C and 0.3 C, respectively. The synergetic effects of multicomponent sandwich-type composite interlayer provided a new strategy for ultra-small self-discharge and stable of Li-S batteries. [ABSTRACT FROM AUTHOR]

The rapid development of lithium (Li)-ion and sodium (Na)-ion batteries requires advanced solid electrolytes that possess both favorable electrochemical performance and safety assurance. Herein we report a hierarchical poly (ionic liquid)-based solid electrolyte (HPILSE) for high-safety Li-ion and Na-ion batteries. This hybrid solid electrolyte is fabricated via in situ polymerizing 1,4-bis[3-(2-acryloyloxyethyl)imidazolium-1-yl]butane bis[bis(trifluoromethanesulfonyl)imide] (C1-4TFSI) monomer in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMITFSI)-based electrolyte which is filled in poly(diallyldimethylammonium) bis(trifluoromethanesulfonyl)imide (PDDATFSI) porous membrane. The well-designed hierarchical structure simultaneously provides the prepared HPILSE with high ionic conductivity (>10 −3 S cm −1 at 25 °C), satisfied electrochemical stability, inherent incombustibility, good mechanical strength and flexibility. More intriguingly, the in situ assembled LiFePO 4 /Li and Na 0.9 [Cu 0.22 Fe 0.30 Mn 0.48 ]O 2 /Na cells using HPILSE exhibit superior cycling performances with high specific capacities. Both the excellent performance of HPILSE and the simple fabricating process of HPILSE-based solid-state cells make it potentially as one of the most promising electrolyte materials for next generation Li-ion and Na-ion batteries. [ABSTRACT FROM AUTHOR]

The high solubility of polysulfides in the electrolyte, together with the resulting poor cycling performance, is one of the main obstacles to the industrial production and use of lithium-sulfur (Li-S) batteries. We have developed a novel hybrid and dense separator coating that greatly improves the cycling and rate performance of the battery. The coating is fabricated by mono-dispersed Li 4 Ti 5 O 12 (LTO) nanospheres uniformly embedded in graphene layers. In this hybrid dense coating, the LTO nanospheres have a high chemical affinity for polysulfides and an excellent ionic conductivity to produce highly efficient ionic conductive channels, while the graphene layers play twin roles as a physical barrier for polysulfides and an upper current collector. The unique hybridization guarantees a very dense coating that does not significantly add the volume of the battery and meanwhile achieves an ideal combination of an effective barrier for polysulfide diffusion with a fast ion transport. For a normal coating, a loose and very thick structure is needed to meet these requirements. Cells using a pure sulfur electrode with the dense coating separator show an ultra-high rate performance (709 mA h g −1 at 2 C and 1408 mA h g −1 at 0.1 C) and an excellent cycling performance (697 mA h g −1 after 500 cycles at 1 C with 85.7% capacity retention). The easy achieving of such excellent performance indicates the possibility of producing an industrially practical Li-S battery. [ABSTRACT FROM AUTHOR]

The ability to suppress the dissolution of lithium polysulfides in liquid electrolyte (LE) is emerging and scientifically challenging, representing an important endeavor toward successful commercialization of lithium–sulfur (Li–S) batteries. In this context, a common and effective strategy to address this challenge is to replace the LE with a gel polymer electrolyte (GPE). However, the limited ionic conductivity of state-of-the-art GPEs and poor electrode/GPE interfaces greatly restrict their implementation. Herein, we report, for the first time, a facile in-situ synthesis of pentaerythritol tetraacrylate (PETEA)-based GPE with an extremely high ionic conductivity (1.13×10 −2 S cm −1 ). Quite intriguingly, even interfaced with a bare sulfur cathode, this GPE rendered the resulting polymer Li–S battery with a low electrode/GPE interfacial resistance, high rate capacity (601.2 mA h g −1 at 1 C) and improved capacity retention (81.9% after 400 cycles at 0.5 C). These remarkable performances can be ascribed to the immobilization of soluble polysulfides imparted by PETEA-based GPE and the construction of a robust integrated GPE/electrode interface. Notably, due to the tight adhesion between the PETEA-based GPE and electrodes, a high-performance flexible polymer Li–S battery was successfully crafted. This work therefore opens up a convenient, low-cost and effective way to substantially enhance the capability of Li–S batteries, a key step toward capitalizing on GPE for high-performance Li–S batteries. [ABSTRACT FROM AUTHOR]

The ability to synthesizing monodisperse Li 4 Ti 5 O 12 (LTO) nanospheres is the key to reducing the irreversible capacity of LTO materials, and thus improving their power performance. However, it remains a grand challenge to achieve uniform precursors of LTO nanospheres and maintain their spherical structures after annealing. Herein, we develop a robust strategy for the synthesis of monodisperse LTO nanospheres with an average diameter of 120 nm via the use of titanium nitride (TiN) as a titanium source for lithium ion batteries (LIBs). The precursors composed of uniform TiO 2 /Li + nanospheres were formed in a stable alkaline environment during the course of heating of the solution of peroxo-titanium complex as a result of the dissolution of TiN, while TiO 2 /Li + microspheres were easily yielded with the decrease in pH value of the precursor solution. The OH − anion was found to effectively retard the hydrolysis of peroxo-titanium complex as well as the aggregation of TiO 2 /Li + nanoparticles. Intriguingly, a uniform polyvinyl pyrrolidone (PVP) layer formed in-situ on the surface of TiO 2 /Li + nanospheres rendered LTO to retain the monodisperse spherical morphology after annealing. Notably, the as-prepared monodisperse LTO nanospheres comprised of the interconnected LTO nanograins with an average size of ~15 nm uniformly coated by a carbon layer derived from the carbonization of PVP exhibited a high tap density (1.1 g cm −3 ) and an outstanding rate-cycling capability. The charge specific capacities at 1, 10, 50 and 80 C were 159.5, 151.1, 128.8 and 108.9 mAh g −1 , respectively. More importantly, the capacity retention after 500 cycles at 10 C was as high as 92.6%. This work opens up an avenue to craft the uniform precursors of LTO and thus monodisperse LTO nanospheres that possess superior rate performance with high volumetric energy densities and long-term cyclic stability. [ABSTRACT FROM AUTHOR]

In this study, the deterioration of lithium iron phosphate (LiFePO 4 ) /graphite batteries during cycling at different discharge rates and temperatures is examined, and the degradation under high-rate discharge (10C) cycling is extensively investigated using full batteries combining with post-mortem analysis. The results show that high discharge current results in an instability of electrode/electrolyte interface and unstable solid electrolyte interphase (SEI) layers are expected to form on the newly exposed graphite anode surface, which cause sustainable consumption of active lithium and further lead to the performance degradation of active materials. For LiFePO 4 cathode, the initial capacity is largely recovered under low rate (0.1-0.2C), whereas a decline in the capability is observed at higher rates (0.5-3.0C). For graphite anode, half-cell study shows that considerable capacity loss occurs even at low rates. A small amount of Fe deposition is observed on graphite anode after cycling under 10C discharge at 55 °C. X-ray photoelectron spectroscopy (XPS) analysis confirms that a layer composed of lithium compounds is formed on the surface of anode, which can not participate in the reversible electrochemical reaction again. In addition, electrochemical impedance spectrum (EIS) measurements of half-cell indicate that the increased resistance of the positive electrode is suggested to be the root cause of power fading under high-rate discharge cycling, especially at high temperature. [ABSTRACT FROM AUTHOR]

Li 4 Ti 5 O 12 (LTO) based batteries have severe gassing behavior during charge/discharge and storage process. The interfacial reactions between LTO and electrolyte solution may be the main reason. In this work, the LTO spinel particles are modified with ZnO coating using a chemical process to reduce the surface reactivity of LTO particles. Results show that the ZnO coating can effectively stabilize the electrode/electrolyte interface and suppress the formation of a solid electrolyte interface (SEI) film. Simultaneously, this ZnO modification can improve the electronic conductivity and lithium ion diffusion coefficient, which contributes to a great improvement in cyclic and high rate capabilities of LTO electrode. The ZnO coating on LTO may be an effective method to restrict the gassing behavior of LTO based battery. [ABSTRACT FROM AUTHOR]

A porous tin peroxide/carbon (SnO 2 /C) composite electrode coated with an amorphous carbon layer is prepared using a facile method. In this electrode, spherical graphite particles act as supporter of electrode framework, and the interspace among particles is filled with porous amorphous carbon derived from decomposition of polyvinylidene fluoride and polyacrylonitrile. SnO 2 nanoparticles are uniformly embedded in the porous amorphous carbon matrix. The pores in amorphous carbon matrix are able to buffer the huge volume expansion of SnO 2 during charge/discharge cycling, and the carbon framework can prevent the SnO 2 particles from pulverization and re-aggregation. The carbon coating layer on the outermost surface of electrode can further prevent porous SnO 2 /C electrode from contacting with electrolyte directly. As a result, the repeated formation of solid electrolyte interface is avoided and the cycling stability of electrode is improved. The obtained SnO 2 /C electrode presents an initial coulombic efficiency of 77.3% and a reversible capacity of 742 mA h g −1 after 130 cycles at a current density of 100 mA g −1 . Furthermore, a reversible capacity of 679 mA h g −1 is obtained at 1 A g −1 . [ABSTRACT FROM AUTHOR]

Solid polymer electrolytes (SPEs) are considered as the most promising solid-state electrolytes for next-generation lithium (Li) batteries with high safety and electrochemical performance. Whereas the interfacial side reactions between SPEs and Li metal anode hinder the development of SPEs in solid-state lithium metal batteries (SLMBs). Herein, we propose a g-C 3 N 4 nanosheets (GCNs) reinforced poly(vinylidene fluoride) (PVDF-GCN) composite polymer electrolyte with high ionic conductivity of 6.9 × 10−4 S cm−1 and low activation energy (0.192 eV). The GCNs react with Li metal to in situ produce a Li 3 N-enriched SEI during cycling, which significantly suppresses the continuous side reactions and ensures rapid charge-transfer between PVDF-GCN SPEs and Li metal anode. In addition, the GCNs present a strong adsorption ability to the residual N, N-dimethylformamide molecule, which greatly enhances the electrochemical stability of PVDF-GCN SPEs. As a result, the Li symmetrical cell stably cycled over 2200 h. Moreover, the SLMBs using LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode achieve excellent cycling stability for more than 1700 cycles at 1 C and a high discharge capacity of 108 mAh g−1 at 5 C. This work provides novel insights into the construction of a stable SPEs/Li interface for long lifespan SLMBs. [Display omitted] • A composite solid polymer electrolyte with high ionic conductivity is prepared. • Li 3 N-enriched interfacial layer ensures the rapid interfacial ion transport. • Good compatibility with high-voltage cathode is achieved. • The LiNi 0.8 Co 0.1 Mn 0.1 O 2 /lithium metal batteries show long cycling stability. [ABSTRACT FROM AUTHOR]

A novel Li 4 Ti 5 O 12 (LTO) electrode with a hierarchical carbon-based conducting network has been developed for high rate lithium ion battery. The unique network is constructed by graphene sheets (GS) that are not only dispersed among (inter-) but also inside (intra-) LTO particles, together with a thin carbon layer wrapping around the LTO particles. The intraparticle GS promotes the electron transfer inside LTO particles while the interparticle GS together with carbon coating bridges the particles guaranteeing fast electron transfer among LTO particles, which construct a highway throughout the whole electrode sheet. Quantitatively, only a trace amount of GS (∼ 0.4 wt%) synergistic with carbon coating (∼0.8 wt%) contributes to a more effective conducting network in the produced LTO electrode and as a result much better performance as compared to the LTO case with similar carbon coating but free of GS. Due to the effectiveness of the conducting network, even with a tap density as high as ∼1.0 g cm −3 , the novel LTO possesses both excellent rate performance and cycling behaviors. The capacity of 123.5 mA h g −1 is obtained at a charge/discharge rate as high as 30 C and a very high capacity of 144.8 mAh g −1 is maintained even after 100 cycles at 10 C. Due to such a low fraction of carbon and a high tape density, the novel LTO electrode has a great practical application value in both the power and energy storage lithium ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: Exceptional capacities and excellent rate performance have been achieved by anodes made from electrospun carbon nanofibers (CNFs) that possess synergies of (i) functionalization with carbonyl and carboxyl groups, (ii) presence of nanopores and (iii) embedded graphene layers. The Fe precursor incorporated into the polyacrylonitrile melt functions as both catalyst for graphitization and sacrificial phases. CNFs are functionalized and nanopores surrounded by graphene layers are simultaneously created during the chemical etching of Fe3C particles from the CNFs. The pore size and volume could be tuned by controlling the Fe precursor content. Both the functional groups and nanopores are accessible to Li ions, and the satisfactory electrical conductivity arising from graphitization allows fast transfer of electrons. Remarkable capacities of 983 and 318mAhg−1 are obtained when discharged at 100 and 3000mAg −1, respectively, along with excellent capacity retention after 100 cycles. [Copyright &y& Elsevier]

Abstract: A novel LiFePO4/C composite with 3D carbon network was prepared using Cetyltrimethyl Ammonium Bromid (CTAB) and starch as carbon sources via a facile method. The 3D carbon network structure was composed of a full and uniform carbon coating and a continuous carbon film framework. Good conductive paths enhancing electrons transfer efficiency and porous structure facilitating diffusion of lithium ions have been constructed by the 3D conductive network structure, which contributes the high ionic and electrical conductivities. As a result, the LiFePO4/C composite possesses an excellent electrochemical performance especially the high-rate cyclic performance. It delivers a capacity of 95mAhg−1 at current density of 3.4Ag−1 (20C). After 1200 cycles, the discharge capacity of 74mAhg−1 can still be obtained, almost reaching a retention of 80%, which is higher than the best cyclic performance in previous investigations. [Copyright &y& Elsevier]

Abstract: Understanding the formation of SEI films on Li4Ti5O12 (LTO) anodes offers a major benefit to large-scale applications of lithium ion batteries made therefrom. This paper reveals that an SEI film is formed above 1 V due to the interfacial reaction between the electrode and electrolyte: LTO anodes are previously considered free from SEI films when cycled between 1 and 3 V. The reactivity and the formation of SEI films are much affected by the morphology and surface area of the electrode. To study the above, LTO powders with different morphologies are synthesized using lithium acetate (LA) and lithium hydroxide (LH) as the lithium sources. LTO–LH consisting of agglomerates of primary small particles with a large surface area has higher reactivity than LTO–LA with a cubic structure and small surface area. As a result, the LTO–LH anode with a smooth SEI film offers better cyclic performance than the LTO–LA anode with a porous SEI film. The addition of vinylene carbonate to the electrolyte facilitates rapid formation of a protective SEI film on LTO–LA, greatly improving the rate and cyclic performance: stable specific capacity of 155.6 mAh g−1 and remarkable 135.2 mAh g−1 after 500 cycles at 10 C are recorded. [Copyright &y& Elsevier]

Abstract: This study is trying to demonstrate whether graphene is able to construct an effective conducting network for both electron and ion transports in cathode system of a high-power lithium ion battery (LIB), not based on a coin cell, but by employing a commercial soft-packaged 10Ah battery pack as a model system. Compared with the cells using commercial conductive additive (7wt% carbon black and 3wt% conductive graphite), a 10Ah cell using only 1wt% graphene and 1wt% carbon black shows lower internal resistance and higher energy density due to the excellent conductivity of graphene. However, owing to the fact that the planar structure of the graphene sheets blocks fast Li+ ion transport, the steric effect resulted heavy polarization occurs at a relatively high charge/discharge rate (>3C). That is, although flexible and planar graphene helps construct an effective electron transfer network, it retards Li+ ion transport. Thus, for an energy-storing LIB with a low working charge/discharge rate, graphene additive shows apparent superiority over commercial ones even with much less addition fraction and may find its real commercial applications; while, for a high-power LIB which works at higher charge/discharge rate, fast ion transport path is required to be effectively constructed before a real application. Simulation results indicate that further work should be focused on the adjustment of electrode pore structure and modification of graphene steric structure accordingly to construct an unimpeded ion conducting network and provide high speed path for Li+ ion transport. [Copyright &y& Elsevier]

Abstract: The lithium ion batteries using Li4Ti5O12 as the anode material are easily being inflated during charge and discharge, which, however, does not occur in the batteries using graphite as the anode material. The high reduction reactivity of electrolyte on the Li4Ti5O12 material may be the main reason. In this work, the reduction reactivities of electrolyte on the uncoated and carbon-coated Li4Ti5O12 electrodes are compared for the first time. The results show that the reduction decomposition of electrolyte does occur on the uncoated Li4Ti5O12 electrode at around 0.7V, while it only takes place at the first cycle on the carbon-coated Li4Ti5O12 electrode. The carbon coating layers cover the catalytic active sites of Li4Ti5O12 particles and separate the Li4Ti5O12 particles from the electrolyte. A successive solid electrolyte interface (SEI) film is formed on the carbon layer during the formation process, which can prevent the further reduction decomposition of electrolyte at around 0.7V. The impurity phases of rutile and anatase TiO2 do not influence the reduction reactivity of electrolyte. This work is not only important to understand the reduction decomposition mechanism of electrolyte on the Li4Ti5O12 electrode, but also provides an effective solution to suppress the reduction decomposition of electrolyte in the batteries. [Copyright &y& Elsevier]

Abstract: Li4Ti5O12 anode material is synthesized using TiO2 with different crystal structure as titanium source by solid-state method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical test methods are applied to characterize the effects of TiO2 crystal structure on the structure, morphology and electrochemical performance of Li4Ti5O12. Results show that the reaction of TiO2 with Li2CO3 is an exothermic behavior. The reactivity of TiO2 with Li2CO3 gradually decreases and the particles size of Li4Ti5O12 increases with the TiO2 crystal structure changing from amorphous to rutile. The TiO2 crystal structure has a slight influence on the reversibility of Li4Ti5O12, while the specific capacities of Li4Ti5O12 at different current densities decreases obviously with the TiO2 crystal structure changing from amorphous to rutile and the sample using amorphous TiO2 as titanium sources shows highest specific capacity. The capacity retentions of all Li4Ti5O12 samples are above 97% after 50 cycles and these materials show good cycle performance. The TiO2 crystal structure has not large effects on the cycling performance of Li4Ti5O12 material. [Copyright &y& Elsevier]

Abstract: The structural and thermal stabilities of the layered Li(Ni1/3Co1/3Mn1/3)O2 cathode materials under high rate cycling and abusive conditions are investigated using the commercial 18650 Li(Ni1/3Co1/3Mn1/3)O2/graphite high power batteries. The Li(Ni1/3Co1/3Mn1/3)O2 materials maintain their layered structure even when the power batteries are subjected to 200 cycles with 10C discharge rate at temperatures of 25 and 50°C, whereas their microstructure undergoes obvious distortion, which leads to the relatively poor cycling performance of power batteries at high charge/discharge rates and working temperature. Under abusive conditions, the increase in the battery temperature during overcharge is attributed to both the reactions of electrolyte solvents with overcharged graphite anode and Li(Ni1/3Co1/3Mn1/3)O2 cathode and the Joule heat that results from the great increase in the total resistance (R cell) of batteries. The reactions of fully charged Li(Ni1/3Co1/3Mn1/3)O2 cathodes and graphite anodes with electrolyte cannot be activated during short current test in the fully charged batteries. However, these reactions occur at around 140°C in the fully charged batteries during oven test, which is much lower than the temperature of about 240°C required for the reactions outside batteries. [Copyright &y& Elsevier]

Abstract: The thermogravimetric (TG) and differential thermal analysis (DTA) were used to investigate the thermal stability of fully charged and discharged LiCoO2 cathode and graphite anode in nitrogen and air atmospheres. The results showed that the weight of charged and discharged LiCoO2 cathode samples exhibited an obvious decrease between 100 and 120°C in two atmospheres. The exothermic decomposition reaction of fully charged LiCoO2 cathode occurred at 250°C in two atmospheres. A small decomposition reaction of the discharged LiCoO2 cathode occurred at 300°C. When the temperature of samples was elevated to 600°C, the weight of fully charged and discharged LiCoO2 cathode in air atmosphere did not change; while the weight of samples in nitrogen atmosphere decreased. This was because the Co3O4 as the decomposition product of the cathodes could be reduced to CoO by the carbon black above 600°C in N2 atmosphere. The solid electrolyte interphase (SEI) film of fully charged and discharged graphite anode was decomposed at 100–120°C in two atmospheres, and the weight loss of fully charged graphite anode at 100–120°C was obviously less than that of the fully discharged graphite anode. When the samples were heated to 300°C, there was no fierce exothermic reaction for the lithiated graphite anode in N2 atmosphere, whereas an exothermic reaction in air atmosphere occurred rapidly. [Copyright &y& Elsevier]

Abstract: The commercial 18650 Li(Ni1/3Co1/3Mn1/3)O2/graphite high power batteries were prepared and their electrochemical performance at temperatures of 25 and 50°C was extensively investigated. The results showed that the charge-transfer resistance (R ct) and solid electrolyte interface resistance (R sei) of the high power batteries at 25°C decreased as states of charge (SOC) increased from 0 to 60%, whereas R ct and R sei increased as SOC increased from 60 to 100%. The discharge plateau voltage of batteries reduced greatly with the increase in discharge rate at both 25 and 50°C. The high power batteries could be discharged at a very wide current range to deliver most of their capacity and also showed excellent power cycling performance with discharge rate of as high as 10C at 25°C. The elevated working temperature did not influence the battery discharge capacity and cycling performance at lower discharge rates (e.g. 0.5, 1, and 5C), while it resulted in lower discharge capacity at higher discharge rates (e.g. 10 and 15C) and bad cycling performance at discharge rate of 10C. The batteries also exhibited excellent cycle performance at charge rate of as high as 8C and discharge rate of 10C. [Copyright &y& Elsevier]