LiCoO2 Electrode Research Articles

Utilizing Magnetic‐Field Modulation to Efficiently Improve the Performance of LiCoO2||Graphite Pouch Full Batteries

AbstractThe present lithium‐ion battery technology competition almost focuses on finding new materials, while less effort is invested in electrode engineering improvement with low‐cost. This study proposes a simple method of modulating the preferred orientation of crystal phases in LiCoO2 electrode using a ≈500 mT magnetic‐field, cheaply and efficiently improving the performance of LiCoO2||graphite pouch full batteries, including cycling stability, rate performance, and thermal safety performance. Under 3.0 C and 45 °C strict test conditions, LiCoO2‐M⊥||graphite battery even outputs the capacity retention rate of 42.8% after 1000 cycles, while that of pure‐LiCoO2 battery is only 4.4%. Especially, the thermal runaway temperature of the battery needling experiment decreases by considerable 7.7 °C after magnetic‐field modulation. Comprehensive characterizations reveal that vertical magnetic field causes spin alignment of LiCoO2 crystals along the (003) direction. This arrangement effectively improves the Li+ diffusion dynamic and the interface compatibility of the electrode, suppressing the electrode polarization. During the cycling processes, the preferred orientation of LiCoO2 particles forms an enhanced conductive network due to the formation of cross‐linked “Li+ poor regions” on the surface, ultimately achieving significant performance improvement. This work can provide a potential low‐cost strategy for the production of commercial lithium‐ion batteries.

Al-doped ZnO-coated LiCoO2 thin-film electrode: Understanding the impact of a coating layer on the degradation mechanism

Despite the high theoretical capacity of LiCoO2 electrode, only half of it can be used in commercial cells due to chemical and structural instabilities of the electrode surface at high charge cut-off voltages. Surface modifications by coating layers are among the best approaches used to mitigate the surface degradation. Here, a systematic study of degradation mechanism of uncoated polycrystalline LiCoO2 thin-film electrodes and of the suppression mechanisms induced by an Al-doped ZnO (Al:ZnO) coating layer during electrochemical cycling was performed, using analytical transmission electron microscopy (TEM). The Al:ZnO coating layer was deposited onto the LiCoO2 electrode surface using a wet-chemical dip-coating process. The coating layer increased the first discharge capacity and improved capacity retention. In the case of uncoated LiCoO2 electrode after 40 cycles, an irreversible phase transition from a layered to a spinel phase occurred at the electrode surface due to a direct electrolyte exposure. Moreover, Li and oxygen losses as well as a reduction of the oxidation state of Co ions occurred at the electrode surface. In the case of an Al:ZnO - coated LiCoO2 electrode, the coating layer significantly mitigated the chemical and structural degradation of the electrode surface and, thereby, suppressed the capacity and voltage fading.

Application of Modified Styrene-Acrylic-Rubber-based Latex Binder to LiCoO<sub>2</sub> Composite Electrodes for Lithium-ion Batteries

A new combination of styrene acrylic rubber (SAR) and sodium carboxymethylcellulose was developed as a water-borne binder for LiCoO2 composite electrodes operating at high voltages. Four novel SAR-based latex binders were synthesized with butyl acrylate or 2-ethylhexyl acrylate monomer and styrene via copolymerization with low and high crosslinking degrees. Composite electrodes prepared using lower-crosslinking-degree SAR binders became more stretchable and flexible. Surface analysis using electron microscopy and X-ray photoelectron spectroscopy revealed that the cycled LiCoO2 electrode was covered with approximately 10-nanometer-thick decomposition products when a conventional poly(vinylidene fluoride) binder was used. The electrodes with SAR-based binders with low cross-linkage formed a stable passivation surface during the initial cycle, and further continuous electrolyte decomposition was successfully suppressed. This passivation improved the cycle stability of LiCoO2 electrode up to 4.5 V, i.e., 87.1 % capacity retention, even after 100 cycles and suppressed self-discharge performance at 45 °C.

Impact of gradient porosity in ultrathick electrodes for lithium batteries

Technologies such as electric vehicles and portable electronic devices have an ever-present need for improved energy density and specific energy. To enhance these performance factors and reduce the cost of inactive components, ultrathick electrodes have become a large area of interest within the battery research field. However, ultrathick electrodes have not been incorporated into commercial batteries due to their sluggish kinetics, difficulty of fabrication, and poor high rate performances. To combat these challenges, this manuscript explores the utilization of gradient porosity in highly loaded LiCoO2 (LCO) electrodes of 54 mg/cm2 and an extreme ∼230 μm thickness. Novel gradient porosity electrodes were fabricated by a novel methodology to create monolithic electrodes of predesigned porosity. Homogeneous porosity electrodes of similar thicknesses were also fabricated and analyzed to compare to the gradient electrodes. Transport properties, such as tortuosity and high/low rate capabilities, were investigated for both the gradient and homogeneous porosity electrodes. For the first time, thick gradient porosity electrodes of predesigned porosity distribution have demonstrated much improved high rate capacity densities over benchmark homogeneous porosity electrodes of equivalent average porosity, while retaining low rate capabilities and very high capacity density.

Mixed-linker MOFs-derived cross-linked copolymer electrolyte enables high lithium mobility for dendrite-free all-solid-state batteries

Metal-organic framework (MOF) materials have received extensive attentions as emerging fillers for solid electrolytes. However, MOF particles are served separately as fillers in solid electrolytes that bring limited ion-conduction improvement and interfacial problems between electrolytes and electrodes, which cannot fully exploit the advantages of MOFs. Herein, we propose a novel mixed-linker metal–organic framework to immobilize anions and chemically bond with the loosely coordinated copolymer backbone to form a cross-linked copolymer hybrid solid electrolyte, thus providing continuous ion-conductive paths for lithium ions transport and enhancing the lithium-ion transference number. This novel unique vinyl-functionalized MOF (Vinyl-ZIF-8) only allows tiny lithium ions to pass through its internal nanopores and restricts the movement of anions through electrostatic interaction, and its high specific surface area of 992.62 m2/g further enhances the adsorption of anions on the MOF particles surface, along with the loosely coordinated Li+ sites, showing synergistic effect and resulting in a high lithium-ion transference number reaching up to 0.73. The Li symmetrical battery assembled with this MOF-based solid electrolytes has cycled for 2000 h at 0.1 mA cm−2 with a stable polarization voltage, indicating good dendrite-suppression of lithium metal electrode and good interfacial compatibility between electrolytes and electrodes. Furthermore, the solid-state batteries assembled with MOF-based hybrid electrolytes and LiFePO4 or modified LiCoO2 electrodes also exhibit excellent cycling performance and rate performance at 25 ℃.

Self-Healing Binder for High-Voltage Batteries.

Lithium-ion batteries are core components of flexible electronic devices. However, deformation types, such as impinging, bending, stretching, folding, and twisting, can cause internal cracks and, eventually, damage these batteries. The cracks separate the active particles from the conductive particles and the binder, as well as the electrode from the collector. Self-healing binders can alleviate this mechanical damage and improve the stress response of active material particles during high rates of charging and discharging of these batteries and the operation at a high voltage, thereby enhancing their cycle performance. In the present study, a thermoplastic intrinsic self-healing polymer (TISP) binder is proposed. The TISP is obtained by polymerization of butanediol (2,3-BDO), propylene glycol (1,3-PDO), succinic acid (SuA), sebacic acid (SeA), and iconic acid (IA). The hydroxyl and ester groups in its structure can form diverse bonds including the hydrogen and ion-dipole with active particles and the current collector, thereby producing elevated adhesion. Its properties, including a low glass transition temperature (-60 °C), amorphous structure, and low cross-link density, improve the mobility of polymer chains at 40 °C, and this facilitates structural recovery and the maintenance of strong adhesions. Owing to its higher occupied molecular orbital (HOMO) level than the electrolyte solvent, the TISP is likely oxidized before the main component of the electrolyte during charging. This decomposition produces a chemical passivation interphase on the cathode which reduces side reactions of LiCoO2 and the electrolyte under high-voltage conditions. Tests reveal that a LiCoO2 electrode battery using the TISP as a binder retains 162.4 mAh g-1 after 349 cycles at 4.5 V, and this represents an 86.5% capacity retention. In addition, heating (40 °C, 1 h) of a scratch-damaged electrode can recover a specific capacity of 156.6 mAh g-1 after 349 cycles at 4.5 V. Relative to a battery without any mechanical scratch, this capacity recovery represents approximately 96%, and this demonstrates the importance of the TISP to the high-voltage damaged electrode.

3D-printing of easily recyclable all-ceramic thick LiCoO2 electrodes with enhanced areal capacity for Li-ion batteries using a highly filled thermoplastic filament

In this work, the production of thick ceramic LiCoO2 (LCO) electrodes using a conventional desktop 3D-printing was developed as an alternative to conventional electrode manufacturing for Li-ion batteries. Firstly, the filament formulation, based on LCO powders and a sacrificial polymers blend, is optimized to achieve suitable features (viscosity, flexibility and mechanical consistency) to be used in the 3-D printing. Printing parameters were optimized to produce defect-free bodies with coin geometry (12 mm diameter and 230–850 µm thickness). Thermal debinding and sintering were studied in order to obtain all ceramic LCO electrodes with adequate porosity. The additive-free sintered electrodes (850 µm thickness) have enhanced areal and volumetric capacities (up to 28 mA·h·cm−2 and 354 mA·h·cm−3) due to their extremely high mass loading (up to 285 mg·cm−2). Thus, the Li//LCO half-cell delivered an energy density of 1310 W·h·L-1. The ceramic nature of the electrode permits the use of a thin film of paint gold as current collector, reducing considerably the polarization of thick electrodes. Thus, the whole manufacturing process developed in this work is a complete solvent-free method to produce tuneable shape electrodes with enhanced energy density, opening the door for the manufacturing of high-density batteries with complex geometries and good recyclable.

Reevaluating the stability of the PEO-based solid-state electrolytes for high voltage solid-state batteries

This work shows how PEO-based solid state-electrolyte materials can be more stable than commonly expected when used with some types of high voltage cathode materials. Potentiodynamic and galvanostatic tests were performed in test cells using PEO electrolyte layers with either LiNixMnyCozO2 or LiCoO2 cathode materials. We found that the high voltage instability of PEO-based solid-state cells is profoundly affected by the interfacial instability of the cathode material used Specifically, the in the presence of PEO electrolyte, LiCoO2 electrodes were observed to undergo an irreversible oxidation process where they eventually shattered into small pieces, thus leading to a rapid irreversible loss in capacity. In contrast, we found that the PEO-based solid-state electrolytes could be stably cycled with high-nickel content cathode materials (NCM 811, 532, and 111) stably at a cell potential up to 4.5 V vs. Li/Li+ over many cycles with minimal capacity deterioration; this unexpected degree of stability in light of possible PEO/cathode interfacial stability concepts.

Protons Inside the LiCoO2 Electrode Largely Increase Electrolyte–Electrode Interface Resistance in All-Solid-State Li Batteries

Formation of an electrolyte–electrode interface that allows smooth Li-ion transport is essential for the further development of all-solid-state Li batteries. Water vapor is recognized as one critical origin of increased resistance at the electrolyte–electrode interface. However, the detailed mechanism of the degradation remains unclarified. This study uses a thin-film battery with a LiCoO2 electrode to investigate how protons at the interface contribute to the degradation. Protons were introduced to the LiCoO2 by exposing the surface to water vapor. Electrochemical, compositional, and structural investigations reveal that the protons induce the mixing of Li and Co during the first charging process. The mixing induces the formation of low-temperature-phase LiCoO2; this layer acts as an interphase layer that degrades battery performance. Understanding these interfacial phenomena contributes to increasing the power density of all-solid-state Li batteries.

Improving the high-rate performance of LCO cathode by metal oxide coating: Evaluation using single particle measurement

Surface coating is a key approach for lithium-ion batteries (LIBs) to improve the high-rate performance and stability of batteries. LiCoO2 (LCO) has been one of the promising cathode materials in LIBs due to its high theoretical capacity of 274 mAh/g and high theoretical density (5.1 g cm−3) of material. However, the capacity used is only 140 mAh/g (∼50 % of theoretical capacity) under the voltage condition limited to 4.2 V. Increasing the operation voltage is the prime way to increase the energy density of the LCO electrode. In this study, we synthesize the pristine and Al-Ti oxide coated LCO materials by simple, cost-effective and eco-friendly sol–gel method and its intrinsic parameters are measured by single particle measurement (SPM) technique. A quantitative evaluation of the electrochemical properties of the active material shows a clear difference between pristine LCO and Al-Ti@ LCO. The measured rate characteristics show that Al-Ti@ LCO has higher discharge capacity under the same current rate condition and stable cycling ability. The high voltage rate capability of LCO is exponentially increased with Al-Ti oxide coating with the highest retention of 96 % after 50 cycles within 3.0–4.5 V at 4.2C. From Tafel plot analysis the charge transfer resistance (RCT) of Al-Ti@ LCO was lower in all DOD states than pristine LCO. Also, to investigate mass transfer properties, GITT was carried out. The Al-Ti oxide coating is believed to make the LCO electrode more resistant to interfacial side reactions and fast structural degradation at high voltage and thus reduce the degradation of active material within long cycling. This result shows Al-Ti oxide coating layer contributes to the enhancement of electrochemical performance without interfering with lithium-ion diffusion.

The improvement of the high voltage performance of LiCoO2 by coating LiTaO3via magnetron sputtering

We use magnetron sputtering technology to achieve a uniform LiTaO3 layer on the surface of LiCoO2 electrode. As an artificial CEI layer, this layer inhibits the irreversible phase transition of LiCoO2 crystal under high voltage.

Segmental Motion Adjustment of the Polycarbonate Electrolyte for Lithium-Metal Batteries.

Carbonyl oxygen atoms are the primary active sites to solvate Li salts that provide a migration site for Li ions conducting in a polycarbonate-based polymer electrolyte. We here exploit the conductivity of the polycarbonate electrolyte by tuning the segmental motion of the structural unit with carbonyl oxygen atoms, while its correlation to the mechanical and electrochemical stability of the electrolyte is also discussed. Two linear alkenyl carbonate monomers are designed by molecular engineering to combine methyl acrylate (MA) and the commonly used ethylene carbonate (EC), w/o dimethyl carbonate (DMC) in the structure. The integration of the DMC structural unit in the side chain of the in situ constructed polymer (p-MDE) releases the free motion of the terminal EC units, which leads to a lower glass-transition temperature and higher ionic conductivity. While pure polycarbonates are normally fragile with high Young's modulus, such a prolonged side chain also manipulates the flexibility of the polymer to provide a mechanical stable interface for Li-metal anode. Stable long-term cycling performance is achieved at room temperature for both LiFePO4 and LiCoO2 electrodes based on the p-MDE electrolyte incorporated with a solid plasticizer.

Unraveling the LiNbO3 coating layer on battery performances of lithium argyrodite-based all-solid-state batteries under different cut-off voltages

The coating layer can effectively mitigate the undesirable side effects that occur at the active material/sulfide electrolyte interface in the cathode mixture. Plenty of research has reported the coating layer effect in the typical voltage window, while the influence at different voltage windows is unclear. Herein, the degradation mechanism of the bare and LiNbO3 coated LiCoO2 electrodes in all-solid-state batteries when cycled at different cut-off voltages has been systematically investigated. Thecoated electrodes exhibit superior electrochemical performance than the bare electrodes at different charging/discharging rates when the upper cut-off voltage is 3.6 V, while both electrodes show fast degradation of battery performance at higher cut-off voltages (3.9 and 4.2 V). The electrochemical performances are highly dependent on the interfacial stability between the active material and solid electrolyte in the cathode mixture and the structural instability of LiCoO2 at different voltage windows. The evolution of interfacial resistances is systematically investigated in combination of in-situ EIS, relaxation time distribution (DRT), TEM, and XPS. Structural changes of bare and coated LiCoO2 before and after cycled at different cut-off voltages are studied by XRD, TEM, and dQ/dV analysis. The clarification of complex interfaces and phase stability evolution of LiCoO2 provides a strong theoretical basis for constructing high-performance all-solid-state batteries.

Surface chemical heterogeneous distribution in over-lithiated Li1+xCoO2 electrodes

In commercial Li-ion batteries, the internal short circuits or over-lithiation often cause structural transformation in electrodes and may lead to safety risks. Herein, we investigate the over-discharged mechanism of LiCoO2/graphite pouch cells, especially spatially resolving the morphological, surface phase, and local electronic structure of LiCoO2 electrode. With synchrotron-based X-ray techniques and Raman mapping, together with spectroscopy simulations, we demonstrate that over-lithiation reaction is a surface effect, accompanied by Co reduction and surface structure transformation to Li2CoO2/Co3O4/CoO/Li2O-like phases. This surface chemical distribution variation is relevant to the depth and exposed crystalline planes of LiCoO2 particles, and the distribution of binder/conductive additives. Theoretical calculations confirm that Li2CoO2-phase has lower electronic/ionic conductivity than LiCoO2-phase, further revealing the critical effect of distribution of conductive additives on the surface chemical heterogeneity evolution. Our findings on such surface phenomena are non-trivial and highlight the capability of synchrotron-based X-ray techniques for studying the spatial chemical phase heterogeneity.

Reevaluating the Stability of the PEO-Based Solid-State Electrolytes for High Voltage Solid-State Batteries

Poly(ethylene oxide) (PEO) is a very popular polymer-based solid electrolyte material with relatively high ionic conductivity and dielectric constant1. However, many previous works mentioned that it could not be used in high voltage cells for its low oxidation potential (~3.9V vs. Li/Li+)2. However, only a handful of prior investigations evaluated the stability of the PEO-based solid-state electrolyte considering the contribution of the cathode surface chemistry to electrolyte oxidation and decomposition. Since most of the previous research exploring high voltage cathodes with PEO used LiCoO2, it could be possible the other cathode compositions will erode the PEO-based solid electrolyte in different and less extreme ways.Our work revisits the high voltage electrochemical stability of PEO-based solid state-electrolyte materials. Potentiodynamic and galvanostatic tests were performed in test cells using PEO electrolyte layers with either LiNixMnyCozO2 or LiCoO2 cathode materials. We found that the high voltage instability of PEO-based solid-state cells is profoundly affected by the instability of the cathode material used. Specifically, the LiCoO2 electrodes were observed to undergo an irreversible oxidation process where they shattered into small pieces, which then led to a rapid irreversible loss in capacity. In contrast, we found that the PEO-based solid-state electrolytes could be stably cycled with high-nickel content cathodes stably at a voltage up to 4.5V vs. Li/Li+ over many cycles with minimal capacity deterioration. K. Chrissopoulou, K. S. Andrikopoulos, S. Fotiadou, S. Bollas, C. Karageorgaki, D. Christofilos, G. A. Voyiatzis, and S. H. Anastasiadis, 44, 9710–9722 (2011).J. Qiu, X. Liu, R. Chen, Q. Li, Y. Wang, P. Chen, L. Gan, S.-J. Lee, D. Nordlund, Y. Liu, X. Yu, X. Bai, H. Li, and L. Chen, Adv. Funct. Mater., 30, 1909392 (2020).

Coupling hybrid membrane capacitive deionization (HMCDI) with electric-enhanced direct contact membrane distillation (EE-DCMD) for lithium/cobalt separation and concentration

The increasing usage of electronic devices has added up the generation of spent LiCoO2 (LCO) batteries. Hence there is an urgency to develop high-efficiency and environmentally-friendly approaches for LCO electrode recycling by Li+/Co2+ ion-separation and concentration. In this work, an ion-sieving membrane with a lamellar structure was fabricated by self-assembling MXene nanosheets on a hydrophilic PTFE membrane, and the interlayer spacing between 2D MXene pieces was adjusted by doping a certain amount of polyvinyl alcohol (PVA). Such ion-sieving membrane was inserted between cation exchange membrane (CEM) and activated carbon fiber (ACF) electrode, forming a hybrid membrane capacitive deionization (HMCDI) system to enhance the ion-separating performance. The artificial Li+/Co2+ mixed solution was firstly treated by the HMCDI process with a separating factor over 6. The Li-enriched HMCDI effluent was further concentrated and purified using an electric-enhanced direct contact membrane distillation (EE-DCMD) system, providing an ion-concentrating effect over 40-folds and a Co2+ removal rate over 99 %. On this basis, a membrane-based LCO battery recycling pathway was proposed, showing advantages in energy conservation, zero liquid discharging, and chemical agent saving. Moreover, the mechanism of ion-separating in the HMCDI system was elucidated in terms of energy barrier and Li+ selective adsorption. The mechanism of anti-fouling and ion-separating in EE-DCMD was discussed based on the interfacial electrochemical reactions and transmembrane mass transfer. We believe this study can a provide new insight into ion separation and concentration, which was promising in LCO battery recycling.

Novel NiO surface coating on LiCoO2 cathode for Li-ion batteries

Crystalline LiCoO2 nanoparticles were coated with NiO nanocrystals. The coating was made using a one-pot strategy by solution combustion synthesis with different weight percentages. The method used is simple, economical, and easily scalable. The resulting materials were characterized morphologically, structurally, and electrochemically by transmission and scanning electron microscopy, charge/discharge cycles, rate capability, voltammetry, and electrochemical impedance spectroscopy techniques. The results showed that a uniform coating with crystalline NiO nanoparticles on the LiCoO2 was obtained. For optimal coating, the discharge capacity reached 74% retention after 100 cycles between 3.0 and 4.5V at 0.1C, while the uncoated material retained only 5% of its initial capacity. Thus, the introduced NiO coating protects the LiCoO2 electrode against the unwanted reactions that occur in contact with the electrolyte at high voltage. Therefore, the irreversible loss of the active material capacity will be minimized.

Eutectic Electrolytes Composed of LiN(SO2F)2 and Sulfones for Li-Ion Batteries

Sulfones are polar molecules that can be used as thermally stable electrolyte solvents for Li-ion batteries (LIBs). Li salts form stoichiometric solvates with sulfones in the electrolytes. The melting points of the solvates tend to be higher than room temperature, thereby limiting the operating temperature range of the batteries. In this study, the applicability of ternary eutectic mixtures of LiN(SO2F)2 (LiFSA), sulfolane (SL), and dimethyl sulfone (DMS) as LIB electrolytes was assessed. Relative to the binary LiFSA–sulfone electrolytes, the ternary eutectic electrolytes remained liquid over a wide temperature range due to the increased entropy of mixing. Sulfone-bridged Li+–sulfone–Li+ and anion-bridged Li+–FSA––Li+ network structures were formed in the eutectic electrolyte with a composition of [LiFSA]/[SL]/[DMS] = 1/1.5/1.5. Pulsed-field gradient NMR measurements revealed that the Li+ ion dynamically exchanges sulfones and anions and diffuses more rapidly than these ligands, resulting in the relatively high Li+ transference number of the electrolyte. Highly reversible charge–discharge processes of the LiCoO2 and graphite electrodes were attained using the ternary eutectic electrolyte. The rate capability of the Li/LiCoO2 cell in the eutectic electrolyte was comparable to that of the cell in the conventional 1 M LiPF6 in an ethylene carbonate/dimethyl carbonate solution despite its lower ionic conductivity.

Pushing Lithium Cobalt Oxides to 4.7 V by Lattice‐Matched Interfacial Engineering (Adv. Energy Mater. 23/2022)

Li-ion Batteries In article number 2200197, Yong Yang and co-workers report a novel lattice-coherent LiCoPO4 coating on LiCoO2 (LCO), derived by the in-situ chemical reaction of Co(OH)2 and LiH2PO4, that can effectively alleviate irreversible structure transition and resist electrolyte corrosion, ensuring a high-voltage LCO electrode (≥4.6V), and stable operation in portable electronic devices, such as mobile phones, computers, tablets, etc., to meet the high-energy demand of the coming 5G era.

Superior interfacial stability and conductivity of B-doped LiPON electrolyte for LiCoO2 electrode in solid-state lithium batteries

Lithium cobaltate (LiCoO2) is a promising electrode material in applications of high voltage all-solid-state batteries (ASSBs). However, resistance exists at the interface between LiCoO2 and solid electrolyte still hinders further development of LiCoO2-based ASSBs, and little is known on electronic state and diffusion of ions from atomic-level. In this work, first-principles calculations and ab initio molecular dynamics (AIMD) are applied to investigate interfacial thermodynamic stability, electronic structure and diffusion of lithium between LiCoO2 and B-, Al-, As-doped LiPON for all-solid-state batteries. Based on calculations of interfacial energies and density of states, it is inferred that the LiCoO2/LiPON interface is thermodynamically stable. By the energies related to interfaces and electronic structures, it is demonstrated that the ability on interfacial binding and electronic property are enhanced after doping B, Al and As in LiPON, in particular, LiCoO2/LiBPON system shows the optimal interfacial stability and conductivity. AIMD simulations show that the doping in LiPON can also contribute an improved diffusion property of lithium, and the diffusion of lithium in LiCoO2/LiBPON system is the fastest at 300 and 400 K.