Synthesis and electrochemical properties of Li<Subscript>1.2</Subscript>Mn<Subscript>0.54</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>O<Subscript>2</Subscript> cathode material for lithium-ion battery

The layered Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ lithium-rich manganese-based solid solution cathode material has been synthesized by a simple solid-state method. The as-prepared material has a typical layered structure with R-3m and C2/m space group. The synthesized Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ has an irregular shape with the size range from 200 to 500 nm, and the primary particle of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ has regular sphere morphology with a diameter of 320 nm. Electrochemical performances also have been investigated. The results show that the cathode material Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ prepared at 900 °C for 12 h has a good electrochemical performance, which can deliver a high initial discharge capacity of 233.5, 214.2, 199.3, and 168.1 mAh g^?1 at 0.1, 0.2, 0.5, and 1 C, respectively. After 50 cycles, the capacity retains 178.0, 166.3, 162.1, and 155.9 mAh g^?1 at 0.1, 0.2, 0.5, and 1 C, respectively. The results indicate that the simple method has a great potential in synthesizing manganese-based cathode materials for Li-ion batteries.     

An insight into the influence of crystallite size on the performances of microsized spherical Li(Ni<Subscript>0.5</Subscript>Co<Subscript>0.2</Subscript>Mn<Subscript>0.3</Subscript>)O<Subscript>2</Subscript> cathode material composed of aggregated nanosized particles

Relationships between the performance and the crystallite size of the microsized spherical Li(Ni_0.5Co_0.2Mn_0.3)O₂ cathode material composed of aggregated nanosized primary particles have been comprehensively studied. The cathode material was synthesized by a high-temperature solid-state method. The results obtained by XRD, Rietveld refinement, SEM, HR-TEM, DSC, and galvanostatic test show that the crystallite size (XS) of Li(Ni_0.5Co_0.2Mn_0.3)O₂ is greatly affected by the temperature in the range of 750 to 820 °C. Most of all, the crystallite size plays a unique role in the performance of the material. That is, the electrochemical characteristics of Li(Ni_0.5Co_0.2Mn_0.3)O₂, such as discharge capacity, rate performance, and thermal stability, are closely related to the crystallite size. Furthermore, the retention of discharge capacity is determined by that of crystallite size in Li(Ni_0.5Co_0.2Mn_0.3)O₂ after 100 cycles.     

Improvement in rate capability of lithium-rich cathode material Li[Li<Subscript>0.2</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>Mn<Subscript>0.54</Subscript>]O<Subscript>2</Subscript> by Mo substitution

Lithium-rich cathode material Li[Li_0.2Ni_0.13Co_0.13Mn_0.54]O₂ doped with trace Mo is successfully synthesized by a sol-gel method. The X-ray diffraction patterns show that trace Mo substitution increases the inter-layer space of the material, of which is benefiting to lithium ion insertion/extraction among the electrode materials. The (CV) tests demonstrate the decrease of polarization, and on the other hand, the lithium ion diffusion coefficient (D _Li) of the modified material turns out to be larger, which indicates a faster electrochemical process. As a result, the Mo doped material possesses high rate performance and good cycling stability, and the initial discharge capacity reaches 149.3 mAh g^?1 at a current density of 5.0 °C, and the residual capacity is 144.0 mAh g^?1 after 50 cycles with capacity retention of 96.5 % in the potential range of 2.0–4.8 V at room temperature.     

Improving the electrochemical performance of Li-rich Li<Subscript>1.2</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>Mn<Subscript>0.54</Subscript>O<Subscript>2</Subscript> cathode material by LiF coating

To suppress the capacity fade of Li-rich Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ material as cathode materials for lithium-ion battery, we introduce a LiF coating layer on the surface to improve the cycling performance of Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ material. The modified sample shows a capacity of 163.2 mAh g^?1 with a capacity retention of 95% after 100 cycles at a current density of 250 mA g^?1, while the pristine sample only delivers a capacity of 129.9 mAh g^?1 with a capacity retention of 82%. Compared with the pristine material, the LiF-modified sample exhibits an obvious enhancement in the electrochemical performance, which will be very beneficial for this material to be commercialized on the new energy vehicles and other related areas.     

Improvement of electrochemical performance for AlF<Subscript>3</Subscript>-coated Li<Subscript>1.3</Subscript>Mn<Subscript>4/6</Subscript>Ni<Subscript>1/6</Subscript>Co<Subscript>1/6</Subscript>O<Subscript>2.40</Subscript> cathode materials for Li-ion batteries

Li-rich layered-layered-Spinel structure spherical Li_1.3Mn_4/6Ni_1/6Co_1/6O_2.40 particles was successfully prepared and coated with a uniform layer by a two-step co-precipitation method and evaluated in lithium cells. The structures and electrochemical properties of pristine Li_1.3Mn_4/6Ni_1/6Co_1/6O_2.40 and AlF₃-coated Li_1.3Mn_4/6Ni_1/6Co_1/6O_2.40 were characterized. When the coating amount was 2 wt%, the cathode showed the best cycling performance and rate capability compared to others. The AlF₃-coated Li_1.3Mn_4/6Ni_1/6Co_1/6O_2.40 Li-ion cell cathode had a capacity retention of 90.07 % after 50 cycles at 0.5 C over 2.0–4.8 V, while the pristine Li_1.3Mn_4/6Ni_1/6Co_1/6O_2.40 exhibited capacity retention of only 80.73 %. Moreover, the rate capability and cyclic performance also improved. Electrochemical impedance spectroscopy testing revealed that the improved electrochemical performance might attribute to the AlF₃ coating layer which can suppress the increase of impedance during the charging and discharging process by preventing direct contact between the highly delithiated active material and electrolyte.     

Synthesis of Li(Ni<Subscript>0.6</Subscript>Co<Subscript>0.2</Subscript>Mn<Subscript>0.2</Subscript>)O<Subscript>2</Subscript> with sodium DL-lactate as an eco-friendly chelating agent and its electrochemical performances for lithium-ion batteries

(Ni_0.6Co_0.2Mn_0.2)(OH)₂ precursor has been successfully prepared using hydroxide co-precipitation method. The thermodynamic model of hydroxide co-precipitation with sodium DL-lactate as an eco-friendly chelating agent is proposed. The microstructures of (Ni_0.6Co_0.2Mn_0.2)(OH)₂ precursors and Li(Ni_0.6Co_0.2Mn_0.2)O₂ cathode materials are investigated using X-ray diffractometer and scanning electronic microscopy, while the electrochemical performances of Li(Ni_0.6Co_0.2Mn_0.2)O₂ cathode materials are measured using a charge–discharge test. The influences of pH value on the structure and morphological and electrochemical performances of Li(Ni_0.6Co_0.2Mn_0.2)O₂ cathode materials have been discussed in detail. The results show that the sample at pH?=?11.5 exhibits the best lamellar structure and lowest cation mixing, while the sample at pH?=?11.0 delivers the most uniform and full particles and possesses the highest initial charge–discharge performance of 183.4 mAh/g and the best coulombic efficiency of 77.9% at the voltage range of 3.0–4.3 V. Even after 100 cycles, its discharge capacity still remains 165.2 mAh/g with the best retention rate of 90.1%. Furthermore, the sample at pH?=?11.0 delivers the highest discharge capacity at each current density. Even if discharged at 5C (1000 mA/g), the capacity of 115.6 mAh/g has been achieved. The sample at pH?=?11.0 exhibits the highest Li-ion diffusion coefficients (2.072?×?10^?12 cm²/s).     

Effects of doping Al on the structure and electrochemical performances of Li[Li<Subscript>0.2</Subscript>Mn<Subscript>0.54</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>]O<Subscript>2</Subscript> cathode materials

The Li-rich cathode material Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ had been successfully synthesized by a carbonate coprecipitation method. The effects of substituting traces of Al element for different transitional metal elements on the crystal structure and surface morphology had been investigated by X-ray diffraction (XRD) and field emission scanning electron microscopy. The results revealed that all the materials showed similar XRD patterns and surface morphology. It was demonstrated that LNCMAl1 exhibited the superior electrochemical performance. The discharge capacity was 265.2 mAh g^?1 at 0.1 C and still maintained a discharge capacity of 135.6 mAh g^?1 at 5.0 C. The capacity retention could still be 58.2 and 66.8% after 50 cycles at 1.0 and 2.0 C, respectively. Electrochemical impedance spectra results proved that the remarkably improved rate capability and cycling performance could be ascribed to the low charge transfer resistance and enhanced reaction kinetics.     

Influence of co-precipitation temperature on microstructure and electrochemical properties of Li[Li<Subscript>0.2</Subscript>Mn<Subscript>0.54</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>]O<Subscript>2</Subscript> cathode materials for lithium ion batteries

The layered Li-rich Mn-based cathode materials Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ were prepared by using co-precipitation technique at different temperatures, and their crystal microstructure and particle morphology were observed and analyzed by XRD and SEM. The electrochemical properties of these samples were investigated by using charge-discharge tests, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), respectively. The results indicated that all samples are of high purity. When the precursors were co-precipitated at 50 °C, their cathode materials have the most uniform and full particles and exhibit the highest initial discharge capacity (289.4 mAh/g at 0.1C), the best cycle stability (capacity retention rate of 91.2 % after 100 cycles at 0.5C), and the best rate performance. The EIS results show that the lower charge transfer resistance of 50 °C sample is responsible for its superior discharge capacity and rate performance.     

Enhanced electrochemical properties and thermal stability of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> by surface modification with Eu<Subscript>2</Subscript>O<Subscript>3</Subscript>

Layered LiNi_1/3Co_1/3Mn_1/3O₂ cathode material is synthesized via a sol-gel method and subsequently surface-modified with Eu₂O₃ layer by a wet chemical process. The effect of Eu₂O₃ coating on the electrochemical performances and thermal stability of LiNi_1/3Co_1/3Mn_1/3O₂@Eu₂O₃ cells is investigated systematically by the charge/discharge testing, cyclic voltammograms, AC impedance spectroscopy, and DSC measurements, respectively. In comparison, the Eu₂O₃-coated sample demonstrates better electrochemical performances and thermal stability than that of the pristine one. After 100 cycles at 1C, the Eu₂O₃-coated LiNi_1/3Co_1/3Mn_1/3O₂ cathode demonstrates stable cyclability with capacity retention of 92.9 %, which is higher than that (75.5 %) of the pristine one in voltage range 3.0–4.6 V. Analysis from the electrochemical measurements reveals that the remarkably improved performances of the surface-modified composites are mainly ascribed to the presence of Eu₂O₃-coating layer, which could efficiently suppress the undesirable side reaction and increasing impedance, and enhance the structural stability of active material.     

Synthesis and electrochemical properties of P2-Na<Subscript>2/3</Subscript>Ni<Subscript>1/3</Subscript>Mn<Subscript>2/3</Subscript>O<Subscript>2</Subscript>

The pure phase P2-Na_2/3Ni_1/3Mn_2/3O₂ was synthesized by a solid reaction process. The optimum calcination temperature was 850 °C. The as-prepared product delivered a capacity of 158 mAh g^?1 in the voltage range of 2–4.5 V, and there was a phase transition from P2 to O2 at about 4.2 V in the charge process. The P2 phase exhibited excellent intercalation behavior of Na ions. The reversible capacity is about 88.5 mAh g^?1 at 0.1 C in the voltage range of 2–4 V at room temperature. At an elevated temperature of 55 °C, it could remain as an excellent capacity retention at low current rates. The P2-Na_2/3Ni_1/3Mn_2/3O₂ is a potential cathode material for sodium-ion batteries.     

The properties research of ferrum additive on Li [Ni<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>] O<Subscript>2</Subscript> cathode material for lithium ion batteries

Li[Ni_1/3Co_(1-x)/3Mn_1/3Fe _x/3] O₂(x?=?0.0, 0.1, 0.3, 0.5, 0.7, and 0.9) cathode materials have been synthesized via hydroxide co-precipitation method followed by a solid state reaction. Thermogravimetry (TG) and differential thermal analysis (DTA) measurements were utilized to determine the calcination temperature of precursor sample. The crystal structure features were characterized by X-ray diffraction (XRD). The electrochemical properties of Li[Ni_1/3Co_(1-x)/3Mn_1/3Fe _x/3]O₂ were compared by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy(EIS), and galvanostatic charge/discharge test. Electrochemical test results indicate that Li[Ni_1/3Co_0.9/3Mn_1/3Fe_0.1/3] O₂ decrease charge transfer resistance and enhance Li⁺ ion diffusion velocity and thus improve cycling and high-rate capability compared with Li[Ni_1/3Co_1/3Mn_1/3]O₂. The initial discharge specific capacity of Li[Ni_1/3Co_0.9/3Mn_1/3Fe_0.1/3] O₂ was 178.5 mAh/g and capacity retention was 87.11 % after 30 cycles at 0.1C, with the battery showing good cycle performance.     

Surface-modified Li[Li<Subscript>0.2</Subscript>Mn<Subscript>0.54</Subscript>Ni<Subscript>0.13</Subscript>Co<Subscript>0.13</Subscript>]O<Subscript>2</Subscript> nanoparticles with LaF<Subscript>3</Subscript> as cathode for Li-ion battery

The LaF₃-coated Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ nanoparticles were synthesized via co-precipitation method followed by simple chemical deposition process. The crystal structure, particle morphology, and electrochemical properties of the bare and coated materials were studied by XRD, SEM, TEM, charge–discharge tests. The results showed that the surface coating on Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ nanoparticles were amorphous LaF₃ layer with a thickness of about 10–30 nm. After the surface modification with LaF₃ films, the coating layer served as a protective layer to suppress the side reaction between the positive electrode and electrolyte, and the Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ oxide demonstrated the improved electrochemical properties. The LaF₃-coated Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ electrode delivered the capacities of 270.5, 247.9, 197.1, 170.0, 142.7, and 109.5 mAh g^?1 at current rates of 0.1, 0.2, 0.5, 1, 2, and 5 C rate, respectively. Besides, the capacity retention was increased from 85.1 to 94.8 % after 100 cycles at 0.5 C rate. It implied surface modification with LaF₃ played an important role to improve the cyclic stability and rate capacity of the Li-rich nickel manganese oxides.     

Synthesis and microstructure of Co/Ni: MgGa<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles

This report discusses the preparation and microstructure of Co/Ni co-doped MgGa₂O₄ nanoparticles. The nanoparticles with the size of 20–55 nm were synthesized by sol-gel method. The phase and crystallinity were confirmed by X-ray powder diffraction (XRD) pattern. The particle size was estimated according to XRD data and transmission electron microscopy. The electronic structure was studied using X-ray photoelectron spectroscopy (XPS). The XPS studies showed that Ga³⁺ ions possess tetrahedral and octahedral sites of spinel structure and the inverse degree (two times of the fraction of tetrahedral Ga³⁺ ions) has increased with the increase of the doping concentration of Co²⁺ and Ni²⁺ ions. For Co/Ni co-doped MgGa₂O₄, two broad absorption bands of 350~500 and 550~700 nm were observed in the absorption spectra. The broad band at 350~500 nm was assigned to the combination of the absorption of octahedral Co²⁺ and Ni²⁺ ions, whereas the absorption band at 550~700 nm is mainly due to tetrahedrally coordinated Co²⁺ ions and octahedrally coordinated Ni²⁺ ions.     

Elevated electrochemical property of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript> originated from nano-sized Mn<Subscript>3</Subscript>O<Subscript>4</Subscript>

By employment of nano-sized pre-prepared Mn₃O₄ as precursor, LiMn₂O₄ particles have been successfully prepared by facile solid state method and sol-gel route, respectively. And the reaction mechanism of the used precursors of Mn₃O₄ is studied. The structure, morphology, and element distribution of the as-synthesized LiMn₂O₄ samples are characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Compared with LiMn₂O₄ synthesized by facile solid state method (SS-LMO), LiMn₂O₄ synthesized by modified sol-gel route (SG-LMO) possesses higher crystallinity, smaller average particle size (~175 nm), higher lithium chemical diffusion coefficient (1.17 × 10^?11 cm² s^?1), as well as superior electrochemical performance. For example, the cell based on SG-LMO can deliver a capacity of 85.5 mAh g^?1 at a high rate of 5 °C, and manifests 88.3% capacity retention after 100 cycles at 0.5 °C when cycling at 45 °C. The good electrochemical performance of the cell based on SG-LMO is ascribed mainly to its small particle size, high degree of dispersion, and uniform element distribution in bulk material. In addition, the lower polarization potential accelerates Li⁺ ion migration, and the lower atom location confused degree maintains integrity of crystal structure, both of which can effectively improve the rate capability and cyclability of SG-LMO.     

Improving the rate performance and stability of LiNi<Subscript>0.6</Subscript>Co<Subscript>0.2</Subscript>Mn<Subscript>0.2</Subscript>O<Subscript>2</Subscript> in high voltage lithium-ion battery by using fluoroethylene carbonate as electrolyte additive

Fluoroethylene carbonate (FEC) is investigated as the electrolyte additive to improve the electrochemical performance of high voltage LiNi_0.6Co_0.2Mn_0.2O₂ cathode material. Compared to LiNi_0.6Co_0.2Mn_0.2O₂/Li cells in blank electrolyte, the capacity retention of the cells with 5 wt% FEC in electrolytes after 80 times charge-discharge cycle between 3.0 and 4.5 V significantly improve from 82.0 to 89.7%. Besides, the capacity of LiNi_0.6Co_0.2Mn_0.2O₂/Li only obtains 12.6 mAh g^?1 at 5 C in base electrolyte, while the 5 wt% FEC in electrolyte can reach a high capacity of 71.3 mAh g^?1 at the same rate. The oxidative stability of the electrolyte with 5 wt% FEC is evaluated by linear sweep voltammetry and potentiostatic data. The LSV results show that the oxidation potential of the electrolytes with FEC is higher than 4.5 V vs. Li/Li⁺, while the oxidation peaks begin to appear near 4.3 V in the electrolyte without FEC. In addition, the effect of FEC on surface of LiNi_0.6Co_0.2Mn_0.2O₂ is elucidated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The analysis result indicates that FEC facilitates the formation of a more stable surface film on the LiNi_0.6Co_0.2Mn_0.2O₂ cathode. The electrochemical impedance spectroscopy (EIS) result evidences that the stable surface film could improve cathode electrolyte interfacial resistance. These results demonstrate that the FEC can apply as an additive for 4.5 V high voltage electrolyte system in LiNi_0.6Co_0.2Mn_0.2O₂/Li cells.     

Synthesis and electrochemical performance of spherical LiNi<Subscript>0.8</Subscript>Co<Subscript>0.15</Subscript>Ti<Subscript>0.05</Subscript>O<Subscript>2</Subscript> cathode materials with high tap density

A series of spherical LiNi_0.8Co_0.15Ti_0.05O₂ cathode materials were synthesized through co-oxidation-controlled crystallization method followed by solid-state reaction at different calcination temperatures under oxygen flowing. The crystal structure and particles morphology of the as-prepared powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. All samples correspond to the layered α-NaFeO₂ structure with R-3m space group. The LiNi_0.8Co_0.15Ti_0.05O₂ prepared at 800 °C presents a better hexagonal ordering structure and better spherical particles and possesses a high tap density of 3.22 g cm^?3. Meanwhile, the NCT-2 sample exhibits an advanced electrochemical performance with an initial discharge capacity of 174.2 mAh g^?1 and capacity retention of 86.7 % after 30 cycles at 0.2 C.     

The effects of copper and titanium co-substitution on LiNi<Subscript>0.6</Subscript>Co<Subscript>0.15</Subscript>Mn<Subscript>0.25</Subscript>O<Subscript>2</Subscript> for lithium ion batteries

The Li(Ni_0.6Co_0.15Mn_0.25)_1?x (CuTi) _x O₂ (x = 0.00, 0.01, 0.02, 0.03) cathode materials were synthesized via a hydroxide co-precipitation method followed by a solid-state reaction. The elementary composition, crystal structure features, morphology, and electrochemical performances of the powders were investigated in detail by inductively coupled plasma-atomic emission spectrometry (ICP-AES), X-ray diffraction (XRD), Rietveld refinement, scanning electron microscopy (SEM), galvanostatic charge/discharge test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV), respectively. The results of XRD and Rietveld refinements demonstrate that Cu and Ti co-substitution does not destroy the crystal structure, but can decrease cation ordering level and improve structural integrity. Electrochemical results show that Cu and Ti addition also results in an improved rate and cycling performances compared to pristine LiNi_0.6Co_0.15Mn_0.25O₂. An increase in rate performance and cycle stability upon copper and titanium co-substitution is related to the better hexagonal structure and enhanced kinetics of the intercalation process. Especially, Li(Ni_0.6Co_0.15Mn_0.25)_0.99(CuTi)_0.01O₂ exhibits the best rate performance and cycle stability among all samples with discharge specific capacity of 178.8 mAh/g and capacity retention of 90.6% after 30 cycles at 0.2C, which are higher than those of other materials.     

Hexagonal-like NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> nanostructure based high-performance supercapacitor electrodes

A novel approach of double hydroxide-mediated synthesis of nickel cobaltite (NiCo₂O₄) electro-active material by the hydrothermal method is reported. The obtained NiCo₂O₄ electro-active material displays the spinel cubic phase and hexagonal-like morphology. Thermogravimetry analysis confirms the thermal stability of the electrode material. The functional groups and phase formation of NiCo₂O₄ have been confirmed by FT-IR and Raman spectral analysis. The modified NiCo₂O₄ electrode exhibits the highest specific capacitance of 767.5 F g^?1 at a current density of 0.5 A g^?1 in 3 M KOH electrolyte and excellent cyclic stability (94 % capacitance retention after 1000 cycles at a high current density of 5 A g^?1). The excellent electrochemical performance of the electrode is attributed to the hexagonal-like morphology, which contributes to the rich surface electro-active sites and easy transport pathway for the ions during the electrochemical reaction. The attractive Faradic behavior of NiCo₂O₄ electrode has been ascribed to the redox contribution of Ni²⁺/Ni³⁺ and Co²⁺/Co³⁺ metal species in the alkaline medium. The symmetrical two-electrode cell has been fabricated using the NiCo₂O₄ electro-active material with excellent electrochemical properties for supercapacitor applications.     

NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> polyhedra with controllable particle size as high-performance anode for lithium-ion battery

Different particle sizes of dodecahedron precursors are synthesized by controlling the polarity of the solution. Through the results of scanning electron microscope (SEM) images, it can be found that different particle sizes of precursors present obvious edge angles and their morphology can be well retained after annealing. X-ray diffraction (XRD) measurements suggest that the annealed polyhedral products are pure single-phase NiCo₂O₄. When tested as lithium-ion battery anode, 0.5 μm NiCo₂O₄ polyhedra exhibits a specific capacity of 1050 mAh g^?1 at 0.1 C at the 60th cycle, which was higher than theoretical capacity of single metal oxide (NiO 718 mAh g^?1 and Co₃O₄ 890 mAh g^?1). It also exhibits the highest rate capability with an average discharge capacity of 890, 700, 490, 330, and 300 mAh g^?1 at 0.5, 2, 4, 8, and 10 C, respectively. Those advantages are attributed to that small-sized particle with great surface areas decrease the actual current density at the surface and inner of the prepared electrode.     

Thermoeletrochemical study on LiNi<Subscript>0.8</Subscript>Co<Subscript>0.1</Subscript>Mn<Subscript>0.1</Subscript>O<Subscript>2</Subscript> with in situ modification of Li<Subscript>2</Subscript>ZrO<Subscript>3</Subscript>

To improve the electrochemical performance of Nickel-rich cathode material LiNi_0.8Co_0.1Mn_0.1O₂, an in situ coating technique with Li₂ZrO₃ is successfully applied through wet chemical method, and the thermoelectrochemical properties of the coated material at different ambient temperatures and charge-discharge rates are investigated by electrochemical-calorimetric method. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests demonstrate that the Li₂ZrO₃ coating decreases the electrode polarizatoin and reduces the charge transfer resistance of the material during cycling. Moreover, it is found that with the ambient temperatures and charge-discharge rates increase, the specific capacity decreases, the amount of heat increases, and the enthalpy change (ΔH) increases. The specific capacity of the cells at 30 °C are 203.8, 197.4, 184.0, and 174.5 mAh g^?1 at 0.2, 0.5, 1.0, and 2.0 C, respectively. Under the same rate (2.0 C), the amounts of heat of the cells are 381.64, 645.32, and 710.34 mJ at 30, 40, and 50 °C. These results indicate that Li₂ZrO₃ coating plays an important role to enhance the electrochemical performance of LiNi_0.8Co_0.1Mn_0.1O₂ and reveal that choosing suitable temperature and current is critical for solving battery safety problem.