Synthesis, Modification And Electrochemical Performance Of Transition Metal Layer Oxide Cathode Material For Lithium Ion Battery

The high nickel of layered cathode material has been considered a promisingmaterial for commercial due to high capacity, high voltage platform of discharge, lowcost. However, the poor cycle performance and thermal stability is adverse to itslager-scale application. To optimize the comprehensive electrochemical properties ofthis kind of material, Al inserts into Ni0.83Co0.10Mn0.07(OH)2via replacing Ni inNi0.83Co0.10Mn0.07(OH)2microspheres by cation-exchange method and results in agradient distribution of Al and Ni in the microsphere particles. Then, after mixed withlithium salt and calcining, obtain the final lithium metal oxides materials with similarmetal elements distribution characteristics. In addition, the Al and F were introducedto the materials at the same time by ion exchange method that can be improved thecycle performance. The following are related research results mainly includingseveral parts:(1)The precursor Ni0.83Co0.1Mn0.07(OH)2was modified by Al via cation-exchangemethod at the condition of hydrothermal. A series of Ni0.83-xCo0.1Mn0.07Alx(OH)2canbe obtained by controling the raction time and temperature of the caion-exchangeprocess. The lithiated Li(Ni0.83-xCo0.1Mn0.07Alx)O2materials are obtained by mixedthe obtained Ni0.83-xCo0.1Mn0.07Alx(OH)2with lithium hydroxide monohydrate andthen calcined. The following are related results demonstrate that①the morphologyand structure of the samples after caion-exchange treatment is unchanged;②thecaion-exchange mainly occurred between the Al3+and Ni2+resulted in a gradientdistribution of Al and Ni in the microspheres;③When the reaction temperature ortime increase, the exchange contents of Al3+and Ni2+increase;④Electrochemicaltests carried out that the optimal electrochemical performance come fromLiNi0.783Co0.096Mn0.065Al0.056O2synthesized by the cation exchange method reactionat the150°C with4h. At the discharge current of0.1C, the specific discharge capacityof the obtained sample reaches203.4mAh/g, and it depicts a much higher specificcapacity reaches141.7mAh/g after the30th cycles, compared with the untreated sample only80.8mAh/g.(2) Al was succsseful introduce to the precursor Ni0.83Co0.1Mn0.07(OH)2viacation-exchange method, and the obtained samples display gradient distribution of Aland Ni. However, the high temperature with the hydrothermal reaction was notadvantage of commercial scale production. Thus, it is necessary to explore thecation-exchange reaction with mild condition to solve the above problem. Therefore,the precursor Ni0.83Co0.1Mn0.07(OH)2was modified by Al via element cation-exchangemethod at open water bath, and then a series of Ni0.83-xCo0.1Mn0.07Alx(OH)2obtainedby change the reaction time and temperature, After mixing with Lithium hydroxidemonohydrate, the obtained precursor Ni0.83Co0.1Mn0.07(OH)2was calcined at hightemperature to synthesize the corresponding Li(Ni0.83-xCo0.1Mn0.07Alx)O2. The relatedinvestigations indicate that the Al3+has successfully replaced Ni2+at the water bathcondition of lower temperature with the characteristic of morphology and structureunchanged. The synthesized LiNi0.754Co0.092Mn0.056Al0.098O2by cation exchangemethod at the50°C with6h has the excellent electrochemical performance: at thedischarge current of0.1C, the initial discharge capacity was162.5mAh/g, and itexhibited a high specific capacity about137.8mAh/g after the50th cycles (retaining84.80%of its initial capacity).(3) The precursor Ni0.83Co0.1Mn0.07(OH)2was modified by Al and F elementsvia ion exchange method at the condition of hydrothermal, so that a series ofhydroxide samples with Al and F elements were obtained by changing with the ratiosof reactants and reaction temperature. The corresponding layered oxide materialswere obtained by mixed with Lithium hydroxide monohydrate and calcined at hightemperature. The related investigations manifeste that transition metal layer oxide,synthesized by3%AlF3and Ni0.83Co0.1Mn0.07(OH)2at the160°C for4h, behavesoptimal electrochemical performance. The initial discharge capacity of the obtainedsample was140.3mAh/g and retaining capacity is74.67%after the40th cycles. The initial discharge capacities of the samples obtained by introducing one single ion (Alor F) are167.9and157.9mAh/g, the retaining capacities are53.13%and57.51%after the40th cycles, respectively. Therefore, the exchange of Al and F ion exchangeconcurrently can improve the cycle performance.