Owing to their high theoretical specific capacity and low cost, lithium- and manganese-rich layered oxide (LMR) cathode materials are receiving increasing attention for application in lithium-ion batteries. However, p...Owing to their high theoretical specific capacity and low cost, lithium- and manganese-rich layered oxide (LMR) cathode materials are receiving increasing attention for application in lithium-ion batteries. However, poor lithium ion and electron transport kinetics plus side effects of anion and cation redox reactions hamper power performance and stability of the LMRs. In this study, LMR Li_(1.2)Mn_(0.6)Ni_(0.2)O_(2) was modified by phosphorus (P)-doping to increase Li+ conductivity in the bulk material. This was achieved by increasing the interlayer spacing of the lithium layer, electron transport and structural stability, resulting in improvement of the rate and safety performance. P^(5+) doping increased the distance between the (003) crystal planes from ~0.474 nm to 0.488 nm and enhanced the structural stability by forming strong covalent bonds with oxygen atoms, resulting in an improved rate performance (capacity retention from 38% to 50% at 0.05 C to 5 C) and thermal stability (50% heat release compared with pristine material). First-principles calculations showed the P-doping makes the transfer of excited electrons from the valence band to conduction band easier and P can form a strong covalent bond helping to stabilize material structure. Furthermore, the solid-state electrolyte modified P5+ doped LMR showed an improved cycle performance for up to 200 cycles with capacity retention of 90.5% and enhanced initial coulombic efficiency from 68.5% (pristine) or 81.7% (P-doped LMR) to 88.7%.展开更多
Manganese-rich slag is a raw material for smelting silicon–manganese alloys using an electric furnace.The blast furnace method is the main method for smelting manganese-rich slag.This method has the problems of a lon...Manganese-rich slag is a raw material for smelting silicon–manganese alloys using an electric furnace.The blast furnace method is the main method for smelting manganese-rich slag.This method has the problems of a long process,large coke consumption,and easy volatilization of metals such as lead and zinc,which affects smelting safety.A new technology for smelting manganese-rich slag with low-manganese high-iron ore by smelting reduction optimization was proposed.This technology has the advantages of a short process,low energy consumption,low carbon emissions,and comprehensive recycling of lead,zinc,and other metals.According to the chemical composition,X-ray diffraction analysis,and particle size analysis of Cote d’Ivoire low-manganese ore,an experiment was carried out on manganese-rich slag by reduction–smelting separation.Combined with the design scheme of the Box–Behnken principle,three experimental factors(temperature,basicity,and carbon content)were selected as the influences to study.The influence that each factor has on the recovery rate of manganese was studied by response surface methodology,and the experimental factors were optimized.The results show that under the conditions of a reduction-smelting temperature of 1402℃,basicity of R=0.10,and carbon content of 10 mass%,the recovery rate of manganese is 97%.A verification experiment was carried out under the optimal conditions,and the error was only 1.24%;this proves that the response surface method prediction model is reliable and accurate.This is of great significance for the comprehensive utilization of lean-manganese ore resources.展开更多
Lithium-and manganese-rich(LMR)layered cathode materials hold the great promise in designing the next-generation high energy density lithium ion batteries.However,due to the severe surface phase transformation and str...Lithium-and manganese-rich(LMR)layered cathode materials hold the great promise in designing the next-generation high energy density lithium ion batteries.However,due to the severe surface phase transformation and structure collapse,stabilizing LMR to suppress capacity fade has been a critical challenge.Here,a bifunctional strategy that integrates the advantages of surface modification and structural design is proposed to address the above issues.A model compound Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(2)(MNC)with semi-hollow microsphere structure is synthesized,of which the surface is modified by surface-treated layer and graphene/car-bon nanotube dual layers.The unique structure design enabled high tap density(2.1 g cm^(−3))and bidirectional ion diffusion pathways.The dual surface coatings covalent bonded with MNC via C-O-M linkage greatly improves charge transfer efficiency and mitigates electrode degradation.Owing to the synergistic effect,the obtained MNC cathode is highly conformal with durable structure integrity,exhibiting high volumetric energy density(2234 Wh L^(−1))and predominant capacitive behavior.The assembled full cell,with nanograph-ite as the anode,reveals an energy density of 526.5 Wh kg^(−1),good rate performance(70.3%retention at 20 C)and long cycle life(1000 cycles).The strategy presented in this work may shed light on designing other high-performance energy devices.展开更多
基金This work was supported by the National Natural Science Foundation of China(U1564205)the Project of Construction of Innovative Teams and Teacher Career Development for Universities and Colleges under the Beijing Municipality(IDHT20180508).Naser Tavajohi acknowledges financial support from the Kempe Foundation.
文摘Owing to their high theoretical specific capacity and low cost, lithium- and manganese-rich layered oxide (LMR) cathode materials are receiving increasing attention for application in lithium-ion batteries. However, poor lithium ion and electron transport kinetics plus side effects of anion and cation redox reactions hamper power performance and stability of the LMRs. In this study, LMR Li_(1.2)Mn_(0.6)Ni_(0.2)O_(2) was modified by phosphorus (P)-doping to increase Li+ conductivity in the bulk material. This was achieved by increasing the interlayer spacing of the lithium layer, electron transport and structural stability, resulting in improvement of the rate and safety performance. P^(5+) doping increased the distance between the (003) crystal planes from ~0.474 nm to 0.488 nm and enhanced the structural stability by forming strong covalent bonds with oxygen atoms, resulting in an improved rate performance (capacity retention from 38% to 50% at 0.05 C to 5 C) and thermal stability (50% heat release compared with pristine material). First-principles calculations showed the P-doping makes the transfer of excited electrons from the valence band to conduction band easier and P can form a strong covalent bond helping to stabilize material structure. Furthermore, the solid-state electrolyte modified P5+ doped LMR showed an improved cycle performance for up to 200 cycles with capacity retention of 90.5% and enhanced initial coulombic efficiency from 68.5% (pristine) or 81.7% (P-doped LMR) to 88.7%.
文摘Manganese-rich slag is a raw material for smelting silicon–manganese alloys using an electric furnace.The blast furnace method is the main method for smelting manganese-rich slag.This method has the problems of a long process,large coke consumption,and easy volatilization of metals such as lead and zinc,which affects smelting safety.A new technology for smelting manganese-rich slag with low-manganese high-iron ore by smelting reduction optimization was proposed.This technology has the advantages of a short process,low energy consumption,low carbon emissions,and comprehensive recycling of lead,zinc,and other metals.According to the chemical composition,X-ray diffraction analysis,and particle size analysis of Cote d’Ivoire low-manganese ore,an experiment was carried out on manganese-rich slag by reduction–smelting separation.Combined with the design scheme of the Box–Behnken principle,three experimental factors(temperature,basicity,and carbon content)were selected as the influences to study.The influence that each factor has on the recovery rate of manganese was studied by response surface methodology,and the experimental factors were optimized.The results show that under the conditions of a reduction-smelting temperature of 1402℃,basicity of R=0.10,and carbon content of 10 mass%,the recovery rate of manganese is 97%.A verification experiment was carried out under the optimal conditions,and the error was only 1.24%;this proves that the response surface method prediction model is reliable and accurate.This is of great significance for the comprehensive utilization of lean-manganese ore resources.
基金The authors greatly appreciate the financial support from the National Science Foundation of China(22075048,51173027,21875141)Beijing National Laboratory for Condensed Matter Physics,Shanghai International Collaboration Research Project(19520713900).
文摘Lithium-and manganese-rich(LMR)layered cathode materials hold the great promise in designing the next-generation high energy density lithium ion batteries.However,due to the severe surface phase transformation and structure collapse,stabilizing LMR to suppress capacity fade has been a critical challenge.Here,a bifunctional strategy that integrates the advantages of surface modification and structural design is proposed to address the above issues.A model compound Li_(1.2)Mn_(0.54)Ni_(0.13)Co_(0.13)O_(2)(MNC)with semi-hollow microsphere structure is synthesized,of which the surface is modified by surface-treated layer and graphene/car-bon nanotube dual layers.The unique structure design enabled high tap density(2.1 g cm^(−3))and bidirectional ion diffusion pathways.The dual surface coatings covalent bonded with MNC via C-O-M linkage greatly improves charge transfer efficiency and mitigates electrode degradation.Owing to the synergistic effect,the obtained MNC cathode is highly conformal with durable structure integrity,exhibiting high volumetric energy density(2234 Wh L^(−1))and predominant capacitive behavior.The assembled full cell,with nanograph-ite as the anode,reveals an energy density of 526.5 Wh kg^(−1),good rate performance(70.3%retention at 20 C)and long cycle life(1000 cycles).The strategy presented in this work may shed light on designing other high-performance energy devices.
基金supported by the National Natural Science Foundation of China(U1564205)the Project of Construction of Innovative Teams and Teacher Career Development for Universities and Colleges under Beijing Municipality(IDHT20180508)。
