Pilot Application Of New Energy Ships Powered By Lithium Ion Batteries In Lijiang River Basin And Research On Its New Electrode Materials

Petrol motor ships introduce heavy pollution and large noise,causing disastrous influence on environments.New energy ships rise in response to the pollution problem.Lithium-ion batteries（LIBs）become the preferred energy storage cell of battery power system for electro-new energy ships due to the advantages of good safety,high output voltage,friendliness,mature production technology and design flexibility.Compared with electric vehicles,electric ships have higher requirements for the safety,cycle life and energy density of lithium ion batteries.The energy density can be enhanced by increasing operating voltage and specific capacity of the electrode materials.The Li Ni_0.5Mn_1.5O₄（LNMO）cathode material with a high voltage plateau of 4.7 V vs Li⁺/Li as cathode material and iron oxides with high capacity as anode material can increase the voltage of battery.The lithium ion batteries used LNMO with a high voltage plateau of 4.7 V vs Li⁺/Li as cathode material and iron oxides with high capacity as anode material can obtain high voltage and specific capacity.However,these materials all have serious cycle life problems.The petrol ships tourist cruising on Lijiang River also cause serious pollution and threaten the sustainable development of tourism in Guilin city.Based on the operating condition of the tourist ships on Lijiang River,this work selected the commercial Li Fe PO₄ aluminum shell LIBs with high safety,designed and made a lithium-ion battery system for the ship with a passenger capacity of 28tourists.This work also integrated battery system with electric and built commercially applicable LIBs-derived new energy ships.After more than a year of operation,lithium ion battery power system remains good performance.The expected target for the ships of a good operation with low noise and zero release has been achieved,which ranks in the top among the domestic similar researches.On this basis,the performance of Li Fe PO₄ cathode material was improved according to demand of the battery SOC estimation.In addition,a deep research was conducted to the problem of the LNMO and iron oxides as well as its composites,aiming to enhance battery energy density including the preparation of cathode materials with high performance/voltage and anode materials with high specific capacity.The main research contents are as follows:（1）This work conducted research on lithium-ion battery cells for electric ships on Lijiang,and the performances of the designed and produced cells were also studied.Comprehensively considering electrochemical performances,heat dispersion and mechanical strength and other factors,this work designed the battery system structure,studied separation and making sets of the LFP batteries,structure design of batteries in series and parallel,design and modification of unitized structure for cells and box,as well as electrochemical performances of the battery system.The first trail sailing of the lithium-ion battery power new energy ships with electric propulsion was successfully completed between Mopanshan wharf in Guilin and Longtoushan wharf in Yangshuo,and total distance is 54 km.Under actual operating conditions of still water,forward and reverse flow,the ship achieves a top speed of 16.63 km/h and 8.31 km/h at a minimum speed for not less than 5 h,which meet the navigation requirements of this section.The DC bus of the lithium-ion battery system has a stable voltage,whose voltage drop is lower than 1%and temperature rise is not higher than 3℃in case of an increased output power.By detecting the operation and performances of the ship for 17 months over the water in Lingui New District,the results show that the ship with zero release and low noise（52 db）can be fully available.The test results show that the designed lithium ion battery power system can be absolutely used for Lijiang river cruise ship,and the lithium-ion battery power-driven new energy ship effectively solve the pollution issues from petrol-driven ships.（2）Based on the wet milling method,the Li Fe PO₄/Li₂Fe Si O₄/C composite was prepared using Li Fe PO₄ and Li₂Fe Si O₄as raw materials and Span80 as surfactant.The characterization results of XRD、XPS、SEM and TEM suggest that the prepared sample shows superior particle size dispersion and cycling stability.The electrochemical tests show that the materials have the initial discharge capacity of 165.1 m Ahg^-1 at 0.1 C and good cycling performance.By modification of the electrode structure and electrochemical characteristics of the composite cathode material,the discharge curve presents a slope between the discharged capacities of 110 m Ahg^-1 and 150 m Ahg^-1.The increased slope lead to a corresponding change of the OCV-SOC.Compared with the cell used Li Fe PO₄material as cathode material,the cell with Li Fe PO₄/Li₂Fe Si O₄/C composite shows a slow fall of the voltage-capacity profile when the SOC comes to be 30%,and the voltage decreases from 3.312 to3.134 V in the SOC range of 30%～10%,and the voltage drop is 178 m V.The voltage detection error caused by electronic circuit is greatly reduced,so that the SOC can be estimated more accurately).This work achieves the accurate estimation of SOC by a simple adjustment of electrode material structure and electrochemical performances.（3）The Li₄Ti₅O₁₂（LTO）material selected as surface modification material was firstly coated on high voltage LNMO（4.7 V vs Li⁺/Li）cathode material to improve electrochemical performances.The LNMO material was prepared through a hydrothermal reaction,and when the coating quality of LTO was 1 wt%the LNMO@LTO material displays an initial specific discharge capacity of 141.2m Ah/g at 1 C.The capacity can retain 93.66%after 500 times under a current density of 1 C at room temperature,while about 94.36%of the capacity is maintained after 140 cycling time under0.2 C at 55℃.During long-term process of intercalation and deintercalation for lithium ions,LTO coating suppresses the continuous growth of high impedance film on cathode interface by the decomposition of electrolyte.The LNMO@LTO cathode material with good electrochemical performance is suitable for application in actual LIBs to achieve high specific energy.（4）The strategy of building new structure is introduced to improve the performances of iron oxides.Core-shell Fe₃O₄@Fe nanoparticles embedded into porous N-doped carbon nanosheets was prepared by a facile method with Na Cl as hard-template.The three-dimensional carbon architecture built by carbon nanosheets enhance the conductivity of the encapsulated Fe₃O₄@Fe nanoparticles and strengthen the structure stability suffering from volume expansion during extraction and insertion of lithium ions.Rich pores enhance the surface between electrode and electrolyte,which shorten the transmission path of ions and electrons.The core-shell structure with Fe as core further improves charge transferring inside particles thus lead to high capacity.The discharge capacity of Fe₃O₄@Fe/NC composite is 1164.2 and 514.7 m Ah/g at 0.5 and 20 A/g,respectively.Furthermore,the discharge capacity can reach 722.2 m Ah/g after 500th cycle at 2 A/g.The outstanding electrochemical performance of the Fe₃O₄@Fe/NC composite indicates its application potential as anode material for LIBs.