Multi-scale Structure Design,Fabrication And Performances Of Electrode For High-energy Lithium-ion Battery

The high energy density storage system is the technological foundation for realizing the transformation of new energy and the electrification of vehicles.Due to the low specific capacity and energy density,traditional lithium-ion batteries are unable to meet the future increasing demand for energy.Therefore,improving the energy density of the battery is an important direction for future development.Based on the working mechanism and cell structure of lithium ion battery,the main two strategies to increase the energy density of lithium batteries are listed as followed:1.The development of electrode materials with high specific energy,such as high-energy lithium metal anodes;2.Increasing the loading mass and thickness of the electrode active material on the current collector to reduce the ratio of the non-active material in the electrode.However,the dendrite growth caused by unstable brittle solid electrolyte interface(SEI)and huge volume changes in the discharge-charge process of lithium metal electrode seriously influence on the performance of the electrode cycle performance and security;meanwhile,the diffusion and conduction kinetics of lithium ion in high mass loading and ultra thick electrode is limited resulting poor rate performance.These severely limit their practical application.Recent research had shown that the electrode structure design can effectively improve the electrochemical performance of the electrode.Hence,how to solve the above problems by reasonable multi-scale structure design is an important challenge for improving battery energy density.This paper focuses on the preparation and application of high-energy lithium metal and high mass loading electrodes by the reasonable multi-scale structure design to improve the electrode performance.Firstly,the resent progress of lithium metal batteries and high mass loading electrodes is reviewed including the main exsitting problems and solving strategies.On the base of current theories,a series of reasonable multi-scale electrode structure design and corresponding preparation method are proposed.Meanwhile explore the internal relations between electrode structure and electrochemical performance aiming at resolving the scientific issues in Li metal electrodes or high mass loading electrodes and improving the specific energy of the battery.The main research results are summarized as follows:1.We developed a method for preparing a free-standing copper nanowire(CuNWs)network membrane.The flexible CuNWs membrane was prepared by a facile solvent evaporation assisted assembly technique under ambient conditions and then activated by the H2/Ar(5%/95%)flow at 450 ?.The CuNWs membrane as current collector replacing the traditional copper foil could achieve uniform distribution of lithium ion current so that lithium metal deposition effectively occurs on the surface of copper nanowires.Meanwhile,the Li metal could be accommodated into the three-dimensional network due to its prorous structure.As a result,the cycling stability of the lithium metal anode is significantly improved.This nanostructured current collector provides a new strategy for the efficient inhibition of lithium dendrite growth.2.On the basis of the prepared copper nanowire,the lithiophilic host Cu@Ni was prepare by Ni electrodeposition on the copper nanowire surface.Then the Li-Cu@Ni metallic nanocomposite anode was formed via the facile infusion of molten lithium into the Cu@Ni host.Due to the high conductivity of the three-dimensional Cu@Ni nanowire host,the plating and stripping of lithium metal in the network can be guided during the cycle,and the formation and growth of lithium dendrite can be suppressed.Meanwhile,due to the high mechanical stability of the Cu@Ni nanowire network framework,the volume of anode during battery cycling could be maintained with very small change resulting superior stability of the electrode.3.Inspired by the vertical micro-channels in natural woods as the highway for water transport,we successfully duplicated the microstructures of wood into ultra-thick bulk LiCoO2(LCO)cathode via a sol-gel process to achieve the high areal capacity and excellent rate capability.The X-ray based microtomography demonstrated that the uniform micro-channels were built up throughout the,whole wood-templated LCO cathode bringing in 1.5 times lower of tortuosity and?2 times higher of Li ion conductivity compared to that of random structured LCO cathode.The fabricated wood-inspired LCO cathode delivered high areal capacity up to 22.7 mAh cm-2(five times of the existing electrode)and achieved the dynamic stress test(DST)at such high areal capacity for the first time.The reported wood-inspired design will open a new avenue to adopt natural hierarchical structures to improve the performance of LIBs.