| As an important part of energy technology revolution,the development of advanced battery technology is of great significance for accelerating the transformation of green and low-carbon energy structure and promoting realizing the "Emission peak and Carbon neutralization" strategic goal.Currently,conventional lithium-ion batteries using graphite as a negative electrode have reached the energy density bottleneck,unable to meet the needs of longer life applications.Lithium metal is considered as the most ideal negative electrode choice for high energy batteries because of its theoretical specific capacity ten times that of graphite and the lowest electrode potential.However,there are still many problems hindering the commercialization of lithium metal anode,including huge volume expansion of electrode,low deposition/stripping efficiency and thermal runaway induced by lithium dendrite growth.On the other hand,the battery energy density is determined by the specific capacity and potential difference of positive and negative electrode materials.Only when the lithium metal negative electrode and advanced positive electrode with high specific capacity or high voltage(such as sulfur or high-nickel terre)are used together,can the battery devices with high energy density really be constructed.However,the active substance of the sulfur cathode is easy to dissolve and shuttle and the kinetics of the interface reaction is slow,while the high-nickel ternary cathode also has the problems of interface instability and crystal structure degradation under high-voltage operation.In response to the above scientific challenges,this paper starts with the relationship between the micro-nano structure of the anode/cathode surface and interface and its cycling performance,and constructs an efficient anode/cathode surface and interface simultaneously by designing a charging method suitable for lithium metal batteries,manually pre-constructing the electrode surface-interface force and the composition and structure of the regulatory liquid or solid electrolyte,so as to achieve a lithium metal battery with high energy density and high safety.This paper specifically studies the following contents:1.In Chapter 2,a charging method adapted to lithium metal battery inspired by electrified electrode surface and interface is designed,which simultaneously inhibits the growth of lithium dendrites and increases the specific discharge capacity of sulfur cathode.It has been proved that the adaptive enhanced electric field generated by the constant voltage charging module can inhibit the generation of lithium ion dissipation layer at the anode interface,and make the solvated structure of the interface rich in NO3-,so as to optimize the composition structure of the lithium metal interface nanostructure,stabilize the deposition of lithium metal and improve its reversibility.It is found that large initial constant voltage can promote the migration,adsorption and conversion of polysulfide anions to cathode and improve the utilization of sulfur.Based on the optimization of charging parameters,a new charging method of constant voltageconstant current-constant voltage for Li-sulfur battery was proposed.Under constantvoltage module charging,the lithium metal anode withstands 27 mA cm-2 peak current without short-circuiting,and the Li-sulfur battery based on the proposed charging method shows a capacity improvement of nearly 40%.2.In chapter 3,aiming at the problems that the charging method designed in chapter 2 has limited capacity improvement of the sulfur cathode and low coulomb efficiency cathode,a strategy of electrostatic preregulation on the cathode surface is proposed,and the ionic liquid-three-dimensional carbon fiber composite sulfur cathode is constructed,which greatly improves the capacity and stability of the sulfur cathode.The ionic liquid structure unit is dissociated in the electrolyte,and the positive charge potential of quaternary amine salt fixed on the fiber surface plays a strong electrostatic attraction to the polysulfide anion,inhibits the dissolution and shuttle of lithium polysulfide,and accelerates the transmission and reaction of lithium polysulfide.The preferred piperidine complex positive electrode is stable under the condition of high sulfur load and lean electrolyte.When combined with the optimized charging method in Chapter 2,the specific discharge capacity is further increased from 1210 mAh g-1 to 1330 mAh g-1,and the coulomb efficiency of the whole battery is higher than 99.3%.3.In Chapter 4,a liquid electrolyte based on LiBF4 and LiNO3 dual-salt additives is designed,which can synchronously construct an efficient anode and cathode interphase,stabilize the deposition of lithium metal and improve the stability of the high-nickel ternary cathode.LiBF4 additive can not only form an interfacial film rich in F-and B-components for the high-nickel ternary cathode,improving its stability at 4.4 V high voltage,but also promote the dissolution of insoluble LiNO3 in the carbonate electrolyte through strong interaction between its Lewis acidity and the nitrogen site of LiNO3.The successful introduction of LiNO3 results in a strong Li2O rich interphase at the lithium metal anode,which inhibits the generation of lithium dendrites and increases the coulomb efficiency to 98.7%.In addition,lithium nitride species is produced in both anode and cathode interphase,which improves the reaction kinetics performance of anode and cathode.The lithium-high-nickel ternary battery achieves ultra-high specific capacity of 185.6 mAh g-1 at 5 C charging rate(10 mA cm-2).The full battery still shows 80.3%capacity retention rate after 250 cycles.4.In Chapter 5,the structural design of a three-layer compound sulfide solid electrolyte is proposed,and the relationship between the sulfide interlayer material and the composite electrolyte structure to inhibit the lithium dendrites and stabilize the electrode interface is explored.The lithium-sulfur and lithium-high-nickel ternary batteries without short circuit and stable circulation are realized under large current.The interlayer material,which is rich in metal elements and easy to degrade and alloying with lithium metal,can inhibit the growth of lithium dendrites and increase the critical curVent density of lithium metal negative electrode to 3 mA cm-2.The interlayer material reacts with lithium to produce highly electronic insulating material Li2S,which improves the electrode interface stability and thus stabilizes the electrode overpotential.Optimization of Li6PS5Cl‖LiioSnPSi2‖Li6PS5Cl three electrolytes,inhibit the growth of the lithium dendrite,smooth the electrode potential,to prevent the transition metal sulfur or dissolution of active material,lithium-high-nickel ternary battery in 1 C high rate shows capacity retention as high as 75.3%after 600 cycles;Lithium-sulfur battery exhibit ultra-high specific capacity of over 1200 mAh g-1 at 0.5 C.In summary,this paper mainly focuses on two systematic strategies of charging method design and electrolyte composition and structure regulation.Combined with the method of electrode surface and interface preconstruction,the surface and interface of lithium metal anode and advanced cathodes is co-modified and optimized,which effectively stabilizes the deposition process of lithium metal and synchronously improves the stability of advanced cathodes.It has important reference significance for realizing high energy density and high safety lithium metal battery energy devices. |
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