WO2019000700A1 - 一种应用于锂金属电池的脉冲充电方法 - Google Patents

一种应用于锂金属电池的脉冲充电方法 Download PDF

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WO2019000700A1
WO2019000700A1 PCT/CN2017/105454 CN2017105454W WO2019000700A1 WO 2019000700 A1 WO2019000700 A1 WO 2019000700A1 CN 2017105454 W CN2017105454 W CN 2017105454W WO 2019000700 A1 WO2019000700 A1 WO 2019000700A1
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pulse
lithium metal
lithium
battery
metal battery
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PCT/CN2017/105454
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English (en)
French (fr)
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陆盈盈
何奕
谭深
李琪
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浙江大学
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • the present invention relates to a charging method, and in particular to a pulse charging method applied to a lithium metal battery.
  • lithium-ion battery As a new type of clean energy storage medium, lithium-ion battery is widely used in mobile phones, notebook computers, electric vehicles, etc. It has also been tried in military fields such as unmanned aircraft, and is the next generation of high-energy energy storage equipment. main direction. Although the energy density of lithium-ion batteries is higher than that of traditional lead-acid, nickel-hydrogen and other batteries, it still cannot meet the increasing demand for higher energy density. Therefore, the development of next-generation lithium battery systems has become particularly important. Metallic lithium, which has a high specific capacity (3860 mAhg -1 ) and a low reduction potential (-3.04 V vs. standard hydrogen electrode potential), is considered to be the most promising electrode material for use in next-generation lithium battery systems. However, lithium metal electrodes still have to solve many problems before they are actually applied.
  • lithium ions acquire electrons on the surface of the lithium metal electrode and deposit it into metallic lithium. Due to the complex surface morphology of the lithium metal electrode and the complex chemical reactions occurring on its surface, such electrodeposition is generally non-uniform and difficult to control. At the same time, the rough surface causes the charge distribution to be uneven. In the subsequent cycle, this uneven electrodeposition, or lithium dendrite, becomes more severe. The growth of lithium dendrites is believed to be a major problem limiting the application of lithium metal electrodes. In addition, the lithium metal irreversibly reacts with the electrolyte to form a solid electrolyte interface film (SEI) to passivate the lithium metal with high activity and reduce further consumption of the active material.
  • SEI solid electrolyte interface film
  • the invention of a simple, economical and effective method to protect lithium metal electrodes is of great significance for the development of the next generation lithium metal battery system.
  • the invention provides a pulse charging method applied to a lithium metal battery, which can suppress lithium dendrite growth and reduce volume expansion, thereby effectively protecting the lithium metal electrode, prolonging the service life, stabilizing the cycle, and improving the safety.
  • a pulse charging method applied to a lithium metal battery the electrode material of the lithium metal battery being selected from the group consisting of pure lithium metal, lithium metal alloy or lithium metal-carbon material.
  • the lithium metal alloy includes a lithium aluminum alloy, a lithium magnesium alloy, a lithium boron alloy, a lithium tin alloy, Lithium-lead alloy
  • the carbon material is selected from the group consisting of graphite, graphene, carbon nanotubes, carbon nanowires, and the like.
  • the lithium metal battery uses the above pure lithium metal, lithium metal alloy or lithium metal-carbon material as a negative electrode material, and uses a lithium cobaltate electrode, a lithium manganate electrode, a lithium iron phosphate electrode, a cobalt nickel manganese ternary electrode, and a cobalt.
  • a nickel-aluminum ternary electrode or a sulfur-containing electrode or a pure lithium metal electrode is used as a positive electrode, and then assembled into the lithium metal battery together with an adapted electrolyte and a separator.
  • the charging method employs pulse current charging.
  • the pulse current is connected to the assembled lithium metal battery and charged.
  • the pulse current duty ratio is 10% to 90%.
  • the waveform of the pulse current is not particularly limited, and may be a square wave, a spike wave, a sawtooth wave, a bell wave, a staircase wave, a trapezoidal wave, or a triangular wave.
  • the pulse current has a pulse width of 1 ns to 1000 s, a pulse width (peak current density) of 0.01 ⁇ A cm -2 to 500 mA cm -2 , and a pulse frequency of 0.001 Hz. 10 9 Hz.
  • the pulse current has a duty ratio of 16.67% to 66.67%, a pulse width of 1 ms to 100 s, a pulse width of 0.01 mAcm -2 to 10 mAcm -2 , and a pulse frequency of 0.01 Hz to 1 kHz.
  • the duty ratio of the pulse current is 16.67% to 50%
  • the pulse current has a pulse width of 1 ms to 10 s, a pulse amplitude of 0.1 mA cm -2 to 10 mA cm -2 , and a pulse frequency of 0.1 Hz to 1 kHz.
  • the pulse current has a duty ratio of 16.67% to 50%, a pulse width of 1 ms to 1 s, a pulse width of 0.5 mAcm -2 to 6 mAcm -2 , and a pulse frequency of 0.1 Hz to 500 Hz.
  • the present invention has the following outstanding advantages:
  • the invention proposes to charge a lithium metal battery by using a pulse method instead of the traditional constant current method.
  • the lithium metal electrode is protected simply, conveniently and efficiently, which can effectively inhibit the growth of lithium dendrite, reduce the volume expansion of the lithium metal electrode, prolong the life of the lithium metal electrode, improve the coulombic efficiency, and improve the stability of the electrochemical cycle.
  • FIG. 1 is a schematic diagram showing a square wave pulse current signal used in Embodiment 1 (left), and a schematic diagram of a constant current signal used in Comparative Example 1 (right); in the figure, a-pulse width, b - pulse amplitude, c-pulse period;
  • Example 2 is a plan scanning electron micrograph (left image) of a common lithium metal electrode used in Example 1, and a plane scanning electron micrograph (right image) after 8 cycles of pulse current, and gives a constant ratio of the comparative example.
  • Example 3 is a cross-sectional scanning electron micrograph (left image) of a conventional lithium metal electrode used in Example 1, and a cross-sectional scanning electron micrograph (right image) after 8 cycles of pulse current conditions, and gives a comparative example.
  • FIG. 5 is a time-voltage enlarged view of the dotted line frame of FIG. 4, the left figure of FIG. 5 corresponds to the left figure of FIG. 4, and the right figure of FIG. 5 corresponds to the right figure of FIG.
  • FIG. 7 is a graph showing the time-voltage curve of the pulse current condition of the symmetric battery assembled in the lithium metal electrode of Example 3 at a duty ratio of 66.67% (top), and the symmetry of the lithium metal electrode assembly in the first embodiment. Time-voltage curve of the battery under the condition of 16.677% pulse current (The following figure).
  • the positive electrode and the negative electrode were both lithium metal electrodes, assembled into a symmetrical battery, and the electrolyte was 1 M LiTFSI/PC.
  • the constant current is connected to the charge and discharge cycle test under the following conditions: current density is 3 mA cm 2 , charge and discharge power is 1 mAh cm -2 , and charge and discharge time is 20 min.
  • the lithium metal battery was looped shortly for 20 cycles.
  • the positive electrode and the negative electrode were both lithium metal electrodes, assembled into a symmetrical battery, and the electrolyte was 1 M LiTFSI/PC.
  • pulse current to charge and discharge cycle test the conditions are as follows: square wave pulse current, duty cycle (pulse width / pulse period) is 16.67%, pulse width is 1 s, pulse amplitude (peak current density) is 3 mA cm -2 , pulse The frequency is 0.167 Hz. After charging the same amount of 1 mAh cm -2 , the discharge test was performed, and the same amount of 1 mAh cm -2 was discharged to cycle. The charge and discharge pulse parameters are consistent. In each cycle, the total charge pulse width is accumulated to 20 min, and the total discharge pulse width is also accumulated for 20 min.
  • the lithium metal battery was subjected to pulse current charging using the conditions in the present embodiment, and at least 50 cycles did not occur.
  • FIGS. 2 and 3 are plane and cross-sectional scanning electron micrographs of the symmetrical battery assembled with the lithium metal electrode before charging and 8 cycles after charging conditions of Comparative Example 1 and Example 1, respectively.
  • Observation chart can be found that the pulse current charging cycle in the plan view, lithium metal electrode table Faced more dense than the constant current charging cycle, the gap is also less, and the dendrites are less; in the cross-sectional view through the pulse current charging cycle, the thickness of the lithium metal electrode is less than that after the constant current charging cycle, indicating that the cycle The inner electrode is more compact inside and the volume expansion problem is suppressed.
  • the positive electrode and the negative electrode were both lithium metal electrodes, assembled into a symmetrical battery, and the electrolyte was 1 M LiTFSI/PC.
  • pulse current to charge and discharge cycle test the conditions are as follows: square wave pulse current, duty cycle (pulse width / pulse period) is 50%, pulse width is 1s, pulse amplitude (peak current density) is 6mA cm -2 , pulse The frequency is 0.5 Hz.
  • the discharge test was performed, and the same amount of 1 mAh cm -2 was discharged to cycle. In each cycle, the total charge pulse width plus the stop time is accumulated to 20 min, and the total discharge pulse width plus the stop time accumulation is also 20 min.
  • the lithium metal battery was subjected to pulse current charging using the conditions in the present embodiment, and at least 160 cycles did not occur.
  • the life of the lithium metal battery can be increased by at least 8 times or more under the pulse current condition of the present embodiment.
  • the positive electrode and the negative electrode were both lithium metal electrodes, assembled into a symmetrical battery, and the electrolyte was 1 M LiTFSI/PC.
  • the pulse current is connected to the charge and discharge cycle test under the following conditions: square wave pulse current, duty ratio (pulse width/pulse period) is 66.67%, pulse width is 1 s, pulse amplitude (peak current density) is 3 mA cm -2 , pulse The frequency is 0.6667 Hz. After charging 1 mAh cm -2 of electricity, perform a discharge test and also release 1 mAh cm -2 of electricity to circulate. The charge and discharge pulse parameters are consistent. In each cycle, the total charge pulse width is accumulated to 20 min, and the total discharge pulse width is also accumulated for 20 min.
  • the lithium metal battery with a duty ratio of 66.67% is cyclically short-circuited for 20 cycles, and the lithium metal battery with a duty ratio of 16.67% can be cycled for at least 50 cycles without short circuit.
  • the time-voltage curves of the symmetric battery assembled by the lithium metal electrode in the pulse current charging conditions of the embodiment 1 and the embodiment 3 are respectively shown in Fig. 7, and the lithium metal battery cycle is further under the condition that the duty ratio is 16.67%. Stable, no significant voltage spurt or sudden drop occurred after 210h, and a significant voltage spurt occurred after 25h at a duty cycle of 66.67%.
  • the lithium metal battery is short-circuited under a constant current condition at a current density of 3 mA/cm 2 and a charge and discharge time of 20 min, and the charge current is consistent under the pulse current condition of the present invention.
  • the pulse amplitude is 3 mA/cm 2
  • the duty ratio is 16.67%
  • the pulse width is 1 s
  • the pulse frequency is 16.67 Hz
  • the lithium metal battery can be looped for at least 50 cycles without short circuit.
  • the larger pulse amplitude is 6 mA/cm 2 and the duty ratio is 50%.
  • the width is 1 s
  • the pulse frequency is 0.5 Hz
  • the lithium metal battery can be looped for at least 160 cycles without short circuit.
  • the same lithium metal electrode is assembled into a symmetrical battery, the electrolyte is 1M LiTFSI/DOL:DME (volume ratio is 1:1), the additive is LiNO 3 , and the pulse current is connected for cyclic test.
  • the conditions are as follows: square wave pulse current, accounting The space ratio is 25%, the pulse width is 0.1 s, the pulse amplitude (peak current density) is 1 mA cm -2 , and the pulse frequency is 2.5 Hz. After charging 0.5mAh cm -2 , the pulse current signal is reversed for discharge test, and 0.5mAh cm -2 is also discharged to cycle.
  • the lithium metal battery was subjected to pulse current charging by using the conditions in the present embodiment, and at least 110 cycles did not occur.
  • the electrolyte is 1M LiPF 6 /EC: DEC (volume ratio 1:1), connected with pulse current
  • the cycle test was carried out under the following conditions: square wave pulse current, duty ratio of 25%, pulse width of 0.001 s, pulse amplitude (peak current density) of 0.5 mA g -1 , and pulse repetition frequency of 250 Hz. After charging 1 mAh g -1 of electricity, the pulse current signal is reversed for discharge test, and 1 mAh g -1 of electricity is also discharged, thereby circulating.
  • the lithium metal battery was subjected to pulse current charging using the conditions in the present embodiment, and at least 250 cycles were not observed.
  • the lithium metal electrode and the sulfide electrode are assembled into a lithium sulfur battery, the electrolyte is 1M LiTFSI in DOL: DME (volume ratio is 1:1), the additive is LiNO 3 , and the pulse current is connected for cyclic test under the following conditions: square wave
  • the pulse current has a duty ratio of 50%, a pulse width of 0.001 s, a pulse amplitude (peak current density) of 0.5 mA/g, and a pulse repetition frequency of 500 Hz. After charging 5 mAh/g of electricity, the pulse current signal is reversed for discharge test, and 5 mAh/g of electricity is also discharged, thereby circulating.
  • the lithium metal battery was subjected to pulse current charging using the conditions in the present embodiment, and no short circuit occurred at least for 45 cycles.
  • the same lithium metal electrode is assembled into a symmetrical battery.
  • the electrolyte is 1M LiTFSI/DOL:DME (volume ratio is 1:1), the additive is LiNO 3 , and the pulse current is connected for cyclic test.
  • the conditions are as follows: spike wave pulse current, accounting for The space ratio is 25%, the pulse width is 0.1 s, the pulse amplitude (peak current density) is 2 mA cm -2 , and the pulse frequency is 2.5 Hz.
  • the pulse current signal is reversed for discharge test, and 2 mAh cm -2 is discharged to cycle.
  • the lithium metal battery was subjected to pulse current charging using the conditions in the present embodiment, and at least 80 cycles were not cycled.
  • the same lithium metal electrode is assembled into a symmetrical battery, the electrolyte is 1M LiTFSI/PC (volume ratio is 1:1), and the pulse current is connected for cyclic test under the following conditions: trapezoidal pulse current, duty ratio 25%, pulse The width is 0.1 s, the pulse amplitude (peak current density) is 1 mA cm -2 , and the pulse frequency is 2.5 Hz.
  • the pulse current signal is reversed for discharge test, and 2 mAh cm -2 is discharged to cycle.
  • the lithium metal battery was subjected to pulse current charging using the conditions in the present embodiment, and no short circuit occurred at least for 45 cycles.
  • the same lithium metal electrode is assembled into a symmetrical battery, the electrolyte is 1M LiTFSI/PC (volume ratio is 1:1), and the pulse current is connected for cyclic test under the following conditions: clock pulse current, duty ratio is 25%, The pulse width is 0.1 s, the pulse amplitude (peak current density) is 3 mA cm -2 , and the pulse frequency is 2.5 Hz. After charging 3mAh cm -2 , the pulse current signal is reversed for discharge test, and 3mAh cm -2 is discharged to cycle. After testing, the lithium metal battery was subjected to pulse current charging using the conditions in the present embodiment, and at least 60 cycles did not occur.
  • the same lithium metal electrode is assembled into a symmetrical battery, the electrolyte is 1M LiTFSI/PC (volume ratio is 1:1), and the pulse current is connected for cyclic test under the following conditions: triangular wave pulse current, duty ratio 25%, pulse width For 0.1 s, the pulse amplitude (peak current density) is 2 mA cm -2 and the pulse frequency is 2.5 Hz. After charging 1 mAh cm -2 of electricity, the pulse current signal is reversed for discharge test, and 1 mAh cm -2 of electricity is also discharged, thereby circulating. After testing, the lithium metal battery was subjected to pulse current charging using the conditions in the present embodiment, and at least 40 cycles did not occur.

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Abstract

本发明公开了一种应用于锂金属电池的脉冲充电方法，所述脉冲充电方法为脉冲电流充电；所述锂金属电池的电极材料选自纯锂金属、锂金属合金或锂金属-碳材料。本发明提供了一种应用于锂金属电池的脉冲充电方式，可以实现抑制锂枝晶生长，减少体积膨胀，从而起到有效保护锂金属电极，延长使用寿命，稳定循环，提高安全性的作用。

Description

一种应用于锂金属电池的脉冲充电方法 技术领域
本发明涉及一种充电方法，具体地说，涉及一种应用于锂金属电池的脉冲充电方法。
背景技术
锂离子电池作为一种新型的、清洁的储能介质，广泛被应用于手机、笔记本电脑、电动汽车等，也被尝试应用于无人飞机等军事领域，是发展下一代高能量储能设备的主要方向。虽然锂离子电池的能量密度较传统铅酸、镍氢等电池要高，但仍不能满足人们日益增加对更高能量密度的需求。因此开发下一代锂电池体系变得尤其重要。金属锂，其高比容量(3860mAhg-1)和低还原电位(-3.04V vs.标准氢电极电势)，被认为是应用于下一代锂电池体系中最有前景的电极材料。然而，锂金属电极在真正应用之前仍需解决许多问题。
在一个典型的充电过程中，锂离子在锂金属电极表面获得电子，并沉积成金属锂。由于锂金属电极表面形貌复杂，以及在其表面发生的化学反应很复杂，所以这种电沉积通常是不均匀的，难以控制。同时粗糙表面又造成的电荷分布不均匀。在随后的循环中，这种不均匀的电沉积物或者说是锂枝晶，会变得更加严重。锂枝晶的生长被认为是限制锂金属电极应用的主要问题。另外，锂金属会和电解液发生不可逆反应，形成固体电解质界面膜(SEI)，以钝化活性高的锂金属，减少活性物质的进一步消耗。由于锂金属电极的体积膨胀和锂枝晶的生长，脆弱的SEI可能在循环过程中破裂。SEI的不稳定性也是锂枝晶形成的另一个原因。一旦新鲜的锂再次遇到电解液，反应就会再次发生，形成新的SEI，从而导致不可逆的锂和电 解质的消耗。最终导致锂金属电池的库仑效率降低，容量衰减。电极表面的枝晶可以穿透隔膜，引起短路发热，甚至点燃有机溶剂。此外，锂金属电极的巨大体积变化也会导致电池内部压力变化和界面波动。
大量的研究(Adv.sci.2016,3,1500213；Nature Nanotech.2014,9,618-623；专利:CN104103873A)对锂金属负极进行了调节，一定程度上稳定了锂金属电池的电化学行为。另外研究人员也对锂枝晶的形成原因进行了探索，从理论上分析了锂枝晶成核和扩张的条件。锂枝晶的生长是由锂离子及其对离子在电场力作用下扩散和电迁移造成的。在充电过程中，锂离子和其对离子在相反的方向上传输，形成离子浓度梯度。在大电流密度条件下，对锂离子的情况更糟，因为它们无法形成电极。最终锂离子在负极附近堆积，而正极附近的锂离子不断消耗直至耗尽。这种现象被称为“空间电荷”效应，它决定了锂枝晶的起始时间。
许多科研工作者从实验结果上提供了许多思路，也从理论上分析了锂枝晶的生成的原因，但是却都无法从根本上彻底解决锂枝晶生长给锂金属电池带来的一系列问题如库伦效率低、循环性能差、体积膨胀、容量衰减等问题。
因此，发明简单、经济、有效的方法来保护锂金属电极，对于发展下一代锂金属电池体系具有重要的意义。
发明内容
本发明提供了一种应用于锂金属电池的脉冲充电方式，可以实现抑制锂枝晶生长，减少体积膨胀，从而起到有效保护锂金属电极，延长使用寿命，稳定循环，提高安全性的作用。
具体技术方案如下：
一种应用于锂金属电池的脉冲充电方式，所述锂金属电池的电极材料选自纯锂金属、锂金属合金或锂金属-碳材料。
所述的锂金属合金包括锂铝合金、锂镁合金、锂硼合金、锂锡合金、 锂铅合金等
所述的碳材料选自石墨、石墨烯、碳纳米管、碳纳米线等。
所述的锂金属电池以上述的纯锂金属、锂金属合金或锂金属-碳材料作为负极材料，以钴酸锂电极、锰酸锂电极、磷酸铁锂电极、钴镍锰三元电极、钴镍铝三元电极或含硫电极或纯锂金属电极作为正极，再与适配的电解液和隔膜一起组装成所述的锂金属电池。
作为优选，所述充电方法采用脉冲电流充电。具体是将脉冲电流接入组装好的锂金属电池并进行充电。
经试验发现，采用脉冲电流进行充电，可以抑制锂金属电极枝晶的生长、减少电极体积膨胀，且组装成的电池寿命也更长，循环更加稳定。
作为优选，所述的脉冲电流占空比为10％～90％。
所述的占空比是脉冲宽度与脉冲周期的比值，即占空比＝脉冲宽度/脉冲周期。
本发明中，对所述的脉冲电流的波形没有特殊限定，可以为方波、尖峰波、锯齿波、钟型波、阶梯波、梯形波或三角波。
在选择上述占空比的情况下，作为优选，所述脉冲电流的脉冲宽度为1ns～1000s，脉冲幅度(峰值电流密度)为0.01μA cm-2～500mA cm-2，脉冲频率为0.001Hz～109Hz。
进一步优选，所述脉冲电流的占空比为16.67％～66.67％，脉冲宽度为1ms～100s，脉冲幅度为0.01mAcm-2～10mAcm-2，脉冲频率为0.01Hz～1kHz。
再优选，所述脉冲电流的占空比为16.67％～50％；
所述脉冲电流的脉冲宽度为1ms～10s，脉冲幅度为0.1mA cm-2～10mA cm-2，脉冲频率为0.1Hz～1kHz。
再进一步优选，所述脉冲电流的占空比为16.67％～50％，脉冲宽度为1ms～1s，脉冲幅度为0.5mAcm-2～6mAcm-2，脉冲频率为0.1Hz～500Hz。
与现有技术相比，本发明具有以下突出优势：
本发明提出用脉冲方式代替传统恒电流方式对锂金属电池进行充电， 简单、方便、高效地保护了锂金属电极，可以有效的抑制锂枝晶枝晶生长，减少锂金属电极体积膨胀，延长锂金属电极寿命，提高库伦效率，提高电化学循环稳定性。
附图说明
图1为中分别给出了实施例1中采用的方波脉冲电流信号示意图(左图)，以及对比例1中采用的恒电流信号示意图(右图)；图中，a-脉冲宽度，b-脉冲幅度，c-脉冲周期；
图2为实施例1采用的普通锂金属电极在循环之前平面扫描电镜照片(左图)，以及在脉冲电流条件下循环8圈之后平面扫描电镜照片(右图)，并给出对比例的恒电流条件下循环8圈之后平面扫描电镜照片(中图)作为对比；
图3为实施例1采用的普通锂金属电极在循环之前截面扫描电镜照片(左图)，以及在脉冲电流条件下循环8圈之后截面扫描电镜照片(右图)，并给出对比例的在恒电流条件下循环8圈之后截面扫描电镜照片(中图)作为对比；
图4中分别给出对比例1中锂金属电极组装的对称电池在恒电流的时间-电压曲线(左图)，和实施例1中锂金属电极组装的对称电池在脉冲电流条件下时间-电压曲线(右图)；
图5为图4虚线框中的时间-电压放大图，图5左图对应图4左图，图5右图对应图4右图；
图6中分别给出了对比例1中锂金属电极组装的对称电池在恒电流的时间-电压曲线(曲线1)，和实施例2中锂金属电极组装的对称电池在脉冲电流条件下时间-电压曲线(曲线2)；
图7中分别给出了实施例3中锂金属电极组装的对称电池在占空比为66.67％的脉冲电流条件时间-电压曲线(上图)，以及实施例1中以锂金属电极组装的对称电池在占空比为16.67％脉冲电流条件下时间-电压曲线 (下图)。
具体实施方式
下面结合实施例，更具体的阐述本发明的内容。本发明的实施并不限于下面的实施例，对本发明所做的任何形式上的变通和改变都应在本发明的保护范围内。
对比例1
将正极和负极都是锂金属的电极，组装成对称电池，电解液为1M LiTFSI/PC。
连接恒电流进行充放电循环测试，条件如下：电流密度为3mA cm2，充放电电量为1mAh cm-2，充放电时间为20min。
经测试，锂金属电池20圈循环短路。
实施例1
将正极和负极都是锂金属的电极，组装成对称电池，电解液为1M LiTFSI/PC。
连接脉冲电流进行充放电循环测试，条件如下：方波脉冲电流，占空比(脉冲宽度/脉冲周期)为16.67％，脉冲宽度为1s，脉冲幅度(峰值电流密度)为3mA cm-2，脉冲频率为0.167Hz。同样充入1mAh cm-2电量后，再进行放电测试，同样放出1mAh cm-2电量，以此循环。充放电脉冲参数保持一致。每个循环中，总的充电脉冲宽度累积为20min，总的放电脉冲宽度累积也为20min。
经测试，采用本实施例中的条件对锂金属电池进行脉冲电流充电，至少循环50圈未出现短路现象。
图2和图3中给出了锂金属电极组装的对称电池充电前，以及分别在对比例1和实施例1的充电条件下循环8圈之后的平面、截面扫描电镜照片。观察图可以发现，在平面图中经过脉冲电流充电循环，锂金属电极表 面对比恒电流充电循环后更加致密，空缝隙也比较少，枝晶也较少；在截面图中经过脉冲电流充电循环，锂金属电极厚度对比恒电流充电循环后增加的更少，说明循环后的电极内部更加紧密，体积膨胀问题得到抑制。
实施例2
将正极和负极都是锂金属的电极，组装成对称电池，电解液为1M LiTFSI/PC。
连接脉冲电流进行充放电循环测试，条件如下：方波脉冲电流，占空比(脉冲宽度/脉冲周期)为50％，脉冲宽度为1s，脉冲幅度(峰值电流密度)为6mA cm-2，脉冲频率为0.5Hz。同样充入1mAh cm-2电量后，再进行放电测试，同样放出1mAh cm-2电量，以此循环。每个循环中，总的充电脉冲宽度加停歇的时间累积为20min，总的放电脉冲宽度加停歇的时间累积也为20min。
经测试，采用本实施例中的条件对锂金属电池进行脉冲电流充电，至少循环160圈未出现短路现象。
即保持与对比例1的充放电时间且充入电量一样的情况下，在本实施例脉冲电流条件下，锂金属电池寿命可提高至少8倍以上。
图6中分别给出了锂金属电极组装的对称电池在对比例1的恒电流充电条件和实施例2的脉冲电流充电条件下的时间-电压曲线，可以看出在脉冲电流充电条件下，电池循环更加平稳，直到7000min没有出现明显的电压突增或突降，而在恒电流充电条件下，电压在800min出现明显的突增。
实施例3
将正极和负极都是锂金属的电极，组装成对称电池，电解液为1M LiTFSI/PC。
连接脉冲电流进行充放电循环测试，条件如下：方波脉冲电流，占空 比(脉冲宽度/脉冲周期)为66.67％，脉冲宽度为1s，脉冲幅度(峰值电流密度)为3mA cm-2，脉冲频率为0.6667Hz。充入1mAh cm-2电量后，再进行放电测试，同样放出1mAh cm-2电量，以此循环。充放电脉冲参数保持一致。每个循环中，总的充电脉冲宽度累积为20min，总的放电脉冲宽度累积也为20min。
在同样脉冲电流充电条件下，占空比为66.67％的锂金属电池20圈循环短路，而占空比为16.67％的锂金属电池可以至少循环50圈未出现短路现象。
图7中分别给出了锂金属电极组装的对称电池在实施例1和实施例3不同的脉冲电流充电条件下的时间-电压曲线，在占空比为16.67％脉冲条件下锂金属电池循环更加稳定，210h后未出现明显电压突增或突降，而在在占空比为66.67％脉冲条件下的25h后出现明显的电压突增。
经上述实验表明，锂金属电池在恒电流条件下在3mA/cm2电流密度，充放电时间为20min条件下20圈循环短路，而在本发明所述脉冲电流条件下，保持充入电量一致，脉冲幅度为3mA/cm2，占空比为16.67％，脉冲宽度为1s，脉冲频率为16.67Hz，锂金属电池可以至少循环50圈未出现短路现象。进一步优化实验方案，保持充电效率一致，即充电时间与恒电流条件下保持一致为20min，同样保持充入电量一致，采用更大的脉冲幅度为6mA/cm2，占空比为50％，脉冲宽度为1s，脉冲频率为0.5Hz，锂金属电池可以至少循环160圈未出现短路现象。
实施例4
将同样的锂金属电极组装成对称电池，电解液为1M LiTFSI/DOL:DME(体积比为1:1)，添加剂为LiNO3，连接脉冲电流进行循环测试，条件如下：方波脉冲电流，占空比为25％，脉冲宽度为0.1s，脉冲幅度(峰值电流密度)为1mA cm-2，脉冲频率为2.5Hz。充入0.5mAh cm-2电量后，再反转脉冲电流信号进行放电测试，同样放出0.5mAh cm-2 电量，以此循环。
经测试，采用本实施例中的条件对锂金属电池进行脉冲电流充电，至少循环110圈未出现短路现象。
实施例5
将锂金属电极与磷酸铁锂(LiFePO4)，或钴酸锂(LiCoO2)，或钛酸锂(Li4Ti5O12)，或锰酸锂(LiMn2O4)，或三元材料(LiNixMnyCozO2或LiNi1-y-zCoyAlzO2)组装成锂金属电池，电解液为1M LiPF6/EC:DEC(体积比为1:1)，连接脉冲电流进行循环测试，条件如下：方波脉冲电流，占空比为25％，脉冲宽度为0.001s，脉冲幅度(峰值电流密度)为0.5mA g-1，脉冲的重复频率为250Hz。充入1mAh g-1电量后，再反转脉冲电流信号进行放电测试，同样放出1mAh g-1电量，以此循环。
经测试，采用本实施例中的条件对锂金属电池进行脉冲电流充电，至少循环250圈未出现短路现象。
实施例6
将锂金属电极与硫化物的电极组装成锂硫电池，电解液为1M LiTFSI in DOL:DME(体积比为1:1)，添加剂为LiNO3，连接脉冲电流进行循环测试，条件如下：方波脉冲电流，占空比为50％，脉冲宽度为0.001s，脉冲幅度(峰值电流密度)为0.5mA/g，脉冲的重复频率为500Hz。充入5mAh/g电量后，再反转脉冲电流信号进行放电测试，同样放出5mAh/g电量，以此循环。
经测试，采用本实施例中的条件对锂金属电池进行脉冲电流充电，至少循环45圈未出现短路现象。
实施例7
将同样的锂金属电极组装成对称电池，电解液为1M LiTFSI/DOL:DME(体积比为1:1)，添加剂为LiNO3，连接脉冲电流进行循 环测试，条件如下：尖峰波脉冲电流，占空比为25％，脉冲宽度为0.1s，脉冲幅度(峰值电流密度)为2mA cm-2，脉冲频率为2.5Hz。充入2mAh cm-2电量后，再反转脉冲电流信号进行放电测试，同样放出2mAh cm-2电量，以此循环。经测试，采用本实施例中的条件对锂金属电池进行脉冲电流充电，至少循环80圈未出现短路现象。
实施例8
将同样的锂金属电极组装成对称电池，电解液为1M LiTFSI/PC(体积比为1:1)，连接脉冲电流进行循环测试，条件如下：梯形波脉冲电流，占空比为25％，脉冲宽度为0.1s，脉冲幅度(峰值电流密度)为1mA cm-2，脉冲频率为2.5Hz。充入2mAh cm-2电量后，再反转脉冲电流信号进行放电测试，同样放出2mAh cm-2电量，以此循环。经测试，采用本实施例中的条件对锂金属电池进行脉冲电流充电，至少循环45圈未出现短路现象。
实施例9
将同样的锂金属电极组装成对称电池，电解液为1M LiTFSI/PC(体积比为1:1)，连接脉冲电流进行循环测试，条件如下：钟型波脉冲电流，占空比为25％，脉冲宽度为0.1s，脉冲幅度(峰值电流密度)为3mA cm-2，脉冲频率为2.5Hz。充入3mAh cm-2电量后，再反转脉冲电流信号进行放电测试，同样放出3mAh cm-2电量，以此循环。经测试，采用本实施例中的条件对锂金属电池进行脉冲电流充电，至少循环60圈未出现短路现象。
实施例10
将同样的锂金属电极组装成对称电池，电解液为1M LiTFSI/PC(体积比为1:1)，连接脉冲电流进行循环测试，条件如下：三角波脉冲电流，占空比为25％，脉冲宽度为0.1s，脉冲幅度(峰值电流密度)为2mA cm-2， 脉冲频率为2.5Hz。充入1mAh cm-2电量后，再反转脉冲电流信号进行放电测试，同样放出1mAh cm-2电量，以此循环。经测试，采用本实施例中的条件对锂金属电池进行脉冲电流充电，至少循环40圈未出现短路现象。

Claims (7)

  1. 一种应用于锂金属电池的脉冲充电方法，其特征在于，所述脉冲充电方法为脉冲电流充电；所述锂金属电池的电极材料选自纯锂金属、锂金属合金或锂金属-碳材料。
  2. 根据权利要求1所述的应用于锂金属电池的脉冲充电方法，其特征在于，所述的脉冲电流占空比为10％～90％。
  3. 根据权利要求2所述的应用于锂金属电池的脉冲充电方法，其特征在于，所述的脉冲电流的波形为方波、尖峰波、锯齿波、钟型波、阶梯波、梯形波或三角波。
  4. 根据权利要求3所述的应用于锂金属电池的脉冲充电方法，其特征在于，所述脉冲电流的脉冲宽度为1ns～1000s，脉冲幅度为0.01μAcm-2～500mA cm-2，脉冲频率为0.001Hz～109Hz。
  5. 根据权利要求4所述的应用于锂金属电池的脉冲充电方法，其特征在于，所述脉冲电流的占空比为16.67％～66.67％，脉冲宽度为1ms～100s，脉冲幅度为0.01mA cm-2～10mA cm-2，脉冲频率0.01Hz～1kHz。
  6. 根据权利要求5所述的应用于锂金属电池的脉冲充电方法，其特征在于，所述脉冲电流的占空比为16.67％～50％。
  7. 根据权利要求6所述的应用于锂金属电池的脉冲充电方法，其特征在于，所述脉冲电流的脉冲宽度为1ms～10s，脉冲幅度为0.1mAcm-2～10mA cm-2，脉冲频率为0.1Hz～1kHz。
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