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>Effectively enhanced structural stability and electrochemical properties of LiNi0.5Mn1.5O4 cathode materials via poly-(3,4-ethylenedioxythiophene)-in situ coated for high voltage Li-ion batteries
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Effectively enhanced structural stability and electrochemical properties of LiNi0.5Mn1.5O4 cathode materials via poly-(3,4-ethylenedioxythiophene)-in situ coated for high voltage Li-ion batteries
Spinel LiNi _(0.5) Mn _(1.5) O _(4) shows promise as a potential candidate for Li-ion batteries due to its high energy density and high rate performance. However, LiNi _(0.5) Mn _(1.5) O _(4) (LNMO) spinel oxides usually deliver poor cycle life because of the increasing impedance and gradually dissolving Mn resulting in the destruction of crystal structure. Here, a conductive polymer poly-(3,4-ethylenedioxythiophene) (PEDOT) surface modified strategy is introduced to settle the above challenges. The main purpose is to construct a uniform and dense shell film on the surface of LiNi _(0.5) Mn _(1.5) O _(4) (Industrial Grade), which is prepared by a simple chemical in situ oxidative polymerization method. The Mn dissolving from the lattice during the long-term cycling is well inhibited as the polymer shell protects LiNi _(0.5) Mn _(1.5) O _(4) from direct exposure to the highly active electrolyte. As expected, the 3 wt% poly-(3,4-ethylenedioxythiophene) coated sample reveals long cycle life with acceptable capacity of 114.5 mA h g ~(?1) and high capacity retention of 91.6% after 200 cycles, compared to 70.9 mA h g ~(?1) and 56.5%, respectively, for the bare LiNi _(0.5) Mn _(1.5) O _(4) sample. Furthermore, the coated sample demonstrates a higher capacity of 110 mA h g ~(?1) and 63 mA h g ~(?1) at 5C and 10C rate respectively. The improved performance is believed to be attributed to the formation of high conductivity and stable interface structure between electrolyte and LNMO, which is beneficial to suppress the destruction of crystalline structure due to the Mn dissolution and undesired side-reaction between electrolyte and LiNi _(0.5) Mn _(1.5) O _(4) in long cycle, and improve simultaneously the conductivity and interface stability of LiNi _(0.5) Mn _(1.5) O _(4) for high voltage lithium-ion batteries.
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机译：尖晶石LiNi _（0.5）Mn _（1.5）O _（4）由于其高能量密度和高倍率性能，有望成为锂离子电池的潜在候选者。但是，LiNi_（0.5）Mn_（1.5）O_（4）（LNMO）尖晶石氧化物通常由于阻抗的增加和逐渐溶解的Mn而导致较差的循环寿命，从而导致晶体结构的破坏。在这里，引入了导电聚合物聚（3,4-乙撑二氧噻吩）（PEDOT）表面改性策略来解决上述挑战。主要目的是在LiNi _（0.5）Mn _（1.5）O _（4）（工业级）的表面上构造均匀且致密的壳膜，该膜是通过简单的化学原位氧化聚合方法制备的。由于聚合物壳保护LiNi _（0.5）Mn _（1.5）O _（4）避免直接暴露于高活性电解质中，因此在长期循环中从晶格中溶解的Mn受到了很好的抑制。正如预期的那样，与70.9 mA hg相比，3 wt％的聚-（3,4-乙撑二氧噻吩）涂层样品具有114.5 mA hg〜（？1）的可接受容量和200循环后91.6％的高容量保持率，显示出较长的循环寿命。裸露的LiNi _（0.5）Mn _（1.5）O _（4）样品分别约为〜（？1）和56.5％。此外，经涂覆的样品在5℃和10℃的速率下显示出更高的容量，分别为110mA h g〜（Δ1）和63mA h g〜（Δ1）。认为性能的改善归因于电解质和LNMO之间形成高电导率和稳定的界面结构，这有利于抑制由于Mn溶解以及电解质与LiNi _（0.5之间的不良副反应）导致的晶体结构破坏）Mn _（1.5）O _（4）长周期，同时提高了用于高压锂离子电池的LiNi _（0.5）Mn _（1.5）O _（4）的电导率和界面稳定性。
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