富鎳層狀材料因可大幅提升放電電容量是目前大家積極開發的對象。但NMC811仍然有許多問題需要克服像是電容量衰退快速、熱穩定性差，並在電池中容易產氣，且其與電解液的反應性高可能會升成更多的副產物等問題，這些都會影響其電化學表現。
在這項研究中，利用新的濕式原子氣相沉積法（Wet Atomic Layer Deposition）來包覆鋁酸鋰保護層層，以作為人工固態電解質介面，穩定富鎳正極材料結構，避免其與電解液直接接觸，來達到減少發生副反應的機率，而實驗結果顯示，塗有鋁酸鋰的正極材料在0.1C充放電速率下，經過100次循環後，電容量保持率仍然維持有87%，比起未包覆NMC811及Al2O3包覆的79%、81%高，此外在CV測試以及阻抗測試也有較小的極化現象及阻抗上升，並且塗覆鋁酸鋰的材料在高電位(5C)充放電速率下，經過100圈後其仍然保有85.49%的容量保持率而Al2O3塗層樣品則是78.38%，至於Pristine NMC僅僅只剩下70.4%的電容量保持率，在變速率測試的部分塗覆鋁酸鋰的材料也顯得更加穩定，其歸因於LiAlO2其導離率優於Al2O3，並且具有更好的可逆循環性。
然而此技術需要透過暴露蒸氣，使前驅物Al(OC2H5)3能與NMC811表面氫氧基反應鍵結來完成包覆，然而我們發現在反應的過程由於Al(OC2H5)3前驅物溶解在無水酒精中，此時溶液中的質子會與NMC結構中的鋰發生質子交換，使NMC811中的鋰被置換出來，而造成初始電容量的損失，影響其電化學表現，因此我們藉由添加不同濃度比的LiOH使溶液成微鹼性，並藉由LiOH來減少質子與NMC中的鋰發生置換現象，並將包覆層由Al2O3轉變為導離率較好並且電化學穩定性也較優的鋁酸鋰(LiAlO2)，藉此來提升其電化學表現。
再來由於製程步驟簡單且快速，並證實在不更改製程參數的條件下，可以將原先5g的量增加至30g並且不會改變其包覆LiAlO2的電化學表現，證實Wet-ALD可簡單擴大製程，而我們也有將LiAlO2 coated NMC811組成正極複合材料運用至全固態電池上(P-LiAlO2 coated_NMC811_1Eq-LiOH-1%VGCF||P-LPSC||In)，而在阻抗測試上，不論正極材料在未充電情況下，或是在高電位情況下，比起Pristine NMC811，皆可抑制阻抗值的上升，歸因於coating LiAlO2 能夠減少NMC與LPSC直接接觸產生化學反應；而在0.05C充放電速率下經過40圈循環後，LiAlO2塗層樣品保持了大約63.5% 的電容量保持率，而Pristine NMC僅剩下42.4%，因此可以證實緻密且導離率好的LiAlO2包覆層能夠有效提高正極材料與LPSC界面穩定性，來提高其在全固態電池上的電化學表現。

Nickel-rich layered materials have been actively developed due to their high specific capacitance. However, NMC811 still has many problems that need to be overcome, such as rapid capacitance decline, poor thermal stability, battery gas production, and high reactivity with the electrolyte may cause more by-products, which will affect electrochemical performance.
In this study, a new coating method Wet-ALD was proposed to coat the metal oxide layer as an artificial solid electrolyte interface layer to stabilize the nickel-rich cathode material, avoid direct contact with the electrolyte, and reduce side reactions. This technology requires exposure to vapor so that the precursor Al(OC2H5)3 can react and bond with the hydroxyl groups on the surface of NMC811. However, when the Al(OC2H5)3 precursor was dissolved in anhydrous alcohol, the proton in the solution would exchange with the lithium in the NMC structure during the coating process. This led to the exhaustion of lithium in the NMC811 and the loss of the initial capacity, affecting the following electrochemical performance. Thus, additional LiOH was added to make the solution slightly alkaline, and it can mitigate the proton exchange phenomenon. Further, the coating material is changed from Al2O3 to lithium aluminate (LiAlO2) because the latter has better conductivity and electrochemical stability, thereby improving its electrochemical performance.
In the experiment, the cathode material coated with lithium aluminate, its capacity retention remained 87% after charge and discharge at 0.1C for 100 cycles, higher than the values of pristine NMC811 and Al2O3 of 79% and 81%. In addition, LiAlO2 coating also had a more negligible polarization in the CV and less rise in impedance test. The cell with lithium aluminate coated cathode maintained capacity retention of 85.49% when cycled at a high rate (5 C) after 100 cycles. In contrast, the Al2O3 coating was 78.38%, and the pristine NMC only had 70.4%. The material coated with lithium aluminate was also more stable in the rate capability test. It can be attributed to LiAlO2 having better conductivity and reversible cyclability than Al2O3.
LiAlO2 coated NMC811 was also employed to form a composite in an all-solid-state battery (P-LiAlO2 coated NMC811_1Eq-LiOH-1%VGCF||P-LPSC||In). In the impedance test, whether the composite cathode was not charged or at high potential, compared with pristine NMC811, it could reduce the impedance increase attributed to LiAlO2 coating and prevent direct contact between NMC and LPSC from producing a chemical reaction. The LiAlO2 coated sample maintained high capacity retention of about 63.5%, while the pristine NMC only had 42.4% at a charge-discharge C-rate of 0.05C after 40 cycles. Therefore, it can be proved that the dense and complete LiAlO2 coating with good conductivity can effectively improve the stability of the interface between the cathode material and LPSC to enhance its electrochemical performance on all-solid-state batteries.

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