LiFePO₄/C was prepared by employing coprecipitation method and carbothermal reduction method using FeSO₄ with different purity as the iron source. The purity of FeSO₄ has a great influence on the morphology of FePO₄, but has little effect on the morphology of LiFePO₄/C. The cycling performance decreases with the decrease of purity, and purity has a significant effect on the specific discharge capacities at low temperature. The specific discharge capacities of the five samples at − 20 °C and 0.5 C were 85.3, 74.2, 65.5, 60.4, and 50.1 mAh g⁻¹, and the capacity retention rates were 53.3%, 47.1%, 42.9%, 38.7%, and 31.9%, respectively. Full battery low temperature performance test results validate the test results of coin cell. The Li⁺ diffusion coefficients are 4.53 × 10⁻¹³, 2.02× 10⁻¹³, 4.73 × 10⁻¹⁴, 2.34× 10⁻¹⁴, and 8.56 × 10⁻¹⁵ cm² s⁻¹, respectively. D_Li⁺ is reduced two orders of magnitude with reduction of raw material purity. This is mainly because the low-purity FeSO₄ contains a large amount of Ti, which enters the LiFePO₄/C crystal lattice, causing the lattice distortion to block the lithium ion diffusion channel. Therefore, improving the purity of raw materials is an important method to improve the low temperature performance of LiFePO₄/C.

中文翻译：

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FeSO 4纯度对LiFePO 4 / C低温性能的影响

采用共沉淀法和碳热还原法，以不同纯度的FeSO ₄作为铁源，制备了LiFePO ₄ / C。FeSO ₄的纯度对FePO ₄的形貌影响很大，但对LiFePO ₄ / C的形貌影响很小。循环性能随着纯度的降低而降低，并且纯度对低温下的比放电容量具有显着影响。五个样品在− 20°C和0.5 C时的比放电容量分别为85.3、74.2、65.5、60.4和50.1 mAh g ^-1，容量保留率分别为53.3％，47.1％，42.9％，38.7％和31.9％。完整的电池低温性能测试结果验证了纽扣电池的测试结果。锂⁺扩散系数4.53×10 ^-13，2.02×10 ^-13，4.73×10 ^-14，2.34×10 ^-14，和8.56×10 ^-15 厘米² 小号^-1，分别。随着原料纯度的降低，D _Li ⁺被降低两个数量级。这主要是因为低纯度的FeSO ₄包含大量的Ti，从而进入LiFePO ₄/ C晶格，导致晶格畸变阻塞锂离子扩散通道。因此，提高原材料的纯度是提高LiFePO ₄ / C的低温性能的重要方法。