Pilot study on comprehensive recycling of waste lithium iron phosphate powder

doi:10.11949/0438-1157.20240004

Abstract

Abstract:

This work aims to evaluate the efficiency of comprehensive recovery of battery-grade iron phosphate (FePO₄) and lithium carbonate (Li₂CO₃) from spent lithium iron phosphate cathode powder (LFP/C) with high fluorine/aluminum content following high-temperature calcination-neutralization precipitation. A pilot-scale platform with an annual processing capacity of 500 tons was established. The investigation includes process stability, product performance characterization, preliminary economic assessment, and the reutilization of secondary slag. The results demonstrate that over 85.63% aluminum removal and 94.70% titanium removal can be achieved through this process, with the Fe/Al mass ratio in the purified liquid increasing from 203 to 1077, laying a foundation for comprehensive recycling of spent LFP/C. The prepared FePO₄ and Li₂CO₃ met the standards for battery-grade materials. The regenerated LFP/C cathode material exhibits a first-cycle coulombic efficiency of 95.2% at 0.1 C, and a capacity retention of 97.1% after 250 cycles at 1 C, indicating its favorable electrochemical performance. In addition, the economic evaluation further highlights the superiority of the process in terms of economic and environmental benefits.

Key words: spent LiFePO₄/C, precursors, electrochemical performance, pilot-scale, economic analysis

摘要：

为研究废旧磷酸铁锂粉料（LFP/C）经高温煅烧-中和沉淀除杂后实现电池级磷酸铁和碳酸锂综合回收的效能，以氟/铝含量较高的废旧LFP/C为对象，构建了年处理规模为500 t的中试平台，从工艺稳定性、产品性能表征、初步经济评估及二次废渣再利用等角度进行研究。结果显示，通过此法可实现高于85.63%铝去除和94.70%钛去除，除铝液中铁铝质量比由203增加至1077，为废旧LFP/C综合回收奠定基础。所制备的FePO₄及Li₂CO₃符合电池级标准，再生的LFP/C正极材料在0.1 C条件下首次充放电库仑效率可达95.2%，1 C条件下经过250圈循环后容量保持率达97.1%，展现出较好的电化学性能。此外，经济评估进一步凸显了该工艺在经济和环境效益方面的优越性。

关键词: 废旧磷酸铁锂, 前体, 电化学性能, 中试规模, 经济分析

CLC Number:

X 703

Yang JIANG, Changhong PENG, Wei CHEN, Hao ZHOU, Zhongbin MA, Hongbo LI, Zairong QIU, Guopeng ZHANG, Kanggen ZHOU. Pilot study on comprehensive recycling of waste lithium iron phosphate powder[J]. CIESC Journal, 2024, 75(6): 2353-2361.

江洋, 彭长宏, 陈伟, 周豪, 马忠彬, 李洪博, 邱在容, 张国鹏, 周康根. 废旧磷酸铁锂粉料综合回收中试研究[J]. 化工学报, 2024, 75(6): 2353-2361.

Figures/Tables 12

Table 1 The reaction equations involved in each step of the process

反应步骤	方程式
煅烧脱氟	$L i P F_{6} + H_{2} O \overset{}{\to} 2 H F ↑ + L i F + P O F_{3}$ $L i F + H_{3} P O_{4} \overset{}{\to} H F ↑ + L i H_{2} P O_{4}$
煅烧脱氟	$P O F_{3} + 3 H_{2} O \overset{}{\to} 3 H F ↑ + H_{3} P O_{4}$
浸出过程	$2 L i F e P O_{4} + 2 H_{2} S O_{4} \overset{}{\to} L i_{2} S O_{4} + F e S O_{4} + F e (H_{2} P O_{4})_{2}$
浸出过程	$2 A l + 3 H_{2} S O_{4} \overset{}{\to} A l_{2} (S O_{4})_{3} + 3 H_{2} ↑$ $T i O_{2} + 2 H_{2} S O_{4} \overset{}{\to} T i (S O_{4})_{2} + 2 H_{2} O$ $2 A l P O_{4} \cdot x H_{2} O + 3 H_{2} S O_{4} \overset{}{\to} A l_{2} (S O_{4})_{3} + 2 H_{3} P O_{4} + 2 x H_{2} O$
中和除杂	$A l_{2} (S O_{4})_{3} + 2 H_{3} P O_{4} + 3 F e + 2 x H_{2} O \overset{}{\to} 2 A l P O_{4} \cdot x H_{2} O ↓ + 3 F e S O_{4} + 3 H_{2} ↑$ $T i (S O_{4})_{2} + 3 H_{2} O \overset{}{\to} H_{2} T i O_{3} ↓ + 2 H_{2} S O_{4}$
沉磷酸铁	$2 F e S O_{4} + H_{2} O_{2} + H_{2} S O_{4} \overset{}{\to} F e_{2} (S O_{4})_{3} + 2 H_{2} O$ $F e_{2} (S O_{4})_{3} + 2 N a H_{2} P O_{4} + 4 H_{2} O \overset{}{\to} 2 F e P O_{4} \cdot 2 H_{2} O ↓ + N a_{2} S O_{4} + 2 H_{2} S O_{4}$ $A l_{2} (S O_{4})_{3} + 2 H_{3} P O_{4} + 2 x H_{2} O \overset{}{\to} 2 A l P O_{4} \cdot x H_{2} O ↓ + 3 H_{2} S O_{4}$
深度除杂	$F e_{2} (S O_{4})_{3} + 6 N a O H \overset{}{\to} 2 F e {(O H)}_{3} ↓ + 3 N a_{2} S O_{4}$ $M e S O_{4} + 2 N a O H \overset{}{\to} M e {(O H)}_{2} ↓ + N a_{2} S O_{4}$ （Me为二价金属离子）
回收锂	$L i_{2} S O_{4} + N a_{2} C O_{3} \overset{}{\to} L i_{2} C O_{3} ↓ + N a_{2} S O_{4}$ $L i_{2} C O_{3} + C O_{2} + H_{2} O \overset{}{\to} 2 L i H C O_{3}$ $2 L i H C O_{3} \overset{}{\to} L i_{2} C O_{3} ↓ + C O_{2} ↑ + H_{2} O$ $3 L i_{2} S O_{4} + 2 N a H_{2} P O_{4} + 4 N a O H \overset{}{\to} 2 L i_{3} P O_{4} ↓ + 3 N a_{2} S O_{4} + 4 H_{2} O$

Table 1 The reaction equations involved in each step of the process

反应步骤	方程式
煅烧脱氟	$L i P F_{6} + H_{2} O \overset{}{\to} 2 H F ↑ + L i F + P O F_{3}$ $L i F + H_{3} P O_{4} \overset{}{\to} H F ↑ + L i H_{2} P O_{4}$
煅烧脱氟	$P O F_{3} + 3 H_{2} O \overset{}{\to} 3 H F ↑ + H_{3} P O_{4}$
浸出过程	$2 L i F e P O_{4} + 2 H_{2} S O_{4} \overset{}{\to} L i_{2} S O_{4} + F e S O_{4} + F e (H_{2} P O_{4})_{2}$
浸出过程	$2 A l + 3 H_{2} S O_{4} \overset{}{\to} A l_{2} (S O_{4})_{3} + 3 H_{2} ↑$ $T i O_{2} + 2 H_{2} S O_{4} \overset{}{\to} T i (S O_{4})_{2} + 2 H_{2} O$ $2 A l P O_{4} \cdot x H_{2} O + 3 H_{2} S O_{4} \overset{}{\to} A l_{2} (S O_{4})_{3} + 2 H_{3} P O_{4} + 2 x H_{2} O$
中和除杂	$A l_{2} (S O_{4})_{3} + 2 H_{3} P O_{4} + 3 F e + 2 x H_{2} O \overset{}{\to} 2 A l P O_{4} \cdot x H_{2} O ↓ + 3 F e S O_{4} + 3 H_{2} ↑$ $T i (S O_{4})_{2} + 3 H_{2} O \overset{}{\to} H_{2} T i O_{3} ↓ + 2 H_{2} S O_{4}$
沉磷酸铁	$2 F e S O_{4} + H_{2} O_{2} + H_{2} S O_{4} \overset{}{\to} F e_{2} (S O_{4})_{3} + 2 H_{2} O$ $F e_{2} (S O_{4})_{3} + 2 N a H_{2} P O_{4} + 4 H_{2} O \overset{}{\to} 2 F e P O_{4} \cdot 2 H_{2} O ↓ + N a_{2} S O_{4} + 2 H_{2} S O_{4}$ $A l_{2} (S O_{4})_{3} + 2 H_{3} P O_{4} + 2 x H_{2} O \overset{}{\to} 2 A l P O_{4} \cdot x H_{2} O ↓ + 3 H_{2} S O_{4}$
深度除杂	$F e_{2} (S O_{4})_{3} + 6 N a O H \overset{}{\to} 2 F e {(O H)}_{3} ↓ + 3 N a_{2} S O_{4}$ $M e S O_{4} + 2 N a O H \overset{}{\to} M e {(O H)}_{2} ↓ + N a_{2} S O_{4}$ （Me为二价金属离子）
回收锂	$L i_{2} S O_{4} + N a_{2} C O_{3} \overset{}{\to} L i_{2} C O_{3} ↓ + N a_{2} S O_{4}$ $L i_{2} C O_{3} + C O_{2} + H_{2} O \overset{}{\to} 2 L i H C O_{3}$ $2 L i H C O_{3} \overset{}{\to} L i_{2} C O_{3} ↓ + C O_{2} ↑ + H_{2} O$ $3 L i_{2} S O_{4} + 2 N a H_{2} P O_{4} + 4 N a O H \overset{}{\to} 2 L i_{3} P O_{4} ↓ + 3 N a_{2} S O_{4} + 4 H_{2} O$

Fig.1 Pilot process flow diagram and physical image

Table 2 Variations in leaching rates of valuable elements in spent LFP/C before and after calcination

项目	浸出率/%
项目	Fe	P	Li	Al	F	Ti	Mn	Ni	Co
煅烧前	97.7	96.5	99.8	83.1	75.2	67.3	95.4	95.8	75.9
煅烧后	90.4	87.8	97.6	42.3	0.03	57.5	94.8	93.7	63.3

Table 3 Alterations in ionic concentrations in solution upon aluminum removal

元素	浸出液中浓度	净化液中浓度	沉降率/%
Fe	77 g/L	82.9 g/L	10.67
P	41.8 g/L	38.4 g/L	13.22
Li	10.7 g/L	12.4 g/L	0.03
Al	380 mg/L	77 mg/L	85.63
Ti	315 mg/L	22 mg/L	94.70
Mn	82 mg/L	80 mg/L	—
Ni	55 mg/L	12 mg/L	—
Co	20 mg/L	14 mg/L	—

Fig.2 Characterization of iron phosphate products

Table 4 Chemical analysis of battery-grade iron phosphate products

元素	含量/%
Fe	36.02
P	20.31
Li	0.004
Al	0.011
Ti	0.002
Mn	0.003
Ni	0.002
Cu	0
Co	0
Ca	0
F	0

Fig.3 Phase composition and microscopic morphology of Li2CO3 products

Fig.4 Electrochemical performance of regenerated LFP/C materials

Fig.5 Phase composition of secondary leaching residue

Table 5 Chemical analysis of FePO4 for ceramic applications

元素	含量/%
Fe	36.18
P	20.48
Li	0.005
Al	0.071
Ti	0.026
Mn	0.003
Ni	0.001
Cu	0
Co	0
Ca	0
F	0

Table 6 Balancing calculations of each element from the expending test

项目	投加或产出/kg
项目	Fe	P	Li
废旧LFP/C粉料	-638.6	-390.6	-87.8
浓磷酸	0	-51.5	0
工业铁粉	-90.3	0	0
磷酸二氢钠	0	-29.1	0
副产亚铁	-55.5	0	0
磷酸铁	+751.9	+416.2	+0.06
碳酸锂	0	0	+71.8
磷酸锂	0	+15.5	+10.4
难溶渣	+16.9	+13.7	+0.96
二浸渣	+4.8	+9.6	+0.43
提锂液	0	0	+0.3
洗涤水（系统循环）	+5.7	+9.8	+3.8
平衡率	99.35%	98.64%	99.94%

Table 7 The input and output for processing 2.0 t of spent LFP/C

序号	消耗/产生	参考价格	消耗/产出量		费用/CNY
17	总利润			+14013 CNY
1	废旧LFP/C粉料	13000 CNY/t	-2.0 t		-26000
2	硫酸	200 CNY/t	-2.0 t		-400
3	磷酸	6800 CNY/t	-170 kg		-1156
4	工业铁粉	2500 CNY/t	-110 kg		-275
5	自来水	4.1 CNY/m³	-10 m³		-41
6	磷酸二氢钠	5800 CNY/t	-150 kg		-870
7	双氧水	1250 CNY/m³	-1.2 m³		-1500
8	氢氧化钠	3500 CNY/t	-3.2 t		-11200
9	碳酸钠	2950 CNY/t	-750 kg		-2212
10	副产亚铁	400 CNY/t	-270 kg		-108
11	一般固废处理	300 CNY/t	1.0 t		-300
12	危废处理	3000 CNY/t	300 kg		-900
13	电池用磷酸铁	11000 CNY/t	1.20 t		+13200
14	陶瓷用磷酸铁	6000 CNY/t	840 kg		+5040
15	电池级碳酸锂	93000 CNY/t	385 kg		+35805
16	磷酸锂	85000 CNY/t	58 kg		+4930

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