这个适用于需要for循环 <el-collapse-item>
负责展开的属性是value

<el-collapse :value="opened">
  <el-collapse-item v-for="o in List" :key="o.aaa":name="o.aaa">
    <div>XXXXXXXXXXXXXXXXXXXXXXXX</div>
  </el-collapse-item>
</el-collapse>

<script>
  export default {
    data() {
      return {
       	List:[
       		{ 
       			aaa:"123"
       		},
       		{
       			aaa:"354"
       		},
       		{
       			aaa:"asfdvg"
       		}
       	]
      };
    },
      computed: {
            opened() {
                return this.List.map((i) => {
                    return i.aaa;
                });
            }
        },
  }
</script>