Question About Stored Procedure And Variable From Dynamic SQL

Ok, so I have this stored procedure that Inserts a record and I need to return the ID inserted to pass to another procedure. I ended up having to use sp_executesql because I need to dynamically add the schema to the table. The issue that I am having is that the variable that I try to pass to the other procedure always ends up null, but it shows the correct output. Just to clarify on this, i am an Applications developer and not a DBA so I may be going about this all wrong. Any help on this would be greatly appreciated.

Here is the SP

set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
GO
ALTER PROCEDURE [dbo].[sp_AddAnalyte]
@Analyt NVarChar(100),
@LName NVarChar(100),
@AtomicNum NVarChar(100),
@AtomicMass NVarChar(100),
@Weight NVarChar(100),
@HalfLife NVarChar(100),
@Units NVarChar(100),
@HF_Secs NVarChar(100),
@Gas NVarChar(100),
@Nat NVarChar(100)
AS
DECLARE @ID INT,@i INT
DECLARE @schema VarChar(50)
DECLARE @sql NVARCHAR(512)
BEGIN
SET @Schema = (SELECT schema_name())
SET @sql = N'INSERT INTO [' + @schema + '].[Analytes] ([Analyte],[LongName],[AnalyteType]) VALUES (''' + @Analyt + ''',''' + @LName + ''',1)';
EXEC sp_executesql @query = @sql;
SET @sql = N'SELECT MAX(AnalytePK) FROM [' + @schema + '].[Analytes]';
EXEC sp_executesql
@query = @sql,
@params = N'@ID INT OUTPUT',
@i = @ID OUTPUT
EXEC sp_AddParameterValue 6, @i, 'AtomicNum', @AtomicNum, '';
EXEC sp_AddParameterValue 6, @i, 'AtomicMass', @AtomicMass, '';
EXEC sp_AddParameterValue 6, @i, 'Weight', @Weight, '';
EXEC sp_AddParameterValue 6, @i, 'HalfLife', @HalfLife, '';
EXEC sp_AddParameterValue 6, @i, 'Units', @Units, '';
EXEC sp_AddParameterValue 6, @i, 'HF_Secs', @HF_Secs, '';
EXEC sp_AddParameterValue 6, @i, 'Gas', @Gas, '';
EXEC sp_AddParameterValue 6, @i, 'Natural', @Nat, '';
END